Expansion valve

Abstract: The present invention provides an expansion valve having a hole on the outer wall of the housing which is sealed with a plug body by an electrical resistance weld, and including a structure to prevent corrosion of the peripheral area of the welded portion on the outer wall of the housing. A heat sensing gas is introduced to a pressure housing via a hole 15 formed on the outer wall 14 of the pressure housing positioned to sense the temperature of the gas-phase refrigerant passing the expansion valve. A plug body 16 formed by cutting a metallic material seals said hole keeping the state where the gas is filled inside the pressure housing. Then the peripheral of the projection weld portion 17 is covered by a corrosion inhibitor 21 so as to prevent water from gathering thereto. The seal of said hole 15 is secured by the projection weld of a line contact portion 162a formed on the tapered surface 162 of the plug body by a cutting process in the circumference direction.

Description: Technical Field of the Invention The present invention relates to expansion valves and, more particularly, to expansion valves applied to a refrigeration systems of air conditioners on vehicles and the like. Background of the Invention FIG 3 shows the prior art structure of an expansion valve placed inside a refrigeration cycle of an air conditioner on a vehicle. The expansion valve comprises a high-pressure refrigerant path 2 where the liquid refrigerant to be decompressed is flown and a low-pressure refrigerant path 3 where the gas-phase refrigerant is flown, further having a valve hole 4 comprising a throttle hole with a small radius positioned on the high-pressure refrigerant path 2 Therefore, the liquid refrigerant flowing into the high-pressure refrigerant path 2 from a receiver tank 32 will experience adiabatic expansion by passing the vaive hole 4 having a small flow area The open-hole portion of the refrigerant flow-in side of said valve orifice 4 is a valve seat, and in this valve seat portion is a ball-shaped valve means 5 positioned so as to change the opening area of the valve orifice 4 Said valve means 5 is supported by a ball receive 7, and a compression coil spring 9 positioned between said ball receiver 7 and an adjusting nut 8 adds force to said valve means 5 toward the closing direction of the valve (pressing said valve means 5 into said valve seat portion of the valve orifice 4). Reference 10 is a pressure housing positioned on the upper end of the valve body 1 for sensing the temperature of the gas-phase refrigerant and comprises a diaphragm 11 for driving the valve means 5 via an operation shaft 6, a sealed chamber 12 for filling the heat sensing gas partitioned by said diaphragm, and a pressure-equivalent chamber 13 connecting to the low-pressure refrigerant path 3. A hole 15 is placed on the outer wall 14 of said housing 10, and when the heat sensing gas is filled from this hole into said sealed chamber, a metallic plug body 16 is utilized to seal said hole 15 on the outer wall keeping the state when the filling is completed. Therefore, said sealed chamber 12 senses the temperature of the gas-phase refrigerant flowing through the low-pressure refrigerant path 3, and following the temperature change of said gas-phase refrigerant the pressure inside the sealed chamber 12 changes On the other hand, the pressure-equivalent chamber 13 positioned on the lower stream of the diaphragm 11 is connected to said low-pressure refrigerant path 3 and has an equivalent pressure as the gas-phase refrigerant flowing through said low-pressure refrigerant path 3, so the diaphragm 11 is displaced by the difference between the pressure inside the sealed chamber 12 and the pressure inside the pressure-equivalent chamber 13. Said displacement is transmitted via the operation shaft 6 to the valve means 5 and the opening of said valve orifice 4 is controlled. Said prior art expansion valves have the hole peripheral area of the housing outer wall 14 and said plug body 16 contacting each other by a tapered surface and welded together by an electrical resistance weld, for example, a projection weld. A concave portion is formed around this projection weld portion, so in order to prevent water from gathering inside said concave portion, a projection 16a of the plug body 16 is inserted to the hole 15 on the outer wall of the housing, and the conical portion 16b of the plug body 16 is welded by a projection weld to form a projection weld portion 17, and the plug body 16 is welded to the outer wall 14 of the housing as is shown in FIG. 4. Then, a corrosion inhibitor 21 of an adhesive and the like is filled on the outer area. The expansion valve having such structure is shown in Japanese Patent Application Laid-Open No. H8-226567 or in EP-A-718 569. In these kinds of prior art expansion valves, the plug body 16 was welded only by projection weld on to the hole 15 on the outer wall of the housing, so the weld strength by the projection weld must be improved in order to perform the seal securely. The present invention provides a heat expansion valve which improves the above-mentioned structure and enables a secure seal of the plug body to the hole on the outer wall of the housing by projection welding only, and preferably at the same time prevents the corrosion of the peripheral of the projection weld on the outer wall of the housing. Summary of the Invention In order to realize the above object, there is provided an expansion valve as defined in claim 1. As a concrete embodiment of the expansion valve of the present invention, the plug body is formed by a cutting process of a metallic material, and the line contact portion in the circumference direction is formed by a cutting bite. In the expansion valve of the present invention having the above-explained structure, a metallic material which went under a cutting process is used as a plug body. The tapered surface of the plug body and the peripheral portion of the hole formed on the outer wall of the housing is welded together by electrical resistance weld, and because the weld is performed on the cutting processed surface, the electrical resistance weld portion is formed on the cutting processed surface. The expansion valve of the present invention further includes a plurality of line contact areas between the tapered surface of the plug body formed by a cutting process and the peripheral portion of the hole, so a plurality of electrical resistance weld areas will be formed on the line contact portion. Therefore, the present invention provides an expansion valve which enables a secure seal of the heat sensing gas inside the pressure housing. Brief Description of the Drawing In the drawing, FIG 1 shows the vertical cross-sectional view showing the main portion of the expansion valve of one embodiment of the present invention; FIG. 2 shows the bottom view of the plug body of the embodiment of FIG 1; FIG. 3 shows the cross-sectional view of the expansion valve positioned inside the refrigeration cycle of the prior art; and FIG. 4 shows the cross-sectional view showing the main portion of the expansion valve of the prior art Detailed Description One embodiment of the present invention will now be explained referring to the drawings FIG 1 is a vertical cross-sectional view of one embodiment of the main portion of the expansion valve of the present invention showing the state where a hole formed on the outer wall of the pressure housing is sealed by a plug body FIG. 2 is a bottom view of the plug body shown in FIG 1 It should be noticed that the structure of the expansion valve of the present invention is basically the same as the expansion valve shown in FIG 3 except for the structure of the plug body for sealing the hole on the outer wall of the housing. Therefore, the same reference number shows either the same or equivalent element As is shown in FIG. 1 and FIG 2, the plug body 160 is formed by a cutting process of a metallic material such as stainless steel, and comprises a projection 160a to be inserted and a conical portion 160b with a tapered surface 162 formed thereto. The tapered surface 162 is formed to have a taper angle in the range of practically 90 to 130 degrees Then, the projection 160a of the plug body 160 is inserted to the hole 15 on the outer wall of the housing, and the tapered surface 162 of the conical portion 160b contacts the peripheral portion of the hole 15, the peripheral portion formed to have a cross-section in a v-shape without a bottom portion having a slope with a tapered angle of about 120 degrees toward the center of the hole 15 and extending toward a lower diagonal direction of the hole The contact surface of the peripheral portion of the hole 15 and the tapered surface 162 is formed to be in the range of 2 mm - 1.5 mm By performing a projection weld, for example, an electrical resistance weld, in such range, the hole 15 could be sealed only by projection weld keeping the state where the heat sensing gas is being filled inside the housing Therefore, a weld portion 17 is formed by projection welding of the cutting processed surface on the tapered surface 162 of the plug body 160 and the peripheral portion of the hole 15 Further, a line contact portion 162a is formed on the tapered surface 162 of the conical portion 160b in the circumference direction of either the same circumference or with a lead This line contact portion 162a in the circumference direction could be formed, for example, by a bite when performing the cutting process of the tapered surface 162 The existence of the line contact portion 162a in the circumference direction enables the projection weld to be performed in a plurality of areas of the peripheral portion of the hole 15 on the outer wall 14 of the housing, and the weld portion 17 could be welded securely, thus improving the sealing character of the pressure housing Then, a concave formed in the periphery of the projection weld portion 17 is filled with a corrosion inhibitor 21 for preventing rust, as was explained regarding FIG. 4. The filling of the heat sensing gas to the sealed chamber of the housing 10 is performed in the below method The pressure housing 10 including an operation shaft 6 and a diaphragm 11 is held in a fixed state where the hole 15 on the outer wall of the housing is positioned facing upwards between a metallic lower block and a non-metallic upper block In this state, the air inside the inner space of the upper block is aspirated The state inside the sealed chamber 12, therefore, will nearly be vacuum Then, the heat sensing gas is injected and filled inside the sealed chamber Then, a movable plunger inside the upper block is pushed down, and the plug body 160 supported by the plunger is inserted to the hole 15 on the outer wall of the housing, and the conical portion 160b of the plug body 160 contacts the peripheral of the hole on the outer wall 14 of the housing Then, a voltage for performing the projection weld is impressed to the plunger and the lower block, and the contact portion between the outer wall 14 of the housing and the plug body 160 is welded together keeping the state where the gas is being filled inside the sealed chamber Further, the operation of the expansion valve of the present invention comprising a pressure housing having a structure where the hole on the outer wall of the housing is sealed by a plug means shown in FIGs 1 and 2 is the same as the operation of the expansion valves of the prior art shown in FIG 3. That is, the hole 15 formed on the outer wall 14 of the housing 10 is sealed by a metallic plug body 16 so as to keep the gas-filled state inside the housing Therefore, a sealed chamber 12 senses the temperature of the gas-phase refrigerant flowing through a low-pressure refrigerant path 3, and the pressure inside the sealed chamber 12 changes according to the temperature change of the gas-phase refrigerant. On the other hand, a pressure-equivalent chamber positioned on the lower stream of a diaphragm 11 is connected to the low-pressure refrigerant path 3 and its pressure is the same as the pressure of the gas-phase refrigerant flowing through the low-pressure refrigerant path 3. Therefore, the diaphragm 11 is displaced according to the pressure difference between the pressure inside the sealed chamber and the pressure inside the pressure-equivalent chamber, and this movement is transmitted via a operation shaft 6 to a valve means 5, and thus controls the opening of the valve orifice 4. The expansion valve of the present invention has a peripheral portion of a hole formed on an outer wall of a housing for filling a heat sensing gas into the housing and a plug body formed by cutting a metallic material for sealing said hole, the contact portion of which are welded by electrical resistance weld to the cut surface. By incorporating such structure, the seal of the hole by said plug body is secure only by the electrical resistance weld, and the seal character of said housing could be improved. Further, the peripheral of the welded portion on the outer wall of the housing is preferably filled by a corrosion inhibitor so that water or vapor is prevented from gathering to the area, and rust is prevented from occurring. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: An expansion valve comprising: a valve body (1) having a high-pressure refrigerant path (2) for flowing a liquid-phase refrigerant to be decompressed and a low-pressure refrigerant path (3) for flowing a gas-phase refrigerant and having a valve orifice (4) formed inside the high-pressure refrigerant path (2); a valve means (5) positioned close to the valve orifice (4) of the valve body (1) for changing the opening of the valve orifice (4); a pressure housing (10) formed on the valve body (1) for sensing the temperature of the gas-phase refrigerant having a diaphragm (11) for driving the valve means (5) for controlling the movement of the valve means (5), a sealed chamber (12) partitioned by the diaphragm (11) for filling a heat sensing gas, and a pressure-equivalent chamber (13) connected to the low-pressure refrigerant path (3); and a plug body (16) positioned inside a hole (15) formed on an outer wall (14) of the pressure housing (10) to seal the heat sensing gas filled inside the sealed chamber (12), the plug body (16) having a line of contact portion (162a) formed on a tapered surface (162) of the plug body (16) contacting the periphery of the hole (15) in the circumferential direction, the plug body (16) and the periphery of the hole (15) being welded together by an electrical resistance weld, characterized in that the plug body (16) is formed by a cutting process of a metallic material, a plurality of concentrically spaced projections being provided on the line of contact portion (162a), so that a plurality of electrical resistance weld areas is formed on the line contact portion (162a). The expansion valve according to claim 1, wherein the line contact portion (162a) is formed by a cutting bite. The expansion valve according to claims 1 or 2, wherein the tapered surface (162) is tapered at an angle in a range of practically 90 to 130 degrees. The expansion valve according to one or more of claims 1-3, further comprising a corrosion inhibitor covering the peripheral of the welded portion.

Inventors: KOBAYASHI KAZUTO, MINOWA MASAKATSU, KOBAYASHI, KAZUTO, MINOWA, MASAKATSU, Kobayashi, Kazuto, c/o Fujikoki Corporation, Minowa, Masakatsu, c/o Fujikoki Corporation
Applicants: FUJIKOKI CORP, FUJIKOKI CORPORATION
Application year: 1997
Main classification: F25B41
IPC codes: B23K11, F25B41