JP5714188B1 - Fully closed main motor - Google Patents

Abstract

A rotor 7 having a cooling fan attached to a rotor core disposed on the inner peripheral side of the stator, a frame 2 containing the stator and the rotor 7, and connected to the frame 2 to support the rotor shaft. The cooling fan 40 includes a main plate 41 that partitions the inside and the outside of the main motor 100, and is provided between the bracket 11 and the main plate 41. A gap 74 is formed, and between the bracket 11 and the stator, a negative pressure generated by the rotation of the rotor 7 generates a positive pressure higher than the atmospheric pressure in a space in which air does not circulate. A pressurizing mechanism 200 communicating with the interior space is formed.

Description

  The present invention relates to a fully-enclosed main motor that drives a railway vehicle.

  Generally, a rotary electric machine for driving a railway vehicle often employs a fully enclosed main motor (a fully closed main motor) from the viewpoint of maintenance saving. This fully-enclosed main motor mainly includes a frame that has a cylindrical shape and a rotor disposed on the inner peripheral side, and a bracket that is disposed opposite to both ends of the frame and rotatably supports the rotor shaft. It is configured. A bearing is provided at the center of the bracket, and a cylindrical stator core that houses the stator coil is attached to the inner peripheral portion of the frame. Between the inner peripheral surface of the stator core and the outer peripheral surface of the rotor. Have uniform voids.

  The fully-enclosed main motor constructed in this way has a structure that seals the inside of the motor, so it cannot cool by taking outside air into the machine, so to dissipate the heat inside the machine to the outside, the frame is enlarged and the heat radiation area It is necessary to take measures such as increasing In order to eliminate the disadvantage of the increase in size, a fully-enclosed main motor using a cooling fan as a part for separating the inside of the machine from the outside of the machine has been proposed. In this fully-enclosed main motor, the main plate and bracket of the cooling fan that separates the inside and outside of the machine are in a relationship between the rotating portion and the fixed portion, and a labyrinth (a minute gap) is provided between the main plate and the bracket. . Therefore, the fully closed main motor has a problem that dust and water slightly enter the machine through the labyrinth.

  In order to solve such a problem, the conventional main motor shown in the following Patent Document 1 applies and fills the labyrinth portion with grease that is the same as or similar to the bearing lubrication grease to prevent intrusion of dust and the like.

Japanese Patent Laying-Open No. 2012-50172 (FIG. 1)

  However, in the structure of the above prior art, it is necessary to take measures to prevent the grease from being discharged during the assembling work of the main motor, and there is a problem that the effect of preventing dust intrusion decreases due to aging of the grease.

  The present invention has been made in view of the above, and provides a fully-enclosed main electric motor that can suppress the intrusion of dust into the machine without applying grease to the labyrinth between the cooling fan and the bracket. With the goal.

In order to solve the above-described problems and achieve the object, the present invention includes a stator, a rotor core disposed on the inner peripheral side of the stator, and a cooling fan attached to the rotor core. A rotor, a frame that includes the stator and the rotor, a bracket that is connected to the frame and supports the rotor shaft, and a bearing portion that is provided on the bracket and supports the rotor shaft. The cooling fan has a main plate that partitions the inside and the outside of the fully closed main motor, a gap is formed between the bracket and the main plate, and the frame is within the frame. An inside air passage that communicates the driving side and the non-driving side of the stator is formed, and the inner surface of the bracket faces the inner wall of the bracket between the bracket and the stator. outer diameter side edge portion provided By an annular member constituting the internal air ventilation Michitan section, the cause high positive pressure above atmospheric pressure inside air ventilating path, and characterized in that the pressure mechanism communicating with the inboard space of the gap is formed And

  According to the present invention, there is an effect that dust can be prevented from entering the machine without applying grease to the labyrinth between the cooling fan and the bracket.

FIG. 1 is a longitudinal sectional view of a fully closed main motor according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is a diagram showing a first modification of the fully closed main motor according to the embodiment of the present invention. FIG. 4 is a diagram showing a second modification of the fully closed main motor according to the embodiment of the present invention. FIG. 5 is a diagram showing a third modification of the fully closed main motor according to the embodiment of the present invention. FIG. 6 is a diagram showing a fourth modification of the fully closed main motor according to the embodiment of the present invention. FIG. 7 is a view showing a fifth modification of the fully closed main motor according to the embodiment of the present invention. FIG. 8 is a diagram showing a sixth modification of the fully closed main motor according to the embodiment of the present invention.

  Embodiments of a fully closed main motor according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a longitudinal sectional view of a fully closed main motor according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of FIG.

  A fully closed main motor (hereinafter referred to as “main motor”) 100 includes a stator 10 composed of a stator core 3 and a fixed coil 8, a rotor 7 disposed in the stator 10, a stator 10 and a rotor. 7, the bracket 1 disposed on the drive side 60 of the frame 2, the bracket 11 disposed on the non-drive side 61 of the frame 2, and the cartridge provided at the axial center of the bracket 1 50 (bearing portion) and a cartridge 51 (bearing portion) provided at the central portion of the shaft of the bracket 11. The bracket 11 is formed integrally with the frame 2.

  The frame 2 is formed with a ventilation path 22 located on the outer peripheral side of the stator core 3. A plurality of ventilation paths 22 are provided, for example, at equal intervals in the circumferential direction of the frame 2 so as to communicate the driving side 60 of the stator 10 and the non-driving side 61 of the stator 10.

  The rotor 7 includes a rotor core 4 formed by laminating electromagnetic steel plates, an iron core retainer 5 that covers the driving side 60 of the rotor core 4, an iron core retainer 6 that covers the non-driving side 61 of the rotor core 4, and an iron core. The cooling fan 30 attached to the presser 5, the cooling fan 40 attached to the iron core retainer 6, the rotor bar 13 embedded in the rotor core 4, and ring-shaped end rings provided at both ends of the rotor bar 13 14 are integrally connected to form a cage rotor of the induction motor.

  A uniform gap is formed between the inner peripheral surface of the stator core 3 and the outer peripheral surface of the rotor core 4. The cartridge 50 is structured to be detachable from the drive side 60, and accommodates a bearing that rotatably supports one end of the rotor shaft 9, and has a labyrinth structure. The labyrinth is a structure that forms the boundary between the rotating part and the fixed part, prevents the lubricating grease from leaking out of the machine, and prevents dust from entering the bearing and the machine from outside the machine. The cartridge 51 is detachable from the non-driving side 61 and houses a bearing that rotatably supports the other end of the rotor shaft 9 and has a labyrinth structure. With such a configuration, the rotational force of the rotor 7 is transmitted to the wheel via a joint and a gear device (not shown) disposed on the drive side 60.

  The cooling fan 30 on the driving side 60 is installed in the main motor 100 and is formed so that the inside air can be agitated. In the illustrated example, the wings are attached to the stator 10 side of the cooling fan 30, but the shape of the cooling fan 30 is not limited to the illustrated example.

  The cooling fan 40 on the counter driving side 61 includes a main plate 41 and a plurality of first blades 42. The main plate 41 has a shape that increases in diameter from the iron core retainer 6 toward the cartridge 51, and is disposed so as to partition the inside and the outside of the main motor 100. An outer peripheral end 43 of the main plate 41 is disposed in the vicinity of the bracket 11, and a labyrinth (a minute gap 74) is provided between the main plate 41 and the bracket 11.

  First wings 42 are formed on the main plate 41 on the bracket 11 side, and the first wings 42 are provided at substantially equal intervals in the circumferential direction of the rotor 7. The shape of the cooling fan 40 is not limited to the illustrated example, and the first wing 42 may not be provided, and the surface of the cooling fan 40 on the stator 10 side is equivalent to the first wing 42. Wings may be provided.

  A through hole 70 for cooling the bearing in the cartridge 51 is formed on the center side of the bracket 11, and the through holes 70 are provided at substantially equal intervals in the circumferential direction of the frame 2.

  An annular member 72 that is interposed between the bracket 11 and the stator 10 and divides the space between the bracket 11 and the stator 10 into a plurality of spaces is provided on the inner side (stator 10 side) of the bracket 11. It has been. The annular member 72 is provided, for example, in parallel with the bracket 11, the outer diameter side edge 79 of the annular member 72 is positioned on the frame 2 side that is radially outward, and the inner diameter side edge 71 of the annular member 72 is Located in the vicinity of the outer peripheral end 43. A labyrinth (a minute gap 78) is provided between the annular member 72 and the outer peripheral end 43.

  A pressure mechanism 200 is formed between the bracket 11 and the stator 10. The pressurizing mechanism 200 includes an annular member 72 and a pressurizing unit 73, and generates a positive pressure higher than the atmospheric pressure in a space where air does not circulate due to the negative pressure generated by the rotation of the rotor 7, and the minute gap 74. It is configured to communicate with the interior space of the aircraft.

  The pressurizing unit 73 is provided, for example, in the vicinity of the outer peripheral end 43 of the main plate 41 on the bracket 11 side so as to communicate with the in-machine space of the minute gap 74, and is formed in an annular shape in the circumferential direction. The pressure unit 73 communicates the space 24 between the bracket 11 and the annular member 72, the minute gap 74, and the minute gap 78. The space 24 is provided such that one end communicates with the ventilation path 22 of the frame 2 and the other end communicates with the pressure unit 73. When a plurality of ventilation paths 22 of the frame 2 are provided, a plurality of spaces 24 may be provided in the circumferential direction so as to communicate with each ventilation path 22. The size of the pressurizing unit 73 is not limited to the illustrated example.

  The operation will be described below. As the cooling fan 30 rotates, the air in the machine flows as indicated by a dotted line. For example, air that has passed through the ventilation path 23 of the rotor core 4 or air that has passed through the gap between the stator core 3 and the rotor core 4 flows into the ventilation path 22, and the air that has passed through the ventilation path 22 is It flows into the ventilation path 23 of the rotor core 4. Here, since the rotational centrifugal force of the cooling fan 30 is generated by the rotation of the rotor 7 inside the main motor 100, the pressure in the in-machine space (hereinafter referred to as "space A") indicated by the reference symbol A in the figure is denoted by the reference symbol C. It becomes a positive pressure higher than the pressure (atmospheric pressure) of the outside space shown (hereinafter “space C”). Further, the pressure in the space indicated by the symbol B in the figure (hereinafter “space B”) is a negative pressure lower than the atmospheric pressure. At this time, when the pressure in the space A near the end (c in the figure) of the ventilation path 22 is the pressure a, the pressure in the vicinity of the space B is the pressure b, and the pressure in the vicinity of the space C is the pressure c. The relationship between the pressures is a> c> b.

  As a result, the pressure in the space 24 is increased to be equal to the pressure a in the space A, and the pressurizing unit 73 communicating with the space 24 is pressurized. Due to the pressure difference between the pressurizing unit 73 and the outside air, intrusion of outside air from the minute gap 74 into the pressurizing unit 73 is suppressed. Therefore, it is possible to prevent dust and the like contained in the outside air from entering the machine.

  Next, an example in which the structure of the main motor 100 is modified will be described. FIG. 3 is a diagram showing a first modification of the fully closed main motor according to the embodiment of the present invention.

  The cooling fan 40 shown in FIG. 3 includes a main plate 41, second wings 76, and first wings 42. The second wing 76 is formed at the outer peripheral end 43 of the main plate 41 on the bracket 11 side, and a plurality of second wings 76 are provided in the circumferential direction of the rotor 7. Note that the shape of the cooling fan 40 is not limited to the illustrated example, and for example, an outer peripheral end 43 of the main plate 41 may be cut into a plurality of portions in the circumferential direction and processed into a concavo-convex shape (blade processing). Even in such a configuration, the same effect as the second wing 76 can be obtained.

  In the inner diameter side edge 71 of the annular member 72, a portion of the main plate 41 facing the second wing 76 is formed in a concave shape in the outer diameter direction. Between the bracket 11, the second wing 76, and the annular member 72, a pressurizing portion 75 that connects the space 24, the minute gap 74, and the minute gap 78 is formed. The pressurizing part 75 formed on the annular member 72 side with respect to the second wing 76 is formed in an annular shape in the circumferential direction. In addition, the magnitude | size of the pressurization part 75 is not limited to the example of illustration.

  The operation will be described below. As the cooling fan 30 rotates, the pressure unit 75 communicating with the space 24 is pressurized. Further, since the pressure is applied by the second wing 76 of the pressurizing unit 75, the pressure of the pressurizing unit 75 is further increased. Therefore, intrusion of outside air from the minute gap 74 to the pressurizing unit 75 is suppressed by the pressure difference between the pressurizing unit 75 and the outside air. As a result, it is possible to prevent dust and the like contained in the outside air from entering the machine.

  FIG. 4 is a diagram showing a second modification of the fully closed main motor according to the embodiment of the present invention. The main motor 100 in FIG. 4 is a configuration example in which the pressurizing unit 73 in FIG. 2 and the pressurizing unit 75 and the cooling fan 40 in FIG. 3 are combined. In the main motor 100, a pressurizing unit 75 (one pressurizing unit) and a pressurizing unit 73 (the other pressurizing unit) communicate with each other, and the main plate 41 is provided with second wings 76. The pressure member 75 formed closer to the annular member 72 than the second wing 76 is formed in an annular shape in the circumferential direction, and the pressure member 73 formed closer to the bracket 11 than the second wing 76 surrounds the circumference. It is formed in an annular shape in the direction.

  In the main motor 100 configured as described above, the pressurizing unit 73 and the pressurizing unit 75 communicating with the space 24 are pressurized by the rotation of the rotor 7. Therefore, intrusion of outside air from the minute gap 74 into the pressurizing units 73 and 75 is suppressed more than the configuration example of FIGS. 2 and 3 due to a pressure difference between the pressurizing units 73 and 75 and the external air.

  FIG. 5 is a diagram showing a third modification of the fully closed main motor according to the embodiment of the present invention. In the cooling fan 40 of FIG. 5, a third wing 77 is provided instead of the second wing 76 of FIG. The third wing 77 is formed at the outer peripheral end 43 of the main plate 41 on the rotor 7 side, and a plurality of third wings 77 are provided in the circumferential direction of the rotor 7. The same effect can be obtained even if the third wing 77 is constituted by the wing processing described above.

  The inner diameter side edge 71 of the annular member 72 is formed such that a portion facing the outer peripheral end 43 of the main plate 41 and the third wing 77 is concave in the outer diameter direction. Between the bracket 11, the outer peripheral end 43, the annular member 72, and the third wing 77, a pressurizing portion 75 that connects the space 24, the minute gap 74, and the minute gap 78 is formed. The pressurizing part 75 formed on the annular member 72 side with respect to the third wing 77 is formed in an annular shape in the circumferential direction. In addition, the magnitude | size of the pressurization part 75 is not limited to the example of illustration.

  In the main motor 100 configured as described above, the pressurizing unit 75 communicating with the space 24 is pressurized by the rotation of the rotor 7. Further, since the pressurizing unit 75 is pressurized by the third wing 77, the pressure of the pressurizing unit 75 is further increased. Accordingly, intrusion of outside air from the minute gap 74 into the pressurizing unit 75 is suppressed by a pressure difference between the pressurizing unit 75 and the outside air.

  FIG. 6 is a diagram showing a fifth modification of the fully closed main motor according to the embodiment of the present invention. The main motor 100 in FIG. 6 is a configuration example in which the pressurizing unit 73 in FIG. 2 is combined with the pressurizing unit 75 and the third wing 77 in FIG. In the main motor 100, a pressurizing unit 75 (one pressurizing unit) and a pressurizing unit 73 (the other pressurizing unit) communicate with each other, and the main plate 41 is provided with a third wing 77. The pressurizing part 75 formed on the annular member 72 side with respect to the third wing 77 is formed in an annular shape in the circumferential direction, and the pressurizing part 73 formed on the bracket 11 side with respect to the outer peripheral end of the main plate 41 It is formed in an annular shape in the direction.

  In the main electric motor 100 configured as described above, both the pressurizing units 73 and 75 communicating with the space 24 are pressurized by the rotation of the rotor 7. Therefore, the intrusion of air from the minute gap 74 into the pressurizing units 73 and 75 is suppressed as compared with the configuration example of FIG. 5 due to the pressure difference between the pressurizing units 73 and 75 and the outside air.

  FIG. 7 is a view showing a fifth modification of the fully closed main motor according to the embodiment of the present invention. The main motor 100 in FIG. 7 is a configuration example in which the second wing 76 in FIG. 3 is combined with the pressurizing unit 73 in FIG. The second wing 76 is provided at a position facing the pressing portion 73 on the bracket 11 side.

  In the main electric motor 100 configured in this way, the pressurizing unit 73 communicating with the space 24 is pressurized by the rotation of the rotor 7. Further, since the pressurizing unit 73 is pressurized by the second wing 76, the pressure of the pressurizing unit 73 is further increased. Accordingly, the pressure of the pressurizing unit 73 becomes higher than the external air pressure, and the intrusion of air from the minute gap 74 into the pressurizing unit 73 is suppressed as compared with the configuration example of FIG.

  FIG. 8 is a diagram showing a sixth modification of the fully closed main motor according to the embodiment of the present invention. In the main motor 100 of FIG. 8, the annular member 72 is located closer to the stator 10 than the annular member 72 of FIGS. In the main motor 100 configured as described above, the rotation of the rotor 7 pressurizes the pressurizing unit 73 communicating with the space 24 as in the main motor 100 illustrated in FIGS. Intrusion of outside air from 74 to the pressurizing unit 73 is suppressed.

  1 to 8, the space 24, the pressurizing unit 73, the pressurizing unit 75, the second wing 76, and the third wing 77 are provided, but the configuration of the main motor 100 is illustrated. For example, when the through hole 70 is provided in the bracket 1 on the driving side 60, these structures may be provided in the bracket 1 and the cooling fan 30.

  Further, in the present embodiment, the pressurizing part 75 is provided in a portion where the inner diameter side edge 71 of the annular member 72 is formed in a concave shape, but the shape of the pressurizing part 75 is not limited to this. Even if the inner diameter side edge 71 of the annular member 72 is not formed in a concave shape, a space having a sectional area similar to the sectional area of the space 24 is formed between the bracket 11, the annular member 72 and the second wing 76. Also good.

As described above, the main motor 100 according to the embodiment includes the stator 10, the rotor core 4 disposed on the inner peripheral side of the stator 10, and the cooling fan 40 attached to the rotor core 4. A rotor 7 including the stator 10 and the rotor 7, brackets 1 and 11 connected to the frame 2 and supporting the rotor shaft 9, and the rotor shaft provided on the brackets 1 and 11 The cooling fan 40 has a main plate 41 that partitions the inside and the outside of the main motor 100, and a minute gap 74 is formed between the bracket 11 and the main plate 41. The positive pressure higher than the atmospheric pressure is generated between the bracket 11 and the stator 10 in a space (space A, space 24, etc.) in which air does not circulate due to the negative pressure generated by the rotation of the rotor 7, and small gap 74 Pressurizing mechanism 200 which communicates with the inboard space is formed. With this configuration, the pressure of the pressurizing unit 73 becomes higher than the external atmospheric pressure (atmospheric pressure), and entry of external air from the minute gap 74 into the pressurizing unit 73 is suppressed by this pressure difference. Accordingly, dust or the like contained in the outside air can be prevented from entering the machine without applying bearing lubrication grease or the like to the minute gap 74 unlike the conventional main motor.

The pressurizing mechanism 200 includes an annular member 72 interposed between the bracket 11 and the stator 10, a space 24 formed between the bracket 11 and the annular member 72, and between the bracket 11 and the main plate 41. comprising the small gap 74, communicates the small gap 78 between the annular member 72 and the main plate 41, a pressing portion 73, 75 Ru is the pressure in the inboard space higher than the atmospheric pressure positive pressure, the . With this configuration, the pressure of the pressurization units 73 and 75 into which air from the space 24 has flowed becomes higher than the external air pressure, and the pressurization units 73 and 75 from the minute gap 74 due to the pressure difference between the pressurization units 73 and 75 and the external air. Intrusion of outside air into is suppressed.

In this embodiment, the configuration example in which the annular member 72 is provided in the bracket 11 has been described. However, the space 24 may be provided directly in the bracket 11 instead of providing the pressurizing unit 73. That is, the bracket 11 of the main motor 100 generates a positive pressure higher than the atmospheric pressure in a space where air does not circulate due to the negative pressure generated by the rotation of the rotor 7, and communicates with the space inside the micro gap 74. A pressure mechanism 200 is formed. With the main motor 100 configured as described above, the same effects as those of the main motor 100 shown in FIGS. 1 to 8 can be obtained.

  In addition, the fully-enclosed main motor according to the embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and within the scope not departing from the gist of the present invention, Of course, it is possible to change the configuration by omitting a part or the like.

  As described above, the present invention is applicable to a fully-enclosed main motor, and in particular, an invention that can suppress the intrusion of dust into the machine without applying grease to the labyrinth between the cooling fan and the bracket. Useful as.

  1 Bracket, 2 Frame, 3 Stator Core, 4 Rotor Core, 5, 6 Core Presser, 7 Rotor, 8 Fixed Coil, 9 Rotor Shaft, 10 Stator, 11 Bracket, 13 Rotor Bar, 14 End Ring, 22 ventilation path, 23 ventilation path, 24 space, 30, 40 cooling fan, 41 main plate, 42 first wing, 43 outer peripheral edge, 50, 51 cartridge, 60 driving side, 61 counter driving side, 70 through hole, 71 inner diameter Side edge part, 72 annular member, 73 pressure part, 74 minute gap, 75 pressure part, 76 second wing, 77 third feather, 78 minute gap, 79 outer diameter side edge, 100 fully closed main motor 200 Pressure mechanism.

Claims (8)

A stator,
A rotor having a rotor core disposed on the inner peripheral side of the stator, and a cooling fan attached to the rotor core;
A frame containing the stator and the rotor;
A bracket connected to the frame and supporting the rotor shaft;
A bearing portion provided on the bracket and supporting a rotor shaft;
A fully-enclosed main motor equipped with
The cooling fan has a main plate that partitions the inside and the outside of the fully closed main motor,
A gap is formed between the bracket and the main plate,
In the frame, an inside air ventilation path that communicates the driving side and the non-driving side of the stator is formed,
Between the bracket and the stator,
A positive pressure higher than the atmospheric pressure on the internal air ventilation path is formed by an annular member in which an outer diameter side edge provided facing the inner wall of the bracket and extending in the entire circumferential direction of the rotor shaft constitutes an end of the internal air ventilation path. And a pressurizing mechanism that communicates with the space inside the machine of the gap is formed. The pressure mechanism is
The annular member;
A space formed between the bracket and the annular member, a gap between the bracket and the main plate, and a gap between the annular member and the main plate are communicated to each other. A pressurizing section for making the pressure a positive pressure higher than atmospheric pressure;
The fully-enclosed main motor according to claim 1, comprising: The main plate is formed with wings at the outer peripheral end on the bracket side,
The fully-enclosed main motor according to claim 2, wherein the pressurizing portion is formed closer to the annular member than the wing. The main plate is formed with wings at the outer peripheral end on the bracket side,
The pressure part is divided into two pressure parts, one pressure part is formed on the annular member side from the wing, and the other pressure part is formed on the bracket side from the wing. The fully-enclosed main motor according to claim 2, wherein: The main plate is formed with wings at the outer peripheral end on the rotor side,
The fully-enclosed main motor according to claim 2, wherein the pressurizing portion is formed closer to the annular member than the wing. The main plate is formed with wings at the outer peripheral end on the rotor side,
The pressure part is divided into two pressure parts, one pressure part is formed on the annular member side from the wing, and the other pressure part is closer to the bracket than the outer peripheral end of the main plate. The fully closed main motor according to claim 2, wherein the main motor is formed. The main plate is formed with wings at the outer peripheral end on the bracket side,
The fully-enclosed main motor according to claim 2, wherein the pressurizing portion is formed on the bracket side with respect to the wing. A stator,
A rotor having a rotor core disposed on the inner peripheral side of the stator and a cooling fan attached to the rotor core;
A frame containing the stator and the rotor;
A bracket connected to the frame and supporting the rotor shaft;
A bearing portion provided on the bracket and supporting a rotor shaft;
A fully-enclosed main motor equipped with
The cooling fan has a main plate that partitions the inside and the outside of the fully closed main motor,
A gap is formed between the bracket and the main plate,
In the frame, an inside air ventilation path that communicates the driving side and the non-driving side of the stator is formed,
It said bracket by an annular member having an outer diameter side edge portion provided in the entire circumferential direction of the rotor shaft facing the inner wall of said bracket constituting the internal air ventilation Michitan part, large in the inside air ventilating path A fully-enclosed main motor characterized in that a pressurizing mechanism that generates a positive pressure higher than the atmospheric pressure and communicates with the space inside the machine in the gap is formed.

Images