JPH1130265A - Variable damping force mechanism for shock absorber, and variable damping force type shock absorber using this variable damping force mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide variable damping force mechanism for a shock absorber that can improve durability of a pilot valve part without lowering attractivity at the time of applying a current to a solenoid. SOLUTION: This variable damping force mechanism 31 variably controls damping force of a shock absorber SA by controlling hydraulic pressure of a back pressure chamber, formed on the back face side of a variable damping force disc valve 61, with pilot hydraulic pressure generated by opening/closing control of a solenoid-driven pilot valve 73. In this case, the pilot valve 73 is formed of a spring steel plate with a fixed part 73a and a movable part 73b, and a magnetic flux reinforcing plate 74 formed of iron material with less carbon content than pilot valve material is laminated in a floatable state on the movable part 73a of the pilot valve 73.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable damping force mechanism for a shock absorber and a variable damping force type shock absorber using the variable damping force mechanism.

[0002]

2. Description of the Related Art Conventionally, as a damping force variable mechanism for changing a damping force characteristic of a shock absorber, for example, a mechanism described in Japanese Patent Application Laid-Open No. 5-118374, "Pressure Adjusting Valve Assembly" is known. Have been. In this conventional damping force variable mechanism, the fluid pressure in the pilot pressure chamber is controlled by a solenoid means, thereby controlling the pressure in the back pressure chamber of a throttle valve (disk valve) that varies the damping force, thereby real-time controlling the damping force. There has been proposed a device having a variable structure. The armature of the solenoid is formed of a tapered plate, one end of which is mounted in a supported state, and is opened and closed like a flapper by the pressure of the fluid in the pilot pressure chamber.

[0003]

However, the conventional variable damping force mechanism has the following problems because it is configured as described above. That is, the tapered armature becomes a part of the magnetic path when the solenoid is energized, and is attracted to the valve seat. When the solenoid is not energized, the armature is lifted from the valve seat by the pressure of the fluid pressure in the pilot pressure chamber. Since the force is repeated at a high frequency in order to vary the force in real time, durability due to wear of the contact portion between the valve seat and the armature becomes a problem. Therefore, it is necessary to increase the surface hardness of the contact portion between the two parts. However, in order to increase the surface hardness, it is possible to increase the carbon content of iron (magnetic substance) by quenching or the like. However, since the armature constitutes a magnetic path as described above, If the content is increased, the maximum saturation magnetic flux density of this part decreases, and the suction force when the solenoid is energized decreases, and as a result, the fluid pressure in the pilot pressure chamber decreases and the maximum generated damping force decreases. The problem described above occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is intended to provide a shock absorber capable of improving the durability of a pilot valve portion without lowering the adsorbability when energizing a solenoid. It is an object of the present invention to provide a damping force variable mechanism.

[0005]

According to a first aspect of the present invention, there is provided a shock absorber according to the first aspect of the present invention.
A shock that variably controls the damping force of the shock absorber by controlling the hydraulic pressure of the back pressure chamber formed on the back side of the variable damping force disk valve with the pilot hydraulic pressure generated by opening and closing control of the pilot valve by solenoid driving. In the damping force variable mechanism of the absorber, the pilot valve is made of a plate material made of spring steel having a fixed portion and a movable portion, and the movable portion of the pilot valve is made of an iron material having a smaller carbon content than the pilot valve material. One or a plurality of magnetic flux reinforcing plates are stacked in a freely floating manner. In the variable damping force type shock absorber according to the second aspect, the piston body which defines the inside of the cylinder into the upper chamber and the lower chamber and slides therein is an extension-side upper communication hole communicating between the upper chamber and the lower chamber. And a compression-side upper communication hole provided at both axial end surfaces of the piston body to restrict the flow of the expansion-side upper communication hole and the compression-side upper communication hole, respectively, to thereby generate a high damping force, thereby increasing the damping force. A valve and a compression side high damping valve are provided, and in the middle of the expansion side bypass flow path and the expansion side bypass flow path that bypasses the expansion side high attenuation valve during the extension stroke and communicates between the upper chamber and the lower chamber of the cylinder. 2. The variable pressure damping mechanism according to claim 1, wherein the variable pressure cross-sectional area is variable, and the pressure-side bypass flow path communicates between the lower chamber and the upper chamber of the cylinder during the pressure stroke. Bypass flow A damping force varying mechanism according to the flow path cross-sectional area of the changeable claim 1 has a means provided it has been interposed in the middle.

[0006]

In the shock absorber variable damping mechanism according to the first aspect of the present invention, the pilot valve is made of a plate material made of spring steel having a fixed portion and a movable portion, thereby eliminating the problem of durability due to wear. And one or more magnetic flux reinforcing plates made of an iron material (ferromagnetic material) having a lower carbon content than the pilot valve material are stacked on the movable portion of the pilot valve so as to float freely. Thus, the suction force of the pilot valve when the solenoid is energized is increased, whereby the maximum damping force set value can be increased, and the degree of freedom in damping force tuning can be increased.

[0007]

Embodiments of the present invention will be described with reference to the drawings. First, a configuration of a shock absorber SA to which a damping force variable mechanism according to an embodiment of the present invention is applied is shown in FIGS.
This will be described with reference to FIG.

FIG. 1 is an overall sectional view showing a shock absorber SA to which a damping force variable mechanism according to an embodiment of the invention is applied, FIG. 2 is an enlarged sectional view showing a later-described extension side damping force variable mechanism, and FIG. FIG. 3 is an enlarged sectional view showing a piston portion described later.

As shown in FIG. 1, the shock absorber SA is slidably provided with a cylinder 21 filled with hydraulic fluid and an upper chamber 21a and a lower chamber 21b defined in the cylinder 21. A piston 24, an outer cylinder 23 forming a reservoir chamber 23a on the outer periphery of the cylinder 21, a base 24 defining a lower end of the cylinder 21 between the lower chamber 21b and the reservoir chamber 23a, and provided on the base 24. The piston 22 is fixed to a lower end of the check passage 24a that allows only the flow from the reservoir chamber 23a to the lower chamber 21b, the check passage 24c that allows only the flow from the lower chamber 21b to the reservoir chamber 23a. The piston rod 25 guides the sliding of the piston rod 25, and the upper end of the cylinder 21 extends between the upper chamber 21a and the reservoir chamber 23a. Guide member 26 which defines the
And an upper communication path formed between the cylinder 21 and the outer cylinder 23 to form an upper annular flow path 28a between the upper peripheral surface of the cylinder 21 and the upper chamber 21a and the upper communication hole 21c. A lower annular flow path 29a is provided between the cylinder 28 and the cylinder 21 and the outer cylinder 23 and communicates with the lower chamber 21b through the lower communication groove 24b between the cylinder 21 and the lower outer peripheral surface of the cylinder 21. As shown in detail in FIG. 2, a lower communication cylinder 29 and an expansion communication path 31 a communicating between the upper annular flow path 28 a and the reservoir chamber 23 a are formed. A variable stroke-side damping force mechanism 31 for variably controlling the flow amount, and a check flow path 32 that allows only the flow from the reservoir chamber 23a to the upper annular flow path 28a by bypassing the variable stroke-side damping force mechanism 31. And also the figure As shown in detail, a pressure-side communication flow path 33a that communicates between the lower annular flow path 29a and the reservoir chamber 23a is formed, and a pressure-stroke-side damping force that variably controls the flow rate of the pressure-side communication flow path 33a. A variable mechanism 33;
A check flow path that allows only the flow from the reservoir chamber 23a toward the lower annular flow path 29a, bypassing the pressure stroke side damping force variable mechanism 33;

As shown in detail in FIG. 3, the piston 22 restricts only the flow from the upper chamber 21a to the lower chamber 21b by the extension disk valve (extension high attenuation valve) 22a. The expansion side communication hole 22b, which generates a high damping force by allowing the pressure, and the compression side disc valve (pressure side high attenuation valve) 22c allow only the flow from the lower chamber 21b to the upper chamber 21a in a limited manner. A pressure-side communication hole 22d for generating a damping force is provided.

Next, the structure of the variable extension stroke side damping force mechanism 31 will be described in detail with reference to FIG. The outer cylinder 23
One end of an annular base 51 is fixedly welded to the opening formed in the opening, and a valve body 52 is fastened and fixed to the other end of the opening end surface side with a bolt 53 so as to close the opening end surface.

On the other hand, an opening formed in the upper communication tube 28 at the coaxial position in the base 51 is provided with a joint 5.
4, one end of the guide tube 56 is press-fitted and connected to the inner peripheral side of the other end of the joint 54 via a seal ring 55. Further, the other end of the guide tube 56 is The inner protruding portion 52a of the valve body 52 is press-fitted and fixed, whereby the space between the upper annular flow passage 28a and the reservoir chamber 23a is
Is defined via the.

One end opening of a casing 57 is fastened and fixed to the outer surface of the valve body 52 by the bolt 53. A space between the inside of the casing 57 and the reservoir chamber 23a is formed on the outer peripheral side of the valve body 52. Communication hole 5
2b is always in communication.

A small-diameter portion of one end of a stator 58 is inserted from the outside toward the inside of the shaft hole of the valve body 52. That is, the coil case 59, the collar 60,
The (extension side) variable damping force variable disc valve 61, valve body 52, (extension side) check valve 62, and collar 63 are sequentially mounted, and finally fastened with a nut 64 to assemble each member. The reservoir body 23a is connected to the valve body 52 through a communication hole 52b.
By opening the (expansion side) check valve 62 from the inside of the casing 57 which is always in communication with the flow path, the flow in the direction of the upper annular flow path 28a is secured (extension side).
2 and a (growing-side) communication flow path 31a that secures a flow in the casing 57 by opening the (growing-side) variable damping force disc valve 61 from the upper annular flow path 28a.

A pilot pressure chamber 65 is formed in the stator 58 so as to penetrate the axial center of the stator 58. An upper annular flow path 28a is formed in a lower end opening of the pilot pressure chamber 65.
A pilot bush 66 having a small hole 66a formed therein for restricting the flow rate of the hydraulic fluid flowing into the pilot pressure chamber 65 is press-fitted. Further, a filter 67 for preventing foreign matter (such as contamination) from entering the pilot pressure chamber 65 is incorporated in the nut 64.

A solenoid coil 68 and a coil assist plate 69 made of a non-magnetic material are accommodated between the outer peripheral surface of the large diameter portion of the stator 58 and the coil case 59.
A mold material 71 integrally formed of a non-magnetic material such as a resin is also housed between the outer peripheral surface on the distal end side of the coil case 59 and the casing 57 to also fix the harness 70. The cover 72 is accommodated in a state in which the cover 72 is in contact with the mold material 71 and the end opening end surface of the coil case 59, and is fixed by bending the end opening edge of the casing 57 inward and caulking.

On the large-diameter end face of the stator 58, a valve seat 58a with which the pilot valve 73 contacts is formed so as to protrude. As shown in detail in FIG. 4, the pilot valve 73 is formed by punching a single thin plate made of hard spring steel, thereby connecting the outer peripheral fixed portion 73a and the inner peripheral movable portion 73b with one connection. It is formed in a structure connected by the portion 73c. The pilot valve 73 is assembled in such a manner that the inner peripheral movable portion 73b abuts on the valve seat 58a without load by fixing the outer peripheral fixing portion 73a between the coil assist plate 69 and the cover 72. Have been.

A recess 72a is formed on the inner surface side of the cover 72 facing the movable portion 73b of the pilot valve 73, and a disc is stacked in the recess 72a while being laminated on the inner peripheral movable portion 73b. A magnetic flux reinforcing plate 74 is housed in a floating manner. As shown in detail in FIG. 4, the magnetic flux reinforcing plate 74 is made of an iron material (ferromagnetic material) having a smaller carbon content than the constituent material of the pilot valve 73.
A cutout portion 74a is formed in the outer peripheral portion to form a flow path for the working fluid so that the movement in the recess 72a can be performed smoothly.

The magnetic flux reinforcing plate 74 includes the pilot valve 73, the stator 58, and the coil case 59.
And the cover 72 together with the cover 72 to form a magnetic path when energizing the solenoid coil 68.

The coil assist plate 69, the coil case 59, and the molding material 71 are formed with a return flow path 75 for communicating between the inside of the recess 72a and the inside of the casing 57.

An assist ring 76 for assisting the valve closing force and forming a back pressure chamber 77 is slidably provided on a base outer peripheral surface of the coil case 59 via a sliding seal member 76a. I have. This assist ring 76
The inner opening end face protruding inward is brought into contact with the outer peripheral edge of the rear surface of the variable damping force disk valve 61, so that the inside of the casing 57 is on the rear side opposite to the pressure receiving side of the variable damping force disk valve 61. Form a defined back pressure chamber 77. Then, the assist ring 76
An assist spring 78 for urging the assist ring 76 in the direction of applying a predetermined light set load in the direction of the damping force variable disc valve 61 is mounted between the outer opening end face of the mold member 71 and the mold material 71.

On the side wall of the small diameter portion of the stator 58 and on the surface of the coil case 59 where the back pressure chamber 77 is formed, a pilot pressure introduction passage 79 for communicating between the inside of the pilot pressure chamber 65 and the back pressure chamber 77 is formed. I have. In the figure, 8
0 denotes a fixed seal member, and 50 denotes a grommet.

Further, the pressure stroke side damping force variable mechanism 33
Has the same structure as that of the variable extension stroke side damping force mechanism 31, the same components are denoted by the same reference numerals, and description thereof is omitted.

Since the shock absorber SA according to the embodiment of the present invention is configured as described above, the flow path through which the fluid can flow during the extension stroke extends from the upper chamber 21a through the extension communication hole 22b. Opening side disk valve 22a is opened and the main flow path on the extension side that flows into lower chamber 21b (see FIG. 3)
And an extension bypass flow path that flows from the upper chamber 21a into the lower chamber 21b via the upper communication hole 21c, the upper annular flow path 28a, the expansion communication path 31a, the reservoir chamber 23a, and the check flow path 24a. There are two flow paths, and the flow path through which fluid can flow during the pressure stroke is a pressure-side main flow path that opens the pressure-side disc valve 22c from the lower chamber 21b via the pressure-side communication hole 22d and flows into the upper chamber 21a. (See Fig. 3)
From the lower chamber 21b to the lower communication groove 24b, the lower annular flow path 29a, the pressure side communication flow path 33a, the reservoir chamber 23a, the check flow path 34, the upper annular flow path 28a, and the upper communication hole 21c.
And a pressure side bypass flow path that flows into the upper chamber 21a via the pressure chamber 21a.

Accordingly, the damping force characteristic on the extension stroke side becomes a hard characteristic when the extension side bypass flow path is closed, and becomes a soft characteristic when the extension side bypass flow path is opened. The characteristic can be variably controlled to an arbitrary characteristic between the characteristic and the soft characteristic.

On the other hand, the damping force characteristic on the compression stroke side becomes a hard characteristic when the compression-side bypass flow path is closed, and becomes a soft characteristic when the compression-side bypass flow path is opened. Any characteristic can be variably controlled between the soft characteristic and the soft characteristic.

The cross-sectional area of the expansion side bypass flow path is variably controlled to an arbitrary flow path cross-sectional area by variably controlling a drive signal for the solenoid coil 68 of the expansion stroke side damping force variable mechanism 31. Can be. The cross-sectional area of the pressure-side bypass flow path can be variably controlled to an arbitrary flow-path cross-sectional area by variably controlling a drive signal for the solenoid coil 68 of the pressure-stroke-side damping force variable mechanism 33.

That is, in a state in which the power supply to the solenoid coil 68 is released (no power supply), the pilot pressure chamber 65
Through the small hole 66a of the pilot bush 66,
The pressurized hydraulic pressure in one chamber of the cylinder 21 defined by the piston 22 is supplied, and the inside of the recess 72 a on the back pressure chamber side of the pilot valve 73 is communicated via a return flow path 75 and the like. Due to the same pressure as the fluid pressure in the reservoir chamber 23a, the inner peripheral movable portion 73b of the pilot valve 73 is pushed away from the valve seat 58a by the differential pressure to open the valve. Hydraulic fluid flows out, the hydraulic pressure in the pilot pressure chamber 65 and the back pressure chamber 77 increases in the reservoir chamber 2
The pressure drops to the same pressure as the liquid pressure in 3a. Accordingly, the variable damping force disc valve 61 easily opens against the light set load of the assist spring 78, and almost the entire flow rate of the hydraulic fluid flows through the bypass flow path side and the piston 22 side and the base 2
Since the flow does not flow on the fourth side, the generated damping force at this time has a soft characteristic determined by the damping force variable disc valve 61.

On the other hand, when the solenoid coil 68 is energized, as shown by the arrow in FIG.
Solenoid coil 68, coil case 59, cover 7
2. A magnetic path is formed around the magnetic flux reinforcing plate 74, the pilot valve 73, and the stator 58, and the pilot valve 73 is attracted to the valve seat 58a.
Is maintained in a closed state, whereby the pressure in the pilot pressure chamber 65 is maintained.

Accordingly, since the pressure receiving side of the damping force variable disk valve 61 and the back pressure chamber 77 into which the pressure in the pilot pressure chamber 65 is introduced have the same pressure, the assist spring 78 is provided.
The variable load damping force disc valve 61 is maintained in the closed state by the set load, and the bypass flow path is completely closed, so that almost all the flow rate of the hydraulic fluid flows through the piston 22 side, and the expansion side disc valve 22a Alternatively, since the compression-side disc valve 22c is opened for circulation, the generated damping force at this time has a hard characteristic determined by the expansion-side disc valve 22a or the compression-side disc valve 22c.

As shown in FIG. 6, the ON / OFF of the current supplied to the solenoid coil 68 is repeatedly given at a predetermined high frequency cycle Ts by PWM (pulse width modulation) control. 0% to 100 of ON time ratio (ON Duty)
As shown in FIG. 7, by variably controlling the damping force characteristic between the soft characteristic (0%) and the hard characteristic (100%), the damping force characteristic according to the ratio (%) is variably controlled. can do.

Further, as described above, since the opening and closing of the pilot valve 73 is repeated at a high frequency cycle, durability of the pilot valve 73 due to abrasion of the contact portion of the valve seat 58a becomes a problem. In the configuration, the valve seat 58a
The pilot valve 73 itself, which is in contact with, is made of a single thin plate made of hard spring steel to eliminate the problem of durability due to wear.

On the other hand, the spring steel constituting the pilot valve 73 has a high carbon content and a low maximum saturation magnetic flux density.
Attraction of the solenoid coil 68 to the valve seat 58a when the solenoid coil 68 is energized causes a problem that the maximum damping force set value is reduced. However, in the embodiment of the present invention, the iron material having a low carbon content ( By providing a magnetic flux reinforcing plate 74 made of a ferromagnetic material in a state where the magnetic flux reinforcing plate 74 is stacked on the inner peripheral movable portion 73b of the pilot valve 73 so as to float, the valve seat 58 when the solenoid coil 68 is energized is provided.
The attraction force of the pilot valve 73 with respect to a is increased, whereby the maximum damping force set value can be increased, and the degree of freedom in damping force tuning can be increased.

As described above in detail, in the shock absorber SA according to the embodiment of the present invention, the magnetic flux reinforcing plate 74 is laminated so that the adsorbing property when the solenoid coil 68 is energized is not reduced, and the pilot valve 73 is used. Is made of a single thin plate made of hard spring steel, the effect that the durability of pilot valve 73 can be improved can be obtained.

In general, since a large amount of magnetic flux flows near the surface of a magnetic body, a laminated sheet having the same cross-sectional area has a larger total amount of magnetic flux than an integrated one. As in the embodiment of the present invention, by using a predetermined number of magnetic flux reinforcing plays 74 of a predetermined thickness in a stacked manner, the weight of the inner peripheral movable portion 74b of the pilot valve 74 can be reduced, and as a result, the damping force variable mechanism 31 The responsiveness of the suspension system can be improved, and the responsiveness of the suspension system can be improved.

Although the embodiments of the present invention have been described above, the specific configuration is not limited to the embodiments of the present invention, and even if there is a design change or the like without departing from the gist of the present invention. Included in the present invention.

For example, in the embodiment of the present invention, only one magnetic flux reinforcing plate is formed, but a plurality of magnetic flux reinforcing plates can be used in a stacked state.

Further, in the embodiment of the present invention, the notch for forming the flow path of the working fluid is formed on the outer periphery of the magnetic flux reinforcing plate, but a plurality of protrusions may be formed on the outer periphery. One or a plurality of through holes may be formed in whole or in part.

In the embodiment of the present invention, the pilot valve has a fixed outer circumference, but the positional relationship between the fixed portion and the movable portion can be set arbitrarily.

[0040]

As described above, the first aspect of the present invention is as follows.
In the described variable damping force type shock absorber, by controlling the hydraulic pressure of the back pressure chamber formed on the back side of the variable damping force disk valve by the pilot hydraulic pressure generated by opening and closing control of the pilot valve by solenoid driving,
In the damping force variable mechanism of the shock absorber for variably controlling the damping force of the shock absorber, the pilot valve is formed of a plate material made of spring steel having a fixed portion and a movable portion, and the pilot valve material is provided on the movable portion of the pilot valve. One or more magnetic flux reinforcing plates made of an iron material with a lower carbon content than the other are floated and stacked, so that the durability of the pilot valve unit can be improved without reducing the adsorbability when energizing the solenoid. The effect of being able to improve is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a shock absorber to which a damping force variable mechanism according to an embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view showing a damping force variable mechanism in the shock absorber according to the embodiment of the present invention.

FIG. 3 is an enlarged sectional view showing a piston portion in the shock absorber according to the embodiment of the present invention.

FIG. 4 is an enlarged perspective view showing a pilot valve and a magnetic flux reinforcing plate in the variable damping force mechanism according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating a magnetic path in the damping force variable mechanism according to the embodiment of the present invention.

FIG. 6 is a time chart showing a PM control state for a solenoid coil in the damping force variable mechanism according to the embodiment of the present invention.

FIG. 7 is a graph showing a damping force variable characteristic with respect to a piston speed in the damping force variable mechanism according to the embodiment of the present invention.

[Explanation of symbols]

 SA Shock absorber 31 Variable damping mechanism 73 Pilot valve 73a Outer fixed part 73b Inner movable part 74 Flux reinforcing plate 61 Variable damping disk valve

Claims (2)

[Claims] 1. The damping force of a shock absorber is controlled by controlling the hydraulic pressure of a back pressure chamber formed on the back side of a variable damping force disk valve by a pilot hydraulic pressure generated by opening / closing control of a pilot valve driven by a solenoid. In the damping force variable mechanism of the shock absorber for variably controlling, the pilot valve is made of a plate material made of spring steel having a fixed portion and a movable portion, and the movable portion of the pilot valve has a carbon content higher than that of the pilot valve material. A variable damping force mechanism for a shock absorber, wherein one or a plurality of magnetic flux reinforcing plates made of an iron material having a small number are stacked so as to float. 2. A piston body which defines an upper chamber and a lower chamber in a cylinder and slides therein is provided with an extension upper communication hole and a compression upper communication hole communicating between the upper chamber and the lower chamber. An expansion-side high damping valve and a compression-side high damping valve that generate high damping force by restricting the flow of the expansion-side upper communication hole and the compression-side upper communication hole, respectively, are provided at both axial end surfaces of the piston body. An extension side bypass flow path that bypasses the extension side high damping valve during the extension stroke and communicates between the upper chamber and the lower chamber of the cylinder; 2. The variable damping force mechanism according to claim 1, wherein a variable cross-sectional area of the cylinder can be changed, a pressure-side bypass flow path communicating between the lower chamber and the upper chamber of the cylinder during the pressure stroke, and a pressure-side bypass flow path interposed therebetween. The cross-sectional area of the flow path Variable damping force type shock absorber, characterized in that the damping force varying mechanism according is provided changeable claim 1.