JPH01278251A - Stepping motor - Google Patents

Abstract

PURPOSE:To reduce the rotating vibration of a motor by opening a hole at front and rear side plates, and using them bearings for supporting the rotation and thrust of the output shaft of the motor. CONSTITUTION:A stepping motor has a motor output shaft 21, a front side plate 22 and a rear side plate 26, and also outer and inner yokes 23, 24. The yokes 23, 24 are formed in a predetermined toothform and set to a predetermined number of teeth to match the stepping angles, opposed at a predetermined angle, and the conductions of coils 25, 25a are sequentially switched by a step signal to rotate a rotor. In this case, bearings 22a, 26a of the shaft 21 are provided by means such as barring at the centers of the plates 22, 26. Thus, since the centering of the shaft 21 is determined only by the assembling accuracy of the plates 22, 26 and the hole inner diameter, its centering is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a step motor using a permanent magnet in a rotor portion.

[Prior Art] The structure of a conventional step motor is as shown in FIG. 4, which is a sectional view thereof.

In Figure 4, 1 is the motor shaft, 2 is the front plate, 3 is the outer yoke, 4 is the inner yoke, 5 is the coil, 6 is the rear plate, and 7 is the rotor magnet magnetized equally in the circumferential direction. There are two, one at the front and one at the rear, and each is magnetized in the same way. To explain the structure of the outer yoke 3 and the inner yoke 4, each yoke has a predetermined tooth profile and number of teeth according to the step angle, and the teeth of the inner yoke 4 and the teeth of the outer yoke 3 face each other at a predetermined angle. Furthermore, the front and rear outer yokes 3
The teeth of the front and rear inner yokes 4 are configured to have a predetermined angular relationship with each other, and by switching the energization of the coil 5, the magnetic circuit is sequentially switched via the rotor magnet 7. The rotor yoke 8 fixes the rotor yoke and also fixes the motor shaft 1.
rotates by a predetermined angle for each step signal. 9 is a bearing that supports the rotation of the motor shaft, and is made of oil-impregnated metal. A thrust washer 10 is rotatably and slidably provided between the bearing 9 and the rotor yoke 8 to receive the force in the axial direction of the motor, and also serves to reduce thrust backlash. 11 is a lead wire, and coil 5
connected to the terminal.

[Problems and Objects to be Solved by the Invention] However, in such conventional step motors, the assembly accuracy of the bearing part is limited to the circular hole diameter of the side plate, the outer diameter of the oil-impregnated metal, the inner diameter accuracy, and the press fit between the side plate and the oil-impregnated metal. Since the accuracy and the accuracy of the combination of the front and rear side plates are involved, it is difficult to achieve coaxiality of the front and rear bearings 9, and it is necessary to increase the inner diameter of the oil-impregnated metal, resulting in large dimensional variations in bearing clearance. Therefore, when a step motor is incorporated into a system, the rotational vibration of the motor increases due to the large bearing clearance, causing resonance with the system casing.
It was a source of noise.

Therefore, in order to solve these problems, the present invention aims to reduce the number of components of the motor bearing, improve assembly accuracy for alignment, minimize bearing clearance, and suppress rotation. do.

[Means for Solving the Problems] In order to solve the above problems, the step motor of the present invention includes: 1) In a step motor using a permanent magnet in the rotor, the bearing portion of the motor output shaft is provided on a side plate attached to the stator yoke. It is characterized by being composed of holes.

2) A bearing clearance in the radial direction between the hole provided in the side plate and the motor output shaft is partially increased.

3) A thrust washer is sandwiched between the side plate and the rotor facing surface facing the side plate, with the motor output shaft interposed therebetween.

[Function] In the step motor configured as described above, since the bearing portion is integrally formed on the side plate, it is easier to achieve coaxiality between the front and rear bearings of the motor because there are fewer parts to be assembled.

Furthermore, if the radial bearing clearance between the hole provided in the steel plate and the motor output shaft is partially increased, this area becomes a pool of lubricating oil.

Furthermore, if a thrust washer is provided between the side plate and the rotor, wear of the rotor and steel plate due to rotation of the rotor is reduced through the thrust washer.

[Example J Embodiments of the present invention will be described below based on the drawings.

1 to 3 are diagrams showing an embodiment of the present invention, in which FIG. 1 is a sectional view of a step motor of the present invention, and FIGS. 2 and 3 are diagrams showing other bearing structures according to the present invention. FIG.

First, a first example will be described. In FIG. 1, 21 is a motor output shaft, and in this embodiment, a gear is formed at one end. Reference numeral 22 denotes a front side plate, and a bearing portion 22a for receiving the motor output shaft 21 is provided at the center thereof by means such as burring. 23 is the outer yoke, 24
is an inner yoke, each formed with a predetermined tooth profile and number of teeth according to the step angle, and the teeth of the outer yoke 23 and the teeth of the inner yoke 24 are configured to face each other at a predetermined angle.
Furthermore, the teeth of the front and rear outer yoke 23 and the teeth of the inner yoke 24 are
The coils 25 and 25a are configured to have a predetermined angular relationship with each other, and by sequentially switching the energization of the coils 25 and 25a using a step signal, the magnets are equally divided in the circumferential direction, and the rotor magnets 27 made of permanent magnets are fixed. In addition, there is one control means for rotating the rotor yoke 31 to which the motor output shaft 21 is fixed by a predetermined angle for each step signal. 26 is a rear side plate, and like the front side plate 22, a bearing portion 26a is provided at the center thereof by means such as burring.

28 and 28a are lead wires, and the coils 25 and 25
Each terminal is connected to the terminal a.

In the step motor having the above structure, the bearing structure is described in detail. By providing a support for the motor output shaft 21 at the center of the front side plate 22 and the rear side plate 26 by means such as burring, a negative body bearing is formed. However, there is no need to separately provide a bearing such as a conventional sintered oil-impregnated metal bearing, and the number of parts can be reduced by IYII.

The bearing portion is formed only from front and rear steel plates, and the assembly accuracy for alignment is advantageous because the number of parts is smaller than before, making it possible to reduce the bearing clearance. Furthermore, when the step motor of the present invention is used, for example, in a head feeding mechanism of a magnetic recording device, the head feeding member is likely to resonate due to the vibration generated when the motor rotates, causing noise, but bearing clearance can be easily adjusted. Due to its small size, step motor rotational vibrations are suppressed and a quiet device can be provided.

Next, a second example will be described. In FIG. 2, reference numeral 30 denotes a gap portion that partially increases the bearing clearance in the radial direction between the bearing portion 22a and the motor output shaft 21, and the gap portion 30 serves as an oil reservoir.
Since it has good oil retention, it is possible to maintain good lubricity of the bearing even when the motor is used for long periods of time. Note that the bearing portion 26a may also have a similar structure.

In addition, with oil-impregnated metal bearings, it is not possible to use low-viscosity oil due to the impregnation property, but in the above-mentioned cavity 3o, it is possible to use grease in addition to oil, which reduces the rotational vibration of the step motor. The high viscosity of grease allows it to be absorbed and, when incorporated into a system, provides a much quieter device.

Further, a third example will be described. In FIG. 3, a thrust washer 29 is installed between the bearing #22a and the rotor yoke 31, and by applying oil, grease, etc. to the bearing gap 30, the surface tension of the oil and the thrust washer 29 are By adding 1 to the advantage, it is possible to further improve the oil retention property compared to the embodiment shown in FIG. In addition, the wear of the front plate 22 and the rotor yoke 31 due to the rotation of the rotor yoke 31 is reduced by inserting the thrust washer 29 therein, and even if wear occurs, the wear of the front plate 22 and the rotor yoke 31 is reduced by the rotation of the rotor yoke 31. can prevent infiltration. Naturally, it is preferable that the rear side plate 26 side has a similar structure.

In the embodiments described above, the front side plate 22 or 19,
! This is a case where the l plate 26 is made of metal, but the front plate 2
It goes without saying that similar effects can be obtained even if the rear plate 2 or the rear plate 26 is made of plastic or sintered.

[Effects of the Invention] As explained above, in the step motor of the present invention, holes are formed in the front and rear side plates, and the holes are used as bearings that receive the rotation and thrust of the motor output shaft, so that the alignment of the motor output shaft is improved. Since it is determined only by the assembly accuracy of the front and rear side plates and the inner diameter of the hole, alignment can be easily performed, and therefore the inner diameter of the hole can be kept small and the bearing clearance can be reduced. Therefore, since the rotational vibration of the motor can be reduced, even when the step motor of the present invention is incorporated into a system, the system noise generated by the motor can be eliminated, and a quiet device can be provided.

Furthermore, by making the bearing part an integral bearing, the number of parts can be reduced, resulting in significant cost reductions.

In addition, regarding oil retention, the present invention has great effects, such as providing an oil pool and having a structure that allows the application of highly viscous grease, making it possible to use the motor for long periods of time.

[Brief explanation of the drawing]

1 to 3 are diagrams showing one embodiment of the present invention, and FIG. 1 is a cross-sectional view of the step motor of the present invention, MS2
3 and 3 are detailed views of main parts showing other examples of the bearing structure according to the present invention. FIG. 4 is a sectional view showing the structure of a conventional step motor. 21. Motor output shaft 22. Front plate 23. , Outer yoke 24 , Inner yoke 25 , Coil 26 , Rear plate 27 , Rotor magnet 28 , Lead wire 31 , , rotor yoke and above Applicant: Seiko Epson Co., Ltd. Agent: Patent attorney Kizo Suzuki and one other person Whistle 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1) A step motor using a permanent magnet in the rotor, characterized in that the bearing portion of the motor output shaft is formed by a hole provided in a side plate attached to a stator yoke. 2) The step motor according to item 1), wherein a bearing clearance in the radial direction between the hole provided in the side plate and the motor output shaft is partially increased. 3) The step motor according to item 2), characterized in that a thrust washer is sandwiched between the side plate and the rotor facing surface facing the side plate, via the motor output shaft.