JPH07186663A - Active type suspension - Google Patents

Abstract

PURPOSE:To provide an active type suspension which controls the movement of a vehicle in an optimum state by individually controlling the resonance frequency of a spring and the damping force. CONSTITUTION:As for the vertical direction acceleration detection signals ZCFL- ZCRR of the vertical direction acceleration sensors 28FL-28RR, the high frequency component which generates the oscillation of a pressure control valve is removed by a low pass filter,and the detection signal is amplified by the fixed gain adjustors 42FL-42RR, and integrated by the low pass filters 41FL-41RR, and the car body vertical speed components XFL'-XRR' are calculated, and then amplified by the variable gain adjustors 43FL-43RR, and both the values are added by adders 44FL-44RL. At this time, the gain of the variable gain adjustors 43FL-43RR is allowed to generate the gain B corresponding to the car speed by a function generator 50 on the basis of the car speed detection value V of a car speed sensor 49, and the damping force is varied according to the car speed, in the state having a constant resonance frequency of a spring, and the gentle movement is realized in the intermediate/low speed region, and the steady movement is realized in the high speed region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an active suspension which detects vertical acceleration of a vehicle body to suppress a change in posture of the vehicle body.

[0002]

2. Description of the Related Art As a conventional active suspension,
There is one described in JP-A-62-289420 previously proposed by the applicant. In this conventional example, a fluid pressure cylinder interposed between each wheel side member and a vehicle body side member, and a pressure control valve capable of changing the operating pressure of the fluid pressure cylinder only in accordance with a command value, In an active suspension equipped with a control device for outputting a command value to the pressure control valve, a vertical acceleration detecting means for detecting vertical acceleration in each substantially right upper portion of each wheel of the vehicle body, and a vertical velocity in each position described above. And a vertical speed detection unit for detecting the vertical speed, and the control unit calculates a command value based on the vertical acceleration detection value of the vertical acceleration detection unit and the vertical speed detection value of the vertical speed detection unit.

[0003]

However, in the above-mentioned conventional active suspension, in order to simply perform the skyhook control, the vertical acceleration of the vehicle body and the vertical velocity of the vehicle body obtained by integrating the acceleration are added to obtain the vertical movement of the vehicle body. The damping force due to the velocity and the sprung mass equivalent control force due to the vertical acceleration of the vehicle body are generated to suppress the posture change of the vehicle body.However, the gain for the vehicle vertical velocity and the vehicle vertical acceleration is fixed to a fixed value. Therefore, for example, in order to lower the sprung resonance frequency and realize slow vehicle movement, it is necessary to set the gain of the vehicle body vertical velocity that generates the damping force to a small value, and conversely suppress the vibration on the spring. In order to
It is necessary to set the gain of the vertical acceleration of the vehicle body that generates the sprung mass equivalent control force to a small value, and it is not possible to make settings that satisfy both of them, and in order to realize a tied vehicle movement, a damping force Even if the gain of the vehicle body vertical velocity for generating the is set to a small value, as shown in FIG. 9, the damping force (bx ′ portion) is caused by the phase delay of the hydraulic control system with respect to the sprung mass equivalent control force Ax ″. Occurs, resulting in a hard-feeling suspension, and there is an unsolved problem that the sprung resonance frequency and the damping force cannot be individually set.

Therefore, the present invention has been made in view of the unsolved problems of the above-mentioned conventional example, and is an active type in which the sprung resonance frequency and the damping force are appropriately controlled to improve the riding comfort. Intended to provide suspension.

[0005]

In order to achieve the above object, an active suspension according to the present invention is arranged between each wheel and a vehicle body, and is capable of controlling a stroke between them by a control signal. An actuator that generates a force, a vertical acceleration detecting unit that detects vertical acceleration of the vehicle body, and a control unit that outputs the control signal based on a vertical acceleration detection signal of the vertical acceleration detecting unit are provided. In the active suspension, the control means integrates a vertical acceleration detection signal of the vertical acceleration detection means to calculate a vehicle vertical speed, and a vertical acceleration detection of the vertical acceleration detection means. The addition means for adding the signal and the vehicle body vertical speed and the gain of the vehicle body vertical speed calculation means with respect to the vehicle body vertical speed are positive and negative. And gain adjustment means for adjusting I,
Control signal forming means for forming the control signal based on the addition output of the adding means.

[0006]

According to the present invention, the gain of the vehicle body vertical velocity calculation means with respect to the vehicle body vertical velocity can be adjusted by the gain adjusting means in the positive and negative directions. Therefore, the vehicle body vertical velocity component with respect to the vehicle body vertical acceleration in the adding means can be changed. Thus, the damping force can be controlled arbitrarily, and the sprung resonance frequency and the damping force can be set individually.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, in which 10 is a vehicle body side member which is a suspension arm, 11FL to 11RR are front left to rear right wheels, and 12 is an active suspension. Show each.

The active suspension 12 is a hydraulic cylinder 1 as a fluid pressure cylinder interposed between the vehicle body side member 10 and each wheel side member 14 of the wheels 11FL to 11RR.
8FL to 18RR and pressure control valves 20FL to 20RR for individually adjusting the operating pressures of these hydraulic cylinders 18FL to 18RR,
While supplying hydraulic oil of a predetermined pressure to these pressure control valves 20FL to 20RR via the supply side pipe 52, the pressure control valve 2
Hydraulic pressure source 22 for collecting return oil from 0FL to 20RR through return side pipe 54, and hydraulic pressure source 22 and pressure control valve 2
Accumulators 24F and 24R for accumulating, which are inserted in the supply pressure side pipe 52 between 0FL and 20RR, and each wheel 11 of the vehicle body.
Vertical acceleration sensors 28FR to 28RR for detecting the vertical acceleration of the FL to 11RR positions, and the output pressures of the pressure control valves 20FL to 20RR are individually based on the respective detected values Z _{GFR to} Z _GRR of the vertical acceleration sensors 28FR to 28RR. And a controller 30 for controlling Also, the hydraulic cylinder 1
Each of the pressure chambers L of 8FL to 18RR, which will be described later, has a throttle valve 32.
Is connected to an accumulator 34 for absorbing unsprung vibration. Further, a coil spring 36, which has a relatively low spring constant and supports a static load of the vehicle body, is arranged between the upper and lower springs of each of the hydraulic cylinders 18FL to 18RR.

Each of the hydraulic cylinders 18FL to 18RR has a cylinder tube 18a.
A lower pressure chamber L separated by a piston 18c having an axial through hole is formed in 8a.
Thrust is generated according to the pressure difference between the upper and lower surfaces and the internal pressure.
The lower end of the cylinder tube 18a is the wheel-side member 1
4 and the upper end of the piston rod 18b is attached to the vehicle body side member 10. Further, each of the pressure chambers L has a pressure control valve 20FL to 20RR via a hydraulic pipe 38.
Connected to the output port of.

Each of the pressure control valves 20FL to 20RR has a conventionally known three-port proportional electromagnetic pressure reducing valve having a cylindrical valve housing in which a spool is slidably mounted and a proportional solenoid integrally provided therein. (For example, JP-A-64-7
No. 4111). Then, by adjusting the command current i (command value) supplied to the exciting coil of the proportional solenoid, the movement distance of the poppet housed in the valve housing, that is, the position of the spool is controlled, and the supply port and the output port or the output are provided. The hydraulic oil flowing between the hydraulic power source 22 and the hydraulic cylinders 18FL to 18RR can be controlled via the port and the return port.

The relationship between the command current i (: i _{FL to} i _RR ) applied to the exciting coil and the control pressure P output from the output port of the pressure control valve 20 _FL (to 20 _RR ) is shown in FIG. As described above, when the minimum current value i _MIN taking noise into consideration, the minimum control pressure P _NIM is reached. When the current value i is increased from this state, the control pressure P increases linearly in proportion to the current value i, and the maximum control pressure P _NIM increases. When the current value is i _MAX , the maximum control pressure P _MAX corresponding to the set line pressure of the hydraulic power source 22 is obtained. This Figure 2
Where i _N is the neutral command current and P _N is the neutral control pressure.

As shown in FIG. 3, each of the vertical acceleration sensors 28FL to 28RR has a voltage of zero when the vertical acceleration is zero, and responds to the acceleration value when the downward acceleration is detected. When a positive voltage and an upward acceleration are detected, a negative voltage corresponding to the acceleration value is output. Further, as shown in FIG. 4, the controller 30 causes the vertical acceleration detection values Z _GFR of the vertical acceleration sensors 28FR to 28RR to be detected.
〜Z _GRR individually input pressure control valve 20FL〜20RR
In order to prevent high-frequency components from being cut off, the digital low-pass filters 40FL to 40RR whose cutoff frequency is set to 5 Hz, and the vertical acceleration detection values Z _{GFR to} Z _GRR are similarly individually input and integrated. As means, digital low-pass filters 41FL to 41RR whose cutoff frequency is set to 1 Hz, fixed gain adjusters 42FL to 42RR for amplifying the outputs of the low-pass filters 40FL to 40RR with a constant gain, and the low-pass filters 42FL to 42FL- Variable gain adjusters 43FL to 43RR for amplifying the output of 42RR with a variable gain ranging from negative to positive;
Outputs of gain adjusters 42FL to 42RR and gain adjuster 43
Adders 44FL to 44RR as adding means for adding the outputs of FL to 43RR, and total gain adjusters 45FL to 45RR for amplifying the added outputs of these adders 44FL to 44RR.
When the adder 46FL~46RR for adding the vehicle height adjusting output P _H for maintaining the output of these total gain adjuster 45FL~45RR preset the target vehicle height, these or adders 46FL~46RR The added output is converted into a command current and supplied to the pressure control valves 20FL to 20RR. For example, a drive circuit 47FL to 47RR composed of a floating type constant current circuit.
And a gain adjusting circuit 48 as a gain adjusting means for controlling the gains of the variable gain adjusters 43FL to 43RR.

The gain adjusting circuit 48 detects a vehicle speed and a function generator 5 that changes the gain B based on the vehicle speed detection value V output from the vehicle speed sensor 49.
It has 0 and. As shown in FIG. 5, in the function generator 50, the gain B becomes a negative predetermined value −B _MAX and the detected vehicle speed value is between the vehicle speed detected value V of zero and the preset low speed side vehicle speed V _1. V is the preset high-speed side vehicle speed V ₂
When the above is reached, the gain B becomes a positive predetermined value + B _MAX , and the gain B is set to increase in accordance with the increase in the vehicle speed detection value V between the low speed side set vehicle speed V ₁ and the high speed set vehicle speed V ₂ . .

Next, the operation of the above embodiment will be described. When the ignition switch is turned on, the controller 30 is powered on and the vertical acceleration sensor 28FL ...
Attitude change suppression processing based on the vertical acceleration detection values Z _{GFL to} Z _GRR from 28 RR is started. At this time, since the vehicle is stopped, the vehicle speed detection value V is zero, and the gain B output from the function generator 50 becomes a negative predetermined value −B _MAX , which is input to the variable gain adjusters 43FL to 43RR. And these gains B are set to −B _MAX .

In this stopped state, assuming that there is no occupant getting on and off and loading and unloading of the load, the vertical acceleration does not occur in the vehicle body, and the vertical acceleration detection values Z _GFL to 28 RR output from the vertical acceleration sensors 28FL to 28RR. Since Z _GRR is zero, the vehicle body vertical acceleration components x _FL ″ to x _RR ″ output from the low pass filters 40 _{FL to} 40 _RR and the vehicle body vertical velocity component x _FL ′ output from the low pass filters 41 _{FL to} 41 _RR.
~x _RR 'order becomes zero, the neutral command current value i _N corresponding to the neutral pressure P _N of the pressure control valve 20FL~20RR from the drive circuit 47FL~47RR command current i _FL through i _RR pressure control valve 20
It is output to FL to 20RR, which causes the hydraulic cylinder 18
The internal pressure of FL to 18RR is controlled to the neutral pressure P _N , and the vehicle body can be maintained at the target vehicle height in a flat state.

The vehicle is slowly started from this stopped state.
Vertical vibration that occurs on the vehicle body when the vehicle runs straight on a good road
Since the vertical acceleration sensor 28FL to 28RR
Vertical acceleration detection value Z_GFL~ Z_GRRNeutral voltage V_NTo
The values are close to each other, and the command current i is the same as when stopped._FL~ I_RRStands for
Neutral current value i_NMaintained at. On the other hand, is the vehicle stopped?
When you take a sudden start from the
The vertical acceleration sensors 28FL and 28FR on the front wheel side
Negative vertical acceleration detection value Z _GFL,Z_GFRIs output to the rear wheel side
The vertical acceleration sensors 28RL and 28RR of the
Lower acceleration detection value Z_GRL,Z_GRRIs output,
Command current i on the front wheel side_FL, I_FRIs the neutral current value i_NLess than
Current value and the command current i on the rear wheel side_RL, I_RRIs Neutral Den
Flow value i_NThe current value is larger and the scatter phenomenon is suppressed.
Can be controlled.

At this time, since the vehicle is running at a low speed, the gain B output from the function generator 50 is a negative value-
While keeping B _MAX , the vehicle vertical velocity components x _FL ′ and x _FR ′ output from the front-wheel side low-pass filters 41 FL and 41 _FR increase in the negative direction, so that the outputs of the variable gain adjusters 43 FL and 43 FR are It will be a positive value. Therefore, in the adders 44FL and 44RR, the negative vehicle body vertical acceleration component −A · x _FL ″, −A · x corresponding to the sprung mass control force is applied.
Positive vehicle body vertical velocity component + B ・ x corresponding to damping force to _FR ″
_{Since FL} ′, + B · x _FR ′ are added, the damping force component is subtracted from the sprung mass control force.
As shown in FIG. 7, the damping force due to the phase delay generated in the hydraulic control system can be canceled out, and the control force only by the sprung mass control force can be generated by the hydraulic cylinders 18FL to 18RR, and as shown in FIG. Thus, when the frequency is plotted on the horizontal axis and the vibration transmissibility is represented by the ratio x / x ₀ of the sprung displacement x and the unsprung displacement x ₀ on the vertical axis, the characteristic curve L ₁ Compared to the case where control based on vehicle vertical acceleration shown in ₃ is not performed, the sprung resonance frequency is lowered and the damping force due to the phase delay generated in the hydraulic control system can also be suppressed, allowing for smooth vehicle movement. Can be realized.

After that, when the detected vehicle speed V increases and becomes equal to or higher than the low speed set vehicle speed V _{1, the} gain B output from the function generator 50 gradually decreases, so that the adder 44
FL-44RR vehicle body vertical velocity component x _FL '
As x _RR ′ decreases, the damping force due to the phase delay of the hydraulic control system gradually increases, and when the vehicle speed detection value V becomes a high-speed running state where the gain B is positive, the damping force due to the phase delay of the hydraulic control system. In addition, the damping force components due to the vehicle body vertical velocity components x _FL ′ to x _RR ′ by the low pass filters 41 _{FL to} 41 _RR are positively added, and as shown by the characteristic curve L ₂ in FIG. By increasing only the damping force without changing ω ₀ , a large vibration damping effect can be exerted, and a solid vehicle movement can be realized.

As described above, according to the above-described embodiment, the gain with respect to the vertical speed of the vehicle body is changed according to the vehicle speed, so that the damping force is small in the middle and low speed regions while keeping the sprung resonance frequency constant. However, the damping force can be increased in the high speed region, and a slow vehicle motion can be realized in the medium and low speed regions and a firm vehicle motion can be realized in the high speed region according to the running state of the vehicle.

Further, when a straight traveling state on a good road is changed to, for example, a left (or right) turning state, a right (or left) side of the vehicle body
Lateral acceleration acts on the vehicle body, and when a roll that inclines to the right (or left) when viewed from the rear side is generated, the vertical acceleration sensors 28FR and 28RR on the right wheel side are positive (or negative), respectively. ) Vertical acceleration detection value Z _GFR,
Z _GRR is output and the vertical acceleration sensor 28 on the left wheel side is output.
Negative (or positive) vertical acceleration detection value Z for FL and 28RL respectively
By outputting _GFL, Z _{GRL ,} the command currents i _FL , i _RL on the left wheel side are negative (or positive), and the command currents i _FR , i _FR on the right wheel side are
_RR becomes positive (or negative), and the anti-roll effect can be exhibited.

Furthermore, when the vehicle travels from a good road to a rough road or a bad road, bounce occurs in the vehicle body, and the bounce suppression command currents i _{FL to} i _FL corresponding to the vertical acceleration generated in the vehicle. By outputting _RR , a good bounce suppression effect can be exhibited.
In the above embodiment, the case where the function generator 50 generates the function shown in FIG. 5 has been described, but the present invention is not limited to this, and a plurality of break points are provided as shown in FIG. As a result, the optimum damping force can be generated for each vehicle speed range.

Further, in the above embodiment, the vertical acceleration detection value Z of the vertical acceleration sensors 28FL to 28RR is detected.
_The case where the posture change of the vehicle body is suppressed only based on _{GFL to} Z _GRR has been described, but the present invention is not limited to this, and rolls based on acceleration detection values of other lateral acceleration sensors, longitudinal acceleration sensors, and the like, A command current for suppressing the pitch may be calculated, and the command currents i _{FL to} i _RR may be added / subtracted to perform total control.

Further, in the above embodiment, the case where the vertical acceleration sensors 28FL to 28RR are provided at the respective wheel positions has been described, but any one vertical acceleration sensor is omitted and the omitted vertical acceleration sensor is omitted. The vertical acceleration detection value of 1 may be estimated from the vertical acceleration detection values of the remaining three vertical acceleration sensors.

Furthermore, in the above embodiment, the case where the pressure control valves 20FL to 20RR are applied as control valves has been described, but the present invention is not limited to this, and other flow rate control type servo valves and the like can be applied. It is a thing. Further, in the above embodiment, the digital filter controller 30, gain adjuster, the function generator has been described as being constituted by an adder, etc., is not limited to this, the vertical acceleration detection value Z _GFL ~ It is also possible to input Z _GRR to a microcomputer and to perform integration processing by low-pass filter processing, gain setting according to the vehicle speed, etc. in this microcomputer.

Further, in the above embodiment, the case where the working oil is used as the working fluid has been described, but the working fluid is not limited to this and any working fluid may be applied as long as the fluid has a low compression rate.

[0026]

As described above, according to the active suspension of the present invention, the detected vehicle vertical acceleration and the vehicle vertical speed obtained by integrating the vehicle vertical acceleration are added by the adding means, Since the command signal of the pressure control valve is formed based on the addition output of the adding means and the gain of the vehicle body vertical speed is adjusted by the gain adjusting means, the vehicle vertical acceleration corresponding to the sprung mass control force is adjusted. By adding the vehicle body vertical velocity corresponding to the damping force, the damping force component due to the phase delay of the hydraulic control system can be adjusted, and both the sprung resonance frequency and the damping force can be controlled independently. Therefore, it is possible to realize a slow vehicle movement.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship of control pressure with respect to a command current of a pressure control valve.

FIG. 3 is a characteristic diagram showing an output characteristic of a vertical acceleration sensor.

FIG. 4 is a block diagram showing an example of a controller.

FIG. 5 is a characteristic diagram showing a gain characteristic with respect to a vehicle speed in the function generator.

FIG. 6 is an explanatory diagram showing a relationship between a vehicle body vertical speed and a vehicle body vertical acceleration.

FIG. 7 is a characteristic diagram showing a relationship of vibration transmissibility with respect to frequency.

FIG. 8 is a characteristic diagram showing a gain characteristic with respect to a vehicle speed in a function generator according to another embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a relationship between a vehicle body vertical velocity and a vehicle body vertical acceleration in a conventional example.

[Explanation of symbols]

 10 Body side member 11FL to 11RR Wheel 14 Wheel side member 18FL to 18RR Hydraulic cylinder 20FL to 20RR Pressure control valve 22 Hydraulic pressure source 28FL to 28RR Vertical acceleration sensor 30 Controller 40FL to 40RR Low pass filter 41FL to 41RR Low pass filter 42FL to 42RR Fixed gain Adjuster 43FL to 43RR Variable gain adjuster 44FL to 44RR Adder 45FL to 45FR Total gain adjuster 47FL to 47RR Drive circuit 48 Gain adjustment circuit 49 Vehicle speed sensor 50 Function generator

Claims (1)

[Claims] 1. An actuator disposed between each wheel and a vehicle body, which generates a control force capable of controlling a stroke therebetween by a control signal, and a vertical acceleration detecting means for detecting a vertical acceleration of the vehicle body. In the active suspension, the control means outputs the control signal based on the vertical acceleration detection signal of the vertical acceleration detection means, wherein the control means detects the vertical acceleration of the vertical acceleration detection means. The vehicle body vertical velocity calculating means for integrating the signal to calculate the vehicle body vertical velocity, the adding means for adding the vertical direction acceleration detection signal of the vertical direction acceleration detecting means and the vehicle body vertical velocity, and the vehicle body vertical velocity calculating means. Gain control means for adjusting the gain with respect to the vehicle body vertical speed over positive and negative, and the control signal based on the addition output of the addition means. An active suspension comprising a control signal forming means for forming.