JPH0361743A - Hydraulic cylinder for suspension - Google Patents

Abstract

PURPOSE:To exert a sufficient damping effect against the vertical vibration of a vehicle body due to the road face input while the internal pressure of a suspension cylinder is decompressed near the control limit by closing a bypass passage with a shutter when the internal pressure of the cylinder is decreased. CONSTITUTION:When the chamber VB of a hydraulic cylinder 1 is decompressed to the atmospheric pressure which is the control limit in the vehicle body attitude control operation during running, the pressure of a void VD is decreased, a shutter member 20 is pushed down to the position shown in the figure by the action of an expansion spring 22, the tip of an extended tube section 20a coincides with a lateral hole 19 to close it, a bypass passage is closed, and the communication between chambers VA and VB is cut off. When a vehicle body is operated in the floating direction by the vehicle body vibration due to the road face input under this condition, the operating oil of the chamber VA flows toward the chamber VB via a communicating passage 8b while being restricted by an expansion damping force valve 16, a pressure difference is generated between chambers VA and VB by the passage resistance, thus the damping action for vehicle body vibration is exerted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic cylinder suitable for use in an active suspension system that also serves as attitude':fAw means.

(Prior art) When the attitude control of a vehicle is actively carried out in accordance with the driving situation of the vehicle in addition to changes in the static gI of a heavy body, the ride comfort of the vehicle is further improved and the handling stability is improved. will improve.

Therefore, in recent years, attention has been paid to the fact that it is effective to control the attitude IvJ of a vehicle by using an active suspension system as a suspension system of the vehicle.

Incidentally, as a posture control device most suitable for use in this type of active suspension system, a structure as shown in No. 31-m, for example, has been proposed. That is, this type of attitude control device consists of a suspension mechanism (2) and a hydraulic supply/discharge mechanism (2), and is configured such that the suspension mechanism (2) is controlled to extend or contract under hydraulic control of the hydraulic supply/discharge mechanism (2).

The suspension mechanism I has a hydraulic cylinder I connected to a suspension arm A whose upper end is connected to the vehicle body B side and whose lower end is connected to the vehicle A side at each of the four wheels of the vehicle.

Therefore, by controlling the hydraulic cylinder 1 to expand and contract, the vehicle height of each of the four wheels of the vehicle is adjusted, and the overall attitude of the vehicle is controlled.

Incidentally, a suspension spring 2 that supports the load from the vehicle body B side is installed in parallel with the hydraulic cylinder l, and the hydraulic circuit system further includes a throttle 3 that provides a predetermined damping effect when the hydraulic cylinder l expands and contracts. and a gas spring 4 that exhibits a predetermined gas spring effect.

On the other hand, although no definitive hydraulic supply/discharge mechanism ■ connected to such a suspension mechanism ■ has been proposed yet, it has at least a control block 11, a hydraulic power source I2, and a tank 13. In addition to supplying hydraulic pressure from the hydraulic source 12 to the hydraulic cylinder l by selected operation of the control valve 11, or releasing the hydraulic pressure in the hydraulic cylinder l to the tank 13, a neutral state is adopted in which the cylinder hydraulic pressure is maintained. A similar structure has been adopted.

That is, the controller C receives the situation signals from the sensor 5 installed on the vehicle body B, and calculates the target pressure calculated based on these signals and y! detected by the pressure sensor 14. A feedback loop mechanism operates so that the actual cylinder pressure always matches the actual cylinder pressure. Therefore, based on this feedback current, the control block jl+ which receives the control current i adjusts the cylinder internal pressure W by the operation selected thereby to bring the vehicle into the optimum state at that time.

Then, during the #2 adjustment of the hydraulic oil supply, the shock absorber a function by the gas spring 4 and the throttle 3 is exhibited.

Next, FIG. 4 shows an example of the configuration of a hydraulic cylinder l and a gas spring 4 that perform the above functions.A piston 6 is slidably disposed inside the hydraulic cylinder l, and thereby the inside of the cylinder is rotated twice. It is divided into two storage compartments, VA and VB. The other end of the piston rod 7, to which the piston 6 is fastened, protrudes outside the cylinder.

Historically, the piston 6 is provided with a hole 8 that communicates between the chambers VA and VB, and furthermore, in the normal movement speed range of the piston 6, movement of hydraulic oil occurs in the chambers VA and VarIri. It has a passage area as large as 1 minute so that there is almost no pressure loss caused by this. - On the other hand, a through hole 9 is provided inside the piston rod 7, and the outer end of the hole 9 is connected to the supply/discharge side boat of the control cell, and the inner end is opened to the chamber vB. be.

On the other hand, the gas spring 4 has a gas chamber Va and an oil chamber V formed inside thereof by a free piston 10. It is divided into
Among them, the oil chamber Vo is connected to the supply/discharge side boat which is common to the cylinder chamber v.

The oil inlet and outlet of the gas spring 4 is formed in the throttle 3, but instead of this orifice control mechanism, a valve mechanism disposed in the flow path Φ like a normal shock absorber may be used. Further, the gas chamber v6 is filled with a predetermined square gas in advance.

Therefore, in the above configuration, assuming that the equivalent car weight hot water is Wt, the cylinder generated force is F□, the sublinker is Fl, and the cylinder internal pressure is P, the above Fe, F, and P when the car body B is in a static state are Let the respective values of Fe, , F,
. and P. Then, W,=F,, +Fc, =F,
,+^r'P.

(However, A7 is the cross-sectional area of the piston rod).

Therefore, when the vehicle turns or accelerates or decelerates while running, an inertial force acts on the vehicle body B, causing the vehicle body posture to change.

This means that, apparently, the weight of the chained vehicle is increased or decreased by the amount of change Δw due to the inertial force. Therefore, regarding the internal pressure P in the hydraulic cylinder l of each wheel.

ΔW, = A, ·ΔP.

The cylinder internal pressure change ΔP required to satisfy the relationship
Add or subtract 1 to 14'! If J, the forces at each wheel are maintained in a balanced state, and the attitude of the vehicle body B at this time does not change.

That is, for the outer wheel side during turning, the rear wheel side during acceleration, and the front wheel side during deceleration, the weight I11 increases by the amount of change Δwp, so the cylinder internal pressure is increased by the amount of change ΔP1,
Conversely, the control valve 11 supplies and drains hydraulic oil to the inner wheels during turning, the front wheels during acceleration, and the rear wheels during deceleration so that the cylinder internal pressure is reduced by the amount of change ΔP4. This allows you to keep the vehicle body in a horizontal position.

On the other hand, when driving straight ahead at a constant speed, the above-mentioned inertial force does not act on the vehicle body B.However, when the vehicle body B moves up and down due to input from an uneven road surface while driving, the vertical speed is proportional to the vertical speed at this time. Since the weight of the chained vehicle 1we changes at the same time, the cylinder internal pressure is adjusted accordingly by a single stage similar to the control means described above.
By changing only P2, this vertical movement of the vehicle body can be suppressed. np, A1·ΔP2 corresponds to the damping force.

Therefore, while the vehicle is turning or accelerating or decelerating, the t! Even if vertical vibration is likely to occur in the vehicle body B due to road surface irregularities caused by debris A, by increasing or decreasing the cylinder internal pressure of each wheel by the amount of change ΔP1r-, and further increasing or decreasing by the amount of change ΔP2,
It is possible to control posture and suppress vibrations.

Incidentally, although the outline of the cylinder internal pressure increase/decrease control operation in such a case has been described above, more specifically, it is performed as follows.

Now, when increasing the cylinder internal pressure, the controller C increases the control current i to the control valve 11 by 31! L, selectively operate the valve 11 so that the supply/discharge side boat and the oil pressure source boat communicate with each other, and feed hydraulic oil into the oil chamber VO of the gas spring 4. As a result, the free piston lO or the gas chamber V
While compressing 3, move to the upper right in Fig. 4 to increase the gas pressure, and then press the oil chamber V. The pressure of is also the same as this gas pressure.

At the same time, the cylinder internal pressure also increases. When the signal from the pressure sensor 14 that detects the cylinder internal pressure matches the target pressure, the voltage ii at the control valve port is readjusted, the communication between the two boats is cut off, and the pressure state is maintained. .

On the other hand, in order to reduce the cylinder internal pressure, the control valve [1 is selected and operated to communicate the supply/discharge side boat and the tank side boat to supply hydraulic oil from the oil chamber vo of the gas spring 4. By discharging into the tank 13, the gas chamber va expands and the gas pressure decreases. Along with this, the cylinder internal pressure also decreases. Then, when the signal from the pressure sensor 14 matches the target pressure, the communication between the boats is cut off in the same way as in the above-described operation, and the current pressure state is maintained.

[AlM to be solved by the invention] By the way, in a mechanism having such a configuration, the inertial force acting on the vehicle body during control operation is large.

Correspondingly, depressurization (change Δ
In a case where the hydraulic cylinder that required pressure (p+) further requires pressure reduction (variation Δpg) to prevent upward movement of the vehicle body due to input from an uneven road surface, the total pressure reduction (
When ΔP1+ΔP2) is greater than the cylinder internal pressure P0 at rest, the corresponding P is applied to the first gap. Decompression width greater than or equal to the value of (
Since the restriction on piston movement cannot be removed, there is a drawback that the suppressing function against the vertical vibration of the vehicle body at this time cannot be fully exerted.

Therefore, in an active suspension that controls the cylinder internal pressure by using such a single-acting cylinder and a suspension spring in combination, the present invention reduces the internal pressure of the suspension cylinder to near the control limit in order to ensure stability of the vehicle body posture. The purpose of this project is to develop a hydraulic cylinder that can be expected to have a sufficient damping effect against vertical vibrations of the vehicle body due to road surface input.

(Means for Solving the Problems) According to the present invention, this object is achieved by providing an active suspension in which a single acting cylinder and a spring are installed in parallel to control the cylinder internal pressure. A communication passage between the cylinder chambers is provided in the piston portion, which is regulated by a rebound damping force valve and a check valve, and a bypass passage of the communication passage is opened in the piston rod, and a spring force is applied to the bypass passage. A shutter member consisting of a free piston body supported in balance with the cylinder internal pressure and slidable in the axial direction is inserted, and the shutter closes the bypass passage when the internal pressure of the cylinder decreases. Suspension oil I [can be achieved by cylinder].

[For production]

Bypass passage provided in the piston rod.

When the vehicle height J adjustment is at the normal height position, the circuit is open,
The piston communication hole is regulated by the check valve and the expansion damping force valve, and functions as a free passage for hydraulic oil between the upper and lower cylinder chambers partitioned by the piston.

In order to control the cow's body posture, when the cylinder internal pressure is lowered and the piston rod is extended to near the upper limit position,
This decrease in internal pressure disrupts the balance with the spring force, and the spring force causes the shutter member to rise relative to the piston rod. This closes the bypass.

Movement of the piston rod after the bypass passage is closed, that is, vertical movement of the vehicle body due to input vibration from the road surface, is subject to the movement of hydraulic fluid between the upper and lower chambers or is regulated by the check valve and the rebound damping force valve. .

The resulting damping force exerts a damping effect in the piston rod extension region.

(Embodiments) A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal side view showing an embodiment of the present invention.1 Similar to a normal shock absorber, a piston 6 slidably fitted into an oil stopper cylinder l divides the inside of the cylinder into a chamber vA and a chamber v.
The piston 6 has a check valve 15 that allows the flow of hydraulic oil from the chamber vfi to the chamber vA through the communication hole 8a, and a check valve 15 that allows the flow of hydraulic oil from the chamber vA to the chamber vA through the communication hole 8b. A rebound damping force valve 16 is provided to increase the flow path resistance to the hydraulic oil flowing toward the engine.

That is, when the piston 6 is fastened to the cylinder inner end of the piston rod 7, the loft end step and the piston 6
Insert the valve spring stopper 17 between the
The stopper! A non-return spring 15b and a non-return valve 15a are interposed between one side of the piston 6 and the piston 6 to form the check valve I5. 6, and sandwich the inner edge of the leaf valve 16a between the nut 18 and the leaf valve 16a.
The expansion-side damping force valve 16 is formed by disposing a main valve +6b movably in the axial direction with a main valve spring 16c interposed therebetween.

A through hole 9 for supplying and discharging hydraulic oil provided in the piston rod 7 is connected to a horizontal hole 19 bored in the rod wall above the piston. A bypass path is formed to communicate vA and chamber vB. Moreover, the through hole 9 and the horizontal hole 19 have a flow passage cross-sectional area of 1=min to such an extent that there is almost no resistance to the flow of hydraulic oil therethrough.

On the other hand, the piston nut 18 connects the small-diameter cylinder portion extending further downward from the tip of the piston rod 7, and slides the shutter member 20 having the free piston portion 20b into the cavity vc sealed with the tip cap 21. [A pressure expansion spring is disposed in one position, and the extension cylindrical portion 20a is inserted into the n-through hole 9 by tightly sliding it, and the pressure expansion spring is interposed between the cap 21 and the shutter member 20. 22, the upper end of the extension 0120a is pushed into the horizontal hole 19.
The member 20 is given an actuation tendency in the direction of penetrating to the position.

The cavity vc is sealed by its internal pressure or the atmospheric pressure at the time of assembly, and another cavity v0 separated by the free piston portion 20b of the piston nut 18 is sealed by the internal pressure or atmospheric pressure at the time of assembly.
It communicates with the container chamber 7 through a small hole 23 drilled in the peripheral wall of the shutter member 20, and further through a through hole 24 in the extended cylindrical portion 20a of the shutter member 20 and a small hole 25 that communicates with the through hole 24 and faces the void space v8. and communicates with the front through hole 9.

Additionally, 26 indicates a rod stopper.

No. 21521 is a vertical side view showing another embodiment of the present invention, in which the shutter member 20 in the first illustrated embodiment is shown.
The extension tube section 20a and the free piston section 20b are divided into two parts, and the extension tube section 20a always moves integrally with the free piston section 20b. 1 part 20
The extension cylindrical portion 20a is moved to the free piston portion 2 by the acting force of another pressure expansion spring 27 disposed on the upper edge of a.
It is weakly pressed against 0b. Other functional components in this embodiment that are similar to those in the first illustrated embodiment include:
They each have a common code.

According to the embodiment having such a configuration, this is used as a hydraulic cylinder in the suspension machine aI, and the hydraulic supply mechanism 4j is assembled thereto, and the mounting base installed between the vehicle body B and the axle A is used. The chamber vII normally has a certain level of internal pressure.

Since the pressure in the cavity VD is equal to the pressure in the chamber Va, the pressure in the cavity vI compresses the pressure expansion spring 22, and the shutter member 20 is in the lowered position. Therefore, in this state, the tip of the extension tube 20a retreats from the position of the horizontal hole 19, and the chamber vA and the chamber Va communicate with each other through the opened bypass path, and the hydraulic oil can freely move between them. Therefore, both the check valve 15 and the expansion-side damping force valve 16 arranged in the piston part do not act at all.

Therefore, at this time, the vehicle height can be adjusted in the same manner as in the conventional mechanism shown in FIGS. 3 and 4 described above.

Next, in the vehicle body posture control operation while driving, oil I [cylinder l]
The storage room v! l pressure or atmospheric pressure (pa” which is the control limit)
o), the pressure in the cavity v0 also decreases, and as a result, the shutter member 20 or the expansion spring 22 pushes it up to the state position shown in tjS1.

Due to this movement of the shutter member 20, the tip of the extended cylindrical portion 20a aligns with the horizontal hole 19 and closes it.

The bypass path is closed, thereby cutting off communication between the chambers vA and vB.

In this state, when the heavy body B lifts due to vehicle body vibration due to road surface input, that is, the cylinder 1 operates in the extension direction, the hydraulic oil in the chamber vA that is fE&& is regulated by the extension side damping force valve 16 of the piston part. It flows toward the chamber vB through the communication hole 8b, and a pressure difference is generated between the chambers due to the flow path resistance at this time, and a Mif force is generated passively.
It exerts a damping effect on vehicle body vibration.

On the other hand, when the hydraulic cylinder 1 operates in the compression direction due to ffi vibration, the pressure in the chamber vlI is increased by the control action of the hydraulic supply/discharge control W tsuki structure (■), so that the shutter member 20
receives the increased pressure in the cavity v0, moves downward against the force of the pressure expansion spring 22, and opens the bypass path of the retraction f from the horizontal hole 19 position at the tip of the extension tube 20a, thereby establishing communication between the chambers. will be done. At this time, even if the pressure increase in the chamber v8 is slight and the bypass passage is incompletely opened, the hydraulic oil in the chamber v6 flows through the check valve 15 to the chamber ■. Therefore, always have a bi-capacity room vA.

v6 becomes equal pressure, and the effect of suppressing vehicle body vibration by the above control can be obtained.

According to the embodiment shown in J421ffi, the shutter member 20 which is divided into two parts is easier to process, and its operation and function are substantially the same as in the first embodiment shown above. .

(Effects of the Invention) As described above, according to the hydraulic cylinder of the present invention, in the active suspension that controls the cylinder internal pressure while being installed in parallel with the #I moving cylinder spring, the rebound damping force is applied to the piston portion of the single acting cylinder. A communication passage between the cylinder compartments regulated by a valve and a check valve is provided, and a bypass passage of the communication passage is opened in the piston rod, and a balance between the spring force and the cylinder internal pressure is provided in the bypass passage. A shutter member consisting of a free piston body supported below and slidable in the axial direction is inserted so that when the internal pressure of the cylinder decreases, the shutter closes the bypass passage. It is possible to passively generate a damping force against external input vibrations even when the pressure in the chamber is reduced, and even when the suspension cylinder pressure is reduced to the vehicle height control limit, vertical vibrations of the vehicle body can be suppressed. It is possible to obtain a sufficient vibration damping effect.

[Brief explanation of drawings]

Fig. 1 is a longitudinal side view showing one embodiment of the hydraulic cylinder of the present invention, Fig. 2 is a longitudinal side view showing another embodiment of the hydraulic cylinder of the invention, and Fig. 3 is an example of a conventional active suspension system. FIG. 4 is a longitudinal sectional side view showing an example of a hydraulic cylinder and a gas spring in the above system. (Explanation of symbols)

Claims (1)

[Claims] In an active suspension that controls cylinder internal pressure by installing a single acting cylinder and a spring in parallel, the piston portion of the single acting cylinder is provided with a communication passage between cylinder chambers regulated by a rebound damping force valve and a check valve. , a bypass passage of the communication passage is opened in the piston rod, and
A shutter member consisting of a free piston body supported under a balance between the spring force and the cylinder internal pressure and slidable in the axial direction is inserted into the bypass passage, and when the internal pressure of the cylinder decreases, the shutter A hydraulic cylinder for suspension, characterized in that it is configured to close the bypass passage.