JP2874477B2 - Operation control method of fluid active suspension - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the operation of a fluid active suspension, and more particularly to a method for controlling the operation delay when a compressive working fluid is supplied and discharged to generate a force for suppressing vertical vibration on a spring. The present invention relates to a method for controlling the operation of a fluid active suspension that can be compensated.

[0002]

2. Description of the Related Art Active suspensions which actively supply vibration by supplying control energy from the outside are known.
According to the active suspension, it is possible to obtain ideal suspension characteristics as compared with a general suspension including a passive element of a spring / damper system.

A pneumatic active suspension mounted on a four-wheel vehicle includes, for example, a variable damping force shock absorber mounted on each of the four wheels, and an air spring integrally provided with the shock absorber and capable of controlling the internal pressure. Various valves provided between the air spring and the reserve tank are drive-controlled to control the supply and exhaust of air to and from the air spring, thereby variably adjusting the internal pressure of the air spring. The internal pressure of the air spring is controlled based on sensor outputs from a steering angular velocity sensor, lateral acceleration sensor, longitudinal acceleration sensor, vehicle speed sensor, etc., based on anti-roll control, anti-dive control, anti-squat control, pitching and bouncing (bounce) control. It is performed as. By this internal pressure control and the damping force control of the shock absorber, a suspension characteristic according to the running state of the vehicle is realized.

[0004] Also, in the suspension of an automobile,
Electronically controlled sky-hook damper theory that uses a hook to fix the damper with a hook in the sky to reduce the vibration transmission system between the vehicle and the road surface and generate a force proportional to only the vertical speed of the vehicle It is known to Active control based on the skyhook damper theory is realized, for example, as bounce control using an electronically controlled active suspension. In order to perform the bounce control, for example, a sensor for detecting a vertical acceleration generated when the vehicle body bounces up and down due to a vertical input from a road surface is provided. Then, by integrating the vertical acceleration detected by the vertical acceleration sensor, the absolute speed in the vertical direction of the vehicle body is obtained, and the input from the road surface is canceled by controlling the force generated by the actuator according to the absolute speed. I have.

[0005] In order to realize the active control by the skyhook damper, a hydraulic active suspension including a hydraulic source and a hydraulic control system is conventionally used. The hydraulic pressure source includes a reservoir tank for storing hydraulic oil, an oil pump for supplying hydraulic oil, and a pump accumulator for removing hydraulic pulsation. The hydraulic control system is responsive to a multi-valve unit integrating various valves, a main accumulator for storing hydraulic pressure supplied from the unit, an actuator for generating a force for canceling the vertical speed of the vehicle, and a controller output. And a pressure control unit for controlling the working oil pressure supplied to the actuator.

[0006]

In the case of the hydraulic active suspension, the pressure control unit and the like must be constituted by high-performance components having the same high precision and high responsiveness as the servo valve, resulting in an increase in cost. On the other hand, the pneumatic active suspension can be configured with an inexpensive control valve, and can reduce the cost of the entire apparatus. However, in the case of a pneumatic active suspension using compressible air as a working medium, after a control signal is sent from a control unit, the supply and exhaust of air to and from the actuator are performed through various valves that respond to the control signal. It takes time for the suspension to actually generate force once it is done. As described above, a fluid active suspension using a compressible fluid as a working medium has a poorer operation response than a hydraulic active suspension. For this reason, even if the actuator is driven and controlled in accordance with the vertical speed of the vehicle body, a force that can cancel the vertical vibration input from the road surface cannot be generated at a suitable timing.

SUMMARY OF THE INVENTION Accordingly, the present invention provides an operation control of a fluid active suspension which compensates for an operation delay of a fluid active suspension using a compressible fluid as a working medium, thereby suppressing vertical vibration on a spring and reducing a device cost. The aim is to provide a method.

[0008]

To achieve the above object, a method for controlling the operation of a fluid active suspension using a compressible fluid as a working medium according to the present invention comprises a step of detecting a vertical acceleration on a spring with a vertical acceleration sensor. When,
The absolute value of the vertical acceleration detected by the vertical acceleration sensor is
The process of determining whether the level is above a certain level, and vertical acceleration
If the absolute value of the degree is equal to or greater than the predetermined level, the vertical acceleration
The vertical acceleration detected by the sensor is negative or
From the point of crossing the positive threshold,
The process of timing the time to cross the negative threshold
And the vertical acceleration on the spring based on the measured time.
Calculating a vibration frequency, and the calculated vibration frequency
The number enters the resonance frequency region near the resonance frequency on the spring
The vertical acceleration detected by the vertical acceleration sensor only when
Control of the supply of compressible fluid to the spring chamber based on speed
Is the vertical acceleration detected by the vertical acceleration sensor.
From the point where the degree crosses said positive or negative threshold
Elapsed time equivalent to half of the vertical acceleration change cycle above
Starting at the point of time .

[0009]

The vertical acceleration on the sprung is detected by the vertical acceleration sensor as the control information whose phase is advanced by 90 degrees from the vertical speed on the sprung.
And the absolute value of vertical acceleration is above a specified level
Is determined. Absolute value of vertical acceleration is predetermined
If it is above the level, the vertical acceleration has a positive or negative threshold
Crossing a negative or positive threshold from the time the value is crossed
The time to the point is timed and the spring is
The vibration frequency of the upper vertical acceleration is calculated. This vibration circumference
If the wave number is not within the sprung resonance frequency range,
Supply and discharge control of compressible fluid to spring chamber based on lower acceleration
Is not done. On the other hand, the vibration frequency is the resonance frequency on the spring
If it is in the area, the supply and discharge control of the compressible fluid is performed.
You. In this case, the vertical acceleration is equal to the positive or negative threshold.
Of the change period of the vertical acceleration on the spring from the point of crossing
When a time equivalent to minutes elapses, the compressible fluid
Supply / discharge control is started. This allows the compressible fluid to:
Suspended or supplied to spring chamber of suspension
Is discharged from the spring chamber . As a result of the supply / discharge control being performed at an early timing in accordance with the vertical acceleration on the sprung, the suspension generates a force for canceling the vertical speed on the sprung at a suitable timing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic active suspension system to which an operation control method according to one embodiment of the present invention is applied will be described below. The suspension system is a skyhook damper theory that suppresses the fluffiness felt by passengers due to the vertical vibration of the vehicle body (spring-up) in addition to the vehicle height control and vehicle body posture control of the four-wheeled vehicle on which it is mounted. It is mainly intended to perform ride comfort control specific to the present invention based on the above. Therefore, the suspension system includes a suspension unit provided for each of the four wheels of the automobile and an air circuit for supplying and discharging air to and from the air spring chambers of the four suspension units, and is provided in the air circuit. Various valves are opened and closed to independently control the supply and discharge of air to and from the four air spring chambers, so that the internal pressure of each air spring chamber can be varied. Further, the suspension system preferably includes four vertical acceleration sensors for detecting the sprung (vehicle) vertical acceleration as control information for air supply / exhaust control, preferably in the vicinity of each of the four wheels. .

More specifically, as shown in FIG. 1, the suspension system includes a control unit 36 having a processor, a memory, an input / output circuit, and the like. The control unit 36 functions as a control unit of the suspension system, and also has a function of driving and controlling various operating units of the vehicle, and executes various controls in parallel according to a control program stored in the memory.

The suspension system includes suspension units FS1, FS2, RS1 and RS2 provided on the left front wheel side, right front wheel side, left rear wheel side and right rear wheel side of the automobile, respectively. The four suspension units have the same configuration as each other, and are collectively indicated by the reference symbol S in the following description, and are distinguished from each other by the reference symbols FS1 to RS2.

Each suspension unit S has a shock absorber 1 which is arranged between the vehicle body and the wheels and has a variable damping force. The shock absorber 1 includes a cylinder mounted on a wheel side, and a piston rod 2 having a piston slidably fitted therein and mounted on a vehicle body side at an upper end, and is disposed in the piston rod 2. The valve 5a is driven by the actuator 6 via the control rod 5 to adjust the damping force.

The suspension unit S further includes an air spring chamber 3 provided integrally with the shock absorber 1. The air spring chamber 3 is arranged coaxially with the piston rod 2 above the shock absorber 1, and a part thereof is formed by the bellows 4. The air spring chamber 3 communicates with an air circuit through a passage 2 a provided in the piston rod 2, so that air can be supplied to and discharged from the air spring chamber 3.

The air circuit of the suspension system includes a high-pressure reserve tank 15a for supplying compressed air to the suspension unit S, and a suspension unit S.
And a low-pressure reserve tank 15b for receiving air discharged from the tank. High pressure reserve tank 15a
In the air circuit, a compressor 11 for compressing the air taken in from the air cleaner 12, a dryer 13 filled with a desiccant such as silica gel, and a check valve 14 are provided. The stored air is stored in the high-pressure reserve tank 15a.

The air circuit includes a return pump 16 whose suction side and discharge side are connected to low-pressure and high-pressure reserve tanks 15b, 15a, a return pump relay 17 for supplying and interrupting supply of pump power, and a low-pressure reserve tank 15b. Pressure switch 18 for detecting the internal pressure of the
And the internal pressure of the low-pressure reserve tank 15b is set to the first pressure.
The pressure is kept below a predetermined pressure (for example, 0.6 kg per square cm). That is, the low-pressure reserve tank 15
When the internal pressure of b becomes equal to or higher than the first predetermined pressure, the pressure switch 18
Is turned on, the return pump relay 17 is turned on in response to a control signal sent from the control unit 36 in response to the switch operation, and the return pump 16 is turned on.
Drives. When the pressure switch 18 is turned off,
The drive of the pump 16 stops.

A high pressure switch 44 for detecting the internal pressure of the high pressure reserve tank 15a and a compressor 1
A compressor relay 43 for supplying power to the power supply 1 is provided to maintain the internal pressure of the high-pressure reserve tank 15a at a second predetermined pressure (for example, 9.5 kg per square cm) or more. That is, when the internal pressure of the high-pressure reserve tank 15a is equal to or lower than the second predetermined pressure, the pressure switch 44 is turned on, and the compressor relay 43 is turned on in response to a control signal sent from the control unit 36 in response to the switch operation. When the pressure switch 44 is turned off while the compressor 11 is driven, the compressor 11 stops driving. However, while the return pump 16 is driving, the driving of the compressor 11 is prohibited.

The supply line of the air circuit extends from the high-pressure reserve tank 15a to the supply flow control valve 19.
The valve 19 allows a small amount of air to flow through an orifice (not shown) when turned on, and allows a large amount of air to flow through the orifice and a large-diameter passage (not shown) when turned off. . The supply line is valve 1
At 9 downstream, it branches into two. From the downstream of the valve 19, the front wheel side suspension units FS1 and FS2
Is provided with a front air supply solenoid valve 20 and a check valve 21, and is further branched into two sub-lines downstream of the check valve 21. One branch sub-line extends to the front left wheel suspension unit FS1 via a front left solenoid valve 22 composed of a three-port switching valve, and the other branch sub-line has a front right solenoid valve similar to the valve 22. 23 via the right front wheel suspension unit FS2
Extending to The valve 20 allows air to flow when turned on, while prohibits air to flow when turned off. The valves 22 and 23 allow the air supply path to communicate with the air supply path when the operation is turned off and an exhaust path to be described later. While the air supply path is shut off and the exhaust path is communicated when the switch is turned on.

Similarly, on the other branch line from the downstream of the valve 19 to the rear wheel suspension units RS1 and RS2, a rear air supply solenoid valve 24 and a check valve 25 similar to the valve 20 are provided. Downstream of the check valve 25, it further branches into two sub-channels. One branch sub-line extends to the left rear wheel suspension unit RS1 via a rear left solenoid valve 26 similar to the valves 22 and 23, and the other branch sub-line includes a rear right solenoid valve 27 similar to the valve 26. Through the right rear wheel suspension unit RS2.

The exhaust-side pipe of the air circuit is connected to the solenoid valves 22 and 2 from the suspension units FS1 and RS2.
3, 26 and 27, each of which includes a sub-branch line common to the air supply side line and the front wheel side suspension unit FS1,
The pair of sub-branch pipes corresponding to FS2 join downstream of the solenoid valves 22 and 23, and are connected to the low-pressure reserve tank 15b via an exhaust direction switching valve 28 composed of a three-port switching valve. Similarly, a pair of sub-branch pipes corresponding to the rear wheel side suspension units RS1 and RS2 join downstream of the solenoids 26 and 27, respectively.
It is connected to the low-pressure reserve tank 15b via an exhaust direction switching valve 32 similar to the valve 28.

The first outlet ports of the valves 28 and 32 communicate with the tank 15b as described above, and the second outlet ports are the check valves 29 and 33, the first outlet ports of the valves 28 and 32, and the tank 15b. Is connected to the dryer 13 via a pipeline L smaller in diameter than the pipeline connecting the two. In the valves 28 and 32, the inlet port and the first outlet port communicate with each other when the valve is turned on, and the inlet port and the second outlet port communicate with each other when the valve is off. And
Between the dryer 13 and the air cleaner 12, both elements 12,
An exhaust solenoid 31 and a check valve 46, which form a part on the exhaust side of the air circuit, are provided in cooperation with the air circuit 13, so that air can be exhausted through the air cleaner 12.

Further, the suspension system has various sensors connected to the control unit 36. That is, a sensor 34F for detecting a front vehicle height is mounted between the lower arm 35 of the front right suspension of the automobile and the vehicle body, and a rear rod is provided between the lateral rod 37 of the rear left suspension and the vehicle body. A sensor 34R for detecting the vehicle height is mounted. A vehicle speed sensor 38 is built in the speedometer, and a vertical acceleration sensor (4) for detecting vertical acceleration, lateral acceleration, and longitudinal acceleration acting on the vehicle body at an appropriate position on the vehicle body.
One of the two is indicated by reference numeral 51), the lateral acceleration sensor 5
2 and a longitudinal acceleration sensor 53 are provided. Reference numeral 40 denotes a steering sensor for detecting the rotational speed of the steering wheel 41, that is, the steering angular velocity.
Denotes an accelerator opening sensor for detecting the depression angle of the accelerator pedal.

Hereinafter, the operation of the active suspension system having the above configuration will be described. As described above, the suspension system performs vehicle height control, vehicle body posture control, and ride comfort control using a skyhook damper. In the vehicle height control, the processor of the control unit 36 determines whether the vehicle height is appropriate based on the outputs of the vehicle height sensors 34F and 34R. When the vehicle height is lower than the proper vehicle height, under the control of the processor, the front and rear air supply solenoid valves 20, 24 are turned on, and the compressed air from the high pressure reserve tank 15a is supplied to the air spring chamber 3 of the suspension unit S. Supplied. Then, when the vehicle height becomes appropriate, the valves 20 and 24 are turned off and the air supply is stopped. On the other hand, when the vehicle height is higher than the proper vehicle height, the solenoid valves 22, 23, 26 and 27 and the exhaust direction switching valves 28 and 32 are turned on, and the compressed air in the air spring chamber 3 is reduced to the low pressure reserve tank 15b. When the vehicle height reaches a proper level, the air discharge is stopped. Note that when the vehicle is in a turning state, the vehicle height adjustment is prohibited.

In roll control of vehicle body attitude control,
When the steering wheel 41 is steered to the right and the vehicle body rolls to the left, the control unit 36 turns on the air supply solenoid valves 20 and 24 for a set time, and the right wheel solenoid valves 23 and 27.
Is turned on, and after the set time elapses, the exhaust direction switching valve 32 is turned on. As a result, a set amount of compressed air is supplied from the high-pressure reserve tank 15a to the air spring chamber 3 of the left suspension unit FS1, RS1.
A set amount of compressed air is discharged from the air spring chamber 3 of the right suspension units FS2 and RS2 to the low-pressure reserve tank 15b. Thereby, the roll of the vehicle body to the left is suppressed. Thereafter, when it is determined that the steering wheel 41 has been returned to the neutral position based on the output of the steering sensor 40 or that the lateral acceleration has decreased based on the output of the lateral acceleration sensor 52, the control unit The processor at 36 determines that the vehicle has shifted from turning to straight running. Immediately after this determination, the processor turns off the solenoid valves 23 and 27 and turns off the exhaust direction switching valve 32, whereby the internal pressures of the air spring chambers 3 of the left and right suspension units become the same pressure.

When the steering wheel 41 is steered to the left, compressed air is supplied to the air spring chambers 3 of the right suspension units FS2 and RS2 in a procedure similar to that described above, and the left suspension unit FS1 and FS1 are supplied with compressed air.
The compressed air is discharged from the air spring chamber 3 of the RS 1, and the right roll of the vehicle body is suppressed. In the anti-nose dive control, the longitudinal acceleration sensor 53
When the negative acceleration becomes equal to or greater than the set value based on the output of the air conditioner, under the control of the processor, the air supply solenoid valve 20 is turned on for the set time, and the solenoid valves 26 and 27 on the rear wheel side are turned on. After the elapse of the set time, the exhaust direction switching valve 32 is turned on. As a result, a set amount of compressed air is supplied from the high-pressure reserve tank 15a to the suspension units FS1 and FS2 on the front wheel side,
Also, a set amount of compressed air is discharged from the suspension units RS1 and RS2 on the rear wheel side to the low-pressure reserve tank 15b, thereby suppressing the nose dive of the vehicle body. Thereafter, when the negative acceleration decreases, the air supply solenoid valves 22 and 23 are turned on for a set time and the rear wheel solenoid valves 26 and 27 are turned off, and the compressed air is discharged from the front wheel side suspension units FS1 and FS2. With the rear suspension units RS1 and RS
2 is supplied with compressed air, and the internal pressures of the four air spring chambers 3 return to the values before the control was started.

In anti-squat control for preventing the front of the vehicle body from rising when the vehicle starts and accelerates, when a rapid acceleration state is detected based on the output of the accelerator opening sensor 43 and the like, the processor of the control unit 36 , The air supply solenoid valve 24 is turned on for a set time, and the front wheel solenoid valve 2 is turned on.
Then, the exhaust direction switching valve 32 is turned on after the set time has elapsed. As a result, the compressed air is discharged from the front wheel side suspension units FS1 and FS2, and the rear wheel side suspension units RS1 and R
Compressed air is supplied to S2. When the rapid acceleration state is resolved, the air supply solenoid valve 20 and the rear wheel solenoid valves 26 and 27 are turned on and the front wheel solenoid valves 22 and 23 are turned off to control the internal pressures of the four air spring chambers 3 before the control. To the state of.

Hereinafter, ride comfort control by the skyhook damper in the above-described pneumatic active suspension system will be described. When the driver turns on the ignition key of the vehicle, the processor of the control unit 36 periodically executes various processes including the above-described vehicle height control, vehicle body posture control, and conventionally known engine control in FIG. 2 and FIG. The ride comfort control shown in FIG. 3 is started. Ride comfort control is preferably performed by independently controlling the internal pressures of the air spring chambers 3 of the four suspension units S using the outputs of the four vertical acceleration sensors as control information. Therefore, the control procedure shown in FIGS. 2 and 3 is executed for each suspension unit S. Hereinafter, a control procedure for one suspension unit will be described for simplification of the description.

In each control cycle of the ride comfort control, the processor first determines whether or not the value of the flag F stored in the register built into the processor is "1" indicating that the supply / exhaust control in the ride comfort control is being performed. Is determined (step S1). If the value of the flag F is not "1", the processor reads the output of the vehicle speed sensor 38, and the vehicle speed V becomes
It is determined whether the vehicle speed is equal to or higher than a predetermined vehicle speed V0, for example, 70 km / h, which indicates the lower limit of the vehicle speed region in which the driver is likely to give a fluffy feeling (step S2). When it is determined that the vehicle speed V is lower than the predetermined vehicle speed V0 and the vehicle speed is in the vehicle speed region where fluffiness is unlikely to occur, the processor ends the ride comfort control of the current cycle without performing substantial control.

On the other hand, if it is determined in step S2 that the vehicle speed V is equal to or higher than the predetermined vehicle speed V0, the processor performs an active control including an air supply / exhaust control (hereinafter referred to as an active control) other than the ride comfort control, for example, the aforementioned vehicle body attitude control. Is determined (step S3). If the active control has been executed, the ride comfort control in the current cycle ends without performing substantial control. That is, active control is performed with priority over ride comfort control.

If it is determined in step S3 that the active control is not being executed, the processor reads the output of the vertical acceleration sensor 51 and obtains the absolute value of the vertical acceleration | ZG |
Is a predetermined level ZG0, for example, 0.
It is determined whether it is 15 G or more (step S4).
The absolute value | ZG | of the vertical acceleration is equal to a predetermined level ZG0.
If so, the vibration frequency fn of the vertical acceleration ZG is calculated (step S5). Therefore, for example, the processor determines the elapsed time TINT from the time when the output of the vertical acceleration sensor 51 crosses the positive or negative threshold value ZG (+) or ZG (-) to the time when the output crosses the negative or positive threshold value. (+) Or TINT
(−) Is counted, and a value (１ ／ TINT (+) or ＴTINT (−)) equal to half the reciprocal of the counted time is calculated as the vibration frequency fn (see FIG. 4).

Next, the processor determines that the calculated vibration frequency fn is equal to or higher than the lower limit value fnL (for example, 0.8 Hz) of the predetermined frequency region including the sprung (body) resonance frequency and the upper limit value fnH (for example, 1. 2 Hz) or less, it is determined whether the calculated frequency fn is within a predetermined frequency range (step S6).
If it is determined that the vibration frequency fn of the vertical acceleration ZG of the vehicle body is not in the vicinity of the resonance frequency of the vehicle body and the fluffiness is unlikely to occur, the processor ends the ride comfort control in the current cycle without performing substantial control.

On the other hand, if it is determined in step S6 that the vehicle body acceleration frequency fn is in the vicinity of the vehicle body resonance frequency, the processor monitors the output of the vertical acceleration sensor and obtains its maximum value ZGm.
ax is detected (step S7). Next, with reference to the supply / exhaust time map stored in the memory of the control unit 36, the processor determines the supply / exhaust control time Tcon corresponding to the maximum value ZGmax of the vertical acceleration (step S).
8). The supply / exhaust time map is set as shown in FIG. That is, the absolute value | ZG | of the sprung vertical acceleration is the acceleration threshold value | ZG0 |
If the air supply / exhaust time Tcon is equal to the first predetermined time Tcon1
And if it is equal to or more than the predetermined value ZG2, the second predetermined time Tco
Set to n2. Also, the absolute value | ZG | is the threshold value | ZG0
│ to the predetermined value │ZG2│, the supply / exhaust time Tcon becomes the first predetermined time T as the absolute value │ZG│ increases.
It increases linearly from con1 to a second predetermined time Tcon2. The threshold for determining the supply / exhaust time Tcon after the supply / exhaust control is once started and the sprung acceleration is reduced is larger than the thresholds ZG0 and -ZG0 at the start of the control. Small values ZG1, -ZG1 are used.

After determining the supply / exhaust time Tcon in step S8, the processor again determines whether or not the active control is being executed (step S9). If the active control is not being executed, the flag F is set. It is further determined whether or not the value is "1" indicating that the supply / exhaust control in the comfort control is being performed (step S10). Here, since the air supply / exhaust control has not been executed yet and the value of the flag F is not "1", the flag F is set to the value "1" (step S1).
1) Then, supply / exhaust control, which will be described in detail later, is separately and independently performed for the four suspension units (step S12).

When the supply / exhaust control in the current cycle is completed, the maximum value of the output of the vertical acceleration sensor is determined again, and the absolute value | ZGmax | of the maximum acceleration is a predetermined value ZG3, for example, 0. It is determined whether or not the speed has become equal to or less than 05G (step S13). In this case, since the supply / exhaust control has just been started, generally, step S13 is performed.
Is negative, so that the ride comfort control in the current cycle is ended without changing the flag F to a value “0” indicating the end of the supply / exhaust control.

Therefore, in step S1 of the next cycle, since the flag F is determined to be the value "1", the process proceeds from step S1 to step S7, and the procedure after step S7 is executed again. Since the value of the flag F is determined to be "1" in step S10, the process immediately shifts from step S10 to supply / exhaust control in step S12 without passing through step S11. When the absolute value | ZGmax | of the maximum vertical acceleration becomes equal to or less than the predetermined value ZG3 in step S13 of a certain cycle thereafter and the fluffiness is not generated, the processor sets the flag F to a value representing the end of the supply / exhaust control. It is reset to "0" (step S14), and the ride comfort control of FIGS. 2 and 3 ends.

Hereinafter, the supply / exhaust control in step S12 will be described in detail. Regarding one suspension unit S, in the supply / exhaust control, the processor determines the sprung vertical acceleration ZG based on the output of the vertical acceleration sensor 51.
Is downward (-), and accordingly, if it is determined that the sprung speed is about to increase downward, the air supply control is performed for the set time Tcon determined in step S8 (see FIG. 4). In this case, the processor turns on the corresponding one of the air supply solenoid valves 20 and 24 so that the set amount of compressed air is supplied from the high pressure reserve tank 15a to the corresponding one of the suspension units S.
Is supplied to the air spring chamber 3. When the compressed air is supplied to the air spring chamber 3 in this manner, the pressure in the air spring chamber increases, and as a result, a force acting in a direction corresponding to the increase in the internal pressure and canceling the downward sprung speed. Occurs. If the air supply control is performed for one or more other suspension units S during the air supply control for the one suspension unit S, the valve 2
4 may be turned on, and if exhaust control is performed on one or more other suspension units S, the solenoid valves 22, 23, 26 and 27
The corresponding exhaust direction switching valves 28 and 32 are turned on.

On the other hand, if it is determined that the sprung acceleration is upward and the upward sprung speed is about to increase, exhaust control is performed for the one suspension unit S for a set time Tcon (FIG. 4). .
That is, the corresponding one of the solenoid valves 22, 23, 26 and 27 and the exhaust direction switching valves 28 and 32 are turned on, whereby the compressed air in the air spring chamber 3 is discharged by a set amount to the low pressure reserve tank 15b. As a result, the pressure in the air spring chamber decreases, and a force is generated which has a magnitude corresponding to the decrease in the internal pressure and acts in a direction to cancel the upward sprung speed.

The above-described supply / exhaust control will be further described with reference to FIG. 4. The supply / exhaust time after a half cycle is determined by the maximum value ZGmax of the sprung vertical acceleration. That is, the value ZGmax
Is positive, the air supply time after a half cycle is determined, while if the value ZGmax is negative, the exhaust time after a half cycle is determined.
In other words, if the sign of the maximum value ZGmax of the sprung vertical acceleration is negative , the sprung vertical acceleration reaches the maximum value ZGmax .
Exhaust control is started when a time corresponding to approximately half of the sprung vertical acceleration change period has elapsed from the point of crossing the negative threshold value ZG (-) just before reaching, and the sign of the maximum value ZGmax is positive. If the sprung vertical acceleration reaches its maximum value ZGmax
The air supply control is started at the time when approximately half a cycle has elapsed from the time when the positive threshold value ZG (+) is crossed immediately before reaching .

The supply / exhaust control is executed so that the number of air supply controls and the number of exhaust controls are the same. Therefore, for example, with the supply / exhaust control being executed only an odd number of times,
If it is determined in step S13 that the ride comfort control should be ended, the process proceeds to auxiliary supply / exhaust control processing not shown in FIGS. 2 and 3 following the ride comfort control in FIGS.
In the control of FIGS. 2 and 3, the exhaust or air supply control that is the reverse of the air supply or exhaust air control that was executed last is executed. For the three suspension units S other than the one suspension unit S, the auxiliary supply / exhaust control process is also performed, and the vehicle height is returned to the same height as before the start of the ride comfort control.

As shown in FIG. 6, the above series of steps S
It takes time to perform the signal processing in 1 to S11, the operation of the valve of the pneumatic circuit according to the result of the signal processing, and the generation of the above-mentioned force by the valve operation. In other words, the pneumatic suspension system has a delay in operation. In particular, since the working medium is compressible air, a pneumatic system requires a considerably longer time after the valve operation is completed until a force is actually generated, as compared with a hydraulic system. Assuming that the force is generated in accordance with the sprung speed as in the case of the conventional hydraulic active suspension system, the phase delay of the force generation with respect to the sprung speed is typically about 90 degrees (see FIGS. 6 and 7). 7) The generation timing of the force becomes inappropriate.

In this embodiment, as described above, the necessity of supply / exhaust control is determined based on the sprung acceleration whose phase is ahead of the sprung speed by 90 degrees instead of the sprung speed in the conventional system. In addition, the air supply and exhaust time is determined. That is,
According to the present embodiment, in the pneumatic system that requires time from completion of the signal processing including the necessity determination of the supply / exhaust control to the actual generation of the force, according to the present embodiment, only the amount corresponding to the operation delay of the pneumatic system is The supply / exhaust control is started at an early timing. As a result, the operation delay of the pneumatic system is substantially eliminated, and a force for suppressing the sprung speed is generated at a required timing.

[0042]

As described above , the compressive flow is applied to the spring chamber.
In a fluid active suspension that supplies and discharges the body ,
The present invention detects the vertical acceleration on the spring, and controls the supply and discharge of the compressible fluid to and from the suspension based on the detected acceleration so that the vertical speed on the spring is canceled. , The vertical movement on the spring can be suppressed, and the apparatus cost can be reduced.

Further , since the supply / discharge control is performed when the detected acceleration is near the sprung resonance frequency, it is possible to prevent a fluffy feeling. Further, when the present invention is applied to a pneumatic suspension using air as a working medium, the device configuration can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a pneumatic suspension system to which a suspension operation control method according to an embodiment of the present invention is applied.

FIG. 2 is a flowchart showing a part of a ride comfort control procedure as a suspension operation control method executed by the control unit of FIG. 1;

FIG. 3 is a flowchart illustrating the remaining part of the procedure of ride comfort control.

FIG. 4 is a graph showing a calculation method of a vibration frequency of a vertical acceleration on a spring and an execution timing of supply / exhaust control in ride comfort control.

FIG. 5 is a graph illustrating a supply / exhaust time map used for ride comfort control.

FIG. 6 is a graph showing an operation delay of the pneumatic suspension system.

FIG. 7 is a diagram showing a generation timing of a force based on sprung acceleration capable of compensating an operation delay of the pneumatic suspension system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Shock absorber 3 Air spring chamber 15a High pressure reserve tank 15b Low pressure reserve tank 20 Air supply solenoid valve 22, 23, 26, 27 Solenoid valve 28, 32 Exhaust direction switching valve 36 Control unit 51 Vertical acceleration sensor FS1, FS2, RS1, RS2 Suspension unit

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriko Hayase 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-63-275413 (JP, A) JP-A-63-275413 JP-A-63-251315 (JP, A) JP-A-4-108016 (JP, A) JP-A-63-116920 (JP, A) JP-A-3-509 (JP, A) JP-A-5-83499 (JP) , U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60G 17/00-17/08

Claims (3)

(57) [Claims] An operation control method of a fluid active suspension for supplying and discharging a compressible fluid to and from a spring chamber ,
Detecting a vertical acceleration of the sprung in vertical acceleration sensor, the
The absolute value of the vertical acceleration detected by the vertical acceleration sensor is
Determine whether the level is equal to or higher than a certain level, and determine the vertical acceleration
If the absolute value is equal to or greater than the predetermined level, the vertical acceleration
If the vertical acceleration detected by the sensor is positive or
A preset negative or
Measure the time to the point where the positive threshold is crossed,
Vibration cycle of vertical acceleration on the spring based on time
The wave number is calculated, and the calculated vibration frequency is
Is in the resonance frequency region near the resonance frequency of
Only the vertical acceleration detected by the vertical acceleration sensor
Supply control of the compressible fluid to the spring chamber based on
Or the discharge control is performed by the vertical acceleration sensor.
From the time the lower acceleration crosses the positive or negative threshold
When it corresponds to half of the change cycle of the vertical acceleration on the spring
An operation control method for a fluid active suspension, wherein the method is started at a point in time when the time has elapsed . 2. A hydraulic control method of a fluid active suspension according to claim 1, characterized in that air is used as the compressible fluid. 3. A sensor other than the vertical acceleration sensor.
The compression of the spring chamber based on the detected detection information
While the supply or discharge control of anaerobic fluid is being performed,
Before based on the vertical acceleration detected by the vertical acceleration sensor
Supply control or discharge of the compressible fluid to the spring chamber
3. The method according to claim 1, wherein the control is not performed .