The invention relates to the cooling of an internal combustion engine of a motor vehicle, in particular a cooling module according to the preamble to claim 1 and to the coordinate Patent claim 13.
Cooling modules are known—in the form of pre-assembled structural units, which are preferably disposed and fastened in the front engine compartment of a motor vehicle. The structural unit or cooling module comprises various cooling components and components of an air-conditioning system, inter alia various heat exchangers such as coolant coolers, charge-air coolers, oil coolers or refrigerant condensers. In addition, one or more cooling-air blowers, comprising fan and drive motor, can also form a constituent part of the cooling module. All cooling components are held together by a frame-like structure, a so-called module carrier, and supported in the vehicle. All of the heat exchangers are cooled by a cooling-air flow, i.e. ambient air, which is generated by ram pressure or by the cooling-air blower. The air flow flowing through the cooling module generates an air resistance, which increases the cw-value of the vehicle. Depending on the arrangement of the heat exchangers in the cooling module, these are impinged upon more or less strongly by the cooling-air flow, which does not always meet the requirements of the respective cooling demand. The cooling demand for the individual heat exchangers is very varied and depends on the respective load states. The cooling demand is usually regulated by an adjustment of the fluid flows in the heat exchangers, whilst the air-mass flow (flow rate) is not generally altered or is adapted to the respective cooling demand of the individual heat exchangers.
Through EP 1 431 698 A2, it is known to regulate the air-mass flow as a whole, a shutter being disposed in the air flow, which shutter extends over the whole of the air flow cross section. Such a shutter can also be used to control a cooling-air flow through the engine compartment for cooling of the motor and gearbox.
DE 197 19 792 B4 of the Applicant has disclosed a method and a device for regulating the cooling air temperature in a motor vehicle, wherein a shutter is likewise disposed in the cooling-air flow, which shutter determines the flow rate of the whole of the cooling-air flow which is branched off from the ram pressure. The share of removal of the cooling air flow from the ram air influences the vehicle resistance: the more the shutter is opened, the stronger is the increase in air resistance, thereby increasing the total energy consumption.
Shutters are known in various forms and different arrangements, for example as louvred or slatted shutters, disclosed by DE 196 52 398 A1 and DE 197 15 352 A1 of the Applicant. In addition, so-called winding shutters are known, in which, the cooler and/or the condenser end face can be covered by a cloth which can be wound up and down (DE 35 22 591 A1 of the Applicant). Shutters are also used for sound insulation.
A drawback with these known solutions is that in each case only the entire air flow, which impinges upon all the heat exchangers of the cooling module, is regulatable.
The object of the invention is to improve a cooling arrangement of the type stated in the introduction such that a differentiated regulation of the air-mass flow, in particular an air flow regulation for individual heat exchangers of the cooling module, is possible, and an adaptation to the variable ram pressure is achievable.
This object is achieved by virtue of the features of Patent claim 1. Advantageous embodiments of the invention derive from the sub-claims.
According to the invention, it is firstly provided that the shutter disposed in the air flow regulates only a partial cross section, i.e. a partial air flow. It is thus possible to regulate the air flow rate purposefully for individual heat exchangers or a specific heat exchanger. The advantage of an improved output regulation for the individual heat exchangers of the cooling module is thus achieved, because, in addition to the regulation of the fluid flow, i.e. of the medium to be cooled, the cooling medium itself, the cooling air, can also be regulated. Depending on the configuration of the shutter, this can be done in steps or steplessly from fully open to fully closed, so that it is possible, for example, no longer to impinge upon selected heat exchangers in specific operating states with cooling air at all. This prevents the heat exchanger in question from not being undercooled or cooled right down. Advantageously, viewed in the air flow direction, the shutter can be disposed both in front of and behind the heat exchanger(s). It can further be provided that in the air flow there is disposed (in the air flow direction) a partition, which sections off one or more partial air flows assigned to specific heat exchangers. These partial air flows are regulated in their flow rate by a shutter or a multipart shutter.
According to an advantageous embodiment of the invention, the fan for conveying the cooling air, and the shutter, are respectively disposed behind the heat exchangers and in a frame adjoining the cooling module. In a further advantageous embodiment of the invention, between the fan and the shutter there can then be provided a swivel flap for separating the air flows or for partitioning off an air flow. This yields the advantage that the air flow, on the one hand, with closed shutter, is restricted and, on the other hand, with closed shutter and swivelled-out separating flap, is fully cut off. Such a solution is advantageous, for example, for a coolant cooler at low external temperatures, since a total cooling of the cooler is thus prevented. It is thus also no longer necessary to reduce the fluid or coolant flow rate in the heat exchanger or coolant cooler in the event of reduced cooling demand, or to heavily reduce it. Finally, when the shutter is restricted or closed, the advantage of a reduced vehicle resistance is obtained, thereby lowering the fuel consumption.
The object of the invention is also achieved by virtue of the features of the coordinated Patent claim 13—advantageous embodiments of the invention derive from the subordinate sub-claims.
According to the invention, a frame with variable geometry, i.e. with a variable intake cross section for the fan and with variable cross section for ram air openings, is provided. The alteration of the intake cross section is preferably achieved by one or more pivotable flaps, which, in particular, simultaneously control the ram air openings. As a result of this variable geometry of the frame, on the one hand an adaptation of the working point of the fan to the various operating conditions such as idling, uphill travel and high-speed travel is achieved, and, on the other hand, an increase in the total air-mass flow is obtained. The fan thus operates at higher efficiency and the cooling output of the cooling module is improved.
In an advantageous embodiment of the invention, the alteration of the intake cross section can be effected in steps, preferably by means of flaps, or steplessly, preferably with a folding flap or a foldable frame rear wall.
The flap or flaps are preferably horizontal, vertical, angled or arc-shaped and are preferably arranged distributed around a fan opening in the frame, the fan opening in all cases being arranged centrically or eccentrically in the, in particular, right-angled frame.
Illustrative embodiments of the invention are represented in the drawing and are described in greater detail below, wherein:
FIG. 1 shows a cooling module with shutter in a first setting (shutter open),
FIG. 2 shows the cooling module in a second setting (shutter closed),
FIG. 3 shows the cooling module in a third setting (shutter closed and flap in blocking position),
FIG. 4 shows the cooling module in a fourth setting (shutter open and flap in separating position),
FIG. 5 shows a cooling module with variable frame geometry (first setting),
FIG. 6 shows the cooling module according to FIG. 5 in a second setting,
FIG. 7 shows the cooling module according to FIG. 5 in a third setting,
FIG. 8 shows the cooling module according to FIG. 5 in a fourth setting,
FIG. 9 shows a modified illustrative embodiment of a cooling module with variable frame geometry (first setting),
FIG. 10 shows the cooling module according to FIG. 9 in a second setting,
FIG. 11 shows the cooling module according to FIG. 9 in a third setting,
FIG. 12 shows a further illustrative embodiment of a cooling module with variable frame geometry,
FIG. 13 shows a further illustrative embodiment of a cooling module with folding flap,
FIG. 14 shows a further illustrative embodiment of a cooling module with foldable frame rear wall,
FIG. 15,
15a, 15b show fan and resistance characteristic curves according to the prior art, and
FIG. 15c shows fan and resistance characteristic curves for the inventive cooling module with variable frame geometry.
FIG. 1 shows a cooling module 1, comprising a coolant cooler 2 and a charge-air cooler 3, a cooling-air blower 4 and a shutter 5. The cooling components 2, 3, 4, 5 are received by a surround or frame 6, represented only schematically, which also receives the cooling-air blower 4, comprising a fan 4a and an electric motor 4b, as well as the shutter 5, which is here configured as a louvred shutter, comprising individual louvres or slats 5a. The coolant cooler 2 and the charge-air cooler 3 are flowed against by cooling air, represented by the arrows L1, L2; they are arranged side by side or one above the other in the air flow direction and are therefore parallelly impinged upon by the air flow. The air flow is fed via an air-conducting device 7 in the form of an air flow duct, the whole of the cooling module 1 being disposed in the front engine compartment (not represented) of a motor vehicle. Between the cooling-air blower 4 and the shutter 5 there is disposed a pivotable flap 8, which can be fastened to the frame 6 in a non-represented manner.
In the represented position of open shutter 5 and vertically disposed flap 8, a maximal air-mass flow, created by ram pressure in high-speed travel of the motor vehicle, can flow through the cooling module, in particular the coolant cooler 2 and the charge-air cooler 3. The air flow L2 flowing through the coolant cooler 2 leaves the shutter 5 as the air flow L4, and the air flow L1 flowing through the charge-air cooler 3 leaves behind the fan 4a as the air flow L3, the respective air-mass flow not necessarily having to be maintained past the vertically disposed flap 8 (L2=L4 and L1=L3) due to possible equalizing flows. When the fan is switched off, a maximal cooling effect can thus be obtained for both heat exchangers.
FIG. 2 shows the cooling module 1 according to FIG. 1 with closed shutter 5. For identical parts, identical reference symbols are used. The total air flow which enters the air-conducting device 7 is divided into a partial air flow L1, which flows through the charge-air cooler 3, and a partial flow L2, which flows through the coolant cooler 2. The air flow L2 leaving the coolant cooler 2 is deflected upwards owing to the closed shutter 5 and is conveyed outwards by the fan 4a as part of the air flow L5. The mass flow L5 corresponds to the sum of the partial air flows L1 and L2. In this position, a maximal air-mass flow L5 during running of the fan 4a can be obtained without ram pressure support, the air outlet cross section being reduced as a result of the closed shutter 5.
FIG. 3 shows the cooling module 1 with closed shutter 5 and horizontally disposed flap 8′. The air flow which passes through the cooling module 1 is represented by an entry arrow L1 and by an exit arrow L5, only the charge-air cooler 3 being flowed through by air. The coolant cooler 2 is partitioned off on the air side by the flap 8′, acting as a partition, the shutter 5 simultaneously being closed, so that no through-flow with cooling air is possible. The flap position 8′ represented horizontally in the drawing lies level with the interstice between the coolant cooler 2 and the charge-air cooler 3 and thus conducts the discharged charge-air flow through the fan 4a. The represented position is advantageous, particularly given a lack of cooling demand of the coolant cooler 2, i.e. at low external temperatures, for example. A total cooling of the coolant cooler and too great a lowering of the coolant temperature are thereby prevented.
FIG. 4 shows the cooling module 1 with horizontally disposed flap 8′ and open shutter 5. As a result of this configuration, a strict separation of the two incoming air flows L1, L2 into a fan discharge flow L3 and an air flow L4 leaving the shutter 5 is made. The cooling of the coolant cooler 2 is thus determined by the vehicle speed or the ram pressure, whilst the cooling of the charge-air cooler 3 is determined by the air flow L3 conveyed by the fan 4a and supported by ram pressure.
The cooling module represented in the drawings is a preferred illustrative embodiment—modifications are possible. For example, additional or other heat exchangers can be provided. Furthermore, the shutter can be disposed in front of the heat exchangers in the air flow direction. In addition, the flap 8 can be disposed as a partition in front of the heat exchangers in the air flow direction and can divide the total air flow into partial air flows or flow paths, which are assigned to the individual heat exchangers. A purposeful regulation of the air-mass flow can thus also be realized for individual heat exchangers, i.e. selectively.
FIG. 5 shows a further illustrative embodiment of the invention for a cooling module 9 having an air-conducting device 7 for the entry of cooling air, a coolant cooler 2 and a charge-air cooler 3, which are disposed one above the other or side by side and are parallelly impinged upon by the air flow, represented by the arrows L. The two heat exchangers 2, 3 are accommodated and fastened in a frame 10 with variable geometry. The frame 10 has a rear wall 10a, which receives the cooling blower 4, comprising fan 4a and motor 4b. In the rear wall 10a there are provided, outside the cross section of the fan 4a, two ram air openings 11, 12, which can be controlled by pivotable flaps 13, 14. In the represented position of the flaps 13, 14, i.e. in the horizontal setting or in the air flow direction, both ram air openings 11, 12 are open, so that from both openings 11, 12 there is respectively discharged an air-mass flow V.κ, which is determined by the ram pressure prevailing in front of the heat exchangers 2, 3. The intake cross section of the fan 4a is reduced by this flap setting to a minimum Amin. The air-mass flow conveyed by the fan 4a and sucked up within the flaps 13, 14 is represented by an arrow V.L. The represented configuration is advantageous in high-speed travel of the motor vehicle and permits a maximal mass flow through both heat exchangers 2, 3 or the cooling module, the fan 4a being at the working point, i.e. it can supply a hydraulic energy to the air flow sucked up and conveyed by it.
FIG. 6 shows the cooling module 9 according to FIG. 5 with an altered flap setting: the upper flap 14 is pivoted into a vertical setting in the drawing and thus closes the upper ram air opening 12. The lower flap 13, on the other hand, is in a horizontal setting and thus frees the ram air opening 11, from which an air-mass flow V.K is discharged. The intake cross section of the fan 4a is thus reduced to an intermediate cross section Az or widened relative to the cross section Amin according to FIG. 5. This flap configuration is advantageous for uphill travel, a maximal mass flow being conveyed through the charge-air cooler 3. Here too, the fan 4a is at its working point and can build up a pressure gradient.
FIG. 7 shows the cooling module 9 with an altered flap configuration. The flaps 13, 14 are both in the closing position, i.e. the ram air openings 11, 12 are closed, so that the fan frame 10 has its maximal intake cross section Amax, which corresponds to the downstream end face of the two heat exchangers 2, 3. This configuration is particularly advantageous when the vehicle is stationary, i.e. without ram pressure: the fan 4a is at the working point and conveys a maximal air-mass flow V.L through both heat exchangers 2, 3 or the cooling module.
FIG. 8 shows the cooling module 9 with the flap 13 in the closed and the flap 14 in the open setting, so that the upper ram air opening 12 is open and permits an air-mass flow V.K induced by ram pressure. The intake cross section AZ corresponds to that in FIG. 6, with the difference that the coolant cooler 2 is here fully impinged upon by the air flow. This configuration is advantageous for uphill travel, with a maximal air-mass flow through the coolant cooler 2 and reduced mass flow through the charge-air cooler 3. Here, too, the fan 4a is at its working point.
As shown by the various flap settings in FIGS. 5 to 8, the cooling module 9 has a “variable frame geometry”, i.e. the air intake cross section and the cross section of the ram air openings are adjustable; in their horizontal position, the flaps respectively seal with their front edges against the rear side of the heat exchanger network.
FIG. 9 shows a further illustrative embodiment of the invention, namely a cooling module 15 with a block 16 of various heat exchangers (not represented in detail), for example coolant cooler, charge-air cooler, refrigerant condenser, oil cooler, inter alia. The block 16 has an end face 16a, through which the air flow, represented by the arrow L, enters, as well as an air outlet face 16b corresponding to the end face 16a. The block 16 is accommodated in a frame 17, which has a rear wall 17a containing a fan 4a. In the upper part of the rear wall 17a in the drawing, two mutually adjacent ram air openings 18, 19 are provided, which are respectively controllable by a swivel flap 20, 21. In the represented horizontal position of the flaps 20, 21, the ram air openings 18, 19 are freed, so that a ram air flow, represented by the arrows V.K, is discharged. The flaps 20, 21 bear with their upstream edges against the rear side 16b of the block 16 and thus effect a sealing and a separation of the air flows conveyed, on the one hand, by the fan 4a and, on the other hand, by the ram pressure. The represented position of the flaps 20, 21 is advantageous in high-speed travel and produces a maximal air-mass flow through the cooling module 15, the fan 4a being at the working point.
FIG. 10 shows the cooling module 15 according to FIG. 9 with an altered flap setting. The outer flap 20 is in horizontal and the inner flap 21 in roughly vertical setting, so that only the outer ram air opening 18 is open and admits a ram-pressure-induced air flow V.K. The intake cross section of the fan 4a thus has an intermediate setting Az, which lies between the maximal and the minimal intake cross section. The flap 20, with its front edge, seals off the intake flow from the rear side 16b of the module block 16. The represented position of the flaps is advantageous for uphill travel, i.e. at lower ram pressure, and allows a maximal air-mass flow through the module 16, made up of the fan flow V.L and the ram air flow V.K.
FIG. 11 shows the cooling module 15 with a third flap setting, namely with closed flaps 20, 21. The intake cross section of the fan 4a is thus widened to the maximal cross section Amax and corresponds to the rear-side end face 16b of the block 16. The represented closing position of the flaps 20, 21 is advantageous when the vehicle is stationary, i.e. without ram pressure—a maximal air-mass flow V.L is obtained through the block 16, which is conveyed solely by the fan 4a. The fan 4a is at the working point. The three represented flap positions according to FIGS. 9, 10 and 11 show the variable frame geometry in a step-by-step alteration from the minimal intake cross section Amin via the intermediate cross section Az to the maximal intake cross section Amax. At each operating point, i.e. in high-speed travel and when the vehicle is stationary, the fan operates at the working point at a relatively high efficiency.
FIG. 12 shows the cooling module 15 with a velocity distribution v over the end face of the module block 16, which is made up of a downstream-situated coolant cooler 22, an upstream-situated charge-air cooler 23 and an engine oil cooler 24 disposed beside the charge-air cooler 23. The engine oil cooler 24 has an end face 24a and the charge-air cooler 23 has an end face 23a. The end face 24a roughly corresponds to the cross section of the two ram air openings 18, 19, and the end face 23a to the intake cross section of the fan 4a. The velocity distribution v over the whole of the module end face is represented for the maximal speed of the vehicle. Owing to the open ram air openings 18, 19, over the end face 24a of the engine oil cooler 24 the velocity VK is obtained, whilst over the end face 23a of the charge-air cooler 23 an increased velocity VL is established. This is conditioned by the increase in energy acquired by the mass flow of the fan 4a operating at the working point. In high-speed travel, i.e. when the cooling output requirement of the charge-air cooler is increased, the charge-air cooler 23 thus acquires an increased cooling air-mass flow. As can be seen from the different velocity distribution, the flow paths for the two mutually adjacent heat exchangers 23, 24 are simultaneously divided, which latter can thus be regulated with respect to their cooling output by an adapted air-mass flow.
FIG. 13 shows as a further illustrative embodiment of the invention a cooling module 25 with variable frame geometry in the form of a so-called folding flap 26, which is integrated in the rear wall of the frame. A module block 27 is adjoined by a frame rear wall 28, in which the fan 4a rotates. The folding flap 26 is integrated in the frame rear wall 28 in such a way that, as a result of different foldings, different intake cross sections for the fan 4a and, at the same time, different cross sections for the ram air openings are freed. In the drawing, three settings 26a (dashed), 26b (dotted) and 26c (solid) are represented. The setting 26c is characterized by a minimal intake cross section Ac for the fan 4a and a maximal ram air opening. The setting 26b of the folding flap 26 produces a medium intake cross section Ab and a ram air opening of medium cross section. In the setting 26a, the frame rear wall 28 is fully closed in the rearward direction, i.e. the air intake cross section Aa is maximal, and the whole of the air flow sucked up through the module block 27 is conveyed by the fan 4a. As in the previous illustrative embodiments, the folding flap 26 here too, with its upstream edge, seals the air flow against the rear side of the module block 27. Between the represented positions 26a, 26b, 26c, intermediate settings are possible, so that, all in all, a continuous, i.e. stepless adjustment of the intake cross section, combined with a corresponding alteration of the ram air opening, is possible. For the various operating points, idling, uphill travel and high-speed travel, it is thereby ensured that the fan operates at the working point and an increased air-mass flow is obtained.
FIG. 14 shows as a further illustrative embodiment of the invention a cooling module 29 with a module block 30 comprising various components (not represented) and a variable frame geometry in the form of a foldable rear wall 31, which also receives the fan 4a. The frame rear wall 31 can be folded transversely to the air flow direction in the manner of a bellows and has at its free end a separating and sealing element 32, which is displaceable likewise transversely to the air flow direction L. The separating and sealing element has a front sealing edge 32a, which slides on the air outlet face 30a of the module block 30 and thus effects a sealing of the air flow sucked up by the fan 4a. Outside the sealing and separating element 32, i.e. on the side facing away from the fan 4a, a ram air opening 33 is created, which allows a ram air flow V.K. The foldable frame rear wall 31, in conjunction with the sealing and separating element 32, allows a stepless adjustment of the fan intake cross section and of the ram air opening 33. At variance with the represented illustrative embodiment, another, equivalent configuration of the frame rear wall is also possible, for example as a roller or winding shutter or in the form of foldable flaps according to the prior art.
FIG. 15 shows a diagram representing a fan characteristic curve LKL (solid) and a resistance characteristic curve WKL, wherein the static pressure ΔPST is plotted over the air-mass flow V.L. The point of intersection of the resistance characteristic curve and the fan characteristic curve is the working point, which is denoted by AP. The diagram shows a resistance characteristic curve without ram pressure support. The fan conveys at the working point a volume flow illustrated with V.L. At the same time, at the working point, a positive ΔP is generated.
FIG. 15a shows a fan characteristic curve LKL and a resistance characteristic curve WKL with ram pressure support, i.e. relative to FIG. 15, the resistance characteristic curve WKL is lowered into the negative range; similarly, the working point AP is in the negative pressure range, i.e. the fan is “blown over” by the ram pressure and can no longer supply energy to the air-mass flow. The right side of FIG. 15a shows the corresponding cooling module with module block 34, fan frame 35 and fan 36. The arrows v represent the flow velocity of the air in the module block 34, i.e. a homogeneous distribution, if the flow from the cooler to the fan is assumed, by way of simplification, to be ideally free from loss.
FIG. 15b shows a further fan characteristic curve LKL and two different resistance characteristic curves, represented by different symbols (squares and triangles). The right-hand part of FIG. 15b shows the associated cooling module with block 34, frame 35, fan 36, as well as with ram pressure flaps 37 in the rear wall of the frame 35. The steeper resistance characteristic curve WKL relates to that part of the module block 34 which is flowed through by the ram air flow V.K. The flatter resistance characteristic curve WKL relates to the lower part of the module block 34, which is flowed through by the fan flow V.L. A dotted flow filament curve 38 represents the dividing line between ram air flow and fan flow. A total air-mass flow V.ges=V.L+V.K is obtained. The fan flow and the ram air flow thus add together to form the overall flow. The point of intersection of the flatter resistance characteristic curve WKL with the fan characteristic curve, i.e. the working point AP, lies at a static pressure of 0, i.e. the fan adds no energy to the air flow. FIGS. 15, 15a, 15b describe the known prior art.
FIG. 15c shows, in contrast, the working method of the invention for a module block 39 adjoined by a frame 40 with variable geometry, i.e. with an intake cross section adjustable for the fan 41. The module block 39 is divided by a separating and sealing element 40a of the frame 40 into two sub-blocks, a lower sub-block 39a and an upper sub-block 39b, and is sealed towards the rear. The sub-block 39a is flowed through by a fan flow V.L, which, supported by the ram pressure, is conveyed by the fan 41. The upper sub-block 39b is flowed through by a ram-pressure-induced bypass flow V.K, a lower flow velocity for the sub-block 39b than for the sub-block 39a, represented by the different length of the arrows v, being obtained. The diagram arranged on the left in FIG. 15c shows a fan characteristic curve LKL and two somewhat differing resistance characteristic curves WKL, the upper resistance characteristic curve (squares) applying to the upper sub-block 39b and the lower one (triangles) to the lower sub-block 39a. The corresponding point of intersection with the fan characteristic curve LKL is the working point AP of the fan 41, which generates a fan flow V.L. It can be seen from the diagram that the working point AP lies in the positive pressure range, i.e. the fan supplies energy to the flow. Due to the ram pressure of the vehicle, for the upper sub-block 39 the bypass flow V.K as the point of intersection of the upper resistance characteristic curve WKL with the abscissa (ΔP=0) is obtained. Both mass flows V.K and V.L add together to form a total air-mass flow V.ges, which is greater than the overall flow in the prior art, represented by way of comparison in FIG. 15b. As a result of the variable frame geometry according to the invention, an adaptation of the cooling module to the respective operating conditions (idling, uphill travel, high-speed travel) can be achieved in such a way that the fan operates at the working point and, at the same time, an increase occurs in the total mass flow.
