JP2002054565A - Piston for variable displacement type swash plate compressor and method of manufacturing the piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the weight of a piston while assuring the mechanical strength of an engaged part. SOLUTION: A relief part 140 to avoid the interference thereof with a swash plate is formed in a crossing part between the inside surfaces 128 of a pair of arm parts 122 of the engaged part 70 of the piston and the inside surface 132 of a connection part 124 at both ends of the swash plate in circumferential direction. The relief part 140 comprises a round part 142 with a radius of curvature of 0.5 to 3.0 mm at the end thereof on the connection part 14 side. The relief part 140 is formed at a position coming out of both end parts of the arm part 122 along an arc formed around a straight line 1 extending in the direction orthogonal to the center axis of a head part. When the relief part 140 is cut by a cut plane including the straight line 1, the cross sectional shape thereof is defined by an orthogonal line (m) generally orthogonal to the straight line 1, a parallel line (n) generally parallel with the straight line 1, a curved line (p) smoothly connecting the orthogonal line (m) to the parallel line (n), and an inclined line (q) extending from the end opposite to the end of the parallel line (n) on the curved line (p) side and inclined to the side close to the straight line 1 as moving away from the end. The relief part 140 is formed by a milling cutter 200.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for a variable displacement swash plate type compressor, and more particularly to an improvement in an engagement portion with a swash plate.

[0002]

2. Description of the Related Art One type of a variable displacement swash plate type compressor changes a stroke of a piston by changing an inclination angle of a swash plate. The piston of this type of compressor usually includes a head that is slidably fitted to the cylinder bore and an engaging portion that engages with the swash plate. The engaging portion has a pair of arms extending parallel to each other, and a connecting portion connecting the base ends of the arms to each other,
The pair of arms engage with both side surfaces of the outer peripheral portion of the swash plate via the respective shoes.

When the swash plate is rotated in this state, the piston is reciprocated between the top dead center and the bottom dead center. In the compression process, the piston is advanced toward the top dead center, and in the suction process, the piston is retracted toward the bottom dead center. The forward speed is reduced before reaching the top dead center, and the retreat speed is increased after reaching the top dead center. At this time, based on the inertial mass of the head and the arm on the head side, the engaging portion A force acts in the direction of increasing the distance between the pair of arms. Based on this force,
Tensile stress acts on the inside of the engaging portion, and compressive stress acts on the outside. Since a corner portion having a small radius of curvature is formed inside the engaging portion, stress concentration occurs at the corner portion. .

[0004] In particular, at both ends in the circumferential direction of the swash plate, at the intersections between the inner surfaces of the pair of arms and the inner surfaces of the connecting portions,
When a relief part is formed to avoid interference with the swash plate, the radius of curvature at the corner of the relief part becomes smaller, so the concentrated stress increases, and in order to secure necessary mechanical strength, The thickness of the engaging portion must be increased, which is one of the factors that hinders the weight reduction of the piston.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce the weight of a piston while ensuring the mechanical strength of an engaging portion. According to the present invention, a piston for a variable displacement swash plate type compressor and a method for manufacturing the piston according to the following aspects are obtained. As in the case of the claims, each aspect is divided into sections, each section is numbered, and if necessary, the other sections are cited in a form in which the numbers are cited. This is for the purpose of facilitating the understanding of the present invention and should not be construed as limiting the technical features and combinations thereof described in the present specification to those described in the following sections. . Further, when a plurality of items are described in one section, the plurality of items need not always be adopted together. It is also possible to select and adopt only some of the items.

(1) It has a pair of arms extending parallel to each other, and a connecting portion for connecting the base ends of the arms to each other, and the pair of arms are respectively connected to the outer peripheral portion of the swash plate via shoes. A piston for a variable displacement swash plate type compressor, comprising: an engaging portion engaging with both side surfaces of the cylinder; and a head formed integrally with the engaging portion and slidably fitted into the cylinder bore. At least the circumferential direction of the swash plate at the intersection of the inner surfaces of the pair of arm portions facing the both side surfaces of the swash plate and the inner surface of the connecting portion facing the outer peripheral surface of the swash plate. At both ends, relief portions are provided to avoid interference with the outer peripheral edge of the swash plate, and rounded portions having a radius of curvature of 0.5 mm or more and 3.0 mm or less are formed at the ends of the relief portions on the connecting portion side. Piston for a variable displacement swash plate type compressor (Claim 1) . As described above, in the piston in which a relief portion is formed in the engagement portion to avoid interference with the swash plate, a large stress concentration has occurred.
According to the present invention, this stress concentration can be effectively alleviated, and accordingly, the thickness of the engagement portion can be reduced, and the weight of the piston can be reduced. Although it is generally desirable to reduce the weight of a reciprocating piston, a variable displacement swash plate compressor is particularly effective in improving the controllability of the inclination angle of the swash plate. The lower limit of the curvature radius is 1.0 mm
Is more preferable, and more preferably, 1.4 mm. The upper limit is desirably 2.4 mm, and more desirably 2.0 mm. (2) The piston for a variable displacement type swash plate type compressor according to (1), wherein the relief portions are provided at both ends in the circumferential direction of the swash plate, and are not provided at portions inside the both end portions. Claim 2). The relief portion may be formed along the entire line of intersection between the inner surface of the arm portion and the inner surface of the connecting portion, but should be formed only at both circumferential ends of the swash plate which easily interfere with the swash plate. However, it is desirable in order to avoid a decrease in the strength of the engaging portion as much as possible while reliably avoiding interference with the swash plate. (3) The relief portion is formed by machining (1)
The piston for a variable displacement type swash plate type compressor according to item (2) or (2) (claim 3). The piston material is usually manufactured by forging or casting, and it is possible to form a relief part by forging or casting.However, the dimensional accuracy of forged or cast products is generally reduced by machining. Since the accuracy is lower than the accuracy, in order to reliably avoid the interference between the engagement portion and the swash plate,
It is necessary to form a relief part larger than the relief part by machining. And if you make the relief part bigger,
Since the mechanical strength of the engaging portion is undesirably reduced by that amount, the relief portion is desirably formed by machining. In addition, forming the relief portion from the material stage complicates the structure of the mold and increases the equipment cost. Therefore, machining is also desirable in this regard. (4) At a position where the relief portion is protruded from both ends of the pair of arm portions in the circumferential direction of the swash plate, along a circular arc centered on a straight line extending in a direction intersecting a central axis of the head. The piston for a variable displacement swash plate type compressor according to the above mode (2) or (3), which is formed by molding. The relief portion of this shape can be formed by a cutting tool such as a milling cutter having a rotation axis as a straight line extending in a direction intersecting with the center axis of the head, and is easy to form. Further, by changing the shape of the blade of the cutting tool, it is possible to arbitrarily change the cross-sectional shape of the relief portion, which is convenient. The rotation axis of the milling cutter can be in a state perpendicular to the central axis of the head of the piston, or in a state inclined at a certain angle from the state perpendicular to the center axis. (5) The cross-sectional shape of the relief portion when cut by a cutting plane including a straight line extending in a direction intersecting with the center axis of the head is at least an orthogonal line substantially orthogonal to the straight line and substantially equal to the straight line. Defined by parallel parallel lines and a curve that smoothly connects the orthogonal and parallel lines
The piston for a variable displacement swash plate type compressor according to item (4). (6) The curve is an arc having a constant radius of curvature.
The piston for a variable displacement swash plate type compressor according to item (5). The rounded portion may be defined by a curve formed by a set of a plurality of arcs having different radii of curvature, or may be defined by a curve having a continuously changing radius of curvature. However, it is simplest to use one circular arc having a constant radius of curvature. In particular, when the relief portion is formed by machining, the manufacture of the working tool is simplified. (7) The cross-sectional shape of the relief part is the orthogonal line, the curve,
In addition to the parallel line, it is also defined by an inclined line extending from the end of the parallel line opposite to the curved side end, and formed in a direction approaching the straight line as the distance from the end increases (5) or
The piston for a variable displacement swash plate type compressor according to item (6). If the cross section of the relief portion has the shape described in this section, the relatively small relief portion can effectively avoid interference with the swash plate. This is most effective when the inclination angle of the inclination line is set substantially equal to the maximum inclination angle of the swash plate. (8) The variable capacitor according to the above mode (1), wherein both inner side surfaces of the pair of arm portions are machined, and the rounded portion is formed at an end of the machined surface on the connecting portion side. Type swash plate type piston. By machining both inner surfaces of the pair of arms, it is possible to improve the dimensional accuracy of a portion of the engaging portion that engages with the swash plate and to reliably avoid interference with the swash plate. Is performed with a normal processing tool, a corner having a very small radius of curvature is formed, and stress is concentrated there.
Despite this stress concentration, in order to secure the mechanical strength of the engagement part, the thickness of the engagement part must be increased,
The weight of the piston increases. On the other hand, in the piston for the variable displacement swash plate type compressor described in this section, since the rounded portion is formed at the corner, stress concentration is eased, and the thickness of the engaging portion can be reduced, Weight reduction becomes possible. (9) A pair of arms extending parallel to each other, and a connecting portion connecting the base ends of the arms to each other, and the pair of arms are respectively provided on both sides of the outer peripheral portion of the swash plate via the shoe. And a head formed integrally with the engaging portion and slidably fitted to the cylinder bore. At least the periphery of the swash plate at the intersection of the inner surfaces of the pair of arms opposed to both sides of the swash plate and the inner surface of the connecting portion opposed to the outer peripheral surface of the swash plate. A relief part is formed at both ends in the direction by machining, and the machining is performed in a direction intersecting with the center axis of the head at a position protruding from both ends in the circumferential direction of the swash plate of the pair of arms. Milling cutter that rotates around a straight line that extends Carried out by jitter, by rounding the intersection vicinity of the blade and one side of the blade of the outer peripheral surface of the milling cutter, the connecting portion side of the edge of the relief portion,
A method of manufacturing a piston for a variable displacement swash plate compressor, wherein a rounded portion having a radius of curvature of 0.5 mm or more and 3.0 mm or less is formed (Claim 4). The features described in the above items (4) to (7) can also be applied to the manufacturing method described in this item. The relief portion may have a shape defined by the rotation locus of the blade when the milling cutter is rotated around the rotation axis, and the rotation axis is moved in a direction orthogonal to the rotation axis while rotating the milling cutter. The shape defined by the movement locus of the blade in that case may be used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a piston for a variable displacement swash plate type compressor used in a vehicle air conditioner according to an embodiment of the present invention and its manufacture will be described in detail with reference to the drawings. . FIG. 1 shows a swash plate type compressor according to the present embodiment. In FIG. 1, reference numeral 10 denotes a cylinder block, and a plurality of cylinder bores 12 extending in the axial direction are formed on one circumference of the cylinder block 10 around the central axis. Each of the cylinder bores 12 is provided with a single-headed piston 14 (hereinafter abbreviated as piston 14) so as to be able to reciprocate. A front housing 16 is attached to one end face in the axial direction of the cylinder block 10, and a rear housing 18 is attached to the other end face via a valve plate 20. Front housing 16, rear housing 18, cylinder block 10
Thus, the housing of the swash plate type compressor is formed.
Between the rear housing 18 and the valve plate 20,
A suction chamber 22 and a discharge chamber 24 are formed, and are connected to a refrigeration circuit (not shown) via a suction port 26 and a supply port 28, respectively. In the valve plate 20, suction holes 32,
A suction valve 34, a discharge hole 36, a discharge valve 38 and the like are provided.

A rotary shaft 50 is provided in the housing so as to be rotatable about a central axis of the cylinder block 10 as a rotational axis. The rotating shaft 50 is rotatably supported at both ends thereof by the front housing 16 and the cylinder block 10 via bearings.
A support hole 56 is formed in the center of the cylinder block 10 and is supported in the support hole 56 via the bearing. The end of the rotating shaft 50 on the front housing 16 side is connected to a drive source (not shown).

A swash plate 60 is attached to the rotating shaft 50 so as to be relatively movable and tiltable in the axial direction. Swash plate 60
Is formed with a through hole 61 passing through the center line, and the rotating shaft 50 passes through the through hole 61. The inner diameter of the through hole 61 is gradually increased in the vertical direction in FIG. A rotating plate 62 is also fixed to the rotating shaft 50, and is engaged with the front housing 16 via a thrust bearing 64. The swash plate 60 is rotated integrally with the rotation shaft 50 by the hinge mechanism 66, and is allowed to tilt with movement in the axial direction. The hinge mechanism 66
A support arm 67 fixedly provided on the rotating plate 62; a guide pin 69 fixedly provided on the swash plate 60 and slidably fitted in a guide hole 68 of the support arm 67; It includes a hole 61 and an outer peripheral surface of the rotating shaft 50.

The piston 14 is a kind of a hollow piston, and is provided integrally with the engaging portion 70 to be engaged with the swash plate 60 and is slidably fitted to the cylinder bore 12. And a head 72 as a hollow head. The head 72, the cylinder bore 12, and the valve plate 20 together form a compression chamber. The outer peripheral portion of the swash plate 60 is engaged with the engaging portion 70 via a pair of hemispherical shoes 76. A detailed description of the shape of the piston 14 will be given 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 suction chamber 22 is supplied to the suction hole 32 and the suction valve 34.
And is sucked into the compression chamber in the cylinder bore 12. 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 compression chamber in the cylinder bore 12 is compressed and discharged to the discharge chamber 24 via the discharge hole 36 and the discharge valve 38. The portion of the swash plate 60 where the piston 14 is located at the top dead center is the top dead center, and the portion where the piston 14 is located at the bottom dead center is the bottom dead center. With the compression of the refrigerant gas, the piston 14
, An axial compression reaction acts. The compression reaction force is received by a housing including the cylinder block 10, the front housing 16, the rear housing 18 and the like via the piston 14, the swash plate 60, the rotating plate 62, and the thrust bearing 64. The engagement portion 70 of the piston 14 is integrally provided with a rotation regulating portion 78 (see FIG. 2). The rotation restricting portion 78 is brought into contact with the inner peripheral surface of the front housing 16, restricts rotation of the piston 14 around the central axis, and avoids collision between the piston 14 and the swash plate 60.

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

A discharge passage 100 is provided inside the rotary shaft 50. The discharge passage 100 has one end opened to the support hole 56 and the other end opened to the space inside the front housing 16, and communicates with the swash plate chamber 86 through the space. The support hole 56 is communicated with the suction chamber 22 via the discharge port 104.

The swash plate type compressor is of a variable displacement type, and the pressure in the swash plate chamber 86 is controlled by utilizing the pressure difference between the discharge chamber 24 as a high pressure source and the suction chamber 22 as a low pressure source. , Cylinder bore 1 acting before and after piston 14
The difference between the pressure of the compression chamber in 2 and the pressure of the swash plate chamber 86 is adjusted, the inclination angle of the swash plate 60 is changed, the stroke of the piston 14 is changed, and the displacement of the compressor is adjusted.
Specifically, the pressure of the swash plate chamber 86 is controlled by controlling the excitation and demagnetization of the electromagnetic control valve 90 so that the swash plate chamber 86 is communicated with the discharge chamber 24 or cut off.

Cylinder block 10 and piston 14
Is made of an aluminum alloy, which is a kind of metal, and the outer peripheral surface of the piston 14 is coated with a fluororesin. However, the material of the cylinder block 10 and the piston 14, the material of the coating layer, and the like are not limited to the above-described materials, and may be other materials.

The piston 14 will be described in more detail. As shown in FIG. 2, the piston 14 is formed by closing an opening of a bottomed cylindrical member 112 constituting a main part of the head 72 by a closing member. The closing part 110 as a closing member is formed integrally with the engaging part 70, and the bottomed cylindrical member 112 has a shape in which one end of the hollow cylinder is closed and the other end is opened. It is fixed by appropriate means such as welding in a state where the opening is closed by the closing portion 110. An annular groove 116 for holding lubricating oil is formed on the outer peripheral surface of the bottomed cylindrical member 112.

The engaging portion 70 of the piston 14 is generally U-shaped, and has a pair of arms 120 and 122 extending parallel to each other in a direction perpendicular to the central axis of the head 72, and a base of the arms 120 and 122. And a connecting portion 124 for connecting the ends to each other. Recesses 130 are formed in the inner surfaces 126 and 128 of the arms 120 and 122, respectively, facing each other. The inner surfaces of these concave portions 130 have a concave spherical shape, and two concave spherical surfaces are located on one spherical surface. The pair of shoes 76 has a concave portion 13 in the spherical portion.
The swash plate 60 is slidably held at 0 and comes into contact with both sides of the outer peripheral portion of the swash plate 60 in the plane portion, and sandwiches the outer peripheral portion of the swash plate 60 from both sides. The closing portion 110 is connected to the arm portion 1 of the engaging portion 70.
It is formed integrally with the 22 side.

Inner side surfaces 126 and 128 of the arm portions 120 and 122 facing both side surfaces of the swash plate 60, and a connecting portion 124
At both ends in the circumferential direction of the swash plate 60 at the intersection between the outer peripheral surface of the swash plate 60 and the inner side surface 132 facing the outer surface of the swash plate 60, as shown in FIG. A relief 140 is formed to avoid interference with the periphery. The escape portion 140 is a portion other than the above both ends,
That is, it is not provided at the center. When the top dead center of the swash plate 60 deviates from a plane including the central axis of the piston 14 and the rotation axis of the rotation shaft 50 by a small angle in the circumferential direction of the swash plate 60, the top dead center and the bottom dead center are shifted. When swinging at a small angle around a straight line connecting the points, the arms 120, 12
2 and inner surface 13 of connecting portion 124
Since it easily interferes with the corner of the intersection with 2, the relief 140 is provided in this part. The relief portion 140 also has a function of avoiding interference (collision) with the swash plate 60 due to rotation of the piston 14 around the central axis. The rotation restricting portion 78 provided on the engaging portion 70 of the piston 14 also
As described above, the rotation of the piston 14 around the central axis is controlled to prevent interference with the swash plate 60. However, the provision of the escape portion 140 further ensures the engagement portion 70 of the piston 14. And the swash plate 60 can be avoided.

As shown in FIG. 4, the escape portion 140 includes arm portions 120 and 122 (FIG. 4 shows one arm portion 122).
(Only shown) at a position outside the both ends in the circumferential direction of the swash plate 60, and is formed along a circular arc centered on a straight line 1 extending in a direction orthogonal to the central axis of the head 72. As shown in FIG. 5, a rounded portion 142 having a radius of curvature of 0.5 mm or more and 3.0 mm or less is formed at an end of the escape portion 140 on the connecting portion 124 side. In the case of this embodiment, 1.4 mm
Is formed. Specifically, as shown in FIG. 5, the cross-sectional shape of the relief portion 140 when cut along a cutting plane including the straight line l is orthogonal to the straight line m and parallel to the straight line l. A line n, a curve p smoothly connecting the orthogonal line m and the parallel line n, and an end of the parallel line n opposite to the end on the curve p side, and approaching the straight line l as the distance from the end increases. And the inclination line q inclined in the direction of the arrow. The curve p defines the rounded portion 142, is a single arc having a constant radius of curvature, and the radius of curvature is 1.4 mm in this embodiment.
It is said that. The inclination angle of the inclination line q with respect to the straight line 1 is equal to the maximum inclination angle of the swash plate 60. It is desirable that a rounded portion is also formed on the outer peripheral edge of the swash plate 60 in order to avoid interference with the engaging portion 70.

As shown in FIG. 6, a piston blank 150 for manufacturing the piston 14 configured as described above has a portion in which the engaging portion 70 and the closing portion 110 are integrally formed, Is a bottomed cylindrical member 1 provided separately.
12 is a dual material in which the two engaging portions 70 are connected to each other. In the present embodiment, the engaging portion 70, the closing portion 110, and the bottomed cylindrical member 112 are both made of an aluminum alloy, which is a kind of metal, and are manufactured by forging or casting. The engaging portions 70 include inner surfaces 126 and 128 of the pair of arm portions 120 and 122 and the connecting portion 1.
The reinforcement rib 172 (see FIG. 6)
(Shown by a two-dot chain line). In addition, the end surface 18 of the bottomed cylindrical member 112 on the opposite side to the opening end surface 178.
A projecting portion 182 is provided at the center of the projection 0. A center hole 184 is formed in the protruding portion 182 before a machining step described later.

The closing portion 110 has a fitting portion 190 smaller in diameter than other portions, and the fitting portion 190 is fitted into the open end of the bottomed cylindrical member 112. Bottomed cylindrical member 1
The bottomed cylindrical member 112 and the closing portion 110 are fixed by appropriate fixing means in a state where the fitting depth is defined by the contact between the opening-side end surface 178 of the 12 and the end surface 194 of the closing portion 110. In the present embodiment, the opening-side end surface 178 and the end surface 194 are used as welding surfaces and fixed by welding. Thus, the head 72 is formed. Thereafter, the center (not shown) is engaged with each of the center holes 184 and supported from both sides in a centered state, and the outer peripheral surface of the head 72 is machined. At this time, the annular groove 116 is formed on the outer peripheral surface of the head 72.

Subsequently, cutting of the engaging portion 70 is performed. Milling cutter, a type of machining tool (not shown)
Is rotated with its rotation axis extending parallel to the central axis of the head 72, the reinforcing rib 172 of the engaging portion 70 is removed, and the arms 120, 122 and the connecting portion 1 are removed.
The inner surfaces 126, 128, 132 of 24 are machined. In FIG. 6, the reinforcing rib 172 has been removed,
The state in which the inner side surfaces 126, 128, 132 have been machined is shown, but the corners where the inner side surfaces 126, 128 of the arm portions 120, 122 and the inner side surface 132 of the connecting portion 124 intersect are rounded. It is attached. This rounding may be performed at the time of forging or casting, but in the present embodiment, the rounding is performed at the time of machining the inner side surfaces 126, 128, and 132.

Next, as shown in FIG.
0, 122 (only one arm portion 122 is shown in FIG. 7)
Inner surfaces 126 and 128 and an inner surface 132 of the connecting portion 124
The relief portions 140 are formed at both ends in the circumferential direction of the swash plate 60 at the intersections with the swash plate 60. The relief portion 140 is formed by cutting with a milling cutter 200 schematically shown in FIG. The milling cutter 200 is a one-side milling cutter, and has a cutting edge 2 on each of an outer peripheral surface and one side surface.
The body 206 includes a body 206 as a cutting unit having the outer blades 202 and 204 (hereinafter, referred to as an outer blade 202 and a side blade 204), and a shank 208 as a shaft. Milling cutter 2
The 00 shank 208 is rotatably held on a tool spindle (not shown). As shown in FIG.
In the vicinity of the intersection between the outer blade 202 and the side blade 204, a rounded portion 212 is formed by being smoothly connected by a curve. The cross-sectional shape of the rounded portion 212 having a plane parallel to the center axis of the milling cutter 200 as a cut surface forms an arc having a constant radius of curvature, and the radius of curvature of the arc is 1.4 mm. In the outer peripheral blade 202, the cutting edge is located on the same cylindrical surface,
A straight outer peripheral edge 216 connected to the rounded portion 212 and a tapered surface which is continuous with an end of the straight outer peripheral edge 216 on the side opposite to the side blade 204, and in which the cutting edge is inclined in a direction approaching the central axis as being away from the end. And a tapered outer peripheral edge 218 located at

As shown in FIG. 7, the milling cutter 200 has its own rotation axis l deviated from one end in the circumferential direction of the swash plate 60 of one arm portion (for example, the arm portion 122). The head 72 is arranged so as to extend in a direction orthogonal to the central axis of the head 72. Then, while being rotated about the rotation axis l, it is moved to a position shown by a two-dot chain line in FIG. 4, and a relief portion 140 (see FIG. 5) is formed at one end of the arm portion 122. Milling cutter 2
The relief trajectory 140 defined by the orthogonal line m, the parallel line n, the curve p, and the inclined line q is formed by the rotation trajectory of the outer peripheral blade 202 and the side blade 204 of FIG. This forms a rounded portion 142 defined by the curve p. Subsequently, the milling cutter 200 is moved in a direction parallel to the central axis of the head 72 to approach the arm unit 120 side, and the escape unit is provided at one end of the arm unit 120 in the same manner as the arm unit 122. 140 is formed. Also, the arm part 120,
A relief portion 140 is similarly formed at the other end of 122. The heads 72 of the arms 120 and 122
The relief portions 140 at the ends facing each other in a direction parallel to the central axis of the sword can be formed at once by a milling cutter. In that case, the rotation axis l is moved in the left-right direction in FIG.

After that, coating is performed on at least the outer peripheral surface of the head 72 to form a coating layer, and after centerless grinding is performed, when the piston 14 becomes
Is formed, and the engaging portion 70 is formed. Further, the protruding portion 182 is cut off, and the piston material 1 is removed.
50 is cut off and two pistons 14 are obtained.

According to the piston 14 of the present embodiment, the escape portion 140 for avoiding interference with the swash plate 60 is provided.
Has a rounded portion having a radius of curvature of 0.5 mm or more and 3.0 mm or less, so that a pair of arm portions 120 and 1 are provided.
The concentration of stress at the intersection between the connecting portion 22 and the connecting portion 124 is reduced, and a decrease in the mechanical strength of the engaging portion 70 (the above-mentioned intersection) is avoided. The connecting portion 124 of the engaging portion 70 receives a bending moment when the swash plate type compressor is operated. As the piston 14 reciprocates, the head 72 and the arm 122
And a force in a direction to move one of the pair of arm portions 120 and 122 away from the other based on the inertial force acting on the arm member and the frictional resistance between the outer peripheral surface of the head 72 and the inner peripheral surface of the cylinder bore 12. Then, a bending moment in a direction of bending the connecting portion 124 so as to protrude toward the swash plate 60 acts, and the pair of arm portions 1
Stress concentration occurs at the intersection of the connecting parts 124 and 122. On the other hand, the relief portion 140 is
2, the stress concentration can be reduced. By setting the radius of curvature of the rounded portion 142 within the above-described appropriate range, it is possible to prevent interference with the swash plate 60 while avoiding an increase in the thickness of the portion of the engaging portion 70 where the relief portion 140 is formed. In addition, despite the large stress concentration, it is necessary to increase the wall thickness in order to secure the mechanical strength, it is possible to avoid increasing the weight, after all, The weight can be reduced while securing the mechanical strength of the engaging portion 70. Also, by providing the relief portions 140 at both ends and not at the center, a decrease in the mechanical strength of the engagement portion 70 can be avoided. Furthermore, the escape unit 14
Reference numeral 0 denotes a shape that can be formed by rotating the milling cutter 200 about the rotation axis l and performing cutting, and is easy to manufacture.

The bottomed cylindrical member and the closed portion may be fixed by a fixing method other than welding, for example, other fixing methods including bonding, tight fitting, screwing, or a combination thereof. The piston may have a form in which a bottomed cylindrical portion and an engaging portion constituting a main portion of the head are integrally formed, and an opening of the bottomed cylindrical portion is closed by a closing member.
The present invention can also be applied to a double-headed piston having a head on both sides of an engagement portion with a swash plate.

Although several embodiments of the present invention have been described above, these are merely examples, and the present invention is described in the section [Problems to be Solved by the Invention, Means for Solving Problems and Effects]. Various modifications and improvements can be made based on the knowledge of those skilled in the art, including the above-described embodiment.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a variable displacement swash plate type compressor having a piston for a variable displacement type swash plate type compressor according to an embodiment of the present invention.

FIG. 2 is a front view of the piston.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a sectional view taken along line CC of FIG. 4;

FIG. 6 is a front view (partial cross section) showing a piston material for producing the piston.

FIG. 7 is a side sectional view for explaining a method of manufacturing the piston.

FIG. 8 is a front view (partially in section) of a milling cutter used in the method for manufacturing a piston.

[Explanation of symbols]

14: Single head piston 60: Swash plate 70: Engagement part
72: head 120, 122: arm 12
4: connecting portions 126, 128, 132: inner surface 140: relief portion 142: rounded portion 200: milling cutter 202: outer peripheral blade 204: side blade 2
12: Roundness

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Osamu Hiramatsu 2-1-1 Toyota-cho, Kariya-shi, Aichi F-term in Toyota Industries Corporation (reference) 3H003 AA03 AB07 AC03 CB00 3H076 AA06 BB28 BB38 BB50 CC31

Claims (4)

[Claims] A pair of arms extending parallel to each other;
A connecting portion for connecting the base ends of the arm portions to each other; an engaging portion in which the pair of arm portions respectively engage with both side surfaces of the outer peripheral portion of the swash plate via shoes; A piston for a variable displacement swash plate compressor having a head formed integrally with the cylinder bore and slidably fitted in the cylinder bore, wherein the pair of arm portions face both side surfaces of the swash plate. A relief for avoiding interference with the outer edge of the swash plate at least at both ends in the circumferential direction of the swash plate at the intersection of the inner surface with the inner surface and the inner surface facing the outer surface of the swash plate. Part is provided, and at the end of the relief part on the connecting part side, 0.5 mm
A piston for a variable displacement swash plate compressor, wherein a rounded portion having a radius of curvature of 3.0 mm or less is formed. 2. The variable displacement type swash plate type compressor piston according to claim 1, wherein the relief portions are provided at both ends in the circumferential direction of the swash plate, and are not provided at portions inside the both end portions. . 3. The variable displacement swash plate type compressor piston according to claim 1, wherein the relief portion is formed by machining. 4. A pair of arms extending parallel to each other,
A connecting portion for connecting the base ends of the arm portions to each other; an engaging portion in which the pair of arm portions respectively engage with both side surfaces of the outer peripheral portion of the swash plate via shoes; And a head formed integrally with the cylinder bore and slidably fitted in the cylinder bore, comprising: a piston for a variable displacement swash plate type compressor; Relief portions are formed by machining at least at both ends in the circumferential direction of the swash plate, at the intersections between the inner surfaces facing the both sides and the inner surface facing the outer peripheral surface of the swash plate of the connecting portion. The machining is performed by a milling cutter that rotates as a rotation axis a straight line extending in a direction intersecting the center axis of the head at a position protruding from both ends in the circumferential direction of the swash plate of the pair of arms, Outside that milling cutter Forming a rounded portion having a radius of curvature of 0.5 mm or more and 3.0 mm or less at the end of the relief portion on the connecting portion side by rounding the vicinity of the intersection between the surface blade and the one side surface blade. A method for manufacturing a piston for a variable displacement swash plate type compressor, characterized by comprising: