OIL PUMP

Abstract

A guide slot having an elongated-hole shape is formed in a capacity adjustment member, so that displacement of the capacity adjustment member is regulated, by a guide pin inserted into the guide slot, to a longitudinal direction of the guide slot. Two spaces separated by the guide pin into one side and the other side in the longitudinal direction of the guide slot are formed inside the guide slot, and a communicating passage is provided so as to communicate the spaces with each other.

Description

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2014-119363 filed on Jun. 10, 2014 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable-capacity oil pump.

2. Description of Related Art

Japanese Patent Application Publication No. 2013-100737 (JP 2013-100737 A) describes an oil pump constituted by an internal gear pump configured to discharge, from a discharge port, oil taken in from an inlet port by rotation of an inner rotor (a drive rotor) and an outer rotor (a driven rotor) meshing with each other.

The oil pump includes an adjustment ring (a capacity adjustment member) so as to rotatably hold the outer rotor from its outer periphery in a housing. The adjustment ring is displaced by receiving a hydraulic pressure introduced into a pressurizing space in the housing. Hereby, relative positions of the inner rotor and the outer rotor to the inlet port and the discharge port are changed. Due to the change of the positions of the inner rotor and the outer rotor, a discharge amount (a so-called displacement volume) per one rotation of an input shaft, that is, a pump capacity, is changed.

In JP 2013-100737 A, the adjustment ring is provided with an elongated hole (a guide slot having an elongated-hole-shaped section). The displacement of the adjustment ring is regulated by a guide pin inserted into the elongated hole. That is, when the adjustment ring is displaced by the hydraulic pressure in the pressurizing space as described above, a direction of the displacement is regulated to a direction where the elongated hole extends.

When the adjustment ring is displaced in the direction where the elongated hole extends, the guide pin is relatively displaced inside the elongated hole in a longitudinal direction of the elongated hole. That is, an inner part of the elongated hole is divided by the guide pin into one side and the other side in the longitudinal direction. When the adjustment ring is displaced, the guide pin is displaced relative to the elongated hole in the longitudinal direction of the elongated hole.

The inner part of the elongated hole thus divided by the guide pin is divided into two spaces on the one side and the other side in the longitudinal direction of the elongated hole. When the guide pin is relatively displaced as described above, oil flows through a gap between an outer peripheral surface of the guide pin and an inner peripheral surface of the elongated hole that makes sliding contact with the outer peripheral surface of the guide pin, so as to go back and forth between the two spaces.

SUMMARY OF THE INVENTION

In order to regulate the direction of the displacement of the adjustment ring with accuracy, it is necessary for the gap between the outer peripheral surface (a guide surface) of the guide pin and the inner peripheral surface (a guided surface) of the guide slot that slides to be narrowed sufficiently. Because of this, a flow resistance of the oil in the narrow gap increases, which may become a resistance to the displacement of the adjustment ring. Particularly, when a viscosity of the oil is high like a case where a temperature is low, the resistance increases, so that the displacement of the adjustment ring becomes slow. Therefore, in this case, response of a control on a pump capacity may decrease.

The present invention provides a variable-capacity oil pump that improves response of control.

One aspect of the present invention relates to an oil pump including an input shaft, an inlet port, a discharge port, a capacity-variable mechanism and a housing. The capacity-variable mechanism is configured to change a discharge amount per one rotation of the input shaft. The capacity-variable mechanism includes a capacity adjustment member. The capacity adjustment member has a guide slot having an elongated-hole shape. The guide slot includes a guided surface provided on an inner periphery of the guide slot. The housing includes a guide pin. The guide pin is inserted into the guide slot. The guide pin includes a guide surface provided on an outer periphery of the guide pin. The guide pin is configured to regulate displacement of the capacity adjustment member to a longitudinal direction of the guide slot. The guide pin is configured to separate the guide slot into a first space and a second space in the longitudinal direction. The guide surface of the guide pin makes sliding contact with the guided surface of the guide slot. Oil flows between the first space and the second space via a gap between the guide surface and the guided surface. At least one of the guide pin and the capacity adjustment member is provided with a communicating passage, and the communicating passage is configured to communicate the first space with the second space.

According to the above configuration, the oil flows through a gap between an outer peripheral surface (the guide surface) of the guide pin and that inner peripheral surface (the guided surface) of the guide slot which makes sliding contact with the outer peripheral surface of the guide pin, so as that the oil goes back and forth between two spaces in the guide slot, and the oil also flows through the communicating passage that communicates the two spaces with each other. Thus, the oil flows through the communicating passage as well as the gap between the guide pin and the guide slot. Hereby, a flow resistance of the oil is reduced, so that the capacity adjustment member is displaced fast. As a result, improvement of response of a control on a pump capacity is achieved.

In the above oil pump, a sectional area of the communicating passage may be larger than a sectional area of the gap between the guide surface and the guided surface. According to the above configuration, an effect to reduce the flow resistance of the oil going back and forth between two spaces in the guide slot is high.

In the above oil pump, the guide pin may include a first sectional area part and a second sectional area part along an axial direction of the guide pin. The first sectional area part may have a sectional area smaller than that of the second sectional area part. The guide pin may include a recess provided on an outer peripheral surface of the guide pin in the first sectional area part. The recess may constitute the communicating passage. According to the above configuration, the communicating passage can be easily configured with a simple structure to change an outer shape of the guide pin.

In this case, the recess on the outer periphery of the guide pin does not function as the guide surface. In view of this, in the above oil pump, the first sectional area part may be provided at an axially intermediate part of the guide pin. According to the above configuration, outer peripheral surfaces of both axial ends of the guide pin function as the guide surface. This accordingly achieves stabilization of a guiding function of the guide pin.

In the above oil pump, the first sectional area part of the guide pin may include a tapered part having a sectional area that gradually increases toward the second sectional area part. In the above configuration, a tip end of the guide pin may be provided as a small sectional area part (the first sectional area part) having a sectional area smaller than that of the other part of the guide pin. With such a configuration, most part of the outer peripheral surface of the guide pin except the tip end thereof exhibits the guiding function, so that the guiding function is easy to be secured. Besides, since the tip end of the guide pin has a tapered shape, demolding can be easily performed in a case where the guide pin is formed integrally with a pump housing at the time of casting the pump housing.

In the above oil pump, the communicating passage may penetrate through the guide pin, and the communicating passage may be configured to communicate the first space with the second space. In the above oil pump, an inner peripheral surface of the guide slot may have a groove extending in a longitudinal direction of the guide slot, and the groove may constitute the communicating passage. In the above oil pump, the communicating passage may be provided inside the capacity adjustment member, and both ends of the communicating passage may be opened on an inner peripheral surface of the guide slot.

In the above oil pump, the housing may include a low hydraulic chamber, and the guide slot may communicate with the inlet port via the low hydraulic chamber. In this case, a negative pressure on an intake side of the oil pump is applied inside the guide slot. In this case, at the time when the guide pin is relatively displaced in the guide slot as described above, the negative pressure increases (a pressure decreases) in a space of which a volume increases along with the displacement, which may cause cavitation.

In contrast, according to the above configuration, at the time when the guide pin is relatively displaced in the guide slot as described above, the flow resistance of the oil going back and forth between two spaces is reduced. This makes it possible to restrain an increase in the negative pressure (a decrease in the pressure) in the space of which the volume increases. Accordingly, an effect to restrain an occurrence of cavitation can be expected.

More specifically, various structures such as a gear pump, a vane pump, and a piston pump can be considered as the oil pump, but, the oil pump may be an internal gear pump, for example. That is, the above oil pump may further include a drive rotor as an external gear rotated by the input shaft, and a driven rotor as an internal gear meshing with the drive rotor so as to be rotated accordingly. The housing may include a control hydraulic chamber. The capacity adjustment member may have an annular holding portion configured to rotatably hold the driven rotor from an outer periphery of the driven rotor. The capacity adjustment member may be configured to be displaced by a hydraulic pressure of the control hydraulic chamber. The capacity-variable mechanism may be configured to change relative positions of the drive rotor and the driven rotor to the inlet port and the discharge port, along with the displacement of the capacity adjustment member, such that a discharge amount of the oil pump is changed.

In a case of the above configuration, at the time of the operation of the capacity-variable mechanism, it is necessary to displace the driven rotor for force-feeding the oil while rotating, and the capacity adjustment member for holding the driven rotor, so that a large force is required. In view of this, the aforementioned configuration that can reduce a resistance at the time when the capacity adjustment member is displaced is effective.

According to the above variable-capacity oil pump, the communicating passage is provided so as to communicate two spaces separated by the guide pin in the guide slot in a case where the displacement of the capacity adjustment member is regulated by the guide pin inserted into the guide slot. Hereby, along with the relative displacement of the guide pin in the guide slot, the oil flows through the communicating passage as well as the gap between the guide pin and the guide slot. Consequently, the flow resistance of the oil going back and forth between two spaces is reduced. This accordingly speeds up the operation of the capacity-variable mechanism, thereby making it possible to improve response of the control on the pump capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a view illustrating a structure of an oil pump according to an embodiment of the present invention, and illustrates a state where a pump capacity is maximum;

FIG. 2 is a view corresponding to FIG. 1 and illustrates a state where a capacity of the oil pump is small;

FIG. 3A is an explanatory view schematically illustrating a guide slot and a guide pin of an adjustment ring, according to a first example;

FIG. 3B is a perspective view of the guide pin according to the first example which guide pin is provided with a reduced diameter portion;

FIGS. 4A, 4B are views corresponding to FIGS. 3A, 3B according to a second example in which a groove is provided on an outer peripheral surface of a guide pin;

FIGS. 5A, 5B are views corresponding to FIGS. 3A, 3B according to a third example in which a tapered part is provided in an tip side of a guide pin;

FIGS. 6A, 6B are views corresponding to FIGS. 3A, 3B according to a fourth example in which a through hole is provided in a guide pin;

FIG. 7 is a view corresponding to FIG. 3A according to a fifth example in which a groove is provided on an inner peripheral surface of a guide slot; and

FIG. 8 is a view corresponding to FIG. 7 according to a sixth example in which a communicating passage is provided inside an adjustment ring.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention is described below with reference to the accompanying drawings. The present embodiment deals with a case where the present invention is applied to an oil supply system of an engine to be provided in an automobile, for example. However, the present embodiment is not limited to this. The description of the present embodiment is just an example, and a configuration, a purpose, and the like of the present invention are not limited in particular.

The following describes a general configuration of an oil pump 1 with reference to FIGS. 1 and 2. As illustrated in these figures, the oil pump 1 is an internal gear pump including a drive rotor 3 as an external gear rotated by an input shaft 2, and a driven rotor 4 as an internal gear meshing with this so as to rotate accordingly. An outer periphery of the driven rotor 4 is held by an adjustment ring 5. As will be described later, the adjustment ring 5 functions as a capacity adjustment member configured to change a pump capacity by displacing the drive rotor 3 and the driven rotor 4.

A housing 10 of the oil pump 1 is a basin-shaped casting, for example. When viewed from a front side of the engine as illustrated in FIGS. 1, 2, the housing 10 has a generally rectangular shape elongated in an up-down direction as a whole. A peripheral wall 11 is formed to surround a whole circumference of the housing 10. From a different viewpoint, a recessed portion 12 surrounded by the peripheral wall 11 opened toward the front side of the engine (a near side in the figures) is formed generally over the whole housing 10.

When the recessed portion 12 is closed by a cover (not shown) superimposed on the housing 10 from the front side, the recessed portion 12 as a receptacle recessed portion (hereinafter, also referred as a receptacle recessed portion 12) configured to receive the drive rotor 3, the driven rotor 4, the adjustment ring 5, and the like is formed. A bottom of the receptacle recessed portion 12 has a through hole (not shown in the figures) having a circular section and formed in a part slightly on an upper side in FIGS. 1, 2 relative to a central part of the bottom, and the input shaft 2 is passed through the through hole.

Although not illustrated herein, a pump sprocket is attached to one end of the input shaft 2, so that the pump sprocket is driven by a chain. In the meantime, the drive rotor 3 is attached to the other end of the input shaft 2 by splines (not shown), for example. An outer periphery of the drive rotor 3 is provided with a plurality of external teeth 3a (eleven external teeth 3a in the example in the figures) having a trochoid curved line or a curved line (e.g., involute, cycloid, or the like) similar to the trochoid curved line.

In the meantime, the driven rotor 4 is formed in a ring shape, and an inner periphery thereof is provided with a plurality of internal teeth 4a meshing with the external teeth 3a of the drive rotor 3. The number of internal teeth 4a is larger by one (i.e., twelve teeth in the example in the figures) than the number of external teeth 3a of the drive rotor 3. A center of the driven rotor 4 is eccentric relative to a center of the drive rotor 3 by a predetermined amount, and the external teeth 3a of the drive rotor 3 mesh with the internal teeth 4a of the driven rotor 4 on a side where the center of the driven rotor 4 is eccentric (on an upper right side in FIG. 1).

The outer periphery of the driven rotor 4 is slidably held by a ring-shaped body portion 50 (a holding portion) of the adjustment ring 5. Thus, a trochoid pump having eleven blades and twelve nodes is constituted by the drive rotor 3 and the driven rotor 4 held as such, in the present embodiment. That is, as illustrated in FIGS. 1, 2, a plurality of chambers R is formed so as to be aligned in a circumferential direction in an annular space between two rotors 3, 4. Volumes of these chambers R increase and decrease while the chambers R move in the circumferential direction along with rotation of the two rotors 3, 4.

More specifically, in a range (a range on the right side in FIG. 1) over approximately 180 degrees in a rotor rotation direction (in a clockwise direction in the figure) indicated by an arrow in FIG. 1 from a position (an upper right position in FIG. 1) where the teeth of the two rotors 3, 4 mesh with each other, the volumes of the chambers R gradually increase along with the rotation of the two rotors 3, 4. Meanwhile, in a remaining range (a range on the left side in FIG. 1) over approximately 180 degrees, the volumes of the chambers R gradually decrease along with the rotation of the two rotors 3, 4.

The range in which the volumes of the chambers R gradually increase between the two rotors 3, 4 is an intake range where oil is taken in from an inlet port 13. In the meantime, the range where the volumes of the chambers R gradually decrease is a discharge range where the oil is sent out to a discharge port 14 while the oil is pressurized. That is, as indicated by broken lines in FIGS. 1, 2, the inlet port 13 is formed for the intake range, and the discharge port 14 is formed for the discharge range on a bottom face of the receptacle recessed portion 12 of the housing 10.

A downstream end 13a of the inlet port 13 of the present embodiment is formed, for the intake range, in a groove shape in the bottom of the receptacle recessed portion 12, as described above. The inlet port 13 communicates with a port upstream portion 13c opened on the bottom face of the receptacle recessed portion 12, via an intermediate groove 13b also formed in the bottom of the receptacle recessed portion 12. Although not illustrated herein, the port upstream portion 13c is formed inside the housing 10 and its upstream end is connected to a pipe that is connected to an oil strainer.

As illustrated in FIGS. 1, 2, the intermediate groove 13b of the inlet port 13 faces the after-mentioned guide slot 54. An opening of the port upstream portion 13c opened on the bottom of the receptacle recessed portion 12 faces a low hydraulic chamber TL (to be described later) formed inside the housing 10 (inside the receptacle recessed portion 12). In the meantime, as indicated by broken lines in FIGS. 1, 2, the discharge port 14 is opened on the bottom of the receptacle recessed portion 12 for the discharge range, and extends inside the housing 10 so that its upper end communicates with an outlet (not shown) of the oil pump 1.

In the oil pump 1 configured as such, a rotational force of a crankshaft of the engine is transmitted to the pump sprocket via the chain so as to drive the input shaft 2, which causes the drive rotor 3 and the driven rotor 4 to rotate while meshing with each other, so that the oil is taken into the chambers R formed therebetween from the inlet port 13, and then discharged from the discharge port 14.

Instead of forming the inlet port 13 and the discharge port 14 in the housing 10 as described above, they may be formed in a cover superimposed on the housing 10. Either one of the inlet port 13 and the discharge port 14 may be formed in the housing 10, and the other one thereof may be formed in the cover. The inlet port 13 and the discharge port 14 may be formed in both the housing 10 and the cover.

The oil pump 1 of the present embodiment includes a capacity-variable mechanism that can change an amount of oil, i.e., a pump capacity, to be discharged per one rotation of the drive rotor 3 described above. The capacity-variable mechanism displaces the adjustment ring 5 by a hydraulic pressure of a control hydraulic chamber TC formed inside the receptacle recessed portion 12 of the housing 10. Due to the displacement of the adjustment ring 5, relative positions of the drive rotor 3 and the driven rotor 4 to the inlet port 13 and the discharge port 14 are changed, so that the pump capacity is changed.

More specifically, the adjustment ring 5 is configured such that the ring-shaped body portion 50 configured to hold the driven rotor 4 as described above, first and second overhanging portions 51, 52 each overhanging outwardly from an outer periphery of the body portion 50, and an arm portion 53 extending further outwardly from an outer periphery of the first overhanging portion 51 are formed integrally. Due to a pressing force of a coiled spring 6 acting on the arm portion 53, the adjustment ring 5 is biased to pivot (displace) around the input shaft 2 in the clockwise direction in FIG. 1.

A direction where the adjustment ring 5 is displaced is regulated by guide pins 7, 7 provided in a projecting manner on the bottom face of the receptacle recessed portion 12 of the housing 10. That is, two overhanging portions 51, 52 of the adjustment ring 5 have guide slots 54, 55 having an elongated-hole-shaped section as illustrated herein, and the guide pins 7 are inserted slidably into the guide slots 54, 55, respectively. Hereby, the displacement of the adjustment ring 5 is regulated to directions where the guide slots 54, 55 extend, that is, to longitudinal directions of the sections of the guide slots 54, 55. The guide slots 54, 55 and the guide pins 7 will be described later in detail.

The arm portion 53 of the adjustment ring 5 separates the control hydraulic chamber TC and the low hydraulic chamber TL from each other, which are formed side by side in the receptacle recessed portion 12 of the housing 10. A first sealant 56 is disposed on an outer periphery of the arm portion 53, so as to move along with the displacement of the adjustment ring 5 while the first sealant 56 makes sliding contact with the peripheral wall 11 of the housing 10 to which the first sealant 56 is opposed. Due to the first sealant 56, flowing of the oil between the control hydraulic chamber TC and the low hydraulic chamber TL is limited.

In FIG. 1, the low hydraulic chamber TL is disposed in a region surrounded by the outer periphery of the adjustment ring 5 and the peripheral wall 11 of the housing 10, from a lower part of the receptacle recessed portion 12 toward its upper part by detouring around a right side of the adjustment ring 5. Further, the openings of the intermediate groove 13b and the port upstream portion 13c of the inlet port 13 are provided so as to face the low hydraulic chamber TL as described above. Accordingly, when the low hydraulic chamber TL receives a suction pressure of the oil by the rotation of the drive rotor 3 and the driven rotor 4, its pressure becomes lower than an atmospheric pressure (the pressure reaches a negative pressure).

In the meantime, the control hydraulic chamber TC is formed in a region which is surrounded by the outer periphery of the adjustment ring 5 and the peripheral wall 11 of the housing 10 and in which flow of the oil is limited by a second sealant 58 provided on the outer periphery of the adjustment ring 5 and the first sealant 56. That is, a protruding portion 57 is formed on the outer periphery of the adjustment ring 5 so as to project toward an upper left side in FIG. 1, and the second sealant 58 disposed in the protruding portion 57 moves along with the displacement of the adjustment ring 5 while the second sealant 58 makes sliding contact with the peripheral wall 11 of the housing 10.

Note that the first and second sealants 56, 58 each have a dimension to the same degree as a thickness of the adjustment ring 5 (a dimension in a direction perpendicular to a plane of paper of FIGS. 1, 2), and are made of a resin material and the like excellent in abrasion resistance.

A supply port 15 for a control hydraulic pressure is opened on the bottom face of the receptacle recessed portion 12 so as to face the control hydraulic chamber TC, so that the control hydraulic pressure is supplied from an oil control valve (not shown) via a control oil passage 16 as indicated by a virtual line in the figure. A pressing force to pivot the adjustment ring 5 counterclockwise in FIGS. 1, 2 is applied to the arm portion 53 due to the control hydraulic pressure, so that a position of the adjustment ring 5 is determined so that the pressing force balances with a pressing force (biasing force) of the coiled spring 6.

The adjustment ring 5 is displaced by adjusting the control hydraulic pressure as such, so that the capacity of the oil pump 1 can be changed. That is, when the control hydraulic pressure is small, the adjustment ring 5 is biased by the pressing force of the coiled spring 6 toward a maximum pump capacity position as illustrated in FIG. 1. When the control hydraulic pressure increases, the adjustment ring 5 that receives the control hydraulic pressure pivots (is displaced) counterclockwise in FIGS. 1, 2 against the pressing force of the coiled spring 6, so that the pump capacity is reduced as illustrated in FIG. 2 as an example.

In the present embodiment described above, the direction where the adjustment ring 5 is displaced is regulated by the guide slots 54, 55 and the guide pins 7. A regulation structure by the guide pin 7 is approximately the same in two guide slots 54, 55. Accordingly, the following description is made about the guide slot 54 provided in the first overhanging portion 51 of the adjustment ring 5.

As schematically illustrated in FIG. 3A, an outer peripheral surface of the guide pin 7 having a generally pillar shape serves as a guide surface that makes sliding contact with an inner peripheral surface (a guided surface) of the guide slot 54. When the adjustment ring 5 is displaced so as to change the pump capacity as described above, the inner peripheral surface of the guide slot 54 is guided by the outer peripheral surface of the guide pin 7 along with the displacement. Hereby, the direction where the adjustment ring 5 is displaced is regulated to the longitudinal direction of the section of the guide slot 54 (hereinafter just referred to as a “longitudinal direction of the guide slot”).

When the guide slot 54 is displaced in its longitudinal direction from a broken line to a continuous line as illustrated in FIG. 3A along with the displacement of the adjustment ring 5, for example, the guide pin 7 is displaced relative to the guide slot 54. That is, an inner part of the guide slot 54 is divided by the guide pin 7 into two spaces A, B on one side and the other side in the longitudinal direction, and the guide pin 7 is relatively displaced inside the guide slot 54 along the longitudinal direction of the guide slot 54, so that volumes of the two spaces A, B are hereby changed.

For example, when the guide slot 54 is displaced from the broken line to the continuous line in FIG. 3A and the guide pin 7 is displaced downward relative to the guide slot 54, the volume of the space A in the guide slot 54 on the one side (an upper side in the figure) in the longitudinal direction increases, and the volume of the space B on the other side (a lower side in the figure) in the longitudinal direction decreases. As a result, as indicated by a continuous-line arrow oil in the figure, the oil flows from the space B toward the space A (upward in the figure) in a gap between the outer peripheral surface of the guide pin 7 and the inner peripheral surface of the guide slot 54 that makes sliding contact with the outer peripheral surface of the guide pin 7.

In order to regulate the direction of the displacement of the adjustment ring 5 with accuracy, it is necessary to sufficiently narrow the gap between the outer peripheral surface of the guide pin 7 and the inner peripheral surface of the guide slot 54 that makes sliding contact therewith. When the gap between the outer peripheral surface of the guide pin 7 and the inner peripheral surface of the guide slot 54 is narrow, a flow resistance of the oil flowing through the gap increases, which also increases a resistance to the operation of the adjustment ring 5. When a viscosity of the oil is high like a case where a temperature is low, the resistance increases as compared with a case where the temperature is normal or high, which may delay the displacement of the adjustment ring 5, so that response of a control on the pump capacity may decrease.

In contrast, in the present embodiment, at least one of the guide pin 7 and the adjustment ring 5 is provided with a communicating passage so that the two spaces A, B separated by the guide pin 7 inside the guide slot 54 as described above communicate with each other.

First Example of Communicating Passage

More specifically, as indicated by a broken line 7a in FIG. 3A and as illustrated in a perspective view of the guide pin 7 in FIG. 3B, a reduced diameter part 7a (a small sectional area part having a sectional area smaller than that of the other part) is provided in an axially intermediate part (partially) of the guide pin 7 in the first example. The guide pin 7 is provided separately from the housing 10, and the reduced diameter part 7a may be formed integrally in a manufacturing process of the guide pin 7, or may be formed by machining.

A recess 70 (a reference sign is shown only in FIG. 3B) formed on the outer periphery of the guide pin 7 at the reduced diameter part 7a thus provided serves as a communicating passage. When the guide pin 7 is relatively displaced in the guide slot 54 along with the displacement of the adjustment ring 5 as described above, the oil flows through the communicating passage (the recess 70) as indicated by the broken-line arrow in FIG. 3A so that the oil goes back and forth between the two spaces A, B. Therefore, in comparison with a case where the oil flows only through the gap between the outer peripheral surface of the guide pin 7 and the inner peripheral surface of the guide slot 54, the flow resistance of the oil can be reduced.

In an example illustrated in FIGS. 3A, 3B, the reduced diameter part 7a is set to a range at an axially central part of the guide pin 7, with about one-third of an axial length of the guide pin 7, and the outer peripheral surface of that part of the guide pin 7 which is within a range of about one-third of the guide pin 7 at either end in the axial direction functions as a guide surface. This makes it possible to achieve stabilization of a function to guide the inner peripheral surface (the guided surface) of the guide slot 54 by the guide surfaces on both ends of the guide pin 7, that is, the direction where the adjustment ring 5 is displaced.

A sectional area of the communicating passage (the recess 70) may be set to be larger than a sectional area (an area of a range C, illustrated in an exaggerated manner, between the guide surface and the guided surface indicated by virtual lines in FIG. 3B) of the gap between the guide surface on the outer periphery of the guide pin 7 and the guided surface on the inner periphery of the guide slot 54 that makes sliding contact therewith. This makes it possible to increase an effect to reduce the flow resistance of the oil going back and forth between the two spaces A, B in the guide slot 54.

In the variable-capacity oil pump 1 according to the present embodiment described above, by displacing the adjustment ring 5 received in the housing 10, it is possible to change the pump capacity. At this time, the direction where the adjustment ring 5 is displaced is regulated to the longitudinal direction of the guide slot 54, 55 by the guide pin 7 inserted into the guide slot 54, 55 formed in the adjustment ring 5.

When the adjustment ring 5 is displaced along the longitudinal direction of the guide slot 54, 55 as such, the guide pin 7 is relatively displaced inside the guide slot 54, 55 along the longitudinal direction thereof. At this time, the oil flows through the gap between the outer peripheral surface of the guide pin 7 and the inner peripheral surface of the guide slot 54, 55 that makes contact therewith, so as to go back and forth between the two spaces A, B in the guide slot 54, 55, and the oil also flows through the communicating passage (the recess 70) formed on the outer periphery of the guide pin 7.

Because of this, even if the gap between the outer peripheral surface of the guide pin 7 and the inner peripheral surface of the guide slot 54, 55 is narrowed sufficiently so as to regulate the direction of the displacement of the adjustment ring 5 with accuracy, the flow resistance of the oil flowing through not only the gap but also the communicating passage (the recess 70) can be reduced sufficiently. This allows the adjustment ring 5 to be displaced fast, thereby making it possible to increase response of a control on the pump capacity. This is effective particularly at the time when the viscosity of the oil is high like a case where the temperature is low.

Second Example

FIGS. 4A, 4B illustrate a second example in which a pair of grooves 71, 71 is formed on an outer periphery of an axially intermediate part (partially) of a guide pin 7 at a generally semicircular interval, so that the intermediate part is provided as a small sectional area part having a sectional area smaller than that of the other part. The pair of grooves 71, 71 may be also formed integrally in a manufacturing process of the guide pin 7, or may be machined. Further, it is preferable that a sectional area of each of the grooves 71 be set to be larger than a sectional area of a gap between a guide surface on an outer periphery of the guide pin 7 and a guided surface on an inner periphery of a guide slot 54.

The guide pin 7 thus provided with the grooves 71 is attached to a housing 10 so that orientations in which the grooves 71 extend are along a longitudinal direction of the guide slot 54, 55. Hereby, the grooves 71 each serve as a communicating passage that communicates two spaces A, B in the guide slot 54 with each other. When the guide pin 7 is relatively displaced in the guide slot 54 along with displacement of an adjustment ring 5, oil flows through the communicating passage (the groove 71) so that the oil goes back and forth between the two spaces A, B.

In a case where the pair of grooves 71, 71 are provided like this example, rigidity and strength of the guide pin 7 can be easily increased as compared with a case where the reduced diameter part 7a is provided like the first example. However, it is necessary to attach the guide pin 7 to the housing 10 with the directions of the grooves 71, 71 being along the longitudinal direction of the guide slot 54, 55. Further, even in the second example, outer peripheral surfaces of both axial ends of the guide pin 7 except the grooves 71, 71 make sliding contact with an inner peripheral surface (a guided surface) of the guide slot 54, which achieves stabilization of a guiding function.

Third Example

FIGS. 5A, 5B illustrate a third example in which a tip end side (an upper side in FIG. 5B) of a guide pin 7 is provided as a small sectional area part and as a tapered part 7b (a sectional-area gradually changing part), so that a space 72 around the tapered part 7b serves as a communicating passage. The tapered part 7b may be also formed integrally in a manufacturing process of the guide pin 7 or may be machined. Alternatively, the guide pin 7 itself may be formed integrally with a bottom of a receptacle recessed portion 12 of a housing 10 at the time of casting the housing 10. In this case, since the tip end side of the guide pin 7 is the tapered part 7b, demolding is performed easily.

In this example, similarly to the first example, the space 72 (a reference sign is shown only in FIG. 5B) around the tapered part 7b (the small sectional area part) of the guide pin 7 serves as the communicating passage, so that oil flows therethrough, which makes it possible to reduce a flow resistance thereof. On the other hand, outer peripheral surfaces of a base end and an intermediate part of the guide pin 7 except the tapered part 7b serve as a guide surface that makes sliding contact with an inner peripheral surface (a guided surface) of a guide slot 54, so that a guiding function can be secured.

Note that a size of the tapered part 7b may be set such that a passage sectional area of the oil flowing through the space 72 around the tapered part 7b is larger than a sectional area of a gap between a guide surface on an outer periphery of the guide pin 7 and a guided surface on an inner periphery of a guide slot 54.

Fourth Example

FIGS. 6A, 6B illustrate a fourth example in which a communicating passage (a through hole 73) is provided so as to penetrate through a guide pin 7. The through hole 73 may be also formed integrally in a manufacturing process of the guide pin 7 or may be machined. Even in this example, oil flows through the communicating passage (the through hole 73), so that a flow resistance thereof can be reduced.

In the fourth example, a whole outer peripheral surface of the guide pin 7 serves as a guide surface and makes sliding contact with an inner peripheral surface (a guided surface) of a guide slot 54, so that a guiding function is easy to be secured. However, similarly to the second example, it is necessary for the guide pin 7 to be attached to a housing 10 so that an orientation in which the through hole 73 extends is along a longitudinal direction of the guide slot 54, 55. Note that it is preferable that a sectional area of the through hole 73 be set to be larger than a sectional area of a gap between a guide surface on an outer periphery of the guide pin 7 and a guided surface on an inner periphery of the guide slot 54.

Fifth Example

FIG. 7 illustrates a fifth example in which a communicating passage is not provided in a guide pin 7, but is provided as a groove 54a opened on an inner peripheral surface of a guide slot 54 with which an outer peripheral surface of the guide pin 7 makes sliding contact. The groove 54a may be molded integrally with the guide slot 54 in a manufacturing process of a housing 10, or may be machined after the guide slot 54 is molded.

As illustrated herein, the groove 54a extends in a longitudinal direction of the guide slot 54, and one end (an upper end in FIG. 7) thereof is placed at an end part (an upper end in FIG. 7) on one side of the guide slot 54 in the longitudinal direction. Even when the guide pin 7 is placed closest to the one side (an upper side in FIG. 7) in the longitudinal direction of the guide slot 54, the groove 54a faces a space A on the one side. In the meantime, the other end (a lower end in FIG. 7) of the groove 54a is placed in the other end (the lower end in FIG. 7) of the guide slot 54 in the longitudinal direction, and even when the guide pin 7 is placed closest to the other side (a lower side in FIG. 7) of the guide slot 54 in the longitudinal direction, the groove 54a faces a space B on the other side.

When the guide pin 7 is relatively displaced in the guide slot 54, the groove 54a formed as such functions as a communicating passage that communicates two spaces A, B in the guide slot 54 without depending on a position of the guide pin 7, so as to allow oil to flow through the communicating passage (the groove 54a) along with relative displacement of the guide pin 7, so that the oil goes back and forth between the two spaces A, B. Note that it is preferable that a sectional area of the groove 54a be set to be larger than a sectional area of a gap between a guide surface on an outer periphery of the guide pin 7 and a guided surface on an inner periphery of the guide slot 54.

Sixth Example

FIG. 8 illustrates a sixth example in which both ends of a communicating passage 59 formed inside an adjustment ring 5 are opened on an inner peripheral surface of a guide slot 54. The communicating passage 59 can be formed by boring by means of a drill or the like, for example, after the guide slot 54 is molded in a manufacturing process of a housing 10.

As illustrated herein, the communicating passage 59 extends in a longitudinal direction of the guide slot 54, and one end (an end part on a upper side in FIG. 8) of the communicating passage 59 is opened in an end part (an upper end in FIG. 8) of the guide slot 54 on one side in the longitudinal direction, so as to face a space A. Further, the other end (an end part on a lower side in FIG. 8) of the communicating passage 59 is opened in an end part (a lower end in FIG. 8) of the guide slot 54 on the other side in the longitudinal direction, so as to face a space B. Note that it is preferable that a sectional area of the communicating passage 59 be set to be larger than a sectional area of a gap between a guide surface on an outer periphery of the guide pin 7 and a guided surface on an inner periphery of the guide slot 54.

When the guide pin 7 is relatively displaced in the guide slot 54, the communicating passage 59 formed as such communicates two spaces A, B with each other without depending on a position of the guide pin 7, that is, even if the guide pin 7 is placed closest to the one side (the upper side in FIG. 8) in the longitudinal direction of the guide slot 54 or even if the guide pin 7 is placed closest to the other side (the lower side in FIG. 8). This allows oil to flow through the communicating passage 59 along with the relative displacement of the guide pin 7, so that the oil goes back and forth between the two spaces A, B.

The embodiment described above deals with a case where the present invention is applied to the oil pump 1 of an automotive engine. However, the present invention is not limited to this, and the present invention can be applied to an oil pump for an engine to be provided in other vehicles except the automobile. The number of cylinders of the engine and a type (a V type, a horizontal opposed type, and the like) of the engine are not limited in particular, and a type of fuel (gasoline, diesel oil, fuel gas, and the like) is also not limited in particular. Further, the present invention can be applied to an oil pump of a transmission.

Examples of the communicating passage to be provided in the guide pin 7 or the guide slot 54, 55 are described as the first to sixth examples. However, these are just examples and do not limit the configuration of the present invention. That is, for example, not one but a plurality of reduced diameter parts 7a in the first example may be provided, or not one but a plurality of through holes 73 in the fourth example may be provided. Further, only one groove 71 in the second example may be provided. Further, two or more grooves 54a in the fifth example or two or more communicating passages 59 in the sixth example may be provided.

Further, positions to provide the reduced diameter part 7a, the grooves 71, 71 the through hole 73, the groove 54a, the communicating passage 59, and the like are also not limited to the first to sixth examples, and the reduced diameter part 7a, the grooves 71, 71, the through hole 73, the groove 54a, the communicating passage 59, and the like may be provided in combination appropriately.

Furthermore, a general structure of the oil pump 1 described in the above embodiment is just an example. For example, instead of using the coiled spring 6 to bias the adjustment ring 5, various elastic members such as a leaf spring can be used. Further, the oil pump is not limited to an inner oil pump, and the present invention is applicable to various variable-capacity oil pumps such as a vane pump or a piston pump, for example.

The above embodiment can increase response to change a pump capacity in a variable-capacity oil pump to be provided in an engine or the like. Accordingly, the above embodiment yields a high effect when the above embodiment is applied to an engine of an automobile in which a driving state is changed largely.

Claims

1. An oil pump comprising:

an input shaft;

an inlet port;

a discharge port;

a capacity-variable mechanism configured to change a discharge amount per one rotation of the input shaft, the capacity-variable mechanism including a capacity adjustment member, the capacity adjustment member having a guide slot having an elongated-hole shape, the guide slot including a guided surface provided on an inner periphery of the guide slot; and

a housing including a guide pin, the guide pin being inserted into the guide slot, the guide pin including a guide surface provided on an outer periphery of the guide pin,

the guide pin being configured to regulate displacement of the capacity adjustment member to a longitudinal direction of the guide slot, the guide pin being configured to separate the guide slot into a first space and a second space in the longitudinal direction, the guide surface of the guide pin making sliding contact with the guided surface of the guide slot, oil flowing between the first space and the second space via a gap between the guide surface and the guided surface, and

at least one of the guide pin and the capacity adjustment member being provided with a communicating passage, the communicating passage being configured to communicate the first space with the second space.

2. The oil pump according claim 1, wherein

a sectional area of the communicating passage is larger than a sectional area of the gap between the guide surface and the guided surface.

3. The oil pump according to claim 1, wherein

the guide pin includes a first sectional area part and a second sectional area part along an axial direction of the guide pin, the first sectional area part having a sectional area smaller than a sectional area of the second sectional area part, and

the guide pin includes a recess provided on an outer peripheral surface of the guide pin in the first sectional area part, the recess constituting the communicating passage.

4. The oil pump according to claim 3, wherein

the first sectional area part is provided at an axially intermediate part of the guide pin.

5. The oil pump according to claim 3, wherein

the first sectional area part of the guide pin includes a tapered part having a sectional area that gradually increases toward the second sectional area part.

6. The oil pump according to claim 1, wherein

the communicating passage penetrates through the guide pin, and

the communicating passage is configured to communicate the first space with the second space.

7. The oil pump according to claim 1, wherein

an inner peripheral surface of the guide slot has a groove extending in the longitudinal direction of the guide slot, and

the groove constitutes the communicating passage.

8. The oil pump according to claim 1, wherein

the communicating passage is provided inside the capacity adjustment member, and

both ends of the communicating passage are opened on an inner peripheral surface of the guide slot.

9. The oil pump according to claim 1, wherein

the housing includes a low hydraulic chamber, and

the guide slot communicates with the inlet port via the low hydraulic chamber.

10. The oil pump according to claim 1, further comprising:

a drive rotor as an external gear rotated by the input shaft; and

a driven rotor as an internal gear meshing with the drive rotor so as to be rotated accordingly, wherein

the housing includes a control hydraulic chamber,

the capacity adjustment member has an annular holding portion configured to rotatably hold the driven rotor from an outer periphery of the driven rotor, the capacity adjustment member is configured to be displaced by a hydraulic pressure of the control hydraulic chamber, and

the capacity-variable mechanism is configured to change relative positions of the drive rotor and the driven rotor to the inlet port and the discharge port, along with the displacement of the capacity adjustment member, such that a discharge amount of the oil pump is changed.