JPH0413068A - Automatic expansion valve - Google Patents

Abstract

PURPOSE:To make it possible to maintain discharge pressure and suction pressure of a compres sor within an allowable range by driving an over heat control mechanism, a discharge pressure control mechanism, and a suction pressure control mechanism according to a predetermined sequence in conformity with an actual operation pressure in terms of a setting pressure. CONSTITUTION:An automatic expansion valve 10 is provided with an over heat control mecha nism, a discharge pressure mechanism, and suction pressure mechanism 13. When the tempera ture of refrigerant at the outlet of a vaporizer 6 rises, the pressure of refrigerant filled in a temperature detection cylinder 22 rises accordingly. This pressure is transmitted into an actuation chamber 29 by way of a lead pipe 23 of the over heat control mechanism 11 so that a diaphragm 24 may be pushed up. Then, a valve disk 26 drops by way of a rod 31, resisting against an elastic expansion force of a spring 28 where the gap between the valve disk 26 and a valve port 32 is increased so that the flow rate of refrigerant may be increased. The discharge pressure control mechanism 12 inhibits the discharge pressure of the compressor 1 by setting the volume of refrigerant to be supplied to the inlet of the vaporizer 6 as a volume which meets the pressure of refrigerant in the inlet of an expansion valve 10 while the suction pressure control mechanism 13 carries out proportional control of the suction pressure of a compressor when the pressure of refrigerant in the outlet of the vaporizer 6 fails to exceed a setting pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic expansion valve suitable for vehicular refrigeration systems, air conditioners, and the like.

(Prior Art) An example of a refrigerant circuit of a conventional refrigeration system is shown in FIG.

In Fig. 4, l is an open type compressor, 2 is a condenser, 3 is a lever, 4 is a temperature type expansion valve, 5 is a constant pressure automatic expansion valve, 6
7 is an evaporator, 7 is a suction pressure regulating valve, 22 is a temperature sensing cylinder, and 23 is a pressure guiding pipe.

The refrigerant gas discharged from the compressor 1 is condensed and liquefied by dissipating heat to the outside air in the pseudo-condensation rM2, and the gas refrigerant contained in the liquid refrigerant is separated in the reverberator 3.Thermal expansion valve 4
The air is adiabatically expanded by being throttled by the evaporator 6, evaporated by cooling the air in the refrigerator 6, the pressure is adjusted by the suction pressure regulating valve 7, and the air is sucked into the compression Ill.

During overload operation or pull-down operation of the refrigeration system, the capacity of the evaporator 6 becomes excessive with respect to the capacity of the condenser 2, and there is a possibility that the discharge pressure of the compressor 1 exceeds the allowable pressure. Therefore, the refrigerant flow rate is restricted by the suction pressure regulating valve 7 so that the pressure of the refrigerant gas sucked into the compressor 1 does not exceed a set pressure, thereby suppressing the discharge pressure of the compressor 1 to below an allowable pressure.

Further, when the outside air temperature is low or when the rotation speed of the compressor 1 is high, the pressure of the refrigerant gas sucked into the compressor 1 decreases to negative pressure. As a result, air may enter the refrigerant circuit through the gap between the sliding surfaces of the mechanical seal of the open compressor 1, or the sliding surface may run out of oil, causing poor lubrication of the mechanical seal.

Therefore, the constant pressure automatic expansion valve 5 automatically performs proportional control so that the evaporation pressure does not fall below a set pressure, thereby suppressing the pressure of the refrigerant gas sucked into the compressor 1 from becoming a negative pressure.

(Problems to be Solved by the Invention) In the above-mentioned conventional refrigeration equipment, even if the suction pressure regulating valve 7 is fully opened in steady operation, there is a flow resistance when the refrigerant gas passes through it, so the steady operation is not possible. Time ability decreases.

Also, in winter, the capacity of the condenser 2 is sufficient, and the compressor l
Even if the pressure of the refrigerant gas discharged from the evaporator 6 is low, if the evaporation pressure of the refrigerant in the evaporator 6, that is, the pressure of the refrigerant gas sucked into the compressor 1, is higher than the set pressure of the suction pressure regulating valve 7. Since this one-person pressure regulating valve 7 limits the flow rate of refrigerant sucked into the compressor 1, the refrigeration system cannot demonstrate its maximum capacity.

Furthermore, when the constant pressure automatic expansion valve 5 opens at low outside temperatures, the constant pressure automatic expansion valve 5 sends out an amount of liquid refrigerant to the evaporator 6 that cannot be completely evaporated by the evaporator 6, so that the liquid refrigerant is supplied to the compressor l. This causes so-called liquid compression.

(Means for Solving the Problems) In view of the above, the present invention aims to eliminate the undesirable side effects of suction pressure regulating valves and constant pressure automatic expansion valves, and the gist of the first invention is as follows: , refrigerant i at the evaporator outlet! In an automatic expansion valve equipped with a superheat degree control mechanism that controls the degree of heat, a discharge valve that controls the amount of refrigerant flowing into the evaporator and controls the discharge pressure of the compressor when the refrigerant pressure at the inlet of the expansion valve is higher than a set pressure. A pressure control mechanism and a suction pressure control mechanism that controls the suction pressure of the compressor by supplying refrigerant gas discharged from the compressor to the evaporator outlet when the refrigerant pressure at the evaporator outlet is below a set pressure are provided. Each of the above-mentioned controls is performed in a predetermined order according to the actual operating pressure for each of the above-mentioned set pressures. An automatic expansion valve characterized by operating a 71 mechanism.

The discharge pressure control mechanism is linked with the superheat control mechanism described in 1- above so that when the refrigerant pressure at the inlet of the expansion valve is equal to or higher than a set pressure, the superheat control mechanism operates to control the pressure as an operating section of the discharge pressure control mechanism. You can also do it.

When the refrigerant pressure at the inlet of the expansion valve is equal to or higher than the set pressure, the discharge pressure control mechanism stops the function of the supermaturity control mechanism described in section 2 above, and supplies the refrigerant amount corresponding to the refrigerant pressure at the inlet of the expansion valve to one blower. You can also do it like this.

Does the above suction pressure control mechanism direct the refrigerant gas discharged from the compressor to the above superheat side? It is also possible to supply the tea at a position closer to the outlet of the tea generator than the thermosensor tube of the 11 mechanism.

(Function) In the first invention, the degree of superheat is determined in a predetermined order according to the actual operating pressure for each preset pressure. 1114ffl side, discharge pressure control mechanism, suction pressure side? 11 mechanisms operate.

In the second invention, when the refrigerant pressure at the inlet of the expansion valve is equal to or higher than the set pressure, the superheat degree control mechanism performs pressure control operation as an operation part of the discharge pressure control mechanism to always suppress the discharge pressure of the compressor to below the allowable pressure. do.

In the third invention, when the refrigerant pressure at the inlet of the expansion valve is equal to or higher than the set pressure, the discharge pressure control mechanism stops the function of the degree of superheat control mechanism and controls the amount of refrigerant corresponding to the refrigerant pressure at the inlet of the expansion valve to the evaporator. Supply at the entrance.

In the fourth invention, the suction pressure control mechanism supplies the refrigerant gas discharged from the compressor to a position closer to the evaporator outlet than the temperature sensing cylinder, and the superheat degree control mechanism supplies the refrigerant gas discharged from the compressor to the evaporator outlet detected by the temperature sensing cylinder. The degree of superheating is controlled according to the temperature of the refrigerant gas that is a mixture of the refrigerant gas flowing out from the refrigerant gas and the refrigerant gas supplied by the suction pressure control mechanism.

(Example) One embodiment of the invention is shown in FIGS. 1 and 2.

As shown in FIG. 2, the suction pressure regulating valve 7 and constant pressure automatic expansion valve 5 in the conventional system shown in FIG. 4 are abolished, and an automatic expansion valve 10 is installed in place of the expansion valve 4.

Details of this automatic expansion valve 10 are shown in FIG. 1, and this automatic expansion valve 10 includes a superheat degree control mechanism 11, a discharge pressure control mechanism 12, and a suction pressure control mechanism 13.

The superheat degree controller tjl 11 includes a main body 21, a temperature sensing tube 22, a pressure pipe 23, a diaphragm 24, a rod 31, a valve body 26,
It consists of a valve port 32, a carrier 27, a spring 28, etc.

The temperature sensing cylinder 22 is attached to the refrigerant pipe at the outlet of the evaporator 6,
and a working chamber 29 bounded above the diaphragm 24.
are connected to each other by a pressure impulse pipe 23.

The temperature-sensitive tube 22, the working chamber 29, and the pressure guiding tube 23 are filled with the same type of refrigerant as the refrigerant sealed in the refrigerant circuit of the refrigeration system. A chamber 3o limited below the diaphragm 24 is connected to the discharge pressure control mechanism 13 via a pressure equalizing joint 25. The diaphragm 624 is the rod 31
The valve body 26 is placed on a carrier 27 and is pushed toward the valve port 32 by a spring 28 disposed below the carrier 27. There is.

Therefore, when the temperature of the refrigerant at the outlet of the evaporator 6 rises, the pressure of the refrigerant filled in the temperature sensing cylinder 22 rises accordingly. This pressure is transmitted into the working chamber 29 via the pressure conduit 23 and pushes the diaphragm 24 downward. diaphragm 2
4 descends, the valve body 26 descends via the rod 31 against the elastic force of the spring 28, and the valve body 26 and the valve port 32
The gap between the two ends increases, and the flow rate of the refrigerant through this gap increases. In this manner, similar to the conventional expansion valve 4, the superheat degree control mechanism 11 maintains the refrigerant superheat degree at the outlet of the evaporator 6 at a preset constant value.

The discharge pressure control mechanism 12 includes a case 33, a bellows 34, a spring 35, a valve body 36, a valve port 37, and the like.

The case 33 communicates with a liquid refrigerant supply pipe 39 through which the liquid refrigerant from the receiver 3 flows through a through hole 38 .

A bellows 34 is disposed inside the case 33, and the inside of the bellows 34 communicates with the atmosphere via a through hole 4o. The bellows 34 is expanded by the elastic force of a spring 35 disposed inside the bellows 34, and pushes a valve body 36 fixed to the tip of the bellows 34 toward a valve port 37. This valve port 37 communicates with a pressure equalizing joint 25, and this pressure equalizing joint 25 communicates with a chamber 47 of the suction pressure control mechanism 13 via an orifice 49, and this chamber 47 communicates with the piping 4.
8, it communicates with the refrigerant pipe at a position closer to the outlet of the evaporator 6 than the temperature sensing cylinder 22.

When the pressure of the liquid refrigerant flowing into the case 33 from the liquid refrigerant supply pipe 39 through the through hole 38 rises above the set pressure, the force of this liquid refrigerant overcomes the elastic force of the rose 34 and the spring 35. Then, the bellows 34 is shortened so that the valve body 36 is spaced from the valve port 37 by one space.

Then, the liquid refrigerant flowing into the case 33 passes through the space between the valve body 36 and the valve port 37, and changes its flow rate characteristics and the orifice 49.
It flows into the chamber 30 through the pressure equalizing joint 25 with a pressure determined by the resistance of the pressure. Then, the pressure in the working chamber 29 (the saturated evaporation pressure corresponding to the refrigerant temperature at the outlet of the evaporator 6) is overcome and the diaphragm 24 rises, causing the valve body 26 and the valve port 3 to rise.
Reduce the gap with 2. Thus, the flow rate of refrigerant supplied to the evaporator 6 is reduced, and the discharge pressure of compression [1] is reduced.

In this way, the discharge pressure control mechanism 12 stops the superheat degree control function of the superheat degree control mechanism 11 when the refrigerant pressure of the expansion valve 10 is equal to or higher than the set pressure, and functions as a viroft valve while simultaneously functioning as a superheat degree control mechanism. 11 as if it were an operating section, the amount of refrigerant supplied to the sputum generator 6 corresponds to the refrigerant pressure at the inlet of the expansion valve 10, thereby suppressing the discharge pressure of the compressor 1.

The suction pressure control mechanism 13 includes a case 41, a bellows 42, a spring 43, a valve body 44, a valve port 45, and the like.

A bellows 42 is disposed within the case 41, and an inert gas such as nitrogen gas is sealed inside the bellows 42. The bellows 42 is expanded by the elastic force of a spring 43 disposed inside the bellows 42, and is bent so as to separate the valve body 44 fixed to one end of the bellows 42 from the valve port 45. This valve port 45 is connected to the compressed ml discharge side via a pipe 46. bellows 42
A chamber 47 bounded on the right side of the evaporator 6 is connected to the evaporator 6 via a pipe 48.
and is connected to the pressure equalizing joint 25 via an orifice 49.

When the pressure of the gas refrigerant sucked into the compressor 1, that is, the refrigerant pressure at the outlet of the evaporator 6, falls below the set pressure, the pressure inside the case 41 decreases through the pipe 48 and the chamber 47, and the bellows 42 Since the force of the nitrogen gas sealed therein shortens the bellows 42 against the elastic force of the bellows 42 and spring 43, the gap between the valve body 44 and the valve port 45 increases. In this way, the refrigerant gas discharged from the compressor 1 enters the case 41 through the pipe 46 and the valve port 45.
Furthermore, it is supplied between the outlet of the evaporator 6 and the temperature sensing tube 22 via a chamber 47 and a pipe 48.

Suction pressure side like this? 21 mechanism 13 proportionally controls the suction pressure of the compressor 1 when the refrigerant pressure at the outlet of the evaporator 6 is below a set pressure.

In this case, the temperature sensing cylinder 22 detects the degree of superheat of the mixed refrigerant made up of the refrigerant gas supplied from the suction pressure control mechanism 13 via the pipe 48 and the refrigerant gas flowing out from the evaporator 6, and the superheat degree control mechanism 11 Superheat degree control is performed in accordance with commands from this temperature sensing cylinder 22. Therefore, the refrigerant sucked into the compressor 1 is the same as that during normal operation, and liquid back-up and overheating of the compressor 1 can be prevented.

As described above, this automatic expansion valve 10 can be operated by selectively switching between the discharge pressure control function, the superheat control R function, and the suction pressure control function. Undesirable side effects of the valve 7 and constant pressure automatic expansion valve 5 can be avoided.

A second embodiment of the invention is shown in FIG.

This second embodiment differs from the first embodiment in the discharge pressure control mechanism 14, but is otherwise similar.

The discharge pressure control mechanism 14 includes a case 51, a bellows 52, a spring 53, a first valve body 54, a valve port 55, a second valve body 56, a valve port 57, and the like.

The case 51 communicates with the liquid refrigerant supply pipe 39 through a through hole 59, and a bellows 52 is disposed within the case 51. The inside of this bellows 52 communicates with the atmosphere via a through hole 60. When the bellows 52 expands due to the elastic force of a spring 53 disposed inside the bellows 52, the valve body 54 fixed to the bellows 52 approaches the valve port 55, and the valve body 56 moves toward the valve port 55. 57. Note that the opening degree of the valve port 55 is configured to be much larger than that of the valve port 57 at the same lift. The valve port 57 communicates with a chamber 62 formed below the carrier 27 via a pipe 61, and the valve port 57 communicates with the inlet side of the evaporator 6 via a pipe 63.

When the pressure of the liquid refrigerant flowing into the case 51 from the through hole 59 rises above the set pressure, the force of the liquid refrigerant overcomes the elastic force of the bellows 52 and the spring 53, causing the bellows 52 to shorten. At the same time as the gap between the valve body 54 and the valve port 55 increases, the gap between the valve body 56 and the valve port 57 decreases. Thus, the liquid refrigerant that has flowed into the case 51 flows into the working chamber 62 through the valve port 55 and the pipe 61, and by pushing up the carrier 27, the valve body 26 closes the valve port 32. At the same time, the liquid refrigerant flowing out from the valve port 57 flows into the inlet of the evaporator 6 via the pipe 63.

In this way, this discharge pressure control mechanism I4
By blocking the superheat degree control mechanism 11, the superheat degree control function is stopped and the amount of refrigerant supplied to the evaporator 6 is controlled to be inversely proportional to the pressure of the liquid refrigerant in the expansion valve IO population. The discharge pressure of the machine 1 is controlled by the discharge pressure control mechanism 14.
The pressure is controlled to be inversely proportional to the pressure of the liquid refrigerant at the inlet of the expansion valve 10.

Other operations are similar to those in the first embodiment.

(Effects of the Invention) The present invention avoids the undesirable side effects of conventional suction pressure control valves and constant pressure automatic expansion valves, and maintains the discharge pressure and suction pressure of the compressor under all operating conditions of the refrigeration system. It is possible to maintain the temperature within the allowable range, prevent liquid banks, and allow the refrigeration system to perform at its maximum capacity.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, with FIG. 1 being a schematic sectional view of an automatic expansion valve, and FIG. 2 being a refrigerant circuit diagram of a refrigeration system. FIG. 3 is a schematic cross-sectional view of an automatic expansion valve according to a second embodiment of the present invention. FIG. 4 is a refrigerant circuit diagram of a conventional refrigeration system. Compressor-1, automatic expansion valve-10, evaporator-6, superheat control mechanism-11, discharge pressure control mechanism-12, suction pressure second
figure

Claims (4)

[Claims] (1) In an automatic expansion valve equipped with a degree of superheating control mechanism that controls the degree of superheating of the refrigerant at the outlet of the evaporator, when the refrigerant pressure at the inlet of the expansion valve is higher than the set pressure, the amount of refrigerant flowing into the evaporator is controlled and compressed. a discharge pressure control mechanism that controls the discharge pressure of the evaporator, and a suction mechanism that controls the suction pressure of the compressor by supplying refrigerant gas discharged from the compressor to the evaporator outlet when the refrigerant pressure at the evaporator outlet is below the set pressure. 1. An automatic expansion valve comprising a pressure control mechanism and operating each of the control mechanisms in a predetermined order according to an actual operating pressure with respect to each of the preset pressures. (2) The discharge pressure control mechanism is linked with the superheat degree control mechanism so that when the refrigerant pressure at the inlet of the expansion valve is equal to or higher than a set pressure, the superheat degree control mechanism operates to control the pressure as an operating section of the discharge pressure control mechanism. (1)
Automatic expansion valve as described in section. (3) The discharge pressure control mechanism stops the function of the superheat degree control mechanism when the refrigerant pressure at the expansion valve inlet is equal to or higher than the set pressure, and supplies the refrigerant amount corresponding to the refrigerant pressure at the expansion valve inlet to the evaporator inlet. The automatic expansion valve according to item (1), characterized in that: (4) The automatic suction pressure control mechanism according to item (1), wherein the suction pressure control mechanism supplies the refrigerant gas discharged from the compressor to a position closer to the evaporator outlet than the temperature sensing tube of the superheat degree control mechanism. expansion valve.