JPH0428986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that detects overfilling of refrigerant circulating in the cooling cycle of an automobile air conditioner, high pressure abnormality of the refrigerant, and performs necessary processing such as issuing an alarm. .

Generally, there is a cooling cycle system for an automobile air conditioner as shown in FIG. A refrigerant circulates within the cooling cycle, and the cooling cycle includes a compressor 1, a condenser 2 that cools and condenses the gaseous refrigerant that has become high temperature and high pressure in the compressor 1, and converts it into a high pressure liquid. A liquid tank 3 that stores a necessary amount of refrigerant, removes moisture and dust from the refrigerant, and separates the refrigerant into gas and liquid; and an expansion valve 4 that rapidly reduces the pressure of the refrigerant to a low-pressure refrigerant that is easily vaporized. , an evaporator 6 that cools the vehicle interior air by taking heat from the vehicle interior air while the refrigerant evaporates, and a temperature sensing tube 5 that senses the temperature of the refrigerant at the outlet of the evaporator 6 and adjusts the opening degree of the expansion valve 4. Become. Also, although not shown, the compressor 1
The magnetic clutch 8 is activated by the driving engine.
The compressor is driven via a compressor, and when the temperature in the vehicle interior falls below a certain level, the operation of the compressor is stopped by the action of a magnetic clutch to prevent the interior of the vehicle from becoming too cold.

In this type of automotive cooling cycle, the compressor is driven by the driving engine, so
The compressor drive rotational speed varies depending on the driving condition, and the amount and pressure of refrigerant circulating in the cooling cycle may vary.

Fluctuations in the amount of refrigerant circulated are alleviated to some extent because the liquid tank 3 adjusts the amount of refrigerant circulated as necessary. However, if the cooling cycle is not filled with an appropriate amount of refrigerant, even if there is a liquid tank, it will not be possible to circulate the appropriate amount of refrigerant within the cycle. In particular, when the refrigerant is overfilled in the cycle, the liquid tank becomes full of liquid refrigerant, and subcooling (supercooling) of the refrigerant develops in the liquid tank as well.
Even after this, the refrigerant becomes difficult to evaporate, and the heat absorption of the refrigerant in the evaporator becomes insufficient, resulting in problems such as a drop in cooling performance.

In addition, the above-mentioned fluctuation in refrigerant pressure can be caused by, for example,
This occurs when there is a sudden change in the vehicle chain and the compressor drive rotational speed suddenly fluctuates. In particular, when the pressure of the refrigerant becomes abnormally high, the temperature of the refrigerant also rises, which may cause deterioration of the lubricating oil contained in the refrigerant and a decrease in cooling performance.

In order to eliminate these inconveniences in advance, conventionally, as shown in Fig. 2, a sight glass 7 is provided on the upper part of the liquid tank 3, and the flow state of the refrigerant is observed through the sight glass 7 to check whether the amount of refrigerant is excessive or insufficient. is detected and filled with the appropriate refrigerant. in this case,
When bubbles are seen in the refrigerant through the sight glass 7, it indicates that the amount of refrigerant is insufficient, and when there are no bubbles, it indicates that the amount of refrigerant is appropriate. However, if no air bubbles are seen in the refrigerant, it is not only possible that the amount of refrigerant charged is appropriate, but also that the refrigerant is overfilled, so it is difficult to accurately determine whether the refrigerant is overfilled. It was hot.

There is also a system that prevents abnormally high pressure of the refrigerant by installing a high pressure switch in the liquid tank 3 to detect the pressure of the refrigerant and stopping the operation of the compressor when the pressure of the refrigerant becomes abnormally high. However, even if a high pressure switch is used, only abnormally high pressure is detected, and overfilling of refrigerant cannot be accurately detected.

The present invention has been made in view of these circumstances, and provides a device that can detect overfilling and abnormally high pressure of refrigerant that degrade cooling performance using the same device, and take necessary measures such as issuing an alarm. The purpose is to provide The feature is that a working fluid is sealed inside the refrigerant passage that guides the high-pressure side liquid refrigerant of the cooling cycle, and it has a movable part that operates due to the pressure difference between the pressure of the working fluid and the refrigerant. A sensor is attached, and a switch interlocked with the movable part is electrically connected to the alarm means, and the working fluid has a characteristic that the saturation pressure is higher than the saturation pressure of the refrigerant, and the pressure of the refrigerant is higher than the saturation pressure of the working fluid. and when the pressure of the refrigerant becomes higher than the pressure at which all of the working fluid is in a vaporized state, the working fluid has the property of operating the switch. It is in.

Hereinafter, the present invention will be explained in detail based on an embodiment shown in the drawings.

FIG. 3 is a schematic diagram showing an embodiment of the abnormal state warning device for a refrigerant for a cooling cycle according to the present invention.

The cooling pipe 15 shown in FIG. 3 is a part of the refrigerant pipe provided between the condenser 2 and the expansion valve 4 in FIG. 1, and a high-pressure liquid refrigerant 12 is guided therein. It's circulating. Refrigerant piping 1
A casing 16 having a space communicating with the inside of the refrigerant pipe 15 through an opening 17 formed therein is attached to the casing 1.
A sensor 14 is attached to the sensor 6 and has a small diameter portion whose tip reaches into the refrigerant pipe 15 and a large diameter portion located inside the casing 16 .

The sensor 14 has a working fluid 13 sealed therein, and has a diaphragm 23 as a movable part that is actuated by a pressure difference between the pressure of the working fluid 13 and the pressure of the refrigerant 12. Fixed contact piece 19 mounted inside the casing 16 and having a switch terminal 22
A switch 10 is electrically connected to the alarm means 11 and includes a movable contact piece 21 mounted in the casing 16 and having a switch terminal 18 and interlocking with a diaphragm 23.

Working fluid 13 sealed within the sensor 14
The relationship between temperature and pressure of the circulating refrigerant is shown in FIG. The vertical axis is pressure P, and the horizontal axis is temperature T.
It is. The symbol H ₁ indicates the saturated liquid line of the working fluid 13 , and the symbol F indicates the saturated liquid line of the circulating refrigerant 12 , and it can be seen that the saturated pressure of the working fluid 13 is higher than the saturated pressure of the circulating refrigerant 12 . Since the capacity of the working fluid 13 sealed in the sensor 14 is limited, while the liquid working fluid 13 is present, the pressure rises on the saturated liquid line _H1 as the temperature T rises. At a certain temperature or higher, all of the working fluid 13 becomes a gas, so the pressure hardly increases as the temperature increases, and the condition is on the straight line _H2 . If the point at which the working fluid 13 changes from a saturated state in which gas and liquid coexist to a state in which only gas exists is defined as an MOP point, the MOP point can be determined by increasing or decreasing the volume of the working fluid 13 sealed in the sensor 14. Can be adjusted.

That is, when the amount of fluid fluid 13 enclosed is increased, the temperature at which all of the working fluid 13 becomes gas increases, so the MOP point rises above the saturated liquid line _H1 .
In other words, MOP which is the maximum pressure of the working fluid 13
(Max. Operating Pressure) is the working fluid 1
By limiting the amount of 3 to be enclosed, it can be set freely.

Since the abnormal state warning device for a refrigerant for a cooling cycle according to the present invention has the above-described configuration, it has the following effects.

Figure 5 shows the cooling cycle shown in Figure 1 on a Mollier diagram, where the vertical axis represents the pressure P;
The horizontal axis shows enthalpy i. In the drawing, symbol F indicates a saturated liquid line of the refrigerant 12, and symbol G indicates a saturated gas line of the refrigerant 12. Also, one cycle of the cooling cycle is the line A→B→C→D→E→A or the dashed line A'→
They are shown as B'→C'→C'→E'→A', which respectively indicate one cycle when the normal amount of refrigerant is filled and one cycle when the refrigerant is overfilled. Straight line D → E → A and dashed line
D'→E'→A', shows the state from the discharge port of compressor 1 to expansion valve 4, straight line E→A and one-dot chain line
E'→A' indicates subcooling (supercooling) of the refrigerant. When the cooling cycle is filled with a regular amount of refrigerant, the refrigerant 12 in the liquid tank 3 contains both gas and liquid and is in a saturated state at point E on the saturated liquid line F. However, when the refrigerant is overfilled, the liquid tank 3 becomes full of liquid refrigerant, and subcooling develops within the liquid tank 3 as well.
As shown in FIG. 5, the amount of subcooling increases. The state change E'→A' in the subcooled state of the refrigerant 12 when the subcooling increases is expressed by the straight line E'→ shown in Fig. 4.
Corresponds to A′. As shown in FIG. 3, since the refrigerant 12 is conducted around the working fluid 13, the working fluid 13 and the refrigerant 12 undergo the same temperature change, so as shown in FIG. When the state changes from ' to A', the state of the working fluid 13 changes from K to L, and the pressure of the working fluid 13 is higher than that of the refrigerant 12.
pressure will be lower than that of For these reasons, when the cooling cycle is overfilled with refrigerant, subcooling increases and the working fluid 13 in the sensor 14 installed in the pipe 15 between the liquid tank 3 and the expansion valve 4 where subcooling is generated increases. The pressure is measured by the sensor 14
It can be seen that the pressure is lower than the pressure of the surrounding refrigerant 12. Moreover, the pressure reversal phenomenon is caused by the sensor 1
It can be seen that this can be adjusted by changing the saturation pressure of the working fluid 13 sealed in the interior of the working fluid 13. In this way, when the pressure of the working fluid 13 in the sensor 14 becomes lower than the pressure of the refrigerant 12, the circuit having the alarm means 11 is switched on by the action of the tire flamm 23. The person or driver of the vehicle may be notified of an abnormal refrigerant condition.

Further, when the pressure of the refrigerant 12 circulating in the cooling cycle becomes abnormally high due to a sudden change in vehicle speed, etc., the abnormal state of the refrigerant can be notified to the driver, etc., as described below.

If the state in which the refrigerant 12 has reached an abnormally high pressure is represented by _{one point} E shown in FIG. The pressure will be lower than the pressure of the refrigerant 12. Therefore, the diaphragm 23 in the pressure switch 10 switches on the circuit having the alarm means 11, thereby notifying the driver of the abnormal state of the refrigerant. In other words, an alarm can be issued when the pressure of the refrigerant 12 exceeds the MOP value of the working fluid 13. Further, as mentioned above, the working fluid 13
Since the MOP value can be set freely, you can also change the pressure at which you want to generate an alarm.

The working fluid 13 used in the above embodiment has a higher saturation pressure than the refrigerant 12, so
For example, when R ₁₂ (fluorocarbon gas) is used as the refrigerant 12, R ₁₂ that is pressurized by adding nitrogen gas or the like is used.

The present invention is not limited to the above-described embodiments, and the following modifications are possible.

Instead of the diaphragm 23 in the casing 16, the upper part of the sensor may be formed into a bellows shape, and the bellows may move up and down due to the differential pressure between the inside and outside of the sensor. Even in this case, the diaphragm 23
It has the same effect as when using .

Further, the warning means 11 may be any means as long as it appeals to the five senses of the operator or driver, such as a warning buzzer or a warning lamp. Furthermore, a switch circuit for stopping the operation of the compressor 1 may be added to the circuit having the alarm means 11. In this case, when the pressure of the refrigerant in the cooling cycle becomes high or when the refrigerant is overfilled, the compressor stops and the cooling cycle can be prevented from operating in an abnormal state.

As is clear from the above description, according to the present invention, overfilling and abnormal high pressure of refrigerant in the cooling cycle that reduce cooling performance are detected by the same device,
Since it is possible to take necessary measures such as issuing a warning to workers performing refrigerant filling work and car drivers, it is a simple and inexpensive device that does not require expensive equipment such as a high pressure switch. It has excellent effects such as detecting abnormalities in the refrigerant in the cooling cycle and allowing the cooling cycle to always operate in a normal state with good cooling performance.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of an automobile cooling cycle, FIG. 2 is a vertical sectional view showing the structure of a liquid tank, and FIG. 3 is a schematic diagram showing an embodiment of an abnormal state warning device for a refrigerant for a cooling cycle according to the present invention. FIG. 4 is a diagram showing the relationship between pressure and temperature of the circulating refrigerant and working fluid, and FIG. 5 is a diagram showing the cooling cycle on a Mollier diagram. 10...Switch, 11...Alarm means, 12...
... Refrigerant, 13 ... Working fluid, 14 ... Sensor.

Claims (1)

[Claims] 1. A sensor is installed in a refrigerant passage that guides the high-pressure side liquid refrigerant of the cooling cycle, the sensor is sealed with a working fluid and has a movable part that is actuated by the pressure difference between the pressure of the working fluid and the refrigerant. A switch interlocked with the movable part and the alarm means are electrically connected, and the working fluid has a characteristic of having a saturation pressure higher than the saturation pressure of the refrigerant, and when the subcooling amount of the refrigerant exceeds a predetermined value, the refrigerant has a characteristic of operating the switch when the pressure of the refrigerant becomes higher than the pressure of the working fluid, and when the pressure of the refrigerant becomes higher than the pressure at which all of the working fluid is in a vaporized state. 1. An abnormal state alarm device for a refrigerant for a cooling cycle, characterized in that it uses a working fluid having: