EP1264979B1 - Piston unit for combustion engine - Google Patents

Piston unit for combustion engine Download PDF

Info

Publication number
EP1264979B1
EP1264979B1 EP02253880A EP02253880A EP1264979B1 EP 1264979 B1 EP1264979 B1 EP 1264979B1 EP 02253880 A EP02253880 A EP 02253880A EP 02253880 A EP02253880 A EP 02253880A EP 1264979 B1 EP1264979 B1 EP 1264979B1
Authority
EP
European Patent Office
Prior art keywords
piston
upper section
skirt
piston assembly
sealing arrangement
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 - Lifetime
Application number
EP02253880A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP1264979A2 (en
EP1264979A3 (en
Inventor
Hannu Nurmi
Carl-Erik Rösgren
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wartsila Finland Oy
Original Assignee
Wartsila Finland Oy
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 Wartsila Finland Oy filed Critical Wartsila Finland Oy
Publication of EP1264979A2 publication Critical patent/EP1264979A2/en
Publication of EP1264979A3 publication Critical patent/EP1264979A3/en
Application granted granted Critical
Publication of EP1264979B1 publication Critical patent/EP1264979B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • F02F3/00—Pistons 
    • F02F3/0015—Multi-part pistons
    • 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
    • F05C2251/00—Material properties
    • F05C2251/04—Thermal properties
    • F05C2251/042—Expansivity

Definitions

  • This invention relates to a piston assembly for a combustion engine in accordance with the preamble of claim 1.
  • Piston assemblies according to the preamble of claim 1 are disclosed in US-A-441925 and US-A-4887518.
  • a piston of a combustion engine to have a number of separate sections, for instance the upper section may be a separate part connected, for example, by screws to the piston body.
  • the known constructions are typically such that the piston rings, or at least the oil rings, are located above such joints, i.e. in the upper section of the piston.
  • An object of the present invention is to provide a new piston assembly for an internal combustion engine, where the problems according to the prior art are minimised.
  • a particular object of the invention is to provide a so-called hot combustion piston assembly having piston rings located below the upper section of the piston, and where the upper section and the rest of the piston are engaged with one another tightly and firmly.
  • a so-called hot combustion piston refers to a piston in which the surface abutting onto the combustion chamber is made of a material having a reduced heat conductivity.
  • the sealing arrangement is at least partly based on the influence of the difference between the mounting and working temperatures of the upper section and the piston skirt, preferably on the different thermal expansion properties of the upper section and the piston skirt.
  • the performance can be enhanced by selecting the materials of the upper section and the piston skirt so that their thermal expansion properties differ from one another, whereby the sealing arrangement comprises counter surfaces provided in the upper section and the piston skirt, which surfaces are arranged with respect to each other so that their mutual distance is minimised at the working temperature of the surfaces.
  • the invention relates especially to a piston assembly in which grooves of the piston rings have such a location that the joining point of the upper section and the skirt has to operate under compression pressure when the piston assembly is in operation.
  • the sealing arrangement between the upper section and the skirt of the piston conveniently comprises several surface sections, the surfaces of the upper section and the skirt being substantially parallel, whereby at mounting temperature the surfaces are spaced at a first distance from each other, and the direction of the normal of which surface sections is at the surface section approximately parallel with the main thermal expansion direction, whereby at working temperature the surfaces are spaced at a second distance from one another, and the second distance is shorter than the first distance.
  • the second distance is substantially such that the surfaces are attached to one another.
  • the sealing arrangement is preferably provided so that it consists of alternating grooves and protrusions in the upper section and the skirt forming the counter surfaces in such a way that the protrusion of one counter surface is always facing the groove of the other counter surface.
  • the counter surfaces form a screw thread in the direction of the longitudinal axis of the piston.
  • the counter surfaces form a trapezoidal thread in the direction of the longitudinal axis of the piston.
  • the counter surfaces can also comprise a sealing surface deviating from the direction of the longitudinal axis of the piston.
  • the sealing arrangement according to the invention suitably comprises several counter surfaces operationally in succession and arranged in relation to each other so that their mutual distance is reduced at the working temperature of the surfaces and that a pressure balancing chamber is formed between two successive, tightly arranged counter surface pairs.
  • the skirt section of the piston is made of such material that its thermal expansion coefficient is from 10 x 10 -6 /K to 13 x 10 -6 /K and the thermal expansion coefficient of the upper section material is typically from 13 x 10 -6 /K to 17 x 10 -6 /K.
  • the reference number 1 generally designates a piston assembly for an internal combustion engine comprising an upper section 2 abutting onto the combustion chamber of the combustion engine cylinder and a piston skirt 3 in connection with the upper section.
  • Fig. 1 is greatly simplified and in practice the piston assembly comprises several kinds of additional arrangements which are not shown herewith.
  • the piston assembly 1 comprises grooves 4 for piston rings.
  • the grooves 4 of the piston rings have such a location that the joining point of the upper section 2 and the skirt 3 has to operate under working pressure when the piston assembly is in operation. This is due to the fact that the material of the upper section is typically such that the piston rings cannot be provided therein.
  • the mating surfaces between the upper section 2 and the skirt 3 of the piston assembly comprises sealing arrangements 1.2, 1.3, which will be described below.
  • the sealing arrangement comprises both an arrangement parallel with the longitudinal axis of the piston and an arrangement deviating from the longitudinal axis.
  • the sealing arrangements 1.2, 1.3 are provided by utilising the influence of the difference between the mounting and working temperatures of the piston assembly.
  • An advantageous sealing effect can be achieved by selecting the upper section and skirt materials so that by any structure of the sealing arrangements 1.2, 1.3, respectively, the reaching of the working temperature makes the counter surfaces included in the sealing arrangement between the upper section 2 and the skirt 3 move with respect to one another, due to different thermal expansion, so that sufficient tightness is achieved or the tightness is considerably improved.
  • the sealing effect can be achieved or it can be improved also by considering the fact that the upper section 2 of the piston is, in operating conditions, at a higher temperature than the rest of the piston assembly.
  • Fig. 2 shows in more detail the sealing arrangement 1.2 adapted to the cylindrical mating surface and which is generally parallel with the longitudinal axis of the piston.
  • the counter surfaces comprise several grooves and protrusions 5 so that the protrusion of one surface is always facing the groove of the other surface.
  • the sealing arrangement 1.2 between the upper section 2 and the skirt 3 of the piston comprises several surface sections 2a, 3b, 2b, 3a, where the surfaces of the upper section and the skirt are substantially parallel.
  • This kind of a mating surface is preferably arranged to form a screw thread in the direction of the longitudinal axis of the piston assembly.
  • the thread is preferably a trapezoid type of thread where the thread top is substantially planar.
  • the grooves on the counter surfaces are preferably somewhat larger than the protrusions, whereby the sealing arrangement includes successive pressure balancing chambers between the surfaces 2b - 3a located between the tight surface contacts 2a - 3b.
  • the sealing arrangement according to the invention comprises several operationally successive surface sections 2a - 3b in each other's immediate vicinity as well as pressure balancing chambers between two such surface sections. Operational successiveness refers to the fact that as a certain pressure difference prevails over the sealing arrangement, the gases tend to flow along a particular flow path towards the low pressure.
  • Fig. 3 shows in more detail the sealing arrangement 1.3 provided in the piston assembly in the direction substantially normal or perpendicular to its longitudinal axis.
  • the grooves and protrusions are concentric with each other.
  • the grooves of the counter surfaces are preferably somewhat larger than the protrusions, whereby successive chambers 2b - 3a located between the tight surface contacts 2a - 3b are provided in the sealing arrangement, while the surface sections move with respect to one another as a result of changes and/or differences of temperature.
  • Figs. 4 and 5 show the influence of the thermal expansion differences of the materials and changes of temperature in the sealing arrangement according to the invention.
  • Fig. 4 shows a sealing surface according to the invention at mounting temperature.
  • the construction and the material of the sections 2, 3 are such that a desired clearance 6 is provided on the sealing surface between such counter surfaces 2b, 3a that, depending on the application, will approach one another in operation. This situation is shown in Fig. 5.
  • the sections 2 and 3 move with respect to each other due to the change in temperature, typically the raising thereof, so that the surface 2b approaches the surface 3a, whereby the clearance 6 is reduced to clearance 6a. Simultaneously, the surface 2a draws away from the surface 3b and the clearance 6b increases.
  • Fig. 4 the surfaces 2b, 3a are spaced at a first distance 6 from one another in mounting conditions.
  • the direction of the normal of these surfaces is approximately parallel with the primary thermal expansion direction at the surface, whereby in operating conditions the surfaces 2b, 3a are spaced at a significantly shorter distance 5.5 from one another.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)
  • Apparatus For Radiation Diagnosis (AREA)
  • Lubrication Of Internal Combustion Engines (AREA)
EP02253880A 2001-06-04 2002-05-31 Piston unit for combustion engine Expired - Lifetime EP1264979B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20011165A FI113683B (sv) 2001-06-04 2001-06-04 Kolvenhet vid en förbränningsmotor
FI20011165 2001-06-04

Publications (3)

Publication Number Publication Date
EP1264979A2 EP1264979A2 (en) 2002-12-11
EP1264979A3 EP1264979A3 (en) 2003-07-30
EP1264979B1 true EP1264979B1 (en) 2007-02-28

Family

ID=8561331

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02253880A Expired - Lifetime EP1264979B1 (en) 2001-06-04 2002-05-31 Piston unit for combustion engine

Country Status (4)

Country Link
EP (1) EP1264979B1 (sv)
AT (1) ATE355450T1 (sv)
DE (1) DE60218382T2 (sv)
FI (1) FI113683B (sv)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006015587A1 (de) 2006-04-04 2007-10-11 Mahle International Gmbh Oberteil eines gebauten Kolbens

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4419925A (en) * 1978-06-15 1983-12-13 Toyota Jidosha Kogyo Kabushiki Kaisha Assembled piston for engine
US4253430A (en) 1979-01-11 1981-03-03 General Motors Corporation Insulated oil cooled piston assembly
DE3110292A1 (de) 1981-03-17 1982-09-30 Rudolf Dr. 6800 Mannheim Wieser "kolben fuer verbrennungsmotor"
JPS61135961A (ja) * 1984-12-05 1986-06-23 Ngk Insulators Ltd セラミツクス製ピストンヘツド付きピストン
US5499572A (en) * 1993-08-26 1996-03-19 Cobble; Daniel L. Bi-tech piston

Also Published As

Publication number Publication date
FI20011165A (sv) 2002-12-05
EP1264979A2 (en) 2002-12-11
DE60218382D1 (de) 2007-04-12
DE60218382T2 (de) 2007-11-22
ATE355450T1 (de) 2006-03-15
FI113683B (sv) 2004-05-31
EP1264979A3 (en) 2003-07-30
FI20011165A0 (sv) 2001-06-04

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