JP2001201078A - Indoor unit and airconditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain desired aerodynamic characteristics by preventing non-return phenomena and the generation of abnormal sounds, and by suppressing the passing resistance of air. SOLUTION: A cross-flow type fan 14, that allows air to flow in a direction crossing to an axis is provided, non-return plates 50A and 50B are provided corresponding to each of left- and right-side end parts of the fan, and beveling parts 55A and 55B for preventing non-return are formed at a corner part of the center side of the fan blow-off part of the non-return plates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indoor unit and an air conditioner for providing a comfortable indoor environment by heating or cooling.

[0002]

2. Description of the Related Art An air conditioner is composed of two major components, an indoor unit and an outdoor unit. Each of these units is provided with an indoor heat exchanger and an outdoor heat exchanger that exchange heat between the refrigerant and the indoor air and between the refrigerant and the outdoor air.

[0003] These indoor heat exchangers and outdoor heat exchangers are:
In addition, components such as a compressor and an expansion valve are added to constitute a refrigerant circuit. Refrigerant physically circulates through this circuit, and follows the circulating process of changing the state of high-temperature and high-pressure gas, low-temperature and low-pressure gas, high-temperature and high-pressure liquid, and low-temperature and low-pressure liquid. . The cooling and heating of the room is directly realized by heat exchange between the refrigerant in the indoor heat exchanger and room air.

By the way, during the heating operation, the gas refrigerant, which has been converted into a high-temperature and high-pressure gas by the compressor, is sent to the indoor heat exchanger.
This is realized by performing heat exchange between the refrigerant and room air. During the cooling operation, the high-temperature and high-pressure gaseous refrigerant is sent to the outdoor heat exchanger to exchange heat with the outdoor air to produce a high-temperature and high-pressure liquid refrigerant, which is further passed through an expansion valve to lower the temperature and lower the pressure, thereby reducing the indoor temperature. This is realized by sending the refrigerant to a heat exchanger and performing heat exchange between the refrigerant and room air.

[0005]

The conventional air conditioner has the following problems. As shown in FIG. 7, the indoor unit generally includes an indoor unit housing 1, an indoor heat exchanger 2 provided in the indoor unit housing 1, and performing heat exchange between indoor air and a refrigerant. A fan 3 is provided in the indoor unit housing 1 and sends a room air to the indoor heat exchanger 2 and returns the air after the heat exchange to the room. As the fan 3, a generally cylindrical cross-flow type fan that allows air to flow in a direction intersecting the axis is often used.

In the cross-flow type fan 3, the left and right sides are a suction portion 3a, and a part of the outside of the cylindrical fan except for the suction portion 3a is a blowout portion 3b. Since the vicinity of the end is close to the suction portion 3a, a so-called backflow phenomenon occurs in which a part of the air blown out from the vicinity of both right and left ends of the blowing portion 3b flows into the suction portion 3a. In order to prevent the occurrence of the backflow phenomenon, backflow prevention plates 4 and 4 are provided so as to respectively correspond to both left and right end portions of the cross flow type fan.
The left and right ends of the blow-out portion 3b of the fan are closed, and the blow-out portion 3b is closed.
Some of them have been developed to prevent a part of the air blown out from flowing back to the suction part 3a.

By the way, in a recent indoor unit, a blower 3b of a fan is provided with a variable louver for adjusting an air blowing angle. However, in a blower having such a variable louver, the blower 3b is provided. , A space for disposing a motor for changing the angle of the louver and an electric part associated therewith is required, and such a motor and electric parts are provided on the back part (outer part) 5 of the backflow prevention plate 4. Often placed. In this case, the backflow prevention plate 4 becomes wide and protrudes largely toward the center of the blowout portion, and the amount of overlap L between the backflow prevention plate 4 and the side end of the fan 3 increases more than necessary. When the overlap amount L between the backflow prevention plate 4 and the side end of the fan 3 increases more than necessary, a backflow phenomenon in which a part of the air blown out from the blowout portion 3b flows back into the suction portion 3a may be observed again. When the air blown out from the blow-out portion 3b hits the backflow prevention plate 4 to generate a turbulent flow, there is a problem that an unusual sound (buzziness sound) is generated.

The occurrence of the backflow phenomenon and the abnormal noise caused by the unnecessary increase of the overlap amount L between the backflow prevention plate 4 and the side end of the fan 3 is caused by the backflow as shown by a two-dot chain line in FIG. By providing the shielding portion 6 on the inner side surface of the prevention plate 4, it can be suppressed to some extent, but in this case, the width of the blowout portion 3 b is narrowed, the air passage resistance is increased, and the aerodynamic characteristics desired for the fan 3 are improved. A new problem arises that it cannot be obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a backflow phenomenon and an abnormal noise from occurring, and to suppress air passage resistance. An object of the present invention is to provide an indoor unit and an air conditioner that can obtain desired aerodynamic characteristics.

[0010]

As means for solving the above-mentioned problems, an indoor unit and an air conditioner having the following configuration are employed. The indoor unit according to claim 1 includes an indoor unit housing, an indoor heat exchanger provided in the indoor unit housing to exchange heat between indoor air and a refrigerant, and an indoor heat exchanger provided in the indoor unit housing. A fan that sends air to the indoor heat exchanger and returns the air after the heat exchange to the room; and a backflow prevention plate provided to cover a blowout portion near a suction portion of the fan, and a blowout portion of the backflow prevention plate. A chamfer for preventing backflow is formed at the corner on the center side. In the indoor unit, even if a part of the air blown out from the fan hits the backflow prevention plate, the air flows to the outlet of the indoor unit housing immediately without forming flow separation along the chamfered portion. Therefore, the backflow phenomenon in which a part of the air blown out from the blowout portion of the fan flows to the suction portion side of the fan does not occur, and no abnormal noise occurs.

The indoor unit according to the second aspect is the first aspect.
In the indoor unit described above, the backflow prevention plate extends in a direction perpendicular to a flow of air blown out from the fan, and extends in the same direction as the flow of air blown out from the fan to form an indoor unit housing. An air guide portion reaching the vicinity of the air outlet is provided, and the chamfered portion is formed at an intersection of the partition portion and the air guide portion. In the indoor unit, even if a part of the air blown out from the fan hits the partition portion of the backflow prevention plate, the air is guided along the chamfered portion without forming separation of the flow, while being guided by the air guide portion,
It immediately flows to the outlet of the indoor unit housing. Therefore, also in this case, the backflow phenomenon in which part of the air blown out from the blowout portion of the fan flows to the suction portion side of the fan does not occur, and no abnormal noise occurs.

[0012] The indoor unit according to the third aspect is the first aspect.
Or the indoor unit according to 2, wherein the fan is:
This is a cross-flow type fan that allows air to flow in a direction intersecting with the axis, wherein the backflow prevention plates are provided corresponding to both left and right end portions of the fan. In the indoor unit, the air blown from the vicinity of the left and right end portions of the blow-out portion of the cross-flow type fan is formed along the respective chamfers of the left and right backflow prevention plates without forming flow separation. While being guided by the guide section, it immediately flows to the outlet of the indoor unit housing.

An indoor unit according to a fourth aspect is the indoor unit according to the third aspect.
In the indoor unit described above, the length of the chamfered portion applied to the backflow prevention plate on the side where the motor is not present is set to be longer than the length of the chamfered portion of the backflow prevention plate on the side where the motor is present. Features. The dimensions are different in order to secure a large storage space for motors and electric components formed on the back surface of the backflow prevention plate. By changing the length of the chamfered portion in response to such structural restrictions, the length of the chamfered portion can be set to an optimum value, and the occurrence of a backflow phenomenon and abnormal noise can be suppressed as much as possible. .

According to a fifth aspect of the present invention, an air conditioner includes the indoor unit according to any one of the first to fourth aspects and an outdoor unit that forms a pair with the indoor unit. The air conditioner has the same function as the indoor unit according to the first to fourth aspects.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an indoor unit and an air conditioner according to the present invention will be described below with reference to FIGS.

FIG. 1 is an explanatory diagram showing the overall configuration of the air conditioner. The air conditioner includes an indoor unit 10 and an outdoor unit 20. These indoor units 10
And the outdoor unit 20 includes a refrigerant pipe 40 through which the refrigerant flows.
And electrical wiring (not shown). Two refrigerant pipes 40 are provided, and the refrigerant flows from the indoor unit 10 to the outdoor unit 20 on one side and flows from the outdoor unit 20 to the indoor unit 10 on the other side.

The indoor unit 10 has an indoor unit housing 11 composed of a base 11A and a front panel 11B. The base 11A has a plate fin & tube type indoor heat exchanger 1 for exchanging heat between indoor air and a refrigerant.
3. Various devices such as a substantially cylindrical cross-flow type fan (indoor fan) 14 for sending indoor air to the indoor heat exchanger and returning the air after the heat exchange to the indoor are arranged inside the indoor unit housing 11. Be prepared to. Base 11A
Is provided with an indoor unit control unit 15 composed of various electric circuit elements in order to perform various operation controls and the like regarding the indoor unit 10. The indoor unit control section 15 is provided with an appropriate indicator 15a for displaying an operation status and an error mode. The indicator 15a can be externally confirmed by a see-through portion 12a provided on the front panel 11B. An installation plate 16 is provided behind the base 11A, so that the indoor unit 10 can be installed on an indoor wall or the like.

On the front panel 11B, a suction grill (suction port) 12b is formed on each of the front and top surfaces. The indoor air is drawn into the indoor unit 10 from these directions by the suction grills 12b. Incidentally, an air filter 17 is provided behind the suction grill 12b, and functions to remove dust such as sucked air. Also, on the front panel 11B,
An air outlet 12c is formed below the air outlet, from which warmed or cooled air is blown out. In addition, this air suction and air blowing
This is performed by rotating the cross-flow type fan 14.

The indoor unit 10 is provided with a ventilator for sucking air inside the room and discharging the air outside the room. This ventilator includes a ventilation fan 18 dedicated to ventilation, a ventilation inlet 12d dedicated to ventilation opened in the front grille 12, and a ventilation hose 19. A ventilation inlet 12d is provided on the suction side of the ventilation fan 18. Communication, ventilation fan 1
One end of a ventilation hose 19 is connected to the discharge side of 8.
During the ventilation operation, the ventilation fan 18 operates to suck the room air from the inlet 12d, so that the sucked room air is discharged outside through the ventilation fan 18 and the ventilation hose 19. The other end of the ventilation hose 19 passes through a sleeve (not shown) provided through the wall on which the indoor unit 10 is installed, together with the refrigerant pipes 40 and 40 covered with a heat insulating material, electric wiring and a drain hose. Open to the outside.

The above-described indoor unit 10 includes a remote controller 41 as an operation unit for performing various driving operations. The remote controller 41 is provided with various switches and the like, and can transmit an operation signal of the air conditioner to a receiving unit (not shown) of the indoor unit control unit 15. Note that the operation of the air conditioner can be partially performed by switches (not shown) provided at appropriate places in the indoor unit.

The outdoor unit 20 includes an outdoor heat exchanger 22, a propeller fan 23, a compressor 24, an outdoor unit controller 25, and the like in a housing 21. The outdoor heat exchanger 22 is configured by a refrigerant pipe having a number of plate-shaped fins around the heat exchanger, and realizes heat exchange between the refrigerant and outdoor air. The propeller fan 23 always takes in new air into the housing 21 by generating an airflow that flows from the back to the front inside the housing 21 to improve the heat exchange efficiency in the outdoor heat exchanger 22. It is provided in.

A back surface of the outdoor unit 20 where the outdoor heat exchanger 22 faces the outside, and a propeller fan 23
The front facing the outside, each fingered 26
And a fan guard 27. The finger 26 is provided so that the plate-shaped fin is not damaged by an unexpected external impact. Similarly, the fan guard 27 is provided for the purpose of protecting the propeller fan 23 from external impact.

The compressor 24 converts a low-temperature and low-pressure gaseous refrigerant into a high-temperature and high-pressure gaseous refrigerant and discharges the refrigerant. The compressor 24 plays a central role in the components constituting the refrigerant circuit. Incidentally, the refrigerant circuit is, in addition to the compressor 24, the indoor heat exchanger 13, the outdoor heat exchanger 22,
A circuit that roughly includes a refrigerant pipe 40, an expansion valve, and a four-way valve (both expansion valves and a four-way valve are not shown) for regulating the flow direction of the refrigerant, and circulates the refrigerant between the indoor unit 10 and the outdoor unit 20. It is.

The outdoor unit control unit 25 controls the operation of the propeller fan 23, the compressor 24, and various other devices provided in the outdoor unit 20, and is composed of various electric circuit elements. .

In addition to the above, the outdoor unit 20 is provided with a base 28 for supporting the side panel 21a and avoiding the influence of external vibration and the like. In addition, a side surface of the side panel 21a close to the compressor 24 is provided with a removable maintenance panel 29 for performing maintenance or the like of the compressor 24.

In the following, the operation of the air conditioner having the above configuration will be described for each of the heating operation and the cooling operation. First, during the heating operation, the refrigerant converted into a high-temperature and high-pressure gas by the compressor 24 is supplied to the refrigerant pipe 4.
0, and is sent to the indoor heat exchanger 13 of the indoor unit 10. In the indoor unit 10, heat is applied from a high-temperature and high-pressure gas refrigerant passing through the indoor heat exchanger 13 to the indoor air taken in from the suction grill 12 b by the cross-flow fan 14. This allows the front panel 1
Warm air is blown from the outlet 12c below 1B. At the same time, the high-temperature and high-pressure gas refrigerant is condensed and liquefied in the indoor heat exchanger 13, and becomes a high-temperature and high-pressure liquid refrigerant.

The high-temperature and high-pressure liquid refrigerant is supplied to the refrigerant pipe 4 again.
0 through the outdoor heat exchanger 22 in the outdoor unit 20
Sent to In the outdoor unit 20, the refrigerant passes through an expansion valve (not shown) and becomes low-temperature and low-pressure liquid refrigerant. Propeller fan 2
From the new outdoor air taken into the housing 21 by 3,
The low-temperature and low-pressure liquid refrigerant passing through the outdoor heat exchanger 22 takes away heat. The low-temperature and low-pressure liquid refrigerant evaporates and evaporates into a low-temperature and low-pressure gas refrigerant. This is sent to the compressor 24 again, and the above process is repeated.

Next, during the cooling operation, the refrigerant flows through the refrigerant circuit in a direction opposite to the above. That is, the refrigerant converted into a high-temperature and high-pressure gas by the compressor 24 passes through the refrigerant pipe 40 and is sent to the outdoor heat exchanger 22, where the air is given heat and condensed and liquefied to become a high-temperature high-pressure liquid refrigerant. The high-temperature and high-pressure liquid refrigerant passes through an expansion valve (not shown) to become a low-temperature and low-pressure liquid refrigerant, and is sent to the indoor heat exchanger 13 again through the refrigerant pipe 40. The low-temperature and low-pressure liquid refrigerant here takes heat from room air to cool the room air, and the refrigerant itself evaporates and becomes a low-temperature and low-pressure gas refrigerant. This is sent to the compressor 24 again, and the above process is repeated.

These operations are performed by the indoor unit control unit 15 and the outdoor unit 20 housed in the indoor unit 10.
It is controlled by the outdoor unit control unit 25 housed therein cooperating. Hereinafter, the characteristic portions of the present invention will be described.

As shown in FIG. 2, a backflow prevention plate 50 is provided on each of the left and right ends of the cross flow type fan 14.
A and 50B are provided. Backflow prevention plates 50A, 50
B is for covering the blowing part 14b near the suction part 14a of the cross flow type fan 14. Backflow prevention plate 50A,
50B is a partition portion 51A, 5A extending in a direction orthogonal to the flow of air blown from the cross flow type fan 14.
1B, and air guides 52A and 52B extending in the same direction as the flow of air blown from the cross flow type fan 14 and reaching the vicinity of the outlet 12c of the front panel 11b.
A suction portion cover 53A that covers a part of the suction portion 14a of the fan,
53B. A chamfered portion 55 is provided at an intersection between the partitioning portions 51A and 51B and the air guiding portions 52A and 52B.
A and 55B are formed. Chamfers 55A, 55B
May be a simple inclined surface shape or a rounded arc shape.

A motor 54 for driving the cross flow type fan 14 is attached to one side of the fan 14. Here, the overlap amount La between the fan-side end on the side where the motor 54 does not exist and the backflow prevention plate 50A is equal to the fan-side end on the side where the motor 54 exists and the backflow prevention plate 50A.
B is set to be larger than the overlap amount Lb with B. That is, the backflow prevention plate 50 on the side where the motor 54 does not exist.
The length of the partition part 51A of A is set to be longer than the length of the partition part 51B of the backflow prevention plate 50B on the side where the motor 54 exists.

The length Ma of the chamfered portion 55A applied to the backflow prevention plate 50A on the side where the motor 54 does not exist is:
The length is set to be longer than the length Mb of the chamfered portion 55B of the backflow prevention plate 50B on the side where the motor 54 exists.

In the air conditioner configured as described above, a part of the air blown from the blowing portion 14b of the cross flow type fan 14 hits the partition portions 51A and 51B of the backflow prevention plates 50A and 50B. This partition 51A,
The air hitting 51B is then chamfered 55A, 55B
The air flows immediately to the outlet 12c of the front panel 11B without forming a separation of the flow along the air flow. Therefore, the backflow phenomenon in which part of the air blown out from the blowout portion 14b of the fan 14 flows toward the suction portion 14a of the fan 14 does not occur, and no abnormal noise occurs.

In addition, as shown in FIG. 7, the shielding portion 6 is not provided on the inner side surfaces of the air guide portions 52A and 52B, so that the width of the blowout portion 14b of the fan 14 is reduced. There is no problem that the air passage resistance increases and the fan 14 cannot obtain the desired aerodynamic characteristics.

In the above air conditioner, the length Ma of the chamfered portion 55A provided on the backflow prevention plate 50A on the side where the motor 54 does not exist is changed by the chamfered portion of the backflow prevention plate 50B on the side where the motor 54 is present. It is set longer than the length Mb of 55B. This is because the length of the chamfered portion 55B is set shorter and the length of the chamfered portion 55A is set longer in order to secure a large storage space for motors, electric components and the like formed on the back portions of the backflow prevention plates 50A and 50B. I have. in this way,
Since the length of the chamfered portions 55A and 55B is set to an optimum value by changing the length of the chamfered portion for structural restrictions, occurrence of a backflow phenomenon and abnormal noise can be suppressed as much as possible.

FIG. 3 is a diagram showing a comparison of noise between the case where the backflow prevention plate is provided with a chamfered portion and the case where no bevel is provided. The vertical axis represents the noise level, and the horizontal axis represents the rotation speed of the fan.

As shown in FIG. 4, the backflow prevention plates 50A and 50B having a chamfered portion in this experimental example have an overhang between the end on the fan side where the motor 54 does not exist and the backflow prevention plate 50A. The lap amount La is 26 mm, the fan-side end on the side where the motor 54 exists and the backflow prevention plate 50B
The length Ma of the chamfered portion 55A applied to the backflow prevention plate 50A on the side where the motor 54 does not exist and on the side where the motor 54 exists does not exceed 10 m.
m. Further, as shown in FIG. 5, the backflow prevention plate 4 having no chamfered portion has an overlap amount La between the fan-side end on the side where the motor 54 does not exist and the backflow prevention plate 4 is 26 mm. A overlap amount L between the fan-side end on the side where there is and the backflow prevention plate 50B
The b used was 17 mm. As is clear from this figure, the chamfers 55A, 55
When B was provided, it was confirmed that the noise was clearly reduced in the low rotation speed range.

FIG. 6 is a diagram showing a comparison of the air flow when the backflow prevention plate is provided with a chamfered portion and when it is not provided. The vertical axis shows the airflow, and the horizontal axis shows the fan speed.
The backflow prevention plate having a chamfered portion and the backflow prevention plate not having a chamfered portion were the same as those shown in FIGS. 4 and 5, respectively. As is apparent from this figure, an increase in the air volume was confirmed over almost the entire rotation speed range from the low rotation range to the high rotation range. As described above, this is because the chamfered portions 5 are formed at the corners of the backflow prevention plates 50A and 50B.
By providing 5A, 55B, after a part of the air blown out from the fan 14 hits the backflow prevention plates 50A, 50B, the room is immediately formed along the chamfered portions 55A, 55B without forming flow separation. It is presumed that the air flowed to the air outlet of the unit housing and the passage resistance was reduced.

[0039]

As described above, according to the present invention, the following excellent effects can be obtained. According to the indoor unit according to the first aspect, even if a part of the air blown out from the fan hits the backflow prevention plate, the air blows along the chamfered portion and quickly blows into the indoor unit housing without forming the flow separation. Since the gas flows to the outlet, even if the amount of overlap between the backflow prevention plate and the end on the side of the fan slightly increases, the backflow phenomenon does not occur and no abnormal noise occurs. Further, since the air passage resistance is reduced, desired aerodynamic characteristics can be obtained.

According to the indoor unit of the second aspect, even if a part of the air blown out from the fan hits the partition portion of the backflow prevention plate, the air does not form flow separation along the chamfered portion. The air flows into the air outlet of the indoor unit housing immediately while being guided by the air guide portion, so that it is possible to further prevent the backflow phenomenon and the generation of abnormal noise.

According to the indoor unit according to the third aspect, the air blown from the vicinity of both right and left ends of the blow-out portion of the cross-flow fan flows along the respective chamfers of the left and right backflow prevention plates. Without separation, the air flows into the air outlet of the indoor unit housing immediately while being guided by the air guide. At the outlets near the left and right suction parts of the cross-flow type fan, the backflow phenomenon and the abnormal noise occur, respectively. Can be prevented from occurring.

According to the indoor unit of the fourth aspect, the length of the chamfered portion applied to the backflow prevention plate on the side where the motor does not exist is longer than the length of the chamfered portion of the backflow prevention plate on the side where the motor is present. Are also set to be long, and have different dimensions in order to secure a large storage space for motors, electric components and the like formed on the back surface of the backflow prevention plate. For such structural restrictions, by changing the length of the chamfer, it is possible to optimize the length of the chamfer, while minimizing the occurrence of backflow and abnormal noise. A large storage space for motors, electric components, and the like formed on the back surface of the backflow prevention plate can be secured.

According to the air conditioner of the fifth aspect, the same effects as those of the first to fourth aspects of the invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment according to the present invention,
It is a perspective sectional view showing the whole composition of an air conditioner.

FIG. 2 is a front view showing a relationship between a cross-flow type fan and a backflow prevention plate of the embodiment.

FIG. 3 is a diagram showing a comparison of noise between a case where a chamfer is provided and a case where a chamfer is not provided on a backflow prevention plate.

FIG. 4 is a front view showing a backflow prevention plate having a chamfer used in the above comparison.

FIG. 5 is a front view showing a backflow prevention plate without a chamfer used in the above comparison.

FIG. 6 is a diagram showing a comparison of air flow when a chamfer is provided on a backflow prevention plate and when a chamfer is not provided.

FIG. 7 is a front view showing a relationship between a conventional cross-flow type fan and a backflow prevention plate.

[Explanation of symbols]

 Reference Signs List 10 indoor unit 11 indoor unit housing 11A base 11B front panel 12b suction grille (suction port) 12c air outlet 13 indoor heat exchanger 14 cross-flow type fan 14a suction unit 14b blowing unit 20 outdoor unit 51A, 51B partitioning unit 52A, 52B Air guide 53A, 53B Suction cover 54 Motor 55A, 55B Chamfer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuya Fujiki 3-1-1 Asahicho, Nishibiwajima-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Air Conditioning Works of Mitsubishi Heavy Industries, Ltd. 3-chome, Mitsubishi Heavy Industries, Ltd. Air Conditioner Works (72) Inventor Hiroshi Kamihara 3-1-1, Asahimachi, Nishibiwajima-cho, Nishikasugai-gun, Aichi Prefecture Mitsubishi Heavy Industries Air Conditioner Works F-term (reference) 3L049 BB05 BC01 BD02 3L050 BA01

Claims (5)

[Claims] 1. An indoor unit housing, an indoor heat exchanger provided in the indoor unit housing for exchanging heat between indoor air and a refrigerant, and an indoor heat exchanger provided in the indoor unit housing for indoor heat A fan that sends the air after heat exchange to the exchanger and returns the air after the heat exchange to the room; and a backflow prevention plate provided so as to cover the blowout portion near the suction portion of the fan. An indoor unit, wherein a corner is formed with a chamfer for preventing backflow. 2. The backflow prevention plate includes a partition extending in a direction orthogonal to a flow of air blown from the fan;
An air guide portion extending in the same direction as the flow of air blown out from the fan and reaching the vicinity of the air outlet of the indoor unit housing, and at the intersection of the partition portion and the air guide portion, the chamfered portion is provided. The indoor unit according to claim 1, wherein the indoor unit is formed. 3. The fan is a cross-flow type fan for flowing air in a direction intersecting with an axis, and the backflow prevention plates are provided corresponding to left and right ends of the fan, respectively. The indoor unit according to claim 1 or 2, wherein: 4. The length of the chamfered portion provided on the backflow prevention plate on the side where the motor does not exist is set longer than the length of the chamfered portion on the backflow prevention plate on the side where the motor does not exist. The indoor unit according to claim 3, wherein 5. An air conditioner comprising: the indoor unit according to claim 1; and an outdoor unit forming a pair with the indoor unit.