EP1913250B1 - Piston for an internal combustion engine and covering ring for the cooling duct of a piston of said type - Google Patents

Description

The present invention relates to a one-piece piston for an internal combustion engine, comprising a piston head and a piston recess spaced therefrom by an annular recess having at least one hub bore for receiving a piston pin, wherein in the piston head, an annular circumferential cooling channel is provided for a coolant which with a made of at least two segments covering ring is closed. The present invention further relates to a cover ring of two or more segments for the annular peripheral cooling passage of a one-piece piston for an internal combustion engine.

A generic piston and a generic cover are from the DE 103 46 822 A1 known. This piston has an annular cooling channel which is closed on the shank side by a cover ring consisting of two semicircular half shells. The cover ring is provided with an inwardly directed groove over which the half-shells can be slid on the outside of the piston for the purpose of mounting on a groove-shaped complementarily shaped projection. In addition, the half-shells in the region of their abutting surfaces latching connections, by means of which the half-shells are quickly connected to each other. The design of the cover with an additional groove or the piston with an additional projection but is expensive and therefore not desirable. In addition, the assembly is difficult, since the two half-shells must be placed specifically on the projections provided on the piston.

Other comparable pistons are from the DD 252 638 A1 and the DE 41 34 530 A1 in which a serving for covering the downwardly open annular cooling channel wall portion is formed as an open sheet metal ring. The sheet metal ring is biased in the radial direction in a groove on the inner circumference of the piston ring zone or on the outer circumference of the combustion chamber wall.

Finally, from the EP 0 561 817 B1 and the EP 0 799 373 B1 one-piece piston with a arranged in the edge region of the piston crown cooling channel, which is also closed with plate spring-like and possibly provided with a collar cover rings.

In all these embodiments, each segment of the plate spring-like cover ring must be individually introduced in the biased state in corresponding supports on the piston head.

The present invention is therefore based on the object to provide a generic piston or a generic cover ring, which contributes to a simplified piston construction and a reduced piston weight.

The solution consists in a piston with the features of claim 1. According to the invention, at least a portion of a cover for the piston at least partially protrudes into the clear opening of the at least one hub bore, such that the cover or at least a portion of the cover at the same time forms the securing element for the piston pin.

The principle of the invention thus consists in that the cover acts as a securing element which limits the axial movement of the piston pin in the hub bore. In the prior art this task is taken over by snap rings or Seeger rings. These rings are used in Bolzensicherungsnuten in the bolt hub. The inventive design of the piston or the Cover ring now allows to dispense with these snap rings or Seeger rings. Thus, the present invention contributes to the reduction of the weight of the piston. The present invention also makes it possible to dispense with the introduction of the bolt securing grooves, whereby the piston construction is simplified.

Advantageous developments emerge from the subclaims.

A particularly preferred embodiment provides that the cover ring has an inner leg and an outer leg, which are interconnected by a bottom web. This embodiment of the cover opens up a variety of ways to cover the cooling channel and / or the annular recess. For example. the inner leg can protrude into the clear opening of the at least one hub bore and in this way form the securing element for the piston pin provided according to the invention on the cover ring. Further, the outer leg may form the piston stem side boundary of the annular recess. The cover ring is preferably formed in cross-section approximately U-shaped or approximately V-shaped. The design of the two legs and the bottom web connecting them can also be made in any other way (trapezoidal, semi-circular, etc.).

Another particularly preferred development consists in that the annular recess is arranged between an end face formed on the annular wall of the piston and at least one shoulder formed on the piston shaft and that the cover ring with its outer leg on the end face and with its bottom web on the at least one Shoulder supported. This development has many other advantages over the prior art. In particular, both the previously necessary in the shank connection projection and the complementary groove in the inner wall of the cover omitted. Thus, the construction of both the piston and the cover ring is further simplified. But above all, the mounting of the cover ring on the piston is much easier than before, since the complex positioning of projection and groove each other is omitted. In addition, the cover now encloses both the previous cooling channel and the annular recess, with the result that the previous cooling channel and the annular recess now form a new, enlarged cooling channel. Thus, the cooling of the piston according to the invention is easier and safer. Finally, the outer leg of the cover ring together with the annular wall and the piston skirt forms a nearly continuous, smooth surface, which improves the running properties of the piston according to the invention.

When the inner leg of the cover ring is supported on the shaft connection of the piston, the cover ring sits particularly firmly and securely in place. In addition, the sealing of the now acting as a cooling channel annular recess is improved to the outside.

For the purpose of controlling the flow characteristics, in particular the flow rate, of the coolant, the configuration of the inner leg of the cover ring may also vary. For example. For example, the height of the inner leg or the angular position of the inner leg relative to the center axis of the cover ring may vary over the circumference of the cover ring. In particular, the flow channel for the coolant formed by the cover ring can be inclined from the inlet opening to the outlet opening.

Fig. 1

eine Schnittdarstellung einer Ausführungsform des erfindungsgemäßen Kolbens;

Fig. 2

der Kolben aus Figur 1 um 90° gedreht, mit strichpunktiert angedeutetem Kolbenbolzen;

Fig. 3

eine perspektivische Draufsicht auf eine Ausführungsform eines erfindungsgemäßen Abdeckrings;

Fig. 4

eine perspektivische Ansicht des Kolbens gemäß Figur 1.

An embodiment of the invention will be explained in more detail below with reference to the accompanying drawings. In a schematic, not to scale representation:

Fig. 1

a sectional view of an embodiment of the piston according to the invention;

Fig. 2

the piston off FIG. 1 rotated by 90 °, with dash-dot indicated piston pin;

Fig. 3

a top perspective view of an embodiment of a cover ring according to the invention;

Fig. 4

a perspective view of the piston according to FIG. 1 ,

The FIGS. 1 . 2 and 4 show a one-piece piston 10 for an internal combustion engine. The piston 10 is made of steel and has a piston head 11 and a piston shaft 12, which are integrally connected to one another via a shaft connection 13. The piston head 11 and has a piston head 14 and a combustion bowl 15. In the radially outer region of the piston head 11, an annular circumferential cooling channel 16 is arranged, whose radially outer boundary is formed by an integrally formed on the piston head 14 ring wall 17 and its radially inner boundary of an annular rib 18. The annular wall 17 serves as a piston ring carrier and closes off with a horizontal, the piston shaft 12 facing end surface 19th

To the piston head 11 are two pin bosses 20, 20 'with two aligned hub bores 21, 21' integrally formed. The end faces of the pin bosses 20, 20 'are set back relative to the annular wall 17 in the direction of the piston longitudinal axis. The pin bosses 20, 20 'are connected to each other via shaft elements 22, 22'. The shaft elements 22, 22 'are integrally formed on the piston head 11 via the shaft connection 13.

The shaft connection 13 is set back in the direction of the piston longitudinal axis and merges into the annular rib 18. As a result, an annular recess 25 is formed which is bounded on one side by the shaft connection 13 and on the other hand by the piston head 11 facing horizontal shoulders 24, 24 ', the shoulders 24, 24' forming the upper boundary of the shaft elements 22, 22 '.

A cover ring 30 with an outer leg 31, an inner leg 32 and a two leg connecting bottom web 33 is between the annular wall 17th and the shaft members 22, 22 'fitted. Here, the upper edge of the outer leg 31 is supported on the end face 19 of the annular wall 17, and the bottom web 33 is supported on the shoulders 24, 24 'of the shaft elements 22, 22' from. The inner leg 32 is supported on the shaft connection 13. In this way, the annular recess 25 is closed and sealed to the outside. The annular circumferential cooling channel 16 and the annular recess 25 now form a new, substantially enlarged cooling channel. In the area of the pin bosses 20, 20 ', which are set back relative to the annular wall 17 and therefore have no shoulders 24, 24' comparable support surfaces, the inner leg 32 of the cover 30 projects into the clear opening of the hub holes 21, 21 'into (see , FIG. 4 ). The inner leg 32 of the cover ring 30 forms a securing element in these areas against the axial movement of the received in the hub bores 21, 21 'piston pin 23, in FIG. 2 indicated by dash-dotted lines. The hitherto necessary security elements in the form of snap rings or Seeger rings are therefore unnecessary. Therefore, the pin bosses 20, 20 'no longer have bolt locking grooves, as in FIGS FIGS. 1 and 2 also clearly visible.

An embodiment of a cover ring 30 according to the invention is shown in FIG FIG. 3 shown. The cover ring 30 can be made of a metallic material such as. Steel or aluminum or a suitable alloy, for example, cast or forged. The cover ring 30 may also be made of a heat-resistant plastic, for example. In injection molding. The cover ring 30 has an outer leg 31, an inner leg 32 and a bottom web 33 connecting both legs. In the exemplary embodiment, the cover ring 30 is approximately U-shaped in cross section; but it can also have other suitable cross-sections. The cover ring 30 is formed in two parts in the embodiment. The two ring segments 30a and 30b are riveted in the embodiment by means of tabs 34. However, the ring segments 30a and 30b can also be connected to each other in any other way, for example by latching, locking, clipping, gluing, welding, soldering, etc.

The cover ring 30 further comprises an inlet opening 35 and a discharge opening 36 diametrically opposite outlet opening 36 for a coolant. In the exemplary embodiment, the inlet opening 35 and the outlet opening 36 are formed in the joint regions of the ring segments 30a and 30b. Accordingly, the lying outside the joint areas 32a and 32b of the inner leg 32, the securing elements for the piston pin 23. The inner leg 32 in the embodiment expediently has a varying in its annular profile height, serving as securing elements areas 32a, 32b highest are formed. In contrast, the height of the outer leg 31 is constant, because this is supported in the installed state of the cover 30 on the end face 19 of the annular wall 17.

The bottom web 33 of the cover ring 30 is formed in the exemplary embodiment so that it has an inclination starting from the inlet opening 35 to the outlet opening 36. As a result, in particular the flow speed of the coolant to the outlet opening 35 is increased, so that a harmful coolant accumulation is avoided. Also, the varying height of the inner leg 32 affects the flow characteristics of the coolant, so that they can be adjusted specifically.

Claims (10)

1. Single-part piston (10) for an internal combustion engine, with a piston head (11) and a piston shaft (12) which is spaced apart from the latter by an annular recess (25) and comprises at least one hub bore (21, 21') for mounting a piston pin (23), wherein an annular cooling duct (16) for a coolant is provided in the piston head (11), which cooling duct (16) is closed off by a cover ring (30) consisting of at least two segments (30a, 30b), characterised in that at least one section of the cover ring (30) projects at least partly into the clear opening of the at least one hub bore (21, 21') in such a way that the cover ring (30) simultaneously forms the locking element for the piston pin (23).
2. Piston according to claim 1, characterised in that the cover ring (30) comprises an inner leg (32) and an outer leg (31), which are joined together by a base web (33).
3. Piston according to claim 2, characterised in that the cover ring (30) is approximately U-shaped or V-shaped in cross section.
4. Piston according to claim 2 or 3, characterised in that the inner leg (32) projects into the clear opening of the at least one hub bore (21, 21') and thus forms the locking element for the piston pin (23).
5. Piston according to one of claims 2 to 4, characterised in that the outer leg (31) forms the piston shaft-side delimitation of the annular recess (25).
6. Piston according to one of claims 2 to 5, characterised in that the annular recess (25) is arranged between a face end (19) formed on the annular wall (17) of the piston (10) and at least one shoulder (22, 22') formed on the piston shaft (12), and in that the cover ring (30) is supported with its outer leg (31) on the face end (19) and with its base web (33) on the at least one shoulder (22, 22').
7. Piston according to one of claims 2 to 6, characterised in that the inner leg (32) of the cover ring is supported on the shaft connection (13) of the piston (10).
8. Piston according to one of claims 2 to 7, characterised in that the height of the inner leg (32) varies over the circumference of the cover ring (30).
9. Piston according to one of claims 2 to 8, characterised in that the angular position of the inner leg (30) relative to the middle axis of the cover ring (30) varies over the circumference of the cover ring (30).
10. Piston according to one of the preceding claims, characterised in that the cover ring (30) comprises an inlet opening (35) and a diametrically opposite outlet opening (36) for a coolant, and in that the flow channel for the coolant formed by the cover ring (30) is inclined from the inlet opening (35) to the outlet opening (36).

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