JP3480141B2 - Vehicle air conditioner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle air conditioner for dehumidifying the interior of a vehicle by cooling the air blown into the interior of the vehicle, and more particularly to a reheat system for reheating air cooled by an evaporator by a heater core. It is suitable for use in an air conditioner that performs a dry dehumidification operation.

[0002]

2. Description of the Related Art For example, in a bus vehicle, there is a great need to enjoy the scenery outside the window through the window glass. Therefore, it is necessary to prevent fogging of the window glass. Ventilation and dehumidification that lowers the humidity inside the vehicle compartment by taking in the air outside the vehicle compartment (outside air) and the low-humidity air that has passed through the evaporator by operating the refrigeration cycle are the measures to prevent the window glass from fogging. There is forced dehumidification that lowers the humidity inside the vehicle by blowing it out. When performing dehumidification in winter or the like, reheat dehumidification is generally performed by operating a heater core arranged downstream of the evaporator to reheat air cooled by the evaporator and introduce the air into the vehicle interior.

[0003]

Fogging of the window glass occurs due to the relationship between the temperature difference between the outside air and the passenger compartment temperature and the humidity in the passenger compartment. Therefore, in order to prevent fogging of the window glass by ventilation dehumidification, the outside air temperature is particularly low, the outside air is humid due to rain, snow, etc., or the humidity generated by the occupants due to the large number of passengers When the humidity rises, it may not be possible to prevent fogging of the window glass.

As a concrete example, in a large bus vehicle,
Ventilation and dehumidification with 50 passengers running at 100 km / h
When the outside has high humidity such as rain or snow, the outside air temperature is 7 to 8 ° C as the antifogging limit.

On the other hand, the reheat dehumidification has a great effect of preventing fogging of the window glass because the humidity in the vehicle compartment can be forcibly lowered. However, when the outside air temperature is low, the evaporator is frosted to lower the dehumidifying ability, or the defrosting function is activated to interrupt the dehumidification by the evaporator.

[0006] As a concrete example, in a large bus vehicle,
When reheat dehumidification is performed with 50 passengers running at 100 km / h, when the outside air temperature drops to 10 to 15 ° C. in the outside air introduction mode, the evaporator is frosted and the dehumidification by the evaporator is interrupted. The outside air temperature is 5 ° C in the inside air circulation mode.
Although the refrigeration cycle can be operated to some extent, the window glass is fogged due to the lack of the dehumidifying effect of ventilation.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to prevent fogging of window glass by suppressing frost formation on the evaporator even when the outside air temperature is low. To provide air conditioners.

[0008]

[Means of Claim 1]

A vehicle air conditioner includes an evaporator that cools air by evaporating a low-pressure refrigerant. The evaporator exchanges heat between the air and the refrigerant on the upstream side of the air flow.
Perform upstream heat exchange and cool the air downstream of the air flow.
Equipped with a downstream heat exchange section that exchanges heat with the medium,
Refrigerant from the downstream heat exchange section to the upstream heat exchange section
The hot water passage for defrost that flows the engine cooling water inside.
A path is disposed between the upstream heat exchange section and the downstream heat exchange section
To be done.

[Operation and Effect of Claim 1] By flowing the engine cooling water through the hot water passage for defrost, it is possible to prevent frost formation on the evaporator while the refrigeration cycle is operating. Alternatively, the frost that has been frosted on the evaporator can be melted while the refrigeration cycle is operating. Therefore, even if the temperature of the evaporator falls to the outside air temperature where frost is formed, the refrigeration cycle can be operated conventionally.
As a result, the dehumidifying operation can be performed inside the vehicle even when the outside air temperature is lower than the conventional temperature. That is, the dehumidifying operation range of the refrigeration cycle can be expanded.

[0010]

Further , in the evaporator, the flow direction of the refrigerant is a counter flow with respect to the flow direction of the air (the low-temperature low-pressure refrigerant flows from the downstream heat exchange section to the upstream heat exchange section), and the wind upper end of the evaporator enters the superheat region. The drain water is unlikely to be generated. However, the temperature of the refrigerant is lower toward the wind lower end side of the evaporator, and as a result, drain water is generated in the central portion of the evaporator. That is, the center portion of the evaporator is most likely to be frosted.

The hot water passage for defrosting is arranged between the upstream heat exchange section and the downstream heat exchange section. For this reason,
When the engine cooling water is passed through the hot water passage for defrosting, the heat of the hot water passage for defrosting heats the central portion of the evaporator that is most likely to form frost, and the heated air is guided to the downstream heat exchange portion. As a result, the engine cooling water guided to the defrosting hot water passage can efficiently melt the frost and quickly defrost it.

[Means for Claim 2 ] The air conditioner for a vehicle according to claim 1 is a low pressure detecting means for detecting a low pressure of the refrigeration cycle, a temperature detecting means for detecting a temperature of the evaporator, and the low pressure. When the low pressure detected by the pressure detecting means is lower than the set pressure and the temperature detected by the temperature detecting means is lower than the set temperature, the control means for flowing the engine cooling water into the hot water passage for defrost for a predetermined time And is provided.

[Operation and Effect of Claim 2 ] When the low-pressure pressure of the refrigeration cycle falls below the set pressure and the temperature of the evaporator falls below the set temperature, the control means supplies the engine cooling water to the hot water passage for defrosting. Run for a specified time. As a result, the temperature of the evaporator rises due to the engine cooling water, and frost formation on the evaporator is prevented. Alternatively, the frosted frost on the evaporator is melted.
Prevention of frost formation on the evaporator or removal of frost that has formed frost can be performed while the refrigeration cycle is operating, so that the defrosting operation range can be expanded as compared with the conventional case.

[Means of claim 3 ] The vehicle air conditioner of claim 1 or claim 2 is a low pressure detection means for detecting the low pressure of the refrigeration cycle, and a temperature detection means for detecting the temperature of the evaporator. And the low pressure detected by the low pressure detecting means is lower than the set pressure and the temperature detected by the temperature detecting means is lower than the set temperature, the low pressure detected by the low pressure detecting means is the set pressure. Control means for causing the engine cooling water to flow through the hot water passage for defrosting.

[Operation and Effect of Claim 3 ] When the low pressure of the refrigeration cycle falls below the set pressure and the temperature of the evaporator falls below the set temperature, the low pressure detected by the low pressure detecting means becomes the set pressure. Until reaching, the control means causes the engine cooling water to flow through the hot water passage for defrosting. As a result, the temperature of the evaporator rises due to the engine cooling water, and frost formation on the evaporator is prevented. Alternatively, the frosted frost on the evaporator is melted. Prevention of frost formation on the evaporator or removal of frost that has formed frost can be performed while the refrigeration cycle is operating, so that the defrosting operation range can be expanded as compared with the conventional case.

[Means of claim 4 ] In the vehicle air conditioner of claim 2 or claim 3 , the low pressure detection means is a low pressure detection sensor capable of continuously detecting the low pressure of the refrigeration cycle. It is characterized by being.

[Means of Claim 5 ] In the vehicle air conditioner of Claim 2 or Claim 3 , the low pressure detection means is a low pressure switch that is turned on and off by the low pressure of the refrigeration cycle. Characterize.

[Means for Claim 6 ] In the vehicle air conditioner according to any one of Claims 1 to 5 , when the engine cooling water is caused to flow through the hot water passage for defrosting, the temperature outside the vehicle compartment is higher than a predetermined temperature. If it is also high, only the air outside the vehicle compartment is supplied into the vehicle compartment through the evaporator, and if the temperature outside the vehicle compartment is lower than a predetermined temperature, the air outside the vehicle compartment and the air inside the vehicle compartment are simultaneously introduced into the vehicle compartment through the evaporator. It is characterized by being supplied.

[Operation and Effect of Claim 6 ] During defrosting operation in which engine cooling water is flown through the hot water passage for defrosting,
When the temperature outside the vehicle compartment is higher than a predetermined temperature, air having a relatively low humidity outside the vehicle compartment is introduced into the vehicle compartment to suppress an increase in humidity in the vehicle compartment even during defrosting. When the temperature outside the vehicle compartment is lower than the specified temperature during the defrosting operation in which the engine cooling water flows through the hot water passage for defrosting, if only the air outside the vehicle compartment with a low temperature flows to the evaporator, the defrosting time will increase and the dehumidification Although there is a problem that the time when the capacity is low becomes long, the defrosting time can be shortened and the time when the dehumidifying capacity is lowered can be shortened by causing the air in the passenger compartment, which has a relatively high temperature, to flow to the evaporator. In addition, if only the air in the passenger compartment having a high temperature is allowed to flow through the evaporator during the defrosting operation, the defrosting time can be shortened, but the humidity in the passenger compartment rises rapidly and the window glass becomes cloudy.

[0021]

[0022]

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a vehicle air conditioner of the present invention will be described based on an embodiment shown in the drawings. [Structure of First Embodiment] FIGS. 1 to 10 show a first embodiment of the present invention. FIG. 1 is a schematic view of an air conditioner mounted on a bus vehicle.

The vehicle air conditioner 1 of this embodiment performs reheat operation during dehumidifying operation, and includes the cooling unit 2 and the condensing unit 3 as the vehicle running engine 4 (corresponding to the engine of the present invention). It is integrated with a sub-engine 5 that is separately provided and is stored under the floor of the passenger seat.

The cooling unit 2 includes a duct 11 for sending air toward the passenger compartment, an inside / outside air switching means 12 provided at an upstream end of the duct 11, an evaporator 13 and a heater core 14 provided inside the duct 11. The blower 15 is provided at the downstream end of the duct 11.

The inside / outside air switching means 12 is provided at the upstream end of the duct 11 as described above, and the inside air introduction port 16 for guiding the air (inside air) in the vehicle interior into the duct 11 and the outside air in the duct 11 are provided. An outside air introducing port 17 for guiding is provided. Further, the inside / outside air switching unit 12 includes two inside air opening / closing dampers 18 for opening / closing the inside air introducing port 16 and an outside air opening / closing damper 19 for opening / closing the outside air introducing port 17.

The two inside air opening / closing dampers 18 are provided so as to be independently operable, and both inside air opening / closing dampers 18 are opened and the inside air inlet 16 is fully opened. One inside air opening / closing damper 18 is opened. Can be set to a state in which the inside air opening / closing damper 18 is closed to open the inside air introducing port 16 halfway, and both inside air opening / closing dampers 18 are closed to completely close the inside air introducing port 16. Further, the outside air opening / closing damper 19 is provided so that the opening degree can be adjusted, and is in a state where the outside air introducing port 17 is fully opened, an outside air introducing port 17 is half opened, and an outside air introducing port 17 is completely closed. It can be set to.

Specifically, the outside air inlet 17 is fully opened,
Open the inside air inlet 16 slightly to increase the outside air introduction ratio to 70
FRE mode and the outside air inlet 17 are fully opened,
Me mode in which the inside air introduction port 16 is half-opened and the outside air introduction ratio is 45%, and the outside air introduction port 17 is half-opened and the inside air introduction port 16 is also half-opened so that the outside air introduction ratio is 20%.
O mode, the outside air inlet 17 is fully closed, and the inside air inlet 1
It is possible to set four modes of REC mode in which 6 is fully opened and only the inside air is introduced into the duct 11, and these modes are selected by the control means 70 described later during the dehumidifying operation or the defrosting operation. The control is performed as shown in Table 1 below based on the outside air temperature.

[0029]

[Table 1] When the outside air temperature is -10 ° C or lower, the sub-engine 5 is stopped, and ventilation dehumidification is performed in the FRE mode.

The evaporator 13 has a structure of a refrigeration cycle 21 for cooling and dehumidifying the air passing through the duct 11 by exchanging heat between the low temperature and low pressure atomized refrigerant supplied inside and the air passing through the duct 11. Parts of this evaporator 1
3 is arranged all over the inside of the duct 11
It is provided so that all the air passing through it can be cooled.

The evaporator 13 is shown in FIGS. 2 to 4, and is provided with a defrosting warm water passage 20 through which the engine cooling water (hereinafter, warm water) of the vehicle running engine 4 flows. The evaporator 13 includes a round tube-shaped upstream heat exchange section 13a that performs heat exchange between air and the refrigerant on the upstream side in the air flow direction, and a round tube that performs heat exchange between the air and the refrigerant on the downstream side in the air flow direction. Tube-shaped downstream heat exchange section 1
3b is a tube-and-fin type heat exchanger, and the low-temperature, low-pressure refrigerant flowing in the evaporator 13 is
The air flows from the downstream heat exchange section 13b toward the upstream heat exchange section 13a so as to face the air flow. Specifically, as shown in a, b, c, and d of FIG. 2, the refrigerant supplied to the evaporator 13 flows from the wind lower end toward the wind upper end.

As described above, since the refrigerant supplied to the evaporator 13 flows from the lower end of the wind toward the upper end of the wind, heat is exchanged between the refrigerant and the air, and the temperature of the refrigerant changes from a at the lower end of the wind to the wind. The temperature rises toward d at the upper end. And
At the upstream end d, the refrigerant is generally superheated.
Enter the area.

Here, the temperature distribution of each part of the evaporator 13 is shown in FIG. In addition, this temperature distribution shows the inside air inlet 1
6 is an example in which the outside air 6 and the outside air inlet 17 are opened, the inside air having a temperature of 25 ° C. and a humidity of 50% is guided to the upper stage of the evaporator 13, and the outside air having a temperature of −5 ° C. and a humidity of 90% is led to the lower stage of the evaporator 13. In the middle of the evaporator 13, the temperature 12
Air having a temperature of 60 ° C and a humidity of 60% is introduced.

As described above, the inside air and the outside air separately pass through the evaporator 13 because the duct 11 on the upstream side of the evaporator 13 is provided with the guide 11a for preventing the outside air from being blown up. Most of the inside air passes from the upper stage to the lower stage, and most of the outside air passes from the middle stage to the lower stage, so that the air having the above-mentioned distribution is evaporated.
Pass through. Even if the guide 11a is not provided, the outside air opening / closing damper 19 allows most of the outside air to pass from the middle stage to the lower stage.

As described above, the temperature of the refrigerant having entered the tube of the evaporator 13 rises from a at the wind bottom to d at the wind top. Therefore, condensed water is generated from the place where the refrigerant flows and the surface temperature of the tube becomes low with respect to the dew point temperature of each air temperature and humidity. The upper and middle positions of the place are near the center of the evaporator 13. The lines in which this condensed water is generated are the upper dew condensation line and the lower dew condensation line in FIG.

The condensed water generated in the upper and lower stages flows down to the lower stage of the evaporator 13 due to gravity. Since the lower stage of the evaporator 13 is below the freezing point of 0 ° C. or lower, the condensed water freezes. The line where the condensed water freezes is the below-freezing line in FIG. As described above, the sub-freezing line where the condensed water freezes is below the middle stage of the evaporator 13. As described above, since condensed water is likely to be generated near the center, it is likely to be frosted near this center, and particularly, it is most likely to be frosted near the center below the middle stage where the condensed water falls.

On the other hand, in the evaporator 13, in order to efficiently melt the frost generated in the evaporator 13 and shorten the defrosting time, the above defrosting hot water passage 20 includes the upstream heat exchange section 13a and the downstream heat exchange section. 13b, that is, so as to flow in the center of the evaporator 13. Also,
As shown in FIG. 2, the distribution of hot water supply to the hot water passage 20 for defrosting is provided such that the flow rate of hot water increases below the middle stage. In other words, the length of the lower hot water passage is shortened to reduce the lower water passage resistance, and conversely, the upper hot water passage is lengthened to increase the lower water passage resistance to the frosted portion. The evaporator 1 is adjusted so that hot water can be efficiently supplied.
It is provided so that the frost generated on the lower side of No. 3 is melted in a short time.

At the lower part of the evaporator 13 and the lower part of the heater core 14, one or a plurality of drain pans 11b are arranged as shown in FIG. Drain pan 1
When condensed water is supplied to 1b, the outside air temperature is 0 ° C, for example.
If it is below, the condensed water freezes in the drain pan 11b, and there arises a problem that the condensed water cannot be discharged from the drain pan 11b. Therefore, in the present embodiment, as shown in FIG. 7, a cord-shaped drain pan heater 30 that generates heat when energized is arranged in the drain pan 11b. The drain pan heater 30 is energized and controlled by the control means 70 described later.

The refrigeration cycle 21 is, as shown in FIG.
In addition to the evaporator 13, a compressor 22 driven by the sub-engine 5 to suck and discharge the refrigerant, a condenser 23 for condensing the high-temperature and high-pressure gas refrigerant discharged by the compressor 22, and a refrigerant liquefied by the condenser 23 A receiver 24 for separation, a decompression device 25 for adiabatically expanding the high-temperature high-pressure liquid-phase refrigerant into a low-temperature low-pressure atomized refrigerant,
And a refrigerant pipe 26 connecting them.
The refrigeration cycle 21 of the present embodiment is provided with a super cooler 27 that further exchanges heat between the liquid-phase refrigerant that has been gas-liquid separated by the receiver 24 and the outside air to provide a supercooling degree.

The heater core 14 is capable of heating the air passing through the duct 11 downstream of the evaporator 13 by exchanging heat with engine cooling water (warm water).
It is arranged over the entire inner surface and is provided so as to heat all the air that has passed through the evaporator 13. The heater core 14 uses engine cooling water for releasing exhaust heat of the vehicle running engine 4 as a heat source.
The engine cooling water has a radiator circuit (not shown) for maintaining the temperature of the vehicle running engine 4 within a predetermined temperature range, and an air conditioning hot water circuit 4 having a heater core 14.
1 and 1.

The hot water circuit 41 for air conditioning comprises the heater core 1
4, a cooling water pump 42 for feeding hot water under pressure, a combustion type preheater 43 for heating the hot water when the temperature of the hot water supplied to the heater core 14 is equal to or lower than a set temperature, and is connected by a cooling water pipe 44. ing. In addition, the hot water circuit 4 for air conditioning
1 includes a defroster core 45 for heating the air blown to the windshield of the vehicle. The defroster core 45 is provided in parallel with the preheater 43 and the heater core 14.

A heating solenoid valve 46 is provided upstream of the preheater 43. This heating solenoid valve 46 is the heater core 1
It is provided so that the valve is opened when 4 is operated. A defroster solenoid valve 47 is provided upstream of the defroster core 45. This defroster solenoid valve 47
Are provided so as to open when the heater core 14 is operated. Reference numeral 48 in the figure is a stop valve that opens and closes by manual operation.

The air conditioning hot water circuit 41 is also provided with a cooling water pipe 44 for flowing the cooling water of the vehicle running engine 4 in parallel to the heater core 14 to the defrosting hot water passage 20.
A cooling water pipe 44 for guiding hot water to the defrosting hot water passage 20 is provided with a defrosting electromagnetic valve 49 for opening and closing the cooling water pipe 44.

The blower 15 is a centrifugal fan driven by the sub-engine 5, sucks the outside air or the inside air selected by the inside / outside air switching means 12, and blows the air passing through the duct 11 toward the passenger compartment. It is a thing. A magnet clutch 51 for connecting and disconnecting rotational power and an electric motor 52 are provided in a transmission path for transmitting a driving force from the sub engine 5 to the blower 15.
The blower 15 is rotatably driven by operating the electric motor 52 while being disconnected from the sub-engine 5 by 1.

The condensing unit 3 is a shroud case 61 in which the outside airflow forcedly flows, a supercooler 27 arranged in the shroud case 61 and forcibly exchanged heat with the outside air, a condenser 23 and a radiator 6.
2. The cooling fan 63 is arranged at the downstream end of the shroud case 61.

Super cooler 27 and condenser 23
Is a component of the refrigeration cycle 21 described above. The super cooler 27 forcibly exchanges heat with the outside air to give a supercooling degree to the liquid-phase refrigerant flowing inside the super cooler 27, and the radiator 62 is forced to communicate with the outside air. The gas refrigerant flowing in the condenser 23 is liquefied and condensed by being heat-exchanged.

The radiator 62 is a heat radiating means for maintaining the temperature of the sub engine 5 within a predetermined temperature range. The cooling fan 63 is an axial fan driven by the sub-engine 5, and when the sub-engine 5 is operated, outside air is sucked into the shroud case 61 and the super cooler 2 is cooled.
7, the condenser 23 and the radiator 62 are forcibly cooled.

The energization of each electric functional component of the vehicle air conditioner 1 is controlled by the control means 70 using a microcomputer. As shown in FIG. 8, the defrosting solenoid valve 49 is energized and opened by turning on the relay switch 71a. The relay switch 71a is turned on when the relay coil 71b is energized. The relay coil 71b is energized by the control means 70. Further, the drain pan heater 30 described above is energized and generates heat by turning on the relay switch 72a. The relay switch 72a is turned on when the relay coil 72b is energized. This relay coil 72b is
Energization is controlled by the control means 70.

First, the energization control of the drain pan heater 30 by the control means 70 will be described. The control means 70
As shown in FIG. 8, an outside air temperature sensor 75 that detects the temperature of outside air is provided. Then, as shown in FIG. 9, when the outside air temperature is 0 ° C. or less, the relay coil 72b is energized to pass a current through the drain pan heater 30, and when the outside air temperature is 2 ° C. or more, the energization of the relay coil 72b is stopped. Supply of electric current to the drain pan heater 30 is stopped. As a result, there is no problem that the condensed water freezes in the drain pan 11b, and the condensed water is reliably discharged.

Next, the defrosting solenoid valve 4 by the control means 70.
The energization control of 9 will be described. The control unit 70 is provided to turn on the relay coil 71b and open the defrosting electromagnetic valve 49 when the evaporator 13 is frosted or when there is a high possibility of frosting. Control means 7
0 is means for detecting frost formation on the evaporator 13,
A low pressure detection sensor 7 capable of continuously detecting the pressure on the low pressure side of the refrigerant pipe 26 (the suction side of the compressor 22).
3 and an outlet temperature sensor 74 that detects the temperature of the fins on the downstream side of the air flow of the evaporator 13, and the low pressure detected by the low pressure detection sensor 73 is set pressure (for example, 1.5 kgf / cm ² G) or less. In addition, when the temperature detected by the outlet temperature sensor 74 is equal to or lower than the set temperature (for example, 3 ° C.), it is determined that the evaporator 13 has started to be frosted, and after a lapse of a predetermined time (for example, after 25 minutes), Or the low pressure is below the set pressure (eg 0.5 kgf / cm ² G
In the following case, the relay coil 72 is turned on for a predetermined time (for example, 2 minutes), and the defrosting electromagnetic valve 49 is opened.

The operation of the defrosting operation by the control means 70 will be described with reference to the flowchart of FIG. When the refrigeration cycle 21 is operated (start), the low pressure is 1.5k.
It is determined whether or not gf / cm ² G or less (step S1
). If the result of this determination is NO, the process advances to the next control. If the determination result is YES, it is determined whether or not the fin temperature downstream of the evaporator 13 is 3 ° C. or lower (step S2).
If the result of this determination is NO, the low pressure is 0.5 kgf /
It is determined whether or not the value is cm ² G or less (step S3). If the result of this determination is NO, the process proceeds to the next control, and if YES, it is determined to be a low pressure abnormality (step S4).

If the decision result in the step S2 is YES,
It is determined whether or not 25 minutes have passed since both steps S1 and S2 became YES (step S5). If the result of this determination is NO, the low pressure is 0.5 kgf / cm ²
G It is determined whether or not the following (step S6). If the result of this determination is NO, the process returns to step S1. If the result is YES, it is determined whether the fin temperature downstream of the evaporator 13 is 0 ° C. or lower (step S7). If the result of this determination is NO, it is determined that there is a low pressure abnormality (step S8).

If the determination results in steps S5 and S7 are YES, the rotation speed of the sub-engine 5 is 900 rpm, the magnet clutch 51 is OFF, and the rotation mode of the electric motor 52 is low (step S9). Turn on the defrosting solenoid valve 49
Yes (step S10). The ventilation mode is selected and set based on the outside air temperature detected by the outside air temperature sensor 75 (step S11). Specifically, during the defrosting operation, as shown in Table 1 above, the FRE mode is set when the outside air temperature is 0 ° C. or higher, and the Lo mode is set when the outside air temperature is lower than 0 ° C. It

It is judged whether or not two minutes have passed since the defrosting solenoid valve 49 was turned on (step S12). If the determination result is NO, the process returns to step S12, and if the determination result is YES, the low pressure is 1.5 kgf / cm ² G It is determined whether or not the above (step S13). If the result of this determination is YES, the defrosting solenoid valve 49 is turned off (step S14). Next, the normal control is returned to (step S15), and then the next control is performed.

When the result of the determination in step S13 is NO, it is determined whether or not 8 minutes have passed after the defrosting solenoid valve 49 was turned on (step S16). If the result of this determination is NO, the process returns to step S13, and if the result is YES, the process proceeds to frost hold control (step S17).

[Operation of Embodiment] Next, an operation in the case of performing dehumidifying and heating for the purpose of preventing the window glass of the bus vehicle from being fogged when the outside air temperature is low, such as in winter, will be described. In the dehumidification heating, the refrigeration cycle 21 operates to cool and dehumidify the air passing through the duct 11 by the evaporator 13, and then the air is reheated and blown into the vehicle interior when passing through the heater core 14.

When the outside air temperature drops, the temperature of the refrigerant passing through the condenser 23 and the super cooler 27 drops. Then, the low-pressure pressure after adiabatic expansion in the decompression device 25 decreases and the temperature of the evaporator 13 also decreases. Then, as the outside air temperature decreases, the low pressure changes to a set pressure (for example, 1.5 kgf / cm ² G ) Or less and when the fin temperature downstream of the evaporator 13 becomes 3 ° C. or less, the evaporator 13 starts frosting. It takes about 30 to 60 minutes until the evaporator 13 is completely frozen, but in the present embodiment, when 25 minutes or more have passed, the defrosting solenoid valve 49 is turned on to allow hot water to flow to the evaporator 13 for 2 minutes. Melt the frost on the evaporator 13. afterwards,
Low pressure is 1.5 kgf / cm ² G If it is above, the defrosting solenoid valve 49 is turned off and the normal dehumidifying operation is performed.

[Effects of Embodiment] In the vehicle air conditioner 1 of this embodiment, when frost formation on the evaporator 13 is detected, hot water is supplied to the defrosting hot water passage 20 as described above. The refrigeration cycle 21 can be operated while removing the frost. Therefore, the conventional anti-fog limit is
The outside air temperature was 7 to 8 ° C, while the outside air temperature was -5
Anti-fog up to ℃. That is, the anti-fog range can be improved by 12 to 13 ° C. as compared with the conventional case.

Further, when performing the defrosting operation, conventionally, there is a means for temporarily stopping the sub-engine 5 and performing a blowing operation to defrost it. The number of times increases, and the occupant feels uncomfortable due to vibration and noise, and the durability and reliability of each functional component (particularly the sub engine 5 and the compressor 22) deteriorate. However, in the present embodiment, the refrigeration cycle 21 and the sub engine 5 are operating even during the defrosting operation, so the number of times the sub engine 5 is started and stopped can be suppressed. As a result, discomfort to the occupant can be suppressed, and the durability and reliability of each functional component can be improved as compared with the conventional one.

On the other hand, in this embodiment, when forced dehumidification is performed by reheating, as shown in Table 1, the outside air temperature is-.
When the temperature is 5 ° C. or higher, the mode becomes Me mode. Outside temperature is -5
When the temperature is higher than ℃, the window glass cannot be fogged only by forcibly dehumidifying the refrigeration cycle 21 by reheating. Therefore, by forcing a large amount of low-humidity outside air into the vehicle interior, the window glass is completely fogged. Can be taken to
Further, as shown in Table 1, when the outside air temperature is lower than -5 ° C, the REC mode is set. When the outside air temperature is lower than −5 ° C., when the outside air is introduced into the passenger compartment, the temperature is too low, the low-pressure pressure of the refrigeration cycle 21 drops quickly, and the amount of frost increases. As a result, the time until the start of defrosting is shortened, and the number of defrosting times increases. Therefore, by guiding only the inside air into the duct 11, the time until the start of defrosting becomes long, and the dehumidifying operation can be performed for a long time.

Further, when the defrosting solenoid valve 49 is turned on and hot water is allowed to flow through the evaporator 13 to perform the defrosting operation, as shown in Table 1, when the outside air temperature is lower than 0 ° C., the Lo mode is selected. Becomes When the outside air temperature is lower than 0 ° C. and the outside air amount is larger than that in the Lo mode, the temperature of the air passing through the evaporator 13 is too low, the time until the defrosting ends becomes long, and the defrosting time when the dehumidifying ability has decreased It will be long. vice versa,
When the amount of outside air is smaller than that in the Lo mode, the defrosting time can be shortened to some extent, but during defrosting with a reduced dehumidifying capacity, high-humidity air circulates and the window easily becomes cloudy. Therefore, when the outside air temperature is 0 ° C. or higher, the Lo mode is optimal. Further, as shown in Table 1, when the outside air temperature is 0 ° C or higher, FR
It becomes E mode. When the outside air temperature is 0 ° C. or higher, the defrosting time is short even with only the outside air. Then, by introducing a large amount of outside air into the vehicle interior, it is possible to prevent an increase in humidity during defrosting operation in which the dehumidifying capacity is lowered, and to suppress the occurrence of fogging on the window glass.

[Second Embodiment] FIGS. 11 to 14 show a second embodiment.
An example is shown. In the first embodiment described above, the refrigeration cycle 2
Although the example of controlling the defrosting operation using the low pressure detection sensor 73 capable of continuously detecting the low pressure of No. 1 has been described, in the present embodiment, the low pressure that is turned on and off by the low pressure of the refrigeration cycle 21 is shown. The dehumidifying operation is controlled using the pressure detection switch 73a.

The low pressure detection switch 73a has a hysteresis that turns on when the pressure drops to a predetermined pressure and turns off when the pressure rises to slightly higher than the predetermined pressure. The low pressure detection switch 73a used in this embodiment has a low pressure of 1.5 kgf / cm ² G as shown in FIG. (First
1. When the pressure drops to the same as the set pressure of the embodiment), 1.
1 kgf / cm ² G As an example, the one that turns off when the temperature rises to is shown.

The control means 70, as shown in FIG.
Only step S13 of FIG. 10 of the first embodiment is different,
In the present embodiment, instead of step S13, step S13b
Is what you do. This step S13b is for low pressure
The force is 2.1 kgf / cm²G Whether or not the above is reached (low pressure
It is determined whether or not the pressure detection switch 73a is turned off.
However, if the result of this judgment is NO, the operation proceeds to step S16.
If the judgment result is YES, the process proceeds to step S14.
is there. The step S1 of this embodiment is for detecting low pressure.
Low pressure is 1.5k depending on whether switch 73a is turned on or not.
gf / cm²G What determines whether or not it has dropped below
Is.

(Operation of the Second Embodiment) In the time chart of FIG. 14, when the defrosting operation is controlled using the low pressure detection sensor 73 (shown by the solid line, the first embodiment),
The difference from the case where the defrosting operation is controlled using the low pressure detection switch 73a (shown by the broken line, the second embodiment) is shown. In this example, the outside air temperature is −5 ° C. and the vehicle speed is 10
0km / h, with 50 passengers on board.
In addition, a solid line G in the figure indicates the vehicle interior humidity due to ventilation dehumidification in which only outside air is introduced into the vehicle interior.

Defrosting is started in the first and second embodiments.
Same as the embodiment, the defrosting operation is started at the same time (25 minutes after the start). When the defrosting operation is started, hot water flows through the evaporator 13, so that the dehumidifying capacity is reduced and the humidity in the vehicle compartment is gradually increased. Here, in the case of the first embodiment using the low pressure detection sensor 73, since the defrosting end pressure is 1.5 kgf / cm, even if the outside air temperature is -5 ° C, the window glass will not fog. Does not occur. In the case of the second embodiment using the low pressure detection switch 73a, the defrosting end pressure is 2.1 kgf due to the switch hysteresis.
/ Cm ² G Therefore, the defrosting time becomes long, and the window glass becomes cloudy just before the end of the defrosting operation. However, compared with the conventional ventilation dehumidification, the fogging of the window glass is significantly suppressed, and there is a marked effect as compared with the conventional one.

[Third Embodiment] A third embodiment shown in FIGS.
An example is shown. In the second embodiment described above, an example in which the low pressure detection switch 73a is turned on and off to control the dehumidifying operation is shown. However, in the third embodiment, the refrigeration cycle 2 is used.
The dehumidifying operation is controlled by the signal of the low pressure detection switch 73a which detects the low pressure abnormality of No. 1 of FIG. The low pressure detection switch 73a of this embodiment is used in the refrigeration cycle 2
Low pressure of 1 is 0.7 kgf / cm ² G The following shows an example of turning on when the voltage drops.

The control means 70 is shown in the flow chart of FIG. 15, and when the refrigeration cycle 21 is operated (start), the low pressure is 0.7 kgf / min, depending on whether the low pressure detection switch 73a is turned on or not. cm ² G It is determined whether or not it has decreased below (step S1c). If the result of this determination is NO, the process advances to the next control. If the determination result is YES, it is determined whether or not the fin temperature downstream of the evaporator 13 is 0 ° C. or lower (step S2c). This judgment result is NO
In the case of, the process proceeds to step S8 and it is determined that the low pressure is abnormal.

If the decision result in the step S2c is YES,
After performing steps S9, S10 and S11 (see the first embodiment), it is determined whether or not 4 minutes have passed since the defrosting solenoid valve 49 was turned on (step S12c). This judgment result is NO
If YES, the process returns to step S12c, and if YES, the process proceeds to step S14 to end the defrosting operation.

(Operation of Third Embodiment) The operation of the third embodiment will be described with reference to FIGS. The inside air temperature is 25 ° C., the rotation speed of the sub-engine 5 is 900 rp
At m, the compressor 22 has a 1/3 capacity and the amount of introduced air is 55
This is the case where the condition is 0 m ³ / h and the amount of introduced outside air is 450 m ³ / h (Me mode in Table 1).

FIG. 16 is a time chart showing the relationship between the outside air temperature and the decrease in air volume due to frost formation on the evaporator 13.
The defrosting start pressure is 0.7 kgf / cm ² G When the temperature is set to 0, the decrease rate of the air volume is different between the outside air temperature of 0 ° C and -5 ° C.
gf / cm ² G When the outside air temperature is -5 ° C,
0.7 kgf / cm ² G after 25 minutes Fall to.

That is, when the outside air temperature is 0 ° C., the humidity inside the vehicle is dehumidified for 50 minutes as shown by the broken line in FIG. 17 (the solid line is the example of the first embodiment using the low pressure detection sensor 73). The cycle of performing the defrosting operation for 4 minutes is repeated. Even in this case, as in the second embodiment, the window glass is fogged just before the end of the defrosting operation, but the fogging of the window glass is significantly suppressed as compared with the conventional ventilation dehumidification (solid line G in the figure). , Has a remarkable effect compared with the conventional one.

When the outside air temperature is -5 ° C., the humidity in the passenger compartment repeats a cycle of dehumidifying operation for 25 minutes and defrosting operation for 4 minutes as shown by the broken line in FIG. Even in this case, the window glass is fogged just before the end of the defrosting operation, but as described above, the fogging of the window glass is significantly suppressed as compared with the conventional ventilation dehumidification (solid line G in the figure). Has a marked effect compared to.

[Fourth Embodiment] FIG. 19 shows a fourth embodiment and is a perspective view of a defrosting hot water passage in an evaporator. In the above-described embodiment, the defrosting warm water passage 20 for flowing the engine cooling water (warm water) to the evaporator 13 is an example in which the warm water passages are connected in parallel below the middle stage so that the warm water flow rate increases. However, the hot water passage 2 for defrosting of this embodiment
No. 0 is arranged in a state of meandering between the upstream heat exchange section 13a and the downstream heat exchange section 13b by a single line of hot water passage.

[0075]

[0076]

[0077]

[0078]

[Modification] In the above embodiment, the example in which the present invention is applied to the air conditioner for a bus vehicle is shown, but it is applied to an air conditioner mounted on another vehicle (passenger car, truck vehicle, etc.). You may. Of course, it can be applied to an air conditioner of a vehicle that does not have a sub engine.

In the above embodiment, the defrosting hot water passage 20 is connected to the cooling water pipe common to the heater core, but the hot water for defrosting is provided independently of the heater core.
It may be provided so that it can be led to. By providing in this way, the dehumidification operation (cooler operation) time can be extended even if the outside air temperature decreases during the dehumidification operation (cooler operation) when the heater core is not operated. of course,
It is also applicable to an air conditioner without a heater core.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an air conditioner mounted on a bus vehicle (first embodiment).

FIG. 2 is a side view of an evaporator (first embodiment).

FIG. 3 is a partial front view of an evaporator (first embodiment).

FIG. 4 is a partial top view of the evaporator (first embodiment).

FIG. 5 is a graph illustrating the temperature distribution of the evaporator (first example).

FIG. 6 is a schematic view of a main part of an air conditioner showing a drain pan (first embodiment).

FIG. 7 is an explanatory diagram showing an arrangement state of drain pan heaters (first embodiment).

FIG. 8 is a main part electric circuit diagram of a control means (first embodiment).

FIG. 9 is a graph showing the operation of the drain pan heater (first embodiment).

FIG. 10 is a flowchart showing defrost control (first
Example).

FIG. 11 is a schematic view of an air conditioner mounted on a bus vehicle (second embodiment).

FIG. 12 is a graph showing ON / OFF hysteresis of a low pressure detection switch (second embodiment).

FIG. 13 is a flowchart showing defrost control (second)
Example).

FIG. 14 is a time chart explaining the operation (second)
Example).

FIG. 15 is a flowchart showing defrost control (third embodiment)
Example).

FIG. 16 is a time chart for explaining a rate of decrease in air volume due to a change in outside air temperature (third embodiment).

FIG. 17 is a time chart for explaining the operation when the outside air temperature is 0 ° C. (third embodiment).

FIG. 18 is a time chart explaining the operation when the outside air temperature is −5 ° C. (third embodiment).

FIG. 19 is a perspective view of a hot water passage for defrosting in the evaporator (fourth embodiment).

[Explanation of symbols]

1 Vehicle Air Conditioner 4 Vehicle Running Engine 13 Evaporator 13a Upstream Heat Exchanger 13b Downstream Heat Exchanger 20 Defrosting Hot Water Passage 21 Refrigeration Cycle 22 Compressor 49 Defrosting Solenoid Valve 70 Control Means 73 Low Pressure Detection Sensor 73a Low Pressure pressure detection switch 74 outlet temperature sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Etsuji Miyata, 1-1, Showa-cho, Kariya city, Aichi Japan Denso Co., Ltd. (56) References JP-A-2-114016 (JP, A) JP-A-6 -174342 (JP, A) Actual Kaihei 5-37522 (JP, U) Japanese Patent Publication No. 50-6387 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60H 1/00- 3/06

Claims (6)

(57) [Claims] 1. A vehicle air conditioner comprising a refrigeration cycle equipped with an evaporator for evaporating a low-pressure refrigerant to cool air, wherein the evaporator cools air on the upstream side of an air flow.
The upstream heat exchange part that exchanges heat with the medium and the downstream side of the air flow
Equipped with a downstream heat exchange section that exchanges heat between air and refrigerant.
The low temperature low pressure refrigerant from the downstream heat exchange section to the upstream heat
The hot water passage for defrost that flows engine cooling water inside the upstream
A vehicle air conditioner arranged between a heat exchange section and the downstream heat exchange section . 2. The vehicle air conditioner according to claim 1 , wherein a low pressure detection means for detecting a low pressure of the refrigeration cycle, a temperature detection means for detecting a temperature of the evaporator, and a detection for the low pressure detection means. When the low pressure to be lower than the set pressure, and the temperature detected by the temperature detecting means is lower than the set temperature, a control means for flowing engine cooling water into the hot water passage for defrost for a predetermined time is provided. A characteristic vehicle air conditioner. 3. The vehicle air conditioner according to claim 1 or 2 , wherein the low pressure detection means detects a low pressure of the refrigeration cycle, the temperature detection means detects a temperature of the evaporator, and the low pressure. When the low pressure detected by the detection means is lower than the set pressure and the temperature detected by the temperature detection means is lower than the set temperature, the low pressure detected by the low pressure detection means reaches the set pressure, An air conditioner for a vehicle, comprising: a control unit that causes engine cooling water to flow in a hot water passage for defrosting. 4. The vehicle air conditioner according to claim 2 or 3 , wherein the low pressure detection means is a low pressure detection sensor capable of continuously detecting low pressure of the refrigeration cycle. A vehicle air conditioner. 5. The vehicle air conditioner according to claim 2 or 3 , wherein the low pressure detection means is a low pressure switch that is turned on and off by the low pressure of the refrigeration cycle. Air conditioner. 6. The vehicle air conditioner according to any one of claims 1 to 5 , wherein when the temperature outside the vehicle compartment is higher than a predetermined temperature when the engine cooling water is flowed through the defrosting hot water passage. Only outdoor air is supplied into the vehicle compartment through the evaporator, and when the temperature outside the vehicle compartment is lower than a predetermined temperature, the outdoor air and the vehicle interior air are simultaneously supplied into the vehicle compartment through the evaporator. A characteristic vehicle air conditioner.