JP2007178235A - Rotary encoder for motor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial-optical-path type rotary encoder for motors, which has high resolution, while keeping to have the merits of the radial optical path type. <P>SOLUTION: The rotary encoder 1 is provided with: a scale 3 which is composed of a disk-shaped hub 5 having at its center a shaft hole in which the output shaft 2a of a motor 2 fits, and a cylindrical rim 6 provided at the circumference edge of the hub, and has light shielding portions and light transmitting portions formed alternately in the circumferential direction of the rim 6; and a sensor 4 comprising a light emitting element and a light receiving element fixed to the motor 2 so as to be inside and outside the rim 6. The hub 5 and the rim 6 are integrally molded of a translucent material, and the light shielding portions are worked so that light incident in the radial direction is reflected into a direction having an angle to the incidence direction, or are printed with a light shielding material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotary encoder for a motor and a manufacturing method thereof.

  In order to detect the rotational displacement amount of the motor, a rotary encoder directly connected to the motor may be used. Usually, a rotary encoder is composed of a disk-shaped or cylindrical scale in which light-shielding portions and light-transmitting portions are alternately formed in the circumferential direction, and a light-emitting element and a light-receiving element disposed so as to face each other with the light-transmitting portion interposed therebetween. And a sensor. Then, a scale is attached to the output shaft of the motor, and the amount of rotational displacement is detected by intermittently connecting the light path with the scale rotating as the motor is driven. There are two types of rotary encoders of this type, one having an optical path in the axial direction (for example, FIG. 3 of Patent Document 1) and one having a radial direction (for example, FIG. 1 in Patent Document 1 and FIG. 3 in Patent Document 2). There are types.

In the case of the axial optical path type, as shown in FIG. 7 (a) as a plan view and as shown in FIG. 7 (b) as an axial cross-sectional view, from a number of slits 23b along the circumferential line close to the outer edge of the disk-shaped scale 23. The translucent part which becomes is formed. Therefore, the scale 23 can easily form a large number of thin light-transmitting portions by etching or punching a thin plate, and the high-resolution encoder 21 can be realized.
However, the characteristic change is large because the timing at which the optical path is interrupted varies due to the vertical movement of the rotating shaft 2a that occurs when the motor 2 is turned ON / OFF, referred to as end play. In addition, due to this end play, the scale 23 and any element inside the sensor 24 may come into contact with each other, making detection impossible. Furthermore, in order to connect the element on the upper side of the scale 23 to the circuit board 7 on the upper surface of the motor 2, the connecting portion between the elements in the sensor 24 must be detoured to the outside of the scale 23. Therefore, it is difficult to reduce the diameter of the entire encoder 21.

On the other hand, in the radial optical path type, the scale 33 is composed of a disk-shaped hub 35 and a cylindrical rim 36 as shown in FIG. The rim 36 is formed with a translucent portion, for example, in a comb shape. Therefore, even if end play occurs, the distance between each element, the light transmitting portion and the light shielding portion does not change, and the characteristics are stable. Since the scale 33 can be inserted into the output shaft 2a after the sensor 34 is attached to the motor 2, assembly is easy. Further, since the connecting portion between the elements in the sensor 34 exists below the scale 33 and the mechanism for suppressing the end play can be omitted, the overall diameter of the encoder 31 or the size of the motor 2 can be reduced. .
However, when the hub 35 and the rim 36 are separately molded and then joined together, a joining cost is required. On the other hand, when the hub 35 and the rim 36 are integrally formed at the same time, since the rim 36 is cylindrical, the pitch and width of the light transmitting portions cannot be made as fine as the axial direction optical path type, and the resolution is rough.

JP-A-5-203464 JP-A-8-145723

As mentioned above, each type has advantages and disadvantages, and none of them has the advantages of both.
Therefore, an object of the present invention is to provide a high-resolution rotary encoder for a motor while maintaining the advantages of the radial optical path type.

In order to solve the problem, a rotary encoder for a motor of the present invention is
Consists of a disc-shaped hub with a shaft hole that fits in the center with the output shaft of the motor, and a cylindrical rim provided on the periphery of the hub. Light-shielding parts and light-transmitting parts are alternately formed in the circumferential direction of the rim. Scaled,
In a rotary encoder comprising a light emitting element and a sensor including a light receiving element fixed to a motor so as to be located inside and outside the rim,
The hub and the rim are integrally formed of a translucent material, and the light shielding portion is processed so that light incident in the radial direction is reflected in a direction having an angle with respect to the incident direction, or It is printed with a light shielding material.

This rotary encoder is a radial optical path type in which a light-shielding part and a light-transmitting part are formed in the circumferential direction of a cylindrical rim, so it is not affected by end play, is easy to assemble, and has a reduced diameter or reduced size. It has the advantage that it can aim at. Since the hub and the rim are integrally formed of a translucent material, the translucent part transmits light to the light receiving element as it is. On the other hand, the light shielding part reflects incident light in a constant or indefinite direction having an angle, or absorbs incident light by a light shielding material. Therefore, the optical path is interrupted by rotating the scale as the motor is driven.
The light-shielding part preferably has a rough surface or a surface that intersects the radial line non-perpendicularly on the outer peripheral surface or the inner peripheral surface. In the case of a rough surface, incident light is diffusely reflected, and in the case of a surface that intersects the radius line at a non-right angle, it is reflected in a certain direction.

A suitable first method for producing this motor rotary encoder is
A disc-shaped hub having a shaft hole that can be fitted to the output shaft of the motor at the center, and a cylindrical rim connected to the periphery of the hub are integrally formed of a translucent material,
Simultaneously with the forming, on the outer peripheral surface or the inner peripheral surface of the rim, a rough surface or a surface that intersects the radial line non-perpendicularly and a smooth surface that intersects the radial line perpendicularly are alternately formed in the circumferential direction,
After fixing the sensor including the light emitting element and the light receiving element to the motor,
The output shaft of the motor is fitted to the shaft hole.

A suitable second manufacturing method is also
A disc-shaped hub having a shaft hole that can be fitted to the output shaft of the motor at the center, and a cylindrical rim connected to the periphery of the hub are integrally formed of a translucent material,
After molding, on the outer peripheral surface or inner peripheral surface of the rim, a rough surface is intermittently formed in the circumferential direction,
After fixing the sensor including the light emitting element and the light receiving element to the motor,
The output shaft of the motor is fitted to the shaft hole.
The third manufacturing method is
A disc-shaped hub having a shaft hole that can be fitted to the output shaft of the motor at the center, and a cylindrical rim connected to the periphery of the hub are integrally formed of a translucent material,
After molding, on the outer peripheral surface or inner peripheral surface of the rim, intermittently printing a light shielding material in the circumferential direction,
After fixing the sensor including the light emitting element and the light receiving element to the motor,
The output shaft of the motor is fitted to the shaft hole.

  The order of description of these production methods is independent of the superiority or inferiority of the methods. According to these manufacturing methods, since the hub and the rim are formed integrally, the step of joining the two after forming can be omitted. The molding means is preferably injection molding. This is because unlike machining such as punching, burrs are not generated and finishing is not required. In the first manufacturing method, the surface that intersects the radius line formed on the scale at a non-right angle functions as a light shielding portion, and the smooth surface functions as a light transmitting portion. The rough surface in the second manufacturing method and the portion printed in the third manufacturing method function as a light-shielding portion, and the portion not roughened and the portion not printed function as a light-transmitting portion. In any method, since the whole is made of a light-transmitting material, the light-transmitting portion does not need to be a space such as a slit, and does not require any special meticulous processing, and may be a smooth surface transferred from a mold. . Therefore, the pitch of the light transmitting part and the light shielding part can be set finely. Since the scale is fixed by fitting the output shaft and the shaft hole of the hub after the sensor is fixed to the motor, assembly is easy.

  As described above, since the rotary encoder according to the present invention is not affected by end play, it accurately outputs a load (Duty) and a phase difference with little difficulty. Since a mechanism for suppressing the end play is unnecessary and assembly is easy, the cost is low. Since the pitch between the light transmitting part and the light shielding part can be set finely, a high-resolution encoder can be constructed.

Embodiment 1
An embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a plan view showing a rotary encoder according to the first embodiment (a motor is omitted), FIG. 1B is an axial sectional view (including a motor), and FIG. 1C is a scale used for the encoder. FIG. 1D is an enlarged view of a portion A in FIG.

  A rotary encoder (hereinafter simply referred to as “encoder”) 1 is attached to an output shaft 2 a of a motor 2 and detects a rotational displacement amount thereof, and includes a scale 3 and a position sensor 4. The scale 3 is made of a transparent resin, and has a disc-shaped hub 5 having a shaft hole that fits the output shaft 2a of the motor 2 at the center, and a cylindrical rim 6 that is continuous with the peripheral edge of the hub 5. It is. In the circumferential direction on the outer peripheral surface of the rim 6, isosceles trapezoidal convex portions and inverted isosceles trapezoidal concave portions in plan view are alternately formed. Both the top surface 6a of the convex portion and the bottom surface 6b of the concave portion are along a circumferential line centering on the output shaft 2a, and function as a translucent portion. Then, both side surfaces 6c and 6d of the convex portion (or concave portion) form an angle of 45 ° with respect to a tangent line passing through the circumferential line, and function as a light shielding portion.

The position sensor 4 is fixed at an eccentric position near the circuit board 7 on the upper surface of the motor 2 so that the light emitting part 4a is located outside the rim 6, the light receiving part 4b is located inside, and the connecting part 4c of both is located below. Yes. The light emitting unit 4a and the light receiving unit 4b each include a light emitting element and a light receiving element (not shown). At least two light receiving elements are built in the circumferential direction, and output signals having different phases can be taken out. The light emitting unit 4a and the light receiving unit 4b are opposed to each other through a gap that allows the rim 6 to rotate without contacting the light transmitting unit and the light blocking unit positioned therebetween.
The encoder 1 is manufactured as follows.
The scale 3 is obtained by injection molding a transparent resin into a mold having an internal space complementary to the scale 3. Then, after fixing the sensor 4 to the upper surface of the motor 2 so that the connecting portion 4c faces down, the shaft hole of the scale 3 is fitted to the output shaft 2a, so that the encoder 1 is completed and assembled to the motor 2 at the same time. It becomes a state.

  In the encoder 1, as shown in FIG. 2, when the light emitted from the light emitting element is incident on the light transmitting portion, the light passes through the rim 6 and reaches the light receiving element. On the other hand, when it enters the light shielding part, it is reflected at a substantially right angle and does not reach the light receiving element. Therefore, the optical path is intermittent with the rotation of the output shaft 2a, and the rotational displacement amount can be detected. As described above, the rim 6 has a cylindrical shape concentric with the output shaft 2a, and the light transmitting portion and the light shielding portion are formed on the outer peripheral surface thereof. Therefore, even if the motor 2 causes end play, the light emitting portion 4a and the rim are formed. Each distance between the light receiving portion 4b and the inner peripheral surface of the rim 6 is kept constant between the six outer peripheral surfaces. Therefore, the output characteristics are stable regardless of the end play. Moreover, since the translucent part and the light-shielding part reflect the shape of the mold processed with high precision with a fine pitch and width, the resolution is high.

Embodiment 2
FIG. 3 is a perspective view showing a scale used in the rotary encoder of the second embodiment. In this embodiment, instead of the slope in the first embodiment, the light shielding portion is formed with a rough surface. Other configurations are the same as those of the first embodiment, and differences will be described in detail below.
That is, the outer peripheral surface of the rim 16 of the scale 13 has no unevenness having a level difference as large as that of the first embodiment, and instead, the rough surface 16a and the smooth surface 16b that are long in the axial direction are alternately formed in the circumferential direction. ing. The rough surface 16a functions as a light shielding portion, and the smooth surface 16b functions as a light transmitting portion.
The scale 13 is manufactured by injecting a transparent resin into a mold having an internal space substantially complementary to the scale 13 and then grinding a region to be the rough surface 16a with a grinder.

When the scale 13 is assembled to the motor 2 together with the same sensor 4 as in the first embodiment, as shown in FIG. 4, when light emitted from the light emitting element enters the light transmitting portion, the light passes through the rim 16 and reaches the light receiving element. . On the other hand, when it enters the light shielding portion, it is irregularly reflected and does not reach the light receiving element. Therefore, the amount of rotational displacement can be detected as in the first embodiment. Moreover, since the distance between each element and the inner and outer surfaces of the rim 16 is constant, the output characteristics are stable regardless of the end play. Further, since the rough surface 16a can be formed with high accuracy at a desired pitch and width by a grinding machine, the resolution is high.
Note that scratching with a needle-like tool connected to the piezoelectric actuator may be applied instead of the grinding process.

Embodiment 3
FIG. 5 is a perspective view showing a scale used in the rotary encoder of the third embodiment. In this embodiment, instead of the slope in the first embodiment, the light shielding portion is printed with a light shielding material. Other configurations are the same as those of the first embodiment, and differences will be described in detail below.
That is, the outer peripheral surface of the rim 46 of the scale 43 has no unevenness having a level difference as large as in the first embodiment, and instead, black square patterns 46a that are long in the axial direction are printed at equal intervals in the circumferential direction. The scale 43 is manufactured by injection-molding a transparent resin in a mold having an interior space substantially complementary to the scale 43, and then printing and heating the square pattern 46a with black ink. Examples of the black ink include pastes containing black pigments such as carbon black and black iron oxide. Printing may be performed via a mesh screen while the scale 43 is rotated intermittently, or a necessary number of patterns may be printed on a strip-shaped film and transferred to the rim 46. Good. Moreover, you may spray by an inkjet system from a fine discharge port. The rectangular pattern 46a functions as a light shielding portion, and the unprinted portion 46b sandwiched between the rectangular patterns 46a functions as a light transmitting portion.

  When the scale 43 is assembled to the motor 2 together with the same sensor 4 as in the first embodiment, as shown in FIG. 6, when light emitted from the light emitting element enters the light transmitting portion, the light passes through the rim 46 and reaches the light receiving element. . On the other hand, the black pigment absorbs light when entering the light-shielding portion, and therefore does not reach the light receiving element. Therefore, the amount of rotational displacement can be detected as in the first embodiment. In addition, since the distance between each element and the inner and outer surfaces of the rim 46 is constant, the output characteristics are stable regardless of the end play. Further, since the rectangular pattern 46a can be formed with high accuracy at a desired pitch and width by a printing press, the resolution is high.

The rotary encoder of Embodiment 1 is shown, (a) is the top view, (b) is an axial sectional view including a motor, (c) is a perspective view of a scale used for the encoder, (d) is a perspective view of (c). It is an A section enlarged view. It is a figure explaining the principle of light shielding of the same scale. It is a perspective view which shows the scale used for Embodiment 2. FIG. It is a figure explaining the principle of light shielding of the same scale. It is a perspective view which shows the scale used for Embodiment 3. FIG. It is a figure explaining the principle of light shielding of the same scale. A conventional rotary encoder is shown, (a) is a plan view thereof, and (b) is an axial sectional view including a motor. The other conventional rotary encoder is shown, (a) is an axial sectional view including a motor, (b) is a perspective view of a scale used in the encoder.

Explanation of symbols

1, 21, 31 Encoder 2 Motor 3, 13, 23, 33, 43 Scale 4, 24, 34 Position sensor 5, 15, 35, 45 Hub 6, 16, 36, 46 Rim 7 Circuit board 2a Output shaft

Claims (7)

Consists of a disc-shaped hub with a shaft hole that fits in the center with the output shaft of the motor, and a cylindrical rim provided on the periphery of the hub. Light-shielding parts and light-transmitting parts are alternately formed in the circumferential direction of the rim. Scaled,
In a rotary encoder comprising a light emitting element and a sensor including a light receiving element fixed to a motor so as to be located inside and outside the rim,
The hub and the rim are integrally formed of a translucent material, and the light shielding portion is processed so that light incident in the radial direction is reflected in a direction having an angle with respect to the incident direction, or A rotary encoder for a motor, which is printed with a light shielding material.   The rotary encoder for motors according to claim 1, wherein the light shielding portion has a rough surface or a surface that intersects the radial line at a non-right angle on an outer peripheral surface or an inner peripheral surface. A disc-shaped hub having a shaft hole that can be fitted to the output shaft of the motor at the center, and a cylindrical rim connected to the periphery of the hub are integrally formed of a translucent material,
Simultaneously with the molding, on the outer peripheral surface or inner peripheral surface of the rim, a surface that intersects the radial line at a non-right angle and a smooth surface that intersects the radial line at a right angle are alternately formed in the circumferential direction.
After fixing the sensor including the light emitting element and the light receiving element to the motor,
A method for manufacturing a rotary encoder for a motor, wherein the output shaft of the motor is fitted into the shaft hole. A disc-shaped hub having a shaft hole that can be fitted to the output shaft of the motor at the center, and a cylindrical rim connected to the periphery of the hub are integrally formed of a translucent material,
After molding, on the outer peripheral surface or inner peripheral surface of the rim, a rough surface is intermittently formed in the circumferential direction,
After fixing the sensor including the light emitting element and the light receiving element to the motor,
A method for manufacturing a rotary encoder for a motor, wherein the output shaft of the motor is fitted into the shaft hole.   5. The method for manufacturing a rotary encoder for a motor according to claim 4, wherein the means for forming the rough surface is scratching with a needle-like tool connected to a piezoelectric actuator. A disc-shaped hub having a shaft hole that can be fitted to the output shaft of the motor at the center, and a cylindrical rim connected to the periphery of the hub are integrally formed of a translucent material,
After molding, on the outer peripheral surface or inner peripheral surface of the rim, intermittently printing a light shielding material in the circumferential direction,
After fixing the sensor including the light emitting element and the light receiving element to the motor,
A method for manufacturing a rotary encoder for a motor, wherein the output shaft of the motor is fitted into the shaft hole.   The method for manufacturing a rotary encoder for a motor according to claim 6, wherein the printing is an inkjet method.

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