JPH05305809A - Suspension control device of vehicle - Google Patents

Abstract

PURPOSE:To improve the responsiveness of a pressure control valve at the time of the very low temperature to restrain the deterioration of riding comfort ableness by using shape memory springs, the spring constants of which are lowered below a preset temperature as both end springs of three-way spool valves of pressure control valves and using variable orifices, the flow resistances of which are lowered below a preset temperature. CONSTITUTION:The suspension characteristics of hydraulic actuators 5FL-5RR of the respective wheels are controlled by the control pressure of operating oil which is supplied from a reservoir tank Assy 1 through a pump Assy 2 and a multi-valve 3 and pressure-control valves assy 4F, 4R. Shape memory springs, the spring constants of which are lowered below a designated preset temperature, are used as return springs 11a, 11b of three-way spool valves 10 of pressure control valves 6FL-6RR, and variable orifices, the flow resistances of which are lowered below a designated preset temperature, are used as orifices 12b, 13 for water-in-oil separation control and pressure control valves 6FL-6RR. Thus, the riding comfortableness of a vehicle is stable even in a low temperature area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension controller for controlling suspension characteristics of a vehicle, and more particularly to a suspension controller suitable for improving temperature dependence of hydraulic characteristics of an active suspension apparatus.

[0002]

2. Description of the Related Art An active suspension device for controlling suspension characteristics of a vehicle in accordance with various conditions such as road conditions, running conditions, steering conditions, etc. has been developed in various ways, and one example thereof is Japanese Patent Laid-Open No. 42321
There is one described in Japanese Patent Publication.

This active suspension device is provided between a control valve for controlling the working fluid pressure supplied between each wheel of the vehicle and the vehicle body and a fluid pressure supply device for generating the working fluid pressure. When the supply pressure to the control valve becomes equal to or lower than a predetermined pressure, a pressure holding portion that closes the control valve side is interposed, and an on-off valve is provided in the supply side pipe between the fluid pressure supply device and the pressure control valve. A throttle and a throttle are provided in parallel, and the opening / closing valve is opened after a predetermined time delay when the fluid pressure supply device is started. According to this active suspension device, since the opening / closing valve is opened by a predetermined time delay when the fluid pressure supply device is started, the fluid pressure control system including the pressure control valve and the fluid pressure cylinder is provided by the pressure holding portion. When the fluid pressure supply device is started after the closed circuit has been closed, the fluid pressure is gradually supplied to the control valve to prevent a sudden increase in vehicle height. In this type of active suspension device, hydraulic oil is mainly used as the working fluid.

[0004]

For example, in the conventional active suspension device described above, there is no particular problem when the temperature of the working oil as the working fluid is relatively high and its viscosity is stable. However, at a low temperature when the viscosity of the hydraulic oil increases, the damping force increases as the viscosity increases, that is, the transmission force from the wheels to the vehicle body increases. There is a problem that the riding comfort deteriorates.

Of course, the temperature dependence of the viscosity of the hydraulic oil has not been improved. For example, there is an active suspension device using a solenoid valve described in Japanese Utility Model Laid-Open No. 2-67177 as an example. However, most of them compensate for the change in the flow rate gain of the control valve at high temperatures, and the actual situation is that sufficient measures have not yet been taken to improve the above-mentioned conditions at extremely low temperatures. ..

It is an object of the present invention to provide a suspension control device for a vehicle which solves the above problems by improving the response of the pressure control valve and reducing wasteful piping resistance at extremely low temperatures. To do.

[0007]

As a result of intensive studies to achieve the above object, the present inventor has found that the spring constant of a pressure control valve used in an active suspension is lowered below a set temperature, and Attention was paid to reducing the flow resistance of the orifice provided at the temperature below the set temperature. Specifically, we have found that in the former case, the spring of the control valve is a shape memory spring whose spring constant decreases below a set temperature, and in the latter case, a variable orifice is provided with an on-off valve. Among them, the use of a shape memory spring for the spring of the control valve is disclosed in the above-mentioned Japanese Utility Model Laid-Open No. 2-67177, but the solenoid valve described in this publication is, as described above, a flow control valve at high temperature. It was developed for compensating for a flow rate gain change, and its technical idea is different from the present invention.

That is, the suspension control device for a vehicle according to claim 1 of the present invention comprises a fluid pressure cylinder interposed between each wheel of the vehicle and the vehicle body, a supply port connected to a fluid pressure source, A three-way spool valve having a return port and a three-way spool valve having an output port connected to the fluid pressure cylinder side. By giving a control pressure command to the pressure control valve, the three-way spool valve A controllable pressing force is applied to one spool end side, the control pressure output from the output port is fed back to the other spool end side, and the control pressure of the output port is adjusted according to the pressing force. In a suspension control device for controlling suspension characteristics of a vehicle by controlling springs provided at both ends of the three-way spool valve of the pressure control valve to a predetermined set temperature or less. Spring constant is characterized in that it has a shape memory spring falls.

According to a second aspect of the present invention, there is provided a suspension control device for a vehicle, wherein a fluid pressure cylinder interposed between each wheel of the vehicle and a vehicle body, a supply port connected to a fluid pressure source, A three-way spool valve having a return port and a three-way spool valve having an output port connected to the fluid pressure cylinder side. By giving a control pressure command to the pressure control valve, the three-way spool valve A controllable pressing force is applied to one spool end side, the control pressure output from the output port is fed back to the other spool end side, and the control pressure of the output port is adjusted according to the pressing force. In a suspension control device that controls the suspension characteristics of a vehicle, an orifice provided in a pipe constructed as a fluid passage is orientated below a predetermined set temperature. Flow resistance of the office is characterized in that it has a variable orifice decreases.

[0010]

In the suspension control device for a vehicle according to the first aspect of the present invention, the springs provided at both ends of the three-way spool valve of the pressure control valve are shape memory springs whose spring constant decreases below a predetermined set temperature. For this reason, in the suspension control device for a vehicle according to claim 2 of the present invention, the orifice provided in the pipe constructed as the fluid passage is changed so that the flow resistance of the orifice is lowered at a predetermined set temperature or lower. Because it was an orifice,
For example, when the working fluid is working oil, the damping force frequency characteristic of the suspension device when the fluid pressure cylinder is vibrated at a constant speed suddenly changes (rapidly increases) according to the fluid temperature (oil temperature). By setting a relatively low temperature, the pressure gain of the hydraulic fluid increases below the inflection point where the damping force that affects the ride comfort of the vehicle drops sharply, and the suspension characteristics control as the original active suspension device is controlled. Functions and the riding comfort of the vehicle is stable even in a low temperature range.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an active suspension system using a vehicle suspension control system according to the present invention. First, a hydraulic valve for hydraulic oil used as a working fluid and a functional valve having various functions ( The configuration of the multi valve will be described. After the pulse pressure of the hydraulic oil of the reservoir tank assembly 1 is reduced by the pump accumulator 30 from the pump assembly 2, the multi-valve 3 having various functions such as filtering, regulation / controlling / holding of the supply pressure, and suppression of oil separation. Via a hydraulic pressure control valve assembly 4F and a rear wheel control valve assembly 4R, and the hydraulic actuators 5FL to 5FL, each of which is composed of a hydraulic cylinder or the like provided on each wheel of the vehicle, are controlled by respective control pressures. The suspension characteristics are controlled by 5RR, and the oil is cooled from the oil cooler 31 to the reservoir tank assembly 1 through the multi-valve 3. The separation in oil means a phenomenon in which a surge pressure is generated when the gas generated in the oil is crushed in the return pipe.

The reservoir tank assembly 1 includes the reservoir tank 32 and the reservoir tank 3 as in the conventional case.
Oil filter 33 installed in return side pipe 35
And a check valve 34 provided in a bypass circuit of the oil filter 33. The pump assembly 2 has an oil pump 3 whose suction side is connected to the reservoir tank 32 and which is rotated by a drive source such as an engine.
6 and a check valve 37 connected to the discharge side of the oil pump 36.

The pump accumulator 30 is connected to the supply side pipe 38 from the pump assembly 2. As in the conventional case, the multi-valve 3 includes a flow control valve 8, a check valve 44, which includes an oil filter 39 and a check valve 40 thereof, a relief valve 41 which regulates the supply pressure, a fixed orifice 42 and an electromagnetic switching valve 43. The operation check valve 45, the fixed orifice 46, and the fail-safe valve 9 including the electromagnetic switching valve 47, the variable orifice 13 that suppresses oil separation, and the like are included in the present invention. It uses a temperature-dependent type that reduces Since this variable orifice is a feature of the present invention, it will be described later in detail together with other variable orifices used in the hydraulic circuit of the embodiment.

In the multi-valve 3 of this configuration example, an oil filter 39 is connected downstream of the pump accumulator 30 in the supply side pipe 38 from the pump assembly 2, and a filter clogging formed in parallel with the filter 39 is provided. The check valve 40 is interposed in the bypass circuit at that time. Further, the pressure on the downstream side of the supply side pipe 38 and the upstream side of the return side pipe 35 corresponds to each wheel of the control valve assemblies 4F, 4R via the pressure holding portion 7 and the fail-safe valve 9. The control valves 6FL to 6RR are connected to the input port i and the return port o.

The pressure holding portion 7 formed between the supply side pipe 38 and the return side pipe 35 on the downstream side of the oil filter 39 has an electromagnetic switching valve 43 connected on the downstream side of the oil filter 39. , The fixed orifice 42 interposed in the bypass circuit of the electromagnetic switching valve 43, and the electromagnetic switching valve 4
3 is a relief valve for setting a line pressure in a normal state, which is interposed by connecting a check valve 44 provided on the downstream side of 3 and an upstream side of the bypass circuit of the electromagnetic switching valve 43 and the return side pipe 35. A valve 41 and an operation check valve 45 to which the line pressure on the return side upstream of the relief valve 41 and downstream of the fail-safe valve 9, that is, on the pressure control valves 6FL to 6RR side is supplied as pilot pressure. Is equipped with. Here, when the pilot pressure is a predetermined neutral pressure which is set in advance, the operation check valve 45 is opened to release the check valve function and bring the return side pipe 35 into the communication state, and the pilot pressure is increased. When the pressure is less than the neutral pressure, the check valve function acts to close the return side pipe 35.

The fail-safe valve 9 comprises a spring-offset 4-port 2-position electromagnetic switching valve 47, which is connected to the pressure holding portion 7 on the downstream side of the check valve and the operating check valve 45. The R port connected to the input port, the A port connected to the input port i of the pressure control valves 6FL to 6RR, and the pressure control valve 6
A state in which it has a B port connected to the return port o of FL to 6RR, and the P port and the R port are in communication with each other and the A port and the B port are in communication with each other at the normal switching position switched by the return spring 47a. In the offset position where the solenoid 47b is turned on in response to a control signal from a control device (not shown), a communication passage that directly communicates with the P port and the A port and a communication passage that directly communicates with the R port and the B port are provided. It is formed.
Further, the R port and the B port of the fail-safe valve 9 are connected via a fixed orifice 46.

Pressure control valves 6FL to 6R of the front wheel side control valve assembly 4F and the rear wheel side control valve assembly 4R.
Each of R has an input port i, a return port o and a control pressure port c as clearly shown in FIG. 2 as a spool type relief pressure reducing valve, and cuts off the control pressure port c from the input port i and the return port o. Or control pressure port c
Is provided with a three-way spool valve 10 having a spool 10c for communicating with either the input port i or the return port o, and the supply pressure is supplied to the right end of the spool 10c as a pilot pressure. Valve 49 controlled by proportional solenoid 48
Is provided, and the pressure of the control pressure port c is constantly controlled so as to be a pressure according to the exciting current supplied from the control device to the proportional solenoid 48. As a result, the right side oil chamber of the three-way spool valve 10 in the figure becomes the operating chamber 10a, and the right side oil chamber becomes the feedback chamber 10b. Further, as described above, the control pressure port of each spool valve 10 has hydraulic actuators 5FL to 5R for each wheel.
It is connected to the R pressure chamber 5a.

Further, as shown in FIG. 2, the input port i
Is connected to the input / output side 48a of the poppet valve 49 via a fixed orifice 50, the return port o is connected to the return side 49b of the poppet valve 49 via a fixed orifice 51, and the operating chamber 10a is connected to the variable orifice 12
It is connected to the input / output side 49a of the poppet valve 49 via a, and the feedback chamber 10b is connected to the control pressure port c via a variable orifice 12b.

Further, the input port i of the three-way spool valve 10 is connected to the A port of the failsafe valve 9, the return port o is connected to the B port of the failsafe valve 9, and the control port c is further connected to the hydraulic actuator 5FL. ~ 5
It is connected to the pressure chamber 5a of the RR. Further, as shown in FIG. 1, a back pressure absorbing accumulator 53 is connected to a return side pipe 52 which communicates between the return port o of each pressure control valve 6FL to 6RR and the B port of the fail-safe valve 9.
These absorb the back pressure generated by the line resistance of the hydraulic oil flowing through the return side pipe 52 and the like. Further, the A port of the fail safe valve 9 and the pressure control valves 6FL to 6RR
An oil filter 55 and an accumulator 54 for accumulating pressure are connected to the hydraulic pipe between the input ports i, and the hydraulic actuators 5FL to 5RR absorb pressure fluctuations in the high frequency range of the vehicle unsprung vibration input from the road surface or the like. A damping valve 56 and an accumulator 57 are connected to each other, and a cock 58 for flushing the hydraulic circuit is attached between the back pressure absorbing accumulator 53 and the pressure accumulator 54.

The operation of the pressure control valves 6FL to 6RR as a vehicle suspension control device will be briefly described. With the pressing force applied by the proportional solenoid 48 applied to the poppet valve 49, the feedback chamber 10b and the operating chamber 10a of the three-way spool valve 10 are operated.
When the pressures of the
An overlapping position is established to shut off between the supply port i and the return port o. Therefore, the pressure in the operating chamber 10a is adjusted depending on the magnitude of the command current to the proportional solenoid, so that the pressing forces of the return springs 11a and 11b arranged at both ends of the spool 10c are balanced. Pressure and feedback chamber 10b
The spool 10c slightly moves until the internal pressure is balanced to perform the pressure adjusting operation, and the control pressure from the control pressure port c can be controlled in proportion to the command current.

Further, there is a vibration input in the sprung resonance region (for example, around 1 Hz) of low frequency from the road surface side, and due to the vibration input, hydraulic pressure fluctuations occur in the pressure chambers 5a of the hydraulic actuators 5FL to 5RR. Suppose This change in hydraulic pressure is transmitted to the feedback chamber 10b of the pressure control valves 6FL to 6RR, and the parallelism between the pressure inside the feedback chamber 10b and the pressure inside the pilot chamber 10a collapses. Here again, the spool 1 is so arranged that the pressing forces of the return springs 11a and 11b arranged at both ends of the spool 10c are balanced.
0c slightly moves to connect the supply port i and the control pressure port c or the control pressure port c and the return port o to supply or return the hydraulic oil to absorb the pressure fluctuation up to a predetermined limit.

In the present invention, the return springs 11 are provided at both ends of the spool 10c of the three-way spool valve 10.
Shape memory springs whose spring constant decreases below a predetermined set temperature are used for a and 11b. Therefore, when the oil temperature is low and its viscosity is low, the pressure of the hydraulic oil that flows in and out of each port decreases, but at such a time, the low constant due to the decrease in the spring constant of the shape memory spring. However, there is an advantage that the spool 10c is moved. The method of determining the set temperature and the spring constant will be described later together with the method of determining the set temperature of the variable orifices 12a, 12b and 13.

On the other hand, of the four orifices arranged as the pressure control valves 6FL to 6RR, the poppet valve 49
The orifice 12a, which is interposed between the input / output side 49a and the operating chamber 10a of the three-way spool valve 10, is for suppressing the turbulence of the pressure in the operating chamber 10a due to the displacement of the spool 10c. Room 1
0b and the control pressure port c are connected to the feedback passage 1 through the orifice 12b.
0b is provided as a damper for the hydraulic oil that flows in and out, and the orifice 50 interposed in the pilot supply passage that connects the supply port i of the three-way spool valve 10 and the input / output side 49a of the poppet valve 49 is a pilot. The orifice 51 provided in the pilot return passage that connects the return port o of the three-way spool valve 10 and the return side 49b of the poppet valve 49 is for restricting the pilot flow rate required to form the pressure. It is provided as a damper for preventing the pilot pressure from being disturbed when a back pressure is generated in the return port o. Therefore, for example, the throttle diameter of the orifice 51 provided in the pilot return passage is set to a value that produces a large damping force when there is a pressure fluctuation of about 1 Hz from the hydraulic actuators 5FL to 5RR. It can be said that the orifice 50 provided in the supply passage and the orifice 51 provided in the pilot return passage have a small flow resistance and a small pressure fluctuation due to the fluctuation of the viscosity of the working oil. On the other hand, the other orifices must have a relatively large flow resistance during normal operation, and it can be said that the pressure fluctuation due to the viscosity fluctuation of the hydraulic oil is large. Therefore, these orifices 1
In the fixed orifices provided in 2a and 12b, when the temperature of the hydraulic oil is low and the viscosity is low, the flow resistance is too large and the spool 10c is not moved. For example, the control pressure is kept too high and the suspension is maintained. Is still extended, or the control pressure is kept too low and the suspension remains low, which causes a reduction in riding comfort.

Therefore, in the present invention, the input / output side 49a of the poppet valve 49 and the operating chamber 10 of the three-way spool valve 10 are described.
an orifice 12a interposed between the feedback chamber 10b and the control pressure port c, and an orifice 12a interposed between the feedback chamber 10b and the control pressure port c. A variable orifice that opens to reduce flow resistance and allows control pressure and supply pressure to change. These variable orifices 12a, 12b
As for the variable orifice 13 for suppressing separation in oil described above, the flow resistance decreases below a predetermined set temperature, and its hydraulic circuit configuration is shown in FIG. 3a. These variable orifices 12a, 12b, 13 are provided in a bypass circuit of a fixed orifice 60 having a predetermined flow resistance,
A switching valve 61 having return springs 14a and 14b arranged at both ends is provided so that the bypass circuit is cut off at the normal switching position and the bypass circuit is connected at the offset position. In this embodiment, by using a shape memory spring whose spring constant decreases below a predetermined set temperature as the normal position return spring 14a which is pressed to the normal switching position, the offset position return spring above the set temperature is used. 14
Since the pressing force of the shape memory spring 14a is higher than the pressing force of b, the switching valve 61 is held in the normal position. However, when the spring constant of the shape memory spring 14a decreases below the set temperature, the pressing force is offset by the offset. The switching valve 61 is moved to the offset position due to the pressing force of the position return spring 14b, the input port and the output port are communicated with each other, and the hydraulic oil flows into the bypass circuit side. A concrete embodiment of the variable orifice 12 is shown in FIG. 4a. Of the return springs 14a and 14b arranged at both ends of a spool 63 slidably arranged in a spool housing 62 in the figure, A shape memory spring whose spring constant decreases at a temperature lower than a set temperature is connected to the right end side of the figure, that is, the normal switching position holding spring 14a that cuts off between the input and output ports. A normal spring with a constant spring constant is used as the offset position switching spring 14b.
As a result, when the oil temperature or the ambient temperature around the housing (however, the temperature of both springs is largely affected by heat transfer from the oil temperature) is equal to or higher than the set temperature, the pressing force of the shape memory spring 14a and the normal spring 14b.
The input / output ports are blocked and the hydraulic oil passes through the fixed orifice 60 side and receives its flow resistance. However, when the oil temperature or the ambient temperature falls below the set temperature, the pressing force of the shape memory spring 14a is reduced. Becomes smaller than the pressing force of the normal spring 14b, the spool 63 moves to the right in the figure to connect the input / output port, and the flow rate to the fixed orifice 60 side decreases. In this way, by arranging the fixed orifice and the on-off valve side by side and changing the amount of inflow to the fixed orifice side, a temperature-dependent variable orifice whose flow resistance decreases below the set temperature is configured.

FIG. 3b shows the variable orifices 12a, 12
It is another example of b and 13. This variable orifice 12a,
The basic configuration of 12b and 13 is a combination of a fixed orifice 60 and a switching valve 61 and is similar to that of FIG. 3a, but the normal switching position holding spring 14a is a normal spring whose spring constant does not change. An electromagnetic solenoid 15 that is provided and presses the offset switching position is provided. A control signal from a control device (not shown) is input to the electromagnetic solenoid 15 so that the electromagnetic solenoid 15 can be switched to the offset position only when the control signal is in the ON state. Further, a detection signal from an oil temperature sensor (not shown) attached to a reservoir tank or the like is input to the control device, and the ON state is set only when the oil temperature detected by the oil temperature sensor is equal to or lower than the set temperature. Control signal is input to the electromagnetic solenoid 15. FIG. 4b shows a concrete embodiment of the variable orifices 12a, 12b, 13
In the spool 63 slidably arranged in the spool housing 62 in the figure, the spring 14a for holding the normal switching position, which shuts off the input / output port on the right end side in the figure, has a constant spring constant. A normal spring is used, and an offset position switching electromagnetic solenoid 15 is provided on the left end side of the figure, that is, the side that communicates between the input and output ports. When the control signal in the ON state is input to the electromagnetic solenoid 15, the spool 63 is pushed to the right in the drawing to move to communicate with the input / output port, the flow rate to the fixed orifice 60 side is reduced, and the set temperature is decreased. Below, a temperature-dependent variable orifice whose flow resistance is reduced is constructed.

The operation of the vehicle suspension control system of this embodiment will be briefly described below. For example, when the engine is started with the ignition switch turned on, when the oil temperature at the present time detected by a temperature sensor (not shown) is equal to or lower than the preset temperature, the control is sent from the control device to the flow control valve 8. The signal is turned off, so that the electromagnetic switching valve 43 of the flow control valve 8 is maintained in the normal switching position and the supply side pipe 38 is in communication with the check valve 44. On the other hand, when the oil temperature detected by the temperature sensor is equal to or higher than the set temperature, the control signal sent from the control device to the flow control valve 8 is turned on after a delay of a predetermined time. The electromagnetic switching valve 43 is offset to the offset switching position, and the supply pipe 38 and the check valve 44 are connected via the fixed orifice 42.

In this state, the supply line pressure output from the A port of the fail-safe valve 9 is equal to the line pressure discharged from the oil pump 36, which is supplied to the pressure control valves 6FL to 6RR and operated. Since the pilot pressure is supplied to the check valve 45, the operated check valve 45 is opened and the pressure holding portion 7 is opened. Further, since the supply line pressure output from the A port of the fail-safe valve 9 is also supplied to the accumulator accumulator 54, the accumulated pressure of these accumulator accumulators 54 is also equal to the line pressure discharged from the oil pump 36. ..

At this time, assuming that the vehicle is traveling straight on a flat road in a standard load state at a constant speed, a neutral pressure necessary for maintaining the standard vehicle height is supplied from the control device (not shown) to the hydraulic actuator 5FL. .. to 5RR, each of the pressure control valves 6FL to 6RR is supplied with an exciting current having a neutral current value.
The pressure of FL to 5RR is maintained at a value equal to the neutral pressure.

Further, since the operate check valve 45 is in the open state, the return line pressure of each of the return side pipes 52, 35 is close to the atmospheric pressure by the back pressure by the oil-separation suppressing variable orifice 13. .. When the vehicle is stopped from this running state and the ignition switch is turned off, the engine is stopped and the oil pump 36 is stopped accordingly. Therefore, the supply pressure from the pump assembly 2 suddenly becomes atmospheric pressure. However, in the supply side pipe 38,
Since the check valve 44 is installed, the pressure control valve 6F
The pressures of L to 6RR, the accumulator 54 for accumulating pressure, and the accumulator 53 for absorbing back pressure do not suddenly decrease. Further, even if the ignition switch is in the OFF state, the control device is configured such that the self-holding timer operates and the power is continuously turned on for a predetermined time, and the attitude change suppression control such as vehicle height adjustment is continued. As a result, the supply line pressure is gradually consumed and reduced. At this time, when the supply line pressure is higher than the neutral pressure, the vehicle height can be adjusted to the standard vehicle height, and the vehicle height is maintained at the standard vehicle height.

After that, when the supply line pressure drops to the neutral pressure, the operate check valve 45 is fully closed, and the return side pipe 35 from the return port of each pressure control valve 6FL to 6RR to the reservoir tank assembly 1 is cut off.
The hydraulic control system on the right side of the pressure holding unit 7 forms a closed circuit, and a pressure holding state is established. When the pressure is maintained in this way,
As the pressure of the return side pipe 35 starts to rise, the pressure of the back pressure absorbing accumulator 53 also rises, and the supply line pressure decreases in accordance with these pressure increases,
It becomes a substantially constant value when this matches the return line pressure.
The vehicle height gradually decreases as the supply line pressure decreases. In this case, the vehicle height is gradually lowered, so that the passenger does not feel uncomfortable.

Thereafter, when the ignition switch is turned on again, the control unit is powered on and the engine is started to be in the idling state, and the rotation of the oil pump 36 also rises as the rotation of the output shaft thereof rises,
The hydraulic oil having the discharge pressure corresponding to the rotation is supplied to the supply side pipe 38. Therefore, when the pressure in the supply side pipe 38 suddenly rises and becomes equal to or higher than the holding pressure held by the pressure holding portion 7, the pressure of the P port of the fail-safe valve 9 also passes through the check valve 44 of the pressure holding portion 7. Soar. However, in this state, the control signal sent from the control device to the fail-safe valve 9 remains off, so the fail-safe valve 9 is in the closed state, and the pressure increase on the P port side is The pressure control valve 6FL is provided only via the fixed orifice 46 connected in parallel with the fail-safe valve 9.
Since the pressure is supplied to the input ports i of 6 to 6RR, the pressure of the i input ports of the pressure control valves 6FL to 6RR is gradually increased, and the control pressures output from these pressure control valves 6FL to 6RR are gradually increased. Therefore, the pressure in the pressure chamber 5a of the hydraulic actuators 5FL to 5RR is gradually increased, and the vehicle height gradually rises to the standard vehicle height without making the occupant feel uncomfortable, and the attitude of the vehicle height suddenly changes. Is reliably prevented.

Particularly, when the vehicle is parked with the engine stopped for a long time, the output side oil leaks from the holding pressure near the neutral pressure immediately after the vehicle stops and the engine is stopped, and the oil temperature decreases. The holding pressure will gradually decrease over time due to volume reduction, etc., and the holding pressure will be lower than the neutral pressure for maintaining the normal reference vehicle height, so the vehicle height will also be lower than the reference vehicle height. Therefore, the vehicle height change amount due to the increase in the pressure of the oil pump 36 due to the engine start increases, but the vehicle height change in this case can be performed gently.

In the meantime, in the pressure holding portion 7, when the pilot pressure, which is the pressure at the A port of the fail-safe valve 9, exceeds the relief pilot pressure, that is, the neutral pressure, the operate check valve 45 is opened to control the pressure. Valve 6FL
A return port o of 6RR is communicated with the reservoir tank assembly 1 via the return side pipe 35. After that, when the pressure of the hydraulic oil discharged from the oil pump 36 increases and the line pressure on the upstream side of the check valve 44 exceeds the set pressure of the relief valve 41, the excess amount passes from the relief valve 41 through the return side pipe 35. Reservoir tank assembly 1
The line pressure is maintained at the set pressure.

After that, when a predetermined time elapses, the control signal sent to the fail-safe valve 9 is turned on, and the fail-safe valve 9 is switched to the lower switching position. Therefore, the pressure holding unit 7 and the pressure control valve 6F
The supply line pressure becomes equal to the set pressure of the line pressure when L to 6RR are in communication with each other, and at the same time, the attitude change suppression control in the normal state is executed by the control device.

Thereafter, the control device detects a vehicle height change due to getting on and off of an occupant or a posture change of the vehicle body due to roll, pitch, bounce, etc., while the vehicle is running, and controls the exciting current of a command value to suppress these changes. By outputting to 6RR, the pressures of the hydraulic actuators 5FL to 5RR are controlled, and the posture change of the vehicle body is suppressed. When an abnormal state such as disconnection or short circuit occurs in the control system for the pressure control valves 6FL to 6RR during execution of the vehicle attitude control, an abnormal state detector (not shown) detects the abnormal state and the abnormal state detection signal is turned on. Therefore, based on this, the control signal output from the control device to the fail-safe valve 9 is turned off, the fail-safe valve 9 is returned to the closed state, and the input ports i of the pressure control valves 6FL to 6RR and Operate check valve 4 with return port o communicating
Therefore, the pilot pressure of No. 5 is reduced, and the control unit shifts to the holding state by the pressure holding unit 7 in substantially the same control mode as in the case where the engine is stopped as described above, and the fall of the vehicle height is prevented and the fail-safe function is exerted. You can

Next, the temperature dependent variable orifice 12
a, 12b, 13 and the three-way spool valve 10, based on the effect of improving the vehicle riding comfort associated with the effect of reducing the transmission force at low temperature, the set oil temperature: T, the control valve spool spring constant Ks,
The analysis result for determining the control valve spool damping orifice diameter: Dd will be described. First, FIG. 5 shows the results of the damping constant frequency characteristics obtained by analytically calculating the frequency characteristics of the damping force with respect to the vibration speed when the hydraulic actuators 5FL to 5RR are vibrated at a constant speed of 0.3 m / s, for example. In the characteristic diagram, it is evaluated that the smaller the damping constant is, the better the riding comfort of the vehicle is in the frequency region other than the sprung resonance frequency region “about 1 Hz” and the unsprung resonance frequency region “about 10 Hz” of the vehicle. In this analysis example, the spool spring constant Ks is constant at 76 N / mm, the spool damping orifice diameter Dd is constant at 0.3 mm, and the damping constant frequency characteristic is calculated when the oil temperature T changes. Thus, it can be seen that the damping constant increases as the oil temperature decreases, and that the damping constant is particularly large on the low frequency side.

Next, FIG. 6 shows a spool spring constant Ks = 76N.
/ Mm constant, oil temperature T = -30 ℃ constant, when the spool damping orifice diameter Dd is changed from 0.3 mm to 3.0 mm, it is the analysis calculation result of the damping constant frequency characteristic. From the figure, it can be seen that at least when the oil temperature is low, increasing the spool damping orifice diameter Dd lowers the damping constant and improves the riding comfort at low temperatures.
At the same time, it can be seen that the effect is limited when the orifice diameter Dd is 0.8 mm or more.

Next, FIG. 7 shows that the oil temperature T is constant at −30 ° C., the large spool damping orifice diameter Dd is constant at 3.0 mm, and the spool damping spring constant Ks is 76 to 9.5.
It is an analysis calculation result of a damping constant frequency characteristic when changing to N / mm. According to this, it is understood that the damping constant is further reduced and the riding comfort is further improved at low temperature when the spool damping orifice diameter Dd is set large and the spool damping spring constant Ks is reduced at least when the oil temperature is low.

On the other hand, FIG. 8 shows that the oil temperature T is constant at -30 ° C. and the spool damping orifice diameter Dd is 0.3 mm which is small.
The spool damping spring constant Ks is fixed at 76-9.
The results of the analytical calculation of the damping constant frequency characteristic when changing to 5 N / mm show that the spool damping spring constant Ks is reduced while keeping the spool damping orifice diameter Dd small when the oil temperature is low. However, it can be seen that the ride quality cannot be further improved.

FIG. 9 shows the correlation between the oil temperature and the damping constant (at a vibration frequency of 1 Hz) based on the analysis results. In the figure, it can be seen that the damping constant rapidly increases when the oil temperature T becomes -10 ° C or lower, and therefore it can be said that the ride comfort can be sufficiently improved only by setting the set temperature to -10 ° C. Therefore, in the present invention, a comparatively low temperature at which the damping force frequency characteristic when the fluid pressure cylinder is vibrated at a constant speed as described above sharply increases due to the oil temperature is set as the set temperature. Kinematic viscosity of hydraulic oil is 100 cSt
The temperature above was set as the set temperature.

The method of determining the set temperature is not limited to the above, and may be appropriately determined according to the viscosity of the working fluid used, the volume temperature change amount, and the like. Further, the specific configuration of the variable orifice is not limited to the above, and another configuration may be used as long as the flow resistance is reduced at the set temperature or lower.

Further, the specific construction of the suspension control device is not limited to that shown in the drawing, and any suspension control device for controlling the supply pressure and control pressure to the hydraulic actuators provided on each wheel may be used. , It is possible to expand to anything. In such a case, the set temperature, the spring constant decrease amount, and the flow resistance decrease amount should be appropriately selected according to each hydraulic circuit and hydraulic pipe.

[0043]

As described above, according to the vehicle suspension control apparatus of the present invention, the spring constants of the springs provided at both ends of the three-way spool valve of the pressure control valve are lowered below a predetermined set temperature. For example, when the working fluid is hydraulic oil, a variable orifice that reduces the flow resistance of the orifice below a predetermined set temperature is provided in the pipe constructed as a shape memory spring or as a fluid passage. The pressure gain is compensated below the inflection point of the hydraulic oil, which affects the ride comfort of the vehicle, and the suspension characteristic control of the original active suspension device functions, resulting in the ride comfort of the vehicle being stable even at low temperatures. To be done.

[Brief description of drawings]

FIG. 1 is a schematic hydraulic configuration diagram showing an embodiment of a vehicle suspension control device of the present invention.

FIG. 2 is a schematic configuration diagram showing a three-way spool valve used as a pressure control valve in the vehicle suspension control device of FIG.

3 is a schematic hydraulic configuration diagram showing a variable orifice used in the suspension control device of the vehicle of FIG. 1, (a)
Is a variable spring, and (b) is an electromagnetic actuator.

FIG. 4 is a specific configuration diagram of the variable orifice shown in FIG. 3, in which (a) uses a shape memory spring,
(B) uses an electromagnetic solenoid.

5 is an explanatory diagram of a damping constant frequency characteristic by the variable orifice and the three-way spool valve in the embodiment of FIG.
The results of analysis calculation of the damping constant frequency characteristics when the oil temperature changes with a constant spool spring constant and a constant spool damping orifice diameter are shown.

FIG. 6 is an explanatory diagram of the analysis calculation result of the damping constant frequency characteristic when the spool damping orifice diameter is changed while the spool spring constant is constant and the oil temperature is constant as in FIG. 5.

FIG. 7 is an explanatory diagram of the analysis calculation result of the damping constant frequency characteristic when the spool damping spring constant is changed with a constant oil temperature and a large spool damping orifice diameter as in FIG. 5.

FIG. 8 is an explanatory diagram of analysis calculation results of damping constant frequency characteristics when the spool damping spring constant is changed with a constant oil temperature and a small spool damping orifice diameter, as in FIG. 5.

FIG. 9 is an explanatory diagram showing the correlation between the oil temperature and the damping constant obtained from the analysis results of FIGS.

[Explanation of symbols]

 1 is a reservoir tank assembly 2 is a pump assembly 3 is a multi-valve 4F, 4R is a control valve assembly 5FL to 5RR is a hydraulic actuator 6FL to 6RR is a pressure control valve 7 is a pressure holding part 8 is a flow control valve 9 is a failsafe valve 10 is Three-way spool valves 11a and 11b are return springs 12a and 12b are variable orifices 13 are variable orifices 14a and 14B are return springs 15 are electromagnetic solenoids

Claims (2)

[Claims] 1. A fluid pressure cylinder interposed between each wheel of a vehicle and a vehicle body, a supply port connected to a fluid pressure source, a return port, and an output port connected to the fluid pressure cylinder side. In a pressure control valve having a three-way spool valve having, by giving a control pressure command to the pressure control valve, a controllable pressing force is applied to one spool end side of the three-way spool valve, In a suspension control device that feeds back the control pressure output from the output port to the other spool end side, controls the control pressure of the output port according to the pressing force, and controls the suspension characteristics of the vehicle, A vehicle characterized in that the springs provided at both ends of the three-way spool valve of the pressure control valve are shape memory springs whose spring constant decreases below a predetermined set temperature. Suspension control device. 2. A fluid pressure cylinder interposed between each wheel of a vehicle and a vehicle body, a supply port connected to a fluid pressure source, a return port, and an output port connected to the fluid pressure cylinder side. In a pressure control valve having a three-way spool valve having, by giving a control pressure command to the pressure control valve, a controllable pressing force is applied to one spool end side of the three-way spool valve, In a suspension control device that feeds back the control pressure output from the output port to the other spool end side, controls the control pressure of the output port according to the pressing force, and controls the suspension characteristics of the vehicle, A vehicle characterized in that an orifice provided in a pipe constructed as a fluid passage is a variable orifice whose flow resistance of the orifice is lowered at a predetermined set temperature or lower. Both suspension control devices.