JPH11150912A - Mechanical stop mechanism for motor driven linear actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mechanical stop mechanism which prevents runaway of a ball screw and nut part due to a failure, a wrong operation or the like of a control device, by a method wherein a key for rotation stop is installed so as to be removed from the ball screw and nut part at a stroke end and a coned disk spring for impact energy absorption can be miniaturized or omitted. SOLUTION: A mechanical stop mechanism for a motor driven linear actuator is constituted of a ball screw rod part 1, of a ball screw and nut part 2 which is assembled to the rod part, of a sleeve 3 which covers the rod part 1 and the nut part 2, of a key 4 for rotation stop, which is installed at the sleeve and which is arranged in a keyway formed in the nut part 2 and of coned disk springs 5 which are installed at both ends of the sleeve 3. Then, the key 4 for rotation stop, which is used to convert rotation of a motor into a linear motion is installed so as to be removed from the ball screw and nut part 2 at a stroke end. Thereby, the coned disk springs 5 for impact energy absorption can be miniaturized or omitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical stop mechanism of an electric linear actuator used in a state of being incorporated in various mechanical devices such as an electric bed, an electric table, an electric chair and a lifter.

[0002]

2. Description of the Related Art FIG. 2 is a partial sectional front view showing the structure of a mechanical stop mechanism of a conventional electric linear actuator. As shown in FIG. 2, for example, a conventional electric linear actuator includes a ball screw rod portion 1, a ball screw nut portion 2 assembled to the rod portion 1, a sleeve 3 covering the rod portion 1 and the nut portion 2, It comprises a detent key 4 attached to the sleeve 3 and arranged in a key groove provided in the nut portion 2, and a disc spring 5 installed at both ends of the sleeve 3. Then, the electric linear actuator operates as follows. The ball screw rod portion 1 is rotated by a motor (not shown) or the like, and a rotational force is transmitted to the ball screw nut portion 2 assembled to the rod portion 1. The nut portion 2 does not rotate because the key groove provided in the nut portion 2 and the detent key 4 interfere with each other, and moves linearly on the rod portion 1 in the A or A 'direction. At this time, the movement of the nut portion 2 becomes uncontrollable, and when the nut portion 2 runs away and moves to the stroke end, the nut portion 2 collides with the disc spring 5 and contracts, so that the kinetic energy of the nut portion 2 is reduced. The disc spring 5
Stops at a position where the potential energy due to the contraction of the is balanced.

[0003]

However, the mechanical stop mechanism of a conventional electric linear actuator is effective for a relatively small linear actuator, but when the shape of the actuator becomes large and the kinetic energy becomes large, The disc spring cannot absorb the collision energy of the ball screw nut portion, and the collision energy is transmitted to the main body of the actuator, which may destroy the main body of the actuator. That is, when the electric linear actuator is developed, there is a problem that the ball screw nut portion may run away due to a failure or erroneous operation of the control device.

[0004]

SUMMARY OF THE INVENTION According to the present invention, there is a limit to the kinetic energy that can be absorbed by a disc spring, so that the inertial mass of the actuator collision is reduced, and the kinetic energy when the disc spring is hit is reduced. A ball screw rod part, a ball screw nut part assembled to the rod part, a sleeve covering the rod part and the nut part, a key screw attached to the sleeve and provided in the key groove provided in the nut part. There is a detent key,
And an electric linear actuator comprising disc springs installed at both ends of the sleeve, wherein the detent key for converting a rotational force from a motor (not shown) into a linear force is provided at the stroke end. It is an object of the present invention to provide a mechanical stop mechanism of an electric linear actuator which is installed so as to be detached from a ball screw nut portion and can reduce or omit the disc spring for absorbing collision energy. .

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a mechanical stop mechanism for an electric linear actuator according to the present invention will be described below with reference to FIG. FIG. 1 is a partial sectional front view showing the configuration of a mechanical stop mechanism of an electric linear actuator according to the present invention. As shown in FIG. 1, the mechanical stop mechanism of the electric linear actuator according to the present invention covers a ball screw rod part 1, a ball screw nut part 2 assembled to the rod part 1, the rod part 1, and the nut part 2. The sleeve 3 includes a detent key 4 attached to the sleeve 3 and disposed in a key groove provided in the nut portion 2, and a disc spring 5 disposed at both ends of the sleeve 3. In the electric linear actuator, a detent key 4 for converting a rotational force from a motor (not shown) into a linear force is provided so as to be disengaged from the ball screw nut portion 2 at a stroke end, so that the collision energy can be reduced. The absorption disc spring 5 can be reduced in size or can be omitted.

More specifically, the ball screw rod 1, ball screw nut 2, sleeve 3, and disc spring 5 are the same as the mechanical stop mechanism of the conventional electric linear actuator shown in FIG. The arrangement of the key 4 is the same as that of the conventional key shown in FIG.
The distance between is free. The operation of the ball screw nut 2 is shown in FIG.
When the nut 2 comes to the stroke end, the keyway of the nut 2 comes off from the detent key 4 and the nut 2
Rotates together with the rod portion 1 and collides with the disc spring 5 or stops shortly.

[0007]

The mechanical stop mechanism of the electric linear actuator according to the present invention is configured as described above, and has the following effects. When the ball screw nut collides with the disc spring, the key groove of the nut is disengaged from the detent key, and the nut rotates with the rod. Therefore, no linear force is transmitted to the nut portion. The moment of inertia of the rod portion and the external motor is not converted into a linear equivalent inertial mass, but appears as rotational energy as it is, and the inertial mass in the linear direction is only the mass of the nut alone, and the kinetic energy is reduced.

[Brief description of the drawings]

FIG. 1 is a partial sectional front view showing a configuration of a mechanical stop mechanism of an electric linear actuator according to the present invention.

FIG. 2 is a partial cross-sectional front view showing a configuration of a mechanical stop mechanism of a conventional electric linear actuator.

[Explanation of symbols]

 1: Ball screw rod part 2: Ball screw nut part 3: Sleeve 4: Lock key 5: Disc spring

Claims (1)

[Claims] 1. A ball screw rod part, a ball screw nut part assembled to the rod part, a sleeve covering the rod part and the nut part, and a key groove attached to the sleeve and provided in the nut part. In a motorized linear actuator composed of a detent key arranged at a position and a disc spring installed at both ends of the sleeve, a detent key for converting a rotational force from the motor into a linear force is provided. The mechanical stop of the electric linear actuator, wherein the disc spring for absorbing the collision energy can be miniaturized or omitted by being installed so as to be detached from the ball screw nut portion at a stroke end. mechanism.