Electric motor

Abstract

An electric motor (100) comprises a first component (1) and a second component (2) that are formed so as to be separated from each other. The electric motor (100) also comprises a screw (3) that fixes the first component (1) and the second component (2), an elastically-deformable elastic packing (4) that is provided around the screw (3) and seals the space between the first component (1) and the second component (2) in the axial direction of the screw (3), and a metal component (5) that is provided between the screw (3) and the elastic packing (4) in the radial direction of the screw (3) and electrically connects the first component (1) and the second component (2).

Description

Electric motor

[0001] The present disclosure relates to an electric motor including two parts formed separately from each other.

[0002] As a conventional electric motor, there is known an electric motor in which a main body of the electric motor having a stator, a rotor, a frame, etc. and accessory parts such as a terminal box are manufactured separately and then the two parts are finally fixed with screws. In this type of electric motor, the space between the two parts cannot be completely sealed only by the tightening force of the screws, and the structure has low waterproof and dustproof properties. Therefore, the above-described electric motor is not suitable for use outdoors or in an environment where water splashes.

[0003] Therefore, as disclosed in Patent Document 1, it is generally performed to sandwich an elastic packing between the two parts to seal the space between the two parts and improve the waterproof and dustproof properties.

[0004] However, in a structure in which an elastic packing is sandwiched between two parts, the grounding conduction path between the two parts consists only of screws. In electrical products including electric motors, reliable grounding conduction is required to prevent electric shock to people in case of electric leakage. However, in a grounding conduction path that depends on screws, the reliability of the grounding conduction is low. In particular, when an elastic packing that is easily deformed and easily deteriorates over time is sandwiched between two parts, the reliability of the grounding conduction becomes even lower. For example, in the safety standard UL1004-1 for electric motors in the United States, when there is an elastic body between two parts, it is not generally recognized that the grounding conduction path consists of screws.

[0005] Japanese Utility Model Publication No. 62-188956

[0006] In the technology disclosed in Patent Document 1, although a spacer ring is placed around the screw between two parts, when the two parts are fixed together with the screw, the thickness of the spacer ring is thinner than the thickness of the elastic packing, and the spacer ring is not always in contact with the two parts. In other words, the spacer ring disclosed in Patent Document 1 does not electrically connect the two parts and does not serve as an earth conduction path. For this reason, even in the technology disclosed in Patent Document 1, the earth conduction path relies solely on the screw, resulting in low reliability of earth conduction. Therefore, there is a need to develop a structure that can always ensure an earth conduction path other than the screw.

[0007] This disclosure has been made in view of the above, and aims to provide an electric motor that ensures waterproofing and dustproofing between two components while always securing an earth connection path other than screws.

[0008] To solve the above-mentioned problems and achieve the objective, the electric motor according to this disclosure comprises a first component and a second component formed separately from each other, and further comprises a screw, an elastic packing, and a metal component. The screw fastens the first component and the second component together. The elastic packing is positioned around the screw and seals the space between the first component and the second component in the axial direction of the screw, and is elastically deformable. The metal component is positioned between the screw and the elastic packing in the radial direction of the screw and electrically connects the first component and the second component.

[0009] The electric motor described herein has the effect of ensuring waterproofing and dustproofing between the two components while always securing an earth connection path other than screws.

[0010] This is a cross-sectional view showing a part of the electric motor according to Embodiment 1, showing the state before the first and second parts are fixed with screws. This is a cross-sectional view showing a part of the electric motor according to Embodiment 1, showing the state after the first and second parts are fixed with screws. This is a cross-sectional view showing a part of the electric motor according to Embodiment 2, showing the state after the first and second parts are fixed with screws. This is a cross-sectional view showing a part of the electric motor according to Embodiment 3, showing the state before the first and second parts are fixed with screws. This is a cross-sectional view showing a part of the electric motor according to Embodiment 3, showing the state after the first and second parts are fixed with screws. This is a cross-sectional view showing a part of the electric motor according to Embodiment 4, showing the state before the first and second parts are fixed with screws. This is a cross-sectional view showing a part of the electric motor according to Embodiment 4, showing the state after the first and second parts are fixed with screws.

[0011] The electric motor according to the embodiment will be described in detail below with reference to the drawings.

[0012] Embodiment 1. Figure 1 is a cross-sectional view showing a part of the electric motor 100 according to Embodiment 1, showing the state before the first component 1 and the second component 2 are fixed together with the screw 3. Figure 2 is a cross-sectional view showing a part of the electric motor 100 according to Embodiment 1, showing the state after the first component 1 and the second component 2 are fixed together with the screw 3. As shown in Figures 1 and 2, the electric motor 100 comprises a first component 1 and a second component 2 which are formed separately from each other. The electric motor 100 also comprises a screw 3, an elastic packing 4, and a metal component 5. When describing the direction of each component of the electric motor 100 below, the direction parallel to the axis AX of the screw 3 will be called the axial direction, the direction perpendicular to the axis AX will be called the radial direction, and the rotational direction around the axis AX will be called the circumferential direction.

[0013] The first component 1 is the motor body, which includes a stator, rotor, and frame 1a. Figures 1 and subsequent figures show a portion of the frame 1a that houses the stator and rotor. The frame 1a is a metal component. The second component 2 is an accessory component attached to the motor body, such as a terminal box 2a. Figures 1 and subsequent figures show a portion of the terminal box 2a. The terminal box 2a is a metal component. The first component 1 and the second component 2 are spaced apart from each other in the axial direction via an elastic packing 4 and a metal component 5. The first component 1 has a first through-hole 1b through which a screw 3 is inserted. The second component 2 has a second through-hole 2b through which a screw 3 is inserted. The first through-hole 1b and the second through-hole 2b are arranged coaxially with the axis AX of the screw 3.

[0014] The screw 3 is a metal component that fixes (fastens) the first component 1 and the second component 2. The shaft portion 3b of the screw 3 is inserted through the second through hole 2b, the inner circumference of the metal component 5, and the first through hole 1b. The shaft portion 3b of the screw 3 is screwed into a screw groove (not shown) formed on the inner circumferential surface of the first through hole 1b. The first through hole 1b functions as a screw hole into which the screw 3 is screwed. The second through hole 2b does not function as a screw hole into which the screw 3 is screwed. As shown in Figure 2, when the first component 1 and the second component 2 are fixed with the screw 3, the head 3a of the screw 3 is in contact with the surface of the second component 2 that faces away from the first component 1.

[0015] The elastic packing 4 is positioned around the screw 3 and seals the space between the first part 1 and the second part 2 in the axial direction, while also being an elastically deformable member. As shown in Figure 1, the elastic packing 4 plays the role of sealing the space between the first part 1 and the second part 2 by compressing it by a mm when the first part 1 and the second part 2 are fixed together with the screw 3. The shape of the elastic packing 4 is an annular shape extending in the circumferential direction. The material of the elastic packing 4 is rubber or the like.

[0016] As shown in Figure 2, the metal part 5 is a metal component positioned radially between the screw 3 and the elastic packing 4, electrically connecting the first component 1 and the second component 2. The metal part 5 is positioned axially between the first component 1 and the second component 2. In this embodiment, the metal part 5 is a spacer. The shape of the metal part 5 is an annular shape extending in the circumferential direction. In this embodiment, the material of the metal part 5 is a soft metal such as aluminum or brass. In other words, the material of the metal part 5 is a metal that can be plastically deformed by the tightening force of the screw 3. The metal part 5 is positioned radially outside the shaft portion 3b of the screw 3, away from the shaft portion 3b.

[0017] As shown in Figure 1, when the first part 1 and the second part 2 are not fixed together by the screw 3 (when no tightening force from the screw 3 is acting), the elastic packing 4 is at its natural length, and the thickness T1 of the elastic packing 4 in the axial direction is greater than the thickness T2 of the metal part 5 in the axial direction. In this state, the metal part 5 is in contact with the first part 1 but not with the second part 2. As shown in Figure 2, when the screw 3 is tightened, the elastic packing 4 is elastically deformed by the tightening force when fixing the first part 1 and the second part 2 together by the screw 3, causing the metal part 5 to come into contact with the second part 2 as well. In other words, the metal part 5 comes into contact with both the first part 1 and the second part 2. As a result, the first part 1 and the second part 2 become electrically connected through the metal part 5.

[0018] In this embodiment, when a metal part 5 made of a soft metal is used, the metal part 5 undergoes plastic deformation due to the tightening force applied when fixing the first part 1 and the second part 2 with a screw 3, causing it to compress. Specifically, as the screw 3 is tightened, the elastic packing 4 begins to elastically deform and compress first. When the elastic packing 4 is compressed to the same thickness T2 as the metal part 5, the tightening force acts on the metal part 5, causing it to begin plastic deformation and compress. Once the metal part 5 has plastically deformed to a certain extent, the contact area between the metal part 5 and the first part 1 and the second part 2 increases, and a greater fastening torque is applied to the screw 3. Ultimately, the metal part 5 will plastically deform to the specified fastening torque. At this point, the elastic packing 4 and the metal part 5 are in a compressed state.

[0019] Next, the effects of the electric motor 100 according to Embodiment 1 will be described.

[0020] In this embodiment, as shown in Figures 1 and 2, the electric motor 100 includes a screw 3 that fixes a first component 1 and a second component 2, and an elastic packing 4 that is arranged around the screw 3 and seals the space between the first component 1 and the second component 2 in the axial direction, while also being elastically deformable. This configuration ensures waterproofing and dustproofing between the two components by sealing the space between the first component 1 and the second component 2. Furthermore, in this embodiment, as shown in Figure 2, the electric motor 100 includes a metal component 5 that is arranged radially between the screw 3 and the elastic packing 4 and electrically connects the first component 1 and the second component 2. With this configuration, the metal component 5, in addition to the screw 3, also becomes an earth conduction path 6, thus ensuring an earth conduction path 6 other than the screw 3 at all times. Therefore, in this embodiment, it is possible to ensure waterproofing and dustproofing between the two components while always ensuring an earth conduction path 6 other than the screw 3.

[0021] In order to ensure waterproofing and dustproofing between the two parts and to secure an earth connection path 6 other than the screw 3, it is necessary to manufacture both parts so that the thickness T1 of the elastic packing 4 and the thickness T2 of the metal part 5 are the same. However, since there are usually tolerances in both the elastic packing 4 and the metal part 5, it is difficult to manufacture both parts so that the thickness T1 of the elastic packing 4 and the thickness T2 of the metal part 5 are the same while taking into account the tolerances of both parts. In other words, a dimensional error occurs between the thickness T1 of the elastic packing 4 and the thickness T2 of the metal part 5 when no force such as tightening force is applied. In this embodiment, as shown in Figure 2, the elastic packing 4 is elastically deformed by the tightening force when the first part 1 and the second part 2 are fixed with the screw 3, causing it to compress. In addition, as the elastic packing 4 deforms, the metal part 5 comes into contact with the first part 1 and the second part 2, and the first part 1 and the second part 2 become electrically connected through the metal part 5. This configuration allows the elastic packing 4 to be elastically deformed when fixing the first component 1 and the second component 2, thereby absorbing dimensional errors between the elastic packing 4 and the metal component 5. In other words, when fixing the first component 1 and the second component 2, the thickness T1 of the elastic packing 4 and the thickness T2 of the metal component 5 can be easily made the same. As a result, even if there is a dimensional error between the thickness T1 of the elastic packing 4 and the thickness T2 of the metal component 5 in their non-elastically deformed state, it is possible to always ensure an earth connection path 6 other than the screw 3 while maintaining waterproof and dustproof properties between the two components.

[0022] Here, we will explain the relationship between the tolerance range of the thickness T1 of the elastic packing 4 and the tolerance range of the thickness T2 of the metal part 5. Here, let b be the reference dimension of the thickness T1 of the elastic packing 4 when the tolerance is 0 (zero), let c be the reference dimension of the thickness T2 of the metal part 5 when the tolerance is 0, and let a be the amount of shrinkage (compression) of the elastic packing 4. Since the elastic packing 4 needs to shrink (compress) to the same thickness T2 as the metal part 5, the relationship between the thickness T1 of the elastic packing 4 and the thickness T2 of the metal part 5 is expressed as T2 < T1 ≤ T2 + a. Next, we will calculate the tolerance range of the thickness T2 of the metal part 5, assuming that the tolerance range of the thickness T1 of the elastic packing 4 is b - 0.2a ≤ T1 ≤ b + 0.2a. When T1 = b + 0.2a, the tolerance range for the thickness T2 of the metal part 5 is T2 < b + 0.2a ≤ T2 + a, so it is expressed as b - 0.8a ≤ T2 < b + 0.2a. On the other hand, when T1 = b - 0.2a, the tolerance range for the thickness T2 of the metal part 5 is T2 < b - 0.2a ≤ T2 + a, so it is expressed as b - 1.2a ≤ T2 < b - 0.2a. Therefore, under the above assumptions, the tolerance range for the thickness T2 of the metal part 5 is expressed as b - 0.8a ≤ T2 < b - 0.2a. For example, when a = 2.0 mm and b = 5.0 mm, the tolerance range for the thickness T2 of the metal part 5 is expressed as 3.4 mm < T2 ≤ 4.6 mm. The tolerance range for the thickness T1 of the elastic packing 4 is b-0.2a ≤ T1 ≤ b+0.2a, and the tolerance range for the thickness T2 of the metal part 5 is b-0.8a ≤ T2 < b-0.2a. Both tolerance ranges change depending on the value of a, but if the elastic packing 4 is made of rubber or a material with a low elastic modulus, the value of a can be made relatively large, and the tolerance ranges for the thickness T1 of the elastic packing 4 and the thickness T2 of the metal part 5 can be made large. For this reason, it becomes relatively easy to design the assembly so that the thickness T1 of the elastic packing 4 and the thickness T2 of the metal part 5 are the same when fixing the first part 1 and the second part 2 together.

[0023] In this embodiment, there is no need to perform any special design on the first component 1 and the second component 2 shown in Figures 1 and 2. Since it is only necessary to use the elastic packing 4 and the metal component 5 together, the electric motor 100 can be designed simply and inexpensively.

[0024] In this embodiment, by simply adding or removing the elastic packing 4 and metal part 5 shown in Figures 1 and 2, it is possible to manufacture an electric motor 100 that ensures waterproofing and dustproofing between the two parts, and an electric motor that does not ensure waterproofing and dustproofing between the two parts. In other words, parts other than the elastic packing 4 and metal part 5 can be common to the two types of electric motors. An electric motor that does not ensure waterproofing and dustproofing between the two parts refers to an electric motor used in a clean indoor environment, for example, an electric motor for which it is not necessary to ensure waterproofing and dustproofing between the two parts. In such an electric motor, the elastic packing 4 and metal part 5 are removed, and the first part 1 and the second part 2 are in direct contact, so the grounding path 6 is always ensured.

[0025] In this embodiment, as shown in Figure 2, the metal part 5 becomes the ground conduction path 6. Therefore, even when an elastic packing 4, which is easily deformed and prone to deterioration over time, is sandwiched between the two parts, reliable and permanent ground conduction can be achieved. Furthermore, in this embodiment, not only the elastic packing 4 but also the metal part 5 receives the tightening force and contacts the first part 1 and the second part 2, thus preventing the screw 3 from loosening. This enables reliable and permanent ground conduction, and further ensures waterproof and dustproof properties between the two parts.

[0026] In this embodiment, as shown in Figures 1 and 2, the material of the metal part 5 is a plastically deformable metal, and the metal part 5 is plastically deformed by the tightening force when the first part 1 and the second part 2 are fixed together with the screw 3, causing it to compress. The tolerance range of the thickness T2 of the metal part 5 can be widened by the amount of plastic deformation of the metal part 5. Furthermore, by elastically deforming the elastic packing 4 and plastically deforming the metal part 5 when fixing the first part 1 and the second part 2, dimensional errors between the elastic packing 4 and the metal part 5 can be absorbed even more effectively. In other words, when fixing the first part 1 and the second part 2, the thickness T1 of the elastic packing 4 and the thickness T2 of the metal part 5 can be easily made the same. As a result, even if there is a dimensional error between the thickness T1 of the elastic packing 4 in its non-elastically deformed state and the thickness T2 of the metal part 5 in its non-plastically deformed state, it is possible to always ensure an earth conduction path 6 by means other than the screw 3 while ensuring waterproofing and dustproofing between the two parts.

[0027] Next, a modified example of Embodiment 1 will be described.

[0028] In this embodiment, the material of the metal part 5 was a metal that could be plastically deformed by the tightening force, but it may also be a metal that cannot be plastically deformed by the tightening force. In this embodiment, the shaft portion 3b of the screw 3 is screwed only into the screw groove formed on the inner circumferential surface of the first through hole 1b, but a screw groove may also be formed on the inner circumferential surface of the second through hole 2b and the shaft portion 3b of the screw 3 may be screwed into the screw groove.

[0029] Embodiment 2. Next, with reference to Figure 3, an electric motor 100A according to Embodiment 2 will be described. This embodiment differs from Embodiment 1 described above in that a metal part 5A on which a projection 50 is formed is used. In Embodiment 2, parts that overlap with Embodiment 1 described above are denoted by the same reference numerals and their descriptions are omitted.

[0030] Figure 3 is a cross-sectional view showing a part of the electric motor 100A according to Embodiment 2, and shows the state after the first component 1 and the second component 2 are fixed with screws 3. As shown in Figure 3, in this embodiment, the metal component 5A is a spacer with projections 50. The metal component 5A has projections 50 that protrude toward the first component 1 and the second component 2, respectively. Multiple projections 50 that protrude toward the first component 1 are formed at one end of the metal component 5A in the axial direction. Multiple projections 50 that protrude toward the second component 2 are formed at the other end of the metal component 5A in the axial direction. Hereinafter, when distinguishing between the projections 50 formed at one end and the other end of the metal component 5A, they will be referred to as projection 50A and projection 50B, respectively.

[0031] Each projection 50 tapers as it moves away from the metal part 5A along the axial direction. The shape of each projection 50 is preferably a pointed shape with a sharp tip, as in this embodiment, but other shapes are also acceptable. The first part 1 has an insulating painted surface 1c over its entire surface. The second part 2 has an insulating painted surface 2c over its entire surface. Due to the tightening force when the first part 1 and the second part 2 are fixed together with screws 3, projection 50A penetrates the painted surface 1c of the first part 1 and contacts the metal part (base material) of the first part 1, and projection 50B penetrates the painted surface 2c of the second part 2 and contacts the metal part of the second part 2.

[0032] Next, the effects of the motor 100A according to Embodiment 2 will be described.

[0033] In this embodiment, as shown in Figure 3, the metal part 5A has projections 50A and 50B that protrude toward the first part 1 and the second part 2, respectively. Due to the tightening force when the first part 1 and the second part 2 are fixed together with screws 3, projection 50A penetrates the painted surface 1c of the first part 1 and contacts the metal part of the first part 1, and projection 50B penetrates the painted surface 2c of the second part 2 and contacts the metal part of the second part 2. With this configuration, even if there are painted surfaces 1c and 2c on the contact surfaces of the first part 1 and the second part 2 that come into contact with the metal part 5A, electrical conductivity can be established between the metal parts of the first part 1 and the second part 2 and the metal part 5A. Furthermore, the projections 50 of the metal part 5A contact the metal parts of the first part 1 and the second part 2, respectively, to create a more reliable ground conductivity path 6.

[0034] Next, a modified example of Embodiment 2 will be described.

[0035] In this embodiment, each of the first component 1 and the second component 2 has insulating painted surfaces 1c and 2c, and the metal component 5A has projections 50 that protrude toward each of the first component 1 and the second component 2, but the embodiment is not limited to this. At least one of the first component 1 and the second component 2 has insulating painted surfaces 1c and 2c, and it is sufficient that the projections 50 protrude toward at least one of the first component 1 and the second component 2 that has the painted surfaces 1c and 2c. In this case, the tightening force when fixing the first component 1 and the second component 2 with screws 3 causes the projections 50 to penetrate the painted surfaces 1c and 2c of at least one of the first component 1 and the second component 2 and come into contact with the metal portion of at least one of the first component 1 and the second component 2.

[0036] Embodiment 3. Next, the electric motor 100B according to Embodiment 3 will be described with reference to Figures 4 and 5. This embodiment differs from Embodiments 1 and 2 described above in that it uses a metal part 5B having a spacer 51 and a washer 52. In Embodiment 3, parts that overlap with Embodiments 1 and 2 described above are denoted by the same reference numerals and their description is omitted.

[0037] Figure 4 is a cross-sectional view showing a part of the electric motor 100B according to Embodiment 3, showing the state before the first component 1 and the second component 2 are fixed with screws 3. Figure 5 is a cross-sectional view showing a part of the electric motor 100B according to Embodiment 3, showing the state after the first component 1 and the second component 2 are fixed with screws 3. As shown in Figure 4, the metal component 5B has a spacer 51 and a washer 52. The spacer 51 is a flange-type spacer including a base 51a and a flange 51b. The inner diameter of the second insertion hole 2b is larger than the outer diameter of the base 51a.

[0038] As shown in Figure 5, the base portion 51a is positioned radially between the screw 3, the elastic packing 4, the second component 2, and the washer 52. The base portion 51a is a cylindrical portion that extends axially. The base portion 51a is inserted through the inner circumference of the elastic packing 4, the second insertion hole 2b, and the inner circumference of the washer 52. The flange 51b extends radially outward from one end of the base portion 51a in the axial direction (in this embodiment, the end of the base portion 51a facing the head 3a of the screw 3). The flange 51b is located axially on the opposite side of the elastic packing 4, with the second component 2 and the washer 52 in between. The other end of the base portion 51a in the axial direction is in contact with the surface of the first component 1 facing the second component 2.

[0039] The washer 52 is a toothed washer. The washer 52 is positioned axially between the flange 51b and the second component 2. The washer 52 has projections 52a that protrude toward the second component 2. Specifically, one end of the washer 52 in the axial direction has multiple projections 52a that protrude toward the second component 2. Each projection 52a tapers as it moves away from the washer 52 along the axial direction. The shape of each projection 52a is preferably a pointed shape with a sharp tip, as in this embodiment, but other shapes are also acceptable.

[0040] Of the first part 1 and the second part 2, only the second part 2 has an insulating painted surface 2c over its entire surface. The first part 1 does not have an insulating painted surface 1c (see Figure 3). As shown in Figure 4, when the first part 1 and the second part 2 are not fixed together by the screw 3, the length L of the base 51a in the axial direction is shorter than the sum of the thickness T1 of the elastic packing 4, the thickness T3 of the second part 2 having the painted surface 2c, and the thickness T4 of the washer 52. The thickness T4 of the washer 52 also includes the thickness of the projection 52a. When the first part 1 and the second part 2 are not fixed together by the screw 3, the elastic packing 4 is at its natural length, and the spacer 51 is axially separated from the first part 1 on one side of the first part 1. The projection 52a is in contact with the painted surface 2c of the second part 2. As shown in Figure 5, when the first part 1 and the second part 2 are fixed together with the screw 3, the tightening force causes the elastic packing 4 to compress and deform elastically, so that the spacer 51 comes into contact with the first part 1, and the projection 52a penetrates the painted surface 2c of the second part 2 and comes into contact with the metal part of the second part 2 that has the painted surface 2c. In other words, the metal part 5 comes into contact with the first part 1 and the second part 2. As a result, the first part 1 and the second part 2 are electrically connected through the metal part 5.

[0041] Next, the effects of the motor 100B according to Embodiment 3 will be described.

[0042] In this embodiment, as shown in FIG. 5, the metal part 5B has a spacer 51 and a washer 52. The spacer 51 includes a base portion 51a and a flange 51b. The base portion 51a is disposed between the screw 3 and the elastic packing 4 in the radial direction and extends in the axial direction. The flange 51b extends radially outward from one end of the base portion 51a in the axial direction and is located on the opposite side of the elastic packing 4 with the second component 2 having the painted surface 2c interposed therebetween in the axial direction. The washer 52 is disposed between the flange 51b and the second component 2 having the painted surface 2c in the axial direction. A protrusion 52a protruding toward the second component 2 having the painted surface 2c is formed on the washer 52. In a state where the first component 1 and the second component 2 are not fixed by the screw 3, the length L of the base portion 51a in the axial direction is shorter than the sum of the thickness T1 of the elastic packing 4, the thickness T3 of the second component 2 having the painted surface 2c, and the thickness T4 of the washer 52. Due to the tightening force when the first component 1 and the second component 2 are fixed by the screw 3, the elastic packing 4 elastically deforms so as to be compressed, and the protrusion 52a penetrates the painted surface 2c of the second component 2 and contacts the metal portion of the second component 2 having the painted surface 2c. With these configurations, even if there is a painted surface 2c on the contact surface of the second component 2 with the washer 52, the protrusion 52a can penetrate the painted surface 2c and electrically connect the metal portion of the second component 2 and the metal part 5B. Further, by the protrusion 52a of the washer 52 contacting the metal portion of the second component 2, a more reliable ground conduction path 6 can be constructed.

[0043] In this embodiment, by using the spacer 51 with the flange 51b, after sandwiching the elastic packing 4 between the first component 1 and the second component 2, the spacer 51 can be disposed on the inner circumferences of the elastic packing 4, the second insertion hole 2b, and the washer 52. Thereby, the workability when assembling the spacer 51 is improved.

[0044] Next, a modification of Embodiment 3 will be described.

[0045] The configuration of the first component 1, the second component 2, the flange 51b, the washer 52, and the projection 52a is not limited to the illustrated example. Only one of the first component 1 and the second component 2 needs to have insulating painted surfaces 1c, 2c. The flange 51b needs to be located on the opposite side of the elastic packing 4 in the axial direction, with the painted surface 1c, 2c of the first component 1 and the second component 2 in between. The washer 52 needs to be positioned in the axial direction between the flange 51b and the painted surface 1c, 2c of the first component 1 and the second component 2. The washer 52 needs to have a projection 52a that protrudes toward the painted surface 1c, 2c of the first component 1 and the second component 2. Furthermore, when the first part 1 and the second part 2 are not fixed together with the screw 3, the length L of the base 51a in the axial direction is shorter than the sum of the thickness T1 of the elastic packing 4, the thickness of either the first part 1 or the second part 2 having painted surfaces 1c or 2c, and the thickness T4 of the washer 52. Moreover, when the first part 1 and the second part 2 are fixed together with the screw 3, the tightening force causes the elastic packing 4 to compress and deform elastically, so that the projection 52a penetrates the painted surfaces 1c or 2c of either the first part 1 or the second part 2 and contacts the metal part of either the first part 1 or the second part 2 having painted surfaces 1c or 2c.

[0046] Embodiment 4. Next, the electric motor 100C according to Embodiment 4 will be described with reference to Figures 6 and 7. This embodiment differs from Embodiments 1 to 3 described above in that it uses a metal component 5C having a first spacer 53, a second spacer 54, a first washer 55, and a second washer 56. In Embodiment 4, parts that overlap with Embodiments 1 to 3 described above are denoted by the same reference numerals and their description is omitted.

[0047] FIG. 6 is a cross-sectional view showing a part of the motor 100C according to Embodiment 4, and is a view showing the state before the first component 1 and the second component 2 are fixed with the screw 3. FIG. 7 is a cross-sectional view showing a part of the motor 100C according to Embodiment 4, and is a view showing the state after the first component 1 and the second component 2 are fixed with the screw 3. As shown in FIG. 6, the metal component 5C has a first spacer 53, a second spacer 54, a first washer 55, and a second washer 56. As shown in FIG. 7, the first spacer 53 and the second spacer 54 are axially overlapped.

[0048] The first spacer 53 is a flange-type spacer including a first base 53a and a first flange 53b. The inner diameter of the second insertion hole 2b is larger than the outer diameter of the first base 53a. The first base 53a is arranged between the screw 3 and the elastic packing 4, the second component 2, and the first washer 55 in the radial direction. The first base 53a is a cylindrical portion extending in the axial direction. The first base 53a is inserted through the inner circumference of the elastic packing 4, the second insertion hole 2b, and the inner circumference of the first washer 55. The first flange 53b extends radially outward from one end of the first base 53a in the axial direction (in this embodiment, the end of the first base 53a facing the head 3a of the screw 3). The first flange 53b is located on the opposite side of the elastic packing 4 with the second component 2 and the first washer 55 interposed therebetween in the axial direction.

[0049] The second spacer 54 is a flange-type spacer including a second base 54a and a second flange 54b. The inner diameter of the first insertion hole 1b is larger than the outer diameter of the second base 54a. The inner diameter of the first insertion hole 1b and the inner diameter of the second insertion hole 2b are the same. Also, the outer diameter of the first base 53a and the outer diameter of the second base 54a are the same. The second base 54a is positioned radially between the screw 3, the elastic packing 4, the first component 1, and the second washer 56. The second base 54a is a cylindrical portion that extends axially. The second base 54a is inserted through the inner circumference of the elastic packing 4, the first insertion hole 1b, and the inner circumference of the second washer 56. One end of the second base 54a in the axial direction is in contact with the other end of the first base 53a in the axial direction. The second flange 54b extends radially outward from the other end of the second base 54a in the axial direction (in this embodiment, the end of the second base 54a facing away from the head 3a of the screw 3). The second flange 54b is located axially opposite the elastic packing 4, with the first component 1 and the second washer 56 in between.

[0050] The first washer 55 is a toothed washer. The first washer 55 is positioned axially between the first flange 53b and the second part 2. The first washer 55 has a first projection 55a that protrudes toward the second part 2. Specifically, one end of the first washer 55 in the axial direction has a plurality of first projections 55a that protrude toward the second part 2. Each first projection 55a tapers away from the first washer 55 along the axial direction. The shape of each first projection 55a is preferably a pointed shape with a sharp tip, as in this embodiment, but other shapes are also possible.

[0051] The second washer 56 is a toothed washer. The second washer 56 is positioned axially between the second flange 54b and the first component 1. The second washer 56 has a second projection 56a that protrudes toward the first component 1. Specifically, one end of the second washer 56 in the axial direction has a plurality of second projections 56a that protrude toward the first component 1. Each second projection 56a tapers away from the second washer 56 along the axial direction. The shape of each second projection 56a is preferably a pointed shape with a sharp tip, as in this embodiment, but other shapes are also possible.

[0052] The first part 1 has an insulating painted surface 1c over its entire surface. The second part 2 has an insulating painted surface 2c over its entire surface. As shown in Figure 6, when the first part 1 and the second part 2 are not fixed together by the screw 3, the sum of the axial length L1 of the first base 53a and the length L2 of the second base 54a is shorter than the sum of the thickness T1 of the elastic packing 4, the thickness T3a of the first part 1, the thickness T3b of the second part 2, the thickness T4a of the first washer 55, and the thickness T4b of the second washer 56. The thickness T4a of the first washer 55 also includes the thickness of the first projection 55a. The thickness T4b of the second washer 56 also includes the thickness of the second projection 56a. When the first part 1 and the second part 2 are not fixed together with the screw 3, the elastic packing 4 is at its natural length, and the first spacer 53 and the second spacer 54 are separated from each other in the axial direction. The first projection 55a is in contact with the painted surface 2c of the second part 2. The second projection 56a is in contact with the painted surface 1c of the first part 1. As shown in Figure 7, when the first part 1 and the second part 2 are fixed together with the screw 3, the tightening force causes the elastic packing 4 to compress and deform elastically, causing the first spacer 53 and the second spacer 54 to come into contact with each other. Also, the second projection 56a penetrates the painted surface 1c of the first part 1 and comes into contact with the metal part of the first part 1, and the first projection 55a penetrates the painted surface 2c of the second part 2 and comes into contact with the metal part of the second part 2. In other words, the metal part 5 comes into contact with the first part 1 and the second part 2. As a result, the first component 1 and the second component 2 are electrically connected via the metal component 5.

[0053] Neither the first insertion hole 1b nor the second insertion hole 2b functions as a screw hole into which the screw 3 is threaded. Therefore, in this embodiment, the tip of the shaft portion 3b of the screw 3 is threaded into the nut 7. The nut 7 is in contact with the end of the second flange 54b that faces away from the head 3a of the screw 3. Between the head 3a of the screw 3 and the nut 7 are the first spacer 53, the second spacer 54, the first washer 55, the second washer 56, the second part 2, the elastic packing 4, and the first part 1.

[0054] Next, the effects of the motor 100C according to Embodiment 4 will be described.

[0055] In this embodiment, as shown in Figure 7, the first component 1 and the second component 2 each have insulating painted surfaces 1c and 2c. The metal component 5C includes a first spacer 53, a second spacer 54, a first washer 55, and a second washer 56. The first spacer 53 includes a first base 53a and a first flange 53b. The first base 53a is positioned radially between the screw 3 and the elastic packing 4 and extends axially. The first flange 53b extends radially outward from one end of the first base 53a in the axial direction and is positioned axially opposite the elastic packing 4 with the second component 2 in between. The second spacer 54 includes a second base 54a and a second flange 54b. The second base 54a is positioned radially between the screw 3 and the elastic packing 4 and extends axially. One end of the second base 54a in the axial direction is in contact with the other end of the first base 53a in the axial direction. The second flange 54b extends radially outward from the other end of the second base 54a in the axial direction and is located on the opposite side of the elastic packing 4 in the axial direction, with the first component 1 in between. The first washer 55 is positioned between the first flange 53b and the second component 2 in the axial direction. The first washer 55 has a first projection 55a that protrudes toward the second component 2. The second washer 56 is positioned between the second flange 54b and the first component 1 in the axial direction. The second washer 56 has a second projection 56a that protrudes toward the first component 1. Furthermore, as shown in Figure 6, when the first part 1 and the second part 2 are not fixed together with the screw 3, the sum of the length L1 of the first base 53a and the length L2 of the second base 54a in the axial direction is shorter than the sum of the thickness T1 of the elastic packing 4, the thickness T3a of the first part 1, the thickness T3b of the second part 2, the thickness T4a of the first washer 55, and the thickness T4b of the second washer 56. Moreover, as shown in Figure 7, when the first part 1 and the second part 2 are fixed together with the screw 3, the elastic packing 4 is elastically deformed to compress, causing the second projection 56a to penetrate the painted surface 1c of the first part 1 and contact the metal part of the first part 1, and the first projection 55a to penetrate the painted surface 2c of the second part 2 and contact the metal part of the second part 2.With these configurations, even if there are painted surfaces 1c and 2c on the contact surface between the first component 1 and the second washer 56, and on the contact surface between the second component 2 and the first washer 55, the respective metal parts of the first component 1 and the metal part 5C can be electrically connected. Furthermore, the second projection 56a of the second washer 56 contacts the metal part of the first component 1, and the first projection 55a of the first washer 55 contacts the metal part of the second component 2, thereby creating a more reliable ground connection path 6.

[0056] In this embodiment, by using a second spacer 54 with a second flange 54b, the second spacer 54 can be positioned on the inner circumference of the elastic packing 4, the first insertion hole 1b, and the inner circumference of the second washer 56 after the elastic packing 4 has been sandwiched between the first part 1 and the second part 2. Alternatively, by using a first spacer 53 with a first flange 53b, the first spacer 53 can be positioned on the inner circumference of the elastic packing 4, the second insertion hole 2b, and the inner circumference of the first washer 55 after the elastic packing 4 has been sandwiched between the first part 1 and the second part 2. This improves the workability when assembling the first spacer 53 and the second spacer 54.

[0057] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0058] 1. First part, 1a. Frame, 1b. First insertion hole, 1c, 2c. Painted surface, 2. Second part, 2a. Terminal box, 2b. Second insertion hole, 3. Screw, 3a. Head, 3b. Shaft, 4. Elastic packing, 5, 5A, 5B, 5C. Metal parts, 6. Ground continuity path, 7. Nut, 50, 50A, 50B, 52a. Projection, 51. Spacer, 51a. Base, 51b. Flange, 52. Washer, 53. First spacer, 53a. First base, 53b. First flange, 54. Second spacer, 54a. Second base, 54b. Second flange, 55. First washer, 55a. First projection, 56. Second washer, 56a. Second projection, 100, 100A, 100B, 100C. Electric motor.

Claims

1. An electric motor comprising a first component and a second component formed separately from each other, characterized by comprising: a screw for fixing the first component and the second component; an elastic packing disposed around the screw and sealing the space between the first component and the second component in the axial direction of the screw, and being elastically deformable; and a metal component disposed between the screw and the elastic packing in the radial direction of the screw, which electrically connects the first component and the second component.

2. The electric motor according to claim 1, characterized in that the elastic packing is elastically deformed by the tightening force when the first part and the second part are fixed together with the screw, so that the metal part comes into contact with the first part and the second part, and the first part and the second part are electrically connected through the metal part.

3. The electric motor according to claim 2, wherein the metal part is positioned between the first part and the second part in the axial direction, and when the first part and the second part are not fixed together by the screw, the thickness of the elastic packing in the axial direction is greater than the thickness of the metal part in the axial direction.

4. The electric motor according to claim 3, characterized in that the material of the metal part is a plastically deformable metal, and the metal part is plastically deformed to compress by the clamping force.

5. The electric motor according to claim 3 or 4, wherein at least one of the first component and the second component has an insulating painted surface, the metal component has a projection that protrudes toward at least one of the first component and the second component that has the painted surface, and the tightening force when the first component and the second component are fixed together with the screw causes the projection to penetrate the painted surface and contact at least one of the first component and the second component that has the painted surface.

6. Only one of the first and second parts has an insulating painted surface, and the metal part has a spacer including a base that is positioned radially between the screw and the elastic packing and extends axially, and a flange that extends radially outward from one end of the base in the axial direction and is positioned axially opposite to the elastic packing with the first and second parts having the painted surface in between, and a washer that is positioned axially between the flange and the first and second parts having the painted surface, wherein the washer has a projection that protrudes toward the first and second parts having the painted surface, and when the first and second parts are not fixed by the screw, the length of the base in the axial direction is shorter than the sum of the thickness of the elastic packing, the thickness of the first and second parts having the painted surface, and the thickness of the washer. The electric motor according to claim 1, characterized in that, due to the tightening force when the first part and the second part are fixed together with the screw, the elastic packing is elastically deformed to compress, and the projection penetrates the painted surface and contacts the metal part of either the first part or the second part that has the painted surface.

7. Each of the first and second parts has an insulating painted surface, and the metal part includes a first spacer comprising: a first base portion positioned radially between the screw and the elastic packing and extending axially; and a first flange extending radially outward from one end of the first base portion in the axial direction and positioned axially opposite to the elastic packing with either the first or second part in between; and a first washer positioned axially between the first flange and either the first or second part. A second spacer comprising: a second base portion disposed radially between the screw and the elastic packing and extending axially, with one end in the axial direction contacting the other end of the first base portion in the axial direction; a second flange extending radially outward from the other end of the second base portion in the axial direction and located axially opposite to the elastic packing with the other of the first and second parts in between; and a second washer disposed axially between the second flange and the other of the first and second parts, wherein the first washer has a first projection projecting toward one of the first and second parts, and the second washer has a second projection projecting toward the other of the first and second parts. The electric motor according to claim 1, characterized in that, when the first part and the second part are not fixed together by the screw, the sum of the length of the first base and the length of the second base in the axial direction is shorter than the sum of the thickness of the elastic packing, the thickness of the first part, the thickness of the second part, the thickness of the first washer, and the thickness of the second washer, and the elastic packing is elastically deformed by the tightening force when the first part and the second part are fixed together by the screw, so that the first projection penetrates the painted surface and contacts the metal part of either the first part or the second part, and the second projection penetrates the painted surface and contacts the metal part of the other of the first part or the second part.

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