PISTON WITH LOW OVERALL HEIGHT

Abstract

A piston for an internal combustion engine having an upper part joined by a positive material connection to a lower part, wherein the lower part includes a skirt and at least one pin bore, wherein the upper part includes a combustion bowl and a piston crown with a crown edge, wherein at least one joining point is located in the area of a ring belt and/or in an outer wall of the combustion bowl. A method for producing a piston for internal combustion engines is disclosed.

Claims

1. A piston for an internal combustion engine having an upper part joined through a positive material connection to a lower part, wherein the lower part includes a skirt and at least one piston pin bore, wherein the upper part includes a combustion chamber bowl and a piston crown with a crown edge, characterized in that at least one joining point is located in the area of a ring belt and/or in an outer wall of the combustion bowl.

2. The piston from claim 1, wherein a location of the inner joining point is provided in the outer wall of the combustion bowl above a finish-machined base of the combustion bowl.

3. The piston from the claim 1, wherein the piston has a low compression height, wherein the ratio of compression height (h.sub.1) to piston diameter (d.sub.1) is between 0.48 and 0.75.

4. The piston from claim 1, wherein at least one recess is provided in the crown of the piston.

5. The piston from claim 4, wherein the at least one recess has a least one opening that at least partially passes through the edge of the piston crown.

6. The piston from claim 5, wherein the at least one opening (28) is shaped as a segment of a circle.

7. The piston from claim 4, wherein the at least one recess forms at least one valve pocket.

8. The piston from claim 7, wherein a distance x.sub.1 between a line, the line between pressure side and counter-pressure side, and a center point of the first valve pocket is greater than a distance x.sub.2 between the line and the center point of the second valve pocket.

9. The piston from claim 8, wherein the distance x.sub.1 between a line, the line between pressure side and counter-pressure side, and the center point of the first valve pocket is at least twice as large as the distance x.sub.2 between the line and the center point of the second valve pocket.

10. The piston from claim 1, wherein the skirt of the piston has a coating to reduce friction.

11. The piston from claim 1, wherein the piston has a cooling gallery.

12. The piston from claim 11, wherein at least one extended feed is provided for oil access to the cooling gallery.

13. The piston from claim 12, wherein the cooling gallery has molded-in recesses in its contour.

14. The piston from claim 13, wherein the molded-in recesses in the cooling gallery correspond to a point where combustion waves impinge on the combustion bowl.

15. The piston from claim 1, wherein the upper part is configured as a semi-hot forged upper part.

16. A method for producing a piston for an internal combustion engine, having an upper part joined by a positive material connection to a lower part, wherein the lower part includes a skirt and at least one piston pin bore, wherein the upper part includes a combustion chamber bowl and a piston crown with a crown edge, characterized by joining the lower part and the upper part by friction welding with an array in position.

17. The method from claim 16, comprising removing an inner friction welding bead when the combustion bowl is produced.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The basic idea is explained in what follows using the Figures. Additional details are described in the Figures using schematically represented embodiments as examples in which:

[0031] FIG. 1 shows a sectioned view of a piston;

[0032] FIG. 2 shows a sectioned view of a piston along the line II in FIG. 1;

[0033] FIG. 3 shows a detail identified in FIG. 2 with III;

[0034] FIG. 4 shows a detail from FIG. 2 identified with IV;

[0035] FIG. 5 shows a sectioned view of a piston along the line V-V in FIG. 2;

[0036] FIG. 6 shows a sectioned view of a piston along the line VI-VI in FIG. 2;

[0037] FIG. 8 shows a sectioned view of a piston area along the line VIII-VIII in FIG. 7;

[0038] FIG. 9 shows a plan view of a piston crown;

[0039] FIG. 10 shows a section from the piston in the area of a valve pocket provided on the piston crown side corresponding to a section taken along X-X in FIG. 9,

[0040] FIG. 11 shows a sectioned view of an additional piston,

[0041] FIGS. 12A and 12B show sectioned views of a lower part and an upper part of a piston from FIG. 11; and

[0042] FIGS. 13A and 13B show sectioned views of a lower part and an upper part of a piston from FIG. 11 rotated by 90 degrees compared with FIGS. 12A and 12B.

DETAILED DESCRIPTION

[0043] In the following description of the Figures, terms such as top, bottom, above, below, left, right, front, back, etc. refer solely to the representation and position of the devices chosen as an example in the respective Figures and other elements. These terms are not to be understood in a restrictive sense, that is to say, these references may change as the result of different positions and/or mirror-image layout or similar.

[0044] A section from a piston 1, or a piston 1 for an internal combustion engine, is shown in FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. A further piston 1 for an internal combustion engine is shown in FIGS. 11, 12A, 12B, 13A and 13B. The piston 1 is constructed identically in the Figures in each case and is described generally at first in what follows. Then the Figures are presented in detail in each instance. Identical components are identified with the same reference numerals, and new reference numerals are used for different components in the Figures.

[0045] The piston 1 for an internal combustion engine in the Figures is produced from a lower part 2 and an upper part 3. At least one joining point 4 is formed between the lower part 2 and the upper part 3. Formed joining surfaces meet in the area of the joining point 4 on lower part 2 and upper part 3. One joining point can be formed in the region of a ring belt 9. Alternatively or supplementally, one joining point 4 can be formed in the outer wall of a combustion bowl 11. The at least one joining point 4 can be carried out as pipe to plate. As long as the piston 1 has at least one cooling gallery 6, the contour of the at least one cooling gallery 6 can be formed in the lower part 2 or the upper part 3, wherein this version is described as pipe. The matching side is executed as a circumferential, plane or almost plane, surface in the lower part 2 or the upper part 3 and correspondingly described as plate.

[0046] A piston crown 5 is configured on the upper part 3. The piston crown 5 is located on the side of the upper part 3 facing away from a cooling gallery 8. A piston skirt 6 is formed on the lower part 2 having piston pin bores 7. The piston 1, joined together from lower part 2 and upper part 3, has a circumferential ring belt 9, furnished with ring grooves 10. The combustion bowl 11 is located in the upper part 3, centrically or eccentrically around a piston stroke axis 12. A piston pin bore axis 13 is located in the region of the piston pin 7, corresponding to the center axis of the piston pin (not shown). Oil return orifices are located in the area of the ring belt 9.

[0047] A piston 1 joined from lower part 2 and upper part 3 is shown in FIG. 1. The piston has a coating 14 in the area of the skirt 6. The coating 14 demonstrates reduced friction. The benefits of this coating 14 are extremely high durability, outstanding sliding properties and a significant increase in the service life of the piston 1. The film thickness of the coating 14 is, for example, about 0.01 mm. The film thickness of the coating 14 can lie between 0.005 mm and 0.1 mm.

[0048] FIGS. 1, 6 and 11 show at which points piston compression height h.sub.1 and the diameter of the piston d.sub.1 are measured. Bowl depth of the combustion bowl h.sub.2 is shown in FIGS. 6 and 11 in addition. Compression height h.sub.1 can be 83 mm, for example, in FIGS. 1 and 6. The diameter d.sub.1 of the piston 1 according to FIGS. 1 and 6 can be 130 mm, for example. The result is a ratio of compression height h.sub.1 of the piston 1 to diameter d.sub.1 of the piston 1 of 0.63. The value for h.sub.1 can vary between 70 mm and 90 mm, preferably lying between 80 mm and 85 mm. The value for d.sub.1 can lie between 120 mm and 145 mm, d.sub.1 preferably lying between 125 mm and 135 mm. Thus the ratio of compression height h.sub.1 to diameter d.sub.1 of the piston 1 varies between 0.48 and 0.75.

[0049] FIG. 5 shows a burr-free area 15 located in the area of pin bore 7. A supplementary locator 16 is shown in the center in addition.

[0050] FIG. 7 shows a feed 17 with a diameter d.sub.2 and a return 18 with a diameter d.sub.3. Oil can enter the cooling area through the feed 17 and can leave this area again through the return 18.

[0051] FIG. 9 shows two recesses 20, configured as valve pockets 21, 22, each having a diameter d.sub.4. This diameter d.sub.4 can be, for example, 47 mm. The diameter d.sub.4 can assume a value between 35 mm and 55 mm, preferably between 40 mm and 50 mm. The diameter d.sub.4 of the valve pockets 21, 22 can also assume different values. Any number of recesses 20, shaped as milled [slots] for example, can be provided. At least one part of the recesses 20 is shaped at least partially as a valve pocket in which gas exchange valves of the reciprocating piston internal combustion engine are accommodated at least partially when they are operating, that is to say, the exchange valves can protrude into the recesses 20. In this way a collision between the gas exchange valves and the piston 1 can be prevented. This design and function of the recesses 20, represents a functional integration that holds down the cost of the piston 1, specifically its manufacturing cost.

[0052] The valve pockets 21, 22 of the piston 1 adjoin the piston 1 in a radial direction, in which the respective, corresponding valve heads of gas exchange valves of the reciprocating piston internal combustion engine can be accommodated. When the piston 1 is at top dead center in the combustion chamber of the reciprocating piston engine, the valve pockets 21, 22 provide a sufficiently large clearance for the respective gas exchange valves, that is, for the corresponding intake and exhaust valves, so that the gas exchange valves can provide desirably large lift in each case to effect gas exchange. In other words, the gas exchange valves can open far enough due to the clearances provided by the valve pockets 21, 22 to efficiently effect an exchange of exhaust gas and air drawn in by the reciprocating piston internal combustion engine, or of a mixture drawn in by the reciprocating piston internal combustion engine.

[0053] A first segment of a circle K1 is located between a first valve pocket 21 and the line 24 standing perpendicular to the line 23 connecting a pressure side (DS) 25 and a counter-pressure side (GDS) 26. A second segment of a circle K2 is located between the line 24 standing perpendicular to the line 23 connecting a pressure side 25 and a counter-pressure side 26 and a second valve pocket 22. A third segment of a circle K3 is located between the second valve pocket 22 and the line 23 connecting the pressure side 25 and the counter-pressure side 26. The first segment of a circle K1 has, for example, a dimension of 23. The first segment of a circle K1 can assume values between 15 and 30, preferably between 20 and 25. The second segment of a circle K2 has, for example, a dimension of 64. The second segment of a circle can assume values between 55 and 70, preferably between 60 and 65. The third segment of a circle K3 has, for example, a dimension of 27. The third segment of a circle K3 can assume values between 15 and 35, preferably between 20 and 30.

[0054] Around its circumference the piston crown l.sub.1 is bounded by a crown edge 27. The edge of the crown 27 has recesses 28 shaped like the segment of a circle in the area of the valve pockets 21, 22. The length l.sub.1 of the recess 28 of the first valve pocket 21 equals the length l.sub.2 of the second valve pocket and is, for example, 25 mm. The lengths l.sub.1 and l.sub.2 can assume values between 15 mm and 35 mm, preferably between 20 mm and 30 mm. In accordance with the embodiment, l.sub.1 and l.sub.2 can have identical values, but do not have to have identical values. The dimensions for l.sub.1 and l.sub.2 can be varied independently of each other.

[0055] The distance x.sub.1 between the line 23 and the center point of the first valve pocket 21 is greater than the distance x.sub.2 between the line 23 and the center point of the second valve pocket 22. The distance x.sub.1 is, for example, 37.3 mm. The distance x.sub.2 is, for example, 18 mm. Thus the distance x.sub.1 is at least twice as great as distance x.sub.2. The distance x.sub.1 can, lie between 30 mm and 45 mm, preferably between 35 mm and 40 mm. The distance x.sub.2 can lie between 15 mm and 22.5 mm, preferably between 17.5 mm and 22.5 mm.

[0056] The distance between the center point of the first valve pocket 21 and the line 24 is identified with x.sub.3. The distance between the line 24 and the center point of the second valve pocket is identified with x.sub.4. The distance x.sub.3 is shorter than the distance x.sub.4. The distance x.sub.4 is, for example, 36 mm, and the distance x.sub.3 15.7 mm. Thus the distance x.sub.3 is at most half as long as distance x.sub.4. The distance x.sub.4 can lie between 25 mm and 45 mm, preferably between 30 mm and 40 mm. The distance x.sub.3 can lie between 12.5 mm and 22.5 mm, preferably between 15 mm and 20 mm.

[0057] FIG. 11 shows a finished piston 1 from which it can be seen at which points the piston compression height h.sub.1 and the diameter d.sub.1 of the piston are measured. The piston 1 shown in FIG. 11 is a two-piece piston, consisting of upper part 3 and lower part 2, which are joined together. However, the piston 1 can also be configured in one piece. This piston 1 has a ratio between the compression height h.sub.1 of the piston 1 and the diameter d.sub.1 of the piston 1 of 0.53.

[0058] FIGS. 12A and 12B and 13A and 13B show views of upper part 3 and lower part 2 before they are joined. This is an example of a design configuration of upper part 3 and lower part 2 which are joined in a suitable manner, for example, by friction welding in order to achieve the desired ratio of 0.53.