JP2000027923A - Actuator for shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator for a shock absorber to be formed in a compact manner radially of the shock absorber. SOLUTION: A nut member 7 is rotatably arranged in a piston 1, and a screw shaft 11 provided at a tip part with a spool valve 15 is threadedly engaged with the nut member 7. A magnet 21 is mounted on the nut member 7, and a stator 22 of which a stepping motor 20 consists in cooperation with the magnet 21 is fixed in the piston 1. The stepping motor 20 is axially deviated in a position from the formation portion of a female screw 10 formed in the inner periphery of the nut member 7 and the piston 1 is decreased in a diameter, resulting in compactified formation of an actuator in the radial direction of a shock absorber.

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 type shock absorber actuator mainly used for automobiles.

[0002]

2. Description of the Related Art As a shock absorber of a variable damping force type, a shock absorber described in Japanese Patent Application Laid-Open No. 7-167192 has been conventionally known. In this shock absorber, a piston is incorporated in a cylinder in which oil is sealed, and a damping force is adjusted by adjusting an oil flow rate by moving a spool valve incorporated in the piston in an axial direction.

In order to move the spool valve in the axial direction, a screw shaft having a spool valve mounted at a tip end thereof is threadedly engaged with a rotatable nut member incorporated in the piston. Attach a magnet to the shaft,
A stator that forms a stepping motor is fixed in the piston with the magnet, the stator is excited to rotate the nut member, and the screw shaft engaged with the nut member is moved in the axial direction.

[0004]

The shock absorber disclosed in the above publication has a structure in which a stepping motor including a magnet and a stator is provided outside a nut engaging portion of a nut member and a screw shaft. ,
Since the outer diameter of the piston is increased, the degree of freedom of design around the scaffold of the vehicle is small, and there is still a point to be improved in giving a margin to the design.

An object of the present invention is to provide an actuator for a shock absorber capable of reducing the size of a piston in the radial direction.

[0006]

In order to solve the above-mentioned problems, according to the present invention, a spool valve for adjusting a damping force is attached to a tip of a nut member rotatably supported in a housing. A shock absorber in which a screw shaft is screw-engaged, a magnet is attached to the outer periphery of the nut member, and a stator that forms a motor with the magnet is provided in the housing, and the stator is excited to rotate the nut member. In the actuator for use, a configuration is employed in which the motor is displaced in the axial direction with respect to a formation position of a female screw formed on an inner periphery of a nut member.

As described above, by shifting the position of the motor consisting of the magnet and the stator in the axial direction with respect to the position of the female screw formed on the inner periphery of the nut member, it is possible to reduce the diameter of the housing. Here, it is preferable to employ a stepping motor for positioning the spool valve with high accuracy.

Here, in order to rotate the nut member smoothly, it is preferable to form the nut member with a synthetic resin to reduce the frictional resistance at the screw engagement portion between the nut member and the screw shaft. Examples of the synthetic resin include a polyimide resin.

Further, in order to reduce the frictional resistance of the screw engagement portion between the nut member and the screw shaft, a female screw formed on the inner periphery of the nut member and a male screw provided on the outer periphery of the screw shaft are advanced. It is preferable to make line contact at two points in the direction.

As a method of making line contact, there is a method in which one of the female screw thread and the external screw thread has a semicircular cross-sectional shape, and a screw groove between the other screw threads is formed by two inclined surfaces inclined in opposite directions. it can.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a piston 1 as a housing is slidably incorporated in a cylinder (not shown) in which oil is sealed. The piston 1 is hollow inside, and a sleeve 2 made of a non-magnetic material such as a synthetic resin is incorporated in the hollow portion.

The sleeve 2 has one end closed and the other end open. The opening end is a large-diameter cylindrical portion 2a, and a holding ring 3 attached on the outer diameter surface of the large-diameter cylindrical portion 2a holds the sleeve 2 coaxially with the piston 1.

A stopper 4 is provided on one side of the holding ring 3. The stopper 4 is pressed into the inner surface of the piston 1. A pin hole 5 is provided at the same position on the opposite surface of the stopper 4 and the holding ring 3, and a connecting pin 6 is inserted into the pin hole 5.

The stopper 4 has a nut insertion hole 4 on its axis.
and a ring fitting hole 4 having a diameter larger than that of the nut insertion hole 4a.
b. The stopper 4 is provided with a connecting cylinder 4 c on the end face facing the holding ring 3, and the connecting cylinder 4 c is inserted into the large-diameter cylinder 2 a of the sleeve 2.

A nut member 7 whose rear end is located in the sleeve 2 and whose front end is inserted into the nut insertion hole 4a of the stopper 4 includes a bearing 8a mounted in the closed end of the sleeve 2;
Both ends are rotatably supported by a bearing 8b mounted in the ring fitting hole 4b of the stopper 4.

The nut member 7 has a screw hole 9 opening at the tip, and a female screw 10 formed on the inner periphery of the screw hole 9 and a male screw 12 provided on the outer periphery of the rear end of the screw shaft 11.
Are engaged by screws.

As shown in FIG. 2, the female screw 10 has a semicircular cross section, while the screw groove between the male screws 12 is formed by two inclined surfaces 12a which are inclined in opposite directions. Are in line contact at two points in the direction of travel of the screw.

The amount of movement of the screw shaft 11 in the axial direction is limited by a stopper ring 13 mounted in a ring fitting hole 4b of the stopper 4. The screw shaft 11 is connected to a guide ring 14 mounted in the ring fitting hole 4 b of the stopper 4.
A guide pin 11 a provided on the screw shaft 11 is inserted into an axial guide groove 14 a formed on the inner periphery of the guide ring 14.
The screw shaft 11 is prevented from rotating by fitting the guide pin 11a and the guide groove 14a.

A spool valve 15 is mounted on the screw shaft 11 at a distal end portion which is located outside through a guide ring 14. The spool valve 15 moves in the axial direction together with the screw shaft 11, and adjusts the damping force by adjusting the oil flow rate in the same manner as the spool valve described in JP-A-7-167192.

The nut member 7 is rotated by a motor 20. Here, a stepping motor is employed as the motor 20 in order to position the spool valve 15 with high accuracy. The stepping motor 20 includes a magnet 21 attached to the nut member 7 and a sleeve 2.
And a stator 22 mounted on the outer diameter surface of the motor.

Here, the magnet 21 is connected to the nut member 7.
Is mounted at a position displaced in the axial direction from the female screw forming portion of the first embodiment. At the time of attachment, the nut member 7 is molded with a synthetic resin such as a polyimide resin, and the magnet 21 is integrated with the molding at the same time.

The stator 22 has a plurality of cores 22a mounted on the outer diameter surface of the sleeve 2 and coils 22b wound on each core 22a. The terminal holding member 23 is fitted to the rear end of the sleeve 2 and prevented from moving in the axial direction.

In the embodiment, the stator 22 is mounted on the sleeve 2. However, the stator 22 may be mounted on the inner diameter surface of the piston 1.

When the coil 22b of the stator 22 is energized, the nut member 7 rotates together with the magnet 21.
The screw shaft 11 that is screw-engaged with the nut member 7 moves in the axial direction. The spool valve 15 moves together with the axial movement of the screw shaft 11 to adjust the damping force.

Here, when the screw shaft 11 moves toward the closed end of the screw hole 9, the oil sealed in the closed end of the screw hole 9 is formed in the screw engagement portion of the female screw 10 and the male screw 12. Leakage enters the piston 1 along the inner circumferences of the stopper ring 13 and the guide ring 14 from the screw gap. Also, when the screw shaft 11 moves in the opposite direction to the above,
Conversely, oil infiltrates into the closed end of the screw hole 9 from the oil flow path, but the flow resistance of the oil is large, and the flow resistance becomes the rotation resistance of the nut member 7, and an excessive load acts on the stepping motor 20. May cause seizure.

In order to eliminate such inconvenience, the closed end of the screw hole 9 and the large-diameter cylindrical portion 2 of the sleeve 2 are provided in the nut member 7.
An oil passage 30 communicating with the inside a is formed. Also,
As shown in FIG. 3, an oil passage 32 is provided between the outer periphery of the square shaft portion 31 and the inner periphery of the nut insertion hole 4 a of the stopper 4.
A steal 33 communicating with the oil passage 32 is formed at the closed end of the ring fitting hole 4b.

As described above, the oil passage 30, the oil passage 32
By providing the thief 33, the oil inside the closed end of the screw hole 9 can be smoothly leaked to the outside of the stopper 4, and the oil outside the stopper 4 can smoothly flow into the closed end of the screw hole 9. Can be done. For this reason, the rotational resistance of the nut member 7 is reduced, and seizure of the stepping motor 20 can be prevented.

[0028]

As described above, according to the present invention, the motor for driving the rotation of the nut member is shifted in the axial direction with respect to the female screw forming portion of the nut member. The radial size of the absorber can be reduced.

Further, by forming the nut member from a synthetic resin molded product, the magnet can be integrated at the time of molding the nut member, thereby facilitating the assembly.

Further, by making the female screw of the nut member and the male screw of the screw shaft come into line contact at two points, the contact resistance at the screw engaging portion is small, the load on the motor that drives the nut member to rotate is reduced, and the burning of the motor is reduced. Sticking and the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an actuator according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the screw engaging portion of the above.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston (housing) 7 Nut member 10 Female screw 11 Screw shaft 12 Male screw 12a Slope 15 Spool valve 20 Stepping motor 21 Magnet 22 Stator

Claims (5)

[Claims] 1. A nut member rotatably supported in a housing, a spool valve for adjusting a damping force is screw-engaged with a screw shaft mounted on a distal end portion thereof, and a magnet is attached to an outer periphery of the nut member. A stator that forms a motor with the magnet is provided in the housing.In a shock absorber actuator that excites the stator and rotates the nut member, the motor is provided with a female screw formed on the inner periphery of the nut member. An actuator for a shock absorber, wherein a position is shifted in an axial direction with respect to a forming position. 2. The actuator for a shock absorber according to claim 1, wherein the nut member is a molded product of a synthetic resin, and a magnet is integrated at the time of molding. 3. The actuator for a shock absorber according to claim 2, wherein the synthetic resin is made of a polyimide synthetic resin. 4. The method according to claim 1, wherein the female screw formed on the inner circumference of the nut member and the male screw provided on the outer circumference of the screw shaft are in linear contact with each other at two points in the screw advancing direction. The actuator for a shock absorber according to the above. 5. A female thread of the nut member and a male thread of a screw shaft, each having a semi-circular cross-sectional shape, and a thread groove between the other threads formed by two inclined surfaces inclined in opposite directions. The actuator for a shock absorber according to claim 4, wherein the actuator is in line contact with a point.