JPH02173401A - Accumulator - Google Patents

Abstract

PURPOSE:To keep nearly constant the ratio of variation in in-flow volume of working fluid to variation in generated pressure in an accumulator by restricting a sudden change of pressure in a second gas chamber, which is caused by the movement of a piston, taking advantage of a pressure change in the reverse direction in a first gas chamber. CONSTITUTION:When the pressure in a pressure chamber L rises (or drops) because of unspringing, exciting input, working fluid flows in (or flows out of) a fluid chamber 73, which is formed with a first piston 71a and first sliding chamber 70a. As a result, a piston 71 moves toward the second gas chamber (72b) side (or toward the fluid chamber 73 side), thereby decreasing (or increasing) the volume of the second gas chamber 72b. At this time, the volume of a first gas chamber 72a, which is formed with a second piston 71b, whose diameter is larger than that of the first piston 71a, and a second sliding chamber 70b, increases (or decreases). As a result, a pressure change, whose direction is reverse of that of the pressure change in the second gas chamber 72b, occurs, thereby preventing the pressure in the second gas chamber 72b from suddenly changes. Thus, the ratio of variation in generated pressure to variation in in-flow volume of the working fluid in an accumulator 40 can be kept nearly constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an accumulator, and in particular, in an active suspension mounted on a vehicle, it is possible to prevent the vehicle height from changing due to changes in the loaded weight of the vehicle, etc. Good control characteristics can be obtained even when the pressure (i.e., control pressure) in the pressure chamber of the fluid pressure cylinder interposed between the upper and lower parts of the spring is increased or decreased as appropriate. .

[Conventional technology]

Conventionally, floating piston type accumulators have been well known as accumulators (Nikkan Kogyo Shimbun, January 1978).
(See page 455 of "Hydraulic Technology Handbook," published on March 30th), and is used, for example, in active suspensions. An example of this active type suspension is one described in Japanese Utility Model Application No. 10551/1983, which was previously filed by the applicant of the present invention.

This conventional active suspension uses a pressure control valve to adjust the pressure in the pressure horn chamber of a fluid pressure cylinder interposed between the upper and lower suspensions according to the acceleration generated on the vehicle body (on the suspension). By doing so, changes in the attitude of the vehicle body are suppressed even when the vehicle is turning or accelerating or decelerating.

In addition, among the vibrations input to the wheels (under the wheels) from the road surface,
Large excitation inputs at relatively low frequencies corresponding to the sprung mass resonance frequency range are absorbed by the pressure regulating action within the pressure control valve that responds to this relatively slow vibration, and relatively high vibration inputs corresponding to the sprung mass resonance frequency range are The low-frequency vibration input is absorbed by an accumulator that communicates with the pressure chamber of the fluid pressure cylinder through a restriction.

[Problem to be solved by the invention]

However, in the prior art, the accumulator that absorbs vibrations in the sprung mass resonance frequency range has the following problems.

That is, in a general floating piston type accumulator, the relationship between the volume Vl of the working fluid that enters the accumulator from the pressure chamber of the fluid pressure cylinder and the pressure P generated by the accumulator is, for example, as shown by the solid line in FIG. It becomes as shown in 1.

According to this, in a region where there is relatively little working fluid entering the accumulator (in a state where the pressure in the pressure chamber of the fluid pressure cylinder is low), the volume is ■. The ratio of the change in pressure P1 to the change in pressure P1 (8P,/ΔV) is relatively small, but in a relatively large area (state where the pressure inside the pressure chamber of the fluid pressure cylinder is high), the ratio becomes relatively large. In other words, the rate of change is the volume ■1. In addition, in the accumulator, the pressure is changed from the pressure chamber to the accumulator (or from the accumulator to the pressure chamber) so that the pressure P is equal to the pressure chamber pressure of the fluid pressure cylinder. ) The volume V1 is adjusted by moving the working fluid.

Therefore, the pressure in the pressure chamber of the fluid pressure cylinder (the pressure controlled by the pressure control valve; approximately equal to the pressure P1 of Accu1 and Rake) is relatively high at about 80±I0kgf/Ca (for example, when the vehicle turns On the outer ring side or when the loaded weight is heavier than usual), the pressure P1 of the accumulator changes quickly as the working fluid flows into or out of the pressure chamber, so the responsiveness of the control pressure by the pressure control valve is good. (See the chain line connecting △ in Figure 7).

However, in a state where the pressure in the pressure chamber of the fluid pressure cylinder is relatively low (30±I Okgf/cffl) (for example, on the inner wheel side when the vehicle turns), the pressure Pl of the accumulator changes relatively slowly, so pressure control is difficult. The responsiveness of the control pressure by the valve deteriorates (see the broken line connecting the x's in FIG. 7).

On the other hand, when the control pressure is high (80±10 kgf/c+f
In case of l), the change in volume in response to the change in control pressure (i.e., pressure P) is slow, so even if the excitation input to the fluid pressure cylinder is a small vibration with a high frequency, an accumulator is sufficient. Therefore, the flow rate generated by pressure fluctuations in the fluid pressure cylinder flows into the pressure control valve side (or is supplied from the pressure control valve side), but the pressure control valve has a high sprung mass resonance frequency range. Unable to respond to vibrations,
As a result, large flow resistance (damping force) occurs at the pressure control valve (
(See the chain line connecting △ in Fig. 8), it is impossible to absorb the above flow rate. Therefore, vibrations generated in the wheels are transmitted to the vehicle body, impairing the ride comfort of the vehicle.

Conversely, when the control pressure is low (30±I0kgf/c+fl
), the volume 1 changes quickly depending on the control pressure, so most of the flow rate generated by pressure fluctuations in the fluid pressure cylinder is absorbed by the accumulator and flows into the pressure control valve side (or from the pressure control valve side). The flow rate (supplied) is small, and the resistance generated by the pressure control valve is small (see the broken line connecting the x's in FIG. 8). Therefore, vibrations generated in the wheels are sufficiently absorbed.

Such a problem is ultimately caused by the fact that the above ratio (Δp+/ΔVl) in the accumulator fluctuates depending on the control pressure.

Here, in order to solve the above problems with the conventional accumulator, the initial sealing pressure P of the accumulator must be adjusted. ■ Larger accumulator capacity. How to reduce (Vo =
100cc, Pa = 50kgf/c (see broken line 12 in Figure 6), or the above capacity ■. The method of use is to increase the size so that a large amount of working fluid can enter in the standard state (Vo = 500cc, P o = 15 kgf/
cf: Broken line in Figure 6! 3), but the former has the disadvantage that the control pressure range becomes narrow, and the latter has the disadvantage that the reservoir tank for recovering the working fluid in the accumulator when the system is not in operation becomes large.

Therefore, conventionally, the neutral pressure (for example, 50 kg
f/c+fl), so that appropriate responsiveness and damping force (see the solid line connecting O in Figures 7 and 8) can be obtained (in other words, the above ratio at normal neutral hour is equal to the ideal slope). The specifications of the accumulator were determined to match the dashed line in Figure 6), but for the reasons mentioned above, this avoids deterioration of the control characteristics when the vehicle turns or when the load changes. I couldn't.

On the other hand, if a honey-free piston type accumulator is used, the ratio of the change in the generated pressure to the change in the penetrating volume in the accumulator will be approximately constant;
In the case of an accumulator that uses springs, sliding resistance due to prying of the spring occurs as the piston of the accumulator slides, which is unfavorable for control purposes.

This invention was made by focusing on these unresolved problems with the conventional technology, and it is possible to always obtain good control characteristics of the active suspension even when the vehicle turns or the load changes. The purpose is to provide an accumulator with a simple configuration.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a piston type accumulator including a cylinder and a piston slidably included in the cylinder, the piston type accumulator having a first piston and a first piston having a larger diameter than the first piston. The piston is constructed by integrating two pistons separated in the axial direction, and the cylinder includes a first sliding chamber in which the first piston slidably resides, and a first sliding chamber in the first sliding chamber. and a second sliding chamber that is continuous and in which the second piston is slidably located, and is formed by the first piston, the second piston, the first sliding chamber, and the second sliding chamber. A predetermined volume of gas is filled in a first gas chamber formed by the second piston and the second sliding chamber, and a predetermined volume of gas is filled in a second gas chamber formed by the second piston and the second sliding chamber. It is characterized in that the fluid chamber formed by the first sliding chamber is communicated with other fluid pressure equipment.

[Effect]

In the present invention, since the fluid chamber formed by the first piston and the first sliding chamber communicates with other fluid pressure equipment,
When the pressure in the pressure chamber increases (or decreases) due to the vibration input to the bottom of the spring, the working fluid enters or flows out of the fluid chamber, and the pressure also increases (or decreases).

Then, when the pressure in the liquid chamber increases (or decreases), the first
The piston, which is integrally configured with the second piston spaced apart in the axial direction, is on the second gas chamber side (or fluid chamber side)
Move to. Then, the volume of the second gas chamber decreases (or increases), but since the distance between the first and second pistons is constant, the proportion of the second sliding chamber that makes up the first gas chamber increases (
or decrease), the volume of the first gas chamber increases (or decreases).

Moreover, the second piston has a larger diameter than the first piston (
Therefore, since the second piston has a larger pressure-receiving area than the first piston, the gas sealed in the first gas chamber exerts a force proportional to the volume of the first gas chamber (volume of the fluid chamber). The piston is urged in a direction in which the second gas chamber is contracted. Therefore, in the present invention, in which the changes in the volume of the first and second gas chambers are in the relationship as described above with respect to the change in the volume of the fluid chamber, the volume of the fluid chamber (operation) can be adjusted by appropriately selecting the dimensions of each member. The biasing force of the piston (
The rate of change in the generated pressure remains approximately constant.

〔Example〕

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

1 to 5 show an embodiment of the present invention, which is a hydraulic active suspension that maintains a constant vehicle height and controls the roll and pitch of the vehicle.

First, the overall configuration of an active suspension to which the accumulator of the present invention can be applied will be explained with reference to FIG. 4 (the figure shows only one system of the hydraulic system for the four wheels of a vehicle). ).

In the figure, 10 is an active suspension, 12 is a wheel, 14 is a wheel side member, and 16 is a vehicle body side member.

The active suspension 10 includes a hydraulic source 18 that supplies hydraulic pressure at a predetermined line pressure, an accumulator 2° for accumulating pressure installed downstream of the hydraulic source 18, and a pressure control system installed downstream of the accumulator 2o. A valve 22, a hydraulic cylinder 24 interposed between the vehicle body side member 16 and the wheel side member 14 (this corresponds to another fluid pressure device in the present invention), the vehicle body side member 16, and the hydraulic cylinder 24. The present invention includes a coil spring 30 disposed between the cylinder tubes 24a to support the static load of the vehicle body, and an attitude change suppression control device 32 that controls the pressure control valve 22.

The posture change suppression control device 32 includes a vehicle height sensor 33 composed of a potentiometer or the like that measures the distance between the vehicle side part 16 and the wheel side member 14, and a lateral acceleration sensor 34 that detects the lateral acceleration of the vehicle body. , a longitudinal acceleration sensor 35 for detecting longitudinal acceleration, and a controller 36 for controlling the pressure control valve 22 based on the vehicle height, lateral acceleration, and longitudinal acceleration detection signals.

Furthermore, the pressure chamber of the hydraulic cylinder 24, which will be described later, is
In order to absorb vibrations in the under-spring resonance frequency range from the road surface side, the throttle valve 38 as a damping element is connected to an accumulator 4° which will be explained in detail later, and these throttle valves 38 and accumulator 40 absorb vibrations. An absorption device is configured.

The hydraulic power source] 8 uses a vehicle engine as a rotational drive source,
It has a hydraulic pump that pressurizes and discharges hydraulic oil in a tank, and outputs hydraulic oil at a predetermined line pressure based on the discharge pressure of this hydraulic pump.

The pressure control valve 22, as shown in FIG.
Consists of a pilot operated proportional solenoid pressure reducing valve.
It includes a valve mechanism section 22A including a three-way spool valve, and a proportional solenoid 22B that controls the valve mechanism section 22A.

Among these, the valve mechanism section 22A has a valve housing 42,
A substantially cylindrical insertion hole 44 is located in the center of the valve housing 42.
is drilled. At a predetermined position of the insertion hole 44, a partition wall 46 having a communication hole 46A of a predetermined diameter and providing variable pilot pressure is installed horizontally with respect to the axial direction.
4 is divided into 1 minute. Of these, a poppet 48 axially biased by the proportional solenoid 22B is slidably disposed in the insertion hole 44 on the proportional solenoid 22B side. On the other hand, a fixed aperture 50 is provided in the insertion hole 44 on the opposite side.
is installed horizontally at a predetermined pressure distance from the partition wall 46, and a pilot chamber PR is formed between the fixed throttle 50 and the partition wall 46. This fixed aperture 50 is a main spool 5 which will be described later.
This is to suppress disturbances in the pressure P in the pilot chamber PR due to the displacement of the fixed throttle 50, and in addition to the central part as shown in the figure, a plurality of hydraulic oil passage holes may be provided around the fixed throttle 50. .

Furthermore, the above-mentioned main spool 52 is disposed in the insertion hole 44 on the side of the fixed throttle 50 so as to be slidable in its axial direction, and the valve housing 42 has a supply ball 1-54s that communicates with the insertion hole 44. , an output capo) 54c, and a return boat 54r. And supply port 1-5
4s is connected to the hydraulic oil supply side of the hydraulic source 18 via a hydraulic piping, and the return boat 54r is connected to the hydraulic oil supply side of the hydraulic source 18 via a hydraulic piping.
8, and an output capo 1-54c is further connected to a pressure chamber of the hydraulic cylinder 24, which will be described later, via hydraulic piping.

A pilot-side pressure chamber FI+ and an output-side pressure chamber PL are each formed at an axial position of the insertion hole 44 facing the main spool 52. And Ryojo Zenzen FBI
, PL are provided with offset springs 60U and 60L, respectively, so that the sliding position of the main spool 52 is centered when the pressures of both pressure chambers F, , F, are parallel (the pressure chamber 52c to be described later is not shown in the figure). The offset amount becomes zero.

The main spool 52 includes a land 52a facing the supply port 54s, a land 52b facing the return boat 54r, an annular groove-shaped pressure chamber 52c formed between the lands 52a and 52b, and the pressure chamber 52c. and output side pressure chamber]? , - is in communication with the feedback passage 52d.
It is formed by As shown in the figure, the feedback passage 52d is provided with an orifice Pc for a damper.

Furthermore, a rectangular parallelepiped notch 52s for adjusting the communication area between the supply ports 1 to 54s and the pressure chamber 520 is provided in a portion of the land 52a adjacent to the supply port 1-54s, and a rectangular parallelepiped notch 52s is provided in a portion adjacent to the supply port 1-54s of the land 52b. A notch 52r is provided in an adjacent portion to adjust the communication area between the return boat 54r and the pressure chamber 52c.

On the other hand, the piston 1~chamber PR communicates with the pylon 1~side pressure chamber F via the fixed throttle 50, and also communicates with the supply boat 54S via the pilot supply passage PP. The poppet 48 side of the insertion hole 44 communicates with the return bow 54r via the pilot return passage PT.

Further, both ends of the boppent 48 in the insertion hole 44 and the pilot return passage PT are connected to each other via a communication passage RR.

The pilot supply passage PP is provided with an orifice Qp that regulates the pilot flow rate, and the pilot return passage PT is provided with an orifice Pr that prevents the pilot pressure P from being disturbed.

Therefore, by adjusting the sliding position of the poppet 48, the opening area of the communication hole 46A changes, and the flow rate of the hydraulic oil flowing through the pilot supply passage PP, the pilot chamber PR, the communication hole 46A, and the pilot return passage PT, i.e. The pilot pressure PP in the pilot chamber PR is adjusted, thereby controlling the pressure in the pilot side pressure chamber FU. and,
If the pressures in the side pressure chambers FU and F are different, the main spool 52 reciprocates in its axial direction due to the pressure difference, and a pressure regulating operation is performed in which the hydraulic fluid in the pressure chamber 52.c is injected or discharged. is carried out transiently. Then, when the pressure in the pressure chamber 52c (that is, the control pressure pc of the output capo-I-54c) and the pilot pressure P are balanced, the hydraulic cylinder 24 is fixed in the subsequent steady state. In this state, the spool position shown in FIG. 2 is always taken, and the control pressure Po, which is set equal to Byron I and pressure P, is maintained.

On the other hand, the proportional solenoid 22B
A cylindrical housing 62 integrally formed with the cylindrical housing 62, an insertion hole 64 formed in the center of the cylindrical housing 62 and communicating with the aforementioned insertion hole 44, and a plunger 66 slidably provided in the axial direction of the insertion hole 64. and an excitation coil 68 that drives the plunger 66 in its axial direction.

The tip of the actuator 66A of the plunger 66 is connected to the boppet 1-
It is in contact with 48. Further, 66B is a communicating hole, which includes an orifice P for damping. 1 is provided.

The excitation coil 68 is supplied with an excitation current I5 as a command value from the attitude change suppression control device 32, which will be described later. Therefore, the excitation coil 68 is excited in accordance with the value of the excitation current Is, and the actuator 66A of the plunger 66 urges the poppet 1-48 downward in FIG. 2 in accordance with its propulsive force.

Returning to FIG. 4, the hydraulic cylinder 24 has the cylinder tube 24a.
The piston 24 is biased inside by the screw rod 24b.
c can slide in its axial direction. Further, a pressure chamber is formed below the cylinder tube 24a and is separated by a piston 24c.

The controller 36 includes a microcomputer, and maintains the vehicle at an appropriate height based on detection signals from the vehicle height sensor 33, lateral acceleration sensor 34, and longitudinal acceleration sensor 35. The value of the excitation current Is as a command value for suppressing changes in vehicle posture due to acceleration is set within a predetermined range of I3.4IN-Is□8 (
(see FIG. 3), and the excitation current I is supplied to the proportional solenoid 22B.

The accumulator 40 that communicates with the pressure chamber of the hydraulic cylinder 24 is a piston type accumulator that includes a cylinder 70 and a free piston 71 that slides within the cylinder 70, as shown in FIG.

The free piston 71 includes first and second pistons 71a,
71b are coaxially integrated via a connecting body 71c while being spaced apart in the axial direction, and the second piston has a larger diameter than the first piston (i.e., has a larger pressure receiving area). is formed.

The cylinder 70 also includes a first sliding chamber 70a in which a first piston 71a is slidably located, and a first sliding chamber 70a in which a first piston 71a is slidably housed.
a second piston that is continuous with a and in which the second piston is slidably included;
A sliding chamber 70b is provided, a first sliding chamber 70a,
Second sliding chamber 70b.

A first gas chamber 72a formed by the first piston 71a and the second piston 71b, and a second gas chamber 72a formed by the second sliding chamber 70b and the second piston 71b.
A predetermined volume of gas is sealed in each of the first sliding chamber 70a and the first piston 71a, and the fluid chamber 73 formed by the first sliding chamber 70a and the first piston 71a is communicated with the pressure chamber of the hydraulic cylinder 24 via the throttle valve 38. There is. Note that 75a and 75b are seal members.

Here, the operating principle of the accumulator 40 will be explained in detail.

That is, the pressure receiving area of the first piston 71a on the fluid chamber 73 side is A1, the pressure receiving area of the second piston 71b on the first gas chamber 72a side is A28, and the pressure receiving area of the first piston on the first gas chamber 72a side is A22. , these pressure receiving areas A z 1 and A2
The difference between □ (A2 + A2□) is Az, the second piston 71
b, the pressure receiving area on the second gas chamber 72b side is A3, and the fluid chamber 73
．． Each pressure in the first gas chamber 72a and the second gas chamber 72b is P
I, P2 and P3, fluid chamber 73. Let the volumes of the first gas chamber 72a and the second gas chamber 72b be v, , V2 and V3,
Pro is the pressure at which the free piston 71 moves toward the second gas chamber 72b, P2O is the initial pressure of gas in the first gas chamber 72a, and P2 is the initial pressure of gas in the second gas chamber 72b.
O, the initial volume of the first gas chamber 72a is ■2°, the initial volume of the second gas chamber 72b is Vzo, and the polytropic coefficient is n(-
1,4), then the following equations (1) to (5) are obtained.

A2-αAI ・・・・・・
(6) A 3 = A + +αAI = (1+α)AI ・・・・・・(7
)■3o−β■2o ・・・・
...(8)P5o-(A2Pzo+A+P
to) / Az-(αA+Pzo+AzP to)
/ (1+α) AI-(αPzo+P+o)/(1+
α) --------(9) And since the above pressure P+ is the pressure generated in the accumulator 40, it can be calculated as shown in the following equation 00).

p+ -(All P3 A2 P2)/A-((1
+α) AlF2-αA IP 2 ) / A +-(
1+α)P3-αP2...θ0) Furthermore, the pressures P2 and P3 of the first and second gas chambers 72a and 72b are expressed by the following equations (11) and θ2).

P3-P2O(V3o/(Vzo (1+α)Vl)
) ”-P:to(βV zo/ (βV20 (1
+α)Vl))"...02) Therefore, the above equation 00) becomes the following equation 03) using the above equations 01) and 02).

In other words, the pressure P3 in the second gas chamber 72b is expressed in (11) above.
As shown in the equation, as the free piston 71 moves upward (or downward) in FIG. ) As shown in the formula, the free piston 71
As it moves upwards (or downwards) in Figure 4, it decreases (
or rise). Then, the pressure PI of the fluid chamber 73
(that is, the pressure generated by the accumulator 40) is the above 0
ω or 03) In the accumulator 40 of this embodiment, the volume of the hydraulic fluid contained in the fluid chamber 73 is
The relationship between and the pressure P is as shown by the solid line 15, which shows the relationship between the ideal volume 1 and the pressure P, as shown in broken in4 in
Approximately matches.

However, the broken line shown in Figure 5! 4 is P20=30k
gf/cf,, Vzo-150cc, cx-1, β-
2, in the case of P 10-0.

Therefore, in this embodiment in which the accumulator 40 is configured as described above, the rate of change in the generated pressure P with respect to the change in the intrusion volume V1 of hydraulic oil in the accumulator 40 (
ΔPl/ΔV, ) is within the control pressure range of the hydraulic cylinder 24 by the pressure control valve 22 (in this embodiment, approximately 15 to 80
kgf/c+fl), which is approximately constant.

Next, the operation of the above embodiment will be explained.

When the ignition switch is turned on, the posture change suppression control device 32 is activated, and the rotation of the engine drives the oil pressure 11i18 as described above to supply a predetermined line pressure.

As described above, the posture change suppression control device 32 detects the current vehicle height and the lateral acceleration 2 and the longitudinal acceleration acting on the vehicle body.
Performs predetermined calculations for setting command values. As a result, when the vehicle is traveling straight on a good road at a constant speed, the excitation current Ts is set to a value near its neutral value rsN, and when the vehicle is turning, etc. where lateral acceleration occurs, the excitation current Ts is set to a value close to its neutral value rsN. IS is set to a higher value (for example, on the outer ring side) and a lower value (for example, on the inner ring side) than the neutral value l5II.

Now, suppose that the vehicle is running as described above and there is no road surface input to the hydraulic cylinder 24, and that the excitation current 3 is set to its neutral value ISN. As a result, the proportional solenoid 22B is energized, the plunger 66 urges the poppet 48 with a predetermined thrust, and the flow resistance between the poppet 48 and the communication hole 46A is set to its neutral value. That is, the pilot pressure P is also set to its neutral value, and the pressures in the pilot side pressure chamber FU and the output side pressure chamber FI4 are compared.

At this time, the pressures in the side pressure chambers Fu and FL were balanced (
In other words, if the control pressure Pc (that is, the pressure in the pressure chamber of the hydraulic cylinder 24 and the pilot pressure P are equal), the position of the main spool 52 will continue to be in the closed state shown in FIG. 2, and the control pressure Pc will also remain the same. It is maintained at neutral pressure PCH.

For example, when the pressure in the pilot side pressure chamber Fu is lower than the pressure in the output side pressure chamber FL, that is, when the control pressure Pc is higher than the pilot pressure P, the main spool 52 moves in the direction of the pilot side pressure chamber FII (in FIG. The output port 54c and the return port 54r are communicated with each other. Therefore, the hydraulic oil returns via the pressure chamber 52c.
54r side, and the pressure in the output side pressure chamber Ft decreases. As a result, when the pressure drops too much and becomes lower than the pressure in the pilot side pressure chamber Fo, the main spool 52 moves in the opposite direction (lower side in FIG. 2), and the supply port 54s and the output boat 54c communicate between. After passing through a transient state that repeats this cycle,
Side pressure chamber FII, F. When the pressures of are balanced, the main spool 52 again assumes the closed position shown in FIG. 2, and the control pressure P is maintained. is its neutral pressure P. It is set to H within a very short time.

Also, the pressure in the pilot pressure chamber FII is higher than the pressure in the output pressure chamber FL, that is, the control pressure PC is the pilot pressure P1. If it is lower, it changes oppositely to the above,
A similar pressure adjustment is performed.

Furthermore, if the excitation current Is is increased from the neutral state where the vehicle height value is within the appropriate range, the pilot pressure P is accordingly set to a high value.

As a result, the pressure equilibrium between both Fu and Ft is disrupted again, and the control pressure P goes through the same transient state as described above. is the pilot pressure Pp, that is, the excitation current ■.

The voltage is boosted according to the value of . On the other hand, if the excitation current I is reduced, the control pressure P will be reduced accordingly. is lowered.

Therefore, in this embodiment, the control pressure P with respect to the change in the excitation current (3). 3, the static characteristics shown in FIG. 3 are obtained.

Here, P CMAX is the maximum control pressure approximately equivalent to the line pressure of the hydraulic source 18 (for example, 80 kg f/crR
) and PCMIN is the minimum control pressure (e.g. 15 k
gf/c+fl).

In this way, in each pressure control valve 22, the control pressure P corresponds to the value of the commanded excitation current I. is supplied to the corresponding hydraulic cylinder 24. For this reason, each hydraulic cylinder 24
In the pressure chambers, for example, biasing forces that resist the rolls are generated individually, thereby controlling the roll rigidity and appropriately suppressing changes in the attitude of the vehicle body.

Moreover, since the accumulator 40 constituting the vibration absorbing device has the characteristics shown in FIG.
The change in pressure P for a change in volume ■1 is control pressure P.

For example, the control pressure P on the inner wheel side when the vehicle turns is approximately constant regardless of the magnitude of the pressure P. Even in a state in which the current is decreased, the responsiveness of the hydraulic cylinder 24 to the excitation current (3) of the posture change suppression control device 32 does not deteriorate.

Assuming that the pressures of both Fu and Ft of the pressure control valve 22 are in equilibrium, the vehicle passes through a relatively gentle bumpy road and the hydraulic cylinder 24 is pressed from the road side. The pressure chamber has a resonance frequency range (I Hz
Suppose that there is a vibration input of (degree). This vibration input results in a corresponding pressure fluctuation, and the pressure chamber 52 of the pressure control valve 22
c. The flow rate change accompanying this pressure fluctuation is usually M
It is larger than that when the pressure is adjusted by jJ magnetic current ■5.

Due to this human power for excitation, the pressure in the output side pressure chamber FL temporarily increases (or decreases) and becomes higher (or lower) than the pressure in the pilot side pressure chamber FI+. This causes the main spool 52 to move toward the pressure chamber Fu side (or F
The output boat 54c and return port) 54r (or supply port) 54s and output port 1-
54c) are in communication, and hydraulic oil is temporarily returned to (or supplied from) the hydraulic source 18. In other words, even if there is an excitation input in the resonant frequency range on the spring, the vibration transmission rate to the vehicle body can be significantly reduced, and deterioration of riding comfort can be reliably prevented.

Furthermore, if the above-mentioned excitation input from the road surface is of a high frequency corresponding to the unsprung resonance frequency due to small irregularities on the road surface, pressure fluctuations in the pressure chambers of each hydraulic cylinder 24 cause the throttle 38 to The signal is transmitted to the accumulator 40 via. As a result, it is possible to significantly reduce the vibration transmission rate to the vehicle body.

For example, when the loaded weight of the vehicle is higher than usual, or when the vehicle turns on the outer wheel side, the control pressure Pc increases and a large amount of hydraulic fluid enters the fluid chamber 73 of the accumulator 40. However, as described above, the change in the pressure P1 with respect to the change in the volume vl of the fluid chamber 73 of the accumulator 40 is approximately constant regardless of the magnitude of the control pressure PC.
Most of the flow rate generated in the pressure chamber I is in the accumulator 4.
0 and the flow rate flowing through the pressure control valve 22 is small, so vibrations are not transmitted to the vehicle body and the ride comfort of the vehicle is not impaired.

In addition, in the second embodiment, the case where the throttle valve 38 is used as the damping element has been described, but for example, if the pressure chamber I and the accumulator 40 are connected by a long pipe with a small inner diameter, this pipe can be Since it acts as a damping element, there is no need to provide any other diaphragm or the like.

Further, in the above embodiment, the case where hydraulic pressure was used as the fluid pressure was explained, but the invention is not limited to this.
Other fluid pressures can also be used, for example pneumatic pressure.

Further, in the above embodiment, an example was shown in which the accumulator of the present invention was used in an active suspension, but it goes without saying that the accumulator of the present invention may be used in other fields.

(Effects of the Invention) As explained above, according to the present invention, the pressure in the second gas chamber fluctuates rapidly (nonlinearly) as the piston moves, but the pressure in the first gas chamber fluctuates in the second gas chamber as the piston moves. Since the pressure in the gas chamber fluctuates in the opposite direction and acts to suppress its rapid fluctuations, the ratio of the change in the generated pressure to the change in the volume of working fluid entering the accumulator depends on the control pressure of the fluid pressure cylinder. It can be kept approximately constant regardless of the relationship.

Therefore, when the present invention is applied to an active suspension, even if the control pressure of the hydraulic cylinder is reduced, such as on the inner wheel side when the vehicle turns, the responsiveness of the hydraulic cylinder will not deteriorate. , even if the control pressure increases and a large amount of hydraulic fluid enters the accumulator, such as when the vehicle's loaded weight is higher than usual or when the vehicle turns, the control pressure increases and a large amount of hydraulic fluid enters the accumulator, Since most of the flow rate generated in the pressure chamber of the hydraulic cylinder due to vibrations is absorbed by the accumulator, the vibrations are transmitted to the vehicle body, thereby preventing deterioration of the ride comfort of the vehicle. If a damping element is provided, vibrations in the under-spring resonance frequency range can be reliably damped.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an accumulator in an embodiment of the present invention, Fig. 2 is a sectional view showing an example of a pressure control valve applicable to an active suspension related to the invention, and Fig. 3 is a sectional view of the pressure control valve. A graph showing the static characteristics of the control pressure PC with respect to the excitation current (3), Fig. 4 is a schematic configuration diagram of the active suspension, and Fig. 5 shows the relationship between the intrusion volume of the working fluid and the generated pressure in the accumulator shown in Fig. 1. Figure 6 is a graph showing the relationship between the intrusion volume of working fluid and the generated pressure in a conventional accumulator. Figure 7 is a graph showing the response of the fluid pressure cylinder in a conventional active suspension. FIG. 8 is a graph showing the damping characteristics of a conventional active suspension according to the volume of working fluid entering the accumulator. DESCRIPTION OF SYMBOLS 10... Active suspension, 14... Wheel side member (unsprung), 16... Vehicle body side member (spring), 22
... Pressure control valve, 24 ... Hydraulic cylinder (other fluid pressure equipment), L ... Pressure chamber, 38 ... Throttle valve, 40.
...Accumulator, 70...Cylinder, 70a...
- First sliding chamber, 70b... Second sliding chamber, 71... Free piston, 71a... First piston, 71b...
- Second piston, 71c...Connection body, 72a...First gas chamber, 72b...Second gas chamber, 73...Fluid chamber, 75a, 75b...Seal member.

Claims (1)

[Claims] (1) A piston-type accumulator comprising a cylinder and a piston slidably included in the cylinder, the accumulator having a first piston and a second piston having a larger diameter than the first piston.
The piston is configured by integrally separating the pistons in the axial direction, and the cylinder is connected to a first sliding chamber in which the first piston is slidably located, and the first sliding chamber is connected to the first sliding chamber. and a second sliding chamber in which the second piston is slidably located, and is formed by the first piston, the second piston, the first sliding chamber, and the second sliding chamber. A first gas chamber is filled with a predetermined volume of gas, and a second gas chamber is formed by the second piston and the second sliding chamber.
1. An accumulator, characterized in that a predetermined volume of gas is sealed in a gas chamber, and further, the fluid chamber formed by the first piston and the first sliding chamber is communicated with another fluid pressure device.