JPH07294072A - Pressure detecting device of refrigeration cycle - Google Patents

Abstract

PURPOSE:To effect pressure detection in a refrigeration cycle having different set pressures by means of one kind of pressure detecting device. CONSTITUTION:A pressure switch 11 for capacity control which functions at a first set pressure P1 is provided on the delivery side of a compressor 1 and a pressure switch 12 for high pressure cut which functions at a second set pressure P1+DELTAP, where pressure drop DELTAP is added, is provided downstream of the switch 11. Thus, the switch 11 and switch 12 can share a pressure switch for the same functioning pressure P1, and hence a pressure switch of one kind can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detecting device for a refrigeration cycle used for controlling a variable displacement compressor or the like.

[0002]

2. Description of the Related Art In a refrigeration cycle equipped with a variable capacity compressor, the capacity of the compressor is lowered before the operation is stopped by a high pressure cut for protecting the equipment under a high load to stop the operation. Control is continued to prevent deterioration of the air conditioning feeling by avoiding stoppage of the compressor.

In order to perform the above control, for example, as shown in FIG. 5, a compressor 1, a condenser 2, a liquid receiver 3, and a decompression device 4 are provided.
In a refrigeration cycle 10 in which the evaporator 5 and the evaporator 5 are sequentially connected, a pressure switch 11 for capacity control whose set pressure is P1.
And a pressure switch 12 for high pressure cut of P2 whose set pressure is higher than P1 are provided on the discharge side of the compressor 1 to individually perform capacity control and high pressure cut of the compressor 1.

Further, as disclosed in Japanese Utility Model Publication No. 62-971, for example, the capacity control of the compressor is carried out by a water temperature sensor for detecting the engine cooling water temperature, and the high pressure cut is carried out by a pressure switch for the high pressure cut as described above. There is something.

[0005]

On the other hand, the former one using the pressure switch having different set pressures for the capacity control and the high pressure cut requires two kinds of pressure switches having different working pressures. Preventing incorrect assembly Considering this measure will significantly increase the cost. On the other hand, the latter one using an engine cooling water temperature sensor for capacity control indirectly detects the refrigerant pressure from the engine cooling water temperature, and therefore has a problem of reliability deterioration due to erroneous detection.

The present invention has been made in view of the above problems, and in the case of performing the capacity control and high pressure cut of the compressor as described above, the cost can be reduced by using one type of pressure detection device. It is an object of the present invention to provide a pressure detection device for a refrigeration cycle that is inexpensive and highly reliable.

[0007]

In order to achieve the above object, the present invention provides: (1) A refrigeration cycle in which a compressor, a condenser, a decompression device and an evaporator are sequentially connected. A first pressure detection device provided inside, which operates when the pressure of the refrigerant detects a first set pressure, and a first pressure detection device provided downstream of the first pressure detection device, wherein the pressure of the refrigerant is the second set pressure. And a second pressure detecting device that operates when
The second set pressure is set to a pressure obtained by adding a pressure close to the pressure loss between the first and second pressure detection devices to the first set pressure.

(2) It is effective that the first and second pressure detecting devices are pressure switches. (3) Further, instead of the first and second pressure detecting devices, the first and second set pressures may be detected by one pressure detecting device. (4) It is effective that this pressure detecting device is a pressure sensor.

[0009]

According to the means of claim 1, the second pressure detecting device provided on the downstream side with respect to the first pressure detecting device provided on the upstream side has the first and second pressures. By operating at a pressure (second set pressure) obtained by adding a pressure close to the pressure loss between the detection devices to the operating pressure (first set pressure) of the first pressure detection device, Since the second pressure detecting device can be performed by using two pressure detecting devices of the same type having the same operating pressure, the cost is low and the reliability is high.

According to the means of claim 2, the first and second
The cost can be further reduced by using one type of pressure switch having a simple structure for the pressure detecting device of FIG. According to the means of claim 3, instead of the first and second pressure detecting devices, the first and second set pressures are detected by one pressure detecting device, so that the pressure detecting device can be mounted. Since only one place is required, the wearability is further improved.

According to the means of claim 4, by using the pressure sensor in the pressure detecting device, the first and second
Since the set pressure of is accurately detected, the reliability is further improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a layout view of a pressure detecting device according to a first embodiment. In FIG. 1, 1 is a compressor that compresses and discharges a refrigerant, 2 is a condenser that condenses and liquefies the high-temperature and high-pressure gas refrigerant that is discharged from the compressor 1, and 3 is a gas-liquid two that is supplied from a condenser 2. A receiver for separating the phase refrigerant into a gas-liquid, 4 is a decompression device for decompressing and expanding the liquid refrigerant led out from the liquid receiver 3, and 5 is for absorbing heat by absorbing the atomized refrigerant decompressed and expanded by the decompression device 4. This is an evaporator for cooling, and these are sequentially connected to form a refrigeration cycle 10. The refrigerant flows and circulates in the direction of the arrow. In addition, 6 is a ventilation fan for condensers, and 7 is a ventilation fan for evaporators.

On the discharge side of the compressor 1, a first set pressure P
A capacity control pressure switch (first pressure detection device in the present invention) 11 that operates at 1 is provided, and on the downstream side thereof, there is provided a second set pressure P1 to which a pressure loss ΔP is added, for example. A high-pressure cutting pressure switch (second pressure detection device in the present invention) 12 that operates at a set pressure P1 + ΔP is provided, and these pressure switches 11 and 12 are, for example, ordinary spring type switches that open above the operating pressure. Pressure switch is used.

FIG. 2 shows an electric circuit diagram of the main part of the first embodiment, in which the operation switch 2 led from the power source 23 is shown.
4, a normally open relay 21, a normally closed relay 22 and normally closed pressure switches 11 and 12 are connected in parallel,
Pressure switch 11 is normally open relay 21, pressure switch 1
2 is connected to a normally closed relay 22 and a normally open relay 21.
The contact 21a is connected to a capacity control device 25 that controls the capacity of the compressor 1, and the contact 22a of the normally closed relay 22 is connected to an electromagnetic clutch 26 that connects and disconnects the compressor 1.

Next, the operation of the first embodiment will be described with reference to FIGS. 1 and 2. When the operation switch 24 is turned on, the electromagnetic clutch 26 is energized via the contact 22a to turn on the electromagnetic clutch 26, the compressor 1 is driven, and the operation of the refrigeration cycle 10 starts. Here, when the load is high, the refrigerant pressure on the discharge side of the compressor 1 rises.
When the pressure detected by the pressure switch 11 provided on the discharge side reaches the first set pressure P1 (for example, 2.6 MPa), the pressure switch 11 opens, so that the contact 21a of the normally open relay 21 closes to control the capacity. The device 25 is activated and the compressor 1
Is reduced by the required amount, and the operation of the compressor 1 is continued.

After that, when the refrigerant pressure further rises and the pressure detected by the pressure switch 12 reaches the second set pressure P1 + ΔP (for example, 2.8 MPa), in other words, the pressure applied to the pressure switch 12 exceeds the operating pressure P1. Then, since the pressure switch 12 opens, the contact 22a of the normally closed relay 22
Is opened, the electromagnetic clutch 26 is de-energized, the electromagnetic clutch 26 is disengaged, and the operation of the compressor 1 is stopped.

From the above, the pressure switch 11 for capacity control
And the pressure switch 12 for high pressure cut, the operating pressure is P1
Since it is possible to use two pressure switches of one type, it is only necessary to use two pressure switches of one type. Therefore, the cost for preventing wrong assembly is unnecessary, and both pressure switches 11 and 12 are used.
Since the refrigerant pressure is directly detected, erroneous detection does not occur, and the reliability is high. Since both pressure switches 11 and 12 can be pressure switches having a simple structure, the cost can be reduced.

[Second Embodiment] FIG. 3 is a layout view of a pressure detecting device according to a second embodiment. The difference from the first embodiment is that the pressure switch 11 for capacity control and the pressure switch 12 for high pressure cut are replaced with a single pressure detection device 13 having the functions of both pressure switches, and the others are the same. Since it is similar to the case of the first embodiment, the same parts are designated by the same reference numerals and the description thereof is omitted.

In FIG. 3, reference numeral 13 denotes a pressure detecting device provided on the discharge side of the compressor 1, which is the above-mentioned first set pressure P1.
And a second set pressure P1 + ΔP are respectively detected to generate a signal, and for example, a pressure sensor composed of a piezoelectric element whose output changes with a change in pressure is used. The pressure detection device 13 does not necessarily have to be provided on the discharge side of the compressor 1, and may be provided anywhere in the high-pressure refrigerant pipe between the compressor 1 and the pressure reducing device 4, but it is provided. It is necessary to correct the first and second set pressures according to the position.

FIG. 4 shows an electric circuit diagram of the main part of the second embodiment, in which the operation switch 3 led from the power source 33 is introduced.
4 and relays 31 and 32 are respectively connected in parallel to the control circuit 30, and a pressure detection device (hereinafter, referred to as a pressure sensor) 13 is connected, and the normally open contact 31a of the relay 31 is a capacity control device. 25, the normally open contact 32a of the relay 32 is connected to the electromagnetic clutch 26.

Next, the operation of the second embodiment will be described with reference to FIGS. 3 and 4. When the operation switch 34 is turned on, the relay 32 is energized, the contact 32a is closed, the electromagnetic clutch 26 is engaged, the compressor 1 is driven, and the operation of the refrigeration cycle 10 is started. Here, when the pressure detected by the pressure sensor 13 reaches the first set pressure P1 due to an increase in the refrigerant pressure during high load, the relay 31a is closed by the control circuit 30 and the capacity control device 25 is activated, and the compressor 1 of the compressor 1 is activated. The capacity is reduced by the required amount, and the operation of the compressor 1 is continued.

After that, when the refrigerant pressure further rises and the pressure detected by the pressure sensor 13 reaches the second set pressure P1 + ΔP, the control circuit 30 cuts off the energization of the relay 32 to open the contact 32a and the electromagnetic clutch 26. And the compressor 1 stops operating. As described above, since one pressure sensor 13 can be used for the capacity control and the high pressure cut of the compressor 1, the mountability of the pressure detecting device is improved as compared with the first embodiment, and the first and second Since the detection accuracy of the pressure sensor 13 with respect to the set pressure of 2 is high, the reliability is improved as compared with the first embodiment.

Next, in the case of the second embodiment, in addition to the capacity control of the compressor and the high-pressure cut, for example, the low-pressure cut when the gas in the refrigeration cycle is insufficient and the rotation speed of the blower fan for the condenser are changed. It can also be applied to the two-step control in. Although the first and second embodiments are applied to the ordinary receiver cycle, they can also be applied to the refrigeration cycle such as the accumulator cycle and the heat pump cycle.

[Brief description of drawings]

FIG. 1 is a layout view of a pressure detection device of a first embodiment in a refrigeration cycle.

FIG. 2 is an electric circuit diagram of a main part of the first embodiment.

FIG. 3 is a layout view of a pressure detection device of a second embodiment in a refrigeration cycle.

FIG. 4 is an electric circuit diagram of a main part of the second embodiment.

FIG. 5 is a layout view of a conventional pressure detection device in a refrigeration cycle.

[Explanation of symbols]

 1 Compressor 2 Condenser 4 Decompression device 5 Evaporator 10 Refrigeration cycle 11 1st pressure switch (1st pressure detection device) 12 2nd pressure switch (2nd pressure detection device) 13 Pressure sensor (pressure detection device) )

Claims (4)

[Claims] 1. A refrigeration cycle in which a compressor, a condenser, a pressure reducing device, and an evaporator are sequentially connected, and the refrigeration cycle is provided in the refrigeration cycle and is activated when the refrigerant pressure detects a first set pressure. A first pressure detecting device; and a second pressure detecting device provided downstream of the first pressure detecting device, the second pressure detecting device being activated when the pressure of the refrigerant detects a second set pressure, Is set to a pressure obtained by adding a pressure close to the pressure loss between the first and second pressure detecting devices to the first setting pressure. 2. The pressure detecting device for a refrigeration cycle according to claim 1, wherein the first and second pressure detecting devices are pressure switches. 3. The pressure detection device for a refrigeration cycle according to claim 1, wherein the first and second pressure detection devices are replaced by a single pressure detection device for detecting the first and second set pressures. A pressure detection device for a refrigeration cycle, characterized in that 4. The refrigeration cycle pressure device according to claim 3, wherein the pressure detection device is a pressure sensor.