Patent Grant
7554239
This application is based on and incorporates herein by reference Japanese Patent Application No. 2005-329335 filed on Nov. 14, 2005.
1. Field of the Invention
The present invention relates to a dynamo-electric machine and a vehicular air blower having the same.
2. Description of Related Art
For example, as recited in Japanese Unexamined Patent Publication No. 2005-29038 (corresponding to U.S. Pat. No. 7,067,946 B2 and U.S. 2006/0192449 A1), there is known a vehicular air blower, which includes a fan rotated by a direct current motor to blow air into a passenger compartment of a vehicle. In an armature of the direct current motor of the above vehicular air blower, electric current is supplied to the armature from brushes, which are slidably engaged with a commutator that is fixed to a rotatable shaft of the armature. When the electric current is supplied to the armature through the brushes, the fan, which is fixed to the rotatable shaft, is rotated together with the rotatable shaft.
In the above direct current motor, at the time of supplying the electric current to the armature, when the rotation of the rotatable shaft is locked or when an excess load is applied to the rotatable shaft, excessive electric current is supplied to the armature through the brushes. In such a case, the brushes may generate abnormal heat due to the excess electric current to cause burnout of the direct current motor. Thus, in order to limit the burnout caused by the abnormal heat generation of the brushes, a protective device, such as a fuse, is provided in the direct current motor or on an upstream side of an electric power source of the direction current motor, so that the supply of the electric current to the armature is stopped whenever the excessive electric current is supplied to the armature.
In a case where the fuse malfunctions due to some reason, the excessive electric current may possibly be supplied to the armature through the brushes. Thus, in general, in addition to the fuse, the direct current motor further includes a safety device, which stops the supply of electric current from the brushes to the commutator when the excessive electric current is supplied to the armature. One such safety device includes a circuit. In this circuit, the electric current, which is supplied to the armature, is measured, and the measured electric current is compared with a predetermined threshold value. When the measured electric current is larger than the threshold value, the circuit stops the supply of electric current to the armature. Furthermore, in order to reduce occurrence of the damage caused by the burnout, the resin components of the direct current motor are made of flame-retarded resin.
When the safety device is provided to the direct current motor in addition to the fuse, a size of the direct current motor becomes large, or a structure of the direct current motor becomes complicated. Furthermore, the flame-retarded resin is generally expensive. Thus, when such expensive flame-retarded resin is used, the manufacturing cost of the direct current motor is disadvantageously increased. The above disadvantages are not limited to the direct current motor of the vehicular air blower and are common to dynamo-electric machines, which are energized through brushes.
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to alleviate at least one of the above disadvantages.
To achieve the objective of the present invention, there is provided a dynamo-electric machine, which includes an armature, a brush, an urging means, a brush box and a pressing means. The armature includes a rotatable shaft and a commutator. The rotatable shaft is rotatably supported. The commutator is fixed to the rotatable shaft. The brush is slidably engaged with the commutator at a radially inner end of the brush to energize the armature. The urging means is for urging the brush against the commutator. The brush box has an opening on a commutator side of the brush box and slidably receives the brush. The brush box includes a deformable side wall, which becomes deformable at a predetermined temperature. The pressing means is for pressing the brush against the deformable side wall of the brush box such that a pressing force of the pressing means, which is conducted to the deformable side wall through the brush, causes deformation of the deformable side wall to disengage the radially inner end of the brush from the commutator when the temperature of the deformable side wall reaches the predetermined temperature due to a temperature increase in the brush. A vehicular air blower may have the above dynamo-electric machine and a fan driven by the above dynamo-electric machine.
To achieve the objective of the present invention, there is also provided a dynamo-electric machine, which includes an armature, a brush, a brush box and a disengaging means. The armature includes a commutator. The brush is slidably engaged with the commutator to energize the armature. The brush box slidably receives the brush. The brush box includes a deformable side wall, which is made of a thermoplastic material and becomes deformable at a predetermined temperature. The disengaging means is for disengaging the brush from the commutator by deforming the deformable side wall of the brush box through the brush and displacing the brush in a deforming direction of the deformable side wall when the temperature of the deformable side wall is increased to the predetermined temperature by heat generated in the dynamo-electric machine. A vehicular air blower may have the above dynamo-electric machine and a fan driven by the above dynamo-electric machine.
The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:
One embodiment of the present invention will be described with reference to the accompanying drawings.
A holding tubular portion 1a of the motor holder 1 is shaped into a generally cylindrical body having a bottom wall. A flange 1b extends radially outward from an axial intermediate part of the holding tubular portion 1a. An axial communication hole 1c, which extends vertically in
Furthermore, an air passage member 5 is installed to the motor holder 1 such that the air passage member 5 covers a lower end of the communication hole 1c and closely contacts an outer peripheral surface of the holding tubular portion 1a and a bottom surface of the flange 1b. The air passage member 5 forms an air passage 5a. The air passage 5a conducts the air, which is drawn through the communication hole 1c and serves as cooling air, into an interior of the motor main body 2.
The motor main body 2 is formed as a direct current motor. A yoke 11 of the motor main body 2, which is fitted into the holding tubular portion 1a, is shaped into a cup-shaped body having a bottom wall. A through hole 11a is formed through the bottom wall of the yoke 11 to conduct the cooling air from the air passage 5a into an interior of the yoke 11. Furthermore, a generally inverted bowl shaped housing 12 is placed at the opening of the yoke 11.
As shown in
In each pair of the first and second installation recesses 15, 16, a brush holding portion 17, which has a generally rectangular cross section, is formed between the first installation recess 15 and the second installation recess 16 to extend radially outward. When the two brush holding portions 17 (only one is shown in
A holding plate 18 is fixed to bottom walls 15a, 16a of the first and second installation recesses 15, 16 to make each brush holding portion 17 into the generally tubular form. The holding plate 18 covers the lower part of the brush holding portion 17 from the interior side (the lower side in
The above housing 12 is made of polybutylene terephthalate (PBT) and is formed through injection molding. When the housing 12, which is made of the PBT, is heated to the temperature equal to or greater than 220 degrees Celsius, the housing 12 becomes thermally deformable. When the housing 12 is installed to the opening of the yoke 11, a closing plate 21 is placed at a radially outer end of the brush holding portion 17 to close a radially outer opening of the brush box 19, as shown in
As shown in
A generally rectangular parallelepiped shaped brush 41 is slidably received in each brush box 19 to slidably engage the commutator 37. The brush 41 is received in the brush box 19 in such a manner that a longitudinal direction of the brush 41 generally coincides with the radial direction of the housing 12. A radially inner end surface 41a of the brush 41, which is radially opposed to the commutator 37, is tilted in such a manner that a space between the radially inner end surface 41a of the brush 41 and the outer peripheral surface of the commutator 37 progressively increases from an upper end of the radially inner end surface 41a to a lower end of the radially inner end surface 41a in the axial direction of the commutator 37. Furthermore, between two sides S1, S2 of the radially inner end surface 41a of the brush 41, which are parallel to each other and are opposed to each other in the axial direction of the commutator 37, the side (the upper side in
Furthermore, a compression coil spring 43 is interposed between the radially outer end surface 41b of the brush 41 and the closing plate 21. The compression coil spring 43 serves an urging means for urging the brush 41 against the commutator 37. Since the radially outer end surface 41b of the brush 41 is tilted to form the acute angle relative to the top surface 41c of the brush 41, the compression coil spring 43 urges the brush 41 against the commutator 37 and also urges the brush 41 against the contact wall 17c. Thereby, the compression coil spring 43 also serves as a pressing means for pressing the brush 41 against the contact wall 17c. In this way, the top surface 41c of the brush 41 contacts the contact wall 17c. Furthermore, the brush 41 is urged by the compression coil spring 43, and thereby a radially inner end 41e of the brush 41 is engaged with the commutator 37.
In the motor main body 2, the space, which permits the movement of the brush 41 that results in the disengagement of the brush 41 from the commutator 37, is provided around the brush holding portion 17.
In the vehicular air blower, which is constructed in the above described manner, when the electric current is supplied to the armature 32, i.e., when the electric current is supplied to the winding 35 through the brushes 41 and the commutator 37 to energize the armature 32, the armature 32 is rotated, thereby resulting in the rotation of the fan 3 together with the rotatable shaft 33 of the armature 32. When the fan 3 is rotated through the rotation of the rotatable shaft 33, the gas (the air), which is taken through the intake opening, is guided radially outward and is discharged through the outlet opening to blow the air from the air blower. Specifically, through the rotation of the fan 3, the air inside or outside of the passenger compartment of the vehicle is drawn into the air blower and is blown out of the air blower toward the interior of the passenger compartment.
Then, for example, when a load is applied to the fan 3 due to some reason to cause application of a load to the rotatable shaft 33 to limit the rotation of the rotatable shaft 33, the electric current, which is supplied from the brushes 41 to the commutator 37, is increased to cause heat generation from the brushes 41. At that time, the radially inner end 41e of each brush 41, which is engaged with the commutator 37, tends to have the highest heat. Then, the heat of the brush 41 is conducted to the contact wall 17c, which contacts the top surface 41c of the brush 41, and thereby the temperature of the contact wall 17c reaches about 220 degrees Celsius. At that time, as shown in
Furthermore, the rotating commutator 37 also urges the brush 41 against the side wall 17a, which is located on a trailing side (a rear side) of the brush holding portion 17 (the brush box 19) in the rotational direction of the commutator 37. Here, it should be noted that the term “trailing side” of the brush holding portion 17 is defined as a side opposite from a leading side (a front side) of the brush holding portion 17 where the side 17b is located. In other words, the trailing side of the brush holding portion 17 is located on the rear side of the leading side of the brush holding portion 17 in the rotational direction of the commutator 37. With the above construction, as shown in
As described above, the present embodiment provides the following advantages.
(1) The brush 41 is urged against the contact wall 17c by the urging force of the compression coil spring 43, so that the brush 41 contacts the contact wall 17c. Therefore, at the time of supplying the electric current to the armature 32, when the brush 41 is heated, the heat of the brush 41 is conducted to the contact wall 17c. Then, when the contact wall 17c, which is heated to about 220 degrees Celsius, is deformed by the urging force of the compression coil spring 43 that is conducted through the brush 41, the brush 41 is moved such that the radially inner end 41e of the brush 41 is spaced from the commutator 37 due to the fact that the brush 41 is urged against the contact wall 17c by the compression coil spring 43. As a result, the brush 41 is disengaged from the commutator 37, and thereby the electric current from the brush 41 to the commutator 37 is stopped. The brush box 19 has the contact wall 17c, which becomes deformable upon reaching the predetermined temperature, and the brush 41 is urged against the contact wall 17c. With this construction, at the time of increasing the temperature of the brush 41, the electric current from the brush 41 to the commutator 37 can be advantageously stopped. Therefore, it is not required to provide an additional safety device in addition to the fuse to limit the burnout of the motor main body 2, which is caused by the abnormal heat generation of the brushes 41. Furthermore, in the motor main body 2, the fuse, which limits the burnout of the motor main body 2, may possibly be eliminated. Furthermore, at the time of increasing the temperature of the brush 41, the contact wall 17c is deformed to limit the burnout of the motor main body 2, so that it is not required to use the flame-retarded resin. Therefore, the occurrence of the burnout of the motor main body 2 caused by the abnormal heat generation of the brushes 41 can be advantageously reduced with the inexpensive and simple structure. Furthermore, it is possible to reduce the occurrence of the burnout of the vehicular air blower, which has the above motor main body 2. In addition, it is possible to limit an increase in the size of the motor main body 2 with the above structure, which limits the burnout of the motor main body 2.
(2) In the brush 41, the radially outer end surface 41b is tilted to form the acute angle with respect to the top surface 41c, so that the brush 41 is urged against the contact wall 17c by the urging force of the compression coil spring 43. Thus, when the compression coil spring 43, which urges the brush 41 against the commutator 37, is also used as the component, which urges the brush 41 against toe contact wall 17c, it is not required to provide a separate urging component, such as a spring, which urges the brush 41 against the contact wall 17c. As a result, the structure, which reduces the occurrence of the burnout of the motor main body 2 caused by the abnormal heat generation of the brush 41, can be advantageously simplified.
(3) Between the two sides S1, S2, which are parallel to each other and are provided in the radially inner end surface 41a of the brush 41, the side S1, which is closer to the contact wall 17c in comparison to the side S2, is engaged with the commutator 37. In the brush 41, the engaging portion of the brush 41, which is engaged with the commutator 37, tends to generate the high heat. Therefore, when the side S1 of the radially inner end surface 41a of the brush 41, which is closer to the contact wall 17c, is constructed to engage with the commutator 37, the engaging portion of the brush 41, which tends to generate the high heat in the brush 41, is placed closer to the contact wall 17c. As a result, in the state where the brush 41 generates the abnormal heat, the deformation of the contact wall 17c can be initiated at the earlier time point when the side S1 of the radially inner end surface 41a of the brush 41, which is closer to the contact wall 17c in comparison to the side S2 of the radially inner end surface 41a, is engaged with the commutator 37 in comparison to the case where the side S2 is engaged with the commutator 37.
(4) The housing 12, which has the brush holding portions 17, is made of the PBT, which is the thermoplastic resin, so that the housing 12 can be easily formed through, for example, the injection molding. Furthermore, the brush holding portions 17 and the bearing holding portion 14 are formed integrally, so that the number of required components and the number of required assembling steps of the motor main body 2 can be reduced.
(5) The length of each pigtail 42 is set to permit the movement of the brush 41 at the time of deformation of the contact wall 17c. Thus, at the time of the abnormal heat generation of the brush 41, the movement of the brush 41 will not be limited by the pigtail 42.
(6) Each of the side walls 17a, 17b and the contact wall 17c is formed to have the uniform wall thickness in the range of 1 mm to 4 mm (i.e., 1 mm≦wall thickness≦4 mm). When the wall thicknesses of the side walls 17a, 17b and of the contact wall 17c becomes less than 1 mm, the durability may be disadvantageously reduced, and the bothersome noise may be generated between the brush 41 and the walls 17a, 17b, 17c due to the vibration of the motor main body 2. In contacts, when the wall thickness of the contact wall 17c is increased beyond 4 mm, the contact wall 17c may not be easily deformed at the time of abnormal heat generation of the brush 41. Thus, when the wall thickness of each of the side walls 17a, 17b and the contact wall 17c is made uniform in the range of 1 mm to 4 mm, the satisfactory durability of each brush box 19 is achieved, and the generation of the bothersome noise between the brush 41 and the walls 17a-17c can be advantageously limited. Also, with the above wall thickness of each of the side walls 17a, 17b and the contact wall 17c, at the time of abnormal heat generation of the brush 41, the contact wall 17c can be easily deformed.
(7) For example, in a case where the side wall(s) 17a, 17b is deformed to disengage the brush 41 from the commutator 37, in order to provide a space, which allows such deformation of the side wall(s) 17a, 17b, the layout of the components of the motor main body 2 may need to be changed. However, the substantial part of the armature 32 except the portion of the rotatable shaft 33 is received in the space, which is surrounded by the yoke 11 and the housing 12. Thus, in the motor main body 2 of the present embodiment, none of the other components of the motor main body 2 is placed on the top of the contact wall 17c. Therefore, as in the present embodiment, when the contact wall 17c, on which the other components of the motor main body 2 are not placed, is formed to be deformable at the time of abnormal heat generation of the brush 41, it is easy to provide the space, which allows the deformation of the contact wall 17c. As a result, a degree of freedom in the designing of the shape of the housing 12 is not limited, and the movement of the side wall (e.g., the contact wall 17c) of the brush holding portion 17, which is urged by the brush 41, is not limited by the other components of the motor main body 2.
The above embodiment may be modified as follows.
In the above embodiment, the housing 12 (the brush holding portions 17) is made of the PBT. Alternatively, the housing 12 (the brush holding portions 17) may be made of any other appropriate thermoplastic resin other than the PBT. Furthermore, the housing 12 (the brush holding portions 17) may be made of any other suitable material, which has the thermoplasticity, other than the thermoplastic resin. Furthermore, as long as each contact wall 17c, which contacts the corresponding brush 41, is made of the thermoplastic resin, the other part of the housing 12 may be made of any other appropriate material other than the thermoplastic resin.
In the above embodiment, each of the side walls 17a, 17b and the contact wall 17c is formed to have the uniform wall thickness in the range of 1 mm to 4 mm (i.e., 1 mm≦wall thickness≦4 mm). However, it may be only required that at least the contact wall 17c is formed to have the wall thickness in the range of 1 mm to 4 mm. Thus, the walls 17a, 17b other than the contact wall 17c may have any other appropriate wall thickness.
In the above embodiment, the brush 41 is urged against the contact wall 17c by the urging force of the compression coil spring 43. Alternatively, as shown in
In the above embodiment, when the two brush holding portions 17 are viewed in the axial direction, the two brush holding portions 17 are diametrically opposed to each other such that the center lines of the two brush holding portions 17 are aligned with the single straight line, which extends perpendicular to the central axis of the commutator 37. In place of the two brush holding portions 17 of the above embodiment, two brush holding portions 81, 91 may be alternatively formed, as shown in
In the structure shown in
In the above embodiment, the radially inner end surface 41a of the brush 41 is tilted in such a manner that the space between the radially inner end surface 41a of the brush 41 and the outer peripheral surface of the commutator 37 progressively increases from the upper end of the radially inner end surface 41a to the lower end of the radially inner end surface 41a in the axial direction of the commutator 37. However, the present invention is not limited to this. For example, the radially inner end surface 41a of the brush 41 may be modified to form a right angle with respect to the top surface 41c of the brush 41.
In the above embodiment, the radially outer end surface 41b of the brush 41 forms the acute angle with respect to the top surface 41c of the brush 41, so that the brush 41 is urged against the contact wall 17c by the urging force of the compression coil spring 43. However, the structure for urging the brush 41 against the contact wall 17c is not limited to this. For example, the brush 41 may be urged against the contact wall 17c by, for example, a spring that is interposed between the bottom surface 41d of the brush 41 and the holding plate 18.
In the above embodiment, the brush 41 is urged against the commutator 37 by the urging force of the compression coil spring 43. However, the urging member, which urges the brush 41 against the commutator 37, is not limited to the compression coil spring 43 and may be, for example, a torsion coil spring.
The motor main body 2 may be provided in an apparatus other than the vehicular air blower. In the above embodiment, the motor main body 2 is described in detail as the exemplary case. Alternatively, the present invention may be implemented in any other appropriate dynamo-electric machine, in which electric current is supplied to an armature through brushes, other than the motor main body 2.
Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-329335 | Nov 2005 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5717271 | Aoki et al. | Feb 1998 | A |
| 6922003 | Uchida | Jul 2005 | B2 |
| 7067946 | Noda et al. | Jun 2006 | B2 |
| 20040164643 | Ortt et al. | Aug 2004 | A1 |
| 20060192449 | Noda et al. | Aug 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 406315251 | Nov 1994 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20070108864 A1 | May 2007 | US |
