Abstract:
To achieve a silent, noiseless operation supercooling degree-controlled expansion valve  10  wherein vibration of a valve element  14  induced by refrigerant flow changes is suppressed and a spring  18  presses valve element  14  in an oblique direction inclined with respect to an axial direction thereof against a surrounding member  12  to thereby restrict vibration of the valve element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     In refrigerating cycles so-called thermostatic expansion valves are widely used. Thermostatic expansion valves are designed to control the flow rate of the refrigerant being introduced into an evaporator in accordance with the temperature and pressure of the low-pressure refrigerant exiting the evaporator. 
     Another possibility to control the flow rate of the refrigerant flowing into the evaporator is to use a so-called supercooling degree-controlled expansion valve, which in contrast to said thermostatic expansion valve detects and controls the degree of supercooling of the high-pressure refrigerant supplied to the evaporator. A supercooling degree-controlled expansion valve performs all required operations at the inlet side of the evaporator without needing any thermostatic equipment or additional temperature or pressure transmitting passages. This is advantageous because a supercooling degree-controlled expansion valve can be made extremely compact. 
     2. Description of the Related Art 
     In a supercooling degree-controlled expansion valve disclosed in U.S. Pat. No. 4,324,112 for example, the valve seat is arranged in a high-pressure refrigerant passage through which the refrigerant is supplied to the evaporator and at a location of an upstream side of a restricted portion formed by narrowing an intermediate portion of the refrigerant passage. The valve element for opening and closing the refrigerant passage faces the valve seat and is urged towards the valve seat by urging means from a downstream side. This valve type is structurally simple and compact and yet is capable of controlling the degree of supercooling of the high-pressure refrigerant at a constant level. However, in said known supercooling degree-controlled expansion valves the valve element freely vibrates due to the refrigerant flow and repeatedly collides against its surrounding member thus producing noise. 
     In high-pressure hydraulic applications it is known to equip, e.g., a relief valve element with a damping piston received in a cylinder chamber to suppress valve rattling. However, supercooling degree-controlled expansion valves need to operate reliably, extremely sensitive and in an environment (most often in the motor compartment of a vehicle) where permanently external vibration and considerable temperature changes occur. For this reason it was believed that the performance of such supercooling degree-controlled expansion valves would unduly suffer when implementing any vibration attenuating measures. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a structurally simple noiseless, silent supercooling degree-controlled expansion valve in which vibrations of the valve element induced by the refrigerant flow are suppressed sufficiently without deteriorating the valve performance, i.e. without harming the capacity of the valve to control an essential constant degree of supercooling. 
     Since the urging means in the supercooling degree-controlled expansion valve is pressing the valve element in an oblique direction inclined with respect to the axial direction of said valve element against a surrounding member or the surrounding when said valve member is moving in relation to said valve seat, noise is prevented from being produced as soon as the valve element has the tendency to collide during vibration under the influence of the refrigerant flow, etc. with its surrounding. Alternatively, a liquid damper using the refrigerant as a vibration absorbing material is coupled to the valve element to restrict vibrations of the valve element. A silent, high-quality supercooling degree-controlled expansion valve can be achieved. 
     A particular simple structure of said expansion valve with a vibration safe valve element is achieved by determining the mechanical co-operation between the compression coil spring and the valve member such that the compression coil spring maintains the valve element during its motions in contact with the lateral surroundings. This either is achieved by a protruding spring turn end contacting the valve element offset to its longitudinal axis or by arranging the active compression coil spring end portion laterally offset with respect to the longitudinal axis of the valve element. Said predetermined co-operation suppresses particularly lateral vibrations of the valve element, because this is maintained in contact with the lateral surroundings while moving in relation to the valve seat, advantageously, said measure does not lead to any detrimental effect on the valve performance. 
     When alternatively coupling the valve element with a liquid damper the refrigerant efficiently can be used to absorb vibrations of the valve element, particularly axial vibrations. The motion of the valve element during operation of the expansion valve sucks in or pumps out refrigerant into or from the cylinder chamber and through a narrow gap. The flow through said narrow gap is restricted and thus suppresses the vibration. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will be described with the help of the drawing. In the drawing is: 
     FIG. 1 a longitudinal section of a first embodiment of an expansion valve in a state where a valve element is lifted from a valve seat, 
     FIG. 2 a longitudinal section as in FIG. 1 with the valve element seated on said valve seat, 
     FIG. 3 a cross-sectional view in section plane III—III of FIG. 2, 
     FIG. 4 a longitudinal section of a refrigerant pipe receiving said expansion valve of FIGS. 1 to  3 , 
     FIG. 5 a longitudinal section of a second embodiment of an expansion valve, 
     FIG. 6 a side view of a third embodiment of a supercooling degree-controlled expansion valve, 
     FIG. 7 a longitudinal section of the third embodiment illustrating a flow direction from the right to the left, 
     FIG. 8 a longitudinal section similar to FIG. 7 illustrating a flow direction from the left to the right, 
     FIG. 9 an enlarged sectional side view of a detail of said third embodiment, 
     FIG. 10 an enlarged sectional side view of another detail of said third embodiment, 
     FIG. 11 a cross-section taken in plane XI—XI in FIG. 9, 
     FIG. 12 a cross-section taken in plane XII—XII in FIG. 9, 
     FIG. 13 a longitudinal sectional view of a fourth embodiment, and 
     FIG. 14 a longitudinal sectional view of a fifth embodiment of a supercooling degree-controlled expansion valve. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to  3  illustrate a first embodiment of a supercooling degree-controlled expansion valve  10 . FIG. 4 shows said expansion valve  10  fitted into a refrigerant pipe  1  of an automobile cooling system, for example. In FIG. 4 high-pressure refrigerant is introduced from an upstream (left) side into refrigerant pipe  1 . Expansion valve  10  abuts against a waist  1   a  formed, e.g. by crimping said refrigerant pipe  1 . A dust-removing filter  11  is attached to an upstream-side half of expansion valve. 
     In FIG. 2 expansion valve  10  is closed. A valve element  14  is resiliently urged from downstream against a valve seat  13  formed in a cylindrical case  12 . Said dust-removing filter  11  (a cap made of fine meshed net) is attached to said cylindrical case  12 . A downstream restricted passage  22  is provided. Dust-removing filter  11  catches impurities greater than a certain size. Accordingly, rubbish, etc. contained in the refrigerant is held back by the filter  11  and is prevented from flowing into the expansion valve or into said restricted passage  22 . O-rings  15  fitted onto cylindrical case  12  seal between said case and the inner surface of refrigerant pipe  1 . 
     Valve seat  13  has inner circular edge at a stepped portion of a refrigerant passage  16  formed in cylindrical case  12 . Said refrigerant passage  16  has an upstream-side passage  16   a  with a small diameter and a downstream-side passage  16   b  with a large diameter. 
     Valve element  14  (FIG. 1) has a closing part  14   a  fitted into the valve seat  13 , a conical part  14   b  facing said valve seat edge from a downstream side, three guide legs  14   c  extending through valve seat  13  and along the inner peripheral surface of the upstream-side passage  16   a,  and three supporting legs  14   d  protruding downstream and extending along the inner peripheral surface of downstream-side passage  16   b.    
     Valve element  14  faces valve seat  13  while being urged from downstream by a compression coil spring  18 , defining said resilient urging means of the expansion valve  10 . Depending on the relative magnitude of the refrigerant pressure difference between the upstream and downstream sides of valve seat  13  and on the urging force of compression coil spring  18 , valve element  14  comes in contact with or is separated from said valve seat edge, in order to control the flow rate of the refrigerant passing through said refrigerant pipe  1 . 
     Said compression coil spring  18  does not have end turns at its opposite ends which end turns would define a plane perpendicular to the longitudinal spring axis, but each end portion is formed by simply cutting the wire member constituting the spring turns. Particularly, a freely terminating turn end is made by cutting the end turn, e.g., perpendicular to the core line of said end turn. Said end turn may extend towards said free turn end with at least essentially the same turn pitch as other spring turns in said compression coil spring. Consequently, the urging force of the compression coil spring  18  acts upon the valve element  14  in a oblique direction inclined with respect thereto. 
     The free turn end of compression coil spring  18  contacts an abutment surface of said valve element  14  which is surrounded by said legs  14   d  and at a force transmission spot which is offset with respect to the longitudinal axis of valve element  14 . Instead or in addition, said abutment surface could be inclined with respect to the longitudinal axis of said valve element  14  by an angle differing from 90°. 
     A spring seat member  20  receives a fixed end portion of said compression coil spring  18 . Seat member  20  is secured to a downstream-side end of cylindrical case  12 . In FIG. 3 spring seat member  20  has an annular restriction defining said restricted passage  22 . It has a small cross-sectional area and is continuing circumferentially distributed refrigerant passage holes  21 . The refrigerant passing therethrough adiabatically expands on the downstream side of said restricted passage  22 . An evaporator (not shown) is connected to the downstream side of expansion valve  10 , so that the refrigerant is introduced into the evaporator while being adiabatically expanded. 
     The high-pressure refrigerant at the upstream side of valve seat  13  is in a supercooled liquid state. After passing the gap between the valve seat edge and lifted valve element  14 , however, it is no longer supercooled but develops bubbles. 
     If the degree of supercooling of the high-pressure refrigerant at the upstream side decreases, more bubbles are produced in the refrigerant on the downstream side of the valve seat  13 , causing a consequent reduction in the refrigerant flow rate. Valve element  14 , therefore, is moved in closing direction (FIG. 2) with the result that the degree of supercooling of the refrigerant at the upstream side does increase again. If the degree of supercooling of the high-pressure refrigerant at the upstream side increases, less bubbles are produced in the refrigerant at the downstream side of valve seat  13 . The refrigerant flow rate increases as well. Valve element  14 , therefore, is moved in opening direction (FIG. 1) thus reducing the degree of supercooling at the upstream side. Thanks to these valve element motions, the degree of supercooling of the high-pressure refrigerant is maintained constant at the upstream side. 
     During its motion valve element  14  remains pressed against the inner peripheral surface of refrigerant passage  16 , since the urging force of compression coil spring  18  is acting upon the valve element  14  in an oblique direction, i.e., is inclined with respect to its axial direction or the direction of its longitudinal axis, respectively. As a result, valve element  14  is never allowed to vibrate freely in lateral directions even if the refrigerant flow changes or more or less bubbles occur, or like occurs, and thus no noise is produced. 
     FIG. 5 (a second embodiment) closing part  14   a  of valve element  14  is not fitted into valve seat  13  (as in FIG.  1 ), but directly abuts against the valve seat  13  from the downstream side to close the refrigerant passage  16 . Valve seat  13  is constituted by an annular, axially extending rib. Closing part  14   a  here is made of an elastic material such as rubber. Other structural features in the operation are the same as with the first embodiment. 
     In FIGS. 7 through 12 a third embodiment is a bi-directional supercooling degree-controlled expansion valve  10  (the refrigerant can flow in opposite directions). In FIG. 6 dust-removing filters  11  are attached to both, front and rear ends of the expansion valve  10 , respectively. 
     In FIGS. 7 and 8 two valve seats  13  are arranged in series and two valve elements  14  are arranged back-to-back between valve seats  13 . Compression coil spring  18  constituting the urging means for both valve elements is interposed between both valve elements  14 . 
     Restricted passages  22  each for adiabatically expanding the refrigerant depending on the flow direction are defined by spherical valve elements  30  arranged within said valve elements  14 . In FIGS. 9 and 10 each valve element  14  has a spherical-valve receiving chamber  32  formed in an intermediate portion of an axially extending refrigerant passage  31  receiving the corresponding spherical valve element  30 . 
     Of the two spherical valve elements  30 , that valve element  30  in the respective upstream-side valve element  14  closes the refrigerant passage  31 , as shown in FIG.  9 . The spherical-valve receiving chamber  32  has a diameter size larger than the diameter of the spherical valve element  30 . A gap is formed around the downstream-side spherical valve element  30 , while this is in contact with and centred by three small protuberances  34  (FIG.  10 ). Restricted passage  22  is defined by said gap in the respective downstream-side valve element  14 . Compression coil spring  18  does not have flattened end turns at its opposite ends but each end portion is formed by simply cutting a wire member, as has been explained in detail in connection with the first embodiment. 
     Consequently, the urging force of compression coil spring  18  acts upon each valve element  14  in an oblique direction inclined with respect to the axial direction of the expansion valve  10 . Thus, the valve elements  14  never are allowed to laterally vibrate when opened or closed due to a change of the refrigerant flow, so that no noise is produced. Instead, they are laterally held in contact with their respective valve seat  13 . 
     In FIG. 13 in a fourth embodiment compression coil spring  18  and valve element  14  are arranged eccentrically with respect to each other, i.e., the longitudinal axis of compression coil spring  18  or at least of its end portion and the longitudinal axis of valve element  14  are offset in lateral direction relative to another. 
     With this eccentric arrangement, even when compression coil spring  18  should have normal flattened end turns formed at its opposite ends, i.e., end turns in planes perpendicular to the longitudinal axes of the coil spring and the valve element, the urging force of the compression coil spring  18  acts upon valve element  14  in an oblique direction inclined with respect to the axial direction thereof. Accordingly, valve element  14  is always pressed against the inner peripheral surface of refrigerant passage  16  and thus is never allowed to vibrate laterally, so that no noise is produced. 
     In FIG. 14 in a fifth embodiment a hydraulic vibration suppressing means is provided. A piston-like part  14   e  formed at the head of valve element  14  is received with a narrow radial gap in a cylinder  40  provided at the upstream-side refrigerant passage  16   a.  With valve element  14  moving, the refrigerant flows into and out of cylinder  40  through said gap defined between piston-like part  14   a  and its cylinder  40 , thus forming a liquid damper using the refrigerant itself as a damping material. Thus, even fine axial vibrations of valve element  14  can be suppressed.