JP3326816B2 - Shock absorber damping force switching mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a damping force switching valve interposed in an oil passage connecting two upper and lower oil chambers partitioned by a piston, and a predetermined balancing position in which the upper and lower oil chambers are not communicated. The present invention relates to a damping force switching mechanism of a shock absorber that switches a damping force by moving a communication position for communicating the upper and lower oil chambers.

[0002]

2. Description of the Related Art Conventionally, as a damping force switching mechanism of a shock absorber mounted on a vehicle or the like and capable of switching a damping force according to a running state or a change in posture of the vehicle, a piston slidably fitted to a cylinder. A damping force switch that is interposed in an oil passage that communicates the partitioned upper and lower oil chambers and is movable between a predetermined balancing position where the upper and lower oil chambers are not communicated and a communication position that communicates the upper and lower oil chambers. The one provided with a valve for use is known.

As a mechanism for moving the damping force switching valve, a mechanism using a piezoelectric body such as a piezo element as an actuator is known. A piezoelectric body is suitable as a driving source because it expands and contracts with extremely responsiveness to an applied voltage, but has a very small displacement. For example, even a laminated piezoelectric body formed by laminating about 100 disk-shaped piezoelectric bodies has a displacement of about several tens of microns, and is used with an enlarged displacement.

[0004] In order to enlarge the minute displacement of the laminated piezoelectric body, the displacement of a piston having a large sectional area driven by expansion and contraction of the laminated piezoelectric body is transmitted to a piston having a small sectional area via hydraulic oil. For example, enlargement to a displacement corresponding to the cross-sectional area ratio is performed (for example, “Hydraulic pressure switching valve provided with piezoelectric actuator” in JP-A-1-310283).
As a result, the displacement of the multilayer piezoelectric body of several tens of microns is 1
A displacement of the order of millimeters is obtained from a piston with a small cross-sectional area. The damping force switching valve is moved by the small cross-sectional area piston, and the damping force is switched by connecting or disconnecting the upper and lower oil chambers.

[0005]

However, in the conventional example in which the above-described laminated piezoelectric body and the displacement enlarging mechanism are combined, a displacement enlarging mechanism is provided in addition to the damping force switching mechanism, and both of them have a precision structure. Have. The displacement enlargement mechanism uses a cylinder and a piston with the least possible oil leakage. However, if the hydraulic oil in the cylinder leaks out, the stroke of the small cross-section piston, which originally has a displacement of only about 1 mm, will decrease. Normal switching operation cannot be performed.

For this reason, it is necessary to provide a check valve mechanism for compensating the outflow of hydraulic oil from the cylinder, and to supply oil into the cylinder via the check valve when the hydraulic oil in the cylinder runs short. The structure became complicated, leading to an increase in cost.

Further, although the displacement is enlarged, in the above-described example, the damping force switching valve can be moved only at most about 1 mm, so that the range of the damping force which can be switched is limited. There is a limit to vehicle vibration control. Further, in the above-described example, in order to make the moving amount of the damping force switching valve about 5 mm (that is, 5 times), for example, it is necessary to make the area of the large cross-sectional area piston 5 times. The diameter of the shock absorber itself becomes very large, making it impractical.

[0008] These are originally due to the fact that the conventional damping force switching mechanism moves the damping force switching valve based on the displacement of the piezoelectric body itself. Therefore, the present invention
By adopting a structure that moves the damping force switching valve using the pressure difference generated in the upper and lower oil chambers of the shock absorber instead of based on the displacement of the piezoelectric body itself, while having a simple configuration, An object of the present invention is to provide a damping force switching mechanism of a shock absorber in which the width of the switchable damping force can be set large.

[0009]

In order to solve the above problems, a damping force switching mechanism of a shock absorber according to the present invention communicates two upper and lower oil chambers defined by a piston slidably fitted to a cylinder. A damping force switch of a shock absorber having a damping force switching valve interposed in an oil passage and movable between a predetermined balancing position in which the upper and lower oil chambers are not in communication and a communication position in which the upper and lower oil chambers are in communication. in mechanism, it on both end faces of the movable direction of the damping force switching valve
They are arranged respectively in contact with, when the oil pressure is equal to act on the both end surfaces, and a holding elastic member for biasing in opposite directions so as to hold the damping force switching valve to the balance position,
Of both end surfaces of the damping force switching valve, the upper and lower oil chambers
While the oil chamber and the end face of the constant communication with the side of the oil-tight chamber in which an end face of the opposite side constitutes a part of the chamber wall of the inner, oil-tight chamber and the upper
Is driven and a communication hole that seen communicating with the other oil chamber of the lower oil chamber, the piezoelectric body expands and contracts in response to the applied voltage, non
When driving, the communication hole is closed, and when driving, the communication hole is closed.
An open / close valve that can be opened.

[0010]

According to the damping force switching mechanism of the shock absorber of the present invention, when a voltage is applied to the piezoelectric body to drive the on-off valve to open the communication hole, the oil-tight chamber communicates with one of the upper and lower oil chambers. I do. When the cylinder and the piston slide relatively, the hydraulic oil in the cylinder divided into an upper oil chamber and a lower oil chamber partitioned by the piston has a smaller volume in one of the oil chambers. Therefore, it cannot keep up with the rapid volume change, and the pressure rises as compared with the pressure in the other oil chamber.

At this time, the high-pressure hydraulic oil in the oil chamber whose pressure has increased flows through the communication hole into the oil-tight chamber. Therefore, the pressure acting on one end face of the damping force switching valve becomes higher than the pressure acting on the other end face, and the damping force switching valve is moved from the equilibrium position to the communicating position against the holding elastic member. .

When the damping force switching valve is switched to the communication position, the high-pressure hydraulic oil in the oil chamber whose pressure has increased flows into the other oil chamber through the oil passage communicating the upper and lower oil chambers.
As the high-pressure hydraulic oil gradually flows into the other oil chamber, the pressure in the increased oil chamber gradually decreases. At this time, the piezoelectric body is kept energized to keep the communication hole open. When the pressure difference between the upper and lower oil chambers disappears,
The damping force switching valve returns to the original balance position by the pressing force of the holding elastic member. However, when the high-pressure hydraulic oil flowing into the oil-tight chamber stops the energization of the piezoelectric body while the damping force switching valve has moved from the equilibrium position and closes the on-off valve, the pressure in the oil-tight chamber is maintained at an increased level. Dripping. Therefore, even if the pressure difference between the upper and lower oil chambers disappears, the two pressures do not balance, and the damping force switching valve is shifted from the balancing position and remains at the communicating position.

In other words, once the pressure difference is generated and the damping force switching valve is moved to the communication position where the upper and lower oil chambers communicate with each other, the pressure difference is eliminated and there is no need to keep the communication. In this case, the damping force switching valve can be returned to the equilibrium position to make it in a non-communication state, or the communication state can be maintained.

As described above, since the magnitude of the damping force can be switched according to the timing, the extremely high responsiveness of the piezoelectric body also increases the controllability of the shock absorber, which is very effective. In addition, based on the displacement of the piezoelectric body itself, instead of moving the damping force switching valve using a displacement magnifying mechanism as in the past, the damping force switching is performed using the pressure difference generated between the upper and lower oil chambers themselves. The width of the switchable damping force can be set to be large because of the configuration in which the valve is moved.

[0015]

Embodiments of the present invention will be described below. In this embodiment, an example in which the present invention is applied to a variable damping force type shock absorber that is provided together with a coil spring between a wheel and a vehicle body will be described. FIG. 1 is a sectional view showing details of a damping force switching mechanism of a shock absorber according to a first embodiment, and FIG. 2 is a partially broken 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, and is mounted on the body at the upper end on the rod 7 via the bearing 9 and the vibration isolating rubber 11. It is fixed to the side member 13. A rod 7 is inserted into the cylinder 3, and a hollow internal cylinder 15 is connected to a lower end of the rod 7. A substantially cylindrical housing 17 is screwed into the inner cylinder 15.
A main piston 20 slidable in the cylinder 3 along the inner peripheral surface thereof is screwed.

The outer periphery of the main piston 20 has an O-ring 19
The main piston 20 seals the interior of the cylinder 3 with an upper oil chamber 21 and a lower oil chamber 2.
The hydraulic oil filled in the cylinder 3 is separated into two upper and lower oil chambers 21 and 23. The two oil chambers 21 and 23, thus communicates with all times by the orifice 20 a, when the main piston 20 slides in the axial direction illustrating the internal cylinder 3 in the arrow A, in B, the upper oil chamber The hydraulic oil inside the lower oil chamber 21 and the lower oil chamber 23
Will be flowing to each other through 20 a, the flow path cross-sectional area of the orifice, the damping force of the shock absorber SA when no control is determined. The damping characteristic when the hydraulic oil flows only through the orifice 20a is a characteristic of a large damping force (hard) because the flow path cross-sectional area is relatively small and the flow rate is small.

On the other hand, the inner cylinder 15 and the housing 17
A piezo load sensor 25 for detecting the magnitude of a force acting on the shock absorber SA from the upper end of the hollow portion formed by the above, a laminated piezoelectric body 27 abutting on the lower end of the piezo load sensor 25, A piston 30 which is in contact with the lower end of the laminated piezoelectric body 27 and whose outer periphery is sealed by an O-ring 29 is incorporated therein.

The housing 17 is mounted on the inner cylinder 15.
Are screwed, the block 31 is fixed in a state sandwiched between them. At the center of the block 31, a through hole 31a through which an on-off valve 33 to be described later passes is bored. On the outer periphery of the block 31, a groove 31b for allowing the hydraulic oil to spread over the entire periphery, and the groove 31b A horizontal hole 31c is formed so as to be perpendicular to the through hole 31a so as to connect to the central through hole 31a.

On the other hand, a block 31 is
A first communication hole 17a is provided at a position corresponding to a groove 31a formed on the outer periphery of the first communication hole 17a. A preset spring 35 is interposed between the piston 30 and the block 31 described above. The preset spring 35 is a disc-shaped spring that is installed between the piston 30 and the block 31 in a crushed state and applies a pressing force to the laminated piezoelectric body 27 via the piston 30.

At the tip of the on-off valve 33, a conical portion 33a for closing the opening of the through hole 31a provided in the block 31 is formed.
Through the through hole 31a and the preset spring 35 to the piston 30. At this time, the balance between the pressing force of the preset spring 35 on the laminated piezoelectric body 27 and the sealing property of the conical portion 33a of the on-off valve 33 causes the on-off valve 3 to move.
The amount of screwing into the piston 30 of No. 3 is adjusted.

The above-mentioned sealing performance is achieved by the conical portion 33a of the on-off valve 33.
When the screw is too tight, the pressing force on the laminated piezoelectric body 27 is small, and when the screwing amount is small, the conical portion 33a is moved from the through hole 31a. Floating state makes sealing impossible. According to the present embodiment, by adjusting the screwing amount, the dimensional variation in the longitudinal direction of the multilayer piezoelectric body 27 and the like are absorbed, and the optimum sealing property can be obtained.

On the other hand, a damping force switching valve 40 is disposed in the housing 17. Damping force switching valve 40
Has a substantially columnar shape, and can slide freely in the vertical direction using the inner periphery of the housing 17 as a cylinder. And it is desirable that the clearance be small so that oil leakage is as small as possible.

Further, an outer peripheral groove 40a is provided on the outer periphery of the damping force switching valve 40 so as to spread the hydraulic oil all around, and as shown by a broken line in FIG. Has a lateral hole 40 communicating the outer peripheral grooves 40 with each other.
b is provided. Further, a vertical hole 40c that opens vertically on the lower end face LF from the horizontal hole 40b to the lower side is provided.

The damping force switching valve 40 has an upper end surface U
When both ends F and LF are pressed by return springs 43 and 45 as holding elastic members, and when the hydraulic pressures acting on both end surfaces UF and LF are equal, they float at a position where the fitting is balanced (hereinafter referred to as a balanced position). Held in state. The pressing force of the return springs 43 and 45 can be determined by the magnitude of the hydraulic pressure that moves the damping force switching valve 40.

The oil-tight chamber 50 is constituted by the upper end face UF of the damping force switching valve 40, the lower end face of the block 31, and the inner periphery of the housing 17. This oil-tight room 50
Is connected to the outside through the through hole 31a of the block 31 only when the on-off valve 33 is in the open state.

On the other hand, as shown in FIG. 1, the housing 17 is provided with a second communication hole 17b and a third communication hole 17c communicating with the upper oil chamber 21 at the outer periphery of the damping force switching valve 40 at the equilibrium position. The groove 40a is provided at a position corresponding to the top and bottom when viewed in the axial direction. Therefore, when the damping force switching valve 40 is at the equilibrium position, neither the second communication hole 17b nor the third communication hole 17c communicates with the outer peripheral groove 40a. If the damping force switching valve 40 is shifted above the equilibrium position, the second communication hole 17b communicates with the outer peripheral groove 40a, and if the damping force switching valve 40 is shifted downward, the third communication hole 17c communicates with the outer peripheral groove 40a. .

Further, a fourth communication hole 17d is provided at a lower end portion of the housing 17, that is, a portion where the main piston 20 is screwed, and the lower oil chamber 23 is formed by passing through the fourth communication hole 17d. The hydraulic oil is guided to the lower end face LF of the damping force switching valve 40.

When any one wheel of the vehicle attempts to pass through, for example, a concave portion, the shock absorber SA senses the impact with the damping force sensor 25, and does not show that the vehicle is going to pass through the concave portion. This is a well-known system that notifies the ECU and applies a voltage to the laminated piezoelectric body 27. Therefore, in the 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 configuration will be described.
The operation of will be described. Now, assume that the wheel is about to pass through the recess. Since the laminated piezoelectric body 27 generates displacement when a voltage is applied, the preset spring 3
5, the on-off valve 33 is pushed down. Normally, on-off valve 3
3 is that the conical portion 33a is a through hole 31a of the block 31.
3 and seals the working oil, but is pressed down by the laminated piezoelectric body 27,
As shown in (A), a gap is formed in the conical seal portion.

On the other hand, when the wheel passes through the concave portion, the position of the cylinder 3 shown in FIG. 1 rapidly lowers relative to the position of the main piston 20 in the direction B in the figure. That is, the working oil in the cylinder 3 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 upper oil chamber 21 is small. The pressure in the upper oil chamber 21 increases as compared with that in the lower oil chamber 23.

At this time, the first communication hole 1 of the housing 17
7a, groove 31b of block 31, side hole 31c, through hole 3
1 a, and the high-pressure hydraulic oil in the upper oil chamber 21 that has passed through the conical seal portion having the gap flows into the oil-tight chamber 50. Therefore, the pressure acting on the upper end surface UF is lower than the lower end surface LF.
And the damping force switching valve 4
0 is pushed downward against the lower return spring 45.

When the damping force switching valve 40 shifts below the balance position as shown in FIG. 3A, the outer peripheral groove 40a communicates with the third communication hole 17c provided in the housing 17,
The high-pressure hydraulic oil in the upper oil chamber 21 flows into the outer peripheral groove 40a of the damping force switching valve 40 through the third communication hole 17c. Then, the hydraulic oil sequentially passes from the outer peripheral groove 40 a through the horizontal hole 40 b and the vertical hole 40 c, and finally flows into the lower oil chamber 23 through the fourth communication hole 17 d provided in the housing 17. The pressure of the upper oil chamber 21 gradually decreases as the high-pressure hydraulic oil in the upper oil chamber 21 flows into the lower oil chamber 23 gradually.

At this time, the conical seal between the on-off valve 33 and the through hole 31a is left open (that is, the laminated piezoelectric body 27).
If the pressure difference between the upper oil chamber 21 and the lower oil chamber 23 disappears, the damping force switching valve 40 will return to the original fishing position by the pressing force of the lower return spring 45. Return to the joint position.

However, when the damping force switching valve 40 is depressed by the pressure of the upper oil chamber 21 and the energization of the laminated piezoelectric body 27 is stopped and the on-off valve 33 is closed, the pressure in the oil-tight chamber 50 is reduced. , The pressure of the upper oil chamber 21 at the time of rising is maintained as it is. Therefore, even if the pressure difference between the upper oil chamber 21 and the lower oil chamber 23 disappears, the two pressures do not balance, and the damping force switching valve 40 remains pressed down from the equilibrium position. The communication hole 17c can be kept open.

That is, once a pressure difference is generated, the damping force switching valve 40 is moved, and the outer peripheral groove 40a is inserted into the third communication hole 17.
If it is moved to the communication position communicating with c, when the pressure difference disappears and there is no need to keep the communication,
It is possible to return the damping force switching valve 40 to the equilibrium position to bring it into a non-communicating state, or to keep the communicating state.

Conversely, when the wheel passes through the convex portion, the position of the cylinder 3 shown in FIG. 1 rises rapidly in the direction A in the figure relative to the position of the main piston 20. That is, the working oil in the cylinder 3 divided into the upper oil chamber 21 and the lower oil chamber 23 by the main piston 20 cannot keep up with its rapid volume change because the volume of the lower oil chamber 23 is small. The pressure in the lower oil chamber 23 increases as compared with that in the upper oil chamber 21. Then, the lower oil chamber 2 that has passed through the fourth communication hole 17d
Due to the high-pressure hydraulic oil of No. 3, the pressure acting on the lower end face LF becomes higher than the pressure acting on the upper end face UF, and the damping force switching valve 40 is pushed upward against the return spring 45.

As shown in FIG. 3B, when the damping force switching valve 40 is displaced above the equilibrium position, the outer peripheral groove 40a communicates with the second communication hole b provided in the housing 17. The high-pressure hydraulic oil in the lower oil chamber 23 sequentially passes through the vertical hole 40c, the horizontal hole 40b, and the outer peripheral groove 40a of the damping force switching valve 40, and finally flows into the upper oil chamber 21 through the second communication hole 17b. . The hydraulic oil in the lower oil chamber 23 having a high pressure gradually flows into the upper oil chamber 21 so that the lower oil chamber 23
Pressure gradually decreases.

When the damping force switching valve 40 is lifted upward, a voltage is applied to the laminated piezoelectric element 27 to push down the on-off valve 33, and the conical seal between the on-off valve 33 and the through hole 31a is formed. There is a gap. Therefore, at the same time when the damping force switching valve 40 is raised,
The oil in the oil-tight chamber 50 passes through the through-hole 31a, the side 31b, and the groove 31a of the block 31 from the conical seal portion and the upper oil chamber 21.
Run out to

As in the case of passing through the recess, the on-off valve 33
When the hydraulic oil in the oil-tight chamber 50 is sealed by closing the valve, the damping force switching valve 40 that has once risen upward is held at the upper communication position, and the outer peripheral groove 40a is connected to the first communication hole 17.
It is also possible to maintain the state of communication with b. On the other hand, if the on-off valve 33 is left open, the upper oil chamber 21
When the pressure difference between the oil pressure and the lower oil chamber 23 disappears, the pressing force of the upper return spring 43 allows the damping force switching valve 40 to return to the original balance position.

If the voltage is not applied to the laminated piezoelectric element 27 and the on-off valve 33 is not moved, the hydraulic oil in the oil-tight chamber 50 loses a relief place. The valve 40 cannot be moved. In other words, even when a pressure difference occurs between the upper oil chamber 21 and the lower oil chamber 23 when the wheel is going to pass through the uneven portion, the damping force of the shock absorber SA is kept high unless the on-off valve 33 is moved. The magnitude of the damping force acting to reduce the pressure difference between the upper oil chamber 21 and the lower oil chamber 23 can be switched according to the timing at which a voltage is applied to the laminated piezoelectric body 27.

As described above, since the magnitude of the damping force can be switched according to the timing, the extremely high responsiveness of the multilayer piezoelectric body 27 also enhances the controllability of the present shock absorber SA, which is very effective. It is. in addition,
Based on the displacement of the multilayer piezoelectric body 27 itself, for example, instead of moving the damping force switching valve 40 using a displacement magnifying mechanism or the like as in the related art, a pressure difference generated between the upper and lower oil chambers 21 and 23 is used. Therefore, since the damping force switching valve 40 is moved, the width of the switchable damping force can be set to a large value with a simple structure.

When the damping force switching valve 40 moves to the communication position, the outer peripheral groove 40a and the second or third communication holes 17b, 17c do not necessarily have to be aligned. The amount of movement of the damping force switching valve 40 is determined by the pressure difference between the upper oil chamber 21 and the lower oil chamber 23, the area of the damping force switching valve 40, and the urging loads of the return springs 43 and 45. If the area of the damping force switching valve 40 and the biasing loads of the return springs 43 and 45 are determined in advance at the design stage, the damping force switching valve 4
0 moves in proportion to only the pressure difference between the upper oil chamber 21 and the lower oil chamber 23.

In order to eliminate the pressure difference between the upper oil chamber 21 and the lower oil chamber 23 when the pressure difference between the upper oil chamber 21 and the lower oil chamber 23 is large, a large amount of hydraulic oil must be moved between the upper oil chamber 21 and the lower oil chamber 23. The communication area at the communication position (the outer peripheral groove 40a and the second or third
It is necessary to increase the cross-sectional area where the communication holes 17b and 17c communicate. When the pressure difference is large, the amount of movement of the damping force switching valve 40 is large, so that the communication area can be increased.

On the other hand, when the pressure difference is small, the amount of movement of the damping force switching valve 40 is small, so that the communication area is small, but the amount of movement of hydraulic oil between the upper oil chamber 21 and the lower oil chamber 23 is also small. So it doesn't matter. In other words, these design specifications (the amount of movement of the damping force switching valve 40, the communication area, the generated pressure difference, etc.) are amounts that can be determined in advance at the design stage.

In the first embodiment described above, the high-pressure hydraulic oil is introduced into the oil-tight chamber 50 from the upper oil chamber 21. However, a configuration in which the high-pressure hydraulic oil is introduced from the lower oil chamber 23 may be adopted. Lower oil chamber 23
A second embodiment in which high-pressure hydraulic oil from the above is introduced into the oil-tight chamber 50 will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

In the second embodiment, the main piston 20 is screwed on the outer periphery of the housing 17 instead of the lower end.
Further, only the outer peripheral groove 40a is provided in the damping force switching valve 40, and the lateral hole 40b and the vertical hole 40c are not provided. And the fourth communication hole 17d shown in the first embodiment.
Is provided at a position not always at the lower end of the housing 17 but at the side surface portion so as to always communicate with the outer peripheral groove 40a.

The second oil-tight chamber 57 is constituted by the bottom surface 55 and the inner peripheral surface in the housing 17 and the lower end surface LF of the damping force switching valve 40. And the groove 31 of the block 31
The first communication hole 17 a provided at a position corresponding to “a” passes through the inside of the housing 17, opens at the lower end of the housing 17, and communicates with the lower oil chamber 23. In addition, a fifth end in which one end opens to the upper oil chamber 21 and the other end opens to the second oiltight chamber 57.
A communication hole 17e is provided.

The second communication hole 17b and the third communication hole 17c are merged inside the housing 17 so as to be united and open outside the housing. As in the first embodiment, when the damping force switching valve 40 is at the balance position, neither the second communication hole 17b nor the third communication hole 17c communicates with the outer peripheral groove 40a. If the position is shifted upward, the second communication hole 17b communicates with the outer peripheral groove 40a. If the position is shifted downward, the third communication hole 17c communicates with the outer peripheral groove 40a.

According to this structure, the operation can be performed in the same manner as in the first embodiment, except that the flow of the hydraulic oil is reversed between the upper and lower oil chambers 21 and 23. Thus, the damping force switching valve 40 is moved, so that the damping force of the shock absorber SA can be switched.

[0051]

As described above, according to the damping force switching mechanism of the shock absorber of the present invention, the damping force switching valve is moved by using the pressure difference generated between the upper and lower oil chambers of the shock absorber. By adopting a configuration that controls whether or not to apply a pressure difference using an on-off valve driven by a piezoelectric body, the width of the switchable damping force can be set large even with a simple configuration. This has the effect of being

[Brief description of the drawings]

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

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

FIG. 3 is a sectional view showing an operation state of the first embodiment.

FIG. 4 is a sectional view showing details of a damping force switching mechanism of a second embodiment.

[Explanation of symbols]

SA: shock absorber, UF: top surface,
LF: Lower end face, 3: Cylinder, 17 ...
Housing, 17a: first communication hole, 17b: second communication hole, 17c: third communication hole, 17d: fourth communication hole, 20: main piston, 20a: orifice, 21: upper oil chamber, 21a: orifice,
23: Lower oil chamber, 27: Laminated piezoelectric body, 30
... piston, 31 ... block, 31a ... through hole, 31b ... groove, 31c ... side hole, 33
... on-off valve, 33a ... conical part, 40 ... damping force switching valve, 40a ... outer peripheral groove, 40b ... side hole, 40c ...
Vertical hole, 43, 45 ... return spring, 50 ...
Oil-tight room

Continuing from the front page (72) Inventor Takehiro 1-1-1 Showa-cho, Kariya-shi, Aichi, Japan Denso Co., Ltd. (72) Inventor Akira Fukami 1-1-1, Showa-cho, Kariya-shi, Aichi Japan, Denso Co., Ltd. ( 72) Inventor Hirokatsu Mukai 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-59-83848 (JP, A) Real-life 1986-38344 (JP, U) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) F16F 9/46 B60G 17/08

Claims (1)

(57) [Claims] A predetermined equilibrium position interposed in an oil passage connecting two upper and lower oil chambers defined by a piston slidably fitted to a cylinder, wherein the upper and lower oil chambers are not communicated;
In a damping force switching mechanism of a shock absorber having a damping force switching valve capable of moving between a communication position for communicating the upper and lower oil chambers, the damping force switching valve is provided on both end faces in the movable direction of the damping force switching valve.
Is arranged in contact with, when the oil pressure is equal to act on the both end surfaces, and a holding elastic member for biasing in opposite directions so as to hold the damping force switching valve to the balancing position, for the damping force switching Of both ends of the valve, the upper and lower oil chambers
While the oil chamber and the end face of the constant communication with the side of the oil-tight chamber in which an end face of the opposite side constitutes a part of the chamber wall of the inner, and the other oil chamber of the oil-tight chamber between the upper and lower oil chambers only It is driven by a communicating hole that communicates and a piezoelectric body that expands and contracts in accordance with an applied voltage, closes the communicating hole when not driven, and closes the communicating hole when driven.
An on-off valve capable of opening a through hole; and a damping force switching mechanism for a shock absorber, comprising: