JP2758057B2 - Vehicle suspension device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a suspension device for a vehicle in which suspension characteristics can be changed by controlling supply / discharge of fluid to / from a cylinder, and more particularly, to a failure when a failure of a fluid supply / discharge control system occurs. It concerns safety measures.

(Prior Art) Conventionally, as a vehicle suspension device, for example, as disclosed in Japanese Patent Application Laid-Open No. 63-130418, a plurality of cylinders provided between a sprung and unsprung for each wheel are disclosed. A so-called active control suspension device (ACS device) comprising a plurality of gas springs respectively connected to the respective cylinders, and independently controlling the supply and discharge of fluid to and from the respective cylinders, thereby making it possible to change suspension characteristics. ) Is known.

(Problems to be Solved by the Invention) By the way, when the above-described ACS device is installed in a general vehicle, devices such as a flow valve and various sensors of a control system that controls supply and discharge of fluid to and from a cylinder are broken. It is necessary to take sufficient fail-safe measures to prevent erroneous control at the time. As this fail-safe countermeasure, it is desirable to take an appropriate measure depending on the degree of failure, instead of taking the same measure uniformly.

Therefore, the applicant of the present invention has previously proposed a configuration in which such fail-safe measures can be taken (Japanese Patent Application No. 63-322847). This proposal basically has a failure detecting means for detecting a failure of each device for flow control, and receiving a signal from the failure detecting means, the failure discharges fluid in the cylinder and lowers the vehicle height. It is determined whether or not one of the first failure mode to be performed, the second failure mode in which the control is stopped while maintaining the current vehicle height, and the third failure mode in which the control is continued with only the warning. And a executing means for receiving a signal from the determining means and executing a failure mode. In this case, the third failure mode is when the failure has little effect on the essence of the control (for example, a decrease in the amount of oil remaining in the reserve tank), and the first failure mode is when the failure occurs at each wheel. Is executed only when the cause of the difference is (for example, a failure of the flow control valve), and almost the second failure mode is executed when a device of the fluid supply / discharge control system fails.

However, when a failure occurs during turning of the vehicle, there are the following problems. That is, during turning of the vehicle, the cylinder pressure is made different between the left and right wheels in response to the load acting differently on the left and right wheels in order to suppress the lateral inclination of the vehicle body due to the lateral acceleration outward (ie, the centrifugal force) turning outward. However, if the control is stopped in this state, when the vehicle returns to straight running (that is, when the loads applied to the left and right wheels return to the same state), the vehicle body is inclined sideways, and safety is impaired.

The present invention has been made in view of such a point, and an object of the present invention is to further improve the above-mentioned proposal to take appropriate fail-safe measures even when a failure occurs during turning. Is what you get.

(Means for Solving the Problems) In order to achieve the above object, a solution of the invention according to claim 1 includes a plurality of cylinders provided between a sprung portion and a unsprung portion for each wheel; A plurality of gas springs respectively connected to the cylinders are provided, and the suspension characteristics of the vehicle can be changed by independently controlling the supply and discharge of the fluid to each of the cylinders. Configuration.

A failure detection means for detecting a failure of each device of the fluid supply / discharge control system, and a first failure mode in which the failure receives a signal from the failure detection means and the failure discharges fluid in the cylinder to lower the vehicle height; Alternatively, there is provided a determining means for determining whether the current mode is the second failure mode in which the control is stopped while maintaining the current vehicle height, and an execution means for receiving the signal of the determining means and executing the failure mode. . Further, a differential pressure detecting means for detecting a state in which there is a differential pressure in the left and right cylinders corresponding to the left and right wheels, and receiving a signal from the differential pressure detecting means, and when there is a differential pressure in the left and right cylinders, For execution means,
And a correcting means for prohibiting execution of the second failure mode.

Here, in the invention of claim 2, the correction means receives the signal of the differential pressure detection means, and when there is a differential pressure in the internal pressure of the left and right cylinders, the correction means performs the first failure mode in the first failure mode. Execution shall be forced.

According to a third aspect of the present invention, in the first or second aspect, when the steering angle is substantially zero, the failure mode is changed by the correction means.

According to a fourth aspect of the present invention, the differential pressure detecting means in the first aspect detects a state in which there is a differential pressure in the internal pressures of the left and right cylinders during the turning state.

Further, in the invention of claim 5, in claim 1 or 2, the failure mode is changed by the correction means when the lateral acceleration of the vehicle is equal to or less than a predetermined value.

(Operation) According to the above configuration, in the invention of claims 1 to 5, when a device of the fluid supply / discharge control system fails, the failure is detected by the failure detection unit, and the determination unit receiving the signal of the failure detection unit It is determined whether the failure is the first failure mode in which the fluid in the cylinder is discharged to lower the vehicle height or the second failure mode in which the control is stopped while maintaining the current vehicle height. Is done. Then, the failure mode is executed by the execution means based on the determination result.

In addition, when a failure occurs during turning of the vehicle, the differential pressure detecting means detects the turning of the vehicle from the differential pressure of the left and right cylinder internal pressures, and the correcting means receiving the signal of the differential pressure detecting means, The execution means is prohibited from executing the second failure mode, and is forced to execute the first failure mode, for example.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a vehicle body, 2F denotes a front wheel, and 2R denotes a rear wheel. The vehicle body 1 is a sprung body, and the front wheels 2F and the rear wheels 2R are unsprung.
And the fluid cylinders 3 are arranged between them. In each of the fluid cylinders 3, a hydraulic chamber 3c is defined by a piston 3b inserted into a cylinder body 3a. The upper end of the rod 3d connected to the piston 3b is connected to the vehicle body 1, and the cylinder body 3a is connected to the wheels 2F, 2R, respectively.

Gas springs 5 are connected to the hydraulic chambers 3c of the respective fluid cylinders 3 via communication passages 4, respectively. Each of the gas springs 5 is partitioned by a diaphragm 5e into a gas chamber 5f and a hydraulic chamber 5g, and the hydraulic chamber 5g communicates with the hydraulic chamber 3c of the fluid cylinder 3.

Reference numeral 8 denotes a hydraulic pump, and reference numerals 9 and 9 denote hydraulic passages as high-pressure lines that communicate the hydraulic pump 8 with each of the fluid cylinders 3.
10 is a flow control valve interposed in the flow control valve 9. The flow control valve 9 supplies and discharges fluid (oil) to and from each fluid cylinder 3 to adjust the internal pressure (the pressure of the hydraulic pressure chamber 3c). Have.

Further, reference numeral 12 denotes a main pressure sensor for detecting the oil discharge pressure of the hydraulic pump 8 (specifically, the pressure of the oil storage in the accumulators 22a and 22b, which will be described later). Cylinder pressure sensor, 14 is the corresponding wheel 2
A vehicle height sensor that detects the vehicle height (cylinder stroke amount) of F and 2R, 15 is a vertical acceleration sensor that detects the vertical acceleration of the vehicle (spring acceleration of wheels 2F and 2R), and 16 is a lateral acceleration of the vehicle A lateral acceleration sensor, 17 is a steering angle sensor that detects the steering angle of the front wheel 2F as a steering wheel, 18 is a vehicle speed sensor that detects the vehicle speed, and the detection signals of these sensors are internally stored in the CP respectively.
It is input to a controller 19 having U and the like, and is provided for variable control of suspension characteristics.

Next, a hydraulic circuit for controlling the supply and discharge of fluid to and from the fluid cylinder 3 is shown in FIG. In the figure, a hydraulic pump 8 is composed of a variable displacement type swash plate piston pump, and is connected to a hydraulic pump 21 for a power steering device driven by a drive source 20 in a duplex manner. Three accumulators 22a, 22a, 22a are connected to the hydraulic passage 10 connected to the hydraulic pump 8 at the same location, and the hydraulic passage 10 is connected to the front wheel side passage 10F and the rear wheel side at that connection point. It is branched into a passage 10R. Further, the front wheel side passage 10F is the left front wheel side passage 10FL.
And the right front wheel side passage 10FR.
The fluid pressure chambers 3c of the fluid cylinders 3FL and 3FR of the corresponding wheels are communicated with. On the other hand, one accumulator 22b is communicatively connected to the rear wheel side passage 10R, and is branched downstream into a left rear wheel side passage 10RL and a right rear wheel side passage 10RR. Is connected to the hydraulic chamber 3c of the fluid cylinder 3RL, 3RR of the corresponding wheel.

Each of the gas springs 5FL, 5FR, 5RL, and 5RR connected to each of the fluid cylinders 3FL, 3FR, 3RL, and 3RR is specifically provided with a plurality (four in the figure) of these gas springs 5a and 5b. , 5c, 5
“d” is connected in parallel to the hydraulic chamber 3 c of the corresponding fluid cylinder 3 via the communication path 4. Further, each of the gas springs 5a to 5d has an orifice 25 provided at a branch portion of the communication path 4, and has a damping action at each of the orifices 25 and a buffer action for the gas sealed in the gas chamber 5f. It is designed to demonstrate both. The first gas spring 5a and the second gas spring 5a
A damping force switching valve 26 for adjusting the passage area of the communication passage 4 is interposed in the communication passage 4 between the gas spring 5b and the gas spring 5b. It has two positions, a throttle position where the passage area is significantly reduced.

An unload valve 27 and a flow control valve 28 are connected to the hydraulic passage 10 on the upstream side of the accumulator 22a. The unload valve 27 is configured to introduce a pressure oil discharged from the hydraulic pump 8 to the swash plate operating cylinder 8a of the hydraulic pump 8 to reduce an oil discharge amount of the hydraulic pump 8, A discharge position for discharging pressurized oil, and the oil discharge pressure of the hydraulic pump 8 is set to a predetermined upper limit oil discharge pressure (160 ± 10 k
gf / cm ² ) or more, the system switches from the discharge position to the introduction position and changes this state to the predetermined lower limit oil discharge pressure (120 ± 10k).
gf / cm ² ) or less, and keeps the oil discharge pressure of the hydraulic pump 8 within a predetermined range (120 to 160).
kg f / cm ² ). The flow control valve 28 is configured to introduce the pressure oil from the hydraulic pump 8 to the swash plate operating cylinder 8a of the hydraulic pump 8 via the unload valve 27, and to unload the pressure oil in the cylinder 8a. A discharge position for discharging from the valve 27 to the reserve tank 29, and when the oil discharge pressure of the hydraulic pump 8 is maintained within a predetermined range by the unload valve 27, the throttle 30 of the hydraulic passage 10 is
Hydraulic pump 8 that maintains the differential pressure between the upstream and downstream
Has a function of maintaining and controlling the oil discharge amount at a constant level. Thus, the supply of oil to each fluid cylinder 3 is performed by oil storage in the accumulators 22a and 22b (this oil pressure is referred to as main pressure).

On the other hand, on the downstream side of the accumulator 22a of the hydraulic passage 10, four flow control valves 9, 9,... Are provided corresponding to the four wheels of the vehicle. Hereinafter, since the configuration of the portion corresponding to each wheel is the same, only the left front wheel side will be described, and the description of the other portions will be omitted. That is, the flow control valve 9 is connected to the first switching valve 35 provided in the left front wheel side passage 10FL of the hydraulic pressure passage 10 and the low pressure line 36 for discharging oil from the left front wheel side passage 10FL to the reserve tank 29. And a second switching valve 37 provided. Each of the switching valves 35 and 37 has two positions, an open position and a closed position, and has a built-in differential pressure valve that maintains the hydraulic pressure at the open position at a predetermined value.

A pilot pressure responsive check valve 38 is provided in the left front wheel passage 10FL between the first switching valve 35 and the fluid cylinder 3FL. In the check valve 38, the hydraulic pressure (that is, the main pressure) in the hydraulic pressure passage 10 upstream of the flow control valve 9 (first switching valve 35) is introduced as a pilot pressure by a pilot line 39, and the pilot pressure is reduced to 40 kgf.
It is provided so as to close when the pressure is less than / cm ² . That is, only when the main pressure is 40 kgf / cm ² or more, the supply of the pressure oil to the fluid cylinder 3 and the discharge of the oil in the fluid cylinder 3 can be performed.

In FIG. 2, reference numeral 41 denotes an accumulator 22a of the hydraulic passage 10.
A fail-safe valve provided in a communication passage 42 that communicates the downstream side with the low-pressure line 36.The fail-safe valve is switched to the open position in the event of a failure to store the oil stored in the accumulators 22a and 22b in the reserve tank 2.
It has the function of returning to 9 and releasing the high pressure state. Also, 43
Is a throttle provided in the pilot line 39 and has a function of delaying the closing of the check valve 38 when the fail-safe valve 41 is opened. Reference numeral 44 denotes a relief valve that opens when the hydraulic pressure in the hydraulic chamber 3c of each of the fluid cylinders 3FL and 3FR on the front wheel side rises abnormally and returns the oil to the low-pressure line 36. Reference numeral 45 denotes a return accumulator connected to the low pressure line 36, which performs a pressure accumulating operation when oil is discharged from the fluid cylinder 3.

The control of the supply and discharge of fluid to and from the fluid cylinders 3 by the controller 19 will not be described in detail with reference to the drawings. A control system for controlling the vehicle height, a control system for reducing the vertical vibration of the vehicle based on the detection signal of the vertical acceleration sensor 15, and a front wheel side and a rear wheel side based on the detection signal of the cylinder pressure sensor 13 of each wheel. And the response of each fluid cylinder 3 based on the detection signals of the lateral acceleration sensor 16, the steering angle sensor 17 and the vehicle speed sensor 18 during turning of the vehicle. And a control system that enhances it.

When a device for such fluid supply / discharge control breaks down, the controller 19 performs fail-safe control based on the flowchart shown in FIG.

That is, first, in step S1, it is determined whether or not the flag F is "1". If the determination is NO, detection signals from the various sensors 12 to 18 are detected in step S2 for failure detection. After being input as a signal, it is determined in step S3 whether or not a failure has occurred based on these failure signals. The step S3 and the various sensors 12 to 18 constitute a failure detecting means 51 for detecting a failure of each device of the fluid supply / discharge control system.

Then, if the determination in step S3 is NO indicating that there is no failure, the process returns as it is, whereas if the determination is YES, the failure is identified in step S4. In other words, the first failure mode (hereinafter, referred to as B failure mode) in which the failure discharges the fluid in the fluid cylinder to lower the vehicle height, and the second failure mode in which control is stopped while maintaining the current vehicle height (hereinafter, referred to as B failure mode) It is determined whether the failure mode is a failure mode (hereinafter, referred to as an A failure mode) or a failure mode in which control is continued by performing only a warning (hereinafter, referred to as a C failure mode). A mode in which the mode is reset when the ignition is off (IG / OFF) (hereinafter referred to as A-1
A failure mode) or a mode in which a failure mode is set until a failure action is performed (hereinafter, referred to as an A-0 failure mode). This step S4 constitutes a determining means 52 for receiving a signal from the failure detecting means 51 and determining a failure.

Subsequently, in step S5, it is determined whether the failure mode is the B failure mode, and if the determination is YES, the process proceeds to step S5.
At 6, the B failure mode is executed. That is, a warning (lighting of an alarm lamp, etc.) is performed, and at the same time, oil is discharged at a maximum flow rate from the hydraulic pressure chamber 3c of the fluid cylinder 3 of each wheel to lower the vehicle height, and thereafter, the fail-safe valve 41 is opened. Switch to position and stop control. After the execution of the B failure mode, the flag F is set to "1" in step S7, and the routine returns.

On the other hand, if the determination in step S5 is NO, step S8
To determine whether the failure mode is the A-0 failure mode, and if the determination is YES, the flow proceeds to step S31 based on the detection signal from the cylinder pressure sensor 13.
The differential pressure (| PFL-PFR |) between the internal pressure of the two fluid cylinders 3FL and 3FR on the 2F side (hydraulic pressure of the hydraulic chamber 3c) and the differential pressure between the internal pressures of the two fluid cylinders 3RL and 3RR on the right and left rear wheels 2R ( | PRL-PRR |), and determines whether or not these differential pressures are respectively equal to or less than a predetermined value PFO or PRO. If this determination is YES, step S
The A failure mode is executed in step 9 and if the judgment is NO, step S
The routine goes to 6 to execute the B failure mode.

If the determination in step S8 is NO, step S1
In step 1, it is determined whether the failure mode is the A-1 failure mode. If the determination is YES, in step S32, based on the detection signal from the cylinder pressure sensor 13, the left and right Both fluid cylinders 3FL, 3FR on front wheel 2F side
The differential pressure of the internal pressure (| PFL-PFR |) and the differential pressure of the internal pressure of both fluid cylinders 3RL and 3RR on the left and right rear wheels 2R (| PRL-PRR |) are calculated,
Further, it is determined whether or not these differential pressures are respectively equal to or less than a predetermined value PF0 or PR0. When the determination is YES, the A failure mode is executed in step S12, and when the determination is NO, the process shifts to step S6 to execute the B failure mode.

The execution of the A failure mode in steps S9 and S12 means that a warning is issued, the failsafe valve 41 is immediately switched to the open position, and the control is stopped at the current vehicle height. After the execution of the A failure mode, the step
In S10 or S13, the flag F is set to "1", and the routine returns.

If the determination in step S11 is NO, it is further determined in step S14 whether the failure mode is the C failure mode, and if the determination is YES, the C failure mode is executed in step S15. That is, control is continued with only a warning.
Thereafter, the flag F is set to "1" in step S16, and the routine returns. On the other hand, when the determination in step S14 is NO (that is, when the failure mode does not correspond to any of the A failure mode, the B failure mode, and the C failure mode), control is temporarily stopped in step S17, and then the process returns.

Here, the execution means 53 for executing the failure mode is constituted by the steps S6, S9, S12 and S15. Also,
The cylinder pressure sensor 13 and steps S31 and S32 constitute a differential pressure detecting means 54 for detecting a state in which there is a differential pressure between the internal pressures of the left and right fluid cylinders 3 corresponding to the right and left wheels, and the steps S31 and S32 and steps S6 and S9 , S12
When the signal from the differential pressure detecting means 54 is received and there is a differential pressure in the internal pressures of the left and right fluid cylinders 3, the execution means 53 is prohibited from executing the A failure mode and is forced to execute the B failure mode. Means 55 are configured.

On the other hand, if the determination in step S1 is YES, step S1
At 18, it is determined whether the failure mode is the B failure mode or the A-0 failure mode. When the determination is YES, the routine returns as it is, while when the determination is NO, it is determined in step S19 whether or not the ignition has been turned off to further stop the engine. When the determination is YES, the flag F is determined in step S20. Is set to "0", and returns when the ignition is turned on NO (that is, when the engine is operating).

Next, the correspondence between the specific failure state of the device of the fluid supply / discharge control system and the failure mode determined by the determination means 52 will be described.

(1) When the ignition is turned on (the fail-safe valve 41 is switched to the closed position at this time), when the vehicle height is lower than the reference vehicle height by 30 mm or more, the C failure mode is set. The cause of the failure at this time is considered to be clogging of dust in the check valve 38 in the hydraulic passage 10,
This is because the pressure oil can be eliminated by flowing the pressure oil and the flow rate control is not hindered.

(2) Several seconds (for example, 5 seconds) from the time the ignition is turned on
When the main pressure after the lapse of time is equal to or lower than the reference pressure (30 kgf / cm ² ), the A-0 failure mode is set. The failure at this time is considered to be caused by sticking at the open position of the fail-safe valve 41, a broken pipe in the hydraulic pressure passage 10, a failure of the main pressure sensor 12, and the like, and is a serious failure that cannot be recovered.

(3) When the output signal of the main pressure sensor 12 is equal to or higher than the upper limit working voltage (4.5 V), the A-0 failure mode is set. The cause of the failure may be a Vcc short of the main pressure sensor 12.

(4) When the output signal of the main pressure sensor 12 is equal to or lower than the lower limit operating voltage (0.5 V), it is the A-1 failure mode. As a cause of the failure, a GND short of the main pressure sensor 12 can be considered. However, unlike the case of the Vcc short, the GND short has a possibility of recovery.

(5) when the main pressure is 185 kg f / cm ² or more, A-0
Failure mode. The cause of the failure may be a failure of the unload valve 27 or the like. In the control of the controller 19, the control is temporarily stopped when the main pressure becomes 100 kgf / cm ² or less (steps in the flowchart shown in FIG. 3).
Control is restored when the pressure reaches 110 kg f / cm ² or more.

(6) If the main pressure does not increase for a predetermined time (about 5 seconds) in spite of the control pause state when the main pressure is 100 kgf / cm ² or less, the A-0 failure mode is set. The cause of the failure is a failure of the unload valve 27, the main pressure sensor 12, and the like.

(7) With respect to the temporal change of the main pressure P, | P (t)-
If the state of P (t−Δt) | ≦ 2 kg f / cm ² (however, Δt = 1 second) continues for 10 minutes or more, it is the A-0 failure mode. The cause of the failure is fixed signal of the main pressure sensor 12.

(8) After the relational expression of G (t) -1G <-0.1G is established between the vertical acceleration G (t) of the vehicle and the gravitational acceleration G, with respect to the temporal change of the main pressure P, | P (t)
−P (t−Δt) | ≦ 2kg f / cm ² (However, Δt = 1 second)
Is in the A-1 failure mode when the state continues for 5 seconds or more. The cause of the failure at this time is fixed to the signal of the main pressure sensor 12 as in the case of the above (7), but the duration of the failure is as short as 5 seconds, and there is a possibility of recovery.

(9) Wheel bumps (current vehicle height H (t) and reference vehicle height H0
H (t) −H0 <30 mm holds), and | P (t) −P (t−Δ)
t) | ≦ 2 kg f / cm ² (However, Δt = 1 second) When the state continues for 5 seconds or more, it is the A-1 failure mode. The cause of the failure is the fixed signal of the cylinder pressure sensor 13.
There is a possibility of recovery as in the case of.

(10) When the main pressure drops below 90 kg f / cm ² ,
-1 failure mode. The cause of the failure is a broken pipe.

(11) When the disconnection of the sensors 12 to 18 and the actuator (such as the hydraulic pump 8) is detected, it is the A-0 failure mode.

(12) If the output signal of the oil level sensor (not shown) for detecting the amount of oil in the reserve tank 29 remains off for one second, the A-0 failure mode is set. The cause of the failure is a broken pipe.

(13) When the output signal of the cylinder pressure sensor 13 becomes higher than the upper limit operating voltage (4.5 V), it is the A-0 failure mode. The cause of the failure is Vcc short of the cylinder pressure sensor 13.

(14) When the output signal of the cylinder pressure sensor 13 falls below the lower limit operating voltage (0.5 V), the A-0 failure mode is set. The cause of the failure is a short circuit of the cylinder pressure sensor 13 to GND.

(15) (cylinder pressure + 10kg f / cm ^2)> when it becomes (main pressure), control for preventing the reverse flow of the oil is temporarily stopped.

(16) In the rebound state of the wheel (H (t) −H0> 0), the wheel further rebounds (H (t) −H (t−Δ)).
t)> 0) and the cylinder pressure has increased (P (t) −P
When the state of (t−Δt)> 0) continuously occurs for 300 ms (0.3 seconds) or more, it is the B failure mode. The failure was caused by the inflow of the flow control valve 9 and the vehicle height was 4
Since it is impossible to control the same height for all the wheels, the oil in the fluid cylinder 3 of each wheel is discharged, and the vehicle height becomes the same for all four wheels in a state where the fluid cylinder 3 is contracted most. Do it.

(17) In the bump state of the wheel (H (t) −H0 <0), the wheel further bumps (H (t) −H (t−Δt) <
0) and the cylinder pressure drops (P (t) -P (t-
When the state of [Delta] t) <0) occurs continuously for 300 ms or more, it is the B failure mode. Failure cause is flow control valve 9
In this case, too, it is impossible to make the vehicle height equal to the predetermined height for all four wheels as in the case of (16), so the vehicle height needs to be reduced. .

(18) Wheel bumps more than 30mm and cylinder pressure is 30
When the state of kg f / cm ² or less continuously occurs for 300 ms or more, it is the B failure mode. The cause of the failure is the inflow fixation of the flow control valve 9 as in (16) above.

(19) If the wheel rebounds by 60 mm or more and the cylinder pressure is 100 kgf / cm ² or more and continuously occurs for 300 ms or more, it is the B failure mode. The cause of failure is described above (1
This is the discharge sticking of the flow control valve 9 as in the case of 7).

(20) The output signal of the vehicle height sensor 14 is
If not less than V), it is A-0 failure mode. The cause of the failure is Vcc short of the vehicle height sensor 14.

(21) The output signal of the vehicle height sensor 14 is
V) The following is the A-0 failure mode. The cause of the failure is a short circuit of the vehicle height sensor 14 to GND.

(22) If the output of the vehicle height sensor 14 of a wheel does not change for 3 seconds after the vertical acceleration of a wheel becomes equal to or more than a predetermined value (0.1 G), the A-1 failure mode is set. The cause of the failure is fixed signal of the vehicle height sensor 14, and there is a possibility of recovery.

(23) When the output signal of the vertical acceleration sensor 15 is higher than the upper limit working voltage (4.5V) for more than 1 second, A
−0 failure mode. Failure cause is vertical acceleration sensor 15
Vcc short.

(24) When the output signal of the vertical acceleration sensor 15 is lower than the lower limit operating voltage (0.5V) for more than 1 second, A
−0 failure mode. Failure cause is vertical acceleration sensor 15
GND short.

(25) While the output of the other two or three vertical acceleration sensors 15 is different from the output 100 ms before, the output of one vertical acceleration sensor 15 is not different from the output 100 ms before. When 500 ms continues, it is the A-1 failure mode. The cause of the failure is a fixed signal of the vertical acceleration sensor 15, and there is a possibility of recovery.

(26) If the output of the vehicle height sensor 14 does not become near the reference value for 10 minutes during traveling, the A-1 failure mode is set. The cause of the failure is fixed signal of vehicle height sensor 14, flow control valve 9
In the case where the signal of the vehicle height sensor 14 is fixed, there is a possibility of recovery.

(27) If the output signal of the lateral acceleration sensor 16 is higher than the upper limit operating voltage (4.5V) for more than 1 second, A
−0 failure mode. The cause of failure is the lateral acceleration sensor 16
Vcc short.

(28) If the output signal of the lateral acceleration sensor 16 is lower than the lower limit operating voltage (0.5 V) for more than 1 second, A
−0 failure mode. The cause of failure is the lateral acceleration sensor 16
GND short.

(29) The output signal of the steering angle sensor 17 is
If V) or more, it is A-0 failure mode. The cause of the failure is Vcc short of the steering angle sensor 17.

(30) The output signal of the steering angle sensor 17 is lower than the lower limit operating voltage (0.5
V) If it becomes below, it is A-0 failure mode. The cause of the failure is a short circuit of the steering angle sensor 17 to GND.

(31) The vehicle speed is calculated from the outputs of the two vehicle speed sensors 18, and the vehicle speeds are compared with each other. If there is a difference equal to or more than a predetermined value, the C failure mode is set. The vehicle speed is used in the control system for improving the responsiveness of each fluid cylinder 3 when the vehicle turns, in the flow control of each fluid cylinder 3 by the controller 19, but also in the control system.
Since it is only the next element, it is not necessary to stop the flow control itself depending on the erroneous detection of the vehicle speed.

(32) When a CPU error occurs, the A-0 failure mode is set.

Next, the operation and effect of the above embodiment will be described.
If a device such as a sensor or valve of the supply / discharge control system fails during supply / discharge control of the controller 19, the failure is detected by the failure detection means 51 of the controller 19, and the A failure mode
It is determined whether the failure mode corresponds to the B failure mode or the C failure mode. In the case of the C failure mode in which the failure does not significantly affect the essence of the control, the control itself is continued with only a warning, and in the case of the A failure mode in which the failure affects the essence of the control, the current vehicle is stopped. In the case of the B failure mode, in which the vehicle height is different at each wheel, the oil in the fluid cylinder 3 of each wheel is discharged to maintain all four wheels. Since the control is stopped after the vehicle height is made the same at a low position, it is necessary to ensure safety in the event of a control failure and effectively improve the maneuverability and the like of the ACS device by controlling the flow rate of the fluid cylinder 3. Can be. In particular, in the case of the embodiment, when it is determined that the failure mode is the A failure mode, the failure mode further includes the A failure mode in which there is no possibility of failure recovery.
It is determined whether the mode is a -0 failure mode or an A-1 failure mode in which there is a possibility of failure recovery. In the A-0 failure mode, the failure mode is maintained until a failure action is taken. , A-1 In the failure mode, it is reset once when the ignition is turned off (operations in steps S18 to S20 of the flowchart shown in FIG. 3), and it is checked whether the failure has recovered. Is more appropriately taken according to the degree of failure, and it is possible to more effectively achieve both safety and maneuverability.

In addition, if a failure occurs while the vehicle is turning,
The differential pressure detecting means 54 detects the turning of the vehicle from the differential pressure between the internal pressures of the left and right fluid cylinders 3, and the correcting means 55 changes to the A failure mode to force the execution of the B failure mode. The oil in the fluid cylinder 3 is discharged, and the vehicle height of all four wheels decreases. For this reason, the vehicle does not return to straight running with the left and right vehicle heights being different while turning, and safety can be further improved.

FIG. 4 shows a modification of the fail-safe control. In the case of this modification, when the determination in step S31 or S32 is NO, that is, when the differential pressure between the left and right fluid cylinders 3 is large and the vehicle is turning, the A failure mode is executed in step S41, and in step S41, After waiting until the steering angle θF of the front wheels becomes substantially zero based on the detection signal from the steering angle sensor 17, the B failure mode is executed in step S6.

As described above, when a failure occurs during turning of the vehicle, the A failure mode is executed until the steering angle θF of the front wheels becomes substantially zero, that is, until the turning is completed, and the B failure mode is executed after the turning is completed. In the meantime, the state in which the lateral inclination of the vehicle body is suppressed is maintained during turning, so that safety can be further improved.

In the case of the above modification, in step 42, instead of determining whether or not the steering angle θF of the front wheels is substantially zero, the lateral acceleration of the vehicle is equal to or less than a predetermined value based on a detection signal from the lateral acceleration sensor 16. May be determined.

In the above embodiment, the differential pressure detecting means 54 detects the internal pressures of the left and right fluid cylinders 3 corresponding to the left and right wheels by the cylinder pressure sensors 13 respectively. Although a certain state was directly detected, the present invention provides a lateral acceleration of a vehicle having a constant relationship with a differential pressure,
Of course, the yaw rate, the vertical acceleration difference between the left and right sides of the vehicle body and the like may be detected by a sensor, and the state with a differential pressure may be indirectly detected from the detection result.

(Effects of the Invention) As described above, according to the vehicle suspension device of the first to fifth aspects of the present invention, not only different measures are taken depending on the degree of failure of the fluid supply / discharge control system, but also during turning. In the event of a failure, the measures to stop the control while maintaining the current vehicle height are prohibited.For example, measures to reduce the vehicle height are taken, so appropriate fail-safe measures are taken according to the degree of the failure and the running state of the vehicle. This can improve the safety especially when returning to straight running.

[Brief description of the drawings]

1 is an overall schematic configuration diagram, FIG. 2 is a hydraulic circuit diagram, and FIG. 3 is a flowchart diagram illustrating fail-safe control by a controller. FIG. 4 is a partial view of a flowchart showing a modification of the fail-safe control. 3 (3FL, 3FR, 3RL, 3RR) ... fluid cylinder 5 (5FL, 5FR, 5RL, 5RR) ... gas spring 9 ... flow control valve 19 ... controller 51 ... failure detection means 52 ... determination means 53 …… Execution means 54 …… Differential pressure detection means 55 …… Correction means

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-262414 (JP, A) JP-A-62-96126 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60G 17/015

Claims (5)

(57) [Claims] A plurality of cylinders provided between a sprung portion and an unsprung portion for each wheel, and a plurality of gas springs respectively connected to the respective cylinders. In a vehicle suspension apparatus capable of changing suspension characteristics by independently controlling supply / discharge of a fluid, failure detection means for detecting a failure of each device of a fluid supply / discharge control system, and receiving a signal from the failure detection means It is determined whether the failure is the first failure mode in which the fluid in the cylinder is discharged to reduce the vehicle height or the second failure mode in which the control is stopped while maintaining the current vehicle height. Determining means for receiving a signal from the determining means and executing a failure mode, further comprising a differential pressure detecting means for detecting a state in which there is a differential pressure in the internal pressure of the left and right cylinders corresponding to the left and right wheels; The differential pressure detection A suspension device for a vehicle, comprising: a correction means for receiving the signal of the step and for inhibiting the execution of the second failure mode when the internal pressure of the left and right cylinders has a differential pressure. . 2. The apparatus according to claim 1, wherein said correction means receives a signal from said differential pressure detection means and forcibly executes said first failure mode to said execution means when there is a differential pressure in the left and right cylinder internal pressures. Item 4. The vehicle suspension device according to item 1. 3. The method according to claim 1, wherein the change of the failure mode by the correction means is performed when the steering angle is substantially zero.
Or the suspension device for a vehicle according to 2. 4. The vehicle suspension device according to claim 1, wherein the differential pressure detecting means detects a state in which there is a differential pressure in the internal pressures of the left and right cylinders when the vehicle is turning. 5. The vehicle suspension device according to claim 1, wherein the failure mode is changed by the correction means when the lateral acceleration of the vehicle is equal to or less than a predetermined value.