JPH0450014A - Active suspension device for vehicle - Google Patents

Abstract

PURPOSE:To improve ride comfortability by changing the hydraulic feed and discharge of a hydraulic suspension means until vibration is inputted into a wheel when a vibration input object has been detected to decrease a supporting load to a limit of hydraulic pressure where no change is made in a vehicle height, thus compensating frictional force between the components of the hydraulic supporting means. CONSTITUTION:A control valve 17 of a suspension unit 12 is provided between an oil passage 16 communicating with the hydraulic chamber 15 of a hydraulic actuator 14 and a feed oil passage 4 and a discharge oil passage 6. At a by-path passage 166 connected between the oil passage 16 and an accumulator 20, a switching valve 22 is disposed. Besides, the control valve 17 and the switching valve 22 are operated by a controller 30, whereas a preview sensor 33 to detect a protrusion or the like on the road surface forward a vehicle at least is connected on the input side of the controller 30. When a vibration input object has been detected by the preview sensor 33, hydraulic pressure is lowered to a limit of hydraulic pressure where no change is made in the vehicle height until a wheel passes the vibration input object.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an active suspension device for a vehicle, which is used in a vehicle such as an automobile, and which uses a hydraulic actuator (hydraulic support means) to reduce impact force when driving over a bump. .

(Prior Art) Conventionally, so-called active suspension devices have been proposed that absorb and alleviate vertical vibrations of a vehicle.

This active suspension system has a hydraulic actuator interposed between each wheel and the vehicle body, the hydraulic chamber of this hydraulic actuator is connected to an accumulator via an orifice, and the hydraulic chamber of each hydraulic actuator is connected from an oil pump to the hydraulic chamber of each hydraulic actuator. A control valve consisting of a proportional electromagnetic valve is arranged in the middle of an oil path that supplies hydraulic oil. When using this active suspension to control the vertical vibration of the vehicle, the controller controls the operation of the control valve described above based on the vibration input information from the sprung G sensor. It is designed to reduce vibrations.

(Problem to be Solved by the Invention) Such conventional active suspension devices can effectively suppress relatively low-frequency vibrations in the vertical direction of the vehicle body, but vibrations that occur when going over bumps or when driving over pavement joints. It was not possible to sufficiently suppress the shocking vibrations that occur.

In order to suppress such shocking vibrations, it is necessary to control the supply and discharge of hydraulic pressure to the hydraulic actuator so that the input impact force can be sufficiently absorbed.

The present invention was made in order to solve such problems, and an object of the present invention is to provide an active suspension device capable of properly controlling the hydraulic pressure of the hydraulic support means in response to input impact vibrations. shall be.

(Means for Solving the Problem) In order to achieve the above-mentioned object, the active suspension device for a vehicle of the present invention is interposed between a vehicle body and a wheel, and supports a load according to the magnitude of the supplied hydraulic pressure. The hydraulic pressure control means includes a hydraulic support means for changing the hydraulic pressure, a hydraulic control means for controlling the magnitude of the hydraulic pressure supplied from a hydraulic source to the hydraulic support means, and a vibration input detection means for detecting a vibration input object in front of the vehicle. is, when the vibration input detection means detects a vibration input object, until the wheel passes the vibration input object,
The hydraulic pressure of the hydraulic support means is reduced to a hydraulic pressure value at which no change in vehicle height occurs.

(Function) The hydraulic support means changes the supported load of the vehicle body in accordance with the hydraulic pressure supplied from the hydraulic control means, but due to the frictional force between the components of the hydraulic support means, the load is slightly smaller than that frictional force. Even if the hydraulic pressure is reduced by an amount corresponding to a smaller value, the hydraulic support means will not expand or contract and the vehicle height will remain constant.

The hydraulic control means takes this frictional force into consideration and limits the amount of frictional force offset between the components of the hydraulic support means, that is, the hydraulic pressure value at which no change in vehicle height occurs, at the latest when the wheel passes a vibration input object such as a protrusion. If the hydraulic pressure of the hydraulic support means is reduced in advance in advance, when the hydraulic pressure of the hydraulic support means is about to increase rapidly when the wheel passes over the vibration input object, the impact force will be alleviated by this reduced pressure. .

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows the configuration of an active suspension device for an automobile according to the present invention. This figure shows a suspension unit 12 (the suspension unit for one wheel is shown as a representative) provided in each axle layer, and a suspension spring 13 of this suspension unit 12 and a single-acting hydraulic Actuator 1
4 is interposed between the vehicle body 7 and the wheels 8.

The hydraulic actuator 14 includes a cylinder 14a and a piston 14 that slides vertically inside the cylinder 14a in a liquid-tight manner.
A hydraulic chamber 15 is defined by the cylinder 14a and the piston 14b.

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, which will be described later. One end of a 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 sealed in the accumulator 20, and due to the compressibility of the gas, a so-called gas spring action is exerted. A throttle (first orifice) 19 is disposed in the middle of the branch path 16a, and a hydraulic chamber 1 of the accumulator 20 and the hydraulic actuator 14 is arranged.
By regulating the amount of hydraulic oil flowing between
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, and a second orifice 21 and a switching valve 22 are connected to the bypass passage 16b.
is installed. The second orifice 21 has a larger orifice diameter than the first orifice 19, and the switching valve 2
2 is in an off state (the state shown in the figure) when not energized, and when the switching valve 22 is opened, the hydraulic oil flows into the accumulator 2 through the opened switching valve 22 and the orifice 21.
0 and the pressure chamber 15, which weakens the vibration damping effect. That is, the support rigidity of the suspension unit 12 changes in two stages by turning the switching valve 22 on and off.

The other end of the supply oil passage 4 mentioned 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 hydraulic oil stored in the reserve tank 3 is discharged to the supply oil path 4 side. Supply oil path 4
In order from the oil pump 1 side, there is an oil filter 9, a check valve 10, and an accumulator for maintaining line pressure] 1
is installed. The check valve 10 is connected to the oil pump 1
Only the flow of hydraulic oil from the side toward the suspension unit 12 is allowed, and high-pressure hydraulic oil can be stored in the accumulator 11 by this check valve lO.

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 path 4 side to the discharge oil path 6 side is adjusted according to this valve opening degree. The pressure acting on the hydraulic actuator 14 is controlled by controlling the pressure. The larger the current value supplied to the control valve 17, the more the hydraulic actuator 14
The structure is such that the supporting force (supporting load) generated by the supporting force increases (see Fig. 2). The hydraulic oil discharged from the control valve 17 to the discharge oil path 6 side is returned to the reserve tank 3 described above.

The control valve 17 and the switching valve 22 are connected to the controller 3
It is electrically connected to the output side of controller 3.
The operation is controlled by a drive signal from 0. On the input side of the controller 30, various sensors for controlling the suspension unit 12 are provided, for example, for each wheel.
A sprung G sensor 31 that detects vertical acceleration acting on the vehicle body, a vehicle height sensor 32 provided for each wheel that detects the stroke amount of the wheel, and a preview sensor that detects protrusions on the road surface in front of the vehicle. 33, a vehicle speed sensor 34 for detecting the running speed of the vehicle is connected. The aforementioned control valve 17 and switching valve 2 are arranged for each wheel.
2 is operated and controlled based on detection signals from these sensors.

Note that, as the preview sensor 33, for example, an ultrasonic sensor is used, and this sensor 33 is attached to the front of the vehicle body, facing diagonally downward and in front of the vehicle body (see FIG. 3).

During normal driving, the switching valve 22 is closed.
Slight vibrations input to the vehicle body from the road surface are absorbed and attenuated because the hydraulic chamber 15 of the hydraulic actuator 14 communicates with the accumulator 2o via the orifice 19. The control valve 17 also includes a sprung G sensor 3.
A current of a required magnitude is supplied in accordance with the first output signal, and the working pressure supplied to the hydraulic actuator 14 becomes P'.
LD control is performed, thereby suppressing vertical vibration of the vehicle body.

On the other hand, when the preview sensor 33 detects a vibration input object such as a protrusion in the front of the vehicle body, the controller 30 switches the switching valve 22 to reduce the support rigidity of the suspension unit 12, and also controls the control valve 17 as described in detail later. The supply current value is lowered by a predetermined value to lower the oil pressure of the hydraulic actuator 14.

To explain in more detail the control of support rigidity by switching the switching valve 22, the controller 30 constantly monitors the signal value input from the preview sensor 33, and detects a protrusion etc. from a change in this signal value. and,
Depending on the vehicle speed detected by the vehicle speed sensor 34, the time delay from the time when a protrusion is detected until the wheel passes over the protrusion is predicted, the switching valve 22 is opened until the wheel passes over the protrusion, and the support is activated when the wheel passes over the protrusion. Switch stiffness to small.

After passing over the protrusion, the switching valve 22 is closed again.

Next, the procedure of hydraulic control (preview control) of the hydraulic actuator 14 when the controller 3G goes over a protrusion will be described with reference to FIGS. 4A, 4B, and 5.

First, the controller 30 reads the detection signal value from the preview sensor 33 (step S1.0).

Then, it is determined whether there is a protrusion or the like in front of the vehicle based on the read detection signal value of the preview sensor 33 (step 512). The determination result in step S12 is negative (N
In the case of O), a flag value FLGPV, which will be described later, is determined in step S14, and whether this flag value FLGPV or l
Confirm that this is not the case and end the routine.

If the determination in step SI2 is affirmative (Yes), the delay time T is calculated (step 516). This delay time is used to measure the timing at which the control valve 17 is controlled to switch to a predetermined oil pressure from the time when a protrusion is detected, just before the wheel passes over the protrusion, etc., and is expressed by the following equation (1). Calculated by (2).

T” (Ll +L2) /V...(
1) T-(L++Lx+Lv)/V
(2) Here, equation (1) is used to find the delay time for the front wheels, and equation (2) is used to find the delay time for the rear wheels. L is the minimum detection distance between the sensor 33 and a detected protrusion, L is the distance between the sensor 33 and the front wheel, Lw is the distance between the wheels (wheelbase), and ■ is the vehicle speed detected by the vehicle speed sensor 34. (See Figure 3).

Next, the process proceeds to step 318, where a holding timer is set to a timer value T', which will be described later, and started. This timer is prepared for the front wheel and the rear wheel, and is an up counter that outputs an on signal when the timer counts up to the set timer value. The current value of the corresponding control valve 17 is returned to its original value as described below.

The timer value T' to be set is calculated by the following equation (3).

T'=T+TO... (3) Here, To is a holding time for maintaining the current value of the control valve 17 in a state where it is decreased by a predetermined value, for example, 0.
It is set to 1 sec. Note that the predetermined value regarding the current of the control valve 17 is determined through experiments or the like, and is set to a current value corresponding to a value slightly smaller than the supporting load equivalent to the frictional force between the suspension unit components. When the control valve 17 is operated with a current value lower by this predetermined value and the oil pressure in the pressure chamber 15 of the hydraulic actuator I4 is reduced, the stroke amount of the hydraulic actuator 14 does not change due to the frictional force between the components of the suspension unit 12. First, the vehicle height is held constant. In addition, T is the previous formula (1) or (
This is the delay time calculated by 2).

Next, it is determined whether the flag value FLGPV is 1 (step 520). This flag FLGPV is a program variable for indicating that preview control is being executed. When this step is executed for the first time after detecting a protrusion, the value is 0, and the process proceeds to step S22, where the delay timer is set to the above-mentioned timer value T and started, and the flag value FLGPV is set to 1. (time to in Figure 5). The delay timer is for counting the delay time T set in step S16 described above, and this timer is also prepared for the front wheels and the rear wheels, respectively. It is an up counter that outputs an on signal when it counts up to the set timer value, and at the time it counts up, the current value of the control valve 17 on the corresponding front wheel side or rear wheel side is lowered by a predetermined value.

Once the delay timer is started, the process proceeds to step S24, where it is determined whether or not this delay timer has counted up. If this step is executed immediately after starting the delay timer, the result of this determination will of course be negative;
End the routine. Then, unless a new protrusion is detected, steps 312, 814 . S24 will be executed repeatedly.

When the delay timer finishes counting up (time t2 shown in FIG. 5), the process proceeds to step 326, where it is determined whether or not the aforementioned holding timer has counted up. Immediately after the delay timer is counted up, the holding timer is still counting (the determination result is negative), and in such a case, the process advances to step S28, where the current value of the control valve I7 is lowered by a predetermined value, and the current value of the control valve I7 is decreased by a predetermined value. End the routine.

As a result, the working oil pressure in the pressure chamber 15 of the hydraulic actuator 14 is reduced in accordance with the lowered predetermined current area.

Until the determination result in step S26 becomes affirmative (time t3 in FIG. 5), that is, until the holding timer finishes counting up, step 828 is continuously executed, and the working oil pressure in the pressure chamber 15 of the hydraulic actuator 14 is in a reduced pressure state. is maintained.

During this time, since the working pressure in the pressure chamber 15 of the hydraulic actuator 14 is reduced, the suspension spring 13.
The spring constant of the entire suspension unit constituted by the orifice 19, 21 and the accumulator 20 is reduced, and impact force can be appropriately alleviated.

If the determination result in step S26 is affirmative, step S26
30 is executed, the current value of the control valve is increased, the working oil pressure of the pressure chamber 15 of the hydraulic actuator I4 is returned to the original oil pressure value, and the flag value FLGPV is reset to 0, and the routine ends (fifth (time t3 in the figure).

By the way, if another protrusion, etc. is detected during the preview control (for example, if another protrusion, etc. is detected at time t1 in FIG. 5), the determination result in step S12 becomes affirmative again, and the delay time Calculation of T (step 816)
and restarting the holding timer (step 818).

On the other hand, since the delay timer is not restarted by determining the flag value FLGPV, the timing for increasing the current value of the control valve to return the working oil pressure in the pressure chamber 15 of the hydraulic actuator 14 to the original oil pressure value is determined by the holding timer. By restarting, there is a delay until time t4 shown by the broken line in FIG. 5, and during this time, the impact force caused by the initially detected protrusions and the later detected protrusions is alleviated.

In the above embodiment, the delay time T is set according to formula (1) or (2) when the front wheel or rear wheel passes a protrusion, etc., but the present invention is not limited to the above embodiment, The control valve 17 may be switched to a low oil pressure state before the passage of the object, for example, the oil pressure may be switched at the same time as the preview sensor 33 detects a vibration input object. However, in this case, in order to obtain the effects of the present invention, it is necessary to set the holding time T0 to at least the time required for the front wheel or the rear wheel to completely pass through the protrusion or the like.

Further, in the above embodiment, the current value of the control valve 17 is lowered to reduce the oil pressure in the pressure chamber 15 of the hydraulic actuator 14, with the oil pressure value at which no change in vehicle height occurs as a limit. Without being limited to the embodiment, the magnitude of the hydraulic pressure to be reduced may be larger than the value corresponding to the frictional force described above, as long as the vehicle height is allowed to fall to some extent.

(Effects of the Invention) As described above in detail, according to the active suspension device for a vehicle of the present invention, when the sensor means detects a vibration input object, by the time vibration is input to the wheel,
The hydraulic control means changes the supply and discharge of hydraulic pressure to the hydraulic support means, and reduces the support load of the hydraulic support means to the limit of the hydraulic pressure value that does not cause a change in the vehicle height. This cancels out the frictional force between the wheels and sufficiently absorbs the impact force when the wheels ride over the vibration-input object, thereby improving riding comfort.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the schematic configuration of an active suspension device for a vehicle according to the present invention, and FIG.
and the actuator pressure generated on the discharge side of the control valve 17 due to the current value (■). 4A and 4B are flowcharts showing preview control means executed by the controller 30, and FIG.
3 is a graph showing the timing at which a protrusion is detected and the change over time in the current value supplied to the control valve 17. 1... Oil pump, 7... Vehicle body, 8... Wheels,
12... Suspension unit (hydraulic support means),
13... Suspension spring, 14... Hydraulic actuator, 15... Hydraulic chamber, 17... Control valve (hydraulic control means), 22... Switching valve, 30...
. . . Controller (hydraulic control means), 33 . . . Preview sensor (vibration input detection means) 34 . . . Vehicle speed sensor.

Claims (1)

[Claims] A hydraulic support means that is interposed between the vehicle body and the wheels and changes the supported load according to the magnitude of the supplied hydraulic pressure, and a hydraulic control means that controls the magnitude of the hydraulic pressure supplied from the hydraulic source to the hydraulic support means. and vibration input detection means for detecting a vibration input object in front of the vehicle, and when the vibration input detection means detects the vibration input object, the hydraulic control means controls the vibration input object until the wheel passes the vibration input object. An active suspension device for a vehicle, characterized in that the hydraulic pressure of the hydraulic support means is lowered to a hydraulic pressure value that does not cause a change in vehicle height.