JPH08491B2 - Hydraulic suspension device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic suspension device having a function of changing a spring constant.

(Prior Art) Conventionally, some hydraulic suspension devices for vehicles have a variable spring constant.

It connects a plurality of accumulators to a suspension strut (hereinafter referred to as a strut) consisting of a hydraulic cylinder interposed between a vehicle body and wheels, one accumulator is directly connected to the strut, and another accumulator is connected via a switching valve. The spring constant can be changed by opening and closing the switching valve to increase or decrease the number of accumulators communicating with the struts to change the volume of the gas chamber in the accumulator.

When such a hydraulic suspension device is used, the spring constant is set low when traveling on a flat road surface to obtain an optimum riding comfort, and the spring constant is set when traveling on an uneven road surface. By increasing the height, vibration such as pitching motion of the vehicle can be reduced and deterioration of riding comfort can be prevented.

The spring constant and damping force can be switched between high and low by adjusting the preliminary vehicle height to a normal state in the "neutral vehicle height area", above a certain height in a "high vehicle height area", below a certain height. Low vehicle height area "
Separately, when the vehicle height sensor detects "high vehicle height area" or "low vehicle height area" due to vibration, the switching valve is closed to increase the spring constant and vibration is attenuated. When the vehicle height returns to the "neutral vehicle height range", the switching valve is opened to reduce the spring constant.

(Problems to be Solved by the Invention) However, the above hydraulic suspension device in which the spring constant is variable has the following problems.

When the vehicle vibrates up and down due to pitching motion etc. and the vehicle height sensor detects "high vehicle height area" or "low vehicle height area" to increase the spring constant, the vehicle height of the vehicle becomes "neutral vehicle height area".
If the switching valve is closed at a position that is further displaced, the pressure in the other accumulators will be the pressure at that vehicle height, and the pitching motion will subside and the switching valve will be opened in the "neutral vehicle height region". Sometimes there is a large pressure difference between the pressure in one accumulator and the other accumulator, and the switching valve cannot be opened, or even if it can be opened, the pressure oil will suddenly flow into the lower accumulator. However, there is a problem that the vehicle height changes with an unpleasant impact.

The present invention has been made in view of the above problems, and an object thereof is to eliminate the pressure difference between accumulators when the spring constant is switched to a low value.

(Means for Solving Problems) As means for solving the above problems and achieving the object, one accumulator that is always connected to a hydraulic cylinder interposed between a vehicle body and wheels, and The hydraulic cylinder and the other accumulator are configured by another accumulator connected to the hydraulic cylinder via a switching valve, and the switching valve is switched based on a detection signal from a vehicle height sensor that detects a vehicle height of the vehicle. In a hydraulic suspension device that can change the spring constant by disconnecting communication between the two, the time when the vehicle height becomes a high vehicle height region above a predetermined height or a low vehicle height region below a predetermined height. Then, the time when the maximum amplitude position is obtained by obtaining the average time of the vehicle height and the time when the vehicle height leaves the high vehicle area or the low vehicle height area,
The switching valve is controlled so that the other accumulator and the hydraulic cylinder are shut off when a predetermined time in which the amplitude becomes substantially 0 from the maximum amplitude position has elapsed from the time when the maximum amplitude position is reached. .

(Function) From the average time between the time when the vehicle starts to vibrate and the vehicle height changes from the neutral vehicle height area to the high vehicle height area or the low vehicle height area and the time when the vehicle height returns to the neutral vehicle height area again, For example, the switching valve is closed after a quarter of the natural vibration period of the vehicle body to increase the spring constant and suppress the vibration.

When the vibration is attenuated after a certain period of time, the switching valve is opened to reduce the spring constant to improve the riding comfort.

Here, the average time is the time midway between the time when the vehicle height enters the high vehicle height area or the low vehicle height area and the time when the vehicle height returns to the neutral vehicle height area. (Maximum amplitude position) is reached, and when 1/4 of the cycle of natural vibration elapses from that time, the vibration amplitude is almost zero.
Therefore, the switching valve is closed when the vehicle height is in the neutral vehicle height range. That is, the natural vibration of the vehicle is
Since the amplitude changes but the cycle is almost constant, the amplitude becomes 0 (neutral vehicle height area) every time a certain time elapses from the maximum amplitude position (high vehicle height area or low vehicle height area), and at that time, switching is performed. When the valves are closed, the pressure in the other accumulators becomes the same as the pressure when the valves are opened, so that there is no pressure difference with one accumulator.

(Example) Next, one example of the present invention will be described with reference to the drawings.

 First, the configuration of this embodiment will be described with reference to FIG.

The hydraulic unit 1 for supplying pressure oil is composed of a pump 2, a motor 3 for operating the pump 2, a filter 5 and a relief valve 6 provided at a suction port for sucking oil liquid from a reservoir tank 4. The pressure oil supplied from the hydraulic unit 1 is stored in the gas filled type accumulator 8 via the check valve 7. Then, the motor 3 is operated by the signal from the pressure switch 9 attached to the gas-filled accumulator 8, the pump 2 is repeatedly started and stopped, and the hydraulic pressure is appropriately supplied.

The gas-filled accumulator 8 and the strut 10 are connected via a refueling side switching valve 11, and the strut is further connected.
10 and the reservoir tank 4 are connected via an oil drain side switching valve 12. Then, when increasing the vehicle height, the refueling side switching valve 11 is opened to supply pressure oil to the struts 10, and when the vehicle height is lowered, the oil draining side switching valve 12 is opened.
Return the pressure oil from 10 into the reservoir tank 4.

Next, a mechanism for changing the spring constant will be described.

The strut 10 has two self-contained accumulators.
13, 14 are connected in parallel, and one of the gas filled type accumulators 14 is connected via a spring constant switching valve 15. Then, the spring constant can be changed in two steps by opening / closing the spring constant switching valve 15 and changing the volume of the gas chamber of the gas-filled accumulator 13.

A variable throttle valve (electromagnetic switching control valve) 16 is provided in the system path connecting the gas-filled accumulators 13, 14 for varying the spring constant and the strut 10, and the throttle of the variable throttle valve 16 is provided. The damping force of the strut 10 can be varied by adjusting the (orifice or the like) using a rotary or latching solenoid valve or a motor. The check valve 17 attached to the variable throttle valve 16 is for changing the damping force on the extension side and the contraction side of the strut 10.

Adjustment of the spring constant switching valve 15 and the variable throttle valve 16 for varying the spring constant and damping force described above is performed by signals from various sensors 18 for detecting vehicle height, road surface condition, roll condition, sudden start, sudden stop, etc. Is received and processed by the controller 19, and the signal is issued from the controller 19 based on the determination result of the running state and the driving state.

Next, FIG. 2 shows an example of the mounting state of the vehicle height sensor, in which a vehicle height sensor 21 is attached to the bottom of the vehicle body 20, and one end of a link 22 extending horizontally in the central portion 21a. Is rotatably attached, and link 22
The other end of the link 23
The other end of each is rotatably connected to the center of the axle 24. Then, as the distance between the vehicle body 20 and the axle 24, that is, the vehicle height increases or decreases, the link 23 moves up and down, and this up and down motion converts the link 22 into a rotational motion.

Here, when the vehicle height becomes high, the link 22 rotates clockwise in the figure, and when the link 22 exits from the preset "neutral vehicle height area" and crosses the "high vehicle height area" boundary. , High vehicle height signal SH is output from vehicle height sensor 21 as “0” → “1”, and conversely, when exiting from “high vehicle height area” and returning to “neutral vehicle height area”, high vehicle height signal SH is output. The output is “1” → “0”. Similarly, when the vehicle height becomes low, the link 22 rotates counterclockwise and the link 22
When the vehicle exits the "neutral vehicle height area" and crosses the "low vehicle height area" boundary, the vehicle height sensor 21 outputs the low vehicle height signal SL from "0" to "1", and conversely, "low vehicle height area" When the vehicle exits the “high range” and returns to the “neutral vehicle height range”, the low vehicle height signal SL is output as “1” → “0”.
Then, these signals SH and SL are input to the controller 19 as described above.

FIG. 3 shows a flow chart of the program of the controller 19 of the present invention, which will be described.

When the power switch is turned on, each set value is initialized in step SP ₁ , and then the output signal of the vehicle height sensor 21 is read in step SP ₂ . Then, in the next step SP ₃ , it is determined whether the spring constant and the damping force are to be increased or decreased, and the spring constant switching valve 15 for adjusting the spring constant and the variable throttle valve 16 for adjusting the damping force are operated. After the completion of step SP ₃ returns to step SP _1.

Subsequently, the subroutine of the switching valve operation request in step SP ₃ will be described with reference to Figure 4.

Step determines if high vehicle height signal SH or low height signal SL or "1" from the vehicle height sensor 21 read in step SP _2. That is, it is determined whether the vehicle height has entered the high vehicle height region or the low vehicle height region. When it is determined that the SH or SL signal is input as “1” in step, the process proceeds to step, and the time t ₁ when the signal is input is stored.

Next, in the step, high vehicle height signal SH or low vehicle height signal
Determine whether SL has changed from "1" to "0". That is, it is determined whether the vehicle height has moved from the high vehicle height area or the low vehicle height area to the neutral vehicle height area side. When the vehicle height signal in Step is determined to become "0" to "1", the process proceeds to step, the time t ₂ at that time is stored, further the time
The average time ta between t ₁ and time t ₂ is obtained.

In the step, it is determined whether or not a constant time T _{1 obtained} by subtracting the operating time of the spring constant switching valve 15 and the variable throttle valve 16 from 1/4 of the cycle of the natural vibration of the vehicle body from the average time ta has elapsed. If the time has not elapsed, proceed to step Spring constant switching valve 15
Is opened and the throttle of the variable throttle valve 16 is adjusted to switch the spring constant and damping force to low. If the predetermined time T ₁ has passed, the process proceeds to step. In step, determining whether the average (1/2 of an integral multiple of the period of natural vibration of the vehicle) the time T ₂ for a certain period of time T ₁ and the vehicle body vibration from time ta to stop attenuated and time plus has passed To do. Then, when it is determined that the time has elapsed, the process proceeds to step, and the spring constant and the damping force are switched to a low level. Adjust to switch spring constant and damping force to high.

Next, the operation of the above configuration and program will be specifically described with reference to FIGS. 5 (a) and 5 (b). 5 (a) shows the natural vibration of the vehicle body, and FIG. 5 (b) shows the pressure inside the gas-filled accumulator at that time.

The vehicle 20 vibrates and the vehicle height sensor 21 detects that the vehicle height has entered the high vehicle height region, and the signal SH outputs "1". This is determined by the step, the process proceeds to the step, and the time when the vehicle height enters the high vehicle height area (the time when the signal SH outputs "1") t ₁
Is memorized. Subsequently, when the vehicle height sensor 21 detects that the vehicle height is out of the high vehicle height region, and the signal SH outputs "0", the step determines this and proceeds to the step. In step, an average time ta of time t ₂ when the vehicle height exits the high vehicle height region and time t ₁ is calculated.

Further, when it is determined that the constant time T ₁ has passed in the step, a request is made to switch the spring constant and the damping force to high in the step, the spring switching valve 15 is closed in step SP ₃ , and the variable throttle valve 16 is turned on. Adjusted to switch high spring constant and damping force. The time T ₁ is the spring constant switching valve.
Since the operating times of 16 and the variable throttle valve 16 are taken into consideration, the time at which the spring constant switching valve closes is t ₄ .

After that, when the step determines that the time obtained by adding the times T ₁ and T ₂ has elapsed, a request is made to reduce the spring constant and the damping force at the step, and the spring constant switching valve 15 is opened at step SP _3. The variable throttle valve 16 is adjusted to switch the spring constant and the damping force to low. Further, the time at which the spring constant switching valve 15 and the variable throttle valve 16 complete their operations is t ₅ .

In this way, when the spring constant switching valve 15 is opened and closed, the pressure in the gas-filled accumulator 14 at the time of valve closing becomes the same as the pressure at the time of valve opening, as can be seen from FIG. 5 (b). Therefore, there will be no pressure difference between the accumulators 13 and 14.

(Effects of the Invention) As described in detail above, the present invention provides that the vehicle height is
Calculate the average time between the time when the vehicle height is above a predetermined height or the low vehicle height area below a predetermined height, and the time when the vehicle height exits from the high vehicle height range or the low vehicle height range Thus, the time when the maximum amplitude position is reached is obtained, and when a predetermined time when the amplitude becomes almost 0 from the maximum amplitude position has passed from the time when the maximum amplitude position is reached, the other accumulators and hydraulic cylinders are disconnected. Since the switching valve is controlled to the above value, the pressure of the other accumulators when switching the spring constant to a high value is almost 0. Therefore, when switching the spring constant to a low value, the pressure difference between the accumulators can be kept small. it can.

Therefore, it is possible to prevent the switching valve from being inoperative, and to prevent an uncomfortable change in vehicle height due to a rapid flow of pressure oil.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a hydraulic suspension system according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a mounting state of a vehicle height sensor, and FIG. 3 is a program of the controller of FIG. FIG. 4, FIG. 4 is a flow chart of the switching valve operation request subroutine of FIG. 3, FIG. 5 (a) is a graph showing the change over time of the vibration of the vehicle body, and FIG. 5 (b) is the inside of the accumulator. 3 is a graph showing the change over time in the pressure of FIG. 13,14 …… Accumulator 15 …… Spring constant switching valve 19 …… Controller 21 …… Vehicle height sensor

Claims (3)

[Claims] 1. A vehicle height of a vehicle, comprising one accumulator which is constantly connected to a hydraulic cylinder interposed between a vehicle body and wheels, and another accumulator which is connected to the hydraulic cylinder via a switching valve. In the hydraulic suspension device in which the spring constant can be varied by switching the switching valve based on a detection signal from a vehicle height sensor that detects, to cut off communication between the hydraulic cylinder and the other accumulator, The average of the time when the height is in the high vehicle height area above a predetermined height or in the low vehicle height area below a predetermined height and the time when the vehicle height exits from the high vehicle height area or the low vehicle height area The time at which the maximum amplitude position is reached is found by finding the time, and when a predetermined time in which the amplitude becomes almost 0 from the maximum amplitude position elapses from the time at which the maximum amplitude position is reached, the other accumulator Hydraulic suspension device which is characterized in that a controller for controlling the switching valve to shut off motor and the hydraulic cylinder. 2. The hydraulic suspension device according to claim 1, wherein the predetermined time for the amplitude to reach approximately 0 from the maximum amplitude position is set to 1/4 of the cycle of the natural vibration of the suspension. 3. A predetermined time after the switching valve is switched to shut off the other accumulator and the hydraulic cylinder,
3. The hydraulic suspension device according to claim 1, wherein the switching valve is controlled so that the other accumulator and the hydraulic cylinder communicate with each other.