JPS6115347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigerant leak detection device for a refrigeration system,
In particular, the present invention relates to an improvement in a refrigerant leak detection device for a refrigeration system used in an automobile air conditioner.

Conventional methods for detecting refrigerant leaks in refrigeration systems include detecting the degree of superheat at the outlet of the evaporator, which is the low-pressure part of the refrigerant, as shown in Japanese Patent Publication No. 51-33289, and Japanese Patent Application Laid-Open No. 52-90846. As shown, there is a method of detecting the pressure at a high pressure section. The former detects the state of the refrigerant after the refrigeration system is activated, so if the refrigerant leaks before the refrigeration system is activated, the compressor may seize immediately after activation. In addition, the latter detects the refrigerant pressure in the high-pressure circuit of the refrigeration cycle, detects the refrigerant temperature in the refrigeration cycle or the ambient temperature, and compares the detected pressure with the detected temperature to determine whether the detected pressure is at the detected temperature. A method for detecting refrigerant gas leakage in a refrigeration cycle that generates a refrigerant gas leakage signal when the pressure drops to a predetermined level below the saturation pressure.This method detects refrigerant gas leakage without using a delay device before operating the refrigeration cycle. Although it can detect refrigerant leaks in the high-pressure parts during operation and operation of the refrigeration system, it has the disadvantage that it cannot detect refrigerant leaks in the low-pressure parts during operation.

The purpose of the invention is to provide a refrigerant leak detection device suitable for detecting refrigerant leaks in all circuits of a refrigeration system before and during operation. an expansion valve for expanding refrigerant from the high-pressure circuit; a low-pressure circuit for absorbing heat from the expansion valve from the outside to vaporize the refrigerant and circulating it to the compressor; When the pressure and temperature of the refrigerant become lower than a set value before and during operation of the compressor, the contact opens and the pressure and temperature of the refrigerant are detected to prevent the compressor from operating. A refrigerant leak detection device for a refrigeration system having a pressure-temperature switch, wherein the pressure-temperature switch includes a metal diaphragm that is displaced by a change in the pressure of the refrigerant, and a side of the diaphragm opposite to the refrigerant side. The first fixed at
and a bimetal having a second contact facing the first contact and connected to a conductor from the outside, and when the refrigerant is at room temperature and below the set pressure,
If the pair of contacts is separated and the compressor is not started, and the refrigerant has a pressure and temperature below the set value after the compressor is activated, the pair of contacts is separated and the compressor is operated. It is characterized by a switch that operates as if to stop the operation.

FIG. 1 is a system diagram of a refrigeration system that is an embodiment of the present invention. The compressor 1 is driven by an automobile engine via an electromagnetic clutch. When the compressor 1 rotates, the refrigerant in the refrigeration system (generally Freon R-12
(used) are condenser 2, receiver 3, expansion valve 4
and is circulated through the evaporator 5 and back to the compressor 1. In the figure, the refrigerant in the circuit from the outlet of the compressor 1 to the inlet of the condenser 2, liquid receiver 3, and expansion valve 4 is in a high pressure state, and the refrigerant in the circuit from the outlet of the expansion valve 4 to the inlet of the compressor 1 is in a low pressure state. is in a state of Therefore, the refrigerant in this system is liquid at the inlet of the expansion valve 4 and gaseous at the inlet of the compressor 1, and both gas and liquid phases coexist in the flow path in the middle. This is the normal operating condition. However, when the compressor 1 stops rotating, the refrigerant in this system is at the same pressure, and normally gas and liquid coexist at room temperature.

However, when this refrigeration system is used for air conditioning in an automobile, refrigerant is likely to leak from the piping connections due to vibrations and shocks. For this purpose, in this embodiment, a pressure-temperature switch 10 is installed in the high-pressure circuit between the liquid receiver 3 and the expansion valve 4 to detect refrigerant leakage and prevent burnout of the compressor 1, as well as to increase efficiency. This provides a cooling effect. The thin tube 6 connecting the expansion valve 4 and the outlet of the evaporator 5 in a bypass manner serves to detect the temperature of the refrigerant at the outlet of the evaporator 5 and automatically adjust the opening degree of the expansion valve 4.

Figure 2 is a diagram showing the relationship between the refrigerant pressure and refrigerant temperature in the refrigeration system shown in Figure 1, and the vertical axis represents the refrigerant pressure.
It is expressed in Kg/cm ² , and the horizontal axis indicates the refrigerant temperature in degrees Celsius. Before the compressor 1 operates, the refrigerant pressure within the refrigeration system is uniform as described above, and shows different values depending on the amount of refrigerant present. When the amount of refrigerant sealed in this refrigeration system is 200g, it shows a vapor pressure characteristic curve as shown by solid line A, and when there is a larger amount of refrigerant, the cooling efficiency of this refrigeration system is at its highest. It shall be assumed that However, when the amount of refrigerant leaks and decreases, the cooling efficiency decreases.When the amount of refrigerant is 100g, solid line B, when it is 50g, solid line C,
When the weight is 30g, the vapor pressure characteristic will be as shown by solid line D.

However, when the compressor 1 starts operating, the pressure and temperature of the refrigerant in the high-pressure circuit rise and settle to a state of pressure and temperature corresponding to the amount of refrigerant. In other words, the amount of refrigerant
When it is 200g, it is at point a, when it is 100g, it is at point b, 50
When it is g, it moves to point c, and when it is 30g, it moves to point d. This shows that when the amount of refrigerant is initially 200 g but decreases to 30 g due to leakage during operation, it changes along the dashed line 7 connecting points a to d.

Here, it is assumed that a refrigerant leak detection device having a detection limit as shown by the broken line A' is installed in the high pressure path.
The shaded area below the broken line A' is the range in which this detection device operates to stop the compressor 1.
When the amount of refrigerant is 200g, the pressure at a room temperature of 20℃ is approximately 4.5Kg/ ^cm2 , and if this point is designated as p, the compressor operates because point p is above the broken line A', but the refrigerant below this The compressor does not operate when the amount of
However, as the compressor operates, point p moves toward point a, crosses the broken line A', and at this time, the refrigerant leak detection device operates to stop the compressor. That is, even when the amount of refrigerant is within a range where the refrigerant efficiency is good, the compressor stops operating, which is inappropriate. In addition, when using a refrigerant leak detection device with a detection limit of dashed line C', the amount of refrigerant is 50g.
If present, the compressor will start. In addition, if the compressor continues to operate and the pressure and temperature of the refrigerant rises, it will continue to operate if there is approximately 60g of refrigerant, but the cooling effect will not only be significantly reduced, but the pressure will be low. The circuit temperature rises abnormally and the compressor burns out.

In consideration of such a relationship, a refrigerant leak detection device having a detection limit indicated by broken line B' was used in this embodiment. Therefore, when the amount of refrigerant is 200 g, point p and point a are above the broken line B', so the refrigeration system continues to operate where the cooling effect is effective. If refrigerant leaks during operation and descends along the dashed line 7 and crosses the broken line B', the refrigerant leak detection device detects this and stops the operation of the compressor. Note that the compressor will also start if the amount of refrigerant has dropped to about 60 g when it is started, but soon the pressure and temperature of the refrigerant in the high-pressure circuit will change across the broken line B', and the compressor will stop. This makes it possible to know that refrigerant is leaking, prevent accidents from occurring, and take measures such as adding refrigerant to maintain a suitable refrigeration effect.

FIG. 3 is an explanatory diagram of the refrigerant leak detection device installed in the refrigeration system shown in FIG. 1, and shows a cross-sectional view of the pressure-temperature switch 10 installed in the high-pressure circuit. FIG. 4 is a sectional view taken along line AA of the pressure-temperature switch of FIG. This pressure-temperature switch 10 is constructed to have a detection limit indicated by the broken line B' in FIG. 2 above. The pressure used in this refrigerant leak detection device -
In the temperature switch 10, a case 11 having a male thread on the outer periphery of the lower part and a hole 20 opened therein is hermetically screwed into a high-pressure refrigerant circuit, and a diaphragm 12 made of stainless steel is mounted on the upper surface of the case 11. This diaphragm 12 includes a case 11 and a housing 13.
The outer edges 14 are welded with argon and are pressure-tight and airtight. metal case 11
is connected to the car body, and housing 1
A terminal 18 made of a conductor is inserted into the housing 13 through an insulator 19 attached to the upper part of the terminal 3. This terminal 18 is a plate-shaped bimetal 17 having a U-shaped space 25 as shown in FIG.
is fixed horizontally to the diaphragm 12, and a small disc-shaped contact 16 is spot welded to the center of the bimetal 17. Note that this contact point 16 is opposed to a contact point 15 fixed to the center of the upper surface of the diaphragm 12 by spot welding.

Terminal 18 is connected to switch 2 via relay 21
3, and a switch 22 in the relay 21 is connected to an electromagnetic clutch 24 for rotating the compressor. This electromagnetic clutch 24 is also connected to the vehicle body.

In the refrigerant leak detection device configured in this way, when the ignition switch of the automobile is turned on to start the engine, the switch 23 is also connected to the automobile's power source 26.
It becomes possible to connect to. When it is desired to cool the inside of the car, a switch 23 is turned on, and current flows through the relay 21 to the pressure-temperature switch 10. That is, since the contact 16 of the bimetal 17 of the pressure-temperature switch 10 is in contact with the contact 15 at room temperature,
The current of the power supply 26 is passed through the relay 21, the terminal 18,
At the same time, the flow passes through the bimetal 17, the contacts 16 and 15, the diaphragm 12, and the case 11, and the contact 2
2 is closed and current is also applied to the coiled electromagnetic clutch 24. When current flows through the electromagnetic clutch 24, the rotating shaft rotated by the automobile engine and the rotating shaft of the compressor 1 of the refrigeration system are connected, and the compressor 1 starts.

When the compressor 1 rotates, the pressure-temperature switch 10
As the pressure and temperature of the refrigerant in the high-pressure circuit increases, the refrigerant filling the hole 20 expands the diaphragm 12 upward, but at this time, the contact 1
The bimetal 17 is bent upward by the heat transmitted through the contacts 15 and 16, so that the contacts 15 and 16 tend to separate. However, when the amount of refrigerant in the refrigeration system is 200 g or more, the force pushing up the diaphragm 12 is strong, so the diaphragm 12 is kept in contact with the diaphragm 12 to maintain the operation of the compressor 1. If refrigerant leaks during operation of the compressor 1, the state of the refrigerant will change along the dashed line 7 from point a to point b in Fig. 2, so the state of the refrigerant will change along the dashed line 7.
It will cross B′. At this time, the pressure mainly decreases, so the force pushing up the diaphragm 12 decreases, and the contacts 15 and 16 separate, so the contacts 22 of the relay 21 open, the electromagnetic clutch 24 moves, and the compressor 1 stops. Furthermore, to specifically explain the operation of the pressure-temperature switch 10 with reference to FIG. 2, if the amount of refrigerant was 200 g and decreased to 100 g during operation, the refrigerant pressure would be 8 Kg/cm 2 and the temperature would be 8 Kg/cm ² . is 142
From point a, which is ℃, to point b, where the pressure is 5.5Kg/cm ² and the temperature is 148℃.
Move to a point. This causes the diaphragm 12 to
Move in the direction to open the contacts by an amount equivalent to a pressure difference of 2.5Kg/cm ² . On the other hand, since the temperature of the refrigerant increases by 6° C., the contact points are displaced in the direction of opening by a corresponding amount. Therefore, the contacts 15 and 16 are separated by the sum of these displacement amounts, and the relay circuit is interrupted with high precision.

As mentioned above, the main parts of this pressure-temperature switch 10 are the diaphragm 12 and the bimetal 17.
The diaphragm 12 is made of a thin plate made of stainless steel that is not attacked by the refrigerant. As shown in FIG. 3, the bimetal 17 has a U-shaped space 25 in its center, and the contact 16 is attached to the tip of the center surrounded by the space 25. This bimetal 17 is installed so that it warps upward when the temperature rises, but at this time, although the contact 16 is located in the center of the bimetal 17, it is located at the tip of the part surrounded by the space 25. Therefore, the amount of displacement is large. In this way, the pressure-temperature switch 10 has a structure that allows it to detect changes in the pressure and temperature of the refrigerant with high accuracy.

If refrigerant leaks when starting compressor 1 as described above, the amount of refrigerant will be approximately 60g as shown in Figure 2.
Contact 15 of pressure-temperature switch 10 when:
16 is far away, the compressor 1 will not start. Also, when the amount of refrigerant decreases to a range of about 180 g to about 60 g, the contacts of the pressure-temperature switch 10 come into contact and start up, but as the pressure and temperature of the refrigerant increases, the contacts separate and the compressor 1 stops rotation.
That is, it is possible to detect a refrigerant leak and prevent a burnout accident of the compressor, and also to estimate the amount of refrigerant remaining in the refrigeration system based on the time from when the compressor 1 is started to when it is stopped.

In addition, since the pressure-temperature switch 10 is installed in the high-pressure circuit, it is possible to detect the state of the refrigerant in the high-pressure circuit with high precision as described above, but in addition, refrigerant leakage in the low-pressure circuit can occur, albeit indirectly. It can be detected for the following reason. Generally, in such a refrigeration system, the expansion valve 4 has a throttling action, so that refrigerant leakage in the low pressure circuit does not significantly reduce the pressure in the high pressure circuit, but rather increases the refrigerant temperature by a relatively large amount. Since the pressure-temperature switch 10 shown in FIG. 3 is equipped with the bimetal 17 that operates sensitively to temperature rises as described above, it has the feature of operating sensitively to refrigerant leaks in such low-pressure circuits. I have it too.

As described above, the refrigerant leak detection device of this embodiment includes a relatively simple pressure-temperature switch that operates by detecting the refrigerant pressure and temperature with high precision between the liquid receiver and the expansion valve, which are the high-pressure refrigerant circuit. By installing one, not only refrigerant leaks in the high pressure circuit but also refrigerant leaks in the low pressure circuit can be sensitively detected and the rotation of the compressor can be stopped to prevent accidents.

In the above embodiment, the pressure-temperature switch 1
It is installed in the refrigerant flow path between the liquid receiver 3 and the expansion valve 4, because this location is a suitable location for pressure detection where the refrigerant pressure fluctuation due to the operation of the compressor 1 is the smallest. be. However, if the diaphragm 12 is made of a thicker stainless steel plate and the pressure-temperature switch is configured to suppress the influence of pressure fluctuations, it is possible to install it in other high-pressure circuits.
Additionally, if a lamp is attached to the relay circuit shown in Figure 3 so that the light goes off when no current flows to the pressure-temperature switch 10 (when the compressor 1 does not operate), the operator can be notified of a refrigerant leak. can.
Although the above embodiment has been explained using an automobile air conditioner as an example, applying such a refrigerant leak detection device to a general refrigeration system is useful for improving the safety of the system and the refrigeration efficiency.

The refrigerant leak detection device for a refrigeration system of the present invention can detect refrigerant leaks in all refrigerant channels with high accuracy before and during operation of the refrigeration system, and has the advantage of helping to operate the refrigeration system safely and efficiently. It has

[Brief explanation of the drawing]

Figure 1 is a system diagram of a refrigeration system that is an embodiment of the present invention, Figure 2 is a diagram showing the relationship between refrigerant pressure and refrigerant temperature in the high pressure circuit of the refrigeration system of Figure 1, and Figure 3 is FIG. 1 is an explanatory diagram of the refrigerant leak detection device, and FIG. 4 is a sectional view taken along line A-A of the pressure-temperature switch in FIG. 3. 1... Compressor, 4... Expansion valve, 10... Pressure -
Temperature switch, 12...Diaphragm, 15...
First contact, 16... Second contact, 17... Bimetal, 18... Conductor (terminal), 25...
Space department.

Claims (1)

[Claims] 1. A high-pressure circuit that cools and liquefies refrigerant gas compressed and sent out by a compressor, an expansion valve that expands the refrigerant from this high-pressure circuit, and a refrigerant from the expansion valve that absorbs heat from the outside. A contact point is provided in the low-pressure circuit that circulates the vaporized refrigerant to the compressor, and the high-pressure circuit, and when the pressure and temperature of the refrigerant become below set values before starting and during operation of the compressor. In the refrigerant leak detection device for a refrigeration system, the pressure-temperature switch has a pressure-temperature switch that detects the pressure and temperature of the refrigerant, and the pressure-temperature switch opens to prevent the compressor from operating. A metal diaphragm that is displaced by a change in temperature, a first contact fixed to the side opposite to the refrigerant side of the diaphragm, and a second contact opposite to the first contact, and a conductor from the outside. and a bimetal connected to the refrigerant, and when the pressure of the refrigerant is below the set value at room temperature, the pair of contacts are separated and the compressor is not started, and after the compressor is operated, the pressure of the refrigerant is below the set value. If the temperature is the same as above 1.
A refrigerant leak detection device for a refrigeration system, characterized in that it is a switch that operates to separate a pair of contacts and stop the operation of the compressor. 2. The bimetal has a U-shaped space toward the free end opposite to the end supported by the conductive wire, and the second contact is provided at the tip of the part surrounded by the space. The refrigerant leak detection device for a refrigeration system according to claim 1, which is a bimetal that is fixed and is displaced in a direction to separate the second contact from the first contact when the temperature rises. 3 The bimetal has a U-shaped space toward the free end in the direction opposite to the end supported by the conductor, and the second contact is placed at the tip of the part surrounded by this space. The refrigerant leak detection device for a refrigeration system according to claim 2, which is a bimetal that is fixed and is displaced in a direction to separate the second contact from the first contact when the temperature rises.