JP2001339910A - Limited rotating motor with position sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor limited in rotation with a position detecting sensor having a small moment of inertia. SOLUTION: The position sensor 100 for detecting a rotating position of a rotating shaft 2 is mounted to the front end of the rotating shaft 2 of the motor 1 limited in rotation. The position sensor 100 is an optical potentiometer, of which the rotating-slit plate 101 is so designed as to be minimum in size necessary for covering only a forming portion of a spiral slit 113 and a fixing portion fixed to the rotating shaft 2. Thereby, the moment of inertia of the position sensor 100 can be reduced, and the rotating shaft 2 fitted with the position sensor 100, or the motor itself as well, can be in a low-inertial state. Consequently, response is improved and a high-speed motion is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finite rotation type electric motor which performs a rotary motion within a predetermined angle range and is used as a laser scanner driving mechanism in a laser printer or the like. The present invention relates to a finite rotation type electric motor having a position sensor.

[0002]

2. Description of the Related Art An electromagnetic finite rotation type electric motor is, for example,
It is used as a light beam deflection mechanism in an optical scanning system or as a scanning mirror driving mechanism. In general, a finite-rotation type electric motor has a stator arranged in a state surrounding an outer periphery of a rotor. The stator has a driving magnetic flux generating mechanism for generating a driving magnetic flux for rotating the rotor within a certain angle range. Is provided. Such an electric motor is disclosed in JP-B-57-5-5.
No. 6304 and Japanese Patent Application Laid-Open No. Hei 7-31119 by the present applicant.
No. 6,086,045.

[0003] In this finite rotation type electric motor, in order to control the rotation accurately and with good response, the rotation information of the rotor,
For example, it is necessary to accurately detect the rotation speed and the rotation angle position. For this purpose, an optical potentiometer is mounted on the rotor.

This optical potentiometer has a configuration in which a laser diode and a light receiving element are opposed to each other with a rotary disk having a slit interposed therebetween. The slit shape is a curved shape such as a spiral shape in which the slit position facing the laser diode and the light receiving element moves in the radial direction with the rotation of the rotor.

[0005]

Here, in order to increase the speed of a laser scanner or the like, it is required to lower the inertia of the rotating portion of the scanner. For this purpose, it is necessary to reduce the inertia of the rotor of the finite-rotation type electric motor as a drive source. For this purpose, an optical potentiometer as a position sensor fixed to the rotor rotation shaft is further required. It is necessary to lower the inertia of the motor.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to propose a finite rotation type electric motor having a position sensor with low inertia.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a stator having a driving coil, a rotor comprising a permanent magnet concentrically surrounding the stator, and In a finite rotation type electric motor having a position sensor for detecting information on the rotation of the rotor used to control the rotation of the rotor, the position sensor is a member with a slit that rotates integrally with the rotor. A light-emitting unit and a light-receiving unit sandwiching the member with the slit and facing the fixed position, wherein the slit has a slit position facing the light-emitting element and the light-receiving element in a radial direction according to a rotation angle of a rotor. Has a curved shape defined to change to, the member with a slit,
It is a contour shape obtained by cutting out only a portion where the slit is formed and a portion fixed to the rotor rotation shaft from a disk or a regular polygonal plate centered on the rotation center of the rotor. And

In the finite-rotation type electric motor having this configuration, the slit member of the position sensor fixed to the rotor rotation shaft has a minimum necessary size including only a slit forming portion and a portion attached to the rotor rotation shaft. It has become.
Therefore, the inertia of the position sensor can be greatly reduced as compared with the case of using a disk-shaped member with a slit, so that the inertia of the position sensor and the inertia of the finite-rotation motor can be reduced.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an electromagnetic finite rotation type electric motor to which the present invention is applied.

FIG. 1 shows the appearance of an electromagnetic finite rotation type electric motor of this embodiment. As shown in this figure, the electromagnetic finite rotation type electric motor 1 has a columnar appearance as a whole, and has a rectangular mounting flange 3a at the tip end side. Rotating shaft 2 protruding from the end face side of motor 1
A driven member, such as a mirror 2b, is attached to the tip 2a of the mirror as shown by an imaginary line.

FIG. 2 is a longitudinal section taken along the line II-II of FIG. As shown in FIG.
A tip side casing 3 on which a flange 3a is formed;
The rear end side casing 4 and the motor stator 5 sandwiched between them are coaxially connected. The motor rotation shaft 2 passes through these centers. On the rotating shaft 2, a two-pole magnetized ring-shaped permanent magnet 6 having substantially the same width as the stator 5 is fixed to an outer peripheral portion facing the motor stator 5, thereby forming a motor stator 7. Have been. With the motor stator 7 interposed, the front and rear ends of the rotating shaft 2 are respectively connected to the front and rear casings 3 and 3,
4 is rotatably supported on the inner peripheral surface thereof via ball bearings 8 and 9.

The distal end of the rotating shaft 2 projects from the distal end casing 3, and the mirror 2 is attached to this portion as described above.
A driving member such as b is attached. The rear end of the rotating shaft 2 also projects from the rear end casing 4, and this member is a cup-shaped lid 4 screwed to the rear end casing 4.
a.

Here, a rotational speed detector 1 for detecting the rotational speed of the electric motor rotating shaft 2 is provided on the rear end side casing 4.
0 is incorporated. In addition, a rotation position detector 100 for detecting the rotation position of the electric motor rotation shaft 2 is incorporated inside the lid 4 a attached to the rear end side casing 4.

Referring to FIGS. 2 and 3, the structure of the motor stator 5 will be described. The motor stator 5 includes a ring-shaped main body portion 51, a pair of magnetic pole portions 52, 53 protruding inward from the inner peripheral surface, and field windings 54, 55 wound around these magnetic pole portions. It is configured. The pair of magnetic pole parts 52 and 53 have one diameter L passing through the rotation axis 1a.
1 are formed along one direction. These magnetic pole parts 5
Arc-shaped magnetic pole faces 521 and 531 having inner diameters slightly larger than the outer diameter of the permanent magnet 6 are formed at the tips of the magnets 2 and 53.

Field windings 54 and 55 for generating driving magnetic flux for the rotor are wound around the outer circumference of the magnetic pole portions 52 and 53. Both ends 54a and 55a of the field winding are connected to a drive power supply (not shown) via a power supply line and a magnetic flux control circuit (not shown). The current applied to the field winding is controlled by the magnetic flux control circuit, so that the rotating shaft 2 is rotationally driven at a finite angle, for example, a width of 30 degrees by the magnetic torque acting on the rotor side. Since the flux control circuit can use a commonly used one,
The description is omitted.

Grooves 521a and 53 extending in the direction of the rotation axis 1a are provided at the centers of the magnetic pole surfaces 521 and 531, respectively.
1a are formed. The gap between the bottom surface of these grooves and the permanent magnet 6 is larger than the gap between the pole faces at both ends and the permanent magnet 6. As shown in the figure, if the width of these grooves is a and the distance between the magnetic pole portions 52 and 53 is b, in the present example, these widths are set so that a> b. ing.

As a result, in the present embodiment, in the non-excitation state, the magnetic poles of the permanent magnet 6 of the rotor are changed to a pair of magnetic pole portions 52,
Position L0 oriented in a direction orthogonal to direction L1 of 53
Magnetic torque acts on the rotor. Therefore, in the non-excitation state, as shown in FIG. 3, the magnetic pole of the rotor 7 is always held at the position L0 at 90 degrees with respect to the magnetic pole of the stator 5. Thus, in this example,
By forming the grooves 521a and 531a, an origin return means of the rotating shaft is configured.

Next, the configuration of the rotational position detector 100 will be described with reference to FIGS. The detector 100 is an optical potentiometer, and includes a rotary slit plate 101 concentrically fixed to the outer periphery of the rotary shaft 2, a laser diode 102 and a semiconductor position detecting element 103 disposed opposite to a fixed position with the rotary slit plate 101 interposed therebetween. Rotating slit plate 10
1 and a fixed slit plate 104 arranged between the semiconductor position detecting element 103.

As shown in FIG. 4, the rotary slit plate 101 has a contour shape obtained by shaping the outer peripheral arc shape of a fan-shaped portion having an arc exceeding a predetermined angle 2φ into a regular polygonal shape. . Angle 2φ is the maximum rotation angle range of the electric motor of this example. A spiral slit 113 for passing light is formed in the rotary slit plate 101 at an angle exceeding an angle 2φ. The slit 113 is a part of a spiral around the center of rotation of the rotary slit plate 101. Therefore, the moving radius r and the slit plate 101
Has a relationship of r = a- (δ / 2π) Θ. Here, δ is the pitch of the helix.

When the rotary slit plate 101 rotates, the slit 113 also rotates with the rotation, so that the position of the slit facing the laser diode 102 moves in the radial direction. As a result, the light receiving position on the light receiving surface of the semiconductor position detecting element 103 changes via the fixed slit plate 104, and an electric signal corresponding to the rotation angle can be obtained.

For example, as shown in FIG. 5, an output voltage proportional to the rotation angle can be obtained. The rotation angle of the electric motor 1 of the present embodiment is 2φ at the maximum, and is usually in the range of 20 to 30 degrees. Therefore, since the value of δ / 2π can be made large, the resolution is increased, and highly accurate position detection can be performed.

In the present embodiment, the contour of the rotary slit plate 101 is a contour obtained by cutting out only a portion of the regular polygon including the slit forming portion and only the central portion fixed to the rotor. Instead, a plate portion cut out from a disk into a fan shape can be used as a rotary slit plate.

Although a spiral is employed as the shape of the slit, it is a matter of course that a curve other than the spiral can be employed as long as the light passing portion changes in the radial direction in accordance with the rotation angle.

[0024]

As described above, in the finite rotation type electric motor with the position sensor according to the present invention, the member with the slit, which is a component of the position sensor, is not a generally used disk but a slit. It is a member of the minimum necessary size including only the forming part and the part to be attached to the rotor. Therefore, since the moment of inertia of the slit member, which is a rotating part of the position sensor, can be greatly reduced,
Low inertia of the electromagnetic finite motor to which the member is attached can be achieved. As a result, the responsiveness of the motor can be improved, and the operation can be speeded up.

[Brief description of the drawings]

FIG. 1 is an external perspective view of an electromagnetic finite rotary electric motor according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a portion of the electric motor of FIG. 1 cut along line II-II, developed on a plane.

FIG. 3 is a cross-sectional view of a portion of the electric motor of FIG. 1 taken along line III-III.

FIG. 4 is a plan view showing a rotary slit plate of a rotary position detector attached to the electric motor of FIG. 1;

FIG. 5 is a graph showing a relationship between an output voltage and a rotation angle in a rotation position detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnetic finite rotation type electric motor 1a Axis 2 Rotation axis 5 Motor stator 6 Permanent magnet of motor 7 Motor rotator 100 Rotary position detector 101 Rotating slit plate 102 Laser diode 103 Semiconductor position detecting element 104 Fixed slit plate 113 Slit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshi Maruyama 1856-1, Oaza-Maki, Hodaka-cho, Minamiazumi-gun, Nagano Prefecture Inside the Harmonic Drive Systems Co., Ltd. Hotaka Plant (72) Inventor Nozomu Tanioka Hotaka, Minamiazumi-gun, Nagano Prefecture 185-1 Machi Oaza Maki Harmonic Drive Systems Co., Ltd. Hotaka Plant F-term (reference) 5H611 AA01 BB10 PP05 QQ02 QQ03 RR04 TT00 TT01 5H633 BB03 GG02 GG22 HH03 HH07 HH15 HH18

Claims (1)

[Claims] The present invention relates to a stator having a drive coil, a rotor composed of a permanent magnet surrounding the stator concentrically, and a rotation of the rotor used for controlling the rotation of the rotor. In a finite rotation type electric motor having a position sensor for detecting information, the position sensor includes a member with a slit that rotates integrally with the rotor, and a light emitting unit that sandwiches the member with the slit and faces a fixed position. And a light receiving means, wherein the slit has a curved shape defined such that a slit position facing the light emitting element and the light receiving element changes in a radial direction according to a rotation angle of a rotor. The member with a slit is formed from a disk or a regular polygonal plate centered on the rotation center of the rotor, and a portion where the slit is formed and the rotor rotation. A finite rotation type electric motor with a position sensor, characterized in that it has a contour shape in which only a portion fixed to a spindle is cut off.