Electric motor

Abstract

An electric motor according to the present disclosure comprises: a cylindrical stator; a rotor disposed inside the stator; a shaft on which the rotor is provided so as to be integrally rotatable; a first support member that rotatably supports one end side in the axial direction of the shaft; a second support member that rotatably supports the other end side in the axial direction of the shaft; a housing in which the first support member and the second support member are provided so as to be capable of moving in the axial direction of the shaft, and in which the shaft is provided so as to be capable of rotating via the first support member and the second support member; a first elastic body that biases the shaft toward the other end side in the axial direction of the shaft via the first support member; a second elastic body that biases the shaft toward the one end side in the axial direction of the shaft via the second support member, the second elastic body having a greater biasing force than the first elastic body; and a restricting member that restricts the shaft from moving toward the one end side in the axial direction of the shaft due to the second elastic body in a state in which the shaft is biased toward the one end side in the axial direction of the shaft by the second elastic body against the biasing force of the first elastic body.

Description

electric motor

[0001] The present disclosure relates to electric motors.

[0002] Conventionally, an electric motor and a rotating device driven by power provided by the electric motor are connected by attaching a shaft of the rotating device to the shaft of the electric motor so that the shaft of the rotating device can rotate integrally with the motor. The shaft of the rotating device is attached to the shaft of the electric motor via a joint so that the shaft of the rotating device can rotate integrally with the motor. Because the electric motor and the rotating device are connected in this way, the rotating device can be driven by rotating the shaft of the electric motor.

[0003] The heat generated by the rotating device while it is running can cause the shaft of the rotating device to expand and contract in the axial direction. The expansion and contraction of the shaft of the rotating device is absorbed by a joint provided between the shaft of the electric motor and the shaft of the rotating device. Because the expansion and contraction of the shaft of the rotating device is absorbed by the joint, the expansion and contraction of the shaft of the rotating device is not transmitted to the shaft of the electric motor. Therefore, the joint provided between the shaft of the electric motor and the shaft of the rotating device protects the motor from loads, preventing early damage to the motor.

[0004] When using the above-mentioned coupling, it is necessary to provide a space between the electric motor and the rotating equipment to accommodate the coupling. Providing a coupling between the electric motor and the rotating equipment increases the overall length of the rotating parts, lowering the critical speed of the electric motor shaft. This makes it impossible to increase the rotational speed of the electric motor shaft. Using the above-mentioned coupling increases the number of parts required by the coupling, resulting in higher costs.

[0005] In order to prevent damage to the electric motor, it has been proposed to provide the electric motor with a member having elastic force instead of the above-mentioned coupling. In an electric motor that provides power to a rotating device, one axial end of a shaft is provided in a housing via a first bearing, and the other axial end of the shaft is provided in the housing via a second bearing, so that the shaft is rotatably supported in the housing. The first bearing and the second bearing are provided in the housing so as to be movable in the axial direction of the shaft. The first bearing is biased toward the other axial end of the shaft by a first preload member, and the second bearing is biased toward one axial end of the shaft by a second preload member.

[0006] When connecting a rotating device to an electric motor having such a configuration, the shaft of the rotating device is attached to the shaft with the shaft biased toward one end in the axial direction against the biasing force of the first preload member or the shaft biased toward the other end in the axial direction against the biasing force of the second preload member. When the rotating device is connected to the electric motor in this manner, if the shaft thermally expands in the axial direction due to heat generated by the electric motor while it is running, or if the shaft vibrates in the axial direction while it is running, the first preload member and the second preload member may not be able to sufficiently absorb the thermal expansion or vibration of the shaft. In other words, the electric motor having the above configuration cannot reliably protect the electric motor from the load, which may result in early damage to the electric motor.

[0007] Japanese Patent Application Laid-Open No. 2002-339962

[0008] In order to solve the above-mentioned problems, there is a demand for an electric motor that can reliably prevent early damage while reducing the number of parts and increasing the rotational speed.

[0009] The electric motor of the present disclosure comprises a cylindrical stator, a rotor disposed inside the stator, a shaft with which the rotor is rotatable integrally, a first support member rotatably supporting one axial end of the shaft, a second support member rotatably supporting the other axial end of the shaft, a housing in which the first support member and the second support member are movably disposed in the axial direction of the shaft and the shaft is rotatably disposed via the first support member and the second support member, a first elastic body that urges the shaft toward the other axial end of the shaft via the first support member, a second elastic body that has a greater urging force than the first elastic body and urges the shaft toward the one axial end of the shaft via the second support member, and a regulating member that regulates the shaft from moving toward the one axial end of the shaft by the second elastic body when the shaft is urged toward the one axial end of the shaft by the second elastic body against the urging force of the first elastic body.

[0010] 1 is a schematic vertical cross-sectional view showing an electric motor according to an embodiment of the present invention;

[0011] An electric motor according to one aspect of the present disclosure will be described below with reference to the drawings. An electric motor 1 according to this embodiment will be described with reference to FIG. 1 . The electric motor 1 is a motor used in a machine tool such as a machining center. The electric motor 1 includes a stator 2, a rotor 3, a shaft 4, a first support member 5, a second support member 6, a housing 7, a sleeve member 8, a restricting member 9, a first elastic body 10, and a second elastic body 11. Hereinafter, the axial direction J1 is defined as the front-rear direction. Hereinafter, one end side of the axial direction J1 (the left side in FIG. 1 ) is defined as the front side, and the other end side of the axial direction J1 (the right side in FIG. 1 ) is defined as the rear side.

[0012] The stator 2 is cylindrical and includes a stator core 12 and coils 13. The stator core 12 is cylindrical with both ends open in the axial direction J1 and is made of a magnetic material. Typically, the stator core 12 has a structure including a plurality of electromagnetic steel plates 14. The plurality of electromagnetic steel plates 14 are stacked in the axial direction J1. The stator core 12 has a plurality of teeth (not shown) that protrude radially inward from its inner peripheral surface. Each of the plurality of teeth extends along the axial direction J1 of the stator core 12. The plurality of teeth are arranged side by side in the circumferential direction of the stator core 12.

[0013] A coil 13 is attached to each of the multiple teeth. When attached to the stator core 12, the coil 13 protrudes forward from the front end surface of the stator core 12 and protrudes rearward from the rear end surface of the stator core 12. The coil 13 has coil ends 15 that protrude outward in the axial direction J1 from the end surface of the stator core 12 in the axial direction J1.

[0014] The rotor 3 is cylindrical and includes a rotor core 16, a plurality of magnets (not shown), and a pair of end plates 17, 17. The rotor core 16 is cylindrical with both ends open in the axial direction J1 and made of a magnetic material. Typically, the rotor core 16 has a structure including a plurality of electromagnetic steel plates 18. The plurality of electromagnetic steel plates 18 are stacked in the axial direction J1. A plurality of magnets are provided in the rotor core 16. The rotor core 16 has a plurality of groove-shaped accommodating portions (not shown) that open radially outward or hole-shaped accommodating portions that penetrate in the axial direction J1. Magnets are respectively accommodated in the plurality of accommodating portions. The pair of end plates 17, 17 are disposed on both ends of the rotor core 16 in the axial direction J1. In this embodiment, the pair of end plates 17, 17 are disk-shaped. The disk-shaped end plate 17 has a circular insertion hole 19 that penetrates in the axial direction J1 at its center.

[0015] As described above, with multiple magnets disposed in the housing, the rotor core 16 is fixed between a pair of end plates 17, 17. Typically, the rotor core 16 is fixed between the pair of end plates 17, 17 by fixing members such as bolts, with the rear plate surface of the front end plate 17 abutting the front end surface of the rotor core 16 and the front plate surface of the rear end plate 17 abutting the rear end surface of the rotor core 16. In this way, the pair of end plates 17, 17 are provided at both the front and rear ends of the rotor core 16. The rotor 3 configured in this manner is disposed inside the stator 2. When the rotor 3 is disposed inside the stator 2, the axial direction J1 of the rotor 3 is aligned with the axial direction J1 of the stator 2.

[0016] The shaft 4 is, for example, columnar and extends in the axial direction J1. The length of the shaft 4 in the axial direction J1 is longer than the length of the rotor 3 in the axial direction J1. The rotor 3 is provided to be rotatable integrally with the shaft 4. Specifically, with the shaft 4 passing through the inner hole 20 of the rotor core 16 and the insertion holes 19, 19 of the pair of end plates 17, 17, the rotor core 16 is fixed to the shaft 4 so as to be rotatable integrally with the shaft 4. With the rotor 3 provided to be rotatable integrally with the shaft 4, the shaft 4 protrudes forward and rearward from the rotor 3. An encoder 21 that detects the rotational position or rotation speed of the shaft 4 is provided at the rear end of the shaft 4.

[0017] In this embodiment, the first support member 5 is a bearing. Typically, the first support member 5 is a rolling bearing having a conventionally known configuration. When the first support member 5 is a rolling bearing, the first support member 5 is configured such that a large number of rolling elements 24 are held between a cylindrical inner ring 22 and a cylindrical outer ring 23 that are concentrically arranged. As shown in FIG. 1 , the first support member 5 is disposed on the front side of the shaft 4. The front side of the shaft 4 is held by the inner ring 22 of the first support member 5. In this case, the outer peripheral surface of the front side of the shaft 4 is fixed to the inner ring 22 of the first support member 5. In this way, the first support member 5 rotatably holds one end side of the shaft 4 in the axial direction J1.

[0018] In this embodiment, the second support member 6 is a bearing. Typically, the second support member 6 is a rolling bearing having a conventionally known configuration. When the second support member 6 is a rolling bearing, the second support member 6 is configured such that a large number of rolling elements 27 are held between a cylindrical inner ring 25 and a cylindrical outer ring 26 that are concentrically arranged. As shown in FIG. 1 , the second support member 6 is disposed on the rear side of the shaft 4. The rear side of the shaft 4 is held by the inner ring 25 of the second support member 6. In this case, the outer peripheral surface of the rear side of the shaft 4 is fixed to the inner ring 25 of the second support member 6. In this way, the second support member 6 rotatably holds the other end side of the shaft 4 in the axial direction J1.

[0019] The housing 7 has a front housing 28 and a rear housing 29. The front housing 28 is disposed in front of the stator 2, and the rear housing 29 is disposed behind the stator 2.

[0020] The front housing 28 has a cylindrical shape that opens rearward. A through-hole 31 that penetrates in the axial direction J1 is formed in a front wall 30 of the front housing 28. A cylindrical support portion 32 that supports the first support member 5 is provided in the front wall 30 of the front housing 28. The support portion 32 protrudes rearward from the front wall 30 of the front housing 28. The axial direction J1 of the support portion 32 is aligned with the axial direction J1 of the front housing 28. The inner diameter of the support portion 32 is larger than the diameter of the through-hole 31 in the front wall 30 of the front housing 28. Therefore, when the support portion 32 is provided in the front housing 28, the inner edge of the front wall 30 of the front housing 28 extends further inward than the support portion 32. The outer diameter of the support portion 32 is smaller than the inner diameter of the peripheral side wall 33 of the front housing 28. Therefore, when the support portion 32 is provided on the front housing 28 , a cylindrical gap 34 is formed between the support portion 32 and the peripheral side wall 33 of the front housing 28 .

[0021] The front housing 28 is fixed to the stator 2. Specifically, the rear end of the front housing 28 is fixed to the front end surface of the stator core 12. With the front housing 28 fixed to the stator 2, the front coil end 15 is positioned in a cylindrical gap 34.

[0022] The rear housing 29 is cylindrical and has open ends in the front-rear direction. The rear housing 29 is fixed to the stator 2. Specifically, the front end of the rear housing 29 is fixed to the rear end surface of the stator core 12.

[0023] A support piece 35 that supports the second support member 6 is disposed inside the rear housing 29. The support piece 35 is cylindrical with both ends open in the front-rear direction. The outer peripheral surface of the support piece 35 is fixed to the inner peripheral surface of the rear housing 29, thereby providing the support piece 35 within the rear housing 29. An annular flange 36 is provided at the rear end of the support piece 35. The flange 36 extends radially inward from the rear end of the support piece 35. The rear opening of the rear housing 29 is closed by a disk-shaped cover material 37. The outer edge of the cover material 37 is fixed to the rear end of the rear housing 29, providing the cover material 37 with a hole 38 that penetrates in the front-rear direction in the center.

[0024] The sleeve member 8 is cylindrical with both ends in the front-rear direction open. An annular flange 39 is provided at the front end of the sleeve member 8. The flange 39 extends radially inward from the front end of the sleeve member 8. The sleeve member 8 is provided in the front housing 28. Specifically, the sleeve member 8 is inserted into the support portion 32 of the front housing 28 with the outer circumferential surface of the sleeve member 8 in contact with the inner circumferential surface of the support portion 32. When the sleeve member 8 is inserted into the support portion 32, the sleeve member 8 is movable in the front-rear direction relative to the support portion 32. When the sleeve member 8 is inserted into the support portion 32, the flange 39 of the sleeve member 8 is located forward. In this manner, the sleeve member 8 is provided in the housing 7 so as to be movable in the axial direction J1 of the shaft 4.

[0025] The restricting member 9 restricts movement of the shaft 4 in the axial direction J1. The restricting member 9 is cylindrical with both ends open in the front-rear direction. An annular flange 40 is provided at the front end of the restricting member 9. The flange 40 extends radially outward from the front end of the restricting member 9. The restricting member 9 is provided on the housing 7. Specifically, the outer peripheral surface of the flange 40 of the restricting member 9 is fixed to the inner peripheral surface of the through-hole 31 of the front housing 28, thereby fixing the restricting member 9 to the front housing 28. When the restricting member 9 is provided on the front housing 28, a peripheral side wall 41 of the restricting member 9 protrudes rearward from the flange 40. Here, the restricting member 9 and the housing 7 are separate bodies, but they may also be formed integrally.

[0026] The front housing 28, on which the restricting member 9 and the sleeve member 8 are provided, is provided with a first support member 5. On the other hand, the rear housing 29, on which the support piece 35 is provided, is provided with a second support member 6.

[0027] 1 , the first support member 5 is provided to the sleeve member 8 by holding the outer ring 23 of the first support member 5 on the inner surface of the circumferential side wall 42 of the sleeve member 8. The outer ring 23 of the first support member 5 is fixed to the circumferential side wall 42 of the sleeve member 8. Therefore, the first support member 5 is provided to the sleeve member 8 so as to be immovable in the axial direction J1 of the shaft 4. The sleeve member 8 with which the first support member 5 is integrally provided is movable in the front-rear direction relative to the support portion 32 of the front housing 28, as described above. Therefore, the first support member 5 is provided to the housing 7 so as to be movable in the axial direction J1 of the shaft 4.

[0028] 1 , the outer ring 26 of the second support member 6 is held on the inner circumferential surface of the support piece 35, whereby the second support member 6 is provided to the support piece 35 of the rear housing 29. The second support member 6 is held on the inner circumferential surface of the support piece 35 so as to be movable in the axial direction J1 of the shaft 4. Therefore, the second support member 6 is provided to the housing 7 via the support piece 35 so as to be movable in the axial direction J1 of the shaft 4.

[0029] As described above, the front side of the shaft 4 is held by the inner ring 22 of the first support member 5, and the rear side of the shaft 4 is held by the inner ring 25 of the second support member 6. Therefore, the shaft 4 is rotatably and movably mounted in the housing 7 via the first support member 5 and the second support member 6. When the shaft 4 is mounted in the housing 7, the front side of the shaft 4 passes through the sleeve member 8 and the restricting member 9, and the rear side of the shaft 4 passes through the support piece 35 and the through-hole 38 of the cover material 37. When the shaft 4 is mounted in the housing 7, a seal material 43 is provided between the shaft 4 and the front housing 28 to prevent foreign matter from entering the housing 7.

[0030] The shaft 4 provided in the housing 7 is biased rearward by a first elastic body 10 having a biasing force. The first elastic body 10 is held between an annular portion formed by the inner edge of the front wall 30 of the front housing 28 and the flange 40 of the restricting member 9, and the flange 39 of the sleeve member 8. Therefore, the first elastic body 10 biases the shaft 4 toward the other end in the axial direction J1 via the sleeve member 8 and the first support member 5. The shaft 4 provided in the housing 7 is biased forward by a second elastic body 11 having a biasing force. The second elastic body 11 is held between the flange 36 of the support piece 35 and the outer ring 26 of the second support member 6. Therefore, the second elastic body 11 biases the shaft 4 toward one end in the axial direction J1 via the second support member 6. Note that the first elastic body 10 and the second elastic body 11 may have any configuration as long as they have a biasing force, and may be, for example, a spring.

[0031] The biasing force of the second elastic body 11 is greater than the biasing force of the first elastic body 10. Therefore, the shaft 4 is biased forward by the second elastic body 11 against the biasing force of the first elastic body 10. With the shaft 4 biased forward in this manner, the first support member 5 is in contact with the restricting member 9 fixed to the front housing 28. In the illustrated example, the outer ring 23 of the first support member 5 abuts against the rear end surface of the restricting member 9. Therefore, with the shaft 4 biased toward one end in the axial direction J1 by the second elastic body 11 against the biasing force of the first elastic body 10, the restricting member 9 can restrict the shaft 4 from moving toward one end in the axial direction J1 by the second elastic body 11.

[0032] In the case of the electric motor 1 of this embodiment, the biasing force F1 of the second elastic body 11 is greater than the biasing force F1' of the first elastic body 10, so the first support member 5 is pressed against and in contact with the restricting member 9. Therefore, according to the electric motor 1 of this embodiment, the position of the shaft 4 in the axial direction J1 can be determined.

[0033] A drive unit of a machine tool is connected to the front end of the shaft 4 of the electric motor 1. This allows the machine tool to be operated by driving the electric motor 1. During operation of the machine tool, a force F2 is applied to the shaft 4 of the electric motor 1 from the machine tool. The force F2 acts on the shaft 4 in a direction that pushes the shaft 4 rearward. When the force F2 is smaller than the biasing force F1 of the second elastic body 11, the first support member 5 is in contact with the restricting member 9. When the force F2 is larger than the biasing force F1 of the second elastic body 11, even if the shaft 4 and the inner ring 22 of the first support member 5 move to the other side in the axial direction J1, the outer ring 23 of the first support member 5 also moves. Therefore, the electric motor 1 of this embodiment can prevent the preload of the first support member 5 from being released.

[0034] In the case of the electric motor 1 of this embodiment, a sleeve member 8 is provided between the front housing 28 and the first support member 5. Therefore, according to the electric motor 1 of this embodiment, the gap between the front housing 28 and the first support member 5 can be filled with the sleeve member 8, so that a common first support member 5 can be used for multiple types of housings 7 having different gaps from the first support member 5.

[0035] According to the present embodiment described above, in a state in which the shaft 4 is urged toward one end in the axial direction J1 by the second elastic body 11 against the urging force of the first elastic body 10, the shaft 4 can be restricted from moving toward one end in the axial direction J1 by the second elastic body 11. Therefore, it is possible to provide an electric motor 1 that can reliably prevent early breakage while reducing the number of parts and improving rotational speed.

[0036] Although the present disclosure has been described in detail, the present disclosure is not limited to the above-described embodiments. Various additions, substitutions, modifications, partial deletions, etc. are possible within the scope of the gist of the present disclosure, or within the scope of the gist of the present disclosure derived from the content of the claims and their equivalents. In the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0037] For example, the configuration of the restricting member 9 may be the configuration shown in Fig. 2. Note that components having the same reference numerals as those in the above embodiment have the same functions, and therefore, the description thereof may be omitted below.

[0038] In the electric motor 1a of this modified example, the inner diameter of the cylindrical support portion 32 is the same as the diameter of the through hole 31 of the front housing 28. Therefore, the inner edge portion of the front wall 30 of the front housing 28 does not extend radially inward from the support portion 32. In other words, the front housing 28 has a large through hole formed by the through hole 31 of the front wall 30 and the inner hole of the support portion 32.

[0039] The restricting member 9 is cylindrical with both ends open in the front-rear direction. An annular flange 40 is provided at the front end of the restricting member 9. The flange 40 extends radially inward from the front end of the restricting member 9. The restricting member 9 is provided to the housing 7. Specifically, the outer peripheral surface of a peripheral wall 41 of the restricting member 9 is fixed to the inner peripheral surface of the front end of the large through hole in the front housing 28, thereby fixing the restricting member 9 to the front housing 28. When the restricting member 9 is provided to the front housing 28, the peripheral wall 41 of the restricting member 9 protrudes rearward from the flange 40. Here, the restricting member 9 and the housing 7 are separate bodies, but they may also be formed integrally.

[0040] The sleeve member 8 is pressed against and contacts the rear end of the peripheral side wall 41 of the regulating member 9 fixed to the housing 7 by the second elastic body 11. When the sleeve member 8 is in contact with the regulating member 9, a gap is formed between the flange 40 of the regulating member 9 and the flange 39 of the sleeve member 8. The first elastic body 10 is held between the flange 40 of the regulating member 9 and the flange 39 of the sleeve member 8.

[0041] In the above embodiment and modified example, the first support member 5 is provided to the housing 7 via the sleeve member 8, but it may also be provided directly to the housing 7. That is, in the electric motors 1 and 1a, the sleeve member 8 may be omitted. In this case, the first support member 5 is provided to the housing 7 so as to be movable in the axial direction J1 of the shaft 4.

[0042] In the above embodiment and modified example, the restricting member 9 is provided on the front housing 28, but it may be provided on the rear housing 29. In a configuration in which the restricting member 9 is provided on the rear housing 29, the biasing force F1' of the first elastic body 10 is greater than the biasing force F1 of the second elastic body 11. This configuration is used when the force F2 applied from the machine tool to the shaft 4 of the electric motor 1, 1a acts in a direction that pulls the shaft 4 forward.

[0043] The following supplementary note is further disclosed regarding the above embodiment. (Supplementary note 1) The electric motor (1) includes a cylindrical stator (2), a rotor (3) disposed inside the stator (2), a shaft (4) on which the rotor (3) is integrally rotatably mounted, a first support member (5) rotatably supporting one end of the shaft (4) in the axial direction (J1), a second support member (6) rotatably supporting the other end of the shaft (4) in the axial direction (J1), a housing (7) in which the first support member (5) and the second support member (6) are movably mounted in the axial direction (J1) of the shaft (4), and the shaft (4) is rotatably mounted via the first support member (5) and the second support member (6), and a first elastic body (10) that urges the shaft (4) toward the other end in the axial direction (J1) of the shaft (4) via the second support member (6); a second elastic body (11) that has a urging force greater than that of the first elastic body (10) and urges the shaft (4) toward one end in the axial direction (J1) of the shaft (4) via the second support member (6); and a regulating member (9) that regulates the shaft (4) from moving toward one end in the axial direction (J1) of the shaft (4) by the second elastic body (11) in a state in which the shaft (4) is urged toward one end in the axial direction (J1) of the shaft (4) by the second elastic body (11) against the urging force of the first elastic body (10). (Appendix 2) In Appendix 1, the electric motor (1) preferably further comprises a sleeve member (8) provided in the housing (7) so as to be movable in the axial direction (J1) of the shaft (4), the first support member (5) being fixed to the sleeve member (8) so as not to be movable in the axial direction (J1) of the shaft (4), and the first elastic body (10) biasing the shaft (4) towards the other end in the axial direction (J1) of the shaft (4) via the sleeve member (8) and the first support member (5).

[0044] REFERENCE SIGNS LIST 1 electric motor 2 stator 3 rotor 4 shaft 5 first support member 6 second support member 7 housing 8 sleeve member 9 restricting member 10 first elastic body 11 second elastic body

Claims

1. An electric motor comprising: a cylindrical stator; a rotor disposed inside the stator; a shaft with which the rotor is mounted so as to rotate integrally; a first support member rotatably supporting one axial end of the shaft; a second support member rotatably supporting the other axial end of the shaft; a housing in which the first support member and the second support member are mounted so as to be movable in the axial direction of the shaft, and the shaft is mounted so as to be rotatable via the first support member and the second support member; a first elastic body that urges the shaft towards the other axial end of the shaft via the first support member; a second elastic body that has a greater urging force than the first elastic body and urges the shaft towards the one axial end of the shaft via the second support member; and a restricting member that restricts the shaft from moving towards the one axial end of the shaft by the second elastic body in a state in which the shaft is urged towards the one axial end of the shaft by the second elastic body against the urging force of the first elastic body.

2. An electric motor as described in claim 1, further comprising a sleeve member that is provided in the housing and is movable in the axial direction of the shaft, the first support member is fixed to the sleeve member so as to be immovable in the axial direction of the shaft, and the first elastic body biases the shaft towards the other end in the axial direction of the shaft via the sleeve member and the first support member.

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