KR20010087152A - Hollow piston for compressor - Google Patents

Abstract

PURPOSE: To lighten a hollow piston, improving durability of the piston. CONSTITUTION: A hollow head part 72 of the piston 14 is provided with a bottomed cylindrical part 120 and a cap 122 for closing opening of the bottomed cylindrical part 120. The cap 122 is formed into a bottomed cylindrical shape provided with a bottom wall 134, a cylindrical large diameter part 136 extending in the axial direction from an outer peripheral part of the bottom wall 134 and a cylindrical small diameter part 139 extending in the axial direction from an inner peripheral part of an end face 138 of the large diameter part 136. An outer peripheral surface 148 of the small diameter part 139 of the cap 122 is fitted into an inner peripheral surface 128 of a cylinder part 126 of the bottomed cylindrical part 120 up to a depth in which the end face 138 and an end face 150 are abutted, and the end face 138 and the end face 150 are coupled by welding. A cap length A to be an axial direction distance from a top surface 146 of the cap 122 to the end face 150 is made larger than thickness B of the bottom wall 134. Therefore, a welding part of the bottomed cylindrical part 120 and the cap 122 becomes far away from a boundary part of the bottom wall 134 to be a portion in which stress concentration is generated when the piston 14 is used and the large diameter part 136.

Description

Hollow piston for compressor {HOLLOW PISTON FOR COMPRESSOR}

The present invention relates to a piston for a compressor, and more particularly to a hollow piston in which the head fitted at least in the cylinder bore is hollow.

The piston for the compressor is reciprocated by the reciprocating drive device to compress the gas. Pistons of this kind usually have a head fitted in the cylinder bore and an engagement portion engaged with the reciprocating drive. Since the piston is reciprocating, it is preferable to be lightweight, so that at least the head fitted with the cylinder bore is hollow. As a method of manufacturing the head of this hollow piston, (a) it is formed integrally with a bottomed cylindrical upper portion having a bottom wall and a cylindrical portion extending in the axial direction from the outer peripheral portion of the bottom wall, and a bottom wall of the bottomed cylindrical upper portion; And a piston body member having an engagement portion integrally engaged with the reciprocating drive, and (b) a disk-shaped blocking member for closing the bottomed cylindrical portion of the piston body member is known. . Joining of both members is proposed to be carried out by welding, friction welding, bonding, physical coupling means (for example, caulking), and the like, and some of them have been put into practical use.

However, the conventional hollow piston manufactured by this kind of method has a problem in that it cannot be sufficiently reduced in weight because the bonding strength must be secured. In the compression stroke when the hollow piston is used, the pressure of the gas to be compressed acts on the blocking member, thereby bending the blocking member into a three-dimensional shape that is convex inwardly of the hollow head. Further, in the suction stroke, an inertial force acts on the obstruction member to bend the obstruction member into a three-dimensional shape that is convex to the outside of the hollow head. Since these curvatures generate stress concentration at the engagement portion between the cylindrical portion of the piston body member and the closure member, thereby lowering the durability of the hollow piston, the closure member has to be thickened to suppress the curvature. In addition, when joining is performed by welding, friction welding, bonding, or the like, in order to increase the bonding strength, the welding area, the pressing area, and the bonding area must be increased, so that the thickness of the cylindrical portion of the piston body member must be relatively thick. As a result, the hollow piston could not be sufficiently reduced in weight.

In view of the above circumstances, the present invention has been made with the object of further reducing the weight while ensuring durability of the hollow piston for a compressor, and according to the present invention, the hollow piston for a compressor of the following aspects is obtained. Each aspect is divided into terms as in the claims, numbered in each term, and described in the form of quoting other term numbers as necessary. This is for the purpose of understanding the present invention to the last, and it is not interpreted that the technical features and combinations thereof described in the present specification are limited to those described in the following sections. In addition, when a plurality of items are described in one term, it is not necessary to always adopt these plurality items. Only a few things can be chosen and adopted.

BRIEF DESCRIPTION OF THE DRAWINGS It is front sectional drawing which shows the swash plate type | mold compressor provided with the hollow piston for compressor which is one Embodiment of this invention.

2 is a front sectional view showing the hollow piston.

Fig. 3 is a front view (partial cross section) showing a piston body member and a closing member constituting a piston production material for producing the hollow piston.

4 is a front sectional view illustrating a method of manufacturing the hollow piston.

5 is a front sectional view showing a part of a hollow piston for a compressor according to another embodiment of the present invention.

6 is a front sectional view showing a part of a hollow piston for a compressor according to still another embodiment of the present invention.

7 is a front sectional view showing a part of a hollow piston for a compressor according to still another embodiment of the present invention.

8 is a front sectional view for explaining a method for manufacturing a hollow piston for a compressor, which is another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

14: migraine piston 70, 166: engaging portion

72: head 120, 170: cylindrical upper part with a bottom

122, 164: cap 124, 172: bottom wall

125, 162: piston body members 126, 174: cylindrical portion

128, 178: inner circumference 134, 192: bottom wall

136, 194: large diameter portion 138, 196: cross section

139, 198: small diameter portion 146: front face

148, 204: outer peripheral surface 150, 220: opening side cross section

300, 400: piston body members 301, 402: cylindrical upper part with a bottom

302, 404: cylindrical section 304, 406: cross section

306, 408: fitting portion 308, 410: inner peripheral surface

320, 420: cap 322, 422: bottom wall

324, 424: cylindrical part 326, 440: outer peripheral surface

328, 430: cross section 338, 444: front

500: lead material

(1) (a) an engagement formed integrally with the bottom wall and the bottom wall having a cylindrical portion extending in the axial direction from the outer circumference of the bottom wall and the bottom wall of the cylindrical section with the bottom and engaged with the reciprocating drive device. The piston body member integrally provided with the portion and (b) the closing member for closing the bottomed cylindrical portion of the piston body member are coupled to each other, thereby providing the hollow head and the engaging portion of the substantially hollow cylindrical portion. A hollow piston for a compressor in a state, wherein the closure member includes a bottom wall and a cylindrical portion extending in the axial direction from the outer peripheral portion of the bottom wall to form a bottomed cylindrical shape, and a cross section of the cylindrical portion of the closure member and the piston body. While the cylindrical sections of the members are in contact with each other, both cylindrical sections are coupled to each other and the cylindrical section is provided at the outer end surface of the bottom wall of the closure member. The distance of the obstruction member to the length of the cross-section, greater than the thickness of the bottom wall of the closure member, and a compressor hollow piston (claim 1), characterized in that less than half of the axial length of the hollow head.

Thus, when a cylindrical part is provided not only in a piston body member but also a closure member, and both cylinder parts are joined in the state which made the end surface of the cylindrical part and the end surface of the cylindrical part of a piston body member contact, both cylinder parts will become later mentioned in detail in the term of embodiment of invention. As will be explained, since the engaging portion is far from the area where stress concentration is likely to occur during elastic deformation of the bottom wall of the blocking member, and the rigidity of the closing member is increased by the formation of the cylindrical portion, the closing member is ensured while ensuring the durability of the hollow piston. It is possible to reduce the thickness of the bottom wall and the thickness of the circumferential wall of the cylindrical portion of the piston body member.

(2) The closure member has a cylindrical fitting portion extending in the axial direction from an end surface inner peripheral portion of the cylindrical portion, and the outer peripheral surface of the fitting portion is fitted to the inner peripheral surface of the cylindrical portion of the piston body member according to (1). Hollow piston for the compressor (claim 2).

When the closure member is fitted inside the fitting portion in this way, relative positioning of the piston body member and the closure member is facilitated, thereby facilitating the coupling of both. In addition, when the bonding is performed by bonding or welding, not only the end faces of the cylindrical portions but also the outer circumferential surface of the fitting portion of the closure member and the inner circumferential surface of the piston body member can be bonded or welded. In this case, the piston body The bonding strength of the member and the occlusion member can be further increased.

(3) The hollow piston for a compressor according to (2), wherein the cylindrical sections of the piston body member and the cylindrical sections of the blocking member are welded together.

Since the weld portion is far from the stress concentration portion, the weight can be reduced while ensuring durability. It is preferable that welding is performed to the inner periphery of the cross section of both cylinder parts. This is because when the inner circumferential portion of the cross section of both cylindrical portions is not welded, the portion acts similar to a crack and the weld portion easily breaks.

(4) The compression according to (2), wherein the cylindrical sections of the piston body member and the cylindrical sections of the closure member, and the outer circumferential surface of the fitting portion and the inner circumferential surface of the cylindrical portion of the piston body member are bonded to each other with an adhesive, respectively. Hollow piston for air (claim 4).

Since the bonding position is far from the stress concentration portion, the stress acting on the adhesive layer may be small, and as described above, weight reduction can be achieved while ensuring durability.

(5) Cross sections of the cylindrical portion of the piston body member and the cylindrical portion of the closing member, the outer peripheral surface of the fitting portion and the inner peripheral surface of the cylindrical portion of the piston body member each have a lower melting point than the material of the piston body member and the closing member, respectively. The hollow piston for a compressor according to (2), which is bonded to each other by a low melting point material (claim 5).

(6) The piston body member has a cylindrical fitting portion extending in the axial direction from an outer peripheral portion of a cross section of the cylindrical portion with the bottom, wherein the inner peripheral surface of the fitting portion and the outer peripheral surface of the closure member are fitted (1) Hollow piston for compressor according to claim (claim 6).

The same effect as described with respect to the above (2) can be obtained.

(7) The hollow piston for the compressor according to (6), wherein the cylindrical sections of the piston body member and the cylindrical sections of the closure member and the inner circumferential surface of the fitting portion and the outer circumferential surface of the closing member are bonded to each other with an adhesive. (Claim 7).

(8) The hollow piston for a compressor according to (6) or (7), wherein a chamfer is performed around the outer end surface of the bottom wall of the closing member, and the tip of the fitting portion is caulked on the chamfer.

(9) The hollow piston for a compressor according to any one of (1) to (8), wherein the closing member length is 1.5 times or more or 2 times or more of the bottom wall thickness of the blocking member.

As the length of the closure member increases, the coupling portion is further away from the stress concentration portion, the stress applied to the coupling portion is closer to the simple compressive or tensile stress, and the rigidity of the closure member is increased. Becomes large. However, the increase rate of the effect decreases as the length of the blocking member increases, while as the length of the blocking member increases, the force acting on the blocking member increases due to friction between the outer circumferential surface of the hollow head and the inner circumferential surface of the cylinder bore. The stress in is increased. From this point of view, it is not preferable to make the obstruction member length more than 1/2 of the axial length of the hollow head, and in general, it is preferable to be 4 times or less of the bottom wall thickness, and more preferably 3 times or less. Do.

(10) The hollow piston for a compressor according to any one of (1) to (9), wherein a corner at which an inner surface of the bottom wall of the bottomed cylindrical closure member intersects with an inner circumferential surface of the cylindrical portion is rounded.

Since the edge is a portion where stress concentration occurs, it is preferable to round the portion to avoid the occurrence of cracks due to the stress concentration.

(11) (a) an engagement formed integrally with the bottom wall and the bottom wall having a cylindrical portion extending in the axial direction from the outer circumference of the bottom wall and the bottom wall of the bottom cylindrical portion and engaged with the reciprocating drive device. A piston body member having integrally a portion, and (b) a closure member for blocking the bottomed cylindrical portion of the piston body member, thereby integrally providing a hollow head of the substantially hollow cylindrical portion and the engagement portion integrally. A method of manufacturing a hollow piston for a compressor, the closure member comprising a bottom wall and a cylindrical portion extending in the axial direction from the outer circumference of the bottom wall to form a bottomed cylindrical shape, the cross section of the cylindrical portion of the closure member and the piston. While the end surfaces of the cylindrical members are brought into contact with each other, the two cylindrical portions are joined to each other and at the outer end surface of the bottom wall of the closure member. The method of manufacturing a hollow piston for a compressor, characterized in that the length of the closure member, which is the distance to the end face of the cylindrical portion, is greater than the thickness of the bottom wall of the closure member and less than half of the axial length of the hollow head.

The features of the above (2) to (10) can also be applied to the manufacturing method of the hollow piston for the compressor of the present invention.

Embodiment of the invention

EMBODIMENT OF THE INVENTION Hereinafter, the hollow piston for swash plate type compressor used for the vehicle air conditioner which is embodiment of this invention is demonstrated in detail based on drawing.

The swash plate type | mold compressor in this embodiment is shown in FIG. In FIG. 1, 10 is a cylinder block, and a plurality of cylinder bores 12 extending in the axial direction are formed on one circumference around the central axis of the cylinder block 10. On each of the cylinder bores 12, a unilateral piston 14 (hereinafter abbreviated as piston 14) is arranged to allow reciprocating motion. The front housing 16 is mounted on one end face in the axial direction of the cylinder block 10 (referred to as the front end face in FIG. 1), and the other end face (refered to the rear end face in FIG. 1 as the rear end face). The rear housing 18 is mounted via the valve plate 20. The main body of the swash plate type compressor is constituted by the front housing 16, the rear housing 18, the cylinder block 10, and the like. An intake chamber 22 and a discharge chamber 24 are formed between the rear housing 18 and the valve plate 20, and are connected to a refrigeration circuit (not shown) via the suction port 26 and the supply port 28, respectively. . The valve plate 20 is provided with a suction hole 32, a suction valve 34, a discharge hole 36, a discharge valve 38, and the like.

On the central axis of the cylinder block 10, the rotating shaft 50 is rotatably provided. The rotating shaft 50 is supported by the front housing 16 and the cylinder block 10 through bearings at both ends, respectively. The center support hole 56 is formed in the center part of the cylinder block 10, and is supported by this center support hole 56. As shown in FIG. The front housing 16 side end part of the rotating shaft 50 is connected to the vehicle engine as an external drive source which is a kind of drive source which is not shown in figure through clutch mechanisms, such as an electromagnetic clutch. Therefore, when the rotating shaft 50 is connected to the vehicle engine by the clutch mechanism during the operation of the vehicle engine, the rotating shaft 50 is rotated around its own axis.

The swash plate 60 is attached to the rotating shaft 50 so that relative movement is possible in the axial direction and the tilting operation is possible. The swash plate 60 is formed with a center hole 61 passing through the center line, and the rotation shaft 50 penetrates the center hole 61. The diameter of the center hole 61 is increasing as it is open at both ends. The rotating plate 50 is further fixed to the rotating shaft 50 as a rotating transmission member, and is engaged with the front housing 16 via the thrust bearing 64. The swash plate 60 is rotated integrally with the rotational shaft 50 by the hinge mechanism 66 and at the same time the tilting operation involving the axial movement is permitted. The hinge mechanism 66 includes a support arm 67 fixedly installed on the rotating plate 62 and a guide pin fixedly installed on the swash plate 60 and slidably fitted into the guide hole 68 of the support arm 67. 69, the central hole 61 of the swash plate 60, and the outer circumferential surface of the rotation shaft 50. In the present embodiment, the swash plate 60, the rotation shaft 50, the hinge mechanism 66 constituting the rotation transmission device, etc. as the drive member constitute a reciprocating drive device for reciprocating the piston 14.

The piston 14 is a type of hollow piston, which is integrally formed with the engaging portion 70 engaged with the swash plate 60 and the engaging portion 70 and fitted into the cylinder bore 12. Tofu 72 is provided. The swash plate 60 is engaged with the groove 74 formed in the engagement portion 70 via a pair of shoes 76 having a spherical shape. The shoe 76 is slidably supported by the engagement portion 70 at the spherical portion, abuts against both sides of the swash plate 60 at the flat portion, and supports the outer peripheral portion of the swash plate 60 so as to be slidable at both sides. have. Detailed description of the shape of the piston 14 will be described later.

The rotational movement of the swash plate 60 is converted into a reciprocating linear movement of the piston 14 via the shoe 76. In the suction stroke in which the piston 14 moves from the top dead center to the bottom dead center, the refrigerant gas in the intake chamber 22 is sucked into the cylinder bore 12 via the suction hole 32 and the suction valve 34. In the compression stroke in which the piston 14 moves from the bottom dead center to the top dead center, the refrigerant gas in the cylinder bore 12 is compressed and discharged to the discharge chamber 24 through the discharge hole 36 and the discharge valve 38. . The compression reaction in the axial direction acts on the piston 14 as the refrigerant gas is compressed. Compression reaction is applied to the front housing 16 via the piston 14, the swash plate 60, the rotating plate 62 and the thrust bearing 64. The engaging portion 70 of the piston 14 is formed integrally with a rotation preventing portion (not shown). The anti-rotation part is brought into contact with the inner circumferential surface of the front housing 16 to restrict rotation around the central axis of the piston 14 to avoid the collision between the piston 14 and the swash plate 60.

An air supply passage 80 is formed through the cylinder block 10. The swash plate chamber 86 formed between the discharge chamber 24 and the front housing 16 and the cylinder block 10 is connected by this air supply passageway 80. The capacity control valve 90 is provided in the middle of the air supply passage 80. The capacity control valve 90 is an solenoid valve, and the solenoid 92 is excited and demagnetized by a control device (not shown) mainly composed of a computer, and the amount of supply current is controlled in accordance with information such as cooling load and the capacity control valve ( 90) is adjusted.

The discharge passage 100 is formed inside the rotary shaft 50. The discharge passage 100 is opened in the central support hole 56 at one end and at the same time in the swash plate chamber 86 at the other end. The central support hole 56 passes through the intake chamber 22 via the discharge port 104.

This swash plate type compressor is a variable displacement type, and the pressure in the swash plate chamber 86 is controlled by using the pressure difference between the discharge chamber 24 serving as a high pressure source and the intake chamber 22 serving as a low pressure source. The difference between the pressure of the cylinder bore 12 as the compression chamber and the pressure of the swash plate chamber 86 is adjusted, the inclination angle of the swash plate 60 is changed, and the stroke of the piston 14 is changed, thereby discharging the compressor capacity. This is regulated. Specifically, the pressure in the swash plate chamber 86 is controlled by passing through or blocking the swash plate chamber 86 through the discharge chamber 24 by the control of the capacity control valve 90. In the element state of the solenoid 92, the capacity control valve 90 is completely opened so that the air supply passage 80 is continuously connected, so that the high-pressure refrigerant gas of the discharge chamber 24 is supplied to the swash plate chamber 86, thereby The pressure in 86 increases, and the inclination angle of the swash plate 60 is minimized. The piston 14 reciprocates in accordance with the rotation of the swash plate 60. When the inclination angle of the swash plate 60 is minimized, the rate of change of the volume of the piston 14 becomes small, so that the discharge capacity of the compressor is minimized. In the excited state, the supply amount of the high-pressure refrigerant gas to the swash plate chamber 86 of the discharge chamber 24 decreases as the supply current amount increases and the opening degree of the capacity control valve 90 decreases (including the opening degree 0). Since the refrigerant gas in the swash plate chamber 86 is discharged to the intake chamber 22 via the discharge passage 100 and the discharge port 104, the pressure in the swash plate chamber 86 is lowered. As a result, the inclination angle of the swash plate 60 increases, and the volume change rate of the piston 14 increases, thereby increasing the discharge capacity of the compressor. In the state where the air supply passage 80 is blocked by the excitation of the solenoid 92, the high pressure refrigerant gas of the discharge chamber 24 is not supplied to the swash plate chamber 86, so that the inclination angle of the swash plate 60 is maximized. The discharge capacity of the compressor is maximized. The maximum inclination angle of the swash plate 60 is defined by the contact of the stopper 106 provided on the swash plate 60 to the rotating plate 62, and the minimum inclination angle of the swash plate 60 to the stopper 107 on the rotation axis 50 of the swash plate 60. Defined by abutment. A swash plate inclination angle control device and a discharge capacity control device are configured by the air supply passage 80, the swash plate chamber 86, the capacity control valve 90, the discharge passage 100, the discharge port 104, and the control device.

The cylinder block 10 and the piston 14 are made of aluminum alloy which is a kind of metal, and the outer peripheral surface of the piston 14 is coated with fluororesin. Coating with a fluororesin makes it possible to narrow the fitting gap with the cylinder bore 12 as much as possible while avoiding baking by avoiding direct contact with the same metal. The cylinder block 10 and the piston 14 are preferably made of an aluminum silicon alloy. However, the material of the cylinder block 10, the piston 14, the material of a coating layer, etc. are not limited to the material mentioned above, A different material may be sufficient as it.

The piston 14 will be described in more detail.

As shown in FIG. 2, the edge part of the side which is far from the head 72 of the engagement part 70 of the piston 14 is substantially U-shaped by formation of the said groove 74, and forms the U-shaped bottom part. A base 108 and a pair of arm portions 110 and 112 extending from the base 108 in a direction orthogonal to the axis of the piston 14 are provided. Recesses 114 are formed on side surfaces of the arm portions 110 and 112 that face each other. The inner surface of these concave portions 114 forms a concave spherical shape, and two concave spherical surfaces are located on one spherical surface. The pair of shoes 76 are in contact with both front and rear surfaces of the outer peripheral portion of the swash plate 60 to sandwich the swash plate 60 therebetween and are supported by the recess 114.

The head 72 of the piston 14 is fixed to the bottomed cylindrical upper part 120 and the bottomed cylindrical upper part 120 having a bottom with one end open and the other end closed. The cap 122 as a blocking member for closing the opening of the cylindrical cylindrical portion 120 is provided. The bottomed cylindrical portion 120 is formed integrally with the arm portion 112 side of the engaging portion 70 in the bottom wall 124. These bottomed cylindrical portions 120 and engaging portions 70 constitute an integral piston body member 125. The bottomed cylindrical portion 120 has a cylindrical portion 126 extending in the axial direction at the outer circumferential portion of the bottom wall 124. The bottom wall 124 constitutes a blocking portion for closing the other end of the cylindrical portion 126. The inner circumferential surface 128 of the bottomed cylindrical portion 120 is a simple cylindrical surface.

The cap 122 has a flat bottom wall 134, a cylindrical large diameter portion 136 extending in the axial direction from the outer peripheral portion of the bottom wall 134, and an inner peripheral portion of the end face 138 of the large diameter portion 136. A cylindrical small diameter portion 139 extending in the axial direction has a cylindrical shape with a bottomed end. A recess opening in the end surface 142 of the small diameter portion 139 inside the cap 122 by the inner diameter surface 141 of the small diameter portion 139, the inner circumferential surface 140 of the large diameter portion 136, and the inner surface 141 of the bottom wall 134 ( 144 is formed and the weight is reduced. In addition, the edge where the inner circumferential surface 140 of the recess 144 intersects the inner surface 141 of the bottom wall 134 is rounded, as shown in FIG. 2, so as to form a boundary between the large diameter portion 136 and the bottom wall 134. Rigidity is improved. The cap length A, which is the axial distance from the front face 146 that is the outer end surface of the bottom wall 134 to the end face 138 of the large diameter portion 136, is larger than the thickness B of the bottom wall 134. For example, it is preferable that the cap length A becomes 1.5 times or more or 2 times or more of the thickness B of the bottom wall 134. More specifically, when B is 3 mm, 5 mm or more is preferable and, as for A, 7 mm or more is more preferable. In addition, this cap length A becomes less than 1/2 of the axial length of the head 72. In addition, in FIG. 2, the thickness of the circumferential wall of the cylindrical part 126, the thickness of the circumferential wall of the large diameter part 136, the thickness of the bottom wall 134, etc. are exaggerated in order to make understanding easy.

The outer circumferential surface 148 of the small diameter portion 139 of the cap 122 is formed on the inner circumferential surface 128 of the cylindrical portion 120 with the bottom, and the open end surface 150 of the cylindrical portion 120 with the bottom is 138. ), The cap 122 and the piston main body member 162 are engaged by being fitted to a depth to abut on the surface thereof and by welding the open end face 150 and the end face 138 as a welding face. The compression reaction force of the refrigerant gas acting on the front face 146 of the head 72 in the compression stroke of the piston 14 acts on the welded portion of the end face 138 and the opening side end face 150.

In the present embodiment, two pistons 14 configured as described above are manufactured from one piston raw material. Therefore, as shown in FIG. 3, the raw material 160 for manufacturing a migraine piston for manufacturing the piston 14 (hereinafter, abbreviated as the raw material 160) is the piston body member 162 (hereinafter, referred to as a body member 162). D) and a cap 164 as a closing member. The main body member 162 includes a bottomed cylindrical portion 170 that forms a cylindrical shape with a bottom open in a direction opposite to the engaging portion 166 and the engaging portion 166. The two main body members 162 are integrally formed with the engaging portions 166 adjacent to each other so that the bottomed cylindrical portions 170 are concentric with each other.

The bottomed cylindrical portion 170 includes a bottom wall 172 and a cylindrical portion 174 extending in the axial direction from the outer circumference of the bottom wall 172, and the engaging portion 166 in the bottom wall 172. It is formed integrally. The inner circumferential surface 178 of the cylindrical portion 174 is a simple cylindrical surface. The inner peripheral surface 178 becomes the inner peripheral surface 128 when it becomes the piston 14 which is a product. As shown in FIG. 3, the bridge portion 182 provided at each engaging portion 166 is a portion that constitutes the base 108 and the arm portions 110 and 112 (the base portion 184 and the arm portions 186 and 188, respectively). Reinforcing the engaging portion 166 against the intervening action during machining by connecting the inner surfaces of the inner surfaces of the main body 162, and being provided as a reinforcing portion for increasing the rigidity of the main body member 162 or suppressing deformation due to heat. have. The main body member 162 is made of aluminum alloy which is a kind of metal in this embodiment, and is manufactured by casting or forging. Casting includes die casting, die casting, vacuum casting, PF (pore-free die casting) method, and Leo casting method, and various die castings. In addition, forging includes normal forging, semi-melting forging (SSF), and the like.

Since the two caps 164 are configured in the same way, one side will be representatively described. As shown in FIG. 3, the cap 164 includes a disk-shaped bottom wall 192, a cylindrical large diameter portion 194 extending axially from the outer circumferential portion of the bottom wall 192, and a cross section of the large diameter portion 194 ( A cylindrical small diameter portion 198 extending in the axial direction from the inner circumferential portion of 196 is formed in a cylindrical shape having a bottomed end. The inside of the cap 164 is formed by the inner circumferential surface of the small diameter portion 198, the large diameter portion 194 and the bottom wall 192, and a concave portion 202 opening in the end face 200 of the small diameter portion 198 is formed and weighed. This is reduced. The recessed portion 202 becomes the recessed portion 144 in the case of the piston 14 which is a product. The diameter of the outer circumferential surface 204 of the small diameter portion 198 is smaller than the outer diameter of the large diameter portion 194, and can fit to the inner circumferential surface 178 of the bottomed cylindrical portion 170. In the example shown in the figure, the support part 212 of a circular cross section protrudes in the center of the cross section 210 on the opposite side to the cross section 200 of the small diameter part 198 side of the cap 164. The cap length, which is the thickness of the bottom wall 192 of the cap 164 and the axial distance from the end face 210 of the bottom wall 192 to the end face 196 of the large-diameter portion 194, is described in cross section 210. ) And the dimensional relationship is set so as to have the same dimensional relationship as the cap 122 of the piston 14 to be a product after machining. The cap 164 comprised in this way is made of aluminum alloy which is a kind of metal in this embodiment, and is manufactured by casting or forging like the main-body member 162. FIG. 3, the thickness of the circumferential wall of the cylindrical part 174, the thickness of the circumferential wall of the large diameter part 194, the thickness of the bottom wall 192, etc. are exaggerated for the ease of understanding.

The process of fixing the cap 164 to the main body member 162 will be described.

As exaggerated and enlarged in FIG. 4, the cap 164 is inserted with the cap 164 positioned coaxially at the opening side of the bottomed cylindrical portion 170 such that the outer circumferential surface 204 of the small diameter portion 198 is the inner circumferential surface 178. ) Is fitted. By the fitting of the inner circumferential surface 178 and the outer circumferential surface 204, the fitting proceeds further in the state where the cap 164 is positioned in the bottomed cylindrical cylindrical portion 170, and the cylindrical section 196 of the cap 164 is cylindrical. The fitting depth of the cap 164 is defined by the abutment of the opening side end face 220 of the part 174. In the state where the end face 220 and the end face 196 contact or approach each other, the electron beam is irradiated from the electron beam irradiation apparatus of the electron beam welding machine which is not shown in figure, and these end faces 220 and 196 are welded as a welding surface. At this time, the main body member 162 and the cap 164 are fitted on both sides by a pair of jigs (not shown) having a receiving hole for accommodating the support portion 212 of the cap 164 to the rotary drive device. The body member 162 and the cap 164 are rotated around their axes, whereby the position of the weld surface in the direction orthogonal to the axis of the body member 162 (direction along a straight line parallel to the weld surface). Irradiating to each other, the welding surfaces are all welded to form a circular ring shape. Since the injury from the main body member 162 of the cap 164 is prevented by the jig, welding is performed favorably. In this embodiment, it welds to the inner periphery of the opening side end surface 220 of the cylindrical part 170 with a bottom.

And in this embodiment, although the irradiation point of an electron beam is moved to a circumferential direction by rotating the raw material for manufacturing a migraine piston 160, you may make it an electron beam irradiation apparatus or an electron beam irradiation point move to a circumferential direction. Electron beam welding is a kind of beam welding, and may be joined by laser beam welding in addition.

After the two caps 164 are fixed to the main body member 162 in this manner, a portion of the head 72 is formed, that is, a plurality of parts including the cylindrical upper portion 170 having the bottom of the main body member 162. Cutting processing is performed. First, a center hole 224 (shown in dashed lines in FIG. 3) is formed in the support portions 212 formed in the two caps 164, respectively. The center is fitted to the center hole 224 to achieve centering, and the rotation of the rotary drive device is performed by the cap 164 and the main body member 162 while the two support portions 212 are gripped by the chuck. ), Processing is good.

Subsequently, painting is performed on the portion including the outer circumferential surface of the bottomed cylindrical portion 170 of the body member 162, for example, a coating layer of polytetrafluoroethylene is formed. After the support portion 212 of the cap 164 is removed by cutting, the end surface 210 is shaved, and then the centerless grinding is performed on the outer circumferential surface of the bottomed cylindrical upper portion 170 on which the coating layer is formed. ) Is completed. Subsequently, the engaging portion 166 is machined, the bridge portion 182 is removed, and the recessed portion 114 that supports the shoe 76 when the piston 14 is formed (see FIG. 3). 2) is processed to complete the engagement portion 70. And the raw material 160 is cut into two, and two piston 14 is obtained.

As can be seen from the above description, the large diameter portions 136 and 194 constitute a cylindrical portion, and the small diameter portions 139 and 198 constitute a fitting portion.

The piston 14 thus manufactured has a bottom wall 134 based on the pressure or inertial force of the refrigerant gas acting on the bottom wall 134 of the piston 14 in the compression stroke and the suction stroke between the weld portions between the end faces 138, 150. ), The stress acting on the end face 150 is reduced to a simple compressive stress or tensile stress because it is far from the portion where the stress concentration occurs when the elastic deformation is performed in the three-dimensional shape (the boundary between the bottom wall 134 and the large diameter portion 136). The stiffness of the cap 122 is increased by the formation of a large cylindrical portion 136 which is close to and extends from the outer circumferential portion of the bottom wall 134, thereby reducing the maximum value of the stress acting in the vicinity of the inner circumferential surface of the cross section 150, in particular. Can be. If the maximum value of the stress acting on the end face 150 is small, the thickness of the cylindrical portion 126 of the piston body member 125 can be made thin, and the thickness of the bottom wall 134 of the cap 122 is made thin. Since a relatively large elastic deformation can be tolerated, sufficient weight reduction can be attained while ensuring durability of the piston 14. Specifically, when the cap length A of the piston 14 is about 1.5 times (5 mm) or about 2 times (7 mm) of the bottom wall 134 thickness B (3 mm), the piston 14 It has been confirmed by experiment that the weight reduction is effective in satisfying the required strength especially during compression. In addition, when welded to the inner circumference of the end face 138,150, the strength of the welded portion is remarkably improved as compared with the case where the weld is made to a depth not reaching the inner circumference. This is because not only the welding area increases, but also the portion not welded as described above can avoid the crack-like action.

The joining method of the piston body member and the closure member is not limited to welding, and various methods can be adopted, and each of the other embodiments will be described based on Figs. 5-8 show only the part different from the embodiment shown to FIGS. 1-4.

For example, the two members may be joined by adhesion. An example thereof is shown in FIG. 5. In addition, since the shape of the cap as a piston main body member and a closure member is the same structure as embodiment shown in FIGS. 1-4, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. As shown in FIG. 5, the cap 122 is fitted into the bottomed cylindrical upper part 120 to the depth where the end face 138 and the opening side end face 150 come into contact with each other, and the outer peripheral surface of the small diameter part 139. 148 is fitted to the inner circumferential surface 128, and the end faces 138, 150, the inner circumferential surface 128, and the outer circumferential surface 148 are joined by adhesion. In FIG. 5, the thickness of the adhesive layer, the thickness of the circumferential wall of the cylindrical portion 126, and the like are exaggerated. Prior to fitting the cap 122 to the bottomed cylindrical portion 120 of the piston body member 125, an adhesive is applied to the end surface 138 of the cap 122 and the outer peripheral surface 148 of the small diameter portion 139. Thereafter, the cap 122 is coaxially fitted to the bottomed cylindrical portion 120, and both members are firmly joined by curing the adhesive in a state where the end faces 138 and 150 abut.

The adhesive may be applied to the inner circumferential surface 128 and the opening side end face 150 of the cylindrical portion 126, but not to both the end face 138 and the outer circumferential face 148 of the cap 122. The adhesive may be a room temperature curing adhesive such as methacrylate, acrylate or acryl, or may be a thermosetting adhesive such as epoxy, polyimide, polyamideimide or phenol. Moreover, normal temperature 2 type adhesive liquid, such as an acryl, can also be used. When using a two-part adhesive, the adhesive agent as a 1st liquid is apply | coated to one side of the main-body member 162 and the cap 164, and the hardening accelerator as a 2nd liquid is apply | coated to the other side. A two-component adhesive is an adhesive of the type which consists of two liquids of the adhesive agent as a 1st liquid, and the hardening accelerator as a 2nd liquid, and hardens | cures by contacting an adhesive agent and a hardening accelerator, and mixing a nutrient solution.

Also in this embodiment, the same effect as what was demonstrated by the said embodiment can be acquired. In addition, the compressive stress or the tensile stress acting on the adhesive layers between the both end surfaces 138 and 150 may be small, and the peeling of the adhesive layer proceeds at this portion, whereby the durability of the hollow piston is preferably prevented.

In each of the above embodiments, the inner circumferential surface 128 and the outer circumferential surface 148 are fit to each other, but the inner circumferential surface 128 and the outer circumferential surface 148 may be firmly fitted.

The shape of the cap as the piston body member and the closing member can be in various shapes, an example of which is shown in FIG. 6. The bottomed cylindrical portion 301 of the piston body member 300 shown in FIG. 6 has a cylindrical portion 302 and a fitting portion 306 extending in the axial direction from an outer circumferential portion of the end face 304 of the cylindrical portion 302. ) Is integrally provided. The inner circumferential surface 308 of the fitting portion 306 is larger in diameter than the inner circumferential surface 310 of the cylindrical portion 302.

The cap 320 as a closing member closing the opening of the bottomed cylindrical portion 301 has a flat bottom wall 322 and a cylindrical portion 324 extending in the axial direction from the outer circumferential portion of the bottom wall 322. have. The diameter of the outer circumferential surface 326 of the cap 320 is a diameter slightly larger than that of the inner circumferential surface 308 of the fitting portion 306, and a negative fitting clearance is formed therebetween. The recessed part 332 which opens to the end surface 328 is formed by the inner peripheral surface of the cylindrical part 324, and the inner surface of the bottom wall 322, and the weight is reduced. Similarly to the above embodiment, the corner at which the inner circumferential surface and the inner surface of the recess 332 intersect is rounded. The axial length A from the front surface 338, which is the outer end surface of the bottom wall 322, to the end face 328 is 1.5 times or more or 2 times or more the thickness B of the bottom wall 322 as in the above-described embodiments. It is.

Prior to the fitting of the cap 320 to the bottomed cylindrical portion 301, an adhesive is applied to the end face 320 and the outer peripheral surface 326 of the cap 320. Alternatively, an adhesive may be applied to the end face 304 of the bottomed cylindrical portion 301 and the inner circumferential surface 308 of the fitting portion 306. After the adhesive is applied, the cylindrical portion 324 of the cap 320 is coaxially fitted into the bottomed cylindrical portion 301 as the tip portion. The outer circumferential surface 326 of the cap 320 is firmly fitted to the inner circumferential surface 308 of the fitting portion 306 so that the fitting depth is defined by the abutment between the end face 304 and the end face 328. Then, the end faces 304 and 328 are bonded to each other by the inner circumferential surface 308 and the outer circumferential surface 326. In addition, by tightly fitting the inner circumferential surface 308 and the outer circumferential surface 326, the bonding strength of both increases, thereby preventing the relative rotation and the escape from the cylindrical upper portion 301 with the bottom of the cap 320 at the same time. The concentricity of the piston body member 300 and the cap 320 is ensured with high precision. Further, the adhesive effect by the adhesive held in the gap formed between the inner circumferential surface 308 and the outer circumferential surface 326 which is tightly fitted by both surfaces can be expected.

The inner circumferential surface 308 and the outer circumferential surface 326 may be fitted to each other with a margin. In this embodiment, the end surfaces 304 and 328 are bonded to each other, and an adhesive is filled in the fitting clearance between the inner circumferential surface 308 and the outer circumferential surface 326 so that both are combined.

The piston body member and the closure member may be joined by caulking. An example thereof is shown in FIG. 7. The bottomed cylindrical portion 402 of the piston body member 400 is integrally provided with a cylindrical portion 404 and a fitting portion 408 extending axially from the outer periphery of the cross section 406 of the cylindrical portion 404. have. The inner circumferential surface 410 of the fitting portion 408 is larger in diameter than the inner circumferential surface 412 of the cylindrical portion 404. The cap 420 as a closing member for closing the opening of the bottomed cylindrical portion 402 includes a flat bottom wall 422 and a cylindrical portion 424 extending in the axial direction from the outer circumferential portion of the bottom wall 422. have. The recess 432 opening to the end surface 430 is formed by the inner circumferential surface of the cylindrical portion 424 and the inner surface of the bottom wall 422 to reduce the weight. The corners at which these inner circumferential surfaces and the inner surface intersect are rounded in the same manner as in the above embodiments. In a portion adjacent to the front surface 444, which is the outer end surface of the bottom wall 422 of the outer circumferential surface 440 of the cap 420, a chamfer 448 that is inclined in a direction in which the diameter increases as the distance from the front surface 444 is formed is formed. have. By forming the chamfer 338, the outer circumferential surface 440 of the cap 420 has a straight outer circumferential surface 450 having a diameter that can be fitted to the inner circumferential surface 410 of the fitting portion 408, and the straight outer circumferential surface 450 ) And a tapered outer circumferential surface 452 which becomes smaller in diameter toward the front face 444 in the cross section 430. The dimensional relationship between the thickness B of the bottom wall 422 and the axial length A from the end face 430 of the bottom wall 422 to the front surface 444 is the same as that of each said embodiment.

The straight outer circumferential surface 450 of the cylindrical portion 424 of the cap 420 is fitted to the inner circumferential surface 410 of the fitting portion 408 of the bottomed cylindrical portion 402, and at the same time, the end surface 430 and the end surface thereof. The fitting depth is defined by the abutment of 406. In this way, in a state where positioning is made in the inner circumferential surface 410 of the cap 420, the distal end portion of the fitting portion 408 is caulked to the inner circumferential side along the tapered outer circumferential surface 452 of the cap 420 so that the piston body The member 400 and the cap 420 are firmly coupled. Alternatively, the adhesive is applied to the end face 430 of the cap 420 and the straight outer peripheral surface 450 of the cap 420 prior to the fitting of the cap 420 to the bottomed cylindrical portion 402 so that the end surfaces 430 and 406 abut. After curing, the fitting portion 408 may be caulked. In this way, the two members can be fixed more firmly. An adhesive may be applied to the end face 406 of the bottomed cylindrical portion 402 and the inner circumferential surface 410 of the fitting portion 408. The kind of adhesive agent can use the same thing as what was demonstrated in embodiment shown in FIG.

By caulking the tip of the fitting portion 408 in this manner, the cocked portion is engaged with the chamfer 448 of the cap 420 to prevent the cap 420 from leaving the fitting portion 408. When the coupling between the piston body member 400 and the cap 420 is performed only by caulking, when the bottom wall 422 of the cap 420 is convexly curved into the bottomed cylindrical upper portion 402, the cylinder Although the compressive stress of the inner circumferential side portion of the end face 406 as the abutting surface of the portion 404 is maximized, the cylindrical portion 424 is also formed in the cap 420 so that the maximum compressive stress is reduced to improve the durability of the hollow piston. Light weight can be achieved while securing. In addition, between both end surfaces 406 and 430 of the cylindrical portions 404 and 424, when both the straight outer peripheral surface 450 of the cap 420 and the inner peripheral surface 410 of the fitting portion 408 are bonded to each other, The compressive stress or tensile stress acting on the adhesive layer sandwiched between the layers may be small, and the adhesion peeling progresses at this portion, whereby the durability of the hollow piston is preferably prevented.

In addition, two members may be joined by soldering instead of the adhesive of the embodiment shown in FIG. 5. An example thereof is shown in FIG. 8. As shown in FIG. 8A, the small-diameter portion 139 of the cap 122 is coaxially fitted into the bottomed cylindrical portion 120 and at the same time, the brazing filler material 500 is formed in the gap between the opening side end face 150 and the end face 138. ). The brazing filler material 500 is made of a material having a lower melting point than the bottomed cylindrical upper portion 120 and the forming material of the cap 122. In the present embodiment, since the bottomed cylindrical portion 120 and the cap 122 are both made of aluminum alloy, the brazing filler material 500 has a melting point lower than the melting point (500 ° C. to 550 ° C.) of the aluminum alloy. Al-Cu alloys (melting point around 400 ° C) are used. With the brazing filler material 500 interposed between the end face 150 and the end face 138, the cap 122 is applied to the bottom of the cylindrical cylindrical portion 120 at a temperature above the melting point of the brazing filler material 500. By heating, the brazing filler metal 500 is melted, the end faces 150 and 138 are soldered to each other, and the molten brazing filler 500 has a small diameter portion 139 of the inner circumferential surface 128 of the cylindrical cylindrical portion 120 having a bottom and the cap 122. Also flows through the gap between the outer circumferential surface 148, and both of these inner circumferential surfaces 128 and the outer circumferential surface 148 are soldered. Instead of the brazing material 500, two members may be joined by a low melting point alloy such as solder.

The piston body member and the closure member may be joined by friction welding, or may be joined by any combination of these described joining methods.

At least one side of the main body member and the blocking member may be formed of a metal material other than an aluminum alloy, for example, a magnesium alloy. In the case where the piston body member and the closure member are joined by adhesion and caulking, the closure member may be formed of a resin suitable for these coupling methods.

The raw material for producing the piston may be a raw material for one piston provided with one piston body member and one closing member.

The structure of the swash plate type compressor is not limited to the above embodiment and may be of a different structure. For example, the capacity control valve 90 is not indispensable, and an opening / closing valve which opens and closes mechanically based on the pressure difference between the pressure in the discharge chamber 24 and the pressure in the swash plate chamber 86 may be provided. In addition to or instead of the capacity control valve 90, the same electronic control valve as the capacity control valve 90 may be provided in the middle of the discharge passage 100, or the pressure and intake air of the swash plate chamber 86 can be provided. An on-off valve that opens and closes mechanically may be provided based on the differential pressure of the pressure in the chamber 22.

The present invention may be applied to both head pistons having heads on both sides of the engagement portion with the swash plate, or may be applied to a piston for a fixed displacement swash plate type compressor.

As mentioned above, although some embodiment of this invention was described in detail, this is only an illustration and this invention is based on the knowledge of the person skilled in the art, including the aspect described in the said [technical problem to be made | formed and the structure of this invention]. It can be implemented in various ways.

As described above, according to the present invention, (a) is formed integrally with a bottomed cylindrical portion having a bottom wall and a cylindrical portion extending in the axial direction from the outer circumferential portion of the bottom wall, and a bottom wall of the bottomed cylindrical portion. A piston body member having an engagement portion integrally engaged with the drive device, and (b) a closure member for closing the bottomed cylindrical portion of the piston body member, thereby being coupled to the hollow head of the substantially hollow cylindrical portion; A hollow piston for a compressor in a state in which the engaging portion is integrally provided, wherein the closing member is formed in a cylindrical shape with a bottom by including a bottom wall and a cylindrical portion extending in the axial direction from the outer peripheral portion of the bottom wall. In the state where the cross section of the cylindrical section of the cylindrical section and the cross section of the cylindrical section of the piston body member abut each other, both cylindrical sections are coupled and The closing member length, which is the distance from the outer end surface of the bottom wall of the blocking member to the end face of the cylindrical portion, is larger than the thickness of the bottom wall of the closing member, and is less than half of the axial length of the hollow head. In this way, when the cylindrical portion is provided not only in the piston body member but also in the closure member, and the two cylindrical portions are joined in such a state that the end face of the cylindrical portion and the end face of the cylindrical portion of the piston body member are brought into contact with each other, the engagement portion elastically deforms the bottom wall of the closure member. The stiffness of the closure member is increased from the site where stress concentration is likely to occur and the cylindrical portion is formed. Therefore, the thickness of the bottom wall of the closure member and the thickness of the circumferential wall of the piston body member are secured while ensuring the durability of the hollow piston. It becomes thin.

Further, according to the present invention, the closure member has a cylindrical fitting portion extending in the axial direction from the end surface inner peripheral portion of the cylindrical portion, and the outer peripheral surface of the fitting portion is fitted to the inner peripheral surface of the cylindrical portion of the piston body member. When the closure member is fitted inside the fitting portion in this way, relative positioning of the piston body member and the closure member is facilitated, thereby facilitating the coupling of both. In addition, when the bonding is performed by bonding or welding, not only the end faces of the cylindrical portions but also the outer circumferential surface of the fitting portion of the closure member and the inner circumferential surface of the piston body member can be bonded or welded. In this case, the piston body The bonding strength of the member and the occlusion member can be further increased.

Further, according to the present invention, the cylindrical sections of the piston body member and the cylindrical sections of the closure member are welded to each other. Since the welded part is far from the stress concentration part, the weight can be reduced while ensuring durability. It is preferable that welding is performed to the inner periphery of the cross section of both cylinder parts. This is because when the inner circumferential portion of the cross section of both cylindrical portions is not welded, the portion acts similar to a crack and the weld portion easily breaks.

Further, according to the present invention, the cylindrical portions of the piston body member and the cylindrical sections of the closure member, the outer circumferential surface of the fitting portion and the inner circumferential surface of the cylindrical portion of the piston body member are adhered to each other by an adhesive. Since the bonding position is far from the stress concentration portion, the stress acting on the adhesive layer may be small, and as described above, weight reduction can be achieved while ensuring durability.

Claims (7)

(a) a bottomed cylindrical portion having a bottom wall and a cylindrical portion extending axially from the outer circumference of the bottom wall, and an engagement portion formed integrally with the bottom wall of the bottomed cylindrical portion and engaged with the reciprocating drive unit; The piston body member provided and (b) the closing member for blocking the bottomed cylindrical portion of the piston body member are joined to each other, so that the hollow head of the substantially hollow cylindrical portion and the engaging portion are integrally provided. As a hollow piston for a compressor, The closure member has a bottom wall and a cylindrical portion extending in the axial direction from the outer circumferential portion of the bottom wall to form a bottomed cylindrical shape, and a cross section of the cylindrical portion of the closure member and a cross section of the cylindrical portion of the piston body member abut each other. At the same time, both the cylindrical portion is coupled, and the closing member length, which is the distance from the outer end surface of the bottom wall of the blocking member to the end face of the cylindrical portion, is larger than the thickness of the bottom wall of the closing member, and 1 / time of the axial length of the hollow head. Hollow piston for the compressor, characterized in that less than 2. The compressor hollow according to claim 1, wherein the closure member has a cylindrical fitting portion extending in the axial direction from an end surface inner peripheral portion of the cylindrical portion, and the outer peripheral surface of the fitting portion is fitted to the inner peripheral surface of the cylindrical portion of the piston body member. piston. 3. The compressor hollow piston according to claim 2, wherein end faces of the cylindrical portion of the piston body member and the cylindrical portion of the closure member are welded. 3. The compressor hollow piston according to claim 2, wherein the cylindrical sections of the piston body member and the cylindrical sections of the closure member, the outer circumferential surface of the fitting portion and the inner circumferential surface of the cylindrical portion of the piston body member are bonded to each other by an adhesive. . 3. The cylindrical section of the piston body member and the cylindrical section of the closure member, and the outer circumferential surface of the fitting portion and the inner circumferential surface of the cylindrical portion of the piston body member are lower than the material of the piston body member and the closure member, respectively. Hollow pistons for compressors joined together by low melting point materials having melting points. 2. The piston body member according to claim 1, wherein the piston body member has a cylindrical fitting portion extending in the axial direction from an outer peripheral portion of a cross section of the cylindrical portion with the bottom, and the inner peripheral surface of the fitting portion and the outer peripheral surface of the closure member are fitted. Hollow piston for the compressor. 7. The hollow piston for a compressor according to claim 6, wherein end faces of the cylindrical portion of the piston body member and the cylindrical portion of the closure member, and the inner circumferential surface of the fitting portion and the outer circumferential surface of the closing member are bonded to each other by an adhesive.