JP2541346B2 - Active suspension system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is used in a vehicle such as an automobile, and uses a hydraulic actuator (hydraulic supporting means) to reduce the impact force when a vehicle overhangs a protrusion or the like. Regarding

(Prior Art) Conventionally, a so-called active suspension device that absorbs and reduces vertical vibration of a vehicle has been proposed. In this active suspension device, for each wheel, a hydraulic actuator is provided between the wheel and the vehicle body, the hydraulic chamber of this hydraulic actuator is connected to an accumulator through an orifice, and the oil pump is connected to the hydraulic chamber of each hydraulic actuator. A control valve composed of a proportional solenoid valve is arranged in the middle of an oil passage for supplying hydraulic oil. When the vertical vibration of the vehicle is controlled by the active suspension, the controller controls the operation of the control valve based on the vibration input information from the sprung G sensor to reduce the vibration generated in the vehicle body. Like that.

(Problems to be Solved by the Invention) In such a conventional active suspension device, although it is possible to favorably suppress the vertical vibration of the vehicle body, it is possible to prevent the shock generated when the vehicle overhangs the projection or when the pavement is traveling at the joint. It was not possible to sufficiently suppress such vibrations.

In order to suppress such a shocking vibration, the support rigidity of the hydraulic pressure support means should be reduced within a range in which a full stroke of the so-called suspension unit does not occur when the shock is large so that the input shock can be sufficiently absorbed. It needs to be changed.

By the way, since an ultrasonic sensor is used to detect a vibration input object such as a protrusion, at a vehicle speed deviating from a predetermined vehicle speed which is the sensitivity setting vehicle speed, the output of the detection signal is reduced due to the Doppler effect, and the size of the vibration input object is Therefore, there is a problem in that it is not possible to accurately detect the height, and therefore it is not accurately determined whether or not to generate a full stroke.

When the suspension has a full stroke, the suspension unit or the like may violently collide with the vehicle body and generate a shock, which may worsen the riding comfort.

The present invention has been made to solve such a problem, and accurately determines the size of a vibration input object such as a protrusion even when the vehicle speed changes, and prevents a full stroke of the suspension unit. It is an object of the present invention to provide an active suspension device for a vehicle, which is designed to optimally control the hydraulic pressure of a hydraulic pressure supporting means against an input shocking vibration.

(Means for Solving the Problems) In order to achieve the above object, an active suspension device for a vehicle according to the present invention is interposed between a vehicle body and wheels,
A hydraulic pressure support means for changing the support rigidity by controlling the supply and discharge of hydraulic pressure, a vibration input detection means for detecting a vibration input object in front of the vehicle and outputting a detection signal according to the size of the vibration input object, a vehicle speed When the vibration input detecting means detects an oscillating force object, the output signal value of the vibration input detecting means outputs a command signal for changing the supply / discharge of the hydraulic pressure of the hydraulic pressure supporting means. And a hydraulic pressure control means for reducing the support rigidity of the hydraulic pressure support means when the output signal value exceeds the predetermined upper limit value. To
The correction is performed according to the vehicle speed detected by the vehicle speed detecting means.

(Operation) The hydraulic pressure support means changes supply and discharge of hydraulic pressure according to a command signal from the hydraulic pressure control means to change the support rigidity of the vehicle body. However, when the magnitude of the impact exceeds the upper limit value, the hydraulic pressure support means is used. When the supporting rigidity of the means is switched to a small value, the suspension unit is fully stroked. Therefore, when the output signal value of the vibration input detecting means exceeds a predetermined upper limit value, it is prohibited to change the supporting rigidity of the hydraulic supporting means to a small value. At this time, the detection signal of the vibration input detecting means is
The output cannot be reduced and the full stroke of the suspension unit cannot be accurately predicted.

In order to prevent the suspension unit from having a full stroke, the hydraulic control means corrects the vehicle speed when discriminating between the output signal value of the vibration input detecting means and the predetermined upper limit value. For this vehicle speed correction, the gain of the output signal value of the vibration input detection means may be corrected according to the vehicle speed, or the predetermined upper limit value may be corrected according to the vehicle speed.

(Embodiment) Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a configuration of an active suspension device for a vehicle according to the present invention. In this figure, a suspension unit (one wheel suspension unit is shown as a representative) 12 provided for each wheel is shown. A suspension spring 13 of this suspension unit 12 and a single-acting hydraulic The actuator 14 is
It is interposed between the vehicle body 7 and the wheels 8.

The control valve 17 of the suspension unit 12 is interposed between an oil passage 16 communicating with the hydraulic chamber 15 of the hydraulic actuator 14 and a supply oil passage 4 and a discharge oil passage 6 described later. One end of the branch passage 16a is connected to the middle of the oil passage 16, and an accumulator 20 is connected to the other end of the branch passage 16a. Gas is enclosed in the accumulator 20, and so-called gas spring action is exerted due to the compressibility of the gas. A throttle (first orifice) 19 is provided in the middle of the branch passage 16a, and by regulating the amount of hydraulic oil flowing between the accumulator 20 and the hydraulic chamber 15 of the hydraulic actuator 14, Vibration damping effect is exhibited.

A bypass passage 16b that bypasses the orifice 19 is connected between the oil passage 16 and the accumulator 20.
A second orifice 21 and a switching valve 22 are provided in the. The second orifice 21 has a larger orifice diameter than the first orifice 19, the switching valve 22 is in the OFF state (the illustrated state) when not energized, and when the switching valve 22 is opened, the hydraulic oil is switched to the opened switching valve. It can flow between the accumulator 20 and the pressure chamber 15 via 22 and the orifice 21, which weakens the vibration damping effect. That is, the support rigidity of the suspension unit 12 changes in two steps depending on whether the switching valve 22 is turned on or off.

The other end of the supply oil passage 4 described above is connected to the discharge side of the oil pump 1, and the suction side of the oil pump 1 communicates with the inside of the reserve tank 3 via the oil passage 2. Therefore, when the oil pump 1 is operated, the working oil stored in the reserve tank 3 is discharged to the supply oil passage 4 side. An oil filter 9, a check valve 10, and an accumulator 11 for maintaining line pressure are arranged in the supply oil passage 4 in order from the oil pump 1 side. The check valve 10 allows only the flow of hydraulic oil from the oil pump 1 side to the suspension unit 12 side, and the check valve 10 can store high-pressure hydraulic oil in the accumulator 11.

The control valve 17 is of a type that changes the valve opening in proportion to the supplied current value, and the amount of oil flowing from the supply oil passage 4 to the discharge oil passage 6 according to the valve opening. By controlling the pressure, the pressure acting on the hydraulic actuator 14 is controlled. The configuration is such that the larger the current value supplied to the control valve 17, the greater the supporting force (supporting load) generated by the hydraulic actuator 14. The hydraulic oil discharged from the control valve 17 to the discharge oil passage 6 is returned to the reserve tank 3 described above.

The control valve 17 and the switching valve 22 are electrically connected to the output side of the controller 30, and their operations are controlled by a drive signal from the controller 30. On the input side of the controller 30, various sensors for controlling the suspension unit 12, for example, a sprung G sensor 31 which is provided for each wheel and detects vertical acceleration acting on the vehicle body, and each wheel are provided. A height sensor 32 for detecting the stroke amount of the wheel, a preview sensor for detecting a protrusion on the road surface in front of the vehicle, and outputting an output signal value according to the size of the protrusion.
33, a vehicle speed sensor 34 for detecting the traveling speed of the vehicle, etc. are connected. The operation of the control valve 17 and the switching valve 22 provided for each wheel is controlled based on the detection signals of these sensors.

An ultrasonic sensor is used as the preview sensor 33, and the sensor 33 is attached to the front portion of the vehicle body in the front of the vehicle and obliquely downward (see FIG. 2).

During normal driving, the switching valve 22 is closed,
The slight vibration input from the road surface to the vehicle body is absorbed and damped by the hydraulic chamber 15 of the hydraulic actuator 14 communicating with the accumulator 20 via the orifice 19.
Further, a current of a required magnitude is supplied to the control valve 17 in accordance with an output signal of the sprung G sensor 31 and the like, and PID control of the working oil pressure supplied to the hydraulic actuator 14 is performed. Vibration is suppressed.

On the other hand, when the preview sensor 33 detects a vibration input object such as a protrusion in front of the vehicle body, the controller 30 switches the switching valve 22 to reduce the support rigidity of the suspension unit 12.

The control of the support rigidity by switching the switching valve 22 will be described more specifically. The controller 30 constantly monitors the output signal value of the preview sensor 33, and detects a protrusion or the like from the change in this signal value. As will be described later in detail, at this time, the controller 30 issues a command for switching the switching valve 22 only when the output signal value of the preview sensor 33 is within a predetermined range optimum for performing preview control. Output a signal.

That is, as shown in FIG. 3, the preview sensor 33
Since the output signal of contains noise components corresponding to small protrusions that do not affect the riding comfort, it may be necessary to perform preview control for all input signals, The supporting rigidity of the unit 12 will be changed. To prevent this, the threshold value V ₁ is set to the lower limit for separating the noise component and performing the optimum preview control. On the other hand, if the supporting rigidity of the suspension unit 12 is reduced even in the case of a protrusion having a large impact force, a so-called full stroke phenomenon of the suspension unit occurs, which rather deteriorates the riding comfort. In order to prevent this, the upper limit threshold value V ₂ for performing the optimum preview control in the range where the full stroke of the suspension unit 12 does not occur is set. Here, V ₂ is set as a signal value after the lapse of a waiting time ΔT (the time from the measurement of V ₁ until the measurement of V ₂ ) set according to the vehicle speed.

Further, as described above, an ultrasonic sensor is used as the preview sensor 33, but the frequency of the sensor is adjusted in consideration of the Doppler effect so that the maximum sensitivity is obtained at a certain predetermined vehicle speed U ₀ . Therefore, at a vehicle speed deviating from the predetermined vehicle speed U ₀ , the receiving sensitivity of the sensor decreases, and the output signal value apparently decreases. To prevent this,
With the controller 30, the above-mentioned threshold values V ₁ and V ₂ are
The vehicle speed is set according to the vehicle speed detected by the vehicle speed sensor 34, and the vehicle speed is corrected accordingly (see FIG. 9).

As a result, the controller 30 causes the preview sensor 33 to
The command signal for switching the switching valve 22 is output only when the output signal value of is in the preview control area set here.

Then, according to the vehicle speed detected by the vehicle speed sensor 34, predict the time delay from the time when the protrusion or the like is detected until the wheel passes over this protrusion, and open the switching valve 22 until the wheel passes over the protrusion or the like. The support rigidity of the suspension unit 12 is switched to a small value when passing over a protrusion or the like. Further, the switching valve 22 is closed again after passing over the protrusion or the like.

Next, the procedure of the control (preview control) of the switching valve 22 when the controller 30 passes over a protrusion will be described with reference to FIGS. 4, 6, 7, and 8.

The control routine for preview control is executed as follows (FIG. 4).

First, the controller 30 detects the vehicle speed U from the vehicle speed sensor 34 (step S6). Then, using the detected vehicle speed U, from the correction map showing the relationship between the preset threshold value and the vehicle speed U in FIG. 9, the lower threshold value V ₁ and the upper threshold value corresponding to the vehicle speed U are calculated. Each V ₂ is determined (step
S8).

Further, the controller 30 constantly monitors the signal value of the preview sensor 33, and reads the output signal value V of the input ultrasonic reflected wave (step S10).

Then, it is determined whether or not the read output signal value of the preview sensor 33 exceeds the lower limit threshold value V ₁ for separating the noise component set as described above (step S12).

If the determination result of step S12 is negative (No), steps S6 to S12 are repeated.

If the determination result in step S12 is affirmative (Yes), the timer for measuring the waiting time ΔT is started (step S14).

Next, the controller 30 reads the output signal value V _n of the preview sensor 33 (step S16). Output signal value V
_It is determined whether or not _n exceeds the maximum signal value Vmax detected after the time when it exceeds the threshold value V ₁ (step S18).

If the determination in step S18 is affirmative (Yes),
The output signal value V _n is rewritten as the maximum signal value V max (step S20).

If the determination in step S18 is negative (No), or after the rewriting of the maximum signal value Vmax in step S20 is completed, it is determined whether or not the waiting time ΔT described above has elapsed (step S22).

If the determination in step S22 is negative (No),
Steps S16, S18 and S20 are executed again, and the maximum signal value Vmax
Is rewritten.

If the determination result in step S22 is affirmative (Yes), the output signal value of the preview sensor 33 is the lower limit threshold value.
Whether the maximum signal value Vmax measured from the time when it exceeds V ₁ to the elapse of the waiting time ΔT exceeds the upper limit threshold value V ₂ that is set to prevent the suspension unit 12 from full stroke It is determined whether or not (step S2
Four).

If the determination result in step S24 is affirmative (Yes),
That is, if the detected protrusion is small and it is determined that the suspension unit 12 does not make a full stroke even when the suspension rigidity of the suspension unit 12 is reduced when the protrusion is passed over, a command signal for switching the switching valve 22 is output. Step S30 is performed.

If the determination result in step S24 is negative (No),
That is, if the detected protrusion is large, and if it is determined that a full stroke of the suspension unit will be generated if the support rigidity of the suspension unit 12 is reduced when the protrusion passes over, the preview output in step S30 described above is not executed, The timer is reset and the Vmax value is erased (step S26), and the routine ends.
Then, the detection of the vehicle speed, the setting of the threshold values V ₁ and V ₂ and the monitoring of the output signal value of the preview sensor 33 are started again,
Prepare for the arrival of the next protrusion (steps S6 to S10).

Here, referring to FIG. 6, showing various aspects of the detected protrusion, in the case of the output signal shown by the curve A, the maximum signal value Vmax (= V _A2 ) until the waiting time ΔT elapses Exceeds the upper limit threshold V ₂ , the preview output in step S30 is not executed. Further, in the case of the output signal shown by the curve B, the maximum signal value until the waiting time ΔT elapses
Since the Vmax (= V _B2) does not exceed the threshold V ₂ of the upper, the preview output of step S30 is executed.

The waiting time ΔT is set according to the vehicle speed as described above, but it may be a constant value. Further, the magnitude of the output signal value after the elapse of ΔT is not subject to the evaluation because the so-called gentle protrusion or the like has a large suspension unit, even if its absolute value is large.
This is because it is predicted that the full stroke of the suspension unit will not occur due to switching the support rigidity of 12 to small.

Next, an output routine of the preview control executed when the above-mentioned command signal is output will be described with reference to FIGS. 7 and 8.

First, the delay time T is calculated (step S32). This delay time is for measuring the timing for opening the switching valve 22 immediately before the wheel passes over the protrusion after receiving the command signal from the above-mentioned control routine (time t2 in FIGS. 3 and 8). And is calculated by the following equations (1) and (2).

T = (L ₁ + L ₂ ) / U−ΔT (1) T = (L ₁ + L ₂ + L _W ) / U−ΔT (2) Here, the formula (1) is for obtaining the delay time with respect to the front wheels. Yes, equation (2) is for obtaining the delay time for the rear wheel. L ₁ is the minimum detection distance of the protrusion time detected by the sensor 33, L ₂ is the distance between the sensor 33 and the front wheels, L _W is the distance between wheels (wheel base), and U is the vehicle speed detected by the vehicle speed sensor 34. (See Figure 2). Further, ΔT is the above-mentioned waiting time.

Next, in step S34, the delay timer and the hold timer are set to timer values T and T ', which will be described later, and the timer is started.

This delay timer is for counting the delay time T set in the above step S32, and this timer is
It is prepared for front wheels and rear wheels respectively. Further, holding timers are prepared for the front wheels and the rear wheels, respectively, and the set timer value T'is calculated by the following equation (3).

T ′ = T + T ₀ (3) Here, T ₀ is a holding time for holding the switching valve 22 in the open state, and is set to, for example, 0 sec. Further, T is the delay time calculated by the equation (1) or (2).

The former delay timer is an up-counter that outputs an ON signal when it counts up to the set tire value. At the time of counting up (time t3 in FIG. 8), the corresponding front wheel or rear wheel side The switching valve 22 is opened (steps S36 and S38). As a result, the second orifice 21 as well as the first orifice 19 is put into the communicating state, so that the supporting rigidity of the suspension unit 12 is switched to a small value. For this reason, when the wheel gets over the protrusion or the like, the suspension unit does not cause a full stroke, and the impact force can be appropriately alleviated.

The latter holding timer is also an up-counter that outputs an ON signal when it counts up to the set timer value T ', and when it counts up (see FIG. 8).
Corresponding switching valve 22 on the front wheel side or the rear wheel side at time t4)
Is closed (steps S40 and S42), and the routine ends. As a result, the support rigidity of the suspension unit 12 is maintained until the preview sensor 33 next detects a vibration input object such as a protrusion and determines that the control routine of the controller 30 is optimal for performing preview control. Is held high.

FIG. 5 shows the above-described preview control routine (fourth control routine).
The figure shows the discriminant value of the second embodiment in which the discriminating procedure of FIG.

Incidentally, the description of the structure of the vehicle active suspension device of FIG. 1 in the above-described first embodiment, the description of the preview sensor 33 of FIG. 2, and the switching valve 22 of FIG.
Since the description of the control area is common to this embodiment, the description thereof is omitted.

First, the controller 30 detects the vehicle speed U from the vehicle speed sensor 34 (step S6 '). Then, using the detected vehicle speed U, FIG. 9 of the preset threshold and from the correction map that shows a relationship between vehicle speed U, the lower limit of the threshold V ₁ and lower threshold corresponding to the vehicle speed U V ₂ is determined for each (step
S8 ').

Further, the controller 30 constantly monitors the output signal value of the preview sensor 33 and reads the output signal value V of the input ultrasonic reflected wave (step S10 ').

Then, it is determined whether or not the read output signal value of the preview sensor 33 exceeds the lower limit threshold V ₁ for separating the noise component described above (step S1).
2 ').

If the determination result of step S12 ′ is negative (No),
Steps S6'-S12 'are repeated.

If the determination result in step S12 'is affirmative (Yes), the timer for measuring the waiting time ΔT is started (step S14').

Next, wait for the waiting time ΔT to elapse (step S22 ′)
When the time passes, the output signal value V of the preview sensor 33 is changed to Vt.
_It is read as ₂ (step S23 '). Then, it is determined whether or not this output signal value Vt ₂ exceeds the upper limit threshold value V ₂ set to prevent the full stroke of the suspension unit (step S24 ').

If the determination result in step S24 ′ is affirmative (Yes), that is, if it is determined that the suspension unit does not make a full stroke even if the support rigidity of the suspension unit 12 is small when the detected protrusion or the like is passed over, the switching is performed. Step S30 of outputting a command signal for switching the valve 22 is executed.

If the determination result in step S24 ′ is negative (No), that is, if it is determined that the support unit rigidity of the suspension unit 12 is reduced when the detected protrusion or the like is passed over, a full stroke of the suspension unit is generated. The preview output in step S30 is not executed, and the timer reset (step S26 ') is executed to end the routine. And again the detection of vehicle speed,
The setting of the threshold values V ₁ and V ₂ and the monitoring of the output signal value of the preview sensor 33 are started to prepare for the arrival of the next protrusion or the like (steps S6 ′ to S10 ′).

When the command signal is output, the preview control output routine of FIG. 7 in the first embodiment described above is executed.

In the above-mentioned first and second embodiments, the approximation characteristics by the combination of straight lines as shown by the solid line in FIG. 9 are used for the threshold values V ₁ and V ₂ for judging whether or not the preview control is carried out. Although the vehicle speed is corrected by the map, the present invention is not limited to the first and second embodiments described above, and the vehicle speed is corrected by using the ideal characteristic map shown by the broken line in FIG. Of course, you may do so.

Further, in the above-mentioned first and second embodiments, the decrease in the output signal value due to the Doppler effect is dealt with by correcting the threshold values V ₁ and V ₂ for comparing the output signal values with the vehicle speed. However, the present invention is not limited to the above-mentioned first and second embodiments, and the gain G of the output signal value of the preview sensor 33 may be corrected as shown in FIG.

(Effect of the Invention) As described in detail above, according to the vehicle active suspension device of the present invention, when the wheels pass over the vibration input object, when the impact force is excessive, the support rigidity of the hydraulic support means is increased. If it is made small, a full stroke of the hydraulic pressure supporting means is generated, so it is determined whether or not the supporting rigidity of the hydraulic pressure supporting means is changed depending on whether or not the output signal value of the vibration input detecting means exceeds a predetermined upper limit value. To do. When determining whether or not the output signal value of the vibration input means exceeds a predetermined upper limit value, the determination error due to the vehicle speed change is corrected according to the vehicle speed detected by the vehicle speed detection means, and more appropriately supports the excessive impact force. Rigid hydraulic control is performed to absorb the impact force, so that the riding comfort can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a schematic configuration of a vehicle active suspension device according to the present invention, and FIG. 2 shows a position where a preview sensor 33 in FIG. FIG. 3 is a graph showing the relationship, and FIG. 3 is a graph showing changes in the output signal value of the preview sensor 33 and time changes for explaining the control region of the switching valve 22 in FIG.
FIG. 4 is a flowchart showing a procedure of a control routine for preview control executed by the controller 30, FIG.
FIG. 6 is a flowchart showing a procedure of a control routine of preview control of another mode executed by the controller 30, and FIG. 6 is a preview sensor for explaining a control routine of preview control executed by the controller 30 by a concrete example. FIG. 7 is a graph showing the time change of the output signal value of 33, FIG. 7 is a flowchart showing the procedure of the output routine of the preview control executed by the controller 30, and FIG. 8 is the time of the switching signal output to the switching valve 22. A graph showing the change, FIG. 9 is a correction map showing the relationship between the threshold and the vehicle speed for determining whether or not the controller 30 performs preview control, and FIG. 10 is an output signal value of the preview sensor 33. 6 is a correction map showing a relationship between a gain and a vehicle speed for explaining the vehicle speed correction of FIG. 1 ... Oil pump, 7 ... Car body, 8 ... Wheels, 12 ...
Suspension unit (hydraulic support means), 13 suspension spring, 14 hydraulic actuator, 15
...... Hydraulic chamber, 17 ...... Control valve (hydraulic control means), 19 ...
… First orifice, 20 …… Accumulator, 21 …… Second
Orifice, 22 ... Switching valve, 30 ... Controller (hydraulic control means), 33 ... Preview sensor (vibration input detection means), 34 ... Vehicle speed sensor.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Naohiro Kishimoto 5-3-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Hiroaki Yoshida 5-33-8, Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation (56) References JP-A-61-235213 (JP, A)

Claims (1)

(57) [Claims] 1. A hydraulic pressure supporting means which is interposed between a vehicle body and a wheel and changes support rigidity by controlling supply and discharge of hydraulic pressure, and a vibration input object in front of the vehicle is detected, and a size of the vibration input object is determined. A vibration input detecting means for outputting a corresponding detection signal; a vehicle speed detecting means for detecting a vehicle speed; and a command signal for changing the hydraulic pressure supply / discharge of the hydraulic pressure supporting means when the vibration input detecting means detects a vibration input object. Is output only when the output signal value of the vibration input detection means does not exceed the predetermined upper limit value, and hydraulic control means for reducing the support rigidity of the hydraulic support means is provided. An active suspension device for a vehicle, wherein when determining whether or not it exceeds, a determination error due to a change in vehicle speed is corrected according to a vehicle speed detected by the vehicle speed detecting means.