JP3208946B2 - Vehicle air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for a vehicle, and more particularly to an air conditioner for a vehicle which changes a stop instruction temperature of a compressor for compressing and discharging a refrigerant evaporated by an evaporator of a refrigeration cycle. Get involved.

[0002]

2. Description of the Related Art At the time of starting a start of an internal combustion engine by getting into a stopped vehicle, the temperature of cooling water flowing from the internal combustion engine into the heater core is low, the temperature in the vehicle interior is not controlled, and the temperature outside the vehicle interior is low. When the temperature falls to 0 ° C or lower, the temperature in the cabin also decreases to a temperature close to the temperature outside the cabin, and the relative humidity in the cabin increases due to exhalation generated by an occupant. Glass is easily fogged.

[0003] Defrosting of the window glass can be removed by starting the dehumidifying operation of the vehicle air conditioner. However, in general, in order to prevent the frost of the evaporator, the cooling temperature of the evaporator is set to the stop instruction temperature of the compressor (for example, 3 ° C). ℃), the compressor is turned off.

[0004] Therefore, when the temperature outside the vehicle compartment is reduced to 0 ° C or less at the start of the start of the internal combustion engine, the cooling temperature of the evaporator does not become higher than that temperature.
Therefore, the dehumidifying operation of the vehicle air conditioner cannot be performed, and the fogging of the window glass is removed for about 5 minutes after the start of the internal combustion engine until the cooling water of the internal combustion engine flowing into the heater core rises above a predetermined water temperature. I couldn't do that.

Therefore, for example, Japanese Utility Model Laid-Open Publication No. Sho 57-85167 discloses that when the temperature outside the vehicle compartment is reduced to 0 ° C. or less, a certain time elapses after the forcible switch provided on the operation panel is manually operated. A technique is described in which the compressor is forcibly operated to remove the fogging of the window glass in winter.

[0006]

However, in the prior art, when the temperature outside the vehicle compartment has dropped to 0 ° C. or less, the compressor is forcibly operated for a fixed time by manually operating the forcible switch. In this case, the cooling temperature of the evaporator is much lower than the stop instruction temperature of the compressor, and there is a problem that the evaporator is frosted.

The present invention provides an air conditioner for a vehicle which can prevent frost of a cooling means and remove fogging of a window glass even when the temperature outside the vehicle compartment falls below a predetermined temperature. For the purpose of providing.

[0008]

SUMMARY OF THE INVENTION The present invention provides a duct for sending air into a vehicle interior, cooling means for cooling the air flowing through the duct, and cooling the inside of the duct by using cooling water of an internal combustion engine. Heating means for heating the flowing air; and cooling temperature detecting means for detecting a cooling temperature of the air cooled by the cooling means, wherein the cooling temperature detected by the cooling temperature detecting means is a stop instruction temperature of the cooling means. A control device for stopping the operation of the cooling means when the temperature decreases to below, the control device includes a vehicle outside temperature detecting means for detecting a temperature outside the vehicle interior, and when the internal combustion engine starts to start, the vehicle If the temperature outside the vehicle cabin detected by the outdoor temperature detecting means has fallen below a predetermined temperature, the stop instruction temperature of the cooling means is set to a target temperature lower than normal until the internal combustion engine reaches a predetermined operating state. Setting The technical means to be adopted.

[0009]

According to the present invention, when the temperature outside the vehicle compartment falls below the predetermined temperature, the cooling water of the internal combustion engine flowing into the heating means is stabilized, that is, the internal combustion engine is brought into the predetermined operating state. Until the temperature reaches, the stop instruction temperature of the cooling means is set to a target temperature lower than usual. Thereby, even if the temperature outside the vehicle compartment falls below the predetermined temperature, the operation of the cooling means is continued until the temperature falls below the target temperature which is lower than usual, so that the air flowing inside the duct toward the vehicle compartment is reduced. Cooled and dehumidified. Therefore, when the internal temperature of the internal combustion engine is started, the temperature outside the vehicle compartment falls below a predetermined temperature, the temperature inside the vehicle compartment is low, and even when the relative humidity inside the vehicle compartment is high, the low humidity dehumidified from the duct is low. The blown air is blown out, so that the fogging of the window glass of the vehicle is removed.

Further, when the temperature outside the vehicle compartment has fallen below a predetermined temperature, the cooling temperature detected by the cooling temperature detecting means is lower than normal until the internal combustion engine reaches a predetermined operating state. By stopping the operation of the cooling means when the temperature falls below the temperature, the cooling temperature of the cooling means does not decrease to the frost temperature. Therefore, even if the stop instruction temperature of the cooling means is set to a target temperature lower than usual, the occurrence of frost of the cooling means is suppressed.

[0011]

【Example】

Next, an air conditioner for a vehicle according to the present invention will be described with reference to an embodiment shown in FIGS.
Here, FIG. 1 is a diagram showing an automobile air conditioner.

An automobile air conditioner 1 is provided with a duct 2 for guiding air into a vehicle interior, and is arranged upstream of the duct 2.
A sirocco-type blower 3 for sending air into the vehicle interior via the duct 2, an evaporator 4 for cooling the air flowing in the duct 2, a heater core 5 for heating the air flowing in the duct 2, and a control device for controlling each air conditioner ( (Hereinafter referred to as ECU).

The blower 3 comprises a blower case 3a, a centrifugal fan 3b, and a blower motor 3c, and the rotation speed of the blower motor 3c is determined according to the voltage applied to the blower motor 3c. The blower voltage is controlled based on a control signal from the ECU 6 via the blower drive circuit 7 (see FIG. 2).

The blower case 3a is formed with an inside air inlet 8 for introducing the vehicle interior air (inside air) and an outside air inlet 9 for introducing the outside air (outside air) inside the vehicle. An inside / outside air switching damper 10 for selectively opening and closing the inside air introduction port 8 and the outside air introduction port 9 is rotatably mounted.

Downstream of the duct 2, a defroster duct 2a, a face duct 2b, and a foot duct 2c are branched, and a defroster outlet 11, a face outlet 12, and a leading end of each of the ducts 2a to 2c open into the vehicle interior. The foot outlet 13 is provided.

Defroster duct 2a and face duct 2
An outlet switching damper 14 for selectively opening and closing the defroster duct 2a and the face duct 2b in accordance with the outlet mode is rotatably attached to the upstream opening of b. An outlet switching damper 15 that opens and closes the foot duct 2c according to the outlet mode is rotatably attached to the upstream opening of the foot duct 2c.

The defroster outlet 11 is opened so that the blown air blows out toward the window glass 16 of the automobile. The face blower outlet 12 is opened so that the blown air blows out toward the occupant's head and chest. The outlet 13 is opened so that the blown air blows out toward the feet of the occupant.

The evaporator 4 is a cooling means of the present invention, and is disposed in the duct 2 on the downstream side of the blower 3 and exchanges heat between the air blown by the blower 3 and the refrigerant flowing therein. Is a refrigerant evaporator that cools the refrigeration cycle, and is one of the components that constitute the refrigeration cycle 23.

The refrigeration cycle 23 is connected by a refrigerant pipe 24 so that the refrigerant circulates to the evaporator 4 via a condenser 20 receiving air from the evaporator 4 from the compressor 18, a cooling fan 19, a receiver 21, and an expansion valve 22. It is. The compressor 18 is driven to rotate by the internal combustion engine via the electromagnetic clutch 17 and discharges a high-temperature, high-pressure gas refrigerant. The electromagnetic clutch 17 is controlled based on a control signal from the ECU 6 via the clutch drive circuit 25.

The heater core 5 is a heating means of the present invention, and is provided in the duct 2 on the downstream side of the evaporator 4.
The air passing through the heater core 5 is heated using the cooling water of the internal combustion engine as a heat source. The heater core 5 has a bypass passage 2 in which air flowing in the duct 2 flows around the heater core 5.
6 are provided at offset positions. The ratio between the amount of air passing through the bypass passage 26 and the amount of air passing through the heater core 5 is adjusted by an air mix damper 27 rotatably mounted upstream of the heater core 5.

The ECU 6 has a built-in CPU, ROM, RAM and the like, and as shown in FIG.
An output operation signal and detection signals from each sensor described later are input. The ECU 6 performs various arithmetic processing based on these input signals and a control program for controlling the air conditioning in the vehicle cabin, and performs the inside / outside air switching damper 1.
0, servo motors 29, 30, 31 for driving the air outlet dampers 14 and 15, the air mix damper 27, a blower driving circuit 7 for driving the blower motor 3c of the blower 3, and a clutch driving circuit 25 for driving the electromagnetic clutch 17
To output a control signal.

The above-mentioned sensors include an internal temperature sensor 32,
An outside air temperature sensor 33, a solar radiation sensor 34, a post-evaporation temperature sensor 35, a water temperature sensor 36, and the like are used. The internal temperature sensor 32 detects the temperature (internal temperature) Tr in the vehicle compartment,
A detection signal corresponding to the detected temperature is output to the ECU 6.
The outside air temperature sensor 33 is a vehicle outside temperature detection means of the present invention, detects the outside air temperature (outside air temperature) Tam, and outputs a detection signal corresponding to the detected temperature to the ECU 6.

The solar radiation sensor 34 detects the amount of solar radiation Ts that has entered the vehicle interior, and outputs a detection signal corresponding to the detected temperature to the EC.
Output to U6. The post-evaporation temperature sensor 35 is a cooling temperature detecting means of the present invention, and detects the cooling temperature of the air cooled by the evaporator 4 (the cooling capacity of the evaporator 4), that is, the outlet air temperature of the evaporator 4 (post-evaporation temperature) Te. And outputs a detection signal corresponding to the detected temperature to the ECU 6. The cooling temperature detecting means may be a temperature sensor that detects the fin temperature of the evaporator 4. The water temperature sensor 36 detects a water temperature Tw of the cooling water of the internal combustion engine, and outputs a detection signal corresponding to the detected temperature to the ECU 6.

The air-conditioner operation panel 28 is provided on an instrument panel in the passenger compartment, and is provided with a temperature setting switch 37 for setting an interior temperature desired by an occupant, and a compressor 18.
Switch 38 for instructing ECU 6 to drive the air conditioner, and outlet mode changeover switch 3 for switching the outlet mode
9, an inlet mode changeover switch 40 for switching the inlet mode, a fan switch 41 for adjusting the air volume of the centrifugal fan 3b, an off switch 42, and the like are provided.

Here, the frost cut control of the compressor 18 when the automatic air conditioner is selected will be described. EC
U6 is, as shown in the control characteristic of FIG. 3, the clutch drive circuit 2 according to the post-evaporation temperature Te of the post-evaporation temperature sensor 35.
By turning on and off the electromagnetic clutch 17 via the control unit 5, the operation of the compressor 18 and the stop of the operation are controlled, and the frost cut control for preventing the frost of the evaporator 4 is performed. The compressor 18 also stops when the air conditioner switch 38 is manually turned off the electromagnetic clutch 17.

More specifically, as shown in the control characteristic of FIG. 3, the post-evaporation temperature Te of the post-evaporation temperature sensor 35 is the normal target temperature TeOFF1 of the stop instruction temperature of the compressor 18.
When the temperature falls below (for example, 3 ° C.), the operation of the compressor 18 is stopped (turned off) by turning off the electromagnetic clutch 17 via the clutch drive circuit 25.

Further, as shown in the control characteristic of FIG. 3, the post-evaporation temperature Te of the post-evaporation temperature sensor 35 is the normal target temperature TeON1 (= Te) of the operation instruction temperature of the compressor 18.
(OFF1 + 1 ° C .: for example, 4 ° C.) or more, the electromagnetic clutch 17 is turned on via the clutch drive circuit 25 to restart (on) the operation of the compressor 18.

In the frost cut control of the compressor 18 of this embodiment, when the outside air temperature is lower than a predetermined temperature (for example, 5 ° C.), a predetermined time (for example, Until 5 minutes have elapsed, the stop instruction temperature of the compressor 18 is set to a target temperature TeOFF2 (for example, −10 ° C.) lower than normal, and the operation instruction temperature of the compressor 18 is set to a target temperature TeON2 (TeOFF2 + 2 ° C .: for example −) lower than normal. 8 ℃)
Is set to.

When setting the target temperature TeOFF2 lower than usual, the target temperature TeOFF2 is set based on the graph of FIG. 4 so that the evaporator 4 does not frost. For example, if the outside air temperature is 5 ° C. at the start of the start of the internal combustion engine, the frost temperature of the evaporator 4 is −9 ° C. Therefore, TeOFF2 may be set to a temperature higher than this temperature (eg, −10 ° C.). If the outside air temperature is 0 ° C. at the start of the start of the internal combustion engine, the frost temperature of the evaporator 4 is −11 ° C. Therefore, TeOFF2 may be set to a temperature higher than this temperature (eg, −10 ° C.). Further, if the outside air temperature is −5 ° C. at the start of the start of the internal combustion engine, the frost temperature of the evaporator 4 is −13 ° C., and thus the TeOF is set to a temperature higher than this temperature (eg, −12 ° C.).
Just set F2. Therefore, the lower the outside air temperature, the lower the normal target temperature TeOFF2 can be set to a lower temperature.

[Operation of the Embodiment] Next, the operation of the automotive air conditioner 1 will be briefly described with reference to FIGS. When the ignition switch is turned on, the ECU 6 starts a control program, and executes calculations and processes according to the flowchart of FIG.

First, various control timers and the like are initialized (step S1). Next, the set temperature Tset is read from the temperature setting switch 37 (step S2). Subsequently, input signals are read from various sensors in order to detect a vehicle environment state that affects the air conditioning state in the vehicle compartment. That is,
The internal air temperature Tr detected by the internal air temperature sensor 32, the external air temperature Tam detected by the external air temperature sensor 33, the solar radiation amount Ts detected by the solar radiation sensor 34, the post-evaporation temperature Te detected by the post-evaporation temperature sensor 35, and the water temperature. The cooling water temperature Tw detected by the sensor 36 is read (step S3).

Next, as described above, various input data (internal temperature Tr, external temperature Tam, insolation T
s) and the target blowing temperature TAO of the air blown into the vehicle compartment is calculated based on the following equation (step S4).

## EQU1 ## TAO = Kset.multidot.Tset-Kr.Tr-Kam.Tam-Ks.Ts + C.

Here, Kset is a temperature setting gain, Tset
Is the set temperature set by the temperature setting switch 37, Kr is the inside temperature gain, Tr is the inside temperature detected by the inside temperature sensor 32, Kam is the outside temperature gain, Tam is the outside temperature detected by the outside temperature sensor 33, Ks is the solar radiation gain, Ts is the amount of solar radiation detected by the solar radiation sensor 34, and C is a correction constant.

Subsequently, the air volume of the centrifugal fan 3b is set based on a control characteristic for determining the blower voltage according to the target blowing temperature TAO stored in advance. That is, a blower voltage to be applied to the blower motor 3c via the blower drive circuit 7 is set (step S5). And
The target opening degree SW of the air mix damper 27 is calculated based on the following equation (step S6).

## EQU2 ## SW = {(TAO−Te) / (Tw−Te)} × 100 (%)

Here, Te is the post-evaporation temperature detected by the post-evaporation temperature sensor 35 (the cooling capacity signal of the evaporator 4), and Tw is the water temperature detected by the water temperature sensor 36.

Next, a target air temperature T stored in advance is stored.
The outlet mode is determined based on the control characteristics for determining the outlet mode according to AO and the setting position of the outlet switch such as the outlet mode switch 39 (step S7). Next, the previously stored target outlet temperature TAO
Then, the suction port mode is determined based on the control characteristics for determining the inside / outside air introduction mode and the set position of the suction port mode changeover switch 40 according to (step S8). Then, frost cut control, which is the main content of the present invention, is performed (step S9).

Next, the control signals determined in steps S5 to S9 are applied to the blower driving circuit 7, the servo motors 29 to 3
1 to the clutch drive circuit 25, etc., and outputs the centrifugal fan 3b, the inside / outside air switching damper 10, and the outlet switching damper 1.
4, 15 and the air mix damper 27 are operated, and the electromagnetic clutch 17 of the compressor 18 is turned on and off (step S10).

Next, it is determined whether or not the control cycle time ta has elapsed since the execution of the processing in step S10 (step S11). If this determination result is No, the control cycle time ta is determined to have elapsed. wait. Also, the judgment result is Yes
In this case, the process returns to step S2, and the above-described calculation and processing are repeated. By repeatedly executing the above calculation and processing, the vehicle auto air conditioner 1 is automatically controlled.

Next, the frost cut control in the ECU 6 will be described in detail. Here, FIG. 6 is a flowchart showing the frost cut control program. The flowchart in FIG. 6 starts when the processing in step S8 in the flowchart in FIG. 5 ends.

First, after the start of the internal combustion engine is started,
That is, it is determined whether or not a fixed time tb (for example, 5 minutes) has elapsed since the ignition switch was turned on (IG.ON) (step S21). This step S
If the result of the determination at 21 is Yes, it is determined whether or not the air conditioner switch 38 is turned on (A / C switch ON) (step S22). If the determination result in step S22 is No, a control signal for turning off the electromagnetic clutch 17 of the compressor 18 is output (step S23), and the process exits the frost cut control.

If the result of the determination in step S22 is Yes
In this case, it is determined whether the electromagnetic clutch 17 is currently turned on (ON) (step S24). If the determination result of step S24 is Yes, it is determined whether or not the post-evaporation temperature Te detected by the post-evaporation temperature sensor 35 has fallen below the normal target temperature TeOFF1 (for example, 3 ° C.) (step S24). S25).

If the decision result in the step S25 is Yes, a process in a step S23 is performed. If the result of the determination in step S25 is No, the process exits the frost cut control.

If the result of the determination in step S24 is No, the post-evaporation temperature Te
Is higher than the normal target temperature TeON1 (for example, 4 ° C.) (step S26). If the determination result of step S26 is Yes, a control signal for turning on (ON) the electromagnetic clutch 17 of the compressor 18 is output (step S27), and the process exits the frost cut control. If the result of the determination in step S26 is No, the process exits the frost cut control.

If the result of the determination in step S21 is No, it is determined whether or not the outside temperature Tam from the outside temperature sensor 33 has fallen below a predetermined temperature TA (for example, 5 ° C.) (step S28). ). If the determination result in step S28 is No, the process proceeds to step S22.

If the result of the determination in step S28 is Yes
In this case, it is determined whether the electromagnetic clutch 17 is currently turned on (ON) (step S29). If the result of the determination in step S29 is Yes, it is determined whether or not the post-evaporation temperature Te from the post-evaporation temperature sensor 35 has decreased to a target temperature TeOFF2 (for example, −10 ° C.) lower than normal (step S29). S30). This step S30
If the determination result is Yes, the process proceeds to step S23. If the result of the determination in step S30 is No, the process exits the frost cut control.

If the result of the determination in step S29 is No, the post-evaporation temperature Te
Is higher than the target temperature TeON2 (for example, −8 ° C.) lower than normal (step S31).
If the determination result in step S31 is Yes, the process moves to step S27. Step S31
If the judgment result is No, the process exits the frost cut control.

As described above, when the outside air temperature Tam drops below the predetermined temperature TA (for example, 5 ° C.) when the user gets on the car, a certain period of time (for example, 5 minutes) after the internal combustion engine is started. Until the time elapses, that is, until the coolant temperature Tw of the internal combustion engine flowing into the heater core 5 reaches a water temperature (for example, 40 ° C.) at which the temperature inside the vehicle compartment can be controlled, the stop instruction temperature of the compressor 18 is set to a target temperature lower than normal. T
eOFF2 (for example, −10 ° C.).
Further, the operation instruction temperature of the compressor 18 is changed to a target temperature TeON2 (for example, −8 ° C.) lower than usual.

As a result, the outside temperature Tam becomes the predetermined temperature TA.
Even if the temperature drops below (for example, 5 ° C.), the operation of the compressor 18 is continued until the temperature drops below the target temperature TeOFF2 (for example, −10 ° C.) which is lower than usual. Therefore, the refrigerant flowing into the evaporator 4 and the air flowing through the duct 2 toward the vehicle interior exchange heat to cool the air, thereby dehumidifying the air blown out into the vehicle interior.

[Effects of the Embodiment] Therefore, when the internal temperature of the internal combustion engine for starting the internal combustion engine in which the occupant gets into the parked automobile and turns on the ignition switch is started, the external air temperature Tam becomes equal to the predetermined temperature TA (for example, 5 degrees). ° C) or lower, the internal temperature Tr is low, and even when the relative humidity in the vehicle interior is high, the dehumidifying operation of the automotive auto air conditioner 1 is performed without performing a troublesome manual operation. And the fogging of the window glass 16 of the automobile can be prevented.

Also, when the outside air temperature Tam falls below a predetermined temperature TA (for example, 5 ° C.), a predetermined time (for example, 5 minutes) has elapsed since the internal combustion engine was started. By the time the evaporator temperature Te falls below the target temperature TeOFF2 lower than normal, the electromagnetic clutch 17 is turned off and the operation of the compressor 18 is stopped, so that the temperature of the evaporator 4 drops below the frost temperature. Therefore, frost of the evaporator 4 can be prevented, and a decrease in the dehumidifying ability of the automotive auto air conditioner 1 can be prevented.

[Modification] In this embodiment, the stop instruction temperature of the compressor is set to a target temperature lower than usual until a certain time has elapsed after the start of the internal combustion engine. When the water temperature is a predetermined water temperature (for example, 4
The stop instruction temperature may be set to a target temperature lower than usual until the temperature rises to 0 ° C. or more. Further, the stop instruction temperature of the compressor may be set to a target temperature lower than usual until the lubricating oil temperature of the internal combustion engine rises above a predetermined oil temperature.
Further, the present invention can also be applied to a type in which the normal target temperature of the compressor stop instruction temperature can be changed, such as economy control.

In this embodiment, the evaporator of the refrigeration cycle is used as the cooling means, but a cooling part such as a Peltier element may be used as the cooling means. In addition, not only the cooling capacity of the cooling means is turned on and off, but also the cooling capacity of the cooling means varies widely by, for example, changing the rotation speed of the compressor by changing the frequency by an inverter or using a variable capacity compressor. The present invention may be applied to a device.

[0053]

According to the present invention, even when the temperature outside the vehicle compartment falls below a predetermined temperature at the start of the start of the internal combustion engine, the temperature inside the vehicle compartment is low, and the relative humidity inside the vehicle compartment is high, the cooling means can be used. By setting the stop instruction temperature to a target temperature lower than usual, it is possible to achieve both prevention of frost of the cooling means and prevention of fogging of the window glass.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a schematic structure of an automobile air conditioner using the present invention.

FIG. 2 is a block diagram showing a schematic structure of an ECU using the present invention.

FIG. 3 is a characteristic diagram showing a frost cut control characteristic with respect to a post-evaporation temperature.

FIG. 4 is a graph showing a relationship between a target temperature lower than usual and an outside air temperature.

FIG. 5 is a flowchart showing a basic control program of the ECU.

FIG. 6 is a flowchart showing a frost cut control program of FIG. 5;

[Explanation of symbols]

 Reference Signs List 1 auto air conditioner for vehicle (air conditioner for vehicle) 2 duct 4 evaporator (cooling means) 5 heater core (heating means) 6 ECU (control device) 17 electromagnetic clutch 18 compressor 33 outside temperature sensor (outside compartment temperature detecting means) 35 ever Rear temperature sensor (cooling temperature detecting means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-34220 (JP, A) JP-A-2-31917 (JP, A) JP-A-1-57916 (JP, U) JP-A-63 40222 (JP, U) Japanese Utility Model 63-41515 (JP, U) Japanese Patent Publication No. 5-248 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60H 3/00 B60H 1 / 32 623

Claims (1)

(57) [Claims] 1. A duct for sending air into a vehicle interior, cooling means for cooling air flowing in the duct, and heating means for heating air flowing in the duct using cooling water of an internal combustion engine. A cooling temperature detecting means for detecting a cooling temperature of the air cooled by the cooling means, the cooling means when the cooling temperature detected by the cooling temperature detecting means falls below the stop instruction temperature of the cooling means. A control device for stopping the operation of the vehicle.The control device has an outside-cabin temperature detecting means for detecting a temperature outside the cabin, and the start-up of the internal combustion engine is detected by the outside-compartment temperature detecting means. When the temperature outside the vehicle compartment has dropped below a predetermined temperature, the vehicle is characterized in that a stop instruction temperature of the cooling means is set to a target temperature lower than usual until the internal combustion engine reaches a predetermined operation state. Use the air conditioner.