Patent Description:
Heretofore, refrigeration cycles used in air conditioning devices installed in automobiles and the like include a thermosensitive expansion valve that controls an amount of flow of refrigerant according to temperature.

For example, Patent Literature <NUM> discloses an expansion valve including an inlet port through which a high-pressure refrigerant is introduced, a valve chamber communicated with the inlet port, and a valve member drive mechanism called a power element arranged at a top portion of a valve body. A spherical valve element arranged within the valve chamber opposes a valve seat opening in the valve chamber, which is operated by a working rod driven by the power element and controls an opening degree of a throttle passage formed between the valve element and the valve seat. Similar valves using a power element are described in Patent Literature <NUM> to <NUM>.

Patent Literature <NUM> discloses a method for manufacturing a power element for a thermal expansion valve including an upper lid member, a receiving member, and a diaphragm interposed between the upper lid member and the receiving member; wherein during a step of charging a working gas is filled in the area between the upper lid and the diaphragm via a single filling hole which is subsequently filled with melted material. Patent Literature <NUM> also discloses a power element according to the preamble of claim <NUM>.

The power element is composed of an upper lid member that constitutes a pressure working chamber, a diaphragm formed of a thin plate that elastically deforms by receiving pressure, and a receiving member fixed to a valve main body. Further, a working gas is sealed in the pressure working chamber formed of the upper lid member and the diaphragm. Moreover, a stopper member is arranged in a lower space defined by the diaphragm and the receiving member.

According to such a power element, when heat transfer is performed between a refrigerant flowing into the lower space from the valve main body and the working gas charged in the pressure working chamber, an inner pressure of the pressure working chamber is relatively increased thereby and the diaphragm deforms in a manner expanding the pressure working chamber, such that pressure is applied to a stopper member that presses the working rod, according to which the valve element is moved away from the valve seat. Meanwhile, if the inner pressure of the pressure working chamber is relatively lowered, the diaphragm returns from the deformed state and the pressure pressing the working rod is lost, such that the valve element is seated on the valve seat.

In general expansion valves, after charging a working gas through a center holeformed at a top portion of the upper lid member, a plug member is sealed onto the center hole by projection welding and the like to prevent leakage of the working gas. Further, the area surrounding the center hole is formed as a tapered surface that is gradually inclined downward toward the center, with the aim to facilitate welding of the plug member. Therefore, water may be pooled on the tapered surface in the area surrounding the plug member after the plug member has been welded onto the center hole. According to the expansion valve disclosed in Patent Literature <NUM>, an anticorrosion material such as an adhesive is injected to fill the tapered surface surrounding the plug member, to thereby cover the area surrounding the welded portion of the plug member by the anticorrosion material such that water is prevented from being pooled in that area.

According to the technique, however, since the plug member is welded to the upper lid member, the number of components is increased, and stress corrosion cracking may be caused by residual stress. Further, since anticorrosion material is filled in the area surrounding the plug member, not only the manufacturing costs of the expansion valve but also the weight of the expansion valve are increased.

In consideration of the above problems, an object of the present invention aims is to provide a method for manufacturing a power element, a power element, and an expansion valve equipped with the power element that enables to reduce the number of components and the weight of the expansion valve, and that is easily manufactured.

In order to achieve the objects mentioned above, a method for manufacturing a power element according to the present invention is defined in claim <NUM>.

Further, the power element according to the present invention is defined in claim <NUM>.

The present invention enables to provide a method for manufacturing a power element, a power element, and an expansion valve equipped with the same, wherein the number of components of the power element and the weight thereof can be cut down, and wherein the power element can be manufactured easily.

In the present specification, a direction from a valve element <NUM> toward a working rod <NUM> is defined as an "upper direction", and a direction from the working rod <NUM> toward the valve element <NUM> is defined as a "lower direction". Therefore, in the present specification, regardless of the orientation of an expansion valve <NUM>, a direction from the valve element <NUM> toward the working rod <NUM> is referred to as the "upper direction".

A general configuration of the expansion valve <NUM> according to the present embodiment will be described with reference to <FIG> and <FIG>. <FIG> is a schematic cross-sectional view illustrating the expansion valve <NUM> according to the present embodiment applied to a refrigerant circulation system <NUM>. <FIG> is a cross-sectional view illustrating a part of a manufacturing process of a power element <NUM> according to the present embodiment. <FIG> is a plan view illustrating a top portion of the power element <NUM> according to the present embodiment in enlarged view, wherein a state immediately prior to welding is illustrated.

In the present embodiment, the expansion valve <NUM> is in fluid connection with a compressor <NUM>, a condenser <NUM>, and an evaporator <NUM>. An axis of the expansion valve <NUM> and the power element <NUM> is denoted as L.

In <FIG>, the expansion valve <NUM> includes a valve main body <NUM> equipped with a valve chamber VS, the valve element <NUM>, an urging device <NUM>, the working rod <NUM>, and the power element <NUM>.

In addition to the valve chamber VS, the valve main body <NUM> includes a first flow path <NUM>, a second flow path <NUM>, an intermediate chamber <NUM>, and a return flow path <NUM>. The first flow path <NUM> is a feed-side flow path, and refrigerant, also referred to as fluid, is supplied to the valve chamber VS via the feed-side flow path. The second flow path <NUM> is a discharge-side flow path, also referred to as an outlet port-side flow path, and the fluid within the valve chamber VS is discharged through a valve communication hole <NUM>, the intermediate chamber <NUM>, and the discharge-side flow path to the exterior of the expansion valve.

The first flow path <NUM> and the valve chamber VS are communicated through a connection path 21a that has a smaller diameter than the first flow path <NUM>. The valve chamber VS and the intermediate chamber <NUM> are communicated via a valve seat <NUM> and the valve communication hole <NUM>.

A working rod insertion hole <NUM> formed above the intermediate chamber <NUM> has a function to guide the working rod <NUM>, and an annular recess <NUM> formed above the working rod insertion hole <NUM> has a function to accommodate a ring spring <NUM>. The ring spring <NUM> applies a predetermined urging force by having a plurality of spring pieces abut against an outer circumference of the working rod <NUM>.

The valve element <NUM> is arranged within the valve chamber VS. When the valve element <NUM> is seated on the valve seat <NUM> of the valve main body <NUM>, the flow of refrigerant through the valve communication hole <NUM> is restricted. This state is referred to as a non-communicated state. However, even if the valve element <NUM> is seated on the valve seat <NUM>, it may be possible to allow a limited amount refrigerant to flow through. Meanwhile, in a state where the valve element <NUM> is left from the valve seat <NUM>, the flow of refrigerant passing through the valve communication hole <NUM> is increased. This state is referred to as a communicated state.

The working rod <NUM> is inserted to the valve communication hole <NUM> with a predetermined clearance formed therebetween. A lower end of the working rod <NUM> is in contact with an upper surface of the valve element <NUM>. An upper end of the working rod <NUM> is fit to a fitting hole 84c of a stopper member <NUM> described later.

The working rod <NUM> can press the valve element <NUM> against the urging force of the urging device <NUM> toward a direction in which the valve is opened. In a state where the working rod <NUM> is moved toward the lower direction, the valve element <NUM> is left from the valve seat <NUM> and the expansion valve <NUM> is opened.

The urging device <NUM> includes a coil spring <NUM> formed by spirally winding a wire having a circular cross-sectional shape, a valve element support <NUM>, and a spring receiving member <NUM>.

The valve element support <NUM> is attached to an upper end of the coil spring <NUM>, and the valve element <NUM> having a spherical shape is welded to an upper surface thereof such that the valve element support <NUM> and the valve element <NUM> are integrated.

The spring receiving member <NUM> that supports a lower end of the coil spring <NUM> can be screwed onto the valve main body <NUM>, and it has a function to seal the valve chamber VS and a function to adjust the urging force of the coil spring <NUM>.

Next, the power element <NUM> will be described. As illustrated in <FIG>, the power element <NUM> includes an upper lid member <NUM>, a diaphragm <NUM>, a receiving member <NUM>, and the stopper member <NUM>.

As illustrated in <FIG>, the upper lid member <NUM> includes a flange portion 82a arranged on an outer circumference, and a truncated cone-shaped portion 82b arranged at a center. Prior to assembly, in the state illustrated in <FIG>, a slit 82c having an arc-shape, that is, C-shape when viewed in an axial direction of the expansion valve, that extends for an angle of approximately <NUM> degrees around a circumference of an axis L is formed on a flat center portion of the truncated cone-shaped portion 82b, and a circular tab 82d is formed at a center surrounded by the slit 82c. The tab 82d is connected to the truncated cone-shaped portion 82b via an end edge 82e illustrated by a dotted line that connects both ends of the slit 82c linearly, and in the state prior to assembly, the tab 82d is in an erected state folded up at the end edge 82e with respect to the truncated cone-shaped portion 82b.

The diaphragm <NUM> is formed of a plate made of a thin metal material, such as SUS, on which multiple concentric circles of concave-convex shapes are formed, and has an outer diameter that is approximately equal to the outer diameters of the upper lid member <NUM> and the receiving member <NUM>.

The receiving member <NUM> includes a first annular flange portion 86a having an outer diameter that is approximately equal to the outer diameter of the upper lid member <NUM>, a first cylindrical portion 86b formed continuously to an inner circumference of the first annular flange portion 86a, a second annular flange portion 86c formed continuously to the lower end of the first cylindrical portion 86b toward the inner side in the radial direction, and a second cylindrical portion 86d formed continuously to an inner circumference of the second annular flange portion 86c. A male screw portion 86e is formed at an outer circumference on a lower end of the second cylindrical portion 86d.

The stopper member <NUM> is formed by connecting an upper flange portion 84a opposed to the diaphragm <NUM> and a main body 84b having a solid cylindrical shape. A fitting hole 84c is formed at the center of the lower end of the main body 84b.

A method for manufacturing the upper lid member <NUM> will be described below. At first, the flange portion 82a and the truncated cone-shaped portion 82b are formed by press-forming a plate member made of metal. At this time, it is preferable to form the slit 82c simultaneously. Further, the tab 82d is pivotably moved starting from the end edge 82e such that the other end is lifted up. Thereby, a relatively large clearance CL is formed between the truncated cone-shaped portion 82b and the tab 82d, as illustrated in <FIG>. Thereby, charging of working gas described later can be performed quickly.

Next, the stopper member <NUM> is arranged between the diaphragm <NUM> and the receiving member <NUM> with the outer circumference portions of each of the upper lid member <NUM>, the diaphragm <NUM>, and the receiving member <NUM> mutually superposed, and the outer circumference portions are subjected to circumferential welding by TIG welding, laser welding, plasma welding and the like and integrated thereby.

Next, regarding the upper lid member <NUM>, a working gas is charged in a space surrounded by the upper lid member <NUM> and the diaphragm <NUM>, which is called a pressure working chamber PO, through the clearance CL formed between the truncated cone-shaped portion 82b and the tab 82d (serving as a step of charging a working gas). Thereafter, as illustrated in <FIG>, the tab 82d is pushed down such that it is flush with the upper surface of the truncated cone-shaped portion 82b, and a laser light LT is irradiated from a laser light source OS to an area in the vicinity along the slit 82c, such that a part of the upper lid member <NUM> constituting the vicinity, in other words, the material constituting the relevant area itself, hereinafter also simply referred to as the material, is melted. As illustrated in <FIG>, the melted material flows to fill and seal the entire slit 82c before being solidified as a welded portion W serving as a sealed mark having an approximately C shape (serving as a step of filling the hole or slit). The welded portion W enables to prevent the working gas from leaking from the pressure working chamber PO. It is also possible to perform laser welding without pushing down the tab 82d.

When assembling the power element <NUM> formed as an assembly to the valve main body <NUM>, the male screw portion 86e provided on the outer circumference of the lower end of the second cylindrical portion 86d of the receiving member <NUM> is screwed onto a female screw 2b formed on an inner circumference of a recessed portion 2a communicated with the return flow path <NUM> of the valve main body <NUM>, as illustrated in <FIG>. When the male screw portion 86e is screwed further onto the female screw 2b, a lower end of the receiving member <NUM> abuts against an upper end surface of an upper end surface of the valve main body <NUM>. Thereby, the power element <NUM> can be fixed to the valve main body <NUM>.

In this state, a seal SL interposed between the power element <NUM> and the valve main body <NUM> prevents leakage of the refrigerant through the recessed portion 2a in a state where the power element <NUM> is attached to the valve main body <NUM>. In such a state, a lower space LS of the power element <NUM> communicates with the return flow path <NUM>, in other words, becomes to have the same internal pressure.

An operation example of the expansion valve <NUM> will be described with reference to <FIG>. The refrigerant pressurized by the compressor <NUM> is liquefied in the condenser <NUM> and sent to the expansion valve <NUM>. Further, the refrigerant subjected to adiabatic expansion in the expansion valve <NUM> is sent out to the evaporator <NUM> and performs heat exchange with air flowing in the circumference of the evaporator <NUM>. The refrigerant returning from the evaporator <NUM> is returned toward the compressor <NUM> through the expansion valve <NUM>, more specifically, through the return flow path <NUM>. At this time, while passing through the evaporator <NUM>, the fluid pressure in the second flow path <NUM> becomes greater than the fluid pressure in the return flow path <NUM>.

The high-pressure refrigerant is supplied from the condenser <NUM> to the expansion valve <NUM>. More specifically, the high-pressure refrigerant from the condenser <NUM> is supplied through the first flow path <NUM> into the valve chamber VS.

When the valve element <NUM> is seated on the valve seat <NUM>, that is, in the non-communicated state, the flow of refrigerant sent out from the valve chamber VS via the valve communication hole <NUM>, the intermediate chamber <NUM>, and the second flow path <NUM> to the evaporator <NUM> is limited. Meanwhile, when the valve element <NUM> is left from the valve seat <NUM>, that is, in the communicated state, the flow of the refrigerant sent out from the valve chamber VS via the valve communication hole <NUM>, the intermediate chamber <NUM>, and the second flow path <NUM> to the evaporator <NUM> is increased. The switching between the closed state and the opened state of the expansion valve <NUM> is performed by the working rod <NUM> connected to the power element <NUM> via the stopper member <NUM>.

In <FIG>, the pressure working chamber PO and the lower space LS divided by the diaphragm <NUM> are provided inside the power element <NUM>. Therefore, when the working gas within the pressure working chamber PO is liquefied, the diaphragm <NUM> and the stopper member <NUM> are lifted, such that the working rod <NUM> moves to the upper direction according to the urging force of the coil spring <NUM>. Meanwhile, in a state where the liquefied working gas is vaporized, the diaphragm <NUM> and the stopper member <NUM> are pushed downward, such that the working rod <NUM> moves to the lower direction. The switching between the opened state and the closed state of the expansion valve <NUM> is performed in this manner.

Further, the lower space LS of the power element <NUM> is communicated with the return flow path <NUM>. Therefore, the volume of the working gas within the pressure working chamber PO is changed according to the temperature and pressure of the refrigerant flowing through the return flow path <NUM>, and the working rod <NUM> is driven. In other words, according to the expansion valve <NUM> illustrated in <FIG>, the amount of refrigerant supplied from the expansion valve <NUM> toward the evaporator <NUM> is adjusted automatically according to the temperature and pressure of the refrigerant returning from the evaporator <NUM> to the expansion valve <NUM>.

According to the power element <NUM> of the present embodiment, working gas can be sealed in the upper lid member <NUM> without providing a plug member, such that the number of components can be reduced, the weight can be cut down, and the manufacturing process can be facilitated. Further, since the center portion of the truncated cone-shaped portion 82b of the upper lid member <NUM> is flat, water is prevented from being pooled in that area, such that there is no need to use an anticorrosion material and costs can be cut down even further.

<FIG> is a plan view of an enlarged view of a top portion of a power element according to a modified example, illustrating a state immediately prior to welding. According to the present modified example, a slit 82Ac having a shape like a symbol formed by removing a horizontal center bar from "E" when viewed in an axial direction about the axis L, or a U-shape when viewed in an axial direction about the axis L is formed to a flat center portion of a truncated cone-shaped portion 82Ab on an upper lid member, and a rectangular tab 82Ad is formed at a center surrounded by the slit 82Ac. The tab 82Ad is connected to the truncated cone-shaped portion 82Ab via an end edge 82Ae illustrated by a dotted line that connects both ends of the slit 82Ac, and in the state prior to assembly, the tab 82Ad is in an erected state folded up at the end edge 82Ae with respect to the truncated cone-shaped portion 82Ab. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated. According to the present modified example <NUM>, the material in a vicinity of the slit 82Ac is heated and melted to seal the slit 82Ac, such that a sealed mark having a shape like a symbol formed by removing a horizontal center bar from "E" when viewed in an axial direction about the axis L, or a U-shape when viewed in the axial direction of the expansion valve will be formed.

<FIG> is a plan view of an enlarged view of a top portion of a power element according to a modified example, illustrating a state immediately prior to welding. According to the present modified example, a slit 82Bc which has a partial shape of a trapezoid when viewed in an axial direction of the expansion valve about the axis L, or a V-shape when viewed in the axial direction of the expansion valve, is formed to a flat center portion of a truncated cone-shaped portion 82Bb on an upper lid member, and a rectangular tab 82Bd is formed at a center surrounded by the slit 82Bc. The tab 82Bd is connected to the truncated cone-shaped portion 82Bb via an end edge 82Be illustrated by a dotted line that connects both ends of the slit 82Bc, and in the state prior to assembly, the tab 82Bd is in an erected state folded up at the end edge 82Be with respect to the truncated cone-shaped portion 82Bb. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated. According to the present modified example <NUM>, the material of a vicinity of the slit 82Bc is heated and melted to seal the slit 82Bc, such that a sealed mark having a partial shape of a trapezoid when viewed in the axial direction of the expansion valve, or a V-shape when viewed in the axial direction of the expansion valve, will be formed. In any of the embodiments and modified examples, the tab can have various shapes.

<FIG> is a cross-sectional view illustrating a portion of a manufacturing process of a power element 8D according to a second embodiment. As illustrated in <FIG>, an upper lid member 82D of the power element 8D includes a flange portion 82Da on an outer circumference side and a truncated cone-shaped portion 82Db at a center. In the state prior to assembly, similar to the first embodiment, a slit 82Dc having an arc-shape, i.e., C-shape, is formed on a flat center portion of the truncated cone-shaped portion 82Db, and a circular tab 82Dd is formed at a center thereof. However, in the state prior to assembly, the tab 82Dd is pushed in with respect to the truncated cone-shaped portion 82Db, and is inclined toward the inner side of the upper lid member 82D. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated.

A laser light LT is irradiated from a laser light source OS to an area in the vicinity of the edge of the slit 82Dc, such that the material constituting the upper lid member 82D in the vicinity of the slit 82Dc is melted, and the melted material fills and seals the entire slit 82Dc before being solidified and forms an arc-shaped, or C-shaped, sealed mark. During the melting process, spattered particles may scatter from the welded portion. According to the present embodiment, as illustrated in <FIG>, since the tab 82Dd is arranged in an opposed manner to the welding portion in the area below the slit 82Dc, the spattered matter scattered from the welding portion is received by the tab 82Dd such that entry thereof into the interior of the upper lid member 82D is suppressed.

<FIG> is a cross-sectional view illustrating a portion of a manufacturing process of a power element 8E according to a third embodiment. As illustrated in <FIG>, an upper lid member 82E of the power element 8E includes a flange portion 82Ea on an outer circumference side and a truncated cone-shaped portion 82Eb at a center. In the state prior to assembly, a small hole 82Ec having an inner diameter of <NUM> or smaller is formed on a flat center portion of the truncated cone-shaped portion 82Eb. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated.

A laser light LT is irradiated from a laser light source OS to a surrounding area of the small hole 82Ec to melt the material, and the melted material fills and seals the entire small hole 82Ec before being solidified to form a welded portion W serving as a sealed mark, as illustrated in <FIG>. The welded portion W prevents the working gas from leaking from the pressure working chamber PO. The flowing of the heated and melted material to the small hole 82Ec and solidifying thereof can be confirmed by cutting and observing the cross section of the welded portion W of the power element, such that it can be specified directly according to the structure.

<FIG> is a plan view of an enlarged view of a top portion of a power element according to a modified example, illustrating a state immediately prior to welding. According to the present modified example, a stepped portion 82Fd that is one step lowered from an upper surface of a truncated cone-shaped portion 82Fb is formed at a circumference of a small hole 82Fc on a flat center portion of a truncated cone-shaped portion 82Fb of an upper lid member. The thinned stepped portion 82Fd is preferably formed by press-forming. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated.

According to the present modified example, with reference to <FIG>, a volume of material that is melted to fill the small hole 82Fc by irradiating the laser light LT from the laser light source OS to the thinned stepped portion 82Fd is reduced, such that rapid welding is realized.

<FIG> is a plan view of an enlarged view of a top portion of a power element according to a modified example, illustrating a state immediately prior to welding. According to the invention, a plurality of pores 82Gc that have a smaller diameter than the small hole 82Ec are formed on a flat center portion of a truncated cone-shaped portion 82Gb of an upper lid member. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated.

According to the invention, the working gas is charged quickly through the plurality of pores 82Gc, and with reference to <FIG>, the pores 82Gc having relatively small cross-sectional areas is filled quickly by irradiating the laser light LT from the laser light source OS to areas between adjacent pores 82Gc.

<FIG> is a cross-sectional view illustrating a portion of a manufacturing process of a power element <NUM> according to a fourth embodiment. As illustrated in <FIG>, an upper lid member <NUM> of the power element <NUM> includes a flange portion 82Ha on an outer circumference side and a truncated cone-shaped portion 82Hb at a center. In the state prior to assembly, a hollow cylindrical portion 82Hc arranged upward is formed on a flat center portion of the truncated cone-shaped portion 82Hb. A center of the cylindrical portion 82Hc constitutes a hole through which the working gas is charged. In other words, the cylindrical portion <NUM> is a portion in the vicinity of the hole through which the working gas is charged. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated.

A laser light LT is irradiated from a laser light source OS to an upper end of the cylindrical portion 82Gc to melt the material, and the melted material fills and seals the inner side of the cylindrical portion 82Hc before being solidified to form a sealed mark. The material melted from the upper end of the cylindrical portion 82Hc can efficiently fill the inner side of the cylindrical portion 82Hc.

<FIG> is a cross-sectional view illustrating a portion of a manufacturing process of a power element 8I according to a fifth embodiment. As illustrated in <FIG>, an upper lid member 82I of the power element 8I includes a flange portion 82Ia on an outer circumference side and a truncated cone-shaped portion 82Ib at a center. In the state prior to assembly, a hollow cylindrical portion 82Ic arranged upward is formed on a flat center portion of the truncated cone-shaped portion 82Ib. A center of the cylindrical portion 82Ic constitutes a hole through which the working gas is charged. In other words, the cylindrical portion 82Ic is a vicinity portion of the hole through which the working gas is charged. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated.

In the present embodiment, after charging the working gas in the pressure working chamber PO, the cylindrical portion 82Ic is squeezed (or crushed) by nipping the cylindrical portion 82Ic from both sides as illustrated in <FIG> using a tool TL equipped with a pair of finger-shaped pressing portions. Then, as illustrated in <FIG>, the laser light LT is irradiated from the laser light source OS to the upper end of the squeezed cylindrical portion 82Ic and the material is melted to seal the squeezed hole. By squeezing the cylindrical portion 82Ic from both sides using the tool TL prior to irradiating the laser light LT, an opening area, i.e., cross-sectional area of the hole, of the cylindrical portion 82Ic can be reduced, such that the irradiation time of the laser light can be shortened.

<FIG> is a cross-sectional view illustrating a portion of a manufacturing process of a power element 8J according to a sixth embodiment. As illustrated in <FIG>, an upper lid member 82J of the power element 8J includes a flange portion 82Ja on an outer circumference side and a dome-shaped portion 82Jb at a center. In the state prior to assembly, a small hole 82Jc is formed on a side surface, i.e., inclined surface inclined with respect to the axis L, of the dome-shaped portion 82Jb. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated.

In a state where the laser light LT from the laser light source OS is irradiated obliquely to the vicinity of the upper portion of the small hole 82Jc to melt the material, the melted material flows downward by gravity to fill and seal the entire small hole 82Jc before being solidified to form a sealed mark. According to the present embodiment, since the top portion of the dome-shaped portion 82Jb is spherical, even if dew condensation water drips from a piping arranged above the expansion valve, the water flows down along the smooth top portion of the dome-shaped portion 82Jb and further flows along the flange portion 82Ja inclined toward the outer circumference edge before dropping down to the outer side of the power element 8J. Thereby, the pooling of dew condensation water can be prevented. Even according to the embodiments described above, the dome-shaped portion can be provided instead of the truncated cone-shaped portion.

<FIG> is a cross-sectional view illustrating a portion of a manufacturing process of a power element <NUM> according to a seventh embodiment. As illustrated in <FIG>, an upper lid member <NUM> of the power element <NUM> includes a flange portion 82Ka on an outer circumference side and a dome-shaped portion 82Kb at a center. In the state prior to assembly, a slit 82Kc and a tab 82Kd as illustrated in <FIG> are formed on the side surface of the dome-shaped portion 82Kb. An end edge 82Ke of the tab 82Kd is arranged above the slit 82Kc, and a lower end side of the tab 82Kd is cut and erected from the dome-shaped portion 82Kb. The other configurations including the diaphragm <NUM>, the stopper member <NUM>, and the receiving member <NUM> are similar to the embodiment described above, such that the same descriptions will not be repeated.

Claim 1:
A method for manufacturing a power element for a thermal expansion valve including an upper lid member, a receiving member, and a diaphragm interposed between the upper lid member and the receiving member, the method for manufacturing the power element comprising:
a step of charging a working gas in an area between the upper lid member and the diaphragm via a plurality of holes formed on the upper lid member; and
a step of heating and melting a material of the upper lid member constituting a vicinity between adjacent holes so as to fill the plurality of holes by the melted material.