JPH0392412A - Active suspension - Google Patents

Abstract

PURPOSE:To improve a sense of security and operating stability in an active suspension device for a vehicle by lowering a ground clearance in turning than that in straight driving based on a detected or estimated transverse acceleration. CONSTITUTION:Acceleration in the transverse direction working on a car body is detected by a transverse acceleration sensor 26, and a signal g is put out to a controller 30. The controller 30 operates a command value for each of wheels so that it drops by a predetermined change rate for the inner wheel side as an absolute value of the transverse acceleration detected value is increased and it rises by the change rate smaller than the change rate of the inner wheel side for the outer wheel side. And each of pressure control valves 20FL to 20RR is controlled by this command value for each wheel so as to operate each of fluid pressure cylinders 18FL to 18RR and to lower a ground clearance than that in straight driving. By this constitution, a sense of security of crews and operating stability can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an active suspension, and in particular, a system that controls the operating pressure of a fluid pressure cylinder disposed between a vehicle body and wheels in accordance with lateral acceleration, This invention relates to an active suspension that adjusts the vehicle height when turning.

[Prior Art] Japanese Patent Application No. 1983 previously filed by the present applicant relates to an active suspension system that controls vehicle roll during turning.
There is one described in No.-331833 (unpublished). One aspect of the active suspension device described in this application includes a vehicle suspension and a rear wheel steering angle control mechanism. Among these, the vehicle suspension includes a fluid pressure cylinder inserted between the vehicle body and each wheel, and a pressure control valve that controls the working fluid pressure of the fluid pressure cylinder according to only a command value.
lateral acceleration detection or estimation means for determining the lateral acceleration of the vehicle body;
It has a control device that outputs a command value according to the detected value or estimated value of the lateral acceleration detection or estimation means. Also,
The rear wheel steering angle control mechanism controls the rear wheel steering angle in the understeer direction based on the detected value or estimated value of the lateral acceleration detection or estimating means, thereby achieving the reduction in energy consumption, which was the objective of the earlier application. It's powerful.

By the way, in the above-mentioned active suspension device,
An example of the control characteristics in which the horizontal axis is the lateral acceleration y (positive value when turning right) and the vertical axis is the operating pressure P of the fluid pressure cylinder (i.e., the output pressure of the pressure control valve) is shown in Figure 10. It is shown in the figure below. In other words, when the lateral acceleration Si=0 when traveling straight, the outer wheel side. The inner ring side working pressure P is both the predetermined neutral pressure P, l
As the lateral acceleration 191 increases due to turning, both the outer wheel side and inner wheel side working pressures P increase or decrease at the same rate of change, resulting in a right turn. The operating pressure changes symmetrically when turning left.

[Problem to be solved by the invention]

However, in the active suspension having the control characteristics shown in FIG.
On the other hand, when turning, the operating pressure on the outer wheel side increases and the operating pressure on the inner wheel side decreases at the same rate, so the vehicle height value during turning is the average value, that is, the neutral value P. A vehicle that maintains the same vehicle height as when driving straight, and when transitioning from driving straight to turning, the height of the center of gravity of the vehicle does not change and the vehicle turns at the specified height, so the vehicle height decreases slightly when turning. For crew members accustomed to
On the contrary, there were inconveniences such as a feeling of uneasiness and a decrease in maneuverability depending on the driving situation.

The present invention has been made focusing on these unresolved inconveniences, and aims to solve the problems by eliminating the feeling of anxiety caused by the vehicle occupants due to the height of the vehicle when turning, and improving the steering stability. This is an issue to be addressed.

[Means to solve the problem]

In order to solve the above problems, the invention according to claims (1) and (3) includes a fluid pressure cylinder interposed between a vehicle body side member and a wheel side member for each wheel, as shown in FIG. , a pressure control valve that individually controls the operating pressure of each fluid pressure cylinder according to a command value, a lateral acceleration detection or estimation means for detecting or estimating the lateral acceleration of the vehicle body, and the lateral acceleration detection or estimation means. a command value calculation means for calculating a command value for each wheel to lower the vehicle height when turning than when driving straight, based on the detected or estimated lateral acceleration of the vehicle; and command value output means for outputting to each valve. Here, the command value calculation means sets a predetermined value when the lateral acceleration detection or estimated value of the lateral acceleration detection or estimation means is zero, and sets the command value to a predetermined value for the inner ring side as the absolute value of the lateral acceleration detection value increases. It is also possible to use means for calculating a command value that decreases at a rate of change and increases for the outer ring side at a smaller rate of change than the rate of change for the inner ring side.

In addition, the invention described in claims (2) and (3) provides a fluid pressure cylinder interposed between a vehicle body side member and a wheel side member for each wheel, and a fluid pressure cylinder provided in this fluid pressure cylinder and said wheel side member. an accumulator that absorbs vibrations of the hydraulic cylinder; a pressure control valve that individually controls the operating pressure of the fluid pressure cylinder according to a command value; and lateral acceleration detection or estimation means that detects or estimates lateral acceleration of the vehicle body; A command value calculation means calculates a command value for each wheel to lower the vehicle height when turning than when driving straight, based on the lateral acceleration detection or estimated value of the lateral acceleration detection or estimation means, and the command value calculation means calculates a command value for each wheel. The main part is provided with a command value output means for outputting the command values to the pressure control valves.

[Effect]

In the invention described in claims (1) and (3), when the vehicle transitions from a straight-ahead state to a turning state, the command value calculation means, for example, when the detected or estimated lateral acceleration value is zero, the command value is set to a predetermined value, As the absolute value of the detected lateral acceleration value increases, a command value is calculated for each wheel that decreases at a predetermined rate of change for the inner wheels and increases at a rate of change smaller than the rate of change for the outer wheels. . Then, each command value is outputted to the pressure control valve by the command value output means.

As a result, the rate of increase in the working pressure of the hydraulic cylinder on the outer ring side is smaller than the rate of decrease in the working pressure of the hydraulic cylinder on the inner ring side. As a result, the height of the center of gravity is moderately lower than when the vehicle is traveling straight, while allowing a certain degree of roll.

Furthermore, in the inventions described in claims (2) and (3), in addition to the above-mentioned effects, since the pressure increase rate of the fluid pressure cylinder on the side of the outer swing ring is relatively small, the accumulator connected thereto may collapse. Therefore, the function of the accumulator to absorb the vibrations of the wheel side members can be activated even when turning, and it is possible to prevent vibrations from being transmitted to the vehicle body side.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 2 to 9. The active suspension of this embodiment shows a case where only the roll control of the vehicle body is performed.

In Fig. 2, lO represents the vehicle body side member which is the suspension arm, IIFL to IIRR represent the front left to rear right wheels,
12 each represents an active type of suspensidin. The active suspension system 12 includes a vehicle body side member 10 and a wheel 1.
Hydraulic cylinders 18FL to 18FL as fluid pressure cylinders interposed between each wheel side member 14 of 1FL to IIRR.
18RR, pressure control valves 20FL to 20RR that individually adjust the operating pressures of the hydraulic cylinders 18FL to 18RR, a hydraulic power source 22 of the hydraulic system, and pressure control valves 20FL to 2ORR inserted between the hydraulic power source 22 and the pressure control valves 20FL to 2ORR. an accumulator 24.24 for accumulating pressure, a lateral acceleration sensor 26 that detects acceleration generated in the lateral direction of the vehicle body, and pressure control valves 20FL to 20R based on the detection signal of the lateral acceleration sensor 26.
It has a controller 30 that individually controls the output pressure of H. Further, each of the pressure chambers L of the hydraulic cylinders 18FL to 18RR, which will be described later, is connected via a throttle valve 32 to an accumulator 34 for absorbing unsprung vibrations. Further, a coil spring 36 having a relatively low spring constant and supporting the static load of the vehicle body is disposed between the sprung and unsprung portions of each of the hydraulic cylinders 18PL-18RR.

Each of the hydraulic cylinders 18FL to 18RH has a cylinder tube 18a, and this cylinder tube 18a includes:
A lower pressure chamber L is defined by the piston 18c. Then, the lower end of the cylinder tube 18a is attached to the wheel side member l4, and the piston rod 18b
The upper end of is attached to the vehicle body side member 10. Also,
Each of the pressure chambers L is connected to the pressure control valve 2 via a hydraulic pipe 38.
Connected to output ports from 0FL to 20RR.

Moreover, each of the pressure control valves 20FL to 20RR is a conventionally well-known three-boat proportional electromagnetic pressure reducing valve (
For example, see Japanese Patent Application Laid-Open No. 64-74111). By adjusting the command current i (command value) supplied to the excitation coil of the proportional solenoid, the moving distance of the boppet housed in the valve housing, that is, the position of the spool, is controlled, and the supply boat, output boat, or output Hydraulic source 22 and hydraulic cylinder 1 via port and return boat
It is possible to control the hydraulic oil that flows between the 8PL-18RR and the 8PL-18RR.

Here, command current i (: I
FL-1 lm) and pressure control valve 20FL (~20RR
) and the control pressure P output from the output boat is as shown in FIG. In other words, when the minimum current value i KIN takes noise into consideration, the minimum control pressure P HI
When the current value l is increased from this state, the control pressure P increases linearly in proportion to the current value i, and when the maximum current value i WAX, the maximum control pressure P MAX corresponds to the set line pressure. Become. This maximum control pressure P WAX is set lower than the value shown in FIG. 10 above. L is the neutral command current, and PM is the neutral control pressure.

On the other hand, a lateral acceleration sensor 26 is installed at a predetermined position ahead of the center of gravity of the vehicle. This lateral acceleration sensor 26
detects the acceleration in the lateral (vehicle width) direction acting on the vehicle body, and outputs to the controller 30 a voltage signal g corresponding to the amount of displacement when, for example, a magnetically suspended mass is displaced by inertial force. As shown in Fig. 4, the detection characteristics are as follows: when the lateral acceleration y=0, the detection signal g=
g N (predetermined neutral value), and increases or decreases in proportion to the lateral acceleration y when turning left or right from this state. Here, the lateral acceleration y has a positive value when turning left, and a negative value when turning right.

Furthermore, as shown in FIG. 5, the controller 30 is an A/D converter that converts the detection signal g corresponding to the input analog lateral acceleration y into a digital quantity. 0, a microcomputer 72 for arithmetic processing, and a digital pressure command value vFL- output from this microcomputer 72.
D/A converter 7 that individually converts Vl, l into analog quantities
3A to 73D and the pressure command value VFL of this analog quantity
"With Vllll1 as the target value, pressure control valves 20FL~2
0Rl? It has drive circuits 74A to 74D that make the command currents t and L%t■, which are individually outputted, follow the target values.

Of these, the microcomputer 72 includes a small number of interface circuits 76, arithmetic processing units 78, RAM, and RAM.
The interface circuit 76 is configured to include a storage device W80 consisting of an OM, etc., and the interface circuit 76 is connected to the /0 port. Further, the arithmetic processing unit 78 reads the detection signal g via the interface circuit 76, and performs arithmetic operations and other processing to be described later based on these signals. The storage device 80 stores in advance a predetermined program, fixed data, etc. necessary for execution of processing by the arithmetic processing device 78, and also stores processing results of the arithmetic processing device 78.

The fixed data stored in the storage device 80 includes ? Figure 6(a). A storage table corresponding to Φ) is included.

Figure (a) shows the front left side. Front right pressure command value vF L
+■■ (voltage value). Figure (b) shows the pressure command values VIL. The graph shows the characteristics of Vllll (voltage value) (in these figures, the horizontal and vertical axes have the same scale). Among these, in the same figure (a), when the lateral acceleration y=O, a predetermined neutral value ■N (=command value to maintain the vehicle height when traveling straight) is taken, and when the lateral acceleration corresponding to a left turn is 9>Q Then, the front right pressure command value V■>■, and the front left pressure command value VFL<Vs. At this time, Q<p≦Yt (y+ is, for example, 0.3 CG
) Between ), the front right pressure command value V■ is ■.

The front left pressure command value VFL increases at a rate of change α from
It decreases from N at a rate of change α3 (1α, 1〉1α1 1). Also, S'l<S'≦yt (S'2 is, for example, 0
．． 5 (G)), the front right pressure command value VFR is V.
The rate of change is up to α. (Iα2 1<1αI 1 increases, and the rate of change α4(lα4
1>1α, 1). Furthermore, in the range of y2<y, the front right pressure command {,! ! V■=■,,? The state of left side pressure command value v2L=v is maintained. On the other hand, when the lateral acceleration y<0 corresponding to a right turn, the front right pressure command value V■ decreases at the same rate of change as the front left pressure command value vyt during a left turn, and the front left pressure command value VFL decreases. It increases at the same rate of change as the front right pressure command value V■ when turning left.

In addition, in the same figure), when the lateral acceleration V=O, the predetermined neutral value v. In addition to taking 4, the pressure command value ■ is taken as in the same figure (a).
The rate of change when increasing lILy v11 is set smaller than the rate of change when decreasing. As a result, the changeable gain is “VE′~VsJ, and vM′〈
V,4 and v,'>v, and are compressed compared to the front wheel side. This is due to the fact that in FF and FR vehicles, the front vehicle weight is greater than the rear load, so the front side requires a larger operating pressure variation range and the desire for an understeer tendency.

In this embodiment, the rate of change when increasing the pressure command value VFL to Vllll+ is set smaller than the rate of change when decreasing it for both the front and rear wheels, and the rate of change for the inner and outer wheels for the same lateral acceleration y is This makes it possible to issue pressure commands with different ranges of change.

Next, the operation of the above embodiment will be explained.

When the ignition switch of the vehicle is turned on, the controller 30 is activated and executes the timer interrupt process shown in FIG. 7 at predetermined intervals (for example, every 20 msec) while a predetermined main program is being executed.

The process shown in FIG. 7 will be explained. First, in step 2 of the figure, the arithmetic processing unit 78 of the microcomputer 72 reads the detection signal g of the lateral acceleration sensor 26, and proceeds to step (3). In this step (2), a lateral acceleration detection signal Δg is obtained by subtracting the neutral value gs from the detection signal g read in step. Next, the process moves to step (2), and the lateral acceleration y corresponding to the detection signal Δg is calculated by, for example, referring to a storage table stored in the storage device 80 in advance.

Next, the process moves to step (2), and the process shown in FIG. 6(a) is performed. (b
), each ? is uniquely determined by the lateral acceleration y calculated in step ■ by referring to the corresponding memory table individually. The pressure command value vFL-V- is read out and the value is temporarily stored.

In this setting, if the stored data in the memory table is the value of the bending point of each curve in Figures 6(a) and (b), the value of the midpoint can be calculated from the calculation based on the known two points. You may ask.

After this, the arithmetic processing unit 78 moves to step (3),
The pressure command values VFL~V■ calculated in step ■ are sent to the D/A converters 73A~73 via the interface circuit 76.
Output to D individually.

Therefore, the change in the cylinder pressure P of each wheel with respect to the change in the lateral acceleration y obtained by performing the above control is as follows:
The result is as shown in FIG.

Next, the overall operation will be explained.

It is now assumed that a vehicle is traveling straight at a constant speed on a flat, smooth road. Since no roll occurs in this state, the detection signal g of the lateral acceleration sensor 26 is at its neutral value g
N, and the lateral acceleration y calculated by the controller 30 becomes zero (see steps 1 to 2 in FIG. 7). For this reason, each pressure command value V set by referring to the memory table
, L-V? =v. 4 (Fig. 6(a), i). 7th
(see figure step ■), this neutral value ■8 is the D/A converter 7
3A to 73D, respectively. The pressure command values V, L-V■ (=VN) converted into analog quantities by the D/A converters 73A to 73D are output as target values to the drive circuits 74A to 74D, respectively.
Target value ■ from 74D. Neutral command currents i, l corresponding to the neutral command currents i and l are supplied to the pressure control valves 20PL to 20RR, respectively. As a result, the pressure control valves 20PL to 201'lR adjust the operating pressures of the hydraulic cylinders 18FL to 18RR to the neutral pressure PH.
(See Figure 3), so the hydraulic cylinder 18PL
-18RR each generates a force corresponding to the neutral pressure PM to maintain the vehicle body in a flat posture at a predetermined vehicle height.

When the vehicle shifts from this constant-speed straight-ahead state to, for example, a left-turning state, an inertial force acts to the right of the vehicle body, causing a roll in which the right side of the vehicle sinks and the left side lifts up when viewed from the rear of the vehicle.

At this time, the detection signal g of the lateral acceleration sensor 26 is the neutral value g
Is it thicker than N depending on the turning speed etc.? Therefore, in the controller 30, the lateral acceleration signal Δg>0, a positive lateral acceleration y corresponding to this Δg is calculated, and pressure command values VFL to ■■ are set respectively according to this lateral acceleration ν. (See Steps ■ to ■ in Figure 7). At this time, the pressure command value VFL~■■ is VFI>VFL, Vll>V+I
L, and while changing from the neutral value vN, the pressure command values V■+Vll for the front right and rear right on the outer wheels are higher than the pressure command values VFL+"IL for the front left and rear left on the inner wheels. The set values VFL~■■ are converted into corresponding command currents Lt~i+u+ and supplied to the pressure control valves 20FL~20RR, and the hydraulic cylinders 18F
The operating pressures L to 18RH are controlled to values corresponding to command currents iFL to io, that is, pressure command values V and LV■.

Therefore, the outer ring side hydraulic cylinder 1 BPR, 1 8
The working pressure of RR is slightly increased from the neutral pressure PM to generate a force that suppresses the sinking of the car body to some extent, and the working pressure of the inner hydraulic cylinders 18FL, 18RL is significantly lowered from the neutral pressure PM. This does not encourage the vehicle body to lift (for example, see point 9''y+ in FIG. 8). As a result, the roll angle when turning left is suppressed to an acceptable and appropriate value.

On the other hand, the vehicle height value in this turning state is determined by the average value of the inner and outer wheel pressure, and the pressure average value is as shown by the dashed-dotted lines H, (front wheel side) and H* (rear wheel side) in Figure 8. In both cases, the pressure is lower than the neutral pressure PM by an amount corresponding to the lateral acceleration y. In other words, as the vehicle transitions into a turn, it maintains its center of gravity while allowing a moderate amount of roll. In other words, since the entire vehicle height is lowered, when turning, the occupants do not feel unnecessarily anxious because the vehicle height does not change, and the steering stability does not deteriorate compared to when driving straight.

In addition, in this turning state, the outer wheel side hydraulic cylinder 1
Since the increase rate of the cylinder pressure P of BPR, 1 8RR is suppressed, the increase rate of the cylinder pressure P of the cylinder 1 BPR, l 8RR is
The accumulators 34, 34 connected to the pump are less prone to collapse, and have a sufficient internal capacity to absorb hydraulic oil.

As a result, the accumulators 34 and 34 do not lose their spring function to absorb hydraulic vibrations, so even if high-frequency vibrations equivalent to the unsprung resonance region are input, such as vibrations caused by small irregularities on the road surface, this vibration input will not be lost. The corresponding hydraulic vibrations can be reliably absorbed, thereby suppressing the vibrations transmitted to the vehicle body during turns, reducing the bumpy feeling, and ensuring a good ride during attitude control.

The reason why this good ride comfort is obtained during posture control is explained in the ninth section.
Let's analyze quantitatively based on Figures (a) and (b).

In the cylinder model shown in Figure (a), assuming that the piston cross-sectional area A, the internal pressure P, the internal volume V, the piston stroke X, and the rod reaction force F, the spring constant K is K=ΔF/ΔX, and F=P- A, ΔF=ΔP-AΔV=A-Δ
Since X, ΔX = ΔV/A, K = ΔF/ΔX = (ΔP-A)/(ΔV/A) = A!・(ΔP/Δ■). In other words, since the spring constant K is proportional to "ΔP/Δ■", in the P-V curve of FIG. 9(b), which shows that PV=constant, when traveling straight at a constant speed, point a is reached. If the vehicle is at point b during a certain turn, the spring constant at point b is greater than the spring constant at point a, resulting in a hard state.

In other words, in the active suspension having the characteristics shown in FIG. 10 described above, since the cylinder pressure P on the outer wheel side is high during turning, vibration human force from the outer wheel side is transmitted to the vehicle body when rolling is suppressed, worsening ride comfort. There was a fear that it would. However, in this embodiment, since the outer ring side cylinder pressure P during turning is lower than that of the prior application, the spring constant can be made into a soft state correspondingly small, and the above-mentioned effects can be enjoyed.

In this way, roll when turning. When the vehicle height control is finished and the vehicle returns to the straight-ahead state again, the sensor detection signal g=gs becomes, and the lateral acceleration y=0 is calculated based on this, and the predetermined flat vehicle height value is maintained as described above.

Furthermore, suppose that the vehicle shifts from the straight-ahead state described above to a right turn. As a result, the detected sensor signal g becomes smaller than the neutral value gH by the amount corresponding to the turning situation, and a negative lateral acceleration '1B is calculated.Similarly to the above, by referring to the memory table, the lateral acceleration '1B' is calculated. A pressure command value VFL#VRR corresponding to "Y" is set. Therefore, even when turning to the right, the height of the center of gravity is lowered than when going straight, while allowing a moderate roll state, similar to when turning to the left, and the above-mentioned effects can be obtained.

By the way, in this embodiment, since the increase rate of the outer ring side cylinder pressure P is made small, the pressure control valves 20FL to 20RR
The maximum value PMAX controlled by is also lower than that described in the prior application. Therefore, the discharge amount of the hydraulic bomb that controls a part of the hydraulic source 22 is required to be smaller, and the relief pressure of the relief valve is also required to be lower, which has the advantage that the entire hydraulic source 22 can be made smaller. . In addition, as shown in Figure 8, the cylinder pressure P with respect to the change in the lateral acceleration y is maintained until the cylinder pressure P is saturated, while maintaining the principle that the rate of change when the pressure increases is smaller than when it decreases. A bending point (0'+, point L) is set at this bending point, and the rate of decrease in cylinder pressure, that is, the rate of decrease in vehicle height is changed at this point. Therefore, by appropriately setting the bending point (y.L), it is possible to change the degree to which the vehicle height is lowered depending on the lateral acceleration 9 that occurs, for example, when driving in a city or driving on a highway.

As described above, in this embodiment, the lateral acceleration sensor 26, the A/D converter 70, and the processing in steps 1 to 2 in FIG. 7 constitute the lateral acceleration detection means, and the step 2 in FIG. Then, step ① in Fig. 7 and D/A converters 73A to 73
D, drive circuits 74A to 74D constitute command value output means.

Note that the means for determining lateral acceleration of the present invention is not limited to a structure that directly detects inertial force using a lateral acceleration sensor as described above, but can also be used, for example, to estimate lateral acceleration based on vehicle speed and steering angle. (for example, Japanese Patent Application Laid-Open No. 62-29
3167). Furthermore, the present invention can naturally be applied to an active suspension that also performs pitch control and bounce control of a vehicle.

Further, the fluid pressure cylinder of the present invention is not limited to the case where the hydraulic cylinder is applied as in the above embodiment,
For example, do you use a pneumatic cylinder? It may be completed.

Further, in the above embodiment, the controller is equipped with a microcomputer, but this can be done by manually inputting the detection signal of the lateral acceleration sensor, as shown in FIG. 6(a), (
It is also possible to provide a function generator that outputs a voltage value having the characteristic shown in c), and to send this output value to the pressure control valve via a drive circuit. On the other hand, as for the processing of the controller, in addition to directly obtaining the pressure command values VFL to VLLN from the lookup of the memory table as described above, the calculated lateral acceleration y is multiplied by the control gain, and the neutral value ■8 is added to this. The pressure command values may be set to V, L-V■, and the control gain thereof may be varied so as to obtain the output characteristics shown in FIG.

Furthermore, in this invention, the command value, that is, the cylinder operating pressure P does not necessarily have a bending point (L, y
+) is not necessary, and the rate of increase only needs to be smaller than the rate of decrease; for example, it increases linearly from a neutral value to a saturated value. It may be decreased. Furthermore, the front wheel. The pressure command values set for the rear wheels may be the same, and the cylinders may have the same pressure characteristics.

〔Effect of the invention〕

As explained above, in the inventions recited in claims (1) and (3), when turning, the command value, that is, the working pressure of the fluid pressure cylinder, is increased on the outer ring side and lowered on the inner ring side. Since the rate of change in the increase in operating pressure is controlled to be smaller than the rate of change in the decrease in operating pressure on the inner wheel side, when the vehicle transitions from a flat predetermined vehicle height state when driving straight to a turning state, it is possible to obtain appropriate roll rigidity. In addition to suppressing the roll angle to an acceptable value, the vehicle height at the center of gravity, which is determined by the average working pressure of the inner and outer wheels, is appropriately lowered, giving passengers a sense of security and improving maneuverability when turning. Effects can be obtained. Furthermore, since the maximum pressure controlled by the pressure control valve is lowered, the maximum discharge amount of a fluid pressure source such as a hydraulic pump may be lowered, which also has the effect of promoting compactness and weight reduction.

Furthermore, in the invention described in claims (2) and (3), in addition to the above-mentioned effects, the accumulator that absorbs the vibration of the wheel side member functions even when the vehicle turns, so that the vibration is transmitted to the vehicle body side. This can further improve riding comfort.

[Brief explanation of drawings]

Figure 1 is a claim correspondence diagram of the invention (Claims (1), (3)
), FIG. 2 is a schematic diagram showing an embodiment of the present invention, FIG. 3 is a graph showing the output characteristics of the pressure control valve, and FIG. 4 is a graph showing the detection characteristics of the lateral acceleration sensor. Fig. 5 is a block diagram showing an example of the controller; Fig. 6 is a block diagram showing an example of the controller;
Figures (a) and (b) are characteristic diagrams corresponding to the pressure command value storage table, Figure 7 is a schematic flowchart showing an example of the processing procedure executed in the controller, and Figure 8 is a characteristic diagram of the vehicle cylinder pressure. , FIGS. 9(a) and 9(b) are explanatory diagrams of the spring function of the accumulator, and FIG. 10 is a characteristic diagram of the cylinder pressure according to the example of the prior application. In the figure, 10 is a vehicle body side member, 12 is an active suspension, 14 is a wheel side member, 18FL to 18RR are front left to rear right hydraulic cylinders (fluid pressure cylinders), 20PL to 20RR.
are front left to rear right pressure control valves, 26 is a lateral acceleration sensor, 30
is a controller, 70 is an A/D converter, 73A to 73D
is a D/A converter, and 74A to 74D are drive circuits.

Claims (3)

[Claims] (1) A fluid pressure cylinder interposed between the vehicle body side member and the wheel side member for each wheel, a pressure control valve that individually controls the operating pressure of each fluid pressure cylinder according to a command value, and the vehicle body lateral acceleration detection or estimation means for detecting or estimating lateral acceleration of a command value calculation means for calculating each wheel separately;
An active suspension comprising command value output means for outputting the command values calculated by the command value calculation means to the pressure control valves. (2) A fluid pressure cylinder interposed between the vehicle body side member and the wheel side member for each wheel, an accumulator provided in the fluid pressure cylinder to absorb vibrations of the wheel side member, and A pressure control valve that individually controls the operating pressure according to a command value, a lateral acceleration detection or estimation means that detects or estimates the lateral acceleration of the vehicle body, and a lateral acceleration detection or estimation value of the lateral acceleration detection or estimation means. a command value calculation means for calculating a command value for each wheel to lower the vehicle height when turning than when driving straight; and command values for outputting the command values calculated by the command value calculation means to the pressure control valves. An active suspension characterized by being equipped with an output means. (3) The command value calculation means sets a predetermined value when the lateral acceleration detection or estimated value of the lateral acceleration detection or estimation means is zero, and as the absolute value of the lateral acceleration detection value increases, 2. The active suspension according to claim 1, wherein the means calculates a command value that decreases at a predetermined rate of change and increases for the outer wheel at a smaller rate of change than the rate of change for the inner wheel.