JP2639135B2 - Vehicle air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle air conditioner improved to prevent a decrease in cooling efficiency due to a decrease in the amount of refrigerant.

B. Prior Art An air conditioner mounted on a vehicle is composed of a vapor compression type refrigeration cycle system and is configured as shown in FIG. 5 (Japanese Patent Laid-Open No. 57-12276).

Referring to FIG. 5, the refrigeration cycle system will be described in order. The compressor 1 is driven by the engine to compress the refrigerant at a high pressure. The condenser 2 cools and liquefies the refrigerant by blowing air from the engine cleaning fan 3. The liquid tank 4 is used for temporarily storing excess refrigerant and separating bubbles from the liquefied refrigerant. The expansion valve 5 adiabatically expands the liquefied refrigerant to vaporize the liquefied refrigerant. Evaporator 6
Absorbs the heat of the wind sent from the blower fan 7 by the heat of vaporization of the refrigerant and cools it. With such a refrigeration cycle system, compression, heat radiation, expansion, and heat absorption of the refrigerant enclosed therein are repeated, and cool air is discharged from the blower fan 7.

C. Problems to be Solved by the Invention However, since the refrigerant sealed in the refrigeration cycle system permeates through rubber pipes connecting each device or leaks from the pipe connection portion, the amount of refrigerant has been reduced over many years of use. Decrease gradually. As shown in FIG. 4, when the amount of the filled refrigerant decreases, the high pressure Pd corresponding to the pressure on the outlet side of the liquid tank 4 decreases, and the efficiency of the evaporator 6 decreases, as shown by the characteristic a in FIG. discharge temperature T ₀ of the discharge air by 7 there is a problem that rises.

A technical object of the present invention is to prevent a rise in the temperature of discharged air due to a decrease in the amount of refrigerant.

D. Means for Solving the Problems The present invention will be described with reference to FIG. 1 showing an embodiment. In the present invention, the refrigerant is supplied to the compressor 1, the condenser 2, the liquid tank 4, the expansion valve and the evaporator 6 in this order. The present invention is applied to a vehicle air conditioner in which air is cooled by an evaporator 6 by the heat of vaporization. The above-mentioned technical problem is that the bypass passage 11 for bypassing the liquid tank 4 and allowing the refrigerant to flow directly from the condenser 2 to the expansion valve 5, the opening / closing means 12 for opening and closing the bypass passage 11, and the amount of the enclosed refrigerant Detecting means 8 and 9 for detecting correlated physical quantities, and the detecting means
This is achieved by providing the determination operation means 13 for opening and closing the opening / closing means 12 when it is determined from the detection results of 8, 9 that the refrigerant amount is equal to or less than the predetermined value.

E. Action Based on the detection signals from the detection means 8 and 9, when the determination operation means 13 determines that the refrigerant amount is equal to or less than a predetermined value, the opening / closing means 12 is opened and the refrigerant passes through the bypass passage 11 and the refrigerant is supplied to the liquid tank. It flows directly into the expansion valve 5 without passing through the expansion valve 5. Therefore, the liquefied refrigerant does not flow into the liquid tank 4 so that more refrigerant can be used, and a decrease in cooling performance can be prevented.

In the above sections D and E for describing the configuration of the present invention, the drawings of the embodiments are used for easy understanding of the present invention, but the present invention is not limited to the embodiments.

F. Embodiment An embodiment of the present invention will be described below with reference to FIGS. The same parts as those in FIG. 5 are denoted by the same reference numerals.

In FIG. 1, a refrigeration cycle system includes a compressor 1 for compressing and increasing the pressure of a refrigerant, a condenser 2 for cooling and liquefying a high-pressure gasified refrigerant, a liquid tank 4 for removing bubbles from the liquefied refrigerant, a high-pressure liquefied refrigerant. And an evaporator 6 that absorbs heat from the air discharged from the blower fan 7 by the heat of vaporization.

A discharge temperature sensor 8 is provided on the discharge side of the evaporator 6, that is, downstream, and a high-pressure liquefaction line between the outlet side of the liquid tank 4 and the expansion valve 5 is provided with a high-pressure pressure sensor 9. This high pressure sensor 9
Is to detect the pressure directly by installing the detection unit inside the pipe, or to detect the pressure indirectly by installing it outside the pipe.

Further, a bypass passage 11 is provided so as to bypass between the inlet and the outlet of the liquid tank 4. The bypass passage 11 is branched from a high-pressure liquid line between the condenser 2 and the liquid tank 4 via an electromagnetic directional control valve 12a, and is connected between the liquid tank 4 and the expansion valve 5 via a directional control valve 12b. Merge into high pressure liquid line. The directional control valves 12a and 12b are constituted by three-port control valves as shown in FIGS. 1 (b) and 1 (c). Directional control valve 12
When the solenoids 12as and 12bs of a and 12b are not energized, they are switched to the position A in FIGS. 1 (b) and 1 (c), and a line passing through the liquid tank 4 is formed.
When the solenoids 12as and 12bs of 12a and 12b are energized, the position is switched to the position B, and the refrigerant is sent to the expansion valve 5 through the bypass passage 11 without passing through the liquid tank 4.

FIG. 2 shows a control system that switches between the electromagnetic directional control valves 12a and 12b by judging that the refrigerant amount has decreased below a predetermined value.

The discharge temperature sensor 8 and the pressure sensor 9 are on the input side of the CPU 13,
Solenoid parts 12as and 12bs of the direction control valves 12a and 12b are connected to the output side, respectively. Also, an ignition switch 14 and a switch 15 for turning on / off the blower fan 7
And air conditioner switch to turn compressor 1 on and off
16 are connected to the input side of the CPU 13. In FIG. 2, the driver on the output side of the CPU 13 is not shown.

In this embodiment, the determination as to whether the refrigerant amount is an appropriate amount is made based on the detection outputs of the high pressure sensor 9 and the discharge temperature sensor 8. As shown in FIG. 4, when the pressure is equal to or lower than the threshold value PT and the discharge temperature is equal to or higher than the threshold value TT, it is determined that the refrigerant amount is not an appropriate amount. This is to ensure that the determination is made.

Next, the operation of the vehicle air conditioner thus configured will be described with reference to FIG.

In the processing procedure shown in FIG. 3, first, in steps S1 to S3, it is detected whether or not the vehicle air conditioner is operating. Here, step S1 determines whether the engine is running or not by turning on / off the ignition (IG) switch 14.
S2 determines whether or not the blower fan air is being discharged by turning on / off the blower fan switch 15, and step S3 determines whether the compressor 2 is turned on / off by turning on / off the air conditioner switch 16.
It is determined whether or not is operating. Then, when any of steps S1 to S3 is negatively determined, the air conditioner is turned off in step S7.

If all of steps S1 to S3 are affirmatively determined, the process proceeds to step S4, and it is determined whether or not the detection value of the high pressure sensor 9 is equal to or less than a threshold value PT. If the value detected by the high pressure sensor 9 is equal to or less than the threshold value PT, it is determined in step S5 whether the value detected by the discharge temperature sensor 8 is equal to or greater than the threshold value TT. A command to switch the direction control valves 12a and 12b is output (step S6). Thereby, the directional control valves 12a, 12
The b is switched to the B position, and the refrigerant bypasses the liquid tank 4 and flows directly into the expansion valve 5 through the bypass passage 11.

If it is determined in Steps S4 and S5 that the value is equal to or greater than the threshold value PT or equal to or less than the threshold value TT, in Step S8, the direction control valve 12a,
12b is switched to the a position, the bypass passage 11 is closed, and the refrigerant flows to the expansion valve 5 via the liquid tank 4.

As described above, when the amount of the refrigerant is reduced, the refrigerant is bypassed in the bypass passage 11. As a result, the characteristic b shown in FIG. 4 can be obtained, and compared with the conventional method in which the refrigerant passes through the liquid tank 4. The discharge temperature can be further reduced with the same amount of refrigerant.

In the configuration of the above embodiment, the direction control valves 12a and 12b constitute opening / closing means, the discharge temperature sensor 8 and the pressure sensor 9 constitute detection means, and the CPU 13 constitutes judgment operation means.

Although the amount of the refrigerant is detected based on the pressure of the refrigerant in the high pressure line and the temperature of the air blown from the evaporator, the amount of the refrigerant can be estimated by detecting the flow rate of the refrigerant and the engine speed.

G. Effects of the Invention As described above, according to the present invention, when the refrigerant amount is equal to or less than the predetermined amount, the refrigerant is bypassed without passing through the liquid tank, thereby reducing the efficiency of the evaporator without refilling the refrigerant. And the temperature rise of the discharge air can be suppressed.

[Brief description of the drawings]

1 (a) is a block diagram of one embodiment of the present invention, FIGS. 1 (b) and 1 (c) are block diagrams of a directional control valve, FIG. 2 is a block diagram of a CPU and its input / output side, FIG. 3 is a flowchart of a bypass control routine, FIG. 4 is a pressure and temperature characteristic diagram with respect to a refrigerant charging amount, and FIG. 5 is a configuration diagram of a conventional example. 1: Compressor, 2: Condenser 4: Liquid tank, 5: Expansion valve 6: Evaporator, 8: Discharge temperature sensor 9: High pressure sensor, 11: Bypass passage 12a, 12b: Direction control valve

Claims (1)

(57) [Claims] 1. An air conditioner for a vehicle in which a refrigerant flows in the order of a compressor, a condenser, a liquid tank, an expansion valve and an evaporator to cool air by an evaporator by heat of vaporization thereof. A bypass passage for flowing the refrigerant, an opening / closing means for opening / closing the bypass passage, a detection means for detecting a physical quantity correlated with the amount of the filled refrigerant, and a detection result of the detection means indicates that the refrigerant quantity is equal to or less than a predetermined value. An air conditioner for a vehicle, comprising: a determination operation means for opening the opening / closing means when the determination is made.