JPH03515A - Active type suspension - Google Patents

Abstract

PURPOSE:To improve the pulse pressure damping effect of a line pressure, by connecting a plurality of accumulators whose enclosing pressures are different, to a line pressure piping between a fluid pressure supply device and a control valve. CONSTITUTION:Two accumulators 25a, 25b whose gas enclosing pressures for pulse pressure damping are different, are in parallel connected to a line pressure piping 5 between a pressure retaining portion 11 and a pressure control valve 13. At this time, the gas enclosing pressure of the accumulator 25a is set lower than a set line pressure regulated by means of the relief valve 15 of the pressure retaining portion 11. Also, the gas enclosing pressure of the accumulator 25b is set at a value lower than the lowest line pressure which is higher than a neutral pressure at the time of the lowering of the line pressure. As a result, a pulse pressure damping effect can be obtained by means of the accumulator 25a under the normal condition and at the time of the lowering of the line pressure, by means of the accumulator 25b, and the pulse pressure damping effect can be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a fluid pressure cylinder interposed between a vehicle body and wheels, and the pressure in a pressure chamber of this fluid pressure cylinder is controlled by a control valve such as a pressure control valve. This active suspension device suppresses and controls posture changes such as roll and pitch of a vehicle by controlling the vehicle, and in particular, the active suspension effectively attenuates the pulsation pressure of the working fluid supplied to the control valve. Regarding equipment.

[Prior Art] As a conventional active suspension device, there is one described in Japanese Patent Laid-Open No. 62-289420, which was previously proposed by the present applicant.

As shown in FIG. 4, this prior art includes fluid pressure cylinders 42 interposed between each wheel 40 and a vehicle body 41, and a working fluid is supplied to these fluid pressure cylinders 42 by the driving force of an engine. A fluid pressure supply device 43 to be operated, a pressure control valve 44 that controls the operating pressure of each fluid pressure cylinder 42 according to a predetermined command value, and a vertical acceleration detector 45 provided at each wheel position of the vehicle body 41. A control device 46 outputs a command value for suppressing changes in the posture of the vehicle body to the pressure control valve 44 based on the detected value, and a line pressure pipe 47 and a Drain piping 48
, and an accumulator 49 for attenuating pulse pressure is connected to the line pressure piping 47.

[Problems to be Solved by the Invention] However, in the above conventional active suspension device, the pressure control valve 44 and the fluid pressure supply device 43 are directly connected via the line pressure pipe 47 and the drain pipe 48, One accumulator 49 in the line pressure piping 47
was connected, there was a problem that the pulse pressure of the working fluid from the fluid pressure supply device 43 could not be sufficiently attenuated. That is, the line pressure Pt is, for example, 100 in the normal state.
kg/ctfl, during slalom driving, long-distance driving on rough roads, etc., the pressure control valve 44 frequently supplies and discharges working fluid to each fluid pressure cylinder 42, so that the pressure decreases to about 60 kg/ctfl, for example. In order for the accumulator 49 to exhibit the pulse pressure attenuation effect under these conditions, the gas filling pressure PA of the accumulator 49 must be 50 kg/ct! In this case, when the line pressure PL is decreasing, the pulse pressure attenuation effect is large, and conversely, the pulse pressure attenuation effect by the accumulator 49 is reduced in the normal state.

To solve this problem, the gas filling pressure PA was increased to 50 kg/cd in order to increase the pulse pressure damping effect at normal line pressure.
It is conceivable to use two accumulators selected to the same degree, but in this case, although it may be possible to somewhat reduce the pulse pressure damping effect at normal line pressure, it may not be possible to obtain a sufficient pulse pressure damping effect. However, in order to obtain a sufficient pulse pressure attenuation effect, it is necessary to provide a large number of accumulators, which poses new problems such as poor vehicle mountability and increased production costs.

Therefore, the present invention has been made by focusing on the above-mentioned problems of the conventional example, and has a sufficient pulse pressure damping effect even when the line pressure from the fluid pressure supply device is in a normal state or in a reduced pressure state. The purpose of the present invention is to provide an active suspension device that can demonstrate the following.

[Means to solve the problem]

In order to achieve the above object, an active suspension device according to the present invention includes a fluid pressure cylinder interposed between each wheel and a vehicle body, and an actuation from a fluid pressure supply device supplied to the fluid pressure cylinder. The active suspension device includes a control valve for controlling fluid pressure, and is characterized in that a plurality of accumulators with different sealed pressures are connected to the line pressure piping between the fluid pressure supply device and the control valve.

[Function] In the active suspension device according to the present invention,
A plurality of accumulators are connected to the line pressure piping between the fluid pressure supply device and the control valve that controls the fluid pressure cylinder, and the gas filling pressures of these accumulators are selected to different values.For example, when there are two accumulators, By setting the gas filling pressure of one of them to 80 kg/cut and the gas filling pressure of the other to 50 kg/cut,
Line pressure PL is 100kg/cn! Under normal conditions, an accumulator with a sealed pressure of 80 kg/c+fl exerts a sufficient pulse pressure damping effect, and the line pressure is 60 kg/a.
When the pressure decreases to about 1.1 liters, an accumulator with a sealed pressure of 50 kg/c can provide a sufficient pulse pressure attenuation effect, and a sufficient pulse pressure attenuation effect can be achieved regardless of line pressure fluctuations.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.

In the figure, FS is a fluid pressure supply device, which has a hydraulic pump 1, whose rotating shaft is connected to an output shaft 2a of an engine 2 and is rotationally driven, and whose suction side is connected to an oil tank 3. A line pressure pipe 5 is connected to the discharge side via a check valve 4.

Further, the fluid pressure supply device FS includes an accumulator 6 for absorbing pulsation connected to the line pressure piping 5, a filter 7 inserted in the line pressure piping 5 on the downstream side of the accumulator 6, and a filter 7 in parallel with the filter 7. a check valve 8 connected to the
It is provided with a drain pipe 10 connected to the oil tank 3 via an oil cooler'-9.

The line pressure pipe 5 and the drain pipe 10 are connected via the pressure holding section 11 to the supply pressure boat 21a and return boat 21b of the pressure control valve 13 corresponding to each wheel.

The pressure holding unit 11 is inserted between a check valve 14 inserted in the line pressure piping 5 and the line pressure piping 5 and the drain piping 10, and sets the line pressure Pt (kg/cnl) in the normal state. It is equipped with a relief valve 15 for normal line pressure setting, and a pilot operated check valve 16 to which the line pressure on the downstream side of the check valve 14 is supplied as pilot pressure P. When the pilot pressure P is equal to or higher than the neutral pressure P of the pressure control valve 13, the pilot-operated check valve 16 is fully opened to establish communication between the input port 16i and the output boat 16o, and the pilot pressure P , becomes less than the neutral pressure PM, the fully closed state is established, and the connection between the input port 16i and the output boat 16o is cut off.

The pressure control valve 13 receives a command value ■ from an attitude change suppression control device 17 that outputs a command value to suppress changes in the attitude of the vehicle body based on detection signals such as vehicle height, lateral acceleration, vertical acceleration, longitudinal acceleration, etc. A control pressure PC is output according to the command value (■), and this is supplied to the hydraulic cylinder 19 that constitutes an active suspension inserted between each wheel and the vehicle body to resist changes in the posture of the vehicle body. Generates a biasing force.

The specific structure of this pressure control valve 13 is, as shown in FIG.
2. The poppet 23 and the plunger 24a of the proportional solenoid 24 are coaxially arranged in that order.

The spool 22 has lands 22a and 22b at both ends,
A pressure chamber 22c is formed between the land 22a and a partition wall 21d having a fluid outlet 21c formed in the valve housing 21, and a pressure chamber 22d is formed between the land 22b and the valve housing 21, and the pressure chamber 22d is formed between the land 22b and the valve housing 21. The chamber 22c communicates with the inlet port 21a via a pilot passage 21e, and the pressure chamber 22d communicates with the control port 21c via a fluid passage 22e formed within the spool 22. Note that 22f and 22g are springs that center the spool 22.

One end of the poppet 23 is a partition wall 2 that separates a pilot passage 21e from a return passage 21f communicating with a return boat 21b.
It faces a valve seat 21h formed at 1g, and the other end faces an actuator 24b of a plunger 24a of an electromagnetic proportional solenoid 24.

The proportional solenoid 24 includes a plunger 24a that is slidable in the axial direction, an actuator 24b that is fixed to the poppet 23 side of the plunger 24a, and an excitation coil 24c that applies a downward thrust to the plunger 24a. and
This excitation coil 24C is appropriately excited by a command value {circle around (2)} which is a direct current from the posture change suppression control device 17. As a result, a downward thrust is applied to the plunger 24a, and the position of the poppet 23 is controlled via the actuator 24b, thereby controlling the flow rate passing through the valve seat 21h. Then, when the thrust by the proportional solenoid 24 is applied to the poppet 23 and the pressures in both the pressure chambers 22C and 22d are balanced, the spool 22 is in the neutral position and the control port 21C, input port 21a, and return port 22 are in a neutral position. It is cut off from the boat 21b.

Here, the relationship between the command value l and the control oil pressure Pc output from the control port 21c is as shown in FIG.
P Mll is output when is near zero, and when the command value I increases in the positive direction from this state, the control output Pc increases with a predetermined proportional gain, and the set line pressure of the pressure holding part 11 increases. Saturates with PLH.

The input port 21a of the pressure control valve 13 is connected to the check valve 14 of the pressure holding part 11, and the return port 2 l b
is connected to the input port 161 of the pilot-operated check valve 16 of the pressure holding part 11, and the control port 21c is connected to the pressure chamber 19a of the hydraulic cylinder 19 inserted between the vehicle body and each wheel. .

On the other hand, two accumulators 25a and 25b having different gas filling pressures for pulsation pressure damping are connected in parallel to the line pressure piping 5 between the pressure holding part 11 and the pressure control valve 13. For these accumulators 25a and 25b, the gas filling pressure PA+ of one of the accumulators 25a is selected to be, for example, about 20 kg/cut lower than the set line pressure PLII regulated by the relief valve 15 of the pressure holding part 11, and the Gas filling pressure P of accumulator 25b
A2 is the minimum line pressure PL which is higher than the neutral pressure PM when the line pressure decreases during slalom driving, long distance driving on rough roads, etc.
The value is selected to be about 10 kg/cnl lower than L.

Note that 26 and 27 are damping valves and accumulators for absorbing pressure fluctuations due to unsprung vibrations of the vehicle inputted to the hydraulic cylinder 19 from the road surface.

Next, the operation of the above embodiment will be explained. Assuming that the vehicle is currently in a stopped state and the ignition switch is in the OFF state, in this state, the engine 2 is in a stopped state, the hydraulic pump 1 is also in a stopped state, and the output side of the line pressure holding part 11 is in a stopped state. It is assumed that the pressure is approximately maintained at the neutral pressure PM of the pressure control valve 13.

In this state, if you turn on the ignition switch and start engine 2 to idle,
As the rotation of the output shaft 2a increases, the rotation of the hydraulic pump 1 also increases, and a discharge amount of hydraulic oil corresponding to the rotation is supplied to the line pressure pipe 5.

Therefore, the pressure within the line pressure pipe 5 increases, and the pilot pressure P2 supplied to the pilot-operated check valve 16 also increases accordingly.

Then, the pilot pressure P, the leaf pilot pressure PP
O, that is, at the point when the neutral pressure PM is exceeded, the pilot operated check valve 16 becomes open and the return port 2 of the pressure control valve 13 is opened.
1b is communicated with the oil tank 3.

After that, when the pressure of the hydraulic fluid discharged from the hydraulic pump 1 increases and the line pressure PL on the upstream side of the check valve 14 exceeds the set pressure PL of the relief valve 15, the excess amount flows through the relief valve 15 and drains. Oil tank 3 through pipe 7
and the line pressure is maintained at the set pressure PL)l.

On the other hand, when the ignition switch is turned on, the attitude change suppression control device 17 is also activated and outputs a command value I to the pressure control valve 13 to suppress changes in the attitude of the vehicle body due to changes in vehicle height due to passengers getting on and off the vehicle. By doing so, the vehicle height is made to match the target vehicle height. When performing this vehicle height adjustment, there is little variation in line pressure, and approximately the set pressure PLH
Since the accumulators 25a and 25b are maintained at
Of these, the gas filling pressure PA+ of the accumulator 25a is 20 kg/c1i from the set pressure PL)l! Since the accumulator 25a is set to a relatively low level, this accumulator 25a exhibits a large pulse pressure damping effect, and the accumulator 25b also exhibits a pulse pressure damping effect, although it is small. It is possible to exert a large pressure damping effect.

After that, when the vehicle is started, the attitude change suppression control device 1
At step 7, changes in the attitude of the vehicle body due to scut during acceleration, nose dive during deceleration, roll during turning, other pitches, bounces, etc. are detected, and a command value ■ to suppress these is output to the pressure control valve 13. This controls the pressure of the hydraulic cylinder 19 and suppresses changes in the attitude of the vehicle body.

Furthermore, when a relatively low-frequency vibration input corresponding to the sprung mass resonance frequency range is transmitted from the wheel side to the hydraulic cylinder 19 while traveling on an undulating road with a relatively small amount of unevenness, the hydraulic cylinder 19 responds to the vibration input. As a result, the pressure in the control boat 21c of the pressure control valve 12 also changes. In this state, pressure control valve 1
The pressure in the pressure chamber 22d of No. 3 changes, and the pressure in the pressure chamber 22 d based on the command value I from the posture change suppression control device 17 changes.
When the pressure is lower than c, the spool 22 is lowered, the input port 21a and the control port 21c are brought into communication, and the line pressures P and H are supplied to the hydraulic cylinder 19. Therefore, the internal pressure of the hydraulic cylinder 19 increases, and the pressure in the pressure chamber 22d increases accordingly, causing the spool 22 to rise. When the pressure in the pressure chamber 22c and the pressure in the pressure chamber 22d become equal, an input signal is generated by the land 22b. Port 21a is closed. On the other hand, when the pressure in the pressure chamber 22d becomes higher than the pressure in the pressure chamber 22c, the spool 22 rises and the return port 21b and the control port 21C are brought into communication, causing the hydraulic oil in the hydraulic cylinder 19 to flow through the drain pipe 10. and return it to oil tank 3. Therefore, the internal pressure of the hydraulic cylinder 19 decreases, and the pressure in the pressure chamber 22c decreases accordingly, causing the spool 22 to descend. When the pressure in the pressure chamber 22c and the pressure in the pressure chamber 22d become equal, the pressure is returned by the land 22a. Port 21b is closed. After all, hydraulic cylinder 1
Vibration input from the road surface transmitted to the vehicle body is absorbed and prevented from being transmitted to the vehicle body.

Furthermore, when vibration input in the unsprung resonance frequency range is transmitted to the hydraulic cylinder 13 from the wheel side, pressure fluctuations in the pressure chamber 13a of the hydraulic cylinder 13 occur due to this vibration input.
In this case, since the accumulator 27 is connected to the pressure chamber L3a via the throttle valve 26, the vibration input is absorbed by the accumulator 27.

Furthermore, when the vehicle performs slalom travel or travels over a long distance on a rough road, pressure fluctuations in the pressure chamber 19a of the hydraulic cylinder 19 increase, and the line pressure increases accordingly. A state may occur where the pressure PA1 or lower drops significantly to the lowest line pressure PLL, but in this state, the line pressure of the accumulator 25a is lower than its gas filling pressure, so the pulse pressure damping effect is not exerted at all. As for the accumulator 25b, its gas filling pressure PA□ is set lower than the lowest line pressure PLL, so it can exhibit a large pulse pressure damping effect.
Compared to the case of LH, the number of accumulators is reduced by one accumulator, which has a smaller pulse pressure damping effect, but when the line pressure decreases extremely, it is a special driving condition and does not occur frequently, so the control of the hydraulic cylinder 19 is necessary. The effect on this can be ignored.

In this running state, when the vehicle is stopped and the ignition switch is turned off, the hydraulic pump 1 of the fluid pressure supply system FS will stop rotating as the engine 2 stops, and its discharge pressure will drop rapidly. However, since the check valves 4 and 14 are inserted in the line pressure piping 5,
The pressure in the pressure control valve 13 and the accumulators 25a, 25b does not decrease suddenly, but is gradually reduced through the pilot passage 21e and return passage 21f of the pressure control valve 13. When the pressures of the accumulators 25a and 25b become less than the neutral pressure P,4, the pilot-operated check valve 16 is fully closed, so that the hydraulic oil in the pressure control valve 13 and the hydraulic cylinder 19 is at approximately neutral pressure. Encapsulated and held in PN.

In addition, in the above embodiment, two accumulators 2
Although the case where the accumulators 5a and 25b are provided has been described, the present invention is not limited to this, and three or more accumulators may be provided and the gas filling pressures thereof may be varied in at least two stages.

Further, in the above embodiment, a case has been described in which a plurality of accumulators 25a and 25b are provided between the pressure holding part 11 and the pressure control valve 13, but the invention is not limited to this. Even if the accumulator 6 is replaced with a plurality of accumulators having different sealing pressures, the same effects as in the above embodiment can be obtained.

Further, in the above embodiment, a case has been described in which the rotational driving force for the hydraulic pump 1 is obtained from the engine, but the invention is not limited to this, and other rotational driving sources such as an electric motor may be applied. Needless to say.

Furthermore, the control valve for the hydraulic suspension is not limited to the pressure control valve 13 described above (other flow control type servo valves, etc. can be applied).

Furthermore, in the above embodiments, a case has been described in which hydraulic oil is used as the working fluid, but the present invention is not limited to this, and any working fluid may be used as long as it has a low compressibility.

〔Effect of the invention〕

As explained above, according to the active suspension device according to the present invention, two accumulators with different gas filling pressures are connected to the line pressure piping between the fluid pressure supply device and the control valve. The maximum pulse pressure damping effect can be obtained in normal conditions where the supplied line pressure is close to the set pressure, and even when the line pressure is extremely reduced, an effective pulse pressure damping effect can be obtained. This provides the effect of reliably preventing the control pressure of the control valve that controls the fluid pressure cylinder from fluctuating due to line pressure.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention, FIG. 2 is a longitudinal sectional view showing an example of a pressure control valve applicable to the present invention,
FIG. 3 is a characteristic diagram showing the relationship between the control pressure and the command value of the pressure control valve, and FIG. 4 is a system diagram showing a conventional example. In the figure, FS is a fluid pressure supply device, 1 is a hydraulic pump, 2 is an engine, 5 is a line pressure pipe, 11 is a pressure holding part, 13 is a pressure control valve, 19 is a hydraulic cylinder, 21a is an input boat, and 21b is a return Port, 21C is a control port, 25a,
25b is an accumulator.

Claims (1)

[Claims] (1) An active suspension device that includes a fluid pressure cylinder interposed between each wheel and the vehicle body, and a control valve that controls the working fluid pressure from a fluid pressure supply device supplied to the fluid pressure cylinder. 2. An active suspension device according to claim 1, wherein a plurality of accumulators having different sealing pressures are connected to the line pressure piping between the fluid pressure supply device and the control valve.