GB2270153A

GB2270153A - Air conditioner

Info

Publication number: GB2270153A
Application number: GB9313532A
Authority: GB
Inventors: Harunobu Nukushina; Akihiro Maejima; Hiroyuki Arakawa
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1992-08-26
Filing date: 1993-06-30
Publication date: 1994-03-02
Anticipated expiration: 2013-06-30
Also published as: KR940005926A; TW241328B; JP3192495B2; CN1057153C; GB9313532D0; GB2270153B; KR0129677B1; JPH0674528A; CN1097499A

Abstract

At the bottom of the front panel of an indoor unit of an air conditioner there is provided a light receiving/monitor section (4) which has a built-in a humidity sensor (8). A decision is made as to which of the low humidity range, the optimum humidity range and the high humidity range the humidity sensed by the humidity sensor (8) lies in. The decision result is indicated by a lamp (9a, 9b or 9c). The optimum humidity range can be varied by a microcomputer by comparison of a sensed indoor temperature with a target preset temperature, or by a user's manual operation. Automatic adjustment is made at the end of a timed interval after cooling or heating is stopped. If a humidifier is provided, operation thereof may be controlled simultaneously with the indication of the sensed humidity. Each lamp may be an LED. <IMAGE>

Description

AIR aem zER The present invention relates to air conditions and, irore specifically, to air conditioners provided with a feature for indicating the humidity of air, for example indoor air.

There is an air conditioner which is equipped with a humidity sensor for sensing the humidity of indoor air and indicates the sensed humidity. An example is disclosed in a Japanese Unexamined Utility Model Publication No. 56-61849 and a Japanese Unexamined Patent Publication No. 1-143623.

A humidifier is installed in a room in which an air conditioner having such a humidity indicating feature is mounted. By user's turning the humidifier on or off according to humidity indications, the humidity of the indoor air can be regulated to a desired level.

Even if the humidity sensed by the humidity sensor is indicated as it is, however, it is very difficult for the user to judge whether or not the indicated humidity is optimum.

For some time after the start of operation of the air conditioner there is a large temperature difference between the neighborhood of the air conditioner and the neighborhood of the the floor surface, thus making the proper humidity indication difficult.

When an indoor fan is stopped during an interruption of the operation of the air conditioner, the indoor air stops convection. Thus, moisture on the indoor heat exchanger, resulting from dehumidification, may raise the humidity in the neighborhood of the air conditioner.

In this case as well, the proper humidity indication is difficult.

When the air conditioner is restarted after the interruption, the indoor fan will scatter the moisture on the indoor heat exchanger around the air conditioner.

This will also make the proper humidity indication difficult for some time.

When the air conditioner is mounted high in the room, there is a large temperature difference between the neighborhood of the air conditioner and the room floor not only at the start of an operation but also during the operation. The temperature difference is large at the time of a heating operation in particular.

In practice, it is absolute humidity that is sensed by the humidity sensor. Relative humidity is obtained by correcting the absolute humidity using indoor temperature. It is the relative humidity that is indicated.

A relative humidity difference proportional to the temperature difference exists between high and low positions in the room. Besides, experimentally the relative humidity difference is greater than the temperature difference. Thus, it is not proper to simply make the relative humidity obtained on the basis of a temperature at a high position in which the air conditioner is mounted a candidate for indication.

During a heating operation, frost is formed gradually on the surface of the outdoor heat exchanger acting as an evaporator, which will result in a deficiency of heat exchange and hence reduced heating capability.

During a heating operation, therefore, a defrosting operation is carried out as needed to remove frost formed on the outdoor heat exchanger.

That is, in the case of a defrosting operation the direction of refrigerant flow is made opposite to that in the case of a heating operation so as to feed hightemperature refrigerant discharged from the compressor into the outdoor heat exchanger as it is, thereby thawing the frost formed on the outdoor heat exchanger.

However, reversing the refrigerant flow causes the indoor heat exchanger to act as an evaporator, so that chill air is discharged into the room. Thus, the user in the room will feel chilly.

For this reason, the indoor fan is stopped during a defrosting operation to prevent chill air from being discharged into the room. However, when the indoor fan is stopped, the proper humidity indication becomes difficult as in the case of the above-described interruption of operation.

It is an object of the present invention to provide an air-conditioner which provides users with an indication of the humidity.

According to the present invention there is provided an air-conditioner for indicating the humidity of indoor air comprising: decision means for making a decision as to whether or not the humidity of the indoor air falls within an optimum humidity range; indicating means for indicating decision results of said decision means; and control means for varying said optimum humidity range.

Reference will now be nade, by way of example, to the ying drawings, in whidi: Fig. 1 is an exterior view of an indoor unit of an air conditioner according to an embodiment of the present invention; Fig. 2 shows a light-receiving/monitor section of the indoor unit of Fig. 1; Fig. 3 shows a portion of the indoor unit of Fig. 1; Fig. 4 shows an arrangement of a refrigerating cycle in the embodiment; Fig. 5 is a block diagram of a control circuit of the embodiment; Fig. 6 is a flowchart for use in explanation of the overall operation of the embodiment; Figs. 7A and 7B are a flowchart for use in explanation of the humidity indication routine illustrated in Fig. 6; Fig. 8 illustrates indoor temperature zone decision conditions; and Fig. 9 is a graph illustrating an example of a change in indoor humidity at the time of a defrosting operation.

Referring now to Fig. 1, there is shown an indoor unit 1 of an air conditioner according to an embodiment of the present invention. The unit 1 is a type which is installed on the wall of a room. The indoor unit 1 is provided, on its front panel 2, with an inlet port 2a and an outlet port 3. At the bottom of the indoor unit 1 a light-receiving/monitor section 4 is provided adjacent to the outlet port 3. Reference numeral 5 denotes a wireless type of remote control unit which transmits the preset contents to the indoor unit 1 by means of infrared rays.

The light-receiving/monitoring section 4 is provided, as shown in Fig. 2, with an infrared-ray receiver 6, a humidity sensing window 7, a humidity sensor 8, a humidity monitor 9, and an operation monitor 10.

The receiver 6 receives infrared rays transmitted from the remote control unit 5. The humidity sensor 8 is provided behind the humidity sensing window 7, which senses the humidity (absolute humidity) of the air in the room through the window 7.

The humidity monitor 9 is a means of indicating the humidity sensed by the sensor 8 in at least two stages of the optimum humidity range and the other range, for example, three stages of the low humidity range, the optimum humidity range, and the high humidity range.

The monitor 9 has a low-humidity indicating lamp 9a, an optimum-humidity indicating lamp 9b, and a high-humidity indicating lamp 9c. The operation unit 10 has a builtin lamp (not shown) which lights during an operation in a color corresponding to the mode of the operation and goes out when the operation is stopped. Use may be made of light-emitting diodes as the humidity indicating lamps 9a, 9b and 9c and the operation unit built-in lamp.

The front panel 2 of the indoor unit 1 can be opened by the user as shown in Fig. 3. When the front panel 2 is opened, a filter 11 and a humidity correction switch 12 can be seen. The filter 11, which removes dust and smell of taken-in air, can be mounted and dismounted. The humidity correction switch 12 is an operation means for shifting the optimum humidity range indicated by the lamp 9b of the humidity monitor 9 manually. The switch is operated by the user when necessary.

The indoor unit 11 is connected with the outdoor unit by pipes and signal lines, thereby forming a refrigerating cycle.

In Fig. 4, 20 denotes the outdoor unit equipped with a variable-capability compressor 21 that takes in, compresses, and discharges a refrigerant. To the discharge port of the compressor 21 is connected via a four-way valve 22 an outdoor heat exchanger 23 that exchanges heat between the outdoor air and the taken-in refrigerant.

To the outdoor heat exchanger 23 is connected via a decompression device, for example, an expansion valve 24 an indoor heat exchanger 25 which exchanges heat between the indoor air and the incoming refrigerant. The indoor heat exchanger 25 is connected to the suction port of the compressor 21 through the four-way valve 22, thus constituting a heat pump type refrigerating cycle.

An outdoor fan 26 is provided near the outdoor heat exchanger 23, while an indoor fan 27 is provided near the indoor heat exchanger 25. The outdoor fan 26 takes in the outdoor air and feeds it to the outdoor heat exchanger 23. The indoor fan 27 takes in the indoor air and discharges it into the room through the indoor heat exchanger 25. An indoor air temperature sensor 28 is provided in the taken-in air passage formed by the indoor fan 27. A temperature sensor 29 is attached to the outdoor heat exchanger 23, which senses the temperature of the outdoor heat exchanger 23.

A control circuit is shown in Fig. 5.

The indoor unit 1 has an indoor controller 30 composed of a microcomputer and its associated peripheral circuits. To the indoor controller 30 are connected an infrared light receiver 6, a humidity sensor 8, a humidity sensor 9, an operation monitor 10, an indoor fan motor 27M, an indoor temperature sensor 28, and a timer 31. The indoor controller 30 is connected to a commercial AC power supply 40.

To the indoor controller 30 is connected an outdoor controller 50 of the outdoor unit 20 through power lines ACL and a serial signal line SL. The outdoor controller 50 is also composed of a microcomputer and its associated peripheral circuits.

To the outdoor controller 50 are connected a fourway valve 22, an outdoor fan motor 26M, a temperature sensor 29, and an inverter 51. The inverter 51 rectifies a voltage on the power lines ACL and converts it to a voltage of a frequency (and a level) corresponding to a command from the outdoor controller 50. The output voltage of the inverter serves as driving power for a compressor motor 21M.

The indoor controller 30 and the outdoor controller 50, which control the air conditioner while making data transfers synchronized with the supply voltage over the serial signal line SL, has the following function means.

[1) Means for, with the four-way valve placed in the neutral state, allowing a refrigerant discharged from the compressor 21 to flow through the four-way valve 22, the outdoor heat exchanger 23, the expansion valve 24, the indoor heat exchanger 25, and the four-way valve 22 and then return to the compressor 21 as indicated by solid arrows in Fig. 4, thereby performing a cooling or dehumidifying operation. That is, a cooling cycle is formed, so that the outdoor heat exchanger 23 serves as a condenser and the indoor heat exchanger 25 serves as an evaporator. At the time of a dehumidifying operation, the air flowing from the indoor heat exchanger 25 is heated by a reheater (not shown) to a temperature substantially equal to a temperature in the room and then discharged into the room.

[2] Means for, with the four-way valve switched, allowing the refrigerant discharged from the compressor 21 to flow through the four-way valve 22, the indoor heat exchanger 25, the expansion valve 24, the outdoor heat exchanger 23, and the four-way valve 22 and then return to the compressor 21 as indicated broken arrows in Fig. 4, thereby performing a heating operation. That is, a heating cycle is formed, so that the indoor heat exchanger 25 serves as a condenser and the outdoor heat exchanger 23 serves as an evaporator.

[3] Means for, when the temperature sensed by the heat exchanger temperature sensor 29 falls to a given value T1 or below, for example, 0 C or below, returning the four-way valve to the neutral state to reverse the refrigerant flow, thereby performing a defrosting operation for the outdoor heat exchanger 23.

[4) Means for, during an operation, obtaining a difference AT (air-conditioning load) between a temperature Ta sensed by the indoor temperature sensor 28 and a preset temperature Ts set by the remote control unit 5 and controlling the operating frequency F (the output frequency of the inverter 51) so that the temperature difference AT may become zero.

[5] Means for correcting the humidity (relative humidity) sensed by the humidity sensor 8 using the temperature Ta sensed by the indoor temperature sensor 28 to obtain the relative humidity and acquiring the relative humidity as the indoor humidity Hs.

[6] Decision means for deciding whether or not the indoor humidity Hs falls within the optimum humidity range.

[7] Means for indicating the result of the decision by the decision means on the temperature monitor 9.

[8] Means for shifting the optimum humidity range according to the difference AT between the indoor temperature Ta and the preset temperature Ts.

[9] Means for shifting the optimum humidity range by an operation of the humidity correcting switch 12.

[10] Means for causing the humidity monitor 9 to perform a specific operation regardless of the decision result of the decision means for a predetermined period of time (for example, five minutes) from the time the air conditioner is started.

[11] Means for, when the indoor fan 27 is stopped and for a predetermined period of time from the start of the indoor fan 27, causing the humidity monitor 9 to perform a specific operation regardless of the decision result of the decision means.

[12] Means for varying the optimum humidity range between the time of a cooling operation and the time of a heating operation.

[13] Means for, during a defrosting operation, retaining the operating state of the humidity monitor 9 as it was prior to the start of the defrosting operation, regardless of the decision result of the decision means.

Hereinafter, the operation of the above-described arrangement will be described with reference to Figs. 6, 7A, and 7B.

When the cooling operation mode is set on the remote control unit 5 and an operation is performed to bring the air conditioner into operation (YES in step 111), the four-way valve 22 is placed in the neutral state (step 112), and the compressor 21, the outdoor fan 26 and the indoor fan 27 are started (steps 113, 114).

In this case, the refrigerant discharged from the compressor 21 flows in the direction indicated by solid arrows in Fig. 4 to form a cooling cycle. Thus, the outdoor heat exchanger 23 acts as a condenser, and the indoor heat exchanger 25 acts as an evaporator, thereby performing a cooling operation.

When the heating operation mode is set on the remote control unit 5 and an operation is performed to bring the air conditioner into operation (YES in step 115), the four-way valve 22 is switched (step 116), and the compressor 21, the outdoor fan 26 and the indoor fan 27 are started (steps 118, 119).

In this case, the refrigerant discharged from the compressor 21 flows in the direction indicated by broken arrows in Fig. 4 to form a heating cycle. Thus, the indoor heat exchanger 25 acts as a condenser, and the outdoor heat exchanger 23 acts as an evaporator, thereby performing a heating operation. During the heating operation, the temperature Te of the outdoor heat exchanger 23, serving as the evaporator, is sensed by the temperature sensor 29 (step 119).

During cooling and heating operations, the temperature Ta of the indoor air is sensed by the indoor temperature sensor 28 (step 120), and the difference AT (air-conditioning load) between the sensed temperature Ta and the preset temperature Ts set on the remote control unit 5 is obtained (step 121). The operating frequency of the compressor 21 (the output frequency of the inverter 51) is controlled so that the temperature difference AT may become zero -(step 122). By controlling the operating frequency F the optimum cooling or heating capability can be shown.

Under the conditions in which the sensed temperature Ta has reached the preset temperature Ts and hence the temperature difference AT has become zero, the compressor 21 is stopped to interrupt the operation.

During cooling and heating operations, a humidity indication routine is carried out (step 123), which will be described later.

During a heating operation, frost is formed gradually on the surface of the outdoor heat exchanger 23 acting as an evaporator, which will result in a deficiency of heat exchange and hence reduced heating capability. For this reason, as described above, the temperature Te of the outdoor heat exchanger 23 is sensed by the temperature sensor 29 during heating operation (step 119). A comparison is made between the sensed temperature Te of the temperature sensor 29 and the a given value T1 (0 C) (step 124). When the sensed temperature Te of the temperature sensor 29 falls to the given value T1 or below (YES in step 124), the four-way valve 22 is returned to the neutral state (step 125).

At the same time, the operating frequency F of the compressor 21 is set to a given value for defrosting operation (step 126), and the indoor fan 27 is stopped (step 127).

When the four-way valve 22 is returned to the neutral state, the refrigerant flow is reversed, so that the high-temperature refrigerant discharged from the compressor 21 is fed into the outdoor heat exchanger 23 through the four-way valve 22 as it is. Thus, the frost formed on the outdoor heat exchanger 23 is thawed out by the refrigerant heat.

At the time of the defrosting operation, the indoor heat exchanger 25 serves as an evaporator, but discharge of chill air into the room is prevented because the indoor fan 27 is stopped. Thus, the user in the room will not feel chilly.

When the sensed temperature Te of the temperature sensor 29 exceeds the given value T2 ( > T1) as a result of defrosting (YES in step 128), the four-way valve 22 is switched (step 129), and the indoor fan 27 is started, thereby restarting the heating operation.

Hereinafter, the humidity indication routine in step 123 will be described with reference to Figs. 7A and 7B.

When an operation is stopped (NO in step 201), the timer 31 is reset (step 202). If this operation stop is not an operation interruption based on the indoor temperature control (NO in step 203), then all the lamps 9a, 9b and 9c in the humidity monitor 9 are turned off (step 204). Even if the operation stop is an operation interruption based on the indoor temperature control (YES in step 203), all the lamps 9a, 9b and 9c in the humidity monitor 9 are turned off (step 205) when the indoor fan 27 is in operation (NO in step 204).

When the operation is started (YES in step 201), the timer 31 is set to initiate a time count operation (step 207). Upon counting five minutes, the timer runout occurs.

For five minutes of a time count operation (NO in step 208), a specific operation is performed in the humidity monitor 9. That is, all the lamps 9a, 9b and 9c in the humidity monitor 9 are turned on (step 206).

Taking into consideration that there is a great temperature difference between the location where the indoor unit 1 is mounted and the floor surface for some time from the start of operation and hence the proper humidity indication is difficult, all the lamps 9a, 9b and 9c in the humidity monitor 9 are turned on as described above. This prevents the conveyance of improper humidity information to the user.

When the timer 31 runs out (YES in step 208), the sensed humidity (absolute humidity) by the humidity sensor 8 is corrected according to the sensed temperature Ta by the indoor temperature sensor 28 for use as the indoor humidity (relative humidity) Hs (step 209).

At this point, a comparison is made between the sensed temperature Ta by the indoor temperature sensor 28 and the indoor temperature zone decision conditions of Fig. 8 previously stored in an internal memory, thereby making a decision of whether the sensed indoor temperature Ta lies in a zone A within a given range centered at the indoor temperature Ts or a zone B outside the given range (step 216). In the given range a temperature difference of 0.5 C is set between the times of rise and fall of the indoor temperature Ta so that no chattering may occur in the decision result, as shown in Fig. 8.

When the sensed indoor temperature Ta lies in the zone B (NO in step 216), a decision is made, on the basis of the humidity range conditions in table 1 below which are stored in the internal memory, as to which range of the low humidity range, the optimum humidity range and the high humidity range the indoor humidity Hs lies in (steps 220, 221, 222, and 223).

TABLE 1

LOW OPTIMUM HIGH RANGE ( % ) RANGE ( % ) RANGE ( % COOL/ Hs S 35 35 < Hs < 65 65 5 Hs DEHUMIDIFYING HEATING ~ Hs S 30 30 < Hs < 60 60 S Hs That is, at the times of cooling and dehumidifying operations (NO in step 220), the optimum humidity range is defined by the lower limit value Hsl = 35% and the upper limit value Hs2 = 65% (step 222). At the time of a heating operation (YES in step 220), on the other hand, the optimum humidity range is defined by the lower limit value Hsl = 30% and the upper limit value Hs2 = 60% (step 222).

If the indoor humidity Hs lies in the optimum humidity range (step 223, Hsl < Hs < Hs2), then only the lamp 9b will be turned on (step 224).

If the indoor humidity Hs lies in the low humidity range (step 223, Hs S Hsl), then only the lamp 9a will be turned on (step 225).

If the indoor humidity Hs lies in the high humidity range (step 223, Hs2 5 Hs), then only the lamp 9c will be turned on (step 226).

When the sensed indoor temperature Ta lies in the A zone (YES in step 216), on the other hand, a decision is made, on the basis of the humidity range conditions in table 2 below which are previously stored in the internal memory, as to which range of the low humidity range, the optimum humidity range and the high humidity range the indoor humidity Hs lies in (steps 217, 218, 219, and 223).

TABLE 2

LOW OPTIMUM HIGH RANGE (%) RANGE (%) RANGE (%) COOL/ Hs S 30 30 < Hs < 70 70 5 Hs DEHUMIDIFY IN HEATING Hs S 25 25 < Hs < 65 65 S Hs That is, at the times of cooling and dehumidifying operations (NO in step 217), the optimum humidity range is defined by the lower limit value Hsl = 30% and the upper limit value Hs2 = 70% (step 218).At the time of a heating operation (YES in step 217), on the other hand, the optimum humidity range is defined by the lower limit value Hsl = 25% and the upper limit value Hs2 = 65% (step 219).

As can be seen, the optimum humidity range is set wider in the zone A in which the indoor temperature Ta is in the neighborhood of the target preset temperature Ts and hence is in the stable state than in the zone B in which, like when an operation is started, there is a large difference between the indoor temperature Ta and the target preset temperature Ts and hence Ta is in the unstable state. Therefore, the proper humidity indication becomes possible without being affected by the indoor temperature Ta.

Furthermore, the optimum humidity range at the time of a heating operation is set not to be wide taking into consideration the fact that there is a large difference in temperature between the place where the indoor unit 1 is mounted and the room floor. In contrast, at the time of a cooling operation, the optimum humidity range is set to be wider because the temperature difference between the indoor unit and the room floor is small.

Therefore, the proper humidity indications are permitted without distinction between heating and cooling operations.

The humidity correction switch 12 is provided inside the front panel 2 of the indoor unit 1 taking into consideration the fact that there is a difference in feeling of comfortableness for humidity among individuals.

When the humidity correction switch 12 is placed by the user to the plus (+) side (YES in step 212), the sensed indoor humidity Hs is corrected so that it is reduced by 10% (step 213). The correction of the humidity in the reducing direction is equivalent to shifting of the optimum humidity range to the high humidity side.

When the humidity correction switch 12 is placed by the user to the minus (-) side (YES in step 214), the sensed indoor humidity Hs is corrected so that it is increased by 10% (step 215). The correction of the humidity in the increasing direction is equivalent to shifting of the optimum humidity range to the low humidity side.

The variability of the optimum humidity range with user's liking permits the proper humidity indications regardless of an individual difference in feeling of comfortableness for humidity and the shape and size of a room in which the indoor unit 1 is installed.

When the indoor temperature Ta reaches the preset temperature Ts, the compressor 21 is stopped, so that an operation interruption occurs. If, at the time of the operation interruption (YES in step 203), the indoor fan 27 is stopped (YES in step 204), then a specific operation is performed in the humidity monitor 9 like when an operation is started. That is, all the lamps 9a, 9b and 9c in the humidity monitor 9 are turned on (step 206).

That is, when the indoor fan 27 is stopped during the operation interruption based on the indoor temperature control, the convection of the indoor air is stopped. As a result, dehumidification moisture on the indoor heat exchanger 25 may cause an increase in humidity in the neighborhood of the place where the indoor unit 1 is mounted. In this case as well, the proper humidity indications become difficult. In this case, therefore, all the lamps 9a, 9b and 9c in the humidity monitor 9 are turned on to thereby avoid improper humidity indications.

When the operation interruption is canceled (YES in step 201), that is, when the indoor fan 27 is restarted, the timer 31 is set, so that the all the lamps 9a, 9b and 9c in the humidity monitor 9 are turned on for five minutes (steps 208, 206).

That is, the proper humidity indications are difficult for some time from the restart of the operation after an interruption because the indoor fan 27 in operation scatters the dehumidification moisture on the indoor heat exchanger 25 in the neighborhood of the place where the indoor unit 1 is mounted. In this case, therefore, all the lamps 9a, 9b and 9c in the humidity monitor 9 are turned on to thereby avoid improper humidity indications.

Suppose that an defrosting operation for the outdoor heat exchanger 23 is performed during a heating operation (YES in step 210). The defrosting operation lasts five or six minutes, during which time the heating operation is interrupted and, at the same time, an action is taken to stop the indoor fan 27 so as to prevent chill air from being discharged into the room.

Therefore, a phenomenon occurs in which the indoor humidity Hs greatly falls immediately after the start of the defrosting operation and then rises as shown in Fig. 9.

In such a defrosting operation in which humidity varies severely, the indication of the humidity monitor 9 is retained at it was prior to the defrosting operation (step 211). For example, if the lamp 9b has been turned on prior to the defrosting operation, the on state of the lamp 9b is continued throughout the defrosting operation.

The above embodiment is arranged to simply indicate the sensed humidity Hs. In the case of an air conditioner equipped with a humidifier, the operation of the humidifier may be controlled simultaneously with the indication of the sensed humidity Hs.

In the above embodiment, the sensed humidity Hs is indicated in three separate stages of low, optimum and high humidity ranges. However, the number of stages of humidity ranges is not restrictive but may be set arbitrarily.

Claims

Claims:

1. An air-conditioner for indicating the humidity of indoor air comprising: decision means for making a decision as to whether or not the humidity of the indoor air falls within an optimum humidity range; indicating means for indicating decision results of said decision means; and control means for varying said optimum humidity range.

2. An air-conditioner according to claim 1, further comprising: said indicating means has a low-humidity indicating lamp, an optimum-humidity indicating lamp and a highhumidity lamp.

3. An air-conditioner according to claim 1, which further comprises an indoor unit housing a lower surface, and in which said indicating means attached to the lower surface of said indoor unit.

4. An air-conditioner according to claim 1, further comprising: a compressor for taking in, compressing and discharging a refrigerant; an outdoor heat exchanger for exchanging heat between outdoor air and the refrigerant; an indoor heat exchanger for exchanging heat between the indoor air and the refrigerant; and controlling means for controlling said compressors, thereby to change temperature of the indoor air to a preset value.

5. An air-conditioner according to claim 4, wherein said control means varies said optimum humidity range according to a difference between the temperature of the indoor air and said preset temperature.

6. An air-conditioner according to claim 1, wherein said control means is responsive to a manual operation to vary said optimum humidity range.

7. An air-conditioner according to claim 1, further comprising: control means for allowing said indicating means to perform a specific operation regardless of decision results of said decision means for a predetermined period of time from the start of an operation.

8. An air-conditioner according to claim 1, further comprising: an indoor fan, and control means for, when said indoor fan is stopped, allowing said indicating means to perform a specific operation regardless of decision results of said decision means.

9. An air-conditioner for indicating the humidity of indoor air comprising: decision means for making a decision as to whether or not the humidity of the indoor air falls within an optimum humidity range; indicating means for indicating decision results of said decision means; a compressor for taking in, compressing and discharging a refrigerant; an outdoor heat exchanger for exchanging heat between outdoor air and the refrigerant; an indoor heat exchanger for exchanging heat between the indoor air and the refrigerant; means for allowing the refrigerant discharged from said compressor to flow through said outdoor heat exchanger first and said indoor heat exchanger next and to return to said compressor, thereby carrying out a cooling operation; ; means for allowing the refrigerant discharged from said compressor to flow through said indoor heat exchanger first and said outdoor heat exchanger next and to return to said compressor, thereby carrying out a heating operation; and control means for varying said optimum humidity range between said cooling operation and said heating operation.

10. An air conditioner for indicating the humidity of indoor air, substantially as hereinbefore described with reference to the accompanying drawings.