JP2012218668A - Hydraulic pressure feeder of driving force distributing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce pressure in an oil passage without damaging parts when an on/off-valve installed at oil passage malfunctions to abnormally increase the oil pressure in the oil passage in a hydraulic pressure feeder provided with a sealed-type oil pressure circuit that seals operating oil in the oil passage to a piston chamber of a clutch.SOLUTION: This device is provided with a relief valve 70 which releases the oil pressure if the oil pressure of the operating oil sealed in the oil passage 49 between a check valve 39 and the piston chamber 15 is equal to or higher than a predetermined threshold P0. If it is determined that a fixing malfunction has occurred at a solenoid valve 43 provided at the oil passage, that is, a sealing oil passage 49 between the check valve 39 and the piston chamber 15 (upon hydraulic sealing malfunction of the piston chamber), an oil pump 35 is driven to generate oil pressure in the oil passage 49 that is higher than normally-adjusted pressure and forcibly actuate the relief valve 70 so as to discharge the operating oil of the oil passage 49.

Description

  The present invention supplies a hydraulic pressure for generating a clutch engagement pressure of a driving force distribution device in a driving force distribution device for a four-wheel drive vehicle that distributes driving force from a prime mover to main driving wheels and auxiliary driving wheels. The present invention relates to a hydraulic pressure supply device.

  2. Description of the Related Art Conventionally, there are four-wheel drive vehicles equipped with a driving force distribution device for distributing driving force generated by a driving source such as an engine to main driving wheels and auxiliary driving wheels. In this type of four-wheel drive vehicle, for example, when the front wheels are main drive wheels and the rear wheels are sub drive wheels, the driving force generated by the drive source is transmitted to the front wheels via the front drive shaft and the front differential. And transmitted to a driving force distribution device having a multi-plate clutch through a propeller shaft. Then, the engagement pressure of the driving force distribution device is controlled by supplying hydraulic oil of a predetermined pressure from the hydraulic pressure supply device to the driving force distribution device. As a result, the driving force of the driving source is transmitted to the rear wheels at a predetermined distribution ratio.

  Conventionally, as a hydraulic pressure supply device for supplying hydraulic pressure to the multi-plate clutch of the driving force distribution device, there are hydraulic pressure supply devices disclosed in Patent Documents 1 and 2. The hydraulic pressure supply devices disclosed in Patent Documents 1 and 2 include an electric oil pump that supplies hydraulic oil to a piston chamber that generates hydraulic pressure for pressing a multi-plate clutch, and the electric oil pump and the piston chamber are connected by a hydraulic pressure supply path. This is the configuration. And in the hydraulic pressure supply apparatus of patent document 1, the rotation speed of an electric pump is controlled so that the discharge value of an electric pump becomes the required operating pressure of a hydraulic clutch. Further, in the hydraulic pressure supply device described in Patent Document 2, the motor drive of the electric pump is controlled so as to generate a hydraulic pressure corresponding to the distribution ratio of the driving force.

  Further, as a configuration other than those shown in Patent Documents 1 and 2, by installing a valve capable of enclosing hydraulic oil such as a check valve or a solenoid valve in the oil passage between the electric oil pump and the piston chamber, There is a hydraulic pressure supply device configured to enclose hydraulic oil in a communicating oil passage. In this hydraulic pressure supply device, an open / close valve such as a solenoid valve for discharging hydraulic oil in the oil passage is installed in the oil passage between the sealing valve and the piston chamber. Then, by driving the electric oil pump with the on-off valve closed, the hydraulic oil is pumped to the oil passage leading from the sealed valve to the piston chamber to pressurize the piston chamber. When the piston chamber reaches the pressure required for clutch engagement, the electric oil pump is stopped. Thereby, the clutch is fastened by the pressure of the oil passage that leads from the sealing valve to the piston chamber. On the other hand, when releasing the clutch, by opening the on-off valve, the hydraulic oil in the oil passage leading to the oil chamber is released from the enclosed valve. As a result, the piston chamber is depressurized to reduce the clutch engagement force.

  By the way, in the hydraulic pressure supply apparatus having the above-described configuration, the piston chamber is decompressed by discharging the hydraulic oil in the oil passage by opening an on-off valve such as a solenoid valve. However, if the on-off valve malfunctions due to clogging of foreign matter (contamination) and does not open normally, the piston chamber cannot be decompressed and the clutch may not be released. Conventionally, when the oil pressure failure in the piston chamber fails, an appropriate fail-safe action cannot be taken, and the driving state of the vehicle remains in the four-wheel driving state, which may cause the vehicle to become unstable. There was a problem that there was.

  In addition, a forced discharge valve is provided in the oil passage that leads from the sealing valve to the piston chamber as described above to discharge the hydraulic oil when the oil pressure or temperature of the oil passage rises beyond the allowable range. Yes. However, since the conventional forced discharge valve is not intended to be operated by a normal hydraulic control operation, it is designed to be damaged with the operation. Therefore, in the unlikely event that this forced discharge valve is activated, it is necessary to disassemble / repair the hydraulic pressure supply device and replace the parts of the forced discharge valve.

Japanese Patent Laid-Open No. 2004-19768 JP 2001-206092 A

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide a hydraulic supply device including an encapsulated hydraulic circuit that encloses hydraulic oil in an oil passage leading to a piston chamber for fastening a clutch. Providing a hydraulic power supply device for a driving force distribution device that can reduce the pressure of oil passages without damaging parts when a malfunction such as a failure occurs in an on-off valve installed in the oil passage and the oil pressure rises abnormally There is to do.

  The present invention for solving the above problems includes a driving force transmission path (20) for transmitting the driving force from the driving source (3) to the main driving wheels (W1, W2) and the auxiliary driving wheels (W3, W4). A four-wheel drive vehicle comprising: a drive force distribution device (10) disposed between the drive source (3) and the auxiliary drive wheels (W3, W4) in the drive force transmission path (20); In 1), the driving force distribution device (10) hydraulically applies a plurality of stacked friction materials (13) and a piston (12) that presses and engages the friction materials (13) in the stacking direction. And an oil pump (35) driven by a motor (37) for supplying hydraulic oil to the piston chamber (15), and a piston chamber (15) for generating hydraulic oil. An oil passage leading from the oil pump (35) to the piston chamber (15) 49) a hydraulic oil sealing valve (39) for sealing the hydraulic oil, and opening and closing for opening and closing the oil passage (49) between the hydraulic oil sealing valve (39) and the piston chamber (15). In the hydraulic pressure supply device (60) of the driving force distribution device having a hydraulic circuit (30) having a valve (43), the oil between the hydraulic oil sealing valve (39) and the piston chamber (15) When the hydraulic pressure of the hydraulic oil sealed in the passage (49) reaches a predetermined threshold (P0) or more, a relief valve (70) for releasing the hydraulic pressure is provided, and the relief valve (70) is connected to the oil pump (35). The first inflow port (81a) and the second inflow port (81b) formed by branching the oil passage (49) through which the working oil flows, and the pressure from the working oil in the first inflow port (81a) are received. The first pressure receiving surface (76a) and the second inflow port (8 a closed position for closing the oil passage (49) by being pressed by the valve spool (76), and a valve spool (76) having a second pressure receiving surface (76b) for receiving pressure from the hydraulic oil of b). A valve body (79) that moves to an open position that opens the oil passage (49), and a biasing means (85) that biases the valve spool (76) away from the valve body (79), The area of the first pressure receiving surface (76a) of the valve spool (76) and the area of the second pressure receiving surface (76b) are different from each other, so that the oil pressure of the oil passage (49) is When the valve spool (76) moves against the urging force of the urging means (85) when the threshold (P0) or more is reached, the valve element (79) is pressed and the oil passage (49) is configured to be opened.

  According to the hydraulic pressure supply device of the driving force distribution device according to the present invention, a malfunction such as a failure occurs in the on-off valve installed in the oil passage between the hydraulic oil sealing valve and the piston chamber, and the oil pressure in the oil passage rises abnormally. In this case, the oil pressure in the oil passage can be released by opening the relief valve. As a result, the oil passage can be depressurized without damage to the parts as in the case of a conventional emergency discharge valve. Therefore, even if the relief valve is activated, the maintenance work of the hydraulic pressure supply device is reduced. In addition, the relief valve has a structure that is not damaged even when it is operated, so that the parts can be used continuously. In addition, since the relief valve opens in conjunction with the oil pressure in the oil passage, it is possible to ensure quick operation responsiveness when the oil pressure in the oil passage increases. Furthermore, since the relief valve according to the present invention also serves as an emergency discharge valve that has been conventionally installed in the oil passage, it does not increase the number of parts of the hydraulic supply device and complicate the structure. In addition, the relief valve of the present invention is a so-called control type valve that operates according to the oil pressure of the oil passage, so that the accuracy of the operating hydraulic pressure is higher than that of a conventional emergency discharge valve that breaks during operation. There are also advantages.

  And although said relief valve is a valve of the simple structure of pressing a valve body and opening an oil path by driving a valve spool, it is in the 1st pressure receiving surface and 2nd pressure receiving surface of a valve spool. Since the valve spool is configured to be driven according to the change in the load of the hydraulic oil, when the oil pressure in the oil passage rises abnormally, the oil pressure can be reliably released.

  Further, the hydraulic pressure supply device of the driving force distribution device according to the present invention includes a control means (50) for controlling driving of the oil pump (35) by the motor (37) and opening / closing of the on-off valve (43), An oil pressure detecting means (45) for detecting the oil pressure of the oil passage (49), and the control means (50) passes a predetermined time (T0) after issuing an open command to the on-off valve (43). Even if the oil pressure of the oil passage (49) detected by the oil pressure detecting means (45) does not fall below a predetermined pressure, the oil pump (35) is driven to reduce the pressure of the oil passage (49). Control forcibly increasing the threshold value (P0) may be performed.

In this configuration, when it is determined that an on-off valve such as a solenoid valve provided in the oil passage (filled oil passage) between the hydraulic oil filling valve and the piston chamber has been closed in the closed state (piston chamber hydraulic filling) When a failure occurs), the relief valve is forcibly operated by generating a hydraulic pressure higher than the normal pressure regulation so that the hydraulic oil sealed in the oil passage can be discharged. According to this, since it is possible to operate the relief valve reliably when it is determined that a failure has occurred in the on-off valve, the oil pressure in the oil passage can be released. In addition, the relief valve is operated by raising the oil pressure in the oil passage by a simple procedure of closing the on-off valve and driving the oil pump, so there is no need for complicated structure and control means, and normal hydraulic control of the piston chamber The relief valve can be reliably operated with the same simple configuration and control as in the case of carrying out.
In addition, the reference code | symbol described in the parenthesis above has illustrated the code | symbol attached | subjected to the corresponding component in embodiment mentioned later for reference.

  According to the hydraulic pressure supply device of the driving force distribution device according to the present invention, in the hydraulic pressure supply device including an enclosed hydraulic circuit that encloses hydraulic oil in an oil passage leading to a piston chamber for fastening a clutch, When the hydraulic pressure rises abnormally due to a failure such as a failure in the on-off valve installed in, the oil passage can be decompressed without damaging the parts.

It is a figure showing a schematic structure of a four-wheel drive vehicle provided with a hydraulic pressure supply device of a driving force distribution device concerning an embodiment of the present invention. It is a figure which shows the hydraulic circuit of a hydraulic supply apparatus. It is a sectional side view which shows the detailed structure of a relief valve. It is a figure for demonstrating operation | movement of a relief valve, (a) is a figure which shows the state which the relief valve does not act | operate at normal time, (b) shows the state which the relief valve act | operated at the time of failure of a solenoid valve FIG. It is a flowchart for demonstrating the control procedure of the hydraulic pressure supply apparatus at the time of operating a relief valve. 6 is a timing chart showing changes in oil pressure (actual oil pressure), motor (oil pump) operation state, and solenoid valve open / closed state before and after the relief valve is opened.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of a four-wheel drive vehicle including a hydraulic pressure supply device for a driving force distribution device according to an embodiment of the present invention. A four-wheel drive vehicle 1 shown in the figure has an engine (drive source) 3 mounted horizontally in the front portion of the vehicle, an automatic transmission 4 installed integrally with the engine 3, and a driving force from the engine 3. A driving force transmission path 20 for transmitting to the front wheels W1, W2 and the rear wheels W3, W4 is provided.

  The output shaft (not shown) of the engine 3 includes an automatic transmission 4, a front differential (hereinafter referred to as "front differential") 5, left and right front drive shafts 6 and 6, and left and right front wheels W1 as main drive wheels. , W2. Further, the output shaft of the engine 3 is an auxiliary drive wheel via an automatic transmission 4, a front differential 5, a propeller shaft 7, a rear differential unit (hereinafter referred to as “rear differential unit”) 8, and left and right rear drive shafts 9, 9. It is connected to certain left and right rear wheels W3, W4.

  The rear differential unit 8 is connected to a rear differential (hereinafter referred to as “rear differential”) 19 for distributing driving force to the left and right rear drive shafts 9 and 9 and a driving force transmission path from the propeller shaft 7 to the rear differential 19. A front-rear torque distribution clutch 10 for cutting is provided. The front-rear torque distributing clutch 10 is a hydraulic clutch and is a driving force distribution device for controlling the driving force distributed to the rear wheels W3, W4 in the driving force transmission path 20. In addition, a hydraulic pressure supply device 60 including a hydraulic circuit 30 for supplying hydraulic oil to the front-rear torque distribution clutch 10 and a 4WD • ECU 50 as a control means for controlling the hydraulic pressure supplied by the hydraulic circuit 30 is installed. ing. The 4WD • ECU 50 is configured by a microcomputer or the like.

  The 4WD • ECU (hereinafter simply referred to as “ECU”) 50 controls the hydraulic pressure supplied by the hydraulic circuit 30 so that the front and rear torque distribution clutch (hereinafter simply referred to as “clutch”) 10 causes the rear wheels W3 and W4. Control the driving force distributed to Thus, drive control is performed with the front wheels W1 and W2 as main drive wheels and the rear wheels W3 and W4 as auxiliary drive wheels.

  That is, the ECU 50 detects the driving force distributed to the rear wheels W3 and W4 and the hydraulic pressure supply amount to the clutch 10 corresponding thereto based on detection by various detection means (not shown) for detecting the traveling state of the vehicle. And a drive signal based on the calculation result is output to the clutch 10. Thus, when the clutch 10 is released (disconnected), the rotation of the propeller shaft 7 is not transmitted to the rear differential 19 side, and all the torque of the engine 3 is transmitted to the front wheels W1 and W2, thereby driving the front wheels (2WD). ) State. On the other hand, when the clutch 10 is connected, the rotation of the propeller shaft 7 is transmitted to the rear differential 19 so that the torque of the engine 3 is distributed to both the front wheels W1 and W2 and the rear wheels W3 and W4. It becomes a drive (4WD) state. At this time, the driving force distributed to the rear wheels W3 and W4 is controlled by appropriately controlling the fastening force of the clutch 10.

  FIG. 2 is a hydraulic circuit diagram showing a detailed configuration of the hydraulic circuit 30. The hydraulic circuit 30 shown in FIG. 1 includes an oil pump 35 that sucks and feeds hydraulic oil stored in the oil tank 31 via a strainer 33, a motor 37 that drives the oil pump 35, and an oil pump 35 to the clutch 10. And an oil passage 40 communicating with the piston chamber 15.

  The clutch 10 includes a cylinder housing 11 and a piston 12 that presses the plurality of friction materials 13 stacked by moving forward and backward in the cylinder housing 11. A piston chamber 15 into which hydraulic oil is introduced between the piston 12 and the piston 12 is defined in the cylinder housing 11. The piston 12 is disposed to face one end of the plurality of friction materials 13 in the stacking direction. Accordingly, the piston 10 presses the friction material 13 in the stacking direction by the hydraulic pressure of the hydraulic oil supplied to the piston chamber 15 so that the clutch 10 is engaged with a predetermined engagement pressure.

  A check valve 39, a relief valve 70, a solenoid valve (open / close valve) 43, and a hydraulic sensor 45 are installed in this order in the oil passage 40 that communicates from the oil pump 35 to the piston chamber 15. The check valve 39 circulates hydraulic oil from the oil pump 35 side toward the piston chamber 15 side, but is configured to prevent the hydraulic oil from flowing in the opposite direction. Thereby, the hydraulic oil sent to the downstream side of the check valve 39 by the drive of the oil pump 35 is referred to as an oil passage (hereinafter referred to as “enclosed oil passage”) between the check valve 39 and the piston chamber 15. Can be contained in 49). An enclosed hydraulic circuit 30 is configured by the oil passage 49 provided with the check valve 39 and the oil pump 35. In the present embodiment, the check valve 39 is a hydraulic oil sealing valve for sealing hydraulic oil in an oil passage 49 that leads from the oil pump 35 to the piston chamber 15.

  The relief valve 70 opens when the pressure in the oil passage 49 between the check valve 39 and the piston chamber 15 exceeds a predetermined threshold (threshold P0 described later) and rises abnormally, thereby discharging hydraulic oil. This is a valve configured to release the oil pressure of the oil passage 49. The hydraulic oil discharged from the relief valve 70 is returned to the oil tank 31 through the oil passage 41. The detailed configuration of the relief valve 70 will be described later. The solenoid valve 43 is an on / off type on-off valve, and can control the opening and closing of the oil passage 49 by PWM control (duty control) based on a command from the ECU 50. Thereby, the hydraulic pressure of the piston chamber 15 can be controlled. The hydraulic oil discharged from the oil passage 49 when the solenoid valve 43 is opened is returned to the oil tank 31. The oil pressure sensor 45 is oil pressure detecting means for detecting the oil pressure of the oil passage 49 and the piston chamber 15, and the detected value is sent to the ECU 50. The piston chamber 15 communicates with the accumulator 18. The accumulator 18 has a function of suppressing a change in hydraulic pressure in the piston chamber 15 and the oil passage 49 at the time of holding the hydraulic pressure described later. Further, an oil temperature sensor 47 for detecting the temperature of the hydraulic oil is provided in the oil tank 31. The detection value of the oil temperature sensor 47 is sent to the ECU 50.

  Next, the configuration of the relief valve 70 will be described. FIG. 3 is a side sectional view showing a detailed configuration of the relief valve 70. In the following description, the term “up” or “down” refers to “up” or “down” in the state shown in FIG. The relief valve 70 shown in the figure is installed between a piston housing 71 and a pump body 72 and a pump cover 73 that are installed on the lower side thereof. The piston housing 71, the pump body 72, and the pump cover 73 are all members that constitute a part of the casing of the driving force distribution device including the hydraulic pressure supply device 60. The relief valve 70 includes a spool housing 74 installed in the piston housing 71, a spool chamber 75 formed from the inside of the spool housing 74 to the inside of the pump body 72, a valve spool 76 installed in the spool chamber 75, And a relief ball (valve element) 79 driven by the valve spool 76.

  An oil passage 49 (see FIG. 2) communicating from the oil pump 35 to the relief valve 70 is bifurcated between the relief valves 70 (the branch portion is not shown), one of which is provided in the piston housing 71. The other inflow port 81a communicates with a second inflow port 81b provided between the pump body 72 and the pump cover 73. On the other hand, an outflow port 81 c provided in the piston housing 71 communicates with an oil passage 49 communicating with the piston chamber 15 from the relief valve 70. An emergency discharge port 81 d provided at the upper end of the piston housing 71 communicates with an oil passage 41 (see FIG. 2) that leads from the relief valve 70 to the oil tank 31.

  Further, the spool housing 74 has a first inflow port 74a communicating with the first inflow port 81a and the spool chamber 75, an outflow port 74c communicating with the outflow port 81c and the spool chamber 75, an emergency discharge port 81d, and the spool chamber 75. Is provided with an emergency discharge port 74d. The pump body 72 is provided with a second inflow port 72 b that communicates the second inflow port 81 b and the spool chamber 75.

  The valve spool 76 is a member having a substantially cylindrical outer shape, and has a double structure of an inner cylinder 77 and an outer cylinder 78. Between the inner cylinder 77 and the outer cylinder 78, a first coil spring 85 described later is provided. A spring engagement groove 76c for engaging one end is formed. The spool chamber 75 is formed of a concave portion provided from the spool housing 74 to the pump body 72 and having a substantially cylindrical inner peripheral surface with the vertical direction as an axial direction. The valve spool 76 disposed in the spool chamber 75 has a shaft It is slidable (moving forward and backward) along the direction. The reason why the valve spool 76 has a double structure of the inner cylinder 77 and the outer cylinder 78 is to provide a spring engagement groove 76c having a large depth therebetween. For this reason, the valve spool 76 does not necessarily have to be constituted by the two parts of the inner cylinder 77 and the outer cylinder 78 as in the present embodiment as long as the spring engagement groove 76c can be provided. It may be.

  An O-ring (seal member) 83 for sealing the gap between the spool housing 74 and the piston housing 71 installed in the piston housing 71 is installed. Further, an O-ring (seal member) 84 for sealing the gap between the outer peripheral surface of the valve spool 76 and the inner peripheral surface of the pump body 72 is installed.

  A first coil spring (biasing means) 85 is installed between the spring engagement groove 76c of the valve spool 76 and the inner wall (upper wall) of the spool chamber 75 opposed thereto. The valve spool 76 is urged toward the lower end side (second inflow port 72 b side) in the spool chamber 75 by the elastic force of the first coil spring 85. In this state, the second inlet 72b is blocked by the lower end surface 76b of the valve spool 76. Further, the valve spool 76 is retracted below the spool chamber 75 in the spool housing 74. Accordingly, the first inflow port 74a (first inflow port 81a) and the outflow port 74c (outflow port 81c) are in communication with each other through the spool chamber 75.

  A ball housing chamber 87 is formed between the emergency discharge port 81d and the emergency discharge port 74d in the piston housing 71. A relief ball (valve element) 79 for closing the emergency discharge port 74d is installed in the ball housing chamber 87. A second coil spring 86 is installed between the upper portion of the relief ball 79 and the inner wall (upper wall) of the ball housing chamber 87 facing it. On the other hand, an emergency discharge port 74 d of the spool housing 74 is provided with a valve seat portion 89 for seating the relief ball 79. The relief ball 79 is urged toward the lower end side (emergency discharge port 74 d side) in the ball housing chamber 87 by the elastic force of the second coil spring 86. As a result, the relief ball 79 is seated on the valve seat portion 89, so that the emergency discharge port 74 d is blocked by the relief ball 79.

  The outer cylinder 78 of the valve spool 76 has an upper end surface (first pressure receiving surface) 76a that receives pressure from the hydraulic fluid of the first inflow port 81a and a lower end surface that receives pressure from the hydraulic fluid of the second inflow port 81b ( Second pressure receiving surface) 76b. The upper end surface 76a and the lower end surface 76b are set to have different areas. Thereby, the resultant force of the load received by the upper end surface 76a from the hydraulic oil of the first inflow port 81a and the urging force of the first coil spring 85 acts on the valve spool 76 from the upper side, and the hydraulic oil of the second inflow port 81b. When the load received by the lower end surface 76b from the lower side acts on the lower side, it moves (drives) in the vertical direction according to the magnitude relationship.

  In addition, a protruding pressing portion 76 d protruding upward is formed at the upper end of the inner cylinder 77 of the valve spool 76. The outer diameter of the pressing portion 76d is smaller than the inner diameter of the emergency discharge port 74d. As a result, the pressing portion 76d inserted into the emergency discharge port 74d presses the lower end of the relief ball 79 in a state where the valve spool 76 is fully moved up in the spool chamber 75, whereby the second coil spring 86 is attached. The relief ball 79 is lifted against the force. As a result, the relief ball 79 is separated from the valve seat 89 and the emergency discharge port 74d is opened.

  Further, the first inflow port 74 a and the outflow port 74 c provided in the spool housing 74 are arranged at positions facing each other on both sides of the spool chamber 75. The outlet 74c is set to have a larger opening height than the first inlet 74a. As a result, in the state where the valve spool 76 is fully moved upward in the spool chamber 75, the first inflow port 74a is completely blocked by the valve spool 76, while the outflow port 74c is a part thereof. Will be opened.

  Next, the operation of the relief valve 70 configured as described above will be described. 4A and 4B are diagrams for explaining the operation of the relief valve 70. FIG. 4A is a diagram showing a state in which the relief valve 70 is not operating normally, and FIG. 4B is a diagram showing a relief when the solenoid valve 43 fails. It is a figure which shows the state which the valve 70 act | operated. The hydraulic oil sent from the oil pump 35 to the oil passage 49 flows into the relief valve 70. This hydraulic oil flows into the relief valve 70 from both the first inflow port 81a and the second inflow port 81b. In the relief valve 70, as described above, the load received by the upper end surface 76a from the hydraulic fluid of the first inlet port 81a (first inlet 74a) and the hydraulic fluid of the second inlet port 81b (second inlet 72b). The valve spool 76 in the spool chamber 75 moves according to the balance with the load received by the lower end surface 76b.

  Specifically, when the hydraulic pressure of the hydraulic oil in the oil passage 49 is lower than a predetermined threshold (threshold value P0 described later), the load applied to the lower end surface 76b of the valve spool 76 by the hydraulic oil in the second inlet 72b is The resultant force between the load applied to the upper end surface 76a of the valve spool 76 and the urging force of the first coil spring 85 by the hydraulic oil at the first inflow port 74a is set to be larger. On the other hand, when the hydraulic pressure of the hydraulic oil in the oil passage 49 becomes higher than the threshold value P0, the load applied to the lower end surface 76b of the valve spool 76 by the hydraulic oil in the second inlet 72b is greater in the first inlet 74a. It is set to be larger than the resultant force of the load applied to the upper end surface 76 a of the valve spool 76 by the hydraulic oil and the urging force of the first coil spring 85.

  Accordingly, when the oil pressure in the oil passage 49 is lower than the threshold value P0, the valve spool 76 is positioned at the lower end of the spool chamber 75 as shown in FIG. Thus, the second inflow port 81b (second inflow port 72b) is blocked, and the first inflow port 81a (first inflow port 74a) and the outflow port 81c (outflow port 74c) block the spool chamber 75. Communicated through. The relief ball 79 is seated on the valve seat 89, and the emergency discharge port 81d (emergency discharge port 74d) is closed. Accordingly, the hydraulic oil in the oil passage 49 is not discharged from the relief valve 70.

  On the other hand, when the oil pressure in the oil passage 49 becomes higher than the threshold value P0, the valve spool 76 moves toward the upper end side of the spool chamber 75 against the urging force of the first coil spring 85 as shown in FIG. Moving. Thereby, the valve spool 76 closes the first inflow port 81a (first inflow port 74a). The second inflow port 81b (second inflow port 72b) continues to be closed. On the other hand, the outflow port 81c (outlet 74c) is partially blocked by the valve spool 76, but a part thereof remains open. Further, the relief ball 79 is pushed up by the pressing portion 76 d of the valve spool 76 moved to the upper end side of the spool chamber 75, whereby the relief ball 79 is separated from the valve seat portion 89. Thereby, the emergency discharge port 81d (emergency discharge port 74d) is opened. Accordingly, the outflow port 81 c and the emergency discharge port 81 d communicate with each other via the spool chamber 75. As a result, the hydraulic oil sealed in the oil passage 49 is discharged from the emergency discharge port 81 d of the relief valve 70 to the oil tank 31. Accordingly, the oil pressure in the oil passage 49 is reduced.

  When the hydraulic oil in the oil passage 49 decreases due to the hydraulic oil being discharged through the relief valve 70, the valve spool 76 is lowered again by the urging force of the first coil spring 85, and FIG. Return to the state shown in. As a result, the emergency discharge port 81d (emergency discharge port 74d) is closed to the original state.

  Next, a procedure for controlling the hydraulic pressure of the hydraulic circuit 30 when the relief valve 70 operates will be described. FIG. 5 is a flowchart for explaining the control procedure. FIG. 6 is a timing chart showing changes in the oil pressure (actual oil pressure) of the oil passage 49, the operation state of the motor 37 (oil pump 35), and the open / close state of the solenoid valve 43 when the relief valve 70 is opened. First, the control procedure will be described with reference to the flowchart of FIG. The ECU 50 determines whether or not a failure (excessive hydraulic pressure failure) has occurred in the solenoid valve 43 in a state where hydraulic oil is sealed in the oil passage 49 and hydraulic pressure is generated in the piston chamber 15 (step ST1). The failure of the solenoid valve 43 here is an excessive hydraulic failure that occurs when the solenoid valve 43 is stuck in a closed state due to blockage of foreign matter (contamination). This excessive hydraulic pressure failure is determined based on whether or not an appropriate decrease in hydraulic pressure is observed when an opening command for the solenoid valve 43 is issued, as will be described later. As a result, if an excessive hydraulic failure has not occurred (NO), the process is terminated, and if an excessive hydraulic failure has occurred (YES), that is, if the hydraulic pressure in the oil passage 49 exceeds the threshold value P0, The motor 37 and the oil pump 35 are activated to supply hydraulic oil to the oil passage 49, and the pressure in the oil passage 49 is increased (step ST2). Thereafter, it is determined whether or not a preset time (set time T0) has elapsed (step ST3). The elapse of the set time T0 here is determined by the added value of the timer. As a result, if the set time T0 has not elapsed (NO), a timer is added (step ST4). On the other hand, if the set time T0 has elapsed (YES), the motor 37 and the oil pump 35 are stopped (step ST5). Thereafter, the timer is initialized (step ST6), and the process is terminated.

  Next, the procedure of the control will be described with reference to the timing chart of FIG. In this control, in a state where the solenoid valve 43 is closed in advance and the oil passage 49 is sealed, the oil pump 35 (motor 37) is started at time T1 to start pressurization of the oil passage 49. As a result, the hydraulic pressure of the hydraulic oil in the oil passage 49 increases. Thereafter, the oil pump 35 (motor 37) is stopped at time T2 to complete the pressurization of the oil passage 49. Thereafter, for a while, the state where the hydraulic pressure of the hydraulic oil sealed in the oil passage 49 is maintained at a substantially constant pressure continues. Then, an opening command is issued to the solenoid valve 43 at time T3. At this time, if the solenoid valve 43 is functioning normally without an abnormality of the fixing failure, the hydraulic oil in the oil passage 49 is discharged by opening the solenoid valve 43. Thereafter, as shown by the dotted line in FIG. The hydraulic pressure of 15 decreases. On the other hand, if the solenoid valve 43 is not properly opened due to an abnormality in the fixing failure, the hydraulic oil in the oil passage 49 cannot be discharged through the solenoid valve 43. As shown by the solid line in the figure, the hydraulic pressure in the piston chamber 15 is maintained high without being lowered. In this way, when the decrease in hydraulic pressure is not seen despite the solenoid valve 43 opening command being issued, the system waits for a predetermined waiting time (set time T0) to elapse, and then at time T4. Then, an excessive hydraulic failure is determined by detecting the failure. At that time, the oil pump 35 (motor 37) is activated to feed hydraulic oil into the oil passage 49, thereby further pressurizing the oil passage 49. The oil pressure in the oil passage 49 increases due to the pressurization by the oil pump 35, and the oil pressure exceeds the threshold value P0 for opening the relief valve 70 at time T5. As a result, the emergency discharge port 81 d of the relief valve 70 is opened, and the hydraulic oil in the oil passage 49 is discharged through the relief valve 70. Further, at time T5, the oil pump 35 (motor 37) is stopped and the pressurization of the oil passage 49 is completed, and thereafter, the hydraulic oil in the oil passage 49 is discharged from the emergency discharge port 81d of the relief valve 70. As a result, the oil pressure in the oil passage 49 decreases.

  As described above, the relief valve 70 provided in the hydraulic pressure supply device 60 according to the present embodiment has a difference in the pressure receiving area between the upper end surface 76a and the lower end surface 76b of the valve spool 76, so Thus, the valve spool 76 is moved. As a result, even when the relief valve 70 has a simple configuration, when the oil pressure in the oil passage 49 is abnormally increased, the oil pressure can be reliably released.

  Further, the relief valve 70 of the present embodiment employs a structure in which the spool housing 74 and the valve spool 76 are sandwiched and installed between the laminated piston housing 71 and the pump body 72 and the pump cover 73. This eliminates the need for separate parts and the like for fixing the spool housing 74 and the valve spool 76, and thus can reduce the number of parts and simplify the configuration. The relief valve 70 is a common part with the existing parts used for the emergency discharge valve of the conventional hydraulic circuit, and includes a pump cover 73, a pump body 72, a piston housing 71, a relief ball 79, and a coil for the relief ball. A spring (second coil spring) 86 is provided. Therefore, when replacing the conventional emergency discharge valve with the relief valve 70 of the present embodiment, fewer parts are newly installed. Thereby, the hydraulic pressure supply device 60 including the relief valve 70 can be configured without increasing the number of new parts and the total number of parts.

  In addition, the hydraulic pressure supply device 60 of the present embodiment includes an enclosed hydraulic circuit 30 that encloses hydraulic oil in an oil passage 49 that communicates with the piston chamber 15 for fastening the clutch 10, and includes a check valve 39 and a piston chamber. 15 is provided with a relief valve 70 that releases the hydraulic pressure when the hydraulic pressure of the hydraulic oil sealed in the oil path 49 between the hydraulic pressure and the hydraulic pressure is greater than or equal to the threshold value P0. Even when a malfunction such as a sticking failure occurs and the oil pressure in the oil passage 49 rises abnormally, the oil pressure in the oil passage 49 can be released by the relief valve 70. Accordingly, the oil passage 49 can be depressurized without damage to parts such as the emergency discharge valve having the conventional structure. Therefore, the maintenance labor of the hydraulic pressure supply device 60 is reduced. Even if the relief valve 70 is operated, the parts can be used continuously. Further, since the relief valve 70 is opened in conjunction with the oil pressure in the oil passage 49, the operation responsiveness when the oil pressure in the oil passage 49 increases is fast. Furthermore, the relief valve 70 of the present embodiment also serves as an emergency discharge valve that has been conventionally installed in the oil passage 49, so that it is not necessary to increase the number of parts of the hydraulic supply device 60 and to complicate the structure. . In addition, as compared with the emergency discharge valve having a conventional structure that is damaged during operation, the relief valve 70 of the present embodiment is a so-called control type valve that operates according to the oil pressure of the oil passage 49. There is also an advantage that is high.

  The relief valve 70 includes a first inflow port 81a and a second inflow port 81b formed by branching an oil passage 49 through which the working oil from the oil pump 35 flows, and the working oil from the working oil in the first inflow port 81a. A valve spool 76 having an upper end surface (first pressure receiving surface) 76a that receives pressure and a lower end surface (second pressure receiving surface) 76b that receives pressure from the hydraulic fluid of the second inflow port 81b, and is pressed by the valve spool 76. Thus, a relief ball (valve element) 79 that moves from a closed position that closes the oil passage 49 to an open position that opens the oil passage 49, and the first coil spring that biases the valve spool 76 away from the relief ball 79. 85. The area of the upper end surface 76a and the area of the lower end surface 76b of the valve spool 76 are different from each other, so that when the oil pressure in the oil passage 49 becomes equal to or greater than the threshold value P0, the valve spool 76 has the first coil spring 85. By moving against the urging force, the relief ball 79 is pressed and the oil passage 49 is opened. Thus, although the relief valve 70 has a simple configuration in which the valve spool 76 is driven according to the oil pressure in the oil passage 49, when the oil pressure in the oil passage 49 rises abnormally, the oil pressure can be reliably released. become able to.

  In the hydraulic pressure supply device 60 of the present embodiment, the ECU 50 reduces the hydraulic pressure of the oil passage 49 detected by the hydraulic pressure sensor 45 to a predetermined pressure even after the predetermined time T0 has elapsed after issuing an opening command to the solenoid valve 43. If not, it is determined that the solenoid valve 43 has failed, and the oil pump 35 is driven to forcibly increase the pressure in the oil passage 49 to the threshold value P0 and release the relief valve 70.

  That is, when it is determined that a sticking failure has occurred in the solenoid valve 43 provided in the oil passage (filled oil passage) 49 between the check valve 39 and the piston chamber 15 (at the time of piston chamber hydraulic filling failure) The relief valve 70 is forcibly operated by generating a hydraulic pressure higher than the pressure regulation, and the hydraulic oil sealed in the oil passage 49 is discharged. According to this, when it is determined that a failure has occurred in the solenoid valve 43, the relief valve 70 can be reliably operated, so that the hydraulic pressure can be reliably released. Further, by driving the oil pump 35, the oil pressure in the oil passage 49 is raised and the relief valve 70 is operated, so that no complicated structure or control means is required, and the same as in the case of controlling the hydraulic pressure of the normal piston chamber 15. With this simple configuration and control, the relief valve 70 can be reliably operated.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea described in the claims and the specification and drawings. Is possible.

1 Four-wheel drive vehicle 10 Front / rear torque distribution clutch (clutch)
15 Piston chamber 30 Hydraulic circuit 35 Oil pump 37 Motor 39 Check valve (hydraulic oil sealing valve)
43 Solenoid valve (open / close valve)
45 Hydraulic sensor (hydraulic detection means)
47 Oil temperature sensor 49 Oil passage (Encapsulated oil passage)
50 ECU (control means)
60 Hydraulic supply device 70 Relief valve 71 Piston housing 72 Pump body 72b Second inlet 73 Pump cover 74 Spool housing 74a First inlet 74c Outlet 74d Emergency outlet 75 Spool chamber 76 Valve spool 76a Upper end surface (first pressure receiving surface) )
76b Lower end surface (second pressure receiving surface)
76c Spring engaging groove 76d Pressing portion 77 Inner cylinder 78 Outer cylinder 79 Relief ball (valve element)
81a 1st inflow port 81b 2nd inflow port 81c Outflow port 81d Emergency discharge port 85 1st coil spring (biasing means)
86 Second coil spring 87 Ball housing chamber 89 Valve seat

Claims (2)

A driving force transmission path for transmitting the driving force from the driving source to the main driving wheel and the sub driving wheel;
In a four-wheel drive vehicle comprising: a drive force distribution device disposed between the drive source and the auxiliary drive wheel in the drive force transmission path;
The driving force distribution device includes a friction engagement element having a plurality of stacked friction materials and a piston chamber that generates hydraulic pressure with respect to a piston that presses and engages the friction materials in the stacking direction. And
An oil pump driven by a motor for supplying hydraulic oil to the piston chamber, a hydraulic oil sealing valve for sealing hydraulic oil in an oil passage leading from the oil pump to the piston chamber, and the hydraulic oil sealing valve; In the hydraulic pressure supply device of the driving force distribution device comprising a hydraulic circuit having an on-off valve for opening and closing the oil passage between the piston chamber,
A relief valve for releasing the hydraulic pressure when the hydraulic pressure of the hydraulic oil sealed in the oil passage between the hydraulic oil sealing valve and the piston chamber is equal to or higher than a predetermined threshold;
The relief valve includes a first inflow port and a second inflow port that branch off the oil passage through which the hydraulic oil from the oil pump flows, and a first pressure receiving pressure that receives pressure from the hydraulic oil in the first inflow port. A valve spool having a surface and a second pressure receiving surface that receives pressure from the hydraulic fluid of the second inflow port, and an opening that opens the oil passage from a closed position that is pressed by the valve spool to close the oil passage. A valve body that moves to a position, and a biasing means that biases the valve spool away from the valve body,
The area of the first pressure receiving surface and the area of the second pressure receiving surface of the valve spool are different from each other, so that the valve spool is energized when the oil pressure in the oil passage exceeds the threshold value. A hydraulic pressure supply device for a driving force distribution device, wherein the valve body is pressed and the oil passage is opened by moving against the urging force of the means. Control means for controlling driving of the oil pump by the motor and opening / closing of the on-off valve;
Oil pressure detecting means for detecting the oil pressure of the oil passage,
The control means drives the oil pump when the hydraulic pressure of the oil passage detected by the hydraulic pressure detection means does not become a predetermined pressure or less even after a predetermined time has elapsed after issuing an opening command to the on-off valve. 2. The hydraulic pressure supply device for a driving force distribution device according to claim 1, wherein control for forcibly increasing the pressure of the oil passage to the threshold value is performed.

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