EP1973691A1

EP1973691A1 - Cooling duct piston for an internal combustion engine

Info

Publication number: EP1973691A1
Application number: EP06792433A
Authority: EP
Inventors: Volker Gniesmer; Norbert Ries
Original assignee: KS Kolbenschmidt GmbH
Current assignee: KS Kolbenschmidt GmbH
Priority date: 2006-01-21
Filing date: 2006-10-18
Publication date: 2008-10-01
Also published as: DE102006002949A1; WO2007082564A1; CN101365559B; JP2009523942A; CN101365559A; US20100299922A1

Abstract

The invention relates to a method for producing a piston (1), for an internal combustion engine, designed as a cooling duct piston for small compression heights. The piston (1) comprises a lower part (2) and an upper part (3) which are supported by means of one or more corresponding joining planes (10, 11, 12) and are connected by means of a friction welding process. The piston (1) encloses an inner, trough-shaped cooling duct (8) and an outer cooling duct (9) which is spaced apart axially from an annular area (4). The inner cooling duct (8) is formed in the lower part (2) of the piston (1) by a mechanical machining process, in particular a forging process. Transfer openings (22, 23) which are assigned to the cooling ducts (8, 9) are formed before the frictional welding of the joining planes (10, 11, 12).

Description

Cooling channel piston for an internal combustion engine

DESCRIPTION

The invention relates to a cooling channel piston made of steel and its manufacturing method, according to the features of the respective preamble of the independent claims.

State of the art

US Pat. No. 6,155,157 discloses a cooling channel piston which comprises two components which can be produced separately from one another and which are joined together in a material-locking manner by means of a friction welding method, to form a one-part cooling channel piston. As a cooling channel is a spaced apart from the annular field of the piston and circumferential, in the direction of the piston inner mold via inlet and outlet holes open, narrow-dimensioned annular channel is provided. About a fixedly positioned spray nozzle of the cooling channel is acted upon by a cooling medium, in particular oil. This relatively easy to realize cooling channel due to the local location does not allow sufficient cooling effect of the piston. Question:

task

Based on the known prior art, the invention is therefore an object of the invention to realize an optimal cooling effect for heavy-duty cooling channel piston made of steel.

This object is solved by the features of the respective independent claims. A first invention relates to a method for producing a cast steel or forged from at least two parts at least one joint by friction welding cooling channel piston, which includes at least one further inner cooling channel with at least one trough-shaped depression in addition to an outer cooling channel. This trough-shaped partial region of the cooling channel, which is produced by means of a mechanical processing, a forging or by a casting method, is connected to an outer cooling channel which is arranged axially spaced from the annular field of the piston via at least one transfer opening. The partially trough-shaped design of the inner cooling channel advantageously increases the cooling oil cavity and consequently the cooling oil intake, which improves the shaker effect of the piston and thus overall the cooling effect of the piston can be significantly increased.

The shaping of the sectionally trough-shaped inner cooling channel also simplifies the introduction of transfer openings between the cooling channels, which are preferably designed as bores. According to the invention, the transfer openings between the cooling channels are introduced before the friction welding of the at least one (shown are three) joining plane in the lower part, via which the upper part and the lower part are supported. The transfer openings can advantageously open in the trough-shaped depression. The self-adjusting degree of freedom for the placement of the transfer openings makes it possible to determine the position of the transfer openings, which can take place exclusively from the point of view of optimal admission and sufficient volume of the coolant. Advantageously, a sufficient distance to the joint planes between the upper part and the lower part can be maintained.

Due to the spatial distance, the already introduced transfer openings are not hindered by the subsequent friction welding of the at least one joining plane and the welding beads which are formed in the process. The inventively integrated in a piston short compression height cooling channels cause an optimal cooling effect over the entire surface of the combustion bowl of the piston. At the same time, the large-volume design reduces Cooling channels advantageous the piston weight. Due to coordinated wall thicknesses of the outer and inner cooling channels, which are extended by the trough-shaped extension above the pin bore, a structurally solid piston is realized, which withstands the highest requirements and can be produced inexpensively.

A preferred embodiment of the cooling channels according to the invention provides that they also extend into the areas of greatest thermal stress of the piston. For this purpose, the sectionally trough-shaped inner cooling channel in the region of the pin bore has a vertically aligned section, to which an angled, rotationally symmetrical section aligned obliquely to an axis of symmetry of the piston adjoins. This inclined portion of the inner cooling channel is spaced from a contour of the combustion bowl of the piston. Radially on the outside, the outer cooling channel adjoins the inner cooling channel. A longitudinal extent of the outer cooling channel arranged at a parallel distance from the piston ring field exceeds a length dimension of the ring field. The cooling channels are placed in the piston so that they are enclosed by walls of almost equal wall thicknesses. For the purpose of simplified processing and production, in particular in the case of short compression heights, all the transfer ports associated with the cooling channels are preferably introduced in the piston lower part.

According to a second invention, there is provided a method of manufacturing a steel cooling channel piston having a central internal cooling space that includes a rolling pressure method. In a dome-shaped, a trough shape tracked central inner region of the piston, an inner cooling chamber or an inner cooling channel is introduced by means of a mechanical processing in conjunction with a cover, the radially offset to an outer cooling channel is assigned. The manufacturing process of the piston provides that cooling oil transfer openings, also referred to as supply bores, are introduced between the cooling channels prior to the final tumbling process. The Wälzdrückverfahren is used to bring the piston ring field by bending in the final position. The invention includes for providing an internal cooling space a cover or molding which closes the interior down. For this purpose, a disk-like or cup-shaped cover is preferably used. For attachment of the cover is preferably a positive and / or non-positive attachment, such as a press connection. Alternatively, a welding or soldering connection is provided for fastening the cover element, which encloses at least one outlet opening for the coolant.

From DE 37 13 191 C1 a method for producing a forged head of a two-part piston is known, in which a method step includes the bending of the ring portion in a final position. This piston comprises only an externally arranged, tightly designed cooling channel, which ensures only locally and therefore no sufficient large-scale cooling effect of the piston. For example, in the known piston no targeted coolant is applied in the region of the inner combustion bowl.

Deviating to the structure of the piston according to the invention allows an optimal cooling effect. By way of the inner cooling channel or cooling space following a central depression shape, in connection with the radially arranged outer cooling passage, all zones of the piston that are subjected to high thermal stress are detected by the cooling passages. By Wälzdrückverfahren connected to the targeted arrangement of the cooling channels a structurally solid steel piston can be realized with an optimized, in particular the entire piston crown detecting cooling effect. The piston according to the invention thus withstands the highest loads and can be used in internal combustion engines with high power density.

The concept according to the invention simplifies or optimizes the production of the piston, in particular the introduction of the transfer openings, which are preferably designed as bores. The preparation of the holes in existing steel pistons required increased production costs. Due to the difficult accessibility within the piston, the always oblique bores could only be produced with long drills. The inventive method provides a large freedom of design for the arrangement of the emanating from the inner cooling channel or the inner cooling chamber, opening into the outer cooling passage transfer openings. The location, orientation and number of the transfer openings can be advantageous only with regard to an improved coolant loading of the cooling channels, in order to achieve an optimum cooling effect of the piston.

A further preferred embodiment of the piston according to the invention provides that for the representation of the inner cooling space of the central, the trough mold tracked inner region in the direction of the pin bore has a circumferential annular groove, which serves as a holding volume for coolant. The annular groove is preferably produced by means of a mechanical processing.

According to a further aspect of the invention, to complete the steel cooling duct piston including a top and a bottom, there is provided a rolling pressure method combined with at least one main weld joint. This procedure comprises the following steps. After introducing an inner cooling channel or an inner cooling chamber into the piston, the corresponding joining regions, by means of which the lower part and the upper part are supported, are welded. Preferably, a friction welding is provided for this purpose. Subsequently, transfer openings are introduced, which connect the inner cooling channel with the outer cooling channel. Optionally, also transfer openings can be introduced before the welding. With a forming process, a Wälzdrückverfahren is finally brought the piston ring field by bending in its final position.

The following description explains various, illustrated in Figures 1 to 7 embodiments of inventively designed cooling channel piston.

Show it:

FIG. 1 shows a first embodiment of a cooling channel piston, FIG. 2 shows the cooling channel piston rotated by 90 ° according to FIG. 1,

FIG. 3 shows a second embodiment of a cooling channel piston,

FIG. 4 shows a third exemplary embodiment of a cooling channel piston,

FIG. 5 shows a fourth exemplary embodiment of a cooling channel piston,

FIG. 6 shows a fifth embodiment of a cooling channel piston,

FIG. 7 shows the cooling channel piston rotated according to FIG. 6 through 90 °.

Figures 1 and 2 each show in a half-sectional view a designed as a cooling channel piston, intended for an internal combustion engine piston 1, which is formed by a lower part 2 and an upper part 3. Furthermore, the piston 1 comprises a ring field 4 intended for three piston rings, a combustion bowl 5, a piston shaft 6 and a pin bore 7. After joining the lower part 2 and the upper part 3, the piston 1 forms an inner cooling channel 8 and an outer cooling channel 9. In this case, the lower part 2 and the upper part 3 via three axially and radially offset from each other joining planes 10,11, 12 are supported, which are connected to create a structural unit by means of a friction welding, but also conceivable a different number of joint planes.

Clarifying the weld, each joining plane 10, 11, 12, in the direction of the cooling channels 8, 9, shows welding beads 13, 14, 15, 16. Through an interaction of joining areas 17a, 17b, 17c of the lower part 2 with corresponding joining areas 18a, 18b, 18c of the upper part 3, the individual joining planes 10, 11, 12 are formed, which simultaneously delimit the cooling channels 8, 9 in the piston 1. The outer bottle-like shaped cooling channel 9 has a ring field 4 surmounting the longitudinal extent. As shown in FIG. 1, the trough-shaped structure of the inner cooling channel 8 forms a vertical section 19 in the region of the pin bore 7, against which an angled, obliquely extending axis of symmetry 20 of the piston 1 extends Section 21 connects. Outside the region above the pin bore of the cooling channel 8 is limited to the portion 21 which extends axially spaced following the contour of the combustion bowl 5. For coolant application, the cooling channels 8, 9, which extend in regions in the lower part 2 and in the upper part 3 of the piston 1, transfer openings 22, 23 assigned. For this purpose, the cooling channel 8 has near the axis of symmetry 20 a transfer opening 22, which can also be referred to as an outlet opening. In an intermediate wall below the joining plane 11, a further, the cooling channel 8 with the cooling channel 9 connecting the transfer opening 23 is introduced.

The construction and the manufacturing method of the piston 1 enables the transfer openings 22, 23 to be produced before the friction welding of the lower part 2 and upper part 3, whereby the introduction of the transfer openings 22, 23 is simplified. The location and number of the transfer openings 22 is not limited and can be made almost arbitrary requirements for the coolant. The position and the number of the transfer openings 23 is limited to the trough-shaped recess 19. As shown in Figures 1 and 2, the cooling channels 8, 9 enclosed by walls of almost equal wall thickness. This measure advantageously improves the heat dissipation and optimizes the structural strength of the piston 1.

Figures 3 to 7 show the piston 31, which is designed to the piston 1 according to Figures 1 and 2 alternatively.

For the production of the piston 31 according to FIG. 3, an inner cooling space 38a is first introduced in a central inner area 53 of the upper part 33. An inner wall of the cooling chamber 38a extends at a distance from the contour of the combustion bowl 35. Furthermore, at least one, the cooling chamber 38a connected to the cooling channel 39 crossing opening 45 is introduced into a wall defining the inner cooling chamber 38a. Alternatively to the obliquely ascending transfer opening 45, this can be made in any shape or position. The lower part 32 and the upper part 33 each have a joining region 41a, 41b, which together form a Form joining plane 40, via which both components are connected by means of a friction welding.

Due to a sufficient distance from the joining plane 40, the transfer opening 45 is not influenced by the self-adjusting welding beads 42, 43 of the friction welding. After welding, the ring field 34 is bent from a not shown in Figure 3 swung-out position into the end position in which a Mantelfäche the ring field 34 concentric with the axis of symmetry 52 of the piston 31, which coincides with the outer contour of the piston skirt 36 simultaneously. Thus, the ring field 34 bounded on the outside of the outer cooling channel 39. The Wälzdrückverfahren ensures a seal of an arc-shaped joint 46, which adjusts between the ring field 34 and the piston skirt 36. The inner cooling space 38a is bounded downward, pointing in the direction of the pin bore 37, by a base 47 integrally connected to the base 32. In order to apply coolant to the cooling space 38a, the floor 47 is provided with at least one central transfer opening 44.

According to FIG. 4, the piston 31 has no joining plane. In an intermediate stage of the production process, not shown, the ring field 34 is pivoted, so that the transfer opening 45 can be introduced without special tools, before the bending of the ring field 34 takes place. For the lower delimitation of the inner cooling chamber 38b is a disc-like, preferably made of sheet metal cover member 48 is provided, which is permanently attached by means of a weld or a clamp on the piston wall. For the purpose of applying coolant, at least one transfer opening 44 is introduced into the cover element 48.

FIG. 5 shows the piston 31, which, in contrast to FIG. 4, encloses a cup-shaped cover element 49 and closes the inner cooling space 38b. The covering element 49, which can advantageously be produced without cutting by a deep drawing process, is assigned to the upper hub region 50 of the piston 31. For attachment is a weld or braze or alternatively a Clamping connection with which the cover 49 can be fixed non-positively to the hub 50.

According to Figure 6, the piston 31 comprises an inner cooling channel 38c, which is preferably made mechanically. For this purpose, an annular channel is introduced into the upper hub region and in the perpendicular region 51, which is open in the direction of the combustion bowl 35. FIG. 7 shows the piston 31 according to FIG. 6 in a half-sectional view offset by 90 °, which illustrates that the region 51 and, consequently, the cooling channel 38c are arranged circumferentially. Furthermore, FIGS. 6 and 7 show the piston 31 with differently oriented transfer openings 45.

LIST OF REFERENCE NUMBERS

1st piston 31st piston

2. lower part 32nd lower part

3. Upper part 33. Upper part

4th ring field 34th ring field

5. Burner trough 35. Burner trough

6. Piston shaft 36. Piston shaft

7. Bolt hole 37. Bolt hole

8. Cooling channel 38a. refrigerator

9. Cooling channel 38b. refrigerator

10. Joining plane 39c. cooling channel

11. Joining level 39. Cooling channel

12. Joining plane 40. Joining plane

13. Welding bead 41a. joining area

14. Weld bead 41 b. joining area

15. Welding bead 42. Welding bead

16. Welding bead 43. Welding bead

17a. Joining area 44. Passage opening

17b. Joining area 45. Crossing opening

17c. Joining area 46. Fugue

18a. Joining area 47. Floor

18b. Joining area 48. Cover element

18c. Joining area 49. Cover element

19. Section 50. Trough edge

20. Symmetry axis 51. Trough edge

21. Section 52. Symmetry axis

22. Transfer opening 53. Interior

23. Transfer opening

Claims

1.

A method of making a steel piston (1) for an internal combustion engine, embodied as a one-piece small-height coolant channel having at least two cooling channels (8, 9) including a base (2) and a top (3) over at least one corresponding joining plane (11) supported and connected by means of a joining method, in particular a friction welding, characterized in that the piston (1) an inner, in a region above the pin bore (7) having a trough-shaped geometry (19), by a mechanical Processing, by forging or by casting produced cooling chamber (8), and an outer, to a ring field (4) of the piston (1) spaced cooling channel (9), wherein the cooling channel (8) at least one transfer opening (23) to the outer cooling channel (9), which opens into the trough-shaped portion of the cooling space (8) and at least one transfer opening (22) in the Piston inner mold opens, wherein the bores before the friction welding of the at least one joining plane (11) are introduced into the piston (1).

Second

Piston (1) produced by the method according to claim 1, characterized in that the upper part (3) and the lower part (2) via exactly three corresponding joining planes (10,11, 12) by means of a joining method, in particular a friction welding, are connected , wherein the walls of the joining planes form subregions of the walls of the two cooling channels (8, 9).

Third

Piston (1) produced by the method according to claim 1, characterized in that the trough-shaped portion (19) of the inner Cooling channel (8) in the region of a pin bore (7) is approximately vertically aligned, and at the end an angled, obliquely to an axis of symmetry (20) of the piston (1) aligned portion (21) adjoins.

4th

Piston according to claim 2 or 3, characterized in that the cooling channels (8,9) are arranged in regions in the lower part (2) and in the upper part (3) of the piston (1).

5th

Piston according to claim 2 or 3, characterized in that the cooling channels

(8.9) are enclosed by walls of almost equal wall thickness.

6th

Piston according to claim 2 or 3, characterized in that the cooling channels (8,9) spaced from a contour of the combustion chamber trough (5) following in the piston (1) are introduced.

7th

Piston according to claim 2 or 3, characterized in that the cooling channels (8,9) associated with the transfer openings (22,23) are associated with the lower part (2) of the piston (1).

8th.

A method of manufacturing a one-piece, in particular forged, steel cooling duct piston for an internal combustion engine, which includes a roll-pressing method, wherein the piston (31) enclosing at least one outer and one inner cooling channel (8, 9) includes a ring field (34) formed by bending in a final position is brought, characterized in that by means of a mechanical processing or in conjunction with a cover (48, 49) in an inner region (53) of the piston (31) an inner cooling chamber (38 a, 38 b) or an inner cooling channel (38 c ) is introduced, the radially spaced an outer cooling channel (39) is assigned, wherein at least one transfer opening (45) connects the outer cooling channel (39) with the inner cooling channel (38c) or inner cooling space (38a, 38b).

9th

The method of claim 8, wherein the piston (31) includes a base (32) and a top (33) characterized by the following steps of manufacturing the piston (31),

Inserting the inner cooling channel (38c) or the inner cooling chamber (38a, 38b),

Welding at least one joining plane (40) between the lower part (32) and the upper part (33),

Inserting at least one transfer opening (45) which connects the inner cooling space (38a, 38b) or the inner cooling passage (38c) to the outer cooling passage (39),

- Turning the ring field (34) in its final position.

10th

Piston produced by the method according to claim 8 or 9, characterized in that a circumferential, a groove enclosing collar (51) on the dome-shaped inner portion (53) forms the inner cooling channel (38c).

11th

Piston produced according to the method according to claim 8, 9 or 10, characterized in that, for forming the inner cooling space (38a, 38b), the inner area (53) of the piston (31) points to a pin bore (37), one in the piston ( 31) used, at least one crossing opening (44) having cover (48,49) is limited.

12th

Piston according to claim 11, characterized in that for the attachment of the cover (48,49) a positive and / or non-positive or cohesive connection is provided.

13th Piston according to claim 11, characterized in that a disc-like or cup-shaped cover member (48,49) closes the inner cooling chamber (38a, 38b).

14th

Piston according to claim 2 or 3 or according to claim 11, characterized in that the outer cooling channel (9, 39) has a ring field (4, 34) exceeding the longitudinal extent.