JPH11342735A - Car air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly perform the frosting judgment of an evaporator and measures, in this car air conditioner which makes a flow of air to be fed out of the upstream side so as to be always passed through the evaporator and a sub-condenser. SOLUTION: In the case where an air temperature (TEVAIN) at the upstream side of an evaporator is lower than the specified temperature, an evaporator's frosting judgment is made possible to be done. An evaporator's frosting state is judged from a variation in the proximate air temperature (TEVAOUT) of the evaporator against per unit change of the air temperature (TEVAIN) at the upstream side of the evaporator or a variation in high pressure line pressure (Pd) of a refrigeration cycle. In the case where this variation is smaller than the specified value, a compressor is intermittently operated, and if it is more than the specified value, this compressor is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a main condenser disposed outside an air-conditioning passage, an evaporator and a sub-condenser disposed within the air-conditioning passage, and always allows air sent from the upstream side to pass through the evaporator and the sub-condenser. The present invention relates to a heat pump type vehicle air conditioner as described above.

[0002]

2. Description of the Related Art In a case where sufficient heating capacity cannot be obtained by using engine waste heat as in a hybrid vehicle or a vehicle equipped with a direct injection engine, or in the case of an electric vehicle, the engine waste heat is in the first place. When it cannot be used, how to secure the heating capacity becomes an issue. For this reason, in the prior art,
No. 3 (hereinafter referred to as a first prior art),
Japanese Unexamined Patent Publication No. 95117 (hereinafter, referred to as a second prior art) and Japanese Patent Laid-Open Publication No. Hei 8-99526 (hereinafter, referred to as a third prior art).
For example, a heat pump type refrigerant cycle shown in, for example, has been considered.

[0003] In each of these, a main condenser is disposed outside the vehicle compartment, a sub-condenser and an evaporator are disposed inside the vehicle compartment, and during cooling operation, refrigerant is supplied in the order of the main condenser, the sub-condenser, the expansion valve, the evaporator, and the compressor. In the dehumidifying and heating operation, the main condenser is bypassed and the refrigerant is circulated in the order of the sub-condenser, expansion valve, evaporator, and compressor in order of operation, regardless of the air conditioning mode, high-pressure refrigerant always flows through the sub-condenser Therefore, the sub-condenser is used as a substitute for the conventional heater core, and an air mixing door is provided upstream of the sub-condenser, and the ratio of the amount of air passing through the sub-condenser and the amount of air bypassing the sub-condenser is determined by the air mixing door. To achieve the desired air temperature.

[0004]

However, in the above-mentioned system, since the work amount of the compressor determines the heating capacity, it is difficult to obtain a sufficient heating capacity as compared with a conventional heater core utilizing engine waste heat. In order to ensure the capacity, it is necessary to further arrange a heat exchanger for auxiliary heating in the air conditioning passage.

[0005] The heat exchanger for auxiliary heating is a heater core that uses engine waste heat if the vehicle is equipped with an engine, or is heated by an electric heater if the vehicle is not equipped with an engine. Although a heater that circulates hot water may be used, since a unit case used in a conventional vehicle is diverted as it is, when a sub-condenser is arranged in a heater unit as in the above-described conventional technology, an auxiliary There is a disadvantage that it is not possible to secure a storage space for the heating heat exchanger in the heater unit.

In order to eliminate this inconvenience, the present inventor has proposed:
The sub-condenser is arranged upstream of the air mix damper, that is, before and after the evaporator in the cooling unit, and accordingly, the structure in which the refrigerant always flows through the sub-condenser is revised. We have begun to develop a system that guides the refrigerant from the sub-condenser to the evaporator via the expansion device during the dehumidifying and heating operation.

In such a system, the air sent from the upstream always passes not only through the evaporator but also through the sub-condenser, and the refrigerant flows through the evaporator even during the dehumidifying heating operation for heating the vehicle interior. . For this reason, when the evaporator frosts, the amount of air passing through the evaporator decreases, so that the amount of air passing through the sub-condenser also decreases, and there is a disadvantage that the vehicle interior cannot be heated.

Therefore, in the present invention, the main condenser is arranged outside the air-conditioning passage, the evaporator and the sub-condenser are arranged in the air-conditioning passage, and the air from the upstream is supplied not only to the evaporator but also to the sub-condenser. It is an object of the present invention to make it possible to appropriately perform frost determination and coping with an evaporator even in a new vehicle air conditioner having a layout that always allows passage.

[0009]

In order to achieve the above object, a vehicle air conditioner according to the present invention is based on the following system configuration and knowledge.

First, the system configuration includes a compressor for compressing a refrigerant, a main condenser disposed outside the air conditioning passage, an evaporator and a sub-condenser disposed inside the air conditioning passage. The refrigerant compressed by the compressor is guided from the main condenser to the evaporator via an expansion device, and the refrigerant compressed by the compressor is guided from the sub-condenser to the evaporator via the expansion device during the dehumidifying and heating operation. It is assumed that a cycle is provided, and air sent from the upstream is always passed through the evaporator and the sub-condenser.

Next, in such a system configuration, when the evaporator frosts, the wind does not flow backward, so that the temperature immediately after the evaporator (TEVAOUT) rises and the sub-condenser does not radiate heat, and the high-pressure side pressure of the refrigerant cycle increases. It has been found that (Pd) increases significantly. The phenomenon that TEVAOUT and Pd increase is
This phenomenon occurs not only when the evaporator is frosted but also when the evaporator is not frosted if the amount of heat radiation from the sub-condenser is insufficient (see FIG. 2). Therefore, it is not possible to simply know the state in which TEVAOUT or Pd has increased by any method, and to judge that case is the case where the evaporator is frosted. Further, even if the occurrence of frost of the evaporator can be determined based on the state of TEVAOUT or Pd being increased, control such as prevention of frost of the evaporator cannot be performed unless the degree of frost can be estimated.

According to the study of the present inventors, the load on the evaporator is different between the phenomenon that TEVAOUT and Pd increase due to the frost of the evaporator and the phenomenon that TEVAOUT and Pd increase due to insufficient heat radiation of the sub-capacitor. I know. That is, if the temperature of the air on the upstream side (TEVAIN) that is going to pass through the evaporator is high, that is, if TEVAOUT and Pd increase when the load on the evaporator is large, the temperature of the air passing through the sub-condenser is high. It can be said that the heat dissipation by the sub-capacitor is not sufficiently performed. On the other hand, when the temperature of the air passing through the evaporator is low, that is, when the load on the evaporator is small, TEVAOUT and Pd increase when the evaporator becomes too cold and freezes. Therefore, it is possible to determine from the load of the evaporator, that is, the magnitude of TEVAIN, whether or not it is an environment in which evaporator frost determination can be performed.

Further, the temperature immediately after the evaporator (TEVAOU
T) and the high-pressure side pressure (Pd) of the refrigerant cycle gradually increase at the initial stage when the evaporator starts to frost, and rapidly increase as the freezing proceeds. From this, it is possible to know the frost situation of the evaporator by monitoring the rate of increase of the TEVAOUT value or Pd value with respect to the upstream air temperature (TEVAIN) of the evaporator, and to control the refrigerant cycle according to the magnitude of the rate of increase. if,
The frost of the evaporator can be prevented beforehand, or the already frosted state can be released.

From the above system configuration and knowledge, in order to perform appropriate control regarding frost of the evaporator, the invention according to claim 1 includes a compressor for compressing a refrigerant,
It has a main condenser arranged outside the air conditioning passage, an evaporator and a sub condenser arranged inside the air conditioning passage,
During the cooling operation, the refrigerant compressed by the compressor is guided from the main condenser to the evaporator via the expansion device, and during the dehumidifying heating operation, the refrigerant compressed by the compressor is transmitted from the sub-condenser through the expansion device to the evaporator. In a vehicle air conditioner having a refrigerant cycle adapted to guide air to the evaporator and the sub-condenser, air sucked from the upstream side of the evaporator is obtained. Temperature acquisition means,
Determining means for determining whether or not the air temperature obtained by the suction air temperature obtaining means is lower than a predetermined temperature, wherein when the air temperature is lower than the predetermined temperature, the frost of the evaporator is stopped. It is characterized in that determination can be made.

Here, as a method of frost determination, there are an air temperature immediately after evaporating means for obtaining the air temperature immediately after the evaporator, and an evaporative air temperature per unit change of air temperature obtained by the suction air temperature obtaining means. Immediately after, a change rate calculating means for calculating a change amount of the air temperature obtained by the air temperature obtaining means is provided, and the frost state of the evaporator is estimated based on the magnitude of the change rate. ), A high pressure detecting means for detecting the pressure of the high pressure line of the refrigerant cycle, and a change in the pressure obtained by the high pressure detecting means per unit change of the air temperature obtained by the suction air temperature obtaining means. And a rate-of-change calculating means for calculating the amount, and estimating the frost state of the evaporator based on the magnitude of the rate of change. 3).

Regardless of which method is used, when the rate of change is smaller than a predetermined value, it is in the initial stage of evaporator frost, and the refrigerant cycle is set to a control mode for preventing the evaporator from frost progressing. Is equal to or more than a predetermined value, since the state is a completely frosted state or a state immediately before that, it is possible to individually respond to the degree of frost as a control mode for releasing the frosted state of the evaporator in the refrigerant cycle. Desirable (claim 4).

For example, the control for preventing the frost from proceeding in the evaporator may be performed by intermittently operating the compressor to suppress the frost from proceeding, or to cancel the initial stage of the frost (claim 5). The control for releasing the frosted state of the evaporator may be dealt with by stopping the compressor (claim 6).

Further, when a control mode for preventing the frost of the evaporator from proceeding or a control mode for canceling the frosted state is executed, if the rate of change becomes small, the refrigerant cycle is returned to the original state. (Claim 7).

Therefore, the main condenser is arranged outside the air-conditioning passage, the evaporator and the sub-condenser are arranged in the air-conditioning passage, and the air from the upstream always passes not only to the evaporator but also to the sub-condenser. Even with the unique configuration of the present system, it is possible to determine and cope with the frost of the evaporator suitable for this system.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the vehicle air conditioner includes:
Front air-conditioning unit 1 for air-conditioning the front seat area of the passenger compartment
And a rear air-conditioning unit 2 for air-conditioning the rear-seat side area are provided in the vehicle interior.

The front air conditioning unit 1 includes an air conditioning passage 3
The air-conditioning duct 4 constituting the blower unit 4
a, a cooling unit 4b and a heater unit 4c are connected in this order.

An intake device 5 is provided in the most upstream blower unit 4 a, and the opening ratio between the inside air inlet 6 and the outside air inlet 7 is adjusted by the intake door 8. Further, the blower unit 4a houses a blower 9 made of, for example, a sirocco fan facing the inside air inlet 6 and the outside air inlet 7, and the air sucked by the rotation of the blower 9 flows downstream of the air conditioning duct 4. It is designed to be pumped.

Downstream of the blower 9, a first evaporator 10, a sub-condenser 11, a first hot water heater 12
Are arranged, and the first evaporator 10 and the sub-condenser 11 are housed in the cooling unit 4b one after the other in the ventilation direction, and the sub-condenser 11 is arranged side by side on the downstream side of the first evaporator 10. . Also, the first
Each of the evaporator 10 and the sub-condenser 11 is provided so as to block the entire cross-section of the passage, and passes all the air sent from the blower 9.

The first hot water heater 12 is used as a heat exchanger for auxiliary heating, and is provided with a cooling unit 4.
The first hot-water heater 12 is housed in a heater unit 4c connected to the heater unit b, and is provided so as to block one of two passages formed by dividing a part in the unit. An air mix door 13 is provided upstream of the first hot water heater 12 for adjusting the ratio of air flowing on one passage in which the hot water heater 12 is provided and air flowing on the other passage. Have been. Here, the opening degree of the air mix door 13 is such that the opening degree at which the ventilation rate of the first hot water type heater 12 is minimum is 0% (the position indicated by the solid line in the figure), and the opening degree which is maximum is 100% ( (Indicated by a dashed line in the figure), and in a normal configuration, the first
Of the air supplied to the hot water heater 12 disappears, all of the air sent from the upstream bypasses the first hot water heater 12, and all of the air sent from the upstream with the opening degree of 100% is the first hot water heater. 12.

The most downstream side of the air-conditioning duct 4 is divided into a defrost outlet 14, a vent outlet 15, and a heat outlet 16 to open into the space on the front seat side of the passenger compartment. 17a, 17b and 17c are provided, and the blowout mode can be switched by operating this mode door.

The rear air-conditioning unit 2 uses a rear-side blower (not shown) to supply only inside air to the air-conditioning duct 20.
, And pressure-feed to the downstream side. Downstream of this blower, a second evaporator 21 and a second hot water heater 22 are arranged, and these second evaporator 21 and second hot water heater 22 are connected to each other in the air conditioning duct 20. The second hot water heater 22 is provided so as to block the entire passage cross section, and is arranged in parallel on the downstream side of the second evaporator 21. Therefore, the rear air conditioning unit 2
In this case, all of the introduced air passes through the second evaporator 21 and then passes through the second rear hot water heater 22 and is supplied to the rear seat space.

The refrigerant outflow side of the first evaporator 10 is connected to the suction side of a compressor 23 by piping, and the discharge side of the compressor 23 branches into two systems. Is connected to a refrigerant inflow side of a main condenser 25 provided in the main condenser 25. A refrigerant outflow side of the main condenser 25 is provided with a liquid tank 26, a check valve 27 that allows only the flow of the refrigerant in the forward direction, and a first expansion valve. 2
8 is connected to the refrigerant inflow side of the first evaporator 10.

The other branch is the second solenoid valve 2
The refrigerant outlet side of the sub-condenser 11 is connected to the refrigerant inlet side of the first evaporator 10 through the orifice 30.
That is, it is connected between the first evaporator 10 and the first expansion valve 28. The orifice 30 may be formed by narrowing the flow path area in the middle of the pipe, or may be formed by inserting an orifice plate into the pipe, regardless of whether the block having the orifice is formed in the middle of the pipe. May be interposed. The expansion device according to the present invention includes the orifice 30 and the first expansion valve 28.

The liquid tank 26 is arranged outside the vehicle compartment (engine room), and the first expansion valve 28 and the orifice 30 are arranged inside the cooling unit 4b.

Further, a bypass that bypasses the liquid tank 26, the check valve 27, the first expansion valve 28, and the first evaporator 10 is provided between the refrigerant outflow side of the main condenser 25 and the suction side of the compressor 23. A passage 31 is provided, and the bypass passage 31 is opened and closed by a third solenoid valve 32.

A second expansion valve disposed in the rear air-conditioning unit 2 via a fourth solenoid valve 33 is provided between the refrigerant outflow side of the liquid tank 26, that is, between the liquid tank 26 and the check valve 27. The second expansion valve 34 is connected to the second evaporator 21 disposed in the rear air conditioning unit. The refrigerant outflow side of the second evaporator 21 is connected to the suction side of the compressor 23.

The hot water heaters 12 and 22 are heat exchangers for heating the passing air using the hot water as a heat source. A pipe for flowing the hot water is drawn out through a dash panel 35 that partitions the inside and outside of the vehicle compartment, and is disposed outside the vehicle compartment. Connected to the hot water heating device 36. The hot water heating device 36 supplies hot water heated by an electric heater 37 such as a sheath type heater to a pump 38.
When the electric heater 37 and the pump 38 are energized, hot water is supplied to the hot water heaters 12 and 22, and the electric heater 37 and the pump 38 are supplied. When the power supply to the heaters is stopped, the supply of hot water to the hot water heaters 12 and 22 is stopped.

If the vehicle is equipped with an engine, the hot water heating device 36 supplies the engine cooling water to the hot water heater 1.
Alternatively, a configuration in which the fluid is circulated through the channels 2 and 22 may be used. A heat storage tank is connected to the hot water heating device 36, and the hot water heating device 3
6. The heat of the hot water heated by step 6 is stored in the heat storage tank, and when the air conditioner is temporarily stopped and restarted, the hot water having a high temperature can be used from the initial stage, so that immediate warming can be achieved. May be improved.

Reference numeral 40 denotes a suction air temperature sensor which is provided near the upstream side of the first evaporator 10 and measures the temperature of air passing through the evaporator 10.
Reference numeral 41 denotes an immediately after-evaporation temperature sensor which is provided near the downstream side of the first evaporator 10 and measures the air temperature immediately after passing through the evaporator 10. Signals from these sensors are transmitted from other sensors and setting devices. Is input to the control unit 45 together with the signal of

The control unit 45 includes a central processing unit (CPU) (not shown), a read-only memory (ROM), a random access memory (RAM), an input / output port (I / O), etc., and controls the rotation of the blower 9. , Intake device 5
Control of the compressor, drive control of the compressor 23, the first to fourth solenoid valves 24, 29, 32, 33, the hot water heating device 3
6. It has a drive circuit for controlling the air mixing door 13 and the like, processes various input signals according to a predetermined program given to the ROM, and switches the blowing capacity.
Switching of the suction mode, operation / stop (ON / OFF) of the compressor 23, the first to fourth solenoid valves 24, 29,
The opening / closing of 32, 33, the energization of the electric heater 37 and the pump 38, the fan speed, the opening of the intake door 8, the opening of the air mix door 13, and the like are controlled.

In the above configuration, during the cooling operation, as shown in Table 1, the first solenoid valve 24 is opened, the second solenoid valve 29 is closed, the third solenoid valve 32 is closed, and the fourth solenoid valve 32 is closed. The solenoid valve 33 is opened. At this time, the electric heater 37 and the pump 38
To the air mix door 13 is stopped.
%, And the ventilation to the first hot water heater 12 disappears.

[0037]

[Table 1]

Then, the refrigerant discharged from the compressor 23 is not supplied to the sub-condenser 11 but directly enters the main condenser 25. Thereafter, the liquid enters the liquid tank 26 and is separated into gas and liquid. Thereafter, the liquid enters the first expansion valve 28 via the check valve 27, where the pressure is reduced and the liquid enters the first evaporator 10. Then, the refrigerant flowing into the first evaporator 10 absorbs heat from the air in the air conditioning duct 4,
Thereafter, it is returned to the compressor 23. At this time, the first
The refrigerant inflow side of the evaporator 10 is connected to the sub-condenser 11 via the orifice 30, but since the second solenoid valve 29 is closed, the refrigerant flowing into the sub-condenser 11 via the orifice 30 There is almost no influence on the cooling capacity of the first evaporator 10.

Thus, although all the air that has passed through the first evaporator 10 passes through the sub-condenser 11, there is no heat exchange by the sub-condenser 11, and the air is sucked into the air conditioning duct 2 by driving the blower 9. The air is cooled by the first evaporator 10 and supplied to the passenger compartment without heat exchange by the sub-condenser 11.
Cools the front seat space of the passenger compartment.

At the same time, the high-pressure refrigerant gas-liquid separated in the liquid tank 26 enters the second expansion valve 34, where it is decompressed and enters the second evaporator 21 to cool the air passing therethrough. Therefore, the air sucked into the air conditioning duct 20 by the driving of the rear blower (not shown) is cooled by the second evaporator 21 and supplied to the vehicle compartment without heat exchange by the second hot water heater 22. Cools the rear seat space of the passenger compartment.

On the other hand, during the dehumidifying and heating operation, as shown in Table 1, the first solenoid valve 24 is closed, the second solenoid valve 29 is opened, and the third solenoid valve 32 is closed. The fourth solenoid valve 33 is closed, and the air mix door 13 is moved to a position where the amount of air flow to the first hot water type heater 12 becomes large, particularly when the vehicle interior temperature is extremely low or when immediate warming is required. Is
Maximum air flow to first hot water heater 12 (100%)
Set to a position where In addition, energization of the electric heater 37 and the pump 38 is started, and the hot water heaters 12 and 2 of the front air conditioning unit 1 and the rear air conditioning unit 2 are started.
2 is supplied with warm water.

Then, the refrigerant discharged from the compressor 23 is not supplied to the main condenser 25 this time, but is supplied to the sub-condenser 11 to exchange heat with the air in the air conditioning duct 4 to heat this air. Thereafter, the refrigerant is depressurized by the orifice 30 and then enters the first evaporator 10 to absorb heat from the air passing therethrough, and then is returned to the compressor 23.

The balance between the amount of heat absorbed by the first evaporator 10 and the amount of heat radiated by the sub-condenser 11 is that the amount of heat radiated by the work of the compressor 23 is large. Although it is cooled and dehumidified by the evaporator 10, it is heated by the sub-condenser 11 more than it is cooled by the evaporator 10, and becomes warm air dehumidified as a whole. Thereafter, the air heated by the sub-condenser 11 is further heated by passing through the first hot-water heater 12, and is supplied to the space on the front seat side of the passenger compartment.

In the rear air conditioning unit 2,
Since the refrigerant does not flow through the main condenser 25, the second
No refrigerant flows into the evaporator 21, and the air passing therethrough is not cooled, but is heated by the second hot water heater 22 and then supplied to the rear seat space of the passenger compartment.

When the dehumidifying and heating operation is being performed, the refrigerant does not flow to the main condenser 25, so that it is expected that the refrigerant will fall into the main condenser 25. The third solenoid valve 32 is opened when collecting such a stagnant refrigerant. Further, in the present configuration example, the evaporator 10
The expansion device on the path from the sub-condenser 11 to the evaporator 10 is constituted by an orifice 30 different from that of the first expansion valve 28. A common inflation device may be passed.

In the above-described system, the evaporator 10 and the sub-condenser 11 are arranged before and after in the cooling unit, and the air introduced through the intake device passes through both the evaporator 10 and the sub-condenser 11. Therefore, the pressure balance of the refrigerant cycle is simultaneously affected by both the evaporator 10 and the sub-condenser 11. In particular, in this refrigerant cycle, when the evaporator 10 frosts, it becomes difficult for air to pass through the evaporator 10, so that the sub-condenser 1
1 becomes difficult to radiate heat and the Pd value increases. Further, even when the evaporator 10 is not frozen, when the intake air temperature (TEVAIN) of the evaporator 10 is high, the amount of heat radiation of the sub-condenser 11 is insufficient and the Pd value increases.

Further, the air temperature immediately after the evaporator (T
EVAOUT) also rises when the evaporator 10 is frosted, because even if TEVAIN is low, air becomes difficult to pass through the evaporator, and TEVAOUT also rises as the evaporator intake air temperature (TEVAIN) increases. .

Therefore, in this configuration example, as shown in FIG. 2, the intake air temperature (TEVAIN) of the evaporator
) Is defined as a frost determination target area when the temperature becomes lower than a predetermined temperature (A) set in advance, thereby eliminating the case where the increase in the Pd value or TEVAOUT value is caused by a cause other than frost. Like that.

By the way, when the evaporator 10 is in the initial stage of frost, Pd or Td per unit change of TEVAIN is changed.
The amount of change in EVAOUT, that is, the slope of the characteristic line in FIG.
As the frost progresses, this inclination tends to increase. From this, it is possible to prevent frost by performing control corresponding to the inclination of the characteristic line in FIG. 2, or
It can be removed.

That is, when the inclination is sufficiently small, there is no possibility that the evaporator will be frosted even if the compressor of the refrigerant cycle is continuously operated, but when the inclination is large to some extent, there is a possibility that the evaporator may be completely frozen. The compressor is intermittently stopped to suppress the progress of frost, or
Avoid the ongoing frost state. When the inclination becomes sufficiently large, it can be considered that the evaporator is completely frozen. In this case, the compressor is stopped and the frozen state is promptly released.

FIG. 3 is a flowchart showing a specific control operation example for realizing this.
First, in step 50, various types of information such as the intake air temperature (TEVAIN) detected by the intake air temperature sensor 40, the air temperature immediately after the evaporator (TEVAIN) detected by the immediately after evaporation temperature sensor 41, and the like. Control unit 4 sends signal from sensor
Take in 5. The Pd value of the refrigerant cycle may be obtained by detecting with a pressure sensor, or may be obtained by calculation.

In the next step 52, it is determined whether or not the intake air temperature (TEVAIN) is lower than the predetermined temperature (A), that is, whether or not the target area is for determining the frost of the evaporator 10.

If the suction air temperature (TEVAIN) is in the range of A or higher, it can be said that even if the Pd value or TEVAOUT value increases, it is not caused by the frost of the evaporator. Does not perform frost control. In this case, it is caused by insufficient heat radiation of the sub-capacitors.For example, by changing the intake opening to increase the outside air introduction ratio, increasing the fan speed, or stopping the compressor, I do.

On the other hand, when TEVAIN is lower than A, the frost judgment of the evaporator 10 is performed in the target area. Therefore, when the Pd value or TEVAOUT value rises, it is caused by the frost of the evaporator. Can be considered to be. Therefore, in step 54,
TEVAOUT change per unit change in TEVAIN or Pd
Is determined as K, and control corresponding to the frost situation is performed based on the magnitude of the change rate (K).

That is, if the rate of change (K) is smaller than the determination value B1 at which it can be determined that frost has not occurred, the control required to prevent or cancel frost is unnecessary, and the compressor is continuously operated. (Steps 56 and 5
8).

If the rate of change (K) is equal to or greater than the determination value B1, but is smaller than the determination value B2 that can be determined to be the initial stage of frost, the frost state is prevented from progressing, or the frost state is prevented. The compressor is operated intermittently to avoid the initial state (steps 56 and 60). In this intermittent operation, the operating time (t1) and the stop time (t2) of the compressor may be set to predetermined fixed values or may be varied according to the magnitude of K.

Further, if the rate of change (K) is equal to or greater than the judgment value B2, the progress of the frost has already progressed greatly, so that the compressor is stopped in an emergency evacuation so that the frosted state of the evaporator 10 is not maintained. (Steps 56 and 62).

Since the above control is repeatedly executed, the frost state is improved when the compressor is operated intermittently at the initial stage of frost or when the compressor is stopped at the final stage of the frost. Step 5
When the change rate (K) indicated by 4 becomes small, the process shifts to compressor control according to the value of K at that time. For example, if the compressor stops and the frost of the evaporator 10 is eliminated, and K becomes smaller than B1,
The compressor starts continuous operation again, and the refrigerant cycle is resumed.

Therefore, according to the above-described control, the frost state of the evaporator 10 can be distinguished from the phenomenon caused by insufficient heat radiation of the sub-condenser 11, and furthermore, by controlling the compressor in accordance with the degree of frost, the entire surface can be controlled. Even if the frozen state is prevented or if the entire surface is frozen, it can be quickly released.

[0060]

As described above, according to the present invention,
A main condenser is arranged outside the air conditioning passage, an evaporator and a sub-condenser are arranged inside the air conditioning passage, and the refrigerant is guided from the main condenser to the evaporator via the expansion device during the cooling operation, and the refrigerant is discharged from the sub-condenser during the dehumidifying heating operation. In a system configuration in which air sent from the upstream side is always passed through the evaporator and the sub-condenser through the expansion device to the evaporator, the evaporator is used only when the air temperature on the upstream side of the evaporator is lower than a predetermined temperature. Is determined, the case where the temperature immediately after the evaporator or the high-pressure side pressure of the refrigerant cycle rises is due to insufficient heat radiation of the sub-condenser or to the frost of the evaporator. Can be distinguished.

The frost state of the evaporator is determined from the amount of air temperature change immediately after the evaporator per unit change of air temperature upstream of the evaporator or the amount of high pressure change of the refrigerant cycle per unit change of air temperature upstream of the evaporator. Since the determination is made, it can be determined whether the frost of the evaporator is in the initial stage or in a completely frosted state.

Regardless of which rate of change is used to determine the frost state, if the rate of change is smaller than a predetermined value, a control mode for preventing the frost from advancing by the evaporator is set, and the rate of change is equal to or greater than the predetermined value. In such a case, by setting the control mode for releasing the frost state of the evaporator, it becomes possible to cope with the degree of frost. For example, as the control for preventing the frost from progressing in the evaporator, the progress of the frost can be suppressed by operating the compressor intermittently, or the initial stage of the frost can be canceled. Also, by stopping the compressor as control to release the frosted state of the evaporator,
Further deterioration of the situation can be suppressed, and continuation of the frosted state can be avoided.

Further, even if the control mode for coping with the frost of the evaporator is being executed, if the refrigerant cycle is returned to the original state when the rate of change becomes small, the frost control is released and other frost control is performed. It is also possible to shift to control, and continuous automatic operation of the system becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the overall configuration of a vehicle air conditioner according to the present invention.

FIG. 2 is a diagram showing the high pressure side pressure (Pd) or the temperature immediately after the evaporator (TEVAOUT) of the refrigerant cycle of the vehicle air conditioner according to the present invention, and the upstream air temperature (T
FIG. 7 is a characteristic diagram showing a relationship with the value (EVAIN).

FIG. 3 is a flowchart showing frost control of the vehicle air conditioner according to the present invention.

[Explanation of symbols]

 Reference Signs List 3 air conditioning passage 10 first evaporator 11 sub-condenser 12 first hot-water heater 21 second evaporator 22 second hot-water heater 23 compressor 25 main condenser 28 first expansion valve 30 orifice 34 second expansion valve 40 Suction air temperature sensor 41 Temperature sensor immediately after evaporation 45 Control unit

Claims (7)

[Claims] 1. A compressor for compressing a refrigerant, a main condenser disposed outside an air-conditioning passage, an evaporator and a sub-condenser disposed in the air-conditioning passage, and a refrigerant compressed by the compressor during a cooling operation. A refrigerant cycle that leads the refrigerant compressed by the compressor from the main condenser to the evaporator through the expansion device from the main condenser to the evaporator through an expansion device, and in the dehumidifying and heating operation, A vehicle air conditioner which always passes air sent from the evaporator and the sub-condenser, comprising: a suction air temperature obtaining means for obtaining an air temperature upstream of the evaporator; and The air temperature obtained by the obtaining means is lower than a predetermined temperature. Whether the determining means is provided, said air conditioning system air temperature, characterized in that to enable frost determination of the evaporator is lower than the predetermined temperature. 2. An air temperature immediately after the evaporator for obtaining an air temperature immediately after the evaporator, and an air temperature immediately after the evaporator per unit change of the air temperature obtained by the suction air temperature obtaining means. A change rate calculating means for calculating a change amount of the air temperature obtained by the means, and estimating a frost state of the evaporator based on a magnitude of the change rate calculated by the change rate calculating means. The vehicle air conditioner according to claim 1. 3. A high-pressure pressure obtaining means for obtaining the pressure of the high-pressure line of the refrigerant cycle, and a high-pressure pressure obtaining means for per unit change of the air temperature obtained by the suction air temperature obtaining means. 2. A change rate calculating means for calculating the amount of change in pressure obtained, wherein the frost state of the evaporator is estimated based on the magnitude of the change rate calculated by the change rate calculating means. Vehicle air conditioner. 4. When the rate of change is smaller than a predetermined value, the refrigerant cycle is set to a control mode for preventing the progress of frost of the evaporator, and when the rate of change is equal to or more than a predetermined value, the refrigerant cycle is controlled. The vehicle air conditioner according to claim 2 or 3, wherein a cycle is a control mode for canceling a frosted state of the evaporator. 5. The air conditioner for a vehicle according to claim 4, wherein the control for preventing the frost from progressing in the evaporator is a control for intermittently operating the compressor. 6. The vehicle air conditioner according to claim 4, wherein the control for releasing the frosted state of the evaporator is a control for stopping the compressor. 7. The air conditioner for a vehicle according to claim 4, wherein when the control mode for the frost of the evaporator is being executed, the refrigerant cycle is restarted when the rate of change becomes small.