JP3934256B2 - Air conditioner for automobile - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automotive air conditioner that performs dehumidification heating in a vehicle interior by a heat pump system having a dehumidification function.
[0002]
[Prior art]
BACKGROUND ART An automobile air conditioner using a heat pump system is used as an automobile air conditioner for a low heat engine vehicle having a low engine cooling water temperature or an electric vehicle not equipped with an engine. This is because, in the case of low heat engine cars and electric cars, the heating heat source is insufficient compared to ordinary engine-equipped cars, so the cycle operation is performed using refrigerant not only for cooling but also for heating, while preventing window fogging. It has been developed as a heat pump type car air conditioner capable of dehumidifying and heating that can heat the passenger compartment (for example, see Japanese Patent Application Laid-Open No. 5-201243 for an electric vehicle).
[0003]
For example, as shown in FIG. 4, this type of automotive air conditioner has a blower device 2 that takes air into a duct 1 provided in a passenger compartment, an evaporator 3, and a chamber that functions mainly during heating operation. An inner sub-capacitor 4 is disposed, and outside the duct 1 is disposed an outdoor main capacitor 5 that functions mainly during cooling operation. In the low heat engine vehicle, a heater core 18 is provided in the duct 1 for using engine cooling water heated by the engine during heating. In an electric vehicle not equipped with an engine, the heater core 18 is not provided, but some of them have an electric heater as an auxiliary heat source.
[0004]
The sub capacitor 4 and the main capacitor 5 are switched between a heating operation and a cooling operation by a four-way valve 6 provided on the downstream side of the compressor 7, and the refrigerant bypasses the main capacitor 5 during the heating operation. The refrigerant discharged from the compressor 7 flows through the four-way valve 6 → the bypass pipe 8 → the sub condenser 4 → the liquid tank 9 → the expansion valve 10 → the evaporator 3 and returns to the compressor 7 (heating cycle). In this circulation process, the gas refrigerant discharged from the compressor 7 and bypassing the main condenser 5 by the four-way valve 6 is condensed and liquefied by the sub condenser 4 to dissipate heat, so that the air dehumidified (and cooled) by the evaporator 3 is sub Heated by the condenser 4, the vehicle interior is dehumidified and heated.
[0005]
A refrigerant recovery passage 11 is provided between the outlet side of the four-way valve 6 (one of the outlet ports) and the suction side of the compressor 7, and an electromagnetic valve 12 is attached to the refrigerant recovery passage 11. Yes. When the outside air temperature is low at the start of the heating operation, the refrigerant recovery passage 11 and the main condenser 5 are communicated with each other by the four-way valve 6 and the solenoid valve 12 is opened so that the so-called sleeping refrigerant mainly staying in the main condenser 5 is removed. Returning to the compressor 7, the shortage of refrigerant in the heating cycle is compensated.
[0006]
Thus, in the case where the heater core 18 is provided, a portion in which the heating capacity by the heater core 18 is insufficient is compensated. On the other hand, in the case where the heater core itself is not provided as in an electric vehicle, the above heat pump is used. The vehicle interior is heated by a cycle.
[0007]
On the other hand, during the cooling operation, by switching the four-way valve 6, the compressor 7 → the four-way valve 6 → the main capacitor 5 → the sub capacitor 4 → the liquid tank 9 → the expansion valve 10 → the evaporator 3, and the cooling cycle returning to the compressor 7. Thus, the vehicle interior is cooled.
[0008]
4, 13, 14, and 15 are check valves, 16 is an air mix door, and 17 is a condenser fan. In the figure, the arrow in the duct 1 indicates the direction of air flow in the duct 1. The refrigerant circulation system excluding the heater core is referred to herein as a heat pump system.
[0009]
[Problems to be solved by the invention]
However, in such a conventional heat pump system, since the outside air temperature is low and the like, it is sufficient when the heating is operated at full hot with the air circulation in the vehicle interior as the inside air circulation in order to warm the vehicle interior faster during heating. The dehumidification could not be performed and the window was fogged.
[0010]
Such window fogging is usually caused by a sudden increase in the temperature in the passenger compartment and an increase in the saturated humidity of the air in the passenger compartment when the vehicle is operated with inside air circulation and full hot. One of the causes of window fogging is a decrease in the dehumidifying performance of the heat pump system itself.
[0011]
The decrease in the dehumidifying performance in the heat pump system naturally increases the temperature of the air passing through the duct 1 due to the increase in the inside air temperature, so that warm air hits the sub condenser 4 and the evaporator 3, and the low pressure pressure on the suction side of the evaporator 3 is increased. Occurs because the cooling capacity of the evaporator 3 decreases.
[0012]
Therefore, in order to prevent such a decrease in dehumidifying performance, it is preferable to prevent an increase in pressure on the evaporator suction side. As the simplest method for that purpose, it is conceivable to increase the pressure reducing capability of the expansion valve 10 provided on the evaporator suction side. However, if the decompression capacity of the expansion valve is simply increased, this time, even when the pressure on the evaporator suction side has not increased so much, the expansion valve with the increased decompression capacity reduces the pressure on the evaporator suction side more than necessary. As a result, there is a problem that the temperature drop of the refrigerant in the evaporator increases and the refrigerant freezes, and the cooling capacity of the evaporator during the cooling operation is also reduced.
[0013]
Therefore, the present invention provides a cooling / heating apparatus for an automobile that uses a heat pump system, for example, when the inside air circulation or a full hot state, the pressure on the suction side of the evaporator is sufficiently lowered to prevent the dehumidification ability from being lowered. An object of the present invention is to provide an automotive air conditioning apparatus that is less likely to cause window fogging.
[0014]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following means.
[0015]
(1) A compressor, an indoor condenser disposed in the vehicle interior, an outdoor condenser disposed outside the vehicle interior, a liquid tank, an expansion valve, and an evaporator disposed in the vehicle interior are connected by piping in this order, and the downstream of the compressor A bypass pipe that bypasses the outdoor condenser and reaches the indoor condenser, and a flow path switching valve that switches a flow path of the refrigerant discharged from the compressor. The refrigerant discharged from the vehicle is circulated in the order of the bypass pipe, the indoor condenser, the liquid tank, the expansion valve, and the evaporator. In a heat pump type automotive air conditioner that performs dehumidification heating, the evaporator Provided with a constant pressure expansion valve on the inlet side for reducing the pressure so that the suction side pressure becomes a pressure within a predetermined range when the suction side pressure becomes equal to or higher than a predetermined pressure. An automotive air conditioning system characterized by the above.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a schematic configuration diagram of an automotive air conditioner according to an embodiment of the present invention. In the figure, members common to those in FIG. 4 are denoted by the same reference numerals.
[0018]
1 is a heat pump system that performs cooling and dehumidification heating of a vehicle interior by performing cycle operation using a refrigerant for both cooling and heating, and the conventional heat pump system shown in FIG. Its basic configuration and operation are the same. Therefore, in the following description, only the part to which the present invention is applied and the operation related thereto will be described.
[0019]
The automotive air conditioner shown in FIG. 1 is provided with a constant pressure expansion valve 20 between the expansion valve 10 and the evaporator 3 that have been conventionally provided on the suction side of the evaporator 3 of the heat pump system.
[0020]
As will be described later, the constant-pressure expansion valve 20 has a pressure of a gas-liquid mixture that passes through the inside thereof (the refrigerant that has passed through the expansion valve 10 passes through, so the liquid and gas are mixed). As a result, the valve opening changes, and the output of the constant pressure expansion valve 20, that is, the suction side pressure of the evaporator 3 is made constant.
[0021]
As a specific structure of the constant pressure expansion valve 20, for example, as shown in FIG. 2, a pressure control type valve 22 supported by a bellows 21 and a flow path 23 whose opening degree is controlled by the valve 22. When the internal pressure becomes very high and the valve 22 completely closes the flow path 23, the narrow rod 24 for allowing the gas-liquid mixture to escape to the output side and the constant pressure expansion valve 20 itself function during the cooling operation. Without being made, it consists of a bypass pipe 25 for passing the gas-liquid mixture coming from the expansion valve 10 as it is to the evaporator 3 and a solenoid valve 26 for switching the flow path to the bypass pipe 25 during the cooling operation.
[0022]
Such a constant pressure expansion valve 20 has a position of the valve 22 changed by the bellows 21 contracting or expanding in accordance with the internal pressure, and the opening of the flow path 23 is changed. It becomes a constant value.
[0023]
Here, for example, when the aim th suction side pressure of the evaporator 3 and 1.8~2.0kg / cm ^2, as the setting of the constant pressure expansion valve 20, when the internal pressure of 2.0 kg / cm ² or less, On the other hand, when the internal pressure becomes 2.0 kg / cm ² or more so that the valve 21 is fully opened and the pressure is not reduced, the valve 22 throttles the opening of the flow path 23 according to the increase in the pressure, The output pressure is set to be in the range of 1.8 to 2.0 kg / cm ² .
[0024]
Thus, when the pressure in the constant pressure expansion valve 20 is such that 2.0 kg / cm ² or more, the output pressure is kept at 1.8~2.0kg / cm ^2. Therefore, as shown in the Mollier diagram shown in FIG. 3, with the conventional expansion valve 10 alone, the suction side pressure of the evaporator 3, that is, the pressure between the condenser (COND) and the evaporator (EVAP) shown in FIG. Even in such a case (the position of the dotted line in the figure), the suction side pressure of the evaporator 3 can be sufficiently lowered by the action of the constant pressure expansion valve 20. Note that COMP in FIG. 3 is a compressor.
[0025]
On the other hand, when the pressure of the gas-liquid mixture coming to the constant pressure expansion valve 20 is 2.0 kg / cm ² or less, the valve 22 is fully opened. What is controlled to 1.8 to 2.0 kg / cm ² which is the target of the suction side pressure passes through the constant pressure expansion valve 20 as it is and enters the evaporator 3.
[0026]
In the above embodiment, the conventional heat pump system is provided with a constant pressure expansion valve that reduces the pressure only when the suction side pressure is equal to or higher than a predetermined pressure. Even when a heating operation is performed by this, the pressure on the evaporator suction side can be sufficiently reduced to bring out the necessary dehumidifying performance. In addition, since this constant pressure expansion valve operates only when the pressure exceeds a predetermined pressure, the pressure on the evaporator suction side is not reduced more than necessary, so that a problem such as freezing of the refrigerant inside the evaporator does not occur. Further, since the constant pressure expansion valve itself is bypassed without functioning during the cooling operation, an unnecessary load is not generated during the cooling operation, so that a reduction in capacity during the cooling operation does not occur.
[0027]
In addition, when the engine is powered by an engine and the power source of the compressor 7 is the engine, the dehumidification performance is reduced due to an increase in the pressure on the evaporator suction side due to a change in the suction input of the compressor caused by a change in the engine speed. Can be prevented.
[0028]
In addition, in embodiment described above, what added the constant pressure expansion valve 20 to the conventional apparatus structure as mentioned above so that this invention can be easily applied with respect to the conventional heat pump system is shown. However, the present invention is not limited to such a form. For example, the pressure is further reduced only when the conventional expansion valve itself becomes a predetermined pressure or more as described above. Such an expansion valve may be used.
[0029]
Moreover, in the above-mentioned embodiment, although what has a heater core was shown, since it is the same structure also in an electric vehicle as a heat pump system, in that case, an electric thing is used as a compressor and it does not have a heater core. The only difference is that the present invention can be applied to a heat pump system in the same manner as in the above-described embodiment.
[0030]
Further, the configuration of the heat pump system itself is not limited to the configuration as in the above-described embodiment. Conventionally, there are various refrigeration cycle paths. For example, in addition to the evaporator provided in the passenger compartment, the sub-evaporator The present invention can also be applied to those provided with the above or those having different piping paths.
[0031]
【The invention's effect】
As described above, according to the present invention, the constant pressure expansion valve for reducing the pressure so that the evaporator suction side pressure becomes a pressure within a predetermined range when the evaporator suction side pressure becomes equal to or higher than the predetermined pressure. Because of the increase in the pressure on the evaporator suction side caused by changes in the outside air temperature and the passenger compartment temperature, etc., or the evaporator caused by changes in the engine speed when the engine is powered by a compressor It is possible to prevent a decrease in dehumidifying performance due to an increase in pressure on the suction side and to suppress the occurrence of window fogging. Further, since this constant pressure expansion valve reduces the pressure only when the pressure on the evaporator suction side is equal to or higher than the predetermined pressure, the evaporator suction side pressure does not decrease more than necessary. The problem of freezing does not occur.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an automotive air conditioner according to an embodiment of the present invention.
FIG. 2 is a schematic view showing an example of the constant pressure expansion valve shown in FIG.
FIG. 3 is a schematic Mollier diagram of the refrigeration cycle of the automotive air conditioning apparatus according to the embodiment.
FIG. 4 is a schematic configuration diagram showing a conventional heat pump type automotive air conditioner.
[Explanation of symbols]
3 ... Evaporator,
4 ... Sub capacitor,
5 ... Main capacitor,
6 ... Four-way valve,
7 ... Compressor,
8 ... Bypass pipe,
9 ... Liquid tank,
10 ... expansion valve,
20 ... constant pressure expansion valve,
21 ... Bellows,
22 ... Valve,
23 ... channel,
24 ...
25. Bypass pipe,
26: Solenoid valve.

Claims (1)

Compressor (7), indoor condenser (4) arranged in the passenger compartment, outdoor condenser (5) arranged outside the passenger compartment, liquid tank (9), expansion valve (10), and evaporator ( 3) are connected by piping in this order, bypassing the outdoor condenser (5) to the downstream side of the compressor (7), the bypass pipe (8) reaching the indoor condenser (4), and the compressor (7) A flow path switching valve (6) for switching the flow path of the discharged refrigerant, and during the heating operation, the flow path switching valve (6) allows the refrigerant discharged from the compressor (7) to flow through the bypass pipe ( 8) Utilizing the heat of the refrigerant that circulates while changing its state by circulating the indoor condenser (4), the liquid tank (9), the expansion valve (10), and the evaporator (3) in this order. Heat pump type self-dehumidifying and heating In vehicle air conditioning systems,
A constant pressure for reducing the pressure on the suction side of the evaporator (3) so that the suction side pressure becomes a pressure within a predetermined range when the suction side pressure is equal to or higher than a predetermined pressure. An automotive air conditioning system comprising an expansion valve (20).

Images