Cross-flow fan and air conditioner

Abstract

The present disclosure addresses the problem of providing a cross-flow fan with which noise can be reduced. A cross-flow fan (101) is provided with a plurality of impellers (30). The impellers have a plurality of blades (31) arrayed in the circumferential direction. Each of the blades has a negative-pressure surface (31a), a pressure surface (31b), and an outer peripheral-side distal end section (31c). Along the rotational axis direction, the location of a pressure surface-side outer peripheral end (31e) periodically repeats a circumferential direction change and a rotational direction change. With respect to the circumferential direction change, the location of a pressure surface-side outer peripheral end passes through a circumferential direction recess location C that is recessed in the circumferential direction and a circumferential direction protrusion location B that protrudes in the circumferential direction. The curvature of the pressure surface changes periodically, following the location of the pressure surface-side outer peripheral end, on the outer peripheral side with respect to the center of the blade. The location of the pressure surface-side outer peripheral end at the circumferential direction recess is forward in the rotational direction with respect to a circumscription section (31f).

Description

Crossflow fan and air conditioner

[0001] The present invention relates to a crossflow fan and an air conditioner.

[0002] Conventionally, indoor units of air conditioners (hereinafter referred to as air conditioning units) that are installed on the side walls of a room rather than on the ceiling, draw in air from the front or top, and blow out conditioned air from outlets at the bottom have become widespread. For example, as shown in Patent Document 1 (Japanese Patent Laid-Open Publication No. 63-124899), the air conditioning unit houses a heat exchanger that exchanges heat between the refrigerant and the air, and a cross-flow fan.

[0003] A problem with crossflow fans is that the fluid blown out from the crossflow fan collides with a solid wall such as a casing, generating noise.

[0004] A crossflow fan according to a first aspect is cylindrical. The crossflow fan includes a plurality of impellers. The impeller has a plurality of blades arranged in the circumferential direction. Each blade has a suction surface, a pressure surface, and an outer peripheral tip. The suction surface is located on the side opposite to the direction of rotation. The suction surface is a curved surface that bulges in the direction opposite to the direction of rotation. The pressure surface is located on the rotation direction side. The pressure surface is a curved surface that concaves in the direction opposite to the direction of rotation. The outer peripheral tip connects the suction surface and the pressure surface. The pressure surface and the outer peripheral tip are connected at a pressure surface side outer peripheral edge. The suction surface and the outer peripheral tip are connected at a circumscribing portion. The circumscribing portion is the portion where the outer peripheral tip and the imaginary circumscribing circle of the blade are in contact. The position of the pressure surface side outer peripheral edge periodically changes in the circumferential direction and the rotation direction along the rotation axis. The position of the pressure surface side outer peripheral end passes through the position of the circumferentially recessed portion that is circumferentially recessed and the position of the circumferentially protruding portion that is circumferentially changed. The curvature of the pressure surface periodically changes on the outer peripheral side relative to the center of the blade, following the position of the pressure surface side outer peripheral end. The position of the pressure surface side outer peripheral end at the circumferential recess is located forward in the direction of rotation relative to the circumferential contact portion.

[0005] Here, the position of the outer peripheral end on the pressure surface side periodically changes in the circumferential direction and the rotational direction along the rotation axis direction, and passes through a circumferential concave position that is recessed in the circumferential direction and a circumferential convex position that protrudes in the circumferential direction in the circumferential change, thereby reducing noise.

[0006] A crossflow fan according to a second aspect is cylindrical. The crossflow fan includes a plurality of impellers. The impeller has a plurality of blades arranged in the circumferential direction. Each blade has a suction surface, a pressure surface, and an outer peripheral tip. The suction surface is located on the side opposite to the direction of rotation. The suction surface is a curved surface that bulges in the direction opposite to the direction of rotation. The pressure surface is located on the rotation direction side. The pressure surface is a curved surface that concaves in the direction opposite to the direction of rotation. The outer peripheral tip connects the suction surface and the pressure surface. The pressure surface and the outer peripheral tip are connected at an outer peripheral end on the pressure surface side. The suction surface and the outer peripheral tip are connected at a circumscribing portion. The circumscribing portion is the portion where the outer peripheral tip and an imaginary circumscribing circle of the blade contact each other. The position of the outer peripheral tip periodically changes in the circumferential direction and the rotational direction along the rotation axis. The position of the outer peripheral tip passes through the position of the circumferentially recessed circumferential portion, which is recessed in the circumferential direction, and the position of the circumferentially protruding circumferential portion, which protrudes in the circumferential direction. The curvatures of the pressure surface and suction surface connected to the outer peripheral tip change periodically, on the outer peripheral side relative to the center of the blade, following the outer peripheral tip. The position of the pressure surface side outer peripheral end of the circumferential recess is located forward in the direction of rotation relative to the circumferentially contacting portion of the circumferential protrusion. The height of the circumferential asperities on the pressure surface side is equal to the height of the circumferential asperities on the suction surface side.

[0007] A crossflow fan according to a third aspect is cylindrical. The crossflow fan includes a plurality of impellers. The impellers have a plurality of blades arranged in the circumferential direction. Each blade has a suction surface, a pressure surface, and an outer circumferential tip. The suction surface is located on the side opposite to the direction of rotation. The suction surface is a curved surface that bulges in the direction opposite to the direction of rotation. The pressure surface is located on the side facing the direction of rotation. The pressure surface is a curved surface that recesses in the direction opposite to the direction of rotation. The outer circumferential tip connects the suction surface and the pressure surface. The circumferential position of each blade cross section in the direction of rotation axis changes periodically and repeatedly along the direction of rotation axis without changing the mounting angle of the blade. When viewed in the direction of rotation axis, the convex cross section, which is a cross section that forms a peak of the period, and the concave cross section, which is a cross section that forms a valley of the period, partially overlap each other.

[0008] A cross flow fan according to a fourth aspect is the cross flow fan according to any one of the first aspect to the third aspect, wherein the blowing air speed is uniform.

[0009] A crossflow fan according to a fifth aspect is the crossflow fan according to any one of the first to fourth aspects, wherein the period of the change along the rotation axis direction is wavy.

[0010] A crossflow fan according to a sixth aspect is the crossflow fan according to the fifth aspect, wherein the blades have inner tips that connect the suction surface and the pressure surface at the inner periphery, and a ratio H / L of a wave height H to a blade chord length L, which is the distance between the outer periphery tip and the inner periphery tip, is 0.041 or less.

[0011] A crossflow fan according to a seventh aspect is the crossflow fan according to the fifth or sixth aspect, wherein the blades have inner circumferential tips that connect the suction surface and the pressure surface at the inner circumferential side. A ratio H / L of a wave height H to a blade chord length L, which is the distance between the outer circumferential tip and the inner circumferential tip, is 0.006 to 0.035.

[0012] A crossflow fan according to an eighth aspect is the crossflow fan according to the fifth aspect, wherein a ratio P / H of wave interval P to wave height H is 0 to 39.

[0013] A crossflow fan according to a ninth aspect is the crossflow fan according to any one of the fifth to eighth aspects, wherein the ratio P / H of the wave interval P to the wave height H is 7 to 31.

[0014] An air conditioner according to a tenth aspect includes the crossflow fan according to any one of the first to ninth aspects.

[0015] 19 is a diagram illustrating the configuration of an air conditioning apparatus comprising an air conditioning outdoor unit and an air conditioning unit. FIG. 19 is a longitudinal cross-sectional view of the air conditioning unit (cross-sectional view of the arrows II-II in FIG. 1). FIG. 20 is a perspective view showing an outline of an impeller of a cross-flow fan. FIG. 21 is a cross-sectional view of a blade of the first embodiment. FIG. 22 is a partially enlarged view of the blade of FIG. 3. FIG. 23 is a top view of the blade of the first embodiment. FIG. 24 is a perspective view of the pressure surface side of the blade of the first embodiment. FIG. 25 is a perspective view of the suction surface side of the blade of the first embodiment. FIG. 26 is a cross-sectional view of a blade of the second embodiment. FIG. 27 is a partially enlarged view of the blade of FIG. 28. FIG. 29 is a top view of the blade of the second embodiment. FIG. 29 is a perspective view of the pressure surface side of the blade of the second embodiment. FIG. 29 is a perspective view of the suction surface side of the blade of the second embodiment. FIG. 20 is a diagram comparing partially enlarged top views of the blades of the first and second embodiments. FIG. 21 is a cross-sectional view of a blade of the third embodiment. FIG. 22 is a top view of a blade of the third embodiment. FIG. 23 is a perspective view of the pressure surface side of the blade of the third embodiment. FIG. 24 is a perspective view of the suction surface side of the blade of the third embodiment. FIG. 25 is a top view of a blade of a modified example. FIG. 26 is a diagram illustrating measurement positions in the examples. FIG. 27 is a graph showing the relationship between axial position and wind speed measured at the X position in FIG. 19. 20 is a graph showing the relationship between axial position and wind speed measured at position Y in Fig. 19. FIG. 21 is a graph showing the relationship between H / L and sound reduction amount when wave height is H and chord length is L. FIG. 22 is a graph showing the relationship between P / H and sound reduction amount when wave spacing is P and wave height is H.

[0016] In the following description, the rotation axis O refers to the rotation axis of the impeller 30. The rotation axis direction refers to the direction in which the rotation axis O of the impeller 30 extends. The rotation direction refers to the direction in which the impeller 30 rotates. The circumferential direction refers to the circumferential direction of a circle centered on the rotation axis O. The radial direction refers to the radial direction of a circle centered on the rotation axis O. Furthermore, expressions indicating directions such as "up," "down," and "front" are used as appropriate, but these refer to the respective directions when the air conditioning unit 100 is installed and in normal use. For example, the up-down direction refers to the vertical direction. Furthermore, expressions such as "same," "uniform," and "parallel" may be used, but these include not only completely same, uniform, parallel, etc., but also substantially same, uniform, parallel, etc.

[0017] <First embodiment> (1) Overall configuration As shown in Fig. 1 , the air conditioning unit 100 is a wall-mounted indoor unit that is attached to a wall surface inside a room. The air conditioning unit 100 is connected to an outdoor air conditioning unit 91 placed outside the room via refrigerant piping 93 to form an air conditioner 90. The air conditioning unit 100 performs cooling operation and heating operation in the room in response to operation using a remote control or the like.

[0018] As shown in FIG. 2A, the air conditioning unit 100 includes a blower, a heat exchanger 20, and a filter 40.

[0019] (2) Blower The blower includes a cross-flow fan 101 including an impeller 30 and a casing 10 .

[0020] (2-1) Crossflow Fan The crossflow fan 101 is cylindrical and includes a plurality of cylindrical impellers 30 that extend horizontally, and a motor that rotates the impellers 30.

[0021] As shown in Fig. 2B, the impeller 30 is formed by connecting a plurality of fan blocks 32. Although not particularly limited, the impeller 30 is formed, for example, by joining the fan blocks 32 and an end plate 33. The end plate 33 is disposed at one end of the impeller 30. The impeller 30 has a metal rotation shaft 34 on a rotation axis O. The fan block 32 disposed at the other end of the impeller 30 has a boss (not shown) at its center that is connected to a fan motor shaft (not shown).

[0022] The impeller 30 rotates to generate an air flow that flows from the heat exchanger 20 side to the air outlet 10b side. When the impeller 30 rotates, air flows from the room to the heat exchanger 20 via the filter 40. The air that has passed through the heat exchanger 20 is blown out into the room. The blowing air speed is uniform.

[0023] The rotation speed of the motor of the impeller 30 is changed by a control device (not shown). The control device built into the air conditioning unit 100 changes the rotation speed of the motor based on an operation input by a user via a remote control or the like.

[0024] In the impeller 30, a plurality of blades 31 are arranged in the circumferential direction.

[0025] 3 to 7, each blade 31 has a suction surface 31a, a pressure surface 31b, an outer circumferential tip 31c, an inner circumferential tip 31d, a pressure surface outer circumferential edge 31e, and a circumscribing portion 31f. In Figures 3 and 4, the outline of the blade 31 shown in solid lines indicates the outline of the blade 31 in cross section C, which will be described later. The outline of the blade 31 shown in dashed lines indicates a portion of the outline of the blade 31 in cross section B, which will be described later, that differs from the outline of the blade 31 in cross section C.

[0026] The suction surface 31a is located on the side opposite to the direction of rotation. The suction surface 31a is a curved surface that bulges in the opposite direction to the direction of rotation. The pressure surface 31b is located on the rotation direction side. The pressure surface 31b is a curved surface that concaves in the opposite direction to the direction of rotation. The outer circumferential tip 31c connects the suction surface 31a and the pressure surface 31b on the outer circumferential side. The inner circumferential tip 31d connects the suction surface 31a and the pressure surface 31b on the inner circumferential side. The circumscribed portion 31f is the portion where the outer circumferential tip 31c and the imaginary circumscribed circle 30a of the blade 31 contact each other. The imaginary circumscribed circle 30a is an imaginary circle connecting the outer ends of the multiple blades 31 (see the circle indicated by the dotted line in Figure 2).

[0027] The pressure surface 31b and the outer circumferential tip 31c are connected at a pressure surface outer circumferential edge 31e, and the negative pressure surface 31a and the outer circumferential tip 31c are connected at an outer contact portion 31f.

[0028] The position of the pressure surface side outer peripheral end 31e periodically changes in the circumferential direction and the rotational direction along the rotation axis direction. The period of change along the rotation axis direction is wave-shaped. The position of the pressure surface side outer peripheral end 31e passes through a circumferential recessed position C that is recessed in the circumferential direction and a circumferential protruding position B that protrudes in the circumferential direction in the circumferential direction. Hereinafter, a cross section perpendicular to the rotation axis direction at the circumferential recessed position C will be referred to as a C cross section, and a cross section perpendicular to the rotation axis direction at the circumferential protruding position B will be referred to as a B cross section. The distance between adjacent C cross sections is equal to the distance between adjacent B cross sections. The pressure surface side outer peripheral end 31e on the C cross section moves circumferentially by a displacement angle θ relative to the pressure surface side outer peripheral end 31e on the B cross section.

[0029] The position of the pressure surface side outer peripheral end 31 e does not change radially throughout the entire rotation axis direction. The distance from the rotation axis O to the pressure surface side outer peripheral end 31 e in cross section C is the same as the distance from the rotation axis O to the pressure surface side outer peripheral end 31 e in cross section B.

[0030] The curvature of the pressure surface 31b changes periodically on the outer circumferential side of the center of the blade 31, following the position of the pressure surface-side outer circumferential end 31e. The center of the blade 31 is a position that is 50% of the blade chord length L. The blade chord length L is the distance between the outer circumferential tip 31c and the inner circumferential tip 31d. In detail, the blade chord length L is the distance between a straight line that is perpendicular to the chord line and that is tangent to the outer circumferential tip 31c and the inner circumferential tip 31d, where the line segment tangent to the outer circumferential tip 31c and the inner circumferential tip 31d on the rotational direction side is defined as the chord line.

[0031] Specifically, the curvature of the pressure surface 31b changes periodically from position F1, which is a predetermined distance away from the center of the blade 31 toward the outer periphery, to the position of the pressure surface-side outer periphery end 31e. The distance from the rotation axis O to position F1 is 90% or more of the radius of the impeller 30. The radius of the impeller 30 is the radius of an imaginary circumscribing circle 30a that connects the outer ends of the multiple blades 31 when viewed in the direction of the rotation axis.

[0032] The curvature of the pressure surface 31b does not change over the entire length of the blade 31 in the axial direction of rotation on the inner circumferential side of the center of the blade 31.

[0033] The curvature of the suction surface 31a does not change over the entire length of the blade 31 in the rotational axis direction.

[0034] The position of the suction surface 31a side of the circumscribing portion 31f does not change over the entire length of the blade 31 in the rotational axis direction. Therefore, the position of the suction surface 31a side of the circumscribing portion 31f is the same in cross section C and cross section B. The position of the imaginary circumscribing circle 30a is the same in cross section C and cross section B. However, the position of the pressure surface 31b of the circumscribing portion 31f may move forward in the direction of rotation in cross section B. Therefore, the area of ​​contact between the circumscribing portion 31f and the imaginary circumscribing circle 30a in cross section B may be increased.

[0035] The position of the pressure surface side outer peripheral end 31e in the C cross section is located forward in the rotation direction relative to the circumferential contact portion 31f.

[0036] The shape of the outer peripheral tip portion 31c periodically changes in the rotation direction along the rotation axis direction.

[0037] The ratio H / L of the wave height H to the blade chord length L is 0.041 or less. The wave height H is defined as H = 2R × sin(θ / 2), where R is the radius (mm) of the impeller 30 and θ is the displacement angle (rad) of the pressure surface side outer peripheral end 31e at the C cross section and the B cross section. In other words, the wave height H is the length of the chord of the displacement angle θ on the imaginary circumscribing circle 30a. The blade chord length L is the distance (mm) between the outer peripheral tip 31c and the inner peripheral tip 31d. The ratio H / L of the wave height H to the blade chord length L is more preferably 0.006 to 0.035. The ratio H / L of the wave height H to the blade chord length L is even more preferably 0.008 to 0.033.

[0038] The ratio P / H of the wave spacing P to the wave height H is 0 to 39. The wave spacing P means the distance between adjacent cross sections B and C. The ratio P / H of the wave spacing P to the wave height H is more preferably 7 to 31.

[0039] (2-2) Casing The casing 10 is an assembly of members that form the outer shell and frame of the air conditioning unit 100. The casing 10 supports and houses the filter 40, the heat exchanger 20, and the impeller 30.

[0040] An intake port 10a is formed in the upper part of the casing 10 to take in indoor air. An outlet port 10b is formed in the lower part of the casing 10 to send conditioned air into the room. The intake port 10a is located higher than the rotation axis O, which is the center of rotation of the impeller 30. More specifically, the intake port 10a is formed in the top surface (upper surface) of the casing 10 and draws in indoor air from the space above the air conditioning unit 100. The outlet port 10b is located lower than the rotation axis O. More specifically, the outlet port 10b is formed in the front portion of the bottom surface of the casing 10 and blows air forward and downward from the air conditioning unit 100.

[0041] The casing 10 includes a front panel 15, a rear guider 18, and a stabilizer 17. The stabilizer 17 and the rear guider 18 form an outlet air flow path 10c for scroll-shaped air flowing from the impeller 30 to the air outlet 10b. The upper part of the rear guider 18 is located higher than the rotation axis O. The front panel 15 is disposed on the front side of the filter 40. The stabilizer 17 is disposed further in front of the rear guider 18. The stabilizer 17 has a tongue portion 71 and a support portion 73. The support portion 73 supports the tongue portion 71.

[0042] When the impeller 30 rotates, air flows from the room through the air inlet 10a and the filter 40 to the heat exchanger 20. The air that has passed through the heat exchanger 20 flows into the outlet air flow path 10c and is blown out into the room from the outlet 10b.

[0043] (3) Heat Exchanger and Filter The heat exchanger 20 is a fin-and-tube heat exchanger having a V-shaped cross section. The shape of the heat exchanger 20 is not particularly limited. The heat exchanger 20 may have, for example, an inverted V-shape. The heat exchanger 20 exchanges heat between air flowing from the suction port 10a side to the impeller 30 side and refrigerant flowing through the tubes. The heat exchanger 20 is composed of a number of aluminum heat transfer fins and a number of tubes that pass through a number of holes drilled in the heat transfer fins. The copper heat transfer tubes have an outer diameter of 5 mm or 4 mm.

[0044] The upstream side of the air flow of the impeller 30 is covered by a filter 40. Specifically, the heat exchanger 20, which is located above and in front of the impeller 30, is covered by the filter 40. The filter 40 collects dust contained in the air flowing from the suction port 10a to the heat exchanger 20.

[0045] (4) Features (4-1) In the blades 31 of the crossflow fan 101, the position of the pressure surface-side outer peripheral end 31e periodically changes in the circumferential direction and the rotational direction along the rotational axis. The position of the pressure surface-side outer peripheral end 31e passes through a circumferential recessed position C that is circumferentially recessed, and a circumferential protruding position B that protrudes circumferentially as the position changes in the circumferential direction. The curvature of the pressure surface 31b periodically changes on the outer circumferential side of the center of the blade, following the position of the pressure surface-side outer peripheral end. The position of the pressure surface-side outer peripheral end 31e at the circumferential recessed position C is located forward in the rotational direction relative to the circumferential contact portion 31f.

[0046] This allows the airflow blown out from the crossflow fan 101 to be diffused. This makes it possible to suppress the systematic and rapid growth of turbulence in the wake of the blade. Furthermore, the size of the unevenness can be reduced, making it possible to suppress the flow from concentrating in the valleys. This reduces the density of the airflow at the peaks and valleys, making it possible to reduce wind turbulence. As a result, noise can be reduced.

[0047] (4-2) The cross-flow fan 101 blows out air at a uniform speed, which reduces wind turbulence.

[0048] (4-3) The period of change along the rotation axis direction is wavy. Therefore, the shape of the blades 31 changes smoothly. This prevents airflow turbulence caused by sudden changes, making it easier to reduce noise.

[0049] (4-4) The ratio H / L of the wave height H to the blade chord length L is 0.041 or less. Here, the wave height H is small relative to the blade chord length L. This makes it possible to suppress deviations in the airflow. This makes it possible to diffuse the airflow and suppress organized turbulence.

[0050] (4-5) The ratio H / L of the wave height H to the chord length L is 0.006 to 0.035. Here, the turbulence of the airflow can be further suppressed.

[0051] (4-6) The ratio P / H of the wave spacing P to the wave height H is 0 to 39. This makes it possible to suppress the bias of the airflow. This allows the airflow to be diffused and systematic turbulence to be suppressed.

[0052] (4-7) The ratio P / H of the wave interval P to the wave height H is 7 to 31. Here, the turbulence of the airflow can be further suppressed.

[0053] (4-8) The air conditioner 90 includes the above-described cross flow fan 101. Here, noise can be reduced.

[0054] Second Embodiment The crossflow fan 101 of this embodiment has most of the same configuration as the crossflow fan 101 of the first embodiment. The following description will focus on the differences between the crossflow fan 101 of this embodiment and the crossflow fan 101 of the first embodiment.

[0055] 8 to 12, the position of the pressure surface side outer peripheral end 31e periodically changes in the circumferential direction and the rotational direction along the rotation axis direction. Therefore, the position of the pressure surface side outer peripheral end 31e changes between cross section C and cross section B. The pressure surface side outer peripheral end 31e on cross section C moves circumferentially by a displacement angle θ relative to the pressure surface side outer peripheral end 31e on cross section B.

[0056] The position of the pressure surface side outer peripheral end 31 e does not change radially throughout the entire rotation axis direction. Therefore, the distance from the rotation axis O to the pressure surface side outer peripheral end 31 e in cross section C is the same as the distance from the rotation axis O to the pressure surface side outer peripheral end 31 e in cross section B.

[0057] The position of the circumscribing portion 31f changes along the rotation axis direction. Therefore, the position of the circumscribing portion 31f changes between cross section C and cross section B. The circumscribing portion 31f on cross section C moves circumferentially by a displacement angle θ relative to the circumscribing portion 31f on cross section B. The position of the imaginary circumscribing circle 30a moves circumferentially by a displacement angle θ between cross section C and cross section B.

[0058] The position of the circumscribing portion 31f does not change radially throughout the entire rotation axis direction, so the distance from the rotation axis O to the circumscribing portion 31f on cross section C is the same as the distance from the rotation axis O to the circumscribing portion 31f on cross section B.

[0059] The position of the outer peripheral tip 31c periodically changes in the circumferential direction and the rotational direction along the rotation axis direction. The period of change along the rotation axis direction is wave-shaped. The position of the outer peripheral tip 31c passes through a circumferential recess position C that is recessed in the circumferential direction and a circumferential protrusion position B that protrudes in the circumferential direction as it changes in the circumferential direction. The outer peripheral tip 31c on cross section C moves circumferentially by a displacement angle θ relative to the outer peripheral tip 31c on cross section B.

[0060] The position of the outer peripheral tip portion 31c does not change in the radial direction over the entire rotation axis direction.

[0061] The curvature of the pressure surface 31b changes periodically to follow the position of the outer peripheral tip 31c on the outer peripheral side relative to the center of the blade 31. Specifically, the curvature of the pressure surface 31b changes periodically to follow the position of the outer peripheral tip 31c from position F1, which is a predetermined distance away from the center of the blade 31 toward the outer peripheral side. The distance from the rotation axis O to position F1 is 90% or more of the radius of the impeller 30.

[0062] The curvature of the pressure surface 31b does not change over the entire length of the blade 31 in the axial direction of rotation on the inner circumferential side of the center of the blade 31.

[0063] The curvature of the suction surface 31 a periodically changes in accordance with the position of the outer peripheral tip 31 c on the outer peripheral side relative to the center of the blade 31. Specifically, the curvature of the suction surface 31 a periodically changes in accordance with the position of the outer peripheral tip 31 c from position F2, which is a predetermined distance away from the center of the blade 31 toward the outer peripheral side. The distance from the rotation axis O to position F2 is 90% or more of the radius of the impeller 30.

[0064] The curvature of the suction surface 31 a does not change over the entire length of the blade 31 in the axial direction of rotation on the inner circumferential side of the center of the blade 31 .

[0065] The position of the pressure surface side outer peripheral end 31e in cross section C is located forward in the rotation direction relative to the circumscribing portion 31f in cross section B.

[0066] The height H2 of the concaves and convexes in the circumferential direction on the pressure surface side is equal to the height H3 of the concaves and convexes in the circumferential direction on the suction surface side.

[0067] Here, the shapes of both sides of the blade 31 are changed. Therefore, as shown in Fig. 13, it is possible to eliminate the portion where the thickness of the outer peripheral tip 31c is increased. This makes it possible to suppress noise generated by loss and turbulence due to collision between the airflow entering the fan and the outer peripheral tip 31c of the blade 31.

[0068] Third Embodiment The crossflow fan 101 of this embodiment has most of the same configuration as the crossflow fan 101 of the first embodiment. The following description will focus on the differences between the crossflow fan 101 of this embodiment and the crossflow fan 101 of the first embodiment.

[0069] 14 to 17, the circumferential position of each blade cross section in the rotation axis direction changes periodically and repeatedly along the rotation axis direction. At this time, the mounting angle θ2 of the blade 31 does not change over the entire rotation axis direction. The mounting angle θ2 of the blade 31 is the angle between the blade chord line and an imaginary line extending from the pressure surface side outer peripheral end 31e to the rotation axis O in a cross section perpendicular to the rotation axis direction. The blade chord line is a line segment tangent to the outer peripheral tip 31c and the inner peripheral tip 31d on the rotation direction side.

[0070] When viewed in the direction of the rotation axis, the convex cross section (cross section B), which is a cross section that forms the peaks of the period, and the concave cross section (cross section C), which is a cross section that forms the valleys of the period, partially overlap. The cross-sectional shape of the blade 31 in cross section B is the same as the cross-sectional shape of the blade 31 in cross section C. The cross section of the blade 31 in cross section B moves circumferentially by a displacement angle θ relative to the cross section of the blade 31 in cross section C.

[0071] The position of the pressure surface side outer peripheral end 31e periodically changes in the circumferential direction and the rotational direction along the rotation axis direction. Therefore, the position of the pressure surface side outer peripheral end 31e changes between cross section C and cross section B. The pressure surface side outer peripheral end 31e on cross section C moves in the circumferential direction by a displacement angle θ relative to the pressure surface side outer peripheral end 31e on cross section B.

[0072] The position of the pressure surface side outer peripheral end 31 e does not change radially throughout the entire rotation axis direction. Therefore, the distance from the rotation axis O to the pressure surface side outer peripheral end 31 e in cross section C is the same as the distance from the rotation axis O to the pressure surface side outer peripheral end 31 e in cross section B.

[0073] The position of the circumscribing portion 31f changes along the rotation axis direction. Therefore, the position of the circumscribing portion 31f changes between cross section C and cross section B. The circumscribing portion 31f on cross section C moves circumferentially by a displacement angle θ relative to the circumscribing portion 31f on cross section B. The position of the imaginary circumscribing circle 30a moves circumferentially by a displacement angle θ between cross section C and cross section B.

[0074] The position of the circumscribing portion 31f does not change radially throughout the entire rotation axis direction, so the distance from the rotation axis O to the circumscribing portion 31f on cross section C is the same as the distance from the rotation axis O to the circumscribing portion 31f on cross section B.

[0075] The position of the outer peripheral tip 31c varies along the rotation axis direction. Therefore, the position of the outer peripheral tip 31c varies between cross section C and cross section B. The outer peripheral tip 31c on cross section C moves in the circumferential direction by a displacement angle θ relative to the outer peripheral tip 31c on cross section B.

[0076] The position of the outer peripheral tip 31c does not change radially throughout the entire rotation axis direction, so the distance from the rotation axis O to the outer peripheral tip 31c in cross section C is the same as the distance from the rotation axis O to the outer peripheral tip 31c in cross section B.

[0077] The position of the inner peripheral tip 31d changes along the rotation axis direction. Therefore, the position of the inner peripheral tip 31d changes between cross section C and cross section B. The inner peripheral tip 31d on cross section C moves circumferentially by a displacement angle θ relative to the inner peripheral tip 31d on cross section B. The position of the imaginary circumscribing circle 30a moves circumferentially by a displacement angle θ between cross section C and cross section B.

[0078] The position of the inner circumferential tip 31 d does not change radially throughout the entire rotation axis direction, so the distance from the rotation axis O to the inner circumferential tip 31 d in cross section C is the same as the distance from the rotation axis O to the inner circumferential tip 31 d in cross section B.

[0079] The curvature of the pressure surface 31b does not change over the entire length of the rotation axis. The curvature of the suction surface 31a does not change over the entire length of the rotation axis.

[0080] Here, on the suction side of the impeller 30, the airflow can be diffused even when it flows out from the blades 31 on the inner peripheral side, thereby suppressing the systematic and sudden growth of turbulence in the blade wake and reducing noise.

[0081] <Modifications> In the above embodiment, the period of the change along the rotation axis direction is wave-shaped. However, the period of the change along the rotation axis direction is not particularly limited to this. For example, as shown in Fig. 18 , the period of the change along the rotation axis direction may be a sawtooth shape.

[0082] Air conditioners to be installed on the side walls of rooms were prepared. Specifically, an air conditioner in which each fan block had blades with the shape of embodiment 1 (new shape) and an air conditioner in which each fan block had blades with a conventional shape (traditional shape) were prepared. For each air conditioner, the wind speed (m / s) was measured at various axial positions (mm) at positions X and Y in Figure 19. Figure 20 shows the measurement results at position X. Figure 21 shows the measurement results at position Y.

[0083] 20 and 21, the new shape reduces the turbulence of the wind speed, which means that the new shape reduces noise.

[0084] An air conditioner to be installed on the side wall of a room was prepared. Specifically, an air conditioner in which each fan block has blades of the shape of embodiment 1 (new shape) and an air conditioner in which each fan block has blades of a conventional shape (conventional shape) were prepared. The ratio H / L of the blade wave height H to the blade chord length L was changed to obtain a large air volume (air volume of 22.3 m ３ / min) and low air volume (air volume 13 m ３The noise reduction (dBA) was measured for both the conventional and new blade configurations. The noise reduction equivalent to that achieved by using an air conditioner with blades of the conventional design is set to 0 dBA, and the results for the air conditioner with blades of the new design are shown in Figure 22.

[0085] 22, when H / L is 0.041 or less, the amount of sound reduction is a negative value at both the large air volume and the small air volume, meaning that noise is suppressed.

[0086] In Figure 22, when H / L is between 0.006 and 0.034, the noise reduction is -0.3 dBA or less at both large and small airflow rates. When H / L is between 0.008 and 0.033, the noise reduction is -0.4 dBA or less at both large and small airflow rates.

[0087] An air conditioner to be installed on the side wall of a room was prepared. Specifically, an air conditioner in which each fan block has blades of the shape of embodiment 1 (new shape) and an air conditioner in which each fan block has blades of a conventional shape (conventional shape) were prepared. The ratio P / H of the wave interval P to the wave height H was changed to generate a large air volume (air volume of 22.3 m ３ / min) and low air volume (air volume 13 m ３ The noise reduction (dBA) was measured for both the conventional and new blade designs. The results are shown in Figure 23. The noise reduction equivalent to that achieved by using an air conditioner with blades of the conventional design is set to 0 dBA, and the results for the air conditioner with blades of the new design are shown in Figure 23.

[0088] 23, when P / H is between 0 and 39, the amount of sound reduction is a negative value at high airflow rates, meaning that noise is suppressed.

[0089] In FIG. 23, when P / H is between 7 and 31, the amount of sound reduction is a negative value at both the large air volume and the small air volume.

[0090] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims.

[0091] REFERENCE SIGNS 10 Casing 20 Heat exchanger 30 Impeller 30a Imaginary circle (imaginary circumscribed circle) connecting outer ends of blades 31 Blade 31a Negative pressure surface 31b Pressure surface 31c Outer circumferential tip 31d Inner circumferential tip 31e Pressure surface side outer circumferential tip 31f Circumscribed part 90 Air conditioner 100 Air conditioning unit 101 Cross flow fan H Wave height L Blade chord length O Rotation axis θ Displacement angle θ2 Mounting angle

[0092] Japanese Unexamined Patent Publication No. 124899 / 1983

Claims

1. A cylindrical crossflow fan (101) comprising a plurality of impellers (30) having a plurality of blades (31) arranged in a circumferential direction, each blade having: a negative pressure surface (31a) arranged on the side opposite to a direction of rotation and being a curved surface bulging in a direction opposite to the direction of rotation; a pressure surface (31b) arranged on the side of the direction of rotation and being a curved surface recessed in a direction opposite to the direction of rotation; and an outer circumferential tip portion (31c) connecting the negative pressure surface and the pressure surface; the pressure surface and the outer circumferential tip portion being connected at a pressure surface side outer circumferential end (31e), the negative pressure surface and the outer circumferential tip portion being connected at a circumferential portion (31f) which is a portion where the outer circumferential tip portion and a virtual circumscribed circle (30a) of the blade are in contact; the position of the pressure surface side outer circumferential end periodically changes in the circumferential direction and in the rotation direction along the direction of the rotation axis, a position of the pressure surface side outer peripheral end passes through a circumferential recess position (C) that is recessed in the circumferential direction and a circumferential protrusion position (B) that protrudes in the circumferential direction as the circumferential direction changes, a curvature of the pressure surface periodically changes on the outer circumferential side of a center of the blade, following the position of the pressure surface side outer peripheral end, and a position of the pressure surface side outer peripheral end at the circumferential recess is located forward in the direction of rotation with respect to the circumferential contact portion.

2. A cylindrical crossflow fan (101) including a plurality of impellers (30) having a plurality of blades (31) arranged in a circumferential direction, each blade having a negative pressure surface (31a) arranged on the side opposite to a rotation direction and being a curved surface bulging in a direction opposite to the rotation direction, a pressure surface (31b) arranged on the side of the rotation direction and being a curved surface recessed in a direction opposite to the rotation direction, and an outer circumferential tip portion (31c) connecting the negative pressure surface and the pressure surface on the outer circumferential side, the pressure surface and the outer circumferential tip portion being connected at a pressure surface side outer circumferential end (31e), the negative pressure surface and the outer circumferential tip portion being connected at a circumferential portion (31f) which is a portion where the outer circumferential tip portion and a virtual circumscribed circle of the blade are in contact, the position of the outer circumferential tip portion periodically changes in the circumferential direction and in the rotation direction along the rotation axis direction, a position of the outer circumferential tip portion passes through a circumferential recess position (C) that is recessed in the circumferential direction as it changes in the circumferential direction, and a circumferential convex portion position (B) that protrudes in the circumferential direction, the curvatures of the pressure surface and the negative pressure surface connected to the outer circumferential tip portion change periodically following the outer circumferential tip portion, on the outer circumferential side of a center of the blade, the position of the pressure surface side outer circumferential end at the circumferential recess is located forward in the direction of rotation with respect to the circumferential contact portion of the circumferential convex portion, and the height of the circumferential concavity and convexity on the pressure surface side and the height of the circumferential concavity and convexity on the negative pressure surface side are equal.

3. A cylindrical crossflow fan (101) having a plurality of impellers (30) with a plurality of blades (31) arranged circumferentially, each blade having: a negative pressure surface (31a) arranged on the side opposite to the direction of rotation and which is a curved surface bulging in the opposite direction to the direction of rotation; a pressure surface (31b) arranged on the side of the direction of rotation and which is a curved surface recessed in the opposite direction to the direction of rotation; and an outer circumferential tip portion (31c) connecting the negative pressure surface and the pressure surface on the outer circumferential side; wherein the circumferential position of each blade cross section in the rotational axis direction changes periodically and repeatedly along the rotational axis without changing the mounting angle of the blade; and wherein, as viewed in the rotational axis direction, a convex cross section (cross section B), which is a cross section that forms a peak of the period, and a concave cross section (cross section C), which is a cross section that forms a valley of the period, partially overlap each other.

4. A cross flow fan according to claims 1 to 3, wherein the blowing air speed is uniform.

5. A cross flow fan according to any one of claims 1 to 4, wherein the period of change along the rotation axis direction is wave-shaped.

6. A crossflow fan as claimed in claim 5, wherein the blade has an inner circumferential tip (31d) connecting the negative pressure surface and the pressure surface on the inner circumferential side, and the ratio H / L of the wave height H to the blade chord length L which is the distance between the outer circumferential tip and the inner circumferential tip is 0.041 or less.

7. A crossflow fan as claimed in claim 5 or 6, wherein the blades have inner circumferential tips connecting the negative pressure surface and the pressure surface on the inner circumferential side, and a ratio H / L of the wave height H to the blade chord length L which is the distance between the outer circumferential tip and the inner circumferential tip is 0.006 to 0.

035.

8. The cross flow fan according to claim 5, wherein a ratio P / H of the wave interval P to the wave height H is 0 to 39.

9. A cross flow fan according to any one of claims 5 to 8, wherein a ratio P / H of a wave interval P to a wave height H is 7 to 31.

10. An air conditioner comprising the crossflow fan according to any one of claims 1 to 9.

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