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Dokumentenidentifikation EP0193591 09.02.1989
EP-Veröffentlichungsnummer 0193591
Titel VERBESSERUNGEN AN KOLBEN.
Anmelder AE PLC, Rugby, Warwickshire, GB
Erfinder MUNRO, Robert, Lymington Hampshire SO4 9GP, GB;
SPEAIGHT, Clement, David, Lymington Hampshire SO4 9HL, GB
Vertreter Grünecker, A., Dipl.-Ing.; Kinkeldey, H., Dipl.-Ing. Dr.-Ing.; Stockmair, W., Dipl.-Ing. Dr.-Ing. Ae.E. Cal Tech; Schumann, K., Dipl.-Phys. Dr.rer.nat.; Jakob, P., Dipl.-Ing.; Bezold, G., Dipl.-Chem. Dr.rer.nat.; Meister, W., Dipl.-Ing.; Hilgers, H., Dipl.-Ing.; Meyer-Plath, H., Dipl.-Ing. Dr.-Ing., Pat.-Anwälte, 8000 München; Kinkeldey, U., Dipl.-Biol. Dr.rer.nat., Pat.-Ass., 8021 Icking; Bott-Bodenhausen, M., Dipl.-Phys. Dr.rer.nat.; Ehnold, A., Dipl.-Ing.; Schuster, T., Dipl.-Phys., Pat.-Anwälte, 8000 München
DE-Aktenzeichen 3567244
Vertragsstaaten DE, FR, IT, NL, SE
Sprache des Dokument En
EP-Anmeldetag 12.09.1985
EP-Aktenzeichen 859046534
WO-Anmeldetag 12.09.1985
PCT-Aktenzeichen GB8500416
WO-Veröffentlichungsnummer 8601858
WO-Veröffentlichungsdatum 27.03.1986
EP-Offenlegungsdatum 10.09.1986
EP date of grant 04.01.1989
Veröffentlichungstag im Patentblatt 09.02.1989
IPC-Hauptklasse F02F 3/00
IPC-Nebenklasse F16J 1/02   

Beschreibung[en]

The invention relates to a piston for an internal combustion engine comprising a crown, a piston axis, a ring band extending around the crown, gudgeon pin bosses supporting the crown and defining a gudgeon pin bore having an axis, and a skirt.

The purpose of the skirt is to transmit lateral thrust forces from the piston to an associted cylinder or liner. In many pistons, the skirt is formed by a generally cylindrical surface extending around the piston and depending from the ring band for lubricated contact with the associated cylinder or liner. Such a skirt has the disadvantage that the oil film between the skirt and the associated cylinder or liner is of substantial area and so the frictional forces generated by such film are also substantial. In addition, such a skirt is comparatively rigid and this requires the skirt to be a comparatively ioose fit in the associated cylinder or liner in order to accommodate changes in piston and cylinder shape due to temperature changes, since the rigidity of the skirt does not allow the skirt to flex to accommodate such changes. Such a loose fit increase the incidence of piston slap so increasing noise.

GB-A-720172 shows a piston in which the skirt is formed by two parts of arcuate skirt portions interconnected by a recessed zone and on opposite sides of the gudgeon pin bore. The pairs of skirt portions and their associated recessed zones are supported by struts. The upper arcuate skirt portions are spaced from the ring band by a gap. The struts provide radial yieldability to distribute the pressure on the cylinder wall throughout the bearing faces of the skirt portions.

EP-A-0154405 shows a piston in which lateral loads from an associated cylinder or liner are supported by bearing pads that are mounted for pivotal movement during reciprocation in the cylinder or liner in order to ensure by hydrodynamic lubrication over the bearing pads during such reciprocation.

US-A-2032849 shows a piston having a double-X-web skirt whose entire surface rides the cylinder wall and which in spite of its cut-out design has more surface contact with the cylinder than a conventional piston. The double-X-skirt is joined at the X-crossing points to pin bosses, which in turn are joined to the lower ends of struts which carry the piston head, the piston head being entirely separated from the skirt. The bosses retain more heat than the skirt and the expansion dissipates itself, at first vertically, then diagonally along the X-webs, and then horizontally to points at right angles to the piston pin. The piston skirt lengthens when its diametric expansion is limited by contact with the cylinder wall consequently reducing the wall pressure whilst at the same time ensuring that during the expansion of the skirt, its cylindrical form is not varied with the result that the pin bosses are not thrown out of alignment and caused to bind tightly upon the piston pin.

There have been various proposals for reducing the load transmitting skirt area, to reduce the frictional forces, but some of these proposals have not provided adequate lubrication of these reduced area. In addition, others of these proposals have not dealt with the problem of the rigidity of these skirt areas.

According to the present invention, there is provided a piston for an internal combustion engine of the kind comprising a crown, a piston axis, a ring band extending around the crown, gudgeon pin bosses supporting the crown and defining a gudgeon pin bore having an axis, and a skirt formed by two pairs of arcuate skirt portions on opposite sides of the gudgeon pin bore and supported by struts, each pair of arcuate skirt portions including upper and lower arcuate skirt portions disposed about a plane including the piston axis and normal to the gudgeon pin bore axis and extending only partially around the piston, the upper arcuate skirt portions being spaced from the ring band by an axially and circumferentially extending gap, said struts being formed by four struts extending from each gudgeon pin boss, two of each said four struts extending upwardly and outwardly of, and from opposite sides of, the associated gudgeon pin boss and being connected to respective upper arcuate skirt portions, the two remaining struts of each said struts extending downwardly and outwardly of, and from opposite sides of, the associated gudgeon pin boss and being connected to respective lower arcuate skirt portions, the lower arcuate skirt portions being spaced from associated upper arcuate skirt portions by an axially and circumferentially extending gap and the arcuate skirt portions being conformable to adapt to the cross-sectional shape of an associated cylinder or liner, each arcuate skirt portion having upper and lower edges each lying in a respective plane normal to the piston axis wherein each arcuate skirt portion has side edges interconnecting said upper and lower edges with said side edges lying in respective planes including the piston axis so that the gap between the ring band and each at least one upper arcuate skirt portion and the gap between each at least one upper arcuate skirt portion and the associated at least one lower arcuate skirt portion is of constant width in a direction parallel to the piston axis.

The following is a more detailed description of two embodiments of the invention, by way of example, reference being made to the accompanying drawings in which:

  • Figure 1 is a section through a first form of piston for an internal combustion engine,
  • Figure 2 is a section on the line II-II of Figure 1,
  • Figure 3 is a section of a second form of piston for an internal combustion engine, and
  • Figure 4 is a section oh the line IV-IV of Figure 3.

Both the piston of Figures 1 and 2 and the piston of Figures 3 and 4 are made by a casting process using either an iron or a steel material, aluminium or an aluminium alloy. They are pistons for Diesel engines.

Referring now to the piston of Figures 1 and 2, this piston comprises a crown 10 surrounded by a ring band 11 and having two gudgeon pin bosses 12a, 12b. The crown 10 is provided with a depression 13 which receives a precision cast steel combustion bowl 14 having on its undersurface projections 15 which space the bowl 14 from the depression 13 and so form an insulating air gap 16 therebetween. The combustion bowl 14 is a shrink-fit in the depression. The crown 10 also has an annular outer surface which is spray-coated with a suitable ceramic 17 to a depth of 2mm in order to provide a heat-resistant coating on the crown 10.

The ring band 11 depends from the crown 10 and is formed with a plurality of piston ring grooves 18. Webs 19 are provided between the crown 10 and the ring band 11 in order to provide a ring band with the required rigidity.

A support 20 extends upwardly from each gudgeon pin boss 12a, 12b and is connected to the undersurface of the depression 13 in order to support the crown 10 and the ring band 11 on the gudgeon pin bosses 12a, 12b. Each gudgeon pin boss 12a, 12b is also formed with four struts 21a, 21b, 21c, 21d. Two of these struts 21a, 21b extend upwardly and outwardly from the associated gudgeon pin boss 12a, 12b on opposite sides thereof (see Fig. 2). The other two struts 21c, 21d extend downwardly and outwardly from the associated boss 12a, 12b on opposite sides thereof (see also Fig. 2). Thus, on each side of the gudgeon pin bosses, there are, considering both bosses, a pair of upwardly and outwardly directed struts 21a or 21b and a pair of downwardly and outwardly directed struts 21a or 21c.

Each pair of struts 21 carries an associated arcuate skirt portion 22. Each arcuate skirt portion 22 has circumferentially extending upper and lower edges 23, 24 which lie in respective planes normal to the piston axis 26. These circumferential edges 23, 24 are interconnected by side edges 26 which lie in respective planes including a piston axis so that each arcuate skirt portion 22 is the shape of a segment of a cylinder. Each arcuate skirt portion 22 is symmetrically disposed about a plane including the piston axis and normal to the gudgeon pin bore axis (the plane of the section of Fig. 2) and is of limited arcuate extent. This extent may be between 70° and 110° but is preferably 80°.

There is thus an axially and circumferentially extending gap 25 both between the upper edges 23 of the upper arcuate skirt portions 22 and between the lower edges 24 of the upper arcuate skirt portions 22a and the upper edges of the lower arcuate skirt portions 22b. The axial width of each gap 25 is constant.

As shown in Figure 2, the axis 28 of the depression 13 and the combustion bowl 14 are symmetrical about an axis 28 which is offset from a vertical plane including the gudgeon pin bore axis 27. This is to provide a correct positioning of the combustion bowl 14 in relation to a fuel injector of the associated Diesel engine.

In use, the piston of Figures 1 and 2 reciprocates in a cylinder of an internal combustion engine, mounted on a connecting rod by a gudgeon pin extending through the gudgeon pin bosses 12a, 12b. The limited arcuate extent of the arcuate skirt portions 22 and their spaced support on the associated struts 21 allow the arcuate skirt portions 22 readily to adapt to the cross-sectional shape of an associated cylinder or liner. In addition, since the arcuate skirt portions 22 are connected to the gudgeon pin bosses 12a, 12b and are not connected directly to the crown 10, the temperature of these parts is much reduced in comparison with pistons where the skirt is connected directly to the crown.

The piston is light in weight because the traditional full cylindrical skirt is dispensed with. Due to its conformability, the piston can be fitted more closely within an associated cylinder or liner than conventional full-skirted pistons and this tends to reduce the noisiness of the engine. Although the arcuate skirt portions provide a reduced area of contact between the piston and the associated cylinder or liner, in comparison with a piston having a cylindrical skirt, it has been found that these arcuate skirt portions are adequately lubricated at all times and that there is no mixed or boundary lubrication. This is due partly to the provision of wide gaps 25 which allow oil, thrown-up from the sump of the associated engine, to pass onto the cylinder liner wall. In this regard, the circumferential edges of the arcuate skirt portions may, be provided with hydrodynamic ramps having a ramp angle of no more than 2°. These, in co-operation with the associated cylinder or liner, provide a hydrodynamic wedge action which foxes oil on the cylinder or liner over the bearing surfaces of the acruate skirt portions and thus ensures hydrodynamic lubrication under all conditions.

Referring next to Figures 3 and 4, parts common to Figures 1 and 2 and to Figures 3 and 4 will be given the same reference numerals and will not be described in detail. In this embodiment, the crown 10 is not insulated by any ceramic material and the combustion bowl 29 is formed directly in the crown surface. In use, this piston operates in substantially the same way as the piston of Figures 1 and 2.


Anspruch[de]
  1. Kolben für eine Brennkraftmaschine, enthaltend eine Krone (10), eine Kolbenachse (28), ein Ringband (11), das sich um die Krone erstreckt, Kolbenbolzenvorsprünge (12a, 12b), die die Krone abstützen und eine Kolbenbolzenbohrung definieren, die eine Achse aufweist, und einen Mantel, gebildet aus zwei Paaren bogenförmiger Mantelabschnitte (22) auf entgegengesetzten Seiten der Kolbenbolzenbohrung und abgestützt durch Streben (21a, 21b, 21c, 21d), wobei jedes Paar bogenförmiger Mantelabschnitte (22) obere und untere bogenförmige Mantelabschnitte (22) enthält, die um eine Ebene angeordnet sind, die die Kolbenachse enthält und senkrecht zur Kolbenbolzenbohrungsachse verläuft und sich nur teilweise um den Kolben erstreckt, wobei die oberen bogenförmigen Mantelabschnitte (22) von dem Ringband (11) durch einen sich axial und in Umfangsrichtung erstreckenden Spalt (25) getrennt sind, wobei die genannten Streben von vier Streben gebildet sind, die sich von jedem Kolbenbolzenvorsprung (12a, 12b) erstrecken, wobei sich zwei (21a, 21b) von jeder der vier Streben nach oben und außen von dem zugehörigen Kolbenbolzenvorsprung (12a, 12b) und von entgegengesetzten Seiten desselben erstrecken und mit entsprechenden oberen bogenförmigen Mantelabschnitten (22a) verbunden sind, die zwei übrigen Streben (21c, 21d) einer jeden der Streben sich nach unten und außen und von entgegengesetzten Seiten des zugehörigen Kolbenbolzenvorsprungs (12a, 12b) erstrecken und mit entsprechenden unteren bogenförmigen Mantelabschnitten (22b) verbunden sind, wobei die unteren bogenförmigen Mantelabschnitte (22b) von zugehörigen oberen bogenförmigen Mantelabschnitten (22a) durch einen sich axial und in Umfangsrichtung erstreckenden Spalt (25) getrennt sind und die bogenförmigen Mantelabschnitte anpaßbar sind, um sich der Querschnittsgestalt eines zugehörigen Zylinders oder einer Laufbüchse anzupassen, wobei jeder bogenförmige Mantelabschnitt obere und untere Ränder (23, 24) aufweist, jeweils in einer entsprechenden Ebene senkrecht zur Kolbenachse (28) liegend, wobei jeder bogenförmige Mantelabschnitt Seitenränder (26) aufweist, die die oberen und unteren Ränder verbinden, wobei die genannten Seitenränder in entsprechenden Ebenen liegen, die die Kolbenachse (28) einschließen, so daß der Spalt (25) zwischen dem Ringband (11) und jedem wenigstens einen oberen bogenförmigen Mantelabschnitt (22a) und der Spalt (25) zwischen jedem wenigstens einen oberen bogenförmigen Mantelabschnitt und dem zugehörigen wenigstens einen unteren bogenförmigen Mantelabschnitt von konstanter Breite in eine Richtung parallel zur Kolbenachse ist.
  2. Kolben nach Anspruch 1, dadurch gekennzeichnet, daß jeder bogenförmige Mantelabschnitt ein Winkelausmaß zwischen 70° und 110°, vorzugsweise von 80° hat.
  3. Kolben nach Anspruch 1 oder Anspruch 2, dadurch gekennzeichnet, daß die Krone (10) und das Ringband (11) von den Kolbenbolzenvorsprüngen (12a, 12b) durch wenigstens zwei Träger (20) abgestützt werden, die sich von den Kolbenbolzenvorsprüngen nach oben erstrecken.
  4. Kolben nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Krone eine Verbrennungsaushöhlung (14) enthält, die symmetrisch um eine Achse (27) ist, die gegenüber einer Vertikalebene versetzt ist, die die Kolbenbolzenbohrungsachse einschließt.
Anspruch[en]
  1. A piston for an internal combustion engine of the kind comprising a crown (10), a piston axis (28), a ring band (11) extending around the crown, gudgeon pin bosses (12a,12b) supporting the crown and defining a gudgeon pin bore having an axis, and a skirt formed by two pairs of arcuate skirt portions (22) on opposite sides of the gudgeon pin bore and supported by struts (21a,21b,21c, 21d), each pair of arcuate skirt portions (23) including upper and lower arcuate skirt portions (22) disposed about a plane including the piston axis and normal to the gudgeon pin bore axis and extending only partially around the piston, the upper arcuate skirt portions (22) being spaced from the ring band (11) by an axially and circumferentially extending gap (25), said struts being formed by four struts extending from each gudgeon pin boss (12a,12b), two (21a,21b) of each said four struts extending upwardly and outwardly of, and from opposite sides of, the associated gudgeon pin boss (12a,12b) and being connected to respective upper arcuate skirt portions (22a), the two remaining struts (21c,21d) of each said struts extending downwardly and outwardly of, and from opposite sides of, the associated gudgeon pin boss (12a,12b) and being connected to respective lower arcuate skirt portions (22b), the lower arcuate skirt portions (22b) being spaced from associated upper arcuate skirt portions (22a) by an axially and circumferentially extending gap (25) and the arcuate skirt portions being conformable to adapt to the cross-sectional shape of an associated cylinder or liner, each arcuate skirt portion having upper and lower edges (23,24) each lying in a respective plane normal to the piston axis (28) wherein each arcuate skirt portion has side edges (26) interconnecting said upper and lower edges with said side edges lying in respective planes including the piston axis (28) so that the gap (25) between the ring band (11) and each at least one upper arcuate skirt portion (22a) and the gap (25) between each at least one upper arcuate skirt portion and the associated at least one lower arcuate skirt portion is of constant width in a direction parallel to the piston axis.
  2. A piston according to claim 1, characterised in that each arcuate skirt portion has an angular extent of between 70° and 110°, preferably 80°.
  3. A piston according to claim 1 or claim 2, characterised in that the crown (10) and the ring band (11) are supported on the gudgeon pin bosses (12a,12b) by at least two supports (20) extending upwardly from the gudgeon pin bosses.
  4. A piston according to any one of claims 1 to 3, characterised in that the crown includes a combustion bowl (14) which is symmetrical about an axis (27) which is offset from a vertical plane including the gudgeon pin bore axis.
Anspruch[fr]
  1. Piston pour moteur à combustion interne, du type comprenant une tête (10), un axe (28) de ce piston, une bande annulaire (11) s'étendant autour de la tête, des bossages (12a, 12b) pour axe de piston, lesquels supportent la tête et définissent un alésage pour axe de piston, doté d'un axe, et une jupe formée par deux paires de parties-jupes arquées (22) situées sur des côtés opposés de l'alésage pour axe de piston et supportées par des entretoises (21a, 21b, 21c, 21d), chaque paire de parties-jupes arquées (23) incluant une partie-jupe supérieure et une partie-jupe inférieure arquées (22) disposées de part et d'autre d'un plan qui contient l'axe du piston et est normal à l'axe des bossages pour axe de piston, et ne s'étendant qu'en partie autour du piston, les parties-jupes arquées supérieures (22) étant séparées de la bande annulaire (11) par un intervalle (25) s'étendant axialement et circonférentiellement, lesdites entretoises étant formées par quatre entretoises s'étendant depuis chaque bossage pour axe de piston (12a, 12b), deux (21a, 21b) desdites quatre entretoises s'étendant vers le haut et vers l'extérieur, depuis des côtés opposés du bossage associé (12a, 12b) pour axe de piston, et étant liées à des parties-jupes arquées supérieures respectives (22a), les deux entretoises restantes (21c, 21d) s'étendant vers le bas et vers l'extérieur, depuis des côtés opposés du bossage associé (12a, 12b) pour axe de piston, et étant liées à des parties-jupes arquées inférieures respectives (22b), les parties-jupes arquées inférieures (22b) étant séparées des parties-jupes arquées supérieures associées (22a) par un intervalle (25) s'étendant axialement et circonférentiellement, et les parties-jupes arquées étant aptes à se conformer pour s'adapter à la forme de la section droite d'un cylindre ou alésage associé, chaque partie-jupe arquée possédant des bords supérieur et inférieur (23, 24) situés chacun dans un plan respectif normal à l'axe (28) du piston, dans lequel chaque partie-jupe arquée possède des bords latéraux (26) reliant lesdits bords supérieur et inférieur, lesdits bords latéraux se trouvant dans des plans respectifs contenant l'axe (28) du piston, de manière que l'intervalle (25) entre la bande annulaire (11) et chaque partie-jupe arquée supérieure (22a) et l'intervalle (25) entre chaque partie-jupe arquée supérieure et la partie-jupe arquée inférieure associée soient de largeur constante dans une direction parallèle à l'axe du piston.
  2. Piston selon la revendication 1, caractérisé en ce que chaque partie-jupe arquée possède une étendue angulaire comprise entre 70° et 110°, de préférence de 80°.
  3. Piston selon la revendication 1 ou la revendication 2, caractérisé en ce que la tête (10) et la bande annulaire (11) sont supportées sur les bossages (12a, 12b) pour axe de piston par au moins deux supports (20) s'étendant vers le haut, depuis les bossages pour axe de piston.
  4. Piston selon l'une quelconque des revendications 1 à 3, caractérisé en ce que la tête comporte une cuvette de combustion (14) qui est symétrique de part et d'autre d'un axe (27) qui est décalé par rapport à un plan vertical contenant l'axe de l'alésage pour axe de piston.






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