Cross flow fan of an air conditioner

[0002] This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application entitled Crossflow Fan for an Air Conditioner earlier filed in the Korean Industrial Property Office on Sep. 10, 1999, and there duly assigned Serial No.99-38647 by that Office.

[0003] 1. Field of the Invention

[0004] The present invention relates to a cross flow fan, and more particularly to a cross flow fan of an air conditioner capable of reducing noise and vibration produced due to a rotation of the cross flow fan, by the improvement in an arrangement of blades on the cross flow fan.

[0005] 2. Discussion of Related Art

[0006] Generally, a separate type air conditioner includes indoor and outdoor units connected with each other. The indoor unit includes an evaporator and a blower for circulating air. The blower sucks the inside air to pass the same through the evaporator, and discharges the heat-exchanged air back into the room. For the circulation of the indoor air, the blower is coupled with a driving source. i.e. a motor. The separate type air conditioner employs a cross flow fan as a blower for its indoor unit.

[0007] The cross flow fan may have multiple fan blades. The interval between the fan blades is called a fan pitch. In general, the cross flow fans have had considerable noise produced due to the rotation of the cross flow fan. Differing arrangements of the fan blades still produce high noise levels and vibration in the fan even at low frequencies (revolutions per unit of time of the cross flow fan).

[0008] An exemplar of the prior art Hamamoto et al. (U.S. Pat. No. 5,573,059, Air Conditioning Machine, Nov. 12, 1996) shows an air conditioning unit with a cross flow fan next to the heat exchanger. Kawabata et al. (U.S. Pat. No. 5,211,219, Air Conditioner, May 18, 1993) shows an air conditioner with a cross flow fan. Sugawara et al. (U.S. Pat. No. 4,462,750, Electric Fan Assembly, Jul. 31, 1984) discloses a cylindrical cross flow fan designed for use in a heating or cooling system. Chiguchi et al. (U.S. Pat. No. 5,924,923, Air Conditioner Indoor Unit, Jul. 20, 1999) discloses an indoor unit in a separate type air conditioner. Baker et al. (U.S. Pat. No. 5,588,484, Refrigeration Fan System, Dec. 31, 1996) discloses a fan system used in air conditioners or refrigerators. Shinobu et al. (U.S. Pat. No. 5,197,850, Cross Flow Fan System, Mar. 30, 1993) discloses a cross flow type fan having a tongue section.

[0009] I have found that none of the exemplar art discloses a cross flow fan that can reduce the noise and vibration produced due to the rotation of the cross flow fan.

[0010] The present invention has been made to overcome the above mentioned problems of the related art, and accordingly, it is an object of the present invention to provide a cross flow fan of an air conditioner capable of significantly reducing the noise produced due to a rotation of the cross flow fan, vibration produced due to an irregularity in the blade arrangement, and even the noise produced in the low frequency range of the cross flow fan.

[0011] It is another object to have a cross flow fan that can control a high volume of air without affecting the stability of an air conditioning system.

[0012] It is yet another object to have a cross flow fan that is optimally designed to be used in an indoor unit of a separate type air conditioning system.

[0013] It is another object to have a cross flow fan that has reduced noise at a high frequency.

[0014] In order to accomplish the above object, in a cross flow fan of an air conditioner installed in an indoor unit of the air conditioner and having a plurality of blades functioning to circulate an inside air according to the present invention, the multiple blades are divided into multiple blade groups of a uniform number of blades, however, angles between the two neighboring blades in the same blade group are gradually increased, and blade arrangements are consistent throughout all the blade groups.

[0015] In the cross flow fan of the air conditioner according to the present invention, the blade arrangement throughout the blade groups is regular, while the blade arrangement in each blade group is irregular. Accordingly, the noise caused due to the rotation of the cross flow fan is significantly reduced. Further, since the angles between the two neighboring blades in each group are gradually varied in a minimum manner, the noise level in the low frequency range is greatly lowered. Also, since the blades are arranged in a consistent manner throughout all the blade groups, the vibration produced due to the rotation of the cross flow fan and the noise in the low frequency range are significantly reduced. As a result, the noise and vibration characteristics of the cross flow fan in the whole frequency range are significantly improved.

[0016] A more complete appreciation of this invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

[0017] FIG. 1A is a view of a cross flow fan of an air conditioner;

[0018] FIG. 1B is a view of a separate type air conditioner in which the cross flow fan of FIG. 1A is installed;

[0019] FIG. 2 is a view showing the cross flow fan of FIG. 1, viewed from the direction of the rotational axis of the cross flow fan;

[0020] FIG. 3 is a view showing a cross flow fan having random pitch, viewed from the direction of the rotational axis of the cross flow fan;

[0021] FIG. 4 is a view showing a cross flow fan according to the present invention, which is viewed from the direction of the rotational axis of the cross flow fan;

[0022] FIG. 5 is a graph for illustrating the noise level of the cross flow fan of FIG. 2 during its rotation;

[0023] FIG. 6 is a graph for illustrating the noise level of the cross flow fan of FIG. 3 during its rotation; and

[0024] FIG. 7 is a graph for illustrating the noise level of the cross flow fan according to the present invention during its rotation.

[0025] Turning now to the drawings, as seen in FIG. 1B, within an indoor unit 32 the cross flow fan 110 sucks the indoor return air 22 through a grill 24 and then through a filter 16. The air then travels through the evaporator 14. The cross flow fan 10 takes the heat-exchanged air 26 from the evaporator 14 and directs the air 28 toward the air outlet 20. As the air travels from the indoor unit toward the air outlet 20 and the air outlet surface 30, dampers (or vanes) 18 control the air outlet flow 20 that discharges the heat-exchanged air back into the room.

[0026] The structure of such a cross flow fan is shown in FIGS. 1A and 1B. FIG. 1A is a view of a cross flow fan of an air conditioner, and FIG. 1B is a view of a separate type air conditioner in which the cross flow fan 10 of FIG. 1A is installed. As shown in FIGS. 1A and 1B, the cross flow fan 10 includes a plurality of sirocco fans (centrifugal multi-blade fans) 11 connected to each other in the direction of a rotational axis (B-B′), and functions to suck the inside air in a perpendicular direction (indicated by dotted line arrow) with respect to the rotational axis (B-B′) and to discharge the air in an extended direction (solid line arrow) with respect to the direction that the inside air is sucked. Each of the sirocco fans 11 includes a plurality of blades 12. The blades 12 are arranged concentrically on the cross flow fan 10 at a given interval. Accordingly, the respective blades 12 are spaced from the respective neighboring blades 12′ at the central angle of the cross flow fan 10. The intervals between the respective blades 12 are called ‘blade pitches’.

[0027] The blade pitch can be clearly explained with reference to FIGS. 2 to 4, showing the cross flow fan in the direction of the rotational axis (B-B′). Referring to FIGS. 2 to 4, reference symbols ‘B₁, B₂, B₃, . . . , and B_n’ refer to the respective blades, and ‘θ₁, θ₂, θ₃, . . . , and θ_n,’ refer to the respective angles between the respective blades B₁, B₂, B₃, . . . , and B_nand the respective clockwise neighboring blades B₂, B₃, . . . , B_n, and B₁.

[0028] FIGS. 2 and 3 show the blade arrangement on the respective cross flow fans 10aand 10b. First, the cross flow fan 10aof FIG. 2 is called an ‘equal pitch fan’, in which the blades 12 on the cross flow fan 10aare arranged at equal intervals. Accordingly, the relation is expressed by the relational expression of ‘θ₁=θ₂=θ₃= . . . =θ_n’. The equal pitch fan 10aof the cross flow fan, however, has a considerable noise which is produced due to the rotation of the cross flow fan 10a. Meanwhile, the cross flow fan 10bshown in FIG. 3 is called a ‘random pitch fan’, in which the blades are arranged at different intervals. Accordingly, the relation is expressed by a relational expression of ‘θ₁≈θ₂≈θ₃≈ . . . ≈θ_n’. The random pitch fan 10bof the cross flow fan, however, also has a shortcoming in that vibration is produced during its rotation due to an irregularity of the blade arrangement, and the noise is produced even in the low revolution per minute (RPM) range (i.e. low frequency range).

[0029] Suggestions have been made to overcome the above-mentioned shortcomings by combining the arrangements in the equal pitch fan and the random pitch fan. These suggestions, however, have not significantly solved the problems, still confirming a need for reducing the noise and vibration produced by the fan.

[0030] FIG. 4 shows a blade arrangement in a cross flow fan 10cof an air conditioner according to the present invention. The cross flow fan 10cis attached to an indoor unit of the air conditioner, functioning to suck the inside air to pass the same through the evaporator, and discharge the heat-exchanged air back into the room. The cross flow fan 10cis coupled with a driving source, i.e. a motor.

[0031] The blades of the cross flow fan 10caccording to the present invention are divided into several groups of a uniform number of blades. Here, the angles between the respective blades and the respective neighboring blades in the same blade group are gradually increased, while the pattern of the blade arrangement of the respective groups is uniformly formed throughout the cross flow fan 10c.

[0032] Meanwhile, the blades in the respective blade groups are arranged at angles increasing with a uniform increment.

[0033] The number of the blade groups and the number of blades in the respective blade groups are determined to be the two factors having a minimum difference there between, which are selected from all the factors of the total number of the blades in the blade groups. For example, if the total number of blades is thirty-five (35) in the cross flow fan, then the blades can be divided into five (5) groups of seven (7) blades. Likewise, if the total number of blades is thirty-six (36), then the blades can be divided into six (6) groups of six (6) blades. This is useful for adjusting the regularity and irregularity of the blade arrangement.

[0034] Here, the preferred embodiment will be described with reference to FIG. 4 on the assumption that the total number (n) of the blades is thirty-five (35). However, it should be noted that the number of blades is not limited to n=35.

[0035] As shown in FIG. 4, the blades on the cross flow fan 10care divided into five groups consisting of seven (7) blades. More specifically, the groups of blades consist of blades B₁to B₇, B₈to B₁₄, B₁₅to B₂₁, B₂₂to B₂₈, and B₂₉to B₃₅, respectively.

[0036] The blades of the respective groups are positioned at respective angles of θ₁to θ₇, θ₈to θ₁₄, θ₁₅to θ₂₁, θ₂₂to θ₂₈, and θ₂₉to θ₃₅, in a manner that the angles between the respective blades and the respective neighboring blades, the angle between θ₁and θ₂for instance, should be increased in a minimum manner. Also, the pattern of the blade arrangement throughout the cross flow fan is uniformly formed.

[0037] Further, the angles between the respective blades and the respective neighboring blades in each blade group are increased with a uniform increment.

[0038] Thus, the blade arrangement can be expressed by the following relational expressions;

[0039] “θ₁=θ₈=θ₁₅=θ₂₂=θ₂₉”,

[0040] “θ₂=θ₉=θ₁₆=θ₂₃=θ₃₀=θ₁+α”,

[0041] “θ₃=θ₁₀=θ₁₅=θ₂₄=θ₃₁=θ₁+2α”,

[0042] “θ₄=θ₁₁=θ₁₅=θ₂₅=θ₃₂=θ₁+3α”,

[0043] “θ₅=θ₁₂=θ₁₅=θ₂₆=θ₃₃=θ₁+4α”,

[0044] “θ₆=θ₁₃=θ₁₅=θ₂₇=θ₃₄=θ₁+5α”,

[0045] “θ₇=θ₈=θ₁₅=θ₂₈=θ₃₅=θ₁+6α”,

[0046] “θ₁+θ₂+θ₃+θ₄+θ₅+θ₆+θ₇=

[0047] θ₈+θ₉+θ₁₀+θ₁₁+θ₁₂+θ₁₃+θ₁₄=

[0048] θ₁₅+θ₁₆+θ₁₇+θ₁₈+θ₁₉+θ₂₀+θ₂₁=

[0049] θ₂₂+θ₂₃+θ₂₄+θ₂₅+θ₂₆+θ₂₇+θ₂₈=

[0050] θ₂₉+θ₃₀+θ₃₁+θ₃₂+θ₃₃+θ₃₄+θ₃₅=72°”

[0051] “α” can be obtained when the value for “θ₁” is set. Supposing “θ₁” as 10° for instance, “α” is obtained by the relational expression; “θ₁+θ₂+θ₃+θ₄+θ₅+θ₆+θ₇=7θ₁+21α=72°”. 72° is obtained by dividing 360° (angle of a circumference of a circle) by 5 (five groups) equaling 72°. Accordingly, the value of “α” is, “α=2/21≈0.095°”. Also, with expressions of “α=(72−7θ₁)/21>0”, and “θ₁<10.28° (=72°/7)”, “θ₁,” can be obtained. Meanwhile, the lowest value of “θ₁” should be determined considering the fact that the “α” is far less than “θ₁”.

[0052] In the cross flow fan constructed as above according to the present invention, the angle between two neighboring blades in each blade group is gradually varied in a minimum manner, while the angle of the two neighboring blades at the boundary area of the respective groups is varied by a relatively greater degree. In other words, the blade arrangement in each group is irregular, while the blade arrangement in all the groups as a whole is uniform.

[0053] FIGS. 5 to 7 are graphs for illustrating the noise level in accordance with the RPM (frequency in revolutions per minute) of the cross flow fan according to the equal pitch fan, the random pitch fan and the present invention, in which the noise characteristics of the present invention are proven to be superior to the noise characteristics of the equal pitch and random pitch fans. In the respective graphs, the horizontal axis is for frequency (Hz), and the vertical axis is for the Sound Pressure Level (dBA).

[0054] FIG. 5 is a graph for illustrating the Sound Pressure Level (dBA) of the equal pitch fan of the cross flow fan, and FIG. 6 is a graph for illustrating the Sound Pressure Level (dBA) of the random pitch fan of the cross flow fan. As indicated in FIGS. 5 and 6, the sound level is high, mostly ranging from 0 dBA to the maximum of 70 dBA. Particularly, the random pitch fan shows a relatively higher noise level reaching 40 dBA even in the low frequency range.

[0055] In contrast, as shown in FIG. 7, the noise level of the cross flow fan according to the present invention stays within 0 dBA, with the maximum level of 30 dBA.

[0056] As described above, by the characteristic structure of the present invention, the noise and vibration are significantly reduced in comparison with the level of noise and vibration of the equal pitch and random pitch fans.

[0057] In the cross flow fan of the air conditioner according to the present invention, the blade arrangement throughout the blade groups is regular, while the blade arrangement in each blade group is irregular. Accordingly, the noise caused due to the rotation of the cross flow fan is significantly reduced. Further, since the angles between the two neighboring blades in each group are gradually varied in a minimum manner, the noise level in the low frequency range is greatly lowered. Also, since the blades are arranged in a consistent manner throughout all the blade groups, the vibration produced due to the rotation of the cross flow fan and the noise in the low frequency range are significantly reduced. As a result, the noise and vibration characteristics of the cross flow fan in the whole frequency range are significantly improved.

[0058] While the present invention has been particularly disclosed with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be affected therein without departing from the spirit and scope of the invention as defined by the appended claims.