WO2012008150A1

WO2012008150A1 - Fixing structure and drive apparatus

Info

Publication number: WO2012008150A1
Application number: PCT/JP2011/003992
Authority: WO
Inventors: Masahiko Nakamura; Machiko Okabayashi; Tomoyoshi Yokogawa
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2010-07-14
Filing date: 2011-07-12
Publication date: 2012-01-19
Anticipated expiration: 2013-01-14
Also published as: JP5696386B2; JP2012023845A

Abstract

A fixing structure is provided which includes a plurality of bend portions each defined integrally with the circumferential wall, arranged to extend obliquely toward the opening at an angle with respect to a central line of the circumferential wall, and bent in a thickness direction of the circumferential wall; and at least one recessed portion defined in a circumferential surface of the fitting portion for the bend portions. The at least one recessed portion includes a plurality of support surfaces arranged to have inclinations corresponding to those of the bend portions. The bend portions include a first bend portion and a second bend portion arranged to extend in mutually opposite directions with respect to a circumferential direction of the circumferential wall. Each of the first and second bend portions is arranged in contact with one of the support surfaces.

Description

FIXING STRUCTURE AND DRIVE APPARATUS

The present invention relates to a fixing structure for suitable use in a drive apparatus such as a motor.

For instance, in the case where a cover is fitted to a bracket of a motor, it is necessary to securely fix the bracket and the cover to each other both in an axial direction and in a circumferential direction. Accordingly, the bracket and the cover are commonly provided with flanges each including a plurality of fitting holes extending in the axial direction defined therein, and screws or the like are inserted into the fitting holes to securely fix the bracket and the cover to each other.

In this case, however, it is necessary to shave contact surfaces of the flanges with precision to achieve perpendicularity of the flanges. Therefore, a material for each of the flanges is required to have an extra thickness for surface treatment, resulting in a reduction in a yield. Moreover, press working is not sufficient to properly fit the flanges to each other. Therefore, an additional machining process is required to complete the surface treatment, and this is disadvantageous in terms of productivity. Furthermore, members such as the screws are necessary, and an operation of fitting the flanges to each other takes time.

In contrast, JP-A 9-205751 discloses a motor in which separate members are fixed to each other through swaging without use of screws.

A housing of this motor is made up of a deep-drawn metallic case, which has a bottom and is cylindrical, and a flange plate. The flange plate is fixed to an opening portion of the case. The case includes a plurality of swaging portions defined in the opening portion thereof. The swaging portions are bent at right angles to fix an outer circumferential portion of the flange plate, so that the flange plate is fixed to the case.

JP-A 9-205751

In the case of the motor described in JP-A 9-205751, however, only the outer circumferential portion of the flange plate is simply held down by the swaging portions. Therefore, the flange plate may be displaced in the circumferential direction. In addition, the (axial) position of the flange plate relative to the case when the flange plate has been fitted to the case is determined depending on where each of the swaging portions is bent (that is, an edge thereof on the opening portion). Therefore, the (axial) position of the flange plate relative to the case would be easily affected by a dimensional error or the like of each of the swaging portions in a molding process. This poses a stability problem in mass production.

Furthermore, it is necessary to bend each swaging portion highly precisely at right angles to bring the swaging portion into close surface contact with the flange plate. It is, however, difficult to bend each swaging portion highly precisely at right angles. It often happens that a top of the swaging portion is bent so excessively that the swaging portion is brought into line contact with the flange plate. If the swaging portion is brought into line contact with the flange plate, the flange plate is shaved to produce shavings. These shavings may cause malfunction of the motor.

The present invention has been conceived to provide a fixing structure that ensures secure fixing and stable mass production.

According to a preferred embodiment of the present invention, a fixing structure is provided which is used to fix, to a metallic receptacle including a cylindrical circumferential wall having an opening at one end thereof, a cylindrical fitting member including a fitting portion to be fitted into the opening. The fixing structure includes a plurality of bend portions each of which is bent in a thickness direction of the circumferential wall, and at least one recessed portion. Each of the bend portions is defined integrally with the circumferential wall, and is arranged to extend obliquely toward the opening at an angle with respect to a central line of the circumferential wall. The at least one recessed portion is defined in a circumferential surface of the fitting portion for the bend portions. The at least one recessed portion includes a plurality of support surfaces arranged to have inclinations corresponding to those of the bend portions. The bend portions include a first bend portion and a second bend portion arranged to extend in mutually opposite directions with respect to a circumferential direction of the circumferential wall. Each of the first and second bend portions is arranged in contact with one of the support surfaces.

In the fixing structure described above, the first and second bend portions are defined in the circumferential wall. The first and second bend portions are arranged to extend obliquely toward the opening and in mutually opposite directions with respect to the circumferential direction of the circumferential wall, and are each bent in the thickness direction of the circumferential wall. Moreover, the at least one recessed portion arranged for the first and second bend portions is provided with the plurality of support surfaces arranged to have the inclinations corresponding to those of the bend portions. Each of the first and second bend portions is arranged in contact with one of the support surfaces. Accordingly, each of the bend portions is arranged to easily achieve surface contact with a corresponding one of the support surfaces. The fitting member is thus fixed to the receptacle securely, and a reduction in production of shavings is achieved.

Also, circumferential positioning of the fitting member relative to the receptacle can be easily accomplished by roughly aligning a cut portion with a corresponding one of the at least one recessed portion and bending each bend portion. Furthermore, each of the bend portions and the support surfaces may be inclined at a specified angle with respect to each of a direction parallel to the central line and the circumferential direction. In this case, even if there is a slight molding error or deviation in any of the bend portions and the support surfaces, the molding error or deviation can be absorbed, leading to excellent productivity. Moreover, according to the fixing structure described above, a component force that contributes to fixing the fitting member in the circumferential direction, and a component force that acts on the fitting member in a direction parallel to the central line and away from the opening, are simultaneously obtained. This contributes to preventing a shake, a displacement, or the like of the fitting member.

Fig. 1 is a schematic perspective view of a drive apparatus according to a preferred embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of the drive apparatus. Fig. 3 is a schematic side view of a cut portion according to the preferred embodiment of the present invention. Fig. 4A is a schematic plan view of a recessed portion according to the preferred embodiment of the present invention, and Fig. 4B is a schematic side view of the recessed portion. Fig. 5 is a schematic side view for explaining actions of a fixing structure according to the preferred embodiment of the present invention. Fig. 6 is a schematic plan view of a drive apparatus according to an example modification of the preferred embodiment of the present invention. Fig. 7 is a schematic plan view of a drive apparatus according to another example modification of the preferred embodiment of the present invention.

Examples

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note, however, that the following description is essentially illustrative and should not be construed to restrict the scope, applications, or purposes of the present invention.

Figs. 1 and 2 each illustrate a motor 1 (i.e., a drive apparatus) to which a fixing structure according to a preferred embodiment of the present invention is applied. An outer circumferential surface of the motor 1 is preferably substantially cylindrical. The motor 1 includes a motor case 20 (i.e., a receptacle), a cover 30 (i.e., a fitting member), a motor body 40, and so on.

The motor case 20 is, for example, a cylindrical metallic receptacle including an opening 21 defined at an end thereof and shaped by press working. The motor case 20 includes a cylindrical circumferential wall 22 and a bottom wall 23. The bottom wall 23 is arranged to close an opposite end of the motor case 20.

The cover 30 is arranged to close the opening 21 of the motor case 20. The cover 30 is made of a synthetic resin or a metal, for example. A through hole 31 is defined in a center of the cover 30. The through hole 31 is arranged to extend through the cover 30 along a central line A of the cover 30. The cover 30 includes a fitting portion that has an outside diameter slightly smaller than the diameter of the opening 21 of the motor case 20. The fitting portion is securely fitted to the opening 21 of the motor case 20, so that the opening 21 of the motor case 20 is closed by the cover 30. In the present preferred embodiment, the cover 30 itself constitutes the fitting portion. An outside surface 32 of the cover 30 is preferably arranged to align with an edge of the circumferential wall 22 on a side where the opening 21 is defined, when the cover 30 has been fixed to the motor case 20.

The motor body 40 is arranged inside the motor case 20 closed by the cover 30. The motor body 40 includes a shaft 41 and so on. The shaft 41 is supported by a lower bearing 2 and an upper bearing 3 such that the shaft 41 is rotatable on the central line A of the cover 30 and the motor case 20. The lower bearing 2 is attached to a central portion of the bottom wall 23 of the motor case 20. The upper bearing 3 is attached to the through hole 31 of the cover 30. One end of the shaft 41 is arranged to project out of the cover 30 through the through hole 31.

The motor body 40 includes a rotor (not shown), a stator (not shown), and so on. The motor body 40 is arranged to drive and rotate the shaft 41 through currents supplied from an external source.

The motor 1 is a screw-less motor that does not involve use of a screw or the like for fixing. The motor 1 is provided with fixing structures 50 where portions of the motor case 20 are bent to fix the cover 30 to the motor case 20.

The fixing structures 50 according to the present preferred embodiment are two in number, and the two fixing structures 50 are arranged at two separate locations in an edge portion of the motor 1 on the side where the opening 21 is defined. The two fixing structures 50 are arranged radially opposite each other. Each of the two fixing structures 50 includes two bend portions 51 and one recessed portion 52. The two bend portions 51 are defined in the motor case 20, and are bent to fix the cover 30 to the motor case 20. The recessed portion 52 is defined in the cover 30.

Fig. 3 illustrates the bend portions 51 prior to bending. Two cut portions 24 are defined in an end portion of the circumferential wall 22 on the side where the opening 21 is defined. Each of the cut portions 24 is substantially in the shape of a trapezoid, and is defined by cutting a portion of the circumferential wall 22. Locations of the two cut portions 24 correspond to those of the two fixing structures 50. Specifically, each of the cut portions 24 includes a bottom edge portion 24a and a pair of side edge portions 24b. The bottom edge portion 24a of each cut portion 24 is positioned at a level lower than that of an edge 22a of the circumferential wall 22. The side edge portions 24b are arranged to extend obliquely so as to spread from the bottom edge portion 24a toward the edge 22a and to be in connection with ends of the bottom edge portion 24a and the edge 22a.

One of the bend portions 51 is defined in each of the side edge portions 24b of each cut portion 24 integrally with the circumferential wall 22. More specifically, in the present preferred embodiment, a first bend portion 51a and a second bend portion 51b, which are arranged to extend in mutually opposite directions with respect to a circumferential direction of the circumferential wall 22, are defined in each cut portion 24. The first bend portion 51a and the second bend portion 51b, each numbering one, are provided for each recessed portion 52. Each of the bend portions 51 is substantially in the shape of a rectangular plate, and arranged to extend toward the opening 21 at an angle (about 45 degrees in the present preferred embodiment) with respect to the central line A of the circumferential wall 22. Each of the bend portions 51 is arranged to extend substantially perpendicularly to a corresponding one of the side edge portions 24b.

Each of the bend portions 51 is arranged inside the cut portion 24 in its entirety. In other words, each bend portion 51 is arranged such that a top thereof does not project outward beyond the edge 22a of the circumferential wall 22. Therefore, it is possible to define all of the cut portions 24 and the bend portions 51 by a single instance of stamping the circumferential wall 22 through press working. The present preferred embodiment is therefore excellent in terms of material costs and mass productivity.

Figs. 4A and 4B illustrate the recessed portion 52 of the cover 30. Fig. 4A is a diagram illustrating the recessed portion 52 when viewed from above in a direction parallel to the central line A of the cover 30. Fig. 4B is a diagram illustrating the recessed portion 52 when viewed from a radial outside in a direction perpendicular to the central axis A. The recessed portions 52 are provided at two locations in a circumferential surface of the cover (i.e., the fitting portion) 30 where the bend portions 51 are defined.

Referring to Figs. 4A and 4B, each of the recessed portions 52 is defined in an edge of an end portion of the cover 30 on the side where the opening 21 is defined. Each recessed portion 52 is substantially in the shape of a trapezoid, and is open both on a side closer to the central line A and on a radial outside. Each recessed portion 52 includes a first support surface 53, a second support surface 54, a bottom surface 55, and an inner side surface 56. The first and second support surfaces 53 and 54 are arranged to have inclinations corresponding to those of the first and

second bend portions

51a and 51b, respectively. The bottom surface 55 is arranged in connection with lower ends of the first and second support surfaces 53 and 54. The inner side surface 56 is arranged in connection with radially inner ends of the bottom surface 55 and the first and second support surfaces 53 and 54.

In more detail, each of the support surfaces 53 and 54 is inclined (at an angle of 45 degrees with respect to the central line A) from the bottom surface 55 of the recessed portion 52 toward the opening 21. Radially

outer edges

53a and 54a of the first and second support surfaces 53 and 54, respectively, are arranged to extend in directions substantially perpendicular to longitudinal directions of the first and

second bend portions

51a and 51b, respectively, when viewed from the radial outside. In addition, the support surfaces 53 and 54 are also arranged to extend obliquely from the inner side surface 56 of the recessed portion 52 toward the radial outside so as to expand in a radial manner away from the central line A.

Referring to Fig. 5, the cut portion 24 is greater in size than the recessed portion 52. The cut portion 24 is arranged relative to the recessed portion 52 such that an edge of the cut portion 24 is displaced outward from an edge of the recessed portion 52. In particular, each of the side edge portions 24b of the cut portion 24 is displaced outward by a predetermined bend margin h from a corresponding portion of the edge of the recessed portion 52 (i.e., the radially outer edge of the corresponding support surface).

After the cover 30 is fitted into the opening 21 of the motor case 20, each of the bend portions 51 is bent in a thickness direction of the bend portion 51 (i.e., radially inward). Each bend portion 51 is thereby brought into surface contact with a corresponding one of the support surfaces 53 and 54 of the recessed portion 52, so that the cover 30 is fixed to the motor case 20.

At this time, because of the bend margin h, the bending of each bend portion 51 is securely achieved at a position away from a base of the bend portion 51 even if, for example, the shape of the recessed portion 52 or that of the cut portion 24 deviates from a desired shape due to an error in a molding process. Therefore, the surface contact of each bend portion 51 with the corresponding one of the support surfaces 53 and 54 is securely achieved, so that the bend portion 51 is firmly fixed to the corresponding one of the support surfaces 53 and 54.

In the present preferred embodiment, each of the first and

second bend portions

51a and 51b, which are arranged to extend obliquely and in mutually opposite directions with respect to the circumferential direction of the circumferential wall 22, is bent with an angle defined with respect to the central line A. Therefore, circumferential positioning of the cover 30 relative to the circumferential wall 22 is easily accomplished by roughly aligning each cut portion 24 with a corresponding one of the recessed portions 52 and bending each bend portion 51, because an oblique component force fr acts to gradually bring the cover 30 into a desired position relative to the circumferential wall 22.

In the present preferred embodiment, each of the bend portions 51 and the support surfaces 53 and 54 is inclined at a specified angle with respect to each of the direction parallel to the central line A and the circumferential direction. This makes it possible to bring each of the bend portions 51 into surface contact with a corresponding one of the support surfaces 53 and 54 securely. Even if there is a slight molding error or deviation in any of the recessed portions 52 and the cut portions 24, the molding error or deviation is easily absorbed. The present preferred embodiment is therefore excellent in terms of productivity as well.

Moreover, referring to Fig. 5, in the present preferred embodiment, the rotation of the shaft 41 may produce a force that acts to lift the cover 30 or displace the cover 30 in the circumferential direction, for example. Even if this happens, the component force fr, which contributes to fixing the cover 30 in the circumferential direction, and a component force fs, which acts in a direction parallel to the central line A and away from the opening 21, are simultaneously obtained at a contact surface between each of the bend portions 51 and the corresponding one of the support surfaces 53 and 54. This contributes, for example, to preventing a shake or a displacement between the cover 30 and the motor case 20, and preventing the cover 30 from coming off the motor case 20, leading to an effective reduction in production of shavings.

Furthermore, in the present preferred embodiment, the support surfaces 53 and 54 of each recessed portion 52 are arranged to extend obliquely from the inner side surface 56 radially outward to be increasingly more distant from each other. This enables each of the bend portions 51 to be brought into contact with the corresponding one of the support surfaces 53 and 54 without a need to bend each of the bend portions 51 at an angle of as great as 90 degrees. This makes it easier to bring each of the bend portions 51 into surface contact with the corresponding one of the support surfaces 53 and 54, and therefore contributes to more effectively preventing the production of shavings.

Note that fixing structures and so on according to the present invention are not limited to those according to the above-described preferred embodiment, and that variations and modifications can be made without departing from the scope and spirit of the present invention.

For example, referring to Fig. 6, the number of fixing structures 50 is not limited to two, but may be one or more than two in other preferred embodiments of the present invention. Also note that, in the case where the number of fixing structures 50 is more than two, the fixing structures 50 may not necessarily be arranged radially opposite one another.

Also note that each fixing structure 50 may not necessarily be provided with both the first and

second bend portions

51a and 51b. It is enough that the motor 1 should include at least one first bend portion 51a and at least one second bend portion 51b, and that at least one recessed portion 52 should be provided for the first and

second bend portions

51a and 51b. For example, referring to Fig. 7, the motor 1 may include two recessed portions 52 arranged radially opposite each other, with one of the recessed portions 52 including only one first bend portion 51a and the other of the recessed portions 52 including only one second bend portion 51b.

Also note that the drive apparatus according to the present invention is not limited to the motor, but may be an actuator or the like.

20 motor case (receptacle)
21 opening
22 circumferential wall
30 cover (fitting member)
50 fixing structures
51 bend portions
51a first bend portions
51b second bend portions
52 recessed portions
53 first support surfaces
54 second support surfaces
A central line

Claims

A fixing structure used to fix, to a metallic receptacle including a cylindrical circumferential wall having an opening at one end thereof, a cylindrical fitting member including a fitting portion to be fitted into the opening, the fixing structure comprising:
a plurality of bend portions each defined integrally with the circumferential wall, arranged to extend obliquely toward the opening at an angle with respect to a central line of the circumferential wall, and bent in a thickness direction of the circumferential wall; and
at least one recessed portion defined in a circumferential surface of the fitting portion for the bend portions;wherein
the at least one recessed portion includes a plurality of support surfaces arranged to have inclinations corresponding to those of the bend portions;
the bend portions include a first bend portion and a second bend portion arranged to extend in mutually opposite directions with respect to a circumferential direction of the circumferential wall; and
each of the first and second bend portions is arranged in contact with one of the support surfaces.
The fixing structure according to claim 1, wherein each of the support surfaces is arranged to extend obliquely from a bottom of the recessed portion toward the opening.
The fixing structure according to one of claims 1 and 2, wherein
the circumferential wall includes a plurality of cut portions each defined by cutting a portion of the circumferential wall; and
each of the bend portions is defined at an edge of any of the cut portions, and is arranged inside the cut portion in its entirety.
The fixing structure according to claim 3, wherein each of the cut portions is arranged to be slightly greater in size than a corresponding one of the at least one recessed portion such that an edge of the cut portion is displaced outward by a predetermined bend margin from an edge of the recessed portion.
The fixing structure according to any one of claims 1 to 4, wherein the first bend portion and the second bend portion, each numbering one, are arranged in each of the at least one recessed portion.
A drive apparatus comprising the fixing structure of any one of claims 1 to 5.