COOLANT COMPRESSOR

Abstract

The invention relates to a coolant compressor comprising an electric drive unit, a cylinder housing (1), a crankshaft (3) which can be driven by the electric drive unit, and a piston (2) that can be driven by the crankshaft (3) and is guided in a working volume of the cylinder housing (1) for cyclically compressing a coolant which can be conveyed via a suction valve into the working volume, said suction valve comprising a suction opening (7) and a valve closure element (8), preferably a valve spring, which closes the suction opening (7) in cycles. The aim of the invention is to ensure a continuous opening movement of the suction valve during the suction cycle. According to the invention, this is achieved by providing an actuation device (14; 15, 23) which is designed to open the valve closure element (8) in cycles.

Description

FIELD OF THE INVENTION

The invention relates to a coolant compressor having an electrical drive unit, a cylinder housing, a crankshaft drivable by the electrical drive unit and a piston drivable by the crankshaft, guided in a working volume of the cylinder housing for cyclical compression of a coolant, which can be conveyed into the working volume via a suction valve comprising a suction opening and a valve-closing element, preferably a valve spring cyclically closing the suction opening.

Generally, a cylinder head arrangement is mounted on the cylinder housing, the cylinder head arrangement comprising a suction opening and a valve-closing element that cyclically closes the suction opening. As a rule, the cylinder head arrangement also comprises a valve plate, which has the suction opening and a pressure opening, as well as a cylinder head cover, which forms a sealed cavity together with the valve plate. The valve-closing element of the suction valve is generally arranged on the side of the valve plate facing the piston, while a valve-closing element of the pressure valve that cyclically closes the pressure opening is arranged on the side of the valve plate facing away from the piston. The suction valve and the pressure valve generally have a valve spring as the valve-closing element. A sealing element, preferably in the form of a flat gasket, is usually arranged between the valve plate and the cylinder housing or between the valve plate and the cylinder head cover. The valve plate is generally pressed via the valve head cover onto the cylinder housing.

PRIOR ART

Coolant compressors, especially hermetically encapsulated coolant compressors having a hermetically sealable compressor housing, have long been known and are primarily used in cooling appliances such as refrigerators or refrigerating shelves. The coolant process as such has likewise been known for a long time. Coolant is heated in an evaporator by absorbing energy from a space to be cooled and finally overheated, and is pumped to a higher pressure level by means of the coolant compressor, by a piston cylinder unit, more specifically by a piston moving translationally in a cylinder housing, where the coolant outputs heat via a condenser and is conveyed back into the evaporator via a throttle valve, in which a pressure reduction and a cooling down of the coolant take place. The movement of the piston is implemented via a crankshaft driven by an electrical drive unit. The electrical drive unit normally comprises a stator and rotor, wherein the rotor is connected for conjoint rotation to the crankshaft in order to drive the piston cylinder unit.

During a revolution of the crankshaft, the piston is moved linearly during the suction cycle from top dead center, in which the distance between a piston crown and the valve plate is minimal, to bottom dead center, in which the distance between the piston crown and the valve plate is maximal, wherein coolant flows or is drawn in via the suction opening into a cylinder formed by the cylinder housing. In the subsequent compression cycle, the valve plate closes the suction opening and the piston moves linearly from bottom dead center to top dead center, compressing coolant present in the cylinder. Starting from a defined crank angle, the pressure valve opens and the compressed coolant flows out of the cylinder via the pressure opening.

According to the prior art, the suction valve does not open in the suction cycle until an opening force that is formed in the cylinder by the vacuum forming due to the piston movement and acts on the suction valve is greater than the closing force of the suction valve. As a rule, the closing force of the suction valve is defined by the spring constant of the valve spring for the suction valve. A disadvantage of the prior art is that an undefined state arises during the opening movement of the suction valve: as soon as the opening force and the closing force are approximately equal, the suction valve opens and coolant flows into the cylinder. This reduces the vacuum, however, and correspondingly also the opening force acting on the suction valve, so that the suction valve carries out a closing movement while it should actually be passing through the opening movement. Thus a “fluttering” of the suction valve occurs in a certain crank angle range, in which the suction valve does not carry out a continuous opening movement but instead only opens offset in the intermediate period, or even passes through a closing movement or several successive closing movements. This firstly reduces the quantity of total coolant reaching the cylinder during the suction cycle, which results in reduced efficiency of the coolant compressor. Secondly, the “fluttering” of the suction valve leads to a pulsation of the coolant in the coolant circuit, which results in an undesired increase of the noise level from the coolant compressor.

OBJECTIVE OF THE INVENTION

An objective of the invention is therefore that of overcoming the drawbacks of the prior art and proposing a coolant compressor in which a continuous opening movement of the suction valve during the suction cycle is ensured.

PRESENTATION OF THE INVENTION

According to the invention, this problem is solved in a coolant compressor of the type mentioned above by providing an actuating device with which the valve-closing element of the suction valve can be cyclically opened. The actuating device is thus designed to open the valve-closing element cyclically. Cyclically means that the actuating device fundamentally opens the valve-closing element in every suction cycle of a working cycle, where a working cycle corresponds to one revolution of the crankshaft. In other words, the valve-closing element is opened in the suction cycle of each working cycle during the operation of the coolant compressor, in which a plurality of working cycles are passed through successively.

The actuating device according to the invention is a device that is provided in addition to the piston, which, in the case of a valve spring according to the prior art, opens the valve spring merely by drawing in coolant in the suction cycle. The actuating device according to the invention can carry out the opening of the suction valve on its own or, as in the case of a valve spring, in support of the piston. For the latter case, it can thus be provided that the valve-closing element can only be opened on a supporting basis by the actuating device.

Generally speaking, the objective is thus achieved in that the suction valve is not opened passively or not only passively by the increasing vacuum in the cylinder during the suction cycle, but the suction valve is actively opened via the actuating device in order to prevent the “fluttering” of the suction valve.

It can be provided that the actuating device has a contact portion that is engaged with, or can be brought into engagement with, the valve-closing element, wherein the valve-closing element can be opened cyclically by moving the contact portion. The actuating device is thus designed to open the valve-closing element cyclically by moving the contact portion. This embodiment variant corresponds to a mechanical actuation of the valve-closing element. A contact portion is moved and opens the valve-closing element in this case. The contact portion can also be fixedly connected to the valve-closing element and actuated by a different element of the actuating device. For example, the valve-closing element can have a contact portion that protrudes outward through the suction opening and is actuated outside the suction opening by a different element of the actuating device. Or the contact portion is fixedly connected to the valve-closing element at one end and, at the other, is also mechanically connected to the piston (directly as a single element of the actuating device or indirectly via additional elements) and is moved by the piston, which thus (also) opens the valve-closing element mechanically via a tensile force due to the movement of the piston in the suction cycle. Or the contact portion is fixedly connected to a different element of the actuating device and is brought into engagement with the valve-closing element at least cyclically. The contact portion can also contact the valve-closing element only during a defined part of the suction cycle, but not during the compression cycle. Or it contacts the valve closing element even during the compression cycle but does not exert any force on the valve-closing element during the compression cycle.

One embodiment provides that the contact portion is or can be brought into contact with the side of the valve-closing element facing away from the piston in order to open the element by exerting a pressure force. This embodiment is easy to implement in existing coolant compressors, because no retrofitting of elements in the working volume or on the piston is necessary. This embodiment makes it possible to control the opening of the suction valve by the actuating device without impairing the operation of the coolant compressor, and to keep the number of components in the actuating device as small as possible. The suction valve generally opens in the direction of the cylinder and is arranged on the side of the valve plate facing the piston. By exerting a pressure force on the side of the suction valve facing away from the piston, in other words, by pressing on the suction valve from the side of the suction valve facing away from the piston at the beginning of the suction cycle, the continuous opening movement of the suction valve can be ensured in a particularly simple manner.

It can be provided that the opening of the valve-closing element can be initiated with the actuating device at an equilibrium of the coolant pressure on both sides of the valve-closing element. This is the ideal time for the opening of the valve-closing element and would also avoid the “fluttering.” This point in time occurs in a defined crank angle range, but is dependent on the counter pressure, the dead space and the piston velocity. This point in time could be determined by measuring the pressure on both sides of the valve-closing element, for example, and the actuating device could be actuated accordingly.

Because the “fluttering” effect only occurs cyclically in a defined, delimitable crank angle range, it is sufficient according to one embodiment of the invention to open the suction valve cyclically via the actuating device as a function of the crank angle of the crankshaft, so that the contact portion of the actuating element is in contact with the suction valve at least in the crank angle range in which the “fluttering” occurs in conventional coolant compressors. The actuating device is thus designed to open the valve-closing element cyclically as a function of the crank angle of the crankshaft. In this way, the closing movements occurring during “fluttering” are blocked by the contact with the contact portion of the actuating element. It is therefore advantageous if the contact portion contacts the suction valve already at a 90° to 60° crank angle before top dead center, i.e. already before the beginning of the suction cycle, preferably continuously. It is particularly advantageous if the contact portion does not contact the suction valve during a large part of the compression cycle in order to prevent undesired opening of the suction valve. A contact can be provided merely shortly before the beginning of the suction cycle. It is also conceivable that the suction valve detaches from the contact portion already during the suction cycle, but at least after the opening movement, so that the abrupt closing movement of the suction valve at the end of the suction cycle or the beginning of the compression cycle is not hampered by the contact portion.

It can be provided, and not only with regard to interference of the contact portion during closure of the suction valve, that the valve-closing element is cyclically closable by means of the actuating device. This would be the case for a completely active suction valve, or if the contact portion is mechanically connected to the piston. Or if a fixed connection between actuating device, contact portion and valve-closing element is provided, so that the contact portion not only presses the valve-closing element into the open position but also pulls it back into the closed position.

In order to implement the dependency of the opening movement of the suction valve in a simple and cost-effective manner, one embodiment provides a mechanical coupling of the actuating device with the crankshaft, since the crank angle and thus also the suction cycle and the compression cycle are naturally defined via the crank angle of the crankshaft. Outside the working volume, the actuator device comprises an actuating element, which has the contact portion that can be brought into contact or is in contact with the valve-closing element. Thus no additional—often expensive—electrical control elements or actuators are necessary. The mechanical coupling can be achieved via a wide variety of kinematic relationships. As will be described below in detail, a single actuating element, designed as a lever, for example, can be provided. It is equally conceivable, however, that the actuating device may comprise one or more additional operatively connected actuating element(s).

One embodiment variant of the invention provides that the actuating element is connected in an articulated manner to the cylinder housing or a cylinder head cover of a cylinder head arrangement. The cylinder head arrangement typically comprises both a valve plate and a cylinder head cover, and the cylinder head arrangement is secured at a front side of the cylinder housing. These components are particularly well-suited for connecting the actuating element so as to enable easy connection of the actuating element to already existing fastening openings on the cylinder head cover or on the cylinder housing. The articulated connection enables a pivoting movement of the actuating element that can achieve movement sequences in the actuating device that are particularly easy to manage kinematically. The spatial proximity to the suction valve is provided by a mounting on the cylinder head arrangement or the cylinder housing.

An additional embodiment of the coolant compressor according to the invention provides that the actuating element is mounted pivotably about a pivot axis oriented parallel to the longitudinal axis of the crankshaft. This type of orientation of the pivot axis ensures that the contact portion moves in a plane aligned parallel to a bore axis of the suction opening, wherein the direction of the bore axis corresponds substantially to the opening direction of the suction valve. An opening movement of the suction valve can therefore be advantageously supported. Similarly, an orientation of the pivot axis of this kind generally leads to a lateral arrangement of the actuating element relative to the cylinder housing, because there is not sufficient installation space available either on the upper side, as viewed in the direction of the longitudinal axis of the crankshaft, or on the underside of the cylinder head arrangement, because the installation space is occupied, for example, by a suction and/or pressure sound absorber.

A preferred embodiment variant of the coolant compressor according to the invention provides that the actuating device has a control element in operative contact with an actuating portion of the actuating element, which control element is connected for conjoint rotation to the crankshaft, wherein actuating element and control element are designed such that a rotational movement of the crankshaft can be converted into a pivoting movement or a translational movement of at least the contact portion of the actuating element. Due to the interaction of the control element and the other components of the actuating device, especially the actuating element, the mechanical coupling of the crankshaft can be implemented simply. The operative connection between the actuating portion and the control element can be established by direct contact, for example, or by the interposition of additional actuating elements. The control element can be designed in the form of a cam for example, so that the different radial distances of the side face of the control element relative to the longitudinal axis of the crankshaft effect a radial deflection, relative to the longitudinal axis of the crankshaft, of an element of the actuating device in direct contact with the control element. In another alternative embodiment variant, the control element can also have elevations and depressions in the form of peaks and valleys on the upper side or the underside of the control element, which effect an axial deflection, relative to the longitudinal axis of the crankshaft, of an element of the actuating device in contact with a control element.

If the actuating portion of the actuating element directly contacts the control element, then the actuating portion is deflected by the control element during a rotation of the crankshaft. Therefore, a conversion of the rotation of the crankshaft by the control element into a translational movement of the contact portion is fundamentally possible. If the actuating element is designed as a lever, then a pivoting movement of the contact portion about a fulcrum of the lever is enabled. If the kinematic relationships are chosen appropriately, the pivoting movement of the contact portion corresponds approximately to a translational movement.

In another preferred embodiment variant, the actuating device consists of the actuating element and the control element, so that it is not necessary to provide any further movable components for kinematic conversion of the crankshaft rotation into a translational movement or a pivoting movement of the actuating portion of the actuating element contacting the control element.

In order to achieve a simple and cost-effectively producible or installable structure of the actuating device, an additional embodiment variant of the invention provides that the control element has a guide surface contacting the actuating portion of the actuating element, the guide surface being formed eccentrically to the longitudinal axis of the crankshaft. Due to the contact between the guide surface and the actuating portion, the eccentric shape of the guide surface directly deflects the actuating portion radially. The guide surface can be designed, for example, as the side face of a cam formed with preferably circular cross section. Then, a spring element can also be provided, which presses the actuating portion against the control element in order to ensure the contact between the control element and the actuating portion. It goes without saying that a guide surface formed in this manner is also conceivable if there is no direct contact with the actuating portion but rather one or more components of the actuating device are interposed.

Another preferred embodiment variant of the invention provides that the guide surface is formed by an annular-running groove arranged on a side face of the control element facing the crankshaft or facing away from the crankshaft. Due to the interaction of the groove and the actuating portion, wherein the actuating portion can be shaped like a pin or bolt, the actuating portion is arranged at least in part within the groove. Thereby the actuating portion is moved both radially inward and radially outward by the control element during a revolution of the crankshaft, without the necessity for an additional force such as a spring force to be exerted on the actuating portion in order to effect deflection inward. The groove is formed as a closed ring, with a circular or elliptical groove track, wherein both side faces of the groove form a guide surface. To reduce the noise level of the coolant compressor and prevent unbalanced running of the crankshaft, it is advantageous if the control element has a rotationally symmetrical shape relative to a longitudinal axis of the crankshaft.

A particularly preferred embodiment variant of the coolant compressor according to the invention provides that the actuating element has a lever-shaped main body, wherein a first lever arm of the main body has the actuating portion and a second lever arm of the main body has the contact portion. Easily controllable kinematic relationships can be utilized thanks to the lever shape of the main body so that the movement of the contact portion can be precisely defined by means of the design and dimensioning of the lever arms and the positioning of a fulcrum of the lever arm, which in general is used for articulated connection of the actuating element to the coolant compressor. Both the contact portion and the actuating portion move on pivoting paths about the fulcrum of the lever arm.

In order to connect the actuating element in an articulated manner to the cylinder head arrangement, an additional embodiment variant provides that the cylinder head cover of the cylinder head arrangement forms a bearing point for the actuating element, or that a bracket, which forms a bearing point for the actuating element, is mounted on the cylinder head cover of the cylinder head arrangement. On the basis of the installation space available, the fact that the cylinder head cover is generally connected by means of fastening elements to the cylinder housing and the spatial proximity to the suction valve, the cylinder head cover is particularly suitable for forming the bearing point for the actuating element. Particularly when retrofitting existing cylinder head covers with actuating devices, it is advantageous if the bearing point is formed by a bracket mounted on the cylinder head cover, preferably by means of the fastening elements for fastening the cylinder head cover itself. It is fundamentally advantageous if the bearing point is used for supporting the fulcrum of the lever-shaped main body.

For designing the geometrical shape of the lever-like main body of the actuating element, which is necessary for mechanical coupling of the movement of the contact portion to the crankshaft, an additional embodiment variant of the coolant compressor according to the invention provides that the main body of the actuating element has at least one bend, preferably at least one bend per lever arm, and a bend axis of each bend is oriented substantially parallel to the longitudinal axis of the crankshaft. The orientation of the bend axis/axes ensures that the main body has at least one continuous base plane, the main body preferably being planar in shape. The bends have angle ranges between 60° and 160°, more particularly between 90° and 160°, preferably between 110° and 150°, and especially preferably between 120° and 140°. In one advantageous embodiment, the first lever arm has at least one bend, preferably two bends, of between 115° and 145°, while the second lever arm has a bend of approximately 90°±10°. It is also advantageous if the second lever arm extends around the cylinder head cover such that the contact portion is arranged flush with the suction opening.

In order to minimize the suction losses of the coolant flowing through the suction valve that are caused by the actuating device, more particularly the contact portion, an additional embodiment variant of the invention provides that a cross-sectional area of the contact portion of the actuating element is small relative to a cross-sectional area of the suction opening. It is advantageous if the cross-sectional area of the contact portion is at most 10% of the cross-sectional area of the suction opening, preferably at most 5%, more particularly at most 2.5%, and especially preferably under 2.5%.

A particularly preferred embodiment variant of the coolant compressor according to the invention provides that the contact portion is formed by a resilient contact element, more particularly made from spring wire or plastic. Due to the resilient properties, in particular of the spring force or the plastic, one or more of the following advantageous effects can be achieved: As a result of the yielding of the contact element, the contact portion can be brought into contact with the suction valve already at the end of the ejection cycle, without the valve being open, because the contact element yields elastically. The opening point of the suction valve can be adjusted precisely by adapting the spring constant of the contact element and the spring constant of the suction valve or of the valve spring of the suction valve. If the actuating element has a lever-shaped main body and the region of the actuating element at which the contact element is fastened undergoes a pivoting movement, the pivoting movement of the contact portion can be compensated by elastic deformation if the contact portion is guided at least in certain portions in a guide so that the contact portion and thus the suction valve contacted by the contact portion are moved only linearly. If the contact element is formed from plastic rather than spring wire, resilient properties equal to those when spring wire is used can be formed by selecting the plastic and by the thickness and shape (straight or bent).

Another particularly preferred embodiment variant provides that the contact element is shaped flat and has a bent connecting portion, wherein the connecting portion optionally connects a preferably lever-shaped main body of the actuating element to the contact portion. Owing to the flat design of the contact element, the spring properties of the contact element can be influenced in a particularly simple manner by the geometric shaping. The resilient properties of the contact element can be adjusted via the bent connecting portion that is bent in such a way, for example, that a pivoting movement of the actuating element is substantially compensated by torsion of the connecting portion and not by a bending of the contact portion.

An additional especially preferred embodiment variant of the invention provides that the contact portion is arranged substantially parallel to a bore axis of the suction opening and that the connecting portion has at least one V-shaped bend, wherein a plane formed by the contact element is preferably oriented parallel to the longitudinal axis of the crankshaft. A contact portion of the contact element, at least portions of which are inside the cylinder head arrangement, for example inside the cylinder head cover or inside a suction sound absorber, is generally designed to run in a straight line in order to avoid flow losses during the inflow of the coolant. A bend of the connecting portion as described above can be achieved by at least one V-shaped bending of the connecting portion. It goes without saying that the straight design of the contact portion is advantageous independently of the shape of the bend. The orientation of the contact element plane ensures that the movement of the actuating element can be used directly for continuous opening of the suction valve.

Another especially preferred embodiment variant of the invention provides that the contact portion of the actuating element is guided, at least in certain sections, in a bore of the cylinder head cover for the cylinder head arrangement and/or in a bore of a suction sound absorber, preferably an outlet of the suction sound absorber. Because the greater part of the actuating device is arranged outside the cylinder head arrangement in order not to influence the flow of the coolant and to bridge between the crankshaft and suction valve, it is necessary that at least the contact portion be guided into the interior of the cylinder head arrangement in order to be able to contact the suction valve. It is therefore necessary to create an access, which can also serve as a guide for the contact portion into the interior of the cylinder head arrangement. This access is achieved in certain embodiment variants by a bore in the cylinder head cover. A suction sound absorber is usually provided, the outlet of which is directly connected to the suction opening. Therefore, an opening in the suction sound absorber is necessary in corresponding cylinder head arrangements in order to guide the contact portion to the suction valve. If the outlet of the suction sound absorber is pressed by a portion of the cylinder head cover onto the valve plate, it can be necessary for the bore to pass through both the cylinder head cover and the outlet of the suction sound absorber.

In addition to the design of the actuating element as substantially a pivotable lever, a translationally movable actuating element is also possible. In such a case, the actuating element comprises a first portion, more particularly a straight portion, that is translationally movable parallel to the piston, and a second, bent portion that reaches behind the suction opening and supports the contact portion so that it is likewise movable translationally parallel to the piston. The control element, which is connected for conjoint rotation to the crankshaft, could have a guide surface, which is in contact with the actuating element and is formed eccentrically with respect to the longitudinal axis of the crankshaft. The guide surface could be the peripheral surface of the control element. The control element could be in the form of a cam or an eccentric disc and allow a movement of the actuating element in the direction toward the crankshaft at the beginning of the suction cycle, perhaps by a smaller radius. This movement could be produced by a spring for example. In this case, the contact portion is also moved in the direction of the crankshaft and presses the valve-closing element open from the outside. Thereafter, the actuating element moves due to the contact with the control element into a position remote from the crankshaft, where no pressure is exerted on the valve-closing element by the contact portion. The straight portion of the actuating element can be guided in the cylinder housing. In particular, the straight portion of the actuating element can be guided through the valve plate so that the bent portion is located completely in the volume of a cylinder head cover and the contact portion is likewise situated in the volume of a cylinder head cover. Thus, no openings for passage of the actuating element are necessary in the cylinder head cover.

The present invention also comprises a method for operating a coolant compressor having an electrical drive unit, a cylinder housing, a crankshaft drivable by the electrical drive unit and a piston that is drivable by the crankshaft and is guided in a working volume of the cylinder housing for cyclical compression of a coolant, which is conveyed into the working volume via a suction valve comprising a suction opening and a valve-closing element, preferably a valve spring, that cyclically closes the suction opening. An actuating device is provided, with which the valve-closing element is opened at least supportively in a cyclical manner, i.e. once per revolution of the crankshaft.

In particular, the actuating device has a contact portion that is engaged with, or can be brought into engagement with, the valve-closing element, wherein the valve-closing element is opened cyclically by movement of the contact portion.

The further embodiment variants of the method follow from the above-described operational mode of the coolant compressor according to the invention.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in detail with reference to an embodiment. The drawings are for the sake of example and are intended to present the inventive concept, but not to restrict it, much less reproduce it exhaustively.

Therein:

FIG. 1 shows a plan view of a coolant compressor according to the invention in a first variant;

FIG. 2 shows a perspective representation of essential components of the coolant compressor according to FIG. 1;

FIG. 3 shows an additional perspective representation according to FIG. 2;

FIG. 4 shows a perspective view of the coolant compressor from FIG. 1;

FIG. 5 shows a section, perpendicular with respect to FIG. 4, through the coolant compressor from FIG. 1;

FIG. 6 shows detailed representations of the actuating element from FIGS. 1-5;

FIG. 7 shows a schematic representation of the crankshaft, the actuating device and a suction valve for selected crank angles;

FIG. 8 shows a plan view of a coolant compressor according to the invention in a second variant;

FIG. 9 shows a section, perpendicular with respect to FIG. 12, through the coolant compressor from FIG. 8;

FIG. 10 shows the plan view from FIG. 1, in a partial section;

FIG. 11 shows a perspective representation of the coolant compressor according to FIG. 8, in a sectional view as in FIG. 10;

FIG. 12 shows a perspective view of a coolant compressor according to FIG. 8.

MODES FOR EMBODYING THE INVENTION

FIG. 1 shows a plan view of a coolant compressor according to the invention, wherein the components of the coolant compressor are enclosed in a hermetically sealable compressor housing, which is not represented here in order to be able to show the interior of the compressor housing.

The coolant compressor comprises an electrical drive unit comprising a stator and a rotor, which is connected for conjoint rotation to a crankshaft 3 (see FIGS. 2 and 3). The crankshaft 3 is drivable by means of the electrical drive unit, and a piston-cylinder unit operatively connected to a crank pin 12 of the crankshaft 3 arranged eccentrically relative to the longitudinal axis 4 of the crankshaft 3 cyclically draws in and compresses coolant. The piston-cylinder unit comprises a cylinder housing 1 enclosing a cylinder, and a piston 2 translationally guided therein (see FIG. 7). The piston 2 is connected via a connecting rod 13 to the crank pin 12 of the crankshaft 3 so that the piston 2 passes through a suction cycle and a compression and discharge cycle during one rotation of the crankshaft 3 (see FIG. 7).

A cylinder head arrangement 5 sealingly closing off the cylinder is attached to a front side of the cylinder housing 1 and comprises a valve plate 6 having a suction opening 7 and a pressure opening 9. A suction valve 8 cyclically closing off the suction opening 7, and a pressure valve 10 cyclically closing off the pressure opening 9, are arranged on the valve plate 6, as can be seen in FIGS. 2 and 3. A cylinder head 11 (see FIG. 4) that forms a cavity with the valve plate 6 closes off the cylinder head arrangement 5. The cylinder head cover 11 is fastened to the cylinder housing 1 via multiple fastening elements, in the present case four fastening elements, preferably bolts, while the valve plate 6 is clamped between cylinder head cover 11 and cylinder housing 1. As a rule, sealing elements, preferably flat gaskets, are arranged between cylinder head 11 and valve plate 6 and between valve plate 6 and cylinder housing 1 in order to guarantee the leak-tightness of the cylinder arrangement 5 relative to the interior of the compressor housing. The pressure conduit that leads away from the pressure opening 9 is formed in this case by the cylinder housing 1, and pressure sound absorbers 41 are provided for the pressure conduit.

According to the invention, an actuating device 14, coupled mechanically to the crankshaft 3, is provided for the suction valve 8 and will be described in detail below. The actuating device 14 comprises an actuating element 15 for actuating the suction valve 8, and a control element 23 that is connected for conjoint rotation to the crankshaft 3 and is operatively connected to an actuating portion 17 of the actuating element 15. The actuating element 15 comprises a lever-shaped main body 18 having a first lever arm 19 and a second lever arm 20, the actuating portion 17 being formed on the first lever arm 19. In the present embodiment, the actuating portion 17 is arranged in an end portion of the first lever arm 19.

The actuating element 15 is articulated to the cylinder head 11 in order to enable a pivoting movement of the actuating element 15. The pivot axis 21 of the actuating element 15 is oriented parallel to the longitudinal axis 4 of the crankshaft 3 in order to achieve an opening movement of the suction valve 8 by pivoting the actuating element 15 about the pivot axis 21. The pivot axis 21 is formed by a bearing point 30, which acts as a pivot of the lever-shaped main body 18. The bearing point 30 is formed in the present embodiment by a bracket 29 mounted on the cylinder head cover 11, the bracket 29 being connected to the cylinder head cover 11 by means of fastening elements, in the present case two fastening elements; see the two fastening openings in the bracket 29 in FIG. 2. The bracket 29 is arranged to the side of the cylinder housing 1 or the cylinder head cover 11, wherein an upper side and a lower side are oriented in or opposite to the direction of the longitudinal axis 4. The bracket 29 is formed as an angle piece; the first limb of the bracket 29 bears against the front side of the cylinder head cover 11 and has at least one, preferably two, fastening openings, and a second limb of the bracket 29 is aligned parallel to a side face of the cylinder head cover 11 and has the bearing point 30. The bearing point 30 is formed in the present embodiment by a pin that is guided through a bearing opening of the actuating element 15, or in other words, the lever-shaped main body 18.

In alternative embodiment variants, the bearing point 30 can be formed directly on the cylinder housing 1 or on the cylinder head cover 11. The bearing point 30 can be formed as a pin-shaped protrusion of the cylinder head cover 11, for example.

In prior-art coolant compressors, the suction valve 8 is actuated passively by the vacuum forming in the cylinder during the suction cycle. During the first opening phase of the suction valve 8, when the opening force exerted by the vacuum corresponds substantially to the closing force of the suction valve 8, coolant flows via the partially released suction opening 7 into the cylinder, whereby the vacuum is reduced and the opening force again decreases. This results in a so-called “fluttering” of the suction valve 8, which is generally formed by a valve spring. During “fluttering,” the suction valve 8 carries out a closing movement one or more times, until the vacuum has been lowered by the inflowing coolant less strongly than is required for applying the opening force. This effect firstly reduces the efficiency of the coolant compressor, because in certain phases during the suction cycle, no coolant or only a small amount of coolant reaches the cylinder. At the same time, the “fluttering” results in pulsations in the suctioned coolant flow or in the coolant circuit, which leads to an undesired noise formation.

FIGS. 2 and 3 show the components of the coolant compressor that are essential to the invention. For the sake of clarity, neither the cylinder head cover 11 nor the cylinder housing 1 of the piston 2 are represented, in order not to cover the other components. As mentioned above, the actuating device 14 is mechanically coupled to the crankshaft 3, so that, depending on the crank angle of the crankshaft 3, the contact portion 16 of the actuating element 15 can be brought into contact with the suction valve 8 so as to achieve a continuous opening movement of the suction valve. Due to the fact that the contact portion 16 contacts the suction valve 8 at least during the opening movement of the suction valve 8 and is moved by means of the mechanical coupling depending on the crank angle of the crankshaft 3, the suction valve 8 is actively opened by means of the actuating element 15, which, due to the contact with the contact portion 16, prevents a closing movement of the suction valve 8 during the opening phase.

In the present embodiment, the second lever arm 20 of the lever-shaped main body 18 of the actuating element 15 comprises the contact portion 16, wherein the contact portion 16 is preferably aligned flush with the suction opening 7 and is fastened to or formed in an end region of the second lever arm 20. The contact portion 16 is positioned in the region of the cylinder head arrangement 5, i.e. on the side of the valve plate 6 opposite from the cylinder housing 1 or the piston 2, so that the contact portion 16 can be contacted with the side of the suction valve 8 opposite from the cylinder housing 1 or the piston 2. In that way, the suction valve 8 can be pressed open by the contact portion 16 because the contact portion 16 exerts a pressure force onto the suction valve 8 due to the coupled movement.

Since the contact portion 16 protrudes into the space of the cylinder head arrangement 5, through which coolant flows during the suction cycle, the contact portion 16 has a small cross section in relation to the cross-sectional area of the suction opening 7, wherein the cross-sectional area of the contact portion 16 in the present example occupies only approximately 1% of the cross-sectional area of the suction opening 7 in order to influence the flow of the coolant as little as possible.

The mechanical coupling of the actuating device 14 takes place as described below: The control element 23 is shaped like a disk and has a rotationally symmetrical outer shape relative to the longitudinal axis 4, wherein the crank pin 12 protrudes through an opening 28 of the control element 23. Thereby the control element 23 is arranged underneath the connecting rod 13. A guide surface 24, which is arranged eccentrically relative to the longitudinal axis 4, is formed on an upper, first end face 25 of the control element 23 and in the present embodiment is in direct contact with the actuating portion 17 of the actuating element 15. The guide surface face 24 is formed by an annular groove 27 into which the actuating portion 17, formed as a pin for example, of the actuating element 15 protrudes. The guide surface 24 is formed at least by the two side walls of the groove 27, whereby the actuating portion 17 can be moved in the groove both radially inward and also radially outward, relative in each case to the longitudinal axis 4. The precise movement sequence will be explained with reference to FIG. 7. It is fundamental that, due to the eccentric arrangement of the guide surface 24, the control element 23 brings about a pivoting movement of the actuating element 15 dependent on the crank angle of the crankshaft 3, more precisely a pivoting movement of the contact portion 16 about the bearing point 30 or the pivot of the lever-shaped main body 18. Thus, the contact portion 16 moves, depending on the crank angle of the crankshaft 3, cyclically in the direction of the suction valve 8, in order to ensure a continuous opening movement of the suction valve 8, or cyclically removes itself from the suction valve 8 in order not to hinder the closing movement of the suction valve 8.

In the present embodiment, the actuating element 15 comprises a contact element 31 made from spring wire forming the contact portion 16, i.e. spring steel having a diameter of less than 1 mm in the present case, which is fastened in an end region of the second lever arm 20 on the lever-shaped main body 18, preferably by means of a clamping device. Due to the construction of the contact element 31 from spring wire, it is possible to adjust a yielding of the contact element 31, for example, in order to adjust the opening time of the suction valve 8 precisely. In the present embodiment, the contact element 31 has a bent connecting portion 32 that connects the contact portion 16 to the actuating element 15. The contact element 31 is formed flat; in other words all the bending axes are aligned parallel to one another. The connecting portion 32 in the present embodiment has a V-shaped bend, which extends downward from the actuating element 15 at an angle in the direction of the longitudinal axis 4 and extends upward at an angle in the direction of the longitudinal axis 4 after the point of the V. The contact portion 16 adjoining the connecting portion 32 is formed straight and is arranged substantially parallel to a bore axis of the suction opening 7, wherein the contact portion 16 preferably contacts the suction valve 8 in the upper half of the suction opening 7.

FIG. 4 presents an additional perspective representation of the coolant compressor, showing the cylinder head cover 11 and a suction sound absorber 33 arranged at least partially inside the cylinder head arrangement 5. The coolant compressor from FIG. 4 is shown in cross section in FIG. 5, while piston 2 and connecting rod 13 are not drawn in. The control element 23 and the lever 18 were omitted from the actuating device 14 and only the contact element 31 was drawn in. As a rule, the coolant flowing into the coolant compressor via a coolant supply line flows via the suction sound absorber 33 to the suction opening 7, an outlet 34 of the suction sound absorber 33 being pressed against the valve plate 6, preferably via the cylinder head cover 11 or a spring arrangement, in order to establish a nearly gas-tight connection between the suction sound absorber 33 and the suction opening 7. In other words, the suction valve 8 is completely covered by the outlet 34 of the suction sound absorber 33. In order to bring the contact portion 16 into contact with the suction valve 8, a bore 35, in which at least portions of the contact portion 16 are guided, is formed in the suction sound absorber 33 or in the outlet 34. Due to the small diameter of the spring wire and the small gap width between the bore wall and the contact element 31, the losses during inflow of the coolant are negligible. If the suction opening 7 is also covered by a portion of the cylinder head cover 11 or by some other element of the cylinder head arrangement 5, it is also necessary to provide a bore 35 in the cylinder head cover 11 or some other element in order to actuate the suction valve 8.

FIG. 6 presents detailed representations of the actuating element 15, consisting substantially of the lever-shaped main body 18 and the contact element 31. A side view, in which the pivot axis 21 of the main body 18 is drawn in, is shown at the very top.

Below that there is a plan view from which individual bends 22a, 22b, 22c of the main body 18 can be seen. The main body 18 has bends 22a, 22b respectively in arms 19, 20 and a bend 22c between the two lever arms 19, 20 at the pivot axis 21. All three bending axes are oriented parallel to the longitudinal axis 4 of the crankshaft 3 (see FIG. 2). The orientation of the bending axes ensures that the main body 18 has a continuous base plane in which the main body 18 is formed flat, i.e. lies in the plane of the drawing here. The first lever arm 19 has a bend 22a of approximately 140°. The bend 22c between the two lever arms 19, 20 has an angle of approximately 160°, while the second lever arm 20 has a bend of approximately 90°. The second lever arm 20 can therefore reach around the cylinder head cover 11 such that the contact portion 16 is arranged aligned with the suction opening 7.

At the lower left in FIG. 6, a perspective view of the actuating element 15 from above is shown, and a perspective view of the actuating element 15 from below is shown on the right-hand side.

FIG. 7 shows four schematic representations of the crankshaft, actuating device and suction valve 8 at selected crank angles or positions of the piston 2. At the upper left, the piston 2 is at the end of the compression cycle, shortly before top dead center. The contact portion 16 is already in contact with the suction valve 8, but the latter is still closed. The contact portion 16 can already be in contact with the suction valve 8 at 90° to 60° before top dead center.

Only after top dead center does the contact portion 16 enter through the suction opening and open the suction valve 8 by pressing it inward away from the valve plate 6. This is shown at the upper right in FIG. 7. The point in time or the crank angle starting from which the contact portion 16 opens the suction valve 8 is specified here by the geometry of the actuating device 14. The valve 8 is also opened by the vacuum in the cylinder in addition to the contact portion 16.

At the lower left in FIG. 7, the suction cycle has already reached its end; the piston has moved to just before lower dead center. The contact portion 16 has opened the suction valve 8 even further.

At the lower right, the beginning of the compression cycle is shown, i.e. a piston position shortly after bottom dead center. The contact portion 16 has again left the suction opening 7 and thus no longer contacts the suction valve 8.

FIG. 8 shows a plan view of a coolant compressor according to the invention in a second variant. The structure of the coolant compressor is substantially identical to that of the first variant in FIGS. 1-7, apart from the actuating device 14.

Here, the actuating device 14 for the suction valve 8, which actuating device is coupled mechanically to the crank shaft 3, comprises an actuating element 36 for actuating the suction valve 8, and a control element 37 connected for conjoint rotation to the crankshaft 3. In order for the actuating element 36 to be more visible, the cylinder head cover 11 has been removed in this figure so that the valve plate 6 is open to the outside.

The actuating element 36 has the shape of a bent rod with a round cross section. The actuating element 36 comprises a first portion 38, straight in this case, which is movable translationally parallel to the piston 2, and a second, bent portion 39, which reaches behind the suction opening 7 and supports the contact portion 16 such that the latter is likewise movable translationally parallel to the piston 2. The bent portion here has the form of a semicircle. The straight contact portion 16 is shorter than the straight portion 38. The straight contact portion 16 is aligned parallel to the movement direction of the piston 2. The contact portion 16 could also be formed as a separate component and/or have a smaller cross section than the rest of actuating element 36. The contact portion 16 could be designed as a resilient contact element, for example, similar to the contact element 31 from FIGS. 1-7.

If the straight portion 38 moves away from the crank pin 12, the contact portion 16 moves out of the valve plate 6. The contact portion 16 is moved away from the suction valve 8 in the process. If the straight portion 38 moves toward the crank pin 12, the contact portion 16 can then pass through the suction opening 7 and open the suction valve 8.

The actuating element 36 is actuated by the control element 37, a disk with a variable diameter. The control element 37 could simultaneously carry out the function of a flywheel. The end of the straight portion 38 protrudes from the cylinder housing 1 in the direction of the crankshaft 3 or crank pin 12. The end of the straight portion 38 is preloaded by means of a spring 40 in the direction of the crank pin 12, so that it can slide along the outer periphery of the control element 37. In the angle ranges of the control element 37 with a small diameter, i.e. approximately in the lower 180° of control element 37 in FIG. 8, the straight portion 38 is thus pulled toward the crank pin 12 and the contact portion 16 opens the suction valve 8. In the angle ranges of the control element 37 having a larger diameter, i.e. in approximately the upper 180° of the outer periphery of the control element 37 in FIG. 8, the end of the straight portion 38 is pressed away from the crank pin 12 and thereby the contact portion 16 is pushed out of the valve plate 6 (i.e. downward in FIG. 8) and the suction valve 8 can close.

In the cross section of the coolant compressor from FIG. 8 shown in FIG. 9, it can be seen that the piston 2 is shortly before its upper dead center and thus the compression and discharge cycle is coming to an end. The pressure valve 10 is still opened. Due to the sectional view, the contact portion 16 cannot be seen here. Only the end of the straight portion 38 is visible, which forms the actuating portion 17 that is in operative contact with the control element 37. The contact portion 16 can already be in contact with the suction valve 8, however, since the beginning of the suction cycle is imminent. The straight portion 38 of the actuating element 36 is guided through the cylinder housing 1, wherein the cylinder housing 1 serves as a guide for the straight portion 38. The bore of the cylinder housing 1 for the straight portion 38 is located here at the side underneath the cylinder bore for the piston 2. Because the straight portion 38 also exits through the valve plate 6, it is possible to accommodate the bent portion 39 inside a cylinder head cover 11. The cylinder head cover 11 is not drawn in here, but could be designed as in FIGS. 4 and 5.

Differently from FIGS. 4 and 5, the cylinder head cover 11 in FIGS. 8-12 would not have to have an opening for the passage of the actuating element 15 or the contact element 16, because the actuating element 36 enters into the cylinder head arrangement inside the cylinder head cover 11.

In FIG. 10, somewhat more than the left half of the coolant compressor has been cut away parallel to the drawing plane. The sectional view along line A-A is shown in perspective in FIG. 11. FIG. 12 shows a perspective representation of the coolant compressor that has not been cut. Here, it is again visible that the straight portion 38 in this embodiment is somewhat lower than the contact portion 16. Here too, the guide surface 24 is recognizable as the circumferential surface of the control element 37.

LIST OF REFERENCE NUMBERS

• 1 Cylinder housing
• 2 Piston
• 3 Crankshaft
• 4 Longitudinal axis of crankshaft 3
• 5 Cylinder head arrangement
• 6 Valve plate
• 7 Suction opening
• 8 Suction valve
• 9 Pressure opening
• 10 Pressure valve
• 11 Cylinder head cover
• 12 Crank pin
• 13 Connecting rod
• 14 Actuating device
• 15 Actuating element
• 16 Contact portion of actuating element 15
• 17 Actuating portion of actuating element 15
• 18 Lever-shaped main body
• 19 First lever arm of main body 18
• 20 Second lever arm of main body 18
• 21 Pivot axis of actuating element 15
• 22 Bend

22a First bend

22b Second bend

22c Third bend

• 23 Control element
• 24 Guide surface of control element 23
• 25 First end face of control element 23
• 26 Second end face of control element 23
• 27 Groove
• 28 Opening
• 29 Bracket
• 30 Bearing point
• 31 Contact element
• 32 Connecting portion of contact element 31
• 33 Suction sound absorber
• 34 Outlet of suction sound absorber 33
• 35 Bore
• 36 Actuating element
• 37 Control element
• 38 Straight portion of actuating element 36
• 39 Bent portion of actuating element 36
• 40 Spring
• 41 Pressure sound absorber

Claims

1. A coolant compressor having an electrical drive unit, a cylinder housing, a crankshaft drivable by the electrical drive unit and a piston drivable by the crankshaft and guided in a working volume of the cylinder housing for cyclical compression of a coolant, which can be conveyed into the working volume via a suction valve comprising a suction opening and a valve-closing element, cyclically closing the suction opening, wherein an actuating device is provided, which is designed to open the valve-closing element cyclically.

2. The coolant compressor according to claim 1, wherein the valve-closing element can only be opened on a supporting basis by the actuating device.

3. The coolant compressor according to claim 1, wherein the actuating device has a contact portion that is engaged with, or can be brought into engagement with, the valve-closing element, wherein the actuating device is designed to open the valve-closing element cyclically by moving the contact portion.

4. The coolant compressor according to claim 3, wherein the contact portion is or can be brought into contact with the side of the valve-closing element facing away from the piston in order to open the element by exerting a pressure force.

5. The coolant compressor according to claim 1, wherein the opening of the valve-closing element can be initiated with the actuating device at an equilibrium of the coolant pressure on both sides of the valve-closing element.

6. The coolant compressor according to claims 1, wherein the valve-closing element is cyclically closable by means of the actuating device.

7. The coolant compressor according to claim 1, wherein the actuating device is designed to open the valve-closing element cyclically as a function of the crank angle of the crankshaft.

8. The coolant compressor according to claim 1, wherein the actuating device is mechanically coupled to the crankshaft and comprises an actuating element, which has a contact portion that can be brought into contact or is in contact with the valve-closing element.

9. The coolant compressor according to claim 8, wherein the actuating element is connected in an articulated manner to the cylinder housing or a cylinder head cover of a cylinder head arrangement.

10. The coolant compressor according to claim 8, wherein the actuating element is mounted pivotably about a pivot axis oriented parallel to the longitudinal axis of the crankshaft.

11. The coolant compressor according to claim 8, wherein the actuating device has a control element in operative contact with an actuating portion of the actuating element, which control element is connected for conjoint rotation to the crankshaft,

wherein actuating element and control element are designed such that a rotational movement of the crankshaft can be converted into a pivoting movement or a translational movement of at least the contact portion of the actuating element.

12. The coolant compressor according to claim 11, wherein the control element has a guide surface contacting the actuating portion of the actuating element, the guide surface being formed eccentrically to the longitudinal axis of the crankshaft.

13. The coolant compressor according to claim 12, wherein the guide surface is formed by an annular groove arranged on an end face of the control element facing the drive unit or on an end face facing away from the drive unit.

14. The coolant compressor according to claim 12, wherein the actuating element has a lever-shaped main body, wherein a first lever arm of the main body has the actuating portion and a second lever arm of the main body has the contact portion.

15. The coolant compressor according to claim 9, wherein the cylinder head cover of the cylinder head arrangement forms a bearing point for the actuating element,

or in that a bracket is formed on the cylinder head cover of the cylinder head arrangement, which bracket forms a bearing point for the actuating element.

16. The coolant compressor according to claim 14, wherein the main body of the actuating element has at least one bend, and a bend axis of each bend is oriented substantially parallel to the longitudinal axis of the crankshaft.

17. The coolant compressor according to claim 3, wherein a cross-sectional area of the contact portion of the actuating element is small relative to a cross-sectional area of the suction opening.

18. The coolant compressor according to claim 3, wherein the contact portion is formed by a resilient contact element.

19. The coolant compressor according to claim 18, wherein the contact element is shaped flat and has a bent connecting portion, wherein the connecting portion connects the actuating element to the contact portion.

20. The coolant compressor according to claim 19, wherein the contact portion is arranged substantially parallel to a bore axis of the suction opening and that the connecting portion has at least one V-shaped bend.

21. The coolant compressor according to claim 3, wherein the contact portion is guided at least in certain sections in a bore of the cylinder head cover for the cylinder head arrangement and/or in a bore of a suction sound absorber.

22. The coolant compressor according to claim 8, wherein the actuating element comprises a first portion, more particularly a straight portion, that is translationally movable parallel to the piston, and a second, bent portion that reaches behind the suction opening and supports the contact portion so that it is likewise movable translationally parallel to the piston.

23. A method for operating a coolant compressor having an electrical drive unit, a cylinder housing, a crankshaft drivable by the electrical drive unit and a piston drivable by the crankshaft and guided in a working volume of the cylinder housing for cyclical compression of a coolant, which is conveyed into the working volume via a suction valve comprising a suction opening and a valve-closing element, cyclically closing the suction opening, wherein an actuating device is provided with which the valve-closing element can be opened cyclically at least in a supporting manner.

24. The method according to claim 23, wherein the actuating device has a contact portion that is engaged with, or can he brought into engagement with, the valve-closing element, wherein the valve-closing element is opened cyclically by moving the contact portion.

25. The coolant compressor according to claim 1 wherein the valve-closing element comprises a valve spring.

26. The coolant compressor according to claim 16, wherein the at least one bend comprises at least one bend per lever arm.

27. The coolant compressor according to claim 18, wherein the resilient contact element is made from spring wire or plastic.

28. The coolant compressor according to claim 19, wherein the actuating element has a lever shaped main body, and the connecting portion connects the lever-shaped main body of the actuating element to the contact portion.

29. The coolant compressor according to claim 8, wherein the contact element is shaped flat and has a bent connecting portion, wherein the connecting portion connects the actuating element to the contact portion.

30. The coolant compressor according to claim 29, wherein the actuating element has a lever shaped main body, and the connecting portion connects the lever-shaped main body of the actuating element to the contact portion.

31. The coolant compressor according to claim 20, wherein a plane formed by the contact element is oriented parallel to the longitudinal axis of the crankshaft.

32. The coolant compressor according to claim 21, wherein the bore of an outlet of the suction sound absorber comprises an outlet of the suction sound absorber.

33. The method according to claim 23, wherein the valve-closing element comprises a valve spring.