# Patent

## Title
Cross flow fan and air-conditioning apparatus including same

## Abstract

A cross flow fan including an impeller having at least two rings arranged with intervals in a fan rotation axis O direction and a plurality of blades that are arranged, between correlated rings, with intervals in a circumferential direction of the rings, in which the blade is divided into plural areas in the fan rotation axis O direction, and both ends adjacent to the rings are denoted as the blade-ring proximate sections and the center portion of the blade is denoted as the inter-blade-ring center section. The blade is formed such that the thickness of the inner peripheral blade end of the blade that is the inner peripheral end of the impeller is smaller in the inter-blade-ring center section than in the blade-ring proximate section.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a U.S. national stage application of PCT/JP2011/005717 filed on Oct. 12, 2011, and claims priority to, and incorporates by reference, Japanese Patent Application No. 2010-249511 filed on Nov. 8, 2010.
TECHNICAL FIELD
The present invention relates to a cross flow fan and to an air-conditioning apparatus equipped with such a cross flow fan.
BACKGROUND ART
In conventional cross flow fans, there has been proposed, for example, a cross flow fan in which “the blade shape of the cross flow fan is configured with an arc-shaped portion defining a position of maximum thickness on the inner circumferential side of the blade, and in which a blade shape has a thickness distribution that gradually reduces its thickness towards the outer circumferential direction from the arc-shaped portion” with an object to “form a stable flow field even when a load is applied” (see Patent Literature 1, for example).
Furthermore, there has been proposed, for example, “a traverse fan in which a plurality of blades is arranged in a circumferential direction in an annual manner with a predetermined mounting pitch and is laterally fixed between a pair of discoid or circular end plates, and in which a partition plate is disposed in an intermediate portion of the blade in the axis direction”, “the blade being formed such that the chord length in the intermediate portion in the axis direction is shorter than the chord length in the two end portions of the blade in the axis direction” with an object to “effectively lower fan noise without reducing air volume” (see Patent Literature 2, for example).
CITATION LIST
Patent Literature


    [Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2001-323891 (paragraphs [0007] and [0008], FIG. 1)
    [Patent Literature 2] Japanese Unexamined Patent Application Publication No. 10-77988 (paragraphs [0009] and [0015], FIGS. 1 and 4)


SUMMARY OF INVENTION
Technical Problem
In the cross flow fan described in Patent Literature 1, a intermediate portion of a ring of the discoid blade mounting plate is not influenced by a boundary layer that develops on a surface of the ring; hence, suction and blowing out of air is facilitated.
However, because the blade has the same blade shape in the impeller shaft direction, the inter-blade distance is small, thus creating air flow resistance in the passage between the blades. As such, there has been a problem in that the fanning efficiency is deteriorated.
Further, owing to the deterioration of fanning efficiency, the power consumption of the fan motor driving the impeller increases. As such, there has been a problem in that the cross flow fan is inferior in energy efficiency.
Furthermore, in the cross flow fan described in Patent Literature 2, the blade chord length in the intermediate portion between the rings is formed smaller than the blade chord length in the portion close to the ring in order to reduce the air velocity in the intermediate portion between the rings and make the overall fan air velocity distribution in the shaft direction uniform.
However, because the chord length is made short in the area where it is easier for the air to flow through, such as the intermediate portion between the rings where there is no obstacles such as a ring, there has been a problem in that the blast volume drops.
That is, because the air velocity distribution in the impeller shaft direction is made uniform by reducing the pressure rise in the blades, there has been a problem in that the fanning efficiency deteriorates.
Further, owing to the deterioration of fanning efficiency, the power consumption of the fan motor driving the impeller increases. As such, there has been a problem in that the cross flow fan is inferior in energy efficiency.
The invention is addressed to overcome the problems described above and provides a cross flow fan that is capable of reducing the air flow resistance in the passage between the blades, as well as an air-conditioning apparatus equipped with this cross flow fan.
Further, the invention provides a cross flow fan that is capable of making the air velocity distribution of the impeller uniform, as well as an air-conditioning apparatus equipped with this cross flow fan.
Furthermore, the invention provides a cross flow fan that is capable of reducing air flow resistance in the impeller and the air passage and that is capable of improving fanning efficiency, as well as an air-conditioning apparatus equipped with this cross flow fan.
Additionally, the invention provides a cross flow fan that is capable of suppressing increase in power consumption of the fan motor driving the impeller and that is capable of improving energy efficiency, as well as an air-conditioning apparatus equipped with this cross flow fan.
Solution to Problem
The cross flow fan according to the invention includes an impeller having at least two support plates arranged with intervals in a rotation axis direction; and a plurality of blades arranged between correlated support plates, the blades being arranged with intervals in a circumferential direction of the support plates, in which each blade between the support plates is divided into a plurality of areas in the rotation axis direction such that both ends adjacent to the support plates are a first area and a center portion of the blade is a second area, and a thickness of an inner peripheral blade end that is an end of a blade on an inner-circumferential side of the impeller is formed such that the second area is smaller in thickness than the first area
The air-conditioning apparatus according to the invention includes the above described cross flow fan; and an heat exchanger disposed in a suction-side passage formed by the cross flow fan, the heat exchanger being configured to exchange heat with sucked-in air.
Advantageous Effects of Invention
In the invention, the thickness of the inner peripheral blade end of the blade is formed smaller in the second region, which is the middle portion, than in the first region, which is adjacent to the support plate; hence, it is possible to reduce the air flow resistance in each passage between the blades.
Further, it is possible to make the air velocity distribution of the impeller uniform.
Furthermore, it is possible to reduce the air flow resistance in the impeller and the air passage, thus improve fanning efficiency.
Moreover, it is possible to suppress increase in power consumption of the fan motor driving the impeller, thus improve energy efficiency.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an external perspective view of an air-conditioning apparatus according to Embodiment 1 of the invention.
FIG. 2 is a longitudinal sectional view of the air-conditioning apparatus of FIG. 1.
FIG. 3 is a front view of an impeller of a cross flow fan of FIG. 1.
FIG. 4 is a perspective view of a single blade of FIG. 3 seen from a blade pressure surface side (rotation direction side).
FIG. 5 is a perspective view of the single blade of FIG. 3 seen from a blade suction pressure surface side (opposite the rotation direction side).
FIG. 6 is an arrow view of the single blade of FIG. 4 taken from the direction of arrow F seen from an inner circumferential side of the fan.
FIG. 7 is a cross-sectional view of the single blade of FIG. 3 taken along the line A-A.
FIG. 8 is a cross-sectional view of the single blade of FIG. 3 taken along the line B-B.
FIG. 9 is a cross-sectional view of the single blade of FIG. 3 taken along the line B-B.
FIG. 10 is an enlarged view of a cross-sectional view of a plurality of blades of FIG. 3 on the fan outlet side taken along the line A-A.
FIG. 11 is a diagram illustrating a noise value change in relation to a ratio Bb/B of a length Bb of an inter-blade-ring center section to an inter-blade-ring length B, under a constant air volume.
FIG. 12 is a diagram illustrating change in fan motor power consumption in relation to the ratio Bb/B under a constant air volume.
FIG. 13 is a perspective view of a cross flow fan of Embodiment 2 that corresponds to that of FIG. 4 and that is mounted to an air-conditioning apparatus.
FIG. 14 is a cross-sectional view of the blade of FIG. 13 corresponding to that of FIG. 9 taken along the line B-B.



DESCRIPTION OF EXEMPLARY EMBODIMENTS
First Exemplary Embodiment
FIG. 1 is an external perspective view of an air-conditioning apparatus according to Embodiment 1 of the invention.
FIG. 2 is a longitudinal sectional view of the air-conditioning apparatus of FIG. 1.
Referring to FIGS. 1 and 2, an air-conditioning apparatus body 1 according to the invention is disposed on a wall 11a of a room 11 to be air-conditioned.
Further, a detachable front grille 6 is attached to a body front 1a. 
Furthermore, an upper inlet port 2, a filter 5 that carries out dust removal of dust, and a heat exchanger 7 that carries out cooling/heating by exchanging heat with air suctioned into the body are arranged in the body upper portion 1b. 
A cross flow fan 8 that is an air-sending device is arranged on the downstream side of the heat exchanger 7.
The cross flow fan 8 includes an impeller 8a; a stabilizer 9 having a tongue portion, which separates a suction side flow path E1 and a discharge side flow path E2, and a drain pan, which temporarily stores water droplets dripping from the heat exchanger 7; and a helical guide wall 10 on the discharge side of the impeller 8a. 
Furthermore, air direction vanes (vertical wind direction vanes 4a and horizontal wind direction vanes 4b) are rotatably attached to the air outlet 3.
FIG. 3 is a front view of the impeller of the cross flow fan of FIG. 1.
Referring to FIG. 3, the impeller 8a of the cross flow fan 8 is, as an example, formed of thermoplastic resin such as AS resin.
The impeller 8a is integrally formed by welding and connecting a plurality of impeller units 8c that includes a plurality of blades 20 that extends from the outer circumference of a disk-shaped ring 8b and that is consecutively installed in the circumferential direction of the ring 8b. 
That is, the plurality of blades 20 that are arranged with intervals in the circumferential direction of the rings 8b are provided between the correlated rings 8b of the impeller unit 8c. 
Furthermore, the impeller 8a sends air by moving rotationally in a fan rotation direction RO with a fan rotation axis O at its center while the two ends are in a supported state such that one end is secured to a fan shaft 8d and the other end is secured by a screw and the like to a fan boss 8e, which protrudes into the internal side of the impeller 8a, and a motor shaft 12a of a motor 12.
Note that the “ring 8b” corresponds to a “support plate” of the invention.
Note that, in Embodiment 1, although the impeller 8a is formed by connecting a plurality of impeller units 8c, the invention is not limited to this and the impeller 8a may be constituted by an impeller unit 8c alone.
Note that, in Embodiment 1, although disk-shaped rings 8b are used, the invention is not limited to this. For example, polygonal support plates may be used.
FIG. 4 is a perspective view of a single blade of FIG. 3 seen from a blade pressure surface side (rotation direction side).
FIG. 5 is a perspective view of the single blade of FIG. 3 seen from a blade suction pressure surface side (opposite the rotation direction side).
FIG. 6 is an arrow view taken from the direction of arrow F showing the single blade of FIG. 4 from an inner circumferential side of the fan.
Referring to FIGS. 4 to 6, the blade 20 is formed with a shape in which its outer peripheral blade end 20d, which is the outer peripheral end of the impeller 8a, is tilted forward in the fan rotation direction RO relative to its inner peripheral blade end 20c, which is the inner peripheral end of the impeller 8a. 
The blade 20 is divided into plural areas in the rotation axis direction such that five areas are formed, namely, blade-ring proximate sections 20a that are both end portions adjacent to the rings 8b, inter-blade-ring center section 20b that is the center portion of the blade 20, and blade connection sections 20e that are areas between the blade-ring proximate sections 20a and the inter-blade-ring center section 20b. 
Note that the “blade-ring proximate sections 20a” corresponds to a “first area” of the invention.
Note that the “inter-blade-ring center section 20b” corresponds to a “second area” of the invention.
Note that the “blade connection sections 20e” corresponds to a “third area” of the invention.
Regarding the thickness of the inner peripheral blade end 20c of the blade 20, the inter-blade-ring center section 20b is formed thinner than the blade-ring proximate sections 20a. 
Furthermore, the thickness of the blade 20 in the blade connection sections 20e is formed to gradually change in shape from the thickness of the blade-ring proximate sections 20a to the thickness of the inter-blade-ring center section 20b. 
That is, the inner peripheral blade end 20c of the blade 20 is formed such that both a blade pressure surface 20p, which is the front surface of the blade 20 with respect to the fan rotation direction RO, and a blade suction pressure surface 20s, which is the rear surface with respect to the fan rotation direction RO, are dented in the inter-blade-ring center section 20b for a predetermined length in the fan rotation axis O direction.
Furthermore, as shown in FIG. 6, in an inter-blade-ring length B that is the total length of the blade 20 in the fan rotation axis O direction, a length Bb of the inter-blade-ring center section 20b in the fan rotation axis O direction, each length Ba of the two blade-ring proximate sections 20a at both ends in the fan rotation axis O direction, and each length Bc of the two blade connection sections 20e in the fan rotation axis O direction hold a relationship of Bb>Ba>Bc.
FIG. 7 is a cross-sectional view taken along the line A-A of the single blade of FIG. 3.
Referring to FIG. 7, a section of a blade-ring proximate section 20a that is orthogonal to the fan rotation axis O is shown.
As shown in FIG. 7, the blade 20 is formed such that its section orthogonal to the fan rotation axis O has an arc shape.
An outer peripheral blade end 20da and an inner peripheral blade end 20ca in the blade-ring proximate section 20a of the blade 20 are both formed into an arc shape. Further, the outer peripheral blade end 20da is positioned on the inner circumferential side relative to the outer circumference of the ring 8b. 
Furthermore, the thickness of the blade 20 in the blade-ring proximate section 20a is formed to gradually increase from the outer peripheral blade end 20da to the inner peripheral blade end 20ca. 
That is, when t1a is the thickness at an arc center point C1a of the inner peripheral blade end 20ca in the blade-ring proximate section 20a, t2a is the thickness at an arc center point C2a of the outer peripheral blade end 20da, and t3a is the thickness at the chord center point C3a (described later), the thickness in the blade-ring proximate section 20a is formed such that: thickness t2a of the outer peripheral blade end 20da<thickness t3a at the chord center point C3a<thickness t1a of the inner peripheral blade end 20ca. 
Here, the thickness t1a of the inner peripheral blade end 20ca corresponds to the diameter of a circle that inscribes the arc of the inner peripheral blade end 20ca. 
Further, the thickness t2a of the outer peripheral blade end 20da corresponds to the diameter of a circle that inscribes the arc of the outer peripheral blade end 20da. 
Furthermore, when a chord line La is the line connecting the arc center point C2a of the outer peripheral blade end 20da and the arc center point C1a of the inner peripheral blade end 20ca, the thickness t3a at the chord center point C3a corresponds to the diameter of a circle inscribing the blade 20 at the chord center point C3a that is an intersection point between a perpendicular bisector of this chord line La and a camber line Sa that is the center line of thickness of the blade 20 in the blade-ring proximate section 20a. 
The blade pressure surface 20p, the camber line Sa, and the blade suction pressure surface 20s are each formed into an arc shape in a section of the blade-ring proximate section 20a orthogonal to the fan rotation axis O.
Furthermore, when Ra1 is the arc radius of the blade pressure surface 20p, Ra2 is the arc radius of the blade suction pressure surface 20s, and Ra3 is the arc radius of the camber line Sa, then, the blade 20 is formed such that: the arc radius Ra1 of the blade pressure surface 20p<the arc radius Ra3 of the camber line Sa<the arc radius Ra2 of the blade suction pressure surface 20s. 
That is, the arc radius Ra1 of the blade pressure surface 20p is formed so as to be smaller than the arc radius Ra2 of the blade suction pressure surface 20s, and the blade 20 is shaped such that the arc radius becomes smaller and the curvature becomes tighter the more on the blade pressure surface 20p side.
Note that in FIG. 7, R01a is the radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C1a of the inner peripheral blade end 20ca in the blade-ring proximate section 20a. 
Furthermore, R02a is the radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C2a of the outer peripheral blade end 20da in the blade-ring proximate section 20a. 
FIG. 8 is a cross-sectional view of the single blade of FIG. 3 taken along the line B-B.
Referring to FIG. 8, a section of the inter-blade-ring center section 20b that is orthogonal to the fan rotation axis O is shown.
As shown in FIG. 8, the blade 20 is formed such that its section orthogonal to the fan rotation axis O is an arc shape.
An outer peripheral blade end 20db and an inner peripheral blade end 20cb in the inter-blade-ring center section 20b of the blade 20 are both formed into an arc shape. Further, the outer peripheral blade end 20db is positioned on the inner circumferential side relative to the outer circumference of the ring 8b. 
Furthermore, the thickness of the blade 20 in the inter-blade-ring center section 20b is formed to gradually increase from the outer peripheral blade end 20db to the middle of the outer peripheral blade end 20db and the inner peripheral blade end 20cb and to gradually decrease from this middle portion to the inner peripheral blade end 20cb. 
That is, when t1b is the thickness at an arc center point C1b of the inner peripheral blade end 20cb in the inter-blade-ring center section 20b, t2b is the thickness at an arc center point C2b of the outer peripheral blade end 20db, and t3a is the thickness at the chord center point C3a′ (described later), the thickness of the blade 20 in the inter-blade-ring center section 20b is formed, for example, such that: thickness t2b of the outer peripheral blade end 20db<the thickness t3a at the chord center point C3a′, and, the thickness t3a at the chord center point C3a′>thickness t1b of the inner peripheral blade end 20cb. 
Here, the thickness t1b of the inner peripheral blade end 20cb corresponds to the diameter of a circle that inscribes the arc of the inner peripheral blade end 20cb. 
Further, the thickness t2b of the outer peripheral blade end 20db corresponds to the diameter of a circle that inscribes the arc of the outer peripheral blade end 20db. 
Furthermore, the chord center point C3a′ is a projected point of the chord center point C3a in the section of FIG. 7 taken along the line A-A onto the section taken along the line B-B. The thickness t3a at the chord center point C3a′ corresponds to the diameter of a circle inscribing the blade 20 at the chord center point C3a′ and is the same as the thickness t3a at the chord center point C3a in the section of FIG. 7 taken along the line A-A.
Note that although in Embodiment 1, a case is given in which the thickness t3a at the chord center point C3a′, which is a projected point of the chord center point C3a in the section of FIG. 7 taken along the line A-A onto the section taken along the line B-B, is the thickest and the thickness is the same as that of the section taken along the line A-A, the invention is not limited to this case.
Note that in FIG. 8, Lb is a chord line connecting the arc center point C2b of the outer peripheral blade end 20db and the arc center point C1b of the inner peripheral blade end 20cb. 
Further, Sb is a camber line that is the center line of thickness of the blade 20 in the inter-blade-ring center section 20b. 
Further, R01b is the radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C1b of the inner peripheral blade end 20cb in the inter-blade-ring center section 20b. 
Furthermore, R02b is the radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C2b of the outer peripheral blade end 20db in the inter-blade-ring center section 20b. 
The blade pressure surface 20p, the camber line Sb, and the blade suction pressure surface 20s are each formed into an arc shape in a section of the inter-blade-ring center section 20b orthogonal to the fan rotation axis O.
Furthermore, when Rb1 is the arc radius of the blade pressure surface 20p, Rb2 is the arc radius of the blade suction pressure surface 20s, and Rb3 is the arc radius of the camber line Sb that is the center line of thickness of the blade 20 in the inter-blade-ring center section 20b, then, the blade 20 is formed such that: the arc radius Rb1 of the blade pressure surface 20p>the arc radius Rb3 of the camber line Sb>the arc radius Rb2 of the blade suction pressure surface 20s. 
That is, the arc radius Rb1 of the blade pressure surface 20p is formed so as to be larger than the arc radius Rb2 of the blade suction pressure surface 20s, and the blade 20 is shaped such that the arc radius becomes smaller and the curvature becomes tighter the more on the blade suction pressure surface 20s side.
FIG. 9 is a cross-sectional view of the single blade of FIG. 3 taken along the line B-B.
Referring to FIG. 9, a shape of the blade-ring proximate section 20a is shown, as well as a section of the inter-blade-ring center section 20b that is orthogonal to the fan rotation axis O.
As shown in FIG. 9, the blade 20 is formed such that the shapes of the blade-ring proximate section 20a and the inter-blade-ring center section 20b are the same from the outer peripheral blade end 20d to the middle of the outer peripheral blade end 20d and the inner peripheral blade end 20c. 
Furthermore, the blade 20 is formed such that the shapes of the blade-ring proximate section 20a, the inter-blade-ring center section 20b, and the blade connection sections 20e vary from the middle of the outer peripheral blade end 20d and the inner peripheral blade end 20c to the inner peripheral blade end 20c. 
For example, the shape of each section is formed so as to be the same from the outer peripheral blade end 20d to the chord center point C3a, and the shape of each section is formed so as to vary from the chord center point C3a to the inner peripheral blade end 20c. 
Furthermore, R01c is a radius of a circle that is centered around the fan rotation axis O and that passes through an end face of the inner peripheral blade end 20cb in the inter-blade-ring center section 20b. R01c is the same as the radius of a circle that is centered around the fan rotation axis O and that passes through an end face of the inner peripheral blade end 20ca in the blade-ring proximate section 20a. 
Moreover, the blade 20 is formed such that the camber line Sa, which is the center line of thickness of the blade 20 in the blade-ring proximate section 20a, and the camber line Sb, which is the center line of thickness in the inter-blade-ring center section 20b, are the same.
FIG. 10 is an enlarged view of a cross-sectional view of the plurality of blades of FIG. 3 on the fan outlet side taken along the line A-A.
As shown in FIG. 10, when a distance between the adjacent blades 20 is depicted by the diameter of a circle that inscribes the surface of each of the respective blades 20, then M1a<M1b, where M1b is an inter-blade distance between the inner peripheral blade ends 20cb in the inter-blade-ring center section 20b and M1a is an inter-blade distance between the inner peripheral blade ends 20ca in the blade-ring proximate section 20a. That is, the inter-blade distance in the inter-blade-ring center section 20b is greater than that in the blade-ring proximate section 20a. 
Further, the inter-blade distance M2a between the outer peripheral blade ends 20da in the blade-ring proximate section 20a is the same as the inter-blade distance M2b between the outer peripheral blade ends 20db in the inter-blade-ring center section 20b. 
Furthermore, the inter-blade distances M2a and M2b between the outer peripheral blade ends 20da and 20db, respectively, are at least formed smaller than the inter-blade distances M1a and M1b between the inner peripheral blade ends 20ca and 20cb, respectively.
Note that in FIG. 10, Ua depicts a blowout flow from the blade-ring proximate section 20a. Furthermore, Ub depicts a blowout flow from the inter-blade-ring center section 20b. 
As described above, in Embodiment 1, the blade 20 is divided into plural areas in the fan rotation axis O direction, and both ends adjacent to the rings 8b are denoted as the blade-ring proximate sections 20a and the center portion of the blade 20 is denoted as the inter-blade-ring center section 20b. The blade 20 is formed such that the thickness of the inner peripheral blade end 20c of the blade 20 that is the inner peripheral end of the impeller 8a is smaller in the inter-blade-ring center section 20b than in the blade-ring proximate section 20a. 
Accordingly, the inter-blade distance M1b between the inner peripheral blade ends 20cb in the inter-blade-ring center section 20b is greater than the inter-blade distance M1a between the inner peripheral blade ends 20ca in the blade-ring proximate section 20a. Therefore, it is possible to blow out air in the fan-blow-out region such that the velocity of air passing between the blades is lower in the inter-blade-ring center section 20b than in the blade-ring proximate section 20a. 
As a result, it is possible to uniformize the air velocity distribution in the fan-blow-out region in the fan rotation axis O direction, reduce the air flow resistance in the blow-out passage, and reduce power consumption of the fan motor. Hence, energy efficiency can be improved.
Furthermore, since the thickness of the inner peripheral blade ends 20ca is large in the blade-ring proximate section 20a, the inter-blade distance M1b between the inner peripheral blade ends 20cb is small.
Accordingly, even if a boundary-layer turbulent flow that develops on the surface of the ring 8b flows in, the flow is accelerated in the blade-ring proximate section 20a and is blown out to the fan blow out side.
That is, it is possible to reduce noise by reducing the turbulence and the air velocity of the flow flowing into the blade 20.
Furthermore, in Embodiment 1, the areas between the blade-ring proximate sections 20a and the inter-blade-ring center section 20b are referred to as the blade connection sections 20e and the thickness of the blade 20 in the blade connection sections 20e is formed to gradually change in shape from the thickness of the blade-ring proximate sections 20a to the thickness of the inter-blade-ring center section 20b. 
Accordingly, it is possible to blow out air while seamlessly reducing the velocity of air passing between the blades.
As a result, it is possible to uniformize the air velocity distribution in the fan-blow-out region in the fan rotation axis O direction, reduce the air flow resistance in the blow-out passage, and reduce power consumption of the fan motor. Hence, energy efficiency can be improved.
Further, in Embodiment 1, the thickness of the blade 20 in the blade-ring proximate section 20a is formed to gradually increase from the outer peripheral blade end 20da to the inner peripheral blade end 20ca. Furthermore, the thickness of the blade 20 in the inter-blade-ring center section 20b is formed to gradually increase from the outer peripheral blade end 20d to the middle of the outer peripheral blade end 20d and the inner peripheral blade end 20c and to gradually decrease from the middle portion to the inner peripheral blade end 20c. 
Accordingly, even if a boundary-layer turbulent flow that develops on the surface of the ring 8b flows in, since the inter-blade distance M1a is small, the turbulence is seamlessly attenuated and is blown out to the fan blow out side. That is, noise can be reduced by reducing the turbulence and the air velocity of the flow flowing into the blade 20.
Furthermore, the inter-blade-ring center section 20b can blow out air while further reducing the velocity of air passing between the blades.
As a result, it is possible to uniformize the air velocity distribution in the fan-blow-out region in the fan rotation axis O direction, reduce the air flow resistance in the blow-out passage, and reduce power consumption of the fan motor. Hence, energy efficiency can be improved.
Further, in Embodiment 1, the blade 20 is formed such that its section orthogonal to the fan rotation axis O is an arc shape, and when the chord center point C3a is referred to as the intersection point between the perpendicular bisector of the chord line, which connects the outer peripheral blade end 20d and the inner peripheral blade end 20c, and the center of thickness of the blade 20, then the thickness of the blade 20 in the blade-ring proximate section 20a is formed such that: thickness of the outer peripheral blade end 20d<thickness at the chord center point C3a<thickness of the inner peripheral blade end 20c. Furthermore, the thickness of the blade 20 in the inter-blade-ring center section 20b is formed such that: thickness of the outer peripheral blade end 20d<the thickness at the chord center point C3a, and, the thickness at the chord center point C3a>thickness of the inner peripheral blade end 20c. 
Accordingly, even if a boundary-layer turbulent flow that develops on the surface of the ring 8b flows in, since the inter-blade distance M1a is small, the turbulence is seamlessly attenuated and is blown out to the fan blow out side. That is, noise can be reduced by reducing the turbulence and the air velocity of the flow flowing into the blade 20.
Furthermore, the inter-blade-ring center section 20b can blow out air while further reducing the velocity of air passing between the blades.
As a result, it is possible to uniformize the air velocity distribution in the fan-blow-out region in the fan rotation axis O direction, reduce the air flow resistance in the blow-out passage, and reduce power consumption of the fan motor. Hence, energy efficiency can be improved.
Further, in Embodiment 1, the arc radius of the blade pressure surface 20p, which is the front surface of the blade 20 with respect to the fan rotation direction RO, is formed so as to be smaller than the arc radius of the blade suction pressure surface 20s, which is the rear surface of the blade 20 with respect to the fan rotation direction RO, in the blade-ring proximate section 20a, and the arc radius of the blade pressure surface 20p is formed so as to be larger than the arc radius of the blade suction pressure surface 20s in the inter-blade-ring center section 20b. 
Accordingly, in the inter-blade-ring center section 20b where volume of air passing therethrough is large, it is possible to reduce the deflection angle of the flow in the blade pressure surface 20p. 
Furthermore, in the blade-ring proximate section 20a where volume of air passing therethrough is small, it is possible to increase the deflection angle of the flow in the blade pressure surface 20p. 
That is, as illustrated in FIG. 10, the blowout flow Ub from the inter-blade-ring center section 20b blows out to the guide wall 10 side from the middle of the height direction of the air outlet 3.
Moreover, the blowout flow Ua from the blade-ring proximate section 20a blows out to the stabilizer 9 side and into a portion above the blowout flow Ub from the middle of the height direction of the air outlet 3.
As a result, in the fan rotation axis O direction, it is possible to blow out air to different directions in the height direction of the air outlet 3. As such, the high-velocity region is diffused, drift is suppressed, the air velocity distribution is uniformized, and thus, air flow resistance is reduced.
Accordingly, it is possible to lower the air flow resistance in the air passage and reduce the power consumption of the fan motor. Hence, energy efficiency can be improved.
Further, in Embodiment 1, in each area of the blade 20, the shape of the section orthogonal to the fan rotation axis O is formed such that the shape in each area is the same from the outer peripheral blade end 20d to the middle of the outer peripheral blade end 20d and the inner peripheral blade end 20c. Furthermore, each area is formed so that the shape varies from the middle of the outer peripheral blade end 20d and the inner peripheral blade end 20c to the inner peripheral blade end 20c. 
Accordingly, adherence of dust to the blade 20 can be suppressed. That is, if there is, on the outer peripheral side of the impeller 8a in the fan rotation axis O direction, a shape-changed portion, such as, for example, waviness or notches in the thickness or the outer peripheral blade end 20d, then there are cases in which the floating dust around the fan is stuck in the shape-changed portion when the cross flow fan 8 is activated, becoming a beginning of adhesion and sticking of dust onto the blade 20. In Embodiment 1, adhesion of dust can be suppressed since the blade 20 from the middle to the inner peripheral blade end 20c is formed to vary its shape.
Accordingly, cleanliness of the cross flow fan 8 can be maintained. As a result, a sanitary air-conditioning apparatus can be obtained.
Furthermore, in Embodiment 1, as shown in FIG. 6, regarding the inter-blade-ring length B in the fan rotation axis O direction, the length Bb of the inter-blade-ring center section 20b in the fan rotation axis O direction, each length Ba of the two blade-ring proximate sections 20a at both ends in the fan rotation axis O direction, and each length Bc of the two blade connection sections 20e in the fan rotation axis O direction hold the relationship of Bb>Ba>Bc.
If the ratio of this length Bb of the inter-blade-ring center section 20b to the inter-blade-ring length B is excessively high, then the flow concentrates too much in the inter-blade-ring center section, and if, conversely, the ratio is excessively low, then the noise reduction effect and the energy saving effect cannot be obtained. As such, there is an optimum range.
FIG. 11 is a diagram illustrating the noise value change in relation to a ratio Bb/B of a length Bb of an inter-blade-ring center section to an inter-blade-ring length B, under a constant air volume.
FIG. 12 is a diagram illustrating change in fan motor power consumption in relation to the ratio Bb/B under a constant air volume.
As illustrated in FIG. 11, when the ratio Bb/B of the blade 20, which is the ratio of the length Bb of the inter-blade-ring center section 20b in the fan rotation axis O direction to the inter-blade-ring length B in the fan rotation axis O direction, is at least between 0.4 and 0.6, then the noise reduction effect can be obtained.
Furthermore, as shown in FIG. 12, when Bb/B is at least between 0.3 and 0.7, then power consumption of the fan motor can be reduced.
Accordingly, if Bb/B is at least between 0.4 and 0.6, then the noise reduction effect and the fan-motor power-consumption reduction effect can be obtained, and thus, a quiet and high energy saving cross flow fan 8 and air-conditioning apparatus can be obtained.
Embodiment 2
FIG. 13 is a perspective view of a cross flow fan of Embodiment 2 that corresponds to that of FIG. 4 and that is mounted to an air-conditioning apparatus.
FIG. 14 is a cross-sectional view of the blade of FIG. 13 corresponding to that of FIG. 9 taken along the line B-B.
Referring to FIG. 14, a shape of the blade-ring proximate section 20a is shown, as well as a section of the inter-blade-ring center section 20b that is a section orthogonal to the fan rotation axis O.
Note that in FIG. 13 and FIG. 14, components that correspond to those in the above-described Embodiment 1 will be denoted with the same reference numerals. Hereinafter, points different from those of Embodiment 1 described above will be mainly described.
As illustrated in FIG. 13, the inner peripheral blade end 20c in the inter-blade-ring center section 20b is formed so as to protrude more to the inner peripheral side of the impeller 8a than the blade-ring proximate section 20a. That is, it has a convex shape.
Further, as illustrated in FIG. 14, the camber line Sb in the inter-blade-ring center section 20b is identical to the camber lines Sa in the blade-ring proximate sections 20a. The camber line Sb protrudes along the extension line of the camber line Sa towards the inner peripheral side of the impeller 8a. That is, the arc radius of the center of thickness in the inter-blade-ring center section 20b is formed so as to have the same arc radius as the center of thickness in the blade-ring proximate sections 20a. 
Furthermore, the arc center point C2a of the outer peripheral blade end 20da in the blade-ring proximate section 20a is the same as the arc center point C2b of the outer peripheral blade end 20db in the inter-blade-ring center section 20b. 
Further, in FIG. 14, La is the chord line of the line connecting the arc center point C1a of the inner peripheral blade end 20ca and the arc center point C2a of the outer peripheral blade end 20da, in the blade-ring proximate section 20a. 
Furthermore, Lb is the chord line of the line connecting the arc center point C1b of the inner peripheral blade end 20cb and the arc center point C2b of the outer peripheral blade end 20db, in the inter-blade-ring center section 20b. 
Now, the length of the chord line Lb is formed to be longer than that of the chord line La.
Further, R01a is the radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C1a of the inner peripheral blade end 20ca in the blade-ring proximate section 20a. 
Further, R01b is the radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C1b of the inner peripheral blade end 20cb in the inter-blade-ring center section 20b. 
Now, the blade 20 is formed such that: radius R01a>radius R01b. 
As above, in Embodiment 2, the inner peripheral blade end 20c in the inter-blade-ring center section 20b is formed so as to protrude more to the inner peripheral side of the impeller 8a than the blade-ring proximate section 20a. 
Accordingly, the chord length in the inter-blade-ring center section 20b (the length of the chord line Lb) becomes longer than the chord length in the blade-ring proximate sections 20a (the length of the chord line La), and thus, it is possible to allow the inter-blade-ring center section 20b to have a higher static pressure rise than the blade-ring proximate sections 20a. 
Accordingly, it is possible to generate a pressure gradient from the inter-blade-ring center section 20b to each blade-ring proximate section 20a on both sides such that the pressure changes from high pressure to low pressure. As a result, it is possible to generate a flow from the inter-blade-ring center section 20b to each blade-ring proximate section 20a. 
In addition to the boundary-layer turbulent flow suppressing effect in the blade-ring proximate sections 20a of Embodiment 1 described above, it is possible to suppress the development of the boundary layer at the surface of the ring 8b with the flow to the blade-ring proximate sections 20a from the inter-blade-ring center section 20b; hence, separated turbulent flow on the outlet side of the blade 20 can be further suppressed.
Accordingly, it is possible to further reduce noise, as well as reducing power consumption of the fan motor by increasing the effective air passage and, thus, reducing the air flow resistance between the blades.
Therefore, a cross flow fan 8 and air-conditioning apparatus that are even more quiet and energy saving can be obtained.
INDUSTRIAL APPLICABILITY
Not limited to the above-described air-conditioning apparatus, the cross flow fan of the invention can be effectively utilized in an air cleaner, a humidifier, a dehumidifier, or the like.
REFERENCE SIGNS LIST
1 air-conditioning apparatus body; 1a body front; 1b body upper portion; 2 upper inlet port; 3 air outlet; 4a vertical wind direction vane; 4b horizontal wind direction vane 4b; 5 filter; 6 front grille; 7 heat exchanger; 8 cross flow fan; 8a impeller; 8b ring; 8c impeller unit; 8d fan shaft; 8e fan boss; 9 stabilizer; 10 guide wall; 11 room; 11a wall; 12 motor; 12a motor shaft; 20 blade; 20a blade-ring proximate section; 20b inter-blade-ring center section; 20c inner peripheral blade end; 20ca inner peripheral blade end at the blade-ring proximate section 20a; 20cb inner peripheral blade end at the inter-blade-ring center section 20b; 20d outer peripheral blade end; 20da peripheral blade end at the blade-ring proximate section 20a; 20db peripheral blade end at the inter-blade-ring center section 20b; 20e blade connection section; 20p blade pressure surface; 20s blade suction pressure surface; B inter-blade-ring length; Ba length of the blade-ring proximate section 20a; Bb length of the inter-blade-ring center section 20b; Bc length of the blade connection section 20e; C1a arc center point of the inner peripheral blade end 20ca in the blade-ring proximate section 20a; C1b arc center point of the inner peripheral blade end 20cb in the inter-blade-ring center section 20b; C2a arc center point of the outer peripheral blade end 20da in the blade-ring proximate section 20a; C2b arc center point of the outer peripheral blade end 20db in the inter-blade-ring center section 20b; C3a chord center point at the blade-ring proximate section 20a; C3a′ projected point of the chord center point C3a onto the section taken along the line B-B; E1 suction side flow path; E2 discharge side flow path; F arrow view; La chord line in the blade-ring proximate section 20a; Lb chord line in the inter-blade-ring center section 20b; Mia inter-blade distance between the inner peripheral blade ends 20ca in the blade-ring proximate section 20a; M1b inter-blade distance between the inner peripheral blade ends 20cb in the inter-blade-ring center section 20b; M2a inter-blade distance between the outer peripheral blade ends 20da in the blade-ring proximate section 20a; M2b inter-blade distance between the outer peripheral blade ends 20db in the inter-blade-ring center section 20b; O fan rotation axis; RO fan rotation direction; R01a radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C1a of the inner peripheral blade end 20ca in the blade-ring proximate section 20a; R01b radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C1a of the inner peripheral blade end 20ca in the inter-blade-ring center section 20b; R02a radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C2a of the outer peripheral blade end 20da in the blade-ring proximate section 20a; R02b radius of a circle that is centered around the fan rotation axis O and that passes through the arc center point C2a of the outer peripheral blade end 20da in the inter-blade-ring center section 20b; Ra1 arc radius of the blade pressure surface 20p in the blade-ring proximate section 20a; Ra2 arc radius of the blade suction pressure surface 20s in the blade-ring proximate section 20a; Ra3 arc radius of the camber line Sa in the blade-ring proximate section 20a, Rb1 arc radius of the blade pressure surface 20p in the inter-blade-ring center section 20b; Rb2 arc radius of the blade suction pressure surface 20s in the inter-blade-ring center section 20b; Rb3 arc radius of the camber line Sb in the inter-blade-ring center section 20b; Sa camber line in the blade-ring proximate sections 20a; Sb camber line in the inter-blade-ring center section 20b; Ua blowout flow from the blade-ring proximate section 20a; Ub blowout flow from the inter-blade-ring center section 20b; t1a thickness at the arc center point C1a of the inner peripheral blade end 20ca in the blade-ring proximate section 20a; t1b thickness at the arc center point C1b of the inner peripheral blade end 20cb in the inter-blade-ring center section 20b; t2a thickness at an arc center point C2a of the outer peripheral blade end 20da in the blade-ring proximate section 20a; t2b thickness at an arc center point C2b of the outer peripheral blade end 20db in the inter-blade-ring center section 20b; t3a thickness at the chord center point C3a in the blade-ring proximate section 20a.

## Claims

1. A cross flow fan, comprising:
an impeller including,
at least two support plates arranged with intervals in a rotation axis direction, and
a plurality of blades arranged between correlated support plates, the blades being arranged with intervals in a circumferential direction of the support plates, wherein

each blade between the support plates is divided into a plurality of areas in the rotation axis direction such that both ends adjacent to the support plates are a first area and a center portion of the blade is a second area,
a thickness of an inner peripheral blade end is formed such that the second area is smaller in thickness than the first area,
an area between the first area and the second area is a third area, and
a thickness of the blade in the third area is formed to gradually change in shape from a thickness of the blade in the first area to a thickness of the blade in the second area.

2. The cross flow fan of claim 1, wherein a thickness of the blade in the first area is formed so as to become gradually thicker from an outer peripheral blade end that is an end of the blade on an outer-circumferential side of the impeller to the inner peripheral blade end.

3. The cross flow fan of claim 1, wherein,
the thickness of the blade in the second area is formed so as to become gradually thinner to an inner peripheral blade end that is an end of the blade on an inner-circumferential side of the impeller after the thickness of the blade in the second area is formed so as to become gradually thicker from an outer peripheral blade end that is an end of the blade on an outer-circumferential side of the impeller to the inner peripheral blade end.

4. The cross flow fan of claim 1, wherein the thickness of the blade in the second area is formed so as to become gradually thicker from an outer peripheral blade end to the middle of the outer peripheral blade end and an inner peripheral blade end and is formed so as to become gradually thinner from the middle to the inner peripheral blade end.

5. The cross flow fan of claim 1, wherein,
each blade is formed such that a section orthogonal to the rotation axis is an arc shape, and
when an intersection point between a perpendicular bisector of a chord line connecting an outer peripheral blade end and the inner peripheral blade end, and a center of thickness of the blade is referred to as a chord center point,
the thickness of each blade in the first area is formed such that: the thickness of the outer peripheral blade end<the thickness at the chord center point<thickness of the inner peripheral blade end, and
the thickness of each blade in the second area is formed such that: thickness of the outer peripheral blade end<the thickness at the chord center point, and, the thickness at the chord center point>thickness of the inner peripheral blade end.

6. The cross flow fan of claim 1, wherein,
each blade is formed such that the section orthogonal to the rotation axis is the arc shape,
in the first area, an arc radius of a blade pressure surface that is a front surface with respect to a rotation direction of the blades is formed so as to be smaller than an arc radius of a blade suction pressure surface that is a rear surface with respect to the rotation direction of the blades, and
in the second area, the arc radius of the blade pressure surface is formed so as to be larger than the arc radius of the blade suction pressure surface.

7. The cross flow fan of claim 1, wherein
in each area of the blade, a shape of a section orthogonal to the rotation axis is formed such that
the shape in each area is identical from an outer peripheral blade end to the middle of the outer peripheral blade end and an inner peripheral blade end, and
the shape in each area varies from the middle of the outer peripheral blade end and the inner peripheral blade end to the inner peripheral blade end.

8. The cross flow fan of claim 1, wherein the inner peripheral blade end in the second area is formed so as to protrude more to an outer-circumferential side of the impeller than the first area.

9. The cross flow fan of claim 8, wherein,
each blade is formed such that the section orthogonal to the rotation axis is the arc shape, and
an arc radius of a center of thickness in the second area is formed so as to have an arc radius equivalent to a center of thickness in the first area.

10. The cross flow fan of claim 1, wherein a ratio (Bb/B) of a length (Bb) of the second area in the rotation axis direction to a total length (B) of the blade in the rotation axis direction is formed to be between 0.4 and 0.6.

11. The cross flow fan of claim 1, wherein the ratio (Bb/B) of the length (Bb) of the second area in the rotation axis direction to the total length (B) of the blade in the rotation axis direction is formed to be between 0.3 and 0.7.

12. An air-conditioning apparatus, comprising:
a cross flow fan, including,
an impeller having,
at least two support plates arranged with intervals in a rotation axis direction, and
a plurality of blades arranged between correlated support plates, the blades being arranged with intervals in a circumferential direction of the support plates, wherein

each blade between the support plates is divided into a plurality of areas in the rotation axis direction such that both ends adjacent to the support plates are a first area and a center portion of the blade is a second area,
a thickness of an inner peripheral blade end is formed such that the second area is smaller in thickness than the first area,
an area between the first area and the second area is a third area, and
a thickness of the blade in the third area is formed to gradually change in shape from a thickness of the blade in the first area to a thickness of the blade in the second area; and
a heat exchanger disposed in a suction-side passage formed by the cross flow fan, the heat exchanger being configured to exchange heat with sucked-in air.

13. The air-conditioning apparatus of claim 12, wherein the thickness of the blade in the first area is formed so as to become gradually thicker from an outer peripheral blade end that is an end of the blade on an outer-circumferential side of the impeller to the inner peripheral blade end.

14. The air-conditioning apparatus of claim 12, wherein the thickness of the blade in the second area is formed so as to become gradually thinner to an inner peripheral blade end that is an end of the blade on an inner-circumferential side of the impeller after the thickness of the blade in the second area is formed so as to become gradually thicker from an outer peripheral blade end that is an end of the blade on an outer-circumferential side of the impeller to the inner peripheral blade end.

15. The air-conditioning apparatus of claim 12, wherein the thickness of the blade in the second area is formed so as to become gradually thicker from an outer peripheral blade end to the middle of the outer peripheral blade end and the inner peripheral blade end and is formed so as to become gradually thinner from the middle to the inner peripheral blade end.

16. The air-conditioning apparatus of claim 12, wherein
each blade is formed such that a section orthogonal to the rotation axis is an arc shape, and
when an intersection point between the perpendicular bisector of a chord line connecting an outer peripheral blade end and the inner peripheral blade end, and a center of thickness of the blade is referred to as a chord center point,
the thickness of each blade in the first area is formed such that: the thickness of the outer peripheral blade end<the thickness at the chord center point<thickness of the inner peripheral blade end, and
the thickness of each blade in the second area is formed such that: thickness of the outer peripheral blade end<the thickness at the chord center point, and, the thickness at the chord center point>thickness of the inner peripheral blade end.

17. The air-conditioning apparatus of claim 12, wherein
each blade is formed such that a section orthogonal to the rotation axis is the arc shape,
in the first area, an arc radius of a blade pressure surface that is a front surface with respect to a rotation direction of the blades is formed so as to be smaller than an arc radius of a blade suction pressure surface that is a rear surface with respect to the rotation direction of the blades, and
in the second area, the arc radius of the blade pressure surface is formed so as to be larger than the arc radius of the blade suction pressure surface.

18. The air-conditioning apparatus of claim 12, wherein
in each area of the blade, a shape of the section orthogonal to the rotation axis is formed such that
the shape in each area is identical from an outer peripheral blade end to the middle of the outer peripheral blade end and the inner peripheral blade end, and
the shape in each area varies from the middle of the outer peripheral blade end and the inner peripheral blade end to the inner peripheral blade end.