JPH0640233A - Suspension control device - Google Patents

Abstract

PURPOSE:To control vehicle height adjusting speed to be almost constant without using a fixed orifice. CONSTITUTION:In a suspension control device for supplying/discharging pressure oil to/from a hydraulic cylinder, interposed between an axle and a body, from a hydraulic power source 2 by the opening/closing of a switching valve 6 so as to adjust the height of a vehicle, a proportional solenoid type relief valve 20 is interposed between the primary side duct 5 of the switching valve 6 and an oil tank 3 in the hydraulic power source 2, and oil pressure in the hydraulic cylinder 1 is detected by a pressure sensor 21 and its signal is taken into a controller 10. The proportional solenoid type relief valve 20 is controlled by a command from the controller 10 to generate difference between relief pressure and cylinder pressure so that the supply-discharge speed of pressure oil is made almost constant to make the vehicle height adjusting speed almost constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension control device capable of arbitrarily controlling a vehicle height.

[0002]

2. Description of the Related Art Conventionally, this type of suspension control device has been constructed as shown in FIG. In the figure,
1 is a hydraulic cylinder interposed between the axle and the vehicle body, 2
Is a hydraulic pressure source including the oil tank 3 and the pump / motor 4. The hydraulic cylinder 1 and the hydraulic pressure source 2 are connected by a pipe line 5, and an electromagnetic on-off valve (supply / exhaust oil valve) is connected to the pipe line 5. 6 is interposed. Further, the pipeline 5 on the hydraulic pressure source 2 side of the on-off valve 6
A sub-pipe 7 is provided that connects the oil tank 3 with the oil tank 3 in the hydraulic power source 2, and a relief valve 8 with an electromagnetic on / off valve is provided in the sub-pipe 7. Further, a vehicle height sensor 9 is attached to the hydraulic cylinder 1, and its signal is sent to a controller 10 provided separately. Controller 10
Determines the necessity of oil supply / drainage based on the signal from the vehicle height sensor 9, and at the time of oil supply, the pump / motor 4 is turned on, the relief valve 8 is turned off, and the opening / closing valve 6 is turned on to turn the hydraulic cylinder 1
Is supplied with high pressure oil, while the relief valve 8 is turned on and the opening / closing valve 6 is turned off when the oil is discharged, the pressure oil in the hydraulic cylinder 1 is returned to the oil tank 3 through the relief valve 8, and thereby the vehicle height is increased. Will be adjusted. Reference numeral 11 is a gas-filled spring means connected to the hydraulic cylinder 1 through an orifice 12, and the spring means 11 provides a soft ride comfort.

By the way, in this type of suspension control device, if the vehicle height adjusting speed is too high, not only does it give an occupant an unpleasant feeling but also a safety problem. Therefore, conventionally, the hydraulic cylinder 1 and the opening / closing valve 6 are conventionally used. A fixed orifice 13 is provided in the pipe line 5 between and to control the flow of pressure oil to suppress a sudden change in vehicle height. Figure 4
Shows one wheel, and other wheels are also provided with the same hydraulic cylinders, opening / closing valves, etc., respectively, and the same pressure oil is supplied to these through a branch pipe 14 branched from the pipe line 5. It is like this.

[0004]

However, according to the conventional suspension control device provided with the fixed orifice 13, the orifice passage is usually very narrow (diameter of about 0.3 mm), so that dust in the circuit is There was a risk of clogging, and there was a problem of poor durability and reliability. Further, in this conventional suspension control device, the vehicle height adjusting speed largely depends on the pressure of the hydraulic cylinder 1, that is, the cylinder pressure. When the cylinder pressure changes due to the change of the load, the vehicle height adjusting speed also changes, and the vehicle height adjusting speed changes. There was also a problem that it was difficult to keep the speed constant.

The present invention has been made in view of the above-mentioned conventional problems, and provides a suspension control device which can control the vehicle height adjusting speed to be substantially constant without using a fixed orifice, and which is therefore highly durable and reliable. With the goal.

[0006]

In order to achieve the above object, the present invention has a hydraulic cylinder interposed between an axle and a vehicle body, and has an opening / closing valve in a pipe line connecting the hydraulic cylinder and the hydraulic source. In a suspension control device that is interposed and controls the on-off valve by a controller to supply and discharge pressurized oil to and from the hydraulic cylinder to adjust the vehicle height, a pipeline on a hydraulic source side of the on-off valve and an oil tank in the hydraulic source. A proportional electromagnetic relief valve is provided in a sub-pipe connecting to and a pressure sensor for detecting the hydraulic pressure in the hydraulic cylinder is provided, and the controller is provided with
A pressure control device for controlling the proportional electromagnetic relief valve based on a signal from the pressure sensor to generate a predetermined differential pressure before and after the opening / closing valve is added.

[0007]

In the suspension control device configured as described above, the differential pressure applied to the front and rear of the on-off valve is set to a predetermined value by controlling the relief pressure of the proportional electromagnetic relief valve according to the magnitude of the cylinder pressure. As a result, the vehicle height adjustment speed is controlled to be substantially constant.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a suspension control device according to this embodiment. Since the basic structure of the hydraulic circuit is the same as that shown in FIG. 4, the same parts are designated by the same reference numerals and the description thereof will be omitted. The feature of this embodiment is that the fixed orifice (13) is eliminated from the pipeline 5, and the auxiliary solenoid valve is replaced by the proportional electromagnetic relief valve (hereinafter, proportional relief valve) in the auxiliary pipeline 7 instead of the relief valve 8 with the electromagnetic ONF valve. The pressure sensor 21 for detecting the oil pressure in the hydraulic cylinder 1 is provided, and the controller 10 controls the proportional electromagnetic relief valve 20 on the basis of a signal from the pressure sensor 21. The point is that a pressure control circuit (not shown) for generating a predetermined differential pressure is added before and after the on-off valve 6. Here, the relief pressure Pr of the proportional electromagnetic relief valve 20 is in a linear relationship with the solenoid current I as shown in FIG. 2, so that the differential pressure control means transfers the proportional solenoid relief valve 20 to a predetermined solenoid. An arbitrary relief pressure Pr can be obtained by outputting the current I. In FIG. 1, 22 is the relief pressure P.
It is a second pressure sensor for monitoring r.

In the suspension control device constructed as described above, when refueling, a predetermined solenoid current I is output from the pressure control device in the controller 10 to the proportional electromagnetic relief valve 20 based on a signal from the pressure sensor 9. The control is performed so that the hydraulic pressure (relief pressure) Pr on the primary side of the opening / closing valve 6 is higher than the cylinder pressure Pc by a predetermined amount, and the pressure oil is supplied to the hydraulic cylinder 1 via the opening / closing valve 6 at a predetermined speed. It On the other hand, at the time of draining the oil, control is performed so that the relief pressure Pr becomes a pressure lower than the cylinder pressure Pc by a predetermined amount, and the pressure oil in the hydraulic cylinder 1 passes through the opening / closing valve 6 and the proportional electromagnetic relief valve 20 to a predetermined speed. Is returned to the oil tank 3. That is, both when the vehicle height is increased (when refueling) and when the vehicle height is decreased (when oil is drained), pressure oil is supplied and discharged at the respective predetermined speeds, so the vehicle height adjustment speed does not depend on the size of the vehicle load. It becomes almost constant both when the vehicle height increases and when the vehicle height decreases.

The control configuration of the pressure control device in the controller 10 of this embodiment will be described below more specifically with reference to FIG.

After the start in step S1 and the initialization in step S2, in step S3, the signals regarding the vehicle height H and the cylinder pressure Pc are read from the vehicle height sensor 9 and the pressure sensor 21, and are written in the memory, and the step S4 is performed.
Then, the deviation ΔH from the target vehicle height H _ref is calculated. Next, in step S5, it is determined whether or not the vehicle height adjustment is necessary depending on whether or not the absolute value of the deviation ΔH is larger than the reference deviation ΔH _th (dead band). If the vehicle height adjustment is completed or unnecessary, the process proceeds to step S18 and thereafter.

If vehicle height adjustment is required, it is first determined in step S6 whether vehicle height adjustment has already been started. If vehicle height adjustment has not been started (J = 0), the following steps are performed in step S7. It is determined whether or not the operations in steps S8 and S9 are. And the operation is the first time (X = 0)
If so, the pump / motor 4 is turned on in step S8. At this time, in order to make the operation of the pump / motor 4 smooth, the relief pressure is set to zero and the pump / motor 4 is started from no load. Next, in step S9, the proportional electromagnetic relief valve 20 outputs a command current (solenoid current) I _(Pr) that obtains the same relief pressure Pr as the cylinder pressure Pc. A low-pass filter (not shown) is provided in the output circuit of the controller 10, and the actual current gradually rises even when the instruction current I _(Pr) is output. Pc
The reason for setting = Pr is to prevent oil hammer when the on-off valve (supply / exhaust oil valve) 6 to be operated thereafter is opened.

Next, in step S10, steps S8 and S
The completion of the process of 9 is counted (X = 1), and the instruction current I _(Pr) is compared with the actual solenoid current I in step S11 to determine whether or not they match. If so, the opening / closing valve 6 is turned on (opened) in step S12. Next, in step S13, it is determined whether the vehicle height is high or low, that is, whether the vehicle is drained or refueled.
H> 0), the relief pressure Pr (= Pc −) in step S14.
ΔP) is determined, and if refueling (ΔH ≦ 0), the relief pressure Pr (= Pc + ΔP) is similarly determined in step S15, and the instruction current I _(Pr) for obtaining each relief pressure Pr is determined in step S16. The flag is output and each flag is set or reset in step S17 (J = 1 indicates that the vehicle height is being adjusted).

On the other hand, in step S18, it is determined whether or not the vehicle height is being adjusted. If the vehicle height is being adjusted (J = 1), then in step S19, it is determined whether or not the operation in the following step S20 is the first operation. Is the first time (Y = 0), the command current I _(Pr) for obtaining the relief pressure Pr that is the same as the cylinder pressure Pc, which is necessary to prevent the oil hammer, is applied to the proportional electromagnetic relief valve 20 in step S20. ₎ Is output. Then, in step S21, the completion of the process in step S20 is counted (Y-1), and in step S22, it is determined whether the following steps 23 to 25 are the first time, and the following operation is the first time (Z = 0). If there is, the instruction current I _(Pr) is compared with the actual solenoid current I in step S23,
It is determined whether or not they match, and if they match, the flow rate in the hydraulic circuit becomes substantially zero and the vehicle height adjustment stops, so the opening / closing valve 6 is turned off (closed) in step S24. Next, in step S25, the instruction current I _(Pr) that makes the relief pressure Pr zero is output, and in step S26, it is determined whether the instruction current I _(Pr) and the solenoid current I (which are zero in this case) match. It is determined and if they match, step S2
The pump / motor 4 is stopped at 7 and each flag is reset at step S28. In this embodiment, since the on-off valve 6 is opened after the cylinder pressure Pc and the relief pressure Pr are made equal to each other, the oil hammer can be eliminated and the noise can be reduced.

It should be noted that the above-mentioned processing has been described for one wheel, but for four wheels, the cylinder pressures do not necessarily match for each wheel, so if the difference between these wheels is considerably large. Therefore, it is difficult to adjust the vehicle height at once. In such a case, either control the wheels one by one, or the cylinder pressures on the left and right wheels are considered to be almost the same, so first adjust the vehicle height for the two front wheels and then the two rear wheels. It is desirable to adjust the vehicle height in two steps, such as adjusting the vehicle height.

In the above embodiment, the vehicle height is adjusted by controlling the relief pressure Pr both when the vehicle height is increased and when the vehicle height is decreased. Since the sudden change in the vehicle height is likely to occur, the pressure of the relief pressure Pr may be controlled only when the vehicle height decreases, and the vehicle height adjustment control similar to the conventional one may be performed when the vehicle height increases. If necessary,
Conversely, the vehicle height may be adjusted by controlling the relief pressure Pr only when the vehicle height increases.

Further, in the above embodiment, the relief pressure P at the time of supply / discharge is set in steps S14 and S15 of FIG.
r is a value obtained by adding and subtracting a predetermined amount ΔP to the cylinder pressure Pc. In this case, the predetermined amount ΔP is set to a different value during refueling and draining, and the vehicle height adjustment speed when the vehicle height increases and when the vehicle height decreases. May be different.

Further, in the above embodiment, the step S11 in FIG. 3, S23 and S25 in the relief pressure Pr is a desired value and became whether the actual solenoid current I _(Pr)
However, the present invention is not limited to this, and it may be seen from the relationship between the actual relief pressure from the second pressure sensor 22 and the desired relief pressure Pr.

[0020]

As described above in detail, according to the suspension control device of the present invention, the proportional electromagnetic relief valve is controlled so that the differential pressure applied to the front and rear of the on-off valve becomes a predetermined value. Therefore, the vehicle height adjustment speed can be controlled to be substantially constant, which has an effect of not only eliminating the discomfort given to the occupant but also greatly contributing to the improvement of safety. Also, since the fixed orifice can be eliminated from the hydraulic circuit, malfunctions due to clogging of dust can be prevented, durability reliability is improved, and a simple on-off valve can be used as it is. Therefore, there is an effect that the reliability of the device is further improved and a cost advantage is established.

[Brief description of drawings]

FIG. 1 is a system diagram showing a structure of a suspension control device according to the present invention.

FIG. 2 is a correlation diagram showing a relationship between relief pressure and solenoid current of an electromagnetic proportional electromagnetic relief valve used in the present invention.

FIG. 3 is a control flow diagram showing the processing contents of the suspension control device.

FIG. 4 is a system diagram showing a structure of a conventional suspension control device.

[Explanation of symbols]

 1 Hydraulic Cylinder 2 Hydraulic Source 3 Oil Tank 5 Pipe Line 6 Opening / Closing Valve 7 Sub Pipeline 10 Controller (Pressure Control Device) 20 Proportional Electromagnetic Relief Valve 21 Pressure Sensor

Claims (1)

[Claims] 1. A hydraulic cylinder is provided between an axle and a vehicle body, and an opening / closing valve is provided in a pipe line connecting the hydraulic cylinder and a hydraulic pressure source. The controller controls the opening / closing valve to control the hydraulic pressure. In a suspension control device for supplying / discharging pressure oil to / from a cylinder to adjust a vehicle height, a proportional electromagnetic relief valve is interposed in a sub-pipe line connecting a pipeline on the hydraulic pressure source side of the on-off valve and an oil tank in the hydraulic pressure source. A pressure sensor for detecting the hydraulic pressure in the hydraulic cylinder is provided, and the controller controls the proportional electromagnetic relief valve based on a signal from the pressure sensor to control a predetermined differential pressure before and after the opening / closing valve. A suspension control device characterized in that a pressure control device for generating is added.