JPH01311845A - Motor - Google Patents

Abstract

PURPOSE:To improve the accuracy of detection by monolithic-molding a ball screw nut to the inner circumferential surface of one end section of a hollow shaft while fixing a high rigidity bearing to the shaft as being adjoined to a revolution detector. CONSTITUTION:When a stator coil 12 is electrified, a shaft 2 is elongated by the heat generation of the coil 12. Elongation in the direction that a ball screw nut 5 is formed is absorbed by a single-row deep-groove ball bearing 6 and an elastic member 20 energized leftward. Even when the shaft 2 is extended in the left direction, the shaft 2 is slid easily by oil seal sections 17a, 17b, thus preventing load concentration to the shaft 2. Accordingly, the quantity of elongation between the starting point of elongation and a rotary disk 13 can be reduced remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electric motor used as a drive source in, for example, an article transfer device that carries articles and moves in a straight line.

2. Description of the Related Art Hereinafter, a conventional electric motor of this type will be explained with reference to FIG.

In the figure, 21 is a rotor, and a hollow rotating shaft 22
A rotor yoke 23 and a permanent magnet 24 are fixed to the outer periphery of the rotor yoke 23 and a permanent magnet 24. A ball screw nut 25 made of a highly rigid body is inserted into the inner periphery of one end of the rotating shaft 22, and the ball screw nut 25 is firmly fixed to the end surface of the rotating shaft 22 by a port 26. ing. A single row deep groove ball bearing 27 and a combination angular contact ball bearing 28 are attached to the outer periphery of the rotating shaft 22. The outer periphery is directly fixed to the motor frame 30. 31 is a stator, which includes an armature 32 and a coil 3 wound around it.
It is composed of 3. 34 is a second rotating shaft coupled to one end of the rotating shaft 22 via a coupling 35, and a rotating disk 36 of an optical encoder is provided with a fixed slit (described later) on the outer periphery of the second rotating shaft 34. The rotating disk 36 is also fixed with an axial gap δ from the light receiving element, and a large number of slits are formed in the rotating disk 36. Moreover, this rotating disk: 36 is the second rotating shaft 34
It rotates at the same time.

37 is a light emitting element, and 38 is a fixed slit. The fixing slit 38 is fixed to a light receiving element 39'', and the light receiving element 39 is further fixed to a base 40 for mounting a detector. The light receiving element 39 receives the light emitted from the light emitting element 37 through the slit of the rotating disk 36 and the fixed slit 38, and outputs the received light signal to the outside. Furthermore, bearings 41 and 42 are attached to both ends of the second rotating shaft 34. Note that 43 is a detector cover.

The first example of the conventional electric motor configured as described above. and second
A ball screw 44 is inserted into the inner periphery of the rotating shaft 22.34, and the ball screw 44 and the ball screw nut 25 are screwed together via a plurality of balls 45.

Next, the operation will be explained.

The control circuit 4 (not shown) causes a predetermined current to flow through the knee coil 33 of the stator 3 through the motor driver to rotate the first and second rotating shafts 22, 34-, and the motor It slides relative to the screw 45. That is, when the electric motor is fixed, the ball screw 45 moves forward and backward, and conversely, when the ball screw 45 is fixed, the electric motor moves the ball screw 45'' forward and backward. The amount of rotation of the first and second rotating shafts is detected by the encoder, and the detection output is fed back to the control circuit, so that the control circuit can manage the amount of rotation with high precision.

Problems to be Solved by the Invention The ball screw nut 25 is often placed at the end of the rotating shaft for reasons of workability (for example, ease of mounting the ball). According to the above-mentioned conventional example, the ball screw nut 25 is attached to the rotating shaft 22 by the bolt 26, so that the stiffness of the ball screw nut 25 is low in some parts, which results in high precision. In power distribution motors, the rigidity of this part is
In order to compensate for 4, as shown in the figure, a combined angular ball bearing (J) is used as the bearing disposed on the blade of this part. By the way, when the coil 33 of the stator 31 is energized, that part generates heat, so The rotating shaft 22 is extended.

This elongation starts from the above-mentioned combination Ann/R leek bearing. In other words, the combination angle gear, bearing 11 rotation shaft 22, and bracket 29 (two are firmly fixed, and the structure 1 is axially directed, and the rotation @ 2 is
2) exhibits high rigidity against loads in the longitudinal direction (along the axial direction of the bracket 29). This is because almost no relative positional deviation occurs. In addition, in order to prevent the elongation of the rotating shaft 22 that occurs in this way from significantly reducing the rotation detection accuracy by the rotation detector having an axial gap as described above, this rotation @ 22 and the second rotation are #I34 is connected by a coupling 35 using a low bolt (S・'\ツ1-) 4.6 etc. with a stiffness of 11゛, and due to the action of the coupling 35 of 1,=, J Even if the shaft 22 is extended, the axial gap of the rotation detector changes too much (-1
I try not to.

However, since the coupling 35 has such low rigidity, vibrations in the coupling have a negative effect on the detection accuracy of the rotation detector 1-21.
- the second axis of rotation 34 relative to the first axis of rotation 22;
This is a problem in that rotational delays, etc., occur (1-7), but this does not adversely affect detection accuracy.

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the electric motor of the present invention has a ball screw put integrally formed on the inner peripheral surface of the end of the hollow rotating shaft, and eliminates the above-mentioned coupling. Then, on the rotating shaft, a load in the front-rear direction and ＼ along the axial direction of the rotating shaft (which exhibits high rigidity for both 7 and 1') is fixed. 1. Ta.

The rigidity of this part of the blade is increased by the integral formation of a ball and a screw nut on the inner circumferential surface of the hollow shaft, and the starting point of elongation of the rotating shaft due to heat and expansion is close to the rotation detector. Therefore, the effect of elongation on the rotation detector is small.

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

FIG. 1 shows a sectional view of an electric motor according to an embodiment.

In the figure, 1 is a rotor, which is constructed by fixing a rotor yoke 3 and permanent magnets 4 to the outer periphery of a rotating shaft 2 having a hollow structure. A ball screw nut 5 is integrally formed on the inner periphery of one end of the rotating shaft 2. A single-row deep groove ball bearing 6 is attached to the outer periphery of the rotating shaft 2 and the portion where the ball screw nut is formed on the inner periphery, and a combination angular ball bearing 6 is installed near a rotation detector to be described later. A bearing 7 is attached.

The outer periphery of this combination angular contact ball bearing 7 is directly
Further, the outer periphery of the single-row deep groove ball bearing 6 is fixed to a motor frame 9 via a bracket 8. A stator 10 is composed of an armature 11 and a coil 12 wound around the armature. Reference numeral 13 denotes a rotating disk fixed to the outer periphery of the rotating shaft in a position close to the combined angular contact ball bearing, and has a large number of slits formed therein, and this rotating disk 13 is fixed to the motor frame 9. It is arranged with a small gap δ in the axial direction from the light receiving element 16a and the fixed slit 16b. In addition, 1
4 is a light emitting element constituting a part of the encoder, 15 is a detector cover, and 17a, 17b are oil seals.

A ball screw 18 is inserted into the inner periphery of the rotating shaft of the conventional electric motor constructed as described above, and the ball screw and the ball screw nut are screwed together via a plurality of balls 19.

Next, the operation will be explained. However, since it is the same as the conventional method, the rotation is performed by the signal from the um circuit and the feedback control is performed by the output from the rotation detector.

In this electric motor as well, when the coil of the stator is energized, that part generates heat, which causes the rotating shaft to extend, as in the conventional motor. However, the starting point of this elongation is the mounting portion of the combination angular bearing that firmly connects the rotating shaft and the motor frame in the axial direction. The axis of rotation starts from this part and extends to the left and right,
The expansion of the single-row deep groove ball bearing in the right direction in FIG. 1, that is, in the direction in which the ball screw nut is formed, is absorbed by the resilient member 20 that urges the single-row deep groove ball bearing to the left in the drawing.

Further, even if the rotating shaft extends to the left in the drawing, the rotating shaft easily slides at the oil seal portion, so there is no load concentration on the rotating shaft. By the way, the amount of elongation of the rotating shaft as a whole is not much different compared to the conventional example, but the amount of elongation between the elongation starting point and the rotating disk is significantly smaller than that of the conventional example. Become. Therefore, the influence of the elongation of the rotating shaft on rotation detection accuracy is extremely small. Furthermore, since this embodiment does not use a coupling unlike the conventional one, there is no time delay in the rotation of the rotating disk relative to the rotation of the rotating shaft. Furthermore, by integrally forming a ball screw nut on the inner periphery of the hollow rotating shaft, the rigidity is significantly improved compared to conventional products that are fixed separately with bolts, etc. There is also no need to arrange a high-rigidity bearing near this part, that is, the part where the ball screw nut is formed.

In this example, a combination angular contact ball bearing was used as a bearing having high rigidity in the axial direction, but other types of bearings include double row angular contact ball bearings, four-point contact ball bearings, double row/multirow tapered roller bearings, Double thrust angular bearings or thrust tapered roller bearings or thrust!・
There is no problem even if a plurality of sets of cylindrical roller bearings or thrust self-aligning roller bearings are arranged with their load bearing directions in opposite directions.

Furthermore, even if these bearings are combined with other bearings, the same effect can be achieved as long as the bearings exhibit high rigidity against loads in the front and rear directions in the axial direction.

Effects of the Invention As explained above, in the electric motor of the present invention, a ball screw nut is integrally formed on the inner circumferential surface of one end of a hollow rotating shaft, and a rotation detector is attached to the rotating shaft to detect its rotation. By fixing a bearing that exhibits high rigidity against loads in the front and rear directions along the axial direction of the shaft, the rigidity of the part where the ball screw nut is formed on the inner circumferential surface increases, so this part There is no need to place a high-rigidity bearing at The elongation of the shaft has a very small effect on rotation detection accuracy. Also, unlike conventional systems, a coupling is not used, so the rotation of the rotating disk has a time delay with respect to the rotation of the rotating shaft. It has such an excellent effect that it never occurs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an electric motor according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional electric motor. 1...rotor, 2...rotating shaft, 3...
...Rotor yoke, 4...Permanent magnet, 5.
... Ball screw nut, 6 ... Single row deep groove ball bearing, 7 ... Combination angular contact ball bearing, 8 ...
...Bracket, 9...Motor frame,
10... Stator, 1.1... Armature,
12... Coil, 13... Rotating disk,
"4...Light emitting element, 15...Detector cover, 16.17...Oil seal, 18...
... Ball screw, 19 ... Ball, 20.
・・・・・・Bulging member

Claims (1)

[Claims] (1) The rotating shaft of the rotor has a hollow structure, a ball screw nut is formed on the inner peripheral surface of one end of the rotating shaft, and the rotation of the rotating shaft is detected through an axial gap near the other end. A rotation detector is arranged to perform the rotation, and a bearing is fixed to the rotation shaft, which is close to the rotation detector and exhibits high rigidity against loads in the front and rear directions along the axial direction of the rotation shaft. An electric motor featuring: