Expansion valve

Abstract: An expansion valve (10) for controlling the flow rate of refrigerant supplied to an evaporator (1) of a refrigerating system comprises a temperature-sensing chamber (30) entirely provided within the housing (11) of said expansion valve in a low pressure passage (12) thereof. Said passage (13) is connected to the outlet of said evaporator (1) and the inlet of a compressor (2), for converting a temperature change into a pressure change in order to actuate a valve mechanism (20) in response to a rise and lowering in pressure of said temperature-sensing chamber to open and close a passage (13) for adiabatic expansion of the refrigerant. Said temperature-sensing chamber (30) contains a sealed gas charge and an adsorbent material (35) for adsorbing and releasing said gaseous medium in accordance with temperature changes sensed.

Description: The invention relates to an expansion valve according to the preamble part of claim 1. In a known expansion valve (US-A-4819443) the hole in the housing is formed from the side of the housing which is adjacent to the passage for adiabatically expanding the refrigerant. The diameter of the hole remains unchanged toward the innermost blind end which is situated in the low-pressure passage. The outer diameter of the connection means connecting the chamber and the valve mechanism body, which outer diameter restricts the pressure responsive area of the diaphragm wall, has to be smaller than the diameter of the hole. Consequently, the actuation force for the valve as generated by the diaphragm wall is restricted. For that reason, the valve is biased in its closing direction only by a weak spring and only the low pressure at the inlet of the evaporator. The valve member is pressure balanced with respect to the high reservoir outlet pressure. This design leads to a compact chamber/valve assembly unit. However, the restricted actuation force of the diaphragm wall and the low counterforce of the pressure-balanced valve member leads to a sensitive response behavior of the expansion valve to high pressure differences or pressure difference variations. In refrigerating systems with a modern load-controlled compressor the response behavior of the expansion valve negatively influences the operation particularly with extreme working- and load-conditions. Another type of expansion valve is known from FR-A-2535483. The temperature sensitive chamber is equipped with a diaphragm wall having a relatively big pressure responsive area. The temperature sensitive chamber is provided outside the housing and is directly affected by the ambient temperature. The valve mechanism contains a ball valve which is biased in a closing direction by a spring and the high reservoir outlet pressure. Moderate ambient temperatures and a low cooling-demand often cause "hunting" of the expansion valve. This means, that the valve periodically and rapidly opens and closes. This instable and undesirable operation may at least partially result from the relatively rapid temperature response of a temperature-sensing chamber containing a charge of pure gaseous medium. The "hunting"-effect might even exclude the desirable use of a modern load-controlled compressor. The first object of the present invention is to provide an expansion valve design so that the operating characteristics (temperature-pressure characteristics) of the temperature-sensing chamber can be set as desired so as to be most conformable to the refrigerating system concerned. A second object is to provide an expansion valve designed so that the temperature-sensing chamber is capable of faithfully sensing the temperature of the refrigerant coming out of the evaporator and accurately effecting the flow rate control without being affected by the ambient temperature. A third object is to provide an expansion valve designed so that the temperature-sensing chamber and the valve mechanism can be readily assembled to and removed from the expansion valve housing. Said objects can be achieved with the features as mentioned in the characterizing part of claim 1. The adsorbent material in the chamber adsorbs gas molecules at relatively low temperatures and releases said molecules at relatively high temperatures. The pressure/temperature curve of the chamber becomes steeper than the relatively flat curve of a conventionally gas-filled temperature sensing chamber. This results in the expansion valve increasing the flow rate of refrigerant compared with the flow rate of an expansion valve with a gas-filled temperature sensing chamber, provided that the superheat condition of the refrigerant is the same. A temperature value can be freely selected at which the new expansion valve closes or opens. With temperatures of the refrigerant lower than said selected temperature value, the new expansion valve is safely maintained closed. An excessive flow rate of the refrigerant towards the evaporator is prevented. Furthermore, it is possible to shift the pressure/temperature curve either in the direction of the temperature or in the direction of the pressure axis. The characteristics of the chamber are no longer fully dependent from Boyle's law or the inherent vapour pressure characteristics of a pure gas charge in the chamber. The adsorbent material allows it to selectively preset the pressure/temperature-characteristics of the temperature-sensing chamber in view of an optimal flow rate of refrigerant under varying operating conditions of the refrigerating system concerned. Due to the adsorbing and releasing effect of the adsorbent material, the chamber responds to temperature changes more slowly than before. "Hunting" of the new expansion valve will be prevented, even when a modern load-controlled compressor is integrated in the refrigerating system, the output of which can be controlled almost to zero despite the fact that the compressor runs with normal speed. Preferred embodiments of the invention are disclosed in the depending claims. A preferable embodiment will subsequently be described with the help of the drawings. In the drawings is: Figure 1 , a schematic view of a refrigerating system, the expansion valve of which being shown in a longitudinal section view, and figure 2, a graph showing in general one possible temperature/pressure-characteristic of a temperature-sensing character of the new expansion valve and the characteristics of a conventionally gas-filled temperature sensing chamber. The present invention may be more fully understood from the description of a preferred embodiment of the invention set forth below, together with the accompanying drawings, in which: Fig. 1 is a sectional front elevational view of one embodiment of the present invention; and Fig. 2 in a graph showing temperature-pressure characteristics which is employed to explain the action of an adsorbent employed in the present invention. Referring to Fig. 1, which shows a refrigerating system according to one embodiment of the present invention, the reference numeral 1 denotes an evaporator, 2 a compressor, 3 a condenser, and 4 a reservoir which is connected to the outlet side of the condenser 3 to accommodate high-pressure liquid refrigerant. The reference numeral 10 denotes an expansion valve. The expansion valve 10 includes a block 11 which is formed with a low-pressure passage 12 for passing low-temperature and low-pressure refrigerant and a passage 13 for adiabatically expanding high-temperature and high-pressure refrigerant. The low-pressure passage 12 has one end (inlet side) 12a thereof connected to the outlet of the evaporator 1 and the other end (outlet side) 12b thereof connected to the inlet of the compressor 2. The passage 13 for adiabatic expansion which is formed in a crank shape has one end (inlet side) 13a thereof connected to the outlet of the reservoir 4 and the other end (outlet side) 13b thereof connected to the inlet of the evaporator 1. The low-pressure passage 12 and the passage 13 for adiabatic expansion are formed so as to be parallel to each other. A hole 14 is bored in the block 11 from the side thereof which is closer to the low-pressure passage 12, the hole 14 vertically extending through the two passages 12 and 13. The diameter of the hole 14 decreases toward the inner side (the lower side as viewed in the figure). The hole 14 does not extend through the block 11 but the innermost portion of the hole 14 terminates within the block 11. A relatively-large bore 14a is formed in the block 11 at the outer side (the upper side as viewed in the figure) of the low-pressure passage 12, the bore 14a opening to the outside of the expansion valve 10. The bore 14a is closed with a plug 15. The reference numeral 16 denotes an O-ring for sealing, and 17 a ring which prevents the plug 15 from coming off. A valve mechanism 20 is provided inside the hole 14. The valve mechanism 20 includes a body 21 which is fitted in the hole 14. The fit portion of the body 21 is sealed with two O-rings 22. A valve seat 23 is formed in the center of the valve mechanism body 21. The arrangement is such that, when the valve seat 23 is closed with a ball valve 25 which is biased toward the valve seat 23 from below by means of a coil spring 24, the passage 13 for adiabatic expansion is closed. The reference numeral 26 denotes a ball valve retainer for supporting the ball valve 25, and 27 an adjusting nut which is in thread engagement with the valve mechanism body 21 for adjusting the level of biasing force from the coil spring 24. A rod 28 is provided in the valve mechanism body 21 in such a manner that it is slidable in the axial direction. The upper end of the rod 28 projects from the valve mechanism body 21, while the lower end of the rod 28 abuts on the upper end of the ball valve 25. Accordingly, if the ball valve 25 is pushed through the rod 28 so as to move downward against the biasing force from the coil spring 24, the passage 13 for adiabatic expansion is opened, and the passage area of the passage 13 changes in accordance with the amount of movement of the rod 28, thus causing a change in the flow rate of the refrigerant supplied to the evaporator 1. A temperature-sensing chamber 30 is provided inside the low-pressure passage 12 between the valve mechanism 20 and the plug 15, the chamber 30 being arranged to change in pressure in response to a change in temperature of the low-pressure refrigerant in the low-pressure passage 12 to thereby drive the rod 28. Since the temperature-sensing chamber 30 is provided inside the low-pressure passage 12, the operation thereof is not affected by the ambient temperature. The temperature-sensing chamber 30 is surrounded by a housing 31, and the lower side thereof is constituted by a diaphragm 32 which is formed from a thin flexible film. A gas which is the same as the refrigerant circulated through the passages 12 and 13 or which is similar in properties to the refrigerant is sealed in the temperature-sensing chamber 30. An injection tube 33 for sealing the gas is crushed at the intermediate portion thereof and an injection port 33a thereof is closed with a silver-alloy brazing material or the like after the gas has been injected into the chamber 30. Accordingly, the temperature-sensing chamber 30 is hermetically sealed completely with the housing 31, the diaphragm 32 and the injection tube 33. A partition plate 34 is secured inside the temperature-sensing chamber 30 with a slight gap provided between the same and the diaphragm 32. The space that is surrounded by the partition plate 34 and the housing 31 is filled with an adsorbent 35. The adsorbent 35 adsorbs the gas in the temperature-sensing chamber 30 when the temperature is relatively low and it releases the adsorbed gas when the temperature is relatively high. For example, activated carbon may be employed as the adsorbent 35. However, any adsorbent may be employed besides activated carbon. The partition plate 34 is provided for the purpose of isolating the diaphragm 32 from the adsorbent 35 to ensure the movement of the diaphragm 32. The partition plate 34 also serves as a stopper which prevents the diaphragm 32 from being excessively deformed toward the inside of the temperature-sensing chamber 30 and thereby damaged or broken. The partition plate 34 is provided with a slit 34a which prevents passage of the adsorbent 35 but allows the gas to pass freely, thereby enabling the levels of pressures at the upper and lower sides of the partition plate 34 to be equal to each other at all times. The temperature-sensing chamber 30 is secured at the lower part thereof to the upper end portion of the valve mechanism body 21. Any means may be employed to secure the temperature-sensing chamber 30. In this embodiment, the chamber 30 is secured by means of caulking using a caulking member 39. It should be noted that the caulking member 39 may be formed as being an integral part of the valve mechanism body 21. The reference numeral 40 denotes a communicating bore for constantly equalizing the pressure at the lower side of the diaphragm 32 with the refrigerant pressure inside the low-pressure passage 12. Thus, the temperature-sensing chamber 30 and the valve mechanism 20 are formed together in one unit through the caulking member 39. The greatest diameter (the greatest outer diameter of the caulking member 39 in this embodiment) is made slightly smaller than the diameter of the plug 15. Therefore, with the plug 15 removed from the block 11 of the expansion valve 10, the temperature-sensing chamber 30 and the valve mechanism 20 can be set inside the block 11 and also removed therefrom in one unit. Accordingly, assembly and maintenance, for example, replacement, of the temperature-sensing chamber 30 and the valve mechanism 20 are facilitated. Even when a trouble which cannot be fixed occurs, it is only necessary to replace the unit comprising the temperature-sensing chamber 30 and the valve mechanism 20 and it is unnecessary to discard the whole expansion valve unit. The top of the rod 28 abuts against the central portion of the lower side of the diaphragm 32 through a backing plate 29. Accordingly, when the pressure inside the temperature-sensing chamber 30 rises relative to the refrigerant pressure inside the low-pressure passage 12, the diaphragm 32 is pushed downward. As a result, the ball valve 35 is pushed downward through the rod 28 to open the passage 13 for adiabatic expansion, thus increasing the flow rate of the refrigerant supplied to the evaporator 1. Conversely, when the pressure inside the temperature-sensing chamber 30 lowers, the diaphragm 32 is pulled up and the ball valve 25 that is constantly biased by the coil spring 24 approaches the valve seat 23 correspondingly, thus reducing the flow rate of the refrigerant supplied to the evaporator 1. The above-described operation is attained on the basis of the fact that the gas inside the temperature-sensing chamber 30 rises and lowers in pressure in accordance with a temperature change and the fact that the adsorbent 35 inside the temperature-sensing chamber 30 adsorbs and releases the gas sealed in the temperature-sensing chamber 30 in accordance with a temperature change. Referring to Fig. 2, which is a graph exemplarily showing the action of the adsorbent 35. When the gas alone is sealed in the temperature-sensing chamber 30, the temperature (T) - pressure (P) characteristic curve is such as that shown by the chain line in Fig. 2, whereas, when the adsorbent 35 is employed, it is possible to obtain temperature-pressure characteristics exemplarily shown by the solid line in Fig. 2. Accordingly, it is possible to control the flow rate of the refrigerant supplied to the evaporator 1 to a level close to an ideal with optimal temperature-pressure characteristics obtained by properly selecting the kind and amount of the adsorbent 35 and the kind and amount of the gas. It is important that the pressure-temperature characteristics of chamber 30 is preset to exactly correspond to not only one optimum super heat setting for one selected particular load value of the refrigerating system, but is further preset to closely approximate to a required optimum operation characteristics of the refrigerating system in a series of different superheat settings corresponding to different load values of the refrigerating system beside the superheat setting belonging to said one particular load value. The pressure-temperature characteristics of chamber 30 can be preset by the volumetric ratio between the charge of gaseous medium and the adsorbent material 35, both contained in chamber 30. The characteristics of chamber 30 can furthermore be preset by the type, the particle size and the amount of the adsorbent material, e.g. activated carbon, and by the pressure of the gaseous medium within chamber 30. Preferably a selected combination of a certain type of the gaseous medium is provided and a selected type of the adsorbent material in chamber 30, using one adsorption performance of the adsorbent material, the adsorption performance of which is different from one type of gaseous medium to another.

Claims: An expansion valve (10) for controlling the flow rate of refrigerant supplied to an evaporator (1) of a refrigerating system, comprising: a housing (11) provided with a low-pressure passage (12) and a parallel passage (13), said low-pressure passage (12) being connected to the outlet of said evaporator (1) and to the inlet of a compressor (2) to pass low-temperature and low-pressure refrigerant; said parallel passage (13) being connected to the outlet of a reservoir (4) accommodating high-pressure liquid refrigerant and to the inlet of said evaporator (1) to abiabatically expand high-temperature and high-pressure refrigerant; a temperature-sensing chamber (30) being entirely provided inside said housing (11) and in said low-pressure passage (12) and being affected by the temperature of the refrigerant in said low-pressure passage (12), said chamber (30) containing a sealed charge of a gaseous medium and an adsorbent material for adsorbing and releasing said gaseous medium in accordance with a temperature change so that said chamber (30) changes in pressure in response to a change in the temperature of the refrigerant in said low-pressure passage, said chamber (30) having a diaphragm wall (32) responding by displacement to pressure changes of said charge in response to a change in the temperature of the refrigerant in said low-pressure-passage (12); and a valve mechanism body (21) with a valve (23,25) in said passage (13), said valve being actuated by displacement of said diaphragm wall (32) in response to a rise and lowering in pressure of said temperature-sensing chamber (30) to open and close said passage (13) for adiabatic expansion of said refrigerant, said chamber (30) being secured at the lower part thereof to the upper end portion of said valve mechanism body (21) by means of an outer connecting means (39) so as to form one assembly unit; said assembly unit being removably mounted in a hole (14) of said housing (11), said hole (14) extending from one side of the housing (11) vertically through both passages (12,13) towards an innermost portion terminating within the housing (11), characterised in that said hole (14) is formed with a diameter decreasing towards the innermost portion and with a relatively large bore (14a) at the side of the low-pressure passage (12), said large bore (14a) opening to the outside of the expansion valve (10) and there being closed with a plug (15), said assembly unit being mounted with said valve mechanism body (21) in the hole (14) and said chamber (30) in said large bore (14a) with the greatest diameter of said connecting means (39) being made slightly smaller than the diameter of said plug (15), so that said chamber (30) is protected against the ambient temperature outside said housing (11) by walls of said housing (11) and said plug (15), said valve (23,25) for opening and closing said passage (13) for adiabatic expansion of the refrigerant being a ball valve provided within said valve mechanism body (21) and being biased by a spring (24) and by the outlet pressure of said reservoir (4), in a direction in which said valve closes said passage (13) and a rod (28) being actuatable by said diaphragm wall (32) acting on the said valve (23,25) in the other direction in which said valve opens said passage (13) for adiabatic expansion of said refrigerant. Expansion valve as in claim 1, characterised in that a partition wall (34) is provided within said chamber (30), that a slight gap is provided between the diaphragm wall (32) and the partition wall (34), and that said partition wall (34) forms a stopper for said diaphragm wall (32) preventing the diaphragm wall (32) from excessive deformations towards the interior of said chamber (30). Expansion valve according to claim 1, characterised in that in use the medium contained in the temperature sensing chamber (30) is the same as the refrigerant contained in the refrigerating system or is a medium having essentially the same inherent vapour pressure characteristics as the refrigerant contained in the refrigerating system.

Inventors: SENDO ISAO, TSUGUWA TOKUMI, SENDO, ISAO, TSUGUWA, TOKUMI
Applicants: CONTROLS GMBH DEUTSCHE, TGK CO LTD, DEUTSCHE CONTROLS GMBH, TGK CO. LTD.
Application year: 1990
Main classification: F25B41
IPC codes: G05D23, F16K31, A44C5, F25B41