JP6576891B2 - Centrifugal blower for vehicle air conditioner - Google Patents

Description

  The present invention relates to a centrifugal blower applied to a two-layer flow type vehicle air conditioner.

  In the field of vehicle air conditioners, two-layer flow type vehicle air conditioners are known. This type of air conditioner includes two air passages that are separated from each other, that is, a first air passage and a second air passage, and a single centrifugal fan that causes air to flow through these two air passages. The centrifugal blower has a scroll housing and an air intake housing for taking in air sent to the scroll housing.

The centrifugal blower has a separation cylinder inserted into a space in the radial direction of the suction port of the scroll housing and the blade row of the impeller (see, for example, Patent Document 1). The space between the radially outer side of the blade row of the impeller and the scroll housing is vertically divided by the separation wall, and thereby the second air passage communicating with the first air passage and the second air passage communicating with the first air passage. An air flow path is formed.
The separation cylinder flows into the first air flow path after the first air flow flowing through the first passage outside the separation cylinder is introduced into the upper half of the blade row, and flows through the second passage inside the separation cylinder. The second air flow is provided so as to flow into the second air flow path after being introduced into the lower half of the blade row.

  The air intake housing has an outside air introduction port for taking in air outside the vehicle compartment (outside air) and an inside air introduction port for taking in air inside the vehicle compartment (inside air). Usually, the outside air introduction port and the inside air introduction port are provided at positions opposite to each other with respect to the scroll housing central axis. In many cases, the outside air introduction port is provided on the front side of the vehicle, and the inside air introduction port is provided on the rear side of the vehicle.

  For example, the first air flow sucked into the scroll housing from the outside air inlet through the first passage through the first passage will be described as a path between the outside air inlet and the scroll housing inlet at a position close to the outside air inlet. Since the length is short, suction is performed relatively easily. However, at a position close to the inside air introduction port, the path length between the outside air introduction port and the suction port of the scroll housing tends to be long, and the suction tends to be difficult.

  For this reason, there is a possibility that the total amount of outside air sucked into the scroll housing cannot be sufficiently increased. Then, the static pressure in the first air flow path above the separation wall of the scroll housing cannot be sufficiently increased. In this case, air flowing in the second air flow path below the separation wall of the scroll housing may enter the first air flow path. At this time, the air flowing through the first air channel is outside air with relatively low humidity, the air flowing through the second air channel is inside air with relatively high humidity, and the air conditioner is in the differential foot mode. If it is operated with the above, the humidity of the air flowing in the first air flow path supplied toward the windshield increases, and there is a possibility that the window clearness of the windshield is reduced.

JP 2004-132342 A

  The present invention relates to a single suction centrifugal blower for a vehicle in which a suction port of a scroll housing is separated by a separation cylinder, and more outside air is provided via a gap between an edge of the suction port and an outer peripheral surface of the separation cylinder. Is intended to be able to be sucked into the scroll housing.

  According to a preferred embodiment of the present invention, there is provided a single suction centrifugal blower for a vehicle, which has a motor and a plurality of blades forming a circumferential blade row, and is rotated around a rotation axis by the motor. An impeller that is driven to blow out air sucked into a radially inner space of the blade row from one end side in the axial direction, an inner space that houses the impeller, and the axial direction A scroll housing having a suction port that opens to one end side and a discharge port that opens in the circumferential direction; and an inner peripheral surface of the scroll housing and an outer peripheral surface of the impeller in the internal space of the scroll housing. A partition wall that divides the internal space of the discharge port and the internal space of the discharge port in the axial direction to form a first air flow channel and a second air flow channel, a radially inner side of the suction port, and the impeller Within the radial direction of the cascade A separation cylinder extending in the axial direction through the first suction air flow passing through the outside of the separation cylinder and an inner side of the separation cylinder. The first air flow is directed radially outward and guided to the first air flow path, and the second air flow is directed radially outward. The separation cylinder, at least one outside air introduction port for taking in outside air of the vehicle, and at least for taking in the inside air of the vehicle, having a guide part that turns in a direction and guides to the second air flow path And an internal air intake port configured to flow outside air taken in from the outside air introduction port to the outside of the separation tube and flow inside air taken from the inside air introduction port to the inside of the separation tube. Air intake A proximal interval, which is an interval between an outer peripheral surface of the separation cylinder and an edge of the suction port on a side close to the outside air introduction port measured in a radial direction of the impeller, There is provided a centrifugal blower that is larger than a distal side interval that is an interval between an outer peripheral surface of the separation cylinder and an edge of the suction port on a side far from the outside air introduction port measured in a radial direction of the vehicle.

  According to the embodiment of the present invention, since the proximal interval is increased, the intake amount of the outside air through the proximal portion of the intake port 22 where air can easily flow from the outside air inlet at a larger flow rate is increased. As a result, the total flow rate of the outside air flowing into the first air flow path (18) can be increased.

It is a longitudinal cross-sectional view which shows the structure of the air intake part of an air conditioner, and the vicinity of a centrifugal blower, and contains the meridian cross section of a centrifugal blower. It is a longitudinal cross-sectional view which shows the structure of the vicinity of the air intake part of an air conditioner and a centrifugal blower cut | disconnected by the cut surface orthogonal to the cut surface in FIG. It is a figure which shows the positional relationship of the suction inlet of a scroll housing and a separation cylinder in the cross section orthogonal to the rotating shaft line of the centrifugal blower including the suction inlet of the scroll housing of the centrifugal blower which concerns on one Embodiment. It is a figure which shows the positional relationship of the suction inlet of a scroll housing, and a separation cylinder in the cross section orthogonal to the rotating shaft line of the centrifugal blower containing the suction inlet of the scroll housing of the centrifugal blower which concerns on other embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG.1 and FIG.2 is sectional drawing which shows the structure of the vicinity of the air intake part and centrifugal blower of an air conditioner for vehicles.

The centrifugal blower 1 is a single suction centrifugal blower. The centrifugal blower 1 has an impeller 2.
The impeller 2 has a plurality of blades 3 forming a blade row 3A arranged in the circumferential direction on the outer peripheral portion thereof. The impeller 2 is driven to rotate about the rotation axis Ax by the motor 13, and the air sucked from the upper side in the axial direction (one end side in the axial direction) into the radially inner space of the blade row of the impeller 2 is directed outward in the radial direction. And blow out.

  In this specification, for convenience of explanation, the direction of the rotation axis Ax is referred to as the axial direction or the vertical direction, and the upper side and the lower side in FIGS. 1 and 2 are respectively referred to as “axially upper side” and “axially lower side”. Call. However, this does not mean that the direction of the rotation axis Ax coincides with the vertical direction when the air conditioner is actually incorporated in a vehicle. In the present specification, unless otherwise noted, the direction of the radius of a circle drawn on a plane perpendicular to the rotation axis Ax around an arbitrary point on the rotation axis Ax is referred to as a radial direction. The circumferential direction of the circle is called the circumferential direction or the circumferential direction.

  The impeller 2 includes an inner deflection member 9 formed integrally with the impeller 2. The inner deflection member 9 is sometimes called a cone portion. The inner deflection member 9 is a rotating body in a geometric sense, and has a side peripheral portion 10 and a disc-shaped central portion 11. In the central portion 11, the rotating shaft 12 of the motor 13 is connected to the impeller 2. In this example, the side peripheral portion 10 is curved such that the contour line in the meridional section of the outer peripheral surface of the side peripheral portion 10 becomes steep as it approaches the central portion 11. In another example (not shown), in the case where the side circumferential portion 10 has a contour line in the meridional section of the outer circumferential surface of the side circumferential portion 10 that does not curve from the central portion 11 toward the blade row 3A (the cross section is linear). There is also.

  The impeller 2 is accommodated in a substantially cylindrical internal space of the scroll housing 17. The scroll housing 17 has a suction port 22 that opens upward in the axial direction, and a discharge port 170. When the scroll housing 17 is viewed from the axial direction, the discharge port 170 extends substantially in the tangential direction of the outer peripheral surface of the scroll housing 17. The discharge port 170 is not visible in FIG.

  The scroll housing 17 has a partition wall 20 that extends radially inward from the outer peripheral wall 17 </ b> A of the scroll housing 17. The partition wall 20 divides the region between the inner peripheral surface of the scroll housing 17 and the outer peripheral surface of the impeller 2 in the internal space of the scroll housing 17 in the axial direction (up and down), and An upper first air flow path 18 and a lower second air flow path 19 extending in the circumferential direction along the outer peripheral wall 17A are formed.

  A separation cylinder 14 is inserted into the scroll housing 17 via a suction port 22. As can be understood by comparing and contrasting FIGS. 1 and 2, the cross section of the upper portion 24 of the separation cylinder 14 is generally rectangular. The cross section of the central portion 15 of the separation cylinder 14 is circular (or generally circular). The cross-sectional shape of the separation cylinder 14 smoothly changes from a rectangular shape to a circular shape (or a generally circular shape) as it approaches the central portion 15 from the upper portion 24. The lower part (guide part) 16 of the separation cylinder 14 has a flare shape whose diameter increases as it approaches the lower end, and the lower end is circular.

  The separation cylinder 14 passes through the space on the radially inner side of the suction port 22 and extends in the axial direction to the space 4 on the radially inner side of the blade row 3 </ b> A of the impeller 2. The upper end opening of the separation cylinder 14 is located outside the scroll housing 17 (above the suction port 22 in the axial direction). The lower end of the separation cylinder 14 is located in the space 4 on the radially inner side of the blade row 3 </ b> A of the impeller 2.

  The entire separation cylinder 14 may be integrally formed by resin injection molding. Instead of this, the upper part 24 of the separation cylinder 14 and the central part 15 and the lower part (guide part) 16 of the separation cylinder 14 may be separately molded and then connected together.

  The separation cylinder 14 is configured to change the flow of air sucked into the scroll housing 17 into a first air flow passing through the first passage 14A outside the separation cylinder 14 and a second passage passing through the second passage 14B inside the separation cylinder 14. Divide into air flow. The first air flow passes through the ring-shaped region outside the outer peripheral surface of the separation cylinder 14 in the suction port 22 of the scroll housing 17, and the upper half 5 (portion close to the suction port 22) of the impeller 2. Flow into. The second air flow enters the inside of the separation cylinder 14 from the upper end of the separation cylinder 14 and flows into the lower half 6 (part far from the suction port 22) of the blade row of the impeller 2. Accordingly, the ring-shaped region outside the outer peripheral surface of the separation cylinder 14 in the suction port 22 of the scroll housing 17 is the first suction port of the scroll housing 17, and the upper end opening of the separation tube 14 is the second suction port of the scroll housing 17, Can also be considered.

The air intake part of the air conditioner has a housing 21. The housing 21 is referred to as an “air intake housing” in order to distinguish it from the scroll housing 17. The scroll housing 17 and the air intake housing 21 may be integrally formed, or may be connected by a method such as screwing, bonding, or fitting after being separately manufactured. The scroll housing 17 and the air intake housing 21 form part of the air conditioner casing.
In a preferred embodiment, the separation cylinder 14 is a separate component from the scroll housing 17 and the air intake housing 21 and is supported at a predetermined position by the air intake housing 21.

  The air intake housing 21 has a first opening 25, a second opening 26, a third opening 27, and a fourth opening 28. Through the first opening 25 and the third opening 27, the inside air (vehicle interior air) is introduced into the internal space 23 of the air intake housing 21 from the outlet 29 (details not shown) of the inside air introduction path provided in the vehicle. Can be introduced. That is, the first opening 25 and the third opening 27 are first and second inside air inlets for taking inside air into the air intake housing 21. Further, through the second opening 26 and the fourth opening 28, the outside air (outside of the vehicle) is introduced into the internal space 23 of the air intake housing 21 from the outlet 30 (details not shown) of the outside air introduction path provided in the vehicle. From the air). That is, the second opening 26 and the fourth opening 28 are first and second outside air inlets for taking outside air into the air intake housing 21.

  By rotating the shut-off valve 31 around the rotation shaft 31A, the inflow of air (inside air) from the first opening 25 into the air intake housing 21 can be allowed or blocked. By rotating the shut-off valve 32 around the rotation shaft 32A, the inflow of air (outside air) from the second opening 26 into the air intake housing 21 can be allowed or blocked. By switching the position by rotating the switching valve 33 around the rotation shaft 33A, air (inside air or outside air) is introduced into the air intake housing 21 through one of the third opening 27 and the fourth opening 28. Can flow in.

  Almost all of the air introduced into the air intake housing 21 from the first opening 25 and / or the second opening 26 passes through the second passage 14B and from the third opening 27 and / or the fourth opening 28. The air intake housing 21 and the separation cylinder 14 are formed so that almost all of the air introduced into the air intake housing 21 passes through the first passage 14A.

  Between the area where the first opening 25, the second opening 26, the third opening 27, and the fourth opening 28 are arranged and the upper end of the separation cylinder 14, dust and particles in the air are contained in the air intake housing 21. The filter 35 for removing contaminants, such as these, is provided. The filter 35 preferably consists of a single filter element.

  3 (also FIG. 4) shows a cross section of the centrifugal blower 1 that includes the suction port 22 and is orthogonal to the rotation axis Ax of the impeller 2 (hereinafter also referred to as “suction port cross section” for the sake of simplicity). . As shown in FIGS. 1 and 3, the interval W1 between the outer peripheral surface 141 of the separation cylinder 14 and the edge 221 of the suction port 22 on the side close to the opening 26 serving as the outside air inlet is separated on the side far from the opening 26. It is larger than the interval W <b> 2 between the outer peripheral surface 141 of the cylinder 14 and the edge 221 of the suction port 22. The intervals W1 and W2 are intervals measured in the radial direction of the impeller 2. Note that the interval W1 is defined as a “proximal side interval” in the sense of an interval on the side close to the opening 26 (proximal side), and the interval W2 is defined as an interval on the side far from the opening 26 (distal side). "

  As shown in FIG. 3, the relationship “proximal space W <b> 1> distal space W <b> 2” indicates that the shape of the region surrounded by the outline of the outer peripheral surface 141 of the separation cylinder 14 in the cross section of the suction port This can be achieved by removing the peripheral edge 143 of the circle 142 centered on the rotational axis Ax of the vehicle 2 on the side close to the outside air inlet 26.

  As shown in FIG. 1 which is a meridional section of the centrifugal blower 1, the curvature radii R1 and R2 of the contour of the outer peripheral surface 141 of the separation cylinder 14 in the guide portion 16 having a flare shape are the outer circumferences of the separation cylinder 14 in the suction port section. The distances W1 and W2 between the surface 141 and the edge 221 of the suction port 22 are set. Specifically, the radius of curvature R1 at a position corresponding to a relatively large proximal space W1 is relatively large, and the radius of curvature R2 at a position corresponding to a relatively small distal space W2 is relatively small.

  Next, the operation of the vehicle air conditioner shown in FIGS. 1 to 3 will be described.

  In the first operation mode of the vehicle air conditioner, the second opening 26 and the fourth opening 28 are opened, and the first opening 25 and the third opening 27 are closed. This state is not shown. In this case, the outside air introduced from the second opening 26 forms a first air flow that passes through the first passage 14A outside the separation cylinder 14 and flows into the upper half 5 of the blade row 3A of the impeller 2. The outside air introduced from the fourth opening 28 forms a second air flow that passes through the second passage 14 </ b> B inside the separation cylinder 14 and flows into the lower half 6 of the blade row of the impeller 2. The first operation mode is sometimes called the outside air mode.

  In the second operation mode, the second opening 26 and the third opening 27 are opened, and the first opening 25 and the fourth opening 28 are closed. This state is shown in FIGS. In this case, the outside air FE introduced from the second opening 26 forms a first air flow that passes through the first passage 14A outside the separation cylinder 14 and flows into the upper half 5 of the blade row 3A of the impeller 2. . The inside air FR introduced from the third opening 27 forms a second air flow that passes through the second passage 14B inside the separation cylinder 14 and flows into the lower half 6 of the blade row 3A of the impeller 2. The second operation mode is sometimes called the inside / outside air two-layer flow mode.

  In the third operation mode, the first opening 25 and the third opening 27 are opened, and the second opening 26 and the fourth opening 28 are closed. This state is not shown. In this case, the inside air introduced from the first opening 25 forms a first air flow that passes through the first passage 14A outside the separation cylinder 14 and flows into the upper half 5 of the blade row 3A of the impeller 2. The inside air introduced from the third opening 27 forms a second air flow that passes through the second passage 14 </ b> B inside the separation cylinder 14 and flows into the lower half 6 of the blade row 3 </ b> A of the impeller 2. The third mode of operation is sometimes referred to as shy mode

  The second operation mode (inside / outside air two-layer flow mode) is a heating operation in which the vehicle interior is heated quickly while preventing the front window from fogging from the cold state, particularly in winter or when the temperature is relatively low. Used when performing. When this heating operation is performed by automatic control, for a while after the start of heating, outside air FE is blown from the defroster outlet (not shown) of the passenger compartment to the front window (not shown), and the inside air FR is changed to the passenger compartment. The air is blown out from the foot air outlet (not shown) toward the feet of the passengers.

When the second operation mode (internal / external air two-layer flow mode) is executed, the external air FE flowing into the upper half 5 of the blade row 3A of the impeller 2 passes through the first air flow path 18 to the defroster outlet. The inside air FR that is supplied and flows into the lower half 6 of the blade row 3 </ b> A of the impeller 2 is supplied to the foot outlet through the second air flow path 19. At this time, if the high-humidity internal air FR is mixed into the external air FE supplied to the defroster outlet, an event that is a safety problem such as fogging of the front window may occur.
Moreover, if the low-temperature outside air FE is mixed into the inside air FR supplied to the foot outlet, it may be a factor that makes passengers feel uncomfortable. Therefore, when the second operation mode is executed, it is desirable that all of the outside air FE flows into the first air flow path 18 and all of the inside air FR flows into the second air flow path 19.

  Note that since only the inside air or only the outside air is used when the first and third operation modes are executed, there is no strict requirement for avoiding the mixture of the inside air and the outside air as much as when the second operation mode is executed.

  Naturally, the length of the path through which the outside air taken into the air intake housing 21 from the second opening 26 that is the outside air introduction port flows from the second opening 26 to the suction port 22 is of course closer to the proximal portion of the suction port 22. Is short, and therefore the flow resistance is small accordingly. In addition to the long path length from the second opening 26 in the distal portion of the suction port 22, the air flow path bypasses the separation cylinder 14, so that the flow resistance increases accordingly. That is, it is easier for the outside air to flow to the proximal portion than to flow from the second opening 26 to the distal portion of the suction port 22. Therefore, the amount of outside air sucked into the scroll housing 17 from the proximal portion of the suction port 22 can be easily increased by widening the proximal space W1 as described above.

  Actually, in the conventional example in which the proximal distance W1 and the distal distance W2 are equal, the flow velocity in the proximal portion of the suction port 22 is higher than that in the distal portion. This means that the pressure loss increases at the proximal portion of the suction port 22, and the actual outside air flow rate is considerably lower than the outside air flow rate that can pass through the proximal portion. To do.

  On the other hand, if the proximal space W1 is increased as in the above embodiment, the pressure loss at the proximal portion of the suction port 22 can be reduced, and the proximal portion of the suction port 22 is interposed. Thus, the flow rate of the outside air taken into the scroll housing 17 (specifically, the first air flow path 18 of the scroll housing 17) can be increased. For this reason, the burden of the motor 13 can be reduced.

  Moreover, the internal pressure (static pressure) of the first air flow path 18 can be increased by increasing the flow rate of the outside air taken into the first air flow path 18. Thereby, particularly when the second operation mode (internal / external air two-layer flow mode) is performed, the internal air flowing into the second air flow path 19 through the inside of the separation cylinder 14 is caused by the pressure difference. Inflow into the path 18 can be prevented or minimized.

  In addition, since the flow path of the inside air flowing into the second air flow path 19 through the inside of the separation cylinder 14 has a simple shape and less pressure loss occurs, in many cases, the inside of the first air flow path 18 The problem is to prevent the pressure and flow rate of the flowing outside air from becoming smaller than the pressure and flow rate of the inside air flowing through the second air flow path 19.

  Moreover, according to the said embodiment, seeing in the meridional section of the centrifugal blower 1, the curvature radius (R1, R2) of the outline of the outer peripheral surface 141 of the guide portion 16 is measured in the radial direction of the impeller (2). It is set according to the distance (W1, W2) between the outer peripheral surface 141 of the cylinder 14 and the edge 221 of the suction port 22. Specifically, for example, the radius of curvature (R1, R2) is set to be larger when the interval (W1, W2) is larger. In a portion where the distance (W1, W2) is increased, the guide portion 16 is close to the inner deflection member 9 (cone portion) of the impeller 2 and the second air flow passage passes through the second passage 14B inside the separation cylinder 14. However, by setting the curvature radii (R1, R2) of the contour of the outer peripheral surface 141 of the guide portion 16 according to the intervals (W1, W2), the guide portion 16 and the inner deflection member 9 can be secured. Can be avoided, the passage of the second air flow can be secured, and the increase in ventilation resistance at the relevant part can be suppressed.

  The shape and / or arrangement of the separation cylinder 14 for establishing the relationship of the proximal space W1> the distal space W2 is not limited to that shown in FIG. For example, as shown in FIG. 4, the separation cylinder 14 is formed so that the outline of the outer peripheral surface 141 has a circular shape in the cross section of the suction port, and the center 144 of the circle is defined by the rotation axis Ax of the impeller 2. Alternatively, the above-mentioned relationship of the proximal distance W1> the distal distance W2 may be realized by disposing the sensor at a position far from the outside air inlet 26.

  The positional relationship between the outside air inlet and the scroll housing 17 is not limited to that shown in FIGS. 3 and 4, and the scroll housing 17 is set to the rotation axis Ax based on the positional relationship shown in FIGS. 3 and 4. You may arrange | position in the position rotated around the predetermined angle (for example, 180 degree | times). Also in this case, it is only necessary to establish a relationship in which the interval W1 (proximal side interval W1) on the side close to the outside air introduction port 26 is the interval W2 (distal side interval W2) on the side far from the outside air introduction port 26.

DESCRIPTION OF SYMBOLS 1 Centrifugal blower 2 Impeller 3 Wing | blade 3A Circumferential cascade 13 Motor 14 Separation cylinder 141 Outer peripheral surface of separation cylinder 16 Guide part 170 Discharge port 17 Scroll housing 18 1st air flow path 19 2nd air flow path 20 Partition wall 21 Air Intake housing 22 Suction port 221 Suction port edge 25 First opening (first inside air inlet)
26 Second opening (first outside air inlet)
27 3rd opening (2nd inside air introduction port)
28 4th opening (2nd outside air introduction port)
Ax Axis of rotation W1 Proximal distance W2 Distal distance

Claims (5)

A single suction centrifugal blower for vehicles,
A motor,
A plurality of blades forming a circumferential blade row, which is rotationally driven around the rotation axis by the motor and sucks air sucked into a space radially inward of the blade row from one end side in the axial direction; An impeller that blows out toward the
A scroll housing having an internal space for accommodating the impeller, a suction port opened on one end side in the axial direction, and a discharge port opened in the circumferential direction;
A region of the inner space of the scroll housing between the inner peripheral surface of the scroll housing and the outer peripheral surface of the impeller and the inner space of the discharge port are divided in the axial direction to generate a first air flow. A partition wall forming a path and a second air flow path;
A separation cylinder extending in the axial direction through a radial inner side of the suction port and a radial inner side of the blade row of the impeller, and a flow of air sucked into the scroll housing from the suction port; The first air flow passing through the outer side of the separation cylinder and the second air flow passing through the inner side of the separation cylinder are provided, and the first air flow is turned radially outward to A separation cylinder having a guide portion that guides to the second air flow path by guiding the second air flow outward in a radial direction while guiding the first air flow path;
The apparatus has at least one outside air introduction port for taking in outside air of the vehicle and at least one inside air introduction port for taking in the inside air of the vehicle, and flows outside air taken in from the outside air introduction port to the outside of the separation cylinder. And an air intake housing configured to allow the inside air taken in from the inside air introduction port to flow inside the separation cylinder;
With
The proximal distance, which is the distance between the outer peripheral surface of the separation cylinder and the edge of the suction port on the side close to the outside air introduction port measured in the radial direction of the impeller, is measured in the radial direction of the impeller. A centrifugal blower that is larger than a distal-side interval that is an interval between the outer peripheral surface of the separation cylinder and the edge of the suction port on the side far from the outside air inlet.   The shape of the region surrounded by the outline of the outer peripheral surface of the separation cylinder when viewed in a cross section of the centrifugal blower that includes the suction port and is orthogonal to the rotation axis of the impeller is the rotation axis of the impeller The centrifugal blower according to claim 1, wherein the proximal interval is made larger than the distal interval by removing a peripheral edge of a circle centered on the side closer to the outside air inlet.   When viewed in a cross section of the centrifugal blower that includes the suction port and is orthogonal to the rotation axis of the impeller, the outer peripheral surface of the separation cylinder has a circular shape, and in the cross section, the circle The centrifugal blower according to claim 1, wherein the distance between the proximal side is made larger than the distance between the distal sides by disposing the center of the fan at a position farther from the outside air inlet than the rotation axis of the impeller.   The guide portion of the separation cylinder has a flare shape that expands as it approaches the tip, and the curvature radius of the contour of the outer peripheral surface of the guide portion is the separation radius when viewed from the meridional section of the centrifugal blower. The centrifugal blower as described in any one of Claims 1 thru | or 3 set according to the space | interval between the said outer peripheral surface of a pipe | tube, and the edge of the said suction inlet. The air intake housing includes a first outside air introduction port and a second outside air introduction port as the at least one outside air introduction port, and a first inside air introduction port and a second outside air as the at least one inside air introduction port. Having a inside air inlet,
Air introduced into the air intake housing from the first outside air inlet and the first inside air inlet forms the first air flow passing outside the separation cylinder, and the second outside air inlet and The air intake housing is configured such that the air introduced into the air intake housing from the second inside air introduction port forms a second air flow passing through the inside of the separation cylinder;
The air intake housing is provided with a switching device for switching the open / close state of the first and second outside air introduction ports and the first and second inside air introduction ports. The outside air introduction port is opened and the second outside air introduction port is closed, and the first inside air introduction port is closed and the second inside air introduction port is opened. The centrifugal blower according to any one of 1 to 4.

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