JP2000116101A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stepping motor which can be driven with a direct current without detecting its angle of rotation. SOLUTION: A stepping motor 10 is rotated at a rotating speed which is R/P (R is the number of teeth of a rotor 20 and P is the number of paired poles) times as fast as that of the rotor 20 by means of a gear train 60 by receiving a direct current from the outside by means of brushes 44a and 44B. A commutator 42 receives the electric current from the brushes 44a and 44b and generates a rotating magnetic field which rotates at a speed which is R/P times as fast as that of the rotor 20 by feeding the current to the winding 34 of a stator 30. Therefore, the motor 10 can be driven by applying the direct current upon the motor 10 without using any encoder for detecting the angle of rotation of the motor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor capable of generating a high torque at a low speed.

[0002]

2. Description of the Related Art A DC motor is generally used as a power source of an electric power steering for an automobile. Here, since the electric power steering requires a high torque at a low speed, a reduction gear is attached to a DC motor for use.

[0003]

However, when a speed reducer is used, power loss of about 15% occurs. In addition, when the motor is reversed to switch the assist direction of the power steering, the speed reducer is required. Backlash appears, and vibration is easily transmitted to the steering side. Further, there is a problem that noise is generated in the speed reducer.

In order to solve the problem associated with such a speed reducer, the present inventor had the idea of using a stepping motor capable of generating a high torque at a low speed instead of a DC motor, thereby omitting the speed reducer. However, in order to drive the stepping motor, it is necessary to detect and excite the rotation angle of the motor, so that an expensive encoder for detecting the rotation angle is required.

An object of the present invention is to provide a stepping motor which can be driven by a direct current without detecting a rotation angle. .

[0006]

According to a first aspect of the present invention, there is provided a stepping motor comprising a stator and a rotor rotating at a speed of 1 / N of a rotating magnetic field of the stator. A brush that receives DC power from the outside and rotates at N times the rotation speed of the rotor, receives power from the brush, supplies power to the stator windings, and generates a rotating magnetic field at N times the speed of the rotor. And a commutator for generating.

The stepping motor according to the second aspect of the present invention
The technical feature of the present invention is characterized in that the brush is held by a brush holder which rotates concentrically with the commutator at a speed N times higher than that of the rotor by a gear pivotally supported on the rotor side.

The stepping motor according to a third aspect of the present invention
A technical feature according to claim 1 or 2, wherein a bearing for supporting a shaft of the rotor is disposed so as to face the brush.

Further, the stepping motor according to claim 4 is
An outer magnet type stepping motor including a stator having a built-in permanent magnet and a rotor rotating at a speed of 1 / N of a rotating magnetic field of a built-in winding, wherein an external DC power is supplied and rotation of the rotor is performed. It is a technical feature that a brush that rotates at N times the speed, and a commutator that receives power from the brush, supplies power to a rotor winding, and generates a rotating magnetic field at a speed N times the speed of the rotor. .

In the stepping motor according to the first aspect, the brush receives DC power from the outside and rotates at N times the rotation speed of the rotor. Then, the commutator receives power from the brush and supplies power to the windings of the stator to generate a rotating magnetic field N times faster than the rotor. Therefore, the DC can be applied to the stepping motor to drive it without detecting the rotation angle.

In the stepping motor according to the second aspect, the brush is held by a brush holder which rotates at a speed N times the speed of the rotor by a gear pivotally supported on the rotor side.

According to the third aspect of the present invention, since the bearing supporting the shaft of the rotor is disposed so as to face the brush, the brush rotating at high speed can be stably brought into contact with the commutator.

According to a fourth aspect of the present invention, the brush receives DC power from the outside and rotates at N times the rotation speed of the rotor. Then, the commutator receives power from the brush and supplies power to the windings of the rotor to generate a rotating magnetic field N times faster than the rotor. Therefore, the DC can be applied to the stepping motor to drive it without detecting the rotation angle.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a stepping motor according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing components of the stepping motor 10 according to the first embodiment, FIG. 2 is a longitudinal sectional view of the stepping motor 10, and FIG. It is A sectional drawing.

The stepping motor 10 includes a stator 3
0 and the rotor 20 supported on the shaft 22. The stator 30 accommodates a winding 34, and the rotor 20 includes a permanent magnet 24 and a cylindrical body 28 having teeth 26 formed thereon. As shown in FIG.
Eight teeth 36 are provided, and the rotor 20 has 21 teeth 26
Are provided, and the winding 34 is configured to have six poles (not shown). Here, assuming that the number of rotor teeth is R, the number of stator teeth is S, and the number of pole pairs (the number of pole pairs = magnetic pole / 2) is P, it is necessary to establish a relationship of S = R ± P. The teeth 26 and 36 are formed so as to make them move. Note that the rotation speed of the rotor 20 is P / R (3
/ 21 = 1/7) times.

In the stepping motor 10, the position of the rotating magnetic field of the stator 30 is switched in synchronization with the rotation angle of the rotor 20 to rotate at a speed R / P times (7 times in this embodiment) the rotation speed of the rotor 20. A magnetic field needs to be set. The stepping motor of the present embodiment includes a rotor 20
And the rotation speed R of the rotor 20
In order to set the rotating magnetic field to / P times, the brush holder 46 is rotated at R / P times the rotation speed of the rotor 20, and the winding 34 of the stator 30 is supplied with power through the commutator 42 to obtain a desired rotating magnetic field. Generate. Here, the brush 44
To rotate A and 44B R / P times the rotor 20,
A brush holder 46 for holding the brushes 44A and 44B,
The rotor 20 is rotated by a gear train 60 that makes the rotation of the rotor 20 R / P times.

The brush holder 46 is connected to the R /
A gear mechanism including a gear train 60 for rotating P times will be described with reference to FIGS. As shown in FIG. 2, a flange 56 is attached to the shaft 22 directly connected to the rotor 20. As shown in FIG.
As shown in the figure, three through holes 56a are formed. The three through holes 56a have three gear trains 60 (FIG. 1).
(Only two of them are shown) are pivotally supported. Here, the small diameter gear 60c of the gear train 60 meshes with the inner gear 54 fixed to the housing 80 side. On the other hand, the large-diameter gear 60b of the gear train 60 is
Is engaged with the gear 52 of the boss flange 50 that holds the boss. The boss flange 50 is rotatably supported on the shaft 22 via a needle bearing 58. The brush holder 46 holds the brushes 44A and 44B slidably with respect to the commutator 42. The commutator 42 is electrically connected to the winding 34 of the stator 30. In this embodiment, three sets of gear trains 60 are provided, but it is also possible to rotate the brush holder 46 with one gear train.

The commutator 42 is held by a holding member 82 having a crank-shaped cross section. A bearing 74 for supporting the shaft 22 is provided on the inner periphery of the holding member 82. The other bearing 72 for supporting the shaft 22 is provided at an end of the housing 80 opposite to the brushes 44A and 44B. It is arranged in.

External DC power supply lines 84A and 84B are
Slip rings 40A, 4A,
0B. The slip ring 40A is connected to the brush 44A via the auxiliary brush 48A.
On the other hand, the slip ring 40B is connected to the brush 44B via the sub brush 48B. Here, the brush 44
Although only one pair of A and 44B is shown in the figure, two or more pairs can be provided.

Here, the small-diameter gear 6 of the gear train 60 described above is used.
The number of teeth of 0c is KP (K: constant, P: number of pole pairs = magnetic pole / 2
(3 in this embodiment), and the number of teeth of the large-diameter gear 60b is KR (R: number of rotor teeth (21 in this embodiment)). For this reason, the rotor 2
With the rotation of 0, the gear train 60 rotates the brush holder 46 at R / P times (7 times in this embodiment) the rotation speed. The operation of the stepping motor 10 according to the present embodiment having the above configuration will be described. Stepping motor 1
The 0 rotor 20 is rotated as follows, and the shaft 22 is rotated. DC current is supplied from the outside to the power supply lines 84A and 84B.
→ Slip ring 40A, 40B → Sub brush 48A, 4
8B is applied to the brushes 44A and 44B. Then, the brush holder 46 is rotated at R / P times the rotation speed of the rotor 20.
Rotates, and a rotating magnetic field having a speed R / P times that of the rotor 20 is generated in the winding 34 of the stator 30 via the commutator 42. As shown in FIG. 3, torque is generated in the teeth 26 of the rotor 20 so as to face the teeth 36 of the stator 30 excited by the rotating magnetic field, and torque is generated in the rotor 20 with the rotation of the rotating magnetic field. Continue to rotate in a certain direction. Here, the stepping motor 10 can reverse the rotation direction of the rotor 20 by reversing the DC power supply polarity by the DC power supply lines 84A and 84B.

In the stepping motor 10 of this embodiment, as described above, the brushes 44A and 44B are supplied with DC power from the outside, and are rotated by the gear train 60 at R / P times the rotation speed of the rotor 20. And commutator 4
2 receives power from the brushes 44A and 44B and
And a rotating magnetic field at a speed R / P times that of the rotor 20 is generated. For this reason, it is possible to drive the stepping motor by applying a direct current without using an encoder for detecting the rotation angle.

Further, when a speed reducer is connected to a DC motor as in the prior art, loss of about 15% occurs due to the speed reducer, and the available output of the motor is reduced. On the other hand, in the present embodiment, the output of the motor does not decrease because the speed reducer is not used. Here, the brushes 44A and 44B are rotated via the gear train 60,
The loss caused by this rotation is small. Furthermore, since no reduction gear is used, no noise is generated, and no backlash occurs when the rotation direction is switched.

Next, a modification of the first embodiment will be described with reference to FIG. This modification is almost the same as the example described above with reference to FIGS. However, in this modification, the bearings 74 are the brushes 44A, 44B.
The second embodiment is different from the first embodiment in that the first and second shafts are disposed so as to face each other on a perpendicular to the shaft 22. For this reason,
Vibration due to the rotation of the shaft 22 is unlikely to occur, and the brushes 44A and 44B rotating at a high speed R / P times the rotor can be stably contacted with the commutator 42.

Next, a stepping motor 110 according to a second embodiment of the present invention will be described with reference to FIG. In the above-described first embodiment, the rotor 20 including the permanent magnet 24 is fixed to the shaft 22. In the second embodiment, the so-called permanent magnet 24 is provided on the side of the stator 30 fixed to the housing 80. It is composed of an outer magnet type.

In the stepping motor 110, the position of the rotating magnetic field is switched in synchronization with the rotation angle of the rotor, and the rotating magnetic field is rotated at a speed of R / P times (7 times in this embodiment) the rotation speed of the rotor 20. Must be set. In order to synchronize with the rotation angle of the rotor 20 and to set the rotating magnetic field to R / P times the rotation speed of the rotor 20, the rotor 2
The brush 46 is rotated at R / P times the rotation speed of 0, and power is supplied to the winding 34 of the stator 30 via the commutator 42 to generate a desired rotating magnetic field.

A gear mechanism including a gear train 60 for rotating the brushes 44A, 44B R / P times the rotor 20 will be described. Shaft 2 directly connected to rotor 20
2, a flange 56 is attached. On the flange 56, three gear trains 60 (only one is shown in the figure) are respectively supported. Here, the small diameter gear 60c of the gear train 60 is connected to the inner gear 54 fixed to the housing 80 side.
Is engaged. On the other hand, the large-diameter gear 60b of the gear train 60
Is a bossed flange 50 for holding the brush holder 46.
Gear 52. The bossed flange 50
Is rotatably supported by the shaft 22 via a needle bearing 58. The brush holder 46 is
The brushes 44A, 4A are slidable with respect to the commutator 42.
Hold 4B. The commutator 42 is attached to the rotor 20 and is electrically connected to the winding 90 of the rotor 20.

External DC power supply lines 84A and 84B are
Slip rings 40A, 40 formed on holding member 82
B. The slip ring 40A is connected to the brush 44A via the auxiliary brush 48A. On the other hand, the slip ring 40B is connected to the brush 44B via the sub brush 48B. Here, the brush 44
Although only one pair of A and 44B is shown in the figure, two or more pairs can be provided.

Here, the small-diameter gear 6 of the gear train 60 described above is used.
0c is KP (K: constant, P: number of pole pairs = magnetic pole /
2), and the number of teeth of the large-diameter gear 60b is formed to be KR (R: number of rotor teeth). R
The brush holder 46 is rotated by a factor of / P. The operation of the stepping motor 110 according to the second embodiment having the above configuration will be described. The rotor 20 of the stepping motor 110 is rotated as follows, and the shaft 22 is rotated.
An external DC current is applied to the brushes 44A, 44B via the power supply lines 84A, 84B → the slip rings 40A, 40B → the sub brushes 48A, 48B. Then, rotor 2
The brush holder 46 rotates at R / P times the rotation speed of 0, and a rotating magnetic field having a speed R / P times that of the rotor 20 is generated in the winding 90 of the rotor 20 via the commutator 42. And
In substantially the same manner as in the first embodiment, torque is generated so that the teeth 26 of the rotor 20 excited by the rotating magnetic field face the teeth 36 of the stator 30, and torque is generated in the rotor 20 with the rotation of the rotating magnetic field. Continue to rotate in a certain direction. Here, the stepping motor 110 is connected to the DC power supply line 84.
By reversing the DC power supply polarity by A and 84B,
The rotation direction of the rotor 20 can be reversed.

The stepping motor 110 of the second embodiment
In this case, as described above, the brushes 44A and 44B receive DC power from the outside and rotate at R / P times the rotation speed of the rotor 20. And the commutator 42 is a brush 44
A, 44B, and power is supplied to the winding 90 of the rotor 20 to generate a rotating magnetic field at a speed R / P times that of the rotor 20. For this reason, it is possible to drive the stepping motor by applying a direct current without using an encoder for detecting the rotation angle.

In the second embodiment, the outer magnet is provided with the permanent magnet 24 on the stator 30 side fixed to the housing 80 side. For this reason, by disposing the cooling fins on the housing 80 side, the permanent magnet 24 can be efficiently cooled, so that a ferromagnetic material having low heat resistance can be used as the permanent magnet.

[0031]

As described above, in the stepping motor according to the first aspect, the brush receives DC power from the outside and rotates at N times the rotation speed of the rotor. Then, the commutator receives power from the brush, supplies power to the windings of the stator, and generates a rotating magnetic field N times faster than the rotor. Therefore, the DC can be applied to the stepping motor and driven without detecting the rotation angle.
Further, since high torque can be generated at a low speed without using a speed reducer, problems such as loss, noise, backlash, etc. associated with the speed reducer do not occur.

In the stepping motor according to the second aspect, the brush is held by the brush holder rotating concentrically with the commutator at N times the speed of the rotor by the gear pivotally supported on the rotor side. Since the brush can be rotated concentrically, even if the brush rotates, the contact between the brush and the commutator can be reliably performed.

In the stepping motor according to the third aspect, since the bearing supporting the shaft is disposed so as to face the brush, the brush rotating at high speed can be stably brought into contact with the commutator.

In the stepping motor according to the fourth aspect, the brush receives DC power from the outside and rotates at N times the rotation speed of the rotor. Then, the commutator receives power from the brush, supplies power to the windings of the rotor, and generates a rotating magnetic field N times faster than the rotor. Therefore, the DC can be applied to the stepping motor and driven without detecting the rotation angle. Further, since a permanent magnet is provided on the outer peripheral side of the stator and the permanent magnet can be efficiently cooled, a ferromagnetic material having low heat resistance can be used as the permanent magnet.

[Brief description of the drawings]

FIG. 1 is a perspective view showing components of a stepping motor according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the stepping motor according to the first embodiment.

FIG. 3 is a sectional view taken along line AA of the stepping motor shown in FIG. 2;

FIG. 4 is a longitudinal sectional view of a stepping motor according to a modification of the first embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a stepping motor according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Stepping motor 20 Rotor 22 Shaft 24 Magnet 26 Teeth 30 Stator 34 Winding 36 Teeth 40A, 40B Slip ring 42 Commutator 44A, 44B Brush 60 Gear train

Claims (4)

[Claims] 1. A stator and one of the rotating magnetic fields of the stator.
/ N a rotor that rotates at a speed of / N, receives a DC power from the outside, and rotates at a speed N times the rotation speed of the rotor; A commutator that supplies power to the rotor and generates a rotating magnetic field at a speed N times faster than the rotor. 2. The brush according to claim 1, wherein the brush is held by a brush that rotates concentrically with the commutator at a speed N times the speed of the rotor by a gear pivotally supported on the rotor side. Stepping motor. 3. The stepping motor according to claim 1, wherein a bearing for supporting a shaft of the rotor is disposed so as to face the brush. 4. An outer magnet type stepping motor comprising a stator having a built-in permanent magnet and a rotor rotating at a speed of 1 / N of the rotating magnetic field of the built-in winding, wherein the stepping motor receives external DC power and A brush that rotates at N times the rotation speed of the rotor, and a commutator that receives power from the brush, supplies power to the windings of the rotor, and generates a rotating magnetic field at N times the speed of the rotor. Characteristic stepping motor.