Information
-
Patent Grant
-
6526869
-
Patent Number
6,526,869
-
Date Filed
Monday, April 2, 200123 years ago
-
Date Issued
Tuesday, March 4, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Look; Edward K.
- Leslie; Michael
Agents
-
CPC
-
US Classifications
Field of Search
US
- 092 172
- 092 176
- 092 255
- 092 260
- 417 269
- 029 88804
- 029 888042
- 029 888044
- 029 888047
- 029 557
-
International Classifications
-
-
Disclaimer
Terminal disclaimer
Abstract
A hollow piston has an end wall that receives the pressure of a cylinder bore of a compressor. Several reinforcing ribs are formed on the inner end face of the end wall. The ribs extend radially from the axis of the piston. Therefore, the piston is light and strong.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a hollow piston, which is reciprocated by rotation of a cam body that rotates integrally with a rotary shaft and a method for producing the same.
A piston disclosed in Japanese Patent Unexamined Publication No. Hei 11-107912 is hollow to reduce its weight. Such a hollow piston improves displacement control for variable displacement type compressors, which control the inclination angle of a swash plate by controlling the pressure in a crank chamber.
The weight of a hollow piston can be reduced by reducing the thickness of a wall surrounding the hollow portion. The pressure of refrigerant gas is applied to the head end of the piston, which reciprocates inside the cylinder bore.
The head end wall of the piston is flat. However, if the head end is too thin, the piston will not have the strength required to withstand the pressure in the cylinder bore.
SUMMARY OF THE INVENTION
An object of the present invention is to reduce the weight of a hollow piston by reducing the weight of the head end wall of the piston.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a hollow piston used in a compressor is provided. The piston is accommodated in a cylinder bore of the compressor. The piston includes an end wall. The end wall receives the pressure of the cylinder bore. The end wall having an outer end face and an inner end face that is opposite to the outer end face. A reinforcing protrusion is formed on the inner end face and is radially symmetrical.
The present invention may be applied to a method for manufacturing a hollow piston used in a compressor. The piston includes a head piece and a body piece that is coupled to the head piece. The head piece has an end wall that receives the pressure of a cylinder bore of the compressor. The body piece includes the remainder of the piston. The end wall has an outer end face and an inner end face that is opposite to the outer end face. The method includes preparing a mold for forming the head piece, wherein the mold is designed such that a temporary protrusion is formed on the inner end face, pouring molten metal into the mold, pushing the temporary protrusion before the molten metal solidifies to prevent formation of shrinkage cavities, and removing part of the temporary protrusion after the molten metal solidifies, wherein the remainder of the temporary protrusion serves as a reinforcing protrusion.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
FIG.
1
(
a
) is a cross-sectional side view of a compressor according to a first embodiment of the present invention;
FIG.
1
(
b
) is a cross-sectional view taken along the line
1
(
b
)—
1
(
b
) in FIG.
1
(
a
);
FIG. 2
is a cross-sectional side view of the piston of FIG.
1
(
a
);
FIG. 3
is a cross-sectional side view taken along the line
3
—
3
in
FIG. 2
;
FIG. 4
is a cross-sectional view taken along the line
4
—
4
in
FIG. 2
;
FIG. 5
is a cross-sectional side view of a piston according to a second embodiment of the present invention;
FIG. 6
is a cross-sectional side view of a piston according to a third embodiment of the present invention;
FIG.
7
(
a
) is a partial cross-sectional view of the head of a piston according to a fourth embodiment of the present invention;
FIG.
7
(
b
) is a cross-sectional view taken along the line
7
(
b
)—
7
(
b
) in FIG.
7
(
a
);
FIG.
8
(
a
) is a partial cross-sectional view of the head of a piston according to a fifth embodiment of the present invention;
FIG.
8
(
b
) is a cross-sectional view taken along the line
8
(
a
)—
8
(
a
) in FIG.
8
(
a
);
FIG.
9
(
a
) is a partial cross-sectional side view of the head of a piston according to a sixth embodiment of the present invention;
FIG.
9
(
b
) is a cross-sectional view taken along the line
9
(
b
)—
9
(
b
) in FIG.
9
(
a
);
FIG.
10
(
a
) is a partial cross-sectional side view of the head of a piston according to a seventh embodiment of the present invention;
FIG.
10
(
b
) is a cross-sectional view taken along the line
10
(
b
)—
10
(
b
) in FIG.
10
(
a
);
FIG.
11
(
a
) is a partial cross-sectional side view of the major part of a piston according to an eighth embodiment of the present invention;
FIG.
11
(
b
) is a cross-sectional view taken along the line
11
(
b
)—
11
(
b
) in FIG.
11
(
a
);
FIG.
12
(
a
) is a partial cross-sectional side view of the head of a piston according to a ninth embodiment of the present invention;
FIG.
12
(
b
) is a cross-sectional view taken along the line
12
(
b
)—
12
(
b
) in FIG.
12
(
a
);
FIG.
13
(
a
) is a partial cross-sectional side view of the head of a piston according to a tenth embodiment of the present invention;
FIG.
13
(
b
) is a cross-sectional view taken along the line
13
(
b
)—
13
(
b
) in FIG.
13
(
a
);
FIG.
14
(
a
) is a partial cross-sectional side view of the head of a piston according to an eleventh embodiment of the present invention;
FIG.
14
(
b
) is a cross-sectional view taken along the line
14
(
b
)—
14
(
b
) in FIG.
14
(
a
);
FIG.
15
(
a
) is a partial cross-sectional side view of the head of a piston according to a twelfth embodiment of the present invention;
FIG.
15
(
b
) is a cross-sectional view taken along the line
15
(
b
)—
15
(
b
) in FIG.
15
(
a
);
FIG.
16
(
a
) is a partial cross-sectional side view of the head of a piston according to a thirteenth embodiment of the present invention,
FIG.
16
(
b
) is a cross-sectional view taken along the line
16
(
b
)—
16
(
b
) in FIG.
16
(
a
);
FIG. 17
is a cross-sectional side view of a piston according to a fourteenth embodiment of the present invention;
FIG. 18
is cross-sectional view taken along the line
18
—
18
in
FIG. 17
;
FIG.
19
(
a
) is a cross-sectional side view showing a mold in which a welding liquid has been poured; and
FIG.
19
(
b
) is a cross-sectional side view illustrating a protrusion
54
for preventing shrinkage of a cavity.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A first embodiment of the present invention will be described below with reference to FIG.
1
(
a
) to FIG.
4
.
FIG.
1
(
a
) shows the internal structure of a variable displacement type compressor. A front housing
12
and a cylinder block
11
form a controlled pressure chamber, or a crank chamber
121
, and a drive shaft
13
is supported in the crank chamber
121
. The drive shaft
13
is driven by an external driving source (for example, a vehicle engine). A rotary support
14
is secured to the drive shaft
13
, and a swash plate
15
is supported on the drive shaft
13
to slide in the axial direction of the drive shaft
13
and to incline with respect to the drive shaft
13
. A guide pin
16
that is fixed to the swash plate
15
is pivotally fitted into a guide hole
141
that is formed onto a rotary support
14
. The swash plate
15
is movable in the axial direction of the drive shaft
13
and rotatable together with the drive shaft
13
in concert with the guide hole
141
and the guide pin
16
.
The inclination of the swash plate
15
is permitted by the pivotal relationship between the guide hole
141
and the guide pin
16
and by the sliding relationship between the drive shaft
13
and the swash plate
15
.
The inclination angle of the swash plate
15
can be changed in accordance with the pressure of the crank chamber
121
. The inclination angle of the swash plate
15
decreases as the pressure in the crank chamber
121
increases, and it increases as the pressure in the crank chamber
121
decreases. The refrigerant in the crank chamber
121
flows into a suction chamber
191
through an unillustrated pressure release passage, and the refrigerant in a discharge chamber
192
, which is in a rear housing
19
, is conducted to the crank chamber
121
through a pressure supply passage (not shown). A displacement control valve
25
is located in the pressure supply passage, and the flow rate of the refrigerant supplied from the discharge chamber
192
to the crank chamber
121
is controlled by the displacement control valve
25
. The pressure in the crank chamber
121
increases as the flow rate of the refrigerant supplied from the discharge chamber
192
to the crank chamber
121
increases, and the pressure in the crank chamber
121
decreases as the flow rate of the refrigerant supplied from the discharge chamber
192
to the crank chamber
121
decreases. In other words, the inclination angle of the swash plate
15
is controlled by the displacement control valve
25
.
The maximum inclination angle of the swash plate
15
is defined by direct contact between the swash plate
15
and the rotary support
14
. The minimum inclination angle of the swash plate
15
is defined by direct contact between a snap ring
24
on the drive shaft
13
and the swash plate
15
.
In the cylinder block
11
, a plurality of cylinder bores
111
(only two are shown in the drawing) are arranged around the drive shaft
13
. An aluminum piston
17
is housed in each cylinder bore
111
. The rotation of the swash plate
15
is converted into the reciprocating movement of the pistons
17
via shoes
18
. The shoes
18
contact and slide with respect to the swash plate
15
.
The refrigerant in the suction chamber
191
flows into one of the cylinder bores
111
and opens a corresponding suction valve
211
, which is formed by an inner valve forming plate
21
, from a corresponding suction port
201
, which is formed in a valve plate
20
, when the corresponding piton moves from right side to left in FIG.
1
(
a
).
The refrigerant in the cylinder bore
111
is discharged into the discharge chamber
192
, which pushes aside a corresponding discharge valve
221
that is formed on an outer valve forming plate
22
, through a discharge port
202
when the corresponding piston
17
moves from left to right side in FIG.
1
(
a
). Each discharge valve
221
contacts a corresponding retainer
231
, which is formed on a retainer forming plate
23
. The retainers
231
limit the maximum opening degree of the discharge valves
221
.
The discharge chamber
192
and the suction chamber
191
are connected with each other through an external refrigerant circuit
26
.
The refrigerant flowing from the discharge chamber
192
to the external refrigerant circuit
26
is circulated to the suction chamber
191
through a condenser
27
, an expansion valve
28
, and an evaporator
29
.
As shown in
FIGS. 2 and 3
, the interior of each piston
17
includes a hollow space
171
. Each piston
17
is constructed by coupling a head
31
, which includes a head end wall
30
, to a body
32
, which contacts the shoes
18
. The body
32
has a coupler portion
33
, which includes a pair of concave portions
331
for holding the shoes
18
, and a peripheral wall
34
. The head
31
includes the head end wall
30
and a rim
35
.
The rim
35
of the head
31
and the peripheral wall
34
of the body
32
are welded together at their mating surfaces to join the head
31
to the body
32
. An inner surface
341
of the peripheral wall
34
is circumferential, and an outer surface
342
of the peripheral wall
34
is circumferential. In addition, an inner surface
351
of the rim
35
and an outer peripheral surface
352
of the rim
35
are circumferential. The inner surface
341
, the outer surface
342
of the peripheral wall
34
, the inner surface
351
and the outer peripheral surface
352
of the rim
35
share a common axis L, and the axis L is surrounded the hollow space
171
.
The head end wall
30
is flat, and an outer end face
36
of the head end wall
30
, which faces the inner valve forming plate
21
, is parallel with the inner valve forming plate
21
. An inner end face
37
of the head end wall
30
also is parallel with the inner valve forming plate
21
. As shown in
FIG. 4
, a plurality of reinforcing projections
39
(6 pieces in the present embodiment) are formed integrally with the inner end face
37
. The reinforcing projections
39
, or ribs, extend radially from the axis L to the inner surface
351
. Inner ends
391
of the reinforcing projections
39
are located at the axis L, and outer ends
392
of the reinforcing projections
39
are connected with the inner peripheral surface
351
of the rim
35
. The reinforcing projections
39
are spaced at the same angular intervals around the axis L along a radial line passing through the axis L. In this embodiment, the reinforcing projections
39
are spaced at the equiangular intervals of 60° about the axis L. That is, the reinforcing projections
39
are radially symmetrical. As shown in
FIGS. 2 and 3
, a projecting end face
393
of the reinforcing projection
39
is parallel to the inner end face
37
, and the dimension of the reinforcing projections
39
are the same.
The following effects occur in the first embodiment.
(1-1) The head end wall, which has a simple flat shape, is formed in a right angle form at the joint between the inner end surface of the head end wall and the inner surface
351
of the rim
35
. The right angle form makes it easy to concentrate the stress working on its connecting portion. If the thickness of the head end wall is increased, strength against the stress concentration working on the connecting portion of the right angle form is obtained, but the increased pressure at the head end wall induces the weight increase in the head end wall. Accordingly, the stress concentrating on the center portion of the head end wall becomes excessive when the weight increase of the head end wall is controlled so as to be as responsive as possible by designing the wall thickness at a minimum enough to be capable of keeping the head end wall from stress concentration working on the connecting portion of the right angle form.
The reinforcing projections
39
on the inner end face
37
increase the surface area of the inner end face
37
. The increase in the surface area of the inner end face
37
reduces stress concentration working against the head end wall
30
. Further, the reinforcing projected portions
39
on the inner end face
37
limit the weight of the head end wall
30
compared to simply increasing the thickness of the head end wall
30
.
(1-2) The reinforcing projections
39
disperse stress in their longitudinal directions. The reinforcing projections
39
extend in the radial direction, and this disperses stress in the radial direction of the head end wall
30
.
(1-3) All the reinforcing projections
39
are connected with the inner surface
351
of the rim
35
, which disperses stress at the joints between the rim
35
and the head end wall
30
.
(1-4) The inner ends
391
of all the reinforcing projections
39
are located at the axis L, and this disperses the stress that occurs near the axis L of the head end wall
30
.
(1-5) Dispersing the stress of the head end wall
30
in the circumferential direction is important, although such dispersal is less than that in the radial direction. The reinforcing projections
39
are spaced at the same intervals around the axis L is advantageous for equalizing the stress dispersion around the axis L, that is, the stress dispersion in the circumferential direction.
(1-6) The head
31
, which includes the head end wall
30
, is formed by casting, cutting, or pressing. The piston
17
, in which the head
31
and the body
32
are coupled, is advantageous for easily forming the reinforcing projection
39
into a predetermined form on the inner end face
37
of the head end wall
30
.
Next, a second embodiment, as shown in
FIG. 5
, will be described. In this embodiment, components that are the same in the first embodiment bear the same reference numerals used in the first embodiment.
A head
31
A, which forms constituting a piston
17
A together with a body
32
A, is fitted in the body
32
A such that the head
31
A is entirely housed in the peripheral wall
34
of the body
32
A.
Next, a third embodiment as shown in
FIG. 6
will be described. In this embodiment, components that are the same in the first embodiment bear the same reference numerals used in the first embodiment.
In a piston
17
B, in this embodiment, a rim
35
B, which corresponds to the peripheral wall
34
in the first embodiment, and the head end wall
30
are formed integrally in a head
31
B. A base rim
38
is formed in a body
32
B. The base rim
38
is fitted into the rim
35
B.
The second embodiment and the third embodiment have the same advantages of the first embodiment.
Next, a fourth embodiment, as shown in FIGS.
7
(
a
) and
7
(
b
), will be described. The same components as in the first embodiment bear the same reference numerals used in the first embodiment.
In a piston
17
C of this embodiment, a plurality of reinforcing projections
47
extend from the axis L, and the reinforcing projections
47
and the inner surface
351
of the rim
35
are not connected. The reinforcing projections
47
are located at equal intervals around the axis L along radial lines. The reinforcing projections
47
mainly perform stress dispersion in the vicinity of the axis L.
This embodiment has the advantages (1-1), (1-2), and (1-4) through (1-6) of the first embodiment.
Next, a fifth embodiment as shown in FIGS.
8
(
a
) and
8
(
b
) will be described. In this embodiment, components that are the same in the first embodiment bear the same reference numerals used in the first embodiment.
A piston
17
D includes a cylindrical reinforcing projection
40
centered on the axis L as shown. The reinforcing projection
40
has a radial dimension, and the reinforcing projection
40
is not connected with the surface
351
of the rim
35
. The reinforcing projection
40
mainly performs stress dispersion in the vicinity of the axis L. A circumferentially continuous reinforcing projection
40
is optimum for stress dispersion around the axis L, i.e., for equalizing the stress dispersion in the circumferential direction.
This embodiment has the advantages (1-1), (1-2), and (1-4) through (1-6).
Next, a sixth embodiment as shown in FIGS.
9
(
a
) and
9
(
b
) will be described. In this embodiment, components that are the same in the first components bear the same reference numerals used in the first embodiment.
A piston
17
E has a reinforcing annular projection
41
centered on the axis L. The reinforcing annular projection
41
is radially spaced from the axis L toward the inner surface
351
of the rim
35
, but the reinforcing annular projection
41
is not connected with the inner surface
351
of the rim
35
. The reinforcing annular projection
41
is optimum for stress dispersion around the axis L, i.e., for equalizing stress dispersion in the circumferential direction.
This embodiment has the advantages (1-1), (1-5) and (1-6) in the first embodiment.
Next, a seventh embodiment as shown in FIGS.
10
(
a
) and
10
(
b
) will be described. In this embodiment, components that are the same in the first embodiment bear the same reference numerals used in the first embodiment.
A piston
17
F has a head
31
F, which includes an end face and an end wall
30
F. The end face
36
is parallel to the inner valve forming plate
21
. An inner face
37
F of the head end wall
30
F includes an annular concave portion
371
, which is continuous with the rim
35
, and a central convex portion
372
, which is inside the annular concave portion
371
. The cross-sectional shape that appears when the annular concave portion
371
is cut at a plane S, which includes the axis L. in FIG.
10
(
b
), is shown by an arc
373
. The annular concave portion
371
is formed by turning the arc
373
once around the axis L. That is, the arc
373
serves as a base line for the annular concave portion
371
. The cross-sectional shape formed when the annular convex portion
37
is cut along the plane S, which includes the axis L, is shown by an arc
374
. The convex portion
372
is formed by turning the arc
374
once around the axis L. That is, the arc
374
serve as a base line for the convex portion
372
. The convex portion
372
is part of a sphere.
The radial immersion of the arc
373
is smaller than that of the arc
374
as shown in FIG.
10
(
b
). On the plane S, the arc
373
joins smoothly with the inner surface
351
of the rim
35
, which forms the hollow space
171
, and the arc
374
joins smoothly with the arc
373
. That is, the annular concave portion
371
blends smoothly with the rim
35
, and the convex portion
372
blends smoothly with the annular concave portion
371
. The annual concave portion
371
and the convex portion
372
share the axis L of the piston
17
.
In FIG.
10
(
b
), the region of the annular concave portion
371
is located between the inner surface
351
and the broken line K, and the region of the convex portion
372
is located inside the broken line K.
A plurality of reinforcing projections
42
(4 pieces in the present embodiment) are formed so that they extend radially from the axis L toward the inner surface
351
.
The reinforcing projections
42
each extend from the axis L to the inner surface
351
of the rim
35
. An end face
421
of the reinforcing projection
42
is parallel with the outer end face
36
. The reinforcing projections
42
are spaced at equal intervals around the axis L along radial lines.
The seventh embodiment has the following advantages:
(7-1) The affects of the reinforcing projections
42
are similar to those of the reinforcing projections
39
in the first embodiment.
(7-2) The arc
373
forming the annular concave portion
371
approaches the outer end face
36
of the head end wall
30
F and then it curves away from the outer end face
36
from the inner surface
351
toward the axis L. The arc
374
forming the convex portion
372
curves away from the outer end face
36
of the head end wall
30
F as it approaches the axis L. The shape of the inner face
37
F of the head end wall
30
F has favorable stress dispersion characteristics. Specifically, the annular concave portion
71
reduces the stress concentrated at the connecting portion between the rim
35
and the head end wall
30
F, and the convex portion
372
reduces the stress concentrated in the head end wall
30
F in the vicinity of the axis L. The shade of the inner face
37
F makes it possible to decrease the material volume and weight of the head end wall
30
F while providing the necessary strength compared with a head end wall that is a simple flat plate.
(7-3) The concave portion
371
and the annular convex portion
372
surrounding the axis L provide optimum stress dispersion and provide adequate strength while decreasing the material volume of the head end wall
30
F.
(7-4) The arc
373
, which serves as the base line of the annular concave portion
371
, is an appropriate shape of the annular concave portion
371
to attain stress dispersion.
(7-5) The arc
374
, which serves as the base line of the annular convex portion
372
, is an appropriate shape of the convex portion
372
to attain stress dispersion.
Next, an eighth embodiment shown in FIGS.
11
(
a
) and
11
(
b
) will be described. In this embodiment, components that are the same in the seventh embodiment bear the same reference numerals used in the seventh embodiment.
In a piston
17
G, radial reinforcing projections
43
are provided on an inner face
37
F of the head
31
G. The reinforcing projections
43
each extend from the axis L to the inner surface
351
of the rim
35
. The reinforcing projections
43
are spaced at equal angular intervals around the axis L along radial lines passing through the axis L. The distance between an end face
431
of the reinforcing projection
43
and the concave and convex surfaces
371
,
372
is constant. The reinforcing projections
42
have same effects as the reinforcing projections
39
in the first embodiment. The material volume necessary for forming the reinforcing projections
43
for improving the strength of the head end wall
30
F is reduced compared to the reinforcing projections
42
of the seventh embodiment.
Next, a ninth embodiment as shown in FIGS.
12
(
a
) and
12
(
b
) will be described. In this embodiment, components that are the same as in the sixth embodiment bear the same reference numeral used in the sixth embodiment.
In a piston
17
H, an annular reinforcing projection
41
and the reinforcing projections
44
are provided on the inner end face
37
of the head end wall
30
. The reinforcing projections
44
are connected to the outer peripheral surface of the annular reinforcing projection
41
and the inner surface
351
of the rim
35
. The reinforcing projections
44
are spaced apart at equal angular intervals around the axis L along radial lines passing through the axis L. The reinforcing annular projection
41
has the same effects as the reinforcing annular projection
41
of the sixth embodiment. The reinforcing projections
44
have advantages (1-2) and (1-3) of the first embodiment.
Next, a tenth embodiment as shown in FIGS.
13
(
a
) and
13
(
b
) will be described. In this embodiment, components that are the same in the first embodiment bear the same reference numerals used in the first embodiment.
In a piston
17
J, a plurality of reinforcing projections
45
are provided on the inner end face
37
of the head end wall
30
. The reinforcing projections
45
each extend radially from the axis L to the inner surface
351
of the rim
35
. The reinforcing projections
45
are spaced apart at equal angular intervals about the axis L along radial lines. An end face
451
of the reinforcing projection
45
approaches the outer end face
36
from the axis L to the inner surface
351
of the rim
35
and then curves away from the outer end face
36
. A concave portion
452
of the reinforcing projections
45
reduces the stress concentrated between the rim
35
and the head end wall
30
. A convex portion
453
of the reinforcing projections
45
reduces the stress concentration in the head end wall
30
in the vicinity of the axis L.
Next, an eleventh embodiment as shown in FIGS.
14
(
a
) and
14
(
b
) will be described. In this embodiment, components that are the same in the first embodiment bear the same reference numerals used in the first embodiment.
In a piston
17
K, a plurality of reinforcing projections
46
are provided on the inner face
37
of the head end wall
30
. The reinforcing projections
46
extend toward the inner surface
351
of the rim
35
from the vicinity of the axis L to the inner surface
351
of the rim
351
. The inner ends
461
of the reinforcing projections
46
are located near the axis L. The reinforcing projections
46
are not located on radial lines passing through the axis L, but the reinforcing projections
46
are located at equal intervals around the axis L. The reinforcing projections
46
have the same effects as the reinforcing projections
39
in the first embodiment.
Next, a twelfth embodiment as shown in FIGS.
15
(
a
) and
15
(
b
) will be described. In this embodiment, components that are the same as in the fifth embodiment bear the same reference numerals used in the fifth embodiment.
In a piston
17
L, a central reinforcing projection
40
and a plurality of outer reinforcing projections
48
are provided on the inner face
37
of the head end wall
30
. The reinforcing projections
48
are joined to the inner surface
351
of the rim
35
and extend radially toward the axis L. The reinforcing projections
48
are located at equal angular intervals around the axis L. The central reinforcing projection
40
has the same effects as the reinforcing projection
40
of the fifth embodiment. The outer reinforcing projections
48
have the advantage (1-2) of the first embodiment.
Next, a thirteenth embodiment as shown in FIGS.
16
(
a
) and
16
(
b
) will be described. In this embodiment, components that are the same in the twelfth embodiment bear the same reference numerals used in the twelfth embodiment.
In a piston
17
M, a plurality of inner reinforcing projections
49
and a plurality of outer reinforcing projections
48
are provided on the inner face
37
of the head end wall
30
. The inner reinforcing projections
49
extend radially along lines that pass through the axis L, and are not joined to the inner surface
351
of the rim
35
. The outer reinforcing projections
48
have the same effects as the reinforcing projections
47
of the fourth embodiment.
Next, a fourteenth embodiment as shown in
FIGS. 17 through 19
will be described. In this embodiment, components that are the same in the first embodiment bear the same reference numerals used in the first embodiment.
In a piston
17
N, a cylindrical reinforcing projection
50
is provided on the inner face
37
of the head end wall
30
. A head
31
, which includes the reinforcing projection
50
is manufactured by pouring molten aluminum into molds
51
and
52
, which are set as shown in FIG.
19
(
a
). A cylindrical pressing rod
53
is fitted in the mold
51
such that it can slide axially, and a protrusion
54
for preventing a shrinkage cavity is formed in the vicinity of the distal end of the pressing rod
53
. The distal end of the pressing rod
53
creates a concave portion
541
in the protrusion
54
for preventing a shrinkage cavity. The molds
51
and
52
form the protrusion
54
for preventing a shrinkage cavity on the inner end face
37
of the head end wall of the head
31
. The pressing rod
53
is forced in the direction of an arrow Q as shown in FIG.
19
(
a
) before the liquid aluminum poured into the molds
51
and
52
solidifies. The pressing rod
53
applies the pressure to the surface of the protrusion
54
for preventing a shrinkage cavity.
After the metal solidifies, a workpiece
310
, which includes the protrusion
54
for preventing a shrinkage cavity, is removed from the molds
51
and
52
, and the protrusion
54
is removed with a cutting tool
55
(for example, an end mill) as shown in
FIG. 19
(
b
). The machined surface on the inner face
37
that results after cutting the protrusion
54
becomes the projection end face
501
. That is, a part of the protrusion
54
becomes the reinforcing projection
50
.
The pressure applied to the surface of the protrusion
54
before solidification of the metal prevents a shrinkage cavity from being formed at the head end wall
30
in the vicinity of the axis L, that is, at the head end wall
30
near the projection end face
501
. The prevention of a shrinkage cavity of the head end wall
30
while providing the necessary strength of the material reduces the weight of the head end wall
30
. The protrusion
54
serves as a reinforcing projection.
The following embodiments are within the scope of the prevent invention.
It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms.
(1) In the ninth embodiment, twelfth embodiment and thirteenth embodiment, the reinforcing projections
41
,
40
, and
49
may be omitted.
(2) In the fourteenth embodiment, the protrusion
54
for preventing a shrinkage cavity may be cut out with the cutting tool
55
so that a part of the concave portion
541
formed in the protrusion
54
for preventing causing of a shrinkage cavity remains by bringing it into contact with the pressing rod
53
.
(3) In the seventh embodiment, an annular concave portion defining smooth concave curve except for an arc as a base line may be employed.
(4) In the seventh embodiment, an annular convex portion defining a convex curve except for the arc as a base line may be employed.
(5) In the seventh embodiment, the annular concave portion and the inner surface
351
of the rim
35
may be connected to each other by a tapered surface.
(6) In the seventh embodiment, the annular concave portion and the convex portion may be connected with each other by a tapered surface.
(7) The convex portion
372
of the seventh embodiment may be defined as a curved surface except for a spherical face.
(8) The head and the body may be connected with each other by adhesive.
(9) The head and the body may be connected with each other by friction welding.
(10) The head and the body may be connected with each other by press fitting.
Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.
Claims
- 1. A hollow piston for use in a swash-plate compressor having a swash-plate and shoes, wherein the piston is accommodated in a cylinder bore of the compressor and rotation of the swash-plate is converted into reciprocating movement of the piston via the shoes, the piston comprising:a body having a coupling portion engageable with said shoes; an end wall affixeded to the body, the end wall receives the pressure of the cylinder bore, the end wall having an outer end face and an inner end face that is opposite to the outer end face; a reinforcing protrusion formed on the inner end face, wherein the reinforcing protrusion is radially symmetrical.
- 2. The piston according to claim 1, further comprising a cylindrical wall that contacts the wall of the cylinder bore, wherein the reinforcing protrusion is separated from the cylindrical wall.
- 3. The piston according to claim 2, wherein the reinforcing protrusion and the axis of the piston intersect.
- 4. The piston according to claim 1, further comprising a cylindrical wall that contacts the wall of the cylinder bore, wherein the reinforcing protrusion is joined to the cylindrical wall.
- 5. The piston according to claim 4, wherein the reinforcing protrusion and the axis of the piston intersect.
- 6. The piston according to claim 1, wherein the reinforcing protrusion includes a plurality of ribs that extend radially on the inner end face.
- 7. The piston according to claim 6, wherein the ribs are arranged at equal angular intervals.
- 8. The piston according to claim 6, wherein the ribs are joined to one another in the vicinity of the axis of the piston.
- 9. The piston according to claim 6, further comprising a cylindrical wall that contacts the wall of the cylinder bore, wherein the ribs are joined to the cylindrical wall.
- 10. The piston according to claim 9, wherein each rib is substantially triangular and is located at a corner defined by the inner end face and the cylindrical wall.
- 11. The piston according to claim 1, wherein the end wall is flat and circular.
- 12. The piston according to claim 1, wherein the contour of the inner end face, from the radially outside portion toward the radially inside portion, first approaches the outer end face and then departs from the outer end face.
- 13. The piston according to claim 12, wherein the inner end face includes an annular concave surface, which is located about the axis of the piston, and a convex surface, wherein the convex surface is located radially inside of and is joined to the concave surface.
- 14. The piston according to claim 13, wherein the annular concave surface is a smooth curved surface, and wherein the cross section of the concave surface is uniform over the entire circumference about the axis of the piston, wherein the convex surface is a smooth curved surface, and wherein the cross section of the convex surface is uniform over the entire circumference about the axis of the piston.
- 15. The piston according to claim 1, further comprising a head piece and a body piece that is coupled to the head piece, wherein the head piece includes the end wall, and the body piece includes the remainder of the piston, and wherein, when the head piece an the body piece are separated, the inner end face is exposed.
- 16. A hollow piston used in a swash-plate compressor having a swash-plate and shoes, wherein the piston is accommodated in a cylinder bore of the compressor and rotation of the swash-plate is converted into reciprocating movement of the piston via the shoes, the piston comprising:a body having a coupling portion engagable with said shoes; a flat circular end wall affixed to the body, the flat circular end wall receives the pressure of the cylinder bore, wherein the end wall has an outer end face and an inner end face that is opposite to the outer end face; and a plurality of reinforcing ribs formed on the inner end face, wherein the ribs extend radially from the axis of the piston.
- 17. A method for manufacturing a hollow piston used in a compressor, where in the piston includes a head piece and a body piece that is coupled to the head piece, wherein the head piece has an end wall that receives the pressure of a cylinder bore of the compressor, and the body piece includes the remainder of the piston, and wherein the end wall has an outer end face and an inner end face that is opposite to the outer end face, the met hod comprising:preparing a mold for forming the head piece, wherein the mold is designed such that a temporary protrusion is formed on the inner end face; pouring molten metal into the mold; pushing the temporary protrusion before the molten metal solidifies to prevent formation of shrinkage cavities; and removing part of the temporary protrusion after the molten metal solidifies, wherein the remainder of the temporary protrusion serves as a reinforcing protrusion.
- 18. A hollow piston used in a compressor, wherein the piston is accommodated in a cylinder bore of the compressor, the piston comprising:an end wall that receives the pressure of the cylinder bore, the end wall having an outer end face and an inner end face that is opposite to the outer end face; a radially symmetrical reinforcing protrusion formed on the inner end face including a plurality of ribs that extend radially on the inner end face, each rib is substantially triangular; and a cylindrical wall that contacts the wall of the cylinder bore, wherein the ribs are located at a corner defined by the inner end face and the cylindrical wall and are joined to the cylindrical wall.
- 19. A hollow piston used in a compressor, wherein the piston is accommodated in a cylinder bore of the compressor, the piston comprising:an end wall that receives the pressure of the cylinder bore, the end wall having an outer end face and an inner end face that is opposite to the outer end face, wherein the contour of the inner end face, from the radially outside portion toward the radially inside portion, first approaches the outer end face and then departs from the outer end face and the inner end face includes an annular concave surface, which is located about the axis of the piston, and a convex surface, wherein the convex surface is located radially inside of and is joined to the concave surface; and a reinforcing protrusion formed on the inner end face, wherein the reinforcing protrusion is radially symmetrical.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-101025 |
Apr 2000 |
JP |
|
US Referenced Citations (18)
Foreign Referenced Citations (8)
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Sep 1990 |
CH |
4114985 |
Nov 1992 |
DE |
0 952 339 |
Oct 1999 |
EP |
10-077965 |
Mar 1998 |
JP |
10-281065 |
Oct 1998 |
JP |
11-107912 |
Apr 1999 |
JP |
11-257218 |
Sep 1999 |
JP |
11-294320 |
Oct 1999 |
JP |