CA1180616A - Heat insulated piston assembly and method of assembling - Google Patents
Heat insulated piston assembly and method of assemblingInfo
- Publication number
- CA1180616A CA1180616A CA000405033A CA405033A CA1180616A CA 1180616 A CA1180616 A CA 1180616A CA 000405033 A CA000405033 A CA 000405033A CA 405033 A CA405033 A CA 405033A CA 1180616 A CA1180616 A CA 1180616A
- Authority
- CA
- Canada
- Prior art keywords
- sleeve
- core
- heat insulated
- connecting rod
- piston
- Prior art date
- 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.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000002485 combustion reaction Methods 0.000 claims abstract description 17
- 239000000919 ceramic Substances 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 6
- 238000002844 melting Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 3
- 230000002093 peripheral effect Effects 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims 1
- 230000013011 mating Effects 0.000 abstract 1
- 239000003779 heat-resistant material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 239000003381 stabilizer Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 241001052209 Cylinder Species 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- CEJLBZWIKQJOAT-UHFFFAOYSA-N dichloroisocyanuric acid Chemical compound ClN1C(=O)NC(=O)N(Cl)C1=O CEJLBZWIKQJOAT-UHFFFAOYSA-N 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical group [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000284 resting effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- -1 silicon nitrides Chemical class 0.000 description 1
Classifications
-
- 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
- F02F7/00—Casings, e.g. crankcases or frames
- F02F7/0085—Materials for constructing engines or their parts
- F02F7/0087—Ceramic materials
-
- 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
- F02F3/0023—Multi-part pistons the parts being bolted or screwed together
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16J—PISTONS; CYLINDERS; SEALINGS
- F16J1/00—Pistons; Trunk pistons; Plungers
- F16J1/10—Connection to driving members
- F16J1/14—Connection to driving members with connecting-rods, i.e. pivotal connections
- F16J1/22—Connection to driving members with connecting-rods, i.e. pivotal connections with universal joint, e.g. ball-joint
-
- 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
-
- 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
- F05C2201/04—Heavy metals
- F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
- F05C2201/0448—Steel
Abstract
AN IMPROVED HEAT INSULATED PISTON ASSEMBLY
AND METHOD OF ASSEMBLING
Abstract of the Disclosure An improved heat insulated piston assembly for an internal combustion engine and a method of assembly. The improved piston assembly includes a piston constructed of a sleeve having an interference fit about a heat insulated core. The core has a first end positioned flush with an end of the sleeve and has a second end located within the sleeve with a concave configured cavity formed therein. Mating in the concave configured cavity of the core is a connecting rod having a spherical ball shaped end. The spherical ball shaped end is securely held in the cavity by a retaining ring which attaches to the piston sleeve.
The retaining ring allows for limited movement of the spherical ball shaped end of the connecting rod in the cavity while providing a means for returning the piston to its bottom position during the intake stroke.
AND METHOD OF ASSEMBLING
Abstract of the Disclosure An improved heat insulated piston assembly for an internal combustion engine and a method of assembly. The improved piston assembly includes a piston constructed of a sleeve having an interference fit about a heat insulated core. The core has a first end positioned flush with an end of the sleeve and has a second end located within the sleeve with a concave configured cavity formed therein. Mating in the concave configured cavity of the core is a connecting rod having a spherical ball shaped end. The spherical ball shaped end is securely held in the cavity by a retaining ring which attaches to the piston sleeve.
The retaining ring allows for limited movement of the spherical ball shaped end of the connecting rod in the cavity while providing a means for returning the piston to its bottom position during the intake stroke.
Description
061~
AN IMPROVED HEAT INSULATED PISTON ASSEMBLY
AND METHOD OF ASSEMBLING
Background of the Invention This invention-relates to an improved heat insulated piston assembly for an internal combustion engine and a method for assembly.
Description of the Prior Art The current trend in the manufacture of internal combustion engines is to design and build engines which can operate at very high temperatures and pressures with little or no coolin~. Prior attempts to do this have resulted in the production of pistons which were coated or capped with a heat insulated or heat resist-ant material. Some U.S. patents which teach such designs include:
1,490,849 issued to Phillips on 15 April 1924; 3,911,891 issued 15 to Dowell on 14 October 1975; 4,018,194 issued to Mitchell et al on l9 April 1~77; and 4,245,611 issued to Mitchell et al on 20 January 1981. These prior art pistons, although being an im-provement over the all steel or all aluminum constructed pistons, have a disadvantage in that the heat insulated material is uti-lized in such a fashion that it is susceptable to breakage due to high tensile stresses. Furthermore, the pistons which use an insertable ceramic cap, such as taught by Mitchell (611~, are limited in their heat insulating capacity and usually require a cushioning layer between the piston body and the cap to reduce and distribute the non-symmetrical stress loads. Now an improved heat insulated p~ston assembly has been invented which is an improvement over the prior art.
Summary of the In~ention Briefly, this invention relates to an improved heat insu-lated piston assembly for use in an internal combustion engineand a method of assem~ly. The piston includes a cylindrical sleeve having helical threads formed on a portion of its inner circumference adjacent to one end. This sleeve is secured to a heat insulated core by an interference fit such that a first end of the core is flush with the top end of the sleeve. The other end of the core contains a hemi-spheri~cally shaped cavity which is completely surrounded by the sleeve and is positioned adjacent to the helical threads. The hemi~-spherically shaped cavity is matable ~ith a connecting rod having a spherical ball shaped end.
The spherical ball shaped end, which is slightly smaller in .
~ 2 --6~L~
diameter than the hemi-spherically shaped cavitv, is securely held in place by a retaining ring which has an arcuately shaped inner circumferential surface and a threaded outer circumference.
As the retaining ring is threaded into the sleeve, the spherical ball shaped end of the connecting rod is joined to the cavity of the core such that stress forces developed during engine opera-tion can be transferred from the core to a large area of the connecting rod. This transfer of developed forces is essentially symmetrical over the entire surface area of the spherical ball and proyides for low unit contact pressures between the core and the connecting rod, and hence low surface stresses. Also, since the insulated core can contact the rod directly without addition-al support, a greater thickness of insulating material can be used without increasing the piston height.
A method for assembli`ng the heat insulated piston assembly is also taught whereby the sleeve is first thermally expanded, the core is inserted into the sleeve and the sleeve is then cooled to room temperature so as to form an interference fit.
The spherical ball shaped end of the connecting rod is then positioned into the hemi-spherically shaped cavity of the core.
While so retained, the retaining ring is placed about the con-necting rod and is attached to the sleeve to hold the members together.
The general object of this invention is to provide an im-proved heat i`nsulated piston assembly and its method of assemblyonto a connecting rod such that a symmetrical stress pattern is realized by the piston during engine operations. A more specific object of this inyention is to provide an improved heat insulated piston assem~ly w~ich can operate at higher combustion tempera-tures with reduced heat losses and with improved engine efficien-cy .
Another object of this invention is to provide an improved heat insulated piston assembly which exhibits lower tensile stresses on the i~nsulating member of the heat insulated piston.
Sti-ll another object of this invention is to provide an improved heat ~nsulated piston assembly which has a longer life e~pectancy than currently available ceramic pistons.
A further object of this invention is to provide an improved heat insulated piston assembly which is economical to build and simple to assemble.
Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the drawing.
~rief Description of the Drawing / The Fig. is a cross-sectional view of the improved heat ~insulated piston assembly.
Detailed Description of the Preferred Embodiment Referring to the Fig., an improved heat insulated piston assembly 10 is shown comprised of a piston 11, a connecting rod 12 and a retaining means 13. The piston 11 is formed of a cylindrical elongated sleeve 14, preferably made of steel, which has at least one piston ring groove 16 formed in its outer periphery approximate a first end 18. Located on the inner cir-cumference of the sleeve 14, approximate a second end 20, is an attachment means 22. The attachment means 22 is depicted as helical threads but other types of fasteners can be used whichare known to those skilled in the fastening arts. Preferably, the attachment means 22 enables assembly and disassembly of the retaining means 13 from the piston ll. A heat insulated core 24 is held in the sleeve 14 by an interference fit. The interfer-ence fit places the core 24 in a pre-stressed state wherein it has an axisymmetric compressive stress state about the central or longitudinal axis of the sleeve 14. The interference fit also secures the sleeve 14 to the core 24 such that no separation will occur during normal piston operation within the cylinder bore of the engine. The desired range of interference fit between the core 24 and the sleeve 14 is determined such that the tensile stresses due to the gas pressure exerted on the piston 11 during combustion never overcomes the initial compressive stresses in the core 24. This feature is important for it reduces and prac-tically eliminates the tensile stress forces felt by the core 24.
One method of establishing the desired interference fit is to thermally expand the sleeve 14 to approximately 60 percent of the melting point of the sleeve material, insert the expanded sleeve 14 around the core 24 and then cool the sleeve 14 back down to room temperature. The resulting interference fit should be approximately 80 to 100 percent of the yield strength of the sleeve 14. Preferably, the interference fit is 95 percent of the yield strength of the sleeve 14.
~ 016~6 - The core 24 i5 constructed of a heat insulated or heat resistant material such as a ceramic, preferably a high density ceramic, which has a relatively high insulative value. Accept-able heat insulated or heat resistant materials include: zirco-nia, silicon nitrides, silicon carbides, and compositions thereof.
A stabilizer can also be added to the material to increase its structural, th.ermal and wear properties~ An example of a stabi-lizer is magnesium oxide.
The core 24 is fitted to the sleeve 14 such that a first end 26 of the core 24 is approximately flush with the first end 18 of the sleeve 14. This design allows the top edge of the piston ll to move close to the inner surface of the cylinder head of the engine during its reciprocative movement within the cylinder.
Formed within the first end 26 of the core 24 is a combustion chamher 28. The combustion chamber 28 can be of various config-uration but should not contai`n any sharp corners because ceramic materials, în general, are notch sensi`tive and tend to crack or deform at such locations. Alternati`ve desi`gns for the combustion chamber 28, including arranglng the combustion chamber 28 com-pletely within. the cylinder head, or partially within the cylin-der head and partially in the core.24 can be utilized. These alternate designs are well known to those skilled in the engine arts.
The core 24 also has a second end 3Q which is retained within the confines of the sleeve. 14 adjacent to the attachment means 22. Th~s second end 30 has formed therein a concave con-figured cavity 32, preferably hemi-spherical in configuration and completely open to the second end 20 of the sleeve 14. Matable with the concave confi`gured cavity 32 is a spherical ball shaped end 34 formed on one end of the conne.cting rod 12. The spherical ball shaped end 34, which has a hollow interior in order to reduce the weight of the assembly, has a diameter ~hich is slightly less than the d~ameter of the concave configured cavity 32. Preferably, a diameter of a few thousand less, from .001-.010 inches for a four inch diameter piston, is sufficient. ThissLight dl~ensional difference between the concave configured cayity 32 and the outer periphery of the spherical ball 34 allows for a certain amount of flexibility while providing for a large contactable su~face through which developed combustion stress forces can be transferred. Although most cerami~c materials 31ali6~L6 , "
exhibit good heat insulating characteristics and can withstand large compressive loads, they are very weak in tension. The arrangement of the spherical ball 34 and the hemi-spherical cavity 32 places the core 24 in an axisymmetric stress state 5 under the gas pressure loads exerted on the piston 11 by the combustion of the fuel and air mixtures in the combustion chamber 28. The greatest forces exerted on the piston assembly 10 occur during the power stroke when the piston 11 is ~orced downward by the combustion of the fuel mixture. ~y distributing the devel-oped stresses on the core 24 symmetri`cally over the entire sur-face of the spherical ball 34, an improved piston assembly 10 is achieved which will have a longer lie expectancy over conven-tional ceramic pistons.
The spherical ball shaped end 34 of the connecting rod 12 is joined to the piston 11 by the retaining means 13. The retaining means 13, is an annular ring containing a central aperture 35 having an arcuately shaped inner surface 36 which approximately conforms to the outer peripheral surface of the spherical ball 34. The smallest diameter of the aperture 35 is large enough to encircle the stem of the connecting rod 12 while preventing the spherical ball 34 from passing therethrough. The diameter of the largest portion of the arcuately shaped surface 36 is slightly larger than the diameter of the spherical ball 34 and approxi-mately equal to the diameter of the concave configured cavity 32.
The purpose of this size di~fference is to allow for limited movement of the spher~cal ball 34 in the area formed by the concave configured cavity 32 and the arcuately shaped surface 36 of the retaining means 13. Located on the outer circumference of the retaining means 13 is an attachin~ device 38, such as screw threads, which mate with the attachment means 22 on the sleeve 14. The retaining ring 13 can contain a slit in its circumfer-ence which will allow the ring 13 to be partially parted and slipped over the shank of the connecting rod 12. The retaining means 13 IS designed to transfer forces from the connecting rod 12 to the core 24 v~a the sleeve 14 during the intake stroke of the cycle when the piston 11 is moving downward. During this portion of the cycle, only low cylinder pressures are present.
It should be noted that during the power stroke, the forces from com~ustion are transmitted through the core 24 to the connecting rod 12 and the retaining means 13 experi`ences little if any 6~6 , ..~. .
1 orces. Likewise, on both of the upstrokes, the retaining means 13 is not transferring any appreciable force between the connect-ing rod 12 and the sleeve 14.
This improved heat insulated piston assembly 10 is capable 3 of handling eng;ne temperatures in the range of from about -40 degrees Celsius to 1000 degrees Celsius and engine combustion pressures up to about 2500 psi.
One method of assemblïng the heat insulated piston 11 to the connecting rod 12 is as follows: first, the heat insulated core 24 is placed on a flat surface in an inverted position (resting on its first end 26); second, the sleeve 14 is thermally expanded by heating it to approxlmately 60 percent of the melting point of the sleeve material; third, the heated sleeve 14 is inverted and placed around the core 24 such that its first end 18 is fl~sh with the first end 26 of the core 24; and fourth, the sleeve 14 is allowed to cool to room temperature thereby forming an inter-ference fit between the out~r diameter of the core 24 and the inner diameter of the sleeve 14. This interference fit places the core 24 in a pre-stressed state having an axisymmetric state of compressive stress about the central axis of the core 24. The retaining ring 13 is then placed around the connecting rod 12 and is slid along its shank towards the spherical end 34. Optionally, the retaining ring 13 can contain a slit which allows the ring 13 to be opened and placed around the shank of the connecting rod 12. The core and sleeve assembly is then positioned on the spherical ball shaped end 34 of the connecting rod 12 such that the spherical end 34 mates with the concave cavity 32 of the core 24. The retaining ring 13 is then attached to the sleeve 14 by the threads 22 and 38. When in place, the retaining ring 13 is tight against the second end 30 of the core 24.
While the invention has been described in conjunction with a specific embodiment, it is to be understood that many alterna-tives, modifications, and variations will be apparent to those skilled in the art in light of the aforegoing description.
Accordingly, it is intended to embrace all such alternatives, ~odifications, and variations which fall within the spirit and scope of the appended claims.
AN IMPROVED HEAT INSULATED PISTON ASSEMBLY
AND METHOD OF ASSEMBLING
Background of the Invention This invention-relates to an improved heat insulated piston assembly for an internal combustion engine and a method for assembly.
Description of the Prior Art The current trend in the manufacture of internal combustion engines is to design and build engines which can operate at very high temperatures and pressures with little or no coolin~. Prior attempts to do this have resulted in the production of pistons which were coated or capped with a heat insulated or heat resist-ant material. Some U.S. patents which teach such designs include:
1,490,849 issued to Phillips on 15 April 1924; 3,911,891 issued 15 to Dowell on 14 October 1975; 4,018,194 issued to Mitchell et al on l9 April 1~77; and 4,245,611 issued to Mitchell et al on 20 January 1981. These prior art pistons, although being an im-provement over the all steel or all aluminum constructed pistons, have a disadvantage in that the heat insulated material is uti-lized in such a fashion that it is susceptable to breakage due to high tensile stresses. Furthermore, the pistons which use an insertable ceramic cap, such as taught by Mitchell (611~, are limited in their heat insulating capacity and usually require a cushioning layer between the piston body and the cap to reduce and distribute the non-symmetrical stress loads. Now an improved heat insulated p~ston assembly has been invented which is an improvement over the prior art.
Summary of the In~ention Briefly, this invention relates to an improved heat insu-lated piston assembly for use in an internal combustion engineand a method of assem~ly. The piston includes a cylindrical sleeve having helical threads formed on a portion of its inner circumference adjacent to one end. This sleeve is secured to a heat insulated core by an interference fit such that a first end of the core is flush with the top end of the sleeve. The other end of the core contains a hemi-spheri~cally shaped cavity which is completely surrounded by the sleeve and is positioned adjacent to the helical threads. The hemi~-spherically shaped cavity is matable ~ith a connecting rod having a spherical ball shaped end.
The spherical ball shaped end, which is slightly smaller in .
~ 2 --6~L~
diameter than the hemi-spherically shaped cavitv, is securely held in place by a retaining ring which has an arcuately shaped inner circumferential surface and a threaded outer circumference.
As the retaining ring is threaded into the sleeve, the spherical ball shaped end of the connecting rod is joined to the cavity of the core such that stress forces developed during engine opera-tion can be transferred from the core to a large area of the connecting rod. This transfer of developed forces is essentially symmetrical over the entire surface area of the spherical ball and proyides for low unit contact pressures between the core and the connecting rod, and hence low surface stresses. Also, since the insulated core can contact the rod directly without addition-al support, a greater thickness of insulating material can be used without increasing the piston height.
A method for assembli`ng the heat insulated piston assembly is also taught whereby the sleeve is first thermally expanded, the core is inserted into the sleeve and the sleeve is then cooled to room temperature so as to form an interference fit.
The spherical ball shaped end of the connecting rod is then positioned into the hemi-spherically shaped cavity of the core.
While so retained, the retaining ring is placed about the con-necting rod and is attached to the sleeve to hold the members together.
The general object of this invention is to provide an im-proved heat i`nsulated piston assembly and its method of assemblyonto a connecting rod such that a symmetrical stress pattern is realized by the piston during engine operations. A more specific object of this inyention is to provide an improved heat insulated piston assem~ly w~ich can operate at higher combustion tempera-tures with reduced heat losses and with improved engine efficien-cy .
Another object of this invention is to provide an improved heat insulated piston assembly which exhibits lower tensile stresses on the i~nsulating member of the heat insulated piston.
Sti-ll another object of this invention is to provide an improved heat ~nsulated piston assembly which has a longer life e~pectancy than currently available ceramic pistons.
A further object of this invention is to provide an improved heat insulated piston assembly which is economical to build and simple to assemble.
Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the drawing.
~rief Description of the Drawing / The Fig. is a cross-sectional view of the improved heat ~insulated piston assembly.
Detailed Description of the Preferred Embodiment Referring to the Fig., an improved heat insulated piston assembly 10 is shown comprised of a piston 11, a connecting rod 12 and a retaining means 13. The piston 11 is formed of a cylindrical elongated sleeve 14, preferably made of steel, which has at least one piston ring groove 16 formed in its outer periphery approximate a first end 18. Located on the inner cir-cumference of the sleeve 14, approximate a second end 20, is an attachment means 22. The attachment means 22 is depicted as helical threads but other types of fasteners can be used whichare known to those skilled in the fastening arts. Preferably, the attachment means 22 enables assembly and disassembly of the retaining means 13 from the piston ll. A heat insulated core 24 is held in the sleeve 14 by an interference fit. The interfer-ence fit places the core 24 in a pre-stressed state wherein it has an axisymmetric compressive stress state about the central or longitudinal axis of the sleeve 14. The interference fit also secures the sleeve 14 to the core 24 such that no separation will occur during normal piston operation within the cylinder bore of the engine. The desired range of interference fit between the core 24 and the sleeve 14 is determined such that the tensile stresses due to the gas pressure exerted on the piston 11 during combustion never overcomes the initial compressive stresses in the core 24. This feature is important for it reduces and prac-tically eliminates the tensile stress forces felt by the core 24.
One method of establishing the desired interference fit is to thermally expand the sleeve 14 to approximately 60 percent of the melting point of the sleeve material, insert the expanded sleeve 14 around the core 24 and then cool the sleeve 14 back down to room temperature. The resulting interference fit should be approximately 80 to 100 percent of the yield strength of the sleeve 14. Preferably, the interference fit is 95 percent of the yield strength of the sleeve 14.
~ 016~6 - The core 24 i5 constructed of a heat insulated or heat resistant material such as a ceramic, preferably a high density ceramic, which has a relatively high insulative value. Accept-able heat insulated or heat resistant materials include: zirco-nia, silicon nitrides, silicon carbides, and compositions thereof.
A stabilizer can also be added to the material to increase its structural, th.ermal and wear properties~ An example of a stabi-lizer is magnesium oxide.
The core 24 is fitted to the sleeve 14 such that a first end 26 of the core 24 is approximately flush with the first end 18 of the sleeve 14. This design allows the top edge of the piston ll to move close to the inner surface of the cylinder head of the engine during its reciprocative movement within the cylinder.
Formed within the first end 26 of the core 24 is a combustion chamher 28. The combustion chamber 28 can be of various config-uration but should not contai`n any sharp corners because ceramic materials, în general, are notch sensi`tive and tend to crack or deform at such locations. Alternati`ve desi`gns for the combustion chamber 28, including arranglng the combustion chamber 28 com-pletely within. the cylinder head, or partially within the cylin-der head and partially in the core.24 can be utilized. These alternate designs are well known to those skilled in the engine arts.
The core 24 also has a second end 3Q which is retained within the confines of the sleeve. 14 adjacent to the attachment means 22. Th~s second end 30 has formed therein a concave con-figured cavity 32, preferably hemi-spherical in configuration and completely open to the second end 20 of the sleeve 14. Matable with the concave confi`gured cavity 32 is a spherical ball shaped end 34 formed on one end of the conne.cting rod 12. The spherical ball shaped end 34, which has a hollow interior in order to reduce the weight of the assembly, has a diameter ~hich is slightly less than the d~ameter of the concave configured cavity 32. Preferably, a diameter of a few thousand less, from .001-.010 inches for a four inch diameter piston, is sufficient. ThissLight dl~ensional difference between the concave configured cayity 32 and the outer periphery of the spherical ball 34 allows for a certain amount of flexibility while providing for a large contactable su~face through which developed combustion stress forces can be transferred. Although most cerami~c materials 31ali6~L6 , "
exhibit good heat insulating characteristics and can withstand large compressive loads, they are very weak in tension. The arrangement of the spherical ball 34 and the hemi-spherical cavity 32 places the core 24 in an axisymmetric stress state 5 under the gas pressure loads exerted on the piston 11 by the combustion of the fuel and air mixtures in the combustion chamber 28. The greatest forces exerted on the piston assembly 10 occur during the power stroke when the piston 11 is ~orced downward by the combustion of the fuel mixture. ~y distributing the devel-oped stresses on the core 24 symmetri`cally over the entire sur-face of the spherical ball 34, an improved piston assembly 10 is achieved which will have a longer lie expectancy over conven-tional ceramic pistons.
The spherical ball shaped end 34 of the connecting rod 12 is joined to the piston 11 by the retaining means 13. The retaining means 13, is an annular ring containing a central aperture 35 having an arcuately shaped inner surface 36 which approximately conforms to the outer peripheral surface of the spherical ball 34. The smallest diameter of the aperture 35 is large enough to encircle the stem of the connecting rod 12 while preventing the spherical ball 34 from passing therethrough. The diameter of the largest portion of the arcuately shaped surface 36 is slightly larger than the diameter of the spherical ball 34 and approxi-mately equal to the diameter of the concave configured cavity 32.
The purpose of this size di~fference is to allow for limited movement of the spher~cal ball 34 in the area formed by the concave configured cavity 32 and the arcuately shaped surface 36 of the retaining means 13. Located on the outer circumference of the retaining means 13 is an attachin~ device 38, such as screw threads, which mate with the attachment means 22 on the sleeve 14. The retaining ring 13 can contain a slit in its circumfer-ence which will allow the ring 13 to be partially parted and slipped over the shank of the connecting rod 12. The retaining means 13 IS designed to transfer forces from the connecting rod 12 to the core 24 v~a the sleeve 14 during the intake stroke of the cycle when the piston 11 is moving downward. During this portion of the cycle, only low cylinder pressures are present.
It should be noted that during the power stroke, the forces from com~ustion are transmitted through the core 24 to the connecting rod 12 and the retaining means 13 experi`ences little if any 6~6 , ..~. .
1 orces. Likewise, on both of the upstrokes, the retaining means 13 is not transferring any appreciable force between the connect-ing rod 12 and the sleeve 14.
This improved heat insulated piston assembly 10 is capable 3 of handling eng;ne temperatures in the range of from about -40 degrees Celsius to 1000 degrees Celsius and engine combustion pressures up to about 2500 psi.
One method of assemblïng the heat insulated piston 11 to the connecting rod 12 is as follows: first, the heat insulated core 24 is placed on a flat surface in an inverted position (resting on its first end 26); second, the sleeve 14 is thermally expanded by heating it to approxlmately 60 percent of the melting point of the sleeve material; third, the heated sleeve 14 is inverted and placed around the core 24 such that its first end 18 is fl~sh with the first end 26 of the core 24; and fourth, the sleeve 14 is allowed to cool to room temperature thereby forming an inter-ference fit between the out~r diameter of the core 24 and the inner diameter of the sleeve 14. This interference fit places the core 24 in a pre-stressed state having an axisymmetric state of compressive stress about the central axis of the core 24. The retaining ring 13 is then placed around the connecting rod 12 and is slid along its shank towards the spherical end 34. Optionally, the retaining ring 13 can contain a slit which allows the ring 13 to be opened and placed around the shank of the connecting rod 12. The core and sleeve assembly is then positioned on the spherical ball shaped end 34 of the connecting rod 12 such that the spherical end 34 mates with the concave cavity 32 of the core 24. The retaining ring 13 is then attached to the sleeve 14 by the threads 22 and 38. When in place, the retaining ring 13 is tight against the second end 30 of the core 24.
While the invention has been described in conjunction with a specific embodiment, it is to be understood that many alterna-tives, modifications, and variations will be apparent to those skilled in the art in light of the aforegoing description.
Accordingly, it is intended to embrace all such alternatives, ~odifications, and variations which fall within the spirit and scope of the appended claims.
Claims (13)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An improved heat insulated piston assembly for an internal combustion engine wherein the improvement comprises:
a) a piston formed of a sleeve and a heat insulated core, said core having a first end positioned flush with one end of said sleeve and a second end containing a concave configured cavity;
b) a connecting rod having a spherical ball shaped end matable in said concave configured cavity of said piston; and c) retaining means for securing said spherical ball shaped end of said connecting rod in said concave configured cavity of said piston.
a) a piston formed of a sleeve and a heat insulated core, said core having a first end positioned flush with one end of said sleeve and a second end containing a concave configured cavity;
b) a connecting rod having a spherical ball shaped end matable in said concave configured cavity of said piston; and c) retaining means for securing said spherical ball shaped end of said connecting rod in said concave configured cavity of said piston.
2. The improved heat insulated piston assembly of claim 1 wherein said core has an interference fit in said sleeve.
3. The improved heat insulated piston assembly of claim 2 wherein said interference fit is approximately 80 to 100 percent of the yield strength of said sleeve.
4. The improved heat insulated piston assembly of claim 2 wherein said core is pre-stressed by said interference fit to have an axisymmetric stress state about the central axis of said sleeve.
5. The improved heat insulated piston assembly of claim 1 wherein said core is a high density ceramic.
6. An improved heat insulated piston assembly for an internal combustion engine wherein the improvement comprises:
a) a piston formed of a cylindrical elongated sleeve having at least one circular groove formed in the outer circum-ference thereof and threads formed on a portion of the inner circumference, and a heat insulated core fitted to said sleeve having a first end positioned approximately flush with one end of said sleeve and having a second end containing a hemi-spherical shaped cavity;
b) a connecting rod having a spherical ball shaped end matable in said hemi-spherical shaped cavity, said spherical ball shaped end having a slightly smaller diameter than the diameter of said hemi-spherical shaped cavity; and c) a retaining ring having a threaded outer circumference engageable with said threads formed in said sleeve and having an arcuately shaped inner circumferential surface matable with the outer peripheral surface of said spherical ball shaped end of said connecting rod for securing said connecting rod to said piston.
a) a piston formed of a cylindrical elongated sleeve having at least one circular groove formed in the outer circum-ference thereof and threads formed on a portion of the inner circumference, and a heat insulated core fitted to said sleeve having a first end positioned approximately flush with one end of said sleeve and having a second end containing a hemi-spherical shaped cavity;
b) a connecting rod having a spherical ball shaped end matable in said hemi-spherical shaped cavity, said spherical ball shaped end having a slightly smaller diameter than the diameter of said hemi-spherical shaped cavity; and c) a retaining ring having a threaded outer circumference engageable with said threads formed in said sleeve and having an arcuately shaped inner circumferential surface matable with the outer peripheral surface of said spherical ball shaped end of said connecting rod for securing said connecting rod to said piston.
7. The improved heat insulated piston assembly of claim 6 wherein said heat insulated core is a high density ceramic.
8. The improved heat insulated piston assembly of claim 6 wherein said core has an interference fit in said sleeve.
9. The improved heat insulated piston assembly of claim 8 wherein said core is pre-stressed by said interference fit to have an axisymmetric stress state about the longitudinal axis of said sleeve.
10. A method of assembling an improved heat insulated piston and attaching the same to a connecting rod having a spheri-cal ball shaped end, said piston including a sleeve surrounding a heat insulated core having a hemi-spherically shaped cavity formed in one end thereof, said method comprising:
a) placing said core on a flat surface in an inverted position with said hemi-spherically shaped cavity facing upward;
b) thermally expanding said sleeve by heating it to approximately 60 percent of the melting point of the sleeve material;
c) placing said thermally expanded sleeve in an inverted position around said core such that one end of said sleeve is flush with the end of said core on the flat surface;
d) cooling said sleeve to room temperature to form an interference fit with said core thereby forming a heat insulated piston;
e) placing said retaining ring around said connecting rod adjacent to said spherical ball shaped end;
f) positioning said heat insulated piston on said spheri-cal ball shaped end of said connecting rod; and g) attaching said retaining ring to said sleeve to form an assembly between said piston and said connecting rod;
a) placing said core on a flat surface in an inverted position with said hemi-spherically shaped cavity facing upward;
b) thermally expanding said sleeve by heating it to approximately 60 percent of the melting point of the sleeve material;
c) placing said thermally expanded sleeve in an inverted position around said core such that one end of said sleeve is flush with the end of said core on the flat surface;
d) cooling said sleeve to room temperature to form an interference fit with said core thereby forming a heat insulated piston;
e) placing said retaining ring around said connecting rod adjacent to said spherical ball shaped end;
f) positioning said heat insulated piston on said spheri-cal ball shaped end of said connecting rod; and g) attaching said retaining ring to said sleeve to form an assembly between said piston and said connecting rod;
11. The method of claim 10 wherein the interference fit is approximately 80 to 100 percent of the yield strength of said sleeve.
12. The method of claim 11 wherein the interference fit is approximately 95 percent of the yield strength of said sleeve.
13. A method of assembling an improved heat insulated piston and attaching the same to a connecting rod having a spherical ball shaped end, said assembly including: a cylindrical elongated sleeve with at least one circular groove formed adja-cent a first end in its outer circumference and having threads formed on a portion of its inner circumference approximate a second end, a heat insulated core containing a hemi-spherically shaped cavity formed therein, and a retaining ring having a threaded outer circumference and an arcuately shaped inner cir-cumferential surface, said method comprising:
a) placing said core on a flat surface in an inverted position with said hemi-spherically shaped cavity facing upward;
b) thermally expanding said sleeve by heating it to ap-proximately 60 percent of the melting point of the sleeve materi-al;
c) placing said thermally expanded sleeve in an inverted position around said core such that one end of said sleeve is flush with the end of said core on the flat surface;
d) allowing said sleeve to cool down to room temperature to form an interference fit with said core, whereby said inter-ference fit is approximately 80 percent of the yield strength of said sleeve;
e) placing said retaining ring around said connecting rod such that said arcuately shaped inner circumferential surface contacts said spherical ball shaped end of said connecting rod;
f) positioning said hemi-spherically shaped cavity of said core on said spherical ball shaped end of said connecting rod;
and g) threading said retaining ring into said threaded por-tion of said sleeve for securing said spherical ball shaped end of said connecting rod to said cavity formed in said core.
a) placing said core on a flat surface in an inverted position with said hemi-spherically shaped cavity facing upward;
b) thermally expanding said sleeve by heating it to ap-proximately 60 percent of the melting point of the sleeve materi-al;
c) placing said thermally expanded sleeve in an inverted position around said core such that one end of said sleeve is flush with the end of said core on the flat surface;
d) allowing said sleeve to cool down to room temperature to form an interference fit with said core, whereby said inter-ference fit is approximately 80 percent of the yield strength of said sleeve;
e) placing said retaining ring around said connecting rod such that said arcuately shaped inner circumferential surface contacts said spherical ball shaped end of said connecting rod;
f) positioning said hemi-spherically shaped cavity of said core on said spherical ball shaped end of said connecting rod;
and g) threading said retaining ring into said threaded por-tion of said sleeve for securing said spherical ball shaped end of said connecting rod to said cavity formed in said core.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/280,403 US4459900A (en) | 1981-07-06 | 1981-07-06 | Heat insulated piston assembly and method of assembling |
| US280,403 | 1988-12-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1180616A true CA1180616A (en) | 1985-01-08 |
Family
ID=23072936
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000405033A Expired CA1180616A (en) | 1981-07-06 | 1982-06-11 | Heat insulated piston assembly and method of assembling |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US4459900A (en) |
| EP (1) | EP0069579B1 (en) |
| JP (1) | JPS5825553A (en) |
| AT (1) | ATE10022T1 (en) |
| BR (1) | BR8203873A (en) |
| CA (1) | CA1180616A (en) |
| DE (2) | DE69579T1 (en) |
| ES (1) | ES513709A0 (en) |
| MX (1) | MX154639A (en) |
| ZA (1) | ZA824774B (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60206960A (en) * | 1984-03-31 | 1985-10-18 | Honda Motor Co Ltd | Piston for internal-combustion engine |
| GB2180321A (en) * | 1985-09-09 | 1987-03-25 | Ford Motor Co | Reciprocating piston assembly |
| US4777844A (en) * | 1986-12-23 | 1988-10-18 | Ford Motor Company | Hybrid ceramic/metal compression link for use in higher temperature applications |
| DE4016723A1 (en) * | 1990-05-24 | 1991-11-28 | Kolbenschmidt Ag | PISTON CONNECTING ROD ARRANGEMENT |
| DE4100854A1 (en) * | 1991-01-14 | 1992-07-23 | Seajet Motor Gmbh | Ceramic piston for piston cylinder unit - has expansion and tension rings holding top and tail of piston together even at high temperatures |
| US5247873A (en) * | 1992-01-28 | 1993-09-28 | Cooper Industries, Inc. | Connecting rod assembly with a crosshead |
| AU4427893A (en) * | 1992-08-25 | 1994-03-03 | Ball Corporation | Apparatus for forming container bodies which utilizes a reinforced composite ram |
| GB9301488D0 (en) * | 1993-01-26 | 1993-03-17 | Metal Box Plc | Ram for long stroke press |
| DE19502926A1 (en) * | 1995-01-31 | 1996-08-01 | Teves Gmbh Alfred | Injection moulded plastic piston for dispenser cylinder |
| GB2346195B (en) * | 1999-01-29 | 2001-01-03 | Aet | Improvements to piston & connecting rod assemblies |
| GB9908844D0 (en) | 1999-04-19 | 1999-06-16 | Seneca Tech Ltd | Piston-connecting rod retention |
| US6311761B1 (en) * | 1999-12-22 | 2001-11-06 | Ronald G. Steininger | Plunger tip for die casting apparatus |
| DE10307908B4 (en) * | 2003-02-19 | 2005-03-03 | Andreas Mozzi | Multi-part piston |
| US20070295299A1 (en) * | 2006-06-12 | 2007-12-27 | Mahle Technology, Inc. | Piston for a combustion engine |
| US20140254965A1 (en) * | 2013-03-06 | 2014-09-11 | Roller Bearing Company Of America, Inc. | Linkage apparatus having a low profile asymmetrical head |
| CN105351106A (en) * | 2015-12-11 | 2016-02-24 | 中国北方发动机研究所(天津) | Novel split-type piston structure |
| CN113458735B (en) * | 2021-07-27 | 2022-08-23 | 绍兴熔岩机械有限公司 | Method for manufacturing pull rod ball head for automobile |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1790664A (en) * | 1931-02-03 | Whstthbop | ||
| US1490849A (en) * | 1922-11-20 | 1924-04-15 | Charles W Philip | Method of making pistons |
| DE667004C (en) * | 1935-09-10 | 1938-11-02 | Cyril Haigh Brooks | Two-metal pistons for internal combustion engines |
| US2296469A (en) * | 1939-01-10 | 1942-09-22 | Paul S Mantonya | Trunk piston |
| US3287039A (en) * | 1962-03-26 | 1966-11-22 | Borg Warner | Piston and piston rod assembly |
| US3408995A (en) * | 1967-05-22 | 1968-11-05 | Thomas A. Johnson | Combustion chamber design and material for internal combustion cylinders and engines |
| US3911891A (en) * | 1973-08-13 | 1975-10-14 | Robert D Dowell | Coating for metal surfaces and method for application |
| US4018194A (en) * | 1975-01-06 | 1977-04-19 | Texaco Inc. | Engine piston with insulated combustion chamber |
| GB1509461A (en) * | 1975-10-08 | 1978-05-04 | Wellworthy Ltd | Pistons |
| US4372179A (en) * | 1978-01-25 | 1983-02-08 | Steyr-Daimler-Puch Aktiengesellschaft | Reciprocating-piston drive mechanism |
| US4245611A (en) * | 1978-09-05 | 1981-01-20 | General Motors Corporation | Ceramic insulated engine pistons |
-
1981
- 1981-07-06 US US06/280,403 patent/US4459900A/en not_active Expired - Fee Related
-
1982
- 1982-06-11 CA CA000405033A patent/CA1180616A/en not_active Expired
- 1982-06-29 MX MX193344A patent/MX154639A/en unknown
- 1982-07-01 BR BR8203873A patent/BR8203873A/en unknown
- 1982-07-05 DE DE198282303525T patent/DE69579T1/en active Pending
- 1982-07-05 ES ES513709A patent/ES513709A0/en active Granted
- 1982-07-05 DE DE8282303525T patent/DE3261060D1/en not_active Expired
- 1982-07-05 ZA ZA824774A patent/ZA824774B/en unknown
- 1982-07-05 EP EP82303525A patent/EP0069579B1/en not_active Expired
- 1982-07-05 AT AT82303525T patent/ATE10022T1/en not_active IP Right Cessation
- 1982-07-06 JP JP57117627A patent/JPS5825553A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ZA824774B (en) | 1984-02-29 |
| BR8203873A (en) | 1983-06-28 |
| EP0069579B1 (en) | 1984-10-24 |
| MX154639A (en) | 1987-10-30 |
| ATE10022T1 (en) | 1984-11-15 |
| US4459900A (en) | 1984-07-17 |
| DE69579T1 (en) | 1983-07-21 |
| ES8307992A1 (en) | 1983-07-01 |
| EP0069579A1 (en) | 1983-01-12 |
| JPS5825553A (en) | 1983-02-15 |
| ES513709A0 (en) | 1983-07-01 |
| DE3261060D1 (en) | 1984-11-29 |
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