air conditioner

Abstract

To provide a highly quiet air conditioner in which noise levels are reduced to between 2NZ and 3NZ. [Solution] The air conditioner (10) includes a heat exchanger (30) and a crossflow fan (40). The cylindrical crossflow fan (40) is provided with a plurality of impellers (41), each having a plurality of blades (42) arranged in the circumferential direction. The heat exchanger (30) is arranged upstream of the airflow of the crossflow fan (40), with a gap (In) of 20% or less of the diameter of the impeller (41). The plurality of impellers (41) are arranged such that at least one of the plurality of blades of adjacent impellers (41) is misaligned. In the crossflow fan (40), 14 to 30 impellers (41) are arranged along the rotation axis.

Description

[Technical Field]

[0001] The present disclosure relates to an air conditioner, and more particularly to an air conditioner equipped with a crossflow fan. [Background technology]

[0002] It has been known for some time that crossflow fans generate noise (hereinafter referred to as NZ noise) with a frequency equal to the product (N×Z) of the number of rotations per second N and the number of blades Z arranged on the circumference, as explained in Patent Document 1 (Japanese Patent No. 3460350), for example. Hereinafter, the value of N×Z will be referred to as NZ. Furthermore, noise with a frequency that is a multiple of NZ, so-called 2NZ noise to 3NZ noise, is also noise generated by crossflow fans that should be suppressed as much as possible. It is also known that the above-mentioned NZ noise and 2NZ noise become louder as the distance between the crossflow fan and the heat exchanger becomes shorter. Summary of the Invention [Problem to be solved by the invention]

[0003] Therefore, in the crossflow fan described in Patent Document 1, for example, ten impellers of the same shape are arranged in the direction of the rotation axis, and adjacent impellers are shifted in the circumferential direction to provide a phase difference (skew angle) between the impellers. In the crossflow fan of Patent Document 1, one phase difference is made different from the other phase differences to reduce noise and the like.

[0004] However, even the crossflow fan invention described in Patent Document 1 does not show much effect in reducing 2NZ and 3NZ noise.

[0005] An object of the present disclosure is to provide a highly quiet air conditioner in which noise levels between 2 NZ and 3 NZ are reduced. [Means for solving the problem]

[0006] An air conditioner according to a first aspect of the present disclosure comprises a cylindrical crossflow fan having a plurality of impellers with a plurality of blades arranged circumferentially, and a heat exchanger arranged upstream of the air flow of the crossflow fan with a gap of 20% or less of the diameter of the impeller, wherein the plurality of impellers are arranged such that at least one of the plurality of blades of adjacent impellers is misaligned, and the crossflow fan has 14 to 30 impellers arranged along the rotation axis.

[0007] According to the air conditioner pertaining to the first aspect, the noises from 2NZ to 3NZ generated by each impeller are sufficiently cancelled out by each other.

[0008] An air conditioner according to a second aspect of the present disclosure is the air conditioner according to the first aspect, wherein the crossflow fan has 17 to 25 impellers.

[0009] In the air conditioner according to the second aspect, the number of impellers is 17 or more, which reduces the range of noise fluctuations, including 2NZ to 3NZ noise, caused by fluctuations due to tolerances in phase shift (skew angle), etc. Also, since the number of impellers is 25 or less, it is possible to prevent the air flow resistance caused by the partition plates from becoming too large.

[0010] An air conditioner according to a third aspect of the present disclosure is the air conditioner according to the first or second aspect, wherein the crossflow fan has a length dimension in the rotational axis direction of each of the multiple impellers that is 40% or less of the diameter.

[0011] According to the air conditioner pertaining to the third aspect, the length of the crossflow fan can also be shortened, and the length of the air conditioner in the direction of its rotation axis can be shortened.

[0012] An air conditioner according to a fourth aspect of the present disclosure is an air conditioner according to any one of the first to third aspects, wherein the heat exchanger is positioned so that the gap is 10% or less of the diameter.

[0013] According to the air conditioner pertaining to the fourth aspect, it is possible to reduce the space occupied by the heat exchanger and the cross flow fan.

[0014] An air conditioner according to a fifth aspect of the present disclosure is an air conditioner according to any one of the first to fourth aspects, wherein the crossflow fan has an impeller diameter of 90 mm or more and 150 mm or less, and a rotation speed of 700 rpm or more and 2000 rpm or less.

[0015] According to the air conditioner pertaining to the fifth aspect, a sufficient amount of air can be blown by the impeller. [Effects of the Invention]

[0016] The air conditioner according to the first aspect of the present disclosure can suppress noise from 2NZ to 3NZ.

[0017] With the air conditioner according to the second aspect of the present disclosure, it is possible to stably provide an air conditioner that has good air blowing performance and is very quiet.

[0018] In the air conditioner according to the third or fourth aspect of the present disclosure, the air conditioner can be made more compact.

[0019] In the air conditioner according to the fifth aspect of the present disclosure, sufficient air blowing performance can be obtained. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view showing the appearance of an air conditioner according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of the air conditioner of FIG. 1. [Figure 3] FIG. 2 is a partially cutaway plan view showing an impeller of the crossflow fan. [Figure 4] Schematic diagram of one impeller viewed from the direction of the rotation axis. [Figure 5] FIG. 4 is a schematic diagram for explaining skew angles for a plurality of impellers. [Figure 6]FIG. 4 is an enlarged partial cross-sectional view of the impeller and its surroundings for explaining the gap between the impeller and the heat exchanger. [Figure 7] 10 is a graph showing an example of the relationship between frequency and relative decibels when the skew angle is 2.4°. [Figure 8] 10 is a graph showing an example of the relationship between frequency and relative decibels when the skew angle is 3.0°. [Figure 9] 10 is a graph showing an example of the relationship between frequency and relative decibels when the skew angle is 4.5°. [Figure 10] Schematic diagram for explaining a simulation method for comparing sound pressure levels. [Figure 11] 1 is a graph showing an example of the relationship between the skew angle and the relative decibels of noise around 1NZ, noise between 2NZ and 3NZ, and low-frequency noise. [Figure 12] 1 is a graph showing an example of the relationship between the skew angle and the sound pressure level at 2.5 NZ. [Figure 13] Graph showing an example of the relationship between frequency and sound pressure level of noise generated by 20 connected impellers at a skew angle of 3.0°. [Figure 14] 1 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 11 impellers. [Figure 15] 1 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 17 impellers. [Figure 16] 1 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 20 impellers. [Figure 17] 1 is a graph showing an example of the relationship between the relative decibels of noise of different frequencies and the skew angle for eight impellers. [Figure 18] 1 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 11 impellers. [Figure 19] 1 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 14 impellers. [Figure 20]1 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 15 impellers. [Figure 21] 1 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 17 impellers. [Figure 22] 1 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 20 impellers. [Figure 23] 2 is a graph showing an example of the relationship between the relative decibels of noise at different frequencies and the skew angle for 23 impellers. [Figure 24] Graph showing an example of the relationship between the relative decibels of noise around 1 NZ and the skew angle for different numbers of impellers. [Figure 25] 10 is a graph showing an example of the relationship between the relative decibels of noise from 2NZ to 3NZ and the skew angle for different numbers of impellers. [Figure 26] 10 is a graph showing an example of the relationship between relative decibels of low frequency noise and skew angle for different numbers of impellers. [Figure 27] 10 is a graph showing an example of the relationship between the number of impellers and the relative decibels of noise at different frequencies when the skew angle is 3.0°. [Figure 28] 10 is a graph showing an example of the relationship between the skew angle and the absolute value of the sound pressure level of noise, and between the skew angle and the protrusion amount of 2.4 NZ sound. [Figure 29] 10 is a graph showing an example of the relationship between the number of impellers and the absolute value of the sound pressure level of noise, and between the skew angle and the amount of protrusion of 2.4 NZ sound. [Figure 30] 10 is a graph showing an example of the relationship between the number of impellers and the absolute value of the sound pressure level for 1NZ sound and 2NZ sound. [Figure 31] 10 is a graph showing an example of the relationship between the size of the gap and the absolute value of the sound pressure level of the noise, and between the skew angle and the protrusion amount of the 2.4 NZ sound. [Figure 32] 10 is a graph showing an example of the relationship between the frequency contained in noise and the absolute value of the sound pressure level when there is a notch and when there is no notch. [Figure 33]10 is a graph showing an example of actual measurement values ​​of noise for ten impellers with no notches and varying pitches. [Figure 34] 10 is a graph showing an example of actual measurement values ​​of noise for ten impellers with notches and uneven pitches. [Figure 35] 10 is a graph showing an example of actual measurement values ​​of noise for 20 impellers with no notches and varying pitches. DETAILED DESCRIPTION OF THE INVENTION

[0021] (1) Overall structure FIG. 1 shows the appearance of an air conditioner 10 according to one embodiment, attached to a wall WA. The positional relationship of each part of the air conditioner 10 will be explained below using the front-to-back, left-to-right, up-to-down directions indicated by arrows in FIG. 1. The shape of the air conditioner 10 is roughly based on a rectangular parallelepiped that is long in the left-to-right direction. Therefore, the casing 20 also has a shape that is long in the left-to-right direction. The air conditioner 10 is formed with an air outlet 11 that extends long in the left-to-right direction from the bottom surface 20b of the casing 20 to the front surface 20c.

[0022] When the air conditioner 10 is stopped, the air outlet 11 is blocked by one of the two horizontal flaps 13 and the front panel 12. When the air conditioner 10 is in heating or cooling operation, one of the horizontal flaps 13 and the front panel 12 move, and the air conditioner 10 is in a state where the air outlet 11 is open, as shown in FIG.

[0023] Fig. 2 shows the cross-sectional structure of the air conditioner 10 cut along a plane perpendicular to the left-right direction at a location including the air outlet 11. Fig. 2 shows the state in which the air outlet 11 is open, as in Fig. 1. In the air conditioner 10 in the state in which the air outlet 11 is open, the air inlet 15 is opened not only on the top surface 20a but also on the front surface 20c.

[0024] An air filter 16 is installed downstream of the air inlet 15. The system is configured so that substantially all of the indoor air drawn in through the air inlet 15 passes through the air filter 16. Dust is removed from the indoor air by the air filter 16. A heat exchanger 30 is installed downstream of the air filter 16.

[0025] The heat exchanger 30 is a fin-and-tube heat exchanger composed of heat transfer fins 36 made of thin metal plates and heat transfer tubes 37 made of metal tubes. The heat exchanger 30 includes a plurality of heat transfer fins 36 arranged along the left-right direction of the air conditioner 10. A plurality of heat transfer tubes 37 extending in the left-right direction penetrate the heat transfer fins 36, which are included in a plane extending up-down and front-rear. The plurality of heat transfer tubes 37 are connected from the refrigerant inlet to the refrigerant outlet of the heat exchanger 30, and the refrigerant flows through the plurality of heat transfer tubes 37. In the heat exchanger 30, heat exchange occurs between the refrigerant flowing through the plurality of heat transfer tubes 37 and the indoor air passing between the plurality of heat transfer fins 36. The heat exchanger 30 can be divided into a first heat exchange section 31 located in front of the Λ-shaped bent portion, a second heat exchange section 32 located behind the Λ-shaped portion, a third heat exchange section 33 located below the first heat exchange section 31, and a fourth heat exchange section 34 located further below the third heat exchange section 33. The left-right lengths of the first heat exchange section 31, second heat exchange section 32, third heat exchange section, and fourth heat exchange section 34 correspond to the left-right length of the air outlet 11. The distance between the front panel 12 and the third heat exchange section 33 during operation is, for example, approximately 30 mm to 60 mm.

[0026] A plurality of impellers 41 of a crossflow fan 40 are disposed downstream of the heat exchanger 30. The crossflow fan 40 includes a motor (not shown) that drives the plurality of impellers 41. In the air conditioner 10, 20 impellers 41 are connected along the left-right direction. FIG. 3 shows the overall configuration of the 20 impellers 41. In FIG. 3, approximately half of the impeller 41 is cut away at the rotation axis, and a cross section of the impeller 41 is also shown. The total length L1 of the 20 impellers 41 corresponds to the length of the air outlet 11 in the left-right direction. The total length L1 of the impeller 41 is, for example, approximately 500 mm to 1000 mm. The boundary portions 46 between the blades 42 and the partition plates 43 of adjacent impellers 41 are joined by ultrasonic welding, thereby integrating the 20 impellers 41.

[0027] As shown in FIG. 4, each impeller 41 has 35 blades 42 arranged circumferentially. In FIG. 4, dashed lines extending radially from the center of the partition plate 43 indicate reference lines BL for determining the pitch angles Pt1 to Pt35. In a plan view, the reference lines BL pass through the center point (rotation axis) of the outer periphery of the partition plate 43 and are tangent to the outer periphery of each of the blades 42. The pitch angles Pt1 to Pt35 of adjacent blades 42 are not all the same; some are different. For example, the pitch angle Pt35 is greater than the pitch angle Pt1. In the following description, an impeller whose pitch angles Pt1 to Pt35 are all the same is referred to as an even-pitch impeller, and an impeller whose pitch is not even (i.e., an impeller with portions having different pitches) is referred to as an uneven-pitch impeller. These 35 blades 42 are fixed to the partition plate 43. However, the impeller 41 at one end has blades 42 fixed to an end plate 44. A shaft 45 extending along the rotation axis is attached to the end plate 44. The length of each impeller 41 is preferably 50 mm or less, and more preferably 30 mm or less, since 20 impellers can be connected together with a total length L1 of 600 mm.

[0028] Here, the diameter D1 of the crossflow fan 40 (see FIG. 4) is the diameter of the largest circle that passes through the outer circumferential edges of the multiple blades 42, with the rotation axis as the center. Blades 42 have three notches 42a formed on the edge toward the outer circumferential edge. The diameter of a circle that passes through the portion of these notches 42a closest to the rotation axis is the smallest. In other words, diameter D1 of the crossflow fan 40 is the diameter of a circle that passes through a portion of the edge toward the outer circumferential edge of each blade 42 where no notches 42a are formed. For example, when diameter D1 of impeller 41 is 90 mm or more and 150 mm or less, crossflow fan 40 can achieve sufficient air blowing performance if the rotation speed is 700 rpm or more and 2000 rpm or less.

[0029] The blades 42 fixed to the partition plates 43 or end plates 44 extend along the rotation axis. Each impeller 41 is formed, for example, by injection molding, with the 35 blades 42 and the partition plates 43 or end plates 44 being integrally molded. All 20 impellers 41 are arranged at the same pitch angles Pt1 to Pt35. In other words, if the positions of the 35 blades 42 of adjacent impellers 41 are to be aligned in the direction of the rotation axis, the positions of the blades 42 of adjacent 41 can be aligned.

[0030] However, as shown in Fig. 5, a skew angle θ is set in the crossflow fan 40. The skew angle θ is the angle by which the blades 42 of adjacent impellers 41 are misaligned. In this case, the 35 blades 42 of each of the adjacent impellers 41 are joined with a misalignment of θ degrees.

[0031] One location where noise is likely to occur in the impeller 41 is where it is close to the heat exchanger 30. FIG. 6 shows an enlarged view of the area where the heat exchanger 30 and impeller 41 are closest to each other. The smaller the gap In shown in FIG. 6, the greater the noise tends to be. This gap In is the distance from the circle that defines the diameter D1 of the crossflow fan 40 to the heat transfer fins 36 of the heat exchanger 30. Increasing the gap In would reduce noise, but increasing the gap In would increase the depth dp of the air conditioner 10 in the front-to-rear direction. The depth dp of the air conditioner 10 is, for example, 150 mm to 200 mm, which is the sum of the diameter D1 and the thickness of the heat exchanger 30.

[0032] (2) Detailed configuration (2-1) Relationship between skew angle and impeller noise Figures 7, 8, and 9 show the relationship between frequency and relative decibels for a crossflow fan 40 having 20 impellers 41 when the skew angles are different (skew angles of 2.4°, 3.0°, and 4.5°). The graphs shown in Figures 7, 8, and 9 are based on simulations. In this simulation, as shown in Figure 10, a point sound source is assumed at the center of each impeller 41. The sounds generated by these point sound sources are combined at an observation point MP to determine the noise level. Fourier analysis of the resulting noise is then performed to calculate the relative decibels of each frequency order. A phase difference corresponding to the skew angle is added to the sounds generated by the point sound sources of each impeller 41. The observation point MP is located on a perpendicular line passing through the centers of all impellers 41 in the rotational axis direction, a predetermined distance L2 from each impeller 41. Since these simulations were conducted to investigate the tendency of sound pressure levels for each frequency and it was sufficient to be able to compare sound pressure levels, the vertical axes of the graphs in Figures 7, 8, and 9 show relative sound pressure levels (relative decibels). Relative decibels are expressed relative to the sound pressure level of 60 dB when ten uniformly pitched impellers with unnotched blades are connected so that the skew angle is 0°. For example, a relative decibel of 20 dB means that the sound pressure level is 40 dB lower.

[0033] 7, 8, and 9, frequencies are expressed as rotational orders, and the frequency expressed as the first rotational order corresponds to the rotational speed of the crossflow fan 40. For example, if the rotational speed of the crossflow fan 40 is 900 rpm, the frequency is 15 Hz (= 900 rpm / 60 sec). Therefore, in the above case, the frequency expressed as the second rotational order is 30 Hz (= 15 × 2). Also, since each impeller 41 has 35 blades 42, the 35th order frequency is 1 NZ. For example, in the above case, 1 NZ is 525 Hz (= 35 × 900 ÷ 60).

[0034] Because each impeller 41 has an uneven pitch, not only does the sound with the 1NZ frequency (35th order frequency) become louder, but sounds with frequencies around that frequency (for example, 33rd, 34th, 36th, and 37th orders) also tend to become louder. Therefore, to analyze the noise of the uneven pitch impellers 41, it is considered more appropriate to observe sounds with frequencies in a predetermined range around 1NZ, including frequencies close to the 1NZ frequency. In the graphs shown in Figures 7 to 9, noise with frequencies in the range from 32nd to 40th orders is defined as noise around 1NZ.

[0035] 7 to 9, sounds with frequencies lower than the noise around 1NZ are called low-frequency noise. In the graphs shown in Fig. 7 to 9, low-frequency noise is defined as noise consisting of sounds with frequencies below the 28th order. Furthermore, noise between 2NZ and 3NZ is defined as noise consisting of sounds with frequencies from the 70th order to the 110th order.

[0036] FIG. 11 shows an example of the relationship between the relative decibels and the skew angle for noise around 1NZ (graph G1), noise between 2NZ and 3NZ (graph G2), and low-frequency noise (graph G3) when 20 impellers 41 are connected. The graph shown in FIG. 11 was created based on the graphs shown in FIGS. 7 to 9. Graph G2 in FIG. 11 indicates that reducing the skew angle reduces noise between 2NZ and 3NZ. In particular, noise between 2NZ and 3NZ is reduced when the skew angle is 3.0° and 2.4°. In contrast, graph G3 in FIG. 11 indicates that increasing the skew angle is preferable for improving low-frequency noise. In other words, a trade-off relationship can be seen from FIG. 11: reducing the skew angle to improve noise between 2NZ and 3NZ increases low-frequency noise, whereas increasing the skew angle to reduce low-frequency noise increases noise between 2NZ and 3NZ.

[0037] Fig. 12 shows an example of measured values ​​of 2.5 NZ noise when the skew angle is changed for a crossflow fan 40 having 20 impellers 41 and a rotation speed of 900 rpm. Graph G2 in Fig. 11 and the graph in Fig. 12 show a similar tendency in that there is little change between skew angles of 2.5° and 3.0°, and the slope of the graph increases from 3.0° to 3.5°.

[0038] Graphs G11, G12, G13, G14, G15, G16, and G17 in Figure 13 show the relationship between frequency and the absolute value of sound pressure level when a crossflow fan 40 having 20 impellers 41 and a skew angle of 3.0° is used and the rotation speed of the crossflow fan 40 is changed to 1650 rpm, 1500 rpm, 1300 rpm, 1100 rpm, 1000 rpm, 900 rpm, and 800 rpm. Figure 13 shows that the sound pressure level of each frequency decreases as the rotation speed decreases. Looking at graphs G11 to G17 for all rotation speeds, it can be seen that the tendency for sound pressure level to change with frequency is similar.

[0039] Figures 14, 15, and 16 show the relationship between the skew angle and the relative decibels of each frequency. Figures 14, 15, and 16 show graphs for cases where the number of impellers 41 is 11, 17, and 20, respectively, but all conditions other than the number of impellers 41 are set to be the same. Graphs G21, G22, and G23 show the relative decibels of noise around 1 NZ for rotation orders ranging from 30 to 40, graphs G24, G25, and G26 show the relative decibels of noise between 2 NZ and 3 NZ for rotation orders ranging from 75 to 100, and graphs G27, G28, and G29 show the relative decibels of low-frequency noise for rotation orders ranging from 5 to 25. A comparison of graphs G27 to G29 shown in Figures 14, 15, and 16 reveals that even when the number of impellers 41 is changed, it tends to be more difficult to find the point at which the relative decibels of low-frequency noise can be reduced as the skew angle becomes smaller. In contrast, a comparison of graphs G24 to G26 shown in Figures 14, 15, and 16 reveals that the skew angle point at which the noise suddenly increases as the skew angle increases shifts toward larger skew angles as the number of impellers 41 increases. For example, in graph G24, which shows 11 impellers 41, the noise level at 2NZ to 3NZ suddenly increases when the skew angle exceeds 2.7°. In graph G25, which shows 17 impellers 41, the noise level at 2NZ to 3NZ suddenly increases when the skew angle exceeds a certain angle between 2.7° and 3.0°. In graph G26, which has 20 impellers 41, the noise of 2NZ to 3NZ suddenly increases when the skew angle exceeds a certain angle between 3.0° and 3.3°.

[0040] (2-2) Appropriate range of skew angle 17, 18, 19, 20, 21, 22, and 23 show graphs for the cases where the number of impellers 41 is 8, 11, 14, 15, 17, 20, and 23, respectively, and the relative decibel values ​​in these graphs were calculated using the method explained using FIG. 10, as with FIGS. 14 to 16. The length of each impeller 41 was adjusted so that the overall length of the multiple impellers 41 was the same even when the number of impellers 41 was changed, and this adjustment is also used in other graphs for comparing the effects of the number of impellers 41. FIGS. 17 to 23 show the results of examining the setting range of the skew angle where noise around 1 NZ and noise between 2 NZ and 3 NZ can be expected to be reduced by about 25 dB or more using uneven-pitch impellers and a skew angle.

[0041] Graphs G31, G32, G33, G34, G35, G36, and G37 show the relative decibels of noise around 1 NZ, which has a frequency range of 30th to 40th rotational order, when the number of impellers 41 is 8, 11, 14, 15, 17, 20, and 23. Graphs G41, G42, G43, G44, G45, G46, and G47 show the relative decibels of noise around 2 NZ to 3 NZ, which has a frequency range of 70th to 110th rotational order, when the number of impellers 41 is 8, 11, 14, 15, 17, 20, and 23. Graphs G51, G52, G53, G54, G55, G56, and G57 show the relative decibels of low-frequency noise having frequencies in the range of 1st to 20th rotational orders when the number of impellers 41 is 8, 11, 14, 15, 17, 20, and 23. Graphs G61, G62, G63, G64, G65, G66, and G67 show the relative decibels of low-frequency noise having frequencies in the range of 1st to 30th rotational orders when the number of impellers 41 is 8, 11, 14, 15, 17, 20, and 23.

[0042] 17 to 23, the ranges enclosed by rectangular frames are the ranges where the relative decibels of graphs G31 to G37, graphs G41 to G47, graphs G51 to G57, and graphs G61 to G67 are 35 dB or less. When ultrasonically welding multiple impellers 41, a variation of, for example, ±0.3° may occur. In such cases, it is preferable to set the tolerance for the skew angle to, for example, 0.6°, and it has been shown that using 17, 20, or 23 impellers 41 may enable a tolerance of 0.6°.

[0043] Fig. 24 shows graphs G31 to G37 shown in Figs. 17 to 23, Fig. 25 shows graphs G41 to G47 shown in Figs. 17 to 23, and Fig. 26 shows graphs G51 to G57 shown in Figs. 17 to 23. Looking at Fig. 24, when the skew angle changes from a small value to a large value, the relative decibels of all of the graphs G31 to G37 showing noise around 1 NZ fluctuate. However, when the number of impellers 41 is small, the period of the fluctuations is large and the amplitude is also large, but as the number of impellers 41 increases, the period of the fluctuations becomes smaller and the amplitude also becomes smaller. Furthermore, in terms of graphs G31 to G37 as a whole (considering the average value of each graph), there is a tendency for the relative decibels to shift in a direction that decreases as the number increases. For example, looking at graph G31, which shows a case where the number of impellers 41 is eight, the period is about 1.3° (for example, peaks are observed at skew angles of 3.2° and 4.7°), and the amplitude is about 10 dB (for example, the relative decibels are observed to be 40 dB at a skew angle of 3.2°, and the relative decibels are observed to be about 30 dB at skew angles of 3.8° to 3.9°). In contrast, looking at graph G37, which shows a case where the number of impellers 41 is 23, the period is about 0.4° (for example, peaks are observed at skew angles of 3.4° and 3.8°), and the amplitude is about 5 dB (for example, the relative decibels are observed to be about 29 dB at a skew angle of 3.2°, and the relative decibels are observed to be about 24 dB at a skew angle of 3.6°). In this way, by increasing the number of impellers 41, it becomes easier to suppress noise around 1 NZ.

[0044] 25, for noise levels between 2NZ and 3NZ, when the skew angle is between 3.4° and 5.0°, the relative decibels fluctuate around relatively large values, ranging from 40dB to 50dB. In contrast, when the skew angle is between 2.0° and 3.0°, the relative decibels range from 20dB to 40dB and tend to increase as the skew angle increases. Among these graphs G41 to G47, graphs G43 to G47, which show cases where the number of impellers 41 is between 14 and 23, have relative decibels ranging from 20dB to 35dB when the skew angle is between 2.0° and 3.0°. In particular, graphs G45, G46, and G47, which show the cases where the number of impellers 41 is 17, 20, and 23, show relative decibels within the range of 20 dB to 30 dB when the skew angle is in the range of 2.0° to 3.0°.

[0045] 26, low-frequency noises with rotational orders from 1st to 20th tend to have smaller relative decibels as the skew angle increases, regardless of the number of impellers 41. Also, as the number of impellers 41 increases, graphs G51 to G57 tend to shift overall (considering the average value of each graph) in the direction of smaller relative decibels.

[0046] Figure 27 shows the change in relative decibels when the number of impellers 41 is changed while the skew angle is fixed at 3.0°. In Figure 27, graph G71 shows the relative decibels of noise around 1 NZ, which has frequencies ranging from the 30th to the 40th rotational order. Graph G72 shows the change in relative decibels of noise around 2 NZ to 3 NZ, which has frequencies ranging from the 75th to the 100th rotational order. Graph G73 shows the change in relative decibels of noise around 2.5 NZ, which has frequencies ranging from the 75th to the 90th rotational order. Graph G74 shows the change in relative decibels of low-frequency noise, which has frequencies ranging from the 5th to the 25th rotational order. Looking at graphs G71 to G74 in Figure 27, it can be seen that the greater the number of impellers 41, the easier it is to set a lower relative decibel.

[0047] 25 and 26 together, it can be seen that, for the same number of impellers 41, increasing the skew angle is preferable to improve low-frequency noise, but conversely, to improve noise at 2NZ to 3NZ, it is preferable to keep the skew angle to 3.2° or less, and more preferably 3.0° or less. This coincides with the ranges indicated by the rectangular boxes described with reference to FIGS. 17 to 23. For example, when the number of impellers 41 is 14, the skew angle is preferably in the range of 2.7° to 3.1°, when the number of impellers 41 is 15, the skew angle is preferably in the range of 2.5° to 3.0°, when the number of impellers 41 is 17, the skew angle is preferably in the range of 2.2° to 3.2°, when the number of impellers 41 is 20, the skew angle is preferably in the range of 2.0° to 3.2°, and when the number of impellers 41 is 23, the skew angle is preferably in the range of 2.0° to 3.2°. In other words, as can be seen from the graph above, when the number of impellers 41 is 14 or more, the skew angle is preferably in the range of 2.7° to 3.0°, and when the number of impellers 41 is 17 or more, the skew angle is preferably in the range of 2.2° to 3.2°.

[0048] Fig. 28 shows the relationship between the skew angle and the absolute value of the sound pressure level of noise and the prominence of the 2.4 NZ sound when the rotation speed of the impeller 41 is 1100 rpm. In the above-described embodiment in which multiple impellers 41 are connected, the prominence of the 2.4 NZ sound is the sound pressure level at which the 2.4 NZ sound stands out as an abnormal sound above sounds with surrounding frequencies. Graph G75 shown in Fig. 28 shows the change in the sound pressure level of noise when 20 impellers 41 are connected, and graph G76 shows the change in the sound pressure level of noise when 11 impellers 41 are connected. Graph G77 shows the prominence of the 2.4 NZ sound when 20 impellers 41 are connected, and graph G78 shows the prominence of the 2.4 NZ sound when 11 impellers 41 are connected. 28, the 2.4 NZ noise can be reduced by reducing the skew angle within a skew angle range of 2.4° to 3.0° for an air conditioner with 20 impellers 41, and within a skew angle range of 3.0° to 4.5° for an air conditioner with 20 impellers 41. The sound pressure level of the noise was measured by installing the impellers 41 inside the air conditioner 10 and measuring the noise generated by the air conditioner 10. This noise can also be reduced by reducing the skew angle within a skew angle range of 2.4° to 3.0° for an air conditioner with 20 impellers 41, and within a skew angle range of 3.0° to 4.5° for an air conditioner with 20 impellers 41.

[0049] (2-3) Effect of the number of impellers 41 FIG. 27 already explains the change in relative decibels when the number of impellers 41 is changed. Here, FIG. 29 further illustrates an example of the relationship between the number of impellers 41 and the absolute value of the sound pressure level of the noise, and an example of the relationship between the number of impellers 41 and the prominence of the 2.4 NZ sound, for a rotation speed of 1100 rpm. Graph G81 in FIG. 29 shows the change in the absolute value of the sound pressure level of the noise, and graph G82 shows the change in the prominence of the 2.4 NZ sound. In both graphs G81 and G82, there is a tendency for both the sound pressure level and the prominence to decrease as the number of impellers 41 increases. However, there is a tendency for the magnitude of these decreases to become smaller when the number of impellers 41 is 17 or more.

[0050] Fig. 30 shows an example of the relationship between the absolute value of the sound pressure level of NZ sound and the number of impellers. Graph G86 is a graph relating to 1NZ sound, and graph G87 is a graph relating to 2NZ sound. For both 1NZ sound and 2NZ sound, the sound pressure level decreases as the number of impellers 41 increases. In particular, the sound pressure level of 2NZ sound tends to decrease at a smaller rate when the number of impellers 41 is 17 or more.

[0051] (2-4) Effect of the number of impellers 41 Fig. 31 shows an example of the relationship between the gap In and the absolute value of the sound pressure level of noise, and between the gap In and the protrusion amount of 2.4 NZ sound, when the skew angle is 3.0° and the rotation speed is 1100 rpm. The gap In is the distance from the impeller 41 to the heat transfer fins 36, and in Fig. 31, it varies over a range of 5 mm to 20 mm. The data shown here is for a case where the diameter D1 of the impeller 41 is 105 mm. Therefore, Fig. 31 shows data for gap In in a range from approximately 5% to approximately 19% of the diameter D1.

[0052] Graph G91 shown in Fig. 31 shows the change in sound pressure level of noise when 20 impellers 41 are connected, and graph G92 shows the change in sound pressure level of noise when 11 impellers 41 are connected. Graph G93 shows the change in the amount of prominence of the 2.4 NZ sound when 20 impellers 41 are connected, and graph G94 shows the change in the amount of prominence of the 2.4 NZ sound when 11 impellers 41 are connected. Graphs G92 and G94 show that with 11 impellers 41, as the gap In becomes smaller, both the sound pressure level of the noise and the amount of prominence of the 2.4 NZ sound tend to increase, and that both the sound pressure level of the noise and the amount of prominence of the 2.4 NZ sound tend to vary greatly depending on the size of the gap In. In contrast, looking at graphs G91 and G93, with 20 impellers 41, even if the gap In becomes smaller, there is not much change in the sound pressure level of the noise or the prominence of the 2.4 NZ sound, and it can be seen that the range of variation in the sound pressure level of the noise and the prominence of the 2.4 NZ sound depending on the size of the gap In is also small.

[0053] (2-5) Influence of the notch 42a of the blade 42 Fig. 32 shows an example of the relationship between the frequency contained in noise and the absolute value of the sound pressure level for a system having 20 impellers 41, a gap In of 5 mm, a skew angle of 3.0°, and a rotation speed of 1400 rpm. In Fig. 32, graph G101 shows the results of measurements using impellers 41 with notches 42a, and graph G102 shows the results of measurements using impellers 41 without notches 42a. The major difference between graphs G101 and G102 is the amount of protrusion of the 2.4 NZ sound, which is the portion surrounded by an ellipse in Fig. 32. Using impellers 41 with notches 42a reduces the amount of protrusion of the 2.4 NZ sound by about 3 dB compared to using impellers 41 without notches 42a.

[0054] (2-6) Reduction effect of NZ noise Fig. 33 shows the analysis results of actual noise measurements for ten impellers 41 with no notches 42a and variable pitches connected at a skew angle of 4.5°. Fig. 34 shows the analysis results of actual noise measurements for ten impellers 41 with notches 42a and variable pitches connected by appropriately adjusting the skew angle. Fig. 35 shows the analysis results of actual noise measurements for twenty impellers 41 with no notches 42a and variable pitches connected by appropriately adjusting the skew angle. In Figs. 33, 34, and 35, graphs G111 to G118, graphs G121 to G128, and graphs G131 to G138 show the analysis results when the rotation speeds are 1400 rpm, 1300 rpm, 1200 rpm, 1100 rpm, 1000 rpm, 900 rpm, 800 rpm, and 700 rpm, respectively. Comparing the areas surrounded by ellipses in Figures 33, 34 and 35, it can be seen that sounds with frequencies related to NZ have been reduced by doubling the number of notches 42a and impellers 41.

[0055] (3) Variations (3-1) Variation 1A In the above embodiment, by setting a skew angle, all of the corresponding blades 42 of the 35 blades 42 of adjacent impellers 41 are offset. The uneven pitch arrangements of adjacent impellers 41 do not have to be the same; for example, impellers 41 with uneven pitches that are different may be used, and the blades 42 of adjacent impellers 41 may be arranged in the same position. In this way, it is not necessary for all of the corresponding blades 42 of adjacent impellers 41 to be offset from each other; it is sufficient that at least one blade 42 is offset from the adjacent impeller 41.

[0056] (3-2) Variation 1B In the above embodiment, for example, 20 impellers 41 are all connected and integrated into one connected body. However, they do not have to be integrated into one connected body. For example, they may be connected in groups of 10 to form two connected bodies. In this case, the two connected bodies are configured to rotate in conjunction with each other.

[0057] (3-3) Variation 1C In the above embodiment, the air conditioner 10 is described as a wall-mounted type that is attached to a wall WA, but the air conditioner 10 is not limited to a wall-mounted type. For example, the air conditioner 10 may be an air conditioner that is suspended from the ceiling.

[0058] (4) Features (4-1) As described above, the multiple impellers 41 are arranged such that at least one of the multiple blades 42 of adjacent impellers 41 is misaligned. In the above embodiment, the case where the number of impellers 41 is 20 has been mainly described, but if the number of multiple impellers 41 arranged along the rotation axis of the crossflow fan 40 is 14 to 30, the noises from 2NZ to 3NZ generated by each impeller 41 can be sufficiently canceled out. As a result, the noises from 2NZ to 3NZ generated by the crossflow fan 40 can be sufficiently suppressed. As described above, it may be determined that noise from 2 NZ to 3 NZ has been suppressed based on a reduction in sound pressure level in a specific range between 2 NZ and 3 NZ (for example, sounds having frequencies from the 70th to 110th orders (2 NZ to 3 NZ noise) as described above). Alternatively, it may be determined that noise from 2 NZ to 3 NZ has been suppressed based on a reduction in sound pressure level of a sound having a specific frequency within 2 NZ to 3 NZ sounds that is desired to be reduced (for example, the 2.4 NZ and 2.5 NZ sounds as described above). When determining that noise from 2 NZ to 3 NZ has been suppressed based on a reduction in sound pressure level in a specific range between 2 NZ and 3 NZ, the setting of that range may be determined appropriately depending on the situation and is not limited to the example described above. Furthermore, when focusing on sounds having a specific frequency, the frequency of the sound to be focused on may be determined appropriately depending on the situation and is not limited to the example described above.

[0059] (4-2) When the number of impellers 41 is 17 or more, the range of noise fluctuations, including 2NZ to 3NZ noise caused by fluctuations due to tolerances of phase shift (skew angle), is reduced, as explained using Fig. 25. Furthermore, since the number of impellers 41 is 25 or less, it is possible to prevent the air flow resistance caused by the partition plate 43 from becoming too large. As a result, it is possible to stably provide an air conditioner 10 with good air flow performance and high quietness.

[0060] (4-3) If the length dimension of each of the multiple impellers 41 in the rotational axis direction is 40% or less of the diameter D1, the length of the crossflow fan 40 can be shortened, and the length in the rotational axis direction (length in the left-right direction) of the air conditioner 10 can be shortened. With this structure, the air conditioner 10 is made compact.

[0061] (4-4) The heat exchanger 30 is positioned so that the gap In is 10% or less of the diameter D1 of the impeller 41. This structure reduces the space occupied by the heat exchanger 30 and the crossflow fan 40, thereby reducing the depth dp of the air conditioner 10 in the front-to-rear direction and making the air conditioner 10 more compact.

[0062] (4-5) In the above embodiment, the diameter D1 of the impeller 41 is described as 105 mm, but the cross-flow fan 40 can achieve sufficient air blowing performance if the diameter D1 of the impeller 41 is 90 mm or more and 150 mm or less, and the rotation speed is 700 rpm or more and 2000 rpm or less. [Explanation of symbols]

[0063] 10 Air conditioner 20 Casing 30 heat exchanger 36 Heat transfer fin 37 Heat transfer tube 40 Crossflow Fan 41 Impeller 42 Wings 43 Divider [Preliminary Technology Documents] [License]

[0064] [License 1] Patent No. 3460350

Claims

1. a cylindrical cross-flow fan (40) provided with a plurality of impellers (41) each having a plurality of blades (42) arranged in a circumferential direction; a heat exchanger (30) including a first heat exchange section (31), a second heat exchange section (32) disposed behind the first heat exchange section (31), and a third heat exchange section (33) disposed below the first heat exchange section, the heat exchanger (30) being disposed upstream of the air flow of the cross-flow fan; Equipped with The cross-flow fan is disposed at a distance from the third heat exchange section (33) with a gap of 20% or less of the diameter of the impeller, The plurality of impellers are arranged such that at least one of the plurality of blades of adjacent impellers is shifted from one another, the crossflow fan has 17 or more and 25 or less impellers arranged along the rotation shaft, The diameter of the impeller is 90 mm or more and 150 mm or less, The depth (dp) of the air conditioner in the front-to-rear direction is 150 mm or more and 200 mm or less. Air conditioner.

2. The crossflow fan blows air at a rotation speed of 2000 rpm or less. The air conditioner according to claim 1.

3. In the crossflow fan, the length dimension of each of the plurality of impellers in the rotation axis direction is 40% or less of the diameter. The air conditioner according to claim 1 or 2.

4. The heat exchanger is arranged so that the gap is 10% or less of the diameter. The air conditioner according to any one of claims 1 to 3.

5. The cross flow fan has a rotation speed of 700 rpm or more and 2000 rpm or less. The air conditioner according to any one of claims 1 to 4.

Images