JP2805981B2 - Active suspension - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention detects a posture change occurring in a vehicle body by a vertical acceleration detecting means, and interposes the vehicle between a wheel and the vehicle body based on the detected acceleration value. The present invention relates to an active suspension in which a working fluid supplied to a fluid actuator is controlled to suppress a change in posture of a vehicle body.

[Conventional technology]

An example of this type of active suspension is described in Japanese Patent Application Laid-Open No. 62-289420, which was previously proposed by the present applicant.

In this conventional example, a change in the posture of a vehicle body is detected by a vertical acceleration sensor, an acceleration detection value of the vertical acceleration sensor is integrated to calculate a vertical speed, and a pressure control valve is calculated based on the vertical acceleration detection value and the vertical speed. Is calculated, a so-called skyhook damper function is exerted to effectively suppress a change in the posture of the vehicle body.

[Problems to be solved by the invention]

However, in the above-mentioned conventional active suspension, the damping rate of the skyhook damper is set to be constant, so that when viewed as a vehicle, the motion in any direction of roll, pitch and bounce is uniform. Therefore, if the vibration in the roll and pitch directions related to steering stability is damped faster, the vibration in the bounce direction will inevitably also be damped faster, giving the occupant a hard feeling of riding comfort and a softer ride. There was an unsolved problem that it was not possible to secure comfort.

In view of the above, the present invention has been made by focusing on the unsolved problems of the above-described conventional example, and individually controls the attenuation of roll, pitch and bounce directions generated in a vehicle to secure a soft ride. It is an object of the present invention to provide an active suspension capable of performing the above-described operations.

[Means for solving the problem]

In order to achieve the above object, an active suspension according to claim (1) has a fluid actuator interposed between wheels and a vehicle body as shown in a basic configuration diagram of FIG.
100, a fluid control valve 101 for controlling a working fluid supplied to the fluid actuator 100 in accordance with a control signal, a vertical acceleration detecting means 102 for detecting vertical acceleration at at least three points of the vehicle body, and a vertical acceleration detecting means 102 A control device 103 that outputs a control signal for controlling the fluid control valve based on the acceleration detection value of the active suspension,
The vertical acceleration detecting means 102 is disposed in the vehicle interior, and one of the vertical acceleration detecting means 102 is located on one side in the vehicle longitudinal direction with respect to the pitch center of the vehicle, and is provided on the roll center of the vehicle. And a line connecting one of the left and right front wheels and the rear wheel, and the other two of the vertical acceleration detecting means 102 are disposed on the other side in the vehicle longitudinal direction with the pitch center interposed therebetween. The vertical acceleration detection is disposed at a target position on the side, inside a line connecting both the left and right front wheels and the rear wheels and across the roll center, and disposed on the vehicle rear side of the pitch center. The means 102 is arranged further behind the line connecting the rear wheels, and the control device 103 controls the roll angular acceleration, the pitch angular acceleration and the bounce acceleration of the vehicle body based on the detected acceleration value of the vertical acceleration detecting means 102. Acceleration to calculate Calculating means 104; speed converting means 105 for converting each acceleration calculated by the acceleration calculating means 104 into a velocity; and multiplying the roll angular velocity, the pitch angular velocity and the bounce velocity converted by the speed converting means 105 by different control gains individually. Command value calculating means 106 for calculating the command value.

The active suspension according to claim (2) is:
In each control gain of the command value calculating means 106, the roll direction control gain and the pitch direction control gain are set to be larger than the bounce direction control gain.

Further, in the active suspension according to claim (3), the speed conversion means 105 is constituted by a low-pass filter which acts as an integrator at a resonance frequency in a direction of action of each acceleration and has a different cutoff frequency. .

Still further, in the active suspension according to claim (4), one of the vertical acceleration detecting means 102 is disposed on the front side in the vehicle longitudinal direction with the pitch center interposed therebetween. The other two of them are disposed on the rear side in the vehicle longitudinal direction with the pitch center interposed therebetween.

[Action]

In the active suspension according to claim (1), the acceleration detection value detected by the vertical acceleration detecting means 102 disposed at at least three positions as described above includes only the bounce direction (vertical direction) acceleration of the vehicle body. However, the three vertical acceleration detection means 102 include the vertical components of the roll direction acceleration and the pitch direction acceleration.
The roll angle acceleration, the pitch angle acceleration, and the bounce acceleration are calculated by the acceleration calculation means 104 based on the acceleration detection value of Then, the obtained accelerations are converted into speeds by the speed conversion means 105, and multiplied by different control gains individually set by the command value calculation means 106 to obtain a command value for the fluid control valve, whereby the roll direction is obtained. , The damping rates of the vibrations in the pitch direction and the bounce direction can be set to different values.

Further, the vertical acceleration detecting means disposed on the rear side of the vehicle
Since 102 is disposed further to the rear of the vehicle than the line connecting the rear wheels, the distance in the front-rear direction of the vertical acceleration detecting means disposed before and after the pitch center is extremely long. For this reason, even if the actual position of the pitch center moves in the front-back direction, the calculation accuracy of the pitch angular acceleration does not need to be significantly reduced. Therefore, for example, by increasing the damping rate in the roll direction and the pitch direction related to the steering stability and decreasing the bounce direction-related damping rate according to claim (2), a soft ride comfort is ensured while ensuring the steering stability. Can be secured.

Here, the vehicle speed conversion means 105 acts as an integrator in the resonance frequency range in the roll, pitch and bounce directions, and has different cutoff frequencies, as in the active suspension according to claim (3). Thereby, the vibration in each direction can be effectively attenuated.

In the case of the active suspension according to claim (4), one vertical acceleration detecting means is disposed on the front side of the vehicle having a small space allowance, and two vertical acceleration detection means are provided on the vehicle rear side having a large space allowance. Since the detection means is provided, it is advantageous in terms of space efficiency.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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

In the figure, 11FL to 11RR are respectively the vehicle body side member 12 and each wheel.
13FL to 13RR are active suspensions interposed between the wheel side members 14 individually supporting the hydraulic cylinders 15FL to 15RR as fluid actuators, respectively, and are interposed in parallel with the hydraulic cylinders 15FL to 15RR. It includes coil springs 16FL to 16RR mounted thereon and pressure control valves 17FL to 17RR for controlling the operating oil pressure for the hydraulic cylinders 15FL to 14RR in response to a command value from a control device 31 described later.

Here, in each of the hydraulic cylinders 15FL to 15RR, their cylinder tube 15a is attached to the wheel side member 14, the piston rod 15b is attached to the vehicle body side member 12,
A thrust corresponding to the operating oil pressure supplied from the pressure control valves 17FL to 17RR is generated by a pressure receiving area difference between the piston 15c and the upper and lower pressure chambers defined by the piston 15c having the through hole in the cylinder tube 15a. Further, each of the coil springs 16FL to 16RR supports a static load of the vehicle body, and may have a low spring constant that only supports the static load.

Each of the pressure control valves 17FL to 17RR has an input port 17i, a return port 17o, and a control pressure port 17c, and shuts off the control pressure port 17c, the input port 17i, and the return port 17o, or inputs the control pressure port 17c. It has a spool that switches to an interlocking state that communicates with one of the port 17i and the return port 17o.Supply pressure and control pressure are supplied as pilot pressure to both ends of this spool, and further controlled by a proportional solenoid 17s on the supply pressure side. a is has a configuration in which the poppet valve is disposed is, pressure corresponding to the exciting current I _FL ~I _RR supplied from the control device 31 the pressure P _C of the control pressure port 17c will be described later always proportional solenoid 17s Is controlled as follows.

Here, the relationship between the control hydraulic pressure P _C which is output from the excitation current I _FL ~I _RR control pressure port 17c, as shown in FIG. 3,
P _MIN is output when the excitation currents I _{FL to} I _RR are near zero,
When the exciting currents I _{FL to} I _RR increase in the positive direction from this state,
This with a predetermined proportional gain K ₁ increases the control pressure P _C is saturated with setting the line pressure P _H from the hydraulic source 23 to be described later.

The input port 17i and the return port 17o of the pressure control valves 17FL to 17RR are connected to the supply pipe 21 and the return pipe 2 respectively.
The control pressure port 17c is connected to the pressure chambers of the hydraulic cylinders 15FL to 15RR via a hydraulic pipe 24.

In FIG. 2, reference numeral 25 denotes a high-pressure accumulator connected in the middle of the supply pipe 24, and reference numerals 26 denote pressure control valves 17FL to 17FL.
Throttle to hydraulic piping 24 between RR and hydraulic cylinders 15FL to 15RR
27 is an accumulator for absorbing unsprung vibration which is communicated via 27.

On the other hand, the vehicle body is provided with three vertical acceleration sensors 28FL, 28RL and 28RR as vertical acceleration detecting means.

That is, the specific arrangement positions of the vertical acceleration sensors 28FL, 28RL and 28RR are as shown in FIG. That is, one vertical acceleration sensor 28FL disposed on the front side of the vehicle with respect to the pitch center is composed of the roll center and the front wheel on the right side of the vehicle.
Another two vertical acceleration sensors 28RL disposed in a region surrounded by a line connecting the 13FR and the rear wheel 13RR and a line connecting the front wheels 13FL and 13FR and disposed on the vehicle rear side of the pitch center.
And 28RR are further rearward than the rear wheels 13RL and 13RR in a region between the line connecting the front left wheel 13FL and the rear wheel 13RL on the left side of the vehicle and the line connecting the front wheel 13FR and the rear wheel 13RR on the right side of the vehicle. Are disposed at target positions with the roll center interposed therebetween.
As shown in FIG. 4, each of the vertical acceleration sensors 28FR to 28RR outputs a zero voltage when the acceleration is zero, and generates a positive voltage in response to an upward acceleration. outputs the detection value Z _G, and outputs the acceleration detection value Z _G comprising a negative voltage in response thereto when the downward acceleration occurs. Vertical acceleration sensors 28FR to 28RR in the positions as above
As shown in FIG. 5, when the bounce acceleration, the roll angular acceleration, and the pitch angular acceleration are generated in the vehicle, the following equations (1) to (3) are respectively obtained from the vertical acceleration sensors 28FR to 28RR. Acceleration detection value Z _GFR
~ Z _GRR is output.

Z _GFR = + l ₁ -l ₂ ... (1) Z _GRL = -l ₃ + l ₄ ... (2) Z _GRR = + l ₃ + l ₄ ... (3) where l ₁ passes through the roll center of the vehicle. lateral direction distance between the longitudinal direction line and the front right vertical acceleration sensor 28FR, l ₂ is longitudinal distance between the left-right direction line and the front right vertical acceleration sensor 28FR through the pitch center of the vehicle, l ₃ is the vehicle Front and rear direction lines passing through the roll center and rear left and rear right vertical acceleration sensors
Left and right between 28RL and 28RR direction distance, l ₄ is the left-right direction line and the rear left and rear right acceleration sensor 28 through the pitch center of the vehicle
This is the distance in the front-rear direction between RL and 28RR.

Further, between the vehicle body-side member 12 and the wheel-side member 14, vehicle height detectors 30FL to 30RR for detecting a relative distance therebetween are provided, and these vehicle height detectors 30FL to 30RR are configured by, for example, potentiometers. , And outputs vehicle height detection values H _{FL to} H _RR which are analog voltages corresponding to the relative distances.

And vertical acceleration sensors 28FR-28RR and vehicle height detector
The detected values of 30FL to 30RR are supplied to the control device 31.

As shown in FIG. 6, the control device 31 includes a microcomputer 32 and a control valve drive circuit 33FL to which pressure command values P _{FL to} P _RR output from the microcomputer 32 are input.
~ 33RR.

The microcomputer 32 has at least an interface circuit 32a, an arithmetic processing device 32b, and a storage device 32c,
In the interface circuit 32a, the acceleration detection values Z _{GFR to} Z _GRR of the vertical acceleration detectors 28FR to 28RR are input to the input side thereof via A / D converters 34FR to 34RR, and the respective vehicle height detectors 30FL to 30RR vehicle height detection values H _{FL to} H _RR are A / D converters 35FL to 3
The pressure command values P _{FL to} P _RR input through the 5RR and output from the output side are converted into analog voltages by the D / A converters 36FL to 36RR and supplied to the control valve drive circuits 33FL to 33RR.

The arithmetic processing unit 32b reads the vehicle height detection values H _{FL to} H _RR of the vehicle height detectors 30FL to 30RR via the interface circuit 32a,
These and compared with a preset target vehicle height H _S, calculates the height command value PH _FL ~PH _RR as the vehicle height detected values H _FL to H _RR coincides with the target vehicle height H _S, and Vertical acceleration sensor 28FR ~
The acceleration detection values Z _{GFR to} Z _GRR of 28RR are read, and the calculations of the following equations (4) to (6) are performed based on the acceleration detection values Z _{GFR to} Z _GRR to calculate the bounce acceleration, roll angular acceleration, and pitch angular velocity. Calculated and converted into bounce speed, roll angular speed, and pitch angular speed by performing low-pass filter processing with different cutoff frequencies for each of them, acting as an integrator at the resonance frequency in each direction of motion. The control gains K ₁ , K _2, and K ₃ are multiplied to calculate a bounce suppression pressure command value P _Z , a roll suppression pressure command value P _L, and a pitch suppression pressure command value P _P , and based on these, the total pressure command value P is calculated. calculating a _TFL to P _TRR, these via the interface circuit 32a outputs to the D / a converter 34FL～34RR.

The storage device 32c is composed of a ROM, a RAM, and the like, stores programs necessary for the arithmetic processing of the arithmetic processing device 32b in advance, and sequentially stores the calculation results of the arithmetic processing device 32b.

The control valve Each of the driving circuit 33FL～33RR, for example, a constant current circuit of the floating type, the excitation current I _FL ~I _RR of the pressure control valve according to the pressure command voltage V _FL ~V _RR input Supply to proportional solenoid 17s of 15FL ~ 15RR.

Next, the operation of the above embodiment will be described with reference to the flowchart of FIG. 7 showing the processing procedure of the arithmetic processing unit 32b.

When the ignition switch is turned on, the control device 31 is turned on, and the arithmetic processing device 32b executes the posture change suppression process shown in FIG.

That is, first, in each step, each of the pressure control valves 15FL to 15RR
Set the pressure command value P _S that required to maintain the target vehicle height H _S of the standard loading state pressure command value P _FL to P _RR for.

Next, the process proceeds to the step, and each vehicle height detector 30FL ~
The vehicle height detection values H _{FL to} H _RR of 30RR are read, and these vehicle height detection values are read.
For H _{i (i} = FL~RR) by performing the processes of steps - calculating a vehicle height adjustment pressure command value PH _i.

That is, high target vehicle height detection value H _i in step H _S
Determines whether equal when either when in H _i ≠ H _S, the process proceeds to step it is determined that the required vehicle height adjustment, vehicle height detection value H _i is greater than the target vehicle height H _S Determine whether or not. Given that this time, when a H _i> H _S is preset in the pressure command value at the time of the previous processing proceeds to step determines that it is necessary to lower the vehicle height PH _{i (j-1)} The value obtained by subtracting the value ΔH is used as a new pressure command value PH _{i (j)} (=
PH _{i (j−1)} −ΔH) and calculate this as a storage device
32c vehicle height adjusting pressure command value to update stored in the storage area proceeds to step from, when in H _i <H _S is migrated to the previous processing step is determined that it is necessary to raise the vehicle height The value obtained by adding a predetermined value ΔH to the pressure command value PH _{i (j−1)} at the time is a new pressure command value PH.
_{i (j)} (= PH _{i (j-1)} + ΔH), which is updated and stored in the vehicle height adjustment pressure command value storage area of the storage device 32c, and then the vehicle height adjustment processing is completed and the process proceeds to the step. I do.

In this step, the acceleration detection values Z _{GFR to} Z _GRR of the vertical acceleration sensors 28FR to 28RR are read, and then the process proceeds to step and the above-described equations (4) to (6) are based on the acceleration detection values Z _{GFR to} Z _GRR. The bounce acceleration, the roll angular acceleration, and the pitch angular acceleration are calculated by performing the calculation of the equation.

Then, go to the step, bounce acceleration,
With respect to the roll angular acceleration and the pitch angular acceleration, the bounce speed, the roll angular speed, and the pitch angular speed are calculated by performing a low-pass filter process that acts as an integrator in a resonance frequency region in each direction and that has a different cutoff frequency.

Then, the processing proceeds to step, bounce rate calculated in the step, respectively to the roll angular velocity and the pitch angular velocity s individual bounce control gain K _B, roll control gain K _R and the pitch control gain K _P to be multiplied bounce suppression pressure command value P _B, calculates the roll restraining pressure command value P _R and pitch restrain pressure command value P _P, the bounce suppression pressure command value storage region of the storage device 32c, the roll restraining pressure command value storage area and pitch control pressure command value Each of them is updated and stored in the storage area. Here, the bounce control gain K _B is selected to be smaller than the roll control gain K _R and the pitch control gain K _P related to steering stability (K _B <K _R = K _P ).

Next, the process proceeds to step S3 where the vehicle height adjustment pressure command value storage area, the bounce suppression pressure command value storage area, the roll suppression pressure command value storage area, and the pitch suppression pressure command value storage area of the storage device 32c are stored. each pressure command value _{PH FL ~PH RR, P B,} P R and reads the P _P, following on the basis of these (7) to (10) of performing an operation the pressure control valve 15
Calculate pressure command values P _{FL to} P _RR for _{FL to} 15 _RR .

P _FL = PH _FL -P _B + P _R + P _P (7) P _FR = PH _FR -P _B -P _R + P _P (8) P _RL = PH _RL -P _B + P _R -P _P ... (9) P _RR = PH _RR -P _B -P _R -P _P (10) Then, the process proceeds to the step, and outputs the pressure command values P _{FL to} P _RR calculated in the above step, and then proceeds to the step. Transition to determine whether the specified control end condition is satisfied,
When the control end condition is not satisfied, the process returns to the above step, and when the control end condition is satisfied, the process ends. Here, the control end condition is set when a predetermined time has elapsed after the ignition switch is switched from the on state to the off state, and the power supply of the control device 31 is maintained even after the ignition switch is turned off. Self-hold state

In the processing of FIG. 7, the processing of the step corresponds to the acceleration calculating means 104, the processing of the step corresponds to the speed converting means 105, and the processing of steps 1 to 6 corresponds to the command value calculating means 106.

Therefore, now the vehicle is stopped on a flat road,
When there is no movement of the occupant and the load, zero-voltage acceleration detection values Z _{GFR to} Z _GRR are output from the vertical acceleration sensors 28FR to 28RR. For this reason, when the bounce acceleration, the roll angular acceleration, and the pitch angular acceleration calculated in the processing of the step in FIG. 7 are all zero, the bounce suppression pressure command value P _B and the roll suppression pressure command value calculated in the step are calculated. P _R and pitch suppression pressure command value P _P become zero,
The pressure command values P _{FL to} P _RR are only vehicle height change suppression pressure command values PH _{FL to} PH _RR that suppress the vehicle height change due to the weight of the occupant and the load, and these are output to the D / A converters 35 _{FL to} 35 _RR. As a result, the exciting currents I _{FL to} I _RR corresponding to the command voltages V _{FL to} V _RR output from the D / A converters 35 _FL to 35 _RR are output from the control valve driving circuits 33 _FL to 33 _RR to the pressure control valves 17 FL to 17 _RR . is output to the proportional solenoid 17s, by the thrust of the hydraulic cylinder 15FL~15RR is change control pressure P _C of the pressure control valve 17FL~17RR to increase and decrease the vehicle height is equal to the target vehicle height.

That is, the passenger boarding (or getting off), when the vehicle height is lowered (or raised), in the processing of FIG. 7, the process proceeds to step through the step and, H _i <
Since the H _S (or H _i> H _S), a step (or steps) proceeds to the previous height adjustment pressure command value PH
_By adding (or subtracting) the predetermined value ΔH to _{i (j−1)} , the vehicle height adjustment pressure command value PH _{i (j)} increases (or decreases), and the pressure command value P _FL . by P _RR is increased (or decreased), the vehicle height internal pressure of the hydraulic cylinders 15FL~15RR increases are raised (or lowered), and the vehicle height increase process is repeated, the vehicle height detected values H _i is increase in vehicle height to match the target vehicle height H _S (or decrease) is stopped, the vehicle height is maintained at the target vehicle height.

When the vehicle is started from this stopped state, pitching occurs due to the scut phenomenon in which the rear wheel sinks into the vehicle body, and this pitching outputs a positive acceleration detection value Z _GFR from the front wheel vertical acceleration sensor 28FR. The negative acceleration detection values Z _GRL and Z _GRR are output from the vertical acceleration sensors 28RL and 28RR on the rear wheel side. For this reason, in the processing of the step, the pitch angular acceleration becomes a negative value, so that the pitch suppression pressure command value P _P also becomes a negative value, and the rear wheel side pressure command values P _RL and P _RR are described above ( 9)
As is clear from the equations (10) and (10), the pitch pressure command value _PP is added to the vehicle height adjustment pressure command values PH _RL and PH _RR . Conversely, the front wheel pressure command values P _FL and P _FR are obtained. Is
Aforementioned (7) the formula and (8) minus the pitch pressure command value P _P from the vehicle height adjusting pressure command value as apparent PH _FL and PH _FR from the equation. For this reason, the hydraulic cylinder on the rear wheel side
The thrust of 15RL and 15RR increases, and the hydraulic cylinder 15 on the front wheel side
Since the thrust of FL and 15RR is reduced, the so-called scut phenomenon in which the rear wheel side sinks due to acceleration generated in the vehicle can be suppressed, and the vehicle body can be kept flat.

Further, when the vehicle changes from the constant speed running state to the braking state, pitching occurs due to a nose dive phenomenon in which the front wheel side sinks, and a negative acceleration detection value Z _GFR is output from the vertical acceleration sensor 28FR on the front wheel side due to this pitching. At the same time, positive acceleration detection values Z _GRL and Z _GRR are output from the vertical acceleration sensors 28RL and 28RR on the rear wheel side, and conversely, the hydraulic cylinders 15FL and 15FR on the front wheel side
Of the rear wheel side hydraulic cylinders 15RL and 15RR
, The so-called nose dive phenomenon in which the front wheels sink due to the deceleration generated in the vehicle can be suppressed, and the vehicle body can be maintained in a substantially flat state.

Thus, when causing pitching in the vehicle, since the pitch control gain K _P is selected relatively large value in the processing of the step, by suppressing the pitch damping ratio increases rapidly damped pitching As a result, steering stability can be ensured.

Further, when the vehicle is turned right (or left) from the straight running state, the vehicle body rolls down (or down) to the left, and this rolling causes a negative (or positive) signal from the left vertical acceleration sensor 28RL. Acceleration detection value
Z _GRL is output and the right vertical acceleration sensor 28FR
(Or negative) acceleration detection values Z _GFR and Z _GRR
Is output. Thus, is the value of the roll angle acceleration is positive calculated in step (or negative), since the value of the rolling-restraining pressure command value P _R positive (or negative) in response thereto, the left side of the hydraulic cylinder 15FR and The thrust of 15RR is increased (or decreased), and the thrust of the right hydraulic cylinders 15FL and 15RL is decreased (or increased), so that the roll of the vehicle body is suppressed and the vehicle body can be maintained in a substantially flat state.

As described above, even when a roll occurs in the vehicle, the roll control gain K _R in the step processing is selected to be a relatively large value, so that the roll can be rapidly attenuated to ensure steering stability. it can.

Further, when the vehicle travels on a rough road and a vertical bouncing occurs in the vehicle body, acceleration detection values Z _{GFR to} Z _GRR output from each of the vertical acceleration sensors 28FR to 28RR in the bouncing direction of the vehicle. Has a positive value, and has a negative value in the rebound direction. For this reason, the bounce acceleration calculated in the step is positive on the bounce side, negative on the rebound side, and the bounce suppression pressure command value P _B is also positive on the bounce side and negative on the rebound side, so the hydraulic cylinder 15FL
By reducing the thrust of ~ 15RR on the bounce side and increasing it on the rebound side, it is possible to suppress the bounce and maintain the vehicle body in a substantially flat state.

Thus, if the bounce of the vehicle has occurred, since the bounce control gain K _B in the processing of the step are selected other control gain K _R, a K _P value less than, to reduce the attenuation rate of bounce And secure a soft ride.

Further, in the present embodiment, each of the vertical acceleration sensors 28FL, 28RL
And 28RR, the center in the vehicle width direction is arranged at a position separated from the roll center extending in the vehicle front-rear direction. Therefore, in the vehicle cabin, the arrangement density of the device is higher than the surroundings. There is no need to increase the density, and there is no need to make significant design changes or the like in order to secure the arrangement positions of the vertical acceleration sensors 28FL, 28RL, and 28RR.

And two vertical acceleration sensors disposed on the rear side of the vehicle.
28RL and 28RR are further behind the rear wheels 13RL and 13RR (in the trunk on the rear side of the rear seat for ordinary cars)
The vertical acceleration sensors 28RL and 28RL
The distance l ₄ from the pitch center 28RR can be maximized. Also, a vertical acceleration sensor 28FR installed on the front side of the vehicle
Is arranged at the foot position of the front seat, but if it is arranged further forward than that, it will be within the engine rule, so actually the arrangement position of the vertical acceleration sensor 28FR in this embodiment is a full front, distance l ₂ from the pitch center of the vertical acceleration sensors 28FR are also again turned up.

On the other hand, the pitch center slightly shifts in the front-rear direction according to the actual behavior of the vehicle, so that the distances l ₂ and l ₄ actually change according to the situation. When so as to calculate the distance l ₂ and l ₄ and, calculation load of the microcomputer 32 will be greatly increased. Therefore, if the distances l ₂ and l ₄ are maximized as in the present embodiment, even if the pitch center slightly changes, the influence can be minimized. It is not necessary to greatly reduce the calculation accuracy of.

In the above embodiment, one of the three vertical acceleration sensors 28FR to 28RR is connected to two vertical acceleration sensors 28FR on the vehicle front side of the pitch center.
The RL and 28RR are arranged on the rear side of the vehicle with respect to the pitch center. This is because the two vertical acceleration sensors 28RL and 28RR are further rearward of the vehicle than the rear wheels having a large space allowance.
Is because the space efficiency of the whole vehicle is better. Therefore, depending on the case, conversely, two vertical acceleration sensors may be disposed on the front side and one vertical acceleration sensor on the rear side, or two vertical acceleration sensors may be disposed on the front side and the rear side, respectively. May be. Also, the vertical acceleration sensor 28FR disposed on the front side of the vehicle may be disposed on the left side of the vehicle with the roll center interposed.

Further, in the above embodiment, the case where the control device 31 includes the microcomputer 32 has been described. However, the present invention is not limited to this, and the control device 31 may be configured by combining electronic circuits such as a comparison circuit and a logic circuit.

Further, as control valves, pressure control valves 17FL to 17RR
The present invention is not limited to this, and other flow control type servo valves and the like can be applied.

Further, in the above-described embodiment, the case where the working oil is used as the working fluid has been described. However, the present invention is not limited to this, and any working fluid may be used as long as the fluid has a low compression ratio.

〔The invention's effect〕

As described above, according to the active suspension of the present invention, the roll angle acceleration and the pitch are calculated by the acceleration calculation means based on the acceleration detection values of the vertical acceleration detection means arranged at at least three points on the vehicle body. Calculate the angular acceleration and bounce acceleration, convert these accelerations to speed by speed conversion means, and multiply the converted roll angular velocity, pitch angular velocity and bounce speed by control gains of different values by the command value calculation means, respectively, to obtain a fluid control valve. , It is not necessary to separately provide an attitude change detecting means such as a lateral acceleration detecting means and a longitudinal acceleration detecting means, and it is possible to set different control gains for each roll, pitch and bounce. Rolls and pitch vibrations that affect steering stability are quickly attenuated because
For vibrations in the bounce direction that affect the ride quality, a softer ride quality can be obtained by reducing the damping rate. In addition, the vertical acceleration sensor that is located behind the Since it is arranged on the side, even if the pitch center moves a little, the effect that the calculation accuracy of the pitch angular acceleration and the bounce acceleration does not need to be greatly reduced can be obtained.

According to the active suspension of the present invention, the control gain of the command value calculation means is set smaller than the pitch control gain and the roll control gain by the bounce control gain. By increasing the damping rate of the vehicle and speeding up the convergence, the steering stability can be ensured, and the bounce damping rate can be reduced to ensure a soft ride.

Further, according to the active suspension according to claim (3), the speed conversion means functions as an integrator in a resonance frequency region in a direction of action of the angular acceleration, and is constituted by low-pass filters having different cutoff frequencies. Therefore, vibrations in the bounce direction, the roll direction, and the pitch direction can be effectively attenuated.

Further, according to the active suspension of the present invention, the space efficiency of the whole vehicle is improved.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram showing a schematic configuration of an active suspension according to the present invention, FIG. 2 is a configuration diagram showing one embodiment of the present invention, and FIG. 3 is a diagram showing a relationship between an exciting current of a pressure control valve and a control pressure. FIG. 4 is a characteristic diagram showing the relationship between the detected acceleration of the vertical acceleration sensor and the output voltage, FIG. 5 is a diagram showing the arrangement relationship of the vertical acceleration sensor, and FIG. FIG. 7 is a block diagram showing an example, and FIG. 7 is a flowchart showing an example of a processing procedure of the control device. In the figure, 11FL-11RR is an active suspension, 12 is a vehicle body side member, 13FL-13RR is a wheel, 14 is a wheel side member, 15FL-15RR
Is a hydraulic cylinder (fluid actuator), 17FL-17RR is a pressure control valve, 21 is a hydraulic power source, 28FR-28RR is a vertical acceleration sensor, 31 is a control device, 32 is a microcomputer, 33FL ~
33RR is a control valve drive circuit.

Claims (4)

(57) [Claims] 1. A fluid actuator interposed between a wheel and a vehicle body, a fluid control valve for controlling a working fluid supplied to the fluid actuator according to a control signal, and a vertical acceleration at at least three points of the vehicle body. An active suspension comprising: a vertical acceleration detecting means for detecting; and a control device for outputting a control signal for controlling the fluid control valve based on an acceleration detection value of the vertical acceleration detecting means. One is disposed on one side in the vehicle front-rear direction across the pitch center of the vehicle, and is disposed in an area between the roll center of the vehicle and a line connecting one of the left and right front wheels and the rear wheel, The other two of the vertical acceleration detecting means are on the other side in the vehicle longitudinal direction with the pitch center interposed, inside the line connecting both the left and right front wheels and the rear wheels, and The vertical acceleration detecting means disposed at a target position with the data interposed therebetween, and disposed at a rear side of the vehicle with respect to the pitch center, further disposed rearward of the vehicle than a line connecting rear wheels; Is acceleration calculation means for calculating the roll angular acceleration, pitch angular acceleration, and bounce acceleration of the vehicle body based on the acceleration detection value of the vertical acceleration detection means, and speed conversion for converting each acceleration calculated by the acceleration calculation means into speed. Means for calculating the command value by individually multiplying the roll angular velocity, the pitch angular velocity and the bounce speed converted by the speed converting means by different control gains, and calculating the command value. . 2. The active suspension according to claim 1, wherein the control gain of the command value calculating means is set so that the roll direction control gain and the pitch direction control gain are larger than the bounce direction control gain. 3. The speed conversion means according to claim 1, wherein said speed conversion means functions as an integrator at a resonance frequency in a direction of action of each acceleration, and is constituted by low-pass filters having different cutoff frequencies. An active suspension as described. 4. One of the vertical acceleration detecting means is disposed on the front side in the vehicle longitudinal direction with the pitch center interposed therebetween.
The active suspension according to any one of claims 1 to 3, wherein the other two of the vertical acceleration detecting means are disposed on the rear side in the vehicle longitudinal direction with the pitch center interposed therebetween.