JP7162512B2 - centrifugal fan - Google Patents

Description

The present invention relates to centrifugal fans.

Patent Document 1 discloses an air supply fan device that is an example of a conventional centrifugal fan. This air supply fan device includes a combustion chamber wall, a fan motor, an air supply fan, and a cooling fan for the fan motor.

The combustion chamber wall defines a portion of the combustion chamber. A ventilation hole is provided through the combustion chamber wall. The fan motor is arranged on the opposite side of the combustion chamber wall from the combustion chamber. The fan motor has a motor wall, a boss and a rotating shaft. The motor wall is supported by the combustion chamber wall with a mounting plate interposed therebetween. A boss is formed in the center of the motor wall. The rotating shaft protrudes into the combustion chamber from the boss portion through the ventilation hole. The entire motor wall and boss are spaced from the combustion chamber wall in the axial direction of the rotating shaft.

The air supply fan is arranged in the combustion chamber. The supply fan has a main plate and a plurality of blades. The main plate is fixed to the rotating shaft so that it can rotate integrally. Each blade is arranged along the outer peripheral edge of the main plate.

In addition to the air supply fan, a cooling fan for the fan motor is attached to the rotating shaft together with two stoppers and a spring. The fan motor cooling fan is arranged between the boss portion and the combustion chamber wall.

In this air supply fan device, the fan motor operates to rotate the fan motor cooling fan together with the rotating shaft and the air supply fan, so that the air around the fan motor passes between the boss and the wall of the combustion chamber. It then flows through the vent into the combustion chamber. This air flow cools the fan motor.

JP-A-5-52321

However, in the above-described conventional centrifugal fan, since the fan motor cooling fan and the like are assembled to the rotating shaft, it is difficult to reduce the number of parts and to simplify the rotating shaft and its surroundings.

In addition, in this centrifugal fan, a fan for cooling the fan motor is assembled to the rotating shaft, and the rotating shaft projects from the boss portion of the fan motor through the ventilation hole into the accommodation space, thereby protruding the rotating shaft. Due to the lengthened configuration, dynamic imbalance tends to occur in the rotating shaft, and the rotating shaft and the air supply fan tend to vibrate due to rotation.

As a result, with this centrifugal fan, there is a problem that it is difficult to effectively cool the motor while reducing the manufacturing cost and suppressing vibration during operation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a centrifugal fan capable of effectively cooling a motor while reducing manufacturing costs and suppressing vibration during operation. are issues to be resolved.

The centrifugal fan of the present invention has a cochlear-shaped casing that defines an accommodation space and has a motor support wall with an opening extending therethrough;
a motor wall disposed on the side opposite to the housing space with respect to the motor support wall and supported by the motor support wall; a motor having a boss portion protruding outward and a drive shaft protruding from the boss portion within the accommodation space;
An impeller having a main plate disposed in the accommodation space and fixed to the drive shaft so as to be integrally rotatable, and a plurality of blades arranged along the outer peripheral edge of the main plate,
Between the motor support wall and the motor wall, at least a part of the motor support wall extends from the outer peripheral edge of the motor wall to the boss portion in the axial direction of the drive shaft from the motor wall. a first gap spaced apart from each other is formed,
A second gap is formed between the opening and the boss, wherein at least a portion of the inner peripheral edge of the opening is spaced apart from the boss in the radial direction of the drive shaft ,
A gap region is formed between the motor support wall and the main plate,
the gap region communicates with the first gap and the second gap;
A region surrounding the opening in the motor support wall is a recess formed in a substantially truncated cone shape so as to be spaced apart from the motor wall in the axial direction of the drive shaft,
The first gap is formed by separating the recess from the motor wall in the axial direction of the drive shaft over the range from the outer peripheral edge of the motor wall to the boss,
A region of the motor support wall located outside the recess in the radial direction of the drive shaft is defined as an outer region,
the recessed portion and the outer region face the main plate and partition a part of the gap region;
The impeller is formed with a plurality of auxiliary blades, each of which partially penetrates the main plate and protrudes toward the motor support wall,
Each of the auxiliary blades is characterized by protruding into the gap region outside the recess in the radial direction of the drive shaft .

In the centrifugal fan of the present invention, since no motor cooling fan is provided on the drive shaft of the motor, it is possible to reduce the number of parts and simplify the drive shaft and its surroundings.

In addition, in this centrifugal fan, a motor cooling fan is not provided on the drive shaft, and the boss of the motor passes through the opening of the motor support wall and protrudes into the accommodation space, thereby reducing the length of protrusion of the drive shaft. Due to the structure that can be shortened, the dynamic imbalance of the drive shaft is less likely to occur, and the drive shaft and impeller are less likely to vibrate due to rotation.

Furthermore, in this centrifugal fan, when the motor operates and the drive shaft and the impeller rotate, in the housing space, compared to the inner region located radially inward of the drive shaft from the blades of the impeller, The pressure in the outer region located radially outside of the drive shaft is higher than the blades of the impeller. Then, the air with increased pressure is discharged from the housing space. Here, according to the result of extensive research by the inventor, the air flow generated in the gap area between the stationary motor support wall and the rotating main plate of the impeller lowers the pressure in the gap area. Then, the air around the motor flows through the first gap and the second gap into the gap area, joins the air in the outer area in the accommodation space, and is discharged from the accommodation space. . At this time, the air around the motor flows through the first gap and contacts the motor wall, and further flows through the second gap and contacts the boss, thereby effectively removing heat from the motor.
Further, the rotation of the auxiliary blades together with the drive shaft and the impeller can further promote the flow of air in the gap region. As a result, in this centrifugal fan, the air around the motor flows through the first and second gaps more easily into the gap region, so that the heat of the motor can be removed more effectively.

Therefore, with the centrifugal fan of the present invention, the motor can be effectively cooled while reducing the manufacturing cost and suppressing vibration during operation.

A region surrounding the opening in the motor support wall is a concave portion formed in a substantially truncated cone shape so as to be spaced apart from the motor wall in the axial direction of the drive shaft . In the first gap, the concave portion is separated from the motor wall in the axial direction of the drive shaft over the range from the outer peripheral edge of the motor wall to the boss portion.

In this case, since the first gap can be easily formed by drawing, the manufacturing cost can be further reduced. Further, in this case, the rigidity of the motor support wall can be improved by drawing the motor support wall into a three-dimensional shape.

The casing preferably has a motor support wall and a peripheral wall joined to the outer peripheral edge of the motor support wall. The motor support wall preferably has a motor support wall body including the outer peripheral edge of the motor support wall, and a motor mounting plate assembled to the motor support wall body. The motor mounting plate preferably has an opening, a recess, and a mounting portion to which the motor wall is mounted.

In this case, the motor mounting plate, which is separate from the motor support wall main body, can be easily manufactured using a processing method such as press working, punching, drawing, etc., so that the manufacturing cost can be reduced. Further, the motor mounting plate can be easily processed into a shape that can suitably form the first gap and the second gap.

According to the centrifugal fan of the present invention, the motor can be effectively cooled while reducing the manufacturing cost and suppressing vibration during operation.

FIG. 1 is a schematic diagram of a water heater to which the centrifugal fan of the embodiment is applied. FIG. 2 is a front view of the centrifugal fan of the embodiment. FIG. 3 is a cross-sectional view showing the AA cross section of FIG. FIG. 4 is an exploded perspective view of the centrifugal fan of the embodiment. FIG. 5 is an enlarged cross-sectional view of a main part of FIG. 3, and is a diagram schematically showing the flow of air passing through the first and second gaps.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

(Example)
As shown in FIG. 1, the centrifugal fan 1 of the embodiment is an example of a specific embodiment of the centrifugal fan of the present invention, and is applied to a water heater 8. As shown in FIG. After describing the schematic configuration of the water heater 8, the specific configuration of the centrifugal fan 1 will be described.

<General configuration of water heater>
The water heater 8 is a forced air supply/exhaust water heater. The water heater 8 has a housing 80 , a combustion chamber 82 and a double pipe 89 . Combustion chamber 82 is housed inside housing 80 . An air supply space 81 is formed between the inner wall surface of the housing 80 and the combustion chamber 82 .

The double pipe 89 has an air supply pipe 87 and an exhaust pipe 88 housed inside the air supply pipe 87 . A lower end of the air supply pipe 87 is connected to the upper portion of the housing 80 and communicates with the air supply space 81 . A lower end of the exhaust pipe 88 passes through the upper portion of the housing 80 and communicates with the combustion chamber 82 . The double pipe 89 extends upward from the housing 80, then bends to pass through the wall W1 and protrude to the outside.

The water heater 8 also has a centrifugal fan 1 . A specific configuration of the centrifugal fan 1 will be described in detail later, but the centrifugal fan 1 is connected to the lower portion of the combustion chamber 82 . A centrifugal fan 1 includes a casing 9 , a motor 3 and an impeller 50 .

The casing 9 defines a housing space 90 with a side wall 92, a motor support wall 93, and the like. The side wall 92 is formed with an intake port 9</b>A that connects the air supply space 81 and the housing space 90 . A discharge port 9</b>B is formed in the upper portion of the casing 9 to communicate with the housing space 90 and the combustion chamber 82 .

The motor 3 is arranged on the opposite side of the housing space 90 with respect to the motor support wall 93 . The impeller 50 is arranged in the housing space 90 and connected to the drive shaft 35 of the motor 3 .

Furthermore, the water heater 8 includes a burner 83 and a heat exchanger 84 housed in the combustion chamber 82, respectively. A gas supply pipe (not shown) is connected to the burner 83 . The heat exchanger 84 is arranged above the burner 83 . The heat exchanger 84 is connected to a water supply pipe (not shown) for supplying water from outside the housing 80 and a hot water supply pipe (not shown) for discharging hot water to the outside of the housing 80 .

<Hot water supply operation of water heater>
In the water heater 8 configured as described above, when the hot water supply operation is started, the motor 3 of the centrifugal fan 1 operates to rotate the impeller 50 . As a result, outdoor air is sucked into the accommodation space 90 of the centrifugal fan 1 via the air supply pipe 87, the air supply space 81 and the intake port 9A, and is forcibly supplied to the combustion chamber 82 via the discharge port 9B. be done.

The burner 83 mixes and ignites air supplied to the combustion chamber 82 with fuel gas supplied from a gas supply pipe (not shown) to generate combustion exhaust gas. The heat exchanger 84 heats the water by exchanging heat between water supplied from a water supply pipe (not shown) and combustion exhaust gas from the burner 83 . The hot water heated to a desired temperature in the heat exchanger 84 is discharged to the outside of the housing 80 through a hot water outlet pipe (not shown) and supplied to a hot water destination.

The combustion exhaust gas used for heat exchange in the heat exchanger 84 is discharged to the outside through an exhaust pipe 88 . At this time, heat is exchanged between the air flowing through the air supply pipe 87 and the combustion exhaust gas flowing through the exhaust pipe 88 . Therefore, the combustion exhaust gas flowing through the exhaust pipe 88 is cooled to a low temperature before being discharged to the outside, so that the environmental load can be reduced. Moreover, since the air flowing through the air supply pipe 87 is heated to a high temperature before it is introduced into the air supply space 81, the thermal efficiency can be improved.

<Specific Configuration of Centrifugal Fan>
Next, the centrifugal fan 1 will be described in detail with reference to FIGS. 2 to 5. FIG. In the following explanation, the axis of the drive shaft 35 of the motor 3 is shown in FIGS. explain. The drive axis X35 direction is an example of the "axial direction of the drive shaft" in the present invention. The radial direction of the drive shaft center X35 is an example of the "radial direction of the drive shaft" in the present invention.

<Casing>
As shown in FIGS. 3 and 4, etc., in the centrifugal fan 1, the casing 9 has a peripheral wall 91, a side wall 92, and a motor support wall 93 each made of steel. In the casing 9, the peripheral wall 91 is joined to the outer peripheral edge of the side wall 92 and the outer peripheral edge of the motor supporting wall 93 in a state in which the side wall 92 and the motor supporting wall 93 face each other with a predetermined gap in the direction of the drive axis X35. It has a cochlear shape that partitions the accommodation space 90 by being formed.

As shown in FIG. 4, the suction port 9A is a circular hole penetrating through the side wall 92 with the drive axis X35 as the center. The peripheral wall 91 has one end edge 91E and the other end edge 91F extending in the drive axis X35 direction. The ejection port 9B is a rectangular hole formed between one end edge 91E and the other end edge 91F of the peripheral wall 91 .

The motor support wall 93 has a motor support wall body 94 and a motor mounting plate 95 . The motor support wall main body 94 includes an outer peripheral edge of the motor support wall 93 to which the peripheral wall 91 is joined, and an impeller insertion hole 94H is provided through the center thereof.

The impeller insertion hole 94H is a large-diameter circular hole centered on the drive shaft center X35. The impeller insertion hole 94</b>H is set to a size such that the motor support wall main body 94 does not interfere with the impeller 50 when the impeller 50 is arranged in the housing space 90 .

The motor mounting plate 95 has a substantially disc shape centered on the drive axis X35, and has an opening 97 penetrating through its center. The opening 97 is a circular hole centered on the drive axis X35. The opening 97 is set to have a size sufficient to secure a sufficient gap with the outer peripheral surface of the boss portion 33, which will be described later.

The motor mounting plate 95 is configured as shown in FIGS. 2 and 3 by inserting setscrews 95F into screw holes (not shown) penetrating the outer periphery of the plate 95 and screwing the setscrews 95F into the motor support wall main body 94. As shown, it is assembled to the motor support wall main body 94 and closes the impeller insertion hole 94H.

As shown in FIG. 4, the motor mounting plate 95 is formed with a recess 98 and a mounting portion 96 .

The recessed portion 98 is drawn into a substantially truncated cone shape so that the area surrounding the opening 97 in the motor mounting plate 95 of the motor support wall 93 approaches the side wall 92 in the direction of the drive axis X35.

The recess 98 includes an inclined portion 98A and a flat portion 98B. The inclined portion 98A is inclined so as to bite into the accommodation space 90 from the outer peripheral edge of the recessed portion 98 . The flat portion 98B connects to the inner peripheral edge of the inclined portion 98A and extends close to the drive axis X35 to reach the opening portion 97 .

An outer region 95D is defined as a region of the motor mounting plate 95 located radially outward of the drive shaft center X35 from the inclined portion 98A. The flat portion 98B is positioned closer to the side wall 92 than the outer region 95D and extends parallel to the outer region 95D.

The mounting portion 96 is connected to the inner peripheral edge of the outer region 95D and has three bulging portions that bulge closer to the drive axis X35 and divide the inclined portion 98A of the recess 98 into three arc portions. The attachment portion 96 extends parallel to the outer region 95D. A screw hole 96</b>F is formed in the mounting portion 96 .

<Motor>
As shown in FIG. 3 , the motor 3 has a motor housing 32 , a motor wall 31 and bosses 33 . The motor housing 32 is made of steel and has a substantially cylindrical shape with a bottom centered on the drive axis X35. A bearing 32T is assembled to the bottom of the motor housing 32 .

The motor wall 31 and the boss portion 33 are integrally formed by drawing or cutting a steel plate. The motor wall 31 has a substantially disc shape centered on the drive axis X35, and a boss portion 33 is formed in the center thereof. The boss portion 33 has a substantially cylindrical shape centered on the drive axis X35. A bearing 33T is assembled in the boss portion 33 .

A motor chamber 3A surrounded by the motor housing 32, the motor wall 31 and the boss portion 33 is formed by joining the opening edge of the motor housing 32 and the outer peripheral edge 31E of the motor wall 31 together.

The drive shaft 35 is rotatable around the drive axis X35 by being supported by the motor housing 32, the motor wall 31 and the boss portion 33 via bearings 32T and 33T.

A stator 3S is fixed to the inner peripheral surface of the motor housing 32 . A rotor 3R is fixed to a portion of the drive shaft 35 located within the motor chamber 3A so as to be rotatable therewith. The rotor 3R is arranged inside the stator 3S. A control board 3C is fixed to the surface of the motor wall 31 on the side of the motor chamber 3A. The control board 3C includes a control IC, power transistors, resistors, and the like. The motor 3 rotates the rotor 3R and the drive shaft 35 around the drive axis X35 by supplying power to the stator 3S via the control board 3C.

As shown in FIGS. 2 and 4, the motor wall 31 is formed with three small pieces 31F projecting radially outward from the outer peripheral edge 31E of the drive shaft center X35. A set screw 3F is inserted into a screw hole (not shown) penetrating the small piece 31F, and the set screw 3F is screwed into a screw hole 96F formed in the mounting portion 96 of the motor mounting plate 95, thereby fixing the motor wall 31 to the mounting portion. 96 and supported by the motor mounting plate 95 of the motor support wall 93 . Thus, the motor 3 is arranged on the opposite side of the housing space 90 with respect to the motor support wall 93 .

As shown in FIG. 3 , with the motor wall 31 supported by the motor mounting plate 95 , the boss 33 protrudes into the accommodation space 90 through the opening 97 of the motor mounting plate 95 . The drive shaft 35 protrudes from the boss portion 33 within the housing space 90 .

<First Gap and Second Gap>
As shown in FIGS. 3 and 5, between the motor mounting plate 95 of the motor support wall 93 and the motor wall 31, a first space S1 is formed.

The first gap portion S1 is such that the inclined portion 98A and the flat portion 98B of the concave portion 98 formed in the motor mounting plate 95 extend from the outer peripheral edge 31E of the motor wall 31 to the outer peripheral surface of the boss portion 33. , in the drive axis X35 direction.

The first space S1 is formed by narrowing the area surrounding the opening 97 in the motor mounting plate 95, ie, the recess 98, away from the motor wall 31 in the direction of the drive axis X35.

A second space S<b>2 is formed between the opening 97 of the motor mounting plate 95 and the boss 33 .

The second gap portion S2 is formed by separating the entire circumference of the inner peripheral edge 97E of the opening 97 of the motor mounting plate 95 from the outer peripheral surface of the boss portion 33 in the radial direction of the drive shaft center X35.

<Impeller>
As shown in FIGS. 3 and 4 , the impeller 50 has a main plate 51 , an opposing plate 52 and a plurality of blades 53 . In this embodiment, the main plate 51, the opposing plate 52 and the plurality of blades 53 are made of steel.

The main plate 51 has a substantially disc shape centered on the drive axis X35, and has a shaft hole 51H penetrating through its center.

As shown in FIG. 3, the opposing plate 52 has a substantially annular shape centered on the drive axis X35, and has a large-diameter hole 52H penetrating through its center. The large-diameter hole 52H has a larger diameter than the suction port 9A of the side wall 92. As shown in FIG. The opposing plate 52 faces the main plate 51 in the drive axis X35 direction.

As shown in FIGS. 3 and 4, each blade 53 is arranged along the outer peripheral edge 51E of the main plate 51 . The impeller 50 is configured such that one end side of each blade 53 in the direction of the drive axis X35 is joined to the main plate 51, and the other end side of each blade 53 in the direction of the drive axis X35 is joined to the opposing plate 52. there is

A plurality of auxiliary blades 54 are formed on the impeller 50 . Each auxiliary blade 54 is configured such that a part of each blade 53 penetrates the main plate 51 and protrudes toward the side opposite to the opposing plate 52 . The cross-sectional shape of the auxiliary blade 54 is the same as that of the blade 53 except for the portion located radially inward of the drive axis X35 in the cross-sectional shape of the blade 53 .

As shown in FIG. 3, the drive shaft 35 is inserted into the shaft hole 51H of the main plate 51 with the impeller 50 arranged in the accommodation space 90, and the nut 35F is attached to the tip of the drive shaft 35 with a washer or the like interposed therebetween. The main plate 51 is fixed to the drive shaft 35 so as to be rotatable integrally with the main plate 51 by being screwed into the main plate 51 . In this state, the main plate 51 faces the motor mounting plate 95 of the motor support wall 93 , the facing plate 52 faces the side wall 92 , and each auxiliary blade 54 protrudes toward the motor mounting plate 95 .

As shown in FIGS. 3 and 4, the main plate 51 is formed with relief portions 51A. The relief portion 51A is formed by drawing a region surrounding the shaft hole 51H in the main plate 51 into a substantially truncated cone shape so as to escape from the boss portion 33 in the drive axis X35 direction.

In the centrifugal fan 1 having such a configuration, the impeller 50 rotates in the rotation direction R1 shown in FIG. 4 by operating the motor 3 . Each blade 53 is inclined in the rotational direction R1 toward the radially outer side of the drive axis X35. That is, the impeller 50 is a sirocco fan. Each auxiliary blade 54, like each blade 53, is also inclined in the rotational direction R1 toward the outside in the radial direction of the drive axis X35.

The centrifugal fan 1 sucks air into the housing space 90 through the suction port 9A as the impeller 50 rotates. The sucked air receives centrifugal force as it rotates together with the blades 53 of the impeller 50, is drawn toward the peripheral wall 91 in the housing space 90, is compressed, and is discharged from the discharge port 9B.

<Effect>
In the centrifugal fan 1 of the embodiment, since the drive shaft 35 of the motor 3 is not provided with a motor cooling fan, the number of parts can be reduced and the drive shaft 35 and its surroundings can be simplified.

Further, in this centrifugal fan 1, the motor cooling fan is not provided on the drive shaft 35, and the boss portion 33 of the motor 3 passes through the opening portion 97 provided through the motor mounting plate 95 of the motor support wall 93. Since the drive shaft 35 protrudes into the housing space 90, the protruding length of the drive shaft 35 can be shortened, so that dynamic imbalance of the drive shaft 35 is less likely to occur, and the drive shaft 35 and the impeller 50 are less likely to vibrate due to rotation.

Furthermore, the inventors analyzed the air flow around the motor wall 31, the boss portion 33, the motor support wall 93, the impeller 50, etc. of the centrifugal fan 1, and operated the centrifugal fan 1 under predetermined operating conditions. Effects of the first gap S1 and the second gap S2 were confirmed as follows by conducting an experiment to measure temperature changes of the control board 3C and the bearings 32T, 33T, etc. during long-term operation. The flow analysis results described above are schematically shown in FIG. 5 with a plurality of arrows.

In this centrifugal fan 1, when the motor 3 is operated to rotate the drive shaft 35 and the impeller 50, the blades 53 of the impeller 50 are positioned radially inward of the drive axis X35 in the housing space 90. Compared to the inner region E1, the pressure in the outer region E2 located radially outside of the drive shaft center X35 relative to the blades 53 of the impeller 50 is higher. Then, the air whose pressure is increased in the outer region E2 is discharged from the accommodation space 90 via the discharge port 9B.

Here, the air flow generated in the gap region E3 between the motor mounting plate 95 of the stationary motor support wall 93 and the main plate 51 of the rotating impeller 50 reduces the pressure in the gap region E3. Then, the air around the motor 3 flows through the first gap S1 and the second gap S2 to the gap area E3, joins the air in the outer area E2 in the accommodation space 90, and is discharged from the accommodation space 90. will be At this time, the air around the motor 3 flows through the first gap S1 and contacts the motor wall 31, and further flows through the second gap S2 and contacts the boss 33, thereby effectively dissipating the heat of the motor 3. can take away.

Therefore, in the centrifugal fan 1 of the embodiment, the motor 3 can be effectively cooled while realizing a reduction in manufacturing cost and suppression of vibration during operation. As a result, abnormal overheating of the control board 3C and the bearings 32T and 33T of the motor 3 can be suppressed, and the stability and durability of the motor 3 can be improved.

In the centrifugal fan 1, as shown in FIGS. 3 and 4, the first space S1 is the area surrounding the opening 97 in the motor mounting plate 95 of the motor support wall 93, that is, the recess 98 is the motor wall 31. , in the drive axis X35 direction. That is, since the first gap S1 can be easily formed by drawing, the manufacturing cost can be further reduced. Further, since the motor mounting plate 95 is drawn into a three-dimensional shape, the rigidity of the motor mounting plate 95 can be improved, so that the motor mounting plate 95 can reliably support the motor wall 31 .

Furthermore, in this centrifugal fan 1 , the motor support wall 93 has a motor support wall main body 94 and a motor mounting plate 95 which is separate from the motor support wall main body 94 . Therefore, the motor mounting plate 95 can be easily manufactured by using a working method such as press working, punching, drawing, etc., so that the manufacturing cost can be reduced. Further, the motor mounting plate 95 can be easily processed into a shape that can suitably form the first space S1 and the second space S2.

Further, in the centrifugal fan 1, as shown in FIG. 5, the auxiliary blades 54 rotate together with the drive shaft 35 and the impeller 50, thereby further promoting the flow of air in the gap region E3. As a result, in the centrifugal fan 1, the air around the motor 3 flows through the first space S1 and the second space S2 into the space E3 more easily, so that the heat of the motor 3 is removed more effectively. be able to.

Although the present invention has been described above with reference to the embodiments, it goes without saying that the present invention is not limited to the above embodiments, and can be modified and applied without departing from the scope of the invention.

For example, in the embodiment, one recess 98 forms one first space S1, but the configuration is not limited to this. For example, the recess 98 may be changed to a plurality of recesses, and the recesses may form a plurality of first voids. Also, the first gap may be uneven around the drive shaft. Furthermore, in the embodiment, the first gap portion S1 is such that the concave portion 98 of the motor mounting plate 95, which is a part of the motor support wall 93, extends from the outer peripheral edge 31E of the motor wall 31 to the boss portion 33. 31 in the direction of the drive axis X35, but the configuration is not limited to this. For example, the first gap may be formed so that the entire motor support wall extends from the outer peripheral edge of the motor wall to the boss portion, and is separated from the motor wall in the axial direction of the drive shaft.

In the embodiment, the second gap portion S2 is formed by separating the entire circumference of the inner peripheral edge 97E of the opening 97 from the outer peripheral surface of the boss portion 33 in the radial direction of the drive axis X35, but is not limited to this configuration. For example, a part of the inner peripheral edge 97</b>E of the opening 97 may protrude inward in the radial direction of the drive shaft center X<b>35 and be brought into contact with the outer peripheral surface of the boss portion 33 .

It is also possible to employ a configuration in which the first space is formed by interposing a spacer between the motor supporting walls or by providing legs on at least one of the motor supporting wall and the motor wall.

INDUSTRIAL APPLICABILITY The present invention can be used, for example, in a forced-air combustion device, a water heater, or a heat source for heating.

Reference Signs List 1 centrifugal fan 90 accommodation space 97 opening 93 motor support wall 9 casing 31 motor wall 33 boss 35 drive shaft 3 motor 51 main plate 51E outer peripheral edge of main plate 53 plural blades 50 Impeller 31E Outer peripheral edge of motor wall S1 First gap 97E Inner peripheral edge of opening S2 Second gap 94 Motor support wall main body 96 Mounting part 95 Motor mounting plate 54 A plurality of auxiliary blades

Claims (3)

a casing having a cochlea-shaped motor support wall with an opening penetrating therethrough for defining an accommodation space;
a motor wall disposed on the side opposite to the housing space with respect to the motor support wall and supported by the motor support wall; a motor having a boss portion protruding outward and a drive shaft protruding from the boss portion within the accommodation space;
An impeller having a main plate disposed in the accommodation space and fixed to the drive shaft so as to be integrally rotatable, and a plurality of blades arranged along the outer peripheral edge of the main plate,
Between the motor support wall and the motor wall, at least a part of the motor support wall extends from the outer peripheral edge of the motor wall to the boss portion in the axial direction of the drive shaft from the motor wall. a first gap spaced apart from each other is formed,
A second gap is formed between the opening and the boss, wherein at least a portion of the inner peripheral edge of the opening is spaced apart from the boss in the radial direction of the drive shaft ,
A gap region is formed between the motor support wall and the main plate,
the gap region communicates with the first gap and the second gap;
A region surrounding the opening in the motor support wall is a recess formed in a substantially truncated cone shape so as to be spaced apart from the motor wall in the axial direction of the drive shaft,
The first gap is formed by separating the recess from the motor wall in the axial direction of the drive shaft over the range from the outer peripheral edge of the motor wall to the boss,
A region of the motor support wall located outside the recess in the radial direction of the drive shaft is defined as an outer region,
the recessed portion and the outer region face the main plate and partition a part of the gap region;
The impeller is formed with a plurality of auxiliary blades, each of which partially penetrates the main plate and protrudes toward the motor support wall,
The centrifugal fan , wherein each of the auxiliary blades protrudes into the gap region outside the recess in a radial direction of the drive shaft . The casing has the motor support wall and a peripheral wall joined to the outer peripheral edge of the motor support wall,
The motor support wall includes a motor support wall main body including the outer peripheral edge of the motor support wall;
a motor mounting plate assembled to the motor support wall body ;
2. The centrifugal fan according to claim 1 , wherein the motor mounting plate is formed with the opening, the recess, and a mounting portion to which the motor wall is mounted . the concave portion has an inclined portion that is inclined so as to bite into the accommodation space from an inner peripheral edge of the outer region;
3. The centrifugal fan according to claim 1, further comprising a flat portion connected to the inner peripheral edge of the inclined portion and extending to approach the drive shaft and reach the opening.

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