Encoder and motor

Abstract

To provide an encoder and a motor, which can prevent breakage and peeling of a sensor element and an electronic component that are mounted on a circuit board.SOLUTION: An encoder 1 includes: a sensor element 14 that outputs an electric signal corresponding to a position (a rotation position of a rotation shaft 41) of an object; an electronic component 15 that constitutes an electric circuit together with the sensor element 14; and a circuit board 13 on which the sensor element 14 and the electronic component 15 are mounted. The circuit board 13 is molded with an insulating resin and integrated with a mold resin portion 12 formed of the resin. The sensor element 14 and the electronic component 15 are not molded with the resin (are not covered by the mold resin portion 12). A motor comprises the encoder 1.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to an encoder and a motor. [Background technology]

[0002] Known encoders (position detection devices) that detect the rotational position of a motor's rotating shaft include those in which a sensor element and electronic components mounted on a circuit board are molded with resin (insert molding) together with the circuit board (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5389188 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-194186 Summary of the Invention [Problem to be solved by the invention]

[0004] When the sensor element and electronic components mounted on the circuit board are molded with resin together with the circuit board, there is a risk that the sensor element and electronic components may be damaged or peeled off from the circuit board due to the heat generated during molding and the hardening shrinkage of the resin.

[0005] The present invention has been made in consideration of such problems, and aims to provide an encoder and motor that can prevent damage to or peeling off of the sensor element and electronic components mounted on the circuit board. [Means for solving the problem]

[0006] An encoder for detecting the position of an object, comprising: a sensor element that outputs an electrical signal corresponding to the position of the object; electronic components that form an electrical circuit together with the sensor element; and a circuit board on which the sensor element and the electronic components are mounted, wherein the circuit board is molded with insulating resin and is integrated with a molded resin part made of the resin, and the sensor element and the electronic components are not molded with the resin.

[0007] The present invention also provides a motor equipped with this encoder. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an encoder and a motor that can prevent damage to or separation of the sensor element and electronic components mounted on the circuit board. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a cross-sectional view of an encoder according to a first embodiment of the present invention. [Figure 1B] FIG. 1 is a plan view of an encoder according to a first embodiment of the present invention. [Figure 2] 1 is a side view of a motor equipped with an encoder according to a first embodiment of the present invention. [Figure 3A] FIG. 10 is a cross-sectional view of an encoder according to a second embodiment of the present invention. [Figure 3B] FIG. 10 is a plan view of an encoder according to a second embodiment of the present invention. [Figure 4A] FIG. 10 is a cross-sectional view of an encoder according to a third embodiment of the present invention. [Figure 4B] FIG. 10 is a plan view of an encoder according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Examples of the present invention will be described below. [Example]

[0011] Fig. 1A is a cross-sectional view of an encoder according to a first embodiment of the present invention. Fig. 1B is a plan view of the encoder according to the first embodiment of the present invention. Fig. 2 is a side view of a motor equipped with an encoder according to the first embodiment of the present invention. Fig. 1A shows a cross-section taken along the extension direction (axial direction) of the rotation shaft of the motor, and Fig. 1B shows a plan view seen from the rear end side of the motor.

[0012] As shown in Fig. 2, the encoder 1 in the first embodiment of the present invention is attached to the rear end of the motor 40. As shown in Fig. 1A, the encoder 1 is a rotary encoder and includes a housing 11, a molded resin part 12, a circuit board 13, a sensor element 14, electronic components 15, a cable 16, a sensor magnet 17, and a magnet holder 18. The motor 40 is a brushed motor and includes, as components shown in Fig. 1A, a rotating shaft 41, a commutator 42, brushes 43, and a brush base 44, and further includes, as components not shown in Fig. 1A, a cylindrical rotor coil (coreless coil) fixed to the rotating shaft 41, a cylindrical stator magnet arranged inside the rotor coil, a bearing that supports the rotating shaft 41, and a motor case that houses these components.

[0013] The housing 11 is a generally cylindrical member surrounding the rear end of the rotary shaft 41 and is integrally formed with the brush base 44. The molded resin portion 12 is a generally disk-shaped member integrated with the circuit board 13 by insert molding and fixed to the rear end of the housing 11 by concave-convex fitting and adhesive. The sensor element 14 is mounted on one main surface of the circuit board 13. The electronic component 15 and the cable 16 are mounted on the other main surface of the circuit board 13. The sensor element 14 is a magnetic detection element (Hall element) that detects the magnetism of the sensor magnet 17. The electronic component 15, together with the sensor element 14, constitutes the electric circuit of the encoder 1 and is, for example, a resistor, a capacitor, a diode, an IC chip, etc. Note that a plurality of the sensor element 14 and the electronic component 15 may be provided, as necessary. The sensor magnet 17 is fixed to one end of the magnet holder 18 so as to be oriented in a predetermined direction. The magnet holder 18 is a generally cylindrical member and fixed to the rear end of the rotary shaft 41 by press-fitting and adhesive.

[0014] The molded resin portion 12 is made of insulating resin (plastic or the like) that is hardened by a molding process. The housing 11, the magnet holder 18, and the brush base 44 are also made of insulating resin similar to the molded resin portion 12.

[0015] The circuit board 13 is covered (molded) with the molded resin part 12, but the sensor element 14 and electronic components 15 mounted on the circuit board 13 are not covered (molded) with the molded resin part 12. Note that if multiple sensor elements 14 and multiple electronic components 15 are mounted on the circuit board 13, not all of them are covered with the molded resin part 12. In other words, the sensor element 14 and the electronic components 15 are not insert-molded together with the circuit board 13, and stress due to heat during insert molding or curing shrinkage of the resin does not act on the sensor element 14 and the electronic components 15. This prevents the sensor element 14 and the electronic components 15 from being damaged or peeling off from the circuit board 13.

[0016] The cable 16 is covered (molded) with the molded resin part 12, but since the cable 16 is usually more resistant to heat and stress than the sensor element 14 and the electronic component 15, there is no particular problem with the cable 16 being covered with the molded resin part 12. In fact, by being covered with the molded resin part 12, the cable 16 has improved strength against pulling in a direction away from the circuit board 13, and is prevented from peeling off from the circuit board 13. However, if there is a risk that the cable 16 will be damaged or peeled off from the circuit board 13 due to the heat or stress that occurs during insert molding, it is preferable that the cable 16 not be covered with the molded resin part 12.

[0017] The upper surface (the surface opposite to the mounting surface) and outer peripheral surface (side surface) of sensor element 14 are exposed to the inside of housing 11 through a circular first opening 121 provided in molded resin part 12, and the upper surface (the surface opposite to the mounting surface) and outer peripheral surface (side surface) of electronic component 15 are exposed to the outside of housing 11 through a circular second opening 122 provided in molded resin part 12. However, if this does not pose any particular problem in terms of product quality, they may remain exposed. The shapes of first opening 121 and second opening 122 are not limited to circles and may be other shapes such as squares.

[0018] Because the circuit board 13 is covered with the molded resin portion 12, the covered portion is protected from impacts and foreign objects. Furthermore, because the circuit board 13 is configured as a single component integrated with the molded resin portion 12, it can be easily handled by an operator. In particular, in Example 1, the outer periphery of the circuit board 13, which is a portion that is easily gripped by an operator, is covered with the molded resin portion 12, which is particularly effective. However, the portion of the circuit board 13 covered with the molded resin portion 12 is not limited to the outer periphery of the circuit board 13. Furthermore, because the circuit board 13 is attached to the housing 11 via the molded resin portion 12, which is integrated with the housing 11, the number of components and assembly steps can be reduced compared to when the circuit board 13 is attached to the housing 11 via separate components that are not integrated with the housing 11. Furthermore, the relative positional deviation between the housing 11 and the circuit board 13, which occurs due to dimensional variations between the components, can be reduced. This ultimately contributes to improving the positional accuracy of the sensor element 14 relative to the sensor magnet 17.

[0019] The molded resin part 12 is fixed to the rear end of the housing 11 by recessed and protruding engagement and adhesion, but for example, it may be fixed to the rear end of the housing 11 by recessed and protruding engagement and screws, or it may be fixed only by adhesion or screws without using recessed and protruding engagement.

[0020] In the encoder 1, the magnetism emitted from the sensor magnet 17 is converted into an electric signal by the sensor element 14, and this electric signal is output to the outside from the cable 16 via a predetermined electric circuit formed on the circuit board 13. The electric signal output to the outside is input to the control circuit of the motor 40, and the control circuit of the motor 40 obtains rotational position information of the rotating shaft 41 based on this electric signal. [Example]

[0021] Fig. 3A is a cross-sectional view of an encoder according to a second embodiment of the present invention. Fig. 3B is a plan view of the encoder according to the second embodiment of the present invention. Fig. 3A shows a cross section taken along the extension direction (axial direction) of the rotation shaft of the motor, and Fig. 3B shows a plan view seen from the rear end side of the motor.

[0022] The encoder 2 according to the second embodiment of the present invention differs from the encoder 1 according to the first embodiment of the present invention in the following respects: In the encoder 2, the surface of the sensor element 14 exposed to the inside of the housing 11 through the first opening 121 provided in the molded resin part 12 is covered with a first insulating member 21a, and the surface of the electronic component 15 exposed to the outside of the housing 11 through the second opening 122 provided in the molded resin part 12 is covered with a second insulating member 21b.

[0023] The first insulating member 21a and the second insulating member 21b are insulating adhesives, paints, coatings, etc., made of a material different from that of the molded resin portion 12. The first insulating member 21a and the second insulating member 21b are preferably made of a material that is not thermosetting (e.g., a room-temperature curing or photocuring material) and whose cure shrinkage is smaller than that of the molded resin portion 12. When configured in this manner, damage or peeling of the sensor element 14 and the electronic component 15 due to heat or stress can be suppressed compared to when the sensor element 14 and the electronic component 15 are covered with the molded resin portion 12. However, the first insulating member 21a and the second insulating member 21b are not limited to these materials. The first insulating member 21a and the second insulating member 21b may be made of the same material.

[0024] First insulating member 21a fills the inside of first opening 121 and covers not only the surface of sensor element 14 but also the surface of circuit board 13 exposed from the gap between the outer circumferential surface of sensor element 14 and the inner circumferential surface of first opening 121. Second insulating member 21b fills the inside of second opening 122 and covers not only the surface of electronic component 15 but also the surface of circuit board 13 exposed from the gap between the outer circumferential surface of electronic component 15 and the inner circumferential surface of second opening 122.

[0025] As described above, in Example 2, the surfaces of the circuit board 13, the sensor element 14, and the electronic components 15 that are not covered by the molded resin portion 12 are covered with the first insulating member 21a and the second insulating member 21b, so that these surfaces can be protected from impacts and foreign matter. In particular, inside the housing 11, conductive sliding powder generated by the sliding of the commutator 42 and the brush 43 may adhere to the circuit board 13 or the sensor element 14 and cause an electrical short circuit. However, in Example 2, this can be prevented by the first insulating member 21a. Furthermore, outside the housing 11, the circuit board 13 and the electronic components 15 are susceptible to damage due to being susceptible to external impacts and being exposed to various foreign matter and environments. However, in Example 2, this can be prevented by the second insulating member 21b.

[0026] The first insulating member 21a and the second insulating member 21b do not have to cover all of the surfaces of the circuit board 13, the sensor element 14, and the electronic components 15 that are not covered by the molded resin portion 12, and may cover only a portion of these surfaces. However, in order to reliably protect these surfaces, it is preferable that the first insulating member 21a and the second insulating member 21b cover all of these surfaces. In any case, which areas of these surfaces are covered by the first insulating member 21a and the second insulating member 21b can be selected appropriately depending on the situation. [Example]

[0027] Fig. 4A is a cross-sectional view of an encoder according to a third embodiment of the present invention. Fig. 4B is a plan view of the encoder according to the third embodiment of the present invention. Fig. 4A shows a cross section taken along the extension direction (axial direction) of the rotation shaft of the motor, and Fig. 4B shows a plan view seen from the rear end side of the motor.

[0028] The encoder 3 according to the third embodiment of the present invention differs from the encoder 1 according to the first embodiment of the present invention in the following respects: In the encoder 3, a first cover 311 is attached to a first opening 121 provided in the molded resin part 12, and a second cover 312 is attached to a second opening 122 provided in the molded resin part 12.

[0029] The first cover 311 is a circular cap-shaped member, and is fixed to the molded resin portion 12 by adhesive or press-fitting, with the outer peripheral surface on the open end side of the first cover 311 fitted into the inner peripheral surface of the first opening 121. The first cover 311 is made of, for example, insulating resin (plastic, etc.). However, the first cover 311 may be made of other materials such as metal. When the first cover 311 is made of metal, by appropriately selecting the shape of the first cover 311 (for example, by making the central portion of the first cover 311 relatively thicker than the other portions), the first cover 311 can be made to function as a yoke, and the magnetic flux density of the sensor magnet 17 can be increased.

[0030] The first cover 311 may be fixed to the circuit board 13. In this case, possible means for fixing the first cover 311 to the circuit board 13 include, for example, adhesives and screws. However, if the first cover 311 is made of metal, the first cover 311 may be fixed by soldering or welding to a metal pattern (such as a dummy pattern that is not connected to an electric circuit) formed on the surface of the circuit board 13. Furthermore, if the first cover 311 is fixed to the circuit board 13, the outer surface of the first cover 311 may be covered together with the circuit board 13 by the molded resin part 12 by insert molding. With this configuration, the fixing strength of the first cover 311 can be improved.

[0031] The first cover 311 may be made of the same material as the molded resin part 12. When configured in this manner, it is possible to reduce stress that occurs due to the difference in the thermal expansion coefficient of the materials between the first cover 311 and the molded resin part 12. This contributes to reducing warping and distortion of the first cover 311 and the molded resin part 12, and as a result, contributes to improving the positional accuracy of the sensor element 14 with respect to the sensor magnet 17.

[0032] The second cover 312 is a circular screw-like member, and a male thread (not shown) formed on the outer peripheral surface of the tip of the second cover 312 is screwed into a female thread (not shown) formed on the inner peripheral surface of the second opening 122, thereby fixing the second cover 312 to the molded resin portion 12. Because the second cover 312 is a screw-like member, it can be firmly fixed to the molded resin portion 12. The second cover 312 is made of, for example, an insulating resin (plastic, etc.). However, the second cover 312 may be made of other materials such as metal. If the second cover 312 is made of a conductor such as metal, the second cover 312 serves as an electromagnetic shield and can protect the electronic components 15 from electrical noise coming from outside. Furthermore, in this case, if the second cover 312 is electrically connected to a GND terminal of the housing 11 or the circuit board 13, this effect can be enhanced.

[0033] Possible methods for electrically connecting second cover 312 to housing 11 or circuit board 13 include, for example, embedding a conductor (metal or the like) in part of the inner surface of second opening 122 by insert molding, or forming the entire inner surface of second opening 122 from a cylindrical conductor (metal or the like) by insert molding, and electrically connecting second cover 312 to housing 11 or circuit board 13 via the conductor. In particular, when the entire inner surface of second opening 122 is formed from a cylindrical conductor by insert molding, as in the latter case, electronic component 15 is surrounded by the cylindrical conductor and second cover 312 (conductor), and therefore electronic component 15 can be effectively protected from electrical noise coming from outside.

[0034] The second cover 312 may be made of the same material as the molded resin part 12. When configured in this manner, it is possible to reduce stress that occurs due to the difference in the thermal expansion coefficient of the materials between the second cover 312 and the molded resin part 12. This contributes to reducing warping and distortion of the second cover 312 and the molded resin part 12, and as a result, contributes to improving the positional accuracy of the sensor element 14 with respect to the sensor magnet 17.

[0035] The rear end of the second cover 312 is provided with a circular flange 312a protruding radially and a cross-shaped groove 312b extending radially. The flange 312a abuts against the rear end surface of the molded resin portion 12, thereby serving as a stopper to prevent the tip of the second cover 312 from contacting the electronic component 15. Furthermore, the flange 312a also serves to shield and seal the gap (boundary) between the outer peripheral surface of the tip of the second cover 312 and the inner peripheral surface of the second opening 122. The groove 312b is a groove into which the tip of a predetermined tool (such as a screwdriver) engages when attaching the second cover 312 to the second opening 122. An operator can easily attach the second cover 312 to the second opening 122 by engaging the tip of the predetermined tool with the groove 312b and rotating the second cover 312 in a predetermined direction. The shape of the groove 312b is not limited to a cross shape, and other shapes may be selected as appropriate depending on the shape of the tool being used.

[0036] The first cover 311 may not be a cap-shaped member, but may be a screw-shaped member like the second cover 312. In this case, the thickness of the molded resin portion 12 surrounding the sensor element 14 is configured to be sufficiently larger than the thickness of the sensor element 14, and the outer peripheral surface of the screw-shaped first cover 311 is screwed into the upper inner peripheral surface of the first opening 121 (the inner peripheral surface located above the upper surface of the sensor element 14) formed by the difference in thickness. Furthermore, the second cover 312 may not be a screw-shaped member, but may be a cap-shaped member like the first cover 311. Furthermore, the first cover 311 and the second cover 312 may be pin-shaped members or flat plate-shaped members. The shapes of the first cover 311 and the second cover 312 are not limited to these and may be selected as appropriate.

[0037] As described above, in Example 3, the sensor element 14 is covered with the first cover 311 and the electronic component 15 is covered with the second cover 312, so that, similar to Example 2, the sensor element 14 and the electronic component 15 can be protected from impacts and foreign matter.

[0038] The present invention is not limited to the above examples, and other embodiments are possible. The configurations of Examples 1 to 3 can be implemented in appropriate combination with each other. The present invention is not limited to rotary encoders, but can also be applied to linear encoders, etc. The present invention is not limited to magnetic encoders, but can also be applied to optical encoders, etc. The present invention is not limited to brushed motors, but can also be applied to brushless motors, etc. [Explanation of symbols]

[0039] 1 Encoder 11. Housing 12 Molded resin part 121 First opening 122 Second opening 13 Circuit Board 14 Sensor element 15 Electronic Components 16 Cable 17 Sensor magnet 18 Magnet holder 2 Encoders 21a First insulating member 21b Second insulating member 3 Encoders 311 First Cover 312 Second Cover 312a flange 312b Groove 40 Motor 41 Rotation axis 42 Commutator 43 Brush 44 Brush stand

Claims

1. An encoder for detecting a position of an object, a sensor element that outputs an electrical signal according to the position of the object; an electronic component that configures an electric circuit together with the sensor element; a circuit board on which the sensor element and the electronic components are mounted, the circuit board is molded with insulating resin and is integrated with a molded resin part made of the resin, the sensor element and the electronic component are not molded with the resin; An encoder characterized by:

2. 2. The encoder according to claim 1, wherein an outer periphery of the circuit board is molded with the resin.

3. 2. The encoder according to claim 1, wherein at least one of the sensor element and the electronic component is covered with an insulating material different from the resin.

4. 2. The encoder according to claim 1, wherein at least one of the sensor element and the electronic component is covered with a cover attached to the circuit board or the molded resin portion.

5. 5. The encoder according to claim 4, wherein the cover is a cap-shaped member, and an outer surface of the cover is molded with the resin.

6. 5. The encoder according to claim 4, wherein the cover is a screw-like member, and the cover is attached to the molded resin portion by being screwed.

7. 5. The encoder according to claim 4, wherein the cover is made of a conductor, the molded resin portion has an opening to which the cover is attached, and an inner circumferential surface of the opening is made of a conductor.

8. The encoder according to claim 7, wherein the cover is electrically connected to a housing made of a conductor.

9. 8. The encoder according to claim 7, wherein the cover is electrically connected to a GND terminal of the circuit board.

10. 5. The encoder according to claim 4, wherein the cover is made of the same material as the resin.

11. An encoder according to any one of claims 1 to 10, A motor characterized by:

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