Degree-of-supercooling control type expansion valve

Abstract: An expansion valve of the degree-of-supercooling control type can be easily adjusted when assembling the degree-of-supercooling of a high-pressure refrigerant control to be held constant if an exerting force adjusting member (7,7') is used for finely adjusting the exerting force. If either a throttling portion (8,8') or a valve seat (4,4') is formed with said exerting force adjusting member (7,7') a simple and compact design or construction can be achieved.

Description: The invention relates to a degree-of-supercooling control type expansion valve upstream of an evaporator in a refrigerating cycle and containing a valve seat, a valve body, a throttling portion and a force exerting means biasing said valve body towards said valve seat, according to the preamble part of claim 1. A conventionally used expansion valve in a refrigerating cycle is a so-called temperature type expansion valve controlling the discharge of a refrigerant entering an evaporator in response to the temperature and the pressure of a low-pressure refrigerant discharge from the evaporator. Instead of a temperature type expansion valve and disclosed in Laid-Open JP-application SHO 56-7959 an expansion valve of a degree-of-supercooling control type can be used. Said expansion valve is designed with a simple configuration and is able to constantly control the degree-of-supercooling of the high-pressure refrigerant. This allows to achieve a very simple, compact configuration of the valve and the refrigerating cycle. However, said known expansion valve of the degree-of-supercooling control type has a drawback because the degree-of-supercooling cannot be adjusted finely when the valve is assembled, which degree-of-supercooling, however, must be kept constant, e.g. in a series of production of a identical valves of said type. US-A-5,004,008 discloses a refrigerant flow metering device the metering piston of which is loaded by a coil spring symmetrically surrounding the longitudinal axis of the metering piston. In an open state of the metering piston the flow dynamics of the refrigerant may cause lateral vibrations of the metering piston. US-A-4,194,527 discloses a pressure limiting valve for general hydraulic applications. A valve disk secured to a guide rod is moveable in relation to a valve seat opening. The guide rod guided in a stationary abutment and is titled sidewardly relative to the abutment to apply an eccentric force on the valve disk in order to achieve damping effect. DE-A-30 45 892 discloses an expansion valve for a refrigerating system. Vibrations of a valve body in relation to a stationary valve seat are suppressed by a liquid cushion generated at the upstream side of the expansion valve by at least one throttling line. Further prior art is to be found in US-A-5,264,438, US-A-4,614,327, US-A-4,896,696, EP-A-09 87 505 and CH285258. It is an object of the present invention to provide an expansion valve of the degree-of-supercooling control type which can be finely adjusted when being assembled in order to keep the degree-of-supercooling of a high-pressure refrigerant constant and without losing the simplicity and compactness of the construction. The above-mentioned object can be achieved by providing an exerting force adjusting member for finely adjusting the exerting force and by forming either the throttling portion or the valve seat structurally with the exerting force adjusting member. Said exerting force adjusting member is provided such that it allows to adjust the exerting force either during assembly or even after assembly of the expansion valve in a series of such expansion valve having identical structural features. Said adjustment can be carried out in order to keep the degree-of-supercooling of a high-pressure refrigerant constant, e.g. among a series of identical expansion valves. In case that said exerting force adjusting member simultaneously is forming said valve seat, it does indirectly support said force exerting means via said valve body. In case that said exertion force adjustment member simultaneously is forming said valve seat, said throttling portion is formed with said valve body co-operating with said valve seat. In both cases said exerting force adjusting member is carrying out a dual function, while in the second case even the valve body is carrying out a dual function. As a result the overall design is simplified. The dimensions of the expansion valve can be kept compact. Alternatively, with said valve seat formed with said exerting force adjusting member said counterfort is formed with said throttling portion. Also in this case, both components carry out dual function. Alternatively, with said throttling portion formed with said exerting force adjusting member said counterfort is formed with said valve seat. Again, said counterfort and said force exerting adjusting member fulfil dual functions and allow to achieve a compact and structurally simple design. According to a further aspect of the invention both said exerting force adjusting member and said counterfort are formed with a respective valve seat and two opposed valve bodies are associated to both valve seats so that both valve bodies are biased in opposite directions by a common force exerting means and both valve bodies being formed with respective throttling portions. In this case both valve seats are located oppositely with a certain intermediate distance between them. A controlled flow in both directions is possible, which might be desirable e.g. for a refrigerating cycle also used as a heating cycle. This design results in a bi-directional expansion valve. In the latter case it is desirable to have check valves restricting the inflow of refrigerant from the external side into the expansion valve. Structurally simple said check valves are integrated into the throttling portions wherein the throttle openings simultaneously constitute valve seats for the check valves. Said force exerting means can be at least one spring. Advantageously, said spring is made from a shape memorising alloy providing a temperature depending variable spring constant. Of particular advantage is if the spring is responsive to a temperature rise in the refrigerant by a spring constant increase. This leads to the positive effect that the degree-of-supercooling as controlled constantly increases when a load for the refrigerating cycle is large and consequently the temperature of the refrigerant starts to rise. Thereby, the cooling power increases permitting the adaptation of the cooling effect to the outside condition. Expediently the force exerting adjusting member is threadably received in the refrigerant passage. This allows to gradually adjust the exerting force or to steplessly vary the preload of the force exerting means. Alternatively, said exerting force adjusting member can be positioned by a press-fit in axial direction within the refrigerant passage in the proper position in order to adjust the exerting force to a desired value. Finally, said throttling portion, which conventionally is a through bore, instead may be shaped with an annular or ring-shaped cross-section. Having the same throttling factor across the throttling portion a ring-shaped throttling portion is providing an enlarged contact surface for the refrigerant leading to the positive effect of a greatly reduced passing sound of the refrigerant. A ring-shaped throttling portion avoids the formation of an undesirable operation noise source. Said ring-shaped cross-section can be formed by discrete ring segments or with a continuous ring shape. Embodiments of the inventions will be described with the help of the drawings. In the drawings is: Fig. 1 A longitudinal section of an expansion valve of the degree-of-supercooling control type, corresponding to a first embodiment, Fig. 2 A longitudinal section of a second embodiment, Fig. 3 A longitudinal section of a third embodiment, Fig. 4 A longitudinal section of a fourth embodiment, Fig. 5 Two cross-sectional detail views of the embodiment of Fig. 4 in section planes A-A B-B, Fig. 6 A longitudinal section of a fifth embodiment, Fig. 7 A longitudinal section of a sixth embodiment, Fig. 8 A longitudinal section of a seventh embodiment, and Fig. 9 A temperature/pressure characteristic diagram illustrating the degree-of-supercooling of the refrigerant by the expansion valve of at least one of the preceding embodiments. In Fig. 1 in the middle of a refrigerant line 1 of a refrigerating cycle of a cooling equipment for an automobile (not shown in detail) a stepped cylindrical body 2 is fixedly arranged. Said cylindrical body 2 is designed to allow that a high-pressure refrigerant flows from the upstream side (left) to the downstream side (right) and into a not shown evaporator. At an edge portion of the mouth of a refrigerant passage hole 3a a valve seat 4 is formed at the inlet side of cylindrical body 2. A valve body 5 is arranged oppositely to valve seat 4 in a state in which valve body 5 is exerted from the downstream side by the exciting force of a compression coil spring defining a force exerting means 6. With a balance between the pressure difference of the refrigerant pressure from the upstream side to the downstream side of valve seat 4 and the force of spring 6, valve body 5 is separated from valve seat 4 in order to control the discharge of refrigerant passing the refrigerant line 1. Valve body 5 has a circular conical surface facing valve seat 4 and is loosely fitted to refrigerant passage hole 3b by means of e.g. three foot pieces 5b projecting from valve body 5 and entering refrigerant passage hole 3b, e.g. in order to guide valve body 5 during its movements in relation to valve seat 4. Valve seat 4 is shown as a conical valve seat. At the downstream side of valve body 5, e.g. three foot pieces 5a protrude from valve body 5. Foot pieces 5a are arranged along the inner periphery of refrigerant passage hole 3b, e.g. in order to also guide valve body 5 during its operational movement. As a result, vibrations of valve body 5 due to the dynamic behaviour of a refrigerant flow is suppressed greatly. Noise generation by valve body 5 is avoided or at least suppressed to a large extent. At the downstream end side of cylindrical body 2 and internal thread portion 3c is formed. An exerting force adjusting member 7 formed as a nut in this embodiment and having an external thread is threadably received in internal thread portion 3c. Compression coil spring 6 directly abuts against member 7. The other end of spring 6 is abutting the rear side of valve body 5 within a cavity confined by foot pieces 5a. During assembly, or even after assembly, of the expansion valve the exerted force of the compression coil spring 6 applied to valve body 5 can be finely adjusted arbitrarily. For example, in the centre line of member 7 a refrigerant passage hole is drilled defining a throttling portion 8 for generating an adiabatic expansion to the passing refrigerant. Said throttling portion 8 at least partially is formed very thin in order to define a flow restrictor. To the downstream side of the expansion valve a not shown evaporator is connected. The refrigerant passing throttling portion 8 is sent to the evaporator while being subjected to an adiabatic expansion. The high-pressure refrigerant at the upstream side of valve seat 4 is a liquid in supercooled state. The refrigerant looses supercooling due to foams occurring within the liquid after passing through the operating nip between valve seat 4 and valve body 5. Therefore, if the degree-of-supercooling of high-pressure refrigerant at the upstream side is lowered, the amount of foam in the refrigerant downstream of valve seat 4 is increasing, and, as a result, the discharge of refrigerant is decreasing as well, and the degree-of-supercooling of the refrigerant at the upstream side is increasing again. To the contrary, if the degree-of-supercooling of the high-pressure refrigerant at the upstream side of expansion valve rises, the foam amount in the refrigerant downstream of valve seat 4 is decreasing, and, as a result, the discharge amount of refrigerant is increasing. As a consequence, the degree-of-supercooling of the refrigerant at the upstream side is lowered. By operations of valve 4, 5, the degree-of-supercooling of the high-pressure refrigerant at the upstream side can be maintain constant. By threading exerting force adjusting member 7 inside cylindrical body 2 further inwardly or outwardly, the exerting force of spring 6 can be changed, e.g. during assembly of the expansion valve. In this way the magnitude of the degree-of-supercooling of the high-pressure refrigerant which degree is to be maintained constant can be finely adjusted arbitrarily. Moreover, forming throttling portion 8 in member 7 leads to an extremely simple and compact configuration. In all embodiments as shown and described, it might be advantageous to coat the throttling portion 8 with a material having good lubricity. A suitable material might be ethylene tetrafluoride resin. Instead a part could be inserted into member 7 forming throttling portion 8 of such material. As a further alternative, member 7 entirely could be formed of such material. With the good lubricating effect of said material clogging of the throttling portion 8 due to sticking of sludge contained in the refrigerant can be prevented. In the embodiment of the expansion valve as shown in Fig. 2 refrigerant passage hole 3a and valve seat 4 both are formed by a narrowed section of a pipe 1a of the refrigerant line 1 (pressing deformation of the pipe). Exerting force adjusting member 7 in this embodiment is disk-shaped and is a press-in member pressed into pipe 1a into a suitable axial position, e.g. during assembly of the expansion valve, and is fixed to the inner periphery of pipe 1a. The degree-of-supercooling finally can be adjusted depending on the axial position of member 7 by solely pressing member 7 into the right position. No threading work is required and a simpler, more compact configuration can be achieved. In the embodiment of the expansion valve shown in Fig. 3 exerting force adjusting member 7' is in the form of a cylindrical member in which the refrigerant passage hole 3a at the inlet side and valve seat 4 at the outlet side are integrally formed. Member 10 is pressed in and fixed to the inner periphery of pipe 1 a of the refrigerant line 1. As a fixed counterfort 10 for spring 6 a disk-shaped member is axially fixed in its position, e.g. by caulking pipe 1a, and with a certain axial distance from member 7' which distance suffices to receive valve body 5 and spring 6. Member 7' indirectly supports the force of spring 6 via valve body 5. Counterfort 10 is formed with throttling portion 8 in the form of a central through bore. The degree-of-supercooling finely can be adjusted by selecting the position of member T when pressing cylindrical member 7' into the pipe section 1a of the refrigerant line 1, e.g. during assembly. A simple and compact design is achieved. In the embodiment of the expansion valve shown in Fig. 4, similar to the embodiment of Fig. 2, exerting force adjusting member 7' is pressed into its proper position into refrigerant passage pipe 1a and is fixed to its inner periphery. Here throttling portion 8 does not have the form of a centre bore but is made with a ring-shaped cross-section as shown in Fig. 5. With a ring-shape of the throttling portion 8 the passing sound of the refrigerant is very quiet compared to a throttling portion with the form of a round hole shape. A ring-shaped cross-section of the throttling portion 8 thus provides the advantage of causing no noise source. Said throttling portion 8 might be formed with a continuous ring-shape as shown in section B-B or can consist of a plurality of separated slots as shown in section A-A. Separated slots are provided in order to form member 7' as one unitary body. In the embodiment of the expansion valve as shown in Fig. 6 (similar to the embodiment of Fig. 4) in the throttling portion 8 a continuous ring-shaped portion (corresponding to section B-B of Fig. 5 is located at the upstream side of the plurality of separated arcuate slots (corresponding to section A-A of Fig. 5). This arrangement leads to the same effect as the form of the throttling portion 8 in Fig. 4. In the embodiment of the expansion valve as shown in Fig. 7 a pair of valve bodies 5, 5' are arranged reversely to each other, and completely the same effect can be obtained even thought the flow of refrigerant may be reversed. This embodiment relates to a so-called bi-directional expansion valve. Valve seat 4 is formed by throttling the pipe 1a itself of the refrigerant line 1. Exerting force adjusting member 7' (a cylindrical body) is pressed in and fixed into pipe 1a. Member 7' is formed with valve seat 4' co-operating with the second valve body 5'. Both valve bodies 5, 5' are arranged oppositely with a certain axial interspace between them for co-operation with their associated to valve seats 4, 4'. Between both valve bodies 5, 5' as force exerting means a compression coil spring 6 is provided so that both valve bodies 5, 5' are exerted towards their valve seats 4, 4'. By adjusting the position of pressed in member 7', e.g. during assembly, the magnitude of the discharge amount of the high-pressure refrigerant to be maintained constant can be finely adjusted. In this embodiment the respective throttling portions 8, 8' are central through holes in both valve bodies 5, 5'. As a result, valve body 5 at the upstream side of the flow of refrigerant performs the discharge control of the refrigerant and throttling portion 8' formed in valve body 5' at the downstream side is acting as the flow restrictor for adiabatic expansion of the refrigerant towards the evaporator. The expansion valve of Fig. 7 is a so-called bi-directional expansion valve. The embodiment shown in Fig. 8 is also a bi-directional expansion valve. In each throttling portion 8, 8' provided in the respective valve bodies 5, 5' furthermore a check valve 11 is arranged blocking the flow from the outer side against the mouth of each throttling portion 8, thereby restricting the inflow of refrigerant from the outside into each throttling portion 8, 8'. Blocking throttling portion 8 at the upstream side avoids a leakage flow of refrigerant. Both check valves 11 are operating automatically. They have a valve body co-operating with a valve seat defined by the mouth of the associated to throttling portion 8, 8'. The valve bodies are guided by foot pieces 5a. The position of press-in exerting force adjusting member 7' determines the exerting force for both valve bodies 5, 5'. As already mentioned, by using a force exerting means 6 (compression coil spring)having a spring constant which varies in response to the temperature so that a temperature rise generates a larger spring constant by using the shape memorising alloy as the material for spring 6, the degree-of-supercooling controlled constantly increases when a load for the refrigerating cycle is large and the temperature of the refrigerant is rising. In consequence, the degree-of-supercooling controlled constantly increases as the load becomes larger and the cooling power becomes larger thereby permitting to adapt the cooling to the outside conditions. Forming either the throttling portion 8, 8' or valve seat 4, 4' with the exerting force adjusting member 7, 7' allows to achieve a very simple, compact configuration. By using the exerting force adjusting member to set the exerting force by selectively varying the axial position of the member a fine adjustment can be performed easily when setting the degree-of-supercooling of the high-pressure refrigerant at the upstream side which should be maintained constant and should be controlled. If the force exerting means is constituted by a spring 6 move from a shape memorising alloy so that the spring constant of the spring increases in response to a temperature rise, the degree-of-supercooling can be controlled more constantly. If the load becomes larger, it can be made much higher to intensify the cooling power, thereby adapting the cooling power corresponding to the surrounding conditions.

Claims: An expansion valve for controlling the degree of supercooling, comprising: a valve seat (4) in a refrigerant passage (1, 1a) upstream of a throttling portion (8) provided within said refrigerant passage (1) through which throttling portion (8) the refrigerant is sent to an evaporator, a valve body (5) for closing/opening said refrigerant passage and arranged opposite to said valve seat (4) loaded by an axial exerting force from a force exerting means (6) provided at a downstream side of said valve body (5), said refrigerant being subjected to adiabatic expansion in a state where the degree of supercooling upstream of said valve seat (4) becomes constant, characterised by a dual function exerting force adjusting member (7, 7') forming either said throttling portion (8, 8') or said valve seat (4, 4') for finely adjusting said exerting force of said force exerting means (6) by its relative axial position within said refrigerant passage, said exerting force adjusting member axial position being selectively fixed by an axial threaded connection or press fit connection between said exerting force adjusting member and said refrigerant passage. Expansion valve as in claim 1, characterised in that said exerting force adjusting member (7) forming said throttling portion (8) is a threadable member formed with an extemal thread engaging into an internal thread section (3c) formed along an inner periphery of said refrigerant passage (1). Expansion valve as in claim 1, characterised in that said exerting force adjusting member (7, 7') forming either said throttling portion (8) or said valve seat (4) is a press-in member pressed in axially and fixed at the selected axial position to the inner periphery of said refrigerant passage (1). Expansion valve as in claim 1, characterised in that said exerting force adjusting member (7') forming said valve seat (4) indirectly supports said force exerting means (6) via said valve body (5). Expansion valve as in at least one of claims 1 to 4, characterised in that said force exerting means (6) is a spring made from a shape memorising alloy providing a temperature depending variable spring constant. Expansion valve as in claim 5, characterised. in that said spring is responsive to a temperature rise of said refrigerant in said refrigerant passage by a spring constant increase, and vice versa. Expansion valve as in claim 1, characterised in that said exertion force adjusting member (7') and an additional spring counterfort (10) both form a respective valve seat (4, 4') to which an own valve body (5, 5') is associated, that both valve bodies (5, 5') are biased in opposite directions by a common force exerting means (6) towards their valve seat (4, 4'), and that both valve bodies (5, 5') each form a respective throttling portion (8, 8'). Expansion valve as in claim 7, characterised in that each of said valve bodies (5, 5') contains an automatically openable check valve (11) blocking in flow direction towards said force exerting means (6), and that each check valve (11) structurally is received within said throttling portion (8, 8') formed by said valve body (5, 5'). Expansion valve as in at least one of claims 1 to 8, characterised in that said throttling portion (8, 8') is formed with a ring-shaped cross-section.

Inventors: HIROTA HISATOSHI, INOUE YUUSUKE, KOYAMA KATSUMI, SAEKI SHINJI, TSUGAWA TOKUMI, HIROTA, HISATOSHI, INOUE, YUUSUKE, KOYAMA, KATSUMI, SAEKI, SHINJI, TSUGAWA, TOKUMI, Hirota, Hisatoshi, c/o TGK Co., Ltd., Inoue, Yuusuke, c/o TGK Co., Ltd., Koyama, Katsumi, c/o TGK Co., Ltd., Saeki, Shinji, c/o TGK Co., Ltd., Tsugawa, Tokumi, c/o TGK Co., Ltd.
Applicants: TGK CO LTD, TGK CO., LTD.
Application year: 1999
Main classification: F25B41
IPC codes: F16K31, F25B41