JPH02113153A - Electric linear drive device - Google Patents

Abstract

PURPOSE:To shorten the length of a ball screw shaft against the necessary stroke and support the moment force acting on the ball screw shaft by engaging an antirotation mechanism on the flat surface formed at a ball nut part, which is outward fitted to the ball screw shaft and receives and holds balls engaged with screw grooves endlessly and rollably. CONSTITUTION:A plurality of balls 4 are assembled able to roll and circulate in a ball passage formed with the ball screw groove 11 of the inner circumference of a ball nut 5 and the ball screw groove 2 of a ball screw shaft 1, and in a ball circulating part 11a. By adjusting the gap of jointing part of two disc-like members of an antirotation mechanism 15 for the ball screw shaft 1 at the one end part of a housing 6, slide resistance of the ball screw shaft 1 can be controlled. By providing the antirotation mechanism 15 on the separated position from the ball rolling part, moment force in all direction can be also supported with the antirotation mechanism 15.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is an electric linear drive device that converts the rotational motion of an electric motor into linear motion, and in particular uses a ball screw in the threaded portion to precisely move the ball screw axis in a linear manner. The present invention relates to an electric linear drive device that can perform the following functions.

[Conventional technology]

This type of apparatus is conventionally described in, for example, Japanese Unexamined Patent Publication No. 609342 and Japanese Unexamined Patent Publication No. 62-165057.

In the former conventional example, a ball screw groove is formed in one half of the ball screw shaft, a spline groove is formed in the other half, a ball nut is engaged with the ball screw groove, and a ball spline is engaged with the spline groove. By driving the ball nut with an electric motor, it is configured to move linearly forward and backward while preventing rotation of the ball screw shaft.

The latter conventional example has a ball screw groove and a spline groove, a ball screw nut and a ball spline nut, and the screw shaft is moved forward and backward by the rotation of the pole screw nut, and the ball spline nut is driven by a rotation mechanism. It is configured to rotate the screw shaft.

[Problem to be solved by the invention]

However, in the former conventional device described above, the ball screw groove and the spline groove are formed separately, so in order to obtain the required stroke, both the ball screw groove and the spline groove require a stroke length of 10 Nd. However, there is a problem in that the length of the ball screw shaft is longer than its stroke, making the entire device larger, or the stroke is limited to about half the length of the ball screw shaft.

In addition, in the latter conventional device, a spline is used to prevent the screw shaft from rotating, so the length of the stroke + ball screw nut + ball spline nut is required.
Since the pole screw nut and the ball spline nut are arranged close to each other, there is a problem that the structure is complicated and requires a long length in the axial direction.

Therefore, an object of the present invention was made in view of the above-mentioned problems of the conventional method, and the object is to provide an electric linear drive device that can reduce the length of the ball screw shaft relative to the stroke and downsize the entire device. It is said that

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention includes a ball screw shaft having a flat surface parallel to the axis on the outer peripheral surface provided with a thread groove, and a ball that fits externally on the ball screw shaft and engages with the thread groove. A ball nut that is stored and held in an endless manner so that it can freely roll,
an electric motor that rotationally drives the pole nut; a housing that supports the electric motor; and an electric motor that is attached to the housing;
This structure includes a rotation prevention mechanism that engages with a flat surface formed on the ball screw shaft.

[Effect]

In this invention, a flat surface parallel to the axis is formed on the ball screw shaft, and the rotation prevention 8g side attached to the housing is engaged with the flat surface, thereby shortening the length of the ball screw shaft relative to the stroke. To make the overall configuration compact and to move a ball screw shaft forward and backward with appropriate sliding resistance by rotating a ball nut.

[Example] Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a longitudinal cross-sectional view of the electric linear drive device. In the figure, ball screw grooves 2 with a predetermined pitch are screwed on the outer circumferential surface of a ball screw shaft 1, and a flat surface 3 parallel to the axis. Four rows are arranged in the axial direction at equal circumferential locations. The flat surface 3 is set to be shallower than the bottom of the ball screw groove 2 so that rolling of the ball 4 on the inner circumference of the pole screw groove 2 is not hindered.

A cylindrical ball nut 5 that rotatably accommodates the balls 4 in an endless manner is rotatably supported on the inner periphery of the housing 6 via bearings 7.7 while being fitted onto the ball screw shaft 1. In addition, 8 is a collar for positioning the bearing 7.7,
S is a locking nut that fixes the bearing 7.7 through the spacer 10. A ball screw groove 11 is provided on the inner peripheral surface of the ball nut 5.
is screwed therein, and a ball circulation part 11a is arranged on the outer peripheral surface, and a large number of balls 4 are disposed in the ball passage formed by the ball screw groove 11 and the ball screw groove 2 of the ball screw shaft 1, and in the ball circulation part 11a. are incorporated so that they can roll and circulate freely.

On the other hand, on the outer peripheral surface of the cylindrical rotor yoke 5a that extends integrally with the pole nut 5, a rotor 12a of a permanent magnet electric motor 4a12 serving as a rotational drive mechanism that provides rotational force to the pole nut 5 is fitted. 12b is a coil, and t2c is a stator fixed to the inner peripheral surface of the housing 6. 13
1 is a rotary encoder that detects the rotational phase angle of the pole nut 5, and 14 is a seal.

Furthermore, a rotation prevention mechanism 15 for the ball screw shaft 1 is attached to one end of the housing 6 .

FIG. 2 shows a first embodiment of the rotation prevention mechanism 15, which is composed of two half-split disk-shaped members 17 and 17 arranged on both sides of the ball screw shaft 1, and is made up of two half-disk-shaped members 17 and 17. A flat surface 16 corresponding to the flat surface 3 of the ball screw shaft 1 is provided on the inner peripheral surface of the plate member 17.17.

By adjusting the gap between the mating portions 18 of the hundred-disc plate member 17.17, the gap between the two flat surfaces 3.16 is changed, and the sliding resistance of the ball screw shaft 1 is controlled. Therefore, for installation, the fixing bolt (
It is formed to have a slightly larger diameter than the shaft diameter of the disc-shaped member 17.17 (not shown), and the position of the disc-shaped member 17.17 can be adjusted freely. When a moment force acts on the ball screw shaft 1, only the ball rolling portion of the ball nut 5 supports it, but this rotation can be prevented by providing the rotation prevention mechanism 15 at a position away from the ball rolling portion. Mechanism 15 can also support moment forces in any direction.

FIG. 3 shows a second embodiment of the anti-rotation mechanism.

Components that are the same as those in the first embodiment shown in FIG. 2 are designated by the same reference numerals, and their description will be omitted.

This anti-rotation mechanism 20 is composed of a half-disk-shaped member 21, as in the first embodiment, and four needle pins 22 are fixed to the inner peripheral surface thereof. That is, the needle pin 22
is fixed at a position corresponding to the flat surface 3 of the ball screw shaft 1, and is in line contact with the flat surface 3. Therefore, in the case of this embodiment, the ball screw shaft 1 can be slid while the gap between the mating portions 18 is closed and a light preload is applied, and the play of the ball screw shaft 1 can be suppressed as much as possible.

FIG. 4 shows a third embodiment of the rotation prevention mechanism 30, and if the direction of the moment acting on the ball screw shaft 1 is determined, rotation prevention using two lines is possible in this way.

In the same figure, reference numeral 23 denotes a rotation prevention member having a pair of protruding fingers 24 that are externally fitted onto the ball screw shaft 1. A needle pin 22 is fixed to the opposite surface of the fingers 24, and the needle pin 22 is attached to the flat surface 3 of the ball screw shaft 1. Rotation is prevented by making them contact each other. Therefore, the ball screw shaft 1 of this embodiment has flat surfaces 3 formed on both sides. A slit 25 is formed between the fingers 24 of the rotation prevention member 23, and even if a slight installation error occurs, it can be absorbed by the spring action. Further, reference numeral 26 denotes an adjustment bolt, and by tightening the adjustment bolt, the sliding resistance of the ball screw shaft 1 can be freely adjusted. 27 is a long hole for attaching the rotation prevention member 23 to the housing 6.

The electric linear drive device of the present invention has the above-described configuration, and when the electric motor 12 is energized and started, the ball nut 5
rotates, and the ball screw shaft 1, which is held in a non-rotating state by the rotation prevention mechanism 15 or 20, 30, is linearly driven in the axial direction by the feeding action of the balls 4 and the screw grooves 2.

The ball screw shaft 1 moves in the axial direction while its flat surface 3 slides against the rotation prevention mechanism 15 or 20.30,
Precise positioning is possible with the sliding resistance generated by the anti-rotation mechanism.

〔effect〕

With the above configuration, the present invention exhibits special effects as an electric linear drive device as described below.

(a) The length of the ball screw shaft relative to the required stroke can be shortened, making the entire device simple and compact.

(b) The rotation of the ball screw shaft can be prevented with a simple configuration, and the rigidity of the ball screw shaft is not reduced and processing is easy.

(c) The sliding resistance of the ball screw shaft can be easily adjusted, and the moment force acting on the ball screw shaft can also be received.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an electric linear drive device according to the present invention;
FIG. 2 is a vertical cross-sectional side view showing a first embodiment of the rotation prevention mechanism used in the above, and FIGS. 3 and 4 are a second embodiment of the rotation prevention mechanism.
FIG. 4 is a vertical cross-sectional side view showing an example and a third example. 1...Ball screw shaft, 2.11...Ball screw groove, 3.16...Flat surface, 4...
...Ball, 5...Natsuto, 6...
...Housing, 12...Electric motor, 15.20.30...Rotation prevention mechanism, 17.2
1...Disc-shaped member, 22...Needle pin, 23...Rotation prevention member. Patent applicant: ShinMaywa Industries Co., Ltd.; NCHN Toyo Bearing Co., Ltd.

Claims (5)

[Claims] (1) A ball screw shaft having a flat surface parallel to the axis on the outer peripheral surface provided with a threaded groove, and a ball that fits externally on the ball screw shaft and engages with the threaded groove are housed and held in an endless manner so as to be able to freely roll. An electric motor comprising a ball nut, an electric motor that rotationally drives the ball nut, a housing that supports the electric motor, and a rotation prevention mechanism that is attached to the housing and engages with a flat surface formed on a ball screw shaft. Linear drive. (2) The flat surface formed on the outer peripheral surface of the ball screw shaft is
The electric linear drive device according to claim 1, wherein the electric linear drive device is set shallowly with respect to the thread groove. (3) The electric linear drive device according to claim 1, wherein the rotation prevention mechanism is made of a half-disk-shaped member, and has a flat surface on an inner circumferential surface that engages with a flat surface of a ball screw shaft. (4) The electric linear drive device according to claim 1, wherein the rotation prevention mechanism comprises an integral member having a slit that fits around the ball screw shaft. (5) Claim 3, wherein the engagement portion of the rotation prevention mechanism with respect to the flat surface of the ball screw shaft is formed of a needle pin.
or 4. The electric linear drive device according to any one of 4.