WO2011018142A1

WO2011018142A1 - Bore profile for a piston pin bearing

Info

Publication number: WO2011018142A1
Application number: PCT/EP2010/004227
Authority: WO
Inventors: Volker Gniesmer
Original assignee: Ks Kolbenschmidt Gmbh
Priority date: 2009-08-11
Filing date: 2010-07-12
Publication date: 2011-02-17
Also published as: EP2464900A1; DE102009036784A1

Abstract

The invention relates to a bearing of a piston pin (11) in a piston (1) of an internal combustion engine, by way of which a connecting rod (2) is hinged to the piston (1). To this end, a piston shaft (8) is provided with two mutually spaced piston pin hubs (9), each having a hub bore (10), designed to receive the piston pin (11), which at the same time is guided through a bore (12) of a connecting rod eye (13). Each bore (10, 12), at least in a portion, has a bore profile (14) that deviates from a cylindrical shape and has an asymmetric precision geometry. In the circumferential direction, the bore profile (14) thus includes at least one superimposed ovality (15, 16), which in a bore inlet (19) and/or a bore outlet (20) between an X-axis and a Y-axis has a deviating contour. Likewise, in at least one section adjacent to the X-axis and/or the Y-axis, the bore profile (14) has a different design as compared to a corresponding opposing section. Furthermore, in an internal portion (21), the contour of the bore profile (14) deviates from that of the bore inlet (19) and/or the bore outlet (20).

Description

Bore profile for a piston pin bearing

description

The invention relates to the mounting of a piston pin in a piston, via which a connecting rod is pivotally connected to the piston. For this purpose, a piston skirt on two spaced piston pin bosses, in each of which a hub bore is introduced, which are intended to receive the piston pin, which is guided simultaneously through a bore of a connecting rod eye. Each bore includes in at least a portion of a deviating from a cylindrical shape bore profile.

In internal combustion engines with a crank mechanism, the connecting rod connects the piston with the crankshaft. In two spaced-apart hub bores of the piston, a piston pin is mounted on the outside, which is further guided by a connecting rod eye of the connecting rod, while the connecting rod with another large connecting rod eye encloses a crank pin of the crankshaft. Due to the crank mechanism, the hub bores and the bore in the connecting rod eye are subjected to tensile, compressive and bending stress both horizontally and in the vertical plane, in particular in the zenith and nadir. In the operating state, the crank rocking plane is loaded by gas forces acting on the piston head, whereby changing, directed in the pressure side and the counter-pressure side different lateral forces on the piston and on the connecting rod. A transfer of the gas forces takes place from the piston via the piston pin bosses on the piston pin and then into the connecting rod. This results in a periodic elastic deformation of the piston pin. Due to increased combustion pressures, the surface pressure increases in the area intended for receiving the piston pin Holes. Exceeding limit values causes consequential damage, such as material cracks or pin gap fractures, which lead to a limited service life or premature failure of the piston. The greatest stress of the piston pin is established in the region of a Boio crown, a combustion chamber-side main load zone of the piston. It is known, due to the adjusting in the operating state tensile and compressive forces and the resulting deformations of the piston pin to make geometric changes to relieve the piston pin bearing and to do the holes in the piston pin bosses not exactly cylindrical.

In order to avoid inadmissible deformation in the bores of the piston pin bosses due to mechanical and thermal loads, a piston is known from DE 44 31 990 A, in which the hub bores are designed as a form of holes. As a measure to give the piston pin more room for deformation, an oval hub bore is proposed according to DE 16 50 206 A1, in which the large axis of the oval is transverse to the longitudinal axis of the piston. This should be achieved at the same time the improved seizure safety between the piston pin and the holes in the piston pin bosses. From DE 102 22 463 A1 a high ovality of the hub bore executed in the hub region is known, in which the generatrix of the oval arranged in the zenith of the piston pin hub runs parallel to the hub bore axis. This is to ensure that the lying outside the piston axis lateral areas of the hub bore are charged higher. The solutions according to the known prior art try to compensate for the deformation of bores of the piston pin bosses by these sections are designed to be oval. A shape of the bore, which maps exactly the deformation of the piston pin and the hub bore in the load case, can not be achieved with the solutions according to the prior art. On top of that, for the Hole in the connecting rod so far no deformations in the operating condition adapted bore profiles are proposed.

The invention is based on the object to provide a load of the piston pin corresponding load and deformation-oriented bore profile for the hub bores of the piston and the connecting rod bore.

To solve the problem it is proposed according to claim 1 that the holes in the piston pin bosses and / or the bore in the connecting rod in the circumferential direction is at least a double ovality superimposed to form a bore profile with an asymmetric fine geometry. The asymmetrical fine geometry according to the invention, which is designed as a mold bore, forms a bore profile which has areas in a bore entry and / or in a bore exit that are deviated between an X-axis and a Y-axis. Another inventive design criterion provides that at least one of the X-axis and / or the Y-axis adjacent portion of the bore profile to the associated opposite portion in the bore inlet and / or in the hole outlet is designed differently. In addition, the bore profile according to the invention comprises an inner cylindrically shaped or deviating from a cylindrical portion, which differs from the profiling of the bore entry and / or the bore exit. The inventive measures advantageous for the piston pin specific bore profiling can be realized in the piston pin bosses and / or the connecting rod, which is adapted to any temperature-induced and load-dependent deformation of the piston and the piston pin. A preferred design provides that the superposed ovality, in particular the bolt deformation is adjusted taking into account the lateral forces. For this purpose, the asymmetric bore profile according to the invention offers the possibility to Achieving an advantageous higher component load capacity of the piston to optimize a distribution of forces in the direction of the pressure side (DS) and the counter-pressure side (GDS). This results in an improved mechanical performance, combined with significantly reduced mechanical stresses in the piston, which in particular stress-dependent, undesirable deformations or contact pressures of the bolo-vertex in the hub bores and / or the connecting rod bore omitted. The bore profiling according to the invention simultaneously improves the piston life and also has a positive influence on the noise formation of the piston pin bearing.

A preferred embodiment of the invention provides that at least one bore has an asymmetrical bore profile to which a multiple, i. more than double ovality is superimposed in the circumferential direction. The ovality or the ovality of the bore profile are aligned in the respective bore of the piston hub and / or the connecting rod, in particular at an angle of 45 ° to the X and Y axis.

Furthermore, it is provided according to the invention to place the asymmetry of the bore profile of at least one bore preferably in the direction of a pressure side (DS) of the piston in order to optimize a pressure distribution in the pressure-loaded zone targeted. Alternatively, according to the invention, the asymmetric fine geometry in the direction of the pressure side (DS) and / or in the direction of the counterpressure side (GDS) can be arranged in the bores of the piston hubs and / or in the bore of the connecting rod eye. The staggered ovalities of the asymmetrical bore profile between the pressure side (DS) and the counter-pressure side (GDS) are formed according to the invention geometrically deviating. A preferred embodiment of the invention provides a stepped ovality, in which an outer region increases in several sections, each section adjoining the preceding section in a continuous manner. Furthermore, the asymmetrical fine geometry according to the invention includes, at least in the bores of the piston hubs, a radial widening designed as an oblique trumpet shape in end zones of the bores. This aligned in particular to the piston crown and / or crankshaft inner contour advantageously forms a uniformly radially expanded trumpet-shaped course, which is adapted to a deflection or elastic deformation of the piston pin in the operating state, the trumpet-shaped course both circumferentially and between the bore inlet and the bore outlet deviating can be executed. In addition, the invention also includes trumpet-shaped flared end zones of the bore in the connecting rod eye.

The asymmetrical fine geometry including bore profile according to the invention is further designed so that a setting from a center of the bore to a bore inner wall dimension X1 of the X-axis coincides or differs from a dimension Y1 of the Y-axis. The geometric design of the bore profile according to the invention also provides that the first as well as the second ovality is defined by a deviating from a cylindrical shape radial inner dimension and a radial outer dimension. The inner dimensions and the outer dimensions of each ovality are according to the invention designed to coincide or deviate from each other. Furthermore, the dimensions of the first ovality differ from the dimensions of the second ovality. This diversity of design makes it possible to provide an optimum stress and deformation-commensurate bore profile for the hub bores of the piston and the connecting-rod bore corresponding to the load of the piston pin.

In the following the invention will be explained in more detail with reference to an embodiment with reference to four drawings. Show it:

FIG. 1 shows a sectional view of a piston according to the invention,

FIG. 2 shows a front view of a hub bore designed according to the invention;

FIG. 3 shows the hub bore according to FIG. 2 in a sectional view 3-3,

FIG. 4 shows the hub bore according to FIG. 2 in a sectional view 4-4.

FIG. 1 shows a piston 1 in connection with a connecting rod 2 in a sectional view. A piston upper part 3 of the piston 1 comprises a piston head 4 with integrated combustion chamber trough 5 and forms on the outside a flank 6 adjoining the piston head 4, to which a piston ring field 7 adjoins. In a piston lower part forming a piston skirt 8, two diametrically opposed piston pin bosses 9 are arranged, in each of which a hub bore 10 is introduced. The hub bores 10 are intended for receiving a piston pin 11, via which the piston 1 is pivotally connected to the connecting rod 2. The piston pin 11 is further guided by a bore 12 of a connecting rod 13. In the operating state of the internal combustion engine, the piston 1 is periodically acted upon by a gas force in the arrow direction, which is transmitted via the piston pin 11 to the connecting rod 2. This results in an elastic deformation or deflection of the piston pin 11. For this purpose, the hub bores 10 and the bore 12 in the connecting rod 13 are profiled accordingly, especially in a bore inlet and a bore outlet locally expanded radially. The hub bores 10 form a bore profile 14 for this purpose.

FIG. 2 shows the hub bore 10 shaped as a shaped bore on an enlarged scale, as a result of which the asymmetric fine geometry of the hub bore 10 is shown Hole profile 14 is illustrated, which is superimposed in the circumferential direction of a double ovality. For this purpose, the bore profile 14 is designed circumferentially in several areas deviating from a cylindrical shape and includes largely by 90 ° staggered ovalities 15, 16 which at an angle α1, α2 in each case by 45 ° to an X-axis or Y- Axis are arranged. The first ovality 15 oriented at an angle α ₂ to the X axis includes a radial inner dimension OV1 deviating from a cylindrical shape and a radial outer dimension OV3. The second ovality 16 oriented at an angle αi to the X axis includes a radial inner dimension OV2 deviating from a cylindrical contour and a radial outer dimension OV4. The ovalities 15, 16 are arranged such that the radial inner dimensions OV1, OV2 of a pressure side (DS) and the radial dimensions OV3, OV4 of a counter-pressure side (GDS) of the piston 1 are assigned. The asymmetric fine geometry of the bore profile 14 comprises different dimensions OV1 and OV3 of the ovality 15 and different dimensions OV2 and OV4 of the ovality 16. In addition, the ovalities 15, 16 also differ in their design. Regardless of the shape, the bore profile 14 includes stepless, rounded transitions between the ovalities 15, 16 so that each section joins steplessly to the next section or degree of ovality. The bore profile 14 also comprises an X-axis dimension X1, which adjusts itself between a bore inner wall 17 and a bore center 18 and which differs from the Y-axis distance measure Y1 offset by 90 °.

FIG. 3 shows the bore profile 14 of the hub bore 10 in a view according to the section line 3-3 of FIG. 2. The hub bore 10 is radially widened both on a bore inlet 19 assigned to the piston skirt 8 and on the bore outlet 20 directed to the connecting rod eye 13, correspondingly an adjusting elastic deformation of the piston pin 11 in the operating state of the internal combustion engine. The dimensions of all radial extensions A1, A2, B1, B2 are designed to differ from each other. The widenings A1, B1 facing the pressure side (DS) exceed the opposite widenings A2, B2 associated with the counterpressure side (GDS). In addition, the widenings A1, A2 of the bore exit 20 exceed the widenings B1, B2 of the bore entry 19. Regardless of the size or extension, all radial widenings A1, A2, B1, B2 each form a stepless rounded contour or transition to a largely centered setting cylindrical section 21 of the hub bore 10. To illustrate the radial widening of the course of the cylindrical portion 21 is shown in phantom over the entire length of the hub bore 20.

FIG. 4 shows the bore profile 14 of the hub bore 10 in a view according to a section line 4-4 according to FIG. 2. In accordance with FIG. 3, the dimensions of all the radial extensions A1, A3; B1, B3 designed differently from each other. The widenings A1, B1 aligned in the direction of the piston crown 4 exceed the opposite widenings A3, B3 assigned to the connecting rod 2. In addition, the expansions A1, A3 facing the bore outlet 20 are designed to be larger than the widenings B1, B3 of the bore inlet 19.

LIST OF REFERENCE NUMBERS

1 piston

2 connecting rods

3 piston upper part

4 piston bottom

5 combustion bowl

6 lancet

7 ring field

8 piston stem

9 piston pin hub

10 hub bore

11 piston pin

12 hole

13 connecting eye

14 bore profile

15 ovality

16 ovality

17 bore inner wall

18 bore center

19 hole entry

20 hole exit

21 subarea

Claims

Bore profile for a piston pin bearing claims

1. Bearing of a piston pin (11) in a piston (1) of an internal combustion engine, via which a connecting rod (2) with the piston (1) is articulated, wherein a piston shaft (8) has two spaced, diametrically opposed piston pin bosses (9) each having a hub bore (10) which is intended to receive the piston pin (11) which is guided simultaneously through a bore (12) of a connecting rod eye (13) and each bore (10; 12) at least locally deviates from a cylindrical shape Bore profile (14), characterized in that for forming an asymmetric fine geometry of the bore profile (14) at least one bore (10, 12) of the piston pin bosses (9) and / or the connecting rod eye (13),

^Includes in the circumferential direction at least a double superposed ovality (15, 16),

^■ in a bore inlet (19) and / or in a bore outlet (20) is profiled in deviation between an X axis and a Y-axis,

^■ is configured differently in at least one of the X-axis and / or the Y-axis adjacent section to an associated opposite section,

^■ having an inner portion (21) which is profiled differently from the bore inlet (19) and / or the bore outlet (20).

2. Bearing of a piston pin according to claim 1, characterized in that at least one bore (10, 12) has an asymmetrical bore profile (14). having more than double ovality superimposed in the circumferential direction.

3. Bearing of a piston pin according to one of claims 1 or 2, characterized in that the ovality (15, 16) of the bore profile (14) of the hub bore (10) at an angle α1, α2 to the X-axis and the Y- Axis is arranged.

4. Bearing of a piston pin according to one of the preceding claims, characterized in that the asymmetry of the bore profile (14) at least one bore (10, 12) in the direction of a pressure side (DS) of the piston (1) is placed.

5. Bearing of a piston pin according to one of the preceding claims, characterized in that two staggered ovalities (15, 16) of the bore profile (14) between the pressure side (DS) and the counter-pressure side (GDS) are formed geometrically deviating.

6. Bearing of a piston pin according to one of the preceding claims, characterized in that the degree of ovality (15, 16) increases in several sections, each section adjoins the previous section continuously.

7. Bearing of a piston pin according to one of the preceding claims, characterized in that the asymmetric fine geometry of at least one bore (10, 12) in the region of the bore inlet (19) and / or the bore outlet (20) designed as a crooked trumpet shape radial expansion (A1 , A2, A3, B1, B2, B3).

8. Bearing of a piston pin according to one of the preceding claims, characterized in that a dimension X1 of the X-axis from a bore center (18) to a bore inner wall (17) is designed equal to or different from a dimension Y1 of the Y-axis.

9. Bearing of a piston pin according to one of the preceding claims, characterized in that a first ovality (15) deviates from a cylindrical shape radial inner dimension OV1 and a radial outer dimension OV3, wherein the dimension OV1 equal or not equal to the dimension OV3 can be interpreted.

10. Bearing of a piston pin according to one of the preceding claims, characterized in that a second ovality (16) deviates from a cylindrical shape radial inner dimension OV2 and a radial outer dimension OV4, wherein the dimension OV2 equal or not equal to the dimension OV4 can be interpreted.

11. Bearing of a piston pin according to one of the preceding claims, characterized in that the dimensions OV1, OV3 of the ovality (15) are designed unequal to the dimensions OV2, OV4 of the ovality (16).