JPH0573349U - Ball screw device - Google Patents

Abstract

(57) [Summary] [Object] The present invention aims to shorten the longitudinal dimension of a device for driving a ball screw shaft by a motor. A rotor 8 is connected to the outer circumference of a hollow motor shaft 5, and a ball screw nut 11 is attached to the tip of the motor shaft 5. The ball screw shaft 13 is moved in and out of the shaft hole 7 of the motor shaft 5, and the tip of the screw shaft 13 is prevented from rotating by the spline groove 16 and the spline nut 17.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a ball screw device.

[0002]

[Prior Art]

 Conventionally, as a ball screw device in which a ball screw shaft is driven by using a motor, there is a ball screw device previously proposed by the present applicant in Japanese Utility Model Laid-Open No. 2-186157. As shown in FIG. 3, in the proposed device, a ball screw nut 32 screwed onto a ball screw shaft 31 and a rotor 34 of a motor 33 are connected via a joint 35, and the ball screw shaft 31 and the case are connected. A rotation preventing means 37 for preventing the screw shaft from rotating is provided between the screws 36.

The rotation preventing means 37 is composed of bearings 38 and 39 mounted eccentrically on the ball screw shaft 31, rolling blocks 40 and a preload block for linearly guiding the bearings along the ball screw shaft 31. When the ball screw nut 32 is rotated by the motor 33, the rotation of the bearings 38 and 39 prevents the ball screw shaft 31 from moving straight.

[0004]

[Problems to be solved by the device]

 However, in the above ball screw device, since the ball screw shaft 31, the ball screw nut 32, and the motor 33 are connected in series via the joint 35, the dimension in the longitudinal direction with respect to the outer diameter is small. It becomes relatively large. Therefore, when it is used for driving an XY table or the like, the height of the entire table can be reduced, but a large installation space on the plane must be taken, which is a limitation in saving space.

In view of the above, the present invention aims to provide a structure in a ball screw device in which a ball screw shaft is driven by a motor, the longitudinal dimension of which can be significantly reduced.

[0006]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention provides a shaft through which a ball screw shaft is movably inserted inside a motor shaft having a rotor connected to the outer periphery, and a ball screw shaft is provided at an end of the motor shaft. The structure is such that a ball screw nut that engages with the ball screw nut is attached, and a rotation preventing means is provided to face the ball screw nut and prevent the ball screw shaft from rotating around the fixed member.

The rotation preventing means may be composed of a spline shaft formed on the ball screw shaft and a spline nut that rotatably holds the ball engaging with the spline groove.

[0008]

[Action]

 In the above structure, when the motor shaft rotates, the ball screw shaft moves linearly by the guide of the ball screw nut that rotates integrally with the motor shaft, and moves in and out of the shaft hole of the motor shaft.

[0009]

【Example】

 FIG. 1 shows a ball screw device of the embodiment. The housing 1 is formed by connecting a front lid 3 and a rear lid 4 to the rear end of a cylindrical case 2, and inside the both lids 3 and 4, a hollow motor shaft 5 via bearings 6 and 6. Is supported by rotation.

The motor shaft 5 has a flange portion 5a formed at the front end and a hollow shaft portion 5b at the rear end, and the rotor 8 is connected to the outer periphery of the shaft portion 5b. A stator (stator) 9 is arranged outside the rotor 8, and the stator 9 and the rotor 8 constitute a motor 10 for driving the motor shaft 5.

A ball screw nut 11 with which a ball screw shaft 13 is screwed is fixed to the flange portion 5 a of the motor shaft 5 with a bolt 12, and the ball screw shaft 13 screwed with the ball screw nut 11 is fixed. The end portion is configured to move in and out of the shaft hole 7 inside the motor shaft 5.

The ball screw shaft 13 is arranged coaxially with the motor shaft 5 in the housing 1, and a spline shaft portion 14 having a plurality of spline grooves 16 on its peripheral surface is integrally formed on the tip side thereof. ing. The spline shaft portion 14 is fitted to a spline nut 17 attached to the housing 1 so as to face the ball screw nut 11, and the spline nut 17 and the spline groove 16 form a rotation preventing means 15 for the ball screw shaft 13. Is configured.

As shown in FIG. 2, the spline nut 17 includes an outer cylinder 18 fitted to the spline shaft portion 14, side lids 19 and 19 attached to both ends of the outer cylinder 18, and the outer cylinder 1 8 and a large number of balls 20 that are aligned and circulated between the spline grooves 16, and the balls 20 engage with the spline grooves 16 and roll, thereby preventing the ball screw shaft 13 from rotating and axially moving. Guide straight.

The bearings 6, 6 for supporting the motor shaft 5 are bearings that can simultaneously receive axial and radial loads applied from the ball screw nut 11, such as angular bearings and combined bearings. Be done.

The ball screw device of the embodiment has the structure as described above, and when the motor shaft 5 is rotated by the stator 9 and the rotor 8, the ball screw nut 11 that rotates integrally with the motor shaft 5 is provided. The ball screw shaft 13 and the anti-rotation means 15 prevent the ball screw shaft 13 from moving linearly and move back and forth with respect to the shaft hole 7 of the motor shaft 5.

In this structure, the inside of the motor shaft 5 is used in the space where the ball screw shaft 13 moves linearly, and the motor shaft 5 and the ball screw nut 11 are directly connected to each other and the joint is omitted. The lengthwise dimension of the device can be greatly reduced compared to the structure.

When used for driving an XY table or the like, the ball screw shaft 13 is supported by the ball screw nut 11 and the spline nut 17 facing each other with a relatively short span, and is connected to the ball screw nut 11. Since both ends of the motor shaft 5 are supported by the housing 1 by the bearings 6, 6, a large supporting rigidity can be obtained for the ball screw shaft 13.

In the above embodiments, the spline groove 16 and the ball spline nut 17 are used as the rotation preventing means 15 of the ball screw shaft 13, but if the screw shaft has a function of preventing rotation. Other structures can be adopted, for example, a structure using the bearings 38 and 39, the rolling block 40 and the preload block as shown in FIG. 3 can be used.

Although the shaft hole 7 of the motor shaft 5 is a through hole, the shaft hole 7 may not be a through hole as long as it does not interfere with the moving stroke of the ball screw shaft 13.

[0020]

【effect】

 As described above, according to the present invention, the ball screw nut is directly connected to the motor shaft without using a joint, and the inside of the motor shaft is used as a space in which the ball screw shaft moves linearly. The longitudinal dimension can be greatly reduced, and the mounting space can be made compact and the support rigidity can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing a ball screw device according to an embodiment.

FIG. 2 is a partially longitudinal front view showing the internal structure of the above spline nut.

FIG. 3 is a vertical sectional front view showing a conventional example.

[Explanation of symbols]

 1 Housing 5 Motor Shaft 7 Shaft Hole 8 Rotor 9 Stator 11 Ball Screw Nut 13 Ball Screw Shaft 15 Rotation Preventing Device 16 Spline Groove 17 Spline Nut

Claims (2)

[Scope of utility model registration request] 1. A ball screw nut, which is provided with a shaft hole through which a ball screw shaft is movably inserted, inside a motor shaft having a rotor connected to its outer periphery, and which is screwed into the ball screw shaft at the end of the motor shaft. A ball screw device provided with a rotation preventing means that attaches a ball screw nut to the ball screw nut so as to prevent the ball screw shaft from rotating around the fixing member. 2. The ball screw according to claim 1, wherein the rotation preventing means includes a spline shaft formed on a ball screw shaft and a spline nut that rotatably holds a ball engaging with the spline groove. apparatus.