Encoder cover and motor

Abstract

The present invention keeps heat from being transmitted from a motor body part to an encoder. This encoder cover (10) is to cover an encoder (20) that detects the rotational position of a shaft (41) of a motor (1). The encoder cover (10) comprises a flange (11) that is attached to the encoder (20), a first cover member (12) that is provided at an opposite position from the flange (11) as seen from the encoder (20) and covers a portion of the encoder (20), and a second cover member (13) that connects the flange (11) and the first cover member (12) and covers a portion of the encoder (20). The thermal conductivity of the second cover member (13) of the encoder cover (10) is lower than the thermal conductivity of the flange (11) and the thermal conductivity of the first cover member (12).

Description

Encoder cover and motor

[0001] The present disclosure relates to an encoder cover that covers an encoder that detects the rotational position of a shaft of a motor, and a motor including the encoder cover.

[0002] Conventionally, an encoder cover for covering an encoder that detects the rotational position of a motor shaft has been known (for example, see Patent Document 1). The encoder cover in Patent Document 1 includes an encoder housing portion for housing the encoder and a flange portion for joining to a bracket of the motor. The encoder housing portion and the flange portion are integrally formed from a conductive die-cast alloy.

[0003] Japanese Patent Application Laid-Open No. 2015-1511

[0004] In the encoder cover of Patent Document 1, heat from the motor main body (including the magnetic circuit having the rotor and stator) may interfere with normal operation of the encoder. Specifically, because the encoder housing and flange are integrally formed from a die-cast alloy with high thermal conductivity, heat from the motor main body is easily transferred to the encoder housing via the flange. This builds up heat inside the encoder housing, i.e., in the space where the encoder is housed, and this heat interferes with normal operation of the encoder. In light of this situation, one of the objectives of the present disclosure is to prevent heat from being transferred from the motor main body to the encoder.

[0005] One aspect of the present disclosure relates to an encoder cover including: a flange for mounting an encoder; a first cover member provided on a side opposite the flange from the encoder and covering a portion of the encoder; and a second cover member connecting the flange and the first cover member and covering a portion of the encoder, wherein the second cover member has a lower thermal conductivity than both the flange and the first cover member.

[0006] Another aspect of the present disclosure relates to a motor including the above-described encoder cover, an encoder housed in the encoder cover, and a main body having a shaft whose rotation position is detected by the encoder.

[0007] According to the present disclosure, it is possible to prevent heat from being transferred from the motor main body to the encoder.

[0008] 1 is a perspective view showing an example of an encoder cover according to an embodiment of the present disclosure, a top view of the encoder cover according to an embodiment of the present disclosure, and a cross-sectional view taken along line III-III in FIG.

[0009] An example of an encoder cover and a motor according to an embodiment of the present disclosure will be described below. However, the present disclosure is not limited to the example described below. While specific numerical values ​​and materials may be used in the following description, other numerical values ​​and materials may be used as long as the effects of the present disclosure are achieved.

[0010] (Encoder Cover) The encoder cover according to the present disclosure is an encoder cover for covering an encoder that detects the rotational position of a shaft of a motor, and includes a flange, a first cover member, and a second cover member. The motor includes a main body having a rotor including a shaft and a stator facing the rotor across a gap.

[0011] The flange is a member for mounting the encoder. The flange may have insertion holes through which mounting screws are inserted to mount the flange to the motor bracket. The flange may be fitted with an encoder and a bearing that rotatably supports the motor shaft. A rotating plate provided with the encoder may be attached to the motor shaft.

[0012] The first cover member is provided on a side opposite the flange from the encoder, and covers a part of the encoder. The first cover member may be in the form of a lid.

[0013] The second cover member connects the flange and the first cover member. The second cover member covers a portion of the encoder. The second cover member may be provided between the flange and the first cover member. The second cover member may be cylindrical.

[0014] The flange, the first cover member, and the second cover member may define an accommodation space for accommodating the encoder. This accommodation space may be a sealed space.

[0015] The thermal conductivity of the second cover member is lower than that of the flange and that of the first cover member. This second cover member suppresses heat conduction between the flange and the first and second cover members. Therefore, even if heat is generated in the motor main body, the heat is less likely to be transferred to the first and second cover members via the flange, and heat is less likely to build up inside the encoder cover, i.e., the space where the encoder is housed. This prevents heat from being transferred from the motor main body to the encoder.

[0016] The first cover member and the flange may each be made of a conductive material, such as a metal, a carbon material such as glassy carbon, or a conductive resin.

[0017] The first cover member may be made of a first metal (e.g., aluminum or an aluminum alloy). A first cover member made of a first metal has high thermal conductivity. Therefore, even if heat builds up inside the encoder cover, the heat can be dissipated to the outside through the first cover member. This further prevents heat from interfering with normal operation of the encoder.

[0018] The second cover member may be made of a first resin (e.g., nylon resin). The second cover member made of the first resin has low thermal conductivity, which makes it easy to ensure the heat insulating function of the second cover member.

[0019] The encoder cover may further include a magnetic shield member fixed to the first cover member and covering at least a portion of the encoder. The magnetic shield member may be made of a second metal (e.g., iron or an iron alloy) and may not be in contact with the flange. Such a magnetic shield member can suppress the effects of magnetic noise on the encoder. Furthermore, the magnetic shield member is made of the second metal, which has high thermal conductivity, due to its function. When the magnetic shield member is not in contact with the flange, heat is prevented from being transferred from the flange to the first cover member via the magnetic shield member, preventing heat from building up inside the encoder cover. The second metal may be the same or different from the first metal.

[0020] The first cover member may be fixed to the flange with conductive bolts (e.g., steel bolts). With this configuration, even if electric field noise penetrates the first cover member, the electric field noise is dissipated to the flange via the bolts. This makes it difficult for the electric field noise to be transmitted to the encoder, thereby preventing malfunction of the encoder. Note that the electric field noise transmitted to the flange may also be transmitted to a bracket provided on the motor main body.

[0021] The second cover member may have a connector housing. The housing may be made of a second resin (e.g., nylon resin). The connector may be a connector to which wiring for transmitting a detection signal from the encoder is connected. With this configuration, there is no need to provide a connector housing separately from the second cover member, thereby reducing the manufacturing cost of the encoder cover. Note that the second resin may be the same type as or a different type from the first resin.

[0022] The portion of the second cover member other than the housing may be integrally formed with the housing. This configuration makes it possible to easily manufacture the second cover member having the housing. Furthermore, compared to when the portion of the second cover member other than the housing is separate from the housing, it is possible to more easily assemble the encoder cover.

[0023] The length of the second cover member in the axial direction of the motor shaft (the direction in which the flange and the first cover member face each other) may be at least half the length of the encoder cover, which further enhances the heat insulating function of the second cover member.

[0024] (Motor) A motor according to another embodiment of the present disclosure includes the above-described encoder cover, an encoder housed in the encoder cover, and a main body having a shaft whose rotational position is detected by the encoder. The main body may include a rotor including the shaft and a stator facing the rotor across a gap. The motor may be, but is not limited to, an inner rotor type three-phase synchronous motor. The encoder may be, but is not limited to, a multi-rotation absolute encoder (an absolute type encoder that detects the rotational position and rotation speed of the shaft). The encoder may or may not include a battery.

[0025] As described above, according to the present disclosure, it is possible to prevent heat from being transferred from the motor main body to the encoder, thereby enabling the encoder to operate normally.

[0026] An example of an encoder cover and a motor according to the present disclosure will be described in detail below with reference to the drawings. The components described above can be applied to the components of the example encoder cover and motor described below. The components of the example encoder cover and motor described below can be modified based on the above description. The matters described below may also be applied to the above embodiment. Of the components of the example encoder cover and motor described below, components that are not essential to the encoder cover and motor according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and number of actual components.

[0027] Fig. 1 is a perspective view showing an example of an encoder cover 10 according to an embodiment of the present disclosure. Fig. 2 is a top view of the encoder cover 10. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2, showing the shaft 41 of the motor 1 and the like.

[0028] 1 to 3, the motor 1 includes an encoder cover 10, an encoder 20, and a main body 40 having a rotor including a shaft 41 and a stator. The motor 1 of this embodiment is an inner rotor type three-phase synchronous motor, but is not limited to this.

[0029] The encoder cover 10 is an element that covers the encoder 20 and includes a flange 11 , a first cover member 12 , a second cover member 13 , and a magnetic shield member 14 .

[0030] The flange 11 is a member for mounting the encoder 20. In this embodiment, the flange 11 is made of aluminum (an example of a third metal), but is not limited to this. For example, the flange 11 may be made of stainless steel. The flange 11 has insertion holes 11a through which mounting screws are inserted to mount the flange 11 to the bracket 42 of the motor 1. In this example, four insertion holes 11a are provided, but the number of insertion holes 11a is not limited to this. In addition to mounting the encoder 20 to the flange 11, a bearing 50 that rotatably supports the shaft 41 is also mounted. An annular magnetic shield plate 11c made of, for example, iron is embedded in the flange 11. Note that a magnetic material is preferable as the material for the magnetic shield plate 11c, and iron alloys such as stainless steel can be used in addition to iron.

[0031] The first cover member 12 is provided at a position opposite the flange 11 when viewed from the encoder 20 (to the left of the encoder 20 in the plane of FIG. 3 ). In this embodiment, the first cover member 12 is made of aluminum (first metal) as a conductive material, but is not limited to this. A material with high thermal conductivity is particularly desirable as the material for the first cover member 12, and other than aluminum, aluminum alloys such as duralumin, copper, or alloys containing copper can be used. The first cover member 12 covers a portion of the encoder 20. In this example, the first cover member 12 covers the top of the encoder 20. The first cover member 12 is lid-shaped, but is not limited to this.

[0032] The first cover member 12 and the flange 11 may each be made of a conductive material. Examples of conductive materials that can be used include metals, carbon materials such as glassy carbon, and conductive resins, in addition to the materials described above. The first cover member 12 and the flange 11 may be made of the same material or different materials.

[0033] The first cover member 12 is fixed to the flange 11 by iron bolts 60. In this example, four bolts 60 are provided, but the number of bolts 60 is not limited to this. Each bolt 60 is threaded into a bolt hole 11b of the flange 11 via a first through hole 12a of the first cover member 12 and a second through hole 13b of the second cover member 13. The material of the bolts 60 is preferably conductive, and is not limited to iron; for example, aluminum, stainless steel, brass, etc. can be used.

[0034] The second cover member 13 is provided between the flange 11 and the first cover member 12. The second cover member 13 connects the flange 11 and the first cover member 12. The second cover member 13 is fixed to the first cover member 12 at one end 13e and to the flange 11 at the other end 13f. In this embodiment, the second cover member 13 is made of nylon resin (first resin), but is not limited to this. A material with low thermal conductivity is desirable for the second cover member 13, and polystyrene, etc., can be used in addition to nylon resin. The second cover member 13 covers a portion of the encoder 20. In this example, the second cover member 13 covers the side portion of the encoder 20. The second cover member 13 is cylindrical, but is not limited to this.

[0035] The second cover member 13 has a housing 13a for the connector 31. The housing 13a accommodates the connector 31 so that the external terminals 31a of the connector 31 are exposed. The housing 13a is integrally formed with the portions of the second cover member 13 other than the housing 13a. In this embodiment, the housing 13a is made of nylon resin (second resin), but this is not limited to this. A material with low thermal conductivity is desirable for the housing 13a, and polystyrene, etc., can be used in addition to nylon resin. Wiring 32 for transmitting detection signals from the encoder 20 is connected to the connector 31. The first resin and the second resin may be the same type of material or different types of materials.

[0036] Here, the thermal conductivity of the nylon resin second cover member 13 is lower than the thermal conductivity of the aluminum flange 11 and the thermal conductivity of the aluminum first cover member 12. Therefore, even if heat is generated in the main body 40, the heat is unlikely to be transferred to the first cover member 12 or the second cover member 13 via the flange 11. This prevents heat from being trapped in the housing space S, which will be described later, and prevents heat from being transferred from the main body 40 to the encoder 20.

[0037] 3, the flange 11, the first cover member 12, and the second cover member 13 define an accommodation space S in which the encoder 20 is accommodated. The accommodation space S is a sealed space.

[0038] The magnetic shield member 14 is fixed to the first cover member 12. In this embodiment, the magnetic shield member 14 is made of iron (second metal), but is not limited to this. A magnetic material is preferable for the magnetic shield member 14, and other materials such as nickel or stainless steel can be used as the material in addition to iron. The magnetic shield member 14 covers at least a portion of the encoder 20. In this example, the magnetic shield member 14 covers the top and side portions of the encoder 20. In this embodiment, the magnetic shield member 14 is cylindrical with a bottom, but is not limited to this. The magnetic shield member 14 does not contact the flange 11. In this example, there is a predetermined gap between the tip 14e of the magnetic shield member 14 and the flange 11.

[0039] The encoder 20 is an element that detects the rotational position and rotation speed of the shaft 41. In this embodiment, the encoder 20 is a battery-powered multi-rotation absolute encoder, but is not limited to this. The encoder 20 has a rotating plate 21 that is fixed to the shaft 41. The encoder 20 detects the rotational position and rotation speed of the shaft 41 by reading a predetermined pattern that the rotating plate 21 has.

[0040] The shaft 41 is a member extending in a direction along the rotation axis C of the rotor (the left-right direction on the plane of FIG. 3 ). The shaft 41 is fixed to the rotor and rotates together with the rotor. The shaft 41 is rotatably supported by bearings 50.

[0041] The present disclosure can be used for an encoder cover and a motor.

[0042] 1: Motor 10: Encoder cover 11: Flange 11a: Insertion hole 11b: Bolt hole 11c: Magnetic shield plate 12: First cover member 12a: First through hole 13: Second cover member 13a: Housing 13b: Second through hole 13e: One end 13f: Other end 14: Magnetic shield member 14e: Tip 20: Encoder 21: Rotating plate 31: Connector 31a: External terminal 32: Wiring 40: Main body 41: Shaft 42: Bracket 50: Bearing 60: Bolt S: Storage space

Claims

1. An encoder cover that covers an encoder for detecting the rotational position of a motor shaft, a flange for attaching the encoder, a first cover member provided on the side opposite to the flange with respect to the encoder and covering a part of the encoder, a second cover member that connects the flange and the first cover member and covers a part of the encoder, and comprising The encoder cover, wherein the thermal conductivity of the second cover member is smaller than the thermal conductivity of the flange and the thermal conductivity of the first cover member.

2. The encoder cover according to claim 1, wherein the first cover member and the flange are each made of a conductive material.

3. The encoder cover according to claim 1 or 2, wherein the first cover member is made of a first metal.

4. The encoder cover according to claim 1 or 2, wherein the second cover member is made of a first resin.

5. Further comprising a magnetic shield member fixed to the first cover member and covering at least a part of the encoder, The encoder cover according to claim 1 or 2, wherein the magnetic shield member is made of a second metal and does not contact the flange.

6. The encoder cover according to claim 1 or 2, wherein the first cover member is fixed to the flange by a conductive bolt.

7. The second cover member has a housing of a connector, The encoder cover according to claim 1 or 2, wherein the housing is made of a second resin.

8. The encoder cover according to claim 7, wherein a portion of the second cover member other than the housing and the housing are integrally formed.

9. The encoder cover according to claim 1 or 2, an encoder housed in the encoder cover, a main body having a shaft whose rotational position is detected by the encoder, and a motor comprising the same.