JPS63130419A - Hydraulic suspension device - Google Patents

Abstract

PURPOSE:To prevent production of unpleasant sensation during switching of a spring constant in a hydraulic suspension device for vehicle by a method wherein after elapse of a specified time commencing in an average time of a time when a ground clearance enters a high or a low ground clearance region and a time when it is returned to a neutral ground clearance region, a spring constant is increased, and further after elapse of a specified time, a spring constant is returned to its original value. CONSTITUTION:A controller 19 detects a time when a ground clearance inputted from a sensor 18 enters a high or a low ground clearance region and a time when it is returned to its original value to determine an average time of the two times. A switching valve 15 is regulated so that after elapse of a specified time T1, obtained by subtracting the motion times of the switching valve 15 and a variable throttle valve 16 from 1/4 of a period of car body natural vibration, commencing in the average time, a spring constant is increased. Further, after elapse of a time T2 in which a car body vibration is damped and stopped, the spring constant is returned to its original value. This constitution prevents inoperation of the switching valve, and enables prevention of production of a sudden change in a ground clearance due to a sudden change in an oil pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic suspension device having a function of varying a spring constant.

(Conventional technology) Conventionally, hydraulic suspension systems for vehicles.

Some have variable spring constants.

In this system, multiple accumulators are connected to a suspension strut (hereinafter referred to as strut), one accumulator is connected horizontally to the strut, and the other seven accumulators are connected via switching valves. The spring constant can be varied by reducing the number of accumulators that open and close to communicate with the struts and change the gas chamber volume within the accumulators.

When such a hydraulic suspension 'A W is used, when driving on a flat road surface, the spring constant can be set low to obtain the optimum ride comfort, and the spring constant can be set high to adjust the pitching of the vehicle, etc. It is possible to reduce vibration and prevent deterioration of riding comfort.

In addition, the spring constant and g-damping force can be changed in advance by setting the vehicle height to a "neutral vehicle height region" where the vehicle is in a normal state, a "high vehicle height region" where the vehicle height is above a certain height, and a "high vehicle height region" where the vehicle height is below a certain height. "Low vehicle height area"
When the vehicle height sensor detects the ``high vehicle height area'' or ``low vehicle height area'' due to vibration, the switch fan is closed and the spring constant is increased to damp the vibration. When the vehicle height returns to the "neutral vehicle height region," the switching valve is opened to lower the spring constant.

(Problems to be Solved by the Invention) However, the above-mentioned hydraulic suspension installation in which the spring constant can be varied has the following problems.

When the vehicle vibrates up and down due to pitching motion etc. and the vehicle height sensor detects the "high vehicle height region" or "low vehicle height region" and increases the spring constant, the vehicle height may be lower than the "neutral vehicle height region". When the switching valve is closed at the position where the vehicle height has collapsed, the pressure in the other accumulators becomes the pressure at that vehicle height, the pitching motion subsides, and the switching valve opens when the vehicle height is in the "neutral vehicle height region". Sometimes, there is a large pressure difference between the pressure in one accumulator and the other, and the switching valve may not be able to open, or even if it can be opened, the pressure oil will suddenly flow into the lower accumulator. However, there was a problem in that changes in vehicle height caused unpleasant shocks.

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

(Means for Solving the Problems) As a means for solving the above problems and achieving the objective, an accumulator is connected directly to the suspension strut, and an accumulator is connected to the suspension strut via a switching valve. Consists of other accumulators,
In a hydraulic suspension device in which a spring constant can be varied by switching the switching valve based on a detection signal from a vehicle height sensor that detects the vehicle height, the vehicle height is
The time when the vehicle height changes from a preset neutral vehicle height region to a high vehicle height region above a certain height or a low vehicle height region below a certain height, and when the vehicle height changes to the above high vehicle height region or low vehicle height region. The switching valve is configured to increase the spring constant after a predetermined time has elapsed from the average time when the spring constant has been increased, and to return the spring constant to the original height after a predetermined time has elapsed from the time when the spring constant was increased. It controls the

(Function) Based on the average time of the time when the vehicle starts vibrating and the vehicle height changes from the neutral vehicle height range to the high vehicle height range or the low vehicle height range, and the time when the vehicle height returns to the neutral vehicle height range, For example, after 18 hours of the natural vibration period of the vehicle body have elapsed, the switching valve is closed to increase the spring constant and suppress vibration.

After a certain period of time has elapsed and the vibrations have attenuated, the switching valve is opened and the spring constant is lowered to improve riding comfort.

Here, the average time is the time between the time when the vehicle height enters the high vehicle height region or the low vehicle height region and the time when the vehicle height returns to the neutral vehicle height region. When 1/4 of the period of the natural vibration has passed from that time, the vibration reaches a position where the amplitude is O, so the switching valve is turned on when the vehicle height is in the neutral vehicle height region. The valve will be closed. In other words, the natural vibration of a vehicle changes in amplitude but has a constant period, so the maximum amplitude position (
If the amplitude becomes 0 (neutral vehicle height region) after a certain period of time (from the high vehicle height region or low vehicle height region) and the switching valve is closed at that time, the pressure in the other accumulators will be lower than when the valves are opened. Since the pressure in the accumulator is the same as that in the accumulator, there is no pressure difference between the accumulator and the accumulator.

(Example) Next, one embodiment of the present invention will be described based on the drawings.

First, the configuration of this embodiment will be explained using FIG.

The right 1f pressure unit 1 that supplies the pressure 1 mountain is a pump 2, a motor 3 that operates the pump 2, and a reservoir tank 4.
It consists of a filter 5 and a relief valve 6 provided at an inlet for sucking oil from the hydraulic unit 1. Pressure oil supplied from the hydraulic unit 1 passes through a check valve 7 and is stored in a gas-filled accumulator 8. Then, the motor 3 is activated by a signal from the pressure switch 9 attached to the gas-filled atomizer 8, and the pump 2 is repeatedly started and stopped, thereby properly supplying pressure oil.

The gas-filled accumulator 8 and the strand are connected via an oil supply side switching valve 11, and the strut l
O and the reservoir tank 4 are connected via an oil drain side switching valve 12. When raising the vehicle height, the oil supply side switching valve 11 is opened to supply pressure oil to the strut 10,
When lowering the vehicle height, the oil drain side switching valve 12 is opened to return pressure oil from the strut 10 into the reservoir tank 4.

Next, the mechanism for varying the spring constant will be explained.

Two gas-filled human-type accumulators 13 and 14 are connected to the strut 10 in parallel, and one of the gas-filled accumulators 14 is connected via a spring constant switching valve 15. The spring constant can be varied in two stages by opening and closing the spring constant switching valve 15 to change the gas chamber capacity and depletion of the gas-filled accumulator I3.

In addition, a variable throttle valve (electromagnetic switching adjustment valve) 16 is provided in the thread path connecting the strut 10 and the gas-filled accumulator 13, 14 for varying the spring constant.
The damping force of the strut 10 can be varied by adjusting the throttle (orifice, etc.) of the variable throttle valve IB using a rotary or launching type solenoid valve, a motor, or the like. Further, 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 IO.

The adjustment of the spring constant 9J exchange valve 15 and variable throttle valve 18 for varying the spring constant and damping force described above is performed using signals from various sensors IB that detect vehicle height, road surface conditions, roll conditions, sudden starts, sudden stops, etc. The controller 19 receives and processes the information, and the controller 19 issues a signal based on the determination result of the running state and driving situation.

Next, FIG. 2 shows an example of how the vehicle height sensor is installed, and the vehicle height sensor 21 is installed at the bottom of the vehicle body 20.
is attached, one end of a link 22 extending in the horizontal direction is rotatably attached to the central part 21a, the other end of the link 22 is attached to one end of a link 23 extending in the vertical direction, and the other end of the link 23 is attached to an axle. 24, and are rotatably connected to the central portions of each. 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 movement converts the link 22 into rotational motion.

Here, as the vehicle height increases, the link 22 rotates clockwise in the figure, and when the link 22 leaves the preset "neutral vehicle height area" and crosses the boundary of the "high vehicle height area", the link 22 rotates clockwise in the figure. , the high vehicle height signal SH is outputted from the vehicle height sensor 21 as "0"→"1", and conversely, when the vehicle leaves the "high vehicle height area" and returns to the "neutral vehicle height area", the high vehicle height signal ST( is output as "1" → "0".As in ρ1, when the vehicle height becomes lower, the link 22 rotates counterclockwise, and the link 22 moves out of the "neutral vehicle height area" and enters the "low vehicle height area". When the vehicle height sensor 21 crosses the boundary, the low vehicle height signal SL is output from "0" to "1", and conversely,
When the vehicle leaves the low vehicle height region J and returns to the "neutral vehicle height region", the low vehicle height signal SL is output from "l" to "O". These signals S)I and SL are input to the controller 19 as described above.

FIG. 3 shows a program 20 of the controller 19 of the present invention.
- Show and explain the chart.

When the power switch is turned on, each 1 predetermined value is initialized in step SPI, and then step SP2
The output signal of the vehicle height sensor 21 is read. Then, in the next step S23, it is determined whether to increase or decrease the spring constant and damping force, and the spring constant switching valve 15 that adjusts the spring constant and the variable throttle valve 18 that adjusts the g damping force are operated. . After completing step SP3, the process returns to step SP1.

Next, the subroutine for requesting the switching valve operation in step SP3 will be explained using FIG.

In step (2), the high vehicle height signal SH or the low vehicle height signal S from the vehicle height sensor 21 read in step SP2 is
It is determined whether L is 1". In other words, it is determined whether the vehicle height has entered the high vehicle height region or the low vehicle height region. In step (2), it is determined that the SH or SL signal has been input as "1". The process advances to step 1), and the time 1 at which the signal was input is stored.

Next, the high vehicle height signal S) at the step constant ■! Alternatively, it is determined whether the low vehicle height signal SL has changed from "1" to "0". That is, it is determined whether the vehicle height has moved from the high vehicle height region or the low vehicle height region to the neutral vehicle height region. When it is determined in step ■ that the vehicle height signal has changed from l'' to "0", the process proceeds to step ■, and the time t2 at that time is memorized.
Further, the time 1. An average time ta between and time t2 is determined.

In step (2), the spring constant switching valve 15 and the variable throttle valve 1 are
It is determined whether a certain period of time T1, which is obtained by subtracting the operation time of 6, has elapsed. If the time has not passed, proceed to step ①, open the spring constant switching valve 15, adjust the throttle of the variable throttle valve 16,
Switch the spring constant and damping force to low values. Further, if the fixed time T1 has elapsed, proceed to step ■. In step ■, the fixed time T1 from the average time ta and the time T when the vibration of the vehicle body is attenuated and stopped! (1 of the period of the vehicle's natural vibration
/2 (integer multiple of 2) has elapsed. If it is determined that the time has elapsed, the process proceeds to step 2, where the spring constant and damping force are switched to a lower value, and if it is determined that the time has not elapsed, the process proceeds to step 2, where the spring constant switching valve 15 is closed and the variable throttle valve 16 to increase the spring constant and damping force.

Next, the operations related to the above configuration and program will be specifically explained based on FIGS. 5(a) and 5(b). Note that Fig. 5(a) shows the natural vibration of the vehicle body, and Fig. 5(b) shows the natural vibration of the vehicle body.
) indicates the pressure inside the gas-filled accumulator at that time.

When the vehicle 20 vibrates, the vehicle height sensor 21 detects that the vehicle height has entered the high vehicle height region, and the signal SH outputs "■".

This is determined in step (2), and the process proceeds to step (2), where the time tr when the vehicle height enters the high vehicle height region (the time when the signal SH outputs "1") is stored. Subsequently, the vehicle height sensor 21 detects that the vehicle height has gone out of the high vehicle height region, and the signal S
When H outputs 0'', step (2) determines this and proceeds to step (2). In step (2), the average time ta between the time t2 when the vehicle height exits the high vehicle height region and the time tl is calculated. .

Furthermore, when it is determined in step (i) that a certain period of time has passed, a request is issued to switch the spring constant and damping force to a higher value in step (2), and in step SP3, the spring switching valve 15 is
is closed, the variable throttle valve 16 is adjusted, and the spring constant and damping force are switched to a high value. Note that since the time T1 takes into account the operating time of the spring constant switching valve 16 and the variable throttle valve 16, the time when the spring constant switching valve closes is t.
It becomes 4.

After that, when step (2) determines that the sum of time T1 and 1 has elapsed, a request to lower the spring constant and damping force is issued in step (2), and the spring constant switching valve 15 is opened in step SP3. The variable throttle valve 16 is adjusted,
The spring constant and damping force are switched low. Further, the time when the spring constant switching valve 15 and the variable throttle valve 16 complete their operation is t5.

When the spring constant switching valve 15 is opened and closed in this way, the pressure in the gas-filled accumulator 14 when the valve is closed becomes the same as the pressure when the valve is open, as can be seen from FIG. , there will be no pressure difference between each accumulator 13,14.

(Effects of the Invention) As explained in detail above, the present invention provides a method for determining the time when the vehicle height reaches a high vehicle height region of a certain height or more or a low vehicle height region of a certain height or less. After a certain period of time has elapsed from the average time when the vehicle height returns to the neutral vehicle height region, the spring constant is increased, and furthermore, after a certain period of time has elapsed from the time when the spring constant was increased, the spring constant and damping force are increased. Since it is configured to return to its original height, it is possible to create a state in which there is no pressure difference between the accumulators when switching the spring constant to a low value.

Therefore, the switching valve can be prevented from operating, and unpleasant changes in vehicle height due to rapid flow of pressure oil will not occur.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a hydraulic suspension device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the state of installation of a vehicle height sensor, and FIG.・Flowchart of the roller program. FIG. 4 is a flowchart of the switching valve operation request subroutine of FIG. FIG. 5(a) is a graph showing temporal changes in vibration of the vehicle body, and FIG. 5(b) is a graph showing temporal changes in pressure within the accumulator. 13.14...Accumulator 15...Spring constant switching valve 19・II@Controller 21 order...Vehicle height sensor fan] Figure 2

Claims (1)

[Claims] (1) Consists of one accumulator that is directly connected to the suspension strut and another accumulator that is connected to the suspension strut via a switching valve, and is based on a detection signal from a vehicle height sensor that detects the vehicle height. In a hydraulic suspension device in which a spring constant can be varied by switching the switching valve, the vehicle height is set in a high vehicle height range above a certain height from a preset neutral vehicle height range, or a certain height. After a certain period of time has elapsed from the average time of the time when the vehicle height reaches the following low vehicle height region and the time when the vehicle height leaves the high vehicle height region or the low vehicle height region,
A hydraulic suspension characterized by increasing the spring constant and further comprising a controller that controls a switching valve so as to return the spring constant to its original height after a certain period of time has elapsed from the time when the spring constant was increased. Device.