JPH02162113A - Suspension device for vehicle - Google Patents

Abstract

PURPOSE:To prevent a sudden variation of car height when an ignition switch is OFF by making the pressure setting of a hydraulic actuator by control valves for a specific period under the condition same as the object car height regulation condition, when the ignition switch is turned off. CONSTITUTION:A control unit 10 controls the current flowing time to control valves 7 by converting an ignition switch 11 ON and OFF. That is, when the ignition switch 11 is ON, the current is started to apply to the control valves 7 when the hydraulic pressure of an oil pump reaches a specific value. On the other hand, when the ignition switch 11 is OFF, the control valves 7 are operated delaying a specific time from the time of the switch OFF. As a result, the current flowing control condition so far is maintained for a specific time after the ignition switch is OFF. By such a constitution, a sudden variation of the car height owing to turning OFF of the ignition switch is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vehicle suspension device, and more particularly to a control device for adjusting road clearance in a suspension.

(Prior Art) As is well known, in automobile suspensions, a chamber is placed on the axis of a normal shock absorber.
By changing the supply/discharge amount of fluid, such as oil, in this chamber, the spring constant, spring stroke, and load clearance, so-called vehicle height, can be changed, resulting in changes in roll and nose. Improvements in ride comfort and vehicle body posture during dives or swashes.

Vehicle heights that can be set according to driving conditions have been realized.

Among the above-mentioned suspension functions, the vehicle height adjustment structure includes, for example, a switching valve that switches the supply and discharge direction when supplying and discharging oil from a hydraulic source to the cylinder chamber of a hydraulic actuator, which is arranged in the oil conduit. In addition, the hydraulic power source system for the hydraulic actuator is two systems: an oil pump driven by the engine and an accumulator that operates when the engine is stopped.While the engine is running, the vehicle height is controlled by the oil pump as the hydraulic power source. adjustment, and
When the engine is stopped, there is a structure that allows vehicle height adjustment using an accumulator as a hydraulic power source (for example,
85005).

In addition to this structure, as shown in FIG. When discharging, a control valve D consisting of a proportional pressure reducing valve with an unloading function is placed in the oil path C leading to the hydraulic actuator B, and this control valve D
For example, the on/off control required for oil supply/drain settings by vehicle height sensor (FLS, FR5, RLS, RR)
3) Control unit E including a microcomputer connected to
This is done by the output of

The above-mentioned control valve D is, as shown in FIG.
A pilot-operated type is used that adjusts the operating pressure on the hydraulic actuator side based on the pilot pressure, and the operating pressure at this control valve D is adjusted to adjust the pilot pressure as shown in Figure 8. It is designed to be obtained in proportion to the set valve current.

(Problems to be Solved by the Invention) By the way, in the vehicle height adjustment structure as described above,
First, in the case of the former structure, the vehicle height adjustment mechanism on each supply side is designed assuming that oil from the oil pump is supplied to the hydraulic actuator and oil from the accumulator is supplied to the hydraulic actuator. Because this mechanism enables the vehicle height to be maintained, there is a risk that the structure for maintaining the vehicle height may become complicated.

In addition, in the case of the latter structure, as is clear from Fig. 8, for example, when the ignition switch is turned off and the valve current to control valve D decreases, the opening of the pilot return pipe increases. Even if an attempt is made to maintain the pilot pressure by interposing an accumulator in the pipe leading to the control valve, the pilot pressure will inevitably decrease, and the operating pressure will follow suit. There is a problem in that the stroke of the hydraulic actuator that was previously set suddenly becomes smaller, causing the vehicle height to suddenly change to its lowest state.

SUMMARY OF THE INVENTION In view of the above-mentioned problems with the vehicle height adjustment structure, an object of the present invention is to use a simple structure to prevent oil from rapidly flowing out from within the hydraulic actuator even when the ignition switch is turned off. To provide a suspension device for a vehicle capable of suppressing sudden changes in vehicle height set up to 100 degrees.

(Means for Solving the Problems) In order to achieve this object, the present invention controls the supply and discharge state of hydraulic pressure to the hydraulic actuator by operating a control valve provided between the hydraulic actuator and the hydraulic power source. A vehicle suspension device that controls a vehicle height by controlling a vehicle height, the control section being connected to an output side of the control valve and inputting the on/off state of an ignition switch, the control section being configured to control a vehicle height by controlling a vehicle height. It is proposed that the pressure setting of the hydraulic actuator by the control valve be performed for a predetermined period of time when the vehicle is switched to the OFF state so as to obtain the same state as when adjusting the vehicle height to the target vehicle height.

(Function) According to the present invention, when the ignition switch is turned off, the pilot return conduit in the control valve is maintained at the previously set opening degree, and the control valve is connected to the hydraulic actuator via the control valve. Prevents sudden changes in vehicle height by suppressing the sudden loss of oil.

(Embodiment) Hereinafter, details of an embodiment of the present invention will be explained with reference to FIGS. 1 to 5.

FIG. 1 is a symbolic circuit diagram corresponding to FIG. 6 for explaining a hydraulic control system in a vehicle suspension system according to an embodiment of the present invention.

The feature of this embodiment is that the hydraulic control valve disposed between the hydraulic power source and the hydraulic actuator is set in a controlled state, in other words, in a single energized state, for a predetermined period of time after the ignition switch is turned off. Therefore, after maintaining the pressure in the hydraulic actuator that has been set so far, the suspension stroke, so-called, the disappearance of oil from the hydraulic actuator is performed slowly.

That is, a pipe line 3 leading from an oil pump 1 driven by an engine to a hydraulic actuator 2 includes an oil pressure sensor IA, an accumulator 4 for correcting oil pulsation, a filter 5. Check valves 6 for preventing backflow of oil from the hydraulic actuator 2 are arranged respectively, and on the downstream side of the above-mentioned accumulator 4 and the upstream side of the hydraulic actuator 2, a pressure control valve 7 (for example, a proportional pressure reducing valve) is arranged. A control valve (hereinafter referred to as a control valve) is arranged. In FIG. 1, the reference numeral 8 indicates a constant pressure relief valve, and the reference numeral 9 indicates a reservoir.

The control valve 7 described above is configured to set the pressure for the hydraulic actuator 2 by a control section 10 shown in FIG.

That is, the control unit 10 described above, as shown in the second diagram,
A microcomputer 10A that performs arithmetic control processing, and an ROI that stores a basic program containing basic data for arithmetic control in this microcomputer IOA.
A memory IOB consisting of a memory I and a RAM that captures input data from each sensor, which will be described later, is used.

An I10 interface IOC serving as an input/output signal processing unit is connected to each of these processing units, and the input port of this I10 interface IOC detects an on signal from the ignition switch 11 and outputs the signal. A waveform shaping circuit 12 that shapes the waveform of the waveform, an oil pressure sensor IA that detects the oil pressure from the oil pump 1, and a vehicle height sensor A connected to vehicle height sensors 13 to 16, which are installed on each wheel side and include, for example, a rotary encoder. /D converters 17 are connected to each.

Further, a constant current circuit 18 for driving the control valve 7 for pressure control for the hydraulic actuator of each wheel is connected to the output boat of the above-mentioned I10 interface IOC.

In the control section 7 including such processing sections, the energization control time for the control valves from the time when the ignition switch is turned on and off is set as shown in the third figure.

That is, in FIG. 3, when the ignition switch 11 is turned on and the oil pressure from the oil pump 1 reaches a predetermined value, the control valve 7 is energized and starts setting the pressure, and in conjunction with this, the vehicle height is adjusted. This is to obtain the output from the sensor.

Furthermore, when the ignition switch 11 is turned off, the operation of the control valve is stopped after a predetermined time delay.

Therefore, even if the ignition switch 11 is turned off and the oil pressure from the oil pump 1 disappears, the energization control at the control valve 7 will be maintained in the state that has been set up until now. The pilot pressure from 7 is supplied via the supply pressure from the accumulator 4 to the control valve 7 whose opening degree corresponds to the current set so far, and the hydraulic pressure setting for the hydraulic actuator 2 is maintained. That will happen.

By setting the operating time of the control valve 7 in this manner, within the predetermined delay time after the ignition switch 11 is turned off, the high pressure is applied from the accumulator 4 to the control valve 7 to prevent the ignition switch 11 from being turned off. In other words, the pressure to the hydraulic actuator 2 is set in the same state as IJRa to satisfy the target vehicle height, so sudden stroke changes on the hydraulic actuator 2 side can be suppressed, and the vehicle height remains the same. is maintained in the state of

On the other hand, as the vehicle height is maintained by the front pressure of the control valve 7 described above, the accumulator 4
As explained in FIGS. 7 and 8, the pilot oil to the
Since the pilot pressure is refluxed, the reduced pilot pressure obtained by the reflux appears as a decrease in the stroke of the hydraulic actuator 2, and as this pressure reduction is gradually carried out, the stroke of the hydraulic actuator is reduced, in other words. , the vehicle height will be lowered relatively slowly.

Since this embodiment has the above structure, its operation is performed according to the flowchart shown in FIG.

That is, after determining the operation state of the ignition switch 11, if the switch 11 is in the on state, the engine rotation speed is calculated, the oil pressure value from the oil pressure sensor is detected, and the engine is determined from the above calculation. It is determined whether the rotation speed and oil pressure value are below a predetermined value. That is, in this determination, it is determined whether the engine is stalled or not, and whether or not an oil pressure reduction accident has occurred in the oil supply path is determined.

On the other hand, by determining the state of the ignition switch 11 described above, if the ignition switch 11 is set to the OFF state, and if the engine speed or oil pressure value is below a predetermined value, the state shown in FIG. Set a timer to set the delay time in
According to the time setting by this timer, the timing for stopping the operation of the control valve is determined, and the return path of the pilot pressure in the control valve 7 is maintained at the opening degree set so far.

Therefore, the oil return from the hydraulic actuator 2 is
This is done in accordance with the opening degree of the return path that has been set up until now. period), the drop in vehicle height is suppressed, and in the subsequent period (period indicated by the reference numerals in Figure 5), the vehicle height decreases relatively slowly. This will suppress the decline in

According to this embodiment, even when the oil pressure in the oil pressure source disappears, such as when the engine stalls when the oil pump is inactive, or when the pipe line from the oil pump breaks, the vehicle height will be lowered. can be prevented.

(Effects of the Invention) As described above, according to the present invention, the control valve for pressure control provided between the hydraulic power source and the hydraulic actuator is controlled to be energized for a predetermined period of time after the ignition switch is turned off. As a result, in the return path of the pilot pressure from the control valve, the return of oil from the hydraulic actuator via the control valve is suppressed and occurs relatively slowly. This makes it possible to suppress changes in vehicle height, and by simply controlling the energization time to the control valve, it is possible to avoid causing discomfort to the occupants.

[Brief explanation of the drawing]

Fig. 1 is a symbolic circuit diagram of a vehicle suspension device according to an embodiment of the present invention, Fig. 2 is a block diagram showing a control unit used in the hydraulic circuit shown in Fig. 1, and Fig. 3 is a block diagram showing the control unit used in the hydraulic circuit shown in Fig. 2. A diagram showing the characteristics of the control section, FIG. 4 is a flowchart for explaining one action in the control section shown in FIG. 2,
Fig. 5 is a diagram for explaining the characteristics according to the embodiment of the present invention, Fig. 6 is a symbolic circuit diagram showing an example of a vehicle height adjustment structure in a suspension device, and Fig. 7 is a diagram used in the circuit shown in Fig. 6. A combination circuit diagram showing the structure of the control valve,
FIG. 8 is a diagram for explaining the characteristics of the control valve shown in FIG. 7. 1... Oil pump, IA... Oil pressure sensor, 2...
- Hydraulic actuator, 3... Oil passage, 3A... Bypass passage, 7... Control valve forming a hydraulic control valve, 9.
...Reservoir, 10...Control unit, 11...Ignition switch, 13-16...Vehicle height sensor. 21st! i Figure 3 Figure 5 Figure 4 Figure 8 Figure 02 0.4 0.60B +, 0 No Lua? , i destination I(A)

Claims (1)

[Claims] In a vehicle suspension device that controls vehicle height by controlling the supply and discharge state of hydraulic pressure to the hydraulic actuator by operating a control valve provided between the hydraulic actuator and a hydraulic source. , a control unit connected to the output side of the control valve and inputted with the on/off state of the ignition switch, and the control unit, when the ignition switch is switched to the off state, for a predetermined period of time, A suspension device for a vehicle, characterized in that the pressure setting of the hydraulic actuator by the control valve is performed so as to obtain the same state as when adjusting the target vehicle height.