JP7254648B2 - centrifugal blower - Google Patents

Description

The present invention relates to centrifugal blowers.

Centrifugal fans are widely used for blowing, ventilating, cooling, etc. in household electrical appliances, OA equipment, industrial use, and vehicles. A centrifugal fan has a casing having a spiral air passage and an impeller (impeller) arranged inside the casing (see, for example, Patent Document 1).

FIG. 7 shows a centrifugal multi-blade blower mainly used in air conditioners for automobiles, which is described in Patent Document 1. As shown in FIG. One side wall of the casing 14 in the axial direction of the fan is provided with a suction port 17 for drawing air into the casing 14 , and the other side wall facing the suction port 17 is provided with a motor 12 . A spiral scroll chamber 13 is formed around the outer periphery of the multi-blade fan 11 in the casing 14 . The rotation center (axial center) of the multi-blade fan 11 is arranged at the center point O of the scroll chamber 13 . The scroll chamber 13 is spirally formed so that the clearance from the outer periphery of the multi-blade fan 11 , that is, the passage height H gradually expands from the tongue portion 15 toward the discharge port 16 . The centrifugal blower of Patent Document 1 aims at reducing noise associated with the generation of backflow in the vicinity of the tongue portion 15 .

JP 2004-360497 A

In general, a casing having a spiral shape extends in a tangential direction from a joint where the spiral has a predetermined winding angle to communicate with the discharge port so as to have a predetermined size of the discharge port. In the centrifugal blower of Patent Document 1, the plane side plate 25 on the discharge side extends horizontally from the winding end point B toward the discharge port 16 . The air that has flowed into the impeller from the suction port is blown out of the casing from the discharge port while swirling along the spiral air passage 13 due to the rotation of the impeller. The airflow flows along the spiral ventilation path, changes from the winding end point B into a straight flow, and goes to the discharge port 16 through the discharge flow path. At this time, the swirling flow flowing through the spiral ventilation passage 13 does not become a completely straight flow because the cross-sectional area of the flow passage at the joint (winding end point B) suddenly expands, and the flow is not completely straight. The flow velocity of the airflow increases on the side of the nozzle, and the pressure distribution at the discharge port 16 becomes uneven, resulting in turbulence in the airflow. This results in increased noise.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a centrifugal fan that suppresses turbulence in the air flow and reduces noise.

The present invention comprises an impeller that constitutes a centrifugal fan, a flow path that is arranged at a position surrounding the impeller and pumps gas discharged in a centrifugal direction from the impeller along a circumferential direction, and a flow path that is pumped through the flow path. a discharge port for discharging the gas, wherein the flow channel has a spiral-shaped spiral flow channel portion whose cross-sectional area increases as it goes downstream, and between the spiral flow channel portion and the discharge port. and an enlarged channel portion whose cross-sectional area increases at a rate greater than that of the spiral channel portion, wherein the cross-sectional area of the discharge port is larger than the cross-sectional area at the downstream end of the spiral channel portion, and Upstream of the downstream end of the spiral flow path portion , there is a middle portion in which the gas flows in the same direction as the discharge port. The opening angle between the downstream end of the portion is 25° to 45°, and the opening between the intermediate portion and the minimum cross-sectional portion of the spiral flow path portion as viewed from the rotation center of the impeller. It is a centrifugal blower with an angle of 60°-70° .

In the present invention, the inner wall of the spiral flow path portion on the side opposite to the impeller curves from the midway portion toward the downstream end of the spiral flow path portion toward the rotation center of the impeller. The inner wall of the portion of the spiral flow path portion extending from the downstream end toward the expanded flow path portion has a rounded surface protruding into the flow path from the spiral flow path portion to the expanded flow path portion. Structures that are formed are preferred.

ADVANTAGE OF THE INVENTION According to this invention, the centrifugal fan which suppressed the turbulence of the airflow and reduced the noise is obtained.

1 is a perspective view of a centrifugal fan according to a first embodiment; FIG. FIG. 2 is a top view of the centrifugal fan shown in FIG. 1; It is the side view which looked at the centrifugal fan shown in FIG. 2 from the side. FIG. 4 is a bottom view taken along line AA of FIG. 3; FIG. 2 is a cross-sectional view of the centrifugal blower 100 taken along a plane including the rotation axis; It is a sectional view of a centrifugal fan of a 2nd embodiment. It is a figure which shows the conventional centrifugal fan (patent document 1).

1. 1. First Embodiment (1) Structure of Centrifugal Fan FIG. 1 is a perspective view of a centrifugal fan 100 of the first embodiment. FIG. 2 is a cross-sectional view of centrifugal fan 100 shown in FIG. FIG. 3 is a side view of the centrifugal blower shown in FIG. 2, viewed from the side. FIG. 4 is a bottom view of a cross section taken along line AA in FIG. 3, viewed from the axial direction (negative Z-axis direction). FIG. 5 is a cross-sectional view of centrifugal blower 100 taken along a plane including the rotation axis.

Air blower 100 has resin casing 110 . The casing 110 is composed of an upper casing 111 and a lower casing 112 . Casing 110 has a spiral shape and accommodates therein an impeller (corresponding to an impeller) 120 having a large number of blades in a rotatable state.

A spiral flow path portion 130 (see FIG. 4) is formed around the impeller 120 inside the casing 110 . The spiral flow path portion 130 has a spiral shape in which the cross-sectional area gradually increases while swirling from a portion 139 (a portion of the tongue portion 131) having the smallest cross-sectional area toward the discharge port 132 (downstream). have. A wall surface on the outer peripheral side of the spiral flow path portion 130 follows an involute curve, and the cross-sectional area of the spiral flow path portion 130 increases along this involute curve as it goes downstream.

The upper casing 111 has a suction port 113 that opens in the axial direction of the impeller 120 . A motor 140 (see FIG. 5) for rotating the impeller 120 is attached to the lower casing 112 . Rotating the motor 140 causes the impeller 120 to rotate. As the impeller 120 rotates, the gas (air) sucked from the suction port 113 is blown out from the inside of the impeller 120 in the centrifugal direction. The blown air is pumped through the spiral flow path portion 130 from the portion 139 with the minimum cross section toward the discharge port 132 along a spiral path, and passes through the expanded flow path portion 136 and the discharge port flow path portion 133. , is exhausted from the discharge port 132 .

(2) Structure of Impeller As shown in FIG. 5, the impeller 120 includes a cup-shaped hub 122 forming a bottom surface and a plurality of shafts arranged in an outer annular portion on the hub 122 so as to stand in the axial direction. The blades 121 have an annular connecting ring 123 that connects the ends of the plurality of blades 121 opposite to the hub 122 . The blades 121 all have the same shape, have a forward-facing blade shape that is recessed with respect to the rotation direction of the impeller 120, and are evenly arranged in the circumferential direction.

The hub 122 has a raised boss portion 124 in the center, and a through hole is formed in the boss portion 124 . A shaft 141 of the motor 140 is press-fitted into this through hole, and the impeller 120 is coupled to the shaft 141 . The shaft 141 is the rotating shaft of the motor 140 and is coupled with the impeller 120 so that it also serves as the rotating shaft of the impeller 120 . The hub 122, the plurality of blades 121, and the connecting ring 123 are integrally formed of resin.

(3) Casing structure
The casing 110 is composed of an upper casing 111 and a lower casing 112, and the upper casing 111 and the lower casing 112 are connected to form the spiral casing 110. As shown in FIG. A circular opening serving as a suction port 113 is formed in the center of the upper casing 111 . Further, the casing 110 is provided with a discharge port 132 for discharging the airflow pressure-fed through the spiral flow path portion 130 to the outside.

As shown in FIG. 4, the downstream end (terminal portion) 137 of the spiral flow path portion 130 inside the casing 110 is located at an angular distance of 25° to 35° downstream from the position of the reference line 135 in FIG. be. The reference line 135 is a line that is translated from the end of the discharge port 132 toward the impeller 120 and passes through the center of rotation of the impeller 120 .

The direction of the flow velocity on the reference line 135 (the tangential direction of the swirling flow) substantially coincides with the direction of the flow velocity at the discharge port 132 . That is, the position of the reference line 135 is defined as a portion where the tangential direction of the swirling flow matches the exhaust direction of the discharge port 132 . Here, the portion of the spiral flow path portion 130 at the reference line 135 is defined as an intermediate portion 138 . The position of the downstream end 137 of the spiral flow path portion 130 is 25° to 35° downstream of the midway portion 138 as viewed from the angular position in FIG.

From the downstream end 137 of the spiral channel portion 130 , it is connected to an enlarged channel portion 136 . The enlarged channel portion 136 smoothly and gradually expands in cross section as it goes downstream. The expansion rate of the flow path in the expanded flow path portion 136 (the extent to which the cross-sectional area increases toward the downstream) is greater than the expansion rate of the flow path in the spiral flow path portion 130 .

The enlarged channel portion 136 is connected to the outlet channel portion 133 . The outlet channel portion 133 has a tubular structure with a constant cross-sectional area of the channel toward the outlet 132 . The discharge port flow path portion 133 serves as a connection portion to a duct to which air is sent from the centrifugal blower 100 and equipment.

The space around the impeller 120 is continuously connected in an annular shape. Then, the spiral channel portion 130 starts at the channel minimum cross-sectional portion 139, turns clockwise from the viewpoint of FIG. , and then continues to the enlarged channel portion 136 .

A minimum cross-sectional portion 139 of the spiral flow path portion 130 is positioned 60° to 70° downstream from the reference line 135 . This angle is measured along the swirl direction of the swirl flow (clockwise direction in FIG. 4).

As described above, the centrifugal blower 100 includes an impeller 120 that constitutes a centrifugal fan, and is arranged at a position surrounding the impeller 120. Gas (air) discharged from the impeller 120 in the centrifugal direction is distributed along the circumferential direction. It has a spiral flow path portion 130 for pumping, and a discharge port 132 for discharging the gas (air) pumped through the spiral flow path portion 130 . Here, the spiral flow path portion 130 has a structure in which the cross-sectional area increases toward the downstream side. Between the spiral flow path portion 130 and the discharge port 132, an enlarged flow path portion 136 is arranged, the cross-sectional area of which increases at a rate greater than that of the spiral flow path portion 130. As shown in FIG. Here, the cross-sectional area of the discharge port 132 is larger than the cross-sectional area at the downstream end 137 of the spiral flow path portion 130, and the direction of gas (air) flow is at the upstream of the downstream end 137 of the spiral flow path portion 130. There is a middle portion 138 which is the same as the outlet 132 . Further, the opening angle between the midway portion 138 and the downstream end 137 of the spiral flow path portion 130 as viewed from the center of rotation of the impeller 120 is 25° to 35°.

In the centrifugal fan 100, the spiral flow path portion 130 is extended from the middle portion 138 by a distance of 25° to 35° in the angle range viewed from the center of rotation, and the enlarged flow path portion 136 and the discharge port flow path portion 133 are formed therefrom. The exhaust is guided to the discharge port 132 via the outlet. By further extending the spiral flow path portion 130 from the midway portion 138 in the range of 25° to 35°, the swirling flow state can be maintained as much as possible, and a difference in flow velocity occurs between the outer side and the inner side of the flow path. is suppressed, and the occurrence of turbulence is suppressed.

However, if the length of the extension portion is less than 25° in the angle range of FIG. 4, the effect of providing the extension portion is diminished, and turbulence occurs.

Further, in the centrifugal fan 100, the opening angle between the midway portion 138 and the minimum cross-sectional portion 139 of the spiral flow path portion 130 when viewed from the rotation center of the impeller 120 is 60° to 70°. Reference numeral 150 in FIG. 4 is a line indicating the angular position of the minimum cross-section portion 139 of the spiral channel portion 130 . If the opening angle is less than 60°, the cross-sectional area of the enlarged flow path portion 136 cannot be secured, and the air resistance in the flow path increases, resulting in increased noise and reduced exhaust efficiency of the centrifugal fan 100. .

Further, when the opening angle exceeds 70°, the distance in the circumferential direction between the portion 139 with the smallest cross-section and the downstream end 137 of the spiral flow path portion 130 increases, and the spiral flow path portion 130 increases accordingly. The channel length becomes shorter. Since the impeller 120 uniformly exhausts air in the centrifugal direction, the exhaust air from the impeller 120 effectively contributes to the formation of a swirling flow in the portion around the impeller 120 where the spiral flow path portion 130 does not exist. do not. The air flow that does not contribute to the formation of the swirl flow, in other words, the air flow that is not recovered as the swirl flow causes turbulence, induces noise, and further reduces the exhaust efficiency of the centrifugal fan 100 . For the above reasons, the opening angle between the intermediate portion 138 and the minimum cross-sectional portion 139 of the spiral flow path portion 130 is preferably 70° or less.

2. Second Embodiment FIG. 6 shows a centrifugal fan 200 according to a second embodiment. FIG. 6 is created from the same viewpoint as FIG. Centrifugal blower 200 includes casing 201 . The casing 201 is composed of an upper casing and a lower casing like the centrifugal fan 100 of the first embodiment, and the spiral casing 201 is composed by connecting the upper casing and the lower casing. The schematic appearance of the casing 201 is roughly the same as those shown in FIGS. 1, 2 and 3, and the schematic of the cross section cut along the plane including the rotating shaft is roughly the same as that shown in FIG.

An impeller 210 is housed inside the casing 201 in a rotatable state. The impeller 210 and related structures are the same as the centrifugal blower 100 of the first embodiment.

An opening serving as a suction port is formed in the center of the casing 201, and a spiral channel portion 202, which is a spiral channel whose cross-sectional area increases as it goes downstream, is provided inside. . The spiral flow path portion 202 has a spiral shape whose cross-sectional area increases according to an involute curve, and is arranged at a position surrounding the impeller 210, as in the first embodiment.

A downstream end (terminus) 207 of the spiral channel portion 202 is connected to an enlarged channel portion 203 that increases in cross-sectional area at a greater rate than the spiral channel portion 202 . A discharge port 204 serving as a discharge port is formed at the end of the enlarged flow path portion 203 .

The direction of the flow velocity on the reference line 205 (the tangential direction of the swirling flow) substantially coincides with the direction of the flow velocity at the discharge port 204 . The position of the reference line 205 is defined as a portion where the tangential direction of the swirling flow coincides with the exhaust direction of the discharge port 204 . Here, the portion of the spiral flow path portion 202 at the reference line 205 is defined as an intermediate portion 208 . The position of the downstream end 207 of the spiral flow path portion 202 is 25° to 45° downstream of the intermediate portion 208 as viewed from the angle position in FIG. The middle portion 208 (reference line 205) corresponds to the reference line 135 in the centrifugal fan 100 of the first embodiment.

An inner wall 202 a of the spiral flow path portion 202 on the far side from the impeller 210 (the inner wall facing the rotation center side of the impeller 210 ) continues downstream from the middle portion 208 , and this portion is curved toward the center. The downstream end 207 of the spiral channel portion 202 connects to the enlarged channel portion 203 . In this portion, the inner wall of the enlarged flow path portion 203 on the far side from the impeller 210 (downstream portion of reference numeral 202a) is formed into an R surface 211, which is a gently curved surface protruding toward the flow path.

In the centrifugal fan 200 , the downstream end of the enlarged flow path portion 203 serves as a discharge port 204 . The outer wall near the discharge port 204 does not have a cylindrical shape in which the wall surfaces surrounding the space are parallel to each other like near the reference numeral 132 in FIG. Since this shape is not suitable for connection to a duct, the enlarged channel portion 203 is provided with a side wall 209 forming a duct connection on the outside. The outer side wall of the side wall 209 constituting the duct connection portion is parallel to the flow of the airflow flowing out from the discharge port 204, and the external shape of the vicinity of the discharge port 204 has four wall surfaces similar to those near the reference numeral 132 in FIG. It has a parallel rectangular tubular shape. This portion is used to fix the centrifugal fan 200 to a duct (not shown).

Compared to the structure of FIG. 4, the centrifugal blower 200 moderately increases the pressure in the portion toward the discharge port 204 and rectifies the airflow. This is because the position of the downstream end of the spiral flow path portion 202 is extended further downstream compared to the structure of FIG. 4, and the length of the expanded flow path portion 203 is increased compared to the structure of FIG. This is because the non-uniformity in the flow velocity of the airflow is suppressed. In addition, by suppressing the deviation of the flow velocity, it becomes difficult to generate a dead water area. In this way, noise is reduced by suppressing flow turbulence and formation of dead water areas.

Further, by providing an R surface 211 that is formed at the boundary between the spiral flow path portion 202 and the enlarged flow path portion 203 and protrudes in the direction of the flow path, the spiral flow path 202 and the enlarged flow path portion 203 are separated from each other. The generation of vortices and turbulence in the flow to is suppressed. This also contributes to suppression of noise generation.

When the angular position of the downstream end 207 of the spiral flow path portion 202 with respect to the intermediate portion 208 is less than 25°, the effective length of the spiral flow path portion 202 is shortened, and the air discharged from the impeller 210 is swirled. The function of the spiral flow path portion 202 that collects as is deteriorated. As a result, an efficient air flow is not formed, noise caused by turbulence in the air flow increases, and the efficiency of the centrifugal fan is significantly reduced.

Further, if the above angular position exceeds 45°, the flow path length of the expanded flow path portion 203 cannot be ensured, and the direction of the flow path from the spiral flow path portion 202 to the expanded flow path portion 203 is abruptly changed. , and the occurrence of vortices and turbulence at that portion becomes apparent. Therefore, the angular position of the downstream end 207 of the spiral channel portion 202 with respect to the intermediate portion 208 is suitably selected from the range of 25° to 45°.

An inner wall 202 a of the spiral flow path portion 202 opposite to the impeller 210 curves from the middle portion 208 toward the downstream end 207 of the spiral flow path portion 202 toward the rotation center of the impeller 210 . The inner wall (downstream side of the wall surface of reference numeral 202a) of the portion from the downstream end 207 of the spiral flow path portion 202 toward the enlarged flow path portion 203 is provided with a flow path from the spiral flow path portion 202 to the enlarged flow path portion 203. An R surface 211 projecting in the direction of the road is formed.

In order to efficiently collect the exhaust gas blown out from the impeller 210, the inner wall 202a of the impeller 210 extends toward the downstream end 207 of the spiral flow path portion 202. There is no choice but to bend toward the direction of the center of rotation. Here, by providing the R surface 211 , flow turbulence in the flow path from the downstream end 207 of the spiral flow path portion 202 to the expanded flow path portion 203 is suppressed.

DESCRIPTION OF SYMBOLS 100... Centrifugal blower, 110... Casing, 112... Lower casing, 113... Suction port, 120... Impeller, 121... Blade, 122... Hub, 123... Connection ring, 124... Boss part, 130... Spiral flow path part, 131 Tongue 132 Discharge port 133 Discharge port channel portion 135 Reference line 136 Enlarged channel portion 137 Downstream end of spiral channel portion 138 Intermediate portion 139 Minimum cross section Part 140 Motor 141 Shaft 200 Centrifugal blower 201 Casing 202 Spiral flow path portion 202a Inner wall 203 Enlarged flow path portion 204 Protruding port 207 Spiral flow path portion 208 Midway portion 209 Side wall forming a duct connecting portion 210 Impeller.

Claims (3)

an impeller that constitutes a centrifugal fan;
a flow path disposed at a position surrounding the impeller for pumping gas discharged from the impeller in a centrifugal direction along a circumferential direction;
a discharge port for discharging the gas pumped through the channel,
The flow path is
a spiral flow path portion having a spiral shape whose cross-sectional area increases as it goes downstream;
an enlarged flow path portion located between the spiral flow path portion and the discharge port, the enlarged flow path portion increasing in cross-sectional area at a greater rate of increase than the spiral flow path portion;
the cross-sectional area of the discharge port is larger than the cross-sectional area at the downstream end of the spiral flow path portion;
upstream of the downstream end of the spiral flow path portion , there is a midway portion in which the direction of flow of the gas is the same as that of the discharge port;
an opening angle between the intermediate portion and the downstream end of the spiral flow path portion as viewed from the rotation center of the impeller is 25° to 45°;
A centrifugal blower having an opening angle of 60° to 70° between the midway portion and the minimum cross-sectional portion of the spiral flow path portion when viewed from the rotation center of the impeller. 2. The centrifugal fan according to claim 1, wherein the spiral flow path portion increases in cross-sectional area according to an involute curve. an inner wall of the spiral flow path portion on the opposite side of the impeller is curved from the intermediate portion toward the downstream end of the spiral flow path portion toward the rotation center of the impeller;
The inner wall of the portion from the downstream end of the spiral flow path portion toward the enlarged flow path portion is formed with an R surface protruding into the flow path from the spiral flow path portion to the enlarged flow path portion. 3. The centrifugal fan according to claim 1 or 2 .

Images