JPH0858359A - Air-conditioner for vehicle - Google Patents

Abstract

PURPOSE: To prevent blur of a window glass by dehumidifying inside a car room ventilated while defrosted, even when frost is produced in an evaporator. CONSTITUTION: An evaporator in a duct 3 is arranged to be divided into the first/second evaporators 16, 17, to provide a solenoid opening/closing valve in the upstream of a refrigerant of the second evaporator 17. During operating a refrigerating cycle, when frosting is detected, a defrosting operation is started. In the defrosting operation, the solenoid opening/closing valve is closed to supply a refrigerant to only the first evaporator 16 and to stop operating the second evaporator 17. The inside air is guided to the first evaporator 16, and the outside air is guided to the second evaporator 17. Then in the first evaporator 16, it is defrosted by warm inside air, also to dehumidify the inside air. The second evaporator 17 is defrosted by the outside air of passing. As a result, the dehumidified inside air and the fresh outside air of low humidity are supplied to inside a car room, to perform ventilating it further dehumidified, so as to prevent blur of a window glass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle air conditioner capable of cooling the interior of a vehicle with air passing through an evaporator of a refrigeration cycle.

[0002]

2. Description of the Related Art An example of an air conditioner currently installed in a bus vehicle is shown in the schematic view of FIG. In this air conditioner, an evaporator 102 for a refrigeration cycle and a heater core 103 downstream of the evaporator 102 are arranged in a duct 101 that blows air-conditioned air into the passenger compartment, and the evaporator 1 is used during cooling and dehumidification.
02 is operated to operate the heater core 103 during heating and dehumidification. In addition, the duct 101 includes an inside air introduction port 104 that introduces vehicle interior air (hereinafter, inside air) and an outside air introduction port 105 that introduces vehicle outside air (hereinafter, outside air), and the inside air that opens and closes the inside air introduction port 104. Shutter 10
6, and the outside air door 10 for opening and closing the outside air inlet 105
The open / closed state of No. 7 is controlled to adjust the introduction ratio of the inside air and the outside air introduced into the duct 101.

[0003]

In a bus vehicle, the evaporator 102 may be operated to cool or dehumidify the passenger compartment even when the outside air temperature is low such as in winter. When the evaporator 102 is operated in a state where only the inside air is introduced into the duct 101, a relatively high temperature (for example, 25
(° C.) is supplied to the evaporator 102, so frost is unlikely to be generated on the evaporator 102. Therefore, when the outside air temperature decreases, the air conditioner may automatically select the inside air mode or set the inside air mode by manual operation. However, in the state where only the inside air is introduced into the duct 101, the passenger compartment is not ventilated, so that the smoke of the cigarette is difficult to be exhausted, and the carbon dioxide due to the breathing of the occupant rises, and the oxygen amount decreases, so that the occupant becomes uncomfortable. A problem that gives a pleasant feeling occurs. Further, in the inside air mode, the outside glass having low humidity is taken into the passenger compartment, and there is no effect of discharging a part of the inside air having high humidity to suppress the increase in humidity. Therefore, in the inside air mode, the window glass is easily fogged.

Therefore, when the inside / outside air mode for introducing the inside air and the outside air at the same time is set, the inside air having a relatively high temperature and the outside air having a low temperature are mixed and supplied to the evaporator 102. Frost is generated in the evaporator 102 at about 13 ° C. For example, the temperature of the outlet temperature sensor 108 that detects the temperature of the fins on the air downstream side of the evaporator 102 decreases to a predetermined temperature.
When the occurrence of frost is detected, the operation of the evaporator 102 is stopped and the frost is removed (defrosting), so dehumidification is not performed during defrosting, and the window glass easily becomes cloudy. Become.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. An object of the present invention is to perform ventilation while removing frost even if frost is generated on the evaporator to dehumidify the interior of the vehicle to defrost the window. (EN) Provided is an air conditioner for a vehicle, which prevents the occurrence of fogging of glass.

[0006]

The vehicle air conditioner of the present invention employs the following technical means. [Means of Claim 1] An air conditioner for a vehicle comprises: (a) an inside air inlet for introducing air into the vehicle compartment; an outside air inlet for introducing air outside the vehicle compartment; and a duct for guiding the introduced air to the vehicle interior.
(B) a blower for generating an air flow toward the vehicle interior in this duct; and (c) a fan that is arranged in parallel with the air flow in the duct to cool the air passing through the duct. A refrigeration cycle including first and second evaporators; and (d) introducing the vehicle interior air introduced from the inside air introduction port to the first evaporator and the vehicle exterior air introduced from the outside air introduction port to the second Introduction passage forming means for leading to the evaporator; (e) stopping means for stopping the flow of the refrigerant supplied to the second evaporator;
(F) Frost detection means for detecting frost on at least one of the first evaporator and the second evaporator;
(G) When the frost formation detecting means detects the frost formation, the introduction passage forming means guides the vehicle interior air to the first evaporator and the vehicle exterior air to the second evaporator, and the stopping means causes the vehicle exterior air to flow to the second evaporator. And a frost prevention means for stopping the supply of the refrigerant to the second evaporator and supplying the refrigerant only to the first evaporator.

[Means for Claim 2] The vehicle air conditioner according to claim 1 is (h) an inside air shutter which is provided at the inside air introduction port, and which switches between introduction and stoppage of introduction of air in the vehicle interior,
(I) An outside air door provided at the outside air introduction port and switching between introduction and stoppage of introduction of the air outside the vehicle compartment; (j) introduction into the duct by controlling open / closed states of the inside air shutter and the outside air door. And an air quality adjusting means for adjusting the introduction ratio of the vehicle interior air and the vehicle exterior air.

[Means of Claim 3] In the vehicle air conditioner of Claim 1, the frost formation detecting means (f-1) is a first outlet temperature for detecting the temperature of the air passing through the first evaporator. Detection means, (f-2) second outlet temperature detection means for detecting the temperature of the air passing through the second evaporator, and (f-3) low pressure detection means for detecting the low pressure of the refrigeration cycle, (F-4) When the temperature detected by the first and second outlet temperature detecting means is lower than a predetermined temperature and the low pressure value detected by the low pressure detecting means is lower than a predetermined pressure value, frost formation is determined. And a means for determining frost formation.

[0009]

When the normal refrigeration cycle is operating, the stop means is not operated, and the refrigerant is supplied to both the first and second evaporators to cool the air in the duct passing through the first and second evaporators. To do. When the frost detection means detects frost,
The refrigerant supply to the second evaporator is stopped by the stopping means in a state in which the introduction air forming means guides the inside air to the first evaporator and the outside air to the second evaporator.
Refrigerant is supplied only to the evaporator.

Then, in the normal operation, the air was cooled by both the first and second evaporators, whereas
Since the air is cooled only by the evaporator, the cooling capacity of the air is reduced and the first evaporator is
Inner air having a relatively high temperature is guided. Therefore, the generation of frost in the first evaporator is prevented, and the inside air passing through the first evaporator is cooled and dehumidified. Then, the dehumidified air is blown into the vehicle compartment through the duct.

On the other hand, the frost is removed by the outside air when the outside air passes through the second evaporator while the supply of the refrigerant is stopped. When the outside air temperature is low such as in winter, the humidity is low and the outside air containing a large amount of oxygen is
After passing through the evaporator, it is blown out into the passenger compartment from the duct, and the air contaminated with cigarette smoke, carbon dioxide, etc. and the humid air in the passenger compartment are exhausted to the outside of the passenger compartment.

[0012]

According to the vehicle air conditioner of the present invention, as described above, even if frost is generated due to a decrease in outside air temperature, the inside air is dehumidified by removing the frost while removing the frost. In addition to supplying air, it also supplies fresh outside air with low humidity to the passenger compartment while removing frost. In other words, it is possible to perform ventilation while removing the frost and prevent the fogging of the window glass.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a vehicle air conditioner of the present invention will be described based on an embodiment shown in the drawings. [Structure of Embodiment] FIGS. 1 to 5 show an embodiment of the present invention, and FIG. 1 shows a schematic structure of an air conditioning apparatus for a vehicle. The vehicle air conditioner of the present embodiment is mounted on a bus vehicle, and is an air conditioning unit 1 for air conditioning the interior of the vehicle.
And a controller 2 (see FIG. 4) that controls the air conditioning unit 1.

[Description of Air Conditioning Unit 1] Air Conditioning Unit 1
Includes a duct 3 arranged under the floor of the vehicle. The upstream side upper surface of the duct 3 is provided with an inside air introduction port 6 for introducing inside air into the duct 3 from a communication port 5 provided in the floor 4 of the vehicle. Further, the upstream side surface of the duct 3 is provided with an outside air introduction port 8 for introducing outside air into the duct 3 from an opening 7 provided on the side surface of the vehicle.

The inside air introduction port 6 is provided with two inside air shutters 11 for opening and closing the inside air introduction port 6 and switching between introduction and stop of introduction of the inside air into the duct 3. The inside air shutter 11 is two plate-shaped doors that rotate at the center and is driven to rotate by two inside air servomotors 12 (see FIG. 4). The two inside air shutters 11 are both in state A (outside air mode) of FIG. 2 in which all the inside air inlets 6 are closed.
2, the inside air introduction port 6 is half opened and half closed. One of the states shown in FIG. 2 is state A and the other is state B (inside and outside air mode in which the inside air and the outside air are introduced at the same time), and the inside air introduction port 6 is fully opened in FIG. C (inside air mode).

The outside air introduction port 8 is provided with an outside air door 13 which opens and closes the outside air introduction port 8 and switches between introduction and stop of introduction of the outside air into the duct 3. This outside air door 1
3 is a servo motor for outside air 14 with one end of the plate-like door as an axis.
(See FIG. 4), the external air introducing port 8 is closed and the state C in FIG. 2 (internal air mode) is opened, and the external air introducing port 8 is opened and the external air guide wall 3a provided in the duct 3 is opened. 2 is set to the state D (inside / outside air mode) and the outside air introduction port 8 is opened, and the rotation end is rotated to the inside air introduction port 6 side in state E (outside air mode). To be done.

The inside air servo motor 12 of the inside air shutter 11 and the outside air servo motor 14 of the outside air door 13 are controlled by the controller 2 as described later. Then, the controller 2 controls the open / close state of the inside air shutter 11 and the outside air door 13, and the introduction ratio of the inside air and the outside air introduced into the duct 3 is adjusted. That is, the controller 2 operates the air quality adjusting means of the present invention.

At the downstream end of the duct 3, the inside air or the outside air is sucked from the inside air introduction port 6 or the outside air introduction port 8, the sucked air is passed through the inside of the duct 3, and then, through a blowout duct (not shown). Blower 15 blown into the passenger compartment
Is provided. In addition, as an example of the blowing duct,
The air outlet ducts are arranged on the left and right of the ceiling and extend in the front-rear direction. The air outlet ducts are provided in the air outlet ducts to blow out conditioned air.

Inside the duct 3, two first and second evaporators 16, which are arranged in parallel to the air flow,
17 are arranged. This first and second evaporator 1
Reference numerals 6 and 17 are components of the refrigeration cycle 18 shown in FIG.
The air passing through the second evaporators 16 and 17 is cooled and dehumidified. The refrigeration cycle 18 will be described later.

A fixed partition wall 21 is provided between the first and second evaporators 16 and 17, as shown in FIG. Upstream of the fixed partition wall 21, it is possible to change between a partition mode for partitioning upstream of the first and second evaporators 16 and 17, and a communication mode for communicating upstream of the first and second evaporators 16 and 17, respectively. Two partition doors 22 are provided. This partition door 22 rotates about the center 2
Two partitioning servo motors 23 (see FIG.
2) in which the first and second evaporators 16 and 17 communicate with each other and the state F (communication mode) in FIG. 2 that communicates with the upstreams of the first and second evaporators 16 and 17 and the upstream of the first and second evaporators 16 and 17 respectively. State G (compartment mode) of.

The inside air shutter 11 is set to the inside air mode (state C in FIG. 2), and the outside air door 13 is set to the inside and outside air mode (FIG. 2).
State D), the partition door 22 is set to the partition mode (state F in FIG. 2) to guide the inside air introduced from the inside air inlet 6 to the first evaporator 16 and the outside air introduced from the outside air inlet 8. Is the introduction passage forming means of the present invention for guiding the gas to the second evaporator 17.

On the other hand, the first and second evaporators 16 and 17
Inside the duct 3 on the downstream side of the
Is arranged. The heater core 24 is supplied with cooling water (warm water) for a vehicle driving engine (not shown) to radiate heat and heat the air that has passed through the first and second evaporators 16 and 17. A hot water valve (not shown) is provided in the hot water circuit of the heater core 24, and by opening this hot water valve, the cooling water heats the air passing through the heater core 24 and passing through the duct 3. The hot water valve is a valve whose opening is adjusted in the dehumidifying mode.

[Description of Refrigeration Cycle 18] Here, the above-mentioned refrigeration cycle 18 will be described with reference to the refrigerant circuit diagram of FIG. The refrigeration cycle 18 includes the above-mentioned first and second
In addition to the evaporators 16 and 17, a compressor 31 that sucks, compresses, and discharges a refrigerant, a condenser 32 that liquefies and condenses the refrigerant that is discharged by the compressor 31 by heat exchange with outside air, and a liquid refrigerant that is condensed by the condenser 32 A receiver 33 for storing and discharging the liquid refrigerant, a supercooler 34 for supercooling the liquid refrigerant supplied from the receiver 33, a dryer 35 for removing water contained in the refrigerant, and a state for visually recognizing the state of the refrigerant flowing inside. Sight glass 36, a first pressure reducing device 37 (for example, a low-pressure pressure expansion valve) that decompresses and atomizes the liquid refrigerant that is introduced to the first evaporator 16, and a second decompression that decompresses and atomizes the liquid refrigerant that is introduced to the second evaporator 17. It is composed of a device 38 (for example, a low pressure expansion valve) and is connected by a refrigerant pipe 39. The compressor 31 is provided so as to be driven by the operation of the air conditioning engine 40.

Further, in the refrigeration cycle 18, in the refrigerant pipe 39 for guiding the refrigerant to the second pressure reducing device 38 and the second evaporator 17, an electromagnetic on-off valve 41 (main valve) for stopping the flow of the refrigerant supplied to the second evaporator 17 is provided. (Corresponding to the stopping means of the invention) is provided. This solenoid valve 41
Is a valve that closes when energized and opens when it is not energized, and is controlled by the controller 2 to open and close.

[Description of Controller 2] Next, the controller 2 will be described. The controller 2 includes the inside air servo motor 12, the outside air servo motor 14, and the blower 1.
5, command signals from a control panel (not shown), electric functional parts of the air conditioner such as the partitioning servo motor 23, the air conditioning engine 40, and the electromagnetic opening / closing valve 41.
The energization control is performed based on the input signal of each sensor.

In this embodiment, the inside air servo motor 1 is used.
2, servomotor 14 for outside air, servomotor 2 for partitioning
3 and the controller 2 that controls the energization of the electromagnetic opening / closing valve 41 will be described with reference to the electric circuit diagram of FIG. The controller 2 receives the inside air thermistor 42 that detects the temperature inside the vehicle compartment, the outside air thermistor 43 that detects the temperature outside the vehicle compartment, and the temperature of the air that has passed through the first evaporator 16 as input signals. First fin thermistor 44 attached to fins on the air downstream side
The second fin thermistor 45 (corresponding to the first outlet temperature detecting means) attached to the fin on the air downstream side of the second evaporator 17 (second outlet) in order to detect the temperature of the air passing through the second evaporator 17. Equivalent to temperature detection means), air quality in the passenger compartment (reducing gas concentration, oxygen content, etc.)
The inside air gas sensor 46 for detecting the temperature, the outside air gas sensor 47 for detecting the air quality outside the vehicle compartment, the low pressure sensor 48 for detecting the low pressure of the refrigeration cycle 18 (corresponding to the low pressure detection means), and the high pressure of the refrigeration cycle 18 are set. A signal from the high pressure switch 49 that turns ON when the value exceeds the value is input.

In the controller 2, the temperature detected by the first and second fin thermistors 44, 45 is lower than the first predetermined temperature (for example, 5 ° C.), and the low pressure value detected by the low pressure sensor 48 is the first. 1 predetermined pressure value (for example, 1.6
If it is lower than kgf / cm ² ) it is determined that frost is formed, and after the frost formation is determined, the temperatures detected by the first and second fin thermistors 44 and 45 are higher than the second predetermined temperature (for example, 9.5 ° C.),
When the low pressure value detected by the low pressure sensor 48 is higher than the second predetermined pressure value (for example, 2.4 kgf / cm ² ), the frost formation determining means for determining that the frost formation is released is operated. It should be noted that the first fin thermistor 44, the second fin thermistor 45, and the controller 2 that operates the frost formation determining means constitute the frost formation detecting means of the present invention.

The solenoid on-off valve 41 of this embodiment is a relay 51.
The energization of the controller 2 is controlled via the controller 2. When the controller 2 turns on the relay coil 51a,
The relay contact 51b is turned on so that the current of the battery 52 flows to the electromagnetic opening / closing valve 41.

In the controller 2, when frost formation is determined by the frost formation determining means, the introduction passage forming means guides the inside air to the first evaporator 16 and the outside air to the second evaporator 17, and the solenoid opening / closing valve 41 is used. Is provided to stop the supply of the refrigerant to the second evaporator 17, and to supply the refrigerant only to the first evaporator 16 is provided with frost prevention means.

The operation of this frost prevention means will be described with reference to the flow chart of FIG. When the cooling mode or the dehumidifying mode is set by the operation of the control panel (not shown), the air conditioning engine is started and the refrigeration cycle 18 is operated (start). Then, the refrigeration cycle 18 is normally operated (step S1). In this normal operation, the solenoid on-off valve 41 is turned off,
Operation panel setting modes (inside air mode, outside air mode, inside / outside air mode, automatic control mode) as shown in Table 1 below.
The states of the inside air shutter 11, the outside air door 13, and the partition door 22 are set accordingly. The automatic control mode is
The inside air gas sensor and the outside air gas sensor detect dirt in the inside air and the outside air and automatically determine the mode.

[Table 1]

Next, it is judged whether the temperature of the first fin thermistor 44 is 5 ° C. or lower (step S2). If the result of this judgment is NO, it is judged whether the temperature of the second fin thermistor 45 is 5 ° C. or lower (step S3). Determination in step S2, S3 is the If YES, performs low pressure detected by the low pressure sensor 48 is 1.6 kgf / cm ² or less whether or not (step S4). If the result of this determination is YES, it is determined that frost has formed on at least one of the first evaporator 16 and the second evaporator 17 (frost formation), and the defrosting operation is performed (step S5
) And then returns to step S2. This defrosting operation is
The electromagnetic on-off valve 41 is turned on to stop the supply of the refrigerant to the second evaporator 17, and as shown in Table 1 above, the two inside air shutters 11 are set to the state B and the outside air door 1
3 is in a state D, and two partition doors 22 are in a state G.

If the determination results of steps S3 and S4 are NO, it is determined whether the temperature of the first fin thermistor 44 is 9.5 ° C. or higher (step S6). This judgment result is NO
In the case of, the temperature of the second fin thermistor 45 is 9.5 ° C.
It is determined whether or not the above (step S7). Step S
6, if the judgment result of S7 is YES, low pressure sensor 4
It is determined whether the low pressure detected by 8 is 2.4 kgf / cm ² or more (step S8). This judgment result is YES
In the case of, it returns to step S1. Also, in step S7,
If the determination result in S8 is NO, the current operating state is maintained (step S9), and then the process returns to step S1.

[Operation of Embodiment] Next, an operation for preventing frost will be described. When the outside air temperature is low, such as in winter, the refrigeration cycle 18 is operated, and during operation of the refrigeration cycle 18, at least the temperature detected by the first fin thermistor 44 or the second fin thermistor 45 decreases to 5 ° C. or lower, and When the low pressure detected by the low pressure sensor 48 is 1.6 kgf / cm ² or less, the controller 2
Determines that frost has occurred and performs defrosting operation.
In the defrosting operation, the electromagnetic on-off valve 41 is turned on, the refrigeration cycle 18 is operated while the supply of the refrigerant to the second evaporator 17 is stopped, and, as shown in Table 1 above,
Guide the inside air from the inside air inlet 6 to the first evaporator 16,
The outside air is introduced from the outside air introduction port 8 to the second evaporator 17.

By switching from the operation of the first and second evaporators 16 and 17 to the operation of only the first evaporator 16, the cooling capacity of the air by the air unit 1 is reduced and the first evaporator 16 is warm in the room. Since the inside air is supplied, the temperature of the first evaporator 16 rises and frost is removed (specifically, frost is less likely to occur). On the other hand, since the operation of the second evaporator 17 is stopped, the temperature of the second evaporator 17 rises due to the outside air passing therethrough, and the frost is removed (specifically, frost is less likely to occur). Then, the inside air passing through the first evaporator 16 is cooled and dehumidified when passing through the first evaporator 16 and guided into the vehicle compartment, and the low-humidity low temperature outside air passing through the second evaporator 17 is also introduced into the vehicle compartment. Get burned.

[Effects of the Embodiment] In the present embodiment, as shown by the above-described operation, even during the defrosting operation, the internal air that has passed through the first evaporator 16 is cooled and dehumidified by the first evaporator 16. Guided to the passenger compartment, the second evaporator 1
Low-temperature low-temperature outside air that has passed through 7 is also introduced into the vehicle interior. Therefore, during the dehumidifying operation, dehumidified inside air and fresh outside air having a low humidity and a large amount of oxygen are introduced from the air conditioning unit 1 into the vehicle interior. As a result, even during the defrosting operation, the inside of the vehicle is ventilated and the outside air temperature is 0 to 5 ° C.
It is possible to prevent the fogging of the window glass from occurring until it is lowered to a certain degree. Further, as compared with the air conditioning unit shown in the related art (see FIG. 6), the air conditioning unit 1 of the present embodiment is mainly configured by dividing the evaporator and providing a partition door 22 upstream thereof. In other words, the air conditioning unit 1 of the present embodiment can be implemented without making a great change to the conventional air conditioning unit, so that the increase in cost can be suppressed and the mounting space does not increase.

[Modification] Numerical values shown in the above embodiment,
The shape of the door, the drive type of the door, the frost determination means, etc. are examples shown for easy understanding, and can be variously changed. Specifically, the example in which the present invention is applied to an air conditioner mounted on a bus vehicle is shown, but the present invention may be applied to an air conditioner mounted on another vehicle such as a passenger car. Although an example in which the inside air and the outside air are switched by the independent inside air shutter and the outside air door is shown, the opening / closing state of the inside air introduction port and the outside air introduction port may be changed by the common inside / outside air door.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a vehicle air conditioner (embodiment).

FIG. 2 is an explanatory diagram showing a setting state of each door (embodiment).

FIG. 3 is a refrigerant circuit diagram of a refrigeration cycle (embodiment).

FIG. 4 is an electric circuit diagram of a controller (embodiment).

FIG. 5 is a flowchart showing the operation of the controller (embodiment).

FIG. 6 is a schematic view of an air conditioning unit (prior art).

[Explanation of symbols]

1 Air Conditioning Unit (Vehicle Air Conditioner) 2 Controller (Frost Preventing Means, Air Quality Adjusting Means, Frost Determining Means) 3 Duct 6 Inside Air Introduction Port 8 Outside Air Introduction Port 11 Inside Air Shutter 13 Outside Air Door 15 Blower 16 First Evaporator 17 Second evaporator 18 Refrigeration cycle 41 Electromagnetic on-off valve (stopping means) 44 First fin thermistor (first outlet temperature detecting means) 45 Second fin thermistor (second outlet temperature detecting means) 48 Low pressure sensor (low pressure detecting means)

Claims (3)

[Claims] 1. An inside air inlet for introducing air into a vehicle compartment,
A duct provided with an outside air introduction port for introducing outside air into the vehicle compartment, for guiding the introduced air into the vehicle compartment; (b) a blower for generating an air flow toward the vehicle interior in the duct; and (c) air in the duct. Of the refrigerating cycle, which is arranged in parallel with respect to the flow of No. 1, and has divided first and second evaporators for cooling the air passing through the duct, and (d) the vehicle interior air introduced from the inside air inlet. Introducing passage forming means for guiding the outside-cabin air introduced from the outside air introduction port to the second evaporator while leading to the first evaporator, and (e) a stop for stopping the flow of the refrigerant supplied to the second evaporator. Means, (f) frost formation detecting means for detecting frost formation on at least one of the first evaporator and the second evaporator, and (g) when the frost formation detection means detects frost formation. In the state where the air inside the vehicle is guided to the first evaporator by the introduction passage forming means and the air outside the vehicle is guided to the second evaporator, the supply of the refrigerant to the second evaporator is stopped by the stopping means, and An air conditioner for a vehicle, comprising: a frost prevention unit that supplies a refrigerant only to an evaporator. 2. The vehicle air conditioner according to claim 1, wherein: (h) an inside air shutter provided at the inside air introduction port and switching between introduction and stoppage of introduction of air in the vehicle compartment; and (i) at the outside air introduction port. An outside air door that is provided to switch between introduction and stoppage of introduction of the outside air of the vehicle compartment; and (j) opening and closing states of the inside air shutter and the outside air door to control the inside air and the outside air of the vehicle compartment introduced into the duct. An air conditioner for a vehicle, comprising: 3. The vehicle air conditioner according to claim 1, wherein the frost formation detecting means comprises: (f-1) first outlet temperature detecting means for detecting the temperature of the air passing through the first evaporator; f-2) second outlet temperature detecting means for detecting the temperature of the air passing through the second evaporator; (f-3) low pressure detecting means for detecting the low pressure of the refrigeration cycle; (f-4) Frost judging means for judging frost formation when the temperature detected by the first and second outlet temperature detecting means is lower than a predetermined temperature and the low pressure pressure value detected by the low pressure detecting means is lower than a predetermined pressure value. An air conditioner for a vehicle, comprising: