JPH01247209A - Active type suspension - Google Patents

Abstract

PURPOSE:To improve responsiveness to the change in air resistance by determining a pressure-control valve command value based on the estimated value of a force in the vertical direction based on air resistance during traveling and a target command value for a pressure control valve which is determined from a target vehicle height. CONSTITUTION:A vertical force which acts on a vehicle body based on air resistance is estimated by a vertical force estimating means from a vehicle speed outputted by a vehicle speed sensor. On the other hand, as a target vehicle height determining means determines a target vehicle height, based on this, a target command value determining means calculates the target command value for a pressure control valve and output same to a command value control means. The command value control means determines the command value for the pressure control valve based on the target command value and the estimated vertical force and outputs same to the pressure control valve to control a fluid pressure cylinder. By this structure, the responsiveness to change in air resistance can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an active suspension used in a vehicle, and in particular, the invention relates to an active suspension used in a vehicle, and in particular, to a hydraulic cylinder that responds to the vertical force generated on the vehicle body due to air resistance while driving. By adjusting the working fluid pressure, it is possible to maintain a good vehicle body posture.

[Conventional technology]

As a conventional active type suspension, one described in Japanese Patent Application Laid-Open No. 62-295714, which was previously filed by the present applicant, is known.

This conventional active suspension detects or estimates the lateral acceleration or longitudinal acceleration of the vehicle, and supplies a command value corresponding to the detected value or estimated value to the pressure control valve that controls the pressure of the hydraulic cylinder. It was designed to improve responsiveness to changes in vehicle body posture.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, the command value for the pressure control valve is controlled according to the lateral acceleration or longitudinal acceleration occurring in the vehicle. Dynamic side such as roll motion and pitch motion caused by the system; ■The responsiveness to the system was excellent, but for example, even if air resistance increases during high-speed driving and vertical force is generated on the vehicle body, acceleration is not detected. Since the pressure control valve does not operate, the vehicle height fluctuates depending on the amount of air resistance, causing an unresolved problem in that the vehicle feels less stable.

Therefore, the present invention has been made by focusing on such unresolved problems in the conventional technology, and provides a means for estimating the vertical force generated on the vehicle body due to air resistance during running. The present invention aims to provide an active suspension that is highly responsive to changes in air resistance by correcting the command value of a pressure control valve so that the estimated vertical force is canceled out.

[Means for Solving the Problems] In order to achieve the above object, the active suspension of the present invention uses a fluid interposed between the vehicle body and each wheel, as shown in the basic configuration diagram of FIG. a pressure cylinder, a pressure control valve that controls the working fluid pressure of the fluid pressure cylinder only according to a command value, and upper and lower blade estimating means that estimates the vertical force generated on the vehicle body due to air resistance during running; a target vehicle height determining means for determining a target vehicle height of the vehicle body; a target command value determining means for determining a target command value for the pressure control valve based on the target vehicle height; an estimated value of the upper and lower blade estimating means; and command value control means for calculating the command value based on the target command value and outputting the command value to the pressure control valve.

[Effect]

The vertical force generated on the vehicle body due to air resistance during running is estimated by the upper and lower blade estimating means. On the other hand, a target value for the vehicle height is determined by a target vehicle height value determining means, and a target command value for the pressure control valve is determined by the target command value determining means based on this target vehicle height.

Then, the command value control means calculates a command value based on the upper and lower blades estimated by the upper and lower blade estimation means and the target command value determined by the target command value determination means, and outputs the command value to the pressure control valve. Therefore, the pressure of the fluid pressure cylinder changes appropriately, and fluctuations in the vehicle body posture are prevented. In this case, the command value output to the pressure control valve is calculated based on the target vehicle height value and the vertical force on the vehicle body generated by air resistance, so the vehicle height will fluctuate due to changes in air resistance. There isn't.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIGS. 2 to 6 show an embodiment of the present invention.

In Figure 2, IFL, IFR, IRL, I
RR is the vehicle body side member 2 and each wheel 3FL, 3, respectively.
FR, 3RL.

It is an active suspension that is interposed between the wheel side member 4 that individually supports 3RR, and includes hydraulic cylinders 5FL to 5RR, coil springs 6FL to 6RR, and hydraulic cylinders 5FL to 5RR as fluid pressure cylinders, respectively.
The pressure control valves 7FL to 7RR are provided to control the hydraulic pressure for the hydraulic pressure in response only to a command value from a control device 30, which will be described later.

Here, each of the hydraulic cylinders 5FL to 5RR has its cylinder tube 5a attached to the wheel side member 4,
The piston rod 5b is attached to the vehicle body side member 2, and the working oil pressure in the pressure chamber 19 closed by the piston 5c is controlled by pressure control valves 7FL to 7RR. Each of the coil springs 6FL to 6RR is connected to a hydraulic cylinder 5FL to 5R between the vehicle body side member 2 and the wheel side member 4.
It is installed in parallel with R to support the static load of the vehicle body. Note that the coil springs 6FL to 6RR may have low spring constants that only support the static load of the vehicle body.

Pressure control valve? FL to 7RR are supplied with command values 1a to Id from the control device 30 that outputs command values for suppressing changes in the attitude of the vehicle body based on the vehicle's lateral acceleration, longitudinal acceleration, and vehicle speed. Hydraulic cylinders 5FL each output a corresponding control pressure and constitute an active suspension inserted between each wheel and the vehicle body.
~5RR is individually supplied to generate a biasing force that resists changes in the attitude of the vehicle body. The specific configuration of this pressure control valve 7 is as follows:
As shown in FIG. 3, the valve housing 11 includes a cylindrical valve housing 11 and a proportional solenoid 12 integrally provided therein. A valve seat 1 with a predetermined diameter is provided in the center of the valve housing 11.
The upper insertion hole 11U in FIG. 3 defined by the partition wall 11A having 1a and the lower insertion hole 11 in the same figure
L and are formed coaxially. Further, a fixed throttle 13 is provided at a lower position above the insertion hole 11L and spaced a predetermined distance from the partition wall 11A.
A pilot chamber C is formed between the partition wall 11A and the partition wall 11A. Further, a main spool 14 is disposed below the fixed throttle 13 in the insertion hole 11L so as to be slidable in its axial direction, and feedback chambers Fu and F are formed above and below the main spool 14, respectively. At the same time, the upper and lower ends of the main spool 14 are connected to feed bank chambers FU and FL.
Offset springs 15A and 15B respectively arranged in
regulated by. Then, the input port 111. is inserted into the insertion hole 11L. The control boat lln and drain boat 1 and 110 are connected in this order, and the input port 111 is connected to the hydraulic pipe 2.
Drain bow 1-11o is connected to the drain side of the hydraulic source 24 via hydraulic piping 26, and is connected to the pressure chambers 19 of the hydraulic cylinders 7FL to 7RR. There is.

The main spool 14 has a land 14a facing the input port 11i and a land 1 facing the drainboard 1110.
4b, and both of these lands 14a.

It includes a pressure chamber 14C formed by an annular groove formed between the pressure chambers 14b and a pilot passage 14d that communicates the pressure chamber 14C with the lower feed bank chamber FL.

In addition, a poppet 16 is disposed in the upper insertion hole 11LJ so as to be slidable in the axial direction with the valve portion facing the valve seat 11a. The flow rate of the hydraulic oil flowing through the valve seat 11C, that is, the pressure in the pilot chamber C can be adjusted.

Furthermore, the input port Ili is connected to the pi-nisso1-passage 11
5, and the drain boat 110 is connected to the insertion hole 11U via the drain passage lit.
is communicated with.

On the other hand, the proportional solenoid 12 includes a plunger 17 that is slidable in the axial direction, and a poppet 16 of the plunger 17.
It has an actuator 17A fixed to the side and an excitation coil 18 that drives the plunger 17 in its axial direction. be done. As a result, movement of the plunger 17 controls the position of the poppet 16 via the actuator 17A, thereby controlling the flow rate passing through the communication hole IIA. Then, when the pressure in the feedback chambers Ft and Fo is balanced while the pushing force by the proportional solenoid 12 is being applied to the poppet 16, the spool 14 is in the neutral position and the control boat lln and the input port 111 and The drain port 110 is cut off.

Here, the command value I and the control oil pressure P output from the control valve 11n. As shown in FIG. 4, the relationship between the command value I
P1418 is output when is near zero, and when the command value I increases in the positive direction from this state, the control output P increases with a predetermined proportional gain of 1, and the hydraulic power source 24
It is saturated at line pressure PL of .

In addition, in FIG. 2, 28H indicates pressure control valves 7FL to 7.
The high pressure side accumulator 28L connected to the middle of the hydraulic piping 25 between the RR and the hydraulic power source 24 is the pressure control valve 7FL~
This is a low-pressure side accumulator that communicates with the hydraulic pipe 27 between the hydraulic cylinder 7RR and the hydraulic cylinders 5FL to 5RR via a throttle valve 28V.

On the other hand, the vehicle body is equipped with a vehicle speed sensor 29 that detects, for example, the rotation speed of the output shaft of the transmission and outputs a vehicle speed detection signal ■ consisting of a corresponding periodic pulse signal, and a vehicle speed sensor 29 that detects the lateral acceleration occurring in the vehicle body. A lateral acceleration detector 31 as a lateral acceleration detection means for detecting, and a longitudinal acceleration detector 32 as a longitudinal acceleration detection means for detecting longitudinal acceleration occurring in the vehicle body.
The vehicle speed detection signal (2) of the vehicle speed sensor 29, the lateral acceleration detector 31 of the lateral acceleration detector 31, and the longitudinal acceleration detection value y of the longitudinal acceleration detector 32 are respectively provided at appropriate locations. It is supplied to the control device 30.

Further, stroke sensors 33FL-33RR for detecting displacements of the fluid pressure cylinders 5FL-5RR are provided at appropriate positions of the fluid pressure cylinders 5FL-5RR, and detection signals 5FL-3RR of these stroke sensors 33FL-33RR are provided. , is supplied to the control device 30.

Further, as shown in FIG. 5, the control device 30 controls each of the active suspensions IFL to I so that the vehicle posture is appropriate.
Vehicle height setting device 340 vehicle height signal HFL- output for each RR
I(RR positive input and the stroke sensor 33FL~
It has adders 35FL to 35RR that add the detection signal 5FL of the vehicle height setter 33RR and the inverted input of the vehicle height setter 34.3RR. Each stroke sensor 33FL to 33RR
and adders 35FL to 35RR constitute target vehicle height determining means of the present invention.

Then, amplifiers 36FL to 361' multiply the outputs of the adders 35FL to 35RR by a predetermined gain by 1 to Ka4.
iR, differentiators 37FL to 37RR that differentiate the outputs of the adders 35FL to 35RR, and the differentiators 37FL to 3
amplifiers 38FL to 38RR that multiply the output of 7RR by a predetermined gain C7 to C2; and the amplifiers 36FL to 36RR.
Adders 39FL to 39RR which add the outputs of the amplifiers 38FL to 38RR constitute the target command value determining means of the present invention. Here, the amplifier 3
6FL to 36RR, l- corresponds to the spring constant of the suspension, and the amplifiers 38FL to 38R
Since the amplification degrees 01 to C2 of R correspond to the damping constant of the suspension, by appropriately setting these amplification degrees,
It is possible to change the suspension characteristics of the vehicle.

Furthermore, this control device 30 controls the lateral acceleration detector 31
A front wheel side amplifier 40f and a rear wheel side amplifier 40r to which the detected lateral acceleration value y of the longitudinal acceleration detector 32 is inputted, and a front wheel side amplifier 41' and a rear wheel side amplifier 41r to which the longitudinal acceleration detected value y of the longitudinal acceleration detector 32 is inputted. It is equipped with

An adder 42FL adds the inverting input of the amplifier 40f and the positive input of the amplifier 41f, and an adder 42FR adds the positive input of the amplifier 4(l) and the positive input of the amplifier 42f.
, an adder 42FR that adds the inverting input of the amplifier 40r and the positive input of the amplifier 41r, and an adder 42RR that adds the positive input of the amplifier 40r and the positive input of the amplifier 42r.

Further, based on the vehicle speed detection signal V supplied from the vehicle speed sensor 29, and with reference to a function table as shown in FIG. An estimator 43 is provided. Note that the correspondence relationship between the vehicle speed ■ and the upper and lower blades F shown in FIG.
and the upper and lower blade estimator 43 constitute the upper and lower blade estimating means of the present invention. Then, the upper and lower blade estimated values F a % F d output from the upper and lower blade estimator 43 and the output values of the adders 42FL to 42RR are combined with the output values of the adders 44FL to 42RR.
44 RR is added.

On the other hand, when the output of the adders 35FL to 35RR, that is, the difference value between the vehicle height signal I (PL-HRR and the output signal 5FL-3RR of the stroke sensor) continues to be a predetermined value or more for a predetermined time or more, There are vehicle height adjustment circuits 45FL to 45RR for adjusting oil pressure, and the outputs of the vehicle height adjustment circuits 45FL to 45R [?] and the adders 39FL to
39RR and the outputs of the adders 4.4FL to 44RR are added, and this added value is applied to each pressure control valve 7FL to 7.
Adder 46 outputs as RR command value J a −1d
FL to 46RR are provided, and this adder 46FL
-46RR constitute the command value control means of the present invention.

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

Assuming that the vehicle is now running at a constant speed on a flat road with no unevenness, the lateral acceleration detected by the lateral acceleration detector 31 is The detection value y and the longitudinal acceleration detection value y of the longitudinal acceleration detector 32 are both zero. Therefore, each amplifier 40
f, 4. The outputs of Or, 41f, and 41r become zero, and accordingly, the outputs of each of the adders 42FL to 42RR also become zero. Further, when the vehicle speed sensor 29 detects the vehicle speed at that time and outputs it to the upper and lower blade estimator 43, this upper and lower blade estimator 43 uses a function indicating the relationship between the vehicle speed and the upper and lower blades F as shown in FIG. With reference to the table, the upper and lower blades F a % F d to be added to each wheel 3FL to 3RR are calculated, and the adder 44
Output to FL~44RR.

In addition, in this state, since no vibration is input to each hydraulic cylinder 5FL to 5RR, the output signals 5FL to 3RR of each stroke sensor also become zero, and each adder 46FL
~46RR is the vehicle height signal HFL from the vehicle height setting device 34.
−HRR with a predetermined gain K m I ”' K m 4
, the added value of the vehicle height signal HFL-1 (a value obtained by differentiating RR and multiplying it by a predetermined gain 01 to C2), and the output Fa-Fd of the upper and lower blade estimator 43 are input. Assuming that the value is the command value 1a - 1d, each pressure control valve 7FL to 7RR
is output to. Therefore, each hydraulic cylinder 5FL to 5RR
Since the hydraulic pressure is maintained at a predetermined pressure that balances the vertical force generated on the vehicle body by air resistance while driving and maintains an appropriate vehicle height, a good vehicle body posture is maintained.

Therefore, in this state, the wheels 3FL to 3R are visible from the road surface.
For relatively low frequency vibration input via R, the pressure control valve? Feed bank room F of FL~7RR
[,, It is absorbed by the movement of the spool 14 due to pressure fluctuations of FC+, and relatively high frequency vibration input corresponding to the unsprung resonance frequency due to small irregularities on the road surface is absorbed by the throttle valve 28V and transmitted to the vehicle body. It is possible to reduce the vibration transmission rate and ensure good riding comfort.

Here, a case will be described in which a vehicle performs braking and longitudinal acceleration occurs in the vehicle body, and a pitch moment occurs in the vehicle body in a direction in which the front wheels sink.

That is, when the vehicle brakes, the longitudinal acceleration detection means 32 detects positive longitudinal acceleration (in this case, the acceleration that occurs when the vehicle is braked is positive), and outputs the detected value y to the control device 30. do. On the other hand, since no lateral acceleration is generated in the vehicle body, the detected lateral acceleration value remains zero.

Then, since the outputs of the amplifiers 41f and 41r increase in the positive direction, the outputs of the adders 42FL and 42F increase accordingly.
The output of R increases in the positive direction and the adders 42RL, 4
The output of 2RR increases in the negative direction.

Furthermore, since the vehicle speed ■ decreases with braking, the output of the upper and lower blade estimator 43 also decreases according to the function table in FIG. 6, and the upper and lower blades F a % input to the adders 44FL to 44RR.
F d becomes smaller.

On the other hand, due to the pitch moment, the hydraulic cylinder 5F
When L~5RR changes, the stroke sensor 33FL~
33RR detects the displacement, and the detection signal 5FL-3
RR is supplied to adders 35FL to 35RR. In this case, the hydraulic cylinders 5FL and 5FR on the front wheel side move in the direction of contraction (negative direction), so the output of the adder 35FL and 35PR increases, and the output of the adder 35FL and 35PR whose displacement is fed back increases. 5 R.L.

Since 5RR fluctuates in the extending direction (positive direction), the outputs of adders 35RL and 35RR to which the displacement is fed back decrease. These adders 35FL to 35
The target command value based on the output value of RR is
~36RR, differentiator 37FL~37RR.

Amplifiers 38FL to 38RR and adders 39FL to 391
Calculated after 1R.

As a result, the command values Ia and Ib output from adders 46FL and 46FR become relatively large values, and adder 4611! L, 46RI? The command values Ic and Id outputted from the controller are relatively small values. Therefore, the pressure control valves 7FL and VFR on the front wheel side are connected to the hydraulic cylinder 5.
Since the pressure in the pressure chambers 19 of FL and 5FR is increased, the piston 5c becomes difficult to descend and the front of the vehicle body is prevented from sinking, and the pressure control valves 7RL and 5FR on the rear wheel side are
7RR lowers the pressure in the pressure chambers 19 of the hydraulic cylinders 5RL and 5RR, making it difficult for the piston 5c to rise and preventing the rear of the vehicle from lifting up. Therefore, even when the vehicle is braking, the pitch moment generated in the vehicle body is canceled out, so that the posture of the vehicle body is prevented from changing significantly, and the posture of the vehicle body is suitably maintained.

Additionally, if the vehicle suddenly starts or accelerates and longitudinal acceleration occurs in the opposite direction to the above, and a pitch moment occurs in the vehicle body in the direction in which the rear wheels sink, the longitudinal acceleration detector 3
2 detects negative longitudinal acceleration, adder 4 on the front wheel side
The outputs of 2FL and 42FR increase in the negative direction, and the outputs of the adders 42RL and 42RR on the rear wheel side increase in the positive direction, and the output of the upper and lower blade estimator 43 F a z F
d increases. On the other hand, the hydraulic cylinder 5FL on the front wheel side
, 5FR fluctuates in the stretching direction (positive direction), so
an adder 35FL to which the displacement is fed-banked;
The output of 35FR increases, and the hydraulic cylinders 5RL and 5RR on the rear wheel side change in the direction of contraction (negative direction), so the adder 35RL receives feedback of the displacement.
The output of 35RR decreases. Therefore, the command value 1a,
Since lb is a relatively small value and the command values 1d and Ic are relatively large values, the front wheel side pressure control valves 7FL,
7FR lowers the pressure in the pressure chambers 19 of the hydraulic cylinders 5FL and 5FH, making it difficult for the piston 5c to rise and preventing the front of the vehicle from lifting up, and the pressure control valves 7RL and 7RR on the rear wheel side reduce the pressure cylinder 5
The pressure in the pressure chambers 19 of RL and 5RR is increased, making it difficult for the piston 5c to descend and preventing the rear of the vehicle from sinking, so even when the vehicle suddenly starts or accelerates,
The pitch moment occurring in the car body is canceled out, and a good car body posture is maintained.

A case will be explained in which the vehicle turns right and enters a right turning state.

When the vehicle turns to the right, a rightward lateral acceleration is generated in the vehicle body, so a roll moment is generated in the vehicle body in a direction in which the left side of the vehicle sinks, and the lateral acceleration detector 31 detects a negative direction (in this case, The lateral acceleration generated when the vehicle turns to the right is assumed to be positive.) Detects the lateral acceleration. Then, the stroke sensors 33FL and 33RL on the left side of the vehicle body detect negative displacement, and the stroke sensors 33FR and 33FR on the right side of the vehicle body detect negative displacement.
Since 33RR detects a positive displacement, the target command value for the left side of the vehicle body is a relatively large value, and the target command value for the right side of the vehicle body is a relatively small value.

On the other hand, for the detected lateral acceleration value, the amplifier 4. Of and 40r are supplied and amplified, and the amplified values are directly input to adders 42FL and 42RL on the left side of the vehicle body, and are inverted input to adders 42FR and 42RR on the right side of the vehicle body.

As a result, the outputs of the adders 46FL and 46RL become relatively large values, and the outputs of the adders 46FR and 46RR become relatively small values, so that the pressure control valve 7F on the left side of the vehicle body
L and 7RL increase the pressure in the pressure chambers 19 of the hydraulic cylinders 5FL and 5RL, making it difficult for the piston 5c to descend and preventing the left side of the car body from sinking, and the pressure control valves 7FR and 7RR on the right side of the car body to Since the pressure in the pressure chambers 19 of the hydraulic cylinders 5FR and 5RR is lowered, the piston 5c becomes difficult to rise, and the right side of the vehicle body is prevented from lifting. Therefore, even when the vehicle is turning,
The roll moment occurring in the vehicle body is canceled out, and the vehicle body posture is prevented from changing significantly, so that the vehicle body posture is suitably maintained.

Note that even when the vehicle makes a left turn, the roll moment generated in the vehicle body is canceled out by the same effect as described above, and the posture of the vehicle body can be maintained in a favorable manner.

Furthermore, even if lateral acceleration and longitudinal acceleration occur simultaneously on the vehicle body, such as when accelerating or braking when the vehicle turns, in the above embodiment, the value obtained by multiplying each acceleration by a predetermined gain is calculated as the correct value. Since the input or reverse input is added and the command value 1a-1d is such as to cancel both the roll moment and the pinch moment, these moments generated in the vehicle body are applied to the hydraulic cylinders 5FL to 5.
This is canceled out by the action of RR, and the attitude of the vehicle is maintained appropriately.

Next, a case will be described in which the air resistance force changes while the vehicle is running due to a gradual change in the vehicle speed.

For example, when the vehicle speed gradually increases from 30 km/h to 60 km/h, the air resistance force generated on the vehicle body increases to the square of that speed, or 4 times that amount, so the upper and lower edges of the vehicle body are generated proportionally. Since the detected value y of the longitudinal acceleration detector 32 is minute, the value output from the adders 42FL to 42RR is also small, there is almost no pressure fluctuation in the hydraulic cylinder due to acceleration, and the response to the vehicle body posture due to acceleration is slow. .

On the other hand, the upper and lower blade estimator 43 determines whether each wheel 3FL to 3RR
The upper and lower blades Fa-Fd added to the upper and lower blades Fa-Fd are estimated according to the function table shown in FIG. 6, and are output to adders 44FL to 44RR. Then, even if the rate of change in vehicle speed, that is, the longitudinal acceleration y, is minute, adders 44FL to
The output value of 44RR changes with good responsiveness. In this case, if the function table as shown in FIG. 6 referred to by the upper and lower blade estimator 43 is appropriately set, the air resistance force generated on the vehicle body will vary as the vehicle speed changes and will be applied to each wheel 3FL to 3RR. Even if the force in the vertical direction fluctuates, the adders 44FL to 44R
Since the output of R is added to the command value Ia-1d and the pressure control valves 7FL to 7RR operate, the hydraulic cylinder 5FL
The pressure of ~5RR increases or decreases, so the vehicle height does not fluctuate and a good vehicle body posture is maintained.

In addition, if the vehicle height continues to be inappropriate for a predetermined period of time due to a change in the posted state, etc., the vehicle height adjustment circuits 45FL to 4
Since the 5RR outputs a predetermined value to the adders 46FL to 46RR so that the vehicle height is forcibly raised or lowered, the command values 1a to 1d can be appropriately increased or decreased to bring the vehicle height to an appropriate state. .

As described above, in the above embodiment, the roll moment, pitch moment i, and vertical force generated in the vehicle body are calculated based on the lateral acceleration 9 longitudinal acceleration that causes the change in the posture of the vehicle body, and the air resistance force during running. Estimate the fluid pressure of each hydraulic cylinder that can be balanced with Since the pressure control valve is actuated depending on the value, the hydraulic cylinder responds quickly and operates to cancel out the change before the vehicle's attitude changes significantly, allowing the vehicle to turn, brake, accelerate, etc. By doing so, even if various moments are generated in the vehicle body, large changes in attitude are prevented from occurring.

Moreover, even if the detected acceleration is small, the upper and lower blade estimator 4
3 estimates the upper and lower blades FaxFd applied to each wheel due to air resistance while running from the vehicle speed V, and the estimated upper and lower blades Fa - F d are added to the command values 1a to Id, so the air resistance force Hydraulic cylinders 5FL to 5RR operate with good responsiveness to changes, preventing fluctuations in vehicle height and maintaining a good vehicle body posture.

In the above embodiment, the roll moment, pitch moment, and air resistance during running are independent of the setting state of the gain □~Ka4 corresponding to the spring constant of the suspension, and the gain C, -C, corresponding to the damping constant. Since the force can be canceled out, in order to improve the riding comfort, you can set the gains to 1 to -a and C+ to C2 small to prevent vibrations caused by small irregularities on the road surface from being transmitted to the car body. , the responsiveness of posture change prevention against roll moment, pitch moment, and air resistance force is not impaired.

In the above embodiment, the upper and lower blade estimating means includes the vehicle speed sensor 29 and the upper and lower blade estimator 43 that estimates the upper and lower blades by referring to a function table from the detected value of the vehicle speed sensor 29.
However, for example, a load cell may be disposed between each hydraulic cylinder and the vehicle body, and from this load cell.

It is also possible to measure the transmitted force between the vehicle body and the hydraulic cylinder, and based on this measured signal, estimate the vertical force generated in each wheel due to air resistance occurring in the vehicle body.

Further, in the above embodiment, a case has been described in which a hydraulic cylinder is used as the fluid pressure cylinder, but the present invention is not limited to this, and other fluid pressure cylinders such as a pneumatic cylinder can also be applied.

〔Effect of the invention〕

As explained above, in the active suspension of the present invention, the upper and lower blade estimating means for estimating the vertical force generated on the vehicle body due to air resistance during running is provided, and the estimated value of the upper and lower blade estimating means is used to Since the structure is configured to correct the command value for the pressure control valve, it is possible to prevent fluctuations in vehicle height even if the air resistance force applied to the vehicle body changes and the vertical force applied to each wheel fluctuates. This has the effect of maintaining a good vehicle body posture.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a sectional view showing an example of a pressure control valve, and FIG. 5 is a block diagram showing an example of a control device, and FIG. 6 is a graph showing the relationship between the vehicle speed and the upper and lower blades used in the upper and lower blade estimation means. It is a function table. IFL~IRR...active suspension, 2...
Vehicle side members, 3FL to 3RR...Wheels, 5FL to 5R
G...Hydraulic cylinder, 6FL~6RR...Coil spring, 7FL~7RR...Pressure control valve, 29...
Vehicle speed sensor, 30... Control device, 31... Lateral acceleration detector, 32... Longitudinal acceleration detector, 34... Vehicle height setting device, 33F-33RR... Stroke sensor,
43... Upper and lower blade estimator.

Claims (1)

[Claims] (1) A fluid pressure cylinder interposed between the vehicle body and each wheel, a pressure control valve that controls the working fluid pressure of this fluid pressure cylinder according to only a command value, and vertical force estimating means for estimating a vertical force generated in the vehicle; target vehicle height determining means for determining a target vehicle height of the vehicle body; and determining a target command value for the pressure control valve based on the target vehicle height. It is characterized by comprising a target command value determining means, and a command value control means for calculating the command value based on the estimated value of the vertical force estimating means and the target command value and outputting it to the pressure control valve. active suspension.