JP2594314Y2 - Electric linear actuator - Google Patents

Description

[Detailed description of the invention]

[0001]

The electric linear actuator according to the present invention is used for driving, for example, a flow control valve provided in the middle of various hydraulic circuits.

[0002]

2. Description of the Related Art In order to drive a flow control valve or the like provided in a hydraulic circuit provided in an automobile, for example, based on a command from a controller, an electric linear actuator is required. For this reason, conventionally, an electric linear actuator combining a solenoid and a compression spring has been used.
A conventionally known electric linear actuator used for such an application is configured such that a displacement member such as a rod is urged to one side by the compression spring, and when it becomes necessary to displace the displacement member. When the solenoid is energized, the displacement member is displaced against the elasticity of the compression spring. The amount of displacement of the displacement member is adjusted by controlling the amount of current supplied to the solenoid and changing the magnitude of the force with which the solenoid attracts the displacement member. That is, the displacement member stops at a position where the elastic force of the compression spring and the suction force of the solenoid are balanced.

[0003]

[Description of Prior Art] In the case of a conventional electric linear actuator using the above-described solenoid, a large current needs to flow through the solenoid when the displacement member is displaced. For this reason, for example, when used for switching the hydraulic circuit of a car, it causes a burden on the battery,
Not preferred. The displacement of the displacement member is adjusted by balancing the elastic force of the compression spring and the suction force of the solenoid. However, the structure in which the displacement member is urged by the compression spring has a large hysteresis. For this reason, even if the same electric current is applied to the solenoid, the amount of displacement greatly differs between the case where the displacement member is displaced to one side and the case where the displacement member is displaced to the other side. For this reason, it is difficult to finely adjust the opening of the flow control valve.

In order to solve such a problem, the present applicant has previously filed an application relating to an electric linear actuator as shown in FIGS.
issue). The electric linear actuator according to the present invention has an output shaft 2 which can be freely displaced in the axial direction by a non-circular engaging portion 1 as shown in FIG. A cylinder 3 is provided around the output shaft 2 so as to be concentric with the output shaft 2 and rotatable about the output shaft 2.
Further, between the cylinder 3 and the casing 4, the cylinder 3
Is provided with a torsion coil spring 5 for imparting elasticity in the rotation direction. Further, a feed screw portion 6 is provided between the outer peripheral surface of the output shaft 2 and the inner peripheral surface of the cylinder 3, and the output shaft 2 is rotated by the feed screw portion 6 with the rotation of the cylinder 3. , And is displaced in the axial direction. Further, an electric motor 7 is provided inside the casing 4, and the cylinder 3 is rotated against the elasticity of the torsion coil spring 5 with the energization of the electric motor 7.

[0005] In the case of the electric linear actuator according to the prior art constructed as described above, the cylinder 3 rotates in one direction due to the elastic force of the torsion coil spring 5 when the electric motor 7 is not energized. The output shaft 2 is displaced to one end in the axial direction by the feed screw portion 6. When the electric motor 7 is energized, the cylinder 3 rotates until the rotation torque of the electric motor 7 determined according to the amount of energization and the elasticity of the torsion coil spring 5 are balanced, and the cylinder 3 is stopped in the balanced state. I do. Then, with the rotation of the cylinder 3, the output shaft 2 is displaced toward the other end in the axial direction by the feed screw portion 6.

[0006]

The electric linear actuator according to the present invention configured as described above solves the problems of the conventional electric linear actuator using the above-mentioned solenoid, but still has the problem. There are the following problems to be solved. That is, the feed screw portion 6 for displacing the output shaft 2 in the axial direction with the rotation of the cylinder 3 includes a plurality of balls 8, 8. It is movable along spiral grooves 9 and 10 formed on the outer peripheral surface of the output shaft 2 and the inner peripheral surface of the cylinder 3. Therefore, a return tube for returning the balls 8, 8 having moved to one end of the spiral grooves 9, 10 to the other end of the spiral grooves 9, 10 is required. For this reason, the feed screw portion 6
However, it is unavoidable to increase the complexity and size, and it becomes difficult to design an electric linear actuator installed in a narrow portion.
The electric linear actuator of the present invention solves the above-mentioned disadvantages.

[0007]

The electric linear actuator according to the present invention is provided with an output shaft capable of being displaced in the axial direction and a rotatable concentric with the output shaft and about the output shaft. A feed screw portion provided between the outer peripheral surface of the output shaft and the inner peripheral surface of the cylinder, and displaces the output shaft in the axial direction with the rotation of the cylinder; An electric motor for rotating the cylinder with energization. The feed screw portion has a spiral groove formed on the outer peripheral surface of the output shaft, a nut cylinder fixed to the inner peripheral surface of the cylinder, and a plurality of holes opened on the inner peripheral surface of the nut cylinder. And a plurality of balls which are rotatably housed inside the respective holes and project from the inner peripheral surface of the nut cylinder into engagement with the spiral grooves. Furthermore,
The nut cylinder is formed in a state where a plurality of circular holes communicating the inner peripheral surface and the outer peripheral surface are aligned with the spiral groove, and a cylindrical retainer, and a state of closing the outer diameter side openings of the plurality of circular holes. And a cylindrical closing member disposed around the retainer.

[0008]

In the case of the electric linear actuator of the present invention constructed as described above, the cylinder rotates with the energization of the electric motor, and with the rotation of this cylinder, the output shaft is moved by the feed screw portion. Are displaced in the axial direction. In particular, in the case of the electric linear actuator of the present invention, as described above, when the rotational motion of the cylinder is converted into the displacement in the axial direction of the output shaft by the feed screw portion, the ball constituting the feed screw portion is formed. While rotating inside the hole of the nut cylinder, it moves along a spiral groove formed on the outer peripheral surface of the output shaft. Therefore, a return tube for returning the ball to the original position is not required, and the size of the feed screw portion can be reduced. Further, since the nut cylinder is constituted by a closing member and a cylindrical retainer having a plurality of circular holes, each of which has a cylindrical shape, a plurality of circular holes each opening only to the inner peripheral surface. Can easily be made with a nut cylinder.

[0009]

1 and 2 show a first embodiment of the present invention. The output shaft 2 provided at the center portion is displaced only in the axial direction (left and right directions in FIGS. 1 and 2) without rotating based on the engagement with the connecting rod 11, and drives the valve element of the flow control valve. (Translate). Around the output shaft 2, a cylinder 3 is provided.
The output shaft 2 is provided concentrically with the output shaft 2, and a casing 4 is provided around the cylinder 3. The cylinder 3 is rotatably supported inside the casing 4 via rolling bearings 12 and 12 only for rotation.

A helical groove 9 is formed in a portion of the outer peripheral surface of the output shaft 2 located inside the cylinder 3, and the helical groove 9 is opposed to the helical groove 9, and the inner peripheral surface of the cylinder 3 is Nut tube 1
3 is fixed. As shown in FIG. 2, the nut cylinder 13 is formed by externally fitting a cylindrical cover 15 also made of a slippery material to an outer peripheral surface of a retainer 14 made of a slippery material such as nylon or PTFE. It consists of.

The retainer 14 is formed with a plurality of circular holes 20, 20 for communicating the inner peripheral surface and the outer peripheral surface of the retainer 14, and the inner peripheral end of each circular hole 20, 20 is formed in the retainer 14. An opening is formed on the inner peripheral surface, and the outer peripheral end is covered with the cover 15.
It is closed by. Therefore, in the case of the present embodiment, the cover 15 corresponds to the closing member. And each circular hole 2
The balls 8, 8 such as steel balls are held inside the retainers 14 only in a freely rotatable manner in a state where a part thereof protrudes from the inner peripheral surface of the retainer 14 inward in the diameter direction of the retainer 14.
Then, a part of each of the balls 8, 8, the retainer 1
4 is engaged with a spiral groove 9 formed on the outer peripheral surface of the output shaft 2 to displace the output shaft 2 in the axial direction as the cylinder 3 rotates. The feed screw portion 19 is configured.

Further, an electric motor 16 of, for example, a stepping servo type is provided inside the casing 4 so that the cylinder 3 can be driven to rotate as the electric motor 16 is energized. That is, the permanent magnet 17 is fixed to the outer peripheral surface of the cylinder 3, and the outer peripheral surface of the permanent magnet 17 is opposed to the inner peripheral surface of the stator 18 provided inside the casing 4. In the case of the present embodiment, the casing 4 also serves as the iron core of the stator 18. By energizing the stator 18, the permanent magnet 17 is rotatable in a desired direction by a desired angle.

In order to displace the output shaft 2 in the axial direction by the electric linear actuator of the present invention configured as described above, the stator 18 constituting the electric motor 16 is energized. As the stator 18 is energized, the cylinder 3 on which the permanent magnet 17 facing the stator 18 is fixed is fixed.
The output shaft 2 is displaced in the axial direction by the feed screw portion 19 with the rotation of the cylinder 3.

As described above, when the rotational motion of the cylinder 3 is converted into the displacement in the axial direction of the output shaft 2 by the feed screw portion 19, in the electric linear actuator of the present invention,
A plurality of balls 8, 8 constituting the feed screw portion 19 are rotated inside the circular holes 20, 20 of the retainer 14, constituting the nut tube 13, and a spiral groove 9 formed on the outer peripheral surface of the output shaft 2.
Move along. Then, the plurality of balls 8, 8
However, by pressing the inner surface of the spiral groove 9, the output shaft 2 is displaced in the axial direction.

Therefore, unlike the structure according to the above-mentioned invention, a return tube for returning the balls 8, 8 to the original position is not required, and the size of the feed screw portion 19 can be reduced. Also, the nut tube 13
Is constituted by a cover 15 corresponding to a closing member, each of which has a cylindrical shape, and a cylindrical retainer 14 having a plurality of circular holes 20, 20, each of which opens only to the inner peripheral surface. The nut cylinder 13 having the plurality of circular holes 20 can be easily manufactured. Therefore, the cost of the feed screw portion 19 including the nut tube 13 does not increase.

The structure for regulating the displacement of the output shaft 2 to a desired value is not particularly limited. For example, as in the above-described embodiment, the electric motor 16 can be controlled in rotation angle, such as a stepping servomotor, to control the rotation angle of the electric motor. Is provided in one direction, and the output shaft 2 is balanced by the elasticity of the spring and the output torque of the electric motor.
Can be regulated.

FIG. 3 shows a second embodiment of the present invention. In the case of the present embodiment, between the outer peripheral surface of the retainer 14 that constitutes the nut cylinder 13 and the inner peripheral surface of the cover 15,
A cylindrical space 21 is provided.
Are provided rotatably with respect to the retainer 14 and the cover 15. The opening on the outer peripheral surface side of the circular hole 20 formed in the retainer 14 is closed by the rotary cylinder 22. Therefore, in the case of this embodiment, the rotating cylinder 22
Correspond to the closing member. In the case of the present embodiment, the outer peripheral end of the ball 8 held inside the circular hole 20 is in contact with the inner peripheral surface of the rotary cylinder 22.

In the case of the present embodiment constructed as described above, when the balls 8 held in the respective circular holes 20 rotate with the rotation of the nut cylinder 13, the rotation of the outer peripheral end of each ball 8 comes into contact. The cylinder 22 rotates. Therefore, as in the first embodiment,
The rolling surface of each ball 8 and the inner peripheral surface of the cover 15 do not slide against each other, and the rotation of the nut cylinder 13 can be performed more lightly.

[0019]

[Effect of the Invention] The electric linear actuator of the present invention is constructed and operates as described above, so that a large force can be obtained with low power consumption and the flow rate control valve is used as an electric linear actuator with small hysteresis. It is possible to control various devices delicately. Moreover, a return tube for circulating the ball constituting the feed screw portion is not required, and the design of the electric linear actuator installed in a narrow portion is facilitated by downsizing.
Also, the manufacture of each component is not particularly troublesome,
There is no increase in cost.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a feed screw portion.

FIG. 3 is a half sectional view of a feed screw portion showing a second embodiment of the present invention.

FIG. 4 is a sectional view showing the electric linear actuator of the present invention.

FIG. 5 is an enlarged sectional view taken along line AA of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engagement part 2 Output shaft 3 Cylinder 4 Casing 5 Torsion coil spring 6 Feed screw part 7 Electric motor 8 Ball 9 Helical groove 10 Helical groove 11 Connecting rod 12 Rolling bearing 13 Nut cylinder 14 Retainer 15 Cover 16 Electric motor 17 Permanent magnet Reference Signs List 18 Stator 19 Feed screw part 20 Circular hole 21 Space 22 Rotary cylinder

Continuation of the front page (56) References JP-A-3-117758 (JP, A) JP-A-64-65360 (JP, A) JP-A-63-9342 (JP, A) Jpn. , U) Jikken 41-6328 (JP, Y1) (58) Fields investigated (Int. Cl. ⁶ , DB name) F16H 25/20 F16H 25/22

Claims (1)

(57) [Scope of request for utility model registration] An output shaft capable of only displacing in an axial direction;
A cylinder provided concentrically with the output shaft and rotatably provided about the output shaft, and provided between an outer peripheral surface of the output shaft and an inner peripheral surface of the cylinder; A feed screw portion that displaces the output shaft in the axial direction; and an electric motor that rotates the cylinder with energization, wherein the feed screw portion is formed on an outer peripheral surface of the output shaft. Helical groove, a nut tube fixed to the inner peripheral surface of the cylinder, a plurality of holes opened in the inner peripheral surface of the nut tube, and rotatably housed inside each hole, and the nut A portion projecting from the inner peripheral surface of the cylinder was engaged with the spiral groove,
And a plurality of balls , wherein the nut tube,
A plurality of circular holes communicating the inner peripheral surface and the outer peripheral surface are formed in the spiral groove.
A cylindrical retainer formed so as to match the
This retainer is placed in a state where the outer diameter side openings of these multiple holes are closed.
Consisting of a cylindrical closing member disposed around
There is an electric linear actuator.