JPS6255598B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system, and more particularly to a system for detecting refrigerant shortage in a refrigeration cycle, and is suitable for use in automobile air conditioning.

Conventionally, in order to detect a refrigerant shortage in the refrigeration cycle, a method was used to detect superheat of the refrigerant in the low-pressure side circuit from the evaporator outlet to the compressor inlet using a superheat switch, and display it via electrical means, etc. It has been known. As shown in Figure 1, this method focuses on the fact that when the refrigerant charge amount Q becomes less than the normal charge amount, the low pressure P _L decreases and the super heat SH increases, and this increase in super heat SH is detected using a super heat switch. This is intended to detect refrigerant shortage. In FIG. 1, X indicates a region where the amount of refrigerant charged is normal, and Y indicates a region where the amount of refrigerant charged is insufficient.

By the way, the above-mentioned super heat switch detects a lack of refrigerant when the pressure is set to 1.5, for example.
Assuming that the switch is set to detect super heat of 25° C. or higher at Kg/cm ² G, the characteristics of the super heat switch will be as shown by the solid line A in FIG. 2, depending on the characteristics of the gas sealed inside the switch. However, the condition shown in the shaded area B in Figure 2 occurs transiently in vehicle air conditioners even when the refrigerant is in the correct amount, such as when the engine is racing or when the cooling load is high. This is inconvenient as detection and display may be performed incorrectly.

For this reason, it may be possible to shift the characteristics of the super heat switch shown in solid line A in Figure 2 to the right to make it as shown in broken line C to avoid false detection in the shaded area B, but in this case, there is a shortage of refrigerant. This is not a desirable countermeasure because the detected superheat value sometimes becomes a large value of 30°C or more, causing a delay in detecting refrigerant shortage.

The present invention focuses on the fact that when there is a shortage of refrigerant as shown in Fig. 1, the low pressure _P When the maximum operating pressure (MOP) of the switch is set to 2 kg/m ² G or less, the characteristics of the super heat switch are changed to 1 in Figure 2.
When racing the engine, as shown by the dotted chain line D,
By avoiding the shaded area (b) in Figure 2, which often occurs when the cooling load is high, even when the refrigerant is charged at the correct amount, it is possible to accurately detect refrigerant shortages, and to prevent the occurrence of refrigerant shortages (in other words, a drop in low pressure P _L) . The purpose is to detect refrigerant shortage early in a predetermined superheat.

The present invention will be described below with reference to embodiments shown in the drawings. 3 and 4 illustrate the case where the present invention is applied to an automobile air conditioner. 1 is a compressor installed in the engine room of an automobile (not shown), Driven by an automobile engine (not shown). 3 is a condenser installed in the engine room of a car, and the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 is passed through a cooling fan 4.
It is cooled and liquefied by the blown air.

5 is a capillary tube that serves as a pressure reducing device that reduces the pressure of the liquid refrigerant liquefied in the condenser 3 and turns it into a low-temperature, low-pressure atomized refrigerant; 6 is an evaporator that uses the air blown by the blower fan 7 to evaporate the refrigerant; It is cooled by latent heat. The cold air cooled by the evaporator 6 is blown into the vehicle interior to cool the vehicle interior. Reference numeral 8 denotes an accumulator that separates the refrigerant flowing from the outlet of the evaporator 6 into gas and liquid, and sucks only the gas refrigerant into the compressor 1. Note that R-12 is sealed in the cycle as a refrigerant.

A temperature detector 9 detects the temperature of the air blown from the evaporator 6, and is composed of a thermistor.The detection signal of this detector 9 is sent to a control circuit 10 including a switch circuit 10a.
is input to the switch circuit 1 of this control circuit 10.
By opening and closing 0a, the electromagnetic clutch 2 is energized intermittently. 11 is a power battery for the car. 12 is a refrigeration system operating switch, and 13 is an indicator lamp for warning of refrigerant shortage, which is installed on or around the instrument panel inside the vehicle.
14 is a super heat switch connected in series with this indicator lamp 13, which is attached to the outlet pipe 15 of the evaporator 6 and detects the degree of superheat of the refrigerant at the outlet of the evaporator.
The electrical contacts open and close in response to this.

The concrete structure of the super heat switch 14 is, for example, as shown in FIG. 4, in which a metal lid 17 is screwed onto a metal body 16, and an O-ring 18 is used to prevent leakage. The electrical terminal 19 is fixed to the lid 17 via an insulating sealing material 20. A metal fixing base 21 is screwed and fixed in the center of the body 16, and this fixing base 21 has a hole 21a in its center.
A tube 22 whose lower end is closed is airtightly fixed to 1a. This tube 22 constitutes a heat-sensitive member and is made of a metal with good thermal conductivity such as copper.
It projects into the evaporator outlet pipe 15 through an opening 15a thereof. In the space 23 within the body 16, two metal diaphragms 24 forming flexible members,
25 are airtightly joined together and disposed, and the diaphragm 24 is airtightly fixed to the upper end of the fixing base 21. The space 23 communicates with the outlet pipe 15 through the hole 16a of the body 16. Further, the spaces within the diaphragms 24 and 25 communicate with the hole 21a of the fixing base 21 and the tube 22, and the same refrigerant as the refrigerant in the cycle, ie, R-12, is sealed inside these. An electrical contact 26 is fixed to the upper surface of the diaphragm 25 so as to face the end surface of the electrical terminal 19. The body 16 is screwed and fixed to a mounting seat 27, and this mounting seat 27 is fixed to the outlet pipe 15 of the evaporator 6 by brazing or the like. 28 is lid 1
This is an electrical terminal on the ground side formed integrally with 7.
The contact 26 is a metal part (2) that is a good conductor of electricity.
5→24→21→16→17→28).

In this example, when the pressure inside the diaphragms 24 and 25 becomes higher than the pressure inside the space 23 by 3 kg/cm ² or more, the diaphragms 24 and 25 expand and the contact point 26
is in contact with the terminal 19. The refrigerant gas (R-12) sealed in the diaphragms 24 and 25 is saturated gas with a pressure of 5 kg/cm ² G, and therefore the relationship between the temperature and pressure of the refrigerant sealed in the diaphragms 24 and 25 is as shown in FIG. It becomes as shown in . As a result, the maximum detectable operating pressure of the super heat switch 14 is set to 5-3=2 Kg/cm ² G.

Next, the operation of the above configuration will be explained. now,
If the refrigerant leaks for some reason and the amount of refrigerant charged is reduced to 400g as shown in Figure 1, and the refrigeration system switch 12 is turned on and the refrigeration system is operated, the low pressure P _L will be 1.5Kg/cm ² G, and the super heat reaches 25°C as shown in Figure 2, which means the refrigerant temperature reaches 18.5°C. Then, the tube 22, which is the heat-sensitive part of the super heat switch 14, detects 18.5°C, and as can be understood from ^FIG . Become. On the other hand, since the pressure in the space 23 of the body 16 is 1.5 kg/cm ² G, which is the same as the low pressure P _L due to the passage hole 16a, the pressure difference between the two becomes 3 kg/cm ² G or more, and the electric terminal 19 and the contact 26 The terminals 19 and 28 are brought into contact and conduction is established between the terminals 19 and 28, and the refrigerant shortage indicator lamp 13 lights up.

Further, when operating under a high cooling load, assume that the refrigerant is in the normal amount, the low pressure P _L is 3 kg/cm ² G, and the super heat reaches 20°C, that is, the refrigerant temperature reaches 27.5°C. Then, tube 22 of the heat sensitive part is 27.5
℃ is detected, and the inside of the diaphragms 24 and 25 is
From the figure, it becomes 5.1Kg/cm ² G. The pressure difference between the two is 2.1
Kg/cm ² , so the terminal 19 and contact 26 do not come into contact, and the refrigerant shortage lamp 13 does not light up.

As shown above, with conventional super heat switches, there was a danger that the refrigerant shortage indicator lamp would light up even when the refrigerant was in the correct amount during high cooling loads, etc., but with this invention, when there is a refrigerant shortage, Focusing on the fact that the low pressure P _L decreases, the maximum operating pressure of the super heat switch 14 is set to 2 kg/cm ² G.
By setting the following, it is possible to eliminate malfunctions that occur in conventional devices.

Note that the detected temperature of the detector 9 is the set temperature, for example, 3.
When the temperature drops to .degree. C., the switch circuit 10a of the control circuit 10 is opened and the electromagnetic clutch 2 is de-energized, so that the operation of the compressor 1 is stopped. As a result, when the temperature of the evaporator 6 rises and the temperature detected by the detector 9 rises to the set temperature, for example, 5°C, the switch circuit 10a is closed and the electromagnetic clutch 2 is energized, so that the compressor 1 is turned on again. Operate.

In this way, frosting of the evaporator 6 is prevented by intermittent operation of the compressor 1 depending on the temperature of the air blown out from the evaporator.

The present invention is not limited to the above-described embodiments, and can be modified in various ways.
The installation position can be anywhere on the low pressure side from the evaporator outlet to the compressor inlet.

Further, although the lamp 13 is used to indicate the refrigerant shortage, other display means such as a buzzer may be used instead of the lamp 13.

Also, diaphragms 24 and 25 are used as flexible members.
Bellows may be used instead.

Further, in the embodiment, the diaphragms 24, 2
When the difference between the pressure inside 5 and the pressure inside the space 23 becomes 3 kg/cm ² or more, the super heat switch 14 is activated and R-12 is put into the diaphragms 24 and 25.
The maximum operating pressure of the super heat switch 14 was set to 2 kg/cm ² G by filling it with a saturated gas of Kg/cm ² G, but the characteristics of the super heat switch 14 were not found in the hatched area in Fig. 2. You can change these settings to other values if you can avoid them.

Furthermore, the super heat switch 14 may operate the display means and simultaneously stop the operation of the compressor 1 when there is a shortage of refrigerant.

As described above, in the present invention, focusing on the fact that the drop P _L decreases when there is a refrigerant shortage, the characteristics of the super heat switch are improved by setting the maximum operating pressure of the super heat switch to 2 kg/cm ² G or less. As shown in the dot-dash line D in Figure 2, it is possible to avoid false detection of refrigerant shortage, which occurs even when the correct amount of refrigerant is filled, during engine racing, high cooling load, and accurate detection and display of refrigerant shortage. This has the great effect of not causing any delay in detection when there is a real refrigerant shortage.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between the amount of refrigerant enclosed and super heat and low pressure, Fig. 2 is a graph showing the characteristics of the super heat switch, Fig. 3 is a refrigeration cycle diagram of an embodiment of the present invention, and Fig. 4 is a detailed sectional view of the super heat switch shown in FIG. 3, and FIG. 5 is a graph showing the relationship between the temperature and pressure of the refrigerant sealed in the diaphragm of the super heat switch shown in FIG. 4. 6... Evaporator, 13... Display lamp, 14...
Super heat switch, 19, 28... Electric terminal, 22... Tube forming a heat sensitive member, 23...
Space, 24, 25...Diaphragm forming a flexible member, 26...Electric contact.

Claims (1)

[Claims] 1. In a refrigeration system that uses R-12 as an enclosed refrigerant, a flexible member whose internal space is filled with the same refrigerant as the above-mentioned enclosed refrigerant is installed in the space into which the refrigerant pressure of the evaporator outlet refrigerant passage is introduced, and , a heat-sensitive member integrally communicating with the flexible member is installed to sense the refrigerant temperature in the evaporator outlet refrigerant passage, and an increase in superheat of the evaporator outlet refrigerant is detected by extension of the flexible member. and a super heat switch that opens and closes electrical contacts, and by adjusting the saturated gas pressure of the refrigerant sealed in the flexible member, the maximum detectable operating pressure of the super heat is set to 2 kg/cm ² G or less. A refrigeration device characterized by: