JPH0670541B2 - Expansion valve for refrigeration cycle - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an expansion valve for a refrigeration cycle, which is suitable for use in, for example, a car air conditioner.

2. Description of the Related Art A gas refrigerant discharged from a compressor is condensed by a condenser and separated into a gas-liquid two phase in a receiver, and the liquid refrigerant is guided from the receiver to an expansion valve where the liquid refrigerant is adiabatically expanded to an evaporator. Introduced into the evaporator to evaporate in the evaporator to remove heat from the surroundings of the evaporator, after which, in the refrigeration cycle for returning the gas refrigerant from the evaporator to the compressor, the opening of the expansion valve, the refrigerant pressure on the downstream side of the evaporator, There is a known technology that controls the flow rate of the refrigerant by controlling it based on the temperature of the refrigerant downstream of the evaporator, but this technology requires connection of a temperature-sensing tube, an external equalizing pipe, etc., and the piping is complicated. For this reason, the expansion valve 100 shown in FIG. 2 has been devised.

The expansion valve 100 has a main body 101 in which a first
~ Fourth passages 102, 103, 104 and 105 are formed. The compressor 1 discharges a high-temperature, high-pressure gas refrigerant, the condenser 2 condenses the gas refrigerant, and the condensed refrigerant is separated into a gas-liquid two phase in the receiver 3. The first passage 10
2 is connected to the receiver 3 and receives the high-pressure liquid refrigerant from the receiver. The second passage 103 communicates with the first passage 102 via the expansion orifice 106, and the low-pressure gas-liquid two-phase refrigerant passing through this orifice 106 flows toward the evaporator 4. Third
The passage 104 receives the gas refrigerant from the evaporator 4. The fourth passage 105 communicates with the third passage 104 and returns the gas refrigerant from the evaporator 4 to the compressor 1.

The flow rate of the refrigerant passing through the expansion orifice 106 is determined by the opening degree of the valve body 107. The valve body 107 is spring-loaded toward the valve seat by the spring 108, while the pin 109 exerts a force acting on the valve body 107 so as to push the valve body 107 away from the valve seat. This pin 109 is axially movable by a diaphragm 112 that separates the heat-sensitive chamber 110 and the low-pressure refrigerant chamber 111 from each other.
The internal pressure changes according to the temperature of the refrigerant flowing through the passages 104 and 105, and the low-pressure refrigerant chamber 111 communicates with the passages 104 and 105. Therefore, the position of the valve element 107 with respect to the valve seat is determined by the balance position between the differential pressure between the two chambers 110 and 111 and the spring force of the spring 108. If the temperature of the refrigerant discharged from the evaporator 4 changes, the heat-sensitive chamber The pressure in 110 is changed and the diaphragm 112 is displaced, and as a result, the valve body 107 is displaced and the flow rate of the refrigerant to the evaporator 4 is adjusted.

Problems to be Solved by the Invention However, in the above-described configuration, when the refrigerant circulation amount is large, such as when the compressor 1 rotates at high speed and when the cooling load increases, the proper control of superheat becomes impossible, and the increase of superheat increases. Invite. This causes overheating of the compressor 1, which causes a problem that the compressor itself is damaged or the high pressure hose is damaged. In addition, when some kind of protection device (for example, a control device that detects the discharge temperature of the compressor and controls the ON / OFF of the compressor) is used to solve this problem, another problem such as poor cooling and increased cost occurs. It was

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a first passage for receiving a high-pressure liquid refrigerant and an expansion orifice communicating with the first passage through the expansion orifice. A second passage through which the low-pressure gas-liquid two-phase refrigerant that has passed through is directed toward the evaporator, a third passage that receives the refrigerant from the evaporator, and a refrigerant that is in communication with the third passage and returns the refrigerant from the evaporator to the compressor. In a refrigeration cycle expansion valve including a fourth passage, a bypass passage is provided between a position between the inlet of the third passage and an outlet of the fourth passage and the second passage, There is provided an expansion valve for a refrigeration cycle, comprising a bypass valve that opens and closes the bypass passage according to a pressure difference between a refrigerant pressure in the second passage and a refrigerant pressure from the evaporator.

Action During normal operation, the bypass valve closes the bypass passage, and the expansion valve performs the normal expansion valve action.However, if overheating of the compressor poses a problem, refrigerant pressure loss in the evaporator increases. , The pressure difference between the refrigerant pressure in the second passage and the pressure of the refrigerant exiting the evaporator increases, and the bypass valve opens the bypass passage in response to this pressure difference to cool the cooling capacity from the second passage. Bypassing the high-temperature gas-liquid two-phase refrigerant to the fourth passage to prevent overheating of the compressor.

Embodiment FIG. 1 shows an expansion valve 200 embodying the present invention. In FIG. 1, the same parts as those of the conventional example of FIG. 2 are designated by the same reference numerals. The expansion valve 200 has a substantially cylindrical shape. The first passage 102 connected to the receiver 3 extends in the radial direction in the main body 101, and its inner end communicates with a valve chamber 113 formed in the lower end portion of the main body 101. The second passage 103 connected to the evaporator 4 is slightly displaced from the first passage 102 in the axial direction of the main body 101, and in the radial direction of the main body 101 at a position diametrically opposed to the first passage 102. Has been formed. The expansion orifice 106 has a second valve chamber 113.
Is connected to the passage 103. Expansion orifice 106 is the valve chamber
It has a valve seat that opens into 113. The valve body 107 is the valve chamber 113
It consists of a sphere placed inside. This sphere has a spring 10
It is fixed to the upper surface of a disk 114 supported by the inner end of 8.
The outer end of the spring 108 is supported on the inner surface of the bottom wall of a substantially cup-shaped balance adjusting screw 115 screwed into the valve chamber 113 via an O-ring 116. Therefore, the balance adjustment screw
By turning 115, the spring force pushing the valve body 107 toward the valve seat is adjusted.

The greenhouse 110 is provided on the upper end side of the main body 101. More specifically, the outer peripheral edge portions of two substantially circular cap-shaped members 117 and 118 separate from the main body 101 are fixed to each other with the outer peripheral edge portion of the diaphragm 112 being airtightly sandwiched, and the outer cap member 117 and the diaphragm. The greenhouse 110 is formed between this and the greenhouse 112. The inner peripheral edge of the inner cap-shaped member 118 is integrally connected to the cylindrical portion 118a, and this cylindrical portion 118a is connected to the main body 101.
Low-pressure refrigerant chamber 11 consisting of a recess formed in the center of the upper end surface of the
It is hermetically fitted on the inner surface of 1. Gas of a refrigerant (for example, R-12) used in the refrigeration cycle is enclosed in the greenhouse 110.

In the illustrated embodiment, the third passage 104 connected to the evaporator 4 and the fourth passage 105 connected to the compressor 1 are aligned with each other and communicate with each other in the low pressure refrigerant chamber 111 and the second passage 103. Formed in the main body 101 and extends in the radial direction thereof. In the main body 101, a first central shaft hole 119 is formed that extends in the axial direction from the example pressure refrigerant chamber 111 to the joining portion (connecting portion) of the third and fourth passages 104 and 105. Similarly, a second central axial hole 120 extending axially from the meeting portion of the third and fourth passages 104, 105 to the second passage 103.
Are formed in the main body 101. Therefore, although the first and second central shaft holes 119 and 110 are axially aligned with each other, the first central shaft hole 119 has a larger inner diameter than the second central shaft hole 120. The lower half of the second central shaft hole 120 has a smaller diameter than the upper half thereof, and the lower half of this small diameter is the expansion orifice.
It is axially aligned with 106.

On the surface of the diaphragm 112 facing the low pressure refrigerant chamber 111, a contact member 121 made of a material having good heat conductivity is attached. Plungers 122 made of a material having good thermal conductivity (for example, stainless steel) are axially movably arranged in the holes 119 and 120 at the first and second centers. Plungeer 1
The upper end of 22 abuts on the downward bottom surface of the downward recess formed in the center of the lower surface of the contact member 121, and the lower portion of the plunger 122 has an inner surface of the large-diameter upper half of the second central shaft hole 120 and the O-ring 123. Airtight sliding contact through. The gap between the first central shaft hole 119 and the plunger 122 forms an axial passage 119a, and this passage 119a communicates the meeting portion of the third and fourth passages 104, 105 with the low pressure refrigerant chamber 111. . A pin 109 having a diameter smaller than that of the plunger 122 projects from the lower end of the plunger 122 and slidably penetrates the lower half of the second central shaft hole 120, and the lower end of the pin 109 has a second passage 103 and an expansion orifice 106.
To reach the valve body 107. Ie pin 1
The lowermost end of 09 is in contact with the surface of the sphere forming the valve body 107.

A bypass passage 124 is formed in the main body 101 between the second passage 103 and the fourth passage 105. The upstream end of the bypass passage 124, that is, the second passage 103.
The end opened to the downstream end is the fourth passage.
The diameter is smaller than that of the end opening at 105, and a valve seat is formed between the two. A valve body 125 made of a sphere is elastically pressed against the valve seat by a coil spring 126. The end of the coil spring 126 is supported by an adjusting screw 127 that is screwed into an internal screw formed at the downstream end of the bypass passage 124, and the adjusting screw 127 has a small hole at its center. The valve body 125 and the valve seat which cooperates with it constitute the bypass valve 128.

Next, the operation of the expansion valve 200 described above will be described.

The liquid refrigerant from the receiver 3 passes through the first passage 102 and the valve chamber 113.
From this valve chamber, it passes through the expansion orifice 106 and enters the second passage 103, but when it passes through the expansion orifice, it is decompressed and its volume increases to become a gas-liquid two-phase refrigerant. This refrigerant enters the evaporator 4 from the second passage 103 and evaporates therein to become a gas refrigerant. This gas refrigerant enters the third passage 104,
The fourth passage 105 connected to the passage 104 goes toward the compressor 1. At this time, from the evaporator 4 to the third passage
The heat of the gas refrigerant entering 104 causes the plunger 122 and the contact member.
Since it is transferred to the diaphragm 112 through 121 and the heat of this diaphragm is transferred to the gas in the greenhouse 110, the pressure in the greenhouse 110 changes according to the temperature of the gas refrigerant from the evaporator 4. In other words, the greenhouse 110 senses the state of the gas refrigerant passing through the third and fourth passages 104,105.
On the other hand, since the pressure of the gas refrigerant in the third and fourth passages 104, 105 acts on the low-pressure refrigerant chamber 111 via the passage 119a, this pressure acts on the lower surface of the diaphragm 112. In addition, the spring force of the spring 108 that pushes the valve body 107 upward is also pinned.
It acts on the lower surface of the diaphragm 112 via 109, the plunger 122, and the contact member 121. Therefore, the valve body 1 for the valve seat
The position of 07, and hence the opening of the expansion orifice 106, is determined by the position where the differential pressure between the two chambers 110 and 111 and the spring force of the spring 108 are balanced, and thus the expansion valve 200 is normally operated. The flow rate of the refrigerant sent from the evaporator to the evaporator 4 is adjusted.

When the compressor 1 is rotating at high speed, or when the cooling load is increased, or when the overheating of the compressor is a problem,
The refrigerant circulation amount increases, and the refrigerant pressure loss in the evaporator also increases. Therefore, the pressure difference between the second passage 103 and the fourth passage 105 increases, and the valve body 125 pressed by the spring 126 resists the pressing force and opens according to the pressure difference. Open to. As a result, the gas-liquid two-phase refrigerant having an excellent cooling capacity immediately after the expansion orifice 106 is bypassed by the bypass passage 124.
Through the second passage 103 to the fourth passage 105, where it is mixed with the gas refrigerant from the evaporator 4, so that the temperature of the gas refrigerant decreases. In this way, the refrigerant whose temperature has dropped is sucked into the compressor 1, so that overheating of the compressor is prevented.

Since the bypass passage 124 is formed toward the outlet of the fourth passage 105, the bypass passage 124 extends from the second passage 103 to the evaporator 4
The temperature of the refrigerant that bypasses and flows into the fourth passage 105 is
It does not affect the temperature measuring function of the plunger 122 that transmits the temperature of the gas refrigerant from the evaporator to the greenhouse 110.

Further, the pressing force of the spring 126 for pressing the valve element 125 constituting the bypass valve against its valve seat can be freely selected,
If it is too strong, the superheat prevention effect will weaken, and on the contrary,
If it is too weak, the cooling capacity will be deteriorated. Therefore, it is preferable to set the bypass valve 128 in consideration of the diameter of the bypass valve 128 so as to be approximately 0.3 to 0.8 kg / cm ² .

FIG. 3 is a P-i diagram (Mollier diagram) showing a comparison between the control by the conventional expansion valve 100 shown in FIG. 2 and the control by the expansion valve 200 of the above-mentioned embodiment, and the solid line in the figure. Shows the expansion valve 100, and the broken line shows the expansion valve 200 when the bypass valve 128 is opened. In the conventional refrigeration cycle using the expansion valve 100, the gas refrigerant compressed to B is radiated by the condenser and the receiver until it reaches C, and the expansion valve 10 is expanded from C to D.
Adiabatic expansion is performed at 0, heat is exchanged from the D to A by an evaporator, the A state enters the compressor, and the A to B are compressed. On the other hand, in the refrigeration cycle using the expansion valve 200, in the fourth passage 105, the gas refrigerant from the evaporator 4 and the gas-liquid two-phase refrigerant from the bypass passage 124 are mixed, and the temperature of the refrigerant entering the compressor is increased. Is lowered, so that it returns to the compressor in the state of A ', which has a lower enthalpy (i) than A, and is compressed by the compressor and discharged in the state of B'.

As can be seen from FIG. 3, the superheat SH _I when the expansion valve 200 is used is much smaller than the superheat SH _P when the conventional expansion valve 100 is used, and the compressor discharge temperature is correspondingly lower. Become. In the Mollier diagram in Fig. 3, the temperature at point B is 110 ° C and the temperature at B'is 95 ° C.
Although the difference is 15 ° C., about 6% of the refrigerant flow rate generated by the compressor is sufficient as the refrigerant flow rate through the bypass passage 124 to obtain such a temperature difference.

In the above embodiments, the bypass passage 124 is provided between the second passage 103 and the fourth passage 105, but
Any position between the entrance of the passage 104 and the exit of the fourth passage and the second passage may be used. That is, for example, it may be provided between the second passage 103 and the third passage 104. This is because the refrigerant flows through the bypass passage 124 only in the abnormal time, and the flow rate thereof is very small compared with the refrigerant flow rate entering the third passage 104 from the evaporator 4, so that the temperature measuring action of the plunger 122 is prevented. The impact is very small. Further, the valve body 125 of the bypass valve 128 is formed of a sphere, but this is not limited to a sphere, and may be a cone or a flat plate. Further, the spring 126 of the bypass valve is not limited to the coil spring, but may be a disc spring or the like.

Effects As is clear from the above description, the refrigeration cycle expansion valve 200 of the present invention performs a normal expansion valve action during normal operation of the refrigeration cycle, and when the compressor overheat becomes a problem, the bypass valve 128 is used. Open and expand Orifis 1
Immediately after 06, the gas-liquid two-phase refrigerant, which is rich in cooling capacity, is supplied to the fourth passage 10
Since it is flowed to 5 and mixed with the gas refrigerant from the evaporator, the refrigerant returning to the compressor is sucked into the compressor after the temperature is lowered.Therefore, the conventional expansion valve 100 has the bypass passage 124 and the bypass valve 128 having a simple structure. Only by providing it, it is possible to reliably prevent overheating of the compressor.

[Brief description of drawings]

FIG. 1 is a block diagram showing a refrigeration cycle using an expansion valve according to an embodiment of the present invention, FIG. 2 is a block diagram of a refrigeration cycle using a conventional expansion valve, and FIG. 3 is FIG. 1 and FIG. It is a P-i diagram (Mollier diagram) used for description of the operation of the expansion valve shown in the figure. 1 ... Complexer, 2 ... Capacitor, 3 ... Receiver, 4 ... Evaporator, 200 ... Expansion valve, 101 ... Main body, 102 ... First passage, 103 ... Second passage, 104 ...
Third passage, 105 ... Fourth passage, 106 ... Expansion orifice, 107 ... Valve body, 110 ... Sensing greenhouse, 112 ... Diaphragm, 122 ... Plunger, 124 ... Bypass passage, 128 ...
… Bypass valve.

Claims (1)

[Claims] 1. A first passage for receiving a high-pressure liquid refrigerant, and a second passage for communicating a low-pressure gas-liquid two-phase refrigerant passing through the expansion orifice and communicating with the first passage through an expansion orifice toward an evaporator. An expansion valve for a refrigeration cycle, comprising: a passage, a third passage for receiving a refrigerant from the evaporator, and a fourth passage communicating with the third passage and returning the refrigerant from the evaporator to a compressor. A bypass passage is provided between the second passage and a position between the inlet of the third passage and the outlet of the fourth passage, and the pressure of the refrigerant in the second passage and the pressure of the refrigerant from the evaporator. An expansion valve for a refrigeration cycle, comprising a bypass valve that opens and closes the bypass passage in accordance with a pressure difference between the bypass valve and the expansion valve.