JP2017202696A - Suspension system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect failure of bypass valves 63 properly.SOLUTION: Upon raising a ride height, an ECU 100 closes bypass valves 63 and spring switching valves 62, opens leveling valves 61 and a source valve 64, and activates a pump device 71. When an actual ride height reaches a target ride height, the ECU 100 executes the following processing steps for each wheel, maintaining the spring switching valves 62 and the leveling valves 61 in closed condition. The ECU opens the bypass valve 63, causing the pump device 71 to supply hydraulic fluid to a second gas spring 32, so that hydraulic pressure of the second gas spring is equal to hydraulic pressure of a hydraulic cylinder 20. When a detection value of a pressure sensor 90 does not fall although an opening command is outputted to the bypass valve 63, the ECU 100 determines that the bypass valve 63 has a closed failure (failure in which the valve cannot be opened).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a suspension system having a vehicle height adjustment function for adjusting the vehicle height by the hydraulic pressure of a hydraulic cylinder provided between a vehicle body and a wheel holding member.

  Conventionally, as proposed in Patent Document 1, for example, there is a suspension system that adjusts the vehicle height by controlling the hydraulic pressure of a hydraulic cylinder (shock absorber) provided between a vehicle body and a four-wheel wheel holding member. Are known. The hydraulic cylinder of each wheel is connected to the hydraulic oil supply / discharge device via an individual control passage. In this suspension system, the individual control valve that opens and closes the individual control passage and the hydraulic oil supply / discharge device are controlled, and the hydraulic oil is supplied to each hydraulic cylinder to raise the vehicle height, and the hydraulic oil is supplied from each hydraulic cylinder. The vehicle height is lowered by discharging.

  Each hydraulic cylinder is connected to a high pressure accumulator having a large spring constant and a low pressure accumulator having a small spring constant. A passage that connects the hydraulic cylinder and the low-pressure accumulator is provided with a spring switching valve that can be switched between a state in which communication between the hydraulic cylinder and the low-pressure accumulator is allowed. Therefore, the wheel rate can be switched by opening and closing the spring switching valve.

  In this suspension system, during normal traveling, the high pressure accumulator and the low pressure accumulator are communicated with the hydraulic cylinder (spring switching valve: open), and the wheel rate is set to be small (soft). Further, at the time of sudden turning and sudden acceleration / deceleration, the communication between the hydraulic cylinder and the low-pressure accumulator is cut off (spring switching valve: closed), and the wheel rate is set high (hard). The wheel rate is the spring constant at the wheel position, and the ratio of the change in the wheel ground load and the change in the vertical distance (wheel travel) between the vehicle body and the wheel center at that wheel, ie, the unit wheel travel. It represents the amount of change in the ground load of the wheel that is required to be generated.

JP 2008-168861 A

  In the above system, when raising the vehicle height, the hydraulic oil in the hydraulic cylinder is increased by supplying hydraulic oil to the hydraulic cylinder to raise the piston rod. At this time, the low pressure accumulator and the high pressure accumulator are also operated simultaneously. Oil is supplied. For this reason, there is much hydraulic oil amount required in order to raise vehicle height, and in connection with this, time required in order to raise vehicle height becomes long.

  Accordingly, the applicant of the present application has considered a new suspension system capable of independently performing the supply and discharge of hydraulic oil in the hydraulic cylinder and the supply and discharge of hydraulic oil in the low-pressure accumulator. The new suspension system includes a bypass passage that bypasses the individual control valve and the spring switching valve to communicate the low-pressure accumulator and the hydraulic oil supply / discharge device, and a bypass valve that opens and closes the bypass passage. Accordingly, by supplying hydraulic oil from the hydraulic oil supply / discharge device to the hydraulic cylinder with the bypass valve and the spring switching valve closed, the vehicle height can be increased without supplying hydraulic oil to the low-pressure accumulator. it can.

  When the spring switching valve is opened from the state where the vehicle height is raised in this way, the hydraulic cylinder and the low pressure accumulator communicate with each other, and the hydraulic oil moves between the two due to the pressure difference between the two and the vehicle height fluctuates. Resulting in. Therefore, in this new system, after the vehicle height rise is completed, the bypass valve is opened with the individual control valve and the spring switching valve closed, and the hydraulic pressure of the low-pressure accumulator becomes equal to the hydraulic pressure of the hydraulic cylinder. As described above, the hydraulic oil is supplied from the hydraulic oil supply / discharge device to the low-pressure accumulator. Thereby, even if it opens a spring switching valve after that, it can prevent that vehicle height changes.

  However, it is necessary to properly detect the failure of the newly added bypass valve.

  The present invention has been made to solve the above-described problems, and an object thereof is to appropriately detect a failure of a bypass valve.

In order to achieve the above object, the features of the present invention are:
A hydraulic cylinder (20) provided between the wheel holding member and the vehicle body in each of the left and right front and rear wheels of the vehicle, accommodating hydraulic oil, and extending and contracting in accordance with a change in distance between the wheel holding member and the vehicle body; ,
The first oil chamber is provided corresponding to each hydraulic cylinder of the left and right front and rear wheels, and includes a first gas chamber and a first oil chamber communicating with the hydraulic cylinder, the first oil corresponding to the hydraulic pressure of the hydraulic cylinder. A first gas spring (31) that functions as a hydraulic spring by changing the amount of hydraulic oil contained in the chamber;
A second gas chamber and a second oil chamber communicating with the hydraulic cylinder are provided to correspond to the respective hydraulic cylinders, and are accommodated in the second oil chamber according to the hydraulic pressure of the hydraulic cylinder. A second gas spring (32) which functions as a hydraulic spring by changing the amount of hydraulic oil
A spring switching valve (62) provided corresponding to each hydraulic cylinder and capable of switching between a state allowing communication between the hydraulic cylinder and the second gas spring and a state blocking it;
A hydraulic oil supply / discharge device (70) for supplying and discharging hydraulic oil to and from each hydraulic cylinder;
A supply / discharge hydraulic control circuit (54, 64) having a supply / discharge source passage which is connected to the hydraulic oil supply / discharge device and serves as a flow path for hydraulic oil, and a source valve which opens and closes the supply / discharge source passage;
A vehicle height adjusting passage that is provided corresponding to each of the hydraulic cylinders and that communicates each of the hydraulic cylinders with the supply / discharge source passage, and opens and closes the vehicle height adjusting passage. A vehicle height adjustment hydraulic control circuit (51, 61) having a vehicle height adjustment valve to perform;
A hydraulic oil passage provided corresponding to each of the hydraulic cylinders, bypassing the spring switching valve and the vehicle height adjusting valve, and communicating each of the second gas springs with the supply / discharge source passage; A second gas spring hydraulic control circuit (53, 63) having a bypass passage and a bypass valve for opening and closing the bypass passage;
The spring switching valve and the bypass valve are closed, the original valve and the vehicle height adjusting valve are opened, and hydraulic oil is supplied from the hydraulic oil supply / discharge device to the hydraulic cylinders of the wheels. Vehicle height increase control means (100, S10) for increasing the vehicle height at each wheel position to the target vehicle height;
Provided on the hydraulic cylinder side with respect to the original valve, on the original valve side with respect to the bypass valve and on the original valve side with respect to the vehicle height adjusting valve; A hydraulic sensor (90) for detecting the hydraulic pressure of the flow path;
Hydraulic pressure storage means (S15) for storing the hydraulic pressure detected by the hydraulic pressure sensor when the vehicle height rises to the target vehicle height for each wheel position;
After the rise of the vehicle height to the target vehicle height is completed, the spring switching valve and the second gas spring are equalized with the hydraulic pressure corresponding to the wheel position stored in the hydraulic pressure storage means. While maintaining the vehicle height adjustment valve in the closed state, the bypass valve is opened one by one, and the supply of hydraulic oil from the hydraulic oil supply / discharge device to the second gas spring is started, When the hydraulic pressure detected by the hydraulic pressure sensor reaches the hydraulic pressure corresponding to the wheel position stored in the hydraulic pressure storage means, the bypass valve is closed and the hydraulic oil supply / discharge device performs the hydraulic oil supply operation. Second gas spring hydraulic pressure adjusting means (S101 to S106) to be stopped;
A change in oil pressure detected by the oil pressure sensor after the second gas spring oil pressure adjusting means outputs a valve opening command for opening the bypass valve, and the second gas spring oil pressure adjusting means includes the bypass. Based on at least one of changes in hydraulic pressure detected by the hydraulic sensor after outputting a valve closing command for closing the valve and stopping the hydraulic oil supply operation of the hydraulic oil supply / discharge device, There is provided a bypass valve failure detection means (S103, S113, S108, S118) for determining that the bypass valve has failed when the change in hydraulic pressure does not show a predetermined decreasing gradient.

  In the present invention, a hydraulic cylinder is provided between the wheel holding member and the vehicle body in each of the left and right front and rear wheels of the vehicle. The hydraulic cylinder accommodates hydraulic oil and expands and contracts in accordance with a change in distance between the wheel holding member and the vehicle body.

  Each hydraulic cylinder is provided with a first gas spring and a second gas spring. The first gas spring includes a first gas chamber and a first oil chamber that communicates with the hydraulic cylinder, and the amount of hydraulic oil stored in the first oil chamber changes according to the hydraulic pressure of the hydraulic cylinder. Functions as a hydraulic spring. The second gas spring includes a second gas chamber and a second oil chamber that communicates with the hydraulic cylinder, and the amount of hydraulic oil stored in the second oil chamber changes according to the hydraulic pressure of the hydraulic cylinder. Functions as a hydraulic spring.

  About this 2nd gas spring, the state which accept | permits communication with a hydraulic cylinder and the state which interrupts | blocks are switched by the spring switching valve. Therefore, when the spring switching valve is opened, the hydraulic cylinder is in a state where it is in communication with both the first gas spring and the second gas spring, that is, in a state where the wheel rate is set small (soft). Further, by closing the spring switching valve, the hydraulic cylinder is in a state where it communicates only with the first gas spring of the first gas spring and the second gas spring, that is, the wheel rate is set high. State (hard).

  By adjusting the pressure of the hydraulic oil stored in the hydraulic cylinder, the vehicle height at the wheel position where the hydraulic cylinder is provided can be adjusted. In each hydraulic cylinder, hydraulic oil is supplied and discharged by a hydraulic oil supply / discharge device and a hydraulic supply / discharge hydraulic control circuit, thereby adjusting the vehicle height. The hydraulic oil supply / discharge device includes, for example, a high pressure source (for example, a pump) for supplying hydraulic oil to a hydraulic cylinder, and a low pressure source (for example, a reservoir tank) for discharging hydraulic oil from the hydraulic cylinder. Yes. The supply / discharge hydraulic pressure control circuit has a supply / discharge source passage that is connected to the hydraulic oil supply / discharge device and serves as a flow path for the hydraulic oil, and a source valve that opens and closes the supply / discharge source passage.

  The suspension system includes a vehicle height adjustment hydraulic control circuit and a second gas spring hydraulic control circuit provided corresponding to each hydraulic cylinder. The vehicle height adjustment hydraulic control circuit is a vehicle height adjustment passage that opens and closes a vehicle height adjustment passage that is a flow path of hydraulic oil that connects each of the hydraulic cylinders to the supply / discharge source passage. Has a valve. Accordingly, the vehicle height can be adjusted by adjusting the hydraulic pressure of the hydraulic cylinder of the vehicle height adjustment target wheel by opening the original valve and the vehicle height adjustment valve of the vehicle height adjustment target wheel.

The second gas spring hydraulic control circuit bypasses the spring switching valve and the vehicle height adjusting valve to connect each of the second gas springs to the supply / discharge source passage, and a bypass passage that is a flow passage of hydraulic oil, and And a bypass valve for opening and closing the bypass passage. Therefore, the hydraulic pressure of the optional second gas spring can be independently adjusted by opening the original valve and the optional bypass valve.

  The vehicle height increase control means closes the spring switching valve and bypass valve, opens the original valve and the vehicle height adjustment valve, and supplies hydraulic oil from the hydraulic oil supply / discharge device to the hydraulic cylinder of each wheel. Then, the vehicle height at each wheel position is raised to the target vehicle height. Therefore, since the hydraulic pressure of the hydraulic cylinder can be adjusted without supplying hydraulic oil to the second gas spring, the amount of hydraulic oil required for raising the vehicle height can be reduced, and the vehicle height raising time can be shortened. .

  Thus, in the configuration in which hydraulic oil is not supplied to the second gas spring when the vehicle height is raised, when the wheel rate is switched by opening the spring switching valve, the hydraulic cylinder The hydraulic oil flows through the second gas spring, causing the vehicle height to drop suddenly. Therefore, in the present invention, a hydraulic pressure sensor, a hydraulic pressure storage means, and a second gas spring hydraulic pressure adjustment means are provided.

  The hydraulic sensor is provided in a hydraulic oil flow path on the hydraulic cylinder side with respect to the original valve, on the original valve side with respect to the bypass valve, and on the original valve side with respect to the vehicle height adjustment valve. Detect the oil pressure of the road. Therefore, this hydraulic pressure sensor can detect the hydraulic pressure of the hydraulic cylinder when the vehicle height adjusting valve is opened, and can detect the hydraulic pressure of the second gas spring when the bypass valve is opened. it can. The hydraulic pressure storage means stores the hydraulic pressure detected by the hydraulic pressure sensor when the vehicle height rises to the target vehicle height for each wheel position.

  The second gas spring hydraulic pressure adjusting means adjusts the hydraulic pressure of the second gas spring so as to be equal to the hydraulic pressure corresponding to the wheel position stored in the hydraulic pressure storage means after the vehicle height has been raised to the target vehicle height. 2 Adjust the oil pressure of the gas spring. In this case, the second gas spring hydraulic pressure adjusting means keeps the spring switching valve and the vehicle height adjusting valve in the closed state, and opens the bypass valve one by one from the hydraulic oil supply / discharge device one by one. When the supply of hydraulic fluid to the spring is started and the hydraulic pressure detected by the hydraulic pressure sensor reaches the hydraulic pressure corresponding to the wheel position stored in the hydraulic pressure storage means, the bypass valve is closed and the hydraulic fluid is supplied. Stop the hydraulic fluid supply operation of the drainage device. As a result, the hydraulic pressure of the second gas spring can be made the same as the hydraulic pressure of the hydraulic cylinder, and thereafter the vehicle height can be prevented from changing even if the spring switching valve is opened.

  In the suspension system of the present invention, the second gas spring hydraulic pressure adjusting means includes a bypass valve failure detecting means for detecting a failure of the bypass valve in the process of adjusting the hydraulic pressure of the second gas spring.

  For example, when the second gas spring hydraulic pressure adjusting means outputs a valve opening command to the bypass valve in order to start supplying hydraulic oil to the second gas spring, if the bypass valve opens normally, it is detected by the hydraulic sensor. However, if the valve does not open normally, the hydraulic pressure drop that should have been obtained cannot be obtained. Also, when the supply of hydraulic oil to the second gas spring is completed and the second gas spring hydraulic pressure adjusting means stops the hydraulic oil supply operation of the hydraulic oil supply / discharge device and outputs a valve closing command to the bypass valve If the bypass valve closes normally, the oil pressure detected by the oil pressure sensor should decrease, but if the bypass valve does not close normally, the oil pressure drop that should originally be obtained cannot be obtained.

  Paying attention to this, the bypass valve failure detection means includes a change in hydraulic pressure detected by the hydraulic sensor after the second gas spring hydraulic pressure adjustment means outputs a valve opening command for opening the bypass valve, and Change in oil pressure detected by the oil pressure sensor after the second gas spring oil pressure adjusting means outputs a valve closing command for closing the bypass valve and the operation oil supply operation of the operation oil supply / discharge device is stopped. Based on at least one of the above, it is determined that the bypass valve has failed when the change in the hydraulic pressure does not indicate a predetermined decrease gradient.

  Therefore, according to the present invention, a failure of the bypass valve can be properly detected.

  In the above description, in order to assist the understanding of the invention, the reference numerals used in the embodiments are attached to the constituent elements of the invention corresponding to the embodiments in parentheses. It is not limited to the embodiment defined by.

1 is an overall configuration diagram showing an outline of a suspension system according to an embodiment. It is a flowchart showing a vehicle height increase control main routine. It is a flowchart showing a vehicle height increase control subroutine. It is a flowchart showing a low gas spring hydraulic pressure adjustment subroutine. It is a flowchart showing a vehicle height increase control subroutine after failure detection. It is a flowchart showing the low gas spring hydraulic pressure adjustment subroutine after failure detection. It is a graph showing the operating state of each valve | bulb and pump apparatus, and transition of a hydraulic pressure and vehicle height.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram showing an outline of a suspension system 1 of the present embodiment.

  The suspension system 1 includes suspension devices 10FL, 10FR, 10RL, and 10RR that detachably connect the left and right front and rear wheels WFL, WFR, WRL, and WRR to the vehicle body, and suspension devices 10FL, 10FR when adjusting the vehicle height. , 10RL, 10RR, hydraulic oil supply / discharge device 70 for supplying and discharging hydraulic oil, and hydraulic control circuit provided between suspension devices 10FL, 10FR, 10RL, 10RR and hydraulic oil supply / discharge device 70 50 and an electronic control unit 100 (referred to as ECU 100) for controlling the operation of the entire system.

  Hereinafter, regarding the symbols attached to the end of the reference numerals, FL is a member provided corresponding to the left front wheel, FR is a member provided corresponding to the right front wheel, and RL is provided corresponding to the left rear wheel. RR represents a member provided corresponding to the right rear wheel, but in the specification, when there is no need to identify the corresponding wheel, the symbol at the end is omitted.

  The suspension device 10 includes a wheel holding member 11 (for example, a lower arm) that holds the left and right front and rear wheels W, and a hydraulic cylinder 20 that is provided between each wheel holding member 11 and the vehicle body. Although not shown, a suspension spring (coil spring) is provided in parallel with the hydraulic cylinder 20 between each wheel holding member 11 and the vehicle body. The hydraulic cylinder 20 functions as a shock absorber and expands and contracts in accordance with a change in the distance between the wheel holding member 11 and the vehicle body.

  Each hydraulic cylinder 20 has the same structure, and includes a housing 21, a piston 22 fitted inside the housing 21 so as to be movable relative to the housing 21, and from the piston 22 to the outside of the housing 21. And an extended piston rod 23. The housing 21 is connected to the wheel holding member 11, and the piston rod 23 is connected to the vehicle body. The housing 21 is divided into two oil chambers 24 a and 24 b by a piston 22. The piston 22 is formed with a communication path 25 that allows the oil chambers 24a and 24b to communicate with each other, and the communication path 25 is formed with a throttle (not shown). Due to this restriction, a damping force corresponding to the relative moving speed of the piston 22 with respect to the housing 21 is generated.

  An individual supply / discharge passage 51, which is a passage through which hydraulic oil flows, is connected to the oil chamber 24a of each hydraulic cylinder 20. The hydraulic cylinder 20 generates a force in a direction to separate the wheel holding member 11 and the vehicle body by the pressure of the hydraulic oil supplied from the individual supply / discharge passage 51. Therefore, the hydraulic cylinder 20 increases the vehicle height by increasing the distance between the wheel holding member 11 and the vehicle body as the pressure of the hydraulic oil supplied from the individual supply / discharge passage 51 increases.

  A main accumulator 31 and a leveling valve 61 are connected to each individual supply / discharge passage 51 in order from the side closer to the hydraulic cylinder 20. The main accumulator 31 functions as a hydraulic gas spring provided separately from the suspension spring (coil spring).

  The individual supply / discharge passage 51 corresponds to the vehicle height adjustment passage of the present invention. The main accumulator 31 corresponds to the first gas spring of the present invention. The leveling valve 61 corresponds to the vehicle height adjusting valve of the present invention. Therefore, the configuration including the individual supply / discharge passage 51 and the leveling valve 61 corresponds to the vehicle height adjustment hydraulic control circuit of the present invention.

  The main accumulator 31 includes a housing 31a and a partition member 31b that partitions the inside of the housing 31a into two capacity change chambers, and an individual supply / exhaust passage to the oil chamber 31c that is one capacity change chamber partitioned by the partition member 31b. The gas chamber 31d, which is the other volume change chamber, is connected to the gas chamber 31d, which is an elastic body (for example, nitrogen gas). In the main accumulator 31, the volume of the gas chamber 31d decreases due to the increase in the volume of the oil chamber 31c. Accordingly, the main accumulator 31 functions as a hydraulic gas spring that generates an elastic force in the expansion / contraction operation of the hydraulic cylinder 20 by changing the amount of hydraulic oil stored in the oil chamber 31c according to the hydraulic pressure of the hydraulic cylinder 20. To do. The oil chamber 31 c of the main accumulator 31 is always in communication with the oil chamber 24 a of the hydraulic cylinder 20.

  The leveling valve 61 is a normally closed electromagnetic on-off valve that operates during vehicle height adjustment to open and close the individual supply / discharge passage 51.

  An individual rate switching passage 52 is branched and connected to each individual supply / discharge passage 51 at a position between the leveling valve 61 and the hydraulic cylinder 20. A spring switching valve 62 and a sub-accumulator 32 are connected to the individual rate switching passage 52 in order from the side closer to the connection position with the individual supply / discharge passage 51.

  The auxiliary accumulator 32 corresponds to the second gas spring of the present invention.

  The sub accumulator 32 includes a housing 32a and a partition member 32b that partitions the inside of the housing 32a into two capacity change chambers, and an individual rate switching passage to an oil chamber 32c that is one capacity change chamber partitioned by the partition member 32b. 52 is communicated, and the gas chamber 32d which is the other volume change chamber is filled with a gas (for example, nitrogen gas) which is an elastic body. In the sub-accumulator 32, the volume of the gas chamber 32d decreases due to the increase in the volume of the oil chamber 32c. Accordingly, the sub-accumulator 32 functions as a hydraulic gas spring that generates an elastic force in the expansion and contraction operation of the hydraulic cylinder 20 by changing the amount of hydraulic oil stored in the oil chamber 32 c according to the hydraulic pressure of the hydraulic cylinder 20. To do.

  The secondary accumulator 32 has a smaller spring constant than the main accumulator 31. The main accumulator 31 and the sub accumulator 32 can employ any type such as a bellows type, a bladder type, and a piston type. In the present embodiment, the main accumulator 31 is a metal bellows type accumulator excellent in gas permeability resistance at a high compression pressure. Further, as the sub-accumulator 32, a bladder accumulator with a resin film that can secure a relatively large capacity and has excellent gas permeability is adopted.

  The spring switching valve 62 is a normally open electromagnetic on-off valve that operates when the wheel rate is switched. When the spring switching valve 62 is open, the main accumulator 31 and the sub accumulator 32 are connected in parallel to the hydraulic cylinder 20, and when the spring switching valve 62 is closed, the hydraulic cylinder The communication between the main accumulator 32 and the sub accumulator 32 is blocked (it can also be expressed that the communication between the main accumulator 31 and the sub accumulator 32 is blocked). Hereinafter, the main accumulator 31 is referred to as a high gas spring 31, and the sub accumulator 32 is referred to as a low gas spring 32.

  As described above, the suspension device 10 includes the wheel holding member 11, the hydraulic cylinder 20, and the high gas spring 61 and the low gas spring 62 connected in parallel to the hydraulic cylinder 20.

  Each individual supply / discharge passage 51 is connected to a common supply / discharge passage 54. The common supply / discharge passage 54 is connected to the hydraulic oil supply / discharge device 70, and is also a passage for supplying hydraulic oil from the hydraulic oil supply / discharge device 70 to each individual supply / discharge passage 51. It is also a passage for returning oil to the hydraulic oil supply / discharge device 70.

  The common supply / exhaust passage 54 is provided with an original valve 64 which is a normally closed electromagnetic on-off valve. Therefore, only when the original valve 64 is open, each individual supply / discharge passage 51 and the hydraulic oil supply / discharge device 70 communicate with each other, and when the original valve 64 is closed, each individual supply / discharge The communication between the passage 51 and the hydraulic oil supply / discharge device 70 is blocked.

  In FIG. 1, the common supply / discharge passage 54 is downstream of the original valve 64, and is connected to the left / right front wheel individual supply / discharge passages 51FL, 51FR, and the left / right rear wheel individual supply / discharge passages 51RL, 51RR. However, it is not always necessary to make such a branch. For example, the hydraulic oil from the hydraulic oil supply / discharge device 70 to the individual supply / discharge passages 51 such that the individual supply / discharge passages 51FL, 51FR, 51RL, 51RR are directly connected to the common supply / discharge passage 54 common to all four wheels. The passage (that is, the common supply / discharge passage 54) can be arbitrarily configured.

  The common supply / discharge passage 54 corresponds to the supply / discharge source passage of the present invention. The configuration including the common supply / discharge passage 54 and the original valve 64 corresponds to the supply / discharge hydraulic pressure control circuit of the present invention.

  The hydraulic control circuit 50 is provided with an individual bypass passage 53 that bypasses the leveling valve 61 and the spring switching valve 62 and communicates the low gas spring 32 with the common supply / discharge passage 54. Each individual bypass passage 53 is provided with a bypass valve 63. The bypass valve 63 is a normally closed electromagnetic on-off valve. Therefore, in a state where the bypass valve 63 is opened, the low gas spring 32 communicates with the common supply / discharge passage 54 regardless of the state of the leveling valve 61 and the spring switching valve 62. The configuration including the individual bypass passage 53 and the bypass valve 63 corresponds to the second hydraulic control circuit for the gas spring of the present invention.

  The hydraulic oil supply / discharge device 70 includes a pump device 71 as a high pressure source and a reservoir tank 72 as a low pressure source. The pump device 71 includes a pump 71a and a pump motor 71b that drives the pump 71a. The pump device 71 pumps up the hydraulic oil in the reservoir tank 72 and supplies it to the common supply / discharge passage 54. The hydraulic oil supply / discharge device 70 is a common supply / discharge passage 54 on the downstream side of the pump device 71, and includes a check valve 73 (check valve) and a return valve 74 at a position upstream of the original valve 64. In parallel.

  The return valve 74 is a valve that switches between supplying hydraulic oil from the pump device 71 to the original valve 64 and discharging hydraulic oil from the original valve 64 to the reservoir tank 72. The return valve 74 is normally in a state where the passage between the original valve 64 and the reservoir tank 72 is opened by the force of the spring, and when the pump device 71 is driven, its discharge pressure and the common supply / discharge passage 54. The valve body is pushed by the pressure difference from the hydraulic pressure of the oil pressure, and the passage between the original valve 64 and the reservoir tank 72 is closed. As a result, the hydraulic oil discharged from the pump device 71 when the check valve 73 is opened flows to the opened original valve 64.

  Note that the hydraulic oil supply / discharge device 70 of the present embodiment does not include a pressure accumulator that stores the hydraulic pressure pressurized by the pump device 71 in order to reduce the weight.

  The common supply / discharge passage 54 is provided with a pressure sensor 90 for detecting the hydraulic pressure downstream of the original valve 64. The pressure sensor 90 may be provided anywhere as long as it is a hydraulic oil flow path surrounded by the original valve 64, the four leveling valves, and the four bypass valves. That is, the pressure sensor 90 is on the hydraulic cylinder 20 side with respect to the original valve 64, on the original valve 64 side with respect to the four bypass valves 63, and on the original valve 64 side with respect to the leveling valve 61. What is necessary is just to be provided in the flow path. Therefore, according to the pressure sensor 90, when the leveling valve 61 of an arbitrary wheel is opened, the hydraulic pressure of the hydraulic cylinder 20 of the wheel can be detected, and the bypass valve 63 of the arbitrary wheel is opened. In this case, the oil pressure of the low gas spring 32 of the wheel can be detected.

  As described above, the hydraulic control circuit 50 includes the common supply / discharge passage 54, the original valve 64, the individual supply / discharge passage 51, the leveling valve 61, the individual rate switching passage 52, the spring switching valve 62, and the individual bypass passage. 53 and a bypass valve 63.

  The ECU 100 includes a microcomputer and a drive circuit (motor drive circuit and solenoid valve drive circuit) as main parts. In the present specification, the microcomputer includes a CPU, a storage device such as a ROM and a RAM, and the CPU realizes various functions by executing instructions (programs) stored in the ROM.

  The ECU 100 includes various solenoid valves (leveling valve 61, spring switching valve 62, bypass valve 63, and original valve 64) provided in the hydraulic control circuit 50, and a pump motor provided in the hydraulic oil supply / discharge device 70. 71b and the pressure sensor 90 are connected. Further, the ECU 100 is connected with a motion detection sensor 110 that detects a vehicle motion state, an operation detection sensor 120 that detects a driver's operation, and a notification device 130.

  Examples of the motion detection sensor 110 include a vehicle speed sensor that detects the vehicle speed, a vehicle height sensor that detects the vehicle height for each front / rear / left / right wheel position, a vertical acceleration sensor that detects acceleration in the vertical direction of the vehicle body, and a yaw rate of the vehicle body. These include a yaw rate sensor and a horizontal acceleration sensor that detects acceleration in the front-rear and left-right directions of the vehicle body. The vehicle height sensor detects, for example, the distance between the wheel holding member 11 that holds each wheel W and the vehicle body at the wheel position as the vehicle height.

  The operation detection sensor 120 includes a stroke sensor that detects the depression stroke of the brake pedal, a steering angle sensor that detects the steering angle of the steering, and a transfer sensor that detects the range state of the transfer. Note that the ECU 100 does not need to directly connect the motion detection sensor 110 and the operation detection sensor 120, but other in-vehicle ECUs (for example, an engine ECU, a brake ECU, and a steering wheel) that connect these sensors. A detection signal may be input from an ECU or the like. In addition, the ECU 100 connects a vehicle height selection switch and a vehicle height adjustment off switch as the operation detection sensor 120.

  The vehicle height selection switch is a switch for selecting a target vehicle height in three ways, a normal vehicle height, a low vehicle height, and a high vehicle height, by the operation of the driver. The vehicle height adjustment off switch is a switch that prohibits vehicle height control by a driver's operation.

  The alarm device 130 is provided, for example, on a meter display arranged in front of the driver's seat, and displays an icon corresponding to the type of abnormality when an abnormality is detected. In the suspension system of the present embodiment, when an abnormality of the hydraulic control circuit 50 is detected, the notification device 130 is operated by a command from the ECU 100 to notify the driver of the abnormality.

  ECU 100 performs wheel rate switching control and vehicle height control based on detection signals detected by motion detection sensor 110 and operation detection sensor 120.

  First, wheel rate switching control will be described. In the suspension system of the present embodiment, for each wheel W, the wheel rate of the wheel W can be switched by switching communication and blocking between the low gas spring 32 and the hydraulic cylinder 20 at the wheel position. In other words, the open / closed control of the spring switching valve 62 allows the hydraulic cylinder 20 and the low gas spring 32 to be in a communication state / blocking state (can be expressed as a communication state / blocking state between the high gas spring 31 and the low gas spring 32). By switching, the wheel rate can be switched between small (soft) and large (hard).

  For example, the ECU 100 basically keeps the spring switching valve 62 of the four wheels W in an open state, thereby setting the wheel rate to a small (soft) and ensuring the riding comfort. Further, the ECU 100 detects a change in posture when the motion detection sensor 110 and the operation detection sensor 120 detect (or predict) a change in the posture of the vehicle body such as a roll motion during vehicle turning or a pitch motion during vehicle braking. By closing the spring switching valve 62 of the wheel W (for example, the left and right front wheels) according to the situation, the low gas spring 32 is disconnected from the hydraulic cylinder 20 of the wheel W to increase the wheel rate (hard). Thereby, the roll motion and pitch motion (change in the posture of the vehicle body) of the vehicle body can be suppressed.

  Next, vehicle height control will be described. Based on the vehicle height selected by the vehicle height selection switch and the signals detected by the motion detection sensor 110 and the operation detection sensor 120, the ECU 100 operates the hydraulic oil supply / discharge device 70 and the various electromagnetic valves 61, 62, 63, 64. The vehicle height is adjusted by switching the supply / discharge / holding of the hydraulic oil in the hydraulic cylinders 20 of the front, rear, left and right wheels W.

  For example, the ECU 100 performs auto leveling control that always maintains the vehicle height selected by the driver regardless of the load conditions such as the number of passengers and the loading capacity. Further, the ECU 100 has a function of setting an optimum target vehicle height according to the vehicle speed. For example, when the low vehicle height and the high vehicle height are selected by the driver's switch operation, the ECU 100 cancels the driver's selected vehicle height and releases the target vehicle height when the vehicle speed increases above a preset threshold. Change the height to normal vehicle height. Further, the ECU 100 cancels the vehicle height selected by the driver during high-speed traveling, and changes the target vehicle height to a preset low vehicle height for high-speed traveling. In addition, when the transfer setting detected by the transfer sensor is in the L4 range (off-road driving range), the ECU 100 switches the target vehicle height to the high vehicle height when the vehicle speed exceeds a preset vehicle speed. .

  The ECU 100 operates the hydraulic oil supply / discharge device 70, the leveling valve 61, the switching valve 62, the bypass valve 63, and the original valve 64 so that the vehicle height (actual vehicle height) detected by the vehicle height sensor matches the target vehicle height. And drive control. In addition, when switching the state of the leveling valve 61, the switching valve 62, the bypass valve 63, and the original valve 64, the ECU 100 outputs a valve opening command or a valve closing command to these valves. The valve opening command is a drive signal for opening the valve, which indicates that the output of the drive signal is ON for the normally closed solenoid valve, and that the output of the drive signal is OFF for the normally open solenoid valve. . The valve closing command is a drive signal for closing the valve, which indicates that the drive signal output is turned off for a normally closed solenoid valve, and that the drive signal output is turned on for a normally open solenoid valve. Represents.

  When it is necessary to change the vehicle height, the ECU 100 adjusts the vehicle height as follows. Here, control when raising the vehicle height will be described. FIG. 2 shows a vehicle height increase control main routine executed by the ECU 100. When a vehicle height increase request is generated, ECU 100 starts a vehicle height increase control main routine.

  The vehicle height increase control main routine (hereinafter simply referred to as the main routine) includes a vehicle height increase control subroutine and a low gas spring hydraulic pressure adjustment subroutine that is started after execution of the vehicle height increase control subroutine.

  In the suspension system of this embodiment, when raising the vehicle height, the low gas spring 32 is disconnected from the hydraulic cylinder 20 by closing the spring switching valve 62 and the hydraulic oil is supplied to the hydraulic cylinder 20. . Thereby, the amount of hydraulic oil required for raising the vehicle height can be reduced, and the time required for raising the vehicle height can be shortened. When the spring switching valve 62 is opened after the vehicle height has risen, the hydraulic cylinder 20 and the low pressure gas spring 32 communicate with each other, and the hydraulic oil moves between the two due to the differential pressure between the two, causing the vehicle height to fluctuate. End up. Accordingly, the suspension system 1 is provided with the individual bypass passage 53 and the bypass valve 63 so that the hydraulic oil can be supplied to the low pressure gas spring 32 independently of the hydraulic cylinder 20, and after the vehicle height adjustment is completed. The bypass valve 63 is opened, and the hydraulic pressure of the low gas spring 32 is adjusted to be the same as the hydraulic pressure of the hydraulic cylinder 20.

  The vehicle height raising control subroutine is a process for raising the vehicle height by supplying hydraulic oil to the hydraulic cylinder 20 in a state where the low gas spring 32 is disconnected from the hydraulic cylinder 20. On the other hand, the low gas spring hydraulic pressure adjustment subroutine is a process of adjusting the hydraulic pressure of the low pressure gas spring 32 to the same pressure as the hydraulic pressure of the hydraulic cylinder 20. The low gas spring hydraulic pressure adjustment subroutine also includes processing for detecting a failure of the bypass valve 63.

  First, the vehicle height increase control subroutine will be described. FIG. 3 is a flowchart showing a vehicle height increase control subroutine. When the vehicle height increase control subroutine is started, the ECU 100 switches the spring switching valve 62 from the open state to the closed state while maintaining the bypass valve 63 in the closed state for the four wheels W in step S11. The leveling valve 61 is switched from the closed state to the open state.

  Subsequently, in step S12, the ECU 100 switches the original valve 64 from the closed state to the opened state. After opening the original valve 64, the ECU 100 activates the pump device 71 in step S13. As a result, the hydraulic oil accumulated in the reservoir tank 72 is supplied to the hydraulic cylinder 20 and the high gas spring 31 via the hydraulic control circuit 50. Accordingly, the hydraulic pressure of the hydraulic cylinder 20 increases, and the vehicle height of the wheel W increases accordingly. In this case, since the hydraulic oil is not supplied to the low gas spring 32, the vehicle height can be increased quickly with a small amount of oil.

  Subsequently, in step S14, the ECU 100 stands by until the vehicle height Lx detected by the vehicle height sensor (hereinafter referred to as the actual vehicle height Lx) reaches the target vehicle height L0. When the ECU 100 determines that the actual vehicle height Lx at any wheel W has reached the target vehicle height L0 (S14: Yes), at step S15, the wheel (referred to as a corresponding wheel) that has reached the target vehicle height L0 at that point in time. The detected value of the pressure sensor 90 is stored in association with the wheel position as the vehicle height adjustment completion pressure P0. The vehicle height adjustment completion pressure P0 is equal to the hydraulic pressure of the hydraulic cylinder 20 and the high gas spring 31 of the corresponding wheel.

  FIG. 7 is a graph showing the transition of the opening / closing timing of each valve, oil pressure, and vehicle height in an arbitrary wheel. When the vehicle height increase control subroutine is started at time t1, the hydraulic pressure of the hydraulic cylinder 20 (indicated by a broken line) starts to increase. The hydraulic pressure of the hydraulic cylinder 20 is equal to a detection value Px (shown by a solid line) detected by the pressure sensor 90. In this vehicle height raising control subroutine, the low gas spring 32 is disconnected from the hydraulic cylinder 20, so the hydraulic pressure of the low gas spring 32 does not rise.

  In the example of FIG. 7, the actual vehicle height Lx reaches the target vehicle height L0 at time t2. The detected value Px of the pressure sensor 90 at this time is stored as the vehicle height adjustment completion pressure P0.

  Subsequently, in step S16, the ECU 100 switches the leveling valve 61 of the corresponding wheel from the open state to the closed state. Thereby, the vehicle height adjustment at the corresponding wheel is completed. Subsequently, in step S17, the ECU 100 determines whether or not the vehicle height adjustment has been completed for all four wheels, and the wheels for which vehicle height adjustment has not been completed, that is, the actual vehicle height Lx has reached the target vehicle height L0. If no wheels remain, the process returns to step S14 and the same process is repeated.

  Thus, when the vehicle height adjustment for all four wheels is completed, the ECU ends the vehicle height increase control subroutine (s10) and advances the process to the low gas spring hydraulic pressure adjustment subroutine (S100). The timing when the low gas spring hydraulic pressure adjustment subroutine is started corresponds to time t2 in FIG.

  When the low gas spring hydraulic pressure adjustment subroutine is started, the ECU 100 selects one of the four wheels in a predetermined order (for example, left front wheel → right front wheel → left rear wheel → right rear wheel) in step S101. select. This selected wheel is called a selected wheel. Subsequently, in step S102, the ECU 100 switches the bypass valve 63 of the selected wheel from the closed state to the opened state.

  Subsequently, when the ECU 100 opens the bypass valve 63 in step S103, the hydraulic pressure detected by the pressure sensor 90 is larger than a preset decrease determination gradient (a negative gradient having a large absolute value). Judge whether it has fallen. As shown in FIG. 7, when the vehicle height adjustment for raising the vehicle height is completed (time t <b> 2 in FIG. 7), the hydraulic pressure of the low gas spring 32 (indicated by a one-dot chain line) is detected by the pressure sensor 90. The hydraulic pressure on the upstream side of the bypass valve 63 (the hydraulic oil supply / discharge device 70 side) is lower. Accordingly, when the bypass valve 63 is switched from the closed state to the open state, hydraulic oil flows into the bypass valve 63 from the upstream side. Therefore, as shown at time t2 in FIG. 7, the detection value Px detected by the pressure sensor 90 should greatly decrease.

  However, when a failure occurs in which the bypass valve 63 does not open from the closed state (ie, remains closed), that is, even if the ECU 100 outputs a valve opening command to the bypass valve 63, the bypass valve 63 does not open. In this case, the detection value Px of the pressure sensor 90 does not decrease. Therefore, the ECU 100 calculates the gradient (time differential value) of the detected value Px after outputting the valve opening command to the bypass valve 63 in step S103, and determines whether or not the bypass valve 63 has failed based on this gradient. judge. Thus, even if the valve opening command is output from the ECU 100 to the bypass valve 63, a failure in which the bypass valve 63 does not open is called a closed failure.

  In this case, for example, the ECU 100 determines the difference (Px1−) between the detection value Px1 immediately before the valve opening command is output to the bypass valve 63 and the detection value Px2 after a predetermined time has elapsed since the valve opening command is output. When calculating Px2), when the above difference exceeds the determination threshold, it is determined that the detected value Px has decreased with a gradient greater than the decrease determination gradient. Can do.

  When the ECU 100 detects “Yes” in step S103, that is, when a decrease in hydraulic pressure with a gradient greater than the decrease determination gradient is detected, the ECU 100 determines that the bypass valve 63 is not closed and proceeds to step S104. As described above, when the bypass valve 63 is opened in step S102, the four-wheel leveling valve 61 and the spring switching valve 62 are closed. Therefore, when the bypass valve 63 is opened in step S102, the hydraulic oil accumulated in the reservoir tank 72 is supplied only to the low gas spring 32 of the selected wheel. Thus, as shown after time t2 in FIG. 7, the hydraulic pressure of the low gas spring 32 of the selected wheel increases.

  In step S104, ECU 100 stands by until detection value Px of pressure sensor 90 reaches vehicle height adjustment completion pressure P0 of the selected wheel. That is, it waits until the oil pressure of the low gas spring 32 becomes equal to the oil pressure of the hydraulic cylinder 20 and the high gas spring 31 of the selected wheel.

  When the detected value Px reaches the vehicle height adjustment completion pressure P0 (S104: Yes), the ECU 100 switches the bypass valve 63 of the selected wheel from the open state to the closed state in step S105, and in the subsequent step S106, the pump device. 71 is stopped. After stopping the pump device 71, the ECU 100 switches the original valve 64 from the open state to the closed state in step S107. After the pump device 71 is stopped and before the original valve 64 is closed, the hydraulic oil in the common supply / discharge passage 54 can be discharged to the reservoir tank 72.

  Subsequently, in step S108, the ECU 100 determines that the detected value Px detected by the pressure sensor 90 after stopping the pump device 71 is greater than a preset decrease determination gradient (a negative gradient having a large absolute value). ). When the supply of the hydraulic oil to the low gas spring 32 is completed (time t3 in FIG. 7), the bypass valve 63 of the selected wheel is closed and the pump device 71 is stopped, the common supply / discharge passage 54 The hydraulic oil is discharged to the reservoir tank 72. Therefore, as shown at time t3 in FIG. 7, the detected value Px of the pressure sensor 90 should decrease to atmospheric pressure with a predetermined decrease gradient until the original valve 64 is closed.

  However, when a failure occurs in which the bypass valve 63 does not close from the opened state (ie, remains open), that is, even if a valve closing command is output from the ECU 100 to the bypass valve 63, the bypass valve 63 does not close. In this case, the decreasing gradient of the detection value Px of the pressure sensor 90 is small. That is, since the hydraulic oil stored in the low gas spring 32 flows into the common supply / discharge passage 54 so as to compensate for the decrease in the hydraulic pressure of the common supply / discharge passage 54, the detected value Px does not decrease immediately. Therefore, even when the original valve 64 is closed in step S107, the detected value Px shows a considerably high value with respect to the atmospheric pressure.

  Therefore, the ECU 100 calculates the gradient (time differential value) of the detected value Px detected by the pressure sensor 90 after stopping the pump device 71 in step S108, and based on this gradient, the failure of the bypass valve 63 is detected. Determine presence or absence. Thus, even if the valve closing command is output from the ECU 100 to the bypass valve 63, a failure in which the bypass valve 63 does not close is referred to as an open failure.

  When the ECU 100 detects “Yes” in step S108, that is, when a decrease in hydraulic pressure with a gradient greater than the decrease determination gradient is detected, the ECU 100 determines that the bypass valve 63 is not open and proceeds to step S109. In step S109, the ECU 100 switches the spring switching valve 62 of the selected wheel from the closed state to the opened state. As a result, the hydraulic cylinder 20 of the selected wheel and the low gas spring 32 communicate with each other, and the wheel rate is set to be small (soft). In this case, since the hydraulic pressure of the hydraulic cylinder 20 of the selected wheel and the hydraulic pressure of the low gas spring 32 are the same, even if the spring switching valve 62 is opened, the hydraulic oil is transferred from the hydraulic cylinder 20 to the low gas spring 32. Do not move. Therefore, fluctuations in the vehicle height associated with the opening of the spring switching valve 62 are prevented.

  Subsequently, in step S110, the ECU 100 determines whether or not the hydraulic pressure adjustment of the low gas spring 32 has been completed for all four wheels. If all the four wheels have not been completed, the process proceeds to step S111. Proceed. In step S111, the ECU 100 switches the original valve 64 from the closed state to the open state, and subsequently starts the pump device 71 in step S112. When ECU 100 activates pump device 71, ECU 100 returns the process to step S101, sets the next turn wheel as the selected wheel, and repeats the same process. If such a process is repeated and the hydraulic pressure adjustment of all the low gas springs 32 of all four wheels is completed without detecting the failure of the bypass valve 63 (S110: Yes), the low gas spring hydraulic pressure adjustment subroutine ends.

  On the other hand, if “No” in step S103, that is, if a valve opening command is output to the bypass valve 63 of the selected wheel and a hydraulic pressure decrease with a gradient greater than the decrease determination gradient is not detected, the ECU 100 determines in step S113. Then, it is determined that the bypass valve 63 of the selected wheel is closed. This determination result is stored in a non-volatile memory provided in the ECU 100. Subsequently, in step S114, the ECU 100 operates the notification device 130 to notify the driver that an abnormality has occurred.

  When a closed failure of the bypass valve 63 is detected, the ECU 100 does not open the spring switching valve 62 of the selected wheel in this low gas spring hydraulic pressure adjustment subroutine. As described above, when the failure of the bypass valve 63 is not detected, the ECU 100 opens the spring switching valve 62 (S109), and causes the low pressure spring 32 to communicate with the hydraulic cylinder 20. However, when the bypass valve 63 is closed, the hydraulic oil of the low gas spring 32 is lower than the hydraulic cylinder 20 because the hydraulic oil cannot be supplied to the low gas spring 32. For this reason, if the spring switching valve 62 for the selected wheel is opened, the hydraulic oil flows from the hydraulic cylinder 20 to the low gas spring 32, and the vehicle height of the selected wheel suddenly drops, giving the driver a sense of discomfort. . For this reason, when a closed failure of the bypass valve 63 is detected, the ECU 100 does not open the spring switching valve 62 of the wheel. The wheel spring switching valve 62 in which a closed failure of the bypass valve 63 is detected is raised when the vehicle height is raised by a vehicle height raising control subroutine after failure detection, which will be described later, that is, when the vehicle height is low, the hydraulic cylinder 20 The valve is opened when the hydraulic pressure is low.

  Subsequently, in step S115, the ECU 100 determines whether or not the hydraulic pressure adjustment of the low gas spring 32 has been completed for all four wheels. If all the four wheels have not been completed, the process proceeds to step S101. Proceed. If the bypass valve 63 is closed, the hydraulic pressure of the low gas spring 32 cannot actually be adjusted. However, the determination here is that the hydraulic pressure adjustment of the low gas spring 32 has been completed. . When it is determined in step S115 that the hydraulic pressure adjustment of the low gas spring 32 has been completed for all four wheels, the ECU 100 stops the pump device 71 in step S116 and closes the original valve 64 from the open state in step S117. Switch to the state and end the low gas spring hydraulic pressure adjustment subroutine.

  In step S108, “No”, that is, the decrease gradient of the detected value Px of the pressure sensor 90 after the valve closing command is output to the bypass valve 63 of the selected wheel and the pump device 71 is stopped is determined to be decreased. If it is equal to or less than the gradient, the ECU 100 determines in step S118 that the bypass valve 63 of the selected wheel has an open failure. This determination result is stored in a non-volatile memory provided in the ECU 100. Subsequently, in step S119, ECU 100 operates alarm 130 to notify the driver that an abnormality has occurred.

  When the ECU 100 operates the alarm 130, the process proceeds to step S109, the spring switching valve 62 is opened, and the low gas spring 32 is communicated with the hydraulic cylinder 20. In this case, since the bypass valve 63 of the selected wheel has an open failure, the hydraulic pressure of the low gas spring 32 is the same as the hydraulic pressure of the hydraulic cylinder 20. Therefore, even if the spring switching valve 62 is opened, the vehicle height of the selected wheel does not vary.

  The ECU 100 detects the failure of the bypass valve 63 at the same time as adjusting the hydraulic pressure of the low gas spring 32 by executing such a low gas spring hydraulic pressure adjustment subroutine.

  The ECU 100 executes a main routine including the vehicle height increase control subroutine and the low gas spring hydraulic pressure adjustment subroutine described above when no failure of the bypass valve 63 is detected for all four wheels. Further, after a failure of the ECU 100 and the bypass valve 63 is once detected, the vehicle height increase control subroutine after failure detection (FIG. 5) and the failure are replaced with the vehicle height increase control subroutine and the low gas spring hydraulic pressure adjustment subroutine described above. After detection, a main routine including a low gas spring hydraulic pressure adjustment subroutine (FIG. 6) is performed.

  First, the post-failure vehicle height increase control subroutine shown in FIG. 5 will be described. When a vehicle height increase request is generated after a failure (open failure or closed failure) of the bypass valve 63 is detected, the ECU 100 starts a vehicle height increase control subroutine after failure detection. In the following description, a wheel in which an open failure of the bypass valve 63 is detected is called an open failure wheel, and a wheel in which a close failure of the bypass valve 63 is detected is called a closed failure wheel.

  First, in step S21, the ECU 100 switches the spring switching valve 62 of the closed failure wheel from the closed state to the opened state, and switches the spring switching valve 62 of wheels other than the closed failed wheel from the opened state to the closed state. At the same time, the ECU 100 maintains the leveling valve 61 of the open failure wheel in the closed state, and switches the leveling valves 61 of the wheels other than the open failure wheel from the closed state to the open state. At the same time, the ECU 100 maintains the bypass valve 63 of the normal wheel (the wheel that is neither an open failure wheel nor a closed failure wheel) in a closed state. Since the bypass valve 63 of the open failure wheel and the closed failure wheel cannot be controlled to open and close, the state corresponding to the type of failure is maintained.

  Subsequently, in step S22, the ECU 100 switches the original valve 64 from the closed state to the opened state. After opening the original valve 64, the ECU 100 activates the pump device 71 in step S23. As a result, the hydraulic oil accumulated in the reservoir tank 72 is supplied to the hydraulic cylinder 20 and the high gas spring 31 other than the open failure wheel via the hydraulic control circuit 50. As a result, the hydraulic pressure of the hydraulic cylinder 20 increases at wheels other than the open failure wheel, and the vehicle height increases accordingly. When one open failure wheel exists, the vehicle height of the entire vehicle body increases due to the hydraulic pressure increase of the remaining three hydraulic cylinders 20. Further, when there is no open failure wheel, the vehicle height of the entire vehicle body increases due to the hydraulic pressure increase of the four hydraulic cylinders 20. Therefore, the vehicle height can be increased quickly with a small amount of oil. In this case, the hydraulic oil is supplied to the low-pressure gas spring 32 because the bypass valve 63 is kept open in the open failure wheel.

  Subsequently, in step S24, the ECU 100 waits until the actual vehicle height Lx detected by the vehicle height sensor reaches the target vehicle height L0. When the ECU 100 determines that the actual vehicle height Lx at any wheel W excluding the open failure wheel has reached the target vehicle height L0 (S24: Yes), the corresponding wheel that has reached the target vehicle height L0 at that time in step S25. The detected value of the pressure sensor 90 is stored in association with the wheel position as the vehicle height adjustment completion pressure P0.

  Subsequently, in step S26, the ECU 100 switches the leveling valve 61 of the relevant wheel from the open state to the closed state. Thereby, the vehicle height adjustment at the corresponding wheel is completed. Subsequently, in step S27, the ECU 100 determines whether or not the vehicle height adjustment has been completed for all the wheels other than the open failure wheel, and wheels (wheels other than the open failure wheel) for which vehicle height adjustment has not been completed are determined. If it remains, the process returns to step S24 and the same process is repeated.

  Thus, when the vehicle height adjustment is completed for all the wheels other than the open failure wheel, the ECU 100 advances the process to step S28 and switches the leveling valve 61 of the open failure wheel from the closed state to the open state. As a result, the hydraulic pressure of the hydraulic cylinder 20 of the open failure wheel increases. In this case, for the closed failure wheel, the hydraulic oil is supplied to the hydraulic cylinder 20 with the spring switching valve 62 opened, so the hydraulic oil is also supplied to the low gas spring 32 at the same time. This is because the closed valve cannot open the bypass valve 63, so that the low gas spring 32 can be used (the wheel rate is reduced) and the hydraulic cylinder 20 and the low gas spring 32 are used. This is because it is necessary to supply hydraulic oil to the low gas spring 32 by communicating with each other.

  Subsequently, in step S29, the ECU 100 waits until the actual vehicle height Lx detected by the vehicle height sensor reaches the target vehicle height L0 for the open failure wheel. When the ECU 100 determines that the actual vehicle height Lx in the open failed wheel has reached the target vehicle height L0 (S29: Yes), in step S30, the detected value of the pressure sensor 90 at that time is the vehicle height adjustment completion pressure of the open failed wheel. Store as P0. The vehicle height adjustment completion pressure P0 is equal to the hydraulic pressure of the hydraulic cylinder 20 and the high gas spring 31 of the open failure wheel.

  Subsequently, in step S31, the ECU 100 switches the leveling valve 61 of the open failure wheel from the open state to the closed state, ends the vehicle height increase control subroutine after the failure detection, and performs the process after detecting the failure. Proceed to the spring hydraulic pressure adjustment subroutine (FIG. 6). Note that the vehicle height increase control subroutine after failure detection is processing assuming a case where there is only one failed wheel. Therefore, when a failure of the bypass valve 63 is detected in a plurality of wheels, the ECU 100 may stop the process related to the vehicle height control at that time.

  When the vehicle height of the three wheels other than the open failure wheel is increased, the vehicle height of the entire vehicle body increases due to the height increase of the three wheels. For this reason, in the vehicle height increase control subroutine after failure detection, the vehicle height of the three wheels other than the open failure wheel is increased first, and then the vehicle height of the open failure wheel is increased. The time required for the rise is shortened. That is, after the leveling valve 61 for the open failed wheel is closed, the leveling valves 61 for the three wheels other than the open failed wheel are opened to raise the vehicle height of the three wheels, and then the leveling valve for the open failed wheel is set. 61 is opened to raise the vehicle height of the open failure wheel. It should be noted that the leveling valve 61 for the open failure wheel does not necessarily need to be opened after the height of the three wheels other than the open failure wheel has been raised, and the leveling valve 61 may be opened simultaneously for the four wheels.

  Next, the low gas spring hydraulic pressure adjustment subroutine after failure detection will be described. When the low gas spring hydraulic pressure adjustment subroutine is started after failure detection, the ECU 100 selects one of the four normal wheels (wheels that are neither an open failure wheel nor a closed failure wheel) in step S121. Subsequently, in step S122, the ECU 100 performs low gas spring hydraulic pressure adjustment for the selected normal wheel. The process of step S122 is the same process as the low gas spring hydraulic pressure adjustment routine (S100) described above, and the hydraulic pressure of the low pressure gas spring 32 of the normal wheel is increased to the vehicle height adjustment completion pressure P0 stored in step S25. And processing for determining a failure (open failure and closed failure) of the bypass valve 63 based on a change in hydraulic pressure in the process.

  Subsequently, in step S123, the ECU determines whether or not the low gas spring hydraulic pressure adjustment in step S122 has been completed for all the normal wheels, and there are remaining wheels for which the low gas spring hydraulic pressure adjustment has not been completed. In step S121, the process returns to step S121, and one of the remaining normal wheels is selected. In step S122, low gas spring hydraulic pressure adjustment is performed for the normal wheel.

  The ECU 100 repeats such a process, and when the low gas spring hydraulic pressure adjustment is completed for all the normal wheels, the ECU 100 determines whether or not there is an open failure wheel in step S124. If no open fault wheel exists, a closed fault wheel exists. When the closed failure wheel exists (S124: No), the low gas spring 32 of the closed failure wheel has already been supplied with hydraulic oil at the same pressure as the hydraulic cylinder 20 by the vehicle height raising control subroutine after failure detection. Yes. Accordingly, since the hydraulic pressure adjustment of the low gas spring 32 is not necessary, after stopping the pump device 71 in step S125, the original valve 64 is switched from the open state to the closed state in step S126, and the low gas spring after failure detection is detected. End the hydraulic pressure adjustment subroutine.

  On the other hand, if there is an open failure wheel (S124: Yes), the ECU 100 waits in step S127 until the detected value Px of the pressure sensor 90 reaches the vehicle height adjustment completion pressure P0 stored in step S30. When the detected value Px reaches the vehicle height adjustment completion pressure P0 (S127: Yes), the ECU 100 stops the pump device 71 in step S128, and then switches the original valve 64 from the open state to the closed state in step S129.

  Subsequently, in step S130, the ECU 100 switches the spring switching valve 62 of the open failure wheel from the closed state to the open state, and ends the low gas spring hydraulic pressure adjustment subroutine after the failure is detected. In the low gas spring hydraulic pressure adjustment subroutine after the failure detection, the hydraulic pressure adjustment of the low gas spring 32 of the open failure wheel is finally performed. The reason is that in the open failure wheel, since the bypass valve 63 is open, the oil pressure of the low gas spring 32 cannot be adjusted using the bypass valve 63, and therefore the original valve 64 is used instead of the bypass valve 63. This is because it is necessary to adjust the hydraulic pressure of the low gas spring 32. Therefore, after the hydraulic control of the low gas springs 32 of the wheels other than the open failure wheel is completed and the bypass valves 63 are closed, the hydraulic pressure adjustment of the low gas spring 32 of the open failure wheel is performed.

  According to the suspension system of the present embodiment described above, since the individual bypass passage 53 and the bypass valve 63 are provided, supply / discharge of hydraulic oil to / from the hydraulic cylinder 20 and the high gas spring 31 and to the low gas spring 32 are performed. The supply / discharge of the hydraulic oil can be performed independently of each other. As a result, the vehicle height can be adjusted using the hydraulic system excluding the low gas spring 32, so that the vehicle height can be increased quickly with a small amount of oil.

  Accordingly, the required supply flow rate of the hydraulic oil in the hydraulic oil supply / discharge device 70 can be reduced, so that the configuration can be simplified. For example, the discharge flow rate of the pump 71a can be reduced. Further, it is not necessary to provide a pressure accumulator for supplementing the discharge flow rate of the pump as in the conventional apparatus. As a result, the hydraulic oil supply / discharge device 70 can be reduced in weight.

  Further, since the hydraulic pressure of the low gas spring 32 is adjusted to be equal to the hydraulic pressure of the hydraulic cylinder 20 after the vehicle height is adjusted, the vehicle height does not fluctuate even if the spring switching valve 62 is opened and the wheel rate is switched. Can be.

  Further, when the hydraulic pressure adjustment of the low gas spring 32 is performed, the failure of the bypass valve 63 is detected by specifying the wheel in which the failure has occurred and the type of the failure (open failure and closed failure). be able to. Further, when a failure of the bypass valve 63 is detected, vehicle height increase control and low gas spring hydraulic pressure adjustment corresponding to the type of failure are performed, so that the reliability of the suspension system can be improved.

  Further, when detecting the closing failure of the bypass valve 63, the presence or absence of the closing failure is determined based on the decreasing gradient of the detected value Px of the pressure sensor when the vehicle height adjustment is completed and the valve opening command is output to the bypass valve 63. Is determined. Therefore, the closed failure can be detected easily and reliably. Further, when detecting an open failure of the bypass valve 63, a pressure sensor when the hydraulic pressure adjustment of the low gas spring 32 is completed, a valve closing command is output to the bypass valve 63, and the pump device 71 is stopped. Based on the decrease gradient of the detected value Px of 90, the presence or absence of an open failure is determined. Therefore, an open failure can be detected easily and reliably.

  When the vehicle height is controlled to be lowered, the ECU 100 disconnects the low gas spring 32 from the hydraulic cylinder 20 (with the spring switching valve 62 closed) and operates from the hydraulic cylinder 20 similarly to the vehicle height increase control. The oil may be discharged, or the hydraulic oil may be discharged from the hydraulic cylinder 20 in a state where the hydraulic cylinder 20 and the low gas spring 32 are in communication. In the former case, it is necessary to adjust the hydraulic pressure by discharging the hydraulic oil from the low gas spring 32 after the vehicle height control is finished. In the latter case, it is necessary to adjust the hydraulic pressure of the low gas spring 32. Absent.

  The suspension system 1 according to the present embodiment has been described above. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the present embodiment, the number of gas springs provided corresponding to the hydraulic cylinders 20 of each wheel W is two (high gas spring 31 and low gas spring 32), but there is another gas spring. It may be provided. For example, a relief gas spring for allowing the pressure to escape when the pressure in the hydraulic circuit rises abnormally may be in constant communication with the hydraulic cylinder 20.

  In the present embodiment, both the open failure and the closed failure of the bypass valve 63 are detected. However, it is not always necessary to detect both failures, and at least one failure may be detected. In this case, for example, the configuration in which steps S103, S113, and S114 in the low gas spring hydraulic pressure adjustment subroutine (FIG. 4) are omitted to detect the closed failure of the bypass valve 63, or steps S108, S118, and S119 are omitted. A configuration in which detection of an open failure of the bypass valve 63 is omitted can be employed.

  DESCRIPTION OF SYMBOLS 1 ... Suspension system, 10 ... Suspension apparatus, 11 ... Wheel holding member, 20 ... Hydraulic cylinder, 21 ... Housing, 22 ... Piston, 31 ... Main accumulator (high gas spring), 32 ... Sub-accumulator (low gas spring), 50 DESCRIPTION OF SYMBOLS ... Hydraulic control circuit, 51 ... Individual supply / discharge passage, 52 ... Individual rate switching passage, 53 ... Individual bypass passage, 54 ... Common supply / discharge passage, 61 ... Leveling valve, 62 ... Switching valve, 63 ... Bypass valve, 64 ... original Valve, 70 ... Hydraulic oil supply / discharge device, 71 ... Pump device, 71a ... Pump, 71b ... Pump motor, 72 ... Reservoir tank, 73 ... Check valve, 74 ... Return valve, 90 ... Pressure sensor, 100 ... Electronic control unit ( ECU), 110 ... motion detection sensor, 120 ... operation detection sensor, W ... wheel.

Claims (1)

A hydraulic cylinder that is provided between the wheel holding member and the vehicle body in each of the left and right front and rear wheels of the vehicle, accommodates hydraulic oil, and expands and contracts in accordance with a change in distance between the wheel holding member and the vehicle body;
The first oil chamber is provided corresponding to each hydraulic cylinder of the left and right front and rear wheels, and includes a first gas chamber and a first oil chamber communicating with the hydraulic cylinder, the first oil corresponding to the hydraulic pressure of the hydraulic cylinder. A first gas spring that functions as a hydraulic spring by changing the amount of hydraulic oil contained in the chamber;
A second gas chamber and a second oil chamber communicating with the hydraulic cylinder are provided to correspond to the respective hydraulic cylinders, and are accommodated in the second oil chamber according to the hydraulic pressure of the hydraulic cylinder. A second gas spring that functions as a hydraulic spring by changing the amount of hydraulic oil
A spring switching valve provided corresponding to each of the hydraulic cylinders and capable of switching between a state allowing communication between the hydraulic cylinder and the second gas spring and a state blocking the hydraulic cylinder;
A hydraulic oil supply / discharge device for supplying and discharging hydraulic oil to and from each hydraulic cylinder;
A supply / discharge hydraulic control circuit having a supply / discharge source passage which is connected to the hydraulic oil supply / discharge device and serves as a flow path for the hydraulic oil, and an original valve which opens and closes the supply / discharge source passage;
A vehicle height adjusting passage that is provided corresponding to each of the hydraulic cylinders and that communicates each of the hydraulic cylinders with the supply / discharge source passage, and opens and closes the vehicle height adjusting passage. A vehicle height adjustment hydraulic control circuit having a vehicle height adjustment valve;
A hydraulic oil passage provided corresponding to each of the hydraulic cylinders, bypassing the spring switching valve and the vehicle height adjusting valve, and communicating each of the second gas springs with the supply / discharge source passage; A hydraulic control circuit for a second gas spring having a bypass passage and a bypass valve for opening and closing the bypass passage;
The spring switching valve and the bypass valve are closed, the original valve and the vehicle height adjusting valve are opened, and hydraulic oil is supplied from the hydraulic oil supply / discharge device to the hydraulic cylinders of the wheels. Vehicle height increase control means for increasing the vehicle height at each wheel position to the target vehicle height;
Provided on the hydraulic cylinder side with respect to the original valve, on the original valve side with respect to the bypass valve and on the original valve side with respect to the vehicle height adjusting valve; A hydraulic pressure sensor for detecting the hydraulic pressure of the flow path;
Hydraulic storage means for storing the hydraulic pressure detected by the hydraulic sensor when the vehicle height rises to the target vehicle height for each wheel position;
After the rise of the vehicle height to the target vehicle height is completed, the spring switching valve and the second gas spring are equalized with the hydraulic pressure corresponding to the wheel position stored in the hydraulic pressure storage means. While maintaining the vehicle height adjustment valve in the closed state, the bypass valve is opened one by one, and the supply of hydraulic oil from the hydraulic oil supply / discharge device to the second gas spring is started, When the hydraulic pressure detected by the hydraulic pressure sensor reaches the hydraulic pressure corresponding to the wheel position stored in the hydraulic pressure storage means, the bypass valve is closed and the hydraulic oil supply / discharge device performs the hydraulic oil supply operation. Second gas spring hydraulic pressure adjusting means for stopping;
A change in oil pressure detected by the oil pressure sensor after the second gas spring oil pressure adjusting means outputs a valve opening command for opening the bypass valve, and the second gas spring oil pressure adjusting means includes the bypass. Based on at least one of changes in hydraulic pressure detected by the hydraulic sensor after outputting a valve closing command for closing the valve and stopping the hydraulic oil supply operation of the hydraulic oil supply / discharge device, A suspension system comprising: a bypass valve failure detection unit that determines that the bypass valve has failed when the change in hydraulic pressure does not indicate a predetermined decrease gradient.

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