US20030084783A1 - Piston for compressor and method of manufacturing the same - Google Patents
Piston for compressor and method of manufacturing the same Download PDFInfo
- Publication number
- US20030084783A1 US20030084783A1 US10/288,006 US28800602A US2003084783A1 US 20030084783 A1 US20030084783 A1 US 20030084783A1 US 28800602 A US28800602 A US 28800602A US 2003084783 A1 US2003084783 A1 US 2003084783A1
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- United States
- Prior art keywords
- piston
- guide wall
- circumferential surface
- wall
- head portion
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/0873—Component parts, e.g. sealings; Manufacturing or assembly thereof
- F04B27/0878—Pistons
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B13/00—Engines characterised by the introduction of liquid fuel into cylinders by use of auxiliary fluid
- F02B13/02—Compression ignition engines using air or gas for blowing fuel into compressed air in cylinder
- F02B13/04—Arrangements or adaptations of pumps
Definitions
- the present invention generally relates to a piston in a piston type compressor in which refrigerant gas is compressed for an air-conditioning system and a method of manufacturing the piston.
- Japanese Unexamined Patent Publication No. 2000-274350 discloses a piston 110 .
- the piston 110 includes a head portion 111 slidably inserted into a cylinder bore, a neck portion 112 engaged with a swash plate 102 of a compressor through a pair of shoes 103 , and a receiving wall 113 for receiving side force F as indicated by an arrow.
- the receiving wall 113 extends from a lower side of the head portion 111 towards the neck portion 112 and is arranged on a predetermined side in relation to the rotating direction R of the swash plate 102 .
- the receiving wall 113 is formed on the predetermined side where the side force F is applied due to the rotating direction R of the swash plate 102 , there is only a little contact area between the piston 110 and the inner circumferential surface of the cylinder bore 101 on the opposite side to the receiving wall 113 .
- the opposite side hardly receives the side force F, thereby, the piston 110 becomes lighter.
- the side force F is the largest force that is generated by compression reactive force and is received by the piston 110 during a compression process.
- the present invention is directed to obtain a piston whose weight is relatively light and which reciprocates in a relatively stable manner and a method of manufacturing the piston.
- a piston is used for a compressor.
- the compressor has a drive shaft having a central axis and a cam plate rotatably supported by the drive shaft.
- the cam plate converts the rotating movement of the drive shaft into the reciprocating movement of the piston.
- the piston has a central axis, a head portion and a neck portion.
- the head portion is slidably fitted in a cylinder bore.
- the neck portion is connected to the head portion and is engaged with the cam plate
- the cam plate is rotated in a predetermined direction to define a cam plate rotating direction.
- the piston also has a receiving wall for receiving side force and a first guide wall.
- the receiving wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a preceding side in the cam plate rotating direction.
- the receiving wall has an outer circumferential surface that slidably contacts the inner circumferential surface of the cylinder bore.
- the first guide wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston.
- the first guide wall has an outer circumferential surface that is continuous with the receiving wall and slides over the inner circumferential surface of the cylinder bore. A recess is formed in the outer circumferential surface of the first guide wall.
- the present invention also provides a compressor.
- the compressor includes a housing having a cylinder bore.
- a drive shaft is supported by the housing and has a central axis.
- a cam plate is supported by the drive shaft and is rotated in a direction defined as a cam plate rotating direction.
- the compressor also includes a piston having a central axis.
- the piston has a head portion, a neck portion, a receiving wall for receiving side force and a first guide wall.
- the head portion is slidably fitted in a cylinder bore.
- the neck portion is connected to the head portion and is engaged with the cam plate for converting the rotating movement of the cam plate into the reciprocating movement of the piston.
- the receiving wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a preceding side in the cam plate rotating direction
- the receiving wall has an outer circumferential surface that slidably contacts the inner circumferential surface of the cylinder bore
- the first guide wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston.
- the first guide wall has an outer circumferential surface that is continuous with the receiving wall and slides over the inner circumferential surface of the cylinder bore. A recess is formed in the outer circumferential surface of the first guide wall.
- the present invention also provides a method of forming a piston blank that includes two piston components in use for a compressor.
- the compressor has a drive shaft, a cam plate and a piston.
- the drive shaft has a central axis.
- a cam plate is rotated in a predetermined direction.
- the piston has a central axis, a head portion, a neck portion, a receiving wall for receiving side force and a guide wall.
- the neck portion is connected to the head portion.
- the receiving wall extends from the drive shaft side of the head portion towards the neck and is disposed on a preceding side in the predetermined direction.
- the guide wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston.
- the guide wall has an outer circumferential surface that is continuous with the receiving wall.
- the guide wall has a support portion connecting to the receiving wall.
- a recess is formed in the outer circumferential surface of the guide wall.
- the piston blank includes a first predetermined recess and a second predetermined recess.
- the method includes setting a first core in a first mold for forming the first predetermined recess such that the first core moves in a direction in which the first and second mold are separated, further setting a second core in a second mold for forming the second predetermined recess that is open to a substantially opposite side of the first predetermined recess, forming the piston blank by one of die-casting and forging, moving the first core relative to the first mold in order to break adhesion among the receiving wall, the guide wall and the first core, and separating the piston blank with the second mold from the first mold.
- FIG. 1 is a cross-sectional view of a swash plate type variable displacement compressor of a preferred embodiment according to the present invention
- FIG. 2A is a side view of a piston of the preferred embodiment according to the present invention.
- FIG. 2B is another side view opposite to FIG. 2A of the piston of the preferred embodiment according to the present invention.
- FIG. 2C is a cross-sectional view taken along the line I-I in FIG. 2A of the preferred embodiment
- FIG. 3 is a partial diagram of the piston and a drive shaft of the preferred embodiment according to the present invention.
- FIG. 4A is a partially enlarged cross-sectional view of a swash plate type compressor of a first alternative preferred embodiment according to the present invention
- FIG. 4B is a cross-sectional view taken along the line II-II in FIG. 4A of the first alternative embodiment
- FIG. 5A is a side view of a piston of a second alternative preferred embodiment according to the present invention.
- FIG. 5B is a cross-sectional view taken along the line III-III in FIG. 5A of the second alternative embodiment
- FIG. 6 is a side view of a piston of a third alternative preferred embodiment according to the present invention.
- FIG. 7A is a plane view of a piston blank and molds for casting the piston blank of the preferred embodiment according to the present invention.
- FIG. 7B is a cross-sectional view taken along the line IV-IV in FIG. 7A of the preferred embodiment
- FIG. 8A is a side view of a piston according to the prior art
- FIG. 8B is another side view of the piston opposite to FIG. 8A according to the prior art.
- FIG. 8C is a cross-sectional view taken along the line V-V in FIG. 8A of the prior art piston.
- a lug plate 17 is secured to the drive shaft 16 in the crank chamber 15 so as to rotate integrally with the drive shaft 16 .
- a swash plate 18 as a cam plate is accommodated in the crank chamber 15 .
- the drive shaft 16 is inserted through a shaft hole 18 a that is formed at the center of the swash plate 18 .
- the swash plate 18 is supported by the drive shaft 16 so as to slide along a central axis L of the drive shaft 16 and is inclinable with respect to the central axis L of the drive shaft 16 .
- a hinge mechanism 19 is interposed between the lug plate 17 and the swash plate 18 .
- the hinge mechanism 19 includes a pair of support arms 20 placed on the lug plate 17 and a pair of guide pins 21 , which is secured to the swash plate 18 .
- a spherical portion 21 a of each guide pin 21 is slidably interposed into a guide hole 20 a of each support arm 20 .
- the hinge mechanism 19 between the swash plate 18 and the lug plate 17 and the support for the drive shaft 16 allow the swash plate 18 to rotate integrally with the lug plate 17 and to incline with respect to the central axis L of the drive shaft 16 as the swash plate 18 slides along the central axis L of the drive shaft 16 .
- a plurality of cylinder bores 22 is evenly disposed around the drive shaft 16 in the cylinder block 11 and is formed through the cylinder block 11 Only one of cylinder bores 22 is shown in the drawings.
- a single head piston 23 is accommodated in each of the cylinder bores 22 so as to reciprocate therein.
- the piston 23 and the valve plate assembly 13 respectively shut the front and rear openings of the cylinder bore 22 .
- a compression chamber 24 is defined in each cylinder bore 22 .
- the volume of the compression chamber 24 varies in accordance with the reciprocating movement of the piston 23 .
- Each of the pistons 23 is connected to the swash plate 18 through a pair of semispherical shoes 25 . Thereby, the rotating movement of the swash plate 18 by the rotating drive shaft 16 is converted into the linear reciprocating movement of the piston 23 through the shoes 25 .
- the valve plate assembly 13 and the rear housing 14 define a suction chamber 26 and a discharge chamber 27 .
- Each of the piston 23 travels between a top dead center and a bottom dead center. At the top dead center, the piston 23 is at the right most position in the cylinder bore 22 . At the bottom dead center, the piston is the left most position in the cylinder bore 22 .
- refrigerant gas in the suction chamber 26 is introduced into the compression chamber 24 through a corresponding suction port 28 and a corresponding suction valve 29 that are formed in the valve plate assembly 13 .
- the refrigerant gas is compressed to a certain pressure and then discharged to the discharge chamber 27 through a corresponding discharge port 30 and a corresponding discharge valve 31 that are formed in the valve plate assembly 13 .
- a bleed passage 32 , a supply passage 33 and a control valve 34 are provided in a housing of the compressor.
- the bleed passage 32 connects the crank chamber 15 to the suction chamber 26 .
- the supply passage 33 connects the discharge chamber 27 to the crank chamber 15 .
- the control valve 34 is placed on the supply passage 33 .
- the high pressure refrigerant gas is introduced into the crank chamber 15 from the discharge chamber 27 through the supply passage 33 , and the refrigerant gas is discharged from the crank chamber 15 to the suction chamber 26 through the bleed passage 32 .
- the above amount of the high pressure refrigerant gas and the discharged refrigerant gas is controlled by adjusting the opening degree of the control valve 34 . Accordingly, the pressure in the crank chamber 15 is determined.
- the pressure differential between the crank chamber 15 and the compression chamber 24 varies in accordance with the pressure change in the crank chamber 15 , and the inclination angle of the swash plate 18 correspondingly varies with respect to a vertical line to the central axis L of the drive shaft 16 . In consequence, the stroke volume of the piston 23 changes, and the compressor displacement also varies.
- the piston 23 includes a cylindrical head portion 41 and a neck portion 42 parallel to a central axis S of the piston 23 .
- the neck portion 42 and the head portion 41 of the piston 23 respectively correspond to the front side and the rear side of the piston 23 .
- FIG. 2C on the front side end of the head portion 41 , the distant side from the drive shaft 16 is referred to as an upper side, while the close side to the drive shaft 16 is referred to as a lower side
- the head portion 41 is slidably interposed into the cylinder bore 22 .
- the neck portion 42 holds a pair of shoes 25
- the piston 23 is made of aluminum series metal material and is manufactured by die-casting or forging
- An engaging portion 42 a is formed on the neck portion 42 .
- a pair of shoe seats 42 b is formed in the engaging portion 42 a and receives the shoes 25 in such manner that the shoes 25 freely slides therein
- Film made of fluororesin such as PTFE is formed on an outer circumferential surface 41 a of the head portion 41 . Thereby, the head portion 41 smoothly slides over the inner circumferential surface of the cylinder bore 22 .
- a receiving wall 43 for receiving side force F extends from the lower side of the head portion 41 , that is, the drive shaft side of the head portion 41 , towards the neck portion 42
- the receiving wall 43 is disposed on a preceding side in the rotating direction R of the swash plate 18 .
- the rotating direction R of the swash plate 18 is defined as a swash plate rotating direction R hereafter.
- FIG. 3 a diagram is viewed from a side on which the swash plate rotating direction R is clockwise. That is, when it is viewed from the side of the neck portion 42 , a hypothetical plane X includes the central axis L of the drive shaft 16 and the central axis S of the piston 23 . The hypothetical plane X crosses the circumferential surface 41 a of the head portion 41 of the piston 23 at intersectional points P 1 and P 2 The intersectional point P 1 is distant from the central axis L of the drive shaft 16 and is located at 12 o'clock position On the other hand, the intersectional point P 2 is close to the central axis L of the drive shaft 16 and is located at 6 o'clock position. As shown in FIGS.
- the outer circumferential surface 43 a of the receiving wall 43 slides over the inner circumferential surface of the cylinder bore 22 and is disposed substantially in a range of 3 to 6 o'clock.
- the upper side of the head portion 41 corresponds to the area around 12 o'clock position while the lower side of the head portion 41 corresponds to the area around 6 o'clock position.
- the piston 23 receives reactive force from the inner circumferential surface of the cylinder bore 22 .
- the reactive force is generated by compression reactive force and the rotating force of the swash plate 18 .
- the reactive force is applied to a part of the outer circumferential surface 41 a of the head portion 41 after another part in accordance with the position of the piston 23 .
- the reactive force also includes the side force F herein.
- the side force F is defined as the largest force of the reactive force during the compression process.
- the side force F is applied to the outer circumferential surface 41 a of the head portion 41 substantially in the range of 4 to 6 o'clock. Since the receiving wall 43 is continuously connected to the head portion 41 , the piston 23 preferably receives some of the side force F at the receiving wall 43 .
- a first guide wall 44 extends from the lower side of the head portion 41 towards the neck portion 42
- the first guide wall 44 connects with the receiving wall 43 .
- the first guide wall 44 is disposed on the opposite side of the preceding side in the swash plate rotating direction R so as to be symmetrical to a corresponding portion of the receiving wall 43 with respect to the hypothetical plane X over a longitudinal range of the first guide wall 44
- the opposite side of the preceding side in the swash plate rotating direction R is defined as a following side.
- the outer circumferential surface 44 a of the first guide wall 44 extends within a range of 6 o'clock to 9 o'clock.
- the outer circumferential surface 43 a of the receiving wall 43 and the outer circumferential surface 44 a of the first guide wall 44 are continuously arranged within the range of 3 o'clock to 9 o'clock.
- the receiving wall 43 and the guide wall 44 form a semicircular wall
- a support portion 40 extends from the middle of the head portion 41 towards the neck portion 42 .
- the support portion is parallel to a hypothetical line Y passing through 3 o'clock and 9 o'clock when the head portion is viewed from the side of the neck portion 42 on a surface perpendicular to the central axis S of the piston 23 .
- the support portion 40 is connected to the receiving wall 43 and the guide wall 44 .
- the support portion 40 supports the receiving wall 43 and the guide wall 44 .
- the receiving wall 43 , the guide wall 44 and the support portion 40 form recess 45 .
- a rib 47 connects the neck portion 42 so to the support portion 40 and the semicircular wall that includes the first guide wall 44 and the receiving wall 43 .
- the recess 45 is formed in the outer circumferential surface 44 a of the first guide wall 44 that slides over the inner circumferential surface of the cylinder bore 22 .
- the contact area is triangular between the outer circumferential surface 44 a of the first guide wall 44 and the inner circumferential surface of the cylinder bore 22 .
- the recess 45 is relatively deeply formed to minimize the thickness of the receiving wall 43 . For example, if the recess 45 is not formed, a relatively large volume of the piston 23 that forms the receiving wall 43 and the first guide wall 44 is not removed.
- a slantingly cut semi-cylinder axially extends from the middle area of the head portion 41 to the bottom area towards the neck portion 42 .
- the slantingly cut semi-cylinder is disposed on the front end of the head portion 41 in the range of 3 o'clock to 9 o'clock.
- the recess 45 is formed inside the outer circumferential surface of the slantingly cut semi-cylinder that is in contact with the inner circumferential surface of the cylinder bore 22 within the range of 6 o'clock to 9 o'clock.
- the slantingly cut semi-cylinder includes the receiving wall 43 for receiving the side force F, the first guide wall 44 and the support portion 40 .
- the recess 45 is formed by a core of a mold in a process of manufacturing the piston 23 as will be mentioned later.
- the receiving wall 43 is disposed on the following side of the preferred embodiment, and the first guide wall 44 is disposed on the preceding side of the preferred embodiment. Namely, the receiving wall 43 and the first guide wall 44 are placed in a reversed manner.
- the position of the core of the mold is also shifted to form the recess 45 in the receiving wall 43 of the preferred embodiment
- the position of the receiving wall 43 in the above compressor corresponds to the position of the first guide wall 44 of the preferred embodiment.
- the first guide wall 44 is disposed on the preceding side so as to be symmetrical to the corresponding portion of the receiving wall 43 with respect to the hypothetical plane X. Therefore, in the above structure of the piston 23 of the preferred embodiment, the manufacturing process of the above two different pistons having the receiving wall 43 and the first guide wall 44 in the opposite side is facilitated by shifting the position of the core.
- a second guide wall 46 extends from the head portion 41 towards the neck portion 42 on the upper side of the head portion 41 .
- the second guide wall 46 contributes to stabilize the reciprocating movement of the piston 23 .
- a rib 48 connects the second guide wall 46 to the neck portion 42 .
- the space K is further surrounded by the receiving wall 43 , the first guide wall 44 , the support portion 40 , the second guide wall 46 , and the ribs 47 , 48 .
- An interrupting wall 51 is placed in the space K The interrupting wall 51 divides the space K into the preceding and the following sides.
- the film made of fluororesin is coated on the outer surface of the receiving wall 43 , the first guide wall 44 and the second guide wall 46 in a similar manner as the head portion 41 .
- the first guide wall 44 is disposed on the following side in the swash plate rotating direction R so as to be symmetrical to the corresponding portion of the receiving wall 43 with respect to the hypothetical plane X. Therefore, the reciprocating movement of the piston 23 is suitably guided by the first guide wall 44 on the following side so that the piston 23 reciprocates in a stable manner. For this reason, frictional resistance is substantially reduced between the piston 23 and the inner circumferential surface of the cylinder bore 22 , and the compressor power loss and the friction noise are also substantially reduced.
- the recess 45 is formed near the outer circumferential surface 44 a of the first guide wall 44 , the stable reciprocating movement of the piston 23 is highly compatible with the weight reduction of the piston 23 . In consequence, especially in a swash plate type variable displacement compressor, the displacement control is stabilized due to the above compatibility.
- the fluororesin film is coated on the head portion 41 , the receiving wall 43 , the first guide wall 44 and the second guide wall 46 . Therefore, the durability of the fluororesin film is improved for the stable reciprocating movement of the piston 23 .
- the recess 45 is formed in such manner that the contact area is frame-shaped between the outer circumferential surface 44 a of the first guide wall 44 and the inner circumferential surface of the cylinder bore 22 .
- the support portion 40 supports the first guide wall 44 . Accordingly, the strength of the first guide wall 44 is increased in the vicinity of the opening 45 a of the recess 45 .
- the reciprocating movement of the piston 23 is suitably guided by the first guide wall 44 . Therefore, as the volume of the recess 45 is increased, the stable reciprocating movement of the piston 23 is highly compatible with the weight reduction of the piston 23 .
- the recess 45 is formed in such manner that the area is triangular between the outer circumferential surface 44 a of the first guide wall 44 and the inner circurnferential surface of the cylinder bore 22 . Due to the triangular shape, the strength of the guide wall 44 is increased. Therefore, for example, in comparison to the case that the contact area is square-shaped between the outer circumferential surface 44 a of the first guide wall 44 and the inner circumferential surface of the cylinder bore 22 , the above-mentioned strengthening effect is more effectively accomplished in the preferred embodiment.
- the present invention may be modified into the following alternative embodiments within the scope of the present invention.
- the interrupting wall 51 is removed from the above-mentioned piston 23 , and the space K is continuous between the preceding side and the following side. Therefore, the weight of the piston 23 is further reduced.
- the first guide wall 44 has a second support portion 401 .
- the second support portion 401 is formed in the recess 45 such that two recess portions 45 are formed.
- the second support portion 401 reinforces the first guide wall 44 . Therefore, the reduction of the piston 23 in weight is highly compatible with the stable reciprocating movement of the piston 23 .
- the number of recesses 45 is not limited to only two as shown in FIGS. 5A and 5B, and three, four or five recess portions are formed.
- Through holes 49 are formed in the receiving wall 43 . Thereby, lubricant in the recess 45 easily outflows from the recess 45 , and the piston 23 smoothly slides over the cylinder bore 23 .
- the through hole 49 for the outflow of the lubricant is formed in other preferred embodiments.
- the rib 48 as shown in FIGS. 2A, 2B, 4 A and 5 A is removed from the piston 23 in an alternative embodiment. Thereby, the weight of piston 23 is further reduced in the alternative embodiment.
- the interrupting wall 51 properly reinforces the piston 23 .
- the strength of the piston 23 is still substantially maintained by the interrupting wall 51 .
- the recess 45 is formed in such manner that the contact area is square between the outer circumferential surface 44 a of the first guide wall 44 and the inner circumferential surface of the cylinder bore 22 .
- the support portion 40 is removed from the piston 23 in another alternative embodiment. Thereby, the weight of piston 23 is further reduced in the alternative embodiment.
- the recess 45 is formed in such manner that the contact area is frame-shaped between the outer circumferential surface 44 a of the first guide wall 44 and the inner circumferential surface of the cylinder bore 22
- the outer circumferential surface 41 a of the head portion 41 and the outer circumferential surface 44 a of the first guide wall 44 around the opening of the recess 45 do not necessarily form a complete annular structure without break.
- the meaning of the “frame-shaped” is not limited to the above-mentioned structure without break.
- the piston 23 in which the annular structure is broken by a groove 52 is also included.
- the present invention is embodied in a piston of a fixed displacement compressor
- the present invention is also embodied in a piston of a compressor having a wave cam plate as a cam plate.
- FIGS. 7A and 7B a method of die-casting the piston 23 , which is shown in FIGS. 2A through 2C, will be described hereafter
- the neck portions 42 of the two pistons 23 are connected to each other in the direction of the central axis S of the piston 23 , and a piston blank 50 is obtained.
- the recess 45 is formed symmetrically with each other in order to obtain the two pistons 23 substantially in the same shape when the piston blank is separated into two pieces.
- a fixed mold 53 as a first mold is connected to a movable mold 54 as a second mold at a position that corresponds to the central axis S of the piston blank 50 .
- a first core 55 that moves relative to the fixed mold 53 is used in order to cast the recess 45 on the side of the fixed mold 53 as a first predetermined recess.
- the recess 45 on the side of the movable mold 54 as a second predetermined recess is molded by a second core 55 ′ that is fixed to the movable mold 54 .
- a cavity is formed to cast the piston blank 50 in the above-mentioned manner.
- the reference number 56 denotes a reinforce rib of the neck portion 42
- the reference number 57 denotes a holding portion used in machining the piston blank 50
- the reinforce rib 56 and the holding portion 57 are removed by cutting before the piston 23 is completed.
- the first core 55 is pulled and moved before the movable mold 54 is separated from the fixed mold 53 .
- the adhesiveness is removed between the first core 55 and the inner surface of the recess 45 .
- the top of the first core 55 is separated from the recess 45 , and the first core 55 can be separated from the fixed mold 53 .
- the adhesiveness is maintained between the molded piston blank 50 and the second core 55 ′ for the recess 45 at the movable mold side.
- the piston blank 50 and the second core 55 ′ are integrally moved.
- the first core 55 on the fixed mold side is free from the piston blank 50 In consequence, the piston blank 50 with the movable mold 54 is separated from the fixed mold 53 .
- the first core 55 at the fixed mold side is movable, the first core 55 is separated from the recess 45 before the fixed mold 53 is separated from the piston blank 50 and the movable mold 54 . Therefore, the piston blank 50 is smoothly separated from the fixed mold 53 and the movable mold 54 .
- the pistons 23 as shown in FIGS. 4A, 4B, 5 A and 5 B are also manufactured by the above-mentioned method. Especially in the piston 23 which has a plurality of the recess 45 as shown in FIGS. 5A and 5B, since the piston blank 51 contacts the first core 55 in a relatively wide area, the first core 55 strongly adheres to the piston blank 50 . However, one first core 55 for forming a plurality of the recess 45 is placed in the fixed mold 53 Therefore, the recess 45 is easily released from the adhesion to the first core 55 by moving the first core 55 from the recess 45 .
- the present invention may be modified into the following alternative embodiments within the scope of the present invention.
- the first core 55 is used in the movable mold 54 while the second core 55 ′ is used in the fixed mold 53 .
- the first core 55 moves relative to the movable mold 54
- the second core 55 ′ is fixed to the fixed mold 53 .
- the piston blank 50 is formed by forging. Also in this case, a first core at a fixed mold side is moved, and a piston blank 50 is relatively easily separated from the fixed mold.
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- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
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Abstract
Description
- The present invention generally relates to a piston in a piston type compressor in which refrigerant gas is compressed for an air-conditioning system and a method of manufacturing the piston.
- Japanese Unexamined Patent Publication No. 2000-274350 discloses a
piston 110. As shown in FIG. 8A through FIG. 8C, thepiston 110 includes ahead portion 111 slidably inserted into a cylinder bore, aneck portion 112 engaged with aswash plate 102 of a compressor through a pair ofshoes 103, and areceiving wall 113 for receiving side force F as indicated by an arrow. Thereceiving wall 113 extends from a lower side of thehead portion 111 towards theneck portion 112 and is arranged on a predetermined side in relation to the rotating direction R of theswash plate 102. - Since the
receiving wall 113 is formed on the predetermined side where the side force F is applied due to the rotating direction R of theswash plate 102, there is only a little contact area between thepiston 110 and the inner circumferential surface of thecylinder bore 101 on the opposite side to thereceiving wall 113. The opposite side hardly receives the side force F, thereby, thepiston 110 becomes lighter. In this case, the side force F is the largest force that is generated by compression reactive force and is received by thepiston 110 during a compression process. - However, since the
receiving wall 113 is disposed on only one side of thepiston 110 to receive the side force F due to the rotating direction of theswash plate 102, a contact area is relatively small between thepiston 110 and the inner ci rcumferental surface of thecylinder bore 101. Therefore, thepiston 110 reciprocates in a relatively unstable manner, and friction becomes relatively large between thepiston 110 and the inner circumferential surface of thecylinder bore 101. In consequence, the compressor loses power and the friction noise becomes relatively large. - The present invention is directed to obtain a piston whose weight is relatively light and which reciprocates in a relatively stable manner and a method of manufacturing the piston.
- According to the present invention, a piston is used for a compressor. The compressor has a drive shaft having a central axis and a cam plate rotatably supported by the drive shaft. The cam plate converts the rotating movement of the drive shaft into the reciprocating movement of the piston. The piston has a central axis, a head portion and a neck portion. The head portion is slidably fitted in a cylinder bore. The neck portion is connected to the head portion and is engaged with the cam plate The cam plate is rotated in a predetermined direction to define a cam plate rotating direction. The piston also has a receiving wall for receiving side force and a first guide wall. The receiving wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a preceding side in the cam plate rotating direction. The receiving wall has an outer circumferential surface that slidably contacts the inner circumferential surface of the cylinder bore. The first guide wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston. The first guide wall has an outer circumferential surface that is continuous with the receiving wall and slides over the inner circumferential surface of the cylinder bore. A recess is formed in the outer circumferential surface of the first guide wall.
- The present invention also provides a compressor. The compressor includes a housing having a cylinder bore. A drive shaft is supported by the housing and has a central axis. A cam plate is supported by the drive shaft and is rotated in a direction defined as a cam plate rotating direction. The compressor also includes a piston having a central axis. The piston has a head portion, a neck portion, a receiving wall for receiving side force and a first guide wall. The head portion is slidably fitted in a cylinder bore. The neck portion is connected to the head portion and is engaged with the cam plate for converting the rotating movement of the cam plate into the reciprocating movement of the piston. The receiving wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a preceding side in the cam plate rotating direction The receiving wall has an outer circumferential surface that slidably contacts the inner circumferential surface of the cylinder bore The first guide wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston. The first guide wall has an outer circumferential surface that is continuous with the receiving wall and slides over the inner circumferential surface of the cylinder bore. A recess is formed in the outer circumferential surface of the first guide wall.
- The present invention also provides a method of forming a piston blank that includes two piston components in use for a compressor. The compressor has a drive shaft, a cam plate and a piston. The drive shaft has a central axis. A cam plate is rotated in a predetermined direction. The piston has a central axis, a head portion, a neck portion, a receiving wall for receiving side force and a guide wall. The neck portion is connected to the head portion. The receiving wall extends from the drive shaft side of the head portion towards the neck and is disposed on a preceding side in the predetermined direction. The guide wall extends from the drive shaft side of the head portion towards the neck portion and is disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston. The guide wall has an outer circumferential surface that is continuous with the receiving wall. The guide wall has a support portion connecting to the receiving wall. A recess is formed in the outer circumferential surface of the guide wall. The piston blank includes a first predetermined recess and a second predetermined recess. The method includes setting a first core in a first mold for forming the first predetermined recess such that the first core moves in a direction in which the first and second mold are separated, further setting a second core in a second mold for forming the second predetermined recess that is open to a substantially opposite side of the first predetermined recess, forming the piston blank by one of die-casting and forging, moving the first core relative to the first mold in order to break adhesion among the receiving wall, the guide wall and the first core, and separating the piston blank with the second mold from the first mold.
- The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. 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 is a cross-sectional view of a swash plate type variable displacement compressor of a preferred embodiment according to the present invention;
- FIG. 2A is a side view of a piston of the preferred embodiment according to the present invention;
- FIG. 2B is another side view opposite to FIG. 2A of the piston of the preferred embodiment according to the present invention;
- FIG. 2C is a cross-sectional view taken along the line I-I in FIG. 2A of the preferred embodiment;
- FIG. 3 is a partial diagram of the piston and a drive shaft of the preferred embodiment according to the present invention;
- FIG. 4A is a partially enlarged cross-sectional view of a swash plate type compressor of a first alternative preferred embodiment according to the present invention;
- FIG. 4B is a cross-sectional view taken along the line II-II in FIG. 4A of the first alternative embodiment;
- FIG. 5A is a side view of a piston of a second alternative preferred embodiment according to the present invention;
- FIG. 5B is a cross-sectional view taken along the line III-III in FIG. 5A of the second alternative embodiment;
- FIG. 6 is a side view of a piston of a third alternative preferred embodiment according to the present invention;
- FIG. 7A is a plane view of a piston blank and molds for casting the piston blank of the preferred embodiment according to the present invention;
- FIG. 7B is a cross-sectional view taken along the line IV-IV in FIG. 7A of the preferred embodiment;
- FIG. 8A is a side view of a piston according to the prior art;
- FIG. 8B is another side view of the piston opposite to FIG. 8A according to the prior art; and
- FIG. 8C is a cross-sectional view taken along the line V-V in FIG. 8A of the prior art piston.
- A preferred embodiment according to the present invention will be described. As shown in FIG. 1, a swash plate type variable displacement compressor includes a
cylinder block 11 made of aluminum series metal material, afront housing 12 and arear housing 14. In FIG. 1, the left side and the right side of the drawing respectively correspond to the front side and the rear side of the compressor. Thefront housing 12 is fixedly connected to the front end of thecylinder block 11. Therear housing 14 is fixedly connected to the rear end of thecylinder block 11 via avalve plate assembly 13. Thecylinder block 11 and thefront housing 12 define a crankchamber 15. Adrive shaft 16 is rotatably placed in thecrank chamber 15 An engine that is not shown in the drawing is rotatably connected to thedrive shaft 16. Driving power is transmitted from the engine to thedrive shaft 16, and thedrive shaft 16 is rotated. - A
lug plate 17 is secured to thedrive shaft 16 in thecrank chamber 15 so as to rotate integrally with thedrive shaft 16. Aswash plate 18 as a cam plate is accommodated in thecrank chamber 15. Thedrive shaft 16 is inserted through ashaft hole 18 a that is formed at the center of theswash plate 18. Theswash plate 18 is supported by thedrive shaft 16 so as to slide along a central axis L of thedrive shaft 16 and is inclinable with respect to the central axis L of thedrive shaft 16. Ahinge mechanism 19 is interposed between thelug plate 17 and theswash plate 18. Thehinge mechanism 19 includes a pair ofsupport arms 20 placed on thelug plate 17 and a pair of guide pins 21, which is secured to theswash plate 18. Aspherical portion 21 a of each guide pin 21 is slidably interposed into aguide hole 20 a of eachsupport arm 20. - Thereby, the
hinge mechanism 19 between theswash plate 18 and thelug plate 17 and the support for thedrive shaft 16 allow theswash plate 18 to rotate integrally with thelug plate 17 and to incline with respect to the central axis L of thedrive shaft 16 as theswash plate 18 slides along the central axis L of thedrive shaft 16. - A plurality of cylinder bores22 is evenly disposed around the
drive shaft 16 in thecylinder block 11 and is formed through thecylinder block 11 Only one of cylinder bores 22 is shown in the drawings. Asingle head piston 23 is accommodated in each of the cylinder bores 22 so as to reciprocate therein. Thepiston 23 and thevalve plate assembly 13 respectively shut the front and rear openings of the cylinder bore 22. Thereby, acompression chamber 24 is defined in each cylinder bore 22. The volume of thecompression chamber 24 varies in accordance with the reciprocating movement of thepiston 23. Each of thepistons 23 is connected to theswash plate 18 through a pair ofsemispherical shoes 25. Thereby, the rotating movement of theswash plate 18 by the rotatingdrive shaft 16 is converted into the linear reciprocating movement of thepiston 23 through theshoes 25. - The
valve plate assembly 13 and therear housing 14 define asuction chamber 26 and adischarge chamber 27. Each of thepiston 23 travels between a top dead center and a bottom dead center. At the top dead center, thepiston 23 is at the right most position in the cylinder bore 22. At the bottom dead center, the piston is the left most position in the cylinder bore 22. As each of thepistons 23 moves from the top dead center to the bottom dead center, refrigerant gas in thesuction chamber 26 is introduced into thecompression chamber 24 through acorresponding suction port 28 and acorresponding suction valve 29 that are formed in thevalve plate assembly 13. As each of thepistons 23 moves from the bottom dead center to the top dead center, the refrigerant gas is compressed to a certain pressure and then discharged to thedischarge chamber 27 through acorresponding discharge port 30 and acorresponding discharge valve 31 that are formed in thevalve plate assembly 13. - A
bleed passage 32, asupply passage 33 and acontrol valve 34 are provided in a housing of the compressor. Thebleed passage 32 connects thecrank chamber 15 to thesuction chamber 26. Thesupply passage 33 connects thedischarge chamber 27 to the crankchamber 15. Thecontrol valve 34 is placed on thesupply passage 33. - The high pressure refrigerant gas is introduced into the
crank chamber 15 from thedischarge chamber 27 through thesupply passage 33, and the refrigerant gas is discharged from thecrank chamber 15 to thesuction chamber 26 through thebleed passage 32. The above amount of the high pressure refrigerant gas and the discharged refrigerant gas is controlled by adjusting the opening degree of thecontrol valve 34. Accordingly, the pressure in thecrank chamber 15 is determined. The pressure differential between thecrank chamber 15 and thecompression chamber 24 varies in accordance with the pressure change in thecrank chamber 15, and the inclination angle of theswash plate 18 correspondingly varies with respect to a vertical line to the central axis L of thedrive shaft 16. In consequence, the stroke volume of thepiston 23 changes, and the compressor displacement also varies. - For example, as the opening degree of the
control valve 34 decreases, the pressure in thecrank chamber 15 decreases. Therefore, the inclination angle of theswash plate 18 increases, and the stroke volume of thepiston 23 increases. As a result, the displacement of the compressor increases. On the other hand, as the opening degree of thecontrol valve 34 increases, the pressure in thecrank chamber 15 increases. Therefore, the inclination angle of theswash plate 18 decreases and the displacement of the compressor is reduced. - Next, the structure of the
piston 23 is described in detail. As shown in FIGS. 1, 2A through 20, thepiston 23 includes acylindrical head portion 41 and aneck portion 42 parallel to a central axis S of thepiston 23. Theneck portion 42 and thehead portion 41 of thepiston 23 respectively correspond to the front side and the rear side of thepiston 23. Referring to FIG. 2C, on the front side end of thehead portion 41, the distant side from thedrive shaft 16 is referred to as an upper side, while the close side to thedrive shaft 16 is referred to as a lower side Thehead portion 41 is slidably interposed into the cylinder bore 22. Theneck portion 42 holds a pair ofshoes 25 Thepiston 23 is made of aluminum series metal material and is manufactured by die-casting or forging An engagingportion 42 a is formed on theneck portion 42. A pair ofshoe seats 42 b is formed in the engagingportion 42 a and receives theshoes 25 in such manner that theshoes 25 freely slides therein Film made of fluororesin such as PTFE is formed on an outercircumferential surface 41 a of thehead portion 41. Thereby, thehead portion 41 smoothly slides over the inner circumferential surface of the cylinder bore 22. - As shown in FIGS. 2A and 2C, a receiving
wall 43 for receiving side force F extends from the lower side of thehead portion 41, that is, the drive shaft side of thehead portion 41, towards theneck portion 42 The receivingwall 43 is disposed on a preceding side in the rotating direction R of theswash plate 18. The rotating direction R of theswash plate 18 is defined as a swash plate rotating direction R hereafter. - As shown in FIG. 3, a diagram is viewed from a side on which the swash plate rotating direction R is clockwise. That is, when it is viewed from the side of the
neck portion 42, a hypothetical plane X includes the central axis L of thedrive shaft 16 and the central axis S of thepiston 23. The hypothetical plane X crosses thecircumferential surface 41 a of thehead portion 41 of thepiston 23 at intersectional points P1 and P2 The intersectional point P1 is distant from the central axis L of thedrive shaft 16 and is located at 12 o'clock position On the other hand, the intersectional point P2 is close to the central axis L of thedrive shaft 16 and is located at 6 o'clock position. As shown in FIGS. 2A and 2C, the outercircumferential surface 43 a of the receivingwall 43 slides over the inner circumferential surface of the cylinder bore 22 and is disposed substantially in a range of 3 to 6 o'clock. The upper side of thehead portion 41 corresponds to the area around 12 o'clock position while the lower side of thehead portion 41 corresponds to the area around 6 o'clock position. - The
piston 23 receives reactive force from the inner circumferential surface of the cylinder bore 22. The reactive force is generated by compression reactive force and the rotating force of theswash plate 18. The reactive force is applied to a part of the outercircumferential surface 41 a of thehead portion 41 after another part in accordance with the position of thepiston 23. The reactive force also includes the side force F herein. The side force F is defined as the largest force of the reactive force during the compression process. The side force F is applied to the outercircumferential surface 41 a of thehead portion 41 substantially in the range of 4 to 6 o'clock. Since the receivingwall 43 is continuously connected to thehead portion 41, thepiston 23 preferably receives some of the side force F at the receivingwall 43. - As shown in FIGS. 2B and 2C, a
first guide wall 44 extends from the lower side of thehead portion 41 towards theneck portion 42 Thefirst guide wall 44 connects with the receivingwall 43. Thefirst guide wall 44 is disposed on the opposite side of the preceding side in the swash plate rotating direction R so as to be symmetrical to a corresponding portion of the receivingwall 43 with respect to the hypothetical plane X over a longitudinal range of thefirst guide wall 44 The opposite side of the preceding side in the swash plate rotating direction R is defined as a following side. The outercircumferential surface 44 a of thefirst guide wall 44 extends within a range of 6 o'clock to 9 o'clock. Therefore, the outercircumferential surface 43 a of the receivingwall 43 and the outercircumferential surface 44 a of thefirst guide wall 44 are continuously arranged within the range of 3 o'clock to 9 o'clock. The receivingwall 43 and theguide wall 44 form a semicircular wallA support portion 40 extends from the middle of thehead portion 41 towards theneck portion 42. The support portion is parallel to a hypothetical line Y passing through 3 o'clock and 9 o'clock when the head portion is viewed from the side of theneck portion 42 on a surface perpendicular to the central axis S of thepiston 23. Thesupport portion 40 is connected to the receivingwall 43 and theguide wall 44. Thesupport portion 40 supports the receivingwall 43 and theguide wall 44. The receivingwall 43, theguide wall 44 and thesupport portion 40form recess 45. Arib 47 connects theneck portion 42 so to thesupport portion 40 and the semicircular wall that includes thefirst guide wall 44 and the receivingwall 43. - In order to reduce the weight of the
piston 23, therecess 45 is formed in the outercircumferential surface 44 a of thefirst guide wall 44 that slides over the inner circumferential surface of the cylinder bore 22. The contact area is triangular between the outercircumferential surface 44 a of thefirst guide wall 44 and the inner circumferential surface of the cylinder bore 22. Therecess 45 is relatively deeply formed to minimize the thickness of the receivingwall 43. For example, if therecess 45 is not formed, a relatively large volume of thepiston 23 that forms the receivingwall 43 and thefirst guide wall 44 is not removed. In other words, a slantingly cut semi-cylinder axially extends from the middle area of thehead portion 41 to the bottom area towards theneck portion 42. The slantingly cut semi-cylinder is disposed on the front end of thehead portion 41 in the range of 3 o'clock to 9 o'clock. Therecess 45 is formed inside the outer circumferential surface of the slantingly cut semi-cylinder that is in contact with the inner circumferential surface of the cylinder bore 22 within the range of 6 o'clock to 9 o'clock. The slantingly cut semi-cylinder includes the receivingwall 43 for receiving the side force F, thefirst guide wall 44 and thesupport portion 40. Therecess 45 is formed by a core of a mold in a process of manufacturing thepiston 23 as will be mentioned later. - If the
swash plate 18 rotates in the rotating direction that is opposite to the above mentioned swash plate rotating direction R, the receivingwall 43 is disposed on the following side of the preferred embodiment, and thefirst guide wall 44 is disposed on the preceding side of the preferred embodiment. Namely, the receivingwall 43 and thefirst guide wall 44 are placed in a reversed manner. However, when the above piston is manufactured, the position of the core of the mold is also shifted to form therecess 45 in the receivingwall 43 of the preferred embodiment The position of the receivingwall 43 in the above compressor corresponds to the position of thefirst guide wall 44 of the preferred embodiment. Thefirst guide wall 44 is disposed on the preceding side so as to be symmetrical to the corresponding portion of the receivingwall 43 with respect to the hypothetical plane X. Therefore, in the above structure of thepiston 23 of the preferred embodiment, the manufacturing process of the above two different pistons having the receivingwall 43 and thefirst guide wall 44 in the opposite side is facilitated by shifting the position of the core. - A
second guide wall 46 extends from thehead portion 41 towards theneck portion 42 on the upper side of thehead portion 41. Thesecond guide wall 46 contributes to stabilize the reciprocating movement of thepiston 23. Arib 48 connects thesecond guide wall 46 to theneck portion 42. There is a space K between thehead portion 41 and theneck portion 42. The space K is further surrounded by the receivingwall 43, thefirst guide wall 44, thesupport portion 40, thesecond guide wall 46, and theribs wall 51 is placed in the space K The interruptingwall 51 divides the space K into the preceding and the following sides. Although not shown in the drawings, the film made of fluororesin is coated on the outer surface of the receivingwall 43, thefirst guide wall 44 and thesecond guide wall 46 in a similar manner as thehead portion 41. - In the preferred embodiment, following advantageous effects are obtained. (1) In the
piston 23, thefirst guide wall 44 is disposed on the following side in the swash plate rotating direction R so as to be symmetrical to the corresponding portion of the receivingwall 43 with respect to the hypothetical plane X. Therefore, the reciprocating movement of thepiston 23 is suitably guided by thefirst guide wall 44 on the following side so that thepiston 23 reciprocates in a stable manner. For this reason, frictional resistance is substantially reduced between thepiston 23 and the inner circumferential surface of the cylinder bore 22, and the compressor power loss and the friction noise are also substantially reduced. Since therecess 45 is formed near the outercircumferential surface 44 a of thefirst guide wall 44, the stable reciprocating movement of thepiston 23 is highly compatible with the weight reduction of thepiston 23. In consequence, especially in a swash plate type variable displacement compressor, the displacement control is stabilized due to the above compatibility. - The fluororesin film is coated on the
head portion 41, the receivingwall 43, thefirst guide wall 44 and thesecond guide wall 46. Therefore, the durability of the fluororesin film is improved for the stable reciprocating movement of thepiston 23. - (2) The
recess 45 is formed in such manner that the contact area is frame-shaped between the outercircumferential surface 44 a of thefirst guide wall 44 and the inner circumferential surface of the cylinder bore 22. Thesupport portion 40 supports thefirst guide wall 44. Accordingly, the strength of thefirst guide wall 44 is increased in the vicinity of the opening 45 a of therecess 45. The reciprocating movement of thepiston 23 is suitably guided by thefirst guide wall 44. Therefore, as the volume of therecess 45 is increased, the stable reciprocating movement of thepiston 23 is highly compatible with the weight reduction of thepiston 23. - Especially in the preferred embodiment, the
recess 45 is formed in such manner that the area is triangular between the outercircumferential surface 44 a of thefirst guide wall 44 and the inner circurnferential surface of the cylinder bore 22. Due to the triangular shape, the strength of theguide wall 44 is increased. Therefore, for example, in comparison to the case that the contact area is square-shaped between the outercircumferential surface 44 a of thefirst guide wall 44 and the inner circumferential surface of the cylinder bore 22, the above-mentioned strengthening effect is more effectively accomplished in the preferred embodiment. - (3) There is the space K between the
head portion 41 and theneck portion 42 that is surrounded by the receivingwall 43, thefirst guide wall 44, thesupport portion 40, thesecond guide wall 46, and theribs wall 51. Therefore, the interruptingwall 51 properly reinforces the connection between thehead portion 41 and theneck portion 42 by supporting the receivingwall 43, thefirst guide wall 44, thesupport portion 40, thesecond guide wall 46 and theribs piston 23 is strengthened. - The present invention may be modified into the following alternative embodiments within the scope of the present invention. As shown in FIGS. 4A and 4B, the interrupting
wall 51 is removed from the above-mentionedpiston 23, and the space K is continuous between the preceding side and the following side. Therefore, the weight of thepiston 23 is further reduced. - As shown in FIGS. 5A and 5B, the
first guide wall 44 has asecond support portion 401. Thesecond support portion 401 is formed in therecess 45 such that tworecess portions 45 are formed. Thesecond support portion 401 reinforces thefirst guide wall 44. Therefore, the reduction of thepiston 23 in weight is highly compatible with the stable reciprocating movement of thepiston 23. The number ofrecesses 45 is not limited to only two as shown in FIGS. 5A and 5B, and three, four or five recess portions are formed. Throughholes 49 are formed in the receivingwall 43. Thereby, lubricant in therecess 45 easily outflows from therecess 45, and thepiston 23 smoothly slides over the cylinder bore 23. The throughhole 49 for the outflow of the lubricant is formed in other preferred embodiments. - The
rib 48 as shown in FIGS. 2A, 2B, 4A and 5A is removed from thepiston 23 in an alternative embodiment. Thereby, the weight ofpiston 23 is further reduced in the alternative embodiment. In thepistons 23 as shown in FIGS. 2A through 2C, 5A and 5B, the interruptingwall 51 properly reinforces thepiston 23. Thus, even if therib 48 is removed form thepiston 23, the strength of thepiston 23 is still substantially maintained by the interruptingwall 51. - In another alternative embodiment, the
recess 45 is formed in such manner that the contact area is square between the outercircumferential surface 44 a of thefirst guide wall 44 and the inner circumferential surface of the cylinder bore 22. - The
support portion 40 is removed from thepiston 23 in another alternative embodiment. Thereby, the weight ofpiston 23 is further reduced in the alternative embodiment. - As mentioned above, in yet another alternative embodiment, the
recess 45 is formed in such manner that the contact area is frame-shaped between the outercircumferential surface 44 a of thefirst guide wall 44 and the inner circumferential surface of the cylinder bore 22 In thepiston 23 as shown in FIGS. 2A, 2B, 4A and 5A, the outercircumferential surface 41 a of thehead portion 41 and the outercircumferential surface 44 a of thefirst guide wall 44 around the opening of therecess 45 do not necessarily form a complete annular structure without break. The meaning of the “frame-shaped” is not limited to the above-mentioned structure without break. For example, as shown in FIG. 6, thepiston 23 in which the annular structure is broken by agroove 52 is also included. - The present invention is embodied in a piston of a fixed displacement compressor The present invention is also embodied in a piston of a compressor having a wave cam plate as a cam plate.
- Next, a method of manufacturing the piston according to the present invention will be described. As shown in FIGS. 7A and 7B, a method of die-casting the
piston 23, which is shown in FIGS. 2A through 2C, will be described hereafter In order to obtain a single-headedpiston 23, theneck portions 42 of the twopistons 23 are connected to each other in the direction of the central axis S of thepiston 23, and a piston blank 50 is obtained. In this case, as shown in FIG. 7A, therecess 45 is formed symmetrically with each other in order to obtain the twopistons 23 substantially in the same shape when the piston blank is separated into two pieces. A fixedmold 53 as a first mold is connected to amovable mold 54 as a second mold at a position that corresponds to the central axis S of thepiston blank 50. - A
first core 55 that moves relative to the fixedmold 53 is used in order to cast therecess 45 on the side of the fixedmold 53 as a first predetermined recess. Therecess 45 on the side of themovable mold 54 as a second predetermined recess is molded by asecond core 55′ that is fixed to themovable mold 54. A cavity is formed to cast the piston blank 50 in the above-mentioned manner. In FIG. 7A, thereference number 56 denotes a reinforce rib of theneck portion 42, and thereference number 57 denotes a holding portion used in machining the piston blank 50 The reinforcerib 56 and the holdingportion 57 are removed by cutting before thepiston 23 is completed. - After pouring and cooling, the
first core 55 is pulled and moved before themovable mold 54 is separated from the fixedmold 53. Thereby, the adhesiveness is removed between thefirst core 55 and the inner surface of therecess 45. In addition, the top of thefirst core 55 is separated from therecess 45, and thefirst core 55 can be separated from the fixedmold 53. In the above state, the adhesiveness is maintained between the molded piston blank 50 and thesecond core 55′ for therecess 45 at the movable mold side. When themovable mold 54 is separated from the fixedmold 53, the piston blank 50 and thesecond core 55′ are integrally moved. On the other hand, thefirst core 55 on the fixed mold side is free from the piston blank 50 In consequence, the piston blank 50 with themovable mold 54 is separated from the fixedmold 53. - According to the above method, following advantageous effects are obtained. Namely, since the piston blank50 is cast for two pistons that are connected to each other in a row, the
recesses 45 at the fixed mold and movable mold sides are symmetrical to each other across the central axis S, and thecores recess 45 are relatively deeply inserted and adhere to therecess 45 with a relatively wide area. Therefore, when the fixedmold 53 and themovable mold 54 are separated from each other, torsional force is generated since both of thecores piston blank 50. However, since thefirst core 55 at the fixed mold side is movable, thefirst core 55 is separated from therecess 45 before the fixedmold 53 is separated from the piston blank 50 and themovable mold 54. Therefore, the piston blank 50 is smoothly separated from the fixedmold 53 and themovable mold 54. - The
pistons 23 as shown in FIGS. 4A, 4B, 5A and 5B are also manufactured by the above-mentioned method. Especially in thepiston 23 which has a plurality of therecess 45 as shown in FIGS. 5A and 5B, since the piston blank 51 contacts thefirst core 55 in a relatively wide area, thefirst core 55 strongly adheres to thepiston blank 50. However, onefirst core 55 for forming a plurality of therecess 45 is placed in the fixedmold 53 Therefore, therecess 45 is easily released from the adhesion to thefirst core 55 by moving thefirst core 55 from therecess 45. - The present invention may be modified into the following alternative embodiments within the scope of the present invention. The
first core 55 is used in themovable mold 54 while thesecond core 55′ is used in the fixedmold 53. In this case, thefirst core 55 moves relative to themovable mold 54, and thesecond core 55′ is fixed to the fixedmold 53. - The piston blank50 is formed by forging. Also in this case, a first core at a fixed mold side is moved, and a piston blank 50 is relatively easily separated from the fixed mold.
- Any combination of the above described preferred embodiments and or the above described alternative embodiments is practiced according to the current invention 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 of the appended claims.
Claims (29)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2001339656A JP2003139052A (en) | 2001-11-05 | 2001-11-05 | Piston for compressor and method of manufacturing the same |
JPP2001-339656 | 2001-11-05 |
Publications (1)
Publication Number | Publication Date |
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US20030084783A1 true US20030084783A1 (en) | 2003-05-08 |
Family
ID=19153978
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US10/288,006 Abandoned US20030084783A1 (en) | 2001-11-05 | 2002-11-04 | Piston for compressor and method of manufacturing the same |
Country Status (3)
Country | Link |
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US (1) | US20030084783A1 (en) |
JP (1) | JP2003139052A (en) |
DE (1) | DE10251272A1 (en) |
Families Citing this family (1)
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KR100605161B1 (en) | 2005-02-18 | 2006-07-28 | 학교법인 두원학원 | Manufacturing method of piston for compressor |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4519119A (en) * | 1980-11-19 | 1985-05-28 | Kabushiki Kaisha Toyoda Jidoshokki Seisakusho | Method of manufacturing a piston for a swash plate type compressor |
US5899135A (en) * | 1996-05-21 | 1999-05-04 | Sanden Corporation | Reciprocating pistons of piston type compressor |
US5953980A (en) * | 1996-10-25 | 1999-09-21 | Kabushiki Kaisha Toyoda Jidoshokki Seisakusho | Piston type compressors |
US6024009A (en) * | 1997-05-16 | 2000-02-15 | Sanden Corporation | Reciprocating pistons of piston-type compressor |
US6216584B1 (en) * | 1998-03-27 | 2001-04-17 | Sanden Corporation | Piston having an improved barrel portion, and a compressor using the same |
US6332394B1 (en) * | 1999-06-15 | 2001-12-25 | Kabushiki Kaisha Toyoda Jidoshokki Seisakusho | Piston for swash plate type compressor, wherein head portion includes radially inner sliding projection connected to neck portion |
-
2001
- 2001-11-05 JP JP2001339656A patent/JP2003139052A/en active Pending
-
2002
- 2002-11-04 US US10/288,006 patent/US20030084783A1/en not_active Abandoned
- 2002-11-04 DE DE10251272A patent/DE10251272A1/en not_active Withdrawn
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4519119A (en) * | 1980-11-19 | 1985-05-28 | Kabushiki Kaisha Toyoda Jidoshokki Seisakusho | Method of manufacturing a piston for a swash plate type compressor |
US5899135A (en) * | 1996-05-21 | 1999-05-04 | Sanden Corporation | Reciprocating pistons of piston type compressor |
US5953980A (en) * | 1996-10-25 | 1999-09-21 | Kabushiki Kaisha Toyoda Jidoshokki Seisakusho | Piston type compressors |
US6024009A (en) * | 1997-05-16 | 2000-02-15 | Sanden Corporation | Reciprocating pistons of piston-type compressor |
US6216584B1 (en) * | 1998-03-27 | 2001-04-17 | Sanden Corporation | Piston having an improved barrel portion, and a compressor using the same |
US6332394B1 (en) * | 1999-06-15 | 2001-12-25 | Kabushiki Kaisha Toyoda Jidoshokki Seisakusho | Piston for swash plate type compressor, wherein head portion includes radially inner sliding projection connected to neck portion |
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DE10251272A1 (en) | 2003-06-05 |
JP2003139052A (en) | 2003-05-14 |
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