JP3182529B2 - Discharge superheat control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge superheat control device for controlling the superheat of the refrigerant on the discharge side of a compressor when controlling refrigerant in a compression refrigeration cycle.

[0002]

2. Description of the Related Art In a refrigerant control of a compression refrigeration cycle having a compressor, a condenser, an expansion valve and an evaporator as main components, the refrigerant temperature at the outlet of the evaporator generally becomes constant. The control is performed by an expansion valve to control the degree of superheat of the intake gas of the compressor.

In such a conventional refrigerant control system, when the evaporation temperature decreases and the suction pressure of the compressor decreases, the pressure ratio increases and the volume efficiency of the compressor decreases. In addition, the electric motor driving the compressor increases the input of the electric motor due to an increase in the pressure ratio of the compressor.
As a result, the motor loss increases and the amount of heat generated increases. On the other hand, since the electric motor is cooled by the circulating refrigerant, the amount of the circulated refrigerant is reduced, so that the temperature of the electric motor naturally rises and the electric motor may be damaged.

[0004] In order to solve such a disadvantage of the conventional refrigerant control system, it has been proposed to provide a heat-sensitive cylinder for controlling the flow rate of an expansion valve in a discharge system between a compressor and a condenser. In this case, since the discharge gas temperature is detected, the expansion valve is opened in consideration of both the temperature rise of the refrigerant that has cooled the heat generating portion of the electric motor and the temperature rise due to the compression of the refrigerant gas. Is always controlled to a constant degree of superheat.
As a result, the amount of refrigerant circulating is increased by the amount of refrigerant necessary to reduce the heat generated by the motor, thereby preventing damage to the motor.

[0005]

In the apparatus in which the expansion valve is controlled in accordance with the temperature of the gas discharged from the compressor, the pressure on the discharge side of the compressor immediately rises when the refrigeration cycle is started. On the other hand, the refrigerant temperature in the discharge-side conduit rises with a considerable time delay. Therefore, the temperature-sensitive cylinder fixed to the outer wall of the discharge-side pipe increases the temperature of the discharged refrigerant gas, thereby increasing the temperature of the pipe, and further increasing the temperature of the temperature-sensitive cylinder heated by the temperature increase of the pipe. As the temperature rises, the time delay from the start of the refrigeration cycle to the temperature rise of the temperature sensing cylinder is large, the expansion valve does not open easily, and the pressure on the low pressure side of the refrigeration cycle, that is, the suction side of the compressor, decreases rapidly. However, since the pressure is close to the vacuum, a so-called low-pressure cut state occurs, so that normal operation is not performed. Further, there is a disadvantage that it takes much time to reach a steady state.

When it is necessary to forcibly open the expansion valve at the time of defrosting or the like, it is necessary to separately provide a control part for controlling the opening of the expansion valve, and there is a disadvantage that the refrigerator becomes expensive. Was.

Therefore, according to the present invention, in a device for controlling the degree of discharge superheat by providing a temperature-sensitive cylinder for operating an expansion valve in a discharge-side pipe of a compressor, it is possible to quickly start up from a start to a steady operation state. It is another object of the present invention to provide a discharge superheat degree control device in which low pressure cut is not performed, and a means for forcibly opening an expansion valve as necessary is performed by inexpensive equipment.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a discharge superheat control valve for controlling a discharge superheat by providing a temperature sensing cylinder for operating an expansion valve in a discharge pipe of a compressor. A three-way valve that allows the pressure equalizing pipe of the expansion valve to be switchably connected to either the discharge side pipe or the suction side pipe of the compressor, or the pressure equalizing pipe of the expansion valve is connected to the discharge side of the compressor via a throttle. In a device for controlling the degree of superheat of the discharge, which is connected to the pipe line and connected to the suction side pipe line via an on-off valve, thereby providing a temperature-sensitive cylinder for operating the expansion valve in the discharge pipe line of the compressor, It is possible to quickly start up a steady operation from the start, prevent low pressure cutting, and perform means for forcibly opening the expansion valve as necessary using inexpensive equipment.

[0009]

According to the present invention, the three-way valve switches and connects the pressure equalizing pipe to the discharge pipe during steady operation of the refrigeration cycle in the apparatus using the three-way valve.
Therefore, the opening of the expansion valve is controlled by the balance between the working gas pressure of the temperature-sensitive cylinder provided in the discharge pipe and the refrigerant gas pressure in the discharge pipe. On the other hand, at the start of the refrigeration cycle and at the time of defrosting operation, the three-way valve switches and connects the equalizing pipe to the suction side pipeline,
The pressure that opposes the working gas pressure of the temperature-sensitive cylinder is reduced, and the expansion valve is forcibly opened because the temperature of the temperature-sensitive cylinder rises and becomes the same as the state where the working gas pressure increases. .

When the refrigeration cycle in the apparatus using the above-mentioned on-off valve is in a steady operation, the on-off valve is closed, and therefore, the gas is introduced through the working gas of the temperature-sensitive cylinder provided in the discharge side pipe and the throttle. The degree of opening of the expansion valve is controlled by balancing the refrigerant gas pressure in the discharge-side pipe. On the other hand, at the start of the refrigeration cycle and at the time of defrosting operation, the on-off valve is opened, and the influence of the suction-side pressure communicating through the on-off valve on the pressure equalizing pipe rather than the discharge-side pipe-side pressure communicating with the throttle through the throttle. Is large,
Therefore, the pressure in the pressure equalizing tube decreases, the pressure opposing the working gas pressure of the temperature-sensitive cylinder decreases, and the temperature becomes substantially the same as the state in which the temperature of the temperature-sensitive cylinder increases and the working gas pressure increases. Therefore, the expansion valve is forcibly opened.

[0011]

An embodiment of the present invention will be described with reference to the drawings. In the refrigeration cycle shown in FIG. 1, the refrigerant from the discharge pipe 2 of the compressor 1 is switched between a four-way switching valve 3 and a pipe to the outdoor heat exchange unit 4 or a pipe to the indoor heat exchange unit 5. Sent to When this refrigeration cycle is used for cooling, the four-way switching valve 3 switches the discharge pipe line to the outdoor heat exchange unit 4 side, and the outdoor heat exchange unit 4 acts as a condenser, and the condensed refrigerant is It returns to the compressor 1 via the four-way switching valve 3 through the indoor heat exchange unit 5 acting as an evaporator through the expansion valve 6. Hereinafter, a case where this refrigeration cycle is used for cooling will be described. Therefore, the outdoor heat exchange unit 4 will be described as a condenser 7 and the indoor heat exchange unit 5 will be described as an evaporator 8.

The expansion valve 6 has a valve hole 13 communicating the first pipe line 11 and the second pipe line 12 provided in the valve body 10, and the valve hole 13 has a valve element 14. The valve body 14 is a valve body 1
0 is connected to a diaphragm 15 provided on the upper part of the cylinder 0 by a rod 17 via a contact 16.
It operates by the pressure difference between the upper working chamber 18 and the lower working chamber 19.

The upper working chamber 18 includes a discharge pipe 2 of the compressor 1.
The lower working chamber 19 is connected to the discharge pipe 2 and the suction pipe 9 via the three-way valve 30 by the pressure equalizing pipe 23 and the temperature-sensitive cylinder 21 fixed in close contact with the pipe. It is connected to one of them so as to be switchable. The valve body 14 is normally urged in a closing direction by a spring 24, and a rod 17 that slides in a vertical direction is connected by a diaphragm 15. A seal packing 25 is provided on the outer periphery of the rod 17, and is pressed by a spring 27 supported by a nut 26 fixed to the valve body 10. The first pipe 11 and the second pipe 12 communicate with each other by a throttle 28 so as to bypass the valve hole 13.

When starting the refrigerating cycle, the three-way valve 30 is switched so that the pressure equalizing pipe 23 communicates with the suction pipe 9. When the pressure of the suction pipe 9 is reduced by driving the compressor, the pressure acts on the lower working chamber 19 of the expansion valve 6 via the three-way valve 30 and the equalizing pipe 23. Therefore, in a state where the lower working chamber 19 is in communication with the high pressure side of the discharge pipe 2 in advance,
With respect to the expansion valve 6 set to control the opening of the expansion valve by the pressure balance with the upper working chamber 18 corresponding to the temperature of the temperature sensing cylinder 21, the pressure of the discharge pipe is applied to the lower working chamber 19. Because much lower suction tube pressure is introduced, the expansion valve is forced open.

As a result, the high-pressure refrigerant gas in the discharge pipe 2 is liquefied in the condenser 7, and a part thereof reaches the evaporator 8 through the throttle 28, and the others pass through the valve hole 13 of the expansion valve 6. Inflated,
After entering the evaporator 8, the room is cooled and returned to the compressor 1 through the accumulator 20 provided in the suction pipe 9 of the compressor 1 via the four-way switching valve 3.

After the refrigeration cycle is started, when a steady state is reached after a predetermined time, the three-way switching valve 30 is switched, and the pressure equalizing pipe 23 is communicated with the discharge pipe 2. Thus, the opening degree of the expansion valve is controlled by the balance between the working gas pressure corresponding to the preset temperature of the temperature sensing cylinder and the refrigerant gas pressure of the discharge pipe.

In the above embodiment, an example in which this refrigeration circuit is used for cooling is shown. However, when used for heating, the four-way switch 3 is switched to connect the discharge pipe 2 to the indoor heat exchange unit 5. Then, the suction pipe 9 is communicated with the outdoor heat exchange unit 4. At this time, the first valve is connected to the expansion valve 6 from the second pipe 12.
Although the refrigerant flows through the pipeline 11, the operation of the expansion valve, the operation of which is controlled by switching the three-way valve, is the same as described above.

When it is necessary to perform defrosting of the evaporator in the normal operation state of the refrigeration circuit, the control device switches the three-way switching valve and forcibly opens the expansion valve 6 in the same manner as at the start. Since the device for performing the defrosting can be used as it is, no special device for defrosting is required, and the device can be made inexpensive.

As means for forcibly opening the expansion valve in the present invention, a pipe as shown in FIG. 2 may be used instead of the pipe of the pressure equalizing pipe shown in FIG. That is, the pressure equalizing tube 23 is
6 communicates with the discharge pipe 2 via the open / close valve 37, and communicates with the suction pipe 9 via the open / close valve 37. In a normal operation, the open / close valve 37 is closed and communicates with the discharge pipe 2 via the throttle 36. Used in.

On the other hand, during startup and defrosting, the on-off valve 37
Is opened, the low refrigerant gas pressure in the suction pipe 9 causes the on-off valve 3
7 is the same as the device shown in FIG. 1 in that it reaches the pressure equalizing pipe 23 via the, and acts on the lower working chamber of the expansion valve to forcibly open and close. In this device, unlike the device shown in FIG. 1, there is no need to introduce refrigerant gas pressure into the equalizing pipe through a three-way valve during steady operation, so stable control is possible, and an inexpensive valve is used. Equipment cost can be reduced. In addition, by opening this on-off valve when the refrigeration cycle is stopped, the suction pipe and the discharge pipe are connected via a throttle, and after the stop, the pressures of the suction pipe and the discharge pipe are quickly balanced, and when restarting, Can be shortened.

As the expansion valve in each of the above devices,
An expansion valve as shown in FIG. 3 may be used. That is, the upper end surface of the rod 43 receives the pressure from the pressure equalizing tube 45, and the lower end surface receives the pressure of the second conduit 47.

When the expansion valve 40 is used in place of the expansion valve of the refrigeration cycle, the equalizing pipe 45 is connected to the discharge pipe 2 by switching a three-way switching valve 48, and when the refrigeration cycle is used as a cooling device, The operating pressure on the valve body of the expansion valve 40 has the following balance.

That is, the upper working chamber 50 of the diaphragm 41
The pressure from the temperature-sensitive cylinder 51 acting on the pressure equalizing pipe 45 is Pt, the pressure of the discharge pipe from the pressure equalizing pipe 45 is Ph, and the pressure of the first pipe line 46 connected to the condenser is almost the pressure Ph of the discharge pipe. The pressure in the second conduit connected to the vessel is Pi, and the diaphragm 4
1 is A, the area of the connecting rod 43 is B, the area of the valve hole 44 is α, the pressing force of the first spring 51 is W1, and the pressing force of the second spring 52 is W2. The following equation holds: APt = [A− (B−α)] Ph + (B−α) Pi + (W1 + W2) When the valve hole 44 has a sufficiently smaller diameter than the connecting rod 43, α << B B−α ≒ B. If W1 + W2 = W = F × A, then Pt = (A−B / A) Ph + (B / A) Pi + F.

Here, the refrigerant gas flows from the first pipe 46 to the second pipe 46.
During the cooling operation flowing through the pipe 47, the pressure Pi of the second pipe is
Is substantially equal to the suction pipe pressure Ps, so that Pt = (A−B / A) Ph + (B / A) Ps + F. From this equation, it is easy to open the expansion valve when the suction pipe pressure decreases. This has the effect of preventing the absolute temperature on the discharge side from rising too high, because the lower the low pressure, the higher the discharge temperature.

On the other hand, when the expansion valve 40 is used for heating, the refrigerant flows from the second pipe 47 to the first pipe 46. At this time, the second pipe pressure Pi is equal to the discharge pipe pressure. Ph
Is equal to Pt = Ph + F, which indicates that this expansion valve is not affected by the pressure in the suction pipe at all. Therefore, during the cooling operation, the discharge superheat degree is set lower than during the heating operation. This is effective when the optimum discharge superheat degrees during cooling and during heating are different. Here, the set value of the discharge superheat degree is set lower during cooling, but it is apparent that the set value can be set lower during heating if the mounting direction of the valve joint is reversed.

The valve described above can be applied not only to an apparatus using the three-way switching valve but also to an apparatus using an on-off valve shown in FIG.

[0027]

Since the present invention is constructed and operates as described above, an apparatus for controlling the degree of discharge superheat by providing a temperature-sensitive cylinder for operating an expansion valve in the discharge-side pipe of the compressor is a method for controlling the degree of superheat from the start. It is possible to quickly start up in the operating state. Therefore, stable operation can be performed without performing low pressure cut due to excessive reduction of the suction side pressure. Also, when the expansion valve needs to be forcibly opened at the time of defrosting or the like, it is possible to forcibly open the expansion valve by using the same device, and there is no need to use a special device. Equipment costs are reduced.

In a device in which the pressure equalizing pipe is connected to the discharge line of the compressor via a throttle and connected to the suction side via an on-off valve, the suction valve is opened by opening the on-off valve when the apparatus is stopped. The pipe and the discharge pipe are connected via a throttle, so that the time for balancing the pressure can be reduced, and the apparatus can be restarted quickly.

[Brief description of the drawings]

FIG. 1 is a refrigeration cycle diagram showing a first embodiment of the present invention.

FIG. 2 is a partial refrigeration cycle diagram showing another embodiment.

FIG. 3 is a refrigeration cycle diagram using another expansion valve used in the refrigeration cycle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Discharge pipe 3 Four-way switching valve 4 Outdoor heat exchange unit 5 Indoor heat exchange unit 6 Expansion valve 9 Suction pipe 10 Valve body 11 First pipe 12 Second pipe 13 Valve hole 14 Valve body 15 Diaphragm 17 Rod 18 Upper working chamber 19 Lower working chamber 21 Temperature sensing tube 22 Capillary tube 23 Equalizing tube 24 Spring 27 Spring 28 Restrictor 30 Three-way switching valve 36 Restrictor 37 On-off valve

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-28957 (JP, A) JP-A-56-128477 (JP, U) JP-A-62-95257 (JP, U) 2454 (JP, Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) F25B 41/06 F25B 1/00 304

Claims (2)

(57) [Claims] 1. A discharge superheat control valve for controlling a discharge superheat by providing an expansion valve operating temperature-sensitive cylinder in a discharge side pipe of a compressor;
A discharge superheat control device, comprising: a three-way valve that allows a pressure equalizing pipe of an expansion valve to be selectively connected to one of a discharge pipe and a suction pipe of a compressor. 2. A discharge superheat control valve that controls a discharge superheat by providing an expansion valve operating temperature-sensitive cylinder in a discharge-side pipe of the compressor.
A discharge superheat control device, comprising: a throttle connecting an equalizing pipe of an expansion valve to a discharge pipe of a compressor; and an on-off valve connecting to a suction pipe.