WO1998017900A1 - Piston with cavity - Google Patents

Piston with cavity Download PDF

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Publication number
WO1998017900A1
WO1998017900A1 PCT/GB1997/002851 GB9702851W WO9817900A1 WO 1998017900 A1 WO1998017900 A1 WO 1998017900A1 GB 9702851 W GB9702851 W GB 9702851W WO 9817900 A1 WO9817900 A1 WO 9817900A1
Authority
WO
WIPO (PCT)
Prior art keywords
piston
crown portion
projection
crown
cavity
Prior art date
Application number
PCT/GB1997/002851
Other languages
French (fr)
Inventor
Roger Harvey Slee
Alan Charles Hollis
Andrew John Woodward
Original Assignee
T & N Technology Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by T & N Technology Limited filed Critical T & N Technology Limited
Publication of WO1998017900A1 publication Critical patent/WO1998017900A1/en

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Classifications

    • 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
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0675—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston the combustion space being substantially spherical, hemispherical, ellipsoid or parabolic
    • 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
    • F02B21/00—Engines characterised by air-storage chambers
    • F02B21/02—Chamber shapes or constructions
    • 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
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0618—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston having in-cylinder means to influence the charge motion
    • F02B23/0627—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston having in-cylinder means to influence the charge motion having additional bores or grooves machined into the piston for guiding air or charge flow to the piston bowl
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/0015—Multi-part pistons
    • F02F3/003—Multi-part pistons the parts being connected by casting, brazing, welding or clamping
    • 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
    • F02B2275/00—Other engines, components or details, not provided for in other groups of this subclass
    • F02B2275/14—Direct injection into combustion chamber
    • 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
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0603—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston at least part of the interior volume or the wall of the combustion space being made of material different from the surrounding piston part, e.g. combustion space formed within a ceramic part fixed to a metal piston head
    • 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
    • F02B3/00—Engines characterised by air compression and subsequent fuel addition
    • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/0015—Multi-part pistons
    • F02F3/003—Multi-part pistons the parts being connected by casting, brazing, welding or clamping
    • F02F2003/0061—Multi-part pistons the parts being connected by casting, brazing, welding or clamping by welding
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2201/00—Metals
    • F05C2201/02—Light metals
    • F05C2201/021—Aluminium
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • This invention is concerned with a method of manufacturing a piston having a cavity therein and with such a piston.
  • a conventional piston for an internal combustion engine comprises a crown (which, in some cases, defines a combustion recess) , a guidance skirt, and bosses to receive a gudgeon pin.
  • a crown which, in some cases, defines a combustion recess
  • a guidance skirt which, in some cases, defines a combustion recess
  • bosses to receive a gudgeon pin.
  • pistons of this type with cavities.
  • the term "cavity” is used herein to denote a substantially enclosed space having only restricted openings whereas the term “recess” is used to denote a space having a relatively large opening.
  • pistons have been proposed which have cavities in the crown thereof, the cavities having one or more restricted openings which communicate with a combustion recess in the crown.
  • the combustion recess co-operates with the space above the crown of the piston in the cylinder in which it reciprocates to form a combustion chamber in which the fuel charge is burnt.
  • These cavities are intended to provide reaction chambers to shelter radical species of the fuel from being exhausted from the cylinder so that they can return to the cylinder to seed subsequent fuel charges. Such seeding improves the completeness of the combustion of the fuel .
  • a known method of providing a piston with cavities to form the aforementioned reaction chambers involves manufacturing the piston in two portions which are subsequently joined together. These portions are a piston body portion, defining most of the piston including a lower portion of the combustion recess, and an upper portion, defining a side surface of the combustion recess, a top surface of the piston, and a portion of the outer side surface of the piston.
  • the body portion has a generally annular upper surface on to which a matching lower surface of the upper portion is fitted and the two portions are secured together.
  • references herein to surfaces as being “generally annular” are not intended to exclude surfaces which have elliptical outer edges (as most pistons are slightly elliptical in transverse cross-section) and also are not intended to exclude surfaces which have their inner edges non-circular and/or non-central. Also, references herein to surfaces as being “generally cylindrical” are not intended to exclude surfaces which are elliptical in transverse cross-section.
  • the cavities are formed by providing recesses in the lower surface of the upper portion, or in the upper surface of the lower portion, or in both surfaces.
  • the body portion defines a bottom surface of the combustion recess and also lower surfaces of the cavities
  • the upper portion defines a side surface of the combustion recess and upper surfaces of the cavities.
  • the restricted openings to the cavities may be formed by extensions of the recesses which form the cavities or, alternatively, may be formed by boring through the material of the piston after the two portions thereof have been secured together. Where such bores are used, a difficult process is involved as the bores must begin in the combustion recess.
  • the manufacture of such pistons is complex, and the possibility exists that the two portions of the piston, which are only joined at a generally annular surface which is interrupted by the cavities, may become detached in service.
  • WO 94/20241 discloses a method of forming cavities in a piston in which each cavity is formed by a box.
  • the box is mounted in a die cavity and the piston is cast around the box.
  • the box is provided with projections which enter recesses in the wall of the die cavity and support the box. After removing the piston from the die cavity, the projections are machined off.
  • the openings to the cavity can be provided by tubes projecting from the box.
  • the invention provides a method of manufacturing a piston having a cavity therein, wherein the method comprises forming an inner crown portion of the piston which defines a central portion of a crown of the piston including a combustion recess of the piston, and forming an outer crown portion which defines an outer portion of the crown of the piston, the outer crown portion being arranged to fit around the inner crown portion with an inner side surface of the outer crown portion overlying an outer side surface of the inner crown portion, the method also comprising fitting the outer crown portion around the inner crown portion, and securing the inner and the outer crown portions together, characterised in that said cavity is formed by a recess formed in at least one of said side surfaces.
  • the two portions of the piston can be secured together, eg by electron beam welding or brazing, across a generally annular surface which is not interrupted by cavities, and can also be secured across said side surfaces.
  • This gives a more reliable attachment results in a piston having a combustion recess defined by one portion only of the piston, and the method is relatively simple, as the recesses forming the cavities can easily be formed by machining or by being cast-in.
  • the inner crown portion may be formed by a projection of a body portion of the piston, the projection having a top surface by which the combustion recess is defined, and the outer crown portion may be fitted around said projection.
  • the projection may be circular in transverse cross-section or non-circular in order to ensure correct orientation during fitting.
  • the outer crown portion may, alternatively, be formed by a projection of a body portion of the piston, and the inner crown portion may be fitted within a recess defined by said projection.
  • the recess defined by the projection may be circular or non-circular in transverse cross-section.
  • a method according to the invention may comprise forming a plurality of recesses in said side surface.
  • the cavity may be provided with openings into the combustion recess by drilling or boring into said inner crown portion before said outer crown portion is fitted around said inner crown portion. This is relatively easy as the drilling or boring can be carried out from the outside.
  • the outer crown portion may have an outer side surface which defines one or more piston ring grooves. This gives the advantage that the piston ring grooves can be made more wear resistant by making the further piston portion out of a wear resistant material, or by coating it, or giving it a surface treatment before it is attached to the inner crown portion.
  • the inner and the outer crown portions may be formed from a different material to the piston body portion, eg a different aluminium alloy.
  • the different material may give greater wear resistance, as referred to above, or be selected for insulation or thermal shock resistance reasons.
  • the inner crown portion may be reinforced with fibres to improve the performance of the combustion recess.
  • the invention also provides a piston having a cavity therein, the piston comprising an inner crown portion which defines a central portion of a crown of the piston including a combustion recess of the piston, and an outer crown portion which defines an outer portion of the crown, the outer crown portion being fitted around the inner crown portion with an inner side surface of the outer crown portion overlying an outer side surface of the inner crown portion, characterised in that said cavity is formed by a recess formed in at least one of said side surfaces.
  • Figure 1 is a vertical cross-sectional view taken through a first illustrative piston manufactured by a first illustrative method according to the invention.
  • Figure 2 is similar to Figure 1 but shows a second illustrative piston manufactured by a second illustrative method.
  • the first illustrative piston 10 shown in Figure 1 is a piston for an internal combustion engine of the diesel type.
  • the piston 10 has a plurality, viz four, of cavities 12 therein which are equally circumferentially spaced about a combustion recess 14 of the piston.
  • the piston 10 comprises a piston body portion 16 which defines most of the piston. Specifically the portion 16 defines a guiding skirt 18 of the piston 10, two bosses 20 having bores 22 therein to receive a gudgeon pin by which the piston is connected to a connecting rod, and a side surface portion 24 of the piston 10 which defines a bottom piston ring groove 26.
  • the surface portion 24 is slightly elliptical, in transverse cross-section, as is conventional .
  • the body portion 16 also comprises an integral central cylindrical projection 30 extending upwardly from the remainder of the body portion 16.
  • the projection 30 provides an inner crown portion which defines a central portion of a crown of the piston 10 including the combustion recess 14.
  • the projection 30 has a top surface 32 which forms a portion of the top surface of the crown of the piston 10.
  • the surface 32 defines the combustion recess 14.
  • the projection 30 also has a cylindrical outer side surface 34 extending around the projection.
  • the side surface 34 extends longitudinally of the projection from the top surface 32 to a junction of the projection 30 with the remainder of the body portion 16. This junction is surrounded by a generally annular surface 36 of the body portion 16.
  • the surface 36 has a slightly elliptical outer edge which meets the surface portion 24 at a right angle.
  • the piston 10 also comprises an outer crown portion 40 fitted around said projection 30 and secured to said piston body portion 16.
  • the portion 40 is generally in the form of a hollow cylinder, having generally annular top and bottom surfaces 42 and 44, respectively, an inner concave cylindrical side surface 46, and an outer convex generally cylindrical side surface 48.
  • the top surface 42 is flush with the surface 32 of the projection 30.
  • the bottom surface 44 matches the surface 36 of the body portion 16 and overlies it.
  • the inner surface 46 matches the side surface 34 of the projection 30 and is a close fit thereon.
  • the outer surface 48 is flush with the surface portion 24 of the body portion 16.
  • the outer side surface 48 also defines an upper 50 and a central 52 piston ring groove of the piston 10.
  • the grooves 50 and 52, together with the groove 26, enable a conventional set of three piston rings to be mounted on the piston 12.
  • the cavities 12 are formed by recesses in the outer side surface 34 of the projection 30 of said piston body portion 16. Each of these recesses extends arcuately through about 60° about the combustion recess 14 and is closed to complete the cavity 12 by said outer crown portion 40, as the surface 46 overlies the recesses.
  • the cavities 12 are provided with openings into the combustion recess 14 by bores 54 through the projection 30. There are three bores 54 per cavity 12.
  • the first illustrative method of manufacturing the piston 10 comprises forming the piston body portion 16 out of a conventional aluminium alloy containing silicon.
  • the portion 16 is formed by a casting a blank and machining it to the required shape.
  • the machining includes forming the recesses to form the cavities 12 by machining into the surface 34, boring the bores 54 from the outside of the projection 30 into the combustion recess 14, and machining the groove 26.
  • the cavities 12 are provided with openings into the combustion recess 14 by boring from the recesses in the side surface 34 of the projection 30 to the combustion recess 14 before said further piston portion 40 is fitted to the piston 10.
  • the illustrative method also comprises forming the outer crown portion 40 out of a conventional aluminium alloy containing silicon. In this case, a different and harder alloy is used than for the body portion 16.
  • the portion 40 is formed by a casting a blank and machining it to the required shape. The machining includes machining the grooves 50 and 52.
  • the illustrative method also comprises closing the recesses in the surface 34 to form the cavities 12 by fitting the outer crown portion 40 around the inner crown portion provided by the projection 30.
  • the method also comprises securing the portion 40 to the piston body portion 16 by electron beam welding the surface 36 to the surface 44, and the surface 34 to the surface 46.
  • the second illustrative piston 100 shown in Figure 2 is similar, except as hereinafter described, to the first illustrative piston 10 and like parts are given the same reference numerals and are not further described.
  • the piston 100 comprises a body portion 102 which is similar to the body portion 16 except that it lacks the projection 30 and instead has a hollow generally-cylindrical upwards projection 104.
  • the piston 100 also does not have the outer crown portion 40 but instead comprises an inner crown portion 106.
  • the projection 104 defines a recess in which the inner crown portion 106 fits.
  • the projection 104 is generally in the form of a hollow cylinder extending upwardly from the remainder of the body portion 102.
  • the projection 104 provides an outer crown portion of the piston 100.
  • the projection 104 has a top surface 108 which is generally annular and forms a portion of the top surface of the crown of the piston 100.
  • the projection 104 also has a convex outer side surface 110 extending around the projection, the surface 110 being elliptical in transverse cross-section.
  • the side surface 110 extends longitudinally of the projection from the top surface 108 to a junction of the projection 104 with the remainder of the body portion 102 where it is flush with the side surface 24.
  • the surface 110 defines the piston ring grooves 50 and 52.
  • the projection 104 also has a concave cylindrical inner side surface 112.
  • the projection 104 extends around a circular upper surface 114 of the body portion 102.
  • the outer crown portion provided by the projection 104 is fitted around said inner crown portion 106 which is secured to said piston body portion 102.
  • the portion 106 is generally in the form of a cylinder, having a top surface 116 which defines a combustion recess 118, a circular bottom surface 120, and an outer convex cylindrical side surface 122.
  • the top surface 116 is flush with the surface 108 of the projection 104.
  • the bottom surface 120 matches the surface 114 of the body portion 102 and overlies it.
  • the outer side surface 122 matches the inner side surface 112 of the projection 102 and is a close fit therein.
  • the cavities 12 of the piston 100 are formed by recesses in the outer side surface 122 of the inner crown portion 106. Each of these recesses is closed to complete the cavity 12 by said outer crown portion 104, as the surface 112 overlies the recesses.
  • the cavities 12 are provided with openings into the combustion recess 118 by bores 54 through the portion 106.
  • the second illustrative method of manufacturing the piston 100 comprises forming the piston body portion 102 out of a conventional aluminium alloy containing silicon.
  • the portion 102 is formed by a casting a blank and machining it to the required shape.
  • the machining includes forming the ring grooves 26, 50 and 52.
  • the second illustrative method also comprises forming the inner crown portion 106 out of a conventional aluminium alloy containing silicon. In this case, a different and more thermally resistant alloy is used than for the body portion 102.
  • the portion 106 is formed by a casting a blank and machining it to the required shape.
  • the machining includes machining the recesses to form the cavities 12 by machining into the surface 122, and boring the bores 54 from the outside into the combustion recess 118.
  • the cavities 12 are provided with openings into the combustion recess 118 by boring from the recesses in the side surface 122 before said inner crown portion 106 is fitted to the piston 100.
  • the illustrative method also comprises closing the recesses in the surface 122 to form the cavities 12 by fitting the outer crown portion 104 around the inner crown portion 106.
  • the method also comprises securing the portion 40 to the piston body portion 16 by brazing the surface 114 to the surface 120, and the surface 112 to the surface 122.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Geometry (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)

Abstract

A piston (10; 100) containing a cavity (12) is manufactured by forming an inner crown portion (30; 106) by which a combustion recess (14) of the piston is defined, and forming an outer crown portion (40; 104). The outer crown portion (40; 104) is fitted around the inner crown portion (30; 106) with an inner side surface (46; 112) of the outer crown portion overlying an outer side surface (34; 122) of the inner crown portion, said cavity being formed by a recess formed in at least one of said side surfaces (34, 46; 112, 122).

Description

PISTON WITH CAVITY
This invention is concerned with a method of manufacturing a piston having a cavity therein and with such a piston.
A conventional piston for an internal combustion engine comprises a crown (which, in some cases, defines a combustion recess) , a guidance skirt, and bosses to receive a gudgeon pin. In some cases, it is necessary to provide pistons of this type with cavities. The term "cavity" is used herein to denote a substantially enclosed space having only restricted openings whereas the term "recess" is used to denote a space having a relatively large opening. For example, pistons have been proposed which have cavities in the crown thereof, the cavities having one or more restricted openings which communicate with a combustion recess in the crown. The combustion recess co-operates with the space above the crown of the piston in the cylinder in which it reciprocates to form a combustion chamber in which the fuel charge is burnt. These cavities (see US Patent No. 4,898,135) are intended to provide reaction chambers to shelter radical species of the fuel from being exhausted from the cylinder so that they can return to the cylinder to seed subsequent fuel charges. Such seeding improves the completeness of the combustion of the fuel .
A known method of providing a piston with cavities to form the aforementioned reaction chambers involves manufacturing the piston in two portions which are subsequently joined together. These portions are a piston body portion, defining most of the piston including a lower portion of the combustion recess, and an upper portion, defining a side surface of the combustion recess, a top surface of the piston, and a portion of the outer side surface of the piston. The body portion has a generally annular upper surface on to which a matching lower surface of the upper portion is fitted and the two portions are secured together. References herein to surfaces as being "generally annular" are not intended to exclude surfaces which have elliptical outer edges (as most pistons are slightly elliptical in transverse cross-section) and also are not intended to exclude surfaces which have their inner edges non-circular and/or non-central. Also, references herein to surfaces as being "generally cylindrical" are not intended to exclude surfaces which are elliptical in transverse cross-section.
In the known method described above, the cavities are formed by providing recesses in the lower surface of the upper portion, or in the upper surface of the lower portion, or in both surfaces. Thus, in the completed piston, the body portion defines a bottom surface of the combustion recess and also lower surfaces of the cavities, and the upper portion defines a side surface of the combustion recess and upper surfaces of the cavities. The restricted openings to the cavities may be formed by extensions of the recesses which form the cavities or, alternatively, may be formed by boring through the material of the piston after the two portions thereof have been secured together. Where such bores are used, a difficult process is involved as the bores must begin in the combustion recess. Thus, in this method, the manufacture of such pistons is complex, and the possibility exists that the two portions of the piston, which are only joined at a generally annular surface which is interrupted by the cavities, may become detached in service.
WO 94/20241 discloses a method of forming cavities in a piston in which each cavity is formed by a box. The box is mounted in a die cavity and the piston is cast around the box. The box is provided with projections which enter recesses in the wall of the die cavity and support the box. After removing the piston from the die cavity, the projections are machined off. The openings to the cavity can be provided by tubes projecting from the box. This method requires the manufacture of boxes and complicates the casting process.
It is an object of the present invention to provide a method of manufacturing a piston having a cavity therein which is less complex and produces a more reliable piston.
The invention provides a method of manufacturing a piston having a cavity therein, wherein the method comprises forming an inner crown portion of the piston which defines a central portion of a crown of the piston including a combustion recess of the piston, and forming an outer crown portion which defines an outer portion of the crown of the piston, the outer crown portion being arranged to fit around the inner crown portion with an inner side surface of the outer crown portion overlying an outer side surface of the inner crown portion, the method also comprising fitting the outer crown portion around the inner crown portion, and securing the inner and the outer crown portions together, characterised in that said cavity is formed by a recess formed in at least one of said side surfaces.
In a method in accordance with the invention, the two portions of the piston can be secured together, eg by electron beam welding or brazing, across a generally annular surface which is not interrupted by cavities, and can also be secured across said side surfaces. This gives a more reliable attachment, results in a piston having a combustion recess defined by one portion only of the piston, and the method is relatively simple, as the recesses forming the cavities can easily be formed by machining or by being cast-in. In a method according to the invention, the inner crown portion may be formed by a projection of a body portion of the piston, the projection having a top surface by which the combustion recess is defined, and the outer crown portion may be fitted around said projection. The projection may be circular in transverse cross-section or non-circular in order to ensure correct orientation during fitting. The outer crown portion may, alternatively, be formed by a projection of a body portion of the piston, and the inner crown portion may be fitted within a recess defined by said projection. The recess defined by the projection may be circular or non-circular in transverse cross-section.
Since it is frequently required that there should be a plurality of the aforementioned reaction chambers surrounding the combustion recess of a piston, a method according to the invention may comprise forming a plurality of recesses in said side surface.
The cavity may be provided with openings into the combustion recess by drilling or boring into said inner crown portion before said outer crown portion is fitted around said inner crown portion. This is relatively easy as the drilling or boring can be carried out from the outside.
The outer crown portion may have an outer side surface which defines one or more piston ring grooves. This gives the advantage that the piston ring grooves can be made more wear resistant by making the further piston portion out of a wear resistant material, or by coating it, or giving it a surface treatment before it is attached to the inner crown portion.
If desired, the inner and the outer crown portions may be formed from a different material to the piston body portion, eg a different aluminium alloy. The different material may give greater wear resistance, as referred to above, or be selected for insulation or thermal shock resistance reasons. For example, the inner crown portion may be reinforced with fibres to improve the performance of the combustion recess.
The invention also provides a piston having a cavity therein, the piston comprising an inner crown portion which defines a central portion of a crown of the piston including a combustion recess of the piston, and an outer crown portion which defines an outer portion of the crown, the outer crown portion being fitted around the inner crown portion with an inner side surface of the outer crown portion overlying an outer side surface of the inner crown portion, characterised in that said cavity is formed by a recess formed in at least one of said side surfaces.
There now follow detailed descriptions, to be read with reference to the accompanying drawings, of two methods of manufacturing pistons which are illustrative of the invention.
In the drawings:
Figure 1 is a vertical cross-sectional view taken through a first illustrative piston manufactured by a first illustrative method according to the invention; and
Figure 2 is similar to Figure 1 but shows a second illustrative piston manufactured by a second illustrative method.
The first illustrative piston 10 shown in Figure 1 is a piston for an internal combustion engine of the diesel type. The piston 10 has a plurality, viz four, of cavities 12 therein which are equally circumferentially spaced about a combustion recess 14 of the piston. The piston 10 comprises a piston body portion 16 which defines most of the piston. Specifically the portion 16 defines a guiding skirt 18 of the piston 10, two bosses 20 having bores 22 therein to receive a gudgeon pin by which the piston is connected to a connecting rod, and a side surface portion 24 of the piston 10 which defines a bottom piston ring groove 26. The surface portion 24 is slightly elliptical, in transverse cross-section, as is conventional .
The body portion 16 also comprises an integral central cylindrical projection 30 extending upwardly from the remainder of the body portion 16. The projection 30 provides an inner crown portion which defines a central portion of a crown of the piston 10 including the combustion recess 14. The projection 30 has a top surface 32 which forms a portion of the top surface of the crown of the piston 10. The surface 32 defines the combustion recess 14. The projection 30 also has a cylindrical outer side surface 34 extending around the projection. The side surface 34 extends longitudinally of the projection from the top surface 32 to a junction of the projection 30 with the remainder of the body portion 16. This junction is surrounded by a generally annular surface 36 of the body portion 16. The surface 36 has a slightly elliptical outer edge which meets the surface portion 24 at a right angle.
The piston 10 also comprises an outer crown portion 40 fitted around said projection 30 and secured to said piston body portion 16. The portion 40 is generally in the form of a hollow cylinder, having generally annular top and bottom surfaces 42 and 44, respectively, an inner concave cylindrical side surface 46, and an outer convex generally cylindrical side surface 48. The top surface 42 is flush with the surface 32 of the projection 30. The bottom surface 44 matches the surface 36 of the body portion 16 and overlies it. The inner surface 46 matches the side surface 34 of the projection 30 and is a close fit thereon. The outer surface 48 is flush with the surface portion 24 of the body portion 16. The outer side surface 48 also defines an upper 50 and a central 52 piston ring groove of the piston 10. The grooves 50 and 52, together with the groove 26, enable a conventional set of three piston rings to be mounted on the piston 12.
The cavities 12 are formed by recesses in the outer side surface 34 of the projection 30 of said piston body portion 16. Each of these recesses extends arcuately through about 60° about the combustion recess 14 and is closed to complete the cavity 12 by said outer crown portion 40, as the surface 46 overlies the recesses. The cavities 12 are provided with openings into the combustion recess 14 by bores 54 through the projection 30. There are three bores 54 per cavity 12.
The first illustrative method of manufacturing the piston 10 comprises forming the piston body portion 16 out of a conventional aluminium alloy containing silicon. The portion 16 is formed by a casting a blank and machining it to the required shape. The machining includes forming the recesses to form the cavities 12 by machining into the surface 34, boring the bores 54 from the outside of the projection 30 into the combustion recess 14, and machining the groove 26. Thus, the cavities 12 are provided with openings into the combustion recess 14 by boring from the recesses in the side surface 34 of the projection 30 to the combustion recess 14 before said further piston portion 40 is fitted to the piston 10.
The illustrative method also comprises forming the outer crown portion 40 out of a conventional aluminium alloy containing silicon. In this case, a different and harder alloy is used than for the body portion 16. The portion 40 is formed by a casting a blank and machining it to the required shape. The machining includes machining the grooves 50 and 52.
The illustrative method also comprises closing the recesses in the surface 34 to form the cavities 12 by fitting the outer crown portion 40 around the inner crown portion provided by the projection 30. The method also comprises securing the portion 40 to the piston body portion 16 by electron beam welding the surface 36 to the surface 44, and the surface 34 to the surface 46.
The second illustrative piston 100 shown in Figure 2 is similar, except as hereinafter described, to the first illustrative piston 10 and like parts are given the same reference numerals and are not further described. The piston 100 comprises a body portion 102 which is similar to the body portion 16 except that it lacks the projection 30 and instead has a hollow generally-cylindrical upwards projection 104. The piston 100 also does not have the outer crown portion 40 but instead comprises an inner crown portion 106. The projection 104 defines a recess in which the inner crown portion 106 fits.
The projection 104 is generally in the form of a hollow cylinder extending upwardly from the remainder of the body portion 102. The projection 104 provides an outer crown portion of the piston 100. The projection 104 has a top surface 108 which is generally annular and forms a portion of the top surface of the crown of the piston 100. The projection 104 also has a convex outer side surface 110 extending around the projection, the surface 110 being elliptical in transverse cross-section. The side surface 110 extends longitudinally of the projection from the top surface 108 to a junction of the projection 104 with the remainder of the body portion 102 where it is flush with the side surface 24. The surface 110 defines the piston ring grooves 50 and 52. The projection 104 also has a concave cylindrical inner side surface 112. The projection 104 extends around a circular upper surface 114 of the body portion 102.
The outer crown portion provided by the projection 104 is fitted around said inner crown portion 106 which is secured to said piston body portion 102. The portion 106 is generally in the form of a cylinder, having a top surface 116 which defines a combustion recess 118, a circular bottom surface 120, and an outer convex cylindrical side surface 122. The top surface 116 is flush with the surface 108 of the projection 104. The bottom surface 120 matches the surface 114 of the body portion 102 and overlies it. The outer side surface 122 matches the inner side surface 112 of the projection 102 and is a close fit therein.
The cavities 12 of the piston 100 are formed by recesses in the outer side surface 122 of the inner crown portion 106. Each of these recesses is closed to complete the cavity 12 by said outer crown portion 104, as the surface 112 overlies the recesses. The cavities 12 are provided with openings into the combustion recess 118 by bores 54 through the portion 106.
The second illustrative method of manufacturing the piston 100 comprises forming the piston body portion 102 out of a conventional aluminium alloy containing silicon. The portion 102 is formed by a casting a blank and machining it to the required shape. The machining includes forming the ring grooves 26, 50 and 52.
The second illustrative method also comprises forming the inner crown portion 106 out of a conventional aluminium alloy containing silicon. In this case, a different and more thermally resistant alloy is used than for the body portion 102. The portion 106 is formed by a casting a blank and machining it to the required shape. The machining includes machining the recesses to form the cavities 12 by machining into the surface 122, and boring the bores 54 from the outside into the combustion recess 118. Thus, the cavities 12 are provided with openings into the combustion recess 118 by boring from the recesses in the side surface 122 before said inner crown portion 106 is fitted to the piston 100.
The illustrative method also comprises closing the recesses in the surface 122 to form the cavities 12 by fitting the outer crown portion 104 around the inner crown portion 106. The method also comprises securing the portion 40 to the piston body portion 16 by brazing the surface 114 to the surface 120, and the surface 112 to the surface 122.

Claims

A method of manufacturing a piston (10; 100) having a cavity (12) therein, wherein the method comprises forming an inner crown portion (30; 106) of the piston which defines a central portion of a crown of the piston including a combustion recess (14; 118) of the piston, and forming an outer crown portion (40; 104) which defines an outer portion of the crown of the piston, the outer crown portion being arranged to fit around the inner crown portion with an inner side surface (46; 112) of the outer crown portion overlying an outer side surface (34; 122) of the inner crown portion, the method also comprising fitting the outer crown portion (40; 104) around the inner crown portion (30; 106) , and securing the inner and the outer crown portions together, characterised in that said cavity (12) is formed by a recess formed in at least one of said side surfaces (34, 46; 112, 122).
A method according to claim 1, characterised in that the inner crown portion (30) is formed by a projection of a body portion (16) of the piston (10) , the projection having a top surface (32) by which the combustion recess (14) is defined, and the outer crown portion (40) is fitted around said projection.
A method according to claim 1, characterised in that the outer crown portion (104) is formed by a projection of a body portion (102) of the piston (100) , and the inner crown portion (106) is fitted within a recess defined by said projection.
A method according to any one of claims 1 to 3 , characterised in that the method comprises forming a plurality of recesses (12) in said side surface (34, 46; 112, 122). A method according to any one of claims 1 to 4, characterised in that the cavity (12) is provided with openings (54) into the combustion recess (14; 118) by drilling or boring into said inner crown portion (30; 106) before said outer crown portion (40; 104) is fitted around said inner crown portion.
A method according to any one of claims 1 to 5, characterised in that the outer crown portion (40; 104) has an outer side surface (48; 110) which defines one or more piston ring grooves (50, 52) .
A method according to any one of claims 1 to 6, characterised in that said inner (30; 106) and outer (40; 104) crown portions are formed from different materials.
A piston (10; 100) having a cavity (12) therein, the piston comprising an inner crown portion (30; 106) which defines a central portion of a crown of the piston including a combustion recess (14; 118) of the piston, and an outer crown portion (40; 104) which defines an outer portion of the crown, the outer crown portion being fitted around the inner crown portion with an inner side surface (46; 112) of the outer crown portion overlying an outer side surface (34; 122) of the inner crown portion, characterised in that said cavity (12) is formed by a recess formed in at least one of said side surfaces (34, 46; 112, 122).
A piston according to claim 8, manufactured by a method according to any one of claims 1 to 7.
PCT/GB1997/002851 1996-10-17 1997-10-16 Piston with cavity WO1998017900A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9621659.3 1996-10-17
GB9621659A GB2318402A (en) 1996-10-17 1996-10-17 Piston with cavity

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WO1998017900A1 true WO1998017900A1 (en) 1998-04-30

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114227181A (en) * 2021-12-31 2022-03-25 桐乡顺士达精密机械有限公司 Machining method for automobile air conditioner compressor piston

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6178942B1 (en) * 1999-10-19 2001-01-30 Sonex Research, Inc. Piston configuration for reducing smoke and particulate emissions from direct injected engines
GB2375724B (en) * 2001-05-24 2005-01-12 Federal Mogul Technology Ltd Manufacturing pistons
EP1721022A2 (en) * 2004-01-12 2006-11-15 KS Kolbenschmidt GmbH Heat-resistant aluminium-silicon piston alloy

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE646872A (en) * 1900-01-01
EP0072140A1 (en) * 1981-07-31 1983-02-16 Ae Plc Pistons with combustion bowl inserts
GB2184485A (en) * 1985-12-23 1987-06-24 Ford Motor Co Air cell structure of a diesel engine piston combustion chamber
US4898135A (en) 1989-02-16 1990-02-06 Sonex Research, Inc. Piston and process for achieving controlled ignition and combustion of hydrocarbon fuels in internal combustion engines by generation and management of fuel radical species
WO1994020241A1 (en) 1993-03-05 1994-09-15 T & N Technology Limited Piston with cavity

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0351438A1 (en) * 1988-07-16 1990-01-24 Köpke, Günter, Dr.-Ing. Internal combustion engine

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE646872A (en) * 1900-01-01
EP0072140A1 (en) * 1981-07-31 1983-02-16 Ae Plc Pistons with combustion bowl inserts
GB2184485A (en) * 1985-12-23 1987-06-24 Ford Motor Co Air cell structure of a diesel engine piston combustion chamber
US4898135A (en) 1989-02-16 1990-02-06 Sonex Research, Inc. Piston and process for achieving controlled ignition and combustion of hydrocarbon fuels in internal combustion engines by generation and management of fuel radical species
WO1994020241A1 (en) 1993-03-05 1994-09-15 T & N Technology Limited Piston with cavity

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114227181A (en) * 2021-12-31 2022-03-25 桐乡顺士达精密机械有限公司 Machining method for automobile air conditioner compressor piston

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GB2318402A (en) 1998-04-22

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