JPH04274915A - Active type suspension - Google Patents

Abstract

PURPOSE:To maintain fixedly passive damping force against vibration from a road surface and prevent riding comfort from being changed even in a case in which operation neutral pressure is increased/decreased for the purpose of vehicle height adjustment or operation pressure is increased/decreased for the purpose of posture control. CONSTITUTION:The 1st variable throttle 24, is interveniently inserted between a pressure control valve 20 and a hydraulic cylinder 18, and the 2nd variable throttle 26 is interveniently inserted between a cylinder chamber R and an accumulator 28. A controller 34 increases cylinder pressure on the basis of a vehicle height signal H when a carrying weight is increased and the vehicle height is lowered, and raises the vehicle height. Simultaneously, the controller 34 reduces the damping force of the 1st and 2nd variable throttles 24, 26 in opposition to the cylinder pressure increase. As a result, a damping force increase portion accompanying operation pressure increase and a damping force decrease portion of throttles 24, 26 almost cancel each other, and there is no 1 change in riding comfortability. This is the same also in a case in which operation pressure is increased for the purpose of posture control.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to active suspensions, and in particular, when a fluid pressure cylinder such as a hydraulic cylinder is inserted between a vehicle body and wheels, and when vibration is input from the road surface to the fluid pressure cylinder, the vibration input This invention relates to an active suspension equipped with a mechanism consisting of an aperture that damps the

0002

2. Description of the Related Art Conventionally, as an active suspension equipped with a mechanism for passively damping vibration input from the road surface, for example, the one shown in FIG. 11 is known (for example, the one shown in FIG. Utility Model Publication No. 1-116813,
Utility Model Publication No. 2-33109, and Japanese Patent Application Publication No. 1-275217
(see issue).

In the configuration shown in FIG. 11, reference numeral 1 denotes a hydraulic source, a pressure control valve 2 is connected to the hydraulic source 1, and an output port of the pressure control valve 2 is connected to the vehicle body and between the wheels via a pipe 3. It is connected to a hydraulic cylinder 4 interposed therein. A vertical acceleration sensor 5 is installed at a position corresponding to the wheel position of the vehicle body, and a detection signal GZ of this sensor 5 is supplied to a controller 6. The controller 6 calculates the vertical speed by integrating the vertical acceleration signal GZ, for example, and calculates the pressure command value for bounce control by multiplying the vertical speed by a gain.
The command current i is supplied to the proportional solenoid of the pressure control valve 2. The operating pressure of the hydraulic cylinder 4 can be controlled in proportion to this command current i, and a damping force that dampens the bounce of the vehicle body is actively generated.

In addition, a restriction A is provided in the middle of the piping 3 or at the output port of the pressure control valve, and the hydraulic cylinder 4
The cylinder chamber is connected to an accumulator 8 via a pipe 7, and a throttle B is inserted in the middle of the pipe 7. Then, aperture B attenuates relatively high-frequency road surface input (vibration) corresponding to the unsprung resonance region, and aperture A attenuates low-frequency road surface input corresponding to the sprung mass resonance region, thereby obtaining a passive vibration damping effect. Can be done.

[0005]

However, in the conventional active suspension shown in FIG. 11, when the weight of the loaded vehicle increases, in order to maintain the vehicle height at a constant target value, the neutral value P0 of the operating pressure is reduced. When , the friction of the sliding portion of the hydraulic cylinder 4 as an actuator increases, and the equivalent spring constant of the accumulator 8 also increases, increasing the damping force as shown in FIG. 12, for example. In other words, the damping force by the throttles A and B changes depending on the operating pressure. Therefore, as the operating pressure increases, the rate at which vibration input from the road surface is transmitted to the vehicle body increases.
The riding comfort was reduced as shown in FIG. 13. On the other hand, even when the weight of the loaded vehicle was reduced, there was a feeling of discomfort due to the change in ride comfort.

The present invention was developed in view of the above situation, and is applicable when the weight of a loaded vehicle changes and the operating pressure is increased or decreased in order to maintain a constant vehicle height, or when the cylinder pressure is increased or decreased for attitude control. The objective is to prevent changes in riding comfort due to changes in passive damping force even when the damping force is increased or decreased.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a fluid pressure cylinder provided between a vehicle body and a wheel, and a connection between the fluid pressure cylinder and a fluid pressure source, as shown in FIG. a pressure control valve provided between the fluid pressure cylinder and controlling the operating pressure of the fluid pressure cylinder according to a command value; and an acceleration detection means for detecting acceleration generated in at least one of the vertical, lateral, and longitudinal directions of the vehicle body. and attitude control command means that calculates a command value based on the detected value of the acceleration detecting means and provides it to the pressure control valve; a variable damping mechanism that generates a damping force by a throttle according to vibration input from the road surface to the fluid pressure cylinder and is capable of changing the damping force; and a variable damping mechanism capable of changing the damping force; and damping force control means for controlling the damping force of the variable damping mechanism according to a command value of the command means or the attitude control command means.

[0008]

[Operation] The vehicle height adjustment command means outputs a command value for controlling the vehicle height value to the target range to the pressure control valve, thereby increasing or decreasing the operating neutral pressure of the fluid pressure cylinder, and adjusting the vehicle height value to the target range. . In addition, the attitude control command means calculates a command value according to the detected acceleration value and outputs the command value to the pressure control valve, so that, for example, a moment that resists roll or pitch is actively generated, and a bounce is activated. A force is generated that attenuates the Further, when vibrations are input due to unevenness of the road surface, a damping force corresponding to the vibrations is actively generated in the variable damping mechanism, and vibrations transmitted to the vehicle body are suppressed.

On the other hand, for example, when the vehicle height adjustment command means commands an increase in the operating neutral pressure in order to command an increase in the vehicle height in response to an increase in the loaded weight, the damping force control means controls the variable damping mechanism. Reduce damping force. As a result, the increase in damping force due to increase in cylinder friction due to increase in operating neutral pressure is almost canceled out, and the vibration transmission rate to road surface input is kept almost constant, so ride comfort remains almost unchanged. Holds well. On the other hand, the loaded weight decreases from a high state, and in response to this decrease, a command is issued to lower the vehicle height.
When a reduction in the operating neutral pressure is commanded, the damping force of the variable damping mechanism is increased by the damping force control means, so the total damping force remains approximately constant and the riding comfort remains almost unchanged.

Further, for example, when the attitude control command means increases the cylinder operating pressure on the outer wheel side from the neutral pressure in order to suppress roll accompanying turning, the damping force control means increases the damping force of the variable damping mechanism on the outer wheel side. Can be lowered. As a result, the total damping force on the outer ring side is kept almost constant, so
Attitude control such as roll control does not significantly change the vibration transmission rate from the road surface, ensuring a nearly constant and good ride comfort.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a first embodiment will be described based on FIGS. 2 to 6. In FIG. 2, 10 indicates an arbitrary wheel, and 12 indicates a vehicle body. 14 is the actuator part of the wheel 10 and the vehicle body 1
2 shows an active suspension of a vehicle interposed between the vehicle and the vehicle.

The active suspension 14 includes a hydraulic cylinder 18 as a fluid pressure cylinder interposed between the wheels 10 and the vehicle body 12, and a pressure that controls the operating pressure of the hydraulic cylinder 18 based on a command current iC (command value). control valve 20
and a hydraulic source 22 as a fluid pressure source of this suspension system, a first variable throttle 24 as a variable damping mechanism inserted between the pressure control valve 20 and the hydraulic cylinder 18, and a hydraulic cylinder 18. The second variable throttle 26 as a variable damping mechanism is connected to the cylinder chamber R of the cylinder chamber R, and the accumulator 28 is connected to the second variable throttle 26. Furthermore, the active suspension 14 includes, as its electrical system, a vertical acceleration sensor 30 that detects acceleration acting in the vertical direction of the vehicle body, a vehicle height sensor 32 that detects the stroke amount between the vehicle body and the wheels, and receives signals from these sensors. It has a controller 34 which receives input and controls the pressure control valve 20 and the first and second variable throttle valves 24 and 26. A coil spring 36 is provided between the wheels 10 and the vehicle body 12 to support the static load of the vehicle body.

The hydraulic cylinder 18 is a single-acting type cylinder, and the lower end of the cylinder tube 18a is attached to the wheel 10 side, and the upper end of the piston rod 18b is attached to the vehicle body 12 side.
A cylinder chamber R inside a is connected to an output port of the pressure control valve 20 via an output pipe 40. This output piping 40
The first variable diaphragm 24 is interposed therebetween. The cylinder chamber R of the hydraulic cylinder 18 is connected to the accumulator 28 by a sub-piping 48, and the aforementioned second variable throttle 26 is interposed in the middle of the sub-piping 48.

Each of the first and second variable throttles 24 and 26 has at least a proportional electromagnetic solenoid, a poppet valve, and a throttle, and the control current i supplied to the proportional electromagnetic solenoid
The plunger of the solenoid moves in proportion to the magnitude of v and ia, which pushes the poppet valve in the axial direction,
It has a well-known structure that allows the flow path diameter of the throttle to be changed. In other words, the damping coefficient Cv of the first and second variable apertures 24 and 26
, Ca vary in proportion to the control signals iv, ia, respectively. The first variable diaphragm 24 is designed to absorb low frequency pressure changes corresponding to the sprung mass resonance region, and the second variable diaphragm 26 is designed to absorb high frequency pressure changes corresponding to the sprung mass resonance region. It's tuned.

On the other hand, the pressure control valve 20 is, for example,
179524, the supply port of which is connected to the hydraulic pump 58 of the hydraulic power source 22 through the supply pipe 56, and the return port connected to the hydraulic pump 58 of the hydraulic power source 22 through the return pipe 60. It is connected to the reservoir tank 62 of the hydraulic power source 22, and the output pipe 40 is connected to the output port. The proportional solenoid of the pressure control valve 20 receives an excitation command current iC from the controller 34.
Therefore, the pressure control valve 20 can output a control pressure PC proportional to the command current iC from the output port. The hydraulic power source 22 has a structure including the above-described hydraulic pump 58 and the reservoir tank 62.
The vehicle engine is responsible for rotational drive.

[0016] In the portion of the vehicle body 12 corresponding to the wheel position,
The vertical acceleration sensor 30 is installed, and the vertical acceleration sensor 30 senses the acceleration generated in the vertical direction of the vehicle body, and outputs a vertical acceleration signal GZ having a voltage value corresponding to the vertical acceleration to the controller 34. It has become. The vehicle height sensor 32 is, for example, a cylinder tube 18.
A and the vehicle body 12, and a voltage signal H corresponding to the stroke amount is supplied to the controller 34 as a vehicle height signal.

In this embodiment, the controller 34 is an A/D
It is equipped with a converter, a microcomputer, a drive circuit, etc., and the microcomputer receives the vertical acceleration signal GZ.
and a vehicle height signal H, and performs the processing shown in FIGS. 3 to 5, which will be described later. As a result, the controller 34 supplies the command current iC to the pressure control valve 20 as necessary, and also supplies the command current iC to the pressure control valve 20 as necessary.
, the control currents iv and ia are supplied to the second variable apertures 24 and 26, respectively.

Next, the operation of this embodiment will be explained. first,
C of the microcomputer installed in the controller 34
The vehicle height adjustment process executed by the PU will be explained based on FIG. 3. The process shown in FIG. 3 is executed as a forced interruption process for each wheel when a predetermined vehicle height adjustment request occurs while the vehicle is stopped while the main program is being executed. In addition, in the initial value setting process of the main program, an initial value DV0 is preset as a neutral pressure command value DVN, which will be described later. This initial value DV0
is a reference neutral pressure command value that can maintain the target vehicle height value when the vehicle is in a standard weight state, and is stored in the memory in advance. Also,
Vehicle height adjustment and attitude control are designed not to interfere with each other.

When a vehicle height adjustment request occurs, in step 103 of FIG. 3, the CPU inputs the detection signal H of the vehicle height sensor 32, stores the value as a vehicle height value, and then proceeds to step 104. In this step 104, the CPU
Based on the read value H in step 103, it is determined whether or not to increase the vehicle height value at the currently controlled wheel position. If this determination is YES, the CPU recognizes that the vehicle height is to be increased because the loaded weight has increased and the vehicle height value has fallen below the target range, and in step 105
The subsequent processing is performed sequentially.

In step 105, the latest neutral pressure command value DVN is read from the memory. In step 106, in order to gradually increase the vehicle height value, the neutral pressure command value DVN is set using a minute value ΔDVN.
Calculated based on =DVN +ΔDVN. moreover,
In step 107, the calculated command value DVN is output to the control valve drive circuit within the controller 34. Due to this output, a command current iC corresponding to the command value DVN is supplied from the controller 34 to the pressure control valve 20, and the control pressure PC of the pressure control valve 20, that is, the operating neutral pressure of the cylinder 18 is changed to the command current iC (that is, the command value DVN ). Therefore, the hydraulic cylinder 18 extends by an amount corresponding to the minute command value ΔDVN, and the vehicle height value also increases by a minute amount.

Next, the CPU proceeds to step 108, reads the vehicle height detection signal H, and then performs the process of step 109. In step 109, it is determined whether the vehicle height value has reached the target range. If NO, the process from step 106 is repeated, but if YES, the process returns to the main program.

On the other hand, if the determination in step 104 is NO, this means that the loaded weight has been released from the heavy state and the vehicle height value has become larger than the target range.
Processing from 0 to 114 is performed. These processes are equivalent to those for raising the vehicle height.

Next, the process shown in FIG. 4 executed by the microcomputer of the controller will be explained. This process is executed as a timer interrupt process for each wheel and every fixed time Δt.

To explain this in detail, in step 121, C
The PU reads the detection signal GZ of the vertical acceleration sensor 30, stores the value as the vertical acceleration, and then performs step 1.
The process proceeds to step 22. In step 122, the CPU calculates the vertical velocity VZ by integrating the vertical acceleration GZ. In step 123, the latest neutral pressure command value DVN at that time is read from the memory, and then in step 12
4,125 processes are performed.

In step 124, the bounce suppression command value DV is calculated as follows: DV=VZ ・KZ +DVN (KZ:
In step 125, the command value DV is output to the control valve drive circuit in the controller 34. As a result, a command current iC corresponding to the attitude control command value DV is output to the pressure control valve 20, and the cylinder pressure PC is controlled in proportion to this command current iC. Since this command current iC consists of a component for maintaining the vehicle height value and a component for damping bounce, the vehicle height value is maintained within the target range, and active damping force is generated by pressure changes in the cylinder, suppressing bounce. Ru.

Next, the process shown in FIG. 5 executed by the microcomputer of the controller will be explained. This process is also executed as a timer interrupt process for each wheel and every fixed period of time Δt.

At step 131 in FIG. 5, the CPU reads the latest neutral pressure command value DVN from the memory. In step 132, damping force command values DCv and DCa for adjusting the passive damping force are set as follows.
The settings are made with reference to a map corresponding to FIG. 6 that is stored in the memory in advance. In FIG. 6, as the neutral pressure command value DVN increases, the damping force command values DCv and DCa gradually decrease. In this embodiment, the neutral pressure command value DVN at the vertical axis position in FIG. 6 is equal to the command value DV0 for maintaining the vehicle height value at standard weight.

Next, the CPU advances the process to step 133 and sets the command values DCv and DC set in step 132.
a to the aperture drive circuit in the controller 34. As a result, the diaphragm drive circuit receives command values DCv, D of voltage values.
The first,
The second variable apertures 24 and 26 are individually supplied. Therefore, as shown in FIG. 6, the damping coefficients Cv and Ca of both variable apertures 24 and 26 decrease as the control currents iv and ia (ie, command values DCv and DCa) increase, respectively.

In the above configuration and processing, the vertical acceleration sensor 30 and the processing in step 121 in FIG. 4 constitute acceleration detection means, the processing in steps 122 to 125 in FIG. The processing in FIG. 3 forms vehicle height adjustment command means. Further, the process shown in FIG. 5 corresponds to the damping force control means.

Next, the overall operation of the first embodiment will be explained. First, a case will be described in which the vehicle is in a predetermined standard weight state so that the vehicle exhibits the target performance. When the ignition switch is turned on in this standard weight state, the suspension 14 will start, but since it is in the standard weight state,
Since the vehicle height value is maintained within the target range, no vehicle height adjustment request is issued.

When the vehicle is driven straight at a constant speed on a smooth road with no unevenness, the vertical acceleration GZ of the vehicle body is almost zero, so the pressure command value DV=DVN (
=DV0) is set, and a command current iC corresponding to the command value DV0 is output to the pressure control valve 20. As a result, the cylinder pressure PC of the hydraulic cylinder 18 is changed to the command current i
C was controlled to a value corresponding to the target vehicle height, and the target vehicle height was maintained.
The body position is flat on the road surface.

In this straight-ahead state, the neutral pressure command value DVN read by the controller 34 in the process of FIG.
Since N = DV0, passive damping force command values DCv, DCa of predetermined values corresponding to this command value DV0
is set (see Figure 6). Therefore, the damping constants Cv and Ca of the first and second variable apertures 24 and 26 are also set to predetermined values corresponding to the standard weight.

Therefore, while traveling straight, there are small irregularities on the road surface, and these irregularities cause relatively high-frequency vibrations to the wheels 1.
Suppose you input 0. In this case, as described above, the hydraulic oil flows through the second variable throttle 26 between the cylinder chamber R and the accumulator 28 in response to the vibration input, and the hydraulic oil flows through the second variable throttle 26 to meet the predetermined flow path resistance of the second variable throttle 26. It is passively attenuated by the attenuation coefficient Ca. On the other hand, if the road surface is relatively uneven (low frequency) or the road is undulating,
Low frequency vibrations are input to the hydraulic cylinder 18 from the road surface via the wheels 10. With this vibration input, the hydraulic oil flows between the cylinder chamber R and the hydraulic pressure source 22, as described above.
Since the vibration input flows through the variable aperture 24 of the aperture 2,
It is passively attenuated according to a predetermined attenuation coefficient Cv of 4.

[0034] In this way, the passive damping force borne by the hydraulic cylinder 18 is generated in a state in which it is shared by the first and second variable throttles 24 and 26, depending on the frequency band of the excitation input. In addition, for example, when the amplitude of low-frequency vibration input is large and the damping force due to the above-mentioned first variable throttle 24 and the spool slight movement of the pressure control valve 20 cannot be applied, and the vehicle body swings in the vertical direction, the vertical acceleration sensor 30 senses the vibration as vertical acceleration GZ. Therefore, the controller 34 calculates the vertical absolute velocity VZ by integrating the vertical acceleration GZ by the process shown in FIG.
Command current i based on the value obtained by multiplying Z by control gain KZ
C is supplied to the pressure control valve 20. Therefore, the pressure control valve 20 supplies a control pressure PC proportional to the command current iC to the cylinder chamber R of the hydraulic cylinder 18, so that the cylinder chamber R actively generates a force that damps the vibration input. This effectively suppresses the bounce of the vehicle body.

On the other hand, assume that the number of passengers increases and the load weight increases. When the weight increases in this manner and the actual vehicle height value deviates from the target range, a vehicle height adjustment request is issued. As a result, the controller 34 performs the process shown in FIG. 3 to increase the neutral pressure command value DVN, raise the vehicle height value, and maintain the value within the target range.

When the neutral pressure command value DVN increases in this way, the controller 34 performs the process shown in FIG. 5 to lower the passive damping force command values DCv and DCa by an amount corresponding to the increase in the command value DVN. 1. The damping coefficients Cv and Ca of the second variable apertures 24 and 26 also decrease. Therefore, in order to maintain the vehicle height value, the neutral pressure P0 is increased,
As a result, even if the damping force increases due to an increase in the friction of the sliding part of the hydraulic cylinder 18 or an increase in the equivalent spring constant of the accumulator 28, the increase will be reflected in the damping coefficients Cv and Ca of the first and second variable throttles 24 and 26. This is almost offset by the reduction, and the total damping force is almost the same as before the vehicle height adjustment. For this reason, when the vehicle is driven on an uneven road surface as described above with an increased load and vibrations are applied from the road surface, the vibrations are absorbed by the first and second variable apertures 24 and 26 in the same way. However, since the damping force at that time is approximately the same as before the vehicle height adjustment, the vibration transmission rate to the vehicle body is also approximately constant, and ride comfort does not deteriorate. Further, bounce control accompanying vertical movement of the vehicle body is similarly performed by the process shown in FIG.

Furthermore, the weight increases, and the operating neutral pressure P0
Similarly, when the vehicle height is adjusted by increasing
The damping coefficients Cv and Ca of the second variable apertures 24 and 26 are further lowered, and the total passive damping force is kept constant. Furthermore, when the vehicle height is adjusted (lowered) by decreasing the operating neutral pressure P0 because the weight has decreased due to the occupant getting off the vehicle, the damping coefficients Cv and Ca of the first and second variable throttles 24 and 26 are Return (increase) to its original value. Therefore, even when the vehicle height is adjusted, the passive damping force is maintained almost constant, and the rider does not feel uncomfortable due to a large change in ride comfort.

Next, a second embodiment will be explained based on FIGS. 7 to 10 and FIG. 3. Here, the same reference numerals are used for the same components as in the first embodiment. In this second embodiment,
A configuration for performing pitch control and roll control is added to the control in the first embodiment, and a neutral pressure P0 for vehicle height adjustment is included.
The passive damping force is adjusted according to the total operating pressure of each wheel.

Therefore, as shown in FIG. 7, a lateral acceleration sensor 70 and a longitudinal acceleration sensor 72 are installed at, for example, the center of gravity of the vehicle body 12, and their detection signals GY and GX are
is input to the controller 34. controller 3
In addition to the vehicle height adjustment process shown in FIG. 3, which is the same as in the first embodiment, the timer interrupt process shown in FIGS. 8 and 9 is performed for each wheel. Other processing is the same as in the first embodiment.

The processing shown in FIGS. 8 and 9 will be explained. In step 141 of FIG. 8, the controller 34 outputs the lateral acceleration signals GY,
The longitudinal acceleration signal GX and the vertical acceleration signal GZ are respectively read, and in step 142, the vertical acceleration GZ is integrated to calculate the vertical velocity VZ. Then step 143
After reading out the neutral pressure command value DVN at that point from the memory, the process moves to step 144. In step 144, the total pressure command value DV consisting of the vehicle height adjustment command value DVN and the attitude control command values in three directions is calculated as D
V=GY ・KY +GX ・KX +VZ ・KZ
Calculate from the formula +DVN. Here, KY, KX
, KZ is the control gain. Then step 14
5, the command value DV is output.

On the other hand, in step 151 of FIG. 9, the controller 34 reads the latest total pressure command value DV set at that time from the memory. Next, the process moves to step 152, where passive damping force command values DVv and DVa corresponding to the command value DV are set with reference to the map corresponding to the characteristics shown in FIG. In FIG. 10, the passive damping force command values DCv and DCa are characterized as decreasing linearly as the total pressure command value DV increases. Note that the command value DV of the vertical axis position in FIG. 10 in this embodiment is a value when the vehicle body is not subject to roll, pitch, or bounce and is at a standard weight state. Then, in step 153, the controller 3
4 is the set passive damping force command value DCv, DCa
is output in the same manner as in the first embodiment.

In the above, the vertical acceleration sensor 30, the lateral acceleration sensor 70, the longitudinal acceleration sensor 72 and the process of step 141 in FIG.
The processing of steps 142 to 145 constitutes attitude control command means, and the vehicle height sensor 32 and the processing of FIG. 3 constitute vehicle height adjustment command means. Further, the process in FIG. 9 corresponds to the damping force control means.

Therefore, active control of the roll, pitch, and bounce of the vehicle body is performed using each acceleration detection signal GY,
This is carried out based on GX and GZ (see FIG. 8), and the shaking of the vehicle body is accurately suppressed. At the same time, fluctuations in vehicle height due to changes in loaded weight and number of passengers are adjusted by increasing or decreasing the operating neutral pressure P0, as in the first embodiment, and the vehicle height value is always kept within the target vehicle height range.

In parallel with these attitude control and vehicle height adjustments, the controller 34 executes the process shown in FIG. Passive damping forces 24 and 26 are adjusted.

For example, assuming that a steady circular turn is being made in a standard weight state, the calculated total pressure command value DV is equal to the neutral pressure command value DVN for maintaining the vehicle height, and the roll control command value " The value is the sum of ``GY ・KY'' (however, the command value ``GY ・KY'' is in reverse phase for the left and right wheels)
. When this total pressure command value DV is output, the cylinder pressure on the outer ring side increases above the neutral pressure P0, and that on the inner ring side becomes lower than the neutral pressure P0, thereby obtaining an anti-roll moment. At this time, the damping force due to cylinder friction on the outer wheel side of the turn increases, but as shown in Figs.
Through this process, the passive damping force applied to the first and second variable throttles 24 and 26 is lowered by an amount commensurate with the increase in the outer wheel side command pressure, and the total remains almost the same as before the turn. For this reason, even when the outer turning wheel goes over small irregularities on the road surface, the ride comfort does not deteriorate, and even when driving on a complex road surface such as a undulating road or a rough road, the riding comfort of the outer wheel side does not deteriorate. It can definitely be prevented.

[0046] When the steady circular turn returns to a straight-ahead state, the lateral acceleration GY becomes zero, so the operating pressures of the left and right wheels are returned to approximately the same value, and the first and second variable throttles 24, 26 The passive damping coefficients Cv and Ca of the vehicle are raised to the values before the turn, and the total passive damping force is also held constant, so the riding comfort hardly changes.

Furthermore, in the second embodiment, when the loaded weight increases compared to the standard state, the total pressure command value DV is commanded to the value DV=DV1, for example, as shown in FIG. (a state in which no oscillation occurs), and a state in which the bottom is raised. In other words, the damping forces of the first and second variable apertures 24 and 26 can also be adjusted (decreased) by raising the command value DV.
Therefore, if roll or pitch occurs in the vehicle body with this increased weight, the command value DV will swing around DV = DV1, and the passive damping force will simultaneously take in both the loaded weight and attitude change. It has the advantage of being adjusted in the same state.

Furthermore, the same applies to pitch control.
For example, even if the cylinder pressure is increased to suppress nose dive, the vibration transmission rate from the road surface will not increase.

In this second embodiment, either pitch control or roll control can be implemented. Furthermore, the variable damping mechanism in the present invention is not limited to a structure in which the damping coefficient can be continuously changed as described above, but may include, for example, one or two fixed throttles and a pipe that bypasses the throttles. It has a structure in which the damping coefficient can be switched to two or three stages, consisting of an on-off valve inserted in the
The damping force control means may switch the on-off valve so as to lower the damping coefficient in two or three stages in response to an increase in the neutral pressure command value DVN or the total pressure command value DV.

Furthermore, the variable damping mechanism of the present invention does not necessarily need to be provided at the two locations mentioned above, namely, the location between the pressure control valve 20 and the hydraulic cylinder 18, and the location of the sub pipe 48 connected to the hydraulic cylinder 18. There may be no one, and only one of them may be used as needed, and the same effect can be obtained for a specific frequency range (that is, either a low frequency range or a high frequency range).

Furthermore, although the controller 34 in the above embodiment was configured to include a microcomputer,
The configuration may be a combination of analog electronic circuits and digital logic circuits.

[0052]

As described above, the present invention allows passive damping force by a variable damping mechanism to be applied to a command value of a vehicle height adjustment command means or an attitude control command means in response to vibration input from the road surface to a fluid pressure cylinder. For example, even if the operating neutral pressure is increased to raise the vehicle height, or the operating pressure is increased for posture control such as roll suppression, the sliding part of the fluid pressure cylinder The increase in damping force due to an increase in friction, etc. is almost offset by the adjustment (decrease) of the damping force of the variable damping mechanism, so the total passive damping force can be kept almost constant, and the load It is possible to reliably prevent the deterioration of ride comfort due to vibrations from the road surface when adjusting the vehicle height or controlling the attitude during turning due to increased weight.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a block diagram showing the overall configuration of a first embodiment of the present invention.

FIG. 3 is a schematic flowchart showing an example of processing related to vehicle height adjustment by the controller.

FIG. 4 is a schematic flowchart showing an example of processing related to attitude control of the controller.

FIG. 5 is a schematic flowchart showing an example of processing related to passive damping force control of the controller.

FIG. 6 is a graph showing the relationship between a neutral pressure command value and a passive damping force command value.

FIG. 7 is a block diagram showing the overall configuration of a second embodiment of the present invention.

FIG. 8 is a schematic flowchart showing an example of processing related to posture control of the controller.

FIG. 9 is a schematic flowchart showing an example of processing related to passive damping force control of the controller.

FIG. 10 is a graph showing the relationship between pressure command value DV and passive damping force command value.

FIG. 11 is a block diagram showing the configuration of a conventional example.

FIG. 12 is a graph showing the relationship between changes in operating neutral pressure and changes in damping coefficient.

FIG. 13 is a graph showing the relationship between excitation input frequency and vehicle body displacement.

[Explanation of symbols]

10 Wheels 12 Vehicle body 14 Active suspension 18 Hydraulic cylinder 20 Pressure control valve 22 Hydraulic source 24 First variable aperture 26 Second variable aperture 30 Vertical acceleration sensor 32 Vehicle height sensor 34 Controller 70 Lateral acceleration sensor 72 Longitudinal acceleration sensor

Claims (1)

[Claims] Claim 1: A fluid pressure cylinder provided between a vehicle body and a wheel, and a pressure control device provided between the fluid pressure cylinder and a fluid pressure source and controlling the operating pressure of the fluid pressure cylinder according to a command value. a valve, an acceleration detection means for detecting acceleration occurring in at least one of the vertical, lateral, and longitudinal directions of the vehicle body; and a command value based on the detected value of the acceleration detection means is calculated to operate the pressure control valve. and vehicle height adjustment command means for calculating a command value for adjusting the neutral operating pressure of the fluid pressure cylinder and giving it to the pressure control valve. a variable damping mechanism that generates a damping force according to a vibration input through an aperture and is capable of changing the damping force; and a variable damping mechanism that adjusts the damping force of the variable damping mechanism according to a command value of the vehicle height adjustment command means or the attitude control command means. An active suspension characterized by comprising damping force control means for controlling the damping force.