EP1920152B1 - Two-piece piston for an internal combustion engine - Google Patents

Description

The invention relates to a two-part piston for .einen internal combustion engine according to the preambles of the main claim and the dependent claims 5, 8 and 9.

From the patent application with the file number 10 2005 021 427.4 a two-part, consisting of an upper part and a lower part piston for an internal combustion engine is known. The upper part forms the piston crown and, on the underside facing away from the piston crown, has a cylindrical bolt with an external thread lying coaxially with the piston axis. The lower part has an upper, thin-walled and elastically yielding base part, at the central region of which a sleeve pointing in the direction of the piston head is formed with such a thin wall that this sleeve has the function of an expansion sleeve. In this expansion sleeve coaxial with the piston axis opening is formed, in which the bolt is inserted, so that the upper part can be connected to the lower part by means of a nut screwed onto the bolt, wherein the elastic compliance of the upper bottom part and the extensibility of the expansion sleeve, the screw puts under bias and this gives a great security.

The disadvantage is that the production of the upper bottom part of the lower part with the molded-on expansion sleeve is very complicated. Regardless of whether the lower part is cast or forged, a lengthy machining of the central region of the upper bottom part and in particular of the expansion sleeve using a machining process is required, it being important to ensure that narrow tolerance ranges are met, so that the central Area of the upper bottom part and the expansion sleeve obtained the desired elasticity properties.

US 3,465,651 describes a two-part piston whose upper part has, on its underside facing away from the combustion chamber, a central bolt which extends through an opening formed in the lower part. The end portion of the bolt is provided with a thread on which a hex nut is screwed, which is supported under pressure on washers on a shoulder of the base. By tightening the screw, the thin-walled piston crown of the upper part is bent toward the lower part and brought into contact with bearing surfaces provided for this purpose. A disadvantage, in turn, proves that the elasticity properties of areas of the cast or forged piston parts are used for the bias between the upper and lower part, in particular, which have relatively large tolerances, would be required to avoid a high processing cost.

JP 6065361 U describes a similar two-piece piston.

DE 3719469 A1 describes a two-part piston with low compression height, the upper part in the combustion chamber facing away from the bottom has a central threaded bore into which a hexagon screw is screwed. This extends through an opening in the piston lower part and is supported on its head via a plurality of disc springs on a radially inwardly facing projection of a sleeve, which is screwed tightly into the piston lower part. After the upper and lower parts of the piston have been brought into contact by tightening the screw and the disc springs have been compressed, it is also missing on an element with the desired elasticity for permanent securing of the bias.

Proceeding from this, the object of the invention is to simplify and reduce the cost of producing a two-part piston whose upper part and its lower part are connected to one another via an expansion sleeve. This object is achieved by a piston having the features of claim 1 or 5 in two complementary embodiments.

While claim 1 is directed to an embodiment with a hexagon nut on a piston pin belonging to the threaded bolt, claim 5 has a complementary design with a threaded hole in the piston upper part of the object, in which a hexagonal screw is screwed. The advantage of the invention results in both cases from the common feature of a separate expansion sleeve, which undergoes an expansion by the tensile stress exerted on it, exerts a permanent bias on the screw and thereby contributes to their safety.

Advantageous embodiments of the invention are the subject of the dependent claims. This results in the advantage that a separate expansion sleeve is easier and cheaper to produce than a converted to Dehnhülse, central region of the upper bottom part, and that the material used for this purpose may be higher than that material from which the upper bottom part of the lower part consists.

Fig. 1

einen zweiteiligen Kolben, dessen beide Teile über eine Dehnhülse miteinander verbunden sind,

Fig. 2

einen Schnitt durch den Kolben gemäß Fig. 1, der den durchgängigen Kühlölkanal erkennen lässt,

Fig. 3

eine Draufsicht der zum Verschrauben der beiden Teile des Kolbens verwendeten Mutter,

Fig. 4

einen Schnitt durch die Mutter gemäß Fig. 3,

Fig. 5

eine perspektivische Darstellung der Mutter gemäß den Figuren 3 und 4,

Fig. 6

eine Ausgestaltung des Kolbens gemäß der Erfindung, wobei zum Verschrauben der beiden Kolbenteile eine Sechskantschraube verwendet wird,

Fig. 7

eine vergrößerte Darstellung des Bereiches A aus Fig.6,

Fig. 8

eine vergrößerte Darstellung einer weiteren Ausgestaltung der Verschraubung der beiden Kolbenteile unter Verwendung einer Dehnhülse und

Fig. 9

einen Darstellung entsprechend Fig. 8 mit der Sechskantmutter im Schnitt.

Some embodiments of the invention will be described below with reference to the drawings. Show it

Fig. 1

a two-part piston whose two parts are connected to one another via an expansion sleeve,

Fig. 2

a section through the piston according to Fig. 1 , which reveals the continuous cooling oil channel,

Fig. 3

a top view of the nut used to screw the two parts of the piston,

Fig. 4

a section through the mother according to Fig. 3 .

Fig. 5

a perspective view of the mother according to the FIGS. 3 and 4 .

Fig. 6

an embodiment of the piston according to the invention, wherein a hexagonal screw is used for screwing the two piston parts,

Fig. 7

an enlarged view of the area A from Figure 6 .

Fig. 8

an enlarged view of a further embodiment of the screw connection of the two piston parts using an expansion sleeve and

Fig. 9

a representation accordingly Fig. 8 with the hexagon nut on average.

In Fig. 1 is a two-part, cooled piston 1 shown, which consists of an upper part 2 and a lower part 3. The upper part 2 and the lower part 3 may be made of aluminum, steel or cast iron with nodular graphite (GGG cast iron according to DIN 1693). A piston head 4 bounds the axial top side of the upper part 2, the radially inner region of which has a combustion bowl 5. At the outer edge of the piston head 4, an annular wall 6 is integrally formed, the outer surface piston crown side forms a top land 7, which is followed by a shaft ring side 8 with annular grooves for receiving piston rings, not shown in the figure.

At the bottom of the lower part 3 facing away from the piston head 4, two pin bosses 9, 9 'each having a pin bore 10, 10' are arranged. The pin bosses 9, 9 'are connected to each other via shaft elements 13.

The upper part 2 and the lower part 3 of the piston 1 are connected via an inner support 14 and via a concentrically arranged outer support 15 with each other. The upper part 2 and the lower part 3 each have a blind hole 16 and 17, which lie opposite each other with a corresponding position of the upper and lower parts 2, 3. An inserted into the two blind holes 16, 17 fixing pin 11 ensures that the upper part 2 and the lower part 3 always assume the same rotational position to each other.

From the upper part 2 and the lower part 3 of the piston 1, an outer cooling channel 22 is arranged in the piston bottom side edge region of the piston 1 is formed, the radially outer boundary of the annular wall 6, the radially inner boundary part of a arranged on the upper side of the lower part 3 submersible 18th and partly formed by the piston head 4, and the axially lower boundary of the lower part 3 of the piston 1. Via at least one oil feed channel 52 (FIG. Fig. 2 ) Cooling oil is introduced into the cooling channel 22.

The piston 1 has a further, coaxially to the piston axis 12 arranged, annular, inner cooling channel 24, which has a smaller radial diameter than the outer cooling channel 22, and which, viewed in the radial direction, is disposed within the outer cooling channel 22. Axially above the inner cooling channel 24 is bounded by the piston head 4, radially outward of the Unterteilfuß 18, axially below by an upper bottom portion 25 of the lower part 3 and radially inwardly by a bolt 31, wherein the bottom part 25 of the lower part 3 has an opening 27 radially inside ,

The bolt 31 is cylindrical and coaxial with the piston axis 12 formed on the underside of the piston head 4, wherein the lateral surface of the bolt 31 has a piston bottom facing away end portion with an external thread 32 (FIGS. Fig. 2 ), which corresponds to the internal thread of a hex nut 29, so that the hex nut 29 can be screwed onto the external thread 32.

By means of the hex nut 29, the upper part 2 is screwed to the lower part 3 via an expansion sleeve 26 arranged between the upper end face 23 of the hexagonal nut 29 and the upper bottom part 25 of the lower part 3. The expansion sleeve 26 has for this purpose at its end facing away from the piston head an inwardly directed collar 28 and at its end remote from the piston bottom a radially outwardly disposed, in kolbenbodenabgewandte direction radially outwardly conically widening contact surface 19.

When screwing together upper part 2 and lower part 3, the fixing pin 11 is first inserted into the blind hole 17 arranged in the upper bottom part 25 of the lower part 3. Anschießend the upper part 2 and the lower part 3 are aligned coaxially with each other. For this purpose, the piston bottom side edge of the lower part 3 on a support web 46 which has the shape of a radially inward and axially directed in the direction of the piston head 4 stage in section. In addition, a cylindrical recess 47 is formed in the inside of the lower end face of the annular wall 6, whose inner shape is complementary to the outer shape of the support web 46. A coaxial alignment of upper part 2 and lower part 3 is thereby achievable, that the support bar 46 is initially inserted at least partially into the recess 47. In this case, it is still necessary to rotate the upper part 2 about the piston axis 12 until the blind hole 16 comes to lie above the fixing pin, after which the support web 46 can be completely inserted into the recess 47 and also the fixing pin 11 into the blind hole 16.

Subsequently, the expansion sleeve 26 are pushed through the opening 27 and the hex nut 29 screwed onto the external thread 32 of the bolt 31. In this case, the hexagonal nut 29 reach over its upper end face 23 against a piston bottom facing away from the inner surface 20 of the collar 28 and the contact surface 19 of the expansion sleeve 26 to a arranged on the radially inner side of the opening 27, conically downwardly opening surface 21 to the plant. Here, the conicity of the surface 21 is at least approximately equal to the taper of the contact surface 19. Thereafter, the hex nut 29 is screwed with such a torque that due to the pressure of the hex nut 29 on the inner surface 20 of the collar 28 and because of the thereby exerted on the expansion sleeve 26 Tensile stress, the expansion sleeve 26 undergoes an expansion, which exerts a permanent bias on the screw, whereby this screw is given a great deal of security. In addition, in this case the bolt 31 undergoes an expansion and the radially inner part of the piston head 4 a plate spring-like deformation in the direction of pin bosses 9, 9 '. In addition, the expansion sleeve 26 is made of a high-grade steel material, which contributes to the safety of the screw connection between upper part 2 and lower part 3 of the piston 1.

Here, in an embodiment of the invention not shown in the figures, the contact surface 19 on the piston bottom side facing away from the expansion sleeve 26 may also be spherical or spherical, wherein the hereby in contact surface 21 of the upper bottom part 25 of the piston lower part 3 may have a complementary shape for this purpose ,

As in Fig. 2 is clearly visible, the collar 28 defines a circular opening 30 whose radial diameter is greater than the radial diameter of the bolt 31, so that between pin 31 and collar 28, an annular gap 33 results. The hexagonal nut 29 has in its upper end face 23 radially arranged grooves 34 and 34 ', which open radially inward into the gap 33. The radial inner diameter of the expansion sleeve 26 is greater than the radial outer diameter of the hex nut 29, so that between hex nut 29 and expansion sleeve 26, a cylindrical and annular cross-section space 35 results, the piston bottom facing away from the end of the piston interior 36, and its piston bottom facing end with the grooves 34, 34 'is in communication. In addition, the outer cooling channel 22 is connected to the inner cooling channel 24 via radially arranged overflow channels 37, 37 '.

As indicated by the line 38, this results in a continuous oil passage, wherein first via the oil supply passage 52 cooling oil is introduced into the outer cooling passage 22, which flows via the overflow channels 37, 37 'in the inner cooling channel 24 and via the gap 33, flows back into the piston interior 36 via the grooves 34, 34 'and via the intermediate space 35.

The Fig. 3 shows a plan view, Fig. 4 a sectional view and Fig. 5 a perspective view of the hex nut 29 used in the screwing of the upper part 2 with the lower part 3. In Fig. 3 an exemplary arrangement of the grooves 34 to 34 "'shown, with 4 grooves 34 to 34'" with radially extending longitudinal axes 48, 48 ', 48 "and 48"' are evenly distributed over the circumference of the end face 23, so that the longitudinal axis pairs 48th -48 ", 48" -48 ', 48'- 48 "' and 48"'- 48 each enclose an angle of 90 °.

Fig..4 shows a section through the hex nut 29 along the line DD in Fig. 3 with a representation of the U-shaped cross section of the grooves on the example of the groove 34 'and with a plan view of the flanks of the grooves 34 "and 34'".

A perspective view of the hex nut 29 is shown in FIG Fig. 5 represented, in particular, the grooves 34, 34 'and 34 "recognize.

The embodiment of the present invention according to the FIGS. 6 and 7 is different from the one in the Fig. 1 to 5 shown embodiment of the invention, in particular, characterized in that the upper part 2 'and the lower part 3' of the piston 1 'are connected to each other by means of a hexagon screw 39, wherein between the head 40 of the hex screw 39 and the collar 28' of the expansion sleeve 26 'in the axial direction short, tubular intermediate piece 41 with one or more continuous, radially extending bores 42, 42 'is arranged, via which the oil from the gap 33' between the collar 28 'of the expansion sleeve 26' and the shank of the screw 39 in the intermediate space 35 'between the expansion sleeve 26 'and the screw head 40 can flow. From here, the oil enters the piston interior 36 '.

Fig. 7 is an enlarged view of the area A from Fig. 6 ,

In Fig. 8 is in partial section and in Fig. 9 is in full section an embodiment of a Kobens 1 "with an expansion sleeve 26" shown, the radially inwardly directed collar 28 and the piston bottom facing away from the end facing away from the piston skirt has a radially outwardly directed collar 44. On the piston crown side, a radially aligned contact surface 19 'is arranged on the collar 44. In addition, on the inner wall of the opening 27 'in the upper bottom part 25' of the piston lower part 3 "formed in a piston bottom facing away from radially inwardly tapered and elastically yielding projection 45 formed on its side facing away from the piston bottom also a radially oriented surface 21 '.

When screwing the upper piston part 2 "with the lower piston part 3" reaches the contact surface 19 'to rest against the surface 21', which is not only a longitudinal expansion of the expansion sleeve 26 "and the bolt 31 and a plate spring-like deformation of the central region of the piston head 4 'in Direction piston shaft but also a plate spring-like deformation of the projection 45 in the direction of the piston crown 4 'results. The deformations of the latter piston elements lead to an acting on the screw preload that gives this compound a great deal of security.

LIST OF REFERENCE NUMBERS

1, 1 ', 1 "

piston

2, 2 ', 2 "

top

3, 3 ', 3 "

lower part

4, 4 ', 4 "

piston crown

5

combustion bowl

6

ring wall

7

top land

8th

ring belt

9, 9 ', 9 ", 9"'

pin boss

10, 10 ', 10 ", 10"

pin bore

11

locating pin

12

piston axis

13, 13 '

shaft element

14

inner edition

15

outer edition

16, 17

blind

18

Unterteilfuß

19, 19 '

contact area

20

Inner surface of the collar 28

21, 21 ', 21 "

area

22, 22 '

outer cooling channel

23

upper end face of the hex nut 29

24, 24 '

inner cooling channel

25, 25 ', 25 "

upper bottom part of the lower part 3

26, 26 ', 26 "

expansion sleeve

27, 27 ', 27 "

opening

28, 28 '

collar

29

Hex nut

30

Opening the collar 28

31

bolt

32

external thread

33, 33 '

Gap between the collar 28 and the bolt 31st

34, 34 ', 34 ", 34'"

Grooves of the hex nut 29

35

Gap between the hex nut 29 and the expansion sleeve 26th

35 '

third space between the head 40 of the hex screw 39 and the expansion sleeve 26 '

36, 36 '

Piston interior

37, 37 ', 37 "

Overflow channel

38

line

39

Hex bolt

40

Head of the hexagon screw 39

41

connecting piece

42, 42 '

Bore in the intermediate piece 41st

43

expansion sleeve

44

collar

45

projection

46

carrying web

47

recess

48, 48 ', 48 ", 48'"

Longitudinal axes of the grooves 34, 34 ', 34 ", 34"'

49

Blind hole

50

upper end face of the intermediate piece 41st

51

Support surface of the head 40 of the hex screw 39

52, 52 '

oil feed

53

first space between the shank of the hex nut 29 and the intermediate piece 41st

54

second space between the intermediate piece 41 and the expansion sleeve 26 '

Claims (9)

1. A two-part piston (1, 1") for an internal combustion engine

   - comprising an upper part (2, 2"), which forms a piston head (4, 4'),

   - wherein a cylindrical piston pin (31), which has an external thread (32) and extends coaxially with the piston axis (12), is integrally formed with the underside of the upper part (2, 2") facing away from the piston head (4, 4'), and

   - having a lower part (3, 3"), on the underside of which piston-pin bosses (9, 9') are disposed, said piston-pin bosses having piston-pin bores (10, 10') and shank elements (13), which connect the piston-pin bosses (9, 9') to one another,

   - wherein the lower part (3, 3', 3") has an upper head part (25, 25') having an opening (27, 27') located coaxial with the piston axis (12), into which said opening the piston pin (31) is inserted, via which the upper part (2, 2") is screwed together with the lower part (3, 3") by means of a hexagon nut (29) screwed onto the piston pin (31),
   characterized in that

   - the radial inner side of the opening (27) has an annular surface (21), which is disposed on the shank side and is located further from the piston head (4) than the upper end face (23) of the hexagon nut (29), and

   - a resilient sleeve (26) is disposed between the end face (23) and the surface (21) and comprises, on the side facing the piston head, a radially inwardly directed collar (28) having a radially oriented inner surface disposed on the side thereof facing away from the piston head, against which said inner surface the end face (23) of the hexagon nut (29) lies, and wherein said resilient sleeve also has, in the region thereof facing away from the piston head, a contact surface (19), which faces the piston head and lies against the surface (21).
2. The piston according to claim 1, characterized in that the contact surface (19), in the region of the resilient sleeve (26) facing away from the piston head, and the surface on the radially inner side of the opening (27), in the direction facing away from the piston head, are both designed so as to expand radially outwardly in a conical shape.
3. The piston according to claim 1, characterized in that the contact surface (19) is spherical in the region of the resilient sleeve (26) facing away from the piston head.
4. The piston according to claim 1, characterized in that the contact surface (19) has a crowned shape in the region of the resilient sleeve (26) facing away from the piston head.
5. The piston having the features of the preamble of claim 1,

   - wherein the piston (1, 1") comprises an annular, outer cooling duct (22) in the edge region thereof on the piston-head side, which is connected to the piston interior (36) by means of at least one oil supply duct (52),

   - wherein the piston (1, 1") comprises, within the outer cooling duct (22), an inner cooling duct (24), which is disposed so as to be coaxial with the piston axis (12), is annular, and is limited radially inwardly by the piston pin (31), said inner cooling duct being connected to the outer cooling duct (22) by means of at least one overflow duct (37, 37'), and

   - wherein an annular gap (33) is located between the collar (28) of the resilient sleeve (26, 26") and the piston pin (31),
   characterized in that

   - the hexagon nut (29) has, in the upper end face (23) thereof, at least one radially disposed groove (34, 34', 34', 34"'), which leads radially inwardly into the gap (33),

   - an intermediate space (35) is located between the hexagon nut (29) and the resilient sleeve (26, 26"), the end of which on the piston-head side is connected to the at least one groove (34, 34', 34", 34'"),

   - the end of the intermediate space (35) facing away from the piston head leads into the piston interior (36), and

   - a continuous oil duct results, proceeding from the oil supply duct (52), via the outer cooling duct (22), via the at least one overflow duct (37, 37'), via the inner cooling duct (24), via the gap (33) between the collar (28) and the piston pin (31), via the at least one groove (34, 34', 34", 34"') in the end face (23) of the hexagon nut (29) and via the intermediate space (35) between the hexagon nut (29) and the piston pin (31).
6. The piston according to claim 5, characterized in that the hexagon nut (29) comprises four grooves (34, 34', 34", 34"') in the upper end face (23) thereof, said grooves being radially disposed and distributed uniformly around the periphery.
7. The piston according to claim 1, 5 or 6, characterized in that a radially outwardly directed collar (44) is disposed on the end of the resilient sleeve (26') facing away from the piston head, said collar having a radially oriented contact surface (19') on the piston-head side, and in that an elastically resilient overhang (45), which extends radially inwardly in a conical manner in the direction facing away from the piston head, is integrally formed on the inner wall of the opening (27') and has, on the side facing away from the piston head, a radially oriented surface (21'), against which the contact surface (19') lies.
8. A two-part piston (1') for an internal combustion engine

   - comprising an upper part (2'), which forms a piston head (4"),

   - wherein a blind hole (49), which has an internal thread and extends coaxially with the piston axis (12), is disposed on the underside of the upper part (2") facing away from the piston head (4"), and

   - having a lower part (3"), on the underside of which piston-pin bosses (9', 9"') are disposed, said piston-pin bosses having piston-pin bores (10", 10"") and shank elements (13'), which connect the piston-pin bosses (9", 9"") to one another,

   - wherein the lower part (3') comprises a lower head part (25") having a opening (27"), which is located coaxial with the piston axis (12), via which the upper part (2') is connected to the lower part (3') by means of a hexagon bolt (39) screwed into the blind hole (49),
   characterized in that

   - the radial inner side of the opening (27') has an annular surface (21"), which is disposed on the shank side,

   - the head (40) of the hexagon bolt (39) has, on the radial outer side, a mating surface (51) on the piston-head side,

   - a tubular intermediate piece (41) having an upper end face (50) is disposed on the mating surface (51), wherein the end face (50) is located closer to the piston head (4') than is the surface (21"), and

   - a resilient sleeve (26') is disposed between the end face (50) of the intermediate piece (41) and the surface (21") and comprises, on the side facing the piston head, a radially inwardly directed collar (28') having a radially oriented inner surface (20) disposed on the side thereof facing away from the piston head, against which said inner surface the end face (50) lies, and wherein said resilient sleeve also has, in the region thereof facing away from the piston head, a contact surface (19), which faces the piston head and lies against the surface (21").
9. The piston having the features of the preamble of claim 8,

   - wherein the piston (1') comprises an annular, outer cooling duct (22) in the edge region thereof on the piston-head side, which is connected to the piston interior (36') by means of at least one oil supply duct (52'),

   - wherein the piston (1') comprises, within the outer cooling duct (22'), an inner cooling duct (24'), which is disposed so as to be coaxial with the piston axis (12), is annular, and is limited radially inwardly by the hexagon bolt (39), said inner cooling duct being connected to the outer cooling duct (22') by means of at least one overflow duct (37"), and

   - wherein an annular gap (33') is located between the collar (28') of the resilient sleeve (26') and the shank of the hexagon bolt (39),
   characterized in that

   - a tubular intermediate piece (41) is disposed between the head (40) of the hexagon bolt (39) and the collar (28'),

   - wherein the radial inner diameter of the intermediate piece (41) is larger than the radial outer diameter of the shank of the hexagon bolt (39) such that a first intermediate space (53) forms there between, wherein the radial outer diameter of the intermediate piece (41) is smaller than the radial inner diameter of the resilient sleeve (26') such that a second intermediate space (54) forms there between, and

   - wherein the intermediate piece (41) has at least one continuous, radially disposed bore (42, 42'), as the connection between the first intermediate space (53) and the second intermediate space (54), that the radial diameter of the head (40) of the hexagon bolt (39) is smaller than the radial inner diameter of the resilient sleeve (26') such that a third intermediate space (35') between the head (40) and the resilient sleeve (26') results, and

   - a continuous oil duct results, proceeding from the oil supply duct (52'), via the outer cooling duct (22'), via the at least one overflow duct (37"), via the inner cooling duct (24'), via the gap (33'), via the first intermediate space (53), via the at least one bore (42, 42') in the intermediate piece (41), via the second intermediate space (54), and via the third intermediate space (35').

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