JP6836195B2 - Suspension system - Google Patents

Description

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

Conventionally, for example, as proposed in Patent Document 1, a suspension system that adjusts the vehicle height by controlling the oil pressure of a hydraulic cylinder (shock absorber) provided between a vehicle body and a wheel holding member of four wheels has been used. Are known. The hydraulic cylinders of each wheel are connected to the hydraulic oil supply / discharge device via individual control passages. 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 to supply hydraulic oil to each hydraulic cylinder to raise the vehicle height, and hydraulic oil is supplied from each hydraulic cylinder. The vehicle height is lowered by discharging it.

Further, each hydraulic cylinder is communicated with a high-pressure accumulator having a large spring constant and a low-pressure accumulator having a small spring constant. A spring switching valve that can switch between a state in which communication between the hydraulic cylinder and the low-pressure accumulator is allowed and a state in which the communication between the hydraulic cylinder and the low-pressure accumulator is cut off is provided. Therefore, the wheel rate can be switched by opening and closing the spring switching valve.

In this suspension system, the high-pressure accumulator and the low-pressure accumulator are communicated with the hydraulic cylinder during normal driving (spring switching valve: open), and the wheel rate is set to 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 to large (hard). The wheel rate is a spring constant at the wheel position, and is the ratio of the change in the ground contact load of the wheel to the change in the vertical distance between the vehicle body and the wheel center on the wheel (wheel travel), that is, the unit wheel travel. Represents the amount of change in the ground contact load of the wheel required to generate it.

Japanese Unexamined Patent Publication No. 2008-168861

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, but at this time, the low pressure accumulator and the high pressure accumulator are also operated at the same time. Oil is supplied. Therefore, a large amount of hydraulic oil is required to raise the vehicle height, and accordingly, the time required to raise the vehicle height becomes longer.

Therefore, the applicant of the present application has considered a new suspension system capable of independently supplying and discharging the hydraulic oil of the hydraulic cylinder and the hydraulic oil of 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. Therefore, by supplying the 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 raised without supplying the 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 differential pressure between the two, and the vehicle height fluctuates. Resulting in. However, in this new system, after the vehicle height rise is completed, the bypass valve is opened with the individual control valve and spring switching valve closed, so that the hydraulic oil supply / exhaust device operates only on the low-pressure accumulator. Oil can be supplied. Therefore, by raising the oil pressure of the low-pressure accumulator until it becomes equal to the oil pressure of the hydraulic cylinder, it is possible to prevent the vehicle height from changing even if the spring switching valve is opened thereafter.

In such a system, it is necessary to measure the oil pressure of the hydraulic cylinder and the low pressure accumulator individually. For this purpose, a main valve is provided in the supply / discharge source passage, which is a common passage for supplying hydraulic oil from the hydraulic oil supply / discharge device to the hydraulic cylinders of each wheel, and is downstream from the main valve (upstream of the hydraulic supply / discharge device). A hydraulic sensor is provided on the side).

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

The present invention has been made to solve the above problems, and an object of the present invention is to properly detect a failure of the original 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 on each of the left, right, front, and rear wheels of the vehicle, which accommodates hydraulic oil and expands and contracts according to a change in the distance between the wheel holding member and the vehicle body. ,
A first gas spring (31) and a second gas spring (32), which are provided corresponding to the hydraulic cylinders of the left and right front and rear wheels and communicate with the hydraulic cylinders to function as a hydraulic spring,
A spring switching valve (62) provided corresponding to each of the hydraulic cylinders and capable of switching between a state in which communication between the hydraulic cylinder and the second gas spring is permitted and a state in which communication is cut off.
A pump for supplying and discharging hydraulic oil to each of the hydraulic cylinders, and a hydraulic oil supply / discharge device (70) having a reservoir tank.
A main valve provided in parallel with a supply / discharge source passage that is connected to the hydraulic oil supply / discharge device and serves as a flow path for hydraulic oil, and a first source valve and a second source valve that open and close the supply / discharge source passage. Supply / exhaust hydraulic control circuit (54,80) with a pair,
The vehicle height adjustment passage, which is provided corresponding to each of the hydraulic cylinders and is a flow path for hydraulic oil that communicates each of the hydraulic cylinders with the supply / discharge source passage, and the opening / closing of the vehicle height adjustment passage. Vehicle height adjustment hydraulic control circuit (51, 61) having a vehicle height adjustment valve
A flow path of hydraulic oil 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 flood control circuit for a second gas spring (53, 63) having a bypass passage and a bypass valve for opening and closing the bypass passage.
In the flow path of the hydraulic oil which is on the hydraulic cylinder side with respect to the original valve pair, on the side of the original valve with respect to the bypass valve, and on the opposite side of the original valve with respect to the vehicle height adjustment valve. A hydraulic sensor (90) provided to detect the oil pressure in the flow path and
When adjusting the vehicle height in the ascending direction, the first source valve and the second source valve are controlled to be in an open state, and the spring switching valve and the bypass valve of the vehicle height adjustment target wheel are closed. In this state, the vehicle height adjustment valve of the vehicle height adjustment target wheel is controlled to open until the vehicle height reaches the target vehicle height, and the hydraulic oil supply / discharge device supplies hydraulic oil to the hydraulic cylinder to supply the vehicle. The hydraulic pressure detected by the hydraulic sensor when the height reaches the target vehicle height is memorized, and the vehicle height adjustment is performed with the spring switching valve and the vehicle height adjustment valve of the vehicle height adjustment target wheel closed. Vehicle height in which the bypass valve is controlled to open until the hydraulic pressure of the second gas spring of the target wheel becomes equal to the stored hydraulic pressure, and the hydraulic oil is supplied to the second gas spring by the hydraulic oil supply / discharge device. Ascending control means (10, S20) and
When adjusting the vehicle height in the downward direction, when lowering the vehicle height of the front wheels without adjusting the vehicle height on the front and rear wheels at the same time, the first valve is opened and the second valve is opened. By controlling the valve to the first control state (S41) in which the valve is closed and at least the vehicle height adjusting valve of the front wheel is opened, the hydraulic oil of the hydraulic cylinder of the front wheel is sent to the hydraulic oil supply / discharge device. When returning and lowering the vehicle height of the rear wheels, the second main valve is in the valve open state, the first main valve is in the closed state, and at least the rear wheel height adjustment valve is in the open state. A vehicle height lowering control means for returning the hydraulic oil of the hydraulic cylinder of the rear wheel to the hydraulic oil supply / discharge device by controlling to the second control state (S61).
When the change in the detection value of the oil pressure sensor and the change in the vehicle height of the front wheels are not detected when the vehicle height lowering control means controls the first control state, the second valve is closed. When the valve is switched from the state to the valve open state and a change in the detection value of the oil pressure sensor and a change in the vehicle height of the front wheels are detected at that time, it is determined that the first original valve is abnormal (S42). , S46, S47, S48), when the change in the detection value of the oil pressure sensor and the change in the vehicle height of the rear wheels are not detected when the vehicle height lowering control means controls to the second control state. When the first valve is switched from the closed state to the opened state, and a change in the detection value of the oil pressure sensor and a change in the vehicle height of the rear wheel are detected at that time, the second valve is detected. It is provided with an abnormality detecting means for determining that the valve is abnormal (S62, S66, S67, S68).

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

Each of the left and right front and rear wheel hydraulic cylinders is provided with a first gas spring and a second gas spring that communicate with the hydraulic cylinders and function as hydraulic springs. The first gas spring is provided, for example, by partitioning a first gas chamber and a first oil chamber communicating with the hydraulic cylinder, and the amount of hydraulic oil stored in the first oil chamber according to the hydraulic pressure of the hydraulic cylinder is increased. It changes and functions as a hydraulic spring. The second gas spring is provided, for example, by partitioning a second gas chamber and a second oil chamber communicating with the hydraulic cylinder, and the amount of hydraulic oil stored in the second oil chamber according to the hydraulic pressure of the hydraulic cylinder is increased. It changes and functions as a hydraulic spring.

The second gas spring is switched between a state in which communication with the hydraulic cylinder is allowed and a state in which communication with the hydraulic cylinder is cut off by the spring switching valve. Therefore, when the spring switching valve is opened, the hydraulic cylinder is in a state of communicating with both the first gas spring and the second gas spring, that is, a state (soft) in which the wheel rate is set small. Further, when the spring switching valve is closed, the hydraulic cylinder is in a state of communicating only with the first gas spring of the first gas spring and the second gas spring, that is, a state in which the wheel rate is set high. It becomes (hard).

By adjusting the pressure of the hydraulic oil contained 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 supply / discharge hydraulic control circuit, whereby the vehicle height is adjusted. The hydraulic oil supply / discharge device has a pump (high pressure source) for supplying hydraulic oil to the hydraulic cylinder and a reservoir tank (low pressure source) for discharging hydraulic oil from the hydraulic cylinder.

The supply / drainage hydraulic 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 pair that opens and closes the supply / discharge source passage. The original valve pair is configured by providing a first original valve and a second original valve in parallel. Therefore, if either one of the first source valve and the second source valve is opened, the supply / discharge source passage is opened. Further, when both the first valve and the second valve are opened, the passage resistance of the supply / discharge source passage is reduced as compared with the case where one of the valves is opened. be able to. Hereinafter, the valve open state of the original valve pair means a state in which at least one of the first original valve and the second original valve is opened, and the valve closed state of the original valve pair means the first original valve and the first valve. Indicates a state in which both the dual valve and the valve are closed.

The suspension system includes a vehicle height adjusting 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 for vehicle height adjustment that opens and closes the vehicle height adjustment passage, which is a flow path for hydraulic oil that communicates each of the hydraulic cylinders with the supply / discharge source passage, and the vehicle height adjustment passage. Has a valve. Therefore, the vehicle height can be adjusted by adjusting the oil pressure of the hydraulic cylinder of the vehicle height adjustment target wheel by opening the original valve pair and the vehicle height adjustment valve of the vehicle height adjustment target wheel. ..

The flood control circuit for the second gas spring bypasses the spring switching valve and the vehicle height adjustment valve, and is a bypass passage which is a flow path of hydraulic oil for communicating each of the second gas springs with the supply / discharge source passage, and a bypass passage. It has a bypass valve that opens and closes the bypass passage. Therefore, the oil pressure of any second gas spring can be adjusted independently by opening the original valve pair and any bypass valve with the spring switching valve and the vehicle height adjustment valve closed. Can be done.

When adjusting the oil pressure of any second gas spring independently, if the oil pressure of the hydraulic cylinder and the oil pressure of the second gas spring are set to the same pressure, the vehicle height can be changed even if the spring switching valve is opened and closed thereafter. The wheel rate can be switched without changing. Therefore, a hydraulic sensor is provided. The oil pressure sensor is provided in the flow path of the hydraulic oil which is on the hydraulic cylinder side with respect to the original valve pair, on the original valve opposite side with respect to the bypass valve, and on the original valve opposite side with respect to the vehicle height adjustment valve. , Detects the oil pressure in the flow path.

When adjusting the vehicle height in the ascending direction, the vehicle height rise control means controls the first source valve and the second source valve in the open state, and closes the spring switching valve and the bypass valve of the vehicle height adjustment target wheel. With the valve open, the valve for adjusting the height of the vehicle height adjustment target wheel is controlled to open until the vehicle height reaches the target vehicle height, and the hydraulic oil is supplied to the hydraulic cylinder by the hydraulic oil supply / discharge device. The hydraulic pressure detected by the hydraulic sensor when the height reaches the target vehicle height is memorized, and the spring switching valve and the vehicle height adjustment valve of the vehicle height adjustment target wheel are closed, and the vehicle height adjustment target wheel The bypass valve is controlled to open until the hydraulic pressure of the second gas spring becomes equal to the stored hydraulic pressure, and the hydraulic oil is supplied to the second gas spring by the hydraulic oil supply / discharge device. In this case, when the hydraulic oil is supplied to the hydraulic cylinder, the hydraulic oil is not supplied to the second gas spring, so the vehicle height should be raised to the target vehicle height in a short time (by supplying and discharging a small amount of oil). Can be done.

Further, after the vehicle height reaches the target vehicle height, the hydraulic oil is supplied to the second gas spring so that the oil pressure of the second gas spring becomes equal to the oil pressure of the hydraulic cylinder. Therefore, after that, the spring switching valve is opened. Even in the valve open state, the wheel rate can be reduced without causing pressure fluctuations in the hydraulic cylinder (without causing vehicle height fluctuation shocks).

When adjusting the vehicle height in the downward direction, the vehicle height lowering control means does not adjust the vehicle height at the same time for the front wheels and the rear wheels (for the left and right front wheels and for the left and right rear wheels at the same time, respectively). Adjust the vehicle height). When lowering the vehicle height of the front wheels, the vehicle height lowering control means sets the first valve in the valve open state, the second valve in the closed state, and at least the front wheel height adjustment valve in the valve open state. Controlled to the first control state, the hydraulic oil of the hydraulic cylinder of the front wheel is returned to the hydraulic oil supply / discharge device. As a result, the vehicle height of the front wheels is reduced. The hydraulic oil of the hydraulic cylinder is used in the sense of including the hydraulic oil of the gas spring communicating with the hydraulic cylinder.
In addition, "opening at least the vehicle height adjusting valve on the front wheels" means that the bypass valve on the front wheels and the spring switching valve may be in either the open state or the closed state. doing. For example, in addition to the vehicle height adjustment valve, the bypass valve or the spring switching valve can be opened. In this case, the hydraulic oil of the hydraulic cylinder and the hydraulic oil of the second gas spring can be returned to the hydraulic oil supply / discharge device at the same time. Further, when the bypass valve and the spring switching valve are closed, only the hydraulic oil of the hydraulic cylinder is returned to the hydraulic oil supply / discharge device. In this case, after adjusting the vehicle height, it is advisable to adjust the oil pressure of the second gas spring so that it becomes the same as the oil pressure of the hydraulic cylinder.
Further, when lowering the vehicle height of the rear wheels, the vehicle height lowering control means opens the second valve in the valve state, the first valve in the closed state, and opens at least the valve for adjusting the vehicle height of the rear wheels. Controlling to the second control state of the valve state, the hydraulic oil of the hydraulic cylinder of the rear wheel is returned to the hydraulic oil supply / discharge device. As a result, the vehicle height of the rear wheels is reduced. In addition, "the valve for adjusting at least the vehicle height of the rear wheels is opened" means that the bypass valve for the rear wheels and the spring switching valve may be in either the open state or the closed state. Means.

If the original valve pair is closed (failure that cannot be opened), the pump will be locked and the pump motor will fail. Therefore, the suspension system of the present invention is provided with an abnormality detecting means for detecting an abnormality of the original valve pair.

The abnormality detecting means closes the second valve when the change in the detection value of the oil pressure sensor and the change in the vehicle height of the front wheels are not detected when the vehicle height lowering control means controls to the first control state. When the valve is switched from the state to the valve open state and a change in the detection value of the oil pressure sensor and a change in the vehicle height of the front wheels are detected at that time, it is determined that the first valve is abnormal (closed failure). For example, when the change in the detection value of the oil sensor is smaller than the preset set oil pressure change value, it is determined that the change in the detection value of the oil pressure sensor is not detected, and when it is equal to or more than the set oil pressure change value, the oil pressure sensor It is determined that a change in the detected value of is detected. Further, for example, when the change value of the vehicle height of the front wheels is smaller than the preset vehicle height change value, it is determined that the change of the vehicle height of the front wheels has not been detected, and when it is equal to or more than the set vehicle height change value. , It is determined that a change in the vehicle height of the front wheels has been detected.

Further, the abnormality detecting means is the first valve when the change in the detection value of the oil pressure sensor and the change in the vehicle height of the rear wheels are not detected when the vehicle height lowering control means controls to the second control state. When the valve is switched from the closed state to the open state, and a change in the detected value of the oil pressure sensor and a change in the vehicle height of the rear wheels are detected at that time, the second valve is abnormal (closed failure). Is determined. For example, when the change in the detection value of the oil sensor is smaller than the preset set oil pressure change value, it is determined that the change in the detection value of the oil pressure sensor is not detected, and when it is equal to or more than the set oil pressure change value, the oil pressure sensor It is determined that a change in the detected value of is detected. Further, for example, when the change value of the vehicle height of the rear wheels is smaller than the preset vehicle height change value, it is determined that the change of the vehicle height of the rear wheels is not detected, and the change value is equal to or more than the set vehicle height change value. In this case, it is determined that a change in the vehicle height of the rear wheels has been detected.

When the first valve is closed and malfunctions, the hydraulic oil is not discharged to the reservoir tank even if it is controlled to the first control state, and the change in the detection value of the oil pressure sensor and the change in vehicle height are not detected. .. When the second valve is switched from the closed state to the open state in that state, the hydraulic oil is discharged to the reservoir tank, and along with this, changes in the detection value of the oil pressure sensor and changes in vehicle height are detected. Will be done. Therefore, the abnormality detecting means can detect the closing failure of the first original valve by detecting such a phenomenon.

When the second valve is closed and malfunctions, the hydraulic oil is not discharged to the reservoir tank even if it is controlled to the second control state, and the change in the detection value of the oil pressure sensor and the change in vehicle height are not detected. .. When the primary valve is switched from the closed state to the open state in that state, the hydraulic oil is discharged to the reservoir tank, and along with this, changes in the detection value of the oil pressure sensor and changes in vehicle height are detected. Will be done. Therefore, the abnormality detecting means can detect the closing failure of the secondary valve by detecting such a phenomenon.

Thereby, according to the present invention, it is possible to properly detect the closing failure of the first source valve and the second source valve.

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

It is an overall block diagram which shows the outline of the suspension system which concerns on this embodiment. It is a flowchart which shows the vehicle height control routine. It is a flowchart which shows the vehicle height rise control routine (subroutine). It is a flowchart which shows the front vehicle height descent control routine (subroutine). It is a flowchart which shows the rear vehicle height descent control routine (subroutine).

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 the suspension system 1 of the present embodiment.

The suspension system 1 includes suspension devices 10FL, 10FR, 10RL, 10RR that connect each of the left and right front and rear wheels WFL, WFR, WRL, and WRR and the vehicle body so as to be detachable, 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 a hydraulic control circuit provided between the suspension devices 10FL, 10FR, 10RL, 10RR and the hydraulic oil supply / discharge device 70. It includes 50 and an electronic control unit 100 (called ECU 100) that controls the operation of the entire system.

Below, regarding the symbols attached to the end of the code, 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. Although it means that the member is a member to be used and RR is a member provided corresponding to the right rear wheel, the symbol at the end is omitted when it is not necessary to specify the corresponding wheel in the specification. Further, among the members provided corresponding to the left, right, front and rear wheels, when specifying the member provided corresponding to the front wheel, an F is added to the end of the code to specify the member provided corresponding to the rear wheel. If so, add R at the end of the code.

The suspension device 10 includes a wheel holding member 11 (for example, a lower arm) that holds each of the left, right, front, and rear wheels W, and a hydraulic cylinder 20 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 according to a change in the distance between the wheel holding member 11 and the vehicle body.

Each hydraulic cylinder 20 has the same structure as each other, and has a housing 21, a piston 22 fitted inside the housing 21 so as to be relatively movable with respect to the housing 21, and a piston 22 to the outside of the housing 21, respectively. It includes 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 24a and 24b by a piston 22. The piston 22 is formed with a communication passage 25 for communicating the oil chambers 24a and 24b, and the communication passage 25 is formed with a throttle (not shown). By this throttle, 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 the direction of separating 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, in the hydraulic cylinder 20, the higher the pressure of the hydraulic oil supplied from the individual supply / discharge passage 51, the larger the distance between the wheel holding member 11 and the vehicle body to increase the vehicle height.

A main accumulator 31 and a leveling valve 61 are connected to each individual supply / discharge passage 51 in order from the side closest 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 adjusting 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 adjusting hydraulic control circuit of the present invention.

The main accumulator 31 includes a housing 31a and a partition member 31b for partitioning the inside of the housing 31a into two capacity change chambers, and an individual supply / discharge passage to an oil chamber 31c which is one of the capacity change chambers partitioned by the partition member 31b. The gas chamber 31d, which is the other capacity changing chamber, is filled with a gas (for example, nitrogen gas) which is an elastic body. 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. Therefore, the main accumulator 31 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 31c according to the oil pressure of the hydraulic cylinder 20. To do. The oil chamber 31c of the main accumulator 31 always communicates with the oil chamber 24a of the hydraulic cylinder 20.

The leveling valve 61 is a normally closed electromagnetic on-off valve that operates when the vehicle height is adjusted 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. The spring switching valve 62 and the sub-accumulator 32 are connected to the individual rate switching passage 52 in order from the side closest to the connection position with the individual supply / discharge passage 51.

The sub-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 divides the inside of the housing 32a into two capacity change chambers, and an individual rate switching passage is provided in the oil chamber 32c, which is one of the capacity change chambers partitioned by the partition member 32b. 52 is communicated with each other, and the gas chamber 32d, which is the other capacity changing 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. Therefore, 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 32c according to the oil pressure of the hydraulic cylinder 20. To do.

The sub-accumulator 32 has a smaller spring constant than the main accumulator 31. As the main accumulator 31 and the sub accumulator 32, any type such as a bellows type, a bladder type, and a piston type can be adopted. In the present embodiment, the main accumulator 31 is a metal bellows type accumulator having excellent gas permeability at high compression pressure. Further, as the sub-accumulator 32, a bladder type accumulator containing a resin film which 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 20 and the sub-accumulator 32 is cut off (it can also be expressed that the communication between the main accumulator 31 and the sub-accumulator 32 is cut off). 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 is composed of 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, is also a passage for supplying hydraulic oil from the hydraulic oil supply / discharge device 70 to each individual supply / discharge passage 51, and operates from each individual supply / discharge passage 51. It is also a passage for returning oil to the hydraulic oil supply / discharge device 70.

A former valve pair 80 is provided in the common supply / discharge passage 54. The original valve pair 80 includes a first element valve 81, which is a normally closed electromagnetic on-off valve, and a second element valve 82, which is a normally closed electromagnetic on-off valve, in parallel. Therefore, in a state where at least one of the first source valve 81 and the second source valve 82 is open, each individual supply / discharge passage 51 and the hydraulic oil supply / discharge device 70 communicate with each other, and the first source valve 81 In a state where both the valve and the second valve 82 are closed, the communication between each individual supply / discharge passage 51 and the hydraulic oil supply / discharge device 70 is cut off. Hereinafter, the valve open state of the original valve to 80 represents a state in which at least one of the first original valve 81 and the second original valve 82 is opened, and the valve closed state of the original valve to 80 is the first valve. It represents a state in which both the primary valve 81 and the secondary valve 82 are opened.

In FIG. 1, the common supply / discharge passage 54 is a passage that communicates with the individual supply / discharge passages 51FL and 51FR of the left and right front wheels on the downstream side of the original valve pair 80, and the individual supply / discharge passages 51RL of the left and right rear wheels. It branches into a passage that communicates with 51RR, but it is not always necessary to branch in this way. For example, each individual supply / discharge passage 51FL, 51FR, 51RL, 51RR is directly connected to a common supply / discharge passage 54 common to all four wheels, and the hydraulic oil from the hydraulic oil supply / discharge device 70 to each individual supply / discharge passage 51. (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 pair 80 corresponds to the supply / discharge hydraulic 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. A bypass valve 63 is provided in each individual bypass passage 53. The bypass valve 63 is a normally closed electromagnetic on-off valve. Therefore, when the bypass valve 63 is open, 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 gas spring hydraulic control circuit 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 of 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 has a check valve 73 (check valve) and a return valve 74 at positions on the upstream side of the original valve vs. 80. Are provided in parallel.

The return valve 74 is a valve that switches between supplying hydraulic oil from the pump device 71 to the original valve to 80 and discharging hydraulic oil from the original valve to 80 to the reservoir tank 72. The return valve 74 is normally in a state where the passage between the original valve pair 80 and the reservoir tank 72 is opened by the force of the spring, and when the pump device 71 is driven, the discharge pressure and the common supply / discharge passage are shared. The valve body is pushed by the differential pressure with the oil pressure of 54 to close the passage between the original valve pair 80 and the reservoir tank 72. As a result, the check valve 73 is opened and the hydraulic oil discharged from the pump device 71 flows to the opened original valve pair 80.

Further, the common supply / discharge passage 54 is provided with a hydraulic sensor 90 for detecting the hydraulic pressure on the downstream side of the original valve pair 80. The oil pressure sensor 90 may be provided in any flow path of hydraulic oil surrounded by the original valve to 80, the four leveling valves 61, and the four bypass valves 63. That is, the oil pressure sensor 90 is on the hydraulic cylinder 20 side with respect to the original valve to 80, is on the original valve to 80 side with respect to the four bypass valves 63, and is on the original valve to 80 side with respect to the leveling valve 61. It may be provided in the flow path of the hydraulic oil. Therefore, according to the oil pressure sensor 90, when the leveling valve 61 of an arbitrary wheel is opened with the original valve pair 80 closed, the oil pressure of the hydraulic cylinder 20 of that wheel can be detected. When the bypass valve 63 of any wheel is opened, the oil pressure of the low gas spring 32 of that wheel can be detected.

As described above, the hydraulic control circuit 50 includes the common supply / discharge passage 54, the original valve pair 80, 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. It is composed of a 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 and a storage device such as a ROM and a RAM, and the CPU realizes various functions by executing an instruction (program) stored in the ROM.

The ECU 100 includes various solenoid valves (leveling valve 61, spring switching valve 62, bypass valve 63, and original valve pair 80) provided in the hydraulic control circuit 50, and a pump provided in the hydraulic oil supply / discharge device 70. The motor 71b and the oil pressure sensor 90 are connected. Further, the ECU 100 is connected to a motion detection sensor 110 that detects the vehicle motion state and an operation detection sensor 120 that detects the driver's operation.

The motion detection sensor 110 includes, for example, a vehicle speed sensor that detects vehicle speed, a vehicle height sensor that detects vehicle height for each of the front, rear, left, and right wheel positions, a vertical acceleration sensor that detects vertical acceleration of the vehicle body, and a vehicle body yaw rate. These include a yaw rate sensor and a horizontal accelerometer that detects acceleration in the front-rear, 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 wheel, a transfer sensor that detects the range state of the transfer, and the like. The ECU 100 does not need to directly connect the motion detection sensor 110 and the operation detection sensor 120, and other in-vehicle ECUs (for example, engine ECU, brake ECU, and steering) to which these sensors are connected are not required. The detection signal may be input from (ECU, etc.). Further, 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 that selects the target vehicle height in three ways: normal vehicle height, low vehicle height, and high vehicle height by the operation of the driver. The vehicle height adjustment off switch is a switch that prohibits vehicle height control by the driver's operation.

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

<Wheel rate switching control>
First, the wheel rate switching control will be described. In the suspension system of the present embodiment, the wheel rate of the wheel W can be switched by switching the communication and interruption between the low gas spring 32 and the hydraulic cylinder 20 at the wheel position for each wheel W. That is, the communication state / cutoff state between the hydraulic cylinder 20 and the low gas spring 32 is controlled by opening / closing the spring switching valve 62 (it can also be expressed as a communication state / cutoff state between the high gas spring 31 and the low gas spring 32). The wheel rate can be switched between small (soft) and large (hard) by switching.

For example, the ECU 100 basically keeps the spring switching valve 62 of the four wheels W in the open state to set the wheel rate to a small value (soft) and secure the riding comfort. Further, the ECU 100 detects (or predicts) a change in the posture of the vehicle body such as a roll motion during turning of the vehicle or a pitch motion during braking of the vehicle by the motion detection sensor 110 and the operation detection sensor 120. 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 separated from the hydraulic cylinder 20 of the wheel W to increase the wheel rate (hard). As a result, the roll motion and pitch motion (change in posture of the vehicle body) of the vehicle body can be suppressed.

<Vehicle height control>
Next, vehicle height control will be described. The ECU 100 uses the hydraulic oil supply / discharge device 70 and various solenoid valves 61, 62, 63, 81 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. By controlling, 82, the supply, discharge, and holding of hydraulic oil of the hydraulic cylinders 20 of the front, rear, left, and right wheels W are switched to adjust the vehicle height.

For example, the ECU 100 implements auto-leveling control that always maintains the vehicle height selected by the driver regardless of load conditions such as the number of occupants and the load 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 releases the driver's selected vehicle height when the vehicle speed increases beyond a preset threshold value, and the target vehicle is released. Change the height to the normal vehicle height. Further, the ECU 100 releases the driver's selected vehicle height during high-speed driving and changes the target vehicle height to a preset low vehicle height for high-speed driving. Further, 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 the preset vehicle speed. ..

The ECU 100 includes a hydraulic oil supply / discharge device 70, a leveling valve 61, a spring switching valve 62, a bypass valve 63, and a pair of original valves so that the vehicle height (actual vehicle height) detected by the vehicle height sensor matches the target vehicle height. Drive control of 80. When switching the states of the leveling valve 61, the switching valve 62, the bypass valve 63, and the original valve to 80, 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, indicating that the output of the drive signal is turned on for the normally closed solenoid valve (NC) and is driven for the normally open solenoid valve (NO). Indicates that the signal output is off. The valve closing command is a drive signal for closing the valve, and indicates that the output of the drive signal is off for the normally closed solenoid valve, and the output of the drive signal is turned on for the normally open solenoid valve. Represents.

<Vehicle height control routine>
FIG. 2 shows a vehicle height control routine executed by the ECU 100. The vehicle height control routine is executed when the vehicle height control permission condition is satisfied. When the vehicle height control routine is activated, the ECU 100 first determines in step S11 whether or not a vehicle height adjustment request has been generated. For the vehicle height adjustment request, for example, the absolute value (| L0-Lx |) of the deviation between the vehicle height Lx (hereinafter referred to as the actual vehicle height Lx) detected by the vehicle height sensor and the target vehicle height L0 exceeds the permissible value. Occurs when The ECU 100 temporarily terminates this routine when the vehicle height adjustment request has not occurred. The ECU 100 repeats this routine at a predetermined calculation cycle. Therefore, the determination process of step S11 is repeated until the vehicle height adjustment request is generated.

When the vehicle height adjustment request is generated, the ECU 100 determines in step S12 whether or not the vehicle height adjustment request is an ascending request for raising the vehicle height. The ascending request is generated when the value (L0-Lx) obtained by subtracting the actual vehicle height Lx from the target vehicle height L0 exceeds the permissible value. Further, the descent request is generated when the value (Lx−L0) obtained by subtracting the target vehicle height L0 from the actual vehicle height Lx exceeds the permissible value. When the vehicle height adjustment request is an increase request (S12: Yes), the ECU 100 advances the process to step S20 to perform vehicle height increase control.

On the other hand, when the vehicle height adjustment request is a lowering request for lowering the vehicle height (S12: No), the ECU 100 determines in step S13 whether or not there is a lowering request for the vehicle height of the front wheels. When there is a descent request for both the vehicle height of the front wheels and the vehicle height of the rear wheels, it is determined as "Yes" because the descent request includes the descent request for the vehicle height of the front wheels. On the other hand, when there is no lowering request for the vehicle height of the front wheels, that is, when there is a lowering request only for the vehicle height of the rear wheels, it is determined as "No".

When the ECU 100 has a lowering request for the vehicle height of the front wheels, the process proceeds to step S40 to perform front vehicle height lowering control, and when there is a lowering request only for the vehicle height of the rear wheels, the process is stepped. Proceed to S60 to perform rear vehicle height descent control.

When the ECU 100 executes any of the vehicle height rise control (S20), front vehicle height lowering control (S40), and rear vehicle height lowering control (S60), the vehicle height control routine is temporarily terminated and a predetermined interval is set. Open and restart the vehicle height control routine. Therefore, in the present embodiment, the lowering control for lowering the vehicle height is not performed simultaneously for the front wheels and the rear wheels, and the lowering control for the front wheels is performed before the lowering control for the rear wheels. It should be noted that the lowering control of the rear wheels may be configured to be executed before the lowering control of the front wheels. In that case, the process of step S13 may be a determination process of whether or not there is a lowering request for the vehicle height of the rear wheels.

FIG. 3 is a flowchart showing a vehicle height increase control routine (subroutine) which is a process of vehicle height increase control (S20), and FIG. 4 is a front vehicle height decrease control routine (subroutine) which is a process of front vehicle height lowering control (S40). The flowchart showing the subroutine), FIG. 5 is a flowchart showing the rear vehicle height lowering control routine (subroutine) which is the process of the rear vehicle height lowering control (S60). The front vehicle height lowering control routine and the rear vehicle height lowering control routine incorporate a process for detecting an abnormality of the original valve to 80.

<Vehicle height rise control routine>
First, the vehicle height rise control routine shown in FIG. 3 will be described. Here, the vehicle height rise control routine for one wheel will be described. Therefore, the operation description of the configurations (hydraulic cylinder 20, gas springs 31, 32, and valves 61, 62, 63) provided for each wheel is the operation description of the above configuration in the vehicle height adjustment target wheel. When the vehicle height rise control routine is activated, in step S21, the ECU 100 issues a valve opening command to the first main valve 81, the second main valve 82, and the leveling valve 61 while keeping the bypass valve 63 in the closed state. Output to switch the first source valve 81, the second source valve 82, and the leveling valve 61 from the closed state to the opened state, and output a valve closing command to the spring switching valve 62 to output the spring switching valve 62. Is switched from the valve open state to the valve closed state.

Subsequently, the ECU 100 activates the pump device 71 in step S22. 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. As a result, the vehicle height of the wheel is increased. In this case, since hydraulic oil is not supplied to the low gas spring 32, the vehicle height can be raised quickly with a small amount of oil. Further, since both the first original valve 81 and the second original valve 82 are opened, the flow path resistance in the common supply / discharge passage 54 can be reduced to supply hydraulic oil. Therefore, the vehicle height can be raised even faster.

Subsequently, in step S23, the ECU 100 waits until the actual vehicle height Lx detected by the vehicle height sensor reaches the target vehicle height L0, and when the actual vehicle height Lx reaches the target vehicle height L0 (S23: Yes), step S24. At that time, the detected value of the oil pressure sensor 90 is stored as the vehicle height adjustment completion pressure P0. The vehicle height adjustment completion pressure P0 is equal to the oil pressure of the hydraulic cylinder 20 and the high gas spring 31 of the vehicle height adjustment target wheel.

Subsequently, in step S25, the ECU 100 outputs a valve closing command to the leveling valve 61 while maintaining the first source valve 81 and the second source valve 82 in the valve open state and the spring switching valve 62 in the valve closed state. Then, the leveling valve 61 is switched from the valve open state to the valve closed state, and a valve opening command is output to the bypass valve 63 to switch the bypass valve 63 from the valve closed state to the valve open state. As a result, the hydraulic oil accumulated in the reservoir tank 72 while the oil pressure of the hydraulic cylinder 20 and the high gas spring 31 is held is changed to the original valve to 80 (the first original valve 81, and the first original valve 81) by the operation of the pump device 71. , The second source valve 82) and the bypass valve 63 are supplied to the low gas spring 32.

Subsequently, in step S26, the ECU 100 waits until the detected value Px (referred to as the actual oil pressure Px) of the oil pressure sensor 90 reaches the vehicle height adjustment completion pressure P0. That is, the engine 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 wheel.

When the actual oil pressure Px reaches the vehicle height adjustment completion pressure P0 (S26: Yes), the ECU 100 closes the bypass valve 63, the spring switching valve 62, and the first original valve 81 in step S27. A valve command, a valve closing command to the second valve 82, and a stop command to the pump device 71 are output. As a result, the pump 71a is stopped, the bypass valve 63, the first main valve 81, and the second main valve 82 are switched from the valve open state to the valve closed state, and the spring switching valve 62 is changed from the valve closed state to the valve open state. Switch to. In this way, the hydraulic cylinder 20, the high gas spring 31, and the low gas spring 32 are in communication with each other. When the process of step S27 is executed, the ECU 100 ends the vehicle height rise control routine.

According to this vehicle height rise control routine, when raising the vehicle height, the hydraulic oil is not supplied to the low gas spring 32, and the hydraulic oil is supplied to the low gas spring 32 after the vehicle height has risen to the target vehicle height. Therefore, the amount of oil required to raise the vehicle height can be minimized. In addition, the vehicle height can be quickly raised to the target vehicle height. Further, after the vehicle height has risen to the target vehicle height, hydraulic oil is supplied to the low gas spring 32 so that the low gas spring 32 and the high gas spring 31 have the same pressure, so that the spring switching valve 62 is opened. It is possible to prevent vehicle height fluctuations due to valve operation.

When there are a plurality of wheels (target wheels) for which the vehicle height is to be raised, the ECU 100 starts the process of step S21 at the same time for all the target wheels (the valve opening operation of the original valve to 80 is common). ), After that, when the actual vehicle height Lx reaches the target vehicle height L0 for each target wheel, the vehicle height adjustment completion pressure P0 is stored and the leveling valve 61 of the wheel is closed. Then, the ECU 100 starts the oil pressure adjustment of the low gas spring 32 at the timing when the vehicle height adjustment of the last target wheel is completed. In this case, the ECU 100 sets the bypass valve 63 of the target wheel in a state in which the pump device 71 is in the operating state, the first main valve 81 and the second main valve 82 are in the open state, and the spring switching valve 62 is in the closed state. Switch one wheel at a time and open the valve. The bypass valve 63 is closed at the timing when the actual oil pressure Px reaches the vehicle height adjustment completion pressure P0, and at this timing, the bypass valve 63 of the next target wheel is opened. The ECU 100 closes the first original valve 81 and the second original valve 82 at the timing when the hydraulic adjustment of the low gas spring 32 of the last target wheel is completed (at the timing when the bypass valve 63 of the last target wheel is closed). The valve is opened, the spring switching valve 62 is opened, and the pump device 71 is stopped.

<Front vehicle height descent control routine>
Next, the front vehicle height lowering control routine shown in FIG. 4 will be described. In this front vehicle height lowering control routine, solenoid valves (leveling valve 61F, switching valve 62F, bypass valve 63F, and original valve vs. 80) related to vehicle height adjustment of the front wheel WF are controlled.

When the front vehicle height lowering control routine is activated, the ECU 100 outputs a valve opening command to the first original valve 81 and the leveling valve 61F of the front wheel WF in step S41. In this case, the pump device 71 is stopped, the second original valve 82 is maintained in the closed state, the spring switching valve 62F of the front wheel WF is maintained in the valve open state, and the bypass valve 63F of the front wheel W is maintained in the closed state. As a result, the first original valve 81 and the leveling valve 61F of the front wheel WF are switched from the closed state to the open state. Here, the front wheel WF is a front wheel (there may be two left and right wheels or one left and right wheel) for which a vehicle height lowering request is generated. The control states of the valves 61F, 62F, 63F, 81, 82 controlled by step S41 correspond to the first control state of the present invention.

Subsequently, in step S42, the ECU 100 determines whether the vehicle height of the front wheels (vehicles subject to vehicle height adjustment) WF detected by the vehicle height sensor has not changed and the oil pressure detected by the oil pressure sensor 90 has not changed. Is determined. For example, the ECU 100 determines that the vehicle height has not changed when the change value of the vehicle height of the front wheel WF in a predetermined period is smaller than the preset vehicle height change value. Further, for example, the ECU 100 determines that the oil pressure has not changed when the change in the detected value of the oil pressure sensor 90 in a predetermined period is smaller than the preset set oil pressure change value.

When the first original valve 81 and the leveling valve 61F are opened by step S41, if the suspension system 1 is normal, the oil pressure of the front wheel WF is caused by the force (vehicle weight) acting in the direction of contracting the hydraulic cylinder 20. The hydraulic oil of the cylinder 20F (including the hydraulic oil of the high gas spring 31F and the low gas spring 32F communicating with the hydraulic cylinder 20F) is returned to the reservoir tank 72. Therefore, the hydraulic cylinder 20F of the front wheel WF contracts, the vehicle height of the front wheel WF detected by the vehicle height sensor should decrease, and the oil pressure detected by the oil pressure sensor 90 should also decrease.

If the ECU 100 determines "No" in step S42, the process proceeds to step S43, and if it determines "Yes", the ECU 100 proceeds to step S46. The process from step S46 is a process for determining an abnormality of the first original valve 81.

In step S43, the ECU 100 waits until the actual vehicle height Lx drops to the target vehicle height L0 or less, and when the actual vehicle height Lx reaches the target vehicle height L0 or less, the valve closing command is given to the leveling valve 61F of the front wheel WF in step S44. Is output to switch the leveling valve 61F of the front wheel WF from the valve open state to the valve closed state.

When the vehicle height adjustment target wheels are the left and right wheels, the processes of steps S43 and S44 are performed independently and in parallel on the left front wheel WFL and the right front wheel WFR.

When the actual vehicle height Lx of all the vehicle height adjustment target wheels related to the front wheel WF drops to the target vehicle height L0 or less, the ECU 100 outputs a valve closing command to the first original valve 81 in step S45 to output the first original valve. The 81 is switched from the valve open state to the valve closed state. When the second main valve 82 is opened by performing the process of step S46 described later, in this step S45, a valve closing command is also output for the second main valve 82 to be the second main valve. The valve 82 is switched from the valve open state to the valve closed state.

When the process of step S45 is executed, the ECU 100 ends the front vehicle height lowering control routine.

If it is determined as "Yes" in step S42, the hydraulic oil of the hydraulic cylinder 20F of the front wheel WF is not returned to the reservoir tank 72. Therefore, since the hydraulic oil does not flow through the first original valve 81, there is a suspicion of a closing failure of the first original valve 81 (a failure in which the valve cannot be opened because it is stuck in the closed state).

Therefore, the ECU 100 performs the process of step S46 or less. In step S46, the ECU 100 outputs a valve opening command to the second valve 82 to switch the second valve 82 from the closed state to the opened state.

Subsequently, in step S47, the ECU 100 determines whether or not the vehicle height of the front wheel WF detected by the vehicle height sensor has changed and the oil pressure detected by the oil pressure sensor 90 has changed. For example, the ECU 100 determines that the vehicle height has changed when the change value of the vehicle height of the front wheel WF in a predetermined period is equal to or greater than the preset vehicle height change value. Further, for example, the ECU 100 determines that the oil pressure has changed when the change in the detected value of the oil pressure sensor 90 in a predetermined period is equal to or greater than the preset set oil pressure change value.

When the second valve 82 opens according to the valve opening command and the hydraulic oil flows out to the reservoir tank 71, the vehicle height of the front wheel WF detected by the vehicle height sensor changes, and the vehicle height is detected by the oil pressure sensor 90. The oil pressure that is applied changes. In this case, in step S48, the ECU 100 determines that the first original valve 81 is abnormal, assuming that the first original valve 81 is closed and malfunctioning. For example, the ECU 100 stores a diagnosis abnormality code indicating that the first original valve 81 is closed and failed in the non-volatile memory. Further, the ECU 100 lights an abnormality lamp (not shown) to notify the driver that an abnormality has occurred.

Subsequently, the ECU 100 advances the process to 43 and performs the above-mentioned process, that is, the lowering adjustment of the vehicle height. In this case, even if the first original valve 81 is closed and malfunctions, the above-mentioned vehicle height adjustment can be performed by opening the second original valve 82.

On the other hand, if "No" is determined in step S47, the ECU 100 determines the abnormality of the suspension system 1 in step S49. For example, the ECU 100 stores a diagnosis abnormality code indicating that the suspension system 1 is abnormal in the non-volatile memory. Further, the ECU 100 lights an abnormality lamp (not shown) to notify the driver that an abnormality has occurred.

In this case, it is unlikely that not only the first original valve 81 but also the second original valve 82 is closed and failed. Therefore, when it is determined as "No" in step S47, it is considered that a failure has occurred in another hydraulic system component, for example, the hydraulic cylinder 20F or the like. Therefore, when the ECU 100 determines "No" in step S47, it determines that the suspension system 1 is abnormal without determining that the second valve 82 is a closed failure.

In this case, the vehicle height cannot be adjusted. Therefore, in the subsequent step S50, the ECU 100 outputs a valve closing command to the leveling valve 61F of the front wheel WF to switch the leveling valve 61F from the valve open state to the valve closed state.

Subsequently, the ECU 100 advances the process to step S45, outputs a valve closing command to the first original valve 81 and the second original valve 82, and ends the front vehicle height lowering control routine.

When the abnormality of the suspension system 1 is confirmed, the execution of the vehicle height control routine (FIG. 2) is prohibited until the predetermined repair is performed and the diagnosis abnormality code is erased.

<Rear vehicle height descent control routine>
Next, the rear vehicle height lowering control routine shown in FIG. 5 will be described. In this rear vehicle height lowering control routine, the solenoid valves (leveling valve 61R, switching valve 62R, bypass valve 63R, and original valve vs. 80) related to the vehicle height adjustment of the rear wheel WR are controlled.

When the rear vehicle height lowering control routine is activated, the ECU 100 outputs a valve opening command to the second source valve 82 and the leveling valve 61R of the rear wheel WR in step S61. In this case, the pump device 71 is stopped, the first original valve 81 is maintained in the closed state, the spring switching valve 62R of the rear wheel WR is maintained in the valve open state, and the bypass valve 63R of the rear wheel WR is maintained in the closed state. There is. As a result, the second original valve 82 and the leveling valve 61R of the rear wheel WR are switched from the closed state to the open state. Here, the rear wheel WR is a rear wheel (there may be two left and right wheels or one left and right wheel) for which a vehicle height lowering request is generated. The control states of the valves 61R, 62R, 63R, 81, 82 controlled by step S61 correspond to the second control state of the present invention.

Subsequently, in step S62, the ECU 100 did not change the vehicle height of the rear wheel (vehicle height adjustment target wheel) WR detected by the vehicle height sensor, and did the oil pressure detected by the oil pressure sensor 90 change? Judge whether or not. For example, the ECU 100 determines that the vehicle height has not changed when the change value of the vehicle height of the rear wheel WR in a predetermined period is smaller than the preset vehicle height change value. Further, for example, the ECU 100 determines that the oil pressure has not changed when the change in the detected value of the oil pressure sensor 90 in a predetermined period is smaller than the preset set oil pressure change value.

When the second source valve 82 and the leveling valve 61R are opened by step S61, if the suspension system 1 is normal, the force (vehicle weight) acting in the direction of contracting the hydraulic cylinder 20 causes the rear wheel WR The hydraulic oil of the hydraulic cylinder 20R (including the hydraulic oil of the high gas spring 31R and the low gas spring 32R communicating with the hydraulic cylinder 20R) is returned to the reservoir tank 72. Therefore, the hydraulic cylinder 20R of the rear wheel WR contracts, the vehicle height of the rear wheel WR detected by the vehicle height sensor should decrease, and the oil pressure detected by the oil pressure sensor 90 should also decrease.

If the ECU 100 determines "No" in step S62, the process proceeds to step S63, and if it determines "Yes", the ECU 100 proceeds to the process to step S66. The process from step S66 is a process for determining an abnormality of the second source valve 82.

In step S63, the ECU 100 waits until the actual vehicle height Lx drops to the target vehicle height L0 or less, and when the actual vehicle height Lx reaches the target vehicle height L0 or less, the ECU 100 closes to the rear wheel WR leveling valve 61R in step S64. A command is output to switch the leveling valve 61R of the rear wheel WR from the valve open state to the valve closed state.

When the vehicle height adjustment target wheels are the left and right wheels, the processes of steps S63 and S64 are performed independently and in parallel on the left rear wheel WRL and the right rear wheel WRR.

When the actual vehicle height Lx of all the vehicle height adjustment target wheels related to the rear wheel WR drops to the target vehicle height L0 or less, the ECU 100 outputs a valve closing command to the second valve 82 in step S65 to the second valve. The valve 82 is switched from the valve open state to the valve closed state. When the first main valve 81 is opened by performing the process of step S66 described later, in this step S65, the valve closing command is also output for the first main valve 81 to be the first main valve. The 81 is switched from the valve open state to the valve closed state.

When the process of step S65 is executed, the ECU 100 ends the rear vehicle height lowering control routine.

If it is determined as "Yes" in step S62, the hydraulic oil of the hydraulic cylinder 20R of the rear wheel WR is not returned to the reservoir tank 72. Therefore, since the hydraulic oil does not flow through the secondary valve 82, there is a suspicion that the secondary valve 82 is closed or failed.

Therefore, the ECU 100 performs the process of step S66 or less. In step S66, the ECU 100 outputs a valve opening command to the first original valve 81 to switch the first original valve 81 from the closed state to the opened state.

Subsequently, in step S67, the ECU 100 determines whether or not the vehicle height of the rear wheel WR detected by the vehicle height sensor has changed and the oil pressure detected by the oil pressure sensor 90 has changed. For example, the ECU 100 determines that the vehicle height has changed when the change value of the vehicle height of the rear wheel WR in a predetermined period is equal to or greater than the preset vehicle height change value. Further, for example, the ECU 100 determines that the oil pressure has changed when the change in the detected value of the oil pressure sensor 90 in a predetermined period is equal to or greater than the preset set oil pressure change value.

When the primary valve 81 opens according to the valve opening command and the hydraulic oil flows out to the reservoir tank 71, the vehicle height of the rear wheel WR detected by the vehicle height sensor changes, and the oil pressure sensor 90 changes the vehicle height. The detected oil pressure changes. In this case, in step S68, the ECU 100 determines that the second valve 82 is abnormal, assuming that the second valve 82 is closed and malfunctioning. For example, the ECU 100 stores a diagnosis abnormality code indicating that the second valve 82 is closed and failed in the non-volatile memory. Further, the ECU 100 lights an abnormality lamp (not shown) to notify the driver that an abnormality has occurred.

Subsequently, the ECU 100 advances the process to 63 and performs the above-mentioned process, that is, the lowering adjustment of the vehicle height. In this case, even if the second original valve 82 is closed and malfunctions, the above-mentioned vehicle height adjustment can be performed by opening the first original valve 81.

On the other hand, if "No" is determined in step S67, the ECU 100 determines the abnormality of the suspension system 1 in step S69. For example, the ECU 100 stores a diagnosis abnormality code indicating that the suspension system 1 is abnormal in the non-volatile memory. Further, the ECU 100 lights an abnormality lamp (not shown) to notify the driver that an abnormality has occurred.

In this case, it is unlikely that not only the second original valve 82 but also the first original valve 81 has a closed failure. Therefore, when it is determined as "No" in step S67, it is considered that a failure has occurred in another hydraulic system component, for example, the hydraulic cylinder 20F or the like. Therefore, when the ECU 100 determines "No" in step S67, it determines that the suspension system 1 is abnormal without determining that the first valve 81 is a closed failure.

In this case, the vehicle height cannot be adjusted. Therefore, in the subsequent step S70, the ECU 100 outputs a valve closing command to the leveling valve 61R of the rear wheel WR to switch the leveling valve 61R from the valve open state to the valve closed state.

Subsequently, the ECU 100 advances the process to step S65, outputs a valve closing command to the first original valve 81 and the second original valve 82, and ends the rear vehicle height lowering control routine.

If a closing failure of the first original valve 81 is detected in the front vehicle height lowering control routine, or a closing failure of the second original valve 82 is detected in the rear vehicle height lowering control routine, the original valve pair Opening and closing control is possible for one of the valves in 80. Therefore, after the closing failure is detected, it is not always necessary to prohibit the vehicle height control, and the vehicle height control may be continued. In order to continue the vehicle height control, the common supply / discharge passage 54 may be opened / closed by using the original valve 81 (or 82) on which the closing failure has not been detected.

According to the suspension system of the present embodiment described above, since the individual bypass passage 53 and the bypass valve 63 are provided, the supply / discharge of hydraulic oil to the hydraulic cylinder 20 and the high gas spring 31 and the supply / discharge of the hydraulic oil to the low gas spring 32 are provided. The supply / discharge of 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 raised quickly with a small amount of oil.

Along with this, 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. In addition, it is not necessary to provide a pressure accumulator or the like for supplementing the discharge flow rate of the pump as in the conventional device. As a result, the weight of the hydraulic oil supply / discharge device 70 can be reduced.

Further, since the oil pressure of the low gas spring 32 is adjusted to be equal to the oil pressure of the hydraulic cylinder 20 after adjusting the vehicle height in the ascending direction, the vehicle height is changed even if the spring switching valve 62 is opened to switch the wheel rate. It is possible to prevent fluctuations from occurring.

Further, the vehicle height lowering control for adjusting the vehicle height in the downward direction is not performed simultaneously on the front wheel side and the rear wheel side, and the vehicle height lowering control for the front wheels is performed after the first original valve 81 is opened. The vehicle height lowering control of the wheels is carried out by opening the second valve 82. Then, the presence or absence of a closing failure of the first original valve 81 and the second original valve 82 is determined based on the presence or absence of the change in the vehicle height and the change in the oil pressure during the vehicle height lowering control. Therefore, the closing failure of the original valve pair 80 (the first original valve 81 and the second original valve 82) can be appropriately detected. Further, the failure of the original valve pair 80 can be detected by providing a hydraulic sensor between the original valve pair 80 and the hydraulic oil supply / discharge device 70, but it is not necessary to separately provide such a hydraulic sensor, and the cost is low. It can be carried out at.

When adjusting the vehicle height in the upward direction, hydraulic oil is supplied from the pump device 71 to the hydraulic cylinder 20 and the high gas spring 31 against the vehicle weight, so that when the vehicle height is adjusted in the downward direction. Compared with this, it takes time to adjust the vehicle height, but in the present embodiment, since the first source valve 81 and the second source valve 82 are controlled to be in the valve open state at the same time, the flow path in the common supply / discharge passage 54 The resistance is reduced, and the vehicle height adjustment time can be shortened. Further, even if the first valve 81 or the second valve 82 fails to close, the pump 71a does not lock and the pump motor 71b can be prevented from failing.

Further, when the vehicle height is adjusted in the downward direction, the high-pressure hydraulic oil of the hydraulic cylinder 20 is returned to the reservoir tank 72 depending on the vehicle weight, so that the vehicle height is adjusted in the upward direction as compared with the case where the vehicle height is adjusted in the upward direction. The vehicle height changes in a short time. In the present embodiment, since only one of the valves 81 and 82 of the original valve vs. 80 is controlled to the valve open state, the vehicle height can be slowly adjusted downward. That is, the vehicle height can be adjusted at a speed at which a predetermined vehicle height control performance can be secured. Therefore, it is possible to perform accurate vehicle height adjustment. Further, since the vehicle height lowering control does not operate the pump device 71, the suspension system 1 is not damaged even if the first valve 81 or the second valve 82 fails to close.

Although the suspension system according to the present embodiment has been described above, 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, in the vehicle height lowering control routine, the main valve (first main valve 81 or second main valve 82) is opened with the hydraulic cylinder 20 and the low gas spring 32 communicated with each other. The valve is valved, but instead, as in the vehicle height rise control routine, the hydraulic cylinder 20 and the low gas spring 32 are separated (with the spring switching valve 62 closed), and the original valve (first element) is used. The valve 81 or the second source valve 82) may be opened. In this case, each time the vehicle height adjustment of the target wheel is completed, the vehicle height adjustment completion pressure P0 at that time is stored, and after the vehicle height of the target wheel is adjusted, the spring switching valve 62 is maintained in the closed state. Then, the bypass valve may be opened to reduce the oil pressure of the low gas spring 32 to the vehicle height adjustment completion pressure P0. According to this modification, the vehicle height adjustment time in the downward direction can be shortened.

Further, in the present embodiment, when the vehicle height is adjusted in the ascending direction, the hydraulic cylinder 20 and the low gas spring 32 are separated and hydraulic oil is supplied to the hydraulic cylinder 20 first, but this is not always the case. It is not necessary to do so, and it may be configured to do so only in a specific situation. For example, when the driver operates the vehicle height selection switch and it becomes necessary to raise the vehicle height during the operation, it is necessary to raise the vehicle height quickly in order to meet the driver's request. Only in that case, the structure in which the hydraulic cylinder 20 and the low gas spring 32 are separated and the hydraulic oil is supplied to the hydraulic cylinder 20, that is, the vehicle height rise control routine of the embodiment is implemented, and in other cases, The hydraulic cylinder 20 and the low gas spring 32 may be communicated with each other to supply hydraulic oil to both of them.

Further, for example, in the present embodiment, the number of gas springs provided corresponding to the hydraulic cylinder 20 of each wheel W is two (high gas spring 31, low gas spring 32), but another gas is further provided. A spring may be provided. For example, a relief gas spring for releasing the pressure when the pressure of the hydraulic circuit rises abnormally may be always communicated with the hydraulic cylinder 20.

1 ... Suspension system, 10 ... Suspension device, 11 ... Wheel holding member, 20 ... Hydraulic cylinder, 21 ... Housing, 22 ... Piston, 31 ... Main accumulator (high gas spring), 32 ... Sub accumulator (low gas spring), 50 ... 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 ... Spring switching valve, 63 ... Bypass valve, 70 ... Hydraulic oil supply / discharge device, 71 ... Pump device, 71a ... Pump, 71b ... Pump motor, 72 ... Reservoir tank, 73 ... Check valve, 74 ... Return valve, 80 ... Original valve pair, 81 ... First original valve, 82 ... Second valve, 90 ... hydraulic sensor, 100 ... electronic control unit (ECU), 110 ... motion detection sensor, 120 ... operation detection sensor, W ... wheel.

Claims (1)

A hydraulic cylinder provided between the wheel holding member and the vehicle body on each of the left, right, front and rear wheels of the vehicle, which accommodates hydraulic oil and expands and contracts according to a change in the distance between the wheel holding member and the vehicle body.
A first gas spring and a second gas spring, which are provided corresponding to the hydraulic cylinders of the left and right front and rear wheels and communicate with the hydraulic cylinders to function as hydraulic springs.
A spring switching valve provided corresponding to each of the hydraulic cylinders and capable of switching between a state in which communication between the hydraulic cylinder and the second gas spring is permitted and a state in which communication is cut off.
A pump for supplying and discharging hydraulic oil to each of the hydraulic cylinders, a hydraulic oil supply / discharge device having a reservoir tank, and the like.
A main valve provided in parallel with a supply / discharge source passage that is connected to the hydraulic oil supply / discharge device and serves as a flow path for hydraulic oil, and a first source valve and a second source valve that open and close the supply / discharge source passage. A supply / drainage hydraulic control circuit with a pair,
The vehicle height adjustment passage, which is provided corresponding to each of the hydraulic cylinders and is a flow path for hydraulic oil that communicates each of the hydraulic cylinders with the supply / discharge source passage, and the opening / closing of the vehicle height adjustment passage. A vehicle height adjustment hydraulic control circuit with a vehicle height adjustment valve
A hydraulic oil flow path 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 flood control circuit for a second gas spring having a bypass passage and a bypass valve for opening and closing the bypass passage, and
In the flow path of the hydraulic oil which is on the hydraulic cylinder side with respect to the original valve pair, on the side of the original valve with respect to the bypass valve, and on the opposite side of the original valve with respect to the vehicle height adjustment valve. A hydraulic sensor provided to detect the oil pressure in the flow path and
When adjusting the vehicle height in the ascending direction, the first source valve and the second source valve are controlled to be in an open state, and the spring switching valve and the bypass valve of the vehicle height adjustment target wheel are closed. In this state, the vehicle height adjustment valve of the vehicle height adjustment target wheel is controlled to open until the vehicle height reaches the target vehicle height, and the hydraulic oil supply / discharge device supplies hydraulic oil to the hydraulic cylinder to supply the vehicle. The hydraulic pressure detected by the hydraulic sensor when the height reaches the target vehicle height is memorized, and the vehicle height adjustment is performed with the spring switching valve and the vehicle height adjustment valve of the vehicle height adjustment target wheel closed. Vehicle height in which the bypass valve is controlled to open until the hydraulic pressure of the second gas spring of the target wheel becomes equal to the stored hydraulic pressure, and the hydraulic oil is supplied to the second gas spring by the hydraulic oil supply / discharge device. Ascending control means and
When adjusting the vehicle height in the downward direction, when lowering the vehicle height of the front wheels without adjusting the vehicle height on the front and rear wheels at the same time, the first valve is opened and the second valve is opened. The valve is controlled to the first control state in which the valve is closed and at least the vehicle height adjusting valve of the front wheel is opened, and the hydraulic oil of the hydraulic cylinder of the front wheel is returned to the hydraulic oil supply / discharge device. When lowering the vehicle height of the wheels, the second control is such that the second main valve is in the valve open state, the first main valve is in the closed state, and at least the rear wheel height adjustment valve is in the open state. A vehicle height lowering control means for returning the hydraulic oil of the hydraulic cylinder of the rear wheel to the hydraulic oil supply / discharge device by controlling the state.
When the change in the detected value of the hydraulic sensor and the change in the vehicle height of the front wheels are not detected when the vehicle height lowering control means controls the first control state, the second valve is closed. When the valve is switched from the state to the valve open state and a change in the detected value of the hydraulic sensor and a change in the vehicle height of the front wheels are detected at that time, it is determined that the first original valve is abnormal, and the above. When the change in the detected value of the hydraulic sensor and the change in the vehicle height of the rear wheels are not detected when the vehicle height lowering control means controls the second control state, the first valve is closed. When the valve is switched from the state to the valve open state and a change in the detected value of the hydraulic sensor and a change in the vehicle height of the rear wheels are detected at that time, the abnormality in which the second valve is determined to be abnormal is determined. Suspension system with detection means.

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