JP2002051527A - Pulse motor and motor with gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse motor for reducing detent torque and achieving smooth rotary movement. SOLUTION: The pulse motor is provided with a rotor that is made of a rotor 3 having a permanent magnet 2 that is subjected to multipole magnetization in a circumferential direction, two stator yokes 5a arranged at the outer periphery of the rotor, and an excitation coil fitted to the stator yoke. In the stator yoke, a pulse motor is supposed, where magnetic pole surfaces 6a at both ends nearly in a U shape are arranged so that they can oppose each other at the magnetic pole of the permanent magnet. Then, a sectional area is reduced as compared with the area of a magnetic pole surface by providing a thin part 6b at the specific site of the stator yoke for composing a magnetic path. Then, the magnetic pole of the permanent magnet and magnetic flux distribution being generated between the magnetic pole surfaces of the stator yoke become nonuniform, thus reducing detent torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse motor and a geared motor.

[0002]

2. Description of the Related Art With the recent technical improvement of electronic parts such as semiconductors, digital control by a microcomputer or the like has become mainstream instead of mechanical control. Accordingly, for example, a pulse motor that is advantageous for digital control is also being used for driving a pointer of a vehicle or other indicating instrument.

One example of a pulse motor is a rotor composed of a rotor having permanent magnets that are multipolarly magnetized in the circumferential direction, a plurality of stator yokes arranged around the rotor, and a stator yoke thereof. And an excitation coil attached to the motor. The stator yoke is formed in a substantially U-shape (horseshoe shape) by, for example, punching a flat ferromagnetic material, and both ends thereof can be opposed to adjacent magnetic poles of the permanent magnet.

[0004] The stator yokes are arranged so that their phases are shifted by 90 degrees in electrical angle. In other words, there are two stator yokes, and both ends of one stator yoke are
When the two permanent magnetic poles of the permanent magnet constituting the rotor are directly opposed to each other, both ends of the other stator yoke do not face the magnetic poles but have an angle shifted by の of the magnetic pole pitch.

When the excitation coil is energized, N poles or S poles are formed at both ends of the stator yoke on which the energized excitation coil is mounted, so that the S pole and N pole of the rotor are attracted. Therefore, by energizing each excitation coil at a predetermined timing, the rotor (rotor)
Rotates. In particular, this kind of pulse motor has a feature that it is advantageous for positioning by open loop. The principle of the pulse motor is, for example, USP
5,959,378 and the like.

[0006]

However, the conventional pulse motor has the following problems. Due to the attractive force between the permanent magnet and the ferromagnetic stator yoke, torque (detent torque) is generated even without excitation. With this detent torque, there is an advantage that the rotor (rotor) can be stopped at a predetermined angular position in non-excitation without providing a special mechanism.

On the other hand, during normal rotation, the input current (excitation current) is reduced by PW
The smooth rotation is achieved by using a pseudo sine wave by M control. However, if the above-mentioned detent torque is not made sufficiently small with respect to the output torque at the time of rotation, the torque ripple may be increased. And hinders smooth rotation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object to solve the above-described problems and reduce the detent torque of the entire pulse motor.
It is an object of the present invention to provide a pulse motor and a geared motor capable of enabling smooth rotation.

[0009]

In order to achieve the above-mentioned object, a pulse motor according to the present invention comprises: a rotor having a rotor having a permanent magnet multipolarly magnetized in a circumferential direction; A pulse motor including at least two stator yokes arranged on the outer periphery, and an exciting coil mounted on the stator yoke, wherein the pole faces at both ends of the stator yoke are arranged so as to be able to face the magnetic poles of the permanent magnet. Is assumed. Then, the cross-sectional area of a predetermined portion of the stator yoke constituting the magnetic path is made smaller than the area of the magnetic pole surface. The predetermined portion for reducing the cross-sectional area may be a part of the magnetic path or the whole magnetic path. According to experimental results, the detent torque is reduced by making at least a part of the cross-sectional area of the magnetic path smaller than the area of the pole face.

Preferably, a distance from the pole face to the predetermined portion where the cross-sectional area is reduced is smaller than an axial height of the pole face. In this case, a portion having a small cross-sectional area is formed at a position near the magnetic pole surface, and the detent torque is further reduced.

Further, the magnetic pole surface may be formed by bending a tip portion of the flat plate-shaped stator yoke. With this configuration, the stator yoke can be manufactured by press working, and the manufacturing can be easily performed.

On the other hand, in the geared motor according to the present invention,
The pulse motor of each of the above-mentioned inventions, a first gear provided on the rotor of the pulse motor, and a predetermined number of gears associated with the first gear are housed and arranged at predetermined positions in a case. The output shaft is attached to a predetermined gear of the gears, and one end of the output shaft is arranged so as to protrude outside the case.

The term "substantially U-shaped" used in the present invention includes, of course, a plane having a U-shape, but it is not always necessary that the plane be strictly U-shaped. For example, it may be C-shaped or U-shaped,
In short, it is only necessary that the belt-like magnetic path bends or bends as appropriate, and that both ends approach and constitute a magnetic pole surface.

[0014]

FIG. 1 shows a preferred embodiment of a pulse motor according to the present invention. As shown in FIG. 1, a rotor (rotor) 3 is formed by coaxially attaching a cylindrical permanent magnet 2 to a rotating shaft 1. The permanent magnet 2 is multipolar magnetized in the circumferential direction (six poles in the illustrated example).
Have been.

Outside the rotor 3, two stator yokes 5a and 5b are arranged. Stator yoke 5
Each of a and 5b has a substantially U-shaped planar shape, and both ends thereof serve as teeth (magnetic pole portions) 6, and are arranged to face magnetic poles formed on the outer peripheral surface of the permanent magnet 2. I have.

Each tooth 6 is arranged on the same circumference centering on the rotating shaft 1. In addition, the interval between the two teeth 6 formed on one stator yoke is set to match the magnetic pole pitch of the permanent magnet 2. That is, in this embodiment, since the magnetic pole pitch is 60 degrees, the magnetic pole pitch is located at both ends of a fan-shaped arc having a central angle of 60 degrees around the rotation axis 1. Further, the teeth 6 of the stator yoke 5a and the teeth 6 of the stator yoke 5b are arranged so as to be out of phase by 90 degrees in electrical angle.

A bobbin 7 is attached to each of the stator yokes 5a and 5b, and an exciting coil 8 is wound around the bobbin. Thus, a two-phase type pulse motor having the A phase on the stator yoke 5a side and the B phase on the stator yoke 5b side is obtained. Therefore, the pulse motor of the present embodiment is a salient pole type in which the teeth 6 forming the same phase are not uniformly arranged in the circumferential direction.

In this salient pole type, each tooth 6 generates an attractive force with the magnetic pole of the permanent magnet 2 facing each other. In the illustrated example, the teeth 6 of the stator yoke 5a (A phase) have the same pitch as the magnetic pole pitch of the permanent magnet 2, and generate torque in the same direction. The teeth 6 of the other stator yoke 5b (B phase) are
Since the teeth 6 are electrically disposed at 90 degrees with respect to the teeth 6a, a torque is generated magnetically in a direction to cancel the torque of the teeth 6 of the stator yoke 5a. And
The detent torque of each phase has a waveform as shown in FIG. 2 with respect to the mechanical movement angle. Therefore, the detent torque of the entire pulse motor is a combined torque of both, and therefore, as shown in FIG. 2, there is a torque having a cycle twice as long as the waveform of the detent torque of each phase.

In this embodiment, as shown in FIGS. 3 and 4, thin portions are provided near the ends of the stator yokes 5a and 5b. First of all, each figure will be described.
FIG. 3 is an enlarged view of the end portions of the permanent magnet 2 and the teeth 6, and a cross-sectional view taken along a line aa in FIG.
FIG. 4A is a sectional view taken along the line bb in FIG. 4A.

As shown in FIG. 4A, the thickness (height) t1 of the magnetic pole surface 6a, which is the tip end surface of the tooth 6, is substantially the same as the axial length of the permanent magnet 2. A thin portion 6b which is thinner than the magnetic pole surface 6a at the tip is provided at a position inward of the magnetic pole surface 6a by a predetermined distance t2. This thin portion 6b is formed in a rectangular shape having a cross section of width w and thickness (height) t3 as shown in FIG. 4B, and the pole face 6a has the same width w and thickness (height) t1. Is formed in a rectangular shape. And t3
<T1, the cross-sectional area of the thin portion 6b is
Is smaller than the area. The thin portion 6b is formed at a position close to the pole face 6a so that t1> t2 is satisfied.

Further, in the example shown in the figure, the farther side of the thin portion 6b has the same thickness t1 as the magnetic pole surface 6a. Of course, the thickness on the back side of the thin portion 6b is not necessarily the magnetic pole surface 6a.
Does not need to be the same, and may be thicker or thinner than t1. Further, the magnetic pole surface 6a may have the same thickness as the thin portion 6b, that is, the entire magnetic path of the stator yokes 5a and 5b may be the thin portion 6b and the tip portion may have the thickness (t1). In other words, the sectional area of the stator yoke constituting the magnetic path is made smaller than the area of the magnetic pole surface.

With the above configuration, the detent torque of the entire pulse motor obtained by synthesizing the detent torques generated in the two phases is as shown by a chain line in FIG. On the other hand, the detent torque of the conventional product in which the thickness of the stator yoke is made uniform as a whole is as shown by a broken line in FIG.

As is clear from the drawing, the product of the present invention can reduce the detent torque and can ensure a smooth rotation of the pulse motor. Further, it can be estimated that the detent torque is reduced as described above for the following reason. That is, the magnetic resistance of the thin portion 6b is larger than the magnetic resistance of the tooth including the magnetic pole surface 6a on the tip side. Therefore, when the thickness is made uniform as a whole as in the prior art, the magnetic poles and the pole faces 6
The magnetic flux between "a" travels substantially in parallel as a whole. On the other hand, when the thin portion 6b having a small thickness is provided near the inside of the pole face 6a, the magnetic flux entering the teeth 6 from the central portion of the pole face 6a and the teeth from the positions near the upper and lower ends of the pole face 6a are formed. Comparing the magnetic flux entering into 6, the former is easier to flow. As a result, a magnetic field is formed in the gap between the magnetic pole surface 6a and the magnetic pole of the permanent magnet 2 so that the magnetic flux concentrates on the central portion of the surface of the magnetic pole surface 6a, and the magnetic field distribution becomes irregular. As a result, the detent torque can be expected to weaken.

FIG. 6 shows another embodiment. In the above-described embodiment, the thin portion 6b is connected to the central portion in the thickness direction on the distal end side of the tooth 6 in the thickness direction. However, the present invention is not limited to this.
As shown in (a), the thin portion 6b may be shifted to one side (upward in the illustrated example). In other words, the magnetic pole surface 6a is formed by bending the tip of the tooth 6.

That is, in the case of the structure as shown in FIG. 4, it is formed by cutting or the like.
In the case of the shape shown in FIG. Therefore, the latter is easier to manufacture.

Further, in this example, the entire surface of the stator yoke excluding the end portions is made thinner, and both end portions are bent to form the magnetic pole surfaces 6a. However, the central portions of the stator yokes 5a and 5b are formed at the magnetic pole surfaces. It may be thick as in 6a.

Further, in each of the above embodiments,
In any case, the thin portion is provided from a position relatively close to the magnetic pole surface 6a, but the present invention is not limited to this. For example, as shown in FIG. 6, the distance t2 from the magnetic pole surface 6a to the thin portion 6b is reduced. , May be longer than the thickness t1 of the pole face 6a.

An example of the entire detent torque of the pulse motor in this case is shown by a solid line in FIG. In this example, the thin portion 6b is located near the magnetic pole surface 6a.
Although the detent torque is larger than that of the conventional example, it can be smaller than that of the conventional example.

FIG. 7 shows a preferred embodiment of a geared motor according to the present invention. As shown in the figure, the components of the pulse motor 11 shown in each of the above embodiments are inserted and arranged in the flat case 10. Then, a first gear 12 is attached to the tip of the rotating shaft 1, and a second gear 13 is provided so as to mesh with the first gear 12. The torque of the second gear 13 is transmitted to the third gear 14. As a result, the first gear 1
2, the second gear 13 and the third gear 14 rotate sequentially.
An output shaft 15 is attached to the center of the third gear 14, and one end of the output shaft projects outside the case 10 as shown in FIG. Of course, each gear 12-1
By changing the gear ratio of 4, the ratio of the rotation speed of the output shaft 15 to the rotation speed of the rotor 3 is set to a desired value.

With this configuration, by supplying an exciting current to each exciting coil 8 at a predetermined timing, the output shaft 15 can be smoothly rotated and stopped at a predetermined angular position. And, on this output shaft 15,
By attaching a needle or the like of the indicating instrument directly or via another power transmission means, the present invention can be applied to an indicating instrument used in a vehicle or the like.

[0031]

As described above, in the pulse motor and the motor with gears according to the present invention, the cross-sectional area of the predetermined portion of the stator yoke constituting the magnetic path is smaller than the area of the magnetic pole surfaces at both ends of the stator yoke. Thus, the detent torque of the entire pulse motor can be reduced. As a result, smooth rotation can be achieved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a preferred embodiment of a pulse motor according to the present invention.

FIG. 2 is a diagram illustrating detent torque.

FIG. 3 is an enlarged view showing a main part.

FIG. 4A is a sectional view taken along line aa in FIG. 3;
FIG. 4B is a cross-sectional view taken along line bb in FIG.

FIG. 5 is a diagram that demonstrates the effect of the present invention.

FIG. 6 is an enlarged view of a main part showing another embodiment.

FIG. 7 is a plan view showing a preferred embodiment of a geared motor according to the present invention.

FIG. 8 is a front view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary shaft 2 Permanent magnet 3 Rotor (rotor) 5a, 5b Stator yoke 6 Teeth 6a Magnetic pole surface 6b Thin part (magnetic path with small cross-sectional area) 7 Bobbin 8 Exciting coil 10 Case 11 Pulse motor 12 First gear 13 Second Gear 14 Third gear 15 Output shaft

Claims (5)

[Claims] 1. A rotor comprising a rotor having permanent magnets that are multipolarly magnetized in a circumferential direction, at least two stator yokes arranged around the rotor, and mounted on the stator yoke. And a magnetic pole surface at both ends of the stator yoke arranged so as to be able to oppose the magnetic poles of the permanent magnet. A predetermined portion of the stator yoke forming a magnetic path based on an area of the magnetic pole surface A pulse motor having a reduced cross-sectional area. 2. The pulse motor according to claim 1, wherein the predetermined portion is the entire magnetic path. 3. The method according to claim 1, wherein a distance from the pole face to the predetermined portion where the cross-sectional area is reduced is smaller than an axial height of the pole face. The pulse motor as described. 4. The pulse motor according to claim 1, wherein the magnetic pole surface is formed by bending a tip portion of the plate-shaped stator yoke. 5. The pulse motor according to claim 1, a first gear provided on the rotor of the pulse motor, and a predetermined number of gears associated with the first gear. A motor with a gear, which is housed and arranged at a predetermined position in a case, an output shaft is attached to a predetermined gear of the gears, and one end of the output shaft is arranged to protrude outside the case.