JP2015080305A - Electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric motor in which interference of the key of a rotor and the keyway of a stator is prevented at the time of shrink-fitting, while preventing occurrence of detection error of the rotation angle of the rotor.SOLUTION: An electric motor 1 has a rotor 4 provided with a key 4a projecting radially inward, a shaft 5 provided with a keyway 5b fitting to the key 4a of the rotor 4, and a rotation angle detection sensor 9 for detecting the rotation angle of the rotor 4 from the relative positional relationship of the rotor 4 and a stator 5. The rotor 4 and shaft 5 are shrink-fitted. The key 4a and keyway 5b become narrower toward the center side of the shaft 5.

Description

  The present invention relates to an electric motor having means for detecting a rotation angle of a rotor from a relative positional relationship between the rotor and a stator.

  Patent Document 1 discloses a relative positional relationship between a rotor provided with a key protruding inward in the radial direction, a shaft provided with a key groove to be fitted to the key of the rotor, and the rotor and the stator. And a means for detecting the rotation angle of the rotor. The rotor and the shaft are, for example, shrink fitted. Fig.5 (a) is sectional drawing of the direction orthogonal to the axial direction of a rotor and a shaft in the conventional electric motor. Each of the key 100a of the rotor 100 and the key groove 101b of the shaft 101 has a U-shaped (rectangular) cross-sectional shape.

JP-A-11-289729

  In the conventional electric motor, as shown in FIG. 5B, when the rotor 100 is shrink fitted on the shaft 101, when the rotor 100 is thermally expanded, the expanded key 100a and the key groove 101b interfere with each other, There has been a problem that the rotor 100 cannot be shrink-fitted onto the shaft 101.

  FIG. 6A is a cross-sectional view in a direction orthogonal to the axial direction of the rotor and the shaft in another conventional electric motor. The width of the key groove 103 b of the shaft 103 is wider than the width of the key 102 a of the rotor 102. For this reason, as shown in FIG. 6B, when the rotor 102 is shrink-fitted on the shaft 103, even if the rotor 102 is thermally expanded, the expanded key 102a and the key groove 103b do not interfere with each other. The rotor 102 can be shrink fitted on the shaft 103. However, in this case, if the rotor 102 is cooled and contracted after the rotor 102 is shrink fitted on the shaft 103, a gap is formed between the key 102a and the key groove 103b. Due to this gap, the position of the rotor 102 with respect to the shaft 103 is displaced, which causes a problem that a detection error of the rotation angle of the rotor 102 occurs.

  The present invention has been made in view of the above circumstances, and prevents the rotor key and the keyway of the stator from interfering with each other during shrink fitting, and prevents the detection error of the rotation angle of the rotor from occurring. It is to provide an electric motor that can be used.

  The present invention relates to an electric motor having means for detecting the rotation angle of the rotor from the relative positional relationship between the rotor and the stator. The electric motor includes the rotor provided with a key protruding inward in the radial direction, and a shaft provided with a key groove to be fitted to the key of the rotor. The rotor and the shaft And the key and the key groove are narrower toward the center side of the shaft.

  In the present invention, the width of each of the rotor key and the shaft keyway becomes narrower toward the center of the shaft. That is, the width of the keyway of the shaft becomes wider as the distance from the center side of the shaft increases. For this reason, even if the rotor (key) is thermally expanded, the key moves outward in the radial direction, which is wider than the fitting position of the key groove, so that the key and the key groove interfere with each other. Can be prevented. In addition, since the key and the key groove are fitted, the gap between the key and the key groove disappears when the rotor is cooled and contracted after the rotor is shrink fitted on the shaft. As a result, displacement of the rotor relative to the shaft is prevented, so that it is possible to prevent occurrence of a detection error of the rotation angle of the rotor.

It is an axial sectional view of the electric motor concerning the embodiment of the present invention. It is sectional drawing of the direction orthogonal to the axial direction of the rotor and shaft which concern on 1st Embodiment of this invention. It is a figure for demonstrating the process of shrink-fitting a rotor to a shaft. (A) is sectional drawing of the direction orthogonal to the axial direction of the rotor and shaft which concern on 2nd Embodiment of this invention. (B) is a figure for demonstrating the process of shrink-fitting a rotor to a shaft. (A) is sectional drawing of the direction orthogonal to the axial direction of a rotor and a shaft in the conventional electric motor. (B) is a figure for demonstrating the process of shrink-fitting a rotor to a shaft. (A) is sectional drawing of the direction orthogonal to the axial direction of a rotor and a shaft in another conventional electric motor. (B) is a figure for demonstrating the process of shrink-fitting a rotor to a shaft.

(First embodiment)
Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The electric motor 1 which concerns on 1st Embodiment is an electric motor used for apparatuses, such as a construction machine. As shown in FIGS. 1 and 2, the electric motor 1 includes a housing 2, a stator 3, a rotor 4, a shaft 5, a radial ball bearing 6, a rotating unit 7, a thrust ball bearing 8, and a rotation angle detection sensor 9. ing. In FIG. 1, only the casing 2, the stator 3, the rotor 4, the radial ball bearing 6, a casing 16 described later of the rotation unit 7, and the thrust ball bearing 8 are shown in cross-sectional shape.

  The housing | casing 2 is a substantially cylindrical member which consists of metal materials etc., and the accommodation space 11 is formed in the inside. The accommodation space 11 accommodates the stator 3, the rotor 4, the shaft 5, the radial ball bearing 6, the rotation unit 7, the thrust ball bearing 8, the rotation angle detection sensor 9, and the like.

  The stator 3 is fixed to the side wall surface of the accommodation space 11. The rotor 4 is disposed in a region inside the housing space 11 where the stator 3 is disposed.

  The rotor 4 is attached to the shaft 5 so as to be coaxial with the rotation axis of the rotor 4. The structure and method for attaching the rotor 4 to the shaft 5 will be described later. The shaft 5 extends in the up-down direction, and an object to be driven by the electric motor 1 is attached to a lower end portion of the shaft 5. Further, in the central portion including the central axis of the shaft 5, a portion 5 a extending from the portion attached to the rotor 4 to the upper end thereof is made of a material having higher thermal conductivity than the other portions. For example, parts other than the part 5a of the shaft 5 are made of iron or the like, whereas the part 5a of the shaft 5 is made of aluminum, copper or the like.

  The radial ball bearing 6 is made of a metal material or the like, and is arranged between a substantially annular outer ring 6a and a substantially annular inner ring 6b having a smaller diameter than the outer ring 6a along the circumferential direction of the outer ring 6a and the inner ring 6b. A plurality of balls 6c are sandwiched. And thereby, the outer ring | wheel 6a and the inner ring | wheel 6b are mutually rotatable. The outer ring 6 a is attached to the wall of the housing space 11 of the housing 2. The inner ring 6 b is attached to the shaft 5. Thereby, the shaft 5 is rotatably connected to the housing 2.

  The rotation unit 7 is disposed at the upper end portion of the accommodation space 11 that is located almost directly above the rotor 4 and the shaft 5. The rotating unit 7 has a structure in which a rotating member 17 is accommodated in a casing 16. The rotating member 17 includes a rotating member main body 17a and a shaft portion 17b. The rotating member main body 17 a is a water wheel, a propeller, or the like, and is disposed coaxially with the rotor 4 and the shaft 5. The shaft portion 17 b is fixed to the central axis of the rotating member main body 17 a and extends through the casing 16 to a position below the casing 16. A through hole 17c is formed in the substantially central portion of the rotating member main body 17a and the shaft portion 17b. The upper end of the shaft 5 extends above the rotating unit 7 through the through hole 17c. ing.

  The thrust ball bearing 8 is made of a metal material or the like, and is disposed opposite to each other in the vertical direction. The mounting portion 8a, A plurality of balls 8c arranged along the circumferential direction of 8b are sandwiched. In the thrust ball bearing 8, the mounting portion 8a and the mounting portion 8b are rotatable with respect to each other. The lower attachment portion 8 a is attached to the upper end portion of the shaft 5. The upper attachment portion 8 b is attached to the lower end portion of the shaft portion 17 b of the rotating member 17. Thereby, the shaft 5 and the rotating member 17 are rotatably connected to each other.

  The rotation angle detection sensor 9 detects the rotation angle of the rotor 4 from the relative positional relationship between the rotor 4 and the stator 3. The rotation angle detection sensor 9 is provided in the upper end portion of the shaft 5 located above the rotation unit 7 and the region above the rotation unit 7 in the accommodation space 11. In addition, although simplified in FIG. 1, the rotation angle detection sensor 9 is a resolver, for example.

  Next, a structure for attaching the rotor 4 to the shaft 5 will be described. As shown in FIG. 2, the rotor 4 is provided with a key 4 a that protrudes inward in the radial direction. The key 4a is provided at two places, and is provided at a position different by about 180 degrees in the circumferential direction. The cross-sectional shape of the key 4a in the direction orthogonal to the axial direction of the rotor 4 and the shaft 5 is an isosceles triangle. That is, the cross-sectional shape of the key 4a is a line-symmetric shape and a triangular shape. Further, the side wall of the key 4a is tapered, and the angle α of the side wall of the key 4a with respect to the direction perpendicular to the tangent to the base of the key 4a is in the range of 20 to 40 degrees. In other words, the key 4a has a narrow width from the base to the tip. The tip of the key 4a is pointed.

  The shaft 5 is provided with a key groove 5 b that fits into the key 4 a of the rotor 4. The keyway 5b is recessed inward in the radial direction. Two key grooves 5b are provided at positions corresponding to the keys 4a. The cross-sectional shape of the key groove 5b in the direction orthogonal to the axial direction of the rotor 4 and the shaft 5 is an isosceles triangle so as to be fitted to the key 4a. That is, the cross-sectional shape of the key groove 5b is a line-symmetric shape and a triangular shape. Further, the side wall of the key groove 5b is tapered, and the angle α of the side wall of the key groove 5b with respect to the direction perpendicular to the tangent to the base of the key groove 5b is in the range of 20 to 40 degrees. In other words, the width of the keyway 5b is narrow from the root to the tip. The tip of the keyway 5b is sharp. Further, the inner diameter of the rotor 4 and the outer diameter of the shaft 5 are the same.

  Thus, the rotor 4 is attached to the shaft 5 so that the position with respect to the shaft 5 does not shift by fitting the key 4a and the key groove 5b. Note that the number of the keys 4a and the key grooves 5b is not limited to two, and may be one or three or more.

  Next, a method for attaching the rotor 4 to the shaft 5 will be described. The rotor 4 and the shaft 5 are shrink-fitted. When the rotor 4 is heated, the rotor 4 is thermally expanded to increase the outer diameter and the inner diameter. As a result, the shaft 5 can be inserted into the rotor 4. When the shaft 5 is inserted into the rotor 4, as shown in FIG. 3, the key 4a of the rotor 4 is positioned inside the key groove 5b of the shaft 5 (the key 4a is inserted into the key groove 5b). Like that. Although details will be described later, at this time, the key 4a and the key groove 5b are prevented from interfering with each other. When the rotor 4 cools and contracts after the shaft 5 is inserted into the rotor 4, the key 4a and the key groove 5b are fitted. In this way, the rotor 4 is attached to the shaft 5.

  Here, when the rotor 4 is shrink-fitted on the shaft 5, if the rotor 4 is thermally expanded, the inner diameter of the rotor 4 is expanded, so that the key 4 a of the rotor 4 moves to the outer side in the radial direction. Thermal expansion. In the present embodiment, the width of the key 4 a of the rotor 4 and the key groove 5 b of the shaft 5 becomes narrower toward the center side of the shaft 5. That is, the width of the key groove 5 b of the shaft 5 increases as the distance from the center side of the shaft 5 increases. For this reason, even if the rotor 4 (key 4a) is thermally expanded, the key 4a moves outward in the radial direction, which is wider than the fitting position of the key groove 5b. Are prevented from interfering with each other. Further, since the key 4a and the key groove 5b are fitted, when the rotor 4 is cooled and contracted after the rotor 4 is shrink-fitted on the shaft 5, the gap between the key 4a and the key groove 5b. Disappears. Thereby, since the position shift of the rotor 4 with respect to the shaft 5 is prevented, the detection error of the rotation angle of the rotor 4 is prevented from occurring.

  Moreover, in this embodiment, the cross-sectional shape of the key 4a and the key groove 5b in the direction orthogonal to the axial direction of the rotor 4 and the shaft 5 is a line-symmetric shape. For this reason, when the rotor 4 and the shaft 5 rotate, the rotor 4 and the shaft 5 are not easily displaced.

  Moreover, in this embodiment, the cross-sectional shape of the direction orthogonal to the axial direction of the rotor 4 and the shaft 5 of the key 4a and the key groove 5b is a triangular shape. For this reason, it is easy to form the key 4a and the key groove 5b.

  For example, if the angle α of the side walls of the key 4a and the key groove 5b with respect to the direction perpendicular to the tangent line of the key 4a and the key groove 5b is too large, the width of the key 4a and the key groove 5b is narrow. Since the contact area between 4a and the key groove 5b is reduced, and a sufficient fitting force between the key 4a and the key groove 5b cannot be obtained, the rotor 4 and the shaft 5 may be displaced. In the present embodiment, the side walls of the key 4a and the key groove 5b are tapered, and the angle α is in the range of 20 to 40 degrees. Thereby, since the contact area of the key 4a and the key groove 5b is ensured, sufficient fitting force between the key 4a and the key groove 5b is obtained, and the rotor 4 and the shaft 5 are prevented from being displaced. Yes.

  In the present embodiment, the ends of the key 4a and the key groove 5b are sharp. For this reason, when the shaft 5 is inserted into the rotor 4, the key 4a is easily inserted into the key groove 5b.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. Components having the same configuration as in the first embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate. As shown in FIG. 3, in the second embodiment, the key 14a of the rotor 14 and the key groove 15b of the shaft 15 are different from those of the first embodiment.

  In the second embodiment, the cross-sectional shape of the key 14a in the direction orthogonal to the axial direction of the rotor 14 and the shaft 15 is a line-symmetric trapezoidal shape. Moreover, the cross-sectional shape of the key groove 15b in the direction orthogonal to the axial direction of the rotor 14 and the shaft 15 is a line-symmetric trapezoidal shape so as to be fitted to the key 14a. For this reason, the contact area of the key 14a and the keyway 15b is ensured, and it is prevented that the rotor 14 and the shaft 15 slip | deviate.

  The side walls of the key 14a and the key groove 15b are tapered, and the angle β of the side wall of the key 14a and the key groove 15b with respect to the direction perpendicular to the tangent line of the key 14a and the key groove 15b is 20 to 40 degrees. Is within the range. In other words, the width of the key 14a and the key groove 15b is narrow from the root to the tip.

  The embodiment of the present invention has been described above. However, the form to which the present invention can be applied is not limited to the above-described embodiment, and may be changed as appropriate without departing from the spirit of the present invention, as exemplified below. Can be added.

  In the above-described embodiment, the cross-sectional shapes of the keys 4a and 14a and the key grooves 5b and 15b are symmetrical, but they need not be symmetrical. In the first embodiment, the cross-sectional shapes of the key 4a and the key groove 5b are triangular. In the second embodiment, the cross-sectional shapes of the key 14a and the key groove 15b are trapezoidal. Not limited to this, the key and the key groove only need to be narrower toward the center side of the shaft.

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Housing | casing 3 Stator 4 Rotor 4a Key 5 Shaft 5b Key groove 9 Rotation angle detection sensor

Claims (4)

In the electric motor having means for detecting the rotation angle of the rotor from the relative positional relationship between the rotor and the stator,
The rotor provided with a key protruding radially inward;
A shaft provided with a keyway to be fitted to the key of the rotor,
The rotor and the shaft are shrink-fitted,
The electric motor according to claim 1, wherein the key and the key groove each have a width that decreases toward a center side of the shaft.   2. The electric motor according to claim 1, wherein a cross-sectional shape of the key and the key groove in a direction perpendicular to an axial direction of the rotor and the shaft is an axisymmetric shape.   3. The electric motor according to claim 1, wherein a cross-sectional shape of the key and the key groove in a direction orthogonal to an axial direction of the rotor and the shaft is a triangular shape.   The electric motor according to claim 1, wherein a cross-sectional shape of the key and the key groove in a direction orthogonal to an axial direction of the rotor and the shaft is a trapezoidal shape.