JP2765274B2 - 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 an active suspension, and more particularly to an active suspension capable of adjusting a vehicle height while keeping a vehicle body flat.

[0002]

2. Description of the Related Art Conventional active suspensions include:
For example, there is one described in Japanese Patent Application Laid-Open No. 2-95912 previously proposed by the present applicant. In this conventional example, a vehicle height S _{FL to} S _RR at each wheel position is detected by a stroke sensor,
The vehicle height detection values S _{FL to} S _RR are compared with the target vehicle height value _SN to calculate a deviation between the two, and a vehicle height command value is calculated based on these deviations. A roll command value and a pitch command value based on both acceleration detection values of the sensor and the longitudinal acceleration sensor are added and subtracted to calculate a pressure command value for a pressure control valve for controlling a fluid pressure for a fluid cylinder, and output these to the pressure control valve. By doing so, the vehicle height is maintained at the target vehicle height value.

[0003]

However, in the above-mentioned conventional active suspension, the vehicle height is always controlled to the target value. If the vehicle height is to be maintained at the target value under all conditions up to the loading state, a vehicle in which the vehicle weight changes greatly between them requires a wide pressure control range to adjust the vehicle height, and this requires lateral acceleration. When a pressure control range for suppressing a posture change by the vehicle body posture change detection means such as is added, a wider control range is required,
There is an unsolved problem that the consumption horsepower increases. Moreover, even if a wide control range can be set,
Since the ratio of the maximum loading state to the entire loading state is extremely small, there is also a problem that waste increases.

Accordingly, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and restricts the pressure range used for adjusting the vehicle height so as not to affect the steering stability. It is an object of the present invention to provide an active suspension that can maintain a posture of a vehicle body in a horizontal state.

[0005]

In order to solve the above problems, an active suspension according to the present invention comprises a fluid cylinder interposed between each wheel and a vehicle body, as shown in FIG. A control valve for controlling a working fluid from a fluid supply device to be supplied to a cylinder in accordance with a command value input thereto, a vehicle height detecting means for detecting a vehicle height, and at least a detection value based on a detection value of the vehicle height detecting means. Control means for controlling a control valve, wherein the control means controls the pressure so that the vehicle height matches a preset target vehicle height based on a vehicle height detection value of the vehicle height detection means. Command value calculating means for calculating a vehicle height adjustment command value for the control valve;
Limit value determining means for determining whether or not the vehicle height adjustment command value calculated by the command value calculating means is within a preset limit value; and determining that the limit value determining means has exceeded the limit value. And a target vehicle height changing means for changing the target vehicle height to a value lower than the target vehicle height.

Here, it is preferable that the command value calculating means be configured so that the vehicle height adjustment in the roll direction is prioritized over the vehicle height adjustment in the bounce direction, and that the vehicle height adjustment command is issued during the roll direction vehicle height adjustment. When the value reaches the limit ,
To eliminate the roll inclination of the vehicle when it reaches
A value equivalent to the roll direction command value adjustment required on one side
Is preferably configured to shift from the bounce direction command value to the roll direction command value.

[0007]

In the present invention, the limit value judging means judges whether or not the vehicle height adjustment command value is within a preset limit value, and when it is within the limit value, sets the target vehicle height value to a preset value. The command value calculating means calculates a vehicle height adjustment command value based on the vehicle height detection value so as to match the target vehicle height value,
By outputting this to a control valve, vehicle height control is performed.
Therefore, the vehicle height is always maintained at a preset target vehicle height value.

However, when the limit value determining means determines that the vehicle height adjustment command value exceeds the limit value,
Since the target vehicle height is changed to a value lower than the set value by the target vehicle height changing means, the vehicle body can be maintained substantially horizontal with respect to the road surface without requiring high pressure.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing the first embodiment of the present invention, and shows a case of a rear-wheel drive vehicle. In the figure, 10
FL, 10FR are front left wheels, front right wheels, and 10
Reference numerals RL and 10RR denote rear left and rear right wheels serving as driving wheels, 12 denotes a wheel side member, 14 denotes a vehicle body side member, and 16 denotes an active suspension.

The active suspension 16 includes hydraulic cylinders 18FL to 18RR as fluid cylinders separately provided between the vehicle body-side member 14 and the wheel-side members 12.
Pressure control valves 20FL to 20RR for adjusting the operating oil pressures of the hydraulic cylinders 18FL to 18RR, a hydraulic source 22 of the hydraulic system, the hydraulic source 22 and the pressure control valve 20FL.
Accumulator 2 for pressure accumulation interposed between 20 and 20 RR
4, 24, a lateral acceleration sensor 26 for detecting a lateral acceleration acting in the lateral direction of the vehicle body, a vehicle height sensors 28FL to 28RR each comprising, for example, a potentiometer for detecting the vehicle height at the position of each of the wheels 10FL to 10RR. Control valve 20F
Controller 3 for individually controlling the output pressure of L to 20RR
0.

The active type suspension 16 includes coil springs 36,..., 36 which are separately mounted between the wheel side member 12 and the vehicle body member 14 with respect to the hydraulic cylinders 18FL to 18RR, and the hydraulic cylinders 18FL to 18R.
R includes a throttle valve 32 and an accumulator 34 for absorbing vibration individually communicated with a pressure chamber L described later. Here, each coil spring 36 has a relatively low spring constant and supports a static load of the vehicle body.

Each of the hydraulic cylinders 18FL to 18RR has a cylinder tube 18a, and the cylinder tube 18a has upper and lower pressure chambers L defined by a piston 18c, and these pressure chambers are formed in the piston 18c. And a thrust corresponding to the internal pressure is generated by the pressure receiving area difference between the upper and lower surfaces of the piston. The upper end of the cylinder tube 18a is attached to the vehicle body-side member 14, and the lower end of the piston rod 18b is attached to the wheel-side member 12.

Each of the pressure control valves 20FL to 20RR has a valve housing having a spool slidably housed in a cylindrical insertion hole, and a proportional solenoid provided integrally with the valve housing. It is formed in a pilot operation type. This pressure control valve 20FL-20RR
The supply port and the return port for the hydraulic oil are communicated with the hydraulic oil supply side and the hydraulic oil return side of the hydraulic power source 22 through the hydraulic pipes 38 and 39, and the output port is connected to the hydraulic cylinders 18FL to 18RR through the hydraulic pipe 40. Each of the pressure chambers L is communicated.

[0014] Thus, by controlling the value of the exciting current I as a pressure instruction value supplied to the exciting coil of the proportional solenoid, the exciting current hydraulic from the output port a control pressure P _C in accordance with the I cylinder 18FL (~18RR ) Pressure chamber L
Can be supplied. That is, the control pressure P _C, as shown in FIG. 3, the exciting current when i from its minimum value i _MIN changing to the maximum value i _MAX, the maximum pressure P _MAX (hydraulic this from the minimum pressure P _MIN substantially in proportion (The line pressure of the source 22).

Further, as shown in FIG. 4, the lateral acceleration sensor 26 has a positive voltage value corresponding to the lateral acceleration in a straight running state and zero in a straight running state, and in a right turning state in which the vehicle is steered right from the straight running state.
And it outputs the detected lateral acceleration Y _G comprising a negative voltage value corresponding to the lateral acceleration in a left turning state of being left steering in the opposite. As shown in FIG. 5, the controller 30 converts the lateral acceleration detection value Y _G of the lateral acceleration sensor 26 into a digital value, and an A / D converter 82, and the vehicle height detection values H _{FL of the} vehicle height sensors 28FL to 28RR. A / D converter 83 for converting .about.H _RR into a digital value
FL to 83RR, and A / D converters 82 and 83FL to 8
Microcomputer 8 to which 3RR conversion output is input
4, D / A converters 85FL to 85RR for converting the pressure command values I _{FL to} I _RR output from the microcomputer 84 into analog values, and conversion outputs of these D / A converters. Based on each pressure control valve 20FL
Exciting current i _{FL to} i 20RR for proportional solenoid
Solenoid drive circuits 86FL to 86RR for outputting _RR are provided.

The microcomputer 84 includes at least an input interface circuit 84a, an output interface circuit 84b, an arithmetic processing unit 84c, and a storage unit 8.
4d, and the arithmetic processing unit 84c detects the vehicle height detection values H _FL , H _FR and H _RL, H _RR of the left and right wheels on the front wheel side and the rear wheel side.
Detects a change in the vehicle height in the roll direction of the vehicle body, calculates a pressure command value for correcting the change in the vehicle height in the roll direction and outputs it, and then checks whether the pressure command value is within the allowable value. It is determined whether or not it is over the allowable value.
By calculating a pressure command value for maintaining the vehicle body horizontal with respect to the road surface within the allowable value and outputting the pressure command value, appropriate vehicle height control is performed according to the loaded weight.

The storage device 84d stores in advance a processing program necessary for the arithmetic processing of the arithmetic processing device 84c, and sequentially stores the processing results of the arithmetic processing device. next,
The operation of the above embodiment will be described with reference to the flowcharts of FIGS. 6 and 7 showing the processing procedure of the arithmetic processing unit 84c. That is, the flowchart of FIG. 6 shows the front-wheel-side vehicle height adjustment process, which is executed by a timer interrupt process started at a predetermined time (for example, 20 msec) for a predetermined main program. Front wheel side vehicle height sensor 28
The detected values H _FL and H _FR of FL and 28 _FR are read.

Next, the process proceeds to step S2, where
(1) by performing the calculation of the equation to calculate the roll-direction posture variation H _RF of the vehicle. H _RF = then _{(H FR -H FL) / 2} ............ (1), the process proceeds to step S3, the absolute value of the roll direction posture change amount H _RF | H _RF | roll direction posture change a preset It is determined whether or not the threshold value ΔH _R is exceeded, and | H _RF |
If> ΔH _R, it is determined that the change in the roll direction posture is large, and the flow shifts to step S4.

[0019] In step S4, the roll direction posture variation H _RF is equal to or negative, when it is H _RF <0 is, if it is rolled state body is inclined right downward as viewed from the rear side Then, the process proceeds to step S5, and a value obtained by adding a predetermined value α to the roll direction command value I _HR-FR of the pressure command value for the front right pressure control valve 20FR is set as a new roll direction command value I _HR-FR . With the front left pressure control valve 2
Roll direction command value I _HR-FL of pressure command value for 0FL
Is subtracted by the predetermined value α from the new roll direction command value I.
_HR-FL is updated and stored, and then the process proceeds to step S6, where the sum of the front right roll direction command value I _HR-FR and the front wheel bounce direction command value I _HB-F is set to a preset maximum vehicle height adjustment. It is determined whether the pressure is equal to or less than the pressure command value I _HMAX . At this time, if I _HMAX ≧ I _HR-FR + I _HB-F , the process _{proceeds to} step S7 to reset limit determination flags F _{FL and} F _FR described later to “0”, and then to step S8
To calculate the front right vehicle height adjustment pressure command value I _H-FR by adding the right roll direction command value I _HR-FR and the bounce direction command value I _HB-F, and The command value I _HR-FL and the bounce direction command value I _HB-F are added to calculate a front left vehicle height adjustment pressure command value I _H-FL , and then the process proceeds to step S9, where a bounce target value H described later is set. _BF-T to H _B0
And then returns to step S1.

The result of the determination in step S6 is I _HMAX <
If I _HR-FR + I _HB-F , the process proceeds to step S10, where the front right vehicle height adjustment pressure command value I _{H-FR is set} to the maximum vehicle height adjustment pressure command value I _HMAX , and the left roll direction is set. The command value I _HR-FL and the bounce direction command value I _HB-F are added to calculate a front left vehicle height adjustment pressure command value I _H-FL , and then the process proceeds to step S11 to execute a right limit judgment flag F
_After setting _FR to "1", the process returns to step S1.

On the other hand, if the determination result of step S4 is _HRF > 0
When it is determined that the vehicle body is rolling to the lower left when viewed from the rear side, the process proceeds to step S12,
A value obtained by adding a predetermined value α to the roll direction command value I _HR-FL of the pressure command value for the front left pressure control valve 20FL is set as a new roll direction command value I _HR-FL, and the pressure for the front right pressure control valve 20FR is determined. Roll direction command value I of command value
_The value obtained by subtracting the predetermined value α from the _HR-FR is updated and stored as a new roll direction command value I _HR-FR , and then step S13
To determine whether the sum of the front left roll direction command value I _HR-FL and the front wheel bounce direction command value I _HB-F is equal to or less than a preset maximum vehicle height adjustment pressure command value I _HMAX . Is determined. At this time, if I _HMAX ≧ I _HR-FL + I _HB-F , the process _proceeds to step S7, where I _HMAX <I _HR-FR +
If it is I _HB-F , the process _proceeds to step S14, where the front left vehicle height adjustment pressure command value I _{H-FL is set} to the maximum vehicle height adjustment pressure command value I _HMAX , and the right roll direction command value I _HMAX is set.
_HR-FR and the bounce direction command value I _HB-F are added to calculate a front right vehicle height adjustment pressure command value I _H-FR , and then step S
The program proceeds to 15 and sets the left limit determination flag F _FL to “1”.
And then returns to step S1.

Further, the result of determination in step S3 is | H
_{When RF} | ≦ ΔH _R, it is determined that there is no need to adjust the vehicle height in the roll direction, and the flow shifts to step S16.
In the roll direction vehicle height adjustment processing, the limit determination flag F _FL,
When any of F _FR is set to "1", run the pressure command value correcting process, and then proceeds to a predetermined main from running target vehicle height adjustment processing to the target vehicle height in step S17 Return to the program.

The pressure command value correction processing in step S16 is as follows.
As shown in FIG. 7, first, in step S21, the bounce direction vehicle height value _HBF is calculated according to the following equation (2). H _BF = (H _FR + H _FL ) / 2 (2) Next, the process proceeds to step S22, where the right limit determination flag F _FR is set to “1” in the roll direction vehicle height adjustment processing. Is determined. At this time, when the right limit determination flag F _FR is set to "1", it proceeds to step S23 it is determined that the right-hand height adjustment pressure command value I _H-FR becomes a limit value I do.

[0024] In the step S23, the bounce direction wheel height H _BF calculated bounce direction vehicle high target value H _BF-T at step S21, then the process proceeds to step S24, roll sharing corrected in accordance with the following equation (3) to calculate the value ΔI _{R. ΔI R = (I H-FL} + I HMAX -2I HB) / 2 ............
Here (3), why roll sharing correction value [Delta] I _R is represented by formula (3), as shown in FIG. 9, the vehicle has rolled to the right downward as viewed from the rear side, and front right When the vehicle height adjustment pressure command value I _H-FR is assumed to have reached the limit value I _HMAX, in order to eliminate the change in the attitude of the roll direction, the vehicle height adjustment pressure command value I _H-FR is a limit value in the normal state has not been reached I _HMAX, before the intermediate value of the left-wheel side left and right vehicle height i.e. with reduced by the difference x between the bounce direction wheel height H _FB, may be the front right wheel side so as to increase by the difference x However, because the front right wheel pressure adjustment command value I _H-FR of the front right wheel has reached the limit value I _HMAX , the front right wheel cannot be raised. To step S
By repeating the processing of 5, S6, S10, and S11, adjustment is performed such that the vehicle height adjustment pressure command value I _H-FL of the front left wheel lowers the vehicle height by twice the difference x.

At this time, the pressure command value required to lower the vehicle height by 2x is the vehicle height on the front left wheel side at the moment when the front right wheel reaches the limit value I _HMAX from the vehicle height adjustment pressure command value I _H-FL. Value I _H-FL obtained by subtracting the adjustment value (-I _{HR -FL} + I _{HB -F} )
− (− I _{HR -FL} + I _{HB −F} ). Therefore, in order to bear half the vehicle height correction amount on the left and right wheels, the vehicle height must be x
Since it is sufficient only change, its share of words roll sharing correction value [Delta] I _R is [Delta] I _R = represented by _{{I H-FL - - (} I HR -FL + I HB -F)} / 2 ............ (4) be able to.

Here, since the roll direction command value I _HR fluctuates in the roll direction vehicle height adjustment processing in FIG.
By substituting I _{HR -FL} = I _HMAX −I _HB into the above equation (4), the above equation (3) can be obtained. Next, the process proceeds to step S25, where the current bounce direction command value I _HB-F
From updated and stored in a predetermined storage area of the storage device 84d, a value obtained by subtracting the roll sharing correction value [Delta] I _R as a new bounce direction command value I _HB-F.

Next, the process proceeds to step S26, where
According to equation (5), the new front right wheel side roll direction command value I
_HR-FR is calculated, and a value obtained by inverting the sign of the roll direction command value I _HR-FR as shown in the following equation (6) is set as a roll command value I _HR-FL for the front left wheel, and then the pressure command is obtained. After the value correction process is completed, the process proceeds to the target vehicle height adjustment process of FIG. I _HR-FR = I _HMAX −I _HB-F (5) I _HR-FL = −I _HR-FR (6) Also, the result of the determination in step S22 is a right limit determination flag. If _FFR has been reset to "0", the flow shifts to step S27.

In this step S27, it is determined whether or not the left limit determination flag F _FL has been set to "1". If the flag F _FL has been reset to "0", the pressure command value correction processing is performed as it is. When the flag _FFL is set to "1", it is determined that the vehicle body is rolling to the lower left when viewed from the rear side, and the step is performed. The process moves to S28.

In step S28, similarly to step S23 described above, the bounce direction target value H _BF-T is set to the bounce vehicle height value H _BF calculated in step S21, and then the process proceeds to step S29, where the following (7) ) to calculate the roll sharing correction value [Delta] I _R according equation. ΔI _R = I _H−FL + I _HMAX −2P _HB (7) Then, the _process proceeds to step S30, and the current bounce method is performed.
Storage device a value obtained by subtracting the roll sharing correction value [Delta] I _R from direction command value I _HB-F as a new bounce direction command value I _HB-F 8
4d is updated and stored in a predetermined storage area.

Next, the processing shifts to step S31, where
According to equation (8), the new front left wheel side roll command value I_HR-FL
As well as the roll command as shown in equation (9) below.
Value I _HR-FLRoll command for the front right wheel
Value I_HR-FRPressure command value correction processing
Then, the process proceeds to the target vehicle height adjustment process of FIG. I_HR-FL= I_HMAX-I_HB-F ............ (8) I_HR-FR= -I_HR-FL ……… (9) The target vehicle height adjustment process is performed by first step as shown in FIG.
In S41, the data is stored in the storage device 84d according to the following equation (10).
Current bounce direction vehicle height H_BFAnd target vehicle height H
_BF-TΔH_BIs calculated.

ΔH_B= H_BF-H_BF-T (10) Next, the process proceeds to step S42, where the absolute value of the difference value | Δ
H_B| Is the preset vehicle height adjustment threshold ΔH_BTIs greater than
| ΔH_B|> ΔH_BTIf
Judge that it is necessary to adjust the vehicle height in the
The process proceeds to step S43, and the difference_BDetermine if is positive
I do. At this time, ΔH_BWhen <0, the vehicle height is
Step S
44, and the current bounce command value I_HB-FSet in advance
The value obtained by adding the predetermined value β to a new bounce command value I
_HB-FThe process proceeds to step S46 after being updated and stored as
ΔH _BWhen> 0, the vehicle height is higher than the target vehicle height.
And the process proceeds to step S45.
Bounce command value I_HB-FValue obtained by subtracting the predetermined value β from
To the new bounce command value I_HB-FAfter updating and remembering
Move to step S46.

[0032] In the step S46, similarly to step S6 in the roll direction vehicle height adjustment process of FIG. 6 described above, the roll direction command stored in the storage device 84d value I _HR-FR and bounce direction command value I _HB It is determined whether or not the vehicle height adjustment command value obtained by adding _F is _{equal to} or greater than a limit value I _HMAX , and if I _HMAX <I _HR-FR + I _HB-F, it is determined that the limit value has been exceeded. Then, the process proceeds to step S47,
The target vehicle height H _BF-T is updated and stored in accordance with the current bounce vehicle height H _BF , and the process returns to step S41, where I _HMAX ≧
If _IHR-FR + _IHB-F, it is determined that the front right wheel side has not exceeded the limit value, and the routine goes to Step S48.

[0033] In the step S48, the similarly to step S13 in the roll direction vehicle height adjustment process of FIG. 6 described above, the roll direction command value I stored in the storage device 84
It is determined whether or not the vehicle height adjustment pressure command value obtained by adding the _HR-FL and the bounce direction command value I _HB-F is _{equal to} or greater than the limit value I _HMAX , and I _HMAX <I _HR-FL + I _HB-F If there is, it is determined that the limit value has been _exceeded , and the _{process proceeds} to step S47. If I _HMAX ≧ I _HR-FL + I _HB-F , it is determined that the limit value has not been exceeded, and the process _proceeds to step S41. Return.

On the other hand, the judgment result of step S42 is ΔH
When a _B ≦ [Delta] H _BT is, processing proceeds to step S50. In step S50, the above-described vehicle height adjustment processing of FIGS . 6 and 7 is performed on the rear wheel side to calculate the vehicle height adjustment pressure command values I _{HRL and} I _HRR of the rear left and right wheels, and output these. Then, the process proceeds to step S51 to determine whether or not the front-wheel-side bounce target value H _BF-T matches the rear-wheel-side bounce target value H _BR-T, and H _BF-T = H _{If BR-T} , the timer interrupt processing ends and H _BF-T ≠ H
_{If BR-T} , the process proceeds to step S52 to determine whether the front wheel-side bounce target value H _BF-T is larger than the rear wheel-side bounce target value H _BR-T , and H _BF-T > H _{BR- If} it is _T, it is determined that the vehicle height on the front wheel side is high, and step S53 is performed.
Proceeds to, return the rear wheel side bounce target value H _BR-T after updating stored as the front wheel side bounce target value H _BF-T to the target vehicle height adjustment adjustment process of FIG. _{8, H BF-T <H} BR- _{When T}
It is determined that the vehicle height on the rear wheel side is high, and the flow shifts to step S54 to update and store the front wheel side bounce target value H _BF-T as the front wheel side bounce target value H _BR-T , and then to step S50 on the rear wheel side. The process returns to the target vehicle height adjustment adjustment processing of FIG. 8 in the vehicle height processing.

The arithmetic processing unit 84c detects the vehicle height adjustment pressure command values I _{H-FL to} I _H-RR for each wheel determined by the vehicle height adjustment processing, and detects lateral acceleration from the lateral acceleration sensor 26. predetermined time based on the value Y _G (e.g. 20
Each of the pressure control valves 20FL is executed by executing a pressure command value calculation process shown in FIG. 10 by a timer interrupt process having a high priority for the vehicle height adjustment processes shown in FIGS.
The pressure command values I _{FL to} I _RR for 〜20 _RR are calculated.

[0036] That is, the pressure command value calculation process in FIG. 10, first in step S61, reads the lateral acceleration detection value Y _G of the lateral acceleration sensor 26, and then proceeds to step S62, the following equation (11) - (14 ) Is calculated to calculate the pressure command values I _{FL to} I _RR for suppressing the change in the posture of the vehicle body. I _FL = I _H-FL + K _R · Y _G (11) I _FR = I _{H -FR} -K _R · Y _G (12) I _RL = I _{H -RL} + K _R · Y _{G ............ (13) I RR =} I H-RR -K R · Y G ............ (14) where, K _R is a control gain for suppressing the roll previously set, Different values may be set for the front wheel side and the rear wheel side.

Then, the flow shifts to step S63, where the pressure command values I _{FL to} I _RR calculated in step S62 are converted to D
The output is performed individually to the / A converters 85FL to 85RR, and the process is terminated. Here, the processing of FIGS. 6 to 8 corresponds to the command value calculating means, and among them, steps S1 to S5 and S5 of FIG.
7 to S9 and S12 correspond to the roll direction command value calculation unit, the processes of steps S6 and S13 in FIG. 6 correspond to the limit value determining unit, and the processes of FIGS. 7 and 8 correspond to the target vehicle height changing unit. Yes, it is.

Therefore, assuming that the vehicle is in a stopped state with the key switch turned off, the controller 30 is inactive in this state because the key switch is off, and each pressure control valve 20FL
To 20RR are stopped, and each of the pressure control valves 20FL to 20RR and the hydraulic cylinder 18FL
The hydraulic control system including the hydraulic cylinders 18FL to 18RR is maintained at a predetermined pressure by pressure holding means (not shown) constituted by, for example, a pilot operated check valve.
Are equal to each other.

In this state, for example, when a driver gets in,
By previous right vehicle weight is increased, the piston rod 18b of the hydraulic cylinder 18FR of the front right wheel is contracted,
The vehicle height on the front right wheel side decreases. Then, when the driver turns on the key switch after getting on, the controller 30 is activated, and the microcomputer 84 starts executing the processes of FIGS. 6 to 8 and 10,
Then, by turning on the ignition key, the engine is started, and the hydraulic oil pressure discharged from the hydraulic pressure source 22 increases. When the pressure becomes higher than the pressure held by the pressure holding means, the pressure in the pressure holding means is reduced. The pressure holding state is released, and the state shifts to the control state by the normal pressure control valves 20FL to 20RR.

At this time, since the vehicle height adjustment processing shown in FIGS. 6 to 8 is executed, the vehicle height on the front right wheel side is reduced only by the occupant, so the calculation is performed in step S2 in FIG. roll direction vehicle height variation H _RF is becomes negative relatively large value. For this reason, the process proceeds from step S3 to steps S6 through S4 and S5, where the front right roll direction command value I _HR-FR is increased by a predetermined value α, and the front left roll direction command value I _{HR-FL is} increased. Is reduced by a predetermined value α.
In this state, since the occupant is only the driver, the amount of increase in the roll direction command value I _HR-FR does not become very large, and the value obtained by adding this to the bounce direction command value I _HB-F is determined in advance. The set limit value I _HMAX is not reached. Therefore, the process proceeds from step S 6 to step S 7, the limit determination flag F _FL, is reset to the F _FR "0", the process proceeds to step S 8, the pressure adjusting current vehicle height command value I _H calculates the _-FR and I _H-FL, which were output to the D / a converters 85FR and 85FL, then the process proceeds to step S 9, preset initial value as bounce target vehicle height H _BF-T After setting H _B0 , the process returns to step S1. This treatment pre-increased vehicle height adjusting pressure command value I _H-FR for the pressure control valve 20FR of the right wheel side vehicle height adjustment pressure command value for the previous left pressure control valves 20FL to opposite I _H-FL
Decrease. For this reason, every time the command value calculation process of FIG. 10 is executed, the thrust of the hydraulic cylinder 18FR increases, and conversely, the thrust of the hydraulic cylinder 18FL decreases.
The vehicle height on the front right side increases, and the vehicle height on the front left side decreases. Therefore, by repeating the above processing, the smaller the vehicle height difference between the front-wheel-side left and right, the absolute value of the roll direction vehicle height variation H _RF calculated in step S2 | H _RF | is smaller than the predetermined threshold value [Delta] H _R Then, it is determined that the roll height adjustment has been completed, and the process proceeds from step S3 to the pressure command value correction process shown in FIG.

At this time, since the limit determination flags F _{FL and} F _FR have both been reset to “0” in the roll direction vehicle height adjustment processing of FIG. 6, the bounce direction vehicle height H _BF is calculated in step S21. Then, the pressure command value correction process is terminated, and the process proceeds to the target vehicle height adjustment process of FIG. In this target vehicle height adjustment processing, the bounce direction target vehicle height value H _BF-T set in step S10 is subtracted from the bounce direction vehicle height value H _BF calculated in step S21, and the difference value Δ from the target vehicle height is calculated.
Calculate H _B. At this time, assuming that the vehicle height is lower than the target vehicle height in the initial state, step S4
The process proceeds to step S44 via steps S43 and S43, and a value obtained by adding a predetermined value β to the current bounce direction command value I _HB-F is set as a new bounce direction command value I _HB .
S48 proceeds to step S49 through a bounce direction command value I _HB-F and the roll direction command value I _{HR-F L} and I _HR-FL
Are added to calculate the vehicle height adjustment pressure command values I _{H-FL and} I _H-FR , which are updated and stored before returning to step S41.
Therefore, by repeating this process, the vehicle height on the front wheel side is raised until it matches the preset initial target vehicle height, and when it becomes substantially equal to the initial target vehicle height, the process proceeds from step S42 to step S50. After performing the same vehicle height adjustment processing on the rear wheel side, the process proceeds to step S51, where the front wheel side bounce target vehicle height value H _BF-T and the rear wheel side bounce target vehicle height value H _BR-T are _calculated. It is determined whether or not they match, and since the number of occupants is small and the load weight is small, the target vehicle height values H _BF-T and H _BR-T maintain the initial target value H _B0 , so adjustment to the target vehicle height is performed. When it is determined that the processing has been completed, the timer interrupt processing ends, and the processing returns to the predetermined main program.

As described above, when the load weight of the vehicle is small, first, the height adjustment in the roll direction is performed by the processing in FIG. 6, and when the height adjustment in the roll direction is completed, the processing in FIGS. 7 and 8 is performed. Then, the vehicle height is adjusted in the bounce direction, the vehicle height of the front and rear wheels is adjusted, and the vehicle height is adjusted to match the vehicle height with a preset target vehicle height. However, when the occupants are full with two passengers on the front seat side and three occupants on the rear seat side, and the load capacity of the vehicle increases, the vehicle height decreases in accordance with the load capacity. Requires a large thrust in each of the hydraulic cylinders 18FL to 18RR, the pressure command values I _{FL to} I _RR calculated by the arithmetic processing unit 84c naturally become large values.

However, in order to preferentially execute high-priority control such as anti-roll control of the vehicle using the lateral acceleration detection value Y _G as in this embodiment, the hydraulic pressure source 2 must be used.
Since there is a limit to the hydraulic oil pressure P _L generated in Step 2,
The limit pressure P _HMAX that can be used for vehicle height adjustment is the hydraulic oil pressure P
_Since the value obtained by subtracting the maximum pressure P _PMAX used in the priority control from _L is obtained, when the roll direction vehicle height adjustment processing of FIG. 6 is executed, for example, as shown in FIG. While rolling, the front right vehicle height is raised by repeating the processing of steps S1 to S9, and while the front left vehicle height is being lowered, the front right wheel side roll direction command value I _HR-FR and When the value obtained by adding the bounce direction command value I _HB-F exceeds the limit value I _HMAX , the process proceeds from step S6 to step S10, so that the front right wheel-side vehicle height adjustment pressure command value I _H-FR becomes The limit value I _HMAX is regulated, only the front left wheel-side vehicle height adjustment pressure command value I _H-FL is reduced by a predetermined value α, and the front right limit determination flag F _FR is set to “1” in step S11. You. For this reason, the vehicle height rise on the front right wheel side is stopped, and only the vehicle height on the front left wheel side continues to fall.

[0044] Then, before the vehicle height detected values H _FL of the vehicle height detected values H _FR and the front left wheel side of the right wheel side in a state in which substantially coincides, exit roll direction vehicle height adjustment, pressure 7 Move on to command value correction processing. In the pressure command value correction process, first, a bounce direction vehicle height value H _BF is calculated in step S21,
Next, since the front right limit determination flag _FFR is set to "1", the process shifts from step S22 to step S23 to change the bounce target vehicle height value H _BF-T from the initial target value H _B0 to the current bounce direction. Change to vehicle height _HBF ,
Next, the process proceeds to step S24, where the role assignment correction value Δ
_IHR is calculated, and then the process proceeds to step S25, where the roll sharing correction value ΔI _R is calculated from the current bounce direction command value I _HB-F.
Is subtracted to calculate a new bounce direction command value I _HB-F ,
Next, the process _proceeds to step S26 to calculate the regular front right roll direction command value I _HR-FR by subtracting the bounce direction command value I _HB-F from the limit value I _HMAX ,
Together updated and stored code converted value of the roll direction command value I _HR-FR as before left roll direction command value I _HR-FL.

[0045] Thus, rolls share correction value [Delta] I _R min bounce direction command value I _HB-F is reduced, the roll direction command value I _HR-FR that this decrease raises before the right height by x
At the same time, the roll direction command value I _{HR-FL for} lowering the front left vehicle height by x is obtained, and the overall vehicle height adjustment pressure command values I _H-FR and I _H-FL are not changed. The values I _HR-FR and I _HR-FL are corrected to values that properly correspond to the vehicle height adjustment amount x in the roll direction.

Next, the pressure command value correcting process is completed, and the process proceeds to the target vehicle height adjusting process of FIG. In this target vehicle height adjustment processing, in the above-described pressure command value correction processing, step S
Since the bounce direction target vehicle height value H _BF-T is matched with the current bounce direction vehicle height value H _{BF at} 23, step S41 is performed.
The difference value ΔH _B between the two calculated by the above becomes zero, and the process proceeds from step S42 to step S50 without performing the vehicle height adjustment in the bounce direction, and the same processing as described above is performed on the rear wheel side.

Then, the flow shifts to step S51, where the bounce direction target vehicle height values H _BF-T and H _BR-T on the front wheel side and the rear wheel side are set.
It is determined whether or not the values match.If the values match, the timer interrupt process is terminated.If the values do not match, the higher target vehicle height value is changed to the lower target vehicle height value. Then, the process returns to step S41 described above, and the front and rear vehicle heights are matched.

As a result, according to the above embodiment, first, the height of the vehicle in the roll direction is adjusted, and at this time, the roll direction command value I _HR-FR (or I _HR-FL ) and the bounce direction command value I _HB are adjusted. It determines whether _-F vehicle height adjustment pressure command value obtained by adding the I _H-FR (or I _H-FL) has reached the limit value I _HMAX previously set, has reached the limit value I _HMAX Sometimes, the vehicle height value on the side that has reached the limit value I _HMAX is _{left as} it is, while the vehicle height value on the other side is reduced, and the roll direction correction value ΔI
_R is calculated, the bounce direction command value I _{HB -F} is reduced by this amount, the roll direction command value is corrected to a value corresponding to the regular roll adjustment, and further, the vehicle height adjustment is performed for the bounce direction vehicle height adjustment. High adjustment command value I _H-FR or I _{H- FL} is the limit value I
_{When HMAX} has been reached, the current bounce direction vehicle height adjustment is stopped, and the current bounce direction vehicle height value _HBF is maintained.

In each of the above embodiments, a case has been described in which a microcomputer is applied as the controller 30. However, the present invention is not limited to this, and is configured by combining electronic circuits such as a function generator and an arithmetic circuit. You can also. Further, in each of the above embodiments, a case has been described in which pressure control is performed by applying a pressure control valve as a control valve. However, the present invention is not limited to this, and flow control may be performed by applying a flow control valve.

Further, in each of the above embodiments, the active suspension for detecting the lateral acceleration of the vehicle and performing the anti-roll control has been described. However, the present invention is not limited to this. Pitch control, anti-bounce control using vertical acceleration, or the like may be used alone or in combination with each other. Furthermore, in the above embodiment, the case where the working oil is applied as the working fluid has been described. However, the present invention is not limited to this, and another fluid having low compressibility can be applied.

In each of the above embodiments, the case where the hydraulic cylinder is used as the actuator for adjusting the vehicle height has been described. However, the present invention is not limited to this, and another actuator such as a pneumatic cylinder may be used. Can also.

[0052]

As described above, according to the active suspension of the first aspect, based on the vehicle height detection value of the vehicle height detecting means, the vehicle height matches the target vehicle height set in advance. Command value calculating means for calculating a vehicle height adjustment command value for the pressure control valve; and a limit value for determining whether the vehicle height adjustment command value calculated by the command value calculation means is within a preset limit value A determination means, and a target vehicle height changing means for changing the target vehicle height to a value lower than the limit value when the limit value determination means determines that the vehicle height exceeds the limit value. When the adjustment command value reaches the limit value and the vehicle height cannot be adjusted, the target vehicle height value is changed to a low value, so that high pressure is required while maintaining the vehicle height flat. Thus, an effect that can be adjusted without performing is obtained.

According to the active suspension according to the second aspect, the vehicle height adjustment in the roll direction is prioritized over the vehicle height adjustment in the bounce direction, so that the posture change of the vehicle body in the roll direction is reliably prevented. The effect that can be obtained is obtained. Further, according to the active suspension according to the third aspect, when the vehicle height adjustment command value reaches the limit value and the roll direction command value does not correspond to the actual change in the roll direction, one of the bounce direction command values is set. The roll direction command value can be secured by the section, and an effect that a normal roll direction command value can be obtained can be obtained.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram showing an outline of the present invention.

FIG. 2 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 3 is an output characteristic diagram of a pressure control valve applicable to the embodiment.

FIG. 4 is an output characteristic diagram of a lateral acceleration sensor applicable to the embodiment.

FIG. 5 is a block diagram illustrating an example of a controller applicable to the embodiment.

FIG. 6 is a flowchart illustrating an example of a roll direction vehicle height adjustment process of a microcomputer applicable to the controller.

FIG. 7 is a flowchart illustrating an example of a pressure command value correction process of a microcomputer applicable to the controller.

FIG. 8 is a flowchart illustrating an example of a target vehicle height adjustment process of a microcomputer applicable to the controller.

FIG. 9 is an explanatory diagram for explaining vehicle height adjustment when a vehicle height adjustment command value reaches a limit value.

FIG. 10 is a flowchart showing a pressure command value calculation process of a microcomputer applicable to the controller.

[Explanation of symbols]

 10FL, 10FR Front wheel 10RL, 10RR Rear wheel 16 Active suspension 18FL-18RR Hydraulic cylinder 20FL-20RR Pressure control valve 26 Lateral acceleration sensor 28FL-28RR Vehicle height sensor 30 Controller 84 Microcomputer

Claims (3)

(57) [Claims] 1. A fluid valve interposed between each wheel and a vehicle body, a control valve for controlling a working fluid from a fluid supply device supplied to the fluid cylinder in accordance with a command value input, and a vehicle A vehicle height detecting means for detecting a height, and a control means for controlling the control valve based on at least a value detected by the vehicle height detecting means, wherein the control means comprises: Command value calculation means for calculating a vehicle height adjustment command value for the pressure control valve such that the vehicle height matches a preset target vehicle height based on the vehicle height detection value; and a vehicle height calculated by the command value calculation means. Limit value determining means for determining whether or not the adjustment command value is within a preset limit value; and when the limit value determining means determines that the value exceeds the limit value, the target vehicle height is increased. Target vehicle height changing means for changing to a lower value An active suspension comprising: 2. The command value calculating means includes: a roll direction command value calculating section for calculating a roll direction command value of a vehicle; a bounce direction command value calculating section for calculating a bounce direction command value of the vehicle; And a vehicle height adjustment command value calculation unit that calculates the vehicle height adjustment command value by adding the value and the bounce direction command value. The calculation in the roll direction command value calculation unit is prioritized over the bounce direction command value calculation unit. The active suspension according to claim 1, wherein: Wherein the vehicle height adjustment command value calculation unit, when the vehicle height adjustment command value reaches the limit value, when it reaches the該限limit value
Necessary on one side to cancel the roll direction inclination of other vehicles
3. The active suspension according to claim 2 , wherein a value corresponding to the roll direction command value adjustment is shifted from the bounce direction command value to the roll direction command value.