JPH0145249Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a brushless motor with a speed detector used as a drive source for video tape recorders, cassette tape recorders, players, etc.

Configuration of Conventional Examples and Problems thereof In recent years, high-performance and highly reliable DC brushless motors have come into widespread use as motors used in audio equipment and video equipment.

Conventionally, magnetic or optical devices have been proposed as rotational speed detection mechanisms for DC brushless motors, but for motors used in audio equipment, video equipment, etc., high-precision speed control including phase control is required. Frequency generator (hereinafter referred to as Frequency Generator) used for rotation speed detection mechanism
(referred to as FG, which is an abbreviation for generator), must meet the following conditions: 1. FG itself does not generate rotational unevenness signals.

2.Do not adversely affect motor rotation.

3. Strong against external noise induction.

4 High output voltage (good S/N ratio).

5. The structure should be simple and small.

etc., and in order to satisfy these conditions, the first
The full-circumference integral magnetic type FG shown in the figure has been proposed. To briefly explain the FG configuration in FIG. 1, a stator 1 whose inner periphery is cut into a tooth shape, and a rotor 2 whose outer periphery is cut into a tooth shape are provided inside the stator 1. The teeth 2a of the rotor 2 are configured to face each other, and further, a magnet piece is placed in the middle of the yoke 3 from the stator 1 to the rotor 2.
A winding 4 is wound around a part of the wire. The stator 1 and the rotor 2 are made of a soft magnetic material (such as iron), and when the rotor 2 rotates, the teeth 1a of the stator 1 and the teeth 2a of the rotor 2 are opposed to each other; 2a and the opposing valleys 1b and 2b occur alternately, resulting in an increase or decrease in the magnetic resistance of the magnetic circuit, that is, a change in the amount of magnetic flux within the winding 4, and an alternating current voltage is applied to both ends of the winding 4. It is becoming possible to obtain it. Since this magnetic FG is an all-circumference integral type, it can obtain higher precision than a single-point detection type, but it has the following drawbacks: 1. In order to obtain high pulses, the shape must be growing.

2 When rotating at extremely low speeds, the output is low and the S/B ratio deteriorates.

3. Noise is generated by the radiated magnetic flux from the motor.

4. Gives a slight vibration to the motor by the magnetic attraction force of the gear.

and so on. In order to overcome this drawback of the magnetic type, a magnetized optical single-point detection type FG has been proposed as shown in FIG. In Figure 2, the optical single-point detection type
Briefly explaining the configuration of the FG, light 5a from the light emitting source 5 is projected onto a rotating slit plate 7 fixed to a rotating shaft 6, and further passes through a plurality of slits 7a provided on the rotating slit plate 7. The light is projected onto the light receiving source 8. Since the rotating slit plate 7 rotates together with the rotating shaft 6, the light receiving source 8 is rotated as shown in a and b in FIG.
The light 5a emitted from the light emitting source 5 is alternately irradiated and blocked, and the light receiving source 8 outputs an AC signal. However, the optical single-point detection type FG has a drawback that the eccentricity and inclination of the rotating slit plate 7 when the rotating slit plate 7 and the rotating shaft 6 are fixed together, the accuracy of the slit 7a, etc. directly cause detection errors.

In order to eliminate such drawbacks of the conventional examples shown in FIGS. 1 to 3, the applicant first proposed an optical all-round integral type FG shown in FIG. 4. In Figure 4, 9
1 is a light emitting source assembly, 10 is a rotating shaft, and 11 is a slit 1.
A rotary slit plate having n pieces of 1a, and a rotary shaft 10
is attached to. 12 is a rotating slit plate 1
A light shielding member 12 of the same pitch as the slit 11a of No. 1
The photoelectric conversion element 12 is generally composed of a selenium solar cell or an amorphous silicon solar cell, and is fixedly attached. In FIG. 4, the light emitting source assembly 9
The light 9c emitted from the rotary slit plate 11 is projected onto the photoelectric conversion element 12 through the slit 11a of the rotary slit plate 11. Since the rotary slit plate 11 rotates together with the rotation shaft 10, the light 9c emitted from the photoelectric conversion element 1 is projected onto the photoelectric conversion element 12 as shown in FIG. 5a.
2, the light 9c from the light source assembly 9 is projected all around, and the light 9c is not projected, as shown in FIG. Now, the rotational speed of the rotating shaft 10 is M
If it is [rotation/S], a frequency P determined by P=n·M [Hz] can be obtained.

With the above configuration, the optical all-round integral type
FG can be realized, eliminates the drawbacks of the conventional method, and has the following advantages: 1.Compared to the optical single-point detection type FG, since it is an all-round integral type, there is no bias when attaching the rotating slit plate 11 to the rotating shaft 10. There is a large tolerance regarding the accuracy of the center, inclination, and width of the slit 11a, allowing highly accurate rotation detection.

2. Compared to the magnetic type FG, since it is an optical type, high output and high S/N can be obtained even during extremely low speed rotation, and there is no vibration due to the magnetic attraction between the rotor and stator.

3. The size can be reduced.

etc.

FIG. 6 is a diagram showing an example in which an optical full-circumference integral type optical FG having the above-mentioned advantages is applied to a brushless motor. The rotor assembly consists of a drive magnet 14 that is magnetized in a direction parallel to the rotating shaft 13, and a rotor yoke 1 that constitutes a magnetic circuit for the drive magnet 14.
5, and a rotor boss 16 to which the rotor yoke 15 is fixed at one end and the rotary slit plate 11 is fixed at the other end.
and a rotating shaft 13 that is inserted and fixed into the center hole 16a of the rotor boss 16, and each component is fixed by press-fitting, fitting, gluing, etc. as necessary.

The stator assembly includes a stator coil 17 that faces the magnetic pole surface 14a of the drive magnet 14 and generates a driving force, and a wiring pattern 18a to which the stator coil 17 is fixed with an adhesive or an adhesive sheet, and a magnetic circuit of the drive magnet 14. a stator yoke 18 forming a shape, a housing 19 fixed to the stator yoke 18, and an inner circumferential surface 1 of the housing 19.
Bearings 20 and 21 are fixed to 9a and rotatably support the rotary shaft 13, and the tip arc surface 1 of the rotary shaft 13
3a in the thrust direction.

The speed detection section maintains a constant gap with the rotor yoke 15 and a constant gap between the light source assembly 9, which consists of a substrate 9a and a light source 9b, which are fixed to the stator yoke 18 via a support 23, and the light source assembly 9. Photoelectric conversion element 12 fixed via spacer 24
and a rotating slit plate 11 that is placed in the gap between the photoelectric conversion element 12 and the light source assembly 9 and is attached to the rotating shaft 13 and the rotor boss 16 so as to rotate together with the rotating shaft 13. This is as explained in FIGS. 4 to 5.

Now, in the configuration of the brushless motor with a speed detector as described above, the rotating shaft 13 is strongly pressed in the direction of the thrust receiver 22 of the stator assembly by the attraction force acting between the stator yoke 18 and the drive magnet 14. Since the thrust receiver 22 rotates and slides in this state, there is a problem in that the sliding wear of the thrust receiver 22 becomes large. Also, the stator yoke 1 is connected to the rotating shaft 13.
8. If the surface of the drive magnet 14 is unstable,
There is a problem in that the suction force generated in the gap becomes unbalanced, and the impact on the bearings 20 and 21 increases wear on the bearings.

Purpose of the invention The present invention solves the above-mentioned conventional problems and aims to reduce the sliding wear of the thrust bearing and the wear due to the impact of the bearing.

Composition of the invention The brushless motor with a speed detector of the invention is
A speed detector is constructed in the stator yoke by providing multiple holes near the center of the positions corresponding to the respective magnetic poles of the driving magnets of the rotor yoke that make up the rotor assembly, and by maintaining a constant gap in the axial direction with the rotor yoke. A light emitting source assembly consisting of a substrate and a light source is fixed via a support, and by using a magnetic material for the substrate, a magnetic attraction force is generated between the rotor assembly and the substrate, and this attraction force is counteracted. This is to offset the suction force acting between the stator yoke and the rotor assembly that acts in the axial direction, reduce the force acting in the axial direction, and reduce sliding wear on the thrust receiver and impact wear on the bearing.

DESCRIPTION OF EMBODIMENTS FIG. 7 shows a sectional view of a brushless motor with a speed detector according to an embodiment of the present invention.
Note that explanations of the same parts or parts as in the conventional example will be omitted. In Figure 7, the rotor assembly TV
The rotor yoke 25 is provided with a plurality of holes at least in one or more places in the flat part to which the drive magnet 14 is fixed, in a portion close to the inner diameter of each magnetic pole of the drive magnet 14.
A light emitting source assembly 2 consisting of a substrate 26a made of a magnetic material and a light emitting source 26b is mounted while maintaining a constant gap in the axial direction.
6 is fixed to the stator yoke 18 via a support 23.

The operation of the brushless motor with a speed detector of this embodiment configured as described above will be described below. In FIG. 7, rotor yoke 2
A plurality of holes 25b provided in the flat part 25a of No. 5
The magnetic flux emitted from one magnetic pole (for example, the N pole) of the driving magnet 14 passes through the substrate 26 made of a magnetic material.
By forming a magnetic path between adjacent magnetic poles (for example, S poles) passing through a, an attractive force is generated between the rotor yoke 25 having the rotating shaft 13 and the substrate 26a. Stator yoke 18 and drive magnet 1 acting in opposite directions
4, thereby reducing the pressing force in the thrust direction acting on the thrust receiver 22 of the rotating shaft 13.

As described above, according to this embodiment, several holes 25b are provided in the flat part 25a of the rotor yoke 25, and the substrate material of the light emitting source assembly 26 having a substrate is made of a magnetic material, so that the thrust of the rotating shaft 13 is By reducing the pressing force acting in the direction of the receiver 22, 1. The sliding wear of the thrust receiver 22 is reduced.

2. Reduce wear of bearings 20 and 21 due to impact.

It is possible to achieve the following effects.

Effects As is clear from the above explanation, the present invention has several holes in the flat surface of the rotor yoke, and the substrate of the light source assembly is made of magnetic material, thereby connecting the stator yoke and the drive magnet. By generating suction force in the opposite direction to the suction force direction, the pressing force between the rotating shaft and the thrust bearing can be reduced without adding any special parts, thereby reducing sliding wear on the thrust bearing. As well as being able to
An excellent effect can be obtained in that increased wear due to impact on the bearing can be prevented.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional perspective view showing a conventional magnetic all-round integral type frequency generator, and FIG. 2 is a schematic structural perspective view showing a conventional optical single-point detection type frequency generator. Figures 3a and b are explanatory diagrams of the same operation, Figure 4 is a schematic perspective view of the optical full-circumference integrated frequency generator, Figures 5 a and b are explanatory diagrams of the same operation, and Figure 6 is the same speed. 7 is a sectional view of a brushless motor with a speed detector according to an embodiment of the present invention. 11... Rotating slit plate, 11a... Slit, 13... Rotating shaft, 14... Drive magnet,
16...Rotor boss, 17...Stator coil,
18... Stator yoke, 19... Housing,
20, 21... Bearing, 22... Thrust bearing, 25
...Rotor yoke, 25b...hole, 26...light emitting source assembly, 26a...substrate.

Claims (1)

[Scope of utility model registration request] a drive magnet magnetized parallel to the rotation axis;
A rotor assembly including a rotor yoke to which the drive magnet is fixed, a rotor boss to which the rotor yoke is fixed, and a rotating shaft press-fitted and fixed to the rotor boss, and a rotor assembly that is disposed face-to-face with the drive magnet in the axial direction with a gap therebetween. a stator assembly comprising a stator coil, a stator yoke that fixes the stator coil, a bearing that rotatably supports the rotating shaft, and a housing that holds the bearing and is fixed to the stator yoke;
a light emitting source assembly having a substrate facing the rotor yoke with a constant gap maintained in the axial direction and fixed to the stator yoke via a support member; and a photoelectric conversion element fixed to the light emitting source assembly with a constant gap maintained. and a speed detection unit comprising the light emitting source assembly and a rotating slit plate fixed to the rotor boss disposed in the gap between the photoelectric conversion element, the substrate of the light emitting source assembly being made of a magnetic material, A brushless motor with a speed detector, wherein a hole is provided in a surface of the rotor yoke to which the drive magnet is fixed.