JPH1114169A - Air conditioner for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an effective restriction of a cycle hunting which is easily produced under a low load during a freezing cycle using a compressor of variable capacity. SOLUTION: This device is comprised of a bypass pipe 11 communicating an inlet of a condenser 3 with an inside part of a liquid tank 4a, and a solenoid valve 12 for opening or closing this bypass pipe 11. When a pressure at a high pressure side becomes 7 kg/cm<2> G or less, a pressure switch 13 is turned ON, the solenoid valve 12 is turned ON, the bypass pipe 11 is opened and then gaseous refrigerant of high pressure at the inlet port of the condenser 3 is fed into the head part of the liquid tank 4a. The inner diameter of the bypass pipe 11 is 2 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for a vehicle having a refrigeration cycle using a variable capacity compressor, and more particularly to an air conditioner for a vehicle capable of effectively suppressing cycle hunting which is likely to occur at a low load. About.

[0002]

2. Description of the Related Art Today, there is a need for power saving for car air conditioners (automobile air conditioners) and the turning on of compressors.
2. Description of the Related Art Variable displacement compressors (variable displacement compressors) are becoming widespread in order to meet comfort needs such as a change in blowout temperature during OFF control and a reduction in shock transmitted to an occupant.

[0003] A car air conditioner using such a variable capacity compressor is configured with a refrigeration cycle 1 as shown in FIG. 2, like a general car air conditioner. The refrigerating cycle 1 is a variable capacity compressor (hereinafter, also simply referred to as a “compressor”) 2 that draws in heat in a vehicle cabin by an evaporator to suck and compress a vaporized low-temperature and low-pressure gas refrigerant and sends it to a condenser. The condenser 3 cools and condenses and liquefies the high-temperature and high-pressure gas refrigerant by heat exchange with the outside air, and liquefies with the condenser in order to store the excess refrigerant of the refrigeration cycle as liquid mainly in response to a change in the required amount of refrigerant circulation. A liquid tank 4 for temporarily storing the liquid refrigerant of the medium temperature and high pressure and separating it into gas and liquid and sending only the liquid refrigerant to the expansion valve, and a low temperature and low pressure of the medium temperature and high pressure liquid refrigerant which has passed through the liquid tank and which is easily decompressed and expanded to vaporize. Refrigerant flow rate such that the refrigerant is atomized and the evaporation state of the refrigerant at the outlet of the evaporator has an appropriate degree of superheat (superheat (SH)) It has an expansion valve 5 for adjusting, and an evaporator 6 for cooling the air by exchanging heat by evaporating the low-temperature and low-pressure liquid refrigerant sent from the expansion valve with the air in the passenger compartment. It is connected by a pipe 7 and a refrigerant is sealed therein. The amount of refrigerant charged into the refrigeration cycle 1 is determined by the internal volume of the refrigeration cycle and the conditions used. In general, an appropriate value is set in a region where a liquid level can always exist in the liquid tank 4. Have been.

[0004]

However, in a car air conditioner having a refrigeration cycle 1 using such a variable displacement compressor 2 (particularly, a swash plate type variable displacement compressor of an internal variable control type by pressure), the compressor discharge pressure (Pd) and the pressure (Pc) in the crankcase at a low load (for example, at low outside air) at a low load (for example, at low outside air), a unique pulsating gas-liquid two-phase flow called cycle hunting (hereinafter simply referred to as "hunting"). Experiments have confirmed that flow fluctuations may occur. This hunting phenomena appears as fluctuations in cycle pressure, temperature, etc. in a certain cycle, and occurs when the cycle becomes unstable.

FIG. 3 is data showing cycle behavior over time when hunting occurs under certain conditions. Here, a is the liquid level of the condenser 3, b is the liquid level of the liquid tank 4, c is the stroke of the compressor 2, d is the expansion valve inlet temperature (Tex), e is the compressor suction temperature (Ts), f is the compressor discharge pressure (Pd
), G is the expansion valve inlet pressure (Pex), h is the expansion valve 5 stroke, i is the pressure in the crankcase of the compressor 2 (Pc), j is the evaporator outlet pressure (Pe), and k is the compressor suction pressure (Ps). ). Further, as a result of an experiment in which such hunting was performed by combining the outside air temperature (condenser load) and the evaporator intake air temperature, it was found that the hunting occurred when the difference between the outside air temperature and the evaporator intake air temperature was 15 ° C. or more. That is, the hunting occurrence zone when the evaporator intake air temperature is in the range of, for example, 20 to 30 ° C. is as shown by the shaded portion in FIG.

When the hunting shown in FIG. 3 is viewed over time, the behavior is as shown in FIG. Here, for convenience,
The compressor 2 is COMP, the condenser 3 is COND,
L / T for liquid tank 4 and EVAP for evaporator 6
Respectively.

As shown in FIGS. 3 and 5, the state of the refrigerant in each component changes with the occurrence of hunting, but the distribution of the refrigerant during hunting, for example, the distribution of the refrigerant in the condenser 3 and the liquid tank 4, is observed. (Pay attention to the change in Pd), as follows. This will be described with reference to FIG. 6. When the compressor discharge pressure (Pd) rises, as shown in FIG. 6A, the refrigerant liquid level inside the condenser 3 falls, and the refrigerant liquid level inside the liquid tank 4 Rises (# 19 in FIG. 5). Until the discharge pressure Pd falls, the coolant level in the condenser 3 rises and falls while the coolant level in the condenser 3 keeps falling. Therefore, in this case, the refrigerant inflow from the condenser 3 to the liquid tank 4 is larger than the refrigerant outflow from the liquid tank 4 to the expansion valve 5, and the refrigerant outflow from the condenser 3 is It can be seen that it is larger than the inflow. On the other hand, when the compressor discharge pressure (Pd) falls, FIG.
As shown in the figure, the refrigerant level inside the condenser 3 rises,
The coolant level inside the liquid tank 4 drops (# in FIG. 5).
13). Therefore, in this case, the refrigerant inflow from the condenser 3 to the liquid tank 4 is smaller than the refrigerant outflow from the liquid tank 4 to the expansion valve 5, and the refrigerant outflow from the condenser 3 is It turns out that it is smaller than the inflow. Further, when Pd falls, there is a phenomenon that the expansion valve inlet pressure (Pex) instantaneously rises, and at this time, the liquid refrigerant in the liquid tank 4 evaporates (# 18 in FIG. 5).

When the cause of hunting is examined based on the above experimental results and the like, the liquid refrigerant in the liquid tank 4 evaporates when the discharge pressure Pd decreases during hunting (# 18 in FIG. 5). 4 to expansion valve 5
Gas refrigerant (bubbles) mixes with the liquid refrigerant supplied to the
# 14), the fluctuation of the flow rate of the refrigerant passing through the expansion valve 5 is considered to be a main factor of hunting. If hunting occurs, there is a possibility that stable air conditioning performance may not be obtained, and more specifically, a malfunction may occur such that the blowout temperature fluctuates to give a passenger an uncomfortable feeling.

The present invention has been made in view of the above-mentioned problems in an air conditioner for a vehicle having a refrigeration cycle using a variable capacity compressor, and can effectively suppress cycle hunting which easily occurs at a low load. It is an object of the present invention to provide a vehicle air conditioner.

[0010]

According to the present invention, there is provided a refrigeration cycle in which a variable capacity compressor, a condenser, a liquid tank, an expansion valve, and an evaporator are connected by piping and a refrigerant is sealed therein. And a high-pressure introducing means for selectively introducing the high-pressure side pressure of the refrigeration cycle into the inside of the liquid tank.

[0011] Preferably, the high-pressure introducing means includes a bypass pipe communicating the inlet of the condenser with the inside of the liquid tank, and an on-off valve for opening and closing the bypass pipe.

In this case, it is preferable that the refrigeration cycle further includes a detecting means for detecting that cycle hunting may occur, and the on / off valve is opened and closed by an output of the detecting means.

From the experimental results, it is preferable that the inner diameter of the bypass pipe is 2 mm.

Preferably, the detecting means is a pressure switch for detecting a high-pressure side pressure of the refrigeration cycle. When the high-pressure side pressure becomes 7 kg / cm ² G or less, the pressure switch is turned on and the open / close valve is opened. become.

By introducing the high-pressure side pressure of the refrigeration cycle into the liquid tank, evaporation of the liquid refrigerant inside the liquid tank during hunting (see # 18 in FIG. 5) is suppressed. Therefore, the supply of the liquid refrigerant from the liquid tank to the expansion valve is stabilized, and a stable cycle behavior without hunting occurs. Such a hunting prevention effect was also confirmed by experiments.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a refrigeration cycle of an automotive air conditioner according to one embodiment of the present invention. In addition,
Members common to those in FIG. 2 are denoted by the same reference numerals.

This refrigeration cycle 1a includes a swash plate type variable capacity compressor 2, a condenser 3, a liquid tank 4a, an expansion valve 5, and an evaporator 6 in this order, similarly to the conventional refrigeration cycle 1 shown in FIG. Connected by piping 7,
It is configured such that a refrigerant is sealed therein. The amount of refrigerant charged in the refrigeration cycle 1a is determined by the internal volume of the refrigeration cycle and the conditions used. However, an appropriate value is set in an area where the liquid level can always exist in the liquid tank 4a. I have.

According to the present invention, in order to prevent hunting at the time of a low load (at the time of low outside air), the high pressure side of the refrigeration cycle is selectively introduced into the liquid tank 4a. As a specific means, in the embodiment of FIG. 1, the inlet of the condenser 3 and the liquid tank 4a
And a switching valve 12 for opening and closing the bypass pipe 11. One end of the bypass pipe 11 is connected to the head of the liquid tank 4a, and the high-pressure gas refrigerant at the inlet of the condenser 3 is introduced into the head of the liquid tank 4a. Therefore,
The liquid tank 4a has an outlet of the condenser 3 and a pipe 7
b, a high-pressure inlet connected to the inlet of the condenser 3 via the bypass pipe 11, and a refrigerant outlet connected to the inlet of the expansion valve 5 via the pipe 7c. ing. In addition, the on-off valve 12 is formed of, for example, an electromagnetic valve. The high-pressure introducing means includes a bypass pipe 11 and an on-off valve (electromagnetic valve) 12.

A capacitor 3 for preventing hunting
The inside diameter of the bypass pipe 11 for introducing the high-pressure gas refrigerant at the inlet into the liquid tank 4a is to suppress the evaporation of the liquid refrigerant in the liquid tank 4a when the discharge pressure Pd drops, which is considered to be the main cause of hunting as described above. May be any value that is necessary and sufficient to supply as high a pressure as possible into the liquid tank 4a, which has an appropriate zone,
The optimum value (or appropriate zone) will change according to the design specifications of the refrigeration cycle. For example, in the experimental results, 2.0 mm (φ2) was appropriate. Bypass pipe 1
When the inner diameter of 1 was increased, for example, hunting occurred at φ6.

In this embodiment, a pressure switch 13 for detecting the high-pressure side pressure of the refrigeration cycle 1a is mounted at an appropriate position of the high-pressure pipe 7a to control the opening and closing of the solenoid valve 12. By solenoid valve 1
2 is ON-OFF controlled. More specifically, for example, when the high-pressure side pressure becomes 7 kg / cm ² G or less, the pressure switch 13 is turned on, the solenoid valve 12 is turned on (open state), the bypass pipe 11 is opened, and the high pressure at the inlet of the condenser 3 is opened. The gas refrigerant is introduced into the head of the liquid tank 4a. Set pressure switch 13 to 7kg / c
The reason for choosing m ² G is that, as a result of experiments, low
This is because the hunting that occurs in the region is limited to when the high-pressure side pressure is 7 kg / cm ² G or less, and it is considered that hunting may occur in this region.
Therefore, when the high-pressure side pressure is 7 kg / cm ² G or more, there is no danger of hunting. For energy saving, the pressure switch 13 is turned off and the solenoid valve 12 is turned off (closed state).
Then, the bypass pipe 11 is closed. The detecting means is constituted by the pressure switch 13.

Further, the opening / closing control of the solenoid valve 12 is not limited to the above-described example using the pressure switch 13.
For example, an hunting occurrence zone is set in advance by using an appropriate parameter by an experiment, and the electromagnetic valve 12 is turned on when it is detected that the vehicle is in the hunting occurrence zone by appropriate detection means. Is also good. For example, focusing on the hunting occurrence zone as shown in FIG. 4, the outside air temperature and the evaporator intake air temperature are respectively detected by sensors, and the difference between the two temperatures is 15%.
When the temperature exceeds ° C, the solenoid valve 12 may be turned on to open the bypass pipe 11. By performing such control, the accuracy of detecting whether or not the vehicle is in the hunting occurrence zone is higher than in the control using only the pressure switch 13 described above.

Therefore, according to the embodiment shown in FIG. 1, a bypass pipe 11 for communicating the inlet of the condenser 3 with the inside of the liquid tank 4a and an electromagnetic valve 12 for opening and closing the bypass pipe 11 are provided. When the pressure falls below 7 kg / cm ² G, the pressure switch 13 is turned on and the solenoid valve 12
Is turned on, the bypass pipe 11 is opened, and the high-pressure gas refrigerant at the inlet of the condenser 3 is introduced into the head of the liquid tank 4a. Therefore, the discharge pressure Pd in the liquid tank 4a when the discharge pressure Pd, which has conventionally occurred during hunting, decreases. Evaporation of the liquid refrigerant (see # 18 in FIG. 5) is suppressed, and the hunting-causal chain seen in the hunting behavior shown in FIG. 5 is cut off. Therefore, the supply of the liquid refrigerant from the liquid tank 4a to the expansion valve 5 is stabilized, and a stable cycle behavior in which hunting does not occur even under a low load (during low outside air).
As described above, such an effect of preventing hunting was also confirmed by experiments.

[0024]

As described above, according to the present invention, in a refrigeration cycle using a variable capacity compressor, it is possible to effectively suppress cycle hunting which is likely to occur at a low load, and to stabilize performance. Is achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a refrigeration cycle of an automotive air conditioner according to one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a refrigeration cycle of a conventional automotive air conditioner.

FIG. 3 is data showing cycle behavior over time when hunting occurs.

FIG. 4 is a diagram illustrating an example of a hunting occurrence zone.

FIG. 5 is a diagram showing the cycle behavior at the time of hunting as viewed with time.

FIG. 6 is a diagram provided for describing a refrigerant distribution during hunting.

[Explanation of symbols]

 1a Refrigeration cycle 2 ... Swash plate type variable capacity compressor 3 ... Condenser 4a ... Liquid tank 5 ... Expansion valve 6 ... Evaporator 7 ... Piping 11 ... Bypass pipe (high pressure introduction means) 12 ... Solenoid valve (high pressure introduction means, open / close valve) 13 ... Pressure switch (detection means)

Claims (5)

[Claims] 1. A variable capacity compressor (2), a condenser
(3), liquid tank (4a), expansion valve (5), evaporator
(6) is connected by a pipe (7), and in a vehicle air conditioner having a refrigeration cycle (1a) in which a refrigerant is sealed, a high-pressure side pressure of the refrigeration cycle (1a) is increased by the liquid tank (4a High pressure introduction means (11, 12) for selectively introducing inside
An air conditioner for a vehicle, comprising: 2. The capacitor according to claim 2, wherein
A bypass pipe (11) for communicating the inlet of (3) with the inside of the liquid tank (4a); and an on-off valve (12) for opening and closing the bypass pipe (11). The air conditioner for a vehicle according to the above. 3. A detecting means (1) for detecting that cycle hunting may occur in the refrigeration cycle (1a).
The air conditioner according to claim 2, further comprising (3), wherein the on-off valve (12) is opened and closed by an output of the detection means (13). 4. The air conditioner according to claim 2, wherein an inner diameter of the bypass pipe (11) is 2 mm. 5. The pressure switch (13) for detecting a high pressure side pressure of the refrigeration cycle (1a), and the pressure switch (1) when the high pressure side becomes 7 kg / cm ² G or less.
4. The air conditioner for a vehicle according to claim 3, wherein 3) is turned on to open the on-off valve (12).