Fluid Temperature Adjustment Device

Abstract

A fluid temperature adjustment device that includes a circulation flow path that circulates the cooling water in one direction between the engine and the radiator; a first flow path branched from the circulation flow path at a location downstream of the engine and upstream of the radiator; a second flow path branched from the circulation flow path at a location downstream of the radiator and upstream of the engine; a third flow path that communicates with a cooling water outlet of the heat exchanger and that is merged with the circulation flow path at a location downstream of the radiator and upstream of the engine; and a switching valve that selectively communicates between one of the first and second flow paths and a cooling water inlet of the heat exchanger.

Description

TECHNICAL FIELD

[0001] The present invention relates to a fluid temperature adjustment device that includes a radiator that cools cooling water for an engine and a heat exchanger that exchanges heat between the cooling water and a working fluid for a transmission.

BACKGROUND ART

[0002] Hitherto, there has been known a fluid temperature adjustment device of this type, including: a radiator that cools cooling water for an internal combustion engine (engine); a removal-side main flow path for taking out a working fluid (ATF) for use in an automatic transmission or the like from the automatic transmission; first and second flow paths that communicate with the removal-side main flow path via an electromagnetic switching valve; a return-side main flow path for returning the working fluid from the first and second flow paths to the automatic transmission; a first heat exchanger provided in the radiator and disposed at the middle of the first flow path to exchange heat between cooling water for the internal combustion engine and the working fluid; and a second heat exchanger disposed at the middle of the second flow path (see Patent Document 1, for example). In the fluid temperature adjustment device, when the temperature of the working fluid detected by an oil temperature sensor is less than a determination value a, the switching valve is controlled such that the working fluid flows only to the first flow path so that only the first heat exchanger exchanges heat with the working fluid. When the temperature of the working fluid is equal to or more than the determination value a, on the other hand, the switching valve is controlled such that the working fluid flows in both the first and second flow paths so that both the first and second heat exchangers exchange heat with the working fluid. In the fluid temperature adjustment device, in this way, the number of heat exchangers through which the working fluid passes is changed in accordance with the temperature of the working fluid to suppress an excessive rise in temperature of the working fluid, overcooling of the working fluid, and so forth.

[0003] [Related-art Documents]

[0004] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2011-2099 (JP 2011-2099 A)

SUMMARY OF THE INVENTION

[0006] If a plurality of heat exchangers are used to adjust the temperature of the working fluid as in the fluid temperature adjustment device according to the related art described above, the size of the device may be increased. Therefore, it is desirable that the temperature of the working fluid should be adjusted by only the first heat exchanger which exchanges heat between cooling water and the working fluid. In the case where the first heat exchanger exchanges heat between cooling water at a relatively low temperature which has been cooled by the radiator and the working fluid, however, it is difficult to immediately raise the temperature of the working fluid when the temperature of the working fluid is low, and a large loss may be caused in each hydraulic device, object to be lubricated, and so forth of the automatic transmission because of the viscous drag of the working fluid which is at a low temperature and has high viscosity. In the case where the first heat exchanger exchanges heat between cooling water at a relatively high temperature which has not been cooled by the radiator and the working fluid, on the other hand, it is difficult to immediately lower the temperature of the working fluid when the temperature of the working fluid is high, and an oil film on a sliding portion such as each object to be lubricated of the automatic transmission may become thin because of the high temperature and the low viscosity of the working fluid, as a result of which the sliding portion may not be lubricated and cooled well,

[0007] It is therefore a main object of the present invention to adequately adjust the temperature of a working fluid for a transmission using a heat exchanger that exchanges heat between cooling water for an engine and the working fluid.

[0008] In order to achieve the foregoing main object, the fluid temperature adjustment device according to the present invention adopts the following means.

[0009] The present invention provides [0010] a fluid temperature adjustment device that includes a radiator that cools cooling water for an engine and a heat exchanger that exchanges heat between the cooling water and a working fluid for a transmission, characterized by including: [0011] a circulation flow path that circulates the cooling water in one direction between the engine and the radiator; [0012] a first flow path branched from the circulation flow path at a location downstream of the engine and upstream of the radiator; [0013] a second flow path branched from the circulation flow path at a location downstream of the radiator and upstream of the engine; [0014] a third flow path that communicates with a cooling water outlet of the heat exchanger and that is merged with the circulation flow path at a location downstream of the radiator and upstream of the engine; and [0015] a switching valve that selectively communicates between one of the first and second flow paths and a cooling water inlet of the heat exchanger,

[0016] The fluid temperature adjustment device includes the circulation flow path which circulates cooling water for the engine in one direction between the engine and the radiator. The first flow path is branched from the circulation flow path at a location downstream of the engine and upstream of the radiator. The second flow path is branched from the circulation flow path at a location downstream of the radiator and upstream of the engine. In addition, the third flow path which communicates with the cooling water outlet of the heat exchanger is merged with the circulation flow path at a location downstream of the radiator and upstream of the engine. The switching valve selectively communicates between one of the first and second flow paths and the cooling water inlet of the heat exchanger. Consequently, heat can be exchanged between cooling water at a relatively high temperature which has not been cooled by the radiator and the working fluid by causing the switching valve to communicate between the first flow path and the cooling water inlet of the heat exchanger. On the other hand, heat can be exchanged between cooling water at a relatively low temperature which has been cooled by the radiator and the working fluid by causing the switching valve to communicate between the second flow path and the cooling water inlet of the heat exchanger. Thus, with the fluid temperature adjustment device, it is possible to adequately adjust the temperature of the working fluid for the transmission using the heat exchanger which exchanges heat between cooling water for the engine and the working fluid.

[0017] In addition, the switching valve may selectively communicate between one of the first and second flow paths and the cooling water inlet of the heat exchanger in accordance with a temperature of the working fluid. Consequently, the switching valve can switch to exchange heat between cooling water at a relatively high temperature which has not been cooled by the radiator and the working fluid, and to exchange heat between cooling water at a relatively low temperature which has been cooled by the radiator and the working fluid, in accordance with the temperature of the working fluid. Thus, the temperature of the working fluid can be adjusted further more adequately by the heat exchanger which exchanges heat between cooling water and the working fluid.

[0018] Further, the third flow path may be merged with the circulation flow path at a location downstream of a branched portion between the circulation flow path and the second flow path and upstream of the engine. Consequently, it is possible to suppress an inflow of cooling water which has been subjected to heat exchange with the working fluid in the heat exchanger again into the heat exchanger via the second flow path, which enhances the efficiency of heat exchange between cooling water and the working fluid performed in the heat exchanger.

[0019] In addition, the switching valve may communicate between the first flow path and the cooling water inlet of the heat exchanger when the temperature of the working fluid is less than a first temperature, and may communicate between the second flow path and the cooling water inlet of the heat exchanger when the temperature of the working fluid is equal to or more than a second temperature that is higher than the first temperature. Consequently, heat can be exchanged between cooling water at a relatively high temperature which has not been cooled by the radiator and the working fluid by causing the switching valve to communicate between the first flow path and the cooling water inlet of the heat exchanger when the temperature of the working fluid is less than the first temperature which is relatively low and the temperature of the working fluid should be raised. Therefore, the temperature of the working fluid can be raised immediately. On the other hand, heat can be exchanged between cooling water at a relatively low temperature which has been cooled by the radiator and the working fluid by causing the switching valve to communicate between the second flow path and the cooling water inlet of the heat exchanger when the temperature of the working fluid is equal to or more than a relatively high temperature, that is, the second temperature which is higher than the first temperature, and the temperature of the working fluid should be lowered. Therefore, the temperature of the working fluid can be lowered immediately.

[0020] Further, the switching valve may include a first input port that communicates with the first flow path, a second input port that communicates with the second flow path, an output port that communicates with the cooling water inlet of the heat exchanger, a spool that moves in an axial direction to selectively communicate between one of the first and second input ports and the output port, a spring that urges the spool in the axial direction, and a thermally expandable material attached to the spool; and the thermally expandable material may permit the spool to be urged by the spring to be moved, and move the spool against an urging force of the spring, in accordance with the temperature of the working fluid. Consequently, the spool can be automatically moved in the axial direction in accordance with the temperature of the working fluid to selectively communicate between one of the first and second flow paths and the output port, that is, between one of the first and second input ports and the cooling water inlet of the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a diagram illustrating a schematic configuration of a fluid temperature adjustment device according to an embodiment of the present invention.

[0022] FIG. 2 illustrates a switching valve included in the fluid temperature adjustment device.

[0023] FIG. 3 illustrates the switching valve included in the fluid temperature adjustment device.

[0024] FIG. 4 is a schematic diagram illustrating operation of the fluid temperature adjustment device.

[0025] FIG. 5 is a schematic diagram illustrating operation of the fluid temperature adjustment device.

[0026] FIG. 6 is a schematic diagram illustrating operation of the fluid temperature adjustment device.

MODES FOR CARRYING OUT THE INVENTION

[0027] Now, an embodiment of the present invention will be described with reference to the drawings.

[0028] FIG. 1 is a diagram illustrating a schematic configuration of a fluid temperature adjustment device 10 according to an embodiment of the present invention.

[0029] The fluid temperature adjustment device 10 illustrated in the drawing is mounted on a vehicle that includes an engine 12 and a transaxle 20 that transfers power from the engine 12 to drive wheels, and adjusts the temperature of cooling water (LLC) for cooling the engine 12 and a working fluid (ATF) for the transaxle 20.

[0030] The transaxle 20 included in a vehicle that incorporates the fluid temperature adjustment device 10 includes: a transaxle case 22; a fluid transmission apparatus 23 that serves as a starting device; an oil pump 24 driven by power from the engine 12; an automatic transmission 25 that outputs power from the engine 12 transferred via the fluid transmission apparatus 23 with the speed of the power changed by a plurality of shift speeds; a hydraulic control device 26 that supplies a working fluid discharged from the oil pump 24 to each hydraulic device and object to be lubricated such as a clutch included in the fluid transmission apparatus 23 and the automatic transmission 25; and a control device 30 that controls such components. The fluid transmission apparatus 23, the oil pump 24, the automatic transmission 25, and the hydraulic control device 26 are disposed inside the transaxle case 22. It should be noted, however, that the hydraulic control device 26 may be disposed outside the transaxle case 22. In addition, the automatic transmission 25 may be a mechanical or electrical continuous variable transmission.

[0031] The fluid temperature adjustment device 10 is controlled by the control device 30, and includes: a circulation flow path 101 that forms a circulation path for cooling water and that includes a heat exchange portion (not illustrated) formed in a cylinder block or a cylinder head of the engine 12; a bypass flow path 102 branched from the circulation flow path 101; a water pump 103 that is incorporated in the engine 12 and that circulates cooling water in one direction in the circulation flow path 101; a radiator 104 that is disposed at the middle of the circulation flow path 101 and that cools cooling water flowing in the circulation flow path 101 using a wind or an electric fan (not illustrated); and a thermostat 105 disposed in the circulation flow path 101 at a location downstream of the engine 102 and upstream of the radiator 104.

[0032] The circulation flow path 101 is composed of a pre-cooling flow path 101a provided downstream of the water pump 103 and upstream of the radiator 104, and a post-cooling flow path 101b provided downstream of the radiator 104 and upstream of the water pump 103. The bypass flow path 102 is branched from the pre-cooling flow path 101a at a location upstream of the thermostat 105, and merged with the post-cooling flow path 101b at a location before the water pump 103. In the embodiment, the water pump 103 is constituted as an electric pump, and drive of the water pump 103 is controlled by the control device 30. The thermostat 105 blocks an inflow of cooling water into the radiator 104 when a temperature Tw of cooling water flowing in the pre-cooling flow path 101a is less than a cooling start temperature Tws determined in advance, and permits an inflow of cooling water flowing in the circulation flow path 101 into the radiator 104 when the temperature Tw of cooling water is equal to or more than the cooling start temperature Tws. It should be noted, however, that the thermostat 105 may gradually permit an inflow of cooling water into the radiator 104 in accordance with a rise in temperature Tw when the temperature Tw of cooling water is equal to or more than the cooling start temperature Tws.

[0033] The fluid temperature adjustment device 10 further includes: a heat exchanger 110 that exchanges heat between cooling water for the engine 12 and a working fluid used by the transaxle 20, that is, the fluid transmission apparatus 23 and the automatic transmission 25; a first flow path 111 branched from the pre-cooling flow path 101a; a second flow path 112 branched from the post-cooling flow path 101b; a third flow path 113 that communicates with a cooling water outlet 110o of the heat exchanger 110 and that is merged with the post-cooling flow path 101b; and a switching valve 120 that selectively communicates one of the first and second flow paths 111 and 112 with a cooling water inlet 110i of the heat exchanger 110 in accordance with a temperature Ta of the working fluid.

[0034] The heat exchanger 110 is incorporated in a working fluid path 114 that guides a working fluid drained from the hydraulic control device 26 to various objects to be lubricated of the fluid transmission apparatus 23 and the automatic transmission 25 disposed in the transaxle case 22. In the embodiment, the heat exchanger 110 is disposed outside the transaxle case 22. The heat exchanger 110 is configured to exchange heat between cooling water that flows into the cooling water inlet 110i via the switching valve 120 from one of the first and second flow paths 111 and 112 and that flows out from the cooling water outlet 110o and a working fluid drained from the hydraulic control device 26 to flow in the working fluid path 114. The first flow path 111 is branched from the pre-cooling flow path 101a at a location downstream of the engine 12 and upstream of the radiator 104 (thermostat 105), and connected to the switching valve 120. Meanwhile, the second flow path 112 is branched from the post-cooling flow path 101 b at a location downstream of the radiator 104 and upstream of the engine 12, and connected to the switching valve 120. Further, the third flow path 113 is merged with the post-cooling flow path 101b at a location downstream of the branched portion between the post-cooling flow path 101b and the second flow path 112 and upstream of the engine 12 (water pump 103).

[0035] The switching valve 120 is constituted as a thermo-valve that automatically selectively communicates between one of the first and second flow paths 111 and 112 and the cooling water inlet 110i of the heat exchanger 110 in accordance with the temperature Ta of the working fluid, and provided together with the heat exchanger 110. FIG. 2 illustrates the switching valve 120 according to the embodiment. As illustrated in the drawing, the switching valve 120 includes: a first input port 120a that communicates with the first flow path 111; a second input port 120b that communicates with the second flow path 112; an output port 120c that communicates with the cooling water inlet 110i of the heat exchanger 110; a spool 121 that moves in the axial direction to selectively communicate between one of the first and second input ports 120a and 120b and the output port 120c; a spring 122 that abuts against one end (upper end in FIG. 2) of the spool 121 in the axial direction and that urges the spool 121 in the axial direction (downward in FIG. 2); a thermally expandable material 123 attached to a distal end portion 121s of the spool 121 on the other end side (lower side in FIG. 2) in the axial direction; a movement restriction member 124 that restricts movement of the thermally expandable material 123 from one end side toward the other end side (lower side in FIG. 2) of the spool 121; and an in-valve working fluid path 125 connected to the working fluid path 114 and formed such that at least a part of the working fluid before heat exchange by the heat exchanger 110 flows inside the in-valve working fluid path 125 and the working fluid contacts the thermally expandable material 123.

[0036] The spool 121 is configured to be able to establish a first communication state (see FIG. 2) in which the first input port 120a and the output port 120c communicate with each other and a second communication state (see FIG. 3) in which the second input port 120b and the output port 120c communicate with each other. The distal end portion 121s of the spool 121 is formed so as to be reduced in diameter from one end side (upper side in FIG. 2) toward the other end side (lower side in FIG. 2) of the spool 121. That is, the outer peripheral surface of the distal end portion 121s is formed to be tapered so as to approach the axis from one end side toward the other end side of the spool 121. The thermally expandable material 123 is formed to be annular from a metal such as aluminum or magnesium or a resin such as rubber, for example, and is expandable or contractible at least in the radial direction of the spool 121 in accordance with the temperature Ta of the working fluid flowing in the in-valve working fluid path 125. The distal end portion 121 s of the spool 121 is inserted through a center hole of the thermally expandable material 123. The movement restriction member 124 is fixed to a valve body of the switching valve 120 so as to abut against an end surface of the thermally expandable material 123 on the lower side (distal end portion 121s side) in FIG. 2.

[0037] In the switching valve 120 configured as discussed above, when the thermally expandable material 123 is contracted at least in the radial direction of the spool 121 in accordance with the temperature Ta of the working fluid, the distal end portion 121s having an outer peripheral surface formed to be tapered is pressed in the radial direction by the thermally expandable material 123, and the spool 121 receives a force directed upward in the axial direction in FIG. 2, that is, a force in the direction opposite to the direction in which the spool 121 is urged by the spring 122, from the thermally expandable material 123. As a result, the spool 121 can be moved upward in FIG. 2 (toward the side opposite to the direction in which the spool 121 is urged by the spring 122) against the urging force of the spring 122 in accordance with contraction of the thermally expandable material 123, and the spool 121 is held at a position at which the force applied from the thermally expandable material 123 to the spool 121 and the urging force of the spring 122 are balanced with each other (state illustrated in FIG. 2). When the thermally expandable material 123 is expanded at least in the radial direction of the spool 121 in accordance with the temperature Ta of the working fluid, on the other hand, the force which presses the distal end portion 121s of the spool 121 in the radial direction is reduced along with the expansion, and therefore the upward force in the axial direction applied from the thermally expandable material 123 to the spool 121 is also reduced. As a result, the spool 121 is permitted to be urged by the spring 122 to be moved downward in the drawing (direction in which the spool 121 is urged by the spring 122), and the spool 121 is held at a position at which the force applied from the thermally expandable material 123 and the urging force of the spring 122 are balanced with each other (state illustrated in FIG. 3).

[0038] In the embodiment, the switching valve 120 is configured such that the thermally expandable material 123 holds the spool 121 in the first communication state illustrated in FIG. 2 against the urging force of the spring 122 when the temperature Ta of the working fluid flowing in the in-valve working fluid path 125 is less than a first temperature Ta1 (e.g. 90.degree.). Consequently, when the temperature Ta of the working fluid is less than the first temperature Ta1, communication between the first input port 120a, that is, the first flow path 111, and the output port 120c, that is, the cooling water inlet 110i of the heat exchanger 110, is allowed. Meanwhile, the switching valve 120 is configured such that the thermally expandable material 123 is gradually expanded in accordance with a rise in temperature of the working fluid to permit movement of the spool 121 in the direction in which the spool 121 is urged by the spring 122 when the temperature Ta of the working fluid flowing in the in-valve working fluid path 125 is higher than the first temperature Ta1, and such that the thermally expandable material 123 holds the spool 121 in the second communication state illustrated in FIG. 3 when the temperature Ta of the working fluid is equal to or more than a second temperature Ta2 that is higher than the first temperature Ta1. Consequently, when the temperature Ta of the working fluid is equal to or more than the second temperature Ta2, communication between the first input port 120a, that is, the first flow path 111, and the output port 120c, that is, the cooling water inlet 110i of the heat exchanger 110, is blocked, and communication between the second input port 120b, that is, the second flow path 112, and the output port 120c, that is, the cooling water inlet 110i of the heat exchanger 110, is allowed. The second temperature Ta2 is determined in accordance with the characteristics of the thermally expandable material 123, and may be a temperature that is slightly higher than the first temperature Ta1, or may be a temperature that is relatively higher than the first temperature Ta1.

[0039] Subsequently, operation of the fluid temperature adjustment device 10 configured as discussed above will be described with reference to FIGS. 4 to 6. When the temperature Tw of cooling water detected by a temperature sensor (not illustrated) is less than a pump drive start temperature Tw1 (e.g. 60.degree. C.) determined in advance, the control device 30 stops operation of the water pump 103. Consequently, circulation of cooling water is stopped to promote warm-up of the engine 12 when the engine 12 should be warmed up immediately such as when the vehicle is started, for example.

[0040] When the temperature Tw of cooling water is equal to or more than the pump drive start temperature Tw1, in contrast, the control device 30 actuates the water pump 103 so that the water pump 103 circulates cooling water in the circulation flow path 101. In this event, in the case where the temperature Tw of cooling water is less than the cooling start temperature Tws discussed above, an inflow of cooling water into the radiator 104 is blocked by the thermostat 105. Therefore, cooling water flows from the pre-cooling flow path 101a into the post-cooling flow path 101b via the bypass flow path 102 as indicated by the solid arrow in FIG. 4, and is pumped again by the water pump 103 to circulate in one direction in the circulation flow path 101 formed in the engine 12.

[0041] In this event, in addition, cooling water flowing in the circulation flow path 101 also flows from the pre-cooling flow path 101a toward the switching valve 120 via the first flow path 111. In general, the temperature Ta of the working fluid in the transaxle 20 is lower than the temperature Tw of cooling water which has not been cooled by the radiator 104 irrespective of the state of the thermostat 105. When the temperature Tw of cooling water is less than the cooling start temperature Tws, the temperature Ta of the working fluid is basically less than the first temperature Ta1. Thus, the thermally expandable material 123 holds the spool 121 in the first communication state illustrated in FIG. 2 against the urging force of the spring 122, which allows communication between the first flow path 111 and the cooling water inlet 110i of the heat exchanger 110. Consequently, cooling water that has flowed from the pre-cooling flow path 101a to the first flow path 111 flows into the cooling water inlet 110i of the heat exchanger 110 via the switching valve 120. As a result, heat can be exchanged in the heat exchanger 110 between cooling water at a relatively high temperature which has not been cooled by the radiator 104 and the working fluid at a relatively low temperature flowing in the working fluid path 114 to immediately raise the temperature of the working fluid using cooling water when the temperature Ta of the working fluid is less than the first temperature Ta1 which is relatively low and the temperature of the working fluid should be raised. Thus, it is possible to suppress a large loss caused in each hydraulic device and object to be lubricated in the transaxle 20, that is, the fluid transmission apparatus 23 and the automatic transmission 25, because of the viscous drag of the working fluid which is at a low temperature and has high viscosity.

[0042] Then, cooling water that has passed through the heat exchanger 110 flows into the post-cooling flow path 101b via the third flow path 113 to be pumped again to the pre-cooling flow path 101a by the water pump 103. By causing cooling water to flow into the post-cooling flow path 101b via the third flow path 113 which is merged with the post-cooling flow path 101b at a location downstream of the branched portion between the post-cooling flow path 101b and the second flow path 112 in this way, it is possible to suppress an inflow of cooling water that has been subjected to heat exchange with the working fluid performed in the heat exchanger 110 into the heat exchanger 110 again via the second flow path 112, which enhances the efficiency of heat exchange between cooling water and the working fluid performed in the heat exchanger 110.

[0043] When the temperature Tw of cooling water is equal to or more than the cooling start temperature Tws, on the other hand, an inflow of cooling water into the radiator 104 is permitted by the thermostat 105. Therefore, cooling water flows from the pre-cooling flow path 101a into the post-cooling flow path 101b via the radiator 104 as indicated by the solid arrow in FIG. 5, and is pumped again to the pre-cooling flow path 101a by the water pump 103. Consequently, cooling water at a relatively high temperature that is equal to or more than the cooling start temperature Tws can be cooled by the radiator 104, and the engine 12 can be cooled using the cooled cooling water. In this event, in the case where the temperature Ta of the working fluid is still less than the first temperature Ta1, the spool 121 of the switching valve 120 establishes the first communication state to allow communication between the first flow path 111 and the cooling water inlet 110i of the heat exchanger 110. Consequently, cooling water flows from the pre-cooling flow path 101a into the cooling water inlet 110i of the heat exchanger 110 via the first flow path 111 and the switching valve 120 as indicated by the solid allow in FIG. 5. As a result, heat can be exchanged in the heat exchanger 110 between cooling water at a relatively high temperature which has not been cooled by the radiator 104 and the working fluid at a relatively low temperature flowing in the working fluid path 114 to immediately raise the temperature of the working fluid using cooling water. Then, cooling water that has passed through the heat exchanger 110 flows into the post-cooling flow path 101b via the third flow path 113 to be pumped again to the pre-cooling flow path 101a by the water pump 103.

[0044] In the case where the temperature Tw of cooling water is equal to or more than the cooling start temperature Tws and the temperature Ta of the working fluid is equal to or more than the first temperature Ta1, meanwhile, the thermally expandable material 123 of the switching valve 120 is gradually expanded as the temperature Ta of the working fluid is raised, and the spool 121 is permitted to be urged by the spring 122 to be moved downward in the drawing (in the direction in which the spool 121 is urged by the spring 122). Then, when the temperature Ta is equal to or more than the second temperature Ta2, the spool 121 of the switching valve 120 establishes the second communication state. Consequently, communication between the first flow path 111 and the cooling water inlet 110i of the heat exchanger 110 is blocked, communication between the second flow path 112 and the cooling water inlet 110i of the heat exchanger 110 is allowed, and cooling water flows from the post-cooling flow path 101b into the cooling water inlet 110i of the heat exchanger 110 via the second flow path 112 and the switching valve 120 as indicated by the solid arrow in FIG. 6. As a result, heat can be exchanged in the heat exchanger 110 between cooling water at a relatively low temperature which has been cooled by the radiator 104 and the working fluid at a relatively high temperature flowing in the working fluid path 114 to immediately lower the temperature of the working fluid using cooling water when the temperature of the working fluid is equal to or more than a relatively high temperature, that is, the second temperature Ta2 which is higher than the first temperature Ta1, and the temperature of the working fluid should be lowered. Thus, it is possible to better suppress a situation in which an oil film on a sliding portion such as each object to be lubricated of the automatic transmission 25 becomes thin because of the high temperature and the low viscosity of the working fluid, as a result of which the sliding portion may not be lubricated and cooled well. Then, cooling water that has passed through the heat exchanger 110 flows into the post-cooling flow path 101b via the third flow path 113 to be pumped again to the pre-cooling flow path 101a by the water pump 103.

[0045] As described above, the fluid temperature adjustment device 10 includes the circulation flow path 101 which circulates cooling water for the engine 12 in one direction between the engine 12 and the radiator 104, the first flow path 111 is branched from the circulation flow path 101 at a location downstream of the engine 12 and upstream of the radiator 104, and the second flow path 112 is branched from the circulation flow path 101 at a location downstream of the radiator 104 and upstream of the engine 12. In addition, the third flow path 113 which communicates with the cooling water outlet 110o of the heat exchanger 110 is merged with the circulation flow path 101 at a location downstream of the radiator 104 and upstream of the engine 12. In the fluid temperature adjustment device 10, the switching valve 120 selectively communicates between one of the first and second flow paths 111 and 112 and the cooling water inlet 110i of the heat exchanger 110. Consequently, heat can be exchanged between cooling water at a relatively high temperature which has not been cooled by the radiator 104 and the working fluid by causing the switching valve 120 to communicate between the first flow path 111 and the cooling water inlet 110i of the heat exchanger 110. On the other hand, heat can be exchanged between cooling water at a relatively low temperature which has been cooled by the radiator 104 and the working fluid by causing the switching valve 120 to communicate between the second flow path 112 and the cooling water inlet 110i of the heat exchanger 110. Thus, with the fluid temperature adjustment device 10, it is possible to adequately adjust the temperature Ta of the working fluid for the automatic transmission 25 using the heat exchanger 110 which exchanges heat between cooling water for the engine 12 and the working fluid.

[0046] In addition, the switching valve 120 selectively communicates between one of the first and second flow paths 112 and the cooling water inlet 110i of the heat exchanger 110 in accordance with the temperature of the working fluid. Consequently, the switching valve 120 can switch to exchange heat between cooling water at a relatively high temperature which has not been cooled by the radiator 104 and the working fluid, and to exchange heat between cooling water at a relatively low temperature which has been cooled by the radiator 104 and the working fluid, in accordance with the temperature of the working fluid. Thus, the temperature of the working fluid can be adjusted further more adequately by the heat exchanger 110 which exchanges heat between cooling water and the working fluid.

[0047] Further, the third flow path 113 is merged with the circulation flow path 101 at a location downstream of the branched portion between the circulation flow path 101 and the second flow path 112 and upstream of the engine 12. Consequently, it is possible to suppress an inflow of cooling water which has been subjected to heat exchange with the working fluid in the heat exchanger 110 again into the heat exchanger 110 via the second flow path 112, which enhances the efficiency of heat exchange between cooling water and the working fluid performed in the heat exchanger 110. It should be noted, however, that the third flow path 113 may be merged with the circulation flow path 101 at a location upstream of the branched portion between the circulation flow path 101 and the second flow path 112.

[0048] In addition, the switching valve 120 communicates between the first flow path 111 and the cooling water inlet 110i of the heat exchanger 110 when the temperature Ta of the working fluid is less than the first temperature Ta1, and communicates between the second flow path 112 and the cooling water inlet 110i of the heat exchanger 110 when the temperature Ta of the working fluid is equal to or more than the second temperature Ta2 which is higher than the first temperature Ta1. Consequently, heat can be exchanged between cooling water at a relatively high temperature which has not been cooled by the radiator 104 and the working fluid by causing the switching valve 120 to communicate between the first flow path 111 and the cooling water inlet 110i of the heat exchanger 110 when the temperature Ta of the working fluid is less than the first temperature Ta1 which is relatively low and the temperature of the working fluid should be raised. Therefore, the temperature of the working fluid can be raised immediately. On the other hand, heat can be exchanged between cooling water at a relatively low temperature which has been cooled by the radiator 104 and the working fluid by causing the switching valve 120 to communicate between the second flow path 112 and the cooling water inlet 110i of the heat exchanger 110 when the temperature of the working fluid is equal to or more than a relatively high temperature, that is, the second temperature which is higher than the first temperature Ta1, and the temperature of the working fluid should be lowered. Therefore, the temperature of the working fluid can be lowered immediately.

[0049] Further, the switching valve 120 includes: the first input port 120a which communicates with the first flow path 111; the second input port 120b which communicates with the second flow path 112; the output port 120c which communicates with the cooling water inlet 110i of the heat exchanger 110; the spool 121 which moves in the axial direction to selectively communicate between one of the first and second input ports 120a and 120b and the output port 120c; the spring 122 which urges the spool 121 in the axial direction; and the thermally expandable material 123 attached to the spool 121, and the thermally expandable material 123 permits the spool 121 to be urged by the spring 122 to be moved, and moves the spool 121 against the urging force of the spring 122, in accordance with the temperature Ta of the working fluid. Consequently, the spool 121 can be automatically moved in the axial direction in accordance with the temperature Ta of the working fluid to selectively communicate between one of the first and second input ports 120a and 120b and the output port 120c, that is, between one of the first and second input ports 120a and 120b and the cooling water inlet 110i of the heat exchanger 110.

[0050] It should be noted, however, that the switching valve 120 may be constituted as an electronically controlled valve (electromagnetic valve) or a hydraulically controlled valve to be controlled by the control device 30 so as to selectively communicate between one of the first and second flow paths 112 and the cooling water inlet 110i of the heat exchanger 110 in accordance with the temperature Ta of the working fluid. In addition, the switching valve 120 may be incorporated inside the heat exchanger 110, and the heat exchanger 110 and the switching valve 120 may be disposed inside the transaxle case 22. Further the water pump 103 may be a mechanical pump driven by power of the engine 12. In this case, when the engine 12 is in operation, the water pump 103 is driven at all times to circulate cooling water in the circulation flow path 101. In order to lower the temperature of the working fluid more immediately, in addition, a cooling device such as an air-cooling cooler may be separately provided at the middle of the second flow path 112.

[0051] Here, the correspondence between the main elements of the embodiment etc. described above and the main elements of the invention described in the "SUMMARY OF THE INVENTION" section will be described. That is, in the embodiment etc. described above, the fluid temperature adjustment device 10 which includes the radiator 104 which cools cooling water for the engine 12 and the heat exchanger 110 which exchanges heat between cooling water and the working fluid for the automatic transmission 25 corresponds to the "fluid temperature adjustment device". The circulation flow path 101 which circulates cooling water in one direction between the engine and the radiator corresponds to the "circulation flow path". The first flow path 111 which is branched from the circulation flow path 101 at a location downstream of the engine 12 and upstream of the radiator 104 corresponds to the "first flow path". The second flow path 112 which is branched from the circulation flow path 101 at a location downstream of the radiator 104 and upstream of the engine 12 corresponds to the "second flow path". The third flow path 113 which communicates with the cooling water outlet 1100 of the heat exchanger 110 and which is merged with the circulation flow path 101 at a location downstream of the radiator 104 and upstream of the engine 12 corresponds to the "third flow path". The switching valve 120 which selectively communicates between one of the first and second flow paths 111 and 112 and the cooling water inlet 110i of the heat exchanger 110 corresponds to the "switching valve". It should be noted, however, that the correspondence between the main elements of the embodiment described above and the main elements of the invention described in the "SUMMARY OF THE INVENTION" section does not limit the elements of the invention described in the "SUMMARY OF THE INVENTION" section, because the embodiment is an example given for the purpose of specifically describing the invention described in the "SUMMARY OF THE INVENTION" section. That is, the embodiment is merely a specific example of the invention described in the "SUMMARY OF THE INVENTION" section, and the invention described in the "SUMMARY OF THE INVENTION" section should be construed on the basis of the description in that section.

[0052] While an embodiment of the present invention has been described above, it is a matter of course that the present invention is not limited to the embodiment described above in any way, and that the present invention may be modified in various ways without departing from the scope and sprit of the present invention.

INDUSTRIAL APPLICABILITY

[0053] The present invention can be utilized in the fluid temperature adjustment device manufacturing industry etc.

Claims

1. A fluid temperature adjustment device that includes a radiator that cools cooling water for an engine and a heat exchanger that exchanges heat between the cooling water and a working fluid for a transmission, the fluid temperature adjustment e device comprising: a circulation flow path that circulates the cooling water in one direction between the engine and the radiator; a first flow path branched from the circulation flow path at a location downstream of the engine and upstream of the radiator; a second flow path branched from the circulation flow path at a location downstream of the radiator and upstream of the engine; a third flow path that communicates with a cooling water outlet of the heat exchanger and that is merged with the circulation flow path at a location downstream of the radiator and upstream of the engine; and a switching valve that selectively communicates between one of the first and second flow paths and a cooling water inlet of the heat exchanger.

2. The fluid temperature adjustment device according to claim 1, wherein the switching valve selectively communicates between one of the first and second flow paths and the cooling water inlet of the heat exchanger in accordance with a temperature of the working fluid.

3. The fluid temperature adjustment device according to claim 2, wherein the third flow path is merged with the circulation flow path at a location downstream of a branched portion between the circulation flow path and the second flow path and upstream of the engine.

4. The fluid temperature adjustment device according to claim 3, wherein the switching valve communicates between the first flow path and the cooling water inlet of the heat exchanger when the temperature of the working fluid is less than a first temperature, and communicates between the second flow path and the cooling water inlet of the heat exchanger when the temperature of the working fluid is equal to or more than a second temperature that is higher than the first temperature.

5. The fluid temperature adjustment device according to claim 4, wherein the switching valve includes a first input port that communicates with the first flow path, a second input port that communicates with the second flow path, an output port that communicates with the cooling water inlet of the heat exchanger, a spool that moves in an axial direction to selectively communicate between one of the first and second input ports and the output port, a spring that urges the spool in the axial direction, and a thermally expandable material attached to the spool; and the thermally expandable material permits the spool to be urged by the spring to be moved, and moves the spool against an urging force of the spring, in accordance with the temperature of the working fluid.

6. The fluid temperature adjustment device according to claim 2, wherein the switching valve communicates between the first flow path and the cooling water inlet of the heat exchanger when the temperature of the working fluid is less than a first temperature, and communicates between the second flow path and the cooling water inlet of the heat exchanger when the temperature of the working fluid is equal to or more than a second temperature that is higher than the first temperature.

7. The fluid temperature adjustment device according to claim 6, wherein the switching valve includes a first input port that communicates with the first flow path, a second input port that communicates with the second flow path, an output port that communicates with the cooling water inlet of the heat exchanger, a spool that moves in an axial direction to selectively communicate between one of the first and second input ports and the output port, a spring that urges the spool in the axial direction, and a thermally expandable material attached to the spool; and the thermally expandable material permits the spool to be urged by the spring to be moved, and moves the spool against an urging force of the spring, in accordance with the temperature of the working fluid.

8. The fluid temperature adjustment device according to claim 1, wherein the third flow path is merged with the circulation flow path at a location downstream of a branched portion between the circulation flow path and the second flow path and upstream of the engine.

9. The fluid temperature adjustment device according to claim 8, wherein the switching valve includes a first input port that communicates with the first flow path, a second input port that communicates with the second flow path, an output port that communicates with the cooling water inlet of the heat exchanger, a spool that moves in an axial direction to selectively communicate between one of the first and second input ports and the output port, a spring that urges the spool in the axial direction, and a thermally expandable material attached to the spool; and the thermally expandable material permits the spool to be urged by the spring to be moved, and moves the spool against an urging force of the spring, in accordance with the temperature of the working fluid.