JPH06241263A - Damping force selecting mechanism of shock absorber - Google Patents

Abstract

PURPOSE:To provide a shock-absorber damping force selector mechanism that is simple in structure and able to secure a large damping force transfer range. CONSTITUTION:A piston partitions the inside of a cylinder 14 into two oil chambers 15 and 16, and thereby its damping force is produced by an amount of oil flow running into these two oil chamber 15, 16 through an oil hole 8a installed in this piston 2. This damping force in the piston 2 is buffered by an elastic member 7 and transmitted to a piston rod 1. When a clutch plate 4 to lee displaced by expansion or contraction of a piezoelectric actuator 1, whose one end is clamped to the piston rod 11, connects the piston 2 and the piston rod 11, these elements 2 and 11 are connected to each other not through the elastic member 7, therefore the damping force looked from the piston rod 11 is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force switching mechanism that switches the damping force of a shock absorber by utilizing the displacement of a laminated piezoelectric material.

[0002]

2. Description of the Related Art As a conventional example of a damping force switching mechanism for a shock absorber using a laminated piezoelectric material, there is Japanese Patent Application Laid-Open No. 1-312283 filed by the present applicant. This damping force switching mechanism expands the displacement of the laminated piezoelectric body with a displacement magnifying mechanism consisting of a hydraulic piston mechanism that operates on the Pascal principle,
The hydraulic displacement valve is driven by using this enlarged displacement, and the damping passage force is switched by switching the oil passage cross-sectional area of the communication hole that communicates the two oil chambers on both sides of the piston.

[0003]

However, in the above-mentioned prior art, it is necessary to use a hydraulic piston type displacement magnifying mechanism in order to obtain a hydraulic pressure switching valve and a stroke (displacement) necessary for this hydraulic pressure switching valve. There was a problem that a large number of complicated and high-precision parts were required. Further, even if the stroke is expanded by the displacement expansion mechanism with the piston, the stroke of the original laminated piezoelectric body is small, so there is a limit to the stroke that can be obtained, and there is a limit to the amount of change in the oil passage cross-sectional area. There was a problem that there was a limit to the amount of change in damping force.

The present invention has been made in view of the above problems, and its first object is to provide a damping force switching mechanism for a shock absorber having a simple mechanism. A second object of the present invention is not to adjust the cross section of the oil passage, but to directly control the mechanical coupling force between the piston rod and the piston by the piezoelectric actuator, thereby providing a shock absorber with a large damping force switching width. It is to provide a damping force switching mechanism.

[0005]

A damping force switching mechanism for a shock absorber according to the present invention includes a piston which is slidably fitted in a cylinder and which divides the inside of the cylinder into two oil chambers which can communicate with each other through oil holes. A piston rod connected to the piston via an elastic member; a piezoelectric actuator having one end fixed to the piston rod and the other end extending and contracting;
And a clutch plate that is biased by the piezoelectric member to connect and disconnect the piston and the piston rod without using the elastic member.

[0006]

The piston divides the inside of the cylinder into two oil chambers, and the damping force of the piston is generated by the oil flow rate flowing through the two oil chambers through the oil holes provided in the piston. The damping force of the piston is buffered by the elastic member and transmitted to the piston rod. A feature of the present invention is that a clutch plate, which is displaced by expansion and contraction of a piezoelectric actuator whose one end is fixed to a piston rod, connects and disconnects the piston and the piston rod without an elastic member. Similar to a normal clutch mechanism, the clutch plate can be engaged and disengaged with a slight displacement with respect to both facing surfaces (friction contact surfaces) of the piston and the piston rod.

[0007]

As described above, the damping force switching mechanism of the shock absorber according to the present invention is provided with the clutch plate for connecting and disconnecting the piston and the piston rod by the expansion and contraction of the piezoelectric actuator fixed to the piston rod without the elastic member. Therefore, the clutch plate can be engaged and disengaged by a slight displacement of the clutch plate with respect to at least one of the opposing surfaces (friction contact surfaces) of the piston and the piston rod due to the bias of the piezoelectric actuator. As a result, a shock absorber damping force switching mechanism having a simple mechanism can be realized.

Further, although the damping force switching mechanism of the present invention uses the frictional coupling force between the piston rod and the piston without expanding the small displacement of the piezoelectric actuator, a large damping force switching width can be obtained.

[0009]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIGS. This embodiment is a variable damping force type shock absorber installed together with a coil spring between a wheel of an automobile and a vehicle body. FIG. 1 is an enlarged cross-sectional view of an essential part of the shock absorber, and FIG. 2 is a partially broken cross-sectional view of the shock absorber. It is a figure.

As shown in FIG. 2, the shock absorber SA is fixed to the axle side member 21 at the lower end on the cylinder 14 side, while the shock absorber SA is mounted on the vehicle body via the bearing 22 and the vibration isolating rubber 23 at the upper end on the rod 11 side. It is fixed to the side member 24. A rod 11 is fitted and inserted in the cylinder 14, and a substantially cylindrical housing 10 is screwed to the lower end of the rod 11 with openings at both ends. A main piston 8 which is slidable along is connected so as to be relatively displaceable in the axial direction.

As shown in FIG. 1, the main piston 8 has an oil inlet space in a cylinder 14 in which an upper oil chamber 16 and a lower oil chamber 1 are provided.
5 and an oil hole 8a penetrating the main piston 8
Communicates with the oil chambers 15 and 16. The hydraulic oil in the oil chambers 15 and 16 flows through the oil hole 8a as the main piston 8 slides, and the shock absorber S is caused by the flow resistance.
The damping force of A is determined.

A hole 11a is formed in the rod 11 from the lower end surface in the figure along the axis, and a piezo load sensor 17 is provided in the innermost part of the hole 11a.
After the insertion, the disc-shaped cover 13 is locked at a step on the inner peripheral surface of the rod 11 at a predetermined distance from the lower end opening of the hole 11a. After that, a cylindrical spacer 1 having openings at both ends is formed in the hole 11a.
2 is inserted, and the piezoelectric actuator 1 is inserted inside the spacer 12. In the figure of the piezoelectric actuator 1, the upper end is fixed to the lower end surface of the cover 13, and the cable 20 for driving the piezoelectric actuator, which is output from the piezoelectric actuator 1, is the cover 1.
3 extends through the rod 11 to the upper end of the rod 11.

The lower end of the rod 11 is screwed into the upper portion of the hole 10a of the housing 10 in the axial direction.
A sliding surface for slidably holding the piston 2 is formed at the central portion in the axial direction of the 0 hole 10a. Also, the housing 10
Has a female screw surface into which the screw 6 is screwed, and the lower axial half of the hole 10a of the housing 10, that is, between the sliding surface and the female screw surface. It has a plurality of (4) taper surfaces 11b which are located and incline toward the axis as it goes upward in the figure. The respective tapered surfaces 11b are separated from each other about the axis M by 9
The flat surface is arranged at a distance of 0 degrees, but may be a cylindrical surface or the like.

On the other hand, the above-mentioned main piston 8 is located below the housing 10 and is slidably held by the cylinder 14, and a rod-shaped shaft 8b extending upward from the center of the upper end surface of the disc. Consists of. Shaft 8b
Is slidably penetrated through the central shaft hole of the screw 6 and fitted into the hole 10a up to a position facing the tapered surface 11b, and 4 is provided between the outer peripheral surface of the shaft 8b and the tapered surface 11b of the housing 10 described above. An individual wedge-shaped piece (clutch plate in the present invention) 4 is interposed.

The outer peripheral surface of the wedge-shaped piece 4 is a flat surface which slidably contacts the tapered surface 11b, and the inner peripheral surface of the wedge-shaped piece 4 slidably contacts the outer peripheral surface of the shaft 8b. Has become. The clutch surface 4a can be appropriately changed to a flat surface or the like, and the outer peripheral surface shape of the shaft 8b can be changed accordingly. Further, a spring 5 composed of a disc spring is disposed around the shaft 8b between the wedge-shaped piece 4 and the screw 6, one end of the spring 5 is locked to the screw 6, and the other end is The lower end of the wedge-shaped piece 4 is biased upward.
The upper end of the wedge-shaped piece 4 biased upward by the spring 5 biases the lower end surface of the piston 2 upward, so that the upper end surface of the piston 2 is in contact with the lower end surface of the piezoelectric actuator 1. 2a and 8c are O-rings.

Next, the shock absorber SA having the above structure
The operation of will be described. In this shock absorber SA, the impact force (load) transmitted from any one wheel of the vehicle to the rod 11 is detected by the piezo load sensor 17 that detects expansion and contraction of the rod 11 due to this impact force.
The piezo load sensor 17 outputs a signal voltage corresponding to the detected load to an ECU (not shown), and this ECU applies a drive voltage to the piezoelectric actuator 1, whereby the piezoelectric actuator 1 expands and contracts. First, a normal traveling state in which the piezoelectric actuator 1 contracts will be described. In this state,
The spring 5 pushes the wedge-shaped piece 4 upward, as shown in FIG. As a result, each wedge-shaped piece 4 is guided by the tapered surface 11b and approaches the axis M, and the clutch surface 4a of the wedge-shaped piece 4 is strongly pressed against the outer peripheral surface of the shaft 8b, whereby the main piston 8 is wedge-shaped. It is frictionally coupled to the housing 10 through the piece 4.

Next, a state where the piezoelectric actuator 1 is expanded will be described. In this state, the piezoelectric actuator 1
The lower end surface of the wedge pushes the wedge-shaped piece 4 downward through the piston 2, and when the wedge-shaped piece 4 retreats, the wedge-shaped piece 4 is moved to the housing 1.
Guided by the taper surface 11b of 0, and slightly away from the axis M, the frictional contact between the clutch surface 4a of the wedge-shaped piece 4 and the outer peripheral surface of the shaft 8b is relaxed, and the shaft 8b is substantially formed.
Is free to move relative to the housing 10 in the axial direction.
As a result, the main piston 8 is elastically coupled to the housing 10 via the spring 7.

Explaining further concrete examples,
When the wheel passes through the convex portion of the road surface, the piezoelectric load sensor 17 detects it through the rod 11, and the ECU extends the piezoelectric actuator 1. Then, as described above, the wedge-shaped piece 4 is displaced downward, the main piston 8 is elastically coupled to the housing 10 via the spring 7, and the elasticity of the spring 7 reduces the impact. On the other hand, during normal road surface traveling, the spring 7 is killed by the locking of the main piston 8 and the housing 10, and the damping force of the shock absorber SA as a whole is switched between two stages.

If the effective stroke of the piezoelectric actuator 1 is S, the gap (clutch gap) width on the clutch surface 4a is W, and the crossing angle of the tapered surface 11b with respect to the axis M is Θ, then W = S × tan Θ Become.

In the above embodiment, the two-step control is used, but so-called half-clutch control is also possible by controlling the voltage to the piezoelectric actuator 1, and the damping force can be switched in multiple steps or steplessly. Further, in the above-described embodiment, a spring is added between the upper portion and the lower portion of the shaft 8b, and the piezoelectric actuator 1 is extended to extend the housing 10.
The main piston 8 and the main piston 8 can be doubly connected by the additional spring and the spring 67. (Embodiment 2) Another embodiment will be described with reference to FIG. The constituent elements having the same functions as those in the first embodiment are designated by the same reference numerals.

In this embodiment, the housing 10 is omitted, and the screw 6 is attached to the lower end of the hole 11a of the rod 11.
Is screwed in, and the upper end of the shaft 8b of the main piston 8 penetrates the screw 6 and is fitted into the hole 11a.
Further, the screw 32 is screwed into the hole 11 a at a predetermined distance from the lower end opening, and the piston 2 is slidably provided between the upper end surface of the screw 32 and the lower end surface of the piezoelectric actuator 1. . The piston 2 has a screw 3 at the lower end.
It is urged upward by the disc spring 31 that is locked to 2.

The lower end of the piston 2 penetrates the central shaft hole of the screw 32, and the lower end surface of the piston 2 faces the upper end surface of the shaft 8b of the main piston 8 with a predetermined gap. A total of two rotating pawls 34, which are located between the screws 32 and 6, are pivotally supported by a pin 35 on the rod 11 so as to be 180 degrees apart from each other around the shaft center M. 34a is located below the pin 35 in the figure and is in contact with the outer peripheral surface of the shaft 8b so as to be connectable / disconnectable.

On the other hand, the upper end surface 34b of the rotating claw 34 is shown in FIG.
In the above, a piston 33 is opposed to the lower end surface of the piston 2 with a slight distance, and a spring 33 is press-fitted between the rotary claws 34 and located above the shaft 8b. The spring 33 has a surface 34 that faces the axis M of each rotating claw 34.
c is urged in the centrifugal direction, and each urging claw 34 strongly presses the clutch surface 34a against the outer peripheral surface of the shaft 8b by this urging, whereby the rod 11 is frictionally coupled to the main piston 8 through the rotating claw 34. There is.

Therefore, in the state shown in FIG. 3, the main piston 8 is directly connected to the rod 11, and when the piezoelectric actuator 1 extends, the piezoelectric actuator 1 pushes the piston 2 downward, so that the piston 2 moves the rotating claws 34. Three
Is rotated in the direction of the arrow, that is, the centripetal direction, and by this rotation, the clutch surface 34a of the rotating claw 34 is disengaged from the outer peripheral surface of the shaft 8a, and as a result, the main piston 8 is elastically attached to the rod 11 via the spring 7. Be combined.

The operation and effect of the apparatus of this embodiment are the same as those of the first embodiment, but the shapes of the upper end surface 34b of the rotating claw 34 and the lower end surface of the piston 2 can be variously modified. For example, if the lower end surface of the piston 2 is formed into a concave mortar shape and the upper end surface 34b of each rotating pawl 34 is brought into contact with the lower end surface of the conical shape of the piston 2, the downward displacement of the piston 2 causes the rotating pawl 3 to rotate.
4 is guided by the concave surface of the mortar and smoothly rotates to the axis M.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part of a damping force switching mechanism of a shock absorber according to an embodiment of the present invention.

2 is a partially cutaway sectional view of the shock absorber of FIG.

FIG. 3 is an enlarged sectional view of a main part of a shock absorber according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric actuator 4 ... Wedge-shaped piece (clutch plate) 7 ... Spring (elastic member) 8 ... Main piston 11 ... Rod (piston rod) 14 ... Cylinder.

Front page continued (72) Inventor Hitoshi Osawa, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Meeting of inventors, Takehiro, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nidec Within

Claims (1)

[Claims] 1. A piston that is slidably fitted in a cylinder and divides the inside of the cylinder into two oil chambers that can communicate with each other by an oil hole; and a piston rod connected to the piston via an elastic member. A piezoelectric actuator having one end fixed to the piston rod and the other end expanding and contracting; and a clutch plate that is biased by the piezoelectric member to connect and disconnect the piston and the piston rod without using the elastic member. Characteristic shock absorber damping force switching mechanism.