Outdoor unit and control method for same

Abstract

Provided is an outdoor unit capable of reducing noise when adjacent propeller fans rotate in the same direction. An outdoor unit (1) comprises: a plurality of fans (7a, 7b) which are arranged in parallel with their rotation axes (C1, C2) parallel to each other, and which rotate in the same direction; heat exchangers (11a, 11b) to which airflows formed by the fans (7a, 7b) are guided; and a control unit that performs control so that the rotational speeds of adjacent fans (7a, 7b) are different. The difference between the rotational speeds of the adjacent fans (7a, 7b) is 30 rpm or more.

Description

Outdoor unit and control method therefor

[0001] The present disclosure relates to an outdoor unit including a propeller fan and a control method therefor.

[0002] For example, an outdoor unit used in an air conditioner includes a plurality of propeller fans arranged in parallel with rotational axes parallel to each other (Patent Document 1). When propeller fans are arranged in parallel as described above, mutual airflows may interfere with each other to generate noise.

[0003] In Patent Document 1, noise is suppressed by setting adjacent propeller fans to rotate in mutually opposite directions.

[0004] Japanese Patent Application Laid-Open No. 2021-14817

[0005] However, Patent Document 1 sets adjacent fans to rotate in mutually opposite directions, and does not propose an effective noise reduction method for an outdoor unit when all the fans rotate in the same direction.

[0006] The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide an outdoor unit and a control method therefor that can reduce noise when adjacent propeller fans rotate in the same direction, respectively.

[0007] The outdoor unit according to one aspect of the present disclosure includes: a plurality of propeller fans arranged in parallel with rotational axes parallel to each other and each rotating in the same direction; a heat exchanger to which airflow formed by each of the propeller fans is guided; and a control unit configured to perform control such that rotational speeds of adjacent propeller fans are different from each other.

[0008] The outdoor unit according to one aspect of the present disclosure includes: a plurality of propeller fans arranged in parallel with rotational axes parallel to each other and each rotating in the same direction; a heat exchanger to which airflow formed by each of the propeller fans is guided; and a control unit configured to perform control so as to obtain a predetermined phase difference at which a leading edge of a blade of one propeller fan and a trailing edge of a blade of the other propeller fan are closest to each other, at a rotation angle where blades of adjacent propeller fans are closest to each other.

[0009] A control method for an outdoor unit according to one aspect of the present disclosure is a control method for an outdoor unit comprising a plurality of propeller fans arranged in parallel with their rotation axes parallel to each other and each rotating in the same direction, and a heat exchanger to which the airflow formed by each of the propeller fans is directed, wherein the rotation speeds of adjacent propeller fans are controlled to be different.

[0010] A control method for an outdoor unit according to one aspect of the present disclosure comprises a plurality of propeller fans arranged in parallel with their rotation axes parallel to each other and each rotating in the same direction, and a heat exchanger to which the airflow formed by each of the propeller fans is guided, wherein the control is performed so that at the rotation angle in which the blades of adjacent propeller fans are closest together, the leading edge of the blade of one propeller fan and the trailing edge of the blade of the other propeller fan are closest together, resulting in a predetermined phase difference.

[0011] This design can reduce noise from outdoor units where adjacent propeller fans rotate in the same direction.

[0012] This is a front view perspective of the outdoor unit according to the first embodiment of this disclosure. This is a rear view perspective of the outdoor unit according to the first embodiment of this disclosure. This is a plan view of the outdoor unit showing the positional relationship between the fan and the heat exchanger. This is a longitudinal cross-sectional view showing the positional relationship between the first fan and the second fan. This is a plan view showing the receiver, accumulator and compressor arranged in the outdoor unit. This is a graph showing the sound pressure level measured for each order of NZ tone in this embodiment. This is a graph showing the sound pressure level measured for each order of NZ tone in this embodiment. This is a graph showing the sound pressure level measured for each order of NZ tone in the comparative example. This is a plan view showing a modified example of Figure 5. This is a plan view showing the phase of the first fan and the second fan in the second embodiment of this disclosure. This is a longitudinal cross-sectional view showing the positional relationship between the first fan and the second fan in Figure 8.

[0013] The embodiments of this disclosure will be described below with reference to the drawings. [First Embodiment] The first embodiment of this disclosure will be described below. The outdoor unit 1 shown in Figure 1 is used, for example, as an outdoor unit for a multi-split air conditioner in a building.

[0014] The outdoor unit 1 is equipped with a roughly rectangular prism-shaped housing 3. Inside the housing 3 are a fan, heat exchanger, compressor, accumulator, receiver, electric motor for driving the fan, other auxiliary equipment, and an electrical box, which will be described later.

[0015] On the upper surface 3a of the housing 3, a circular first air outlet 5a and a second air outlet 5b are formed side by side. A first fan (propeller fan) 7a is positioned below the first air outlet 5a, and a second fan (propeller fan) 7b is positioned below the second air outlet 5b.

[0016] A right opening 9b is formed on the right side 3b of the housing 3. As shown in Figure 2, a rear opening 9c is formed on the rear 3c of the housing 3. A left opening 9d is formed on the left side 3d of the housing 3. Outside air, induced by fans 7a and 7b, is drawn into the housing 3 through the right opening 9b (see Figure 1), the rear opening 9c (see Figure 2), and the left opening 9d (see Figure 2). The outside air drawn into the housing 3 passes through the heat exchangers 11a and 11b shown in Figure 3, and is discharged to the outside through fans 7a and 7b and outlets 5a and 5b formed on the top surface 3a of the housing 3.

[0017] As shown in Figure 3, the first heat exchanger 11a is located below the first fan 7a, and the second heat exchanger 11b is located below the second fan 7b. Each heat exchanger 11a and 11b operates, for example, as a condenser during cooling operation and as an evaporator during heating operation.

[0018] The first fan 7a and the second fan 7b have the same shape and rotate in the same direction (counterclockwise in Figure 3) around the axes (rotation axes) C1 and C2. Each fan 7a and 7b is equipped with three blades 13 and a boss 15 to which each blade 13 is fixed. The number of blades 13 is not limited to three; for example, there may be two or four or more.

[0019] As shown in Figure 4, the wing 13 is a three-dimensional wing, with its leading edge 13a and trailing edge 13b spaced apart in the direction of axes C1 and C2. Each boss 15 is fixed to the shafts of the first electric motor 17a and the second electric motor 17b, respectively, and rotates around axes C1 and C2 by the electric motors 17a and 17b. The rotational speed and phase of each electric motor 17a and 17b are controlled by a control unit (not shown).

[0020] The control unit consists of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in the storage medium in the form of a program, for example. The CPU reads this program into the RAM and performs information processing and calculations to realize the various functions. The program may be pre-installed on the ROM or other storage medium, provided in a state where it is stored on a computer-readable storage medium, or distributed via wired or wireless communication. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memory, etc.

[0021] As shown in Figures 3 and 4, the first fan 7a and the second fan 7b have the same shape, and are arranged in parallel so that their axes C1 and C2 are parallel to each other and their rotational planes are at the same height. The control unit controls the rotational speed of the first fan 7a to be greater than that of the second fan 7b. The rotational speed difference is set to 30 rpm or more, preferably 80 rpm or more. For example, the rotational speed of the first fan 7a is set to 1040 rpm and the rotational speed of the second fan 7b is set to 960 rpm, resulting in a rotational speed difference of 80 rpm. This reduces noise such as humming caused by the fans 7a and 7b. Such a rotational speed difference is set not when the fans 7a and 7b are started or stopped, but for example, when the outdoor unit is operating steadily in each operating mode (cooling operation, heating operation, etc.).

[0022] The refrigerant flow rate to the first heat exchanger 11a, which corresponds to the first fan 7a with a high rotational speed, is set to be greater than the refrigerant flow rate to the second heat exchanger 11b. The refrigerant flow rate is controlled by the control unit using the pulse opening of the electronic expansion valve, etc. By flowing a large amount of refrigerant to the first heat exchanger 11a, which corresponds to the first fan 7a with a high rotational speed and high airflow rate, the amount of heat exchange can be increased.

[0023] As shown in Figure 5, a receiver 19 is positioned below the first fan 7a, which has a high rotational speed, and an accumulator 21 is positioned below the second fan 7b, which has a low rotational speed. Furthermore, a compressor 23 is positioned below the second fan 7b. The receiver 19 stores excess refrigerant during operation. The accumulator 21 temporarily stores liquid refrigerant that has not been vaporized in the evaporator. In this refrigeration cycle system, the size of the receiver 19 is smaller than the size of the accumulator 21. By positioning the smaller of the two receivers 19 and accumulator 21 below the first fan, which has a high rotational speed, the airflow resistance upstream of the first fan 7a, which has a high rotational speed and high airflow rate, is minimized as much as possible.

[0024] Figures 6A and 6B show experimental examples of noise measurements taken from fans 7a and 7b of the outdoor unit 1 with the above configuration. The rotational speed of the first fan 7a is set to 1180 rpm, and the rotational speed of the second fan 7b is set to 1150 rpm. That is, the rotational speed difference is 30 rpm.

[0025] In each figure, the vertical axis represents sound pressure level [dB], and the horizontal axis represents the order of the NZ tone. The NZ tone is the wing-pass frequency defined by the product of rotational speed (N) and the number of blades (Z).

[0026] As shown in Figures 6A and 6B, the sound pressure level remains approximately constant at each NZ order even after 10 measurements at different times. This confirms that the sound pressure level does not change depending on the measurement time, indicating that noise due to resonance is reduced.

[0027] In contrast, as shown in the comparative example in Figure 6C, when the rotation speeds of the first fan 7a and the second fan 7b are set to the same speed (zero rotation speed difference), the sound pressure level differs significantly for each measurement in each order. This means that the sound pressure level changes at each time, and resonance occurs. Furthermore, the sound pressure level in the comparative example is generally higher than that of this embodiment in Figures 6A and 6B in each order.

[0028] The effects and advantages of this embodiment described above are as follows: By making the rotational speeds of adjacent fans 7a and 7b rotating in the same direction different, the change in sound pressure level at each time point can be minimized, thereby reducing resonance. It was confirmed that resonance was reduced by setting the rotational speed difference to 30 rpm or more (see Figures 6A to C).

[0029] Since a large flow rate of air flows through the heat exchanger 11a corresponding to the first fan 7a with a high rotational speed, the amount of heat exchanged is increased by increasing the refrigerant flow rate. On the other hand, the amount of refrigerant flowing through the heat exchanger 11b corresponding to the second fan 7b with a low rotational speed is adjusted to control the overall amount of heat exchanged so as not to decrease.

[0030] To minimize airflow pressure loss, a receiver 19, which has a smaller container size than the accumulator 21, is placed in the flow path upstream of the first fan 7a, which has a high rotational speed and high airflow rate. This improves the performance of the outdoor unit 1. In contrast, since the second fan 7b has a low rotational speed and low airflow rate, an accumulator 21, which has a larger container size than the receiver 19, is placed in the flow path.

[0031] When there is only one compressor 23, it is positioned in the flow path of the second fan 7b, which has a lower rotational speed, as shown in Figure 5. This makes it possible to relatively reduce the airflow pressure loss in the flow path on the first fan 7a side, which has a higher airflow rate.

[0032] When two compressors 23 are provided, they are arranged as shown in Figure 7. That is, a compressor 23 is provided in both the flow path of the first fan 7a, which has a high rotational speed, and the flow path of the second fan 7b, which has a low rotational speed. Even when the two compressors 23 are distributed to the first fan 7a side and the second fan 7b side in this way, a receiver 19 smaller than the accumulator 21 is provided in the flow path of the first fan 7a, which has a high airflow rate, so the airflow pressure loss in the flow path of the first fan 7a can be reduced.

[0033] [Second Embodiment] Next, a second embodiment of the present disclosure will be described with reference to Figures 8 and 9. This embodiment differs from the first embodiment in that the rotational speeds of the first fan 7a and the second fan 7b are the same, but a phase difference is provided; the other configurations are the same. Therefore, the differences from the first embodiment will be described below.

[0034] The control unit sets the rotational speeds of the first fan 7a and the second fan 7b to be the same, and controls them so that a predetermined phase difference is formed for each rotational angle. Specifically, as shown in Figure 8, the control unit controls them so that at the rotational angle in which the blades 13 of adjacent fans 7a and 7b are closest to each other, the leading edge 13a of the blade 13 of the second fan 7b and the trailing edge 13b of the blade 13 of the first fan 7a are closest to each other, resulting in a predetermined phase difference. Here, the "rotational angle in which they are closest" is the 3 o'clock position for the first fan 7a and the 9 o'clock position for the second fan 7b. Therefore, the control unit controls the blades so that at the timing when the leading edge 13a of the blade 13 of the second fan 7b passes the 9 o'clock position, the trailing edge 13b of the blade 13 of the first fan 7a is within a predetermined range that includes the 3 o'clock position.

[0035] By controlling the phase of each fan 7a and 7b in this way, as shown in Figure 9, the distance d between the leading edge 13a and the trailing edge 13b, which affects noise, can be increased in the direction of the axes C1 and C2 when the blades 13 of the fans 7a and 7b are closest to each other. This is because, in propeller fans like fans 7a and 7b, the leading edge 13a is located furthest upstream (lower in Figure 9) on the axes C1 and C2, and the trailing edge 13b is located furthest downstream (upper in Figure 9) on the axes C1 and C2. By increasing the distance between the leading edge 13a and the trailing edge 13b in this way, noise caused by interference between the two blades can be reduced as much as possible.

[0036] As shown in Figure 8, the phase difference set by the control unit does not mean only the rotation angle at which the leading edge 13a and the trailing edge 13b are closest when viewed from above (i.e., phase difference 0), but any phase difference within a predetermined range that can reduce noise is acceptable. Specifically, as shown in Figure 8, when the leading edge 13a of the second fan 7b is at the rotation angle (9 o'clock position) at which it is closest to the first fan 7a, the position at which the rotation angle of the trailing edge 13b of the first fan 7a is closest to the leading edge 13a of the second fan 7b is defined as the first angular position (3 o'clock position) p1. The phase difference is controlled so that the angular range α1 is from this first angular position p1 to the second angular position p2, which is located further away in the direction of the leading edge 13a of the same blade 13 (counterclockwise direction). This angular range α1 is defined as the same angle α as the angle α2 formed around the axis C1 between the first angular position p1 and the third angular position p3 at the leading edge 13a of another wing 13 located adjacent to it across the gap in the first fan 7a. That is, α1 = α2.

[0037] In the embodiments described above, an outdoor unit 1 with two fans 7a and 7b was explained, but the number of fans is not limited to two; it may be three or more.

[0038] The outdoor unit and its control method described in each embodiment above can be understood, for example, as follows.

[0039] An outdoor unit (1) according to a first aspect of the present disclosure includes a plurality of propeller fans (7a, 7b) arranged in parallel, wherein rotation axes (C1, C2) of the propeller fans are parallel to each other and the propeller fans respectively rotate in the same direction, heat exchangers (11a, 11b) to which airflows formed by the respective propeller fans are guided, and a control unit that controls rotation speeds of adjacent propeller fans to be different from each other.

[0040] By making the rotation speeds of adjacent propeller fans different from each other, changes in noise at each time can be reduced as much as possible, thereby reducing resonance. The control unit controls the rotation speeds of the propeller fans to be different from each other not during starting or stopping, for example, when performing steady operation in each operation mode of the outdoor unit. Note that the number of propeller fans is not limited to two, and may be three or more.

[0041] An outdoor unit according to a second aspect of the present disclosure, in the first aspect, a difference in rotation speed between the adjacent propeller fans is set to 30 rpm or more.

[0042] Beat noise can be reduced by setting the difference in rotation speed to 30 rpm or more. More preferably, the difference in rotation speed is 80 rpm or more.

[0043] An outdoor unit according to a third aspect of the present disclosure, in the first aspect or the second aspect, a flow rate of refrigerant flowing through the heat exchanger corresponding to the propeller fan with a higher rotation speed is larger than a flow rate of refrigerant flowing through the heat exchanger corresponding to the propeller fan with a lower rotation speed.

[0044] Since a large flow rate of airflow flows through the heat exchanger corresponding to the propeller fan with a higher rotation speed, a heat exchange amount can be increased by increasing the refrigerant flow rate. On the other hand, the refrigerant flow rate flowing through the heat exchanger corresponding to the propeller fan with a lower rotation speed is adjusted, so that control is performed such that the overall heat exchange amount does not decrease.

[0045] An outdoor unit according to a fourth aspect of the present disclosure, in any one of the first to third aspects, comprises: a receiver (19) that temporarily stores liquid refrigerant liquefied by a condenser; and an accumulator (21) that separates liquid refrigerant from gas refrigerant vaporized by an evaporator and temporarily stores the separated liquid refrigerant, wherein the receiver or the accumulator having a smaller container size is disposed in an airflow channel formed by the propeller fan having a higher rotation speed, and the accumulator or the receiver having a larger container size is disposed in an airflow channel formed by the propeller fan having a lower rotation speed.

[0046] Even when the receiver or accumulator having a smaller container size is disposed in the flow path of the propeller fan that has a higher rotation speed and a larger airflow flow rate, the air duct pressure loss can be reduced as much as possible. Thereby, the performance of the outdoor unit can be improved.

[0047] An outdoor unit according to a fifth aspect of the present disclosure, in the fourth aspect, comprises two propeller fans, and one compressor (23) that sucks and compresses the gas refrigerant separated by the accumulator, wherein the receiver or the accumulator having a smaller container size is disposed in an airflow channel formed by the propeller fan having a higher rotation speed, and the accumulator or the receiver having a larger container size and the compressor are disposed in an airflow channel formed by the propeller fan having a lower rotation speed.

[0048] The receiver or accumulator having a smaller container size is disposed in the flow path of the propeller fan having a higher rotation speed, and the single compressor is disposed in the flow path of the propeller fan having a lower rotation speed. Thereby, the air duct pressure loss in the flow path having a larger airflow flow rate can be reduced.

[0049] In the sixth aspect of the present disclosure, the outdoor unit has two propeller fans and two compressors that suck in and compress the gaseous refrigerant separated by the accumulator. The receiver or accumulator and one of the compressors are arranged in the airflow path formed by the propeller fan with a high rotational speed, and the accumulator or receiver and one of the compressors are arranged in the airflow path formed by the propeller fan with a low rotational speed.

[0050] When two compressors are installed, one compressor is placed in the airflow path of the high-speed propeller fan and another in the airflow path of the low-speed propeller fan. This reduces the airflow pressure loss in the airflow path with a high airflow rate.

[0051] An outdoor unit according to a seventh aspect of the present disclosure comprises a plurality of propeller fans arranged in parallel with their rotation axes parallel to each other and each rotating in the same direction; a heat exchanger to which the airflow formed by each of the propeller fans is directed; and a control unit that controls the rotation angle at which the blades of adjacent propeller fans are closest together, so that the leading edge of one propeller fan blade and the trailing edge of the other propeller fan blade are closest together, resulting in a predetermined phase difference.

[0052] A propeller fan is a three-dimensional wing with different axial positions for its leading and trailing edges, so the leading and trailing edges are spaced apart in the axial direction. Therefore, at the rotation angle in which the blades of adjacent propeller fans are closest together, the phase difference between the leading edge of one propeller fan's blade and the trailing edge of the other propeller fan's blade is set to be the closest. This increases the axial distance between the leading and trailing edges, which affect noise, when the blades of the two propeller fans are closest together, thereby reducing noise. The "rotation angle in which they are closest together" refers to the angle in which, for example, when viewing two propeller fans from above, the rotation angle of the left propeller fan's blade is at the 3 o'clock position and the rotation angle of the right propeller fan's blade is at the 9 o'clock position. The "predetermined phase difference" does not only refer to the rotation angle in which the phase difference is closest (i.e., phase difference of 0), but also to a predetermined range of phase differences in which noise can be reduced.

[0053] In the eighth aspect of the present disclosure, the outdoor unit, in the seventh aspect, is defined as a range from a first angular position (p1) where the rotation angle of the trailing edge of the blade of one propeller fan is closest to the other propeller fan when the leading edge of the blade of one propeller fan is at the rotation angle closest to the one propeller fan, to a second angular position (p2) which is separated from the first angular position by an angle corresponding to the angle around the rotation axis at which the leading and trailing edges of adjacent blades separated by a gap in the rotational direction of the other propeller fan are separated from each other.

[0054] By setting the predetermined phase difference within the above range, noise can be reduced.

[0055] A control method for an outdoor unit according to a first aspect of the present disclosure is a control method for an outdoor unit comprising a plurality of propeller fans arranged in parallel, with their rotation axes parallel to each other and rotating in the same direction, and a heat exchanger to which the airflow formed by each of the propeller fans is directed, wherein the rotation speeds of adjacent propeller fans are controlled to be different.

[0056] A control method for an outdoor unit according to a second aspect of the present disclosure comprises a plurality of propeller fans arranged in parallel with their rotation axes parallel to each other and each rotating in the same direction, and a heat exchanger to which the airflow formed by each of the propeller fans is guided, wherein the control is performed so that at the rotation angle in which the blades of adjacent propeller fans are closest together, the leading edge of the blade of one propeller fan and the trailing edge of the blade of the other propeller fan are closest together, resulting in a predetermined phase difference.

[0057] 1 Outdoor unit 3 Housing 3a Top view 3b Right side view 5a First air outlet 5b Second air outlet 7a First fan (propeller fan) 7b Second fan (propeller fan) 9b Right opening 9c Rear opening 9d Left opening 11a First heat exchanger 11b Second heat exchanger 13 Blades 13a Leading edge 13b Trailing edge 15 Boss 17a First electric motor 17b Second electric motor 19 Receiver 21 Accumulator 23 Compressor C1 Axis (rotation axis) C2 Axis (rotation axis) p1 First angular position p2 Second angular position p3 Third angular position

Claims

1. An outdoor unit comprising: a plurality of propeller fans arranged in parallel with their rotation axes parallel to each other and each rotating in the same direction; a heat exchanger to which the airflow formed by each of the propeller fans is directed; and a control unit that controls the rotation speeds of adjacent propeller fans to be different.

2. The outdoor unit according to claim 1, wherein the difference in rotational speed between adjacent propeller fans is 30 rpm or more.

3. The outdoor unit according to claim 1 or 2, wherein the refrigerant flow rate to the heat exchanger corresponding to the propeller fan with a high rotational speed is greater than the refrigerant flow rate to the heat exchanger corresponding to the propeller fan with a low rotational speed.

4. An outdoor unit according to claim 1 or 2, comprising: a receiver for temporarily storing liquid refrigerant liquefied in a condenser; and an accumulator for separating liquid refrigerant from gaseous refrigerant vaporized in an evaporator and temporarily storing the liquid refrigerant, wherein the receiver or accumulator, having a small container size, is positioned in the airflow path formed by the propeller fan with a high rotational speed, and the accumulator or receiver, having a large container size, is positioned in the airflow path formed by the propeller fan with a low rotational speed.

5. The outdoor unit according to claim 4, wherein the outdoor unit comprises two propeller fans, one compressor that sucks in and compresses the gaseous refrigerant separated by the accumulator, the receiver or accumulator with a small container size is arranged in the airflow path formed by the propeller fan with a high rotational speed, and the accumulator or receiver with a large container size and the compressor are arranged in the airflow path formed by the propeller fan with a low rotational speed.

6. The outdoor unit according to claim 4, wherein the propeller fan is provided with two, and the unit comprises two compressors that suck in and compress the gaseous refrigerant separated by the accumulator, and the receiver or accumulator with a small container size and one of the compressors are arranged in the airflow path formed by the propeller fan with a high rotational speed, and the accumulator or receiver with a large container size and one of the compressors are arranged in the airflow path formed by the propeller fan with a low rotational speed.

7. An outdoor unit comprising: a plurality of propeller fans arranged in parallel with their rotation axes parallel to each other and each rotating in the same direction; a heat exchanger to which the airflow formed by each of the propeller fans is directed; and a control unit that controls the rotation angle at which the blades of adjacent propeller fans are closest together, so that the leading edge of one propeller fan blade and the trailing edge of the other propeller fan blade are closest together, resulting in a predetermined phase difference.

8. The outdoor unit according to claim 7, wherein the predetermined phase difference is within a range from a first angular position where the leading edge of the blade of one propeller fan is at the rotational angle closest to the other propeller fan, to a second angular position which is separated from the first angular position by an angle in the direction of the leading edge of the blade by an angle corresponding to the angle around the rotational axis at which the leading and trailing edges of adjacent blades separated by a gap in the rotational direction of the other propeller fan are separated from each other.

9. A control method for an outdoor unit comprising: a plurality of propeller fans arranged in parallel with their rotation axes parallel to each other and each rotating in the same direction; and a heat exchanger to which the airflow formed by each of the propeller fans is directed, wherein the control method for an outdoor unit is configured such that the rotation speeds of adjacent propeller fans are different.

10. A control method for an outdoor unit comprising: a plurality of propeller fans arranged in parallel with their rotation axes parallel to each other and each rotating in the same direction; and a heat exchanger to which the airflow formed by each of the propeller fans is directed, wherein the control method for an outdoor unit is such that, at the rotation angle in which the blades of adjacent propeller fans are closest together, the leading edge of the blade of one propeller fan and the trailing edge of the blade of the other propeller fan are closest together, resulting in a predetermined phase difference.

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