JP2000356362A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the fluctuation of periodical noise generated by two sets of centrifugal impellers installed in a rectangular easing. SOLUTION: An air conditioner is provided with an air suction grille 12, attached to a decorative panel on the front surface of a rectangular easing 1, a filter 13, attached to the rear surface of the grille 12, a plurality of bell mouths 8, installed in the casing 1 while facing the opening of the same to the rear surface of the filter 13, a plurality of centrifugal impellers 5-1, 5-2, installed at the rear side of respective bell mouths and driven by motors, a U-shape heat exchanger, installed so as to surround the plurality of centrifugal impellers in parallel, an air discharging flow passage 17 and an air outlet port formed on the decorative panel. In such an air conditioner, the number of revolution per min. N1rpm of one of the plurality of centrifugal impellers and that N2rpm of the other centrifugal impeller are controlled so as to achieve the relation of N1>=N2+30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner provided with a centrifugal impeller, a U-shaped heat exchanger, and the like in a rectangular casing, and more particularly to a flow of air sucked in the casing by the centrifugal impeller. The present invention relates to an air conditioner suitable for reducing noise generated by air conditioners.

[0002]

2. Description of the Related Art In recent years, indoor air conditioners have been required to be downsized while maintaining the same air volume, and accordingly, the fan diameter has tended to decrease and the fan speed has tended to increase. For this reason, in an air conditioner having a rectangular casing, a wind speed distribution occurs near the intake port due to asymmetry with respect to the air flow at the intake port on the front face of the casing, and periodic noise is a problem.

FIG. 10 shows a basic configuration of a conventional indoor air conditioner having two centrifugal blowers in a rectangular housing. This air conditioner has a substantially rectangular casing 1 and a suction grill 1 attached to a decorative panel 11 attached to the front face of the casing 1.
2, a dust collecting filter 13 attached to the rear surface (inner surface) of the suction grill 12, and two bell mouths 8 which are opened in parallel to the inner surface of the dust collecting filter 13 and installed in parallel;
It is composed of two centrifugal impellers 5 installed behind each bell mouth 8 and driven by a motor, and a U-shaped heat exchanger 2 surrounding the two centrifugal impellers 5, and the U-shaped heat exchanger 2 and a housing 1
And the space having a U-shaped cross section formed between
The decorative panel 11 has two air outlets 15. The air outlet 15 is provided with a louver. The opening at the U-shaped top of the U-shaped heat exchanger 2 is covered with a connecting plate 3. The connecting plate 3 divides the inside of the housing 1 into a room for accommodating the U-shaped heat exchanger 2 and a machine room 10.

In such an air conditioner, a blower 4
The grill 12 of the decorative panel 11 and the filter 14
The wind (air) 16 sucked from the suction port 14 made of
It is collected by the bell mouth 8, enters the centrifugal impeller 5, is pressurized, passes through the heat exchanger 2, and is discharged from the outlet 15 of the decorative panel 11 through the discharge channel 17 of the housing 1. Here, FIG. 10 shows one of the indoor air conditioners using two centrifugal impellers.
For example, a partition plate 18 for preventing interference between the flows of the two fans is provided. The rotation directions of the two fans are the same and are indicated by arrows 19. Conventionally, when a circular blower 4 is installed in a rectangular housing, the flow of air tends to be non-uniform around the bell mouth 8. In addition, since the same thing is used for the motor and the control board for driving from the point of emphasizing cost, there is a disadvantage that the fundamental frequencies of the periodic noise match because the rotation speeds of a plurality of centrifugal impellers are the same.

[0005] Here, the result of measuring the wind speed distribution by using an air conditioner having one blower is shown in FIG.
This will be described below. The air conditioner having one blower shown in FIG. 11A has the same basic configuration as the device shown in FIG.
The size is reduced to one blower. As shown in FIG.
There is a difference of about 22% in the circumferential direction at each position in the circumferential direction of the centrifugal impeller 5 at the suction port of the centrifugal impeller 5, and as shown in FIG. There was a circumferential wind speed difference of about 28% at each position.
This difference in the velocity distribution is presumed to be one of the causes due to the fluctuation of the periodic noise.

Since the fluid noise is proportional to the sixth power of the rotational speed, the absolute value of the periodic noise generated in the centrifugal impeller 5 and the fluctuation of the target frequency itself tend to be large. FIG.
FIG. 12 shows a result of analyzing a noise frequency in a rectangular housing of the air conditioner having one blower shown in FIG. This indicates that sharp peak frequencies from the first to fourth order are generated in the low frequency region.

FIG. 13 schematically shows a sound wave having a periodic noise frequency when two centrifugal impellers 5 are driven at the same rotation speed in an air conditioner having two blowers. 14 is a schematic diagram when one centrifugal impeller 5 is driven at the same rotational speed as above. From these figures, it can be seen that when two centrifugal impellers are driven, the amplitude of the sound wave is twice as large as that of one. Since the fluctuation and the amplitude of the periodic noise are large, the blowing noise is extremely unpleasant in hearing.

Conventionally, in order to reduce the periodic noise of the impeller (fan), for example, the pitch between the blades of the fan is made unequal, the diameter of the fan, the number of fans, the mounting angle, the number of revolutions of the fan, the blade shape are reduced. And so on to reduce the periodic noise of the fan. However, it is difficult to reduce the noise effectively only with these means. Therefore, according to the method disclosed in Japanese Patent Application Laid-Open No. 3-43699, the number of rotations of the fan is first detected in order to reduce the periodic noise of the fan. An active type in which a pure tone having the same frequency as the periodic noise caused by the rotation speed is generated by a speaker, and the amplitude and phase of this pure tone are manually or automatically adjusted and superimposed on the periodic noise to mute the periodic noise. Has been proposed.

[0009]

In an air conditioner having a rectangular housing, the fluctuation of the periodic noise is caused by the change in the circumferential velocity distribution of the flow at the suction port 14 unique to the rectangular housing as shown in FIG. This is due to the coincidence of the fundamental frequencies of the periodic noise caused by the bias and the impellers having different workloads being driven at the same rotation speed.

When the above-mentioned active type silencer is used to reduce the periodic noise, the system becomes complicated and the size of the device becomes large, which leads to an increase in cost. In addition, it is very difficult to mount the silencer due to the downsizing of the housing. . Therefore, an object of the present invention is to provide an air conditioner that can reduce the noise generated by a centrifugal impeller installed in a rectangular casing, particularly the fluctuation of periodic noise, at low cost.

[0011]

To achieve the above object, an air conditioner according to the present invention comprises an air intake grill attached to a decorative panel provided on a front surface of a rectangular casing, and an air intake grille. A dust collection filter attached to the rear surface, a plurality of bellmouths arranged in the longitudinal direction of the housing with the opening facing the rear surface of the filter, and a plurality of motor-driven units installed behind each bellmouth. A centrifugal impeller, a heat exchanger installed to surround the plurality of centrifugal impellers from three sides of two long sides and one short side of a rectangular casing; and a heat exchanger and the casing. In an air conditioner having an air discharge passage formed between the air discharge passage and an air outlet formed in a decorative panel and connected to an air discharge passage, a plurality of centrifugal impellers are provided with a difference in rotation speed by a predetermined value or more. It is characterized by driving control.

In the above air conditioner, one of the plurality of centrifugal impellers has a rotation speed of N ₁ rpm and the other has a rotation speed of N ₂ r.
When pm is set, it is preferable to control so that N ₁ ≧ N ₂ +30. By shifting the fundamental frequencies of the impellers in this manner, the fluctuation of the periodic noise is reduced.

Further, another air conditioner of the present invention includes an air intake grill attached to a decorative panel provided on a front surface of a rectangular housing, and a dust collection filter attached to a rear surface of the grill. A plurality of bellmouths arranged in the longitudinal direction of the housing with the opening facing the rear surface of the filter, a plurality of centrifugal impellers installed behind each bellmouth and driven by a motor, and the plurality of centrifugal blades A heat exchanger installed so as to surround the car from three sides of two long sides and one short side of a rectangular casing, and the heat exchanger covers an opening on one side other than the three sides. And a connecting plate for partitioning a chamber for accommodating the heat exchanger from inside the housing, an air discharge passage formed between the heat exchanger and the housing, and an air discharge passage formed in the decorative panel. An air conditioner with a connected air outlet Of the plurality of centrifugal impellers, the rotation direction of the centrifugal impeller in the direction of the connecting plate from the position where the distance between the outer periphery of the centrifugal impeller on the connecting plate side of the heat exchanger and the inner wall of the heat exchanger is minimum A flat resistor is provided between the filter and the grill corresponding to the front area. This resistor improves the speed distribution at the suction port composed of the grill and the filter, and reduces the fluctuation of the periodic noise radiated from the centrifugal impeller.

In the above other air conditioner, instead of providing a flat resistor between the filter and the grill, the resistance of the filter portion located on the connecting plate side of the heat exchanger from an intermediate position between the plurality of centrifugal impellers. Is made larger than the resistance of the other filter portions, the fluctuation of the periodic noise radiated from the centrifugal impeller can also be reduced.

[0015] Still another air conditioner of the present invention is:
A grill for air suction attached to the decorative panel provided on the front of the rectangular casing, a filter for dust collection attached to the rear of the suction grill, and one of the filters installed with the opening facing the rear of the filter A bellmouth, one centrifugal impeller installed behind the bellmouth and driven by a motor, and the centrifugal impeller is connected to two long sides of a rectangular casing and 1
A U-shaped heat exchanger installed so as to surround the three short sides from three sides, and a lid that covers the U-shaped top of the heat exchanger,
A connecting plate for partitioning a chamber for housing the heat exchanger from the inside of the housing, an air discharge passage formed between the heat exchanger and the housing, and an air outlet formed in the decorative panel and connected to the air discharge passage. In the air conditioner provided with, the distance between the outer periphery of the centrifugal impeller and the inner wall of the heat exchanger corresponds to the region in the direction of the connecting plate of the heat exchanger and the rotation direction front of the centrifugal impeller. A flat resistor is provided between the filter and the grill. This resistor improves the velocity distribution at the suction port and reduces the fluctuation of the periodic noise radiated from the centrifugal impeller.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An air conditioner according to an embodiment of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a diagram showing a configuration of an indoor unit in which two centrifugal impellers are arranged in a housing as an air conditioner according to Embodiment 1, and FIG. FIG. 1B is a view taken in the direction of arrows BB in FIG. 1A, and FIG. 1C is a view taken in the direction of arrows AA in FIG.

This air conditioner has a generally rectangular housing 1.
And a suction grill 12 attached to a decorative panel 11 attached to the front of the housing 1 and sucking air from the front.
A dust-collecting filter 13 attached to the rear surface (inner surface) of the suction grill 12; and two ring-shaped bellmouths that are open in parallel with the inner surface of the dust-collecting filter 13 and taper rearward. 8, two centrifugal impellers 5 installed behind the bellmouths 8 with the center axis and the rotation axis of the bellmouths 8 aligned with each other and driven by a motor, and the two centrifugal impellers 5 in a rectangular casing. Two long sides and one short side of
And a heat exchanger 2 surrounding the heat exchanger 2, and a space having a U-shaped cross section formed between the U-shaped heat exchanger 2 and the housing 1 accommodating the heat exchanger 2. The decorative panel 11 has two air outlets 15 corresponding to two U-shaped pillars of the air discharge flow path 17. The two centrifugal impellers 5 (referred to as 5-1 and 5-2) and the motors 6 and 6 constitute centrifugal blowers 4-1 and 4-2. The air outlet 15 is formed so as to sandwich the suction grill 12 and is provided with a louver. The suction grill 12 and the dust collecting filter 13 are detachably attached. Also, the two centrifugal impellers 5 are used for the partition plate 1.
It is divided by eight. Under the heat exchanger 2 is a water receiver 7
The opening of the U-shaped top, which is the other side of the three sides of the U-shaped heat exchanger 2, is covered with a connecting plate 3.
The connecting plate 3 divides the inside of the housing 1 into two rooms, one of which houses the U-shaped heat exchanger 2, and the other of which is a machine room 10. An electric box 9 is installed in the machine room 10.

When the blower 4 is driven, the decorative panel 1
The wind (air) 16 sucked from the suction port 14 of the first case 1 is collected by the bell mouth 8 and enters the impeller 5, where it is pressurized and passes through the heat exchanger 2, Through the outlet 15 of the decorative panel 11.

Here, the two centrifugal impellers 5-1 and 5-2 are
The control is performed so as to provide a rotation speed difference under the condition that the fluctuation amount of the periodic noise shown in FIG. 2 is small. The condition is that the rotation speed of one of the two centrifugal impellers, for example, the centrifugal impeller 5-1 is N ₁
rpm and that of the centrifugal impeller 5-2 as N ₂ rpm, N ₁ ≧
N ₂ +30. The rotation speed is changed by setting different values for the capacitors 23 and 24 for controlling the rotation speeds of the centrifugal impellers 5-1 and 5-2 in the control circuit housed in the electric box 9.

FIG. 2 shows changes in the fundamental frequency of the periodic noise from the first to the third order when the left and right centrifugal impellers 5 are differentiated from the same rotation speed in the air conditioner shown in FIG. This is the result of graphing the amount. The sound pressure level of the periodic noise NZ1 at the fundamental frequency is about 6 dB when there is no rotational speed difference between the two centrifugal impellers, is constant until the rotational speed difference is close to 40 rpm, and decreases after that. The change in the sound pressure level of the periodic noise NZ2 at the secondary frequency is about 16 dB when there is no difference in the rotation speed between the two centrifugal impellers, and decreases as the difference in rotation speed increases. Become. The change in the sound pressure level of the periodic noise NZ3 at the third frequency is about 8 dB when there is no difference in the rotation speed between the two centrifugal impellers, and decreases as the difference in the rotation speed increases. Becomes Conventionally, since both centrifugal impellers were operated without a difference in rotational speed, the amount of change in periodic noise in the first to third orders was large.

Here, the periodic noise NZ (dB) is obtained by the following equation.

[0022]

(Equation 1)

FIG. 3 is a temporal schematic diagram of the sound wave waveform of the periodic noise when the two centrifugal impellers 5-1 and 5-2 are driven under the condition that the rotational speeds are different from each other. From this, it can be seen that the amplitude and cycle of the impeller 5-2 are smaller than those of the impeller 5-1. FIG. 4 shows a synthesis result of the sound waves shown in FIG. FIG. 13 described above in which two impellers are driven identically
It can be seen that the amplitude is smaller than that shown in FIG.

<Embodiment 2> FIG. 5 shows the periodicity of mutual centrifugal impellers 5 when two centrifugal impellers 5 are driven at the same rotational speed with the same configuration as the air conditioner shown in FIG. Fig. 3 shows one means for preventing noise interference, and a partition plate 1 is provided so as to isolate two centrifugal impellers in a U-shaped heat exchanger 2.
8 is provided. Conventionally, as shown in FIG. 10, the partition plate 18 is reduced to about half in the height direction of the housing from the pressure balance surface of the flow in the housing 1. However, in the present invention, the interference between the two centrifugal impellers is prevented. As the main focus, the partition plate 18 is
It was provided in the whole height direction.

<Embodiment 3> FIG. 6 is a view showing another means for reducing the fluctuation of periodic noise in an air conditioner having one centrifugal impeller 5 in a rectangular casing. This is to reduce the fluctuation of the periodic noise by changing the state of the suction flow on the upstream side of the bell mouth 8. That is, at the position where the outer diameter of the U-shaped heat exchanger 2 and the outer diameter of the centrifugal impeller are closest, the U-shaped heat exchanger 2
In this example, a guide 21 as a flat resistor is provided between the grill 12 and the filter 13 on the side of the connecting plate 3 at the top of the U-shape and in front of the wind generated by the centrifugal impeller 5. The circumferential velocity distribution of the suction flow between the connecting plate 3 and the circumferential direction of the centrifugal impeller from the position where the distance between the heat exchanger 2 and the heat exchanger 2 becomes the smallest by the guide 21 is not shown here.
What was about 0% was reduced to about 12.5%. As a result, the fluctuation of the periodic noise can be reduced.

<Embodiment 4> FIG. 7 shows an air conditioner provided with two centrifugal impellers 5-1 and 5-2, in which the outer periphery of the centrifugal impeller 5-2 on the connecting plate 3 side and the U-shape are shown. Between the grill 12 and the filter 13 in the direction of the connecting plate 3 and in the direction of rotation of the centrifugal impeller 5-2 from the position where the interval with the inner wall of the heat exchanger 2 becomes minimum, as a flat resistor, An example in which the guide 21 of FIG. The effect of reducing the periodic noise is the same as in the example shown in FIG.

<Embodiment 5> FIG. 8 shows the state of the suction flow on the upstream side of the bell mouth 8 in an air conditioner provided with one centrifugal impeller 5 in the rectangular casing 1 as in FIG. The invention is to reduce the periodic noise by changing the resistance of the filter 13 on the tie plate 3 side of the U-shaped heat exchanger 2 from the center position of the centrifugal impeller 5 to be larger than the resistance of the other filters. Improves periodic noise.

<Embodiment 6> FIG. 9 shows an air conditioner provided with two centrifugal impellers 5 in a rectangular housing as in FIG. 7 by changing the state of the suction flow on the upstream side of the bell mouth 8. It is an invention for reducing periodic noise, wherein the resistance of the filter 13 on the connecting plate 3 side of the U-shaped heat exchanger 2 from the intermediate position between the two centrifugal impellers 5 is made larger than the resistance of the other filter parts. Thus, the periodic noise radiated from the two centrifugal impellers is improved. The effect of reducing the periodic noise is the same as in FIG.

[0029]

According to the present invention, an air intake grill and a filter provided on the front surface of a rectangular casing, a plurality of centrifugal impellers installed behind each bell mouth in the casing, and a plurality of centrifugal impellers are provided. In an air conditioner provided with a U-shaped heat exchanger or the like surrounding an impeller, a plurality of centrifugal impellers are controlled so that their rotational speeds are different from each other by a predetermined value (for example, 30 rpm) or more. By shifting the fundamental frequencies of the car from each other, the fluctuation of the periodic noise can be reduced.

Further, a flat plate resistor is locally disposed at a part of the suction port so as to reduce the deviation of the circumferential velocity distribution of the air flow sucked by the centrifugal impeller at the suction port around the grill and the filter. By installing or increasing the resistance in a certain area of the filter, the fluctuation of the periodic noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an air conditioner including two centrifugal impellers according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a result of periodic noise analysis in the air conditioner according to Embodiment 1 of the present invention.

FIG. 3 is a schematic diagram of a sound wave waveform in the air conditioner according to Embodiment 1 of the present invention.

FIG. 4 is a schematic diagram of a combined sound wave in the air conditioner according to Embodiment 1 of the present invention.

FIG. 5 is a configuration diagram of an air conditioner including two centrifugal impellers according to Embodiment 2 of the present invention.

FIG. 6 is a configuration diagram of an air conditioner including one centrifugal impeller according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram of an air conditioner including two centrifugal impellers according to Embodiment 4 of the present invention.

FIG. 8 is a configuration diagram of an air conditioner including one centrifugal impeller according to a fifth embodiment of the present invention.

FIG. 9 is a configuration diagram of an air conditioner including two centrifugal impellers according to Embodiment 6 of the present invention.

FIG. 10 is a configuration diagram of a conventional air conditioner including two centrifugal impellers.

FIG. 11 is a view showing a wind speed distribution on a suction side in a conventional air conditioner including one centrifugal impeller.

12 is a diagram showing a result of noise analysis in the air conditioner shown in FIG.

FIG. 13 is a schematic diagram of a sound wave waveform in a conventional air conditioner including two centrifugal impellers.

FIG. 14 is a schematic diagram of a sound wave waveform in a conventional air conditioner including one centrifugal impeller.

[Explanation of Signs] 1: Housing 2: Heat exchanger 3: Connecting plate 4: Centrifugal blower 5: Centrifugal impeller 6: Motor 8: Bell mouth 9: Electric box 10: Machine room 11: Makeup panel 12: Grill 13: Filter 14: Inlet 15: Outlet 16: Air 17: Discharge channel 18: Partition plate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kensaku Oguni 390 Muramatsu, Shimizu-shi, Shizuoka Hitachi Air Conditioning System Shimizu Co., Ltd. (72) Inventor Yoshiki Hata 390 Muramatsu, Shimizu-shi Shizuoka Prefecture Hitachi Air-Conditioning System Shimizu (72) Inventor Makoto Nagai 390 Muramatsu, Shimizu-shi, Shizuoka Pref. Hitachi Air Conditioning Systems Co., Ltd. Shimizu Production Headquarters F-term (reference) 3L049 BB05 BB20 BC03 BD01 BD05

Claims (5)

[Claims] 1. A grill for air suction attached to a decorative panel provided on a front surface of a rectangular housing, a filter for dust collection attached to a rear surface of the grill, and an opening directed toward the rear surface of the filter. A plurality of bellmouths arranged side by side in the longitudinal direction of the housing, a plurality of centrifugal impellers installed behind each bellmouth and driven by a motor, and A heat exchanger installed so as to surround three long sides and one short side from three sides, and an air discharge channel formed between the heat exchanger and the housing;
In the air conditioner provided with an air outlet formed in the decorative panel and connected to the air discharge path, the plurality of centrifugal impellers are driven and controlled such that the rotational speeds are different from each other by a predetermined value or more. Air conditioner. 2. When one of the plurality of centrifugal impellers has a rotation speed of N ₁ rpm and the other has a rotation speed of N ₂ rpm, N ₁ ≧ N ₂ +
2. The air conditioner according to claim 1, wherein the air conditioner is controlled to be 30. 3. A grill for air suction mounted on a decorative panel provided on a front surface of a rectangular casing, a filter for dust collection mounted on a rear surface of the grill, and an opening directed to a rear surface of the filter. A plurality of bellmouths arranged side by side in the longitudinal direction of the housing, a plurality of centrifugal impellers installed behind each bellmouth and driven by a motor, and A heat exchanger installed so as to surround three long sides and one short side from three sides, and the heat exchanger covers the opening on one side other than the three sides, and the housing A connecting plate for partitioning a chamber accommodating the heat exchanger from the inside, an air discharge passage formed between the heat exchanger and the housing, and air formed in the decorative panel and connected to the air discharge passage In an air conditioner with an outlet Of the plurality of centrifugal impellers, from the position where the distance between the outer periphery of the centrifugal impeller on the connecting plate side and the inner wall of the heat exchanger is minimum, the rotation direction of the centrifugal impeller in the rotation direction of the centrifugal impeller in the direction of the connecting plate. An air conditioner, wherein a flat resistor is provided between the filter and the grill corresponding to a region. 4. A grill for air suction attached to a decorative panel provided on a front surface of a rectangular housing, a filter for dust collection attached to a rear surface of the grill, and an opening directed to a rear surface of the filter. A plurality of bellmouths arranged side by side in the longitudinal direction of the housing, a plurality of centrifugal impellers installed behind each bellmouth and driven by a motor, and A heat exchanger installed so as to surround three long sides and one short side from three sides, and the heat exchanger covers the opening on one side other than the three sides, and the housing A connecting plate for partitioning a chamber accommodating the heat exchanger from the inside, an air discharge passage formed between the heat exchanger and the housing, and air formed in the decorative panel and connected to the air discharge passage In an air conditioner with an outlet An air conditioner wherein the resistance of the filter portion on the tie plate side from the intermediate position of the plurality of centrifugal impellers is greater than the resistance of the other filter portions. 5. An air suction grill attached to a decorative panel provided on a front surface of a rectangular housing, a dust collection filter attached to a rear surface of the suction grill,
One bell mouth installed with the opening facing the rear surface of the filter, one centrifugal impeller installed behind the bell mouth and driven by a motor, and the centrifugal impeller A U-shaped heat exchanger installed so as to surround from three sides of a long side and one short side, a heat exchanger connected so as to cover a U-shaped top of the heat exchanger, and the heat exchanger from inside the housing. A connecting plate for partitioning a chamber for accommodating air, an air discharge passage formed between the heat exchanger and the housing, and an air outlet formed in the decorative panel and connected to the air discharge passage. In the air conditioner, the filter corresponds to a region in a rotation direction front of the centrifugal impeller in a direction of the connecting plate from a position where a space between an outer periphery of the centrifugal impeller and an inner wall of the heat exchanger is minimized. A flat resistor is provided between the grills. Air conditioner according to claim.