JP2002362140A - Air conditioner for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner for an electric vehicle capable of achieving sufficient cooling ability even when heat environments are changed, and preventing an excessive load on a motor for a compressor or useless power consumption of it. SOLUTION: Even when temperature of an evaporator 7 becomes lower than a set temperature, the motor for the compressor is not completely stopped, but it is rotated at a low rotation number, so that deterioration of cooling ability of the evaporator 7 is prevented. At this time, a rotation number of a motor 9 for driving a fan is regulated to minimize total of power consumption of the motor 3 for the compressor and power consumption of the motor 9 for driving the fan, thereby total power consumption necessary for actuation of this air conditioner for an electric vehicle can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an air conditioner for an electric vehicle, and more particularly to an improvement for maintaining a comfortable cooling capacity and improving a power saving effect.

[0002]

2. Description of the Related Art A compressor motor is driven and controlled at a target rotation speed corresponding to a set cooling temperature, and compression and expansion of gas are cyclically performed between a condenser and an evaporator by a compressor driven by the compressor motor. An air conditioner for an electric vehicle which performs cooling repeatedly is already known.

In an air conditioner for an electric vehicle, for example, as disclosed in Japanese Patent Application Laid-Open No. 63-116922, when an excessive load on a compressor motor is detected, the compressor motor is completely stopped. When the internal pressure of the condenser is reduced and the load on the compressor motor is reduced, the compressor motor is restarted and the number of revolutions of the compressor motor is adjusted to the desired number of revolutions, that is, the set cooling temperature. It is common to return to the target rotation speed.

[0004]

Such a processing operation is performed to prevent an excessive load from acting on the compressor motor or to prevent excessive power consumption by the compressor motor. However, while the compressor motor is forcibly stopped, there is an adverse effect that sufficient cooling capacity required for the air conditioner cannot be exhibited.

If the compressor motor is completely stopped while the internal pressure of the condenser is still increasing, a large drive torque is required when the compressor motor is restarted. And a driving source (such as an inverter) are required, which causes a problem that the manufacturing cost of the entire apparatus is increased.

[0006] On the other hand, control of a fan drive motor for driving a condenser fan of an automotive air conditioner is based on the outside air temperature, water temperature and vehicle speed as disclosed in, for example, Japanese Utility Model Laid-Open No. 1-145806. There is known one that performs on / off control of a fan driving electric motor.

The on / off control of the fan drive motor disclosed in Japanese Utility Model Laid-Open Publication No. 1-145806 is based on changes in the thermal environment of the outside air temperature and the water temperature and changes in the vehicle speed. If this occurs, the condenser fan stops carelessly and the internal pressure of the condenser rises, causing an excessive load on the compressor motor that drives the compressor, or excessive power consumption by the compressor motor. There is a possibility that it will.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the drawbacks of the prior art, to achieve a sufficient cooling capacity even when there is a change in the thermal environment, and to provide an excessively large amount of electric motor for the compressor. An object of the present invention is to provide an air conditioner for an electric vehicle that can prevent a load and useless power consumption.

[0009]

According to the present invention, a compressor motor is driven and controlled at a target rotation speed corresponding to a set cooling temperature, and a compressor driven by the compressor motor connects a condenser and an evaporator to each other. An air conditioner for an electric vehicle that performs cooling by cyclically repeating compression and expansion of gas, and in order to achieve the above object, in particular, a condenser fan that air-cools a condenser,
A fan drive motor for driving the condenser fan is provided, and an evaporator temperature sensor for detecting the temperature of the evaporator and a compressor motor for detecting that the temperature detected by the evaporator temperature sensor is equal to or lower than a set temperature. A configuration is provided in which a compressor motor drive restricting means for reducing the number of revolutions to a value equal to or lower than the target number of revolutions is provided.

When the temperature detected by the evaporator temperature sensor becomes equal to or lower than the set temperature, the compressor motor drive limiting means is operated to reduce the rotation speed of the compressor motor. The cooling performance can be prevented from being significantly reduced, and a comfortable cooling effect can be obtained. In addition, the occurrence of overload due to excessive operation of the compressor motor, wasteful power consumption and freezing of the evaporator are prevented, and it is not necessary to restart the compressor motor against a large load. And the capacity of power sources (such as inverters) can be reduced.

In addition to the above-mentioned structure, after the operation of the compressor motor drive restricting means is activated, the fan drive is controlled so that the sum of the power consumed by the compressor motor and the power consumed by the fan drive motor is minimized. A fan drive motor drive control means for automatically adjusting the number of revolutions of the motor may be provided.

In order to maintain the rotation speed of the compressor motor at a predetermined value equal to or lower than the target rotation speed, the power consumption required for the compressor motor is large when the rotation speed of the condenser fan is large, that is, when the condenser is strongly cooled. And when the gas pressure in the condenser is reduced, the power consumption required for the fan driving motor for the high-speed rotation of the condenser fan relatively increases. . On the other hand, on the other hand, the power consumption required for the compressor motor in order to maintain the rotation speed of the compressor motor at a predetermined value equal to or lower than the target rotation speed, when the rotation speed of the condenser fan is small, that is, When the cooling of the condenser is inadequate and the gas pressure inside the condenser is insufficiently reduced, the pressure becomes relatively large.However, since the condenser fan can be rotated at a low speed, it is required for the motor for driving the fan. Power consumption is relatively reduced. Therefore, in consideration of the power consumption required for the compressor motor and the power consumption required for the fan drive motor, the fan drive motor drive control means controls the power consumption and the fan required for the compressor motor. By automatically adjusting the rotation speed of the fan drive motor so that the total power consumption required for the drive motor is minimized, the rotation speed of the compressor motor can be reduced below the target rotation speed with the least power consumption. Value can be maintained.

The fan drive motor drive control means includes:
For example, the total power consumption is sequentially obtained while decreasing the rotation speed of the fan driving motor by a predetermined amount, and the rotation speed of the fan driving motor when the total power consumption switches from the decreasing trend to the increasing trend is determined by the fan driving motor. This can be realized by a configuration in which the number of rotations is output.

As described above, the compressor motor drive limiting means reduces the rotational speed of the compressor motor when the temperature detected by the evaporator temperature sensor becomes equal to or lower than the set temperature. In the immediately subsequent stage, the rotation speed of the fan drive motor at that time, that is, the rotation speed of the fan drive motor that has been optimized for the compressor motor rotating at the target rotation speed, is changed to the compressor motor at this time. Is relatively excessive with respect to the number of rotations of the motor, and excessive rotation of the fan driving motor results in wasteful consumption of electric power. Thus, it is clear that the number of revolutions of the fan drive motor is excessive at the stage immediately after the operation of the compressor motor drive restricting means,
The sum of power consumption is sequentially obtained while the rotation speed of the fan drive motor is reduced by a predetermined amount by the fan drive motor drive control means. By detecting the number of revolutions of the fan drive motor when the sum of the power consumption is minimum (minimum), and constantly outputting this revolution number as the revolution number of the fan drive motor,
Power consumption can be reduced.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing a block diagram of a hardware configuration of an electric vehicle air conditioner 1 according to an embodiment to which the present invention is applied.

As shown in FIG. 1, this electric vehicle air conditioner 1 includes a compressor motor 3 for driving a compressor 2, a condenser 4 for cooling and condensing and liquefying the gas compressed by the compressor 2, and a condenser. 4
5 for relaying the liquid refrigerant sent from the receiver 5, an expansion valve 6 for decompressing and expanding the liquid refrigerant sent from the receiver 5, and a cooling effect by removing surrounding heat by using evaporation of the liquid refrigerant. And an evaporator 7 exhibiting the above.

A condenser fan 8 for cooling the condenser 4 is driven to rotate by a fan driving motor 9.

The controller 10 for driving and controlling these elements includes a CPU and an RO required for arithmetic processing.
M and a memory such as a RAM. The deviation between the cooling temperature set by the temperature setting switch provided on the setting panel 15 of the electric vehicle and the current value Tn of the evaporator temperature detected by the evaporator temperature sensor 11 is calculated. Based on this, the compression efficiency of the gas required for the compressor 2 at that time, specifically, the target rotation speed of the compressor motor 3 for driving the compressor 2 is obtained, and the output is output from the compressor motor rotation sensor 12. The actual value of the actual rotation speed is read, the duty ratio of the inverter 13 is adjusted based on the deviation between the actual rotation speed and the target rotation speed, and the substantial drive voltage Vc supplied to the compressor motor 3 is calculated. By controlling, the compressor motor 3 achieves the target rotation speed required at that time.

Also, a compressor motor current detector 1
Reference numeral 4 denotes a load acting on the compressor motor 3, specifically, a value of an actual current Ic flowing through the compressor motor 3, and a fan drive motor current detector 16 detects an actual current flowing through the fan drive motor 9. The value of the current If is detected.

The rotation speed of the fan drive motor 9 for driving the condenser fan 8 is adjusted by the value of the drive voltage Vf applied from the controller 10 to the fan drive motor 9.

The ROM in which the CPU of the controller 10 and its control program are stored is the compressor motor drive restricting means and the fan drive motor drive control means in this embodiment.

Next, referring to the flowchart of the motor drive limiting process of FIG. 2 which is repeatedly executed by the CPU of the controller 10 at predetermined intervals, the compressor motor drive limiting means and the fan drive motor drive control means in this embodiment will be described. Will be described in detail.

The CPU that has started the motor drive restriction process,
First, the current value Tn of the evaporator temperature detected by the evaporator temperature sensor 11 is read (step s1), and whether or not this value is equal to or lower than a preset set temperature α, that is, due to excessive cooling of the evaporator 7, It is determined whether there is a possibility that freezing will occur or an overload will occur due to excessive operation of the compressor motor 3 (step s2). In general, about 2 ° C. is appropriate as the value of the set temperature α for preventing freezing.

If the determination result of step s2 is false, that is, if it is determined that there is no possibility of freezing or overload, the CPU sets the temperature using the temperature setting switch of the setting panel 15 as in the conventional case. The value of the drive voltage to be supplied to the compressor motor 3 is determined based on the deviation between the determined cooling temperature and the current value Tn of the evaporator temperature detected by the evaporator temperature sensor 11, and this value is used to drive the compressor motor. The rotational speed of the fan driving motor 9 for driving the condenser fan 8 based on the magnitude of the load acting on the compressor 2 while updating the voltage storage register Vc, in other words, the fan driving motor 9
Is obtained, and this value is updated and set in the fan drive motor drive voltage storage register Vf (step s1).
1).

Next, the CPU reads the value of the actual current Ic flowing through the compressor motor 3 via the compressor motor current detector 14 and calculates the value of the actual current If flowing through the fan drive motor 9. Reading via the fan drive motor current detector 16 (step s
9) Based on the drive voltage Vc and the actual current Ic of the compressor motor 3 and the values of the drive voltage Vf and the actual current If of the fan drive motor 9, the power consumed by the compressor motor 3 and the fan drive motor 9 The sum [Vc · Ic + Vf · If] of the consumed power is obtained, the value is updated and stored in the previous cycle power consumption storage register Wp (step s10), and the motor drive restriction processing in the processing cycle ends.

The compressor motor 3 is driven and controlled based on the drive voltage set in the compressor motor drive voltage storage register Vc, and the fan drive motor 9 is set in the fan drive motor drive voltage storage register Vf. Drive control is performed based on the drive voltage.

Thus, the current value T of the evaporator temperature
Under the condition that n exceeds the set temperature α, the drive control for the compressor motor 3 and the fan drive motor 9 is exactly the same as the conventional one, and is simply the sum of the power consumption for each processing cycle of the motor drive restriction processing. [Vc ・ Ic + Vf ・
Only] is that the value of [If] is updated and stored in the previous cycle power consumption storage register Wp.

On the other hand, if the result of the determination in step s2 is true, that is, if it is determined that the current value Tn of the evaporator temperature is equal to or lower than the set temperature α and there is a possibility of freezing or overloading, The CPU as the compressor motor drive restricting means determines the drive voltage of the compressor motor 3 required to achieve the set cooling temperature, that is, the step s1 immediately before the determination result of the step s2 becomes true.
The value of the set drive voltage β is updated and set in the compressor motor drive voltage storage register Vc in place of the drive voltage of the compressor motor 3 obtained in the process 1, and the rotation speed of the compressor motor 3 is set to the target rotation speed. By dropping below, freezing of the evaporator 7 and overload of the compressor motor 3 are prevented (step s3).

In the present embodiment, the minimum drive speed of the compressor motor 3 limited by the performance of the inverter 13, for example, the value of the drive voltage corresponding to 500 rpm is used as the set drive voltage β.
Regardless of the value of the compressor motor drive voltage storage register Vc immediately before the determination result of step s2 becomes true, by executing the process of step s3,
The number of revolutions of the compressor motor 3 must be set at step s
Compressor motor 3 immediately before the judgment result of 2 is true
Will be reduced below the number of revolutions.

At this stage, the number of revolutions of the fan driving motor 9, that is, the value of the driving voltage Vf is still set according to the load of the compressor motor 3 before the result of the determination in step s2 becomes true. , Fan driving motor 9
Of the compressor motor 3 has an excessive value with respect to the reduced number of rotations of the compressor motor 3.

FIG. 3 shows an example of the relationship between the power consumption required for the compressor motor 3 and the power consumption of the fan drive motor 9 in order to maintain the rotation speed of the compressor motor 3 at a predetermined value. Show. In this case, the curve indicating the power consumption of the compressor motor 3 is substantially the same as the curve indicating the torque of the compressor motor 3, and
The rotation speed of the fan driving motor 9 is substantially the same as the driving voltage of the fan driving motor 9.

As already described in the section of the means for solving the problems, the power consumption required for the compressor motor 3 to maintain the rotation speed of the compressor motor 3 at a predetermined value is determined by the fan drive motor. 9 is relatively small when the rotation speed of the condenser 9 is large and the condenser 4 is cooled strongly and the gas pressure in the condenser 4 is reduced.
Conversely, when the rotation speed of the electric motor 9 for driving the fan is small and the cooling of the condenser 4 is insufficient and the reduction of the gas pressure in the condenser 4 is insufficient, the rotation becomes relatively large.

An example of the correspondence between the power consumption of the fan driving motor 9 and the power consumption of the compressor motor 3 immediately after the result of the determination in step s2 becomes true is indicated by points P1 and P2 in FIG. . Note that P3 is the total power consumption.

As shown in FIG. 3, as the number of revolutions of the fan driving motor 9 increases, the power consumption required for the compressor motor 3 decreases as the rotation speed increases. As shown in the figure, in a situation where the rotational speed of the fan driving motor 9 is excessive, the rate of decrease in the power consumption of the compressor motor 3 is higher than the rate of increase in the power consumption of the fan driving motor 9. Is smaller, the sum of the power consumption of the compressor motor 3 and the power consumption of the fan drive motor 9 becomes larger than necessary.
As a whole, power consumption is wasted.

As described above, the compressor motor 3
Immediately after the rotation speed is reduced, the rotation speed of the fan driving electric motor 9 is excessive, that is,
Since it is clear that the rotation speed is higher than the rotation speed of the fan driving motor 9 when the total power consumption is minimized, the fan driving motor 9 is changed from the state shown in B in FIG. Number of rotations of motor 9 (substantially driving voltage)
Is gradually reduced by a predetermined amount, the sum of the power consumption at each time point is obtained, and the rotation speed of the motor 9 for driving the fan when the value is minimized is maintained. The rotation speed can be maintained at a predetermined value.

As shown in FIG. 3, the sum of the power consumption of the compressor motor 3 and the power consumption of the fan drive motor 9 is a secondary convex having a downward convex corresponding to the change in the rotation speed of the fan drive motor 9. It is clear that the rotation speed of the fan driving motor 9 is changed to a function, and it is clear that the rotation speed of the fan driving motor 9 is excessively large at this time and is larger than an appropriate rotation speed. From the above, the total power consumption at each time point is obtained while gradually decreasing the power consumption by a predetermined amount, and the rotation speed A (substantially the driving voltage) of the fan driving electric motor 9 when the value is switched from the decreasing tendency to the increasing tendency is obtained. It will be good. That is, the total power consumption Q3 corresponding to the rotation speed A is the minimum value (minimum value) of the total power consumption.

Accordingly, the CPU as the fan drive motor drive control means firstly sets a predetermined value Δ from the current value of the fan drive motor drive voltage storage register Vf.
V is subtracted, and the value obtained by the subtraction is updated and set in the fan drive motor drive voltage storage register Vf.
The number of rotations (drive voltage) of the motor 9 for driving the fan is reduced by a predetermined amount (step 4).

Next, the CPU serving as the fan drive motor drive control means determines the value of the actual current Ic flowing through the compressor motor 3 by the compressor motor current detector 1.
4, the value of the actual current If flowing through the fan driving motor 9 is read through the fan driving motor current detector 16, and the power consumption stored in the previous period power consumption storage register Wp That is, after reading the value Wp of the total power consumption before reducing the rotation speed (drive voltage) of the fan driving electric motor 9 in the process of step s4 (step s5), the total power consumption at the present time [Vc [Ic + Vf · If] is obtained, and the magnitude relation with the total power consumption value Wp in the previous cycle is compared (step s6).

Here, if the result of the determination in step s6 is false, that is, the total power consumption is reduced by reducing the rotation speed (drive voltage) of the fan drive motor 9 in the process in step s4. If determined,
The rotation speed of the fan driving motor 9 at the present time is in the section AB in FIG. 3, and the change in the total power consumption due to the reduction in the rotation speed (driving voltage) of the fan driving motor 9 is maintained in a decreasing trend. That is, it means that the total power consumption may be further reduced by further reducing the rotation speed (drive voltage) of the fan driving motor 9.

Therefore, in this case, the CPU updates and stores the value of the total power consumption [Vc · Ic + Vf · If] obtained in the processing cycle in the previous cycle power consumption storage register Wp (step s7), and then proceeds to step s6. Until the determination result becomes true, the processes of steps s4 to s7 are repeatedly executed in the same manner as described above.

If the result of the determination at step s6 becomes true during the repetitive execution of such processing, the change in the total power consumption due to the reduction in the rotation speed (drive voltage) of the fan drive motor 9 decreases. That is, even if the rotation speed (drive voltage) of the fan driving motor 9 is further reduced, the total power consumption does not decrease. Is increased.

Accordingly, the CPU as the fan drive motor drive control means adds the predetermined value ΔV to the current value of the fan drive motor drive voltage storage register Vf, thereby obtaining the value of the fan drive motor drive voltage storage register Vf. Is returned to the final value at the time when the total power consumption decreases, and this value is stored in the fan driving motor driving voltage storage register Vf as the rotation speed (driving voltage) of the fan driving motor 9 when the total power consumption is minimized. It is held (step s8).

The value of the fan drive motor drive voltage storage register Vf obtained in this way is the number of rotations (drive voltage) of the fan drive motor 9 required to minimize the total power consumption, that is, in short. , A value corresponding to A in FIG.

However, since the predetermined value ΔV has a certain magnitude, strictly speaking, the value of the drive voltage stored in the fan drive motor drive voltage storage register Vf at this time is the total power consumption. In comparison with the drive voltage of the fan drive motor 9 which is actually required for minimizing it, the drive voltage becomes a large value within a range where ΔV is the maximum value of the error.

If it is desired to set the drive voltage of the fan drive motor 9 required to minimize the total power consumption very strictly, the processing time required for optimizing the total power consumption is as follows. Although it becomes longer, the above-described processing is performed by setting the value of ΔV itself to a small value, or the processing itself becomes somewhat complicated.
May be reset to a smaller value, and processing equivalent to steps s4 to s7 described above may be performed again.

When the value of the fan drive motor drive voltage storage register Vf is determined after the process of step s8 is completed, the CPU determines the actual current Ic flowing through the compressor motor 3 in the same manner as described above. The value is read via the compressor motor current detector 14, and the value of the actual current If flowing through the fan drive motor 9 is read via the fan drive motor current detector 16 (step s).
9) Based on the drive voltage Vc and the actual current Ic of the compressor motor 3 and the values of the drive voltage Vf and the actual current If of the fan drive motor 9, the power consumed by the compressor motor 3 and the fan drive motor 9 The sum [Vc · Ic + Vf · If] of the consumed power is obtained, the value is updated and stored in the previous cycle power consumption storage register Wp (step s10), and the motor drive restriction processing in the processing cycle ends.

The total power consumption obtained by the process of step s10 performed at this stage is a value corresponding to Q3 in FIG.

Even after the value of the fan drive motor drive voltage storage register Vf is determined in this way, under the situation where the evaporator temperature Tn is equal to or lower than the set temperature α,
Step s4 in the motor drive restriction process for each predetermined cycle
And the process of step s8 are repeatedly executed, and the fan drive motor drive voltage storage register Vf
However, since the predetermined value ΔV is a sufficiently small value, a change in the value of the register Vf causes substantial inconvenience, for example, the fan driving motor 9.
There is no occurrence of noise or the like due to the speed change of the vehicle.

[0049]

According to the electric vehicle air conditioner of the present invention, the rotational speed of the compressor motor is forcibly reduced when the temperature of the evaporator becomes equal to or lower than the set temperature. A sufficient cooling effect can be prevented beforehand, and a comfortable cooling effect can be obtained.At the same time, freezing of the evaporator due to excessive operation of the compressor motor, overload of the compressor motor and wasteful power consumption are also prevented. Can be.
Further, since it is not necessary to restart the compressor motor against a large load, it is possible to reduce the size of the compressor motor and the capacity of the power source (such as an inverter).

Further, the rotation of the compressor motor is controlled in a state where the rotation speed of the fan drive motor is adjusted so that the total of the power consumed by the compressor motor and the power consumed by the fan drive motor is minimized. Since the motor is maintained, the power consumption of the fan driving motor caused by the excessive rotation of the condenser fan is wasted, and the driving generated in the compressor motor due to the increase in the pressure in the condenser caused by the under rotation of the condenser fan. Waste of power consumption of the compressor motor for coping with the increase in torque can be eliminated.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a block diagram of a hardware configuration of an electric vehicle air conditioner according to an embodiment to which the present invention is applied.

FIG. 2 is a flowchart showing an outline of a motor drive restriction process performed by a controller of the electric vehicle air conditioner of the embodiment.

FIG. 3 is a conceptual diagram showing an example of a relationship between power consumption required for a compressor motor and power consumption of a fan drive motor in order to maintain the rotation speed of the compressor motor at a predetermined value.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electric vehicle air conditioner 2 Compressor 3 Compressor motor 4 Condenser 5 Receiver 6 Expansion valve 7 Evaporator 8 Condenser fan 9 Fan drive motor 10 Controller (compressor motor drive limiting means, fan drive motor drive control means) 11 Evaporator temperature Sensor 12 Compressor motor rotation sensor 13 Inverter 14 Compressor motor current detector 15 Setting panel 16 Fan drive motor current detector

Claims (3)

[Claims] A compressor motor is driven and controlled at a target rotation speed corresponding to a set cooling temperature, and compression and expansion of gas are cyclically performed between a condenser and an evaporator by a compressor driven by the compressor motor. An air conditioner for an electric vehicle that repeatedly performs cooling in an air conditioner, wherein a condenser fan that air-cools the condenser and a fan driving motor that drives the condenser fan are provided, and an evaporator temperature sensor that detects a temperature of the evaporator. A compressor motor drive limiting unit that detects that the temperature detected by the evaporator temperature sensor has become equal to or lower than a set temperature and reduces the rotation speed of the compressor motor to a value equal to or lower than the target rotation speed. Characteristic air conditioner for electric vehicles. 2. A compressor motor is driven and controlled at a target rotation speed corresponding to a set cooling temperature, and compression and expansion of gas are cyclically performed between a condenser and an evaporator by a compressor driven by the compressor motor. An air conditioner for an electric vehicle that repeatedly performs cooling in an air conditioner, wherein a condenser fan that air-cools the condenser and a fan driving motor that drives the condenser fan are provided, and an evaporator temperature sensor that detects a temperature of the evaporator. A compressor motor drive limiting unit that detects that the temperature detected by the evaporator temperature sensor has become equal to or lower than a set temperature and reduces the rotation speed of the compressor motor to a value equal to or lower than the target rotation speed; After the operation of the motor drive restricting means is activated, Fan drive motor drive control means for automatically adjusting the rotation speed of the fan drive motor so that the sum of the power consumed by the fan and the power consumed by the fan drive motor is minimized. An air conditioner for an electric vehicle. 3. The fan drive motor drive control means sequentially obtains the sum of the power consumption while decreasing the rotation speed of the fan drive motor by a predetermined amount, and the sum of the power consumption tends to increase from a decreasing trend. The air conditioner for an electric vehicle according to claim 2, wherein the number of rotations of the fan driving motor at the time of switching to (i) is output as the number of rotations of the fan driving motor.