JPH0585368B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydroneumatic suspension.

(Prior art) Since the car body of a car is elastically supported by the axle via a suspension system, the car body rises and falls according to the weight of the car, and the front part of the car sinks when braking suddenly or going down a slope, and the car body collapses when going up a slope. The rear sinks. On the other hand, if the vehicle body is not raised when driving on rough roads, the vehicle body will be damaged, and if the vehicle body is not lowered when driving at high speeds, running stability will be poor and aerodynamic characteristics will be disadvantageous.

Conventionally, a vehicle height adjustment device has been developed in which a vehicle height sensor is provided between the vehicle body and the axle, and the amount of expansion and contraction of the fluid pressure cylinder of the suspension system is controlled by feedback so that the detected vehicle height falls within the target vehicle height setting range. It has been put into practical use in various ways.

For example, the vehicle height adjustment device described in Japanese Patent Application Laid-open No. 57-118906 uses an air cylinder of a suspension system,
It is equipped with an air supply device that supplies air to the air cylinder, a vehicle height sensor installed in the suspension system, and a vehicle height control device, and compares the vehicle height detected by the vehicle height sensor at each point in time with the time-series smoothed value of the detected vehicle height. The road condition is judged based on the vibration state of the former with respect to the latter, the target vehicle height is automatically set accordingly, the detected vehicle height is compared with the target vehicle height, and the feedback vehicle height is adjusted in the direction where the former matches the latter. This is done so that adjustments can be made.

However, the vehicle height adjustment device described above adjusts the vehicle height by controlling the opening and closing of the air control valve installed in the air passage from the air supply device to the strut, so the vehicle height cannot be adjusted with high precision. However, since the speed of vehicle height adjustment is constant and cannot be adjusted appropriately, external forces acting on the vehicle may suddenly change due to sudden changes in aerodynamic characteristics due to vehicle height adjustment, such as when driving at high speeds. This has the disadvantage that running stability is impaired.

Furthermore, vibrations are likely to occur due to surge pressure when the air control valve opens and closes, and the responsiveness of vehicle height adjustment is also low due to structural limitations of the air control valve that opens and closes the air passage.

(Object of the Invention) The present invention has been made in view of the above-mentioned drawbacks, and is a hydroneumatic suspension system that has a simple configuration and can control the vehicle height and vehicle height adjustment speed with good responsiveness according to the vehicle speed, etc. The purpose is to provide the following.

(Structure of the Invention) The hydroneumatic suspension of the present invention includes a strut that is telescopically attached between an axle and a vehicle body and has a liquid chamber inside, and a pressurized liquid that constantly supplies a predetermined flow rate of pressurized liquid. a supply means, a liquid passage connecting the pressurized liquid supply means and the liquid chamber of the strut, a relief passage connected to the liquid passage and relieving pressurized liquid from the liquid passage to the outside, and attached to the relief passage. A flow rate adjusting means that constantly adjusts the flow rate of the pressurized liquid to be relieved and relieved, the flow rate adjusting means being capable of controlling the flow rate of the pressurized liquid to be relieved and the flow rate adjustment speed, the flow rate adjusting means being able to control the flow rate of the pressurized liquid to be relieved and the flow rate adjustment speed, the flow rate adjusting means being able to control the flow rate of the pressurized liquid to be relieved from the relief passage. The strut is configured to expand and contract by changing the flow rate of pressurized fluid.

(Effects of the Invention) Since the present invention is configured as described above, when the relief flow rate from the relief passage is small compared to the supply flow rate of the pressurized liquid supplied from the pressurized liquid supply means, the vehicle height becomes high. When the relief flow rate is equal, the vehicle height is maintained, and when the relief flow rate is large, the vehicle height is adjusted lower.

Further, the vehicle height adjustment is performed at a speed corresponding to the adjustment speed at which the relief flow rate is adjusted by the flow rate adjustment means of the relief passage.

Therefore, by controlling the flow rate adjustment means provided in the relief passage to control the flow rate and flow rate adjustment speed of the pressurized fluid, not only the vehicle height but also the vehicle height adjustment speed can be appropriately controlled according to the vehicle speed, etc. I can do it.

Moreover, when the flow rate adjustment means is operated by a control signal, the flow rate adjustment means operates with almost no delay, and this is directly connected to a change in the relief flow rate, so that the response is particularly excellent.

As described above, according to the present invention, the vehicle height and the vehicle height adjustment speed can be controlled with good responsiveness in accordance with the vehicle speed etc. using a device with a simple configuration.

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

As shown in FIG. 1, in this hydroneumatic suspension, a hydraulic supply device 1 that supplies pressure oil at a predetermined pressure and a predetermined flow rate Q1 and a strut 4 corresponding to each wheel 3 of a suspension device 2 are connected to an oil passage 5. a variable throttle device 7 corresponding to a flow rate adjusting means connected to a relief oil passage 6 connected to the oil passage 5;
The target vehicle height is calculated in the control unit 10 based on the output signals from the vehicle speed sensor 11 and the road surface condition selection switch 13, and the vehicle height sensor 1
The actual vehicle height obtained from the output signal No. 2 is compared with the target vehicle height, and the vehicle height is adjusted by appropriately adjusting the relief flow rate Q2 from the variable throttle valve 8 accordingly. At the same time, the vehicle height adjustment speed is also adjusted by appropriately controlling the adjustment speed of the variable throttle valve 8 according to the vehicle speed.

The configuration of each device will be explained in detail below.

The hydraulic pressure supply device 1 includes a directional discharge type chamber capacity hydraulic pump 1b driven by a motor 1a, a relief valve 1c, and a flow rate control valve 1d, and the relief valve is connected to an oil passage on the discharge side of the hydraulic pump 1b. 1
The pressure oil is controlled to a set oil pressure by C, and a fixed flow rate control valve 1d connected to an oil path on the downstream side of the relief valve 1c allows pressure oil to flow at a set flow rate Q1. In this way, pressure oil at the set flow rate Q1 at the set pressure is constantly supplied from the hydraulic pressure supply device 1 to the oil path 5.

The other end of the oil passage 5 is connected to an oil chamber 14 of each strut 4 for the front and rear wheels.

The strut 4 is a hydraulic cylinder that is telescopically interposed between the housing 16 and the vehicle body 17 at the joint between the axle 15 and the wheels 3, and functions as a strut and shock absorber for the suspension system 2, and at the same time as a vehicle height adjustment means. It is something to do. Second
As shown in the figure, the lower end of the cylinder body 18 of the strut 4 is fixed to the housing 16 via a sleeve-shaped coupling member 19.
The upper end of the piston rod 20 protruding upward from the piston rod 8 is connected to the vehicle body 17 via a mount washer 21 and an annular cushioning rubber 22.

A piston 23 provided at the lower end of the piston rod 20 of the strut 4 is vertically slidable within the oil chamber 14, and an upper oil chamber 14a on the upper side of the piston 23 and a lower oil chamber 14b on the lower side are connected to the piston 23.
3, and the upper end of an oil hole 25 opened at the lower end of the piston rod 20 and penetrated into the piston rod 20 is connected to the oil passage 5. Pressure oil supplied from the hydraulic pressure supply device 1 to the oil chamber 14 via the oil passage 5 and the oil hole 25 is transferred to the piston rod 20.
The load applied to the strut 4 from the vehicle body 17 is supported by the hydraulic pressure generated by acting on the annular effective pressure receiving area.

The variable throttle device 7, which corresponds to the flow rate adjustment means, includes a variable throttle valve 8 and a variable throttle valve connected in series to one relief oil passage 6 connected to the oil passage 5 between the hydraulic pressure supply device 1 and the strut 4. The drive unit 9 includes a drive unit 9 that drives the eight valve rods 26, and this drive unit 9 is controlled by a control unit 10 as described later.

The variable throttle valve 8 communicates with a valve chamber 28 in the valve box 27 and one end side of the valve chamber 28, and the relief oil passage 6
An inlet passage 29 connected to the valve chamber 28 and an outlet passage 30 communicating with the oil tank 31 at the other end of the valve chamber 28 are provided, and a tapered throttle hole 32 provided at the center of the valve chamber 28 is provided with a tapered throttle hole 32. The throttle valve body 33 of the shape of the shape is installed concentrically with a gap therebetween to form a throttle flow path, and by adjusting the insertion depth of the throttle valve body 33 into the throttle hole 32, the throttle flow path can be throttled. By adjusting the area, the flow rate of the pressure oil relieved from the relief oil passage 6 via the inlet passage 29, the valve chamber 28, and the outlet passage 30 can be adjusted.

The valve stem 26 of the throttle valve body 33 is led out of the valve box 27 and integrally connected to the movable member 34 of the drive section 9.

The drive unit 9 is a proportional solenoid type drive means, and a movable member 34 is fitted into an inner cylinder 35 coaxial with the valve stem 26 so as to be slidable in the axial direction, and is moved toward the valve stem 26 by a compression coil spring 36. energized, the inner cylinder 3
The throttle flow path of the variable throttle valve 8 is controlled by driving the movable member 34 to the side opposite to the valve rod 26 against the spring 36 by the magnetic force of the solenoid 37 mounted on the exterior of the variable throttle valve 5 to appropriately control the position of the movable member 34. The aperture area is adjusted.

When a predetermined current Ib is applied to the solenoid 37, the spring 36 is compressed by a predetermined length, and the spring force and the magnetic force of the solenoid 37 are balanced, and the pressure oil released from the variable throttle valve 8 is relieved. The flow rate Q2 is balanced with the set flow rate Q1 of the pressure oil supplied from the hydraulic pressure supply device 1, and the strut 4
The vehicle height is maintained without expanding or contracting.

On the other hand, when a current larger than the current Ib is applied to the solenoid 37, the magnetic force increases, so that the magnetic force and the spring force are balanced at the further contracted position of the spring 36, and at this time, the variable throttle valve 8 The relief flow rate Q2 from increases to the above set flow rate Q
1, so the oil chamber 14 of the strut 4
Pressure oil decreases and the vehicle height is adjusted to lower.

Further, when a current smaller than the current Ib is applied to the solenoid 37, the vehicle height is adjusted to become higher, contrary to the above.

Moreover, the variable throttle valve 8 is also adjusted slowly or quickly according to the speed of the current change when increasing or decreasing the current supplied to the solenoid 37, so the vehicle height adjustment speed is controlled by appropriately controlling the current adjustment speed. I can do it.

Such control is performed by the control unit 10 in the following manner depending on the vehicle speed and road surface conditions.

The vehicle speed sensor 12 detects the rotation of the main drive shaft using existing rotation detection means (for example, one consisting of a rotating disk with a slit, a light source, and a phototransistor, or one consisting of a rotating disk and a pickup sensor). The signal is output to control unit 10.

The road surface condition selection switch 13 is attached to the instrument panel of the driver's seat, and has 3 to 4 select switches ranked according to the quality of the road surface conditions that affect the vehicle height. One of the select switches is selected, and the signal thereof is output to the control unit 10.

The vehicle height sensor 12 is composed of, for example, a rotary potentiometer, and is mounted on the vehicle body 1 near each wheel 3.
7 and the link arm of the suspension system 2, and its resistance value increases or decreases in accordance with the vertical movement of the link arm corresponding to the rise and fall of the vehicle body 17, and the vehicle height is detected from the fluctuation of this resistance value. The detection signal is output to the control unit 10, but various vehicle height sensors other than this may be used.

As shown in FIG. 3, the control unit 10 includes a target vehicle height calculation circuit 10a, a discrimination circuit 10b, a valve adjustment speed calculation circuit 10c, and a drive circuit 10d.

The target vehicle height calculation circuit 10a receives outputs from the road surface condition selection switch 13 and the vehicle speed sensor 11, and calculates a target vehicle height corresponding to the road surface condition and vehicle speed based on program data inputted and stored in advance. be done. In this case, qualitatively, the vehicle height is set higher in stages as the road surface condition worsens, and the vehicle height is set lower in stages as the vehicle speed becomes faster in order to improve driving stability and aerodynamic characteristics.

In the discrimination circuit 10b, four vehicle height sensors 1
In response to the output signal from 2, the vehicle height average value is calculated every 10 msec, for example, and this vehicle height average value is compared with the above target vehicle height, and the vehicle height average value is within the allowable range of the target vehicle height. Sometimes there is no need to adjust the vehicle height, so the solenoid current is maintained without being output to the drive circuit 10d.On the other hand, when the average vehicle height is higher than the allowable range of the target vehicle height, the difference between the two is handled. Conversely, when the average vehicle height is lower than the allowable range of the target vehicle height, the solenoid current is adjusted to the increasing side via the drive circuit 10d by an amount corresponding to the difference between the two. The current is adjusted downward.

The valve adjustment speed calculation circuit 10c adjusts the speed of adjustment of the variable throttle valve 8 by adjusting the speed of current change when increasing or decreasing the solenoid current as described above, thereby adjusting the speed of adjustment of the vehicle height.

That is, the valve adjustment speed calculation circuit 10c receives the output signal from the vehicle speed sensor 11 and calculates the vehicle speed.
When the vehicle speed is less than the set speed (e.g. 80 km/hr), the drive circuit 1 is adjusted so that the valve adjustment speed is approximately at the set value.
The drive circuit 10d is controlled so that the solenoid current is increased/decreased in a relatively short time via the valve 0d, while the valve adjustment speed is approximately 1/2 to 1/3 of the set value when the vehicle speed is higher than the set speed. The solenoid current is increased or decreased over a relatively long period of time. As a result, when driving at high speeds, it is possible to gently adjust the vehicle height, prevent sudden changes in aerodynamic characteristics, and maintain good driving stability.

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

Pressure oil is always supplied from the hydraulic pressure supply device 1 at a set flow rate Q1, and the pressure oil is constantly relieved via the relief oil passage 6 and the variable throttle device 7 corresponding to the flow rate adjustment means, but this relief flow rate Q2 is adjusted by the degree of throttling of the variable throttle valve 8.

As already mentioned, the control unit 10 compares the target vehicle height obtained based on the output signals from the vehicle speed sensor 11, the road surface condition selection switch 13, and the vehicle height sensor 12 with the actual vehicle height, and raises the vehicle height. When adjusting, the variable throttle valve 8 of the relief flow path 6 is throttled by reducing the solenoid current, and the relief flow rate Q2 is adjusted to be smaller than the set flow rate Q1. Then, a portion of the pressure oil from the hydraulic pressure supply device 1 is supplied to the oil chamber 14 of the strut 4 without being relieved, so that the vehicle height increases. Then, when the actual vehicle height falls within the allowable range of the target vehicle height, the vehicle height must be maintained, so the variable throttle valve 8 is adjusted so that the set flow rate Q1 and the relief flow rate Q2 become equal.

When lowering the vehicle height, contrary to the above, the throttle of the variable throttle valve 8 in the relief flow path 6 is loosened, and the relief flow rate Q2 is adjusted to be greater than the set flow rate Q1, so that the actual vehicle height matches the target vehicle height. When the set flow rate Q1 and the relief flow rate Q2 are within the allowable range, the set flow rate Q1 is adjusted to be equal to the relief flow rate Q2.

Moreover, when the vehicle is traveling at high speeds, the control unit 10 gently adjusts the variable throttle valve 8 to gently adjust the vehicle height, whereas when the vehicle is traveling at low speeds, the vehicle height is quickly adjusted.

Next, when the car is loaded with luggage, the strut 4
The balance between the hydraulic pressure and load acting on the piston rod 20 is broken, and the piston rod 20 momentarily begins to descend, causing the overflowing pressure oil to flow back toward the oil passage 5. However, since the relief flow rate Q2 is equal to the set flow rate Q1, the above-mentioned Only a portion of the overflowing pressure oil is relieved, and the oil pressure in the oil chamber 14 of the strut 4 is increased and balanced by the throttling action of the variable throttle valve 8, and the vehicle height is somewhat lowered and stabilized. Therefore, as described above, the vehicle height is restored to the original vehicle height by making the relief flow rate Q2 smaller than the set flow rate Q1, and then the set flow rate Q1 and the relief flow rate Q2 are adjusted to be equal again.

In addition, when unloading cargo from a car, the vehicle height increases contrary to the above, so by increasing the relief flow rate Q2 than the set flow rate Q1, the vehicle height is lowered to the height of the original vehicle, and then the set flow rate is increased again. Adjust so that Q1 and relief flow rate Q2 are equal.

In the end, according to the vehicle height adjustment device of the above embodiment, the vehicle height and vehicle height adjustment speed can be adjusted precisely and responsively by simply controlling one variable throttle device 7, which corresponds to a flow rate adjustment means with a simple structure. It can be adjusted to

Here, the above embodiment can be partially modified as follows.

First modification: As shown in FIG. 4, the flow rate control valve 1D of the hydraulic pressure supply device 1 is configured with a diversion valve that distributes a set flow rate of pressure oil to the four oil lines 5,
The four oil passages 5 are connected to the struts 4 corresponding to each wheel 3, and the four oil passages 5 are connected to the struts 4 corresponding to each wheel 3.
A relief oil passage 6 is connected to each of the relief oil passages 6, a variable throttle device 7 is attached to each relief oil passage 6, and each variable throttle device 7 is controlled by a control unit 10.

In this way, by independently controlling the struts 4 corresponding to each wheel 3, it is possible to independently control the vehicle height at each wheel 4, and the following vehicle height adjustment is also possible.

For example, in order to prevent rolling when turning, the relief flow rate of the variable throttle valve 8 corresponding to the strut 4 on the outer wheel side is reduced depending on the steering angle, and the relief flow rate of the variable throttle valve 8 corresponding to the strut 4 on the inner wheel side is reduced. increase.

For example, in order to prevent nose dive during braking, a variable throttle valve 8 corresponding to the strut 4 on the front wheel side is required depending on the brake oil pressure.
The relief flow rate of the variable throttle valve 8 corresponding to the strut 4 on the rear wheel side is increased.

Incidentally, reference numeral 38 in the figure is a diaphragm type accumulator connected to the oil chamber 14 of each strut 4, and is for absorbing high frequency vibrations transmitted from the road surface to the wheels 3.

Second modification: Regarding the variable throttle device 7, the structure of the variable throttle valve 8 is not limited to the illustrated structure, and variable throttle valves of various structures can be used, and the drive unit 9 is a proportional solenoid type drive. Alternatively, the valve stem 26 may be controlled by a stepping motor via a rack and pinion mechanism, or by a hydraulic cylinder via a rotary encoder or solenoid valve.

Third modification: Regarding the road surface condition, the control unit 10 may calculate the vehicle height amplitude based on the output signal of the vehicle height sensor 12, and the road surface condition may be determined from this vehicle height amplitude.

Furthermore, an acceleration detection sensor that detects acceleration in the vertical direction may be attached to the axle 15 or the like, and the road surface condition may be determined based on the detection signal.

In addition, unevenness of the road surface, bouncing, pitching, etc.
For the natural vibration of rolling, the time required to return to the proper position after displacement due to the initial disturbance is
Depending on the frequency of the road surface, it is also possible to control the length to be long in low frequency paths and short in high frequency paths.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; Fig. 1 is an overall configuration diagram, Fig. 2 is a vertical sectional view of the strut, Fig. 3 is a block diagram of the control system that controls the variable diaphragm device, and Fig. 4 is a block diagram of the control system that controls the variable diaphragm device. It is a hydraulic system diagram of a modification. 1... Hydraulic supply device, 4... Strut, 5...
... Oil path, 6 ... Relief oil path, 7 ... Variable throttle device (flow rate adjustment means), 8 ... Variable throttle valve, 9 ...
Drive unit, 10...Control unit, 11...Vehicle speed sensor, 12...Vehicle height sensor, 23...Road surface condition selection switch, 14...Oil chamber, 15...Axle, 17
...Car body.

Claims (1)

[Scope of Claims] 1. A strut that is telescopically attached between an axle and a vehicle body and has a liquid chamber therein, a pressurized liquid supply means that always supplies a predetermined flow rate of pressurized liquid, and the pressurized liquid supply described above. a liquid passage connecting the means and the liquid chamber of the strut, a relief passage connected to the liquid passage and relieving the pressurized liquid from the liquid passage to the outside, and a flow rate of the pressurized liquid attached to the relief passage to be relieved. The flow rate adjustment means constantly adjusts the flow rate of the pressurized liquid relieved from the relief passage, the flow rate adjustment means being capable of controlling the flow rate of the pressurized liquid relieved and the flow rate adjustment speed, and changing the flow rate of the pressurized liquid relieved from the relief passage. A hydroneumatic suspension characterized in that the strut is configured to expand and contract.