JPH10285867A - Electric actuator - Google Patents

Abstract

(57) [Problem] To provide an electric actuator having a novel structure which can be applied as a power source of a vertical and horizontal moving table used for precision work. A motor includes a motor mounted on one end of a motor mount, and a housing for accommodating an operating rod that is axially moved forward and backward by the motor. A screw shaft 8 and a nut 9 movably screwed on the screw shaft 8 are accommodated in the through hole 7 of the operating rod 4, and the nut 9 is fixed to the inside of the through hole 7 near the opening side.
The operating rod 4 is connected to the cage 1 in the linear motion bearing 11.
The structure in which the outer peripheral portion of the operating rod 4 is supported on the inner side wall of the cylindrical sleeve 16 inside the housing 5 so as to be able to advance and retreat by a large number of balls b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention can be applied as a power source for a vertical and horizontal moving table used for precision work such as precision measuring instruments, precision processing machines, work under a microscope in IC manufacturing and biotechnology, etc. The present invention relates to an electric actuator having a novel structure.

[0002]

2. Description of the Related Art Conventionally, precision measuring instruments, precision processing machines, I
An electric actuator which is a linear drive mechanism has been used as a drive mechanism for a vertical / horizontal movement table applicable to precision work such as work under a microscope in manufacturing and biotechnology, etc. In the electric actuator, a female screw (nut) is connected to an output shaft of a motor, a male screw (screw shaft) is screwed to the nut, and an operating rod is fixed to a tip of the screw shaft. The operating rod at the tip of the shaft is configured to move forward and backward.

[0003]

However, since the above-described electric actuator has a structure in which the operating rod fixed to the tip of the screw shaft is moved by rotating the nut, if the screw shaft is set to be long, the screw shaft is not moved. There are restrictions on the installation space, such as design, such as the mounting direction. This suggests that a problem arises in how to mount the electric actuator. Furthermore, when the screw shaft is directly used as an operating rod, the movable portion such as the screw shaft is largely exposed, and foreign matter or the like is inevitably mixed, which is likely to cause a failure. Also, since the configuration of the entire electric actuator becomes longer in the axial direction,
In order to prevent this, the center of the motor is made hollow, and the screw shaft is retracted into this hollow. Furthermore, since the operating rod is held in a short range at a position distant from the nut, there is a disadvantage that the operating rod is vulnerable to an external force different from the axial direction of the operating rod. That is,
Low resistance to bending moment load. The present invention has been proposed in view of the above background, and adopts a novel structure that changes a movable member, that is, a power transmission member, thereby achieving compactness and further increasing the degree of freedom in design.
For example, an object of the present invention is to provide a vertical and horizontal moving table applicable to precision work, that is, an electric actuator suitable as a driving mechanism of the moving table.

[0004]

In order to solve the above-mentioned problems, the present invention provides a nut which is screwed on a screw shaft connected to an output shaft of a motor so as to be able to advance and retreat on the screw shaft by driving the motor. An actuating rod having the screw shaft loosely fitted thereto, a nut fixed to the inner wall, and movable in the screw shaft axial direction together with the nut, and the actuating rod is mounted on the housing via a linear motion bearing. It is configured to be able to advance and retreat under preload. Further, in the above-described configuration, the dimension of the linear motion bearing in the range of holding the operation rod can be set to be longer than at least the entire length of the nut.

[0005]

Next, an embodiment of an electric actuator according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an electric actuator 1. The electric actuator 1 is axially moved forward and backward by a motor 3 attached to one end of a motor mount 2 and a motor 3 connected to the other end of the motor mount 2. And a housing 5 for accommodating the operating rod 4. These motor 3, motor mount 2 and housing 5
The whole of the motor shaft 3 and the operating rod 4 are aligned so as to be aligned with each other so that the central axes in the longitudinal direction coincide with each other. The vertical and horizontal dimensions of the edge where the motor 3 and the housing 5 on both ends of the motor mount 2 are mounted are made to match the vertical and horizontal dimensions of the housing 5.

The operating rod 4 has a through hole 7 formed in the axial direction as shown in FIG. 2, and the through hole 7 has a screw shaft 8 connected to the output shaft 6 of the motor 3, A nut 9 screwed movably on the screw shaft 8 is accommodated. The screw shaft 8 is loosely fitted in the through-hole 7 of the operating rod 4 from the opening side toward the tip end side, and the stopper 10 is attached to the screw shaft 8 so that the nut 9 does not come off the tip of the screw shaft 8.
It is fixed to the tip of. On the other hand, the nut 9 is
Is fixed to the inside of the vicinity of the opening side. The operating rod 4 is supported via a linear motion bearing 11 in a housing 5 mounted on the motor mount 2 to the vicinity of the distal end so as to be able to advance and retreat. A screw hole 12 for connecting to a movable portion of a moving table (not shown) is formed at the tip of the operating rod 4.
Is cut off (see FIG. 3).

Next, in the screw shaft 8 and the nut 9 which is movably screwed on the screw shaft 8, the screw shaft 8 is disposed so that the center axis direction of the operating rod 4 coincides with the operating rod 4. The side is rotatably mounted via a bearing 13 on a motor mount 2 on which the motor 3 is mounted so as to coincide with the center axis of the output shaft 6 of the motor 3. Also, the terminal side of the screw shaft 8 and the output shaft 6 of the motor 3 are connected to the motor mount 2.
Are connected by a coupling 14.

A linear motion bearing 1 for supporting an operating rod 4
1 has a retainer 15 which rotatably holds a large number of balls b at appropriate intervals, and a large number of balls b in the retainer 15 inside a cylindrical sleeve 16 in which the housing 5 is interposed. In this case, the operating rod 4 is supported so as to be able to advance and retreat so that the inner wall of the cylindrical sleeve 16 and the outer peripheral portion of the operating rod 4 come into contact with each other with a preload applied thereto. When the electric actuator 1 as described above is used alone, a structure in which the rotation of the operating rod 4 is provided can be provided.

The electric actuator 1 configured as described above
When the motor 3 is started, the power is transmitted to the screw shaft 8 via the coupling 14, and the rotation of the screw shaft 8 causes the nut 9 on the screw shaft 8 to
The nut 9 moves forward and backward on the screw shaft 8.
Is moved forward and backward. Then, the movable section of the movable table connected to the tip of the operating rod 4 is operated to operate the movable table.

As described above, the electric actuator 1 does not move the operation rod fixed to the tip of the screw shaft by rotating the nut, but indirectly operates the operation rod 4 via the operation rod 4 fixed to the nut 9. Since the screw shaft 8 and the nut 9 are housed in the operating rod 4 which moves forward and backward in the housing 5, it is possible to prevent a foreign substance or the like from entering from outside to cause a failure or other trouble. In addition, the motor 3 and the housing 5 are formed in a straight line with the motor mount 2 interposed therebetween, and the housing 5 is formed in a rectangular shape, so that it can be easily installed on a base (not shown) of the moving table. Moreover, since it is compact, restrictions on installation can be reduced.

Further, in this electric actuator 1,
The outer diameter of the operating rod 4 is larger than the outer diameter of the nut 9, and thus the outer diameter of the linear motion bearing 11 holding the operating rod 4 is further increased. In addition, the positioning of the moving table can be adjusted with higher precision.

[0012]

As described above, the present invention does not have a structure in which the operating rod fixed to the tip of the screw shaft is moved by rotating the nut as in the prior art, but accommodates the screw shaft and the nut, and moves the housing together with the operation of the nut. The mechanism to be operated is connected to the tip of the operating rod that is provided so that it can move forward and backward, so it is easy to install by the housing, and failures and other problems due to the inclusion of external obstacles etc. Will not cause Further, the resistance to the external force different from the operation direction of the operating rod is larger than that of the conventional structure, and the operation can be performed with higher accuracy.

[0013]

[Brief description of the drawings]

FIG. 1 is an explanatory perspective perspective view showing an example of an electric actuator according to the present invention.

FIG. 2 is an explanatory sectional view of the electric actuator shown in FIG. 1;

FIG. 3 is an explanatory plan view of the electric actuator shown in FIG. 1 as viewed from the direction of arrow A;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Motor mount 3 Motor 4 Operating rod 5 Housing 6 Output shaft 7 Through hole 8 Screw shaft 9 Nut 10 Stopper 11 Linear motion bearing 12 Screw hole 13 Bearing 14 Coupling 15 Cage 16 Cylindrical sleeve b Ball

Claims (2)

[Claims] 1. An electric actuator having a nut screwed on a screw shaft connected to an output shaft of a motor so as to be able to advance and retreat on the screw shaft by driving of the motor. And an operating rod fixed to the housing and movable in the axial direction of the screw shaft together with the nut. The operating rod is supported by the housing via a linear motion bearing so as to be able to advance and retreat under a preload. Actuator. 2. The electric actuator according to claim 1, wherein a dimension of the linear motion bearing in a range of holding the operation rod is set to be longer than at least a total length of the nut.