Actuators and Machines

Abstract

This actuator comprises: an electric motor; an accommodation part that accommodates the electric motor; a detection part that detects operation of the electric motor; and a fixing part that, at a position further radially outward than the detection part, fixes to a machine housing an end surface of the accommodation part which is on the opposite side from the output side of the electric motor.

Description

[Technical Field]

[0001] The present invention relates to an actuator, and more particularly to an actuator and a machine with improved heat dissipation. [Background technology]

[0002] In general, in an electric motor, heat generated by the windings (copper loss) and the core (iron loss) is transferred to the housing of the motor and then dissipated as radiation to the atmosphere or heat transfer to the housing of a machine such as a robot. However, when the size of the motor is smaller than the housing of the machine and the motor is placed inside the housing, radiation to the outside air is limited. On the other hand, when the heat transfer path to the housing of the machine is long or the cross-sectional area of ​​the heat transfer path is small, the heat transfer efficiency is poor and the heat dissipation performance of the motor is reduced. A reduction in the heat dissipation performance of the motor leads to a reduction in the continuous rated torque. The following documents are known as background art related to this application.

[0003] Patent document 1 describes a robot arm including a first link and a second link that is configured to release heat from the motor into the outside air by including a support part that supports the motor inside the first link and a rotation transmission mechanism that transmits the rotational force of the motor supported by the support part to the first link, and by arranging a heat transfer member between the motor and the first link, so that the heat generated by the motor is transferred to the first link.

[0004] Patent Document 2 describes a valve timing control device for an internal combustion engine, in which a flange portion of a motor housing and a casing of a control mechanism on the opposite side of the motor output side are fixed to a chain case of the engine body with bolts. It also describes that the casing is made of an aluminum alloy material with high heat dissipation properties.

[0005] Patent Document 3 describes an electric actuator in which a plurality of housing components are made of an aluminum alloy with high thermal conductivity.

[0006] Patent Document 4 describes that in an electric drive unit and an electric power steering device, in order to efficiently dissipate heat from the power supply circuit unit and the power conversion circuit unit to the outside, a power supply circuit side heat dissipation unit and a power conversion circuit side heat dissipation unit that transfer heat generated in at least the power supply circuit unit and the power conversion circuit unit to the motor housing are formed on the end face of the motor housing opposite the output part of the rotor shaft of the electric motor, and that the power conversion circuit side heat dissipation unit formed on the end face is formed closer to the electric motor than the sensor magnet of the rotation detection unit that constitutes the rotation detection unit fixed to the end opposite the output part of the rotor shaft. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-15146 [Patent Document 2] Japanese Patent Application Publication No. 2020-197188 [Patent Document 3] Japanese Patent Application Publication No. 2018-078742 [Patent Document 4] Japanese Patent Application Publication No. 2018-057055 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the problems of the prior art, an object of the present invention is to provide a technique for improving the heat dissipation of an actuator. [Means for solving the problem]

[0009] One aspect of the present disclosure is a motor, a housing that houses the motor, a detection unit that detects operation of the motor, and a fixing unit that fixes an end face of the housing that is radially outward of the detection unit and opposite to the output side of the motor to a housing of a machine. the accommodating portion includes an inner cylindrical body that accommodates the electric motor, an outer cylindrical body that surrounds the inner cylindrical body via a gap, and a plurality of ribs that connect the inner cylindrical body and the outer cylindrical body, and the fixing portion fixes the opposite end surface of the outer cylindrical body to a housing of the machine. An actuator is provided. Another aspect of the present disclosure provides a machine including the actuator described above. [Effects of the Invention]

[0010] According to one aspect and another aspect of the present disclosure, even if the radial size of the electric motor is designed to be smaller than the radial size of the housing of the machine, the fixing portion fixes the end face of the accommodation portion opposite the output side of the electric motor to the housing of the machine radially outward from the detection portion, so that heat generated by the electric motor can be directly dissipated from the accommodation portion to the housing of the machine. Furthermore, if the accommodation portion is exposed to the outside air, heat generated by the electric motor can be directly radiated from the accommodation portion to the outside air. Direct heat transfer to the housing and direct radiation to the outside air can improve the heat dissipation performance of the actuator, thereby improving the continuous rated torque of the electric motor. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a longitudinal sectional view of a machine according to a first embodiment; [Figure 2] FIG. 10 is a longitudinal sectional view of a machine according to a second embodiment. [Figure 3] FIG. [Figure 4] FIG. 10 is a rear view of a modified example of the actuator. [Figure 5] FIG. 10 is a longitudinal sectional view of a machine according to a third embodiment. [Figure 6] FIG. 10 is a longitudinal sectional view of a machine according to a fourth embodiment. [Figure 7] FIG. 1 is a longitudinal sectional view of a machine of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In each drawing, the same or similar components are assigned the same or similar reference numerals. Furthermore, the embodiments described below do not limit the technical scope of the invention described in the claims and the meaning of terms. It should be noted that in this specification, the term "front" means the output side or load side of the actuator, and the term "rear" means the side opposite to the output side or anti-load side of the actuator.

[0013] The configuration of the machine 1 of the first embodiment will be described in detail below. FIG. 1 is a longitudinal cross-sectional view of the machine 1 of the first embodiment. The machine 1 is a robot such as a single-axis robot, a multi-axis robot, a parallel-link robot, or a humanoid robot. Alternatively, in other embodiments, the machine 1 may be an industrial machine such as a machine tool, construction machine, agricultural machine, or conveyor, or another machine such as a vehicle or aircraft. The machine 1 of this embodiment is a multi-joint robot and includes multiple actuators 10 (not shown). Alternatively, in other embodiments, the machine 1 may be a single-joint robot and include only one actuator 10. The machine 1 includes a rear housing 2, an actuator 10 fixed to the rear housing 2, and a front housing 3 operated by the actuator 10.

[0014] The housings 2 and 3 are formed of various links such as the torso, arms, and wrists of an articulated robot. Alternatively, in other embodiments, the housings 2 and 3 may be formed of the housings of other machines such as industrial machinery, a vehicle body, or an aircraft body. The housings 2 and 3 are formed as hollow housings and are provided with through holes 2e and 3e, respectively, through which umbilical members (not shown) such as power lines, signal lines, and tubes pass.

[0015] The actuator 10 is an electromagnetic actuator. The actuator 10 includes an electric motor 20, a housing 30 that houses the electric motor 20, and a detection unit 40 that detects the operation of the electric motor 20. Because the radial size of the electric motor 20 is designed to be relatively small compared to the radial size of the rear housing 2, the actuator 10 includes a fixing unit 50 that fixes the rear end face 31 of the housing 30 to the outer surface 2a of the rear housing 2, radially outside the detection unit 40.

[0016] Furthermore, although not essential, the actuator 10 further includes a reducer 60 that reduces the rotational speed of the electric motor 20, a fixing portion 51 that fixes a support portion 63 of the reducer 60 to the front end face 32 of the accommodation portion 30, and a fixing portion 52 that fixes an output portion 62 of the reducer 60 to the front housing 3. Furthermore, although not essential, the actuator 10 may further include a braking portion 70 that brakes the operation of the electric motor 20.

[0017] The electric motor 20 is configured as an AC motor such as an induction motor or a synchronous motor. Alternatively, in other embodiments, the electric motor 20 may be configured as a DC motor. The electric motor 20 includes a stator 21 and a rotor 22. The stator 21 is fixed to the inner surface of the housing portion 30. The rotor 22 is supported rotatably around the axis X by a front reducer 60 and a rear bearing (not shown, but provided, for example, in the detection portion 40).

[0018] The stator 21 includes a stator core 21a formed by laminating electromagnetic steel sheets and a plurality of windings 21b wound around the stator core 21a. The rotor 22 includes a rotor core 22a formed of a squirrel-cage conductor or the like and a rotor shaft 22b to which the rotor core 22a is attached. The rotor shaft 22b includes a through-hole 22c through which a wire (not shown) passes, although this is not essential.

[0019] The housing 30 includes a case that houses the stator 21. Alternatively, in another embodiment, the housing 30 may include a front case and a rear case that are fixed to the front end face and the rear end face of the stator core 21a, respectively. The housing 30 is formed of a metal with a relatively high thermal conductivity (e.g., 100 to 400 W / mK), such as aluminum, copper, or an alloy thereof. Because the radial size of the electric motor 20 is designed to be smaller than the radial size of the rear housing 2, the radial size of the housing 30 is formed thicker than that of a typical housing.

[0020] Although not shown, the detection unit 40 includes an encoder that detects the rotational position, rotational speed, etc. of the rotor 22, and a case that houses the encoder. The encoder is an optical encoder. Alternatively, in other embodiments, the encoder may be a magnetic encoder or an electromagnetic induction encoder. The detection unit 40 is fixed to the rear end face 31 of the accommodating unit 30 via a brake unit 70. The detection unit 40 is also disposed in the through-hole 2e of the rear housing 2. The radial size of the detection unit 40 is designed to be smaller than the radial size of the accommodating unit 30.

[0021] The fixing portion 50 has a fastening structure including a female thread and a male thread. A plurality of fixing portions 50 are arranged at intervals in the circumferential direction on the rear end face 31 of the accommodation portion 30. The fixing portion 50 has a female thread formed on the rear end face 31 of the accommodation portion 30. Alternatively, in another embodiment, the fixing portion 50 may have a male thread formed on the rear end face 31 of the accommodation portion 30. A threaded through-hole is formed in the rear housing 2, and the male thread is inserted into the threaded through-hole and screwed into the female thread, whereby the fixing portion 50 fastens the rear end face 31 of the accommodation portion 30 to the outer surface 2a of the rear housing 2 radially outside the detection unit 40 (radial position R2 of the fixing portion 50 > radial position R1 of the detection unit 40). This fixes the actuator 10 to the outer surface 2a of the rear housing 2.

[0022] The reducer 60 is a wave gear reducer. Alternatively, in other embodiments, the reducer 60 may be another reducer such as a planetary gear reducer. The reducer 60 includes an input unit 61 that receives torque from the rotor shaft 22b of the electric motor 20, an output unit 62 that converts the input torque into torque according to a reduction ratio and outputs the torque, and a support unit 63 that rotatably supports the input unit 61 and the output unit 62. The support unit 63 is fixed to the front end face 32 of the accommodation unit 30, and the output unit 62 is fixed to the housing 3.

[0023] When the reducer 60 is a wave gear reducer, the input section 61 is a wave generator, the output section 62 is either a flexspline or a circular spline, and the support section 63 is the other of the flexspline or the circular spline. Alternatively, in another embodiment, when the reducer 60 is a planetary gear reducer, the input section 61 is a sun gear, the output section 62 is either a planetary gear or an internal gear, and the support section 63 is the other of the planetary gear or the internal gear.

[0024] The fixing portion 51 has a fastening structure including a female thread and a male thread. A plurality of fixing portions 51 are arranged at intervals in the circumferential direction of the front end face 32 of the accommodating portion 30. The fixing portion 51 has a female thread formed on the front end face 32 of the accommodating portion 30. Alternatively, in another embodiment, the fixing portion 51 may have a male thread formed on the front end face 32 of the accommodating portion 30. A threaded through hole is formed in the support portion 63 of the reducer 60, and the fixing portion 51 fastens the support portion 63 of the reducer 60 to the front end face 32 of the accommodating portion 30 by inserting the male screw into the threaded through hole and screwing the male screw into the female screw.

[0025] The fixing portion 52 has a fastening structure composed of a female screw and a male screw. A plurality of fixing portions 52 are arranged at intervals in the circumferential direction of the output portion 62. The fixing portion 52 has a female screw formed in the output portion 62. Alternatively, in another embodiment, the fixing portion 52 may have a male screw formed in the output portion 62. A threaded through-hole is formed in the front housing 3, and the fixing portion 52 fastens the output portion 62 of the reducer 60 to the front housing 3 by inserting the male screw into the threaded through-hole and screwing the male screw into the female screw. In this way, the actuator 10 is fixed to the outer surface 3a of the front housing 3.

[0026] Although not shown, the braking unit 70 includes a brake that brakes the rotor shaft 22b and a case that houses the brake. The brake is configured as an electromagnetic brake. Alternatively, in other embodiments, the brake may be configured as a brake of another type, including a hydraulic brake, a pneumatic brake, or the like. The braking unit 70 is directly fixed to the rear end face 31 of the housing 30. The braking unit 70 is also disposed in the through-hole 2e of the rear housing 2. The radial size of the braking unit 70 is designed to be smaller than the radial size of the housing 30.

[0027] The operation of the machine 1 of the first embodiment will be described in detail below. If the electric motor 20 is, for example, an induction motor, current is supplied sequentially to the multiple windings 21b with a phase shift. A rotating magnetic field is generated in the stator core 21a, an induced current is generated in the rotor core 22a, and the interaction of the current and the magnetic field generates torque in the rotor core 22a, causing the rotor shaft 22b to rotate. The torque of the rotor shaft 22b is input to the input unit 61 of the reducer 60, the input torque is converted into torque according to a reduction ratio, and the converted torque is output from the output unit 62. As a result, the actuator 10 rotates the front housing 3 relative to the rear housing 2.

[0028] The radial size of the electric motor 20 is designed to be smaller than the radial size of the rear housing 2, but the fixing part 50 is located radially outside the detecting part 40 (R2>R1) and the rear end face 31 of the accommodation part 30 is fixed to the rear housing 2. Therefore, the heat generated by the winding 21b (copper loss) and the heat generated by the stator core 21a (iron loss) are transferred to the accommodation part 30 as shown by the heat transfer path H1, and then transferred directly from the rear end face 31 of the accommodation part 30 to the rear housing 2 and dissipated. In other words, because the front of the actuator 10 is fixed to the front housing 3 via the gears of the reducer 60 or the like, the heat generated by the electric motor 20 is transferred to the rear housing 2 and dissipated.

[0029] Furthermore, because actuator 10 is fixed to the outer surface 2a of rear housing 2 and also to the outer surface 3a of front housing 3, accommodating section 30 is exposed to the outside air. As a result, heat generated by winding 21b (copper loss) and heat generated by stator core 21a (iron loss) is transferred to accommodating section 30 as shown by heat transfer path H2, and then directly radiated into the outside air for heat dissipation. In other words, heat generated by electric motor 20 is radiated into the outside air for heat dissipation. As described above, direct heat transfer to housing 2 and direct radiation into the outside air can improve the heat dissipation performance of actuator 10, thereby improving the continuous rated torque of electric motor 20.

[0030] The machine 1 of the second embodiment will be described in detail below. Please note that only parts that differ from the machine 1 of the first embodiment will be described below, and parts that are the same or similar will not be described. FIG. 2 is a longitudinal cross-sectional view of the machine 1 of the second embodiment, and FIG. 3 is a rear view of the actuator 10. The machine 1 of the second embodiment differs from the machine 1 of the first embodiment in that the housing 30 includes an inner cylindrical body 33 that houses the electric motor 20, an outer cylindrical body 34 that surrounds the inner cylindrical body 33 via a gap 36, and a plurality of ribs 35 that connect the inner cylindrical body 33 and the outer cylindrical body 34.

[0031] A plurality of ribs 35 are arranged at intervals around the circumferential direction of the accommodating portion 30. Gaps 36 are formed between the ribs 35. Because the ribs 35 extend straight in the radial direction from the inner cylindrical body 33 to the outer cylindrical body 34, the accommodating portion 30 has a simple structure and is easy to manufacture. The accommodating portion 30 having this shape is formed by casting, such as aluminum die casting. Even if the radial size of the electric motor 20 is designed to be smaller than the radial size of the housing 3 and the accommodating portion 30 is formed to be thicker than a typical accommodating portion, the gaps 36 formed in the accommodating portion 30 enable the weight of the actuator 10 to be reduced.

[0032] Furthermore, the heat generated by winding 21b (copper loss) and the heat generated by stator core 21a (iron loss) are transferred to multiple ribs 35 formed on housing 30, as shown by heat transfer path H1, and then directly transferred from rear end face 31 of housing 30 to rear housing 2 for dissipation. In other words, since the length of heat transfer path H1 in the second embodiment is approximately the same as the length of heat transfer path H1 in the first embodiment, machine 1 in the second embodiment can achieve approximately the same heat dissipation effect as machine 1 in the first embodiment while reducing the weight of actuator 10.

[0033] The machine 1 of the second embodiment also differs from the machine 1 of the first embodiment in that it includes an additional fixing portion 53 that fixes the rear end surface 31 of the storage unit 30 to the outer surface 2a of the rear housing 2. The fixing portion 53 has a fitting structure including a protrusion and a recess. That is, the fixing portion 53 includes a protrusion 2b formed on the rear housing 2 and a recess 37 formed on the rear end surface 31 of the storage unit 30. Alternatively, in other embodiments, the fixing portion 53 may include a protrusion formed on the rear end surface 31 of the storage unit 30 and a recess formed in the rear housing 2.

[0034] A plurality of recesses 37 and protrusions 2b are arranged at intervals in the circumferential direction of the rear end face 31 of the housing 30. Alternatively, in another embodiment, the recesses 37 and the protrusions 2b may be configured with a fitting structure (spigot structure) made of two cylindrical bodies. By fitting the protrusions 2b into the recesses 37, the fixing portion 53 fixes the rear end face 31 of the housing 30 to the outer surface 2a of the rear housing 2. As described above, since the fixing portions 50, 53 of the actuator 10 include both a fastening structure and a fitting structure, the actuator 10 can be easily positioned in the rear housing 2 and can also be easily fastened.

[0035] 4 is a rear view of a modified actuator 10. The modified actuator 10 differs from the above-described one in that, when viewed from the rear of the housing section 30, the multiple ribs 35 form a truss structure in the circumferential direction around the axis X of the actuator 10. In other words, two ribs 35 form an isosceles triangle with equal sides, the inner cylindrical body 33 forms the base of the isosceles triangle, and the outer cylindrical body 34 forms the apex of the isosceles triangle.

[0036] Alternatively, in another embodiment, the inner cylindrical body 33 may form the apex of an isosceles triangle, and the outer cylindrical body 34 may form the base of the isosceles triangle. As described above, the plurality of ribs 35 form a truss structure in the circumferential direction about the axis X of the actuator 10, whereby the housing 30 is less likely to deform when the rotor 22 rotates to transmit torque, and the electric motor 20 is less likely to be damaged while being lighter in weight.

[0037] The machine 1 of the third embodiment will be described in detail below. Note that only the differences from the machine 1 of the first embodiment will be described below, and the same or similar parts will not be described. FIG. 5 is a longitudinal cross-sectional view of the machine 1 of the third embodiment. The machine 1 of the third embodiment differs from the machine 1 of the first embodiment in that the rear housing 2 has, on its inner surface, a flange portion 2c that engages with the rear end surface 31 of the storage portion 30 and a cylindrical portion 2d that extends forward from the flange portion 2c. The storage portion 30 is fitted into the cylindrical portion 2d of the rear housing 2. The flange portion 2c extends inward of the housing 2. The cylindrical portion 2d may also be fitted into the support portion 63 of the reducer 60.

[0038] In other words, the machine 1 of the third embodiment differs from the machine 1 of the first embodiment in that it includes an additional fixing portion 54 that fixes the rear end surface 31 of the storage portion 30 to the flange portion 2c of the rear housing 2. The fixing portion 54 has a fitting structure including a protrusion and a recess. In other words, the fixing portion 54 includes a protrusion, which is the storage portion 30 (and the support portion 63), and a recess, which is the cylindrical portion 2d of the rear housing 2.

[0039] The fixing portion 54 can also be said to have a fitting structure (spigot structure) made up of two cylindrical bodies. By fitting the accommodation portion 30 into the cylindrical portion 2d of the rear housing 2, the fixing portion 54 fixes the rear end surface 31 of the accommodation portion 30 to the flange portion 2c formed on the inner surface of the rear housing 2. As described above, since the fixing portions 50, 54 of the actuator 10 include both a fastening structure and a fitting structure, the actuator 10 can be easily positioned in the rear housing 2 and can also be easily fastened to it.

[0040] Furthermore, it is preferable that the housing 30 (and the support portion 63) be in metallic contact with the cylindrical portion 2d of the rear housing 2. For example, it is preferable that the housing 30 (and the support portion 63) and the cylindrical portion 2d of the rear housing 2 be formed of a metal with a relatively high thermal conductivity (e.g., 100 to 400 W / mK), such as aluminum, copper, or an alloy thereof, and be in surface contact with each other. As a result, heat generated by the winding 21b (copper loss) and heat generated by the stator core 21a (iron loss) are transferred to the housing 30 as shown by heat transfer path H1, and then directly transferred from the housing 30 to the rear housing 2 for heat dissipation, and also transferred from the housing 30 to the rear housing 2 as shown by heat transfer path H2, and then directly radiated to the outside air for heat dissipation. In this way, direct heat transfer to the housing 2 and direct radiation to the outside air can improve the heat dissipation performance of the actuator 10, thereby improving the continuous rated torque of the electric motor 20.

[0041] In another embodiment, when the accommodation section 30 (and the support section 63) and the cylindrical section 2d of the rear housing 2 are not in complete surface contact with each other and there is a gap, a thermally conductive material (not shown) may be filled in the gap between the accommodation section 30 (and the support section 63) and the cylindrical section 2d of the rear housing 2. The thermally conductive material includes, for example, a thermally conductive resin in which thermally conductive fibers are interlinked in a matrix resin.

[0042] The matrix resin includes a heat-resistant resin such as a thermosetting resin, e.g., polyimide resin, silicone resin, epoxy resin, or phenolic resin, or a thermoplastic resin, e.g., polyphenylene sulfide resin, polycarbonate resin, polybutylene terephthalate resin, or polyacetal resin. The heat-conducting fiber includes aluminum nitride, magnesium oxide, boron nitride, alumina, anhydrous magnesium carbonate, silicon oxide, zinc oxide, or the like.

[0043] After the thermally conductive resin prepared as described above is applied to the outer surface of the accommodating section 30 (and the support section 63), the accommodating section 30 (and the support section 63) is fitted into the cylindrical section 2d of the rear housing 2, thereby filling the gap between the accommodating section 30 (and the support section 63) and the cylindrical section 2d of the rear housing 2 with the thermally conductive resin. Alternatively, in another embodiment, the thermally conductive resin may be injected into the gap between the accommodating section 30 (and the support section 63) and the cylindrical section 2d of the rear housing 2, thereby filling the gap between the accommodating section 30 (and the support section 63) and the cylindrical section 2d of the rear housing 2 with the thermally conductive resin. This makes it easier for heat generated by the electric motor 20 to be transferred from the accommodating section 30 (and the support section 63) to the cylindrical section 2d of the rear housing 2 via the thermally conductive resin.

[0044] The machine 1 of the fourth embodiment will be described below. Please note that only the parts that differ from the machine 1 of the first embodiment will be described below, and the same or similar parts will not be described. FIG. 6 is a longitudinal sectional view of the machine 1 of the fourth embodiment. The machine 1 of the fourth embodiment differs from the machine 1 of the first embodiment in that the actuator 10 does not include the reducer 60 and the braking unit 70. In other words, the actuator 10 is configured as a direct drive motor.

[0045] The rotor 22 of the electric motor 20 is supported rotatably about the axis X by a front bearing 80 (fixed to the housing 30, for example) and a rear bearing (not shown, but provided in the detection unit 40, for example). The rotor 22 further includes a rotor flange 22d in addition to a rotor core 22a and a rotor shaft 22b. The rotor flange 22d is fixed to the rotor shaft 22b and extends radially outward from the rotor shaft 22b.

[0046] The fixing portion 52 has a fastening structure composed of a female screw and a male screw. A plurality of fixing portions 52 are arranged at intervals around the rotor flange 22d. The fixing portion 52 has a female screw formed on the rotor flange 22d. Alternatively, in another embodiment, the fixing portion 52 may have a male screw formed on the rotor flange 22d. A threaded through-hole is formed in the front housing 3, and the fixing portion 52 fastens the rotor flange 22d to the front housing 3 by inserting the male screw into the threaded through-hole and screwing the male screw into the female screw. In this way, the actuator 10 is fixed to the outer surface 3a of the front housing 3.

[0047] The detection unit 40 is fixed directly to the rear end surface 31 of the accommodating unit 30. The detection unit 40 is also disposed in the through-hole 2e of the rear housing 2. The radial size of the detection unit 40 is designed to be smaller than the radial size of the accommodating unit 30. The fixing unit 50 fastens the rear end surface 31 of the accommodating unit 30 to the outer surface 2a of the rear housing 2, on the radial outside of the detection unit 40. In this way, the actuator 10 is fixed to the outer surface 2a of the rear housing 2.

[0048] The machine 1 of the fourth embodiment also differs from the machine 1 of the first embodiment in that it includes an additional fixing portion 55 that fixes the rear end surface 31 of the storage portion 30 to the outer surface 2a of the rear housing 2. The fixing portion 55 has a fitting structure including a protrusion and a recess. In other words, the fixing portion 55 includes a protrusion, which is the detection portion 40, and a recess, which is the through-hole 2e of the rear housing 2.

[0049] The fixing portion 55 can also be said to have a fitting structure (spigot structure) made up of two cylindrical bodies. By fitting the detection unit 40 into the through-hole 2e of the rear housing 2, the fixing portion 55 fixes the rear end surface 31 of the accommodating portion 30 to the flange portion 2c formed on the rear housing 2. As described above, since the fixing portions 50, 55 of the actuator 10 include both a fastening structure and a fitting structure, the actuator 10 can be easily positioned in the rear housing 2 and can also be easily fastened to it.

[0050] The following describes the machine 1 of the comparative example. Note that only the configurations different from the machine 1 of the first embodiment will be described below, and the same or similar configurations will not be described. FIG. 7 is a longitudinal cross-sectional view of the machine 1 of the comparative example. The machine 1 of the comparative example differs from the machine 1 of the first embodiment in that the annular flange 90 is fixed to the front end surface of the housing 30 by a fixing portion 58, and the rear end surface 92 of the annular flange 90 is fixed to the outer surface 2a of the rear housing 2 by a fixing portion 57. That is, in the machine 1 of the comparative example, the electric motor 20 is disposed inside the rear housing 2. Furthermore, in the machine 1 of the comparative example, the front end surface 91 of the annular flange 90 is fixed to the support portion 63 of the reducer 60 by a fixing portion 56.

[0051] As shown by heat transfer path H1, the heat generated by winding 21b (copper loss) and the heat generated by stator core 21a (iron loss) are transferred to housing 30, and then transferred from the front end face of housing 30 to rear housing 2 via annular flange 90, where they are dissipated. In other words, the length of heat transfer path H1 in the comparative example is longer than the length of heat transfer path H1 in the first to fourth embodiments, and therefore actuator 10 of the comparative example has a poorer heat dissipation effect than actuator 10 of the above-mentioned embodiments.

[0052] Furthermore, because the electric motor 20 is disposed inside the rear housing 2, the housing 30 is not exposed to the outside air. As a result, the heat generated by the winding 21b (copper loss) and the heat generated by the stator core 21a (iron loss) is transferred to the housing 30 as shown by the heat transfer path H2, and then radiated into the air inside the rear housing 2. This does not improve the heat dissipation performance of the actuator 10.

[0053] However, according to the machine 1 of the first to fourth embodiments, even if the radial size of the electric motor 20 is designed to be smaller than the radial size of the housing 2 of the machine 1, the fixing unit 50 fixes the end face 31 of the accommodation unit 30 opposite the output side of the electric motor 20 to the housing 2 of the machine 1 radially outward of the detection unit 40 (R2>R1). This allows the heat generated by the electric motor 20 to be directly dissipated from the accommodation unit 30 to the housing 2 of the machine 1. Furthermore, if the accommodation unit 30 is exposed to the outside air, the heat generated by the electric motor 20 can be directly radiated from the accommodation unit 30 to the outside air. Direct heat transfer to the housing 2 and direct radiation to the outside air can improve the heat dissipation performance of the actuator 10, and ultimately improve the continuous rated torque of the electric motor 20.

[0054] While various embodiments have been described herein, it should be recognized that the present invention is not limited to the above-described embodiments, but rather can be modified in various ways within the scope of the following claims. [Explanation of symbols]

[0055] 1 machine 2 Rear housing 2a Exterior 2b Convex part 2c Flange part 2d Cylindrical part 2e Through hole 3 Front housing 3a Exterior 3e Through hole 10 Actuator 20 Electric motor 21 Stator 21a stator core 21b Winding 22 rotor 22a rotor core 22b rotor shaft 22c through hole 22d rotor flange 30 Storage section 31 Rear end face 32 Front end face 33 Inner tubular body 34 Outer tubular body 35 Ribs 36 void 37 Recess 40 Detector 50~58 Fixed part 60 Reducer 61 Input section 62 Output section 63 Support part 70 Braking part 80 bearings 90 Annular flange 91 Front end face 92 Rear end face H1, H2 heat transfer path R1 Radial position of the detector R2 Radial position of fixing part X axis

Claims

1. An electric motor, a housing portion that houses the electric motor; a detection unit that detects the operation of the electric motor; a fixing portion that fixes an end face of the accommodating portion on the opposite side to the output side of the electric motor to a housing of a machine, the end face being radially outside the detecting portion, the accommodating portion includes an inner cylindrical body that accommodates the electric motor, an outer cylindrical body that surrounds the inner cylindrical body via a gap, and a plurality of ribs that connect the inner cylindrical body and the outer cylindrical body, the fixing portion fixes the opposite end surface of the outer cylindrical body to a housing of the machine; Actuator.

2. 2. The actuator according to claim 1, wherein the plurality of ribs form a structure in which isosceles triangles, with two adjacent ribs having equal sides in the circumferential direction around an axis of the actuator, are arranged in the circumferential direction.

3. The actuator according to claim 1 or 2, wherein the housing is fitted into a cylindrical portion of the housing.

4. The actuator according to claim 1 , wherein the housing portion is in metal contact with the cylindrical portion of the housing.

5. The actuator according to claim 1 , further comprising a thermally conductive material filled in a gap between the accommodation portion and the cylindrical portion of the housing.

6. The actuator according to claim 1 , wherein the fixing portion includes both a fastening structure and a fitting structure.

7. The actuator according to claim 1 , wherein the housing is exposed to the outside air.

8. The actuator according to claim 1 , further comprising a fixing portion that fixes a reducer to an end surface of the housing portion on an output side of the electric motor.

9. A machine comprising an actuator according to any one of claims 1 to 8.

10. The machine of claim 9 , wherein the actuator is fixed to an exterior surface of the housing.

11. The machine of claim 9 , wherein the actuator fits into a cylindrical portion of the housing.

12. The machine of claim 9 , wherein the machine comprises a robot.

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