This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2014-166094, filed on Aug. 18, 2014, and the entire contents of which are incorporated herein by reference.
The present invention relates to a bearing unit capable of rotatably holding, for example, a rotor, and a motor having the bearing unit.
Conventionally, a rotor shaft of a rotor is rotatably held by a bearing, and the bearing is attached to a stator by a stator housing. The bearing is provided in a cylindrical body of the stator housing so as to rotatably hold the rotor shaft, and a stator core is attached to an outer periphery of the cylindrical body.
The stator housing is composed of a metallic material being easily cut and formed into various shapes, e.g., brass. For example, a sintered metal bearing is press-fitted in the metallic stator housing, and the stator core is fixed to the outer periphery thereof by an adhesive.
On the other hand, some stator housings are composed of resin so as to reduce production costs. To prevent a bearing from shifting, in an axial direction, with respect to the stator housing, a modified bearing structure, in which a retainer for limiting the axial shift of the bearing is provided, has been invented (see Patent Document 1).
However, in case of employing the stator housing composed of resin, strain of an inner diameter of the stator housing will easily occur when the bearing is fitted thereinto. Therefore, a following process of rotary sizing is required in some cases. After press-fitting the bearing, the retainer prohibits only the axial shift of the bearing. By heat shock, etc., cracks will be generated in the stator housing composed of resin, and holding force between the stator housing and the bearing will be weakened. Therefore, the bearing will be slightly turned, in the stator housing, by rotation of a motor, so assembling accuracy of the bearing and the stator housing must be lowered. If the bearing is fitted with play, the bearing must be easily turned and the assembling accuracy must be much lowered.
Further, air pressure difference is occurred, between inside of the bearing housing and outside thereof, by rotating a rotor in the motor. If air circulation in the motor is insufficient, grease of the bearing, for example, will be excessively heated. By the heat effect, a life span of the bearing will be shortened, and cooling efficiency of the motor will be lowered.
The present invention has been invented to solve the above described problems of the conventional technology. Accordingly, a first object of the present invention to provide a bearing unit, in which a metallic bearing section can be prohibited to turn with respect to a bearing housing composed of resin and pressure difference between inside of the bearing housing and outside thereof can be eliminated.
A second object is to provide a motor, which has the bearing unit of the present invention and whose assemblability can be improved.
Patent Document 1: Japanese Patent No. 5039491
To achieve the objects, the inventor studied and conceived the present invention. The present invention has following structures.
Namely, the bearing unit of the present invention comprises:
a cylindrical bearing housing being composed of resin; and
a metallic bearing section being provided in and integrated with the cylindrical bearing housing, the bearing section being capable of rotatably holding a rotor shaft,
a plurality of recessed grooves and a plurality of projected stripes are formed in an inner wall surface of a cylindrical hole of the bearing housing and an outer circumferential surface of the bearing section, extended in an axial direction, and arranged in an circumferential direction, the recessed grooves and the projected stripes are recession/projection-fitted to each other,
number of the recessed grooves is greater than that of the projected stripes,
the bearing section is fitted into the bearing housing from an opening part of one end of the bearing housing toward a bottom part of the other end thereof in a state where the recessed grooves are aligned with the projected stripes, and
the recessed groove not recession/projection-fitted to the projected stripe forms a space communicating to the cylindrical hole.
With the above described structure, the recessed grooves and the projected stripes, which are formed in the inner wall surface of the cylindrical hole of the bearing housing and the outer circumferential surface of the bearing section, are recession/projection-fitted to each other, and the number of the recessed grooves is greater than that of the projected stripes. Further, the recessed groove not recession/projection-fitted to the projected stripe forms the space communicating to the cylindrical hole. Therefore, the pressure difference between the inside of the bearing housing and the outside thereof can be eliminated by the space formed by the recessed groove not fitted, so that bad heat effect of the metallic bearing section can be prevented.
By employing the bearing housing composed of resin, a production cost can be reduced. Since the bearing section can be attached to the bearing housing and prohibited to turn without press fit, no strain of an inner diameter of the bearing housing occurs, so that a following process of rotary sizing is not required.
Preferably, the projected stripes, which are extended in the axial direction, are formed in the inner wall surface of the cylindrical hole of the bearing housing, and
the recessed grooves, whose number is greater than that of the projected stripes, are formed in the outer circumferential surface of the bearing section.
With this structure, the metallic bearing section can be sufficiently cooled because the recessed grooves are formed in the outer circumferential surface of the bearing section.
In the bearing unit, a recessed part, which corresponds to the recessed groove, may be radially formed in an end surface of the bearing section, which faces the bottom part.
With this structure, the rotor shaft is fitted into the bearing section, but air can be circulated, between inside of the motor and outside thereof, through the recessed part formed in the end surface of the bearing section and the recessed groove formed in the outer circumferential surface of the bearing section and communicated to the recessed part.
In the bearing unit, a projected part may be formed in the bottom part of the other end of the bearing housing, and
a gap, which is formed by butting an end surface of the bearing section fitted into the cylindrical hole from the opening part of the one end of the bearing housing against the projected part, may be communicated to the recessed groove not recession/projection-fitted to the projected stripe.
With this structure, the gap is entirely formed, between the bottom part of the other end surface of the bearing housing, except the projected part by aligning the recessed grooves with the projected stripes, fitting the bearing section into the bearing housing from the opening part of the one end and butting the end surface of the bearing section against the projected part of the bottom part of the other end of the bearing housing. Therefore, even if no recessed parts are formed in the end surface of the bearing section, air can be circulated between the inside of the motor and the outside thereof through the recessed groove which is formed in the outer circumferential surface of the bearing section and not recession/projection-fitted to the projected stripe. Further, no oil moves from the bearing section to the bearing housing, so that the oil can be prevented from scattering to the outside of bearing housing.
The motor of the present invention comprises:
the bearing unit of the present invention;
a stator core being attached to the outer circumferential surface of the bearing housing of the bearing unit; and
a rotor having a rotor shaft, which is rotatably held by the bearing section attached in the bearing housing.
With this structure, a production cost of the motor can be reduced, and assemblability of the motor can be improved.
By the present invention, the bearing unit, in which the metallic bearing section can be prohibited to turn with respect to the bearing housing composed of resin and pressure difference between the inside of the bearing housing and the outside thereof can be eliminated, and the motor, which has the bearing unit of the present invention and whose assemblability can be improved, can be provided.
The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.
Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and in which:
Preferred embodiments of the bearing section and the motor of the present invention will now be described in detail with reference to the accompanying drawings. Firstly, an schematic structure of a blower unit, which includes the motor of the present invention, will be explained, as an embodiment, with reference to
In
As shown in
As shown in
A plurality of projected stripes (e.g., three projected stripes) 2a are formed in an inner wall surface (i.e., an inner circumferential surface) 2b of the bearing housing 2. The projected stripes 2a are extended in an axial direction of the bearing housing 2 and can be recession/projection-fitted to the recessed grooves 6a (see
As shown in
Since the number of the recessed grooves 6a is greater than that of the projected stripes 2a recession/projection-fitted to the recessed grooves 6a, the recessed grooves 6a not recession/projection-fitted to the projected stripes 2a form spaces communicating to the cylindrical hole, so that air pressure difference between inside of the bearing housing 2 and outside thereof can be eliminated by releasing air through the spaces of the recessed grooves 6a not recession/projection-fitted. Therefore, applying bad heat effect to the metallic bearing section 6 can be prevented.
Note that, the number of the recessed grooves 6a formed in the outer circumferential surface of the bearing section 6 is not limited to six, and the number of the projected stripes 2a formed in the bearing housing 2 is not limited to three. The numbers may be optionally set as far as the number of the recessed grooves 6a is greater than that of the projected stripes 2a.
As shown in
As shown in
As shown in
A manner of assembling the bearing unit 1 will be explained with reference to
Successively, the retainer projections 2c, which are formed in the inner wall surface 2b of the bearing housing 2 and formed on the one end side (see
In a motor of the present embodiment, the bearing unit 1 is attached to the casing 10 having the sensor 11, and then the stator 3 and the rotor 4 are sequentially assembled as shown in
As described above, the recessed grooves 6a and the projected stripes 2a, which are extended in the axial direction of the bearing unit 1, are recession/projection-fitted to each other, and the number of the recessed grooves 6a is greater than that of the projected stripes 2a. Further, the recessed grooves 6a not recession/projection-fitted to the projected stripes 2a form the spaces communicating to the cylindrical hole of the bearing housing 2. Therefore, the air pressure difference between the inside of the bearing housing 2 and the outside thereof can be eliminated by the spaces formed by the recessed grooves 6a not recession/projection-fitted, so that applying bad heat effect to the metallic bearing section 6 can be prevented.
By employing the bearing housing 2 composed of resin, a production cost can be reduced. Since the bearing section 6 can be attached to the bearing housing 2 and prohibited to turn without press fit, no strain of the inner diameter of the bearing housing 2 occurs, so that a following process of rotary sizing is not required.
The metallic bearing section 6 can be sufficiently cooled because the recessed grooves 6a are formed in the outer circumferential surface of the bearing section 6. The rotor shaft 5 is fitted into the bearing section 6, but air can be circulated between the inside of the motor and the outside thereof through the recessed parts 6d of the bearing section 6, a space around the outer periphery of the bearing section 6 and the recessed grooves 6a thereof.
Further, the retainer projections 2c, which are formed in the inner wall surface 2b of the bearing housing 2 and on the one end side thereof, are deformed to overlap onto the end surface 6b of the bearing section 6 so as to retain the bearing section 6 in the bearing housing 2. Therefore, the metallic bearing section 6 can be efficiently attached to the bearing housing 2 without occurring deformation caused by heat or press fit.
In the motor, the stator core 3a is attached on the outer circumferential surface of the bearing housing 2 of the bearing unit 1 and retained by heat caulking. The rotor shaft 5 is fitted into the bearing section 6, which has been attached in the bearing housing 2, so that the rotor 4 can be rotatably held. Therefore, a production cost of the motor can be reduced, and assemblability of the motor can be improved.
In the above described embodiment, the projected stripes 2a are formed in the inner wall surface 2b of the bearing housing 2; the recessed grooves 6a are formed in the outer circumferential surface of the bearing section 6. The recessed grooves may be formed in the bearing housing 2, and the projected stripes may be formed in the bearing section 6.
Further, in the above described embodiment, the bearing section 6 fitted in the bearing housing 2 is an oil-impregnated sintered bearing, but other bearings, e.g., fluid dynamic bearing, pneumatic bearing, may be employed.
Successively, another embodiment of the bearing unit will be explained with reference to
As shown in
As shown in
As described above, the bearing section 6 is fitted into the bearing housing 2, in the state where the projected stripes 2a are aligned with the recessed grooves 6a, until the end surface of the bearing section 6 contacts the projected parts 2m of the bottom part 2l, so that the gap 12 enclosing the projected parts 2m is formed between an inner surface of the bottom part 2l and the end surface of the bearing section 6. Therefore, even if no recessed parts 6d are formed in the end surface of the bearing section 6, air can be circulated between the inside of the motor and the outside thereof through the recessed grooves 6a which are formed in the outer circumferential surface of the bearing section 6 and not recession/projection-fitted to the projected stripe 2a, and no oil moves from the bearing section 6 to the bearing housing 2, so that the oil can be prevented from scattering to the outside of bearing housing 2, as well as the former embodiment.
Note that, each of the projected parts 2m may be formed into a rectangular parallelepiped shape as shown in
With this structure, the gap 12 is entirely formed between the bottom part 2l of the other end of the bearing housing 2 and the end surface of the bearing section 6 (between the opposite surfaces) except the projected parts 2m. Therefore, air can be circulated, between the inside of the motor and the outside thereof, through the recessed grooves 6a not recession/projection-fitted to the projected stripe 2a, etc., and no oil moves from the bearing section 6 to the bearing housing 2, so that the oil can be prevented from scattering to the outside of bearing housing 2.
In the present embodiment, the recessed parts 6d are not formed in the end surface of the bearing section 6, which contacts the bottom part 2l of the bearing housing 2. The recessed parts 6d may be formed as far as a height of the projected parts 2m is equal to or greater than a depth of the recessed parts 6d.
All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alternations could be made hereto without departing from the spirit and scope of the invention.
Number | Date | Country | Kind |
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2014-166094 | Aug 2014 | JP | national |