Propeller fan and blower device

Abstract

This propeller fan is provided with a rotating shaft part and a blade. The cross-sectional shape of a positive-pressure surface of the blade includes: a first extreme value point located closer to a blowout side than a reference line, the reference line being a virtual straight line passing through a front edge part and a rear edge part in a cross section of the blade; and a second extreme value point provided between the first extreme value point and the rear edge part and positioned closer to the suction side than the reference line. Further, the cross-sectional shape of the positive-pressure surface of the blade includes: a first portion extending from the front edge part to the first extreme value point so as to be inclined to the blowout side; a second portion extending from the first extreme value point to the second extreme value point so as to be inclined to the suction side; and a third portion that extends from the second extreme value point toward the rear edge side of the blade so as to be inclined to the blowout side, and that intersects the reference line.

Description

Propeller fan and blower

[0001] The present disclosure relates to a propeller fan and a blower device.

[0002] Conventionally, propeller fans have been known that aim to improve airflow performance. For example, Patent Document 1 discloses a propeller fan that aligns the positions of axial extreme points and rotational extreme points on the trailing edges of the blades in order to suppress attenuation of wind speed and generate airflow with high wind speed.

[0003] Japanese Patent Application Laid-Open No. 2015-183605

[0004] There is a demand for a propeller fan and a blower that can quietly blow out an airflow with a higher wind speed and / or volume than conventional techniques. The present disclosure aims to provide a propeller fan and a blower that can quietly blow out an airflow with a higher wind speed and / or volume than conventional techniques. Note that one aspect of the present disclosure relates to biomimetics, as it includes a technical concept that focuses on the wing shape of an owl.

[0005] A propeller fan according to one aspect of the present disclosure includes: a rotating shaft portion that rotates about a central axis; and blades that protrude radially outward from the rotating shaft portion and have a negative pressure surface located on an axial intake side of the central axis and a positive pressure surface located on an axial outlet side opposite the suction side of the central axis, wherein the blades include a leading edge portion located on a front side in a rotation direction of the blade and a trailing edge portion located on a rear side in the rotation direction, an aerofoil cross section of the blade is a cross section obtained by cutting the blade in a thickness direction by an imaginary plane that intersects the leading edge portion and the trailing edge portion, and the positive pressure surface extends smoothly and continuously between the leading edge portion and the trailing edge portion. a first extreme point located on the outlet side of the reference line, and a second extreme point located between the first extreme point and the trailing edge portion and located on the suction side of the reference line, the cross-sectional shape of the pressure surface including a first portion extending from the leading edge portion to the first extreme point at an angle to the outlet side, a second portion extending from the first extreme point to the second extreme point at an angle to the suction side, and a third portion extending from the second extreme point towards the trailing edge side of the blade at an angle to the outlet side and intersecting the reference line.

[0006] A blower device according to one aspect of the present disclosure includes the propeller fan and a motor that drives the propeller fan to rotate.

[0007] 6 is a perspective view of the blower device as viewed from above the front right. FIG. 7 is an exploded perspective view of the blower device main body as viewed from above the rear right. FIG. 8 is a front view of the propeller fan. FIG. 9 is a right side view of the propeller fan. FIG. 10 is an enlarged front view of one of the blades. FIG. 11 is a diagram showing a blade cross section as viewed in the direction of the arrows I-I in FIG. 5. FIG. 12 is a two-dimensional graph in which the blade cross section shown in FIG. 10 has been normalized. FIG. 13 is an enlarged view of the leading edge region shown in FIG. 13. FIG. 14 is an enlarged view of the trailing edge region shown in FIG. 14. FIG. 15 is a diagram for explaining the relationship between the blade cross section and airflow. FIG. 16 is a diagram for explaining the relationship between the blade cross section and lift. FIG. 17 is a diagram for explaining the relationship between the blade cross section and lift. FIG. 18 is a right side view of the blower device main body with the front cover removed. FIG. 19 is a longitudinal cross section of the blower device main body.

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0009] The overall configuration of the air blower 1 will be described. The air blower 1 of this embodiment is a circulator capable of blowing air with high linearity. Fig. 1 is a perspective view of the air blower 1 as viewed from the upper right front. Fig. 2 is an exploded perspective view of the main body 11 of the air blower 1 as viewed from the upper right rear. In the following description, the lower left, upper right, upper left, lower right, upper side, and lower side of Fig. 1 will be referred to as the front side, rear side, left side, right side, upper side, and lower side of the air blower 1, respectively.

[0010] 1 and 2, the blower 1 includes a main body 11, a base 12, a pair of arms 13, etc. The main body 11 is a housing that houses a propeller fan 100 (see FIG. 2) and other components. In this example, the main body 11 has a cylindrical outer shape that extends along the central axis AX of the propeller fan 100. An intake port 11A is provided on the rear side of the main body 11 for taking in air into the main body 11. An outlet port 11B is provided on the front side of the main body 11 for blowing air out of the main body 11.

[0011] The base 12 is placed on the installation surface of the blower 1. The pair of arms 13 are aligned at a distance in the left-right direction and extend upward from the base 12. The pair of arms 13 are connected to both the left and right sides of the main body 11 above the base 12, and support the main body 11 so that it can tilt. The base 12 and the pair of arms 13 form a stand that supports the main body 11.

[0012] 1 and 2, main body 11 is supported with central axis AX extending in the front-to-rear direction of blower 1. As will be described later, as propeller fan 100 rotates, air flows from the suction side, which is the rear side of propeller fan 100, toward the outlet side, which is the front side of propeller fan 100. In the example of Figures 1 and 2, the front side of blower 1 coincides with the outlet side, and the rear side of blower 1 coincides with the outlet side.

[0013] As shown in Figure 2, the blower 1 includes a propeller fan 100 and a motor 50 that drives and rotates the propeller fan 100. In this example, the main body 11 has a central cover 51, a rear cover 52, and a front cover 53 that form the outer shape of the main body 11. The central cover 51 has a cylindrical peripheral wall that extends approximately coaxially with the central axis AX. The motor 50 is fixed to the inside surrounded by the peripheral wall of the central cover 51 and rotatably supports the propeller fan 100 on the blowing side of the motor 50. The propeller fan 100 is rotated about the central axis AX by the rotational drive of the motor 50.

[0014] The rear cover 52 is a member that covers the suction side of the central cover 51 and is a cylindrical member with a bottom that extends approximately coaxially with the central axis AX. The rear cover 52 has a rear grill 521 that penetrates almost the entire rear cover 52 in a mesh-like manner. The rear grill 521 forms the suction port 11A of the main body 11 and also prevents the user's fingers, etc. from entering the main body 11.

[0015] The front cover 53 is a member that covers the air outlet side of the central cover 51 and is cylindrical with a bottom that extends approximately coaxially with the central axis AX. The front cover 53 has a front grill 531 that penetrates the end face of the front cover 53 on the air outlet side in a mesh-like pattern. The front grill 531 forms the air outlet 11B of the main body 11 and prevents the user's fingers and the like from entering the main body 11.

[0016] In this example, when blower device 1 is operating to blow air, motor 50 rotates propeller fan 100 in rotation direction R (see FIG. 3 ). Rotation direction R is a clockwise direction about central axis AX when propeller fan 100 is viewed from the outlet side. As propeller fan 100 rotates, air is taken into main body 11 through intake port 11A and discharged as an airflow from outlet port 11B, thereby blowing air from blower device 1.

[0017] The configuration of propeller fan 100 will be described. Fig. 3 is a front view of propeller fan 100. Fig. 4 is a right side view of propeller fan 100. Fig. 5 is an enlarged front view of one of the plurality of blades 200. The front side of propeller fan 100 is the blowing side along central axis AX. The rear side of propeller fan 100 is the suction side along central axis AX.

[0018] As shown in Figures 3 and 4, propeller fan 100 includes a rotating shaft 110 and blades 200. Rotating shaft 110 rotates around central axis AX. In this example, rotating shaft 110 is cylindrical and extends coaxially with central axis AX. Motor 50 (see Figure 2) has a motor shaft that protrudes from motor 50 toward the outlet side. The tip of the motor shaft is coaxially connected to rotating shaft 110. When motor 50 drives and rotates the motor shaft, rotating shaft 110 rotates around central axis AX.

[0019] The blades 200 protrude radially outward from the rotating shaft portion 110 and have a negative pressure surface 201 located on the suction side in the axial direction of the central axis AX and a positive pressure surface 202 located on the blowing side opposite the suction side in the axial direction of the central axis AX. In this example, three blades 200 protrude radially outward from the rotating shaft portion 110 about the central axis AX. The three blades 200 have the same shape and size and are arranged at 120-degree intervals with the central axis AX as the center of rotation.

[0020] The blade 200 has a leading edge 211 located on the front side of the rotation direction R of the blade 200, and a trailing edge 212 located on the rear side of the rotation direction R. The leading edge 211 is located further forward in the rotation direction R than the trailing edge 212. The leading edge 211 and the trailing edge 212 extend radially outward from the rotating shaft 110. Both the leading edge 211 and the trailing edge 212 are curved in an arc shape in a front view so as to be displaced forward in the rotation direction R as they extend radially outward. In the following description, the leading edge side of the blade 200 is synonymous with the front side in the rotation direction R, and the trailing edge side of the blade 200 is synonymous with the rear side in the rotation direction R.

[0021] 4 and 5 , the leading edge 211 extends from a first point 221 at a position where the leading edge 211 connects with the rotating shaft 110 to a second point 222 at a radially outer end of the leading edge 211. The second point 222 is located further forward in the direction of rotation R than the first point 221. The trailing edge 212 extends from a third point 223 at a position where the leading edge 211 connects with the rotating shaft 110 to a fourth point 224 at a radially outer end of the trailing edge 212. The fourth point 224 is located further forward in the direction of rotation R than the third point 223.

[0022] In this example, the leading edge 211 extends radially outward in a curved manner toward the front in the rotational direction R with a greater curvature than the trailing edge 212. Therefore, the length of the leading edge 211 in the rotational direction R is greater than the length of the trailing edge 212 in the rotational direction R. In other words, the length in the rotational direction R from the first point 221 to the second point 222 is greater than the length in the rotational direction R from the third point 223 to the fourth point 224.

[0023] The blade 200 has an outer edge 213 extending along the rotation direction R. The outer edge 213 extends to connect the leading edge 211 and the trailing edge 212 and is curved to bulge radially outward. A second point 222 is located at the position where the leading edge 211 and the outer edge 213 connect. A fourth point 224 is located at the position where the trailing edge 212 and the outer edge 213 connect.

[0024] In this example, the outer edge portion 213 is curved in an arc shape in a front view so as to be displaced radially inward as it moves from the fourth point 224 to the second point 222. In other words, the outer edge portion 213 is inclined inward relative to the rotational direction R so as to approach the central axis AX as it moves forward in the rotational direction R. Because the second point 222 is located radially inward relative to the fourth point 224, the second point 222 is closer to the central axis AX than the fourth point 224. In other words, the distance between the second point 222 and the central axis AX is smaller than the distance between the fourth point 224 and the central axis AX. The leading edge portion 211 and the outer edge portion 213 are connected at the second point 222 so as to form an acute angle. The trailing edge portion 212 and the outer edge portion 213 are connected at the fourth point 224 so as to form a substantially right angle.

[0025] 4, the trailing edge 212 is located on the blowing-end side of the blade 200 and extends substantially perpendicular to the central axis AX. The blade 200 extends from the trailing edge 212 toward the leading edge 211 and tilts toward the suction side as it moves forward in the rotation direction R. The second point 222 is the suction-side end of the blade 200 that is located on the suction-end side.

[0026] The structure of the blade cross section of the blade 200 will be described. Fig. 6 is a diagram showing the blade cross section in the direction of the arrows II in Fig. 5. Fig. 7 is a two-dimensional graph in which the blade cross section shown in Fig. 6 has been normalized. Fig. 8 is an enlarged view of the leading edge region FR shown in Fig. 6. Fig. 9 is an enlarged view of the trailing edge region RR shown in Fig. 6.

[0027] The blade cross section of the blade 200 is the cross-sectional shape when cut by an imaginary plane that passes through the direction of air flow on the blade surface and extends in the thickness direction. Air flowing on the blade surface mainly flows onto the blade surface from the leading edge 211, flows generally in the circumferential direction of the central axis AX, and flows out from the trailing edge 212. Therefore, the direction of air flow on the blade surface extends along a curve that is convex outward in the radial direction and intersects the leading edge 211 and the trailing edge 212. The curve along which air flows on the blade surface is, for example, an arc that intersects the leading edge 211 and the trailing edge 212. In this embodiment, the length of the ridge line of the leading edge 211 is shorter than the length of the ridge line of the trailing edge 212. Assuming that all air that flows onto the blade surface from the leading edge 211 flows out from the trailing edge 212, the air that flows in from the leading edge 211 flows radially inward and out from the trailing edge 212. Therefore, the curve along which the air flows on the blade surface may have a gradually increasing curvature from the leading edge 211 side to the trailing edge 212 side.

[0028] More specifically, an example of a curve along which air flows on the wing surface is shown. Line I-I shown in Figure 5 is an imaginary line passing through an arbitrary point P0 on imaginary line 210. Imaginary line 210 is provided between leading edge 211 and trailing edge 212, and has a shape that approximates both leading edge 211 and trailing edge 212. The closer imaginary line 210 is to leading edge 211, the more it approximates leading edge 211, and the closer it is to trailing edge 212, the more it approximates trailing edge 212. More specifically, line I-I can be defined as follows:

[0029] The blade 200 has an inner edge portion 214 that connects to the rotating shaft portion 110. The inner edge portion 214 extends from a third point 223 to a first point 221 along the rotation direction R. An arbitrary point on the outer edge portion 213 is designated as P3. An arbitrary point on the inner edge portion 214 is designated as P4. However, P3 and P4 satisfy the following (Equation 1): L31 / L32=L41 / L42 (Equation 1) In the above (Equation 1), L31 is the length from P3 to the second point 222 on the outer edge portion 213. L32 is the length from P3 to the fourth point 224 on the outer edge portion 213. L41 is the length from P4 to the first point 221 on the inner edge portion 214. L42 is the length from P4 to the third point 223 on the inner edge portion 214.

[0030] The imaginary line 210 extends to connect P3 and P4. The position and curvature of the imaginary line 210 change according to the ratio expressed by the above equation (1). For example, as L31 becomes smaller relative to L32 and as L41 becomes smaller relative to L42, the imaginary line 210 moves forward in the direction of rotation R so as to approach the leading edge 211, and the curvature of the imaginary line 210 increases so as to approximate the curvature of the leading edge 211. Conversely, as L31 becomes larger relative to L32 and as L41 becomes larger relative to L42, the imaginary line 210 moves rearward in the direction of rotation R so as to approach the trailing edge 212, and the curvature of the imaginary line 210 decreases so as to approximate the curvature of the trailing edge 212.

[0031] An arbitrary point on the virtual line 210 is designated as P0. The length from P0 to P4 on the virtual line 210 is designated as L01. The length from P0 to P3 on the virtual line 210 is designated as L02. For example, a plurality of virtual lines 210 are set by sequentially changing the ratio expressed by (Equation 1) while keeping the ratio of L01 to L02 constant. The virtual line passing through the plurality of P0s that appear on each of these virtual lines 210 is line I-I, as illustrated in FIG.

[0032] The point where line I-I intersects with leading edge 211 is designated as P1. The point where line I-I intersects with trailing edge 212 is designated as P2. P1 and P2 satisfy the following equation (2): L01 / L02=L11 / L12=L21 / L22 (Equation 2) In equation (2), L11 is the length from P1 to first point 221 on leading edge 211. L12 is the length from P1 to second point 222 on leading edge 211. L21 is the length from P2 to third point 223 on trailing edge 212. L22 is the length from P2 to fourth point 224 on trailing edge 212.

[0033] In other words, the position and curvature of the II line change according to the ratio expressed by (Equation 2). For example, if a person sets an arbitrary P1 on the leading edge portion 211, the value of L11 / L12 on the leading edge portion 211 changes, and therefore the ratio expressed by (Equation 2) also changes. The II line passing through the set P1 is automatically determined according to the ratio expressed by (Equation 2). For example, the smaller L11 is relative to L12, the more the II line moves radially inward so as to approach the inner edge portion 214, and the more the curvature of the II line approximates the curvature of the inner edge portion 214. Conversely, the larger L11 is relative to L12, the more the II line moves radially outward so as to approach the outer edge portion 213, and the more the curvature of the II line approximates the curvature of the outer edge portion 213.

[0034] 5 shows line II when the ratio expressed by equation 2 is 1. In this case, L01 is equal to L02, L11 is equal to L12, and L21 is equal to L22. Therefore, line II passes through the longitudinal center of leading edge 211, the longitudinal center of virtual line 210, and the longitudinal center of trailing edge 212.

[0035] As shown in Figure 6, the blade cross section of the blade 200 is a cross section obtained by cutting the blade 200 in the thickness direction by an imaginary plane that intersects the leading edge 211 and the trailing edge 212. In this example, the imaginary plane that intersects the leading edge 211 and the trailing edge 212 is an imaginary plane that passes through the above-mentioned line II. The thickness direction of the blade 200 is the direction in which the suction surface 201 and the pressure surface 202 face each other. Therefore, the blade cross section is synonymous with a longitudinal cross section obtained by cutting the blade 200 by an imaginary plane that passes through the above-mentioned line II and extends in the thickness direction.

[0036] The airfoil cross section of the blade 200 includes a cross-sectional shape of the pressure surface 202 that extends smoothly and continuously between the leading edge 211 and the trailing edge 212. In other words, the cross section of the pressure surface 202 is composed of straight sections in which the extension direction is constant and / or curved sections in which the extension direction changes continuously from the leading edge 211 to the trailing edge 212, and does not include any bent sections in which the extension direction changes suddenly. In this example, the cross section of the pressure surface 202 is composed of curved sections that extend from the leading edge 211 to the trailing edge 212.

[0037] When a reference line SL is defined as an imaginary line passing through leading edge 211 and trailing edge 212 in the aerofoil cross section, the cross-sectional shape of pressure surface 202 includes a first extreme point 301 located on the outlet side of reference line SL, and a second extreme point 302 located between first extreme point 301 and trailing edge 212 and on the suction side of reference line SL. For example, first extreme point 301 is a vertex that protrudes away from reference line SL toward the outlet side in the cross section of pressure surface 202 included in the aerofoil cross section. Second extreme point 302 is a vertex that protrudes away from reference line SL toward the suction side in the cross section of pressure surface 202 included in the aerofoil cross section, located on the trailing edge side of first extreme point 301.

[0038] The example of Figure 7 shows a two-dimensional graph mapping the cross-sectional shape of the pressure surface 202. In this two-dimensional graph, the reference line SL is the X-axis, the trailing edge side is the positive direction of the X-axis, and the leading edge side is the negative direction of the X-axis. In this two-dimensional graph, the thickness direction of the blade 200 is the Y-axis, the suction side is the positive direction of the Y-axis, and the blowing side is the negative direction of the Y-axis. Furthermore, in this two-dimensional graph, the size of the blade 200 is normalized by setting the chord length of the blade 200 to "1". The chord length of the blade 200 is the length of the blade 200 in the fore-aft direction, in other words, the distance between the leading edge 211 and the trailing edge 212. In this two-dimensional graph, the coordinates of the leading edge 211 are (0, 0), and the coordinates of the trailing edge 212 are (1, 0).

[0039] 7, the thickness of the blade 200 is approximately 0.02 mm, excluding a leading end region FR and a trailing end region RR (described later). The first extreme point 301 is located slightly toward the trailing edge of the leading edge 211 in the cross section of the pressure surface 202, and slightly toward the outlet side of the reference line SL. The second extreme point 302 is located approximately in the middle between the leading edge 211 and the trailing edge 212 in the cross section of the pressure surface 202, and slightly toward the suction side of the reference line SL.

[0040] When the blade 200 is divided into three equal regions aligned in the extension direction of the reference line SL in the blade cross section, the three regions are a first region A1 including the leading edge 211, a second region A2 including the trailing edge 212, and a third region A3 located between the first region A1 and the second region A2. The first extreme point 301 may be located in the first region A1, and the second extreme point 302 may be located in the second region A2 or the third region A3. In this example, when the blade 200 is divided into three equal regions in the X direction in the blade cross section, the blade 200 is composed of the first region A1, the second region A2, and the third region A3. The first extreme point 301 is located in the first region A1. The second extreme point 302 is located in the third region A3. Alternatively, the second extreme point 302 may be located in the second region A2.

[0041] As shown in Figures 6 and 7 , the cross-sectional shape of the pressure surface 202 includes a first portion 311 (see Figure 8 ) extending from the leading edge portion 211 to the first extreme point 301, inclining toward the outlet side, a second portion 312 extending from the first extreme point 301 to the second extreme point 302, inclining toward the suction side, and a third portion 313 extending from the second extreme point 302 toward the trailing edge side of the blade 200, inclining toward the outlet side, and intersecting with the reference line SL.

[0042] As shown in Figure 8, the vicinity of the leading edge 211 included in the blade cross section is referred to as the leading end region FR (see Figure 6) of the blade 200. In the leading end region FR, the thickness of the blade 200 gradually decreases so as to taper toward the leading edge 211. In this example, the first portion 311 extends from the leading edge 211 to the first extreme point 301 and is inclined so as to move away from the reference line SL toward the trailing edge side. Furthermore, the first portion 311 is arc-shaped and curves slightly toward the leading edge side and the outlet side.

[0043] The second portion 312 extends from the first extreme point 301 to the second extreme point 302 while inclining toward the suction side and curving in a gentle S-shape. The second portion 312 intersects with the reference line SL slightly on the trailing edge side of the first extreme point 301. That is, the first portion 311 inclines toward the outlet side toward the trailing edge side, whereas the second portion 312 inclines toward the suction side toward the trailing edge side. The first portion 311 and the second portion 312 are smoothly connected at the first extreme point 301. The first extreme point 301 is an inflection point with a curvature of "0" where the inclination of the pressure surface 202 from the leading edge side to the trailing edge side changes from the outlet side to the suction side.

[0044] The acute angle θ11 formed between the first portion 311 and the reference line SL may be larger than the acute angle θ12 formed between the second portion 312 and the reference line SL. In this example, the first portion 311 is curved with a larger curvature than the second portion 312 so that the first portion 311 bulges more toward the blowing side than the second portion 312. As a result, the acute angle θ11 is larger than the acute angle θ12.

[0045] The third portion 313 extends from the second extreme point 302 toward the trailing edge of the blade 200, inclining toward the outlet side and curving in a gentle S-shape. That is, the second portion 312 inclines toward the suction side toward the trailing edge, while the third portion 313 inclines toward the outlet side toward the trailing edge. The second portion 312 and the third portion 313 are smoothly connected at the second extreme point 302. The second extreme point 302 is an inflection point where the inclination of the pressure surface 202 from the leading edge side to the trailing edge side changes from the suction side to the outlet side, and where the curvature is "0".

[0046] 6 and 7 , the cross-sectional shape of the pressure surface 202 further includes a third extreme point 303 located between the second extreme point 302 and the trailing edge portion 212 and closer to the outlet side than the reference line SL. The third portion 313 extends from the second extreme point 302 to the third extreme point 303 so as to incline toward the outlet side. For example, the third extreme point 303 is a vertex located closer to the trailing edge than the second extreme point 302 in the cross section of the pressure surface 202 included in the airfoil cross section, and protruding away from the reference line SL toward the outlet side. The third portion 313 extends from the second extreme point 302 to the third extreme point 303 and intersects with the reference line SL between the second extreme point 302 and the third extreme point 303. The third extreme point 303 is located in the second region A2.

[0047] The cross-sectional shape of pressure surface 202 may further include portion 313B (see FIG. 9 ) located closer to the outlet side than reference line SL, on the trailing edge portion 212 side than second extreme point 302. In this example, portion 313B is a portion of third portion 313 that is closer to the outlet side than reference line SL. In other words, portion 313B extends between intersection 313A and third extreme point 303 in third portion 313. Intersection 313A is the position where third portion 313 intersects with reference line SL.

[0048] The distance between the leading edge 211 and the intersection 312A may be smaller than the distance between the trailing edge 212 and the intersection 313A. The intersection 312A is the position where the second portion 312 intersects with the reference line SL. In this example, the distance X11 in the X direction between the leading edge 211 and the intersection 312A is smaller than the distance X12 in the X direction between the trailing edge 212 and the intersection 313A.

[0049] The distance between the third extreme point 303 and the reference line SL may be greater than the distance between the first extreme point 301 and the reference line SL. In other words, the third extreme point 303 may be farther from the reference line SL than the first extreme point 301. In this example, the distance Y12 in the Y direction between the third extreme point 303 and the reference line SL is greater than the distance Y11 in the Y direction between the first extreme point 301 and the reference line SL.

[0050] As shown in Figure 9, the vicinity of the trailing edge 212 included in the blade cross section is referred to as the trailing end region RR (see Figure 6) of the blade 200. In the trailing end region RR, the thickness of the blade 200 gradually decreases so as to taper toward the trailing edge 212. In this example, the portion 313B of the third portion 313 described above is inclined so as to move away from the reference line SL toward the trailing edge, and has an arc shape that extends so as to bulge slightly toward the leading edge and the outlet side.

[0051] The cross-sectional shape of the pressure surface 202 may further include a fourth portion 314 extending from the third extreme point 303 to the trailing edge 212 so as to slope toward the suction side. The fourth portion 314 slopes toward the reference line SL as it extends from the third extreme point 303 toward the trailing edge. The fourth portion 314 is also arc-shaped, slightly bulging toward the trailing edge and outlet sides. That is, the third portion 313 slopes toward the outlet side toward the trailing edge, while the fourth portion 314 slopes toward the suction side toward the trailing edge. The third portion 313 and the fourth portion 314 are smoothly connected at the third extreme point 303. The third extreme point 303 is an inflection point where the slope of the pressure surface 202 from the leading edge side to the trailing edge side changes from the outlet side to the suction side, and where the curvature is "0."

[0052] The curvature of the fourth portion 314 may be greater than the curvature of the third portion 313. In this example, the third portion 313 has a gently curved arc shape, whereas the fourth portion 314 has a more sharply curved arc shape than the third portion 313. Therefore, the curvature of the fourth portion 314 is greater than the curvature of the third portion 313.

[0053] The following describes the state of the airflow generated when the propeller fan 100 blows air. Fig. 10 is a diagram for explaining the relationship between the blade cross section and the airflow. Figs. 11 and 12 are diagrams for explaining the relationship between the blade cross section and lift. When the propeller fan 100 rotates in the rotation direction R, an airflow flows on the suction surface 201 and the pressure surface 202 of each of the multiple blades 200. Below, the state of the airflow on the pressure surface 202 of one blade 200 will be described, but the same applies to the remaining blades 200.

[0054] 10 , leading edge 211 of blade 200 is located at the front end in the direction of rotation R. As blade 200 rotates, an airflow is generated that flows from leading edge 211 onto pressure surface 202, and this airflow flows along pressure surface 202 toward trailing edge 212 and is delivered to the outlet side. In this example, the cross-sectional shape of pressure surface 202 includes first extreme point 301, second extreme point 302, first portion 311, second portion 312, and third portion 313, as described above. As a result, the airflow flows in the following manner.

[0055] The first portion 311 and the second portion 312 form a convex portion in the cross-sectional shape of the pressure surface 202 that bulges toward the outlet side with the first extreme value point 301 as its apex. In the leading end region FR (see FIG. 6 ), the airflow flows along the first portion 311 toward the trailing edge side and then flows out from the first extreme value point 301. The airflow flowing through the first portion 311 is gradually guided toward the outlet side as it moves toward the trailing edge side in accordance with the curved shape of the first portion 311. Therefore, the airflow that has flowed through the first portion 311 flows out so as to be inclined more toward the outlet side than toward the rear side in the direction of rotation R at the first extreme value point 301; in other words, the airflow flows out from the first extreme value point 301 toward the trailing edge side.

[0056] Because the first portion 311 extends inclined toward the outlet side toward the first extreme point 301 and the second portion 312 extends inclined toward the suction side from the first extreme point 301, it is difficult for the airflow to flow continuously from the first portion 311 to the second portion 312. Therefore, the airflow is released toward the trailing end side at the first extreme point 301 so as to separate from the pressure surface 202. As the blade 200 moves forward in the rotation direction R, this airflow moves relatively toward the suction side as it moves toward the trailing edge side. As a result, the airflow released from the first extreme point 301 moves along an arc-shaped trajectory that curves inclined toward the suction side toward the trailing edge side.

[0057] Second portion 312 and third portion 313 form a recess that is recessed toward the suction side with second extreme point 302 as its bottom in the cross-sectional shape of pressure surface 202. The airflow that has flowed out from first extreme point 301 enters this recess and reaches reattachment point 319 located in second portion 312 or third portion 313. Reattachment point 319 is located between first extreme point 301 and third extreme point 303 in the cross-sectional shape of pressure surface 202.

[0058] The position of reattachment point 319 can be adjusted by the cross-sectional shape of pressure surface 202, the rotational speed of propeller fan 100, etc. In this example, reattachment point 319 is located near second extreme point 302 at the boundary between second portion 312 and third portion 313. This ensures that the airflow flowing out from first extreme point 301 is received near the bottom of the recess formed by second portion 312 and third portion 313, thereby stably forming separation region LSB, which will be described later.

[0059] In this way, the convex portion formed by first portion 311 and second portion 312 causes the airflow to flow out from first extreme point 301, which is located closer to the outlet side than reference line SL. First portion 311 guides the airflow to gradually shift toward the outlet side so that the airflow is released at an angle toward the outlet side from first extreme point 301. This allows the airflow to separate from pressure surface 202 at first extreme point 301, and then reattach to pressure surface 202 at reattachment point 319, which is spaced from first extreme point 301 toward the trailing edge side.

[0060] First portion 311, second portion 312, and third portion 313 extend smoothly and continuously between leading edge 211 and trailing edge 212. Therefore, on pressure surface 202, obstruction of the airflow flowing along pressure surface 202 is suppressed, ensuring a smooth flow of the airflow. Furthermore, the flow velocity of the airflow is increased along first portion 311, and the airflow is forcefully released from first extreme point 301. This ensures a distance between first extreme point 301, where the airflow separates from pressure surface 202, and reattachment point 319, where the airflow reattaches to pressure surface 202.

[0061] The recess formed by second portion 312 and third portion 313 can be recessed up to second extreme point 302 located on the suction side of reference line SL, thereby increasing the depth of the recess in the thickness direction of blade 200. This ensures a distance between first extreme point 301, where the airflow separates from pressure surface 202, and reattachment point 319, where the airflow reattaches to pressure surface 202.

[0062] Third portion 313 extends from second extreme point 302 toward the trailing edge side so as to incline toward the outlet side. Therefore, even if the displacement of the airflow released from first extreme point 301 toward the suction side is smaller than expected, this airflow can be reliably received by third portion 313 on pressure surface 202, and separation region LSB, which will be described later, can be stably formed.

[0063] In this way, by generating an airflow that separates from and reattaches to the pressure surface 202, a laminar separation bubble is generated between the first extreme point 301 and the reattachment point 319 on the pressure surface 202. As shown in Fig. 11 , this separation bubble forms a separation region LSB, which is a negative pressure region where the pressure coefficient (Cp) exhibits a negative value.

[0064] The airflow flows from first extreme point 301 toward reattachment point 319, passing over the outlet side of separation region LSB (see FIG. 10 ). The airflow further flows from reattachment point 319 toward the trailing edge side, along third portion 313 of pressure surface 202. This airflow creates a positive pressure region PR, in which the pressure coefficient (Cp) exhibits a positive value, on the outlet side of pressure surface 202 and on the trailing edge side of separation region LSB.

[0065] The negative pressure difference between the positive pressure region PR and the separation region LSB generates a lift force F1 that flows from the positive pressure region PR to the separation region LSB. The direction in which the lift force F1 acts is between the leading edge side and the suction side, in other words, it is inclined toward the suction side from the fore-and-aft direction of the wing 200. Therefore, the lift force F1 acts to bias the wing 200 toward the suction side.

[0066] The blade 200 is supported rotatably about the central axis AX, and is not displaced toward the suction side even when it receives the lift F1. Therefore, a reaction force of the lift F1 is generated in the blade 200, and this reaction force acts in the opposite direction to the lift F1. Specifically, the direction in which the reaction force of the lift F1 acts is a direction between the trailing edge side and the blowing side, in other words, it is inclined toward the blowing side from the fore-and-aft direction of the blade 200. The reaction force of the lift F1 acts to urge the airflow flowing along the pressure surface 202 toward the blowing side. This improves the air volume and / or wind speed of the airflow sent from the blade 200 to the blowing side.

[0067] Therefore, according to the blower device 1 of this embodiment, it is possible to blow an airflow of sufficient volume and / or speed from the blades 200 while suppressing the rotation speed of the propeller fan 100. In other words, the blower device 1 can quietly blow out an airflow of high volume and / or speed. Furthermore, according to the blower device 1 of this example, it is possible to quietly blow out an airflow of even higher volume and / or speed by the following aspects.

[0068] Because a separation region LSB is formed along second portion 312 of pressure surface 202, lift F1 tends to act toward second portion 312. The portion of second portion 312 from intersection 312A to second extreme point 302 is curved so as to be concave toward the leading edge and suction side (see FIG. 6 ). Therefore, second portion 312 reliably receives lift F1 acting toward the leading edge and suction side, and efficiently generates a reaction force to lift F1.

[0069] As described above, acute angle θ11 is larger than acute angle θ12 (see FIG. 8 ). In other words, the inclination of first portion 311 toward the outlet side with respect to reference line SL is relatively large. The airflow that flows along first portion 311 is released from first extreme point 301 so as to move far away from pressure surface 202 toward the outlet side. The airflow reattaches to pressure surface 202 at reattachment point 319, which is away from first extreme point 301 toward the trailing edge, and therefore separation region LSB can be reliably generated.

[0070] As described above, the first extreme point 301 is located in the first region A1, and the second extreme point 302 is located in the second region A2 or the third region A3 (see FIG. 7 ). Therefore, if the reattachment point 319 is located near the second extreme point 302, the reattachment point 319 will be far away from the first extreme point 301 toward the trailing edge. Therefore, a separation region LSB with a larger volume can be formed between the first extreme point 301 and the reattachment point 319.

[0071] In this example, the second extreme point 302 is located in the third region A3 (see FIG. 7 ). In other words, the second extreme point 302 is located in the third region A3, which is at the center of the wing 200 in the longitudinal direction. Therefore, when the reattachment point 319 is located near the second extreme point 302, the separation region LSB is formed along approximately the leading half of the pressure surface 202 (see FIG. 11 ). The positive pressure region PR is formed along approximately the trailing half of the pressure surface 202. As a result, the volume of the separation region LSB and the volume of the positive pressure region PR become approximately the same, and therefore a large lift force F1 can be efficiently generated.

[0072] As described above, the cross-sectional shape of pressure surface 202 further includes portion 313B (see FIG. 9 ). For example, it is possible that the airflow emitted from first extreme point 301 moves toward the trailing edge side beyond second extreme point 302. In this case, the airflow may pass trailing edge 212 without re-contacting pressure surface 202, and separation region LSB may not be formed. In this example, because third portion 313 has portion 313B extending toward the outlet side beyond reference line SL, third portion 313 can reliably receive the above-described airflow, thereby stably forming separation region LSB.

[0073] Furthermore, as described above, the cross-sectional shape of the pressure surface 202 further includes a fourth portion 314 (see FIG. 9) extending from the third extreme point 303. The state of the airflow in the rear end region RR (see FIG. 9) will be described below.

[0074] 12 , third portion 313 and fourth portion 314 form a convex portion in the cross-sectional shape of pressure surface 202 that bulges toward the outlet side with third extreme point 303 as its apex. In trailing end region RR, the airflow that has passed through separation region LSB flows along third portion 313 toward third extreme point 303. In this example, the curvature near third extreme point 303 is smaller than the curvature near first extreme point 301. Therefore, at least a portion of the airflow that has reached third extreme point 303 flows along fourth portion 314 toward trailing edge portion 212 without separating from pressure surface 202.

[0075] Thus, in the trailing edge region RR, the direction of the airflow, which is inclined toward the outlet side along the third portion 313, changes to incline toward the suction side along the fourth portion 314, with the third extreme point 303 as the boundary. This change in the direction of the airflow increases the momentum of the airflow in the trailing edge region RR. Furthermore, the airflow flowing along the fourth portion 314 flows toward the gap between the trailing edge side and the suction side, thereby urging the blade 200 toward the suction side. As a result, a lift force F2 acting to urge the blade 200 toward the suction side is generated in the trailing edge region RR.

[0076] Even when the blade 200 receives the lift force F2, it is not displaced toward the suction side, and therefore a reaction force of the lift force F2 is generated in the blade 200, and this reaction force acts in the opposite direction to the lift force F2. The reaction force of the lift force F2 acts to urge the airflow flowing along the pressure surface 202 toward the blow-out side. This improves the lift-to-drag ratio of the blade 200, and further improves the volume and / or speed of the airflow sent from the blade 200 to the blow-out side.

[0077] As described above, the curvature of fourth portion 314 is greater than the curvature of third portion 313. As the airflow flows along fourth portion 314, the direction of this airflow changes significantly toward the suction side. This further increases the momentum of the airflow in trailing edge region RR, and the airflow flowing through fourth portion 314 urges wing 200 more strongly toward the suction side, thereby generating a larger lift force F2.

[0078] The relationship between the propeller fan 100 and the cover member will now be described. Fig. 13 is a right side view of the main body 11 of the blower 1 with the front cover 53 removed. Fig. 14 is a longitudinal cross-sectional view of the main body 11 of the blower 1. For ease of understanding, Fig. 14 shows the right side view of the propeller fan 100 rather than the longitudinal cross-section. In this example, at least one of the center cover 51, the rear cover 52, and the front cover 53 constitutes the cover member. This cover member is cylindrical with openings on the suction side and the blowing side, and houses at least a portion of the propeller fan 100.

[0079] As shown in Figures 4 and 5, the radially outer end of leading edge portion 211 is second point 222. Second point 222 is provided at the suction-side end of blade 200 that protrudes furthest toward the suction side. The cover member may house at least the suction-side end of blade 200. In this example, as shown in Figure 13, when front cover 53 is removed from main body 11, blade 200 protrudes from central cover 51 to the outlet side in side view. In this case, because second point 222, which is the suction-side end of blade 200, is housed within central cover 51, which is the cover member, second point 222 is not exposed to the outside when viewed from the radially outer side of central axis AX.

[0080] The second point 222 of the wing 200 is a portion where the leading edge 211 and the outer edge 213 are connected at an acute angle, and may cause harm to a human body if it comes into contact with the human body. In this example, even if a person removes the front cover 53 for maintenance, for example, the second point 222 of the wing 200 is contained within the center cover 51, so that the human hand is prevented from coming into contact with the second point 222.

[0081] 2 and 14 , the cover member has a cylindrical inner surface 54 extending along the axial direction of the central axis AX. The inner surface 54 may be radially opposed to at least the entire trailing edge portion 212 of the blade 200. In this example, the inner circumferential surfaces of the central cover 51 and the front cover 53, which are the cover members, form the inner surface 54 that extends continuously along the axial direction of the central axis AX. The central cover 51 and the front cover 53 house the entire blade 200, and the inner surface 54 is provided radially outward of the central axis AX with respect to the blade 200. Because the inner surface 54 covers the entire trailing edge portion 212 from the radially outer side, the trailing edge portion 212 is not exposed to the outside when viewed from the radially outer side.

[0082] As described above, in the rear end region RR, the airflow flows along the fourth portion 314, generating lift F2. Part of the airflow flowing along the fourth portion 314 may flow from the trailing edge portion 212 in the circumferential direction about the central axis AX rather than flowing rearward from the trailing edge portion 212. The airflow flowing in the circumferential direction from the trailing edge portion 212 has a smaller effect of generating lift F2 than the airflow flowing rearward from the trailing edge portion 212. In this example, the airflow flowing in the circumferential direction from the trailing edge portion 212 heads toward the inner surface 54 that covers the trailing edge portion 212 and is further guided along the inner surface 54 to the blowing side. Therefore, even when an airflow flows out in the circumferential direction from the trailing edge portion 212, a reduction in the volume of the airflow blown to the blowing side by the blower device 1 can be suppressed.

[0083] The propeller fan 100 and blower device 1 of the present disclosure are not limited to the above-described embodiment and may be modified in various ways. For example, the blower device 1 is not limited to a circulator and may be, for example, an electric fan or a blower built into an air conditioner. The number of blades 200 included in the propeller fan 100 is not limited to three and may be any number.

[0084] The shape and size of blade 200 are not limited to those in the above embodiment. For example, acute angle θ11 may be equal to or less than acute angle θ12. The cross-sectional shape of pressure surface 202 may not include portion 313B. In this case, third extreme point 303 located at the blowing-side end of third portion 313 may be located on reference line SL. The cross-sectional shape of pressure surface 202 may not include fourth portion 314. In this case, third extreme point 303 located at the blowing-side end of third portion 313 may be located at trailing edge portion 212. The curvature of fourth portion 314 may be equal to or less than the curvature of third portion 313.

Claims

1. A blade comprising: a rotating shaft portion that rotates around a central axis as a center of rotation; and a blade that protrudes radially outward from the rotating shaft portion, the blade having a negative pressure surface located on the suction side in the axial direction of the central axis, and a positive pressure surface located on the blow side opposite the suction side in the axial direction of the central axis, wherein the blade includes a leading edge portion located on the forward side in the rotation direction of the blade and a trailing edge portion located on the rear side in the rotation direction, an aerofoil cross section of the blade is a cross section obtained by cutting the blade in the thickness direction by an imaginary plane that intersects the leading edge portion and the trailing edge portion, and includes a cross-sectional shape of the positive pressure surface that extends smoothly and continuously between the leading edge portion and the trailing edge portion, and the cross-sectional shape of the positive pressure surface includes: when an imaginary straight line passing through the leading edge portion and the trailing edge portion in the aerofoil cross section is taken as a reference line, a first extreme point located on the blow side of the reference line, and a second extreme point located between the first extreme point and the trailing edge portion and located on the suction side of the reference line, the propeller fan further includes: a first portion extending from the leading edge portion to the first extreme point so as to incline toward the outlet side; a second portion extending from the first extreme point to the second extreme point so as to incline toward the suction side; and a third portion extending from the second extreme point toward a trailing edge side of the blade so as to incline toward the outlet side and intersecting the reference line.

2. A propeller fan according to claim 1, wherein the acute angle formed between said first portion and said reference line is larger than the acute angle formed between said second portion and said reference line.

3. A propeller fan according to claim 1, wherein, when the blade in the aerofoil cross section is divided into three equal regions aligned in the extension direction of the reference line, the three regions comprise a first region including the leading edge portion, a second region including the trailing edge portion, and a third region located between the first region and the second region, and the first extreme point is located in the first region, and the second extreme point is located in the second region or the third region.

4. The propeller fan according to claim 3, wherein the second extreme point is located in the third region.

5. A propeller fan according to claim 1, wherein the cross-sectional shape of the pressure surface further includes a portion located on the trailing edge side of the second extreme point and on the outlet side of the reference line.

6. The propeller fan according to claim 4, wherein the cross-sectional shape of the pressure surface further includes a fourth portion extending inclined toward the suction side from a third extreme point provided between the second extreme point and the trailing edge portion to the trailing edge portion.

7. The propeller fan according to claim 6, wherein the curvature of the fourth portion is greater than the curvature of the third portion.

8. A blower comprising: the propeller fan according to claim 1; and a motor that drives the propeller fan to rotate.

9. A blower device as described in claim 8, further comprising a cylindrical cover member that opens to the suction side and the blowing side and that houses at least a portion of the propeller fan, wherein the radially outer end of the leading edge portion is provided at the suction side end of the blade that protrudes furthest toward the suction side, and wherein the cover member houses at least the suction side end of the blade.

10. A blower comprising: a propeller fan as defined in claim 7; a motor that drives the propeller fan to rotate; and a cylindrical cover member that opens to the suction side and the blowing side and that houses at least a portion of the propeller fan, wherein the cover member has a cylindrical inner surface that extends along the axial direction of the central axis, and the inner surface faces at least the entire trailing edge portion of the blade in the radial direction.

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