JPH0681880A - Damping force switching mechanism for shock absorber - Google Patents

Abstract

PURPOSE:To provide a damping force switching mechanism for a shock absorber wherein also switchable width of damping force can be largely set and a change of damping force due to a thermal expansion difference can be suppressed, although a constitution is simple. CONSTITUTION:When a laminated piezoelectric unit 27 is extended, the second piston 40 is pressed down in an axial line direction by displacement of the laminated piezoelectric unit 27 through the first piston 30. Consequently, a deflecting plate 45 is further deflected inward from the initial deflection condition, to reduce a flow path area of an oil passage. Here is enlarged a deflecting amount to about 10 to 25 times relating to the displacement of the laminated piezoelectric unit 27. A coefficient of linear expansion of the laminated piezoelectric unit 27 is different from a coefficient of linear expansion of a housing 17 or the like, and even when generated a difference in a degree of thermal expansion between both the unit and housing due to an influence of temperature rise or the like of operating oil, since the first piston 30 provides a large coefficient of linear thermal expansion, its thermal expansion degree is increased, to absorb a thermal expansion difference between both the members.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention expands the displacement of a piezoelectric body using a displacement expansion mechanism, and changes the damping force of the shock absorber by changing the flow passage area of the oil passage by the expanded displacement. Regarding the force switching mechanism.

[0002]

2. Description of the Related Art Conventionally, as a damping force switching mechanism of a shock absorber that is mounted on a vehicle or the like and is capable of switching the damping force according to the running state or posture change of the vehicle, a piston slidably fitted to a cylinder is used. It is known that a damping force switching valve provided in an oil passage that connects two partitioned upper and lower oil chambers is moved to change the flow passage area of the oil passage to switch the damping force. There is.

As a mechanism for moving the damping force switching valve, there is known a mechanism using a piezoelectric body such as a piezo element as an actuator. The piezoelectric body is suitable as a drive source because it expands and contracts with extremely high responsiveness to an applied voltage, but its displacement is extremely small. For example, even a laminated piezoelectric body formed by laminating about 100 disc-shaped piezoelectric bodies has a displacement of about several tens of microns,
In practical use, the displacement is expanded and used.

An enlargement mechanism using the so-called Pascal's principle has been conventionally used as a mechanism for magnifying a minute displacement of the laminated piezoelectric material. This is to transfer the displacement of a piston with a large cross-sectional area driven by the expansion and contraction of a laminated piezoelectric material to a piston with a small cross-sectional area via hydraulic oil, and expand it to a displacement corresponding to the cross-sectional area ratio. (For example, refer to “Hydraulic switching valve equipped with piezoelectric actuator” in Japanese Patent Laid-Open No. 1-312283). This allows
A displacement of the laminated piezoelectric substance of several tens of microns can be obtained from a piston having a small sectional area as a displacement of about 1 mm. The damping force switching valve is moved by the small cross-sectional area piston to switch the damping force by connecting or disconnecting the upper and lower oil chambers.

[0005]

However, the conventional example in which the above-mentioned laminated piezoelectric body and the displacement magnifying mechanism are combined is provided with a displacement magnifying mechanism using the Pascal principle in addition to the damping force switching mechanism. , They both have precision structure. In the conventional displacement magnifying mechanism, a cylinder and a piston that minimize oil leakage are used, but if the hydraulic oil in the cylinder leaks out, the stroke of the small cross-sectional area piston that originally has a displacement of about 1 mm decreases. As a result, normal switching operation cannot be performed.

Therefore, it is necessary to provide a check valve mechanism for compensating the outflow of hydraulic oil from the inside of the cylinder, and to supply oil into the cylinder through the check valve when the hydraulic oil in the cylinder is insufficient. The structure became complicated, leading to higher costs.

Further, since the magnification of displacement is determined by the cross-sectional area ratio between the piston having a large cross-sectional area and the piston having a small cross-sectional area, the cross-sectional area ratio also needs to be 30 times in order to obtain a magnification of 30 times, for example. There is. Therefore, a small cross-sectional area piston and a large cross-sectional area piston having a cross-sectional area 30 times larger than that are required, and the size of the piston with a small cross-sectional area cannot be extremely reduced. Will also grow.

Further, usually, the linear expansion coefficient of the laminated piezoelectric material is often different from the linear expansion coefficient of the member arranged on the outer periphery of the laminated piezoelectric material, especially the housing, and the influence of the temperature rise of the hydraulic oil or the like. However, there is also a problem in that a difference in the degree of thermal expansion occurs between the two, causing a change in the expansion ratio = a change in the damping force.

Therefore, according to the present invention, the required space can be made relatively small with a simple structure, the width of the damping force that can be switched can be set large, and the damping force change due to the difference in thermal expansion can be suppressed. An object of the present invention is to provide a damping force switching mechanism of a possible shock absorber.

[0010]

In order to solve the above-mentioned problems, a damping force switching mechanism of a shock absorber according to the present invention is an oil communicating two oil chambers defined by a piston slidably fitted in a cylinder. A damping force switching mechanism of a shock absorber that has a passage and is capable of switching the damping force by changing the flow passage area of the oil passage, and is driven by a piezoelectric body that expands and contracts according to an applied voltage. A sliding member that is slidable in a direction, and is formed in a flat plate shape and is substantially parallel to the sliding direction of the sliding member, one end of which has a fixed position and the other end of which abuts on the sliding member. And,
An elastic switching flexure plate, which is arranged so that an initial flexure is generated on the side that reduces the flow passage area of the oil passage when no voltage is applied to the piezoelectric body; and Between the body and the sliding member, the displacement of the piezoelectric body is transmitted to the sliding member, and the coefficient of linear thermal expansion is larger than that of the piezoelectric body and the members arranged on the outer periphery thereof, It is characterized by comprising a displacement transmitting member that absorbs a difference in thermal expansion.

[0011]

According to the damping force switching mechanism of the shock absorber of the present invention, when a voltage is applied to extend the piezoelectric body, the displacement of the piezoelectric body is transmitted to the sliding member via the displacement transmitting member,
The sliding member slides in the cylinder axis direction. Then, in the switching flexible plate pressed by the sliding member, the end contacting the sliding member approaches the other end. By shortening the distance between both ends in this way, the switching flexible plate further flexes toward the side where the initial flexure had occurred, and reduces the flow passage area of the oil passage. Thus, the damping force can be increased by reducing the flow passage area.

The coefficient of linear expansion of the piezoelectric body differs from the coefficient of linear expansion of the member arranged on the outer periphery of the piezoelectric body, and due to the temperature rise of the hydraulic oil, there is a difference in the degree of thermal expansion between the two. Even if it occurs, the displacement transmitting member has a larger coefficient of linear thermal expansion and a larger degree of thermal expansion than the piezoelectric body and the outer peripheral member, and therefore absorbs the difference in thermal expansion between them. Therefore, it is possible to suppress the change of the enlargement ratio = the change of the damping force.

When the voltage application is stopped, the piezoelectric body returns to its original state, and accordingly, the switching flexible plate returns to its original initial flexible state due to its elastic restoring force. Here, the relationship between the displacement in which the distance between both ends of the switching flexible plate is shortened and the amount of deflection of the switching flexible plate, that is, the displacement enlargement ratio will be described. First, the deflection plate is assumed to be a part of a circular arc, and the displacement magnification rate k1 will be described with reference to FIG. Let R be the radius of curvature in the initial flexed state (indicated by symbol a in the figure), and r be the radius of curvature after the linear distance between the two ends of the arc is reduced by displacement Δx (indicated by symbol b in the figure). , If the displacement at the center of the arc is k1Δx,
From the geometrical relationship shown in (A), the displacement magnifying power k1 is expressed by the following equation.

[0014]

[Equation 1]

FIG. 7B is a graph showing the relationship between the radius of curvature R and the angle θ in FIG. 7A and the displacement enlargement factor k1 when the displacement Δx = 0.025 mm. As you can see from this graph, when it is regarded as an arc,
A magnification of up to about 20 times can be obtained.

Next, the displacement magnifying rate k2 in the case where the degree of deflection near the center of the flexible plate can be approximated by a triangle, as in the case where the degree of deflection is larger than other portions, will be described with reference to FIG. After the initial deflection state (indicated by the symbol c in the figure), the linear distance between both ends is shortened by the displacement Δx (the symbol d in the figure).
Indicate. ), Where k2 · Δx is the displacement of the central portion, the displacement enlargement factor k2 is calculated from the geometrical relationship shown in FIG.
It is expressed as the following equation.

[0017]

[Equation 2]

Then, Δx = 0.025 mm, L = 20
FIG. 8B is a graph showing the relationship between the angle θ and the displacement magnifying power k2 in FIG. 8A when mm is set. As can be seen from this graph, when it is regarded as a triangle, 2
A magnification of up to 5 times can be obtained.

As described above, since the minute displacement of the piezoelectric body is enlarged by the switching flexible plate and the flow passage area is changed by the switching flexible plate, the required space can be relatively reduced with a simple structure. Although it is possible, a sufficient displacement expansion rate can be obtained, the width of the switching damping force can be set large, and further, the displacement transmitting member can suppress the variation of the damping force due to the difference in thermal expansion.

[0020]

EXAMPLES Examples of the present invention will be described below. In the present embodiment, an example is shown in which a damping force variable type shock absorber is installed between a wheel and a vehicle body together with a coil spring. FIG. 1 is a sectional view showing the details of the damping force switching mechanism of the shock absorber of the present embodiment, and FIG. 2 is a partially cutaway sectional view of the shock absorber.

As shown in FIG. 2, the shock absorber SA is fixed to the axle side member 5 at the lower end on the cylinder 3 side, while the shock absorber SA is mounted on the vehicle body via the bearing 9 and the anti-vibration rubber 11 at the upper end on the rod 7 side. It is fixed to the side member 13. A rod 7 is fitted and inserted in the cylinder 3, and a hollow internal cylinder 15 is continuously provided at the lower end of the rod 7. A substantially cylindrical housing 17 is screwed into the inner cylinder 15, and the lower end of the housing 17 is
A main piston 20, which is slidable inside the cylinder 3 along its inner peripheral surface, is screwed.

The outer circumference of the main piston 20 is an O-ring 19
The main piston 20 divides the inside of the cylinder 3 into an upper oil chamber 21 and a lower oil chamber 23, and the working oil filled in the cylinder 3 is divided into two upper and lower oil chambers 21. , 23.

Therefore, the main piston 20 is connected to the cylinder 3
When the inside is slid in the axial directions indicated by arrows A and B in the figure, the working oils inside the upper oil chamber 21 and the lower oil chamber 23 flow through the orifice 20a to each other. The flow path cross-sectional area determines the damping force of the shock absorber SA when not controlled. The damping characteristic when the hydraulic fluid flows only through the orifice 20a has a large damping force (hard) because the flow passage cross-sectional area is relatively small and the flow rate is small.

On the other hand, the inner cylinder 15 and the housing 17
In the hollow portion formed by and, from its upper end, a piezo load sensor 25 for detecting the magnitude of the force acting on the shock absorber SA, a laminated piezoelectric body 27 in contact with the lower end of the piezo load sensor 25, and a laminated type A first piston 30 as a displacement transmitting member that comes into contact with the lower end of the piezoelectric body 27 is built in order.

Further, in the center of the housing 17, the first
A sliding hole 24 through which the sliding protrusion 30a of the piston 30 can slide
A partitioning part 26 having is provided. The first piston 30 is connected to the partition portion 26 so that the preset spring 3
5 and the sliding protrusion 30a is inserted into the sliding hole 24. The preset spring 35 is a disk-shaped spring that is installed in a crushed state and applies a pressing force to the laminated piezoelectric body 27 via the first piston 30.

The sliding protrusion 30a of the first piston 30
An O-ring 37 is provided between the housing 26 and the partition 26 of the housing 17 so that the hydraulic oil does not enter the laminated piezoelectric body 27. On the opposite side of the laminated piezoelectric body 27 with the partition 26 in between, a second piston 40 serving as a sliding member in the present invention, a base 43, an end rod 48, and a switching flexible plate (hereinafter simply referred to as a flexible plate). 45 etc. are stored. The second piston 40 is
It has a disk shape and is slidable in the axial direction along the inner circumference of the housing 17.

The flexible plate 45 has a rectangular plate shape, and is made of, for example, a spring steel plate. In this embodiment, two flexible plates 45 are used, but this structure is similarly established when one or three or more flexible plates 45 are used. The flexible plate 45 is sandwiched between the second piston 40 and the flange portion 44 provided on the lower portion of the base 43 in a state in which the central portion thereof is slightly bent inward.

The collar portion 44 is provided with an engagement groove 44a for positioning the end portion of the flexible plate 45. In this embodiment, as shown in FIG. 4 (A), the end surface of the flexible plate 45 and the bottom of the engagement groove 44a are formed in a curved shape, and the flexible plate 45 itself swings with the end surface of the flexible plate 45 as a fulcrum. It is easy to move. On the other hand, as shown in FIG. 4 (B), the second piston 40 is also provided with a similar engaging groove 40a, and the engaging groove 40a and the end surface of the flexible plate 45 to be engaged are also curved. There is.

Here, a method of giving an initial deflection to the deflection plate 45 will be described. In this embodiment, a screw is formed on the outer circumference of the end rod 48, and the end rod 48 can be screwed in from the lower end of the housing 17. Since the base 43 is only placed on the end rod 48, when the end rod 48 is screwed in, the distance between the second piston 40 and the flange portion 44 of the base 43 is shortened, so that the flexible plate 45 Can be deflected. Further, a lock nut 47 is provided to fix the position of the end rod 48 when the bending amount of the bending plate 45 reaches a desired state.

As shown in FIG. 3 which is a sectional view taken along line CC of FIG. 1, the base 43 has a flat portion in which the flexible plate 45 is disposed, and faces the vicinity of the center of the flexible plate 45. A lateral hole 51 that opens at a position is provided. Then, the base 4 is communicated with the lateral hole 51 and extends in the axial direction.
A vertical hole 53 that opens at the lower end of 3 is provided. In the present embodiment, two flexible plates 45 are arranged so as to face each other with the base 43 interposed therebetween, and both lateral holes 51 communicate with each other.

Further, the end rod 48 is also formed with a through hole 46 in the axial direction, and when the end rod 48 is screwed into the housing 17, the vertical hole 53 of the base 43 is formed.
And the through hole 46 of the end rod 48 communicate with each other. An O-ring 49 is provided between the base 43 and the end rod 48 so that the hydraulic oil does not leak when the hydraulic oil flows from the vertical hole 53 of the base 43 through the through hole 46 of the end rod 48. There is.

On the other hand, when the end rod 48 is screwed into the upper end of the base 43, the flexible plate 45 does not twist and the second
A positioning projection 55 having a square cross section is provided so as to rotate together with the piston 40. Then, the second piston 40 is provided with a square hole 41 with which the positioning projection 55 is engaged.

Further, the positioning projection 55 and the square hole 4 are arranged so as not to be a hindrance when the second piston 40 moves.
A small gap is provided between the bottom and the bottom of 1. However,
When the end rod is screwed in, the positioning protrusion 55 may be omitted if a jig or the like is devised and assembled so that the bending plate is not twisted.

In the above structure, the first piston 30
Is made of a material having a large linear expansion coefficient such as aluminum. In this embodiment, aluminum is used and its linear expansion coefficient is about 23 × 10 ⁻⁶ / K. On the other hand, the members such as the housing 17 other than the first piston are made of steel in consideration of strength and the like. Therefore, the coefficient of linear thermal expansion is about 10.7 × 10 ⁻⁶ / K (medium carbon steel). The linear thermal expansion coefficient of the laminated piezoelectric body 27 is about 4 × 10 ^−6.
/ K.

The shock absorber SA does not show that the vehicle is about to pass through the recess by detecting the impact of any one of the wheels of the vehicle through the recess, for example, when the wheel is about to pass through the recess. It is a known system that notifies the ECU and applies a voltage to the laminated piezoelectric body 27. Therefore, in this shock absorber SA, when the wheel passes through the concave portion or the convex portion, a voltage is immediately applied to the laminated piezoelectric body 27.

Next, the shock absorber SA having the above structure
The operation of will be described. First, the flow of hydraulic oil will be briefly described. Now assume that the wheel is about to pass through the recess. When the wheel passes through the recess,
The position of the cylinder 3 shown in (3) sharply lowers relative to the position of the main piston 20 in the direction B in the figure. That is, the operating oil in the cylinder 3 which is divided into the upper oil chamber 21 and the lower oil chamber 23 by the main piston 20 is
Since the volume of the lower oil chamber is smaller than that of the lower oil chamber 23, the volume of the upper oil chamber 21 cannot keep up with the rapid volume change.

At this time, the high-pressure hydraulic oil in the upper oil chamber 21 that has flowed into the housing 17 through the communication hole 60 provided in the housing 17 serves as the flexible plate 45 and the base 43.
And flows into the lateral hole 51 through Then, the hydraulic oil sequentially passes through the vertical hole 53 and the through hole 46 of the end rod 48 and flows into the lower oil chamber 23. The hydraulic oil in the upper oil chamber 21 thus having a high pressure gradually flows into the lower oil chamber 23, so that the pressure in the upper oil chamber 21 gradually decreases.

On the contrary, when the wheel passes through the convex portion, the position of the cylinder 3 shown in FIG. 1 rapidly rises in the direction A in the figure relative to the position of the main piston 20. That is, the hydraulic oil in the cylinder 3 which is divided into the upper oil chamber 21 and the lower oil chamber 23 by the main piston 20 cannot keep up with the rapid volume change because the volume of the lower oil chamber 23 becomes small. The pressure in the lower oil chamber 23 rises as compared with that in the upper oil chamber 21, and flows opposite to the above-described flow of hydraulic oil.

Next, switching of the damping force when the hydraulic oil flows as described above will be described. As the wheel passes through the concave portion, a voltage is applied to the laminated piezoelectric body 27 to generate a displacement on the extending side. Then, the first piston 30 is pushed down against the preset spring 35. Normal,
Since the second piston 40 is pressed against the first piston 30 by the bending force of the bending plate 45, the second piston 40 is pushed down in the axial direction by the displacement of the laminated piezoelectric body 27 in synchronization with the movement of the first piston 30.

Therefore, the second piston 40 and the base 4
The distance between the rib portion 3 and the collar portion 44 becomes shorter, and the flexible plate 45
Bends further inward than the initial flexed state. The amount of deflection in this case is 10 to the displacement of the laminated piezoelectric body 27.
It is magnified about 25 times. The principle of this displacement enlargement has already been described in the above-mentioned “Operation” section, and thus detailed description thereof will be omitted.

Returning to the operation of the shock absorber SA, the flexure plate 45 bends further inward from the initial flexure state, whereby the distance between the flexure plate 45 and the lateral hole 51 provided in the base 43 becomes shorter. First, the flow passage area S between the flexible plate 45 and the base 43 in the present embodiment.
Becomes as shown in the following equation.

S≈2πr · d where S: flow path area r: radius of lateral hole d: distance between apex of flexible plate and base Note that the symbols used in the above equation correspond to facilitate understanding. The part is shown in FIG.

Therefore, when the flexible plate 45 bends, the flow passage area S decreases by the area change amount ΔS shown in the following equation. ΔS ≈ 2πr · k · Δx · n where ΔS: amount of change in flow passage area k: magnification of displacement Δx: displacement of laminated piezoelectric material n: number of flexible plates and flow passage area decreased The damping force of the shock absorber SA can be increased accordingly. Further, as is clear from the above equation, if the number of the flexible plates 45 is increased, the flow channel area change amount ΔS can be made large. on the other hand,
When the application of the voltage is stopped, the laminated piezoelectric body 27 returns to the original state, and accordingly, the flexible plate 45 returns to the original initial flexible state by its elastic restoring force, and the damping force also returns to the original state. .

Here, as described above, the laminated piezoelectric material 2
7 and the housing 17 have a linear thermal expansion coefficient of about 4 respectively.
Since they are x10 ^-6 / K and approximately 10.7 x 10 ^-6 / K, for example, when the temperature rises by 100 K, the difference in thermal expansion between the laminated piezoelectric body 27 and the housing 17 becomes approximately 35 µm. However, in the present embodiment, the linear thermal expansion coefficient of the first piston 30 is as large as about 23 × 10 ⁻⁶ / K, so the degree of thermal expansion is also large, and the difference in thermal expansion between the two is absorbed. Therefore, the change in damping force can be suppressed.

The experimental results are shown below. FIG. 6 is a graph showing the relationship between the applied voltage to the laminated piezoelectric body 27 and the damping force, which is obtained by examining the optimum value of the length of the first piston 30 in which the temperature change of the damping force is suppressed. is there. Here, 3
With the goal of switching the damping force at 0 ° C,
In order to be able to perform the same switching at 0 ° C. (and below), the length of the first piston 30 is considered. First piston 3
The length of 0 was changed to 13 mm, 15 mm, and 18 mm, and the relationship between the applied voltage and the damping force at the oil temperature of 120 ° C. was investigated.

As can be seen from FIG. 6, the first piston 30
When the length of the oil is 15 mm, the oil temperature is 120 even at 30 ° C.
Even at ℃, the damping force is switched in the same way. The length of the laminated piezoelectric body 27 in this experiment is about 50 m.
m. If the linear expansion coefficient changes depending on the length of the laminated piezoelectric body 27 and the material of the housing, the optimum length of the first piston 30 also changes. Depending on each case,
The optimum value of the length of the first piston 30 is determined, which suppresses the temperature change of the damping force.

As described above, since the minute displacement of the laminated piezoelectric body 27 is enlarged by the flexible plate 45 and the flow passage area is changed by the flexible plate 45, the required space is relatively small with a simple structure. While being able to
The width of switchable damping force can also be set large.

Further, the linear expansion coefficient of the laminated piezoelectric material 27,
Even if the linear expansion coefficient of the housing 17 and the like arranged on the outer periphery of the first piston is different from the linear expansion coefficient of the hydraulic oil and the thermal expansion of the hydraulic oil causes a difference in the degree of thermal expansion between the two, the first piston serving as the displacement transmitting member. Reference numeral 30 denotes the laminated piezoelectric body 27 and the housing 1.
It has a larger coefficient of linear thermal expansion than 7 and a large degree of thermal expansion, and therefore absorbs the difference in thermal expansion between the two. Therefore, it is possible to suppress the change of the expansion ratio = the change of the damping force due to the difference in thermal expansion.

The present invention is not limited to such embodiments as described above, and can be carried out in various modes without departing from the scope of the present invention. For example, in the above embodiment, aluminum was used as the material of the first piston, but theoretically the same effect can be obtained if the linear expansion coefficient is larger than the steel material used for the housing 17 and the like. However, in that case, if the linear expansion coefficient is not much different from that of the steel material, the length of the first piston 30 needs to be considerably increased. Therefore, a linear expansion coefficient of about aluminum is practically used. What you have is appropriate.

[0050]

As described above, according to the damping force switching mechanism of the shock absorber of the present invention, the minute displacement of the piezoelectric body is enlarged by the switching flexure plate, and the flow path area is changed by the switching flexure plate. Therefore, the required space can be relatively reduced with a simple structure, a sufficient displacement expansion rate can be obtained, and the width of the switching force that can be switched can be set large. Thus, it is possible to suppress a change in damping force due to a difference in thermal expansion.

[Brief description of drawings]

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

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

FIG. 3 is a sectional view taken along line CC of FIG.

FIG. 4A is a sectional view showing an engagement state between a base flange portion and a flexible plate, and FIG. 4B is a sectional view showing an engagement state between a second piston and the flexible plate.

FIG. 5 is an explanatory diagram showing a flow passage area S.

FIG. 6 is a graph showing the relationship between the applied voltage to the laminated piezoelectric material and the damping force.

FIG. 7A is an explanatory diagram showing a geometrical relationship when a flexible plate is approximated by an arc, and FIG. 7B is a graph showing a relationship between a radius of curvature R and an angle θ and a displacement magnifying power k1.

FIG. 8A is an explanatory diagram showing a geometrical relationship when the flexible plate is approximated by a triangle, and FIG. 8B is a graph showing a relationship between the angle θ and the displacement magnifying power k2.

[Explanation of symbols]

3 ... Cylinder, 17 ... Housing, 20 ...
Main piston, 21 ... Upper oil chamber, 23 ... Lower oil chamber, 27 ... Multilayer piezoelectric body, 30 ... First piston, 30a ... Sliding protrusion, 40 ... Second piston,
43 ... Base, 44 ... Collar part, 45
… Deflection plate, 51… Horizontal hole, 53… Vertical hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Hayashi 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd. (72) Inventor Junji Moriwaki 1-1-chome, Showa-cho, Kariya city, Aichi Nippondenso Within the corporation

Claims (1)

[Claims] 1. An oil passage for communicating two oil chambers defined by a piston slidably fitted with a cylinder,
A damping force switching mechanism of a shock absorber capable of switching damping force by changing the flow passage area of the oil passage, which is driven by a piezoelectric body that expands and contracts according to an applied voltage and slides in the cylinder axis direction. A slidable member, which is formed in a flat plate shape and is substantially parallel to the sliding direction of the sliding member, one end of which is fixed in position and the other end of which abuts against the sliding member, and An elastic switching flexure plate, which is arranged so as to cause an initial deflection toward the side that reduces the flow passage area of the oil passage when not applied to the body; and Between the sliding member,
A displacement transmission member that transmits the displacement of the piezoelectric body to the sliding member and that has a larger linear thermal expansion coefficient than the piezoelectric body and the members arranged on the outer periphery of the piezoelectric body and that absorbs the difference in thermal expansion between the two is provided. A damping force switching mechanism for shock absorbers.