Air blower

Abstract

To provide an air blower which allows easy maintenance of a cover while maintaining a sufficient air flow.SOLUTION: A double-inversion-type circulator has a rear impeller 24 covered with a rear side cover 30 and a front impeller 26 covered with a front side cover 40. The rear side cover 30 and the front side cover 40 respectively have: a rear side side face part 31a and a front side second member 42 configuring an annular side face; and a rear side bottom face part 31b and a front side first member 41 having a plurality of rear side first beam parts and a plurality of front side first beam parts 41b provided inside the rear side side face part 31a and the front side second member 42 and linearly extending in parallel with each other. A rotation speed ratio per unit time of the front impeller 26 and the rear impeller 24 defined by the following formula (1) during a drive of the circulator satisfies a range shown by the following formula (2): (1) rotation speed ratio=rotation speed of the rear impeller / rotation speed of the front impeller; (2) 1<rotation speed ratio≤1.2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a blower. [Background technology]

[0002] Counter-rotating fans have been known in the past, each of which includes an intake-side impeller located upstream of an air flow passage and an exhaust-side impeller located downstream of the air flow passage, with the exhaust-side impeller rotating in the opposite direction to the intake-side impeller. For example, Patent Document 1 discloses a counter-rotating fan that combines an intake-side fan having a first impeller and an exhaust-side fan having a second impeller. In this counter-rotating fan, the rotation speed of the first impeller is set higher than the rotation speed of the second impeller, thereby increasing the airflow rate of the intake-side fan and ensuring a sufficient airflow rate during operation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 17132 Summary of the Invention [Problem to be solved by the invention]

[0004] In the blower disclosed in Patent Document 1, the beam-like portions (grill portions) of the covers covering each impeller are formed in a radial shape to ensure sufficient airflow during operation. However, covers with beam-like portions formed in a radial shape have the disadvantage of being difficult to clean and maintain. On the other hand, if the beam-like portions were formed in a shape other than radial to facilitate cover maintenance, there is a risk that a sufficient airflow may not be ensured during operation.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a blower that ensures a sufficient air volume while facilitating maintenance of the cover. [Means for solving the problem]

[0006] The blower of the present invention is a counter-rotating blower having a rear impeller that is provided upstream of an air flow path and covered by a rear cover, and a front impeller that is provided downstream of the air flow path and covered by a front cover, wherein at least one of the rear cover and the front cover has a side portion that forms an annular side surface, and a bottom portion that is provided inside the side portion and has a plurality of first beam-shaped portions that extend linearly and parallel to each other, and the rotation speed ratio per unit time of the front impeller to the rear impeller, defined by the following equation (1) when the blower is operating, satisfies the range shown in the following equation (2). Rotation speed ratio = rear impeller rotation speed / front impeller rotation speed (1) 1<Rotational speed ratio≦1.2 (2) [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a blower that ensures a sufficient air volume while allowing for easy maintenance of the cover. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an overall perspective view of a circulator according to an embodiment, seen from the front side; [Figure 2] 1 is a partially exploded perspective view of a circulator according to an embodiment, seen from the front side. FIG. [Figure 3] 3A is a rear view of a rear cover of the circulator according to the embodiment, and FIG. 3B is a cross-sectional view taken along the line IIIb-IIIb in FIG. 3A. [Figure 4] 4A is a front view of a front cover of a circulator according to an embodiment, and FIG. 4B is a cross-sectional view taken along line IVb-IVb in FIG. 4A. [Figure 5] 1(a) is a perspective view of the first rear member of the rear cover of the circulator according to the embodiment, as seen from the front side, and FIG. 1(b) is a perspective view of the second rear member of the rear cover, as seen from the front side. [Figure 6] 1(a) is a perspective view of the front first member of the front cover of the circulator according to the embodiment, as viewed from the front side, and FIG. 1(b) is a perspective view of the front second member of the front cover, as viewed from the front side. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1, a circulator (blower) 1 according to this embodiment is a large circulator 1 that is placed on a floor or the like, and includes an installation unit 10 that is installed on an installation surface, and an air blower head 20 that is supported by the installation unit 10. The air blower head 20 blows air with the right side (the side where the rear impeller 24 is provided) shown in Fig. 1 being the upstream side of the air flow path, and the left side (the side where the front impeller 26 is provided) shown in Fig. 1 being the downstream side of the air flow path. In the following description, the upstream side of the air blower head 20 will be referred to as the rear side of the circulator 1, the downstream side of the air blower head 20 will be referred to as the front side of the circulator 1, and the right and left sides of the air blower head 20 when viewed from the front will be referred to as the right and left sides of the circulator 1.

[0010] First, the installation unit 10 will be described. The installation unit 10 has a thick, disc-shaped disc portion 12 and a pair of support arms 14 extending upward from both the left and right sides of the disc portion 12. A touch panel 12a is provided on the top surface of the disc portion 12 to allow the user to turn the power of the circulator 1 on and off, etc. A control unit 16 is provided inside the disc portion 12 to control the number of rotations per unit time of the rear impeller 24 and the front impeller 26. The manner in which the control unit 16 controls each of the impellers 24, 26 will be described later.

[0011] Each of the pair of support arms 14 is plate-shaped, and the inner surface of the lower end is connected to the disk portion 12. A pivotal support portion 14a that pivotally supports the blower head 20 is provided on the inner surface of the upper end of each support arm 14 (see FIG. 2). The blower head 20 is pivotally supported by the pivotal support portion 14a of each support arm 14 so as to be rotatable around an axis whose axial direction is in the left-right direction, thereby allowing it to swing up and down.

[0012] Next, the configuration of the blower head 20 will be described. As shown in Fig. 2, the blower head 20 has a cover mounting member 22, a rear impeller 24 attached to the rear side of the cover mounting member 22, i.e., on the upstream side of the air flow path, a front impeller 26 attached to the front side of the cover mounting member 22, i.e., on the downstream side of the air flow path, a rear cover 30 attached to the cover mounting member 22 in a manner covering the rear impeller 24, and a front cover 40 attached to the cover mounting member 22 in a manner covering the front impeller 26. In other words, the cover mounting member 22 is provided between the impellers 24, 26.

[0013] The cover mounting member 22 has a generally annular shape overall and includes an outer peripheral annular portion 22a that forms the outer periphery of the cover mounting member 22, a circular portion 22b that is provided inside the outer peripheral annular portion 22a, and three beam-shaped connecting portions 22c that connect the outer peripheral annular portion 22a and the circular portion 22b. Supported portions 22a1 that are supported by the support portions 14a of the support arms 14 are provided on both the left and right sides of the outer surface of the outer peripheral annular portion 22a. A rear housing portion 22b1 is provided on the rear side of the circular portion 22b to accommodate a motor (not shown) that rotates the rear impeller 24. A front housing portion 22b2 is provided on the front side of the circular portion 22b to accommodate a motor (not shown) that rotates the front impeller 26.

[0014] The rear impeller 24 has a substantially cylindrical rear rotating portion 24a connected to the motor and three rear blades 24b extending outward from the outer circumferential surface of the rear rotating portion 24a. The front impeller 26 has a substantially cylindrical front rotating portion 26a connected to the motor and four front blades 26b extending outward from the outer circumferential surface of the front rotating portion 26a. The circulator 1 of this embodiment is a counter-rotating circulator 1. That is, in the circulator 1, the rear impeller 24 and the front impeller 26 are arranged with their rotational axis centers aligned in the axial flow direction (front-rear direction) and rotate in opposite directions.

[0015] 2, 3, and 5, the rear cover 30 has a generally short cylindrical shape with a slightly reduced diameter on the rear side and a bottom, and includes a rear first member 31 and a rear second member 32. The rear first member 31 is generally grill-shaped and made of beam-like portions, and has a rear side portion (side portion) 31a that forms the annular side of the rear cover 30, and a rear bottom portion (bottom portion) 31b that is provided inside the rear side portion 31a and forms the bottom of the rear cover 30. The rear side portion 31a has a plurality of beam-like side beam portions 31c that extend linearly and parallel to each other in the front-to-rear direction, and the rear bottom portion 31b has a plurality of beam-like rear first beam portions (first beam portions) 31d that extend linearly and parallel to each other in the left-to-right direction.

[0016] 5(a), a plurality of rear attachment portions 31a1 extending inward like claws are provided at intervals on the circular edge portion that is the front end of the rear side surface portion 31a. The rear cover 30 is attached to the cover attachment member 22 by engaging the rear attachment portions 31a1 with the rear portions of the outer circumferential annular portion 22a of the cover attachment member 22. In addition, a plurality of rear minute protrusions 31b1 that protrude slightly inward are provided on the outer circumferential portion on the inner surface side (front surface side) of the rear bottom surface portion 31b.

[0017] 5(b), the rear second member 32 has a rear annular portion 32a having an annular shape and a beam-shaped rear second beam portion (second beam portion) 32b extending vertically in the approximately left-right center inside the rear annular portion 32a. When the rear first member 31 and the rear second member 32 are assembled, the rear second beam portion 32b is assembled and extends so as to be approximately perpendicular to each of the multiple rear first beam portions 31d. In addition, notch-shaped rear minute notches 32a1 are provided on the outer circumferential edge of the rear annular portion 32a at positions corresponding to the rear minute protrusions 31b1 of the rear first member 31, with which the rear minute protrusions 31b1 engage. The rear first member 31 and the rear second member 32 are assembled together by engaging the rear minute protrusions 31b1 with the rear minute cutouts 32a1.

[0018] Here, the manner in which the rear first beam-shaped portion 31d and the rear second beam-shaped portion 32b are assembled will be described. As shown in FIG. 5(a), each rear first beam-shaped portion 31d is provided at approximately equal intervals in a generally plate-like shape with both plate surfaces facing up and down. A rear first recess (first recess) 31d1 recessed toward the rear is provided at approximately the center in the left-right direction of each rear first beam-shaped portion 31d. On the other hand, as shown in FIG. 5(b), the rear second beam-shaped portion 32b is provided at approximately equal intervals in a generally plate-like shape with both plate surfaces facing left and right. A plurality of rear second recesses (second recesses) 32b1 recessed toward the front so as to be able to fit into the rear first recesses 31d1 are provided at approximately equal intervals.

[0019] When the rear first member 31 and the rear second member 32 are assembled, as shown in FIG. 3(a), the rear first recess 31d1 of each rear first beam-shaped portion 31d is fitted into the rear second recess 32b1 of the rear second beam-shaped portion 32b, so that the rear second beam-shaped portion 32b is assembled in an orientation that is approximately perpendicular to each rear first beam-shaped portion 31d at approximately the center in the left-right direction of each rear first beam-shaped portion 31d.

[0020] 3(b), the rear first beam-shaped portion 31d and the rear second beam-shaped portion 32b assembled in the above manner are restricted in their left-right movement by the rear first recess 31d1 interfering with both plate surfaces of the rear second beam-shaped portion 32b, their up-down movement by the rear second recess 32b1 interfering with both plate surfaces of the rear first beam-shaped portion 31d, and their front-to-rear movement by the front-to-rear interference between the bottom surfaces of the rear first recess 31d1 and the rear second recess 32b1. This prevents the rear first beam-shaped portion 31d from bending in the up-down direction and the rear second beam-shaped portion 32b from bending in the left-to-right direction, and improves the strength of the rear first beam-shaped portion 31d and the rear second beam-shaped portion 32b in the front-to-rear direction.

[0021] As shown in FIGS. 2, 3, and 6, the front cover 40 has a generally short cylindrical shape with a bottom at the front side, and includes a front first member (bottom surface portion) 41 and a front second member (side surface portion) 42. The front first member 41 is a grill-like member made of beam-like portions and is provided inside the front second member 42 to form the bottom surface of the front cover 40. The front first member 41 has a front annular portion 41a having an annular shape and a plurality of front first beam-like portions (first beam-like portions) 41b extending linearly and parallel in the left-right direction inside the front annular portion 41a. The outer peripheral edge of the front annular portion 41a is provided with a plurality of front small protrusions 41a1 that protrude slightly rearward (see FIG. 6(a)).

[0022] 6(b), the front second member 42 has a generally cylindrical shape overall, and includes a cylindrical portion 42a that forms the annular side surface of the front cover 40, and a beam-shaped front second beam portion (second beam portion) 42b that extends in the up-down direction at a generally left-right center portion within the front opening of the cylindrical portion 42a. When the front first member 41 and the front second member 42 are assembled, the front second beam portion 42b is assembled and extends so as to be generally perpendicular to each of the multiple front first beam portions 41b (see enlarged view E1 in FIG. 2).

[0023] 4(b), a plurality of front mounting portions 42a1 extending inward like claws are provided at intervals on the circular edge portion at the rear end of the cylindrical portion 42a. The front cover 40 is attached to the cover mounting member 22 by engaging the front mounting portions 42a1 with the front portions of the outer circumferential annular portion 22a of the cover mounting member 22. The outer circumferential edge portion at the front end of the cylindrical portion 42a is provided with notched front minute cutouts 42a2 at positions corresponding to the front minute protrusions 41a1 of the front first member 41. The front first member 41 and the front second member 42 are assembled by engaging the front minute protrusions 41a1 with the front minute cutouts 42a2.

[0024] Here, the assembly of the front first beam-shaped portion 41b and the front second beam-shaped portion 42b will be described. As shown in FIG. 6(a), each front first beam-shaped portion 41b is provided at approximately equal intervals in a generally plate-like shape with both plate surfaces facing up and down. A front first recess (first recess) 41b1 recessed toward the front is provided at approximately the center in the left-right direction of each front first beam-shaped portion 41b. On the other hand, as shown in FIG. 6(b), the front second beam-shaped portion 42b is provided at approximately equal intervals in a generally plate-like shape with both plate surfaces facing left and right. A plurality of front second recesses (second recesses) 42b1 recessed toward the rear so as to be able to fit into the front first recesses 41b1 are provided at approximately equal intervals.

[0025] When the front first member 41 and the front second member 42 are assembled, as shown in Figure 4(a), the front first recess 41b1 of each front first beam-shaped portion 41b is fitted into the front second recess 42b1 of the front second beam-shaped portion 42b, so that the front second beam-shaped portion 42b is assembled in an orientation that is approximately perpendicular to each front first beam-shaped portion 41b at approximately the center in the left-right direction of each front first beam-shaped portion 41b.

[0026] As shown in enlarged view E3 in FIG. 4(b), the front first beam-shaped portion 41b and the front second beam-shaped portion 42b assembled in the manner described above are restricted in their left-right movement by the interference of the front first recess 41b1 with both plate surfaces of the front second beam-shaped portion 42b, their up-down movement by the interference of the front second recess 42b1 with both plate surfaces of the front first beam-shaped portion 41b, and their front-to-back movement by the interference of the bottom surfaces of the front first recess 41b1 and the front second recess 42b1 with each other in the front-to-back direction. This prevents the front first beam-shaped portion 41b from bending in the up-down direction and the front second beam-shaped portion 42b from bending in the left-to-right direction, and improves the strength of the front first beam-shaped portion 41b and the front second beam-shaped portion 42b in the front-to-back direction.

[0027] As described above, in the circulator 1 of this embodiment, since the rear cover 30 and the front cover are configured as described above, when cleaning the rear cover 30 and the front cover 40, the rear cover 30 and the front cover 40 can be cleaned with a cleaning brush or the like along the rear first beam portion 31d and the front first beam portion 41b that extend linearly in parallel, making it easy to clean the rear cover 30 and the front cover 40. In other words, a circulator 1 with easy cover maintenance can be realized.

[0028] Next, we will explain the control mode of the rear impeller 24 and the front impeller 26 in the control unit 16. In the circulator 1 of this embodiment, when the circulator 1 is driven, the control unit 16 controls the rear impeller 24 and the front impeller 26 so that the ratio of the rotation speeds per unit time of the rear impeller 24 and the front impeller 26 satisfies the range shown in the following formula (2), where the ratio is defined by the following formula (1): Rotational speed ratio = rotational speed of rear impeller 24 / rotational speed of front impeller 26 (1) 1<Rotational speed ratio≦1.2 (2)

[0029] As an example, the control unit 16 controls the rotation speed of the front impeller 26 to 2200 rpm and the rotation speed of the rear impeller to 2500 rpm when the circulator 1 is driven. In this case, the rotation speed ratio defined by the above formula (1) is 1.14.

[0030] If the rotation speed per unit time of the rear impeller 24 and the front impeller 26 (hereinafter simply referred to as "rotation speed") is the same, as the rotation speed increases, the wind speed at a position away from the circulator 1 (for example, a position 1 m away from the circulator 1; hereinafter referred to as "measurement position") increases, but the current consumption consumed by driving the circulator 1 also increases. If the current consumption exceeds a certain level, the circulator cannot be used in an ordinary home where the power supply is limited.

[0031] Furthermore, in a counter-rotating blower such as the circulator 1 of this embodiment, increasing the rotation speed of only the front impeller 26 without changing the rotation speed of the rear impeller 24 results in almost no increase in the wind speed at the measurement position. By making the rotation speed of the rear impeller 24 higher than that of the front impeller 26, the wind speed at the measurement position increases. However, if the difference between the rotation speeds of the rear impeller 24 and the front impeller 26 becomes large, the wind does not spread, diminishing the benefit of counter-rotating, which allows air to be blown farther, and the efficiency (wind speed at the measurement position / current consumption) decreases. This effect becomes particularly noticeable when the measurement position is far away.

[0032] Therefore, in the circulator 1 of this embodiment, the control unit 16 increases the rotation speed of the rear impeller 24 so that it is faster than the rotation speed of the front impeller 26, while controlling the rotation speed ratio between the rear impeller 24 and the front impeller 26 so that it satisfies 1 < rotation speed ratio ≦ 1.2, thereby increasing the air speed at the measurement position while suppressing an increase in current consumption. This makes it possible to achieve an efficient circulator 1 while ensuring a sufficient air volume.

[0033] As described above, the circulator 1 according to this embodiment is a counter-rotating circulator 1 having a rear impeller 24 that is provided upstream of the air flow path and covered by the rear cover 30, and a front impeller 26 that is provided downstream of the air flow path and covered by the front cover 40, and the rear cover 30 and the front cover 40 have a rear side surface portion 31a and a front second member 42 that form an annular side surface, and a rear bottom surface portion 31b and a front first member 41 that are provided inside the rear side surface portion 31a and the front second member 42 and have a plurality of rear first beam-shaped portions 31d and a plurality of front first beam-shaped portions 41b that extend linearly and parallel to each other, and the rotation speed ratio per unit time of the front impeller 26 and the rear impeller 24 as defined by the following formula (1) when the circulator 1 is operating satisfies the range shown in the following formula (2). Rotation speed ratio = rear impeller rotation speed / front impeller rotation speed (1) 1<Rotational speed ratio≦1.2 (2)

[0034] With the circulator 1 of this embodiment configured as described above, when cleaning the rear cover 30 and the front cover 40, the rear first beam-shaped portions 31d and the front first beam-shaped portions 41b can be easily cleaned with a cleaning brush or the like, facilitating maintenance of the rear cover 30 and the front cover 40. Furthermore, in the counter-rotating circulator 1 of this embodiment, by controlling the rotation speed ratio between the rear impeller 24 and the front impeller 26 to satisfy the range defined by the above formula (2), it is possible to increase the air velocity at a fixed position while suppressing an increase in current consumption, thereby improving efficiency (air velocity at a measurement position / current consumption). In this way, this embodiment realizes a circulator 1 whose covers are easy to maintain while ensuring sufficient airflow.

[0035] Furthermore, in the circulator 1 of this embodiment, the rotation speed per minute of the rear impeller 24 when the circulator 1 is operating is 2500 rotations per minute or less, and the rotation speed ratio is 1.1 or more. If the rotation speed per minute of the rear impeller 24 exceeds 2500 rotations per minute, the current consumption increases, and the efficiency of the circulator 1 tends to decrease. Also, if the rotation speed ratio is less than 1.1, the wind speed at the measurement position decreases, and the efficiency of the circulator 1 tends to decrease. Therefore, by controlling the rear impeller 24 and the front impeller 26 in the above manner, the efficiency of the circulator 1 can be further improved.

[0036] Furthermore, in the circulator 1 of this embodiment, the rear cover 30 and the front cover 40 have rear second beam portions 32b and front second beam portions 42b that are provided inside the rear side surface portion 31a and the front second member 42 and extend substantially perpendicular to the multiple rear first beam portions 31d and the multiple front first beam portions 41b. With this configuration, since each rear first beam portion 31d is reinforced by the rear second beam portion 32b, it is possible to prevent each rear first beam portion 31d from bending when cleaning the rear cover 30, and since each front first beam portion 41b is reinforced by the front second beam portion 42b, it is possible to prevent each front first beam portion 41b from bending when cleaning the front cover 40,

[0037] In the circulator 1 of this embodiment, the plurality of rear first beam-shaped portions 31d and the plurality of front first beam-shaped portions 41b have rear first recesses 31d1 and front first recesses 41b1 that are concavely formed, and the rear second beam-shaped portion 32b and the front second beam-shaped portion 42b have rear second recesses 32b1 and front second recesses 42b1 that are concavely formed so as to be able to fit into the rear first recesses 31d1 and the front first recesses 41b1. b1, and each of the rear first recesses 31d1 of the multiple rear first beam-shaped portions 31d and each of the front first recesses 41b1 of the multiple front first beam-shaped portions 41b are fitted approximately perpendicular to the multiple rear second recesses 32b1 and the multiple front second recesses 42b1, thereby assembling the rear first beam-shaped portion 31d and the rear second beam-shaped portion 32b, and assembling the front first beam-shaped portion 41b and the front second beam-shaped portion 42b.

[0038] According to this configuration, each of the rear first recesses 31d1 is fitted into the plurality of rear second recesses 32b1 so as to be approximately perpendicular to each other, thereby restricting movement of the two recesses in two directions that are approximately perpendicular to each other, and each of the front first recesses 41b1 is fitted into the plurality of front second recesses 42b1 so as to be approximately perpendicular to each other, thereby restricting movement of the two recesses in two directions that are approximately perpendicular to each other. This makes it possible to improve the strength of the plurality of rear first beam-shaped portions 31d and rear second beam-shaped portions 32b, and the strength of the plurality of front first beam-shaped portions 41b and front second beam-shaped portions 42b.

[0039] The above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the inventions and their equivalents as defined in the claims. [Example]

[0040] The present invention will be described in more detail below with reference to examples, but the technical scope of the present invention is not limited thereto. In these examples, a circulator having a configuration similar to that of the circulator 1 described in the above embodiment was used, and the efficiency was calculated based on the wind speed and current consumption at the measurement position while controlling the rotation speed of the rear impeller and the rotation speed of the front impeller, and the rotation speed ratio that results in optimal efficiency was derived. In the circulator used in these examples, the axial dimension of the front impeller (front-to-rear dimension, e.g., 30 mm) was made smaller than the axial dimension of the rear impeller (e.g., 40 mm) so that the wind speed is less likely to decrease even if the rotation speed of the front impeller is made smaller than that of the rear impeller.

[0041] For the rear impeller, wind speed was measured while changing the rotation speed in increments of 50 within the range of 2400 rpm to 2650 rpm. For the front impeller, wind speed was measured while changing the rotation speed within the range of 2000 rpm to 2650 rpm so that the rotation speed ratio (rear impeller rotation speed / front impeller rotation speed) was within the range of 1.0 to 1.4.

[0042] The wind speed was measured at a position 1 m away from the circulator on the front side. To measure the wind speed at the measurement position, an AIR FLOW (model number: LCA501) manufactured by TSI Incorporated was used. To measure the current consumption, a fanless wide-range DC stabilized power supply (model number: PFR-100L50) manufactured by Texio Technology Co., Ltd. was used. The unit of wind speed was m / s, and the unit of current consumption was A. Efficiency (wind speed / current consumption) was calculated from the measured wind speed and current consumption.

[0043] Table 1 below shows a scatter diagram of the measurement results. In Table 1, the horizontal axis represents the rotation speed ratio, and the vertical axis represents the efficiency. The dotted curves in Table 1 represent polynomial approximation curves calculated from the plotted values for each different rotation speed of the rear impeller.

[0044] [Table 1]

[0045] As shown in Table 1, it was found that efficiency tends to decrease when the rotation speed ratio exceeds 1.2 in any range of the rear impeller rotation speed from 2400 rpm to 2650 rpm. From this, it was found that a highly efficient circulator can be realized by setting the rotation speed ratio between the rear impeller and the front impeller in the range of greater than 1 and equal to or less than 1.2.

[0046] Furthermore, as shown in Table 1, when the rotation speed of the rear impeller is 2500 rpm or less (2500 rpm, 2450 rpm, 2400 rpm) and the rotation speed ratio is in the range of 1.1 or more and 1.2 or less, the efficiency is 3.0 or more for all plotted values, indicating that high efficiency can be achieved. [Explanation of symbols]

[0047] 1: Circulator 10: Installation section 12: Disc portion 12a: Touch panel 14: Support arm 14a: Pivot support 16: Control unit 20: Blower head 22: Cover mounting member 22a: Outer peripheral annular portion 22a1: Pivoted support 22b: Circular part 22b1: Rear storage section 22b2: Front storage section 22c: Beam-shaped connection part 24: Rear impeller 24a: Rear rotating part 24b: Rear wing part 26: Front impeller 26a: Front rotating part 26b: Front wing part 30: Rear cover 31: Rear first member 31a: Rear side surface portion 31a1: Rear mounting portion 31b: Rear bottom portion 31b1: Posterior microprotrusion 31c: Side beam-shaped part 31d: rear first beam portion 31d1: rear first recess portion 32: Rear second member 32a: Rear annular portion 32a1: Rear micro notch 32b: Rear second beam-shaped part 32b1: rear second recess 40: front cover 41: Front first member 41a: Front annular portion 41a1: Front microprotrusion 41b: Front first beam-shaped part 41b1: Front first recess 42: Front second member 42a: Cylindrical portion 42a1: Front mounting portion 42a2: Front minute notch 42b: Front second beam-shaped part 42b1: Second front recess

Claims

1. A counter-rotating fan having a rear impeller provided upstream of an air flow path and covered with a rear cover, and a front impeller provided downstream of the air flow path and covered with a front cover, At least one of the rear cover and the front cover has a side surface portion constituting an annular side surface, and a bottom surface portion provided inside the side surface portion and having a plurality of first beam-shaped portions extending linearly and parallel to each other, A blower, wherein a rotation speed ratio per unit time of the front impeller to the rear impeller, defined by the following formula (1), when the blower is driven, satisfies the range shown in the following formula (2): Rotational speed ratio = rear impeller rotational speed / front impeller rotational speed (1) 1 < rotation speed ratio ≦ 1.2 ... (2)

2. The number of revolutions per minute of the rear impeller when the blower is driven is 2500 revolutions per minute or less, The rotation speed ratio is 1.1 or more. The blower of claim 1 .

3. At least one of the rear cover and the front cover has a second beam portion provided inside the side surface portion and extending substantially perpendicular to the first beam portions. The blower according to claim 1 or 2.

4. The plurality of first beam-shaped portions each have a first recessed portion formed in a concave shape, the second beam-shaped portion has a plurality of second recesses provided in a recessed shape so as to be able to fit into the first recesses; the first recesses of the first beam-shaped portions are fitted into the second recesses so as to be substantially perpendicular to each other, thereby assembling the first beam-shaped portions and the second beam-shaped portions. The blower according to claim 3.

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