Roller tappet for a pump or valve train of an internal combustion engine

Abstract

The invention relates to a roller tappet for a pump or valve train of an internal combustion engine, having a cylindrical housing (1) into which, starting from one axial end, a cam roller (2) for picking up a cam lift movement from a camshaft of the internal combustion engine is at least partially received, characterized in that for arranging the cam roller (2) in the housing (1), the latter is widened in the corners by a recess (10 to 13, 17 to 20) on the inside of the housing (1) in a manner adapted to the quadrangular shape of the cam roller (2) in plan view, such that the cam roller (2) is rotatable about a roller axis (6) and is received in the recesses (10 to 13, 17 to 20) with the roller edges (14, 15) formed at its axial ends, without contact.

Description

[0001] The invention relates to a roller tappet for a pump or valve train of an internal combustion engine according to the type defined in more detail in the preamble of claim 1.

[0002] From DE 10 2017 107 100 B3 a multi-part roller tappet for a high-pressure fuel pump is known, which is guided in a housing receptacle in the direction of its longitudinal axis and is driven by cams of a camshaft so as to be displaceable in the longitudinal direction.

[0003] The invention is therefore based on the object of proposing a roller tappet of the aforementioned type which, in a structurally simple manner, enables a space-saving and operationally reliable accommodation of a cam roller.

[0004] The problem is solved by the features of claim 1. Further advantageous and claimed embodiments emerge from the respective subclaims, the description, and the drawings.

[0005] Thus, a roller tappet for a pump or valve train of an internal combustion engine is proposed. The roller tappet has a cylindrical housing into which, starting from one axial end, a cam roller for picking up a cam lift movement from a camshaft of the internal combustion engine is at least partially accommodated. In order to accommodate the cam roller in the housing in a structurally simple manner and in a space-saving manner, it is provided that, for the arrangement of the cam roller in the housing, the housing is widened in each of the corners by a recess on the inside of the housing, adapted to the rectangular shape of the cam roller in plan view, such that the cam roller is rotatable about a roller axis and is accommodated in the recesses with the roller edges formed at its axial ends without contact.

[0006] As a result, the additional clearances in the corners on the inside of the housing easily create additional space for the cam roller, into which the roller edges can protrude in the area where it requires the most space. This achieves optimal clearance for the cam roller in the housing in a space-saving manner. Accordingly, for given external dimensions of the housing, a cam roller with a larger outer diameter and / or axially wider can be arranged in the housing in a space-saving manner. This enables the absorption of larger radial forces while maintaining the maximum permissible Hertzian pressure at the line contact between the cam roller and a cam of the camshaft, thus increasing the power density.

[0007] In addition, a larger outer diameter of the cam roller reduces the cam roller speed under the same drive conditions on the camshaft, thus increasing its service life. Furthermore, an enlarged chamfer on the edges of the cam roller can prevent or minimize damage caused by impact marks during transport.

[0008] Furthermore, in order to avoid stress peaks during operation at the edges of the cam roller, a profile provided on the outer circumference of the cam roller can be further optimized for contact with the camshaft over a larger width of the cam roller and damage caused by edge supports can be reliably avoided.

[0009] Alternatively, it is possible to reduce the outer dimensions of the housing while keeping the same dimensions of the cam roller and thus reduce the installation space required for the roller tappet in the internal combustion engine.

[0010] A preferred particularly simple embodiment of the invention can be achieved if the clearances, starting from the aforementioned axial end of the housing, each form a radial recess on the inside of the housing, which runs as a groove in the axial direction.

[0011] In a further preferred embodiment of the invention, the clearances each form a radial through-opening on the housing, which is arranged in the area where the cam roller requires the most space to accommodate the roller. The area where the cam roller requires the most space is where it protrudes into the housing with its greatest radial width. The cam roller can thus be arranged in the housing with the roller edges protruding into the through-openings, saving installation space.

[0012] A particularly advantageous development of the invention allows the housing design to be further optimized with regard to the installation space required and the cam roller clearance within the housing. For this purpose, a radial through-hole is provided in the housing in the area of ​​the recesses where the cam roller requires the most space, allowing the cam roller to be accommodated contactlessly at the roller edges.

[0013] In this way, in addition to the installation space created by the recesses for accommodating the cam roller at the through holes, axial play of the cam roller along the roller axis and radial play from the radial bearing of the cam roller can be compensated for without contact in the housing. Furthermore, symmetry errors and coaxial deviations can be compensated, manufacturing tolerances optimized, and production costs reduced. The through holes can be manufactured particularly easily and cost-effectively from the outside of the housing.

[0014] Preferably, the radial through holes are arranged at the level of the cam roller axis. This optimally positions them in the area where the cam roller requires the most space.

[0015] It is also conceivable to provide, instead of the respective through-opening, a radial recess extending from the inside of the housing in the area where the cam roller requires the greatest space, to accommodate the cam roller at the roller edges.

[0016] It is also advantageous if the recesses preferably form a circular cross-sectional profile in the axial plan view. This makes them particularly easy to manufacture.

[0017] In a further preferred embodiment of the invention, it is provided that, for arranging the cam roller in the housing, the latter forms a receptacle starting from said axial end with a square shape adapted to the shape of the cam roller in the axial plan view, and a clearance is provided in each of the corners on the inside of the housing.

[0018] The cutouts are preferably created in a particularly simple and cost-effective manner by drilling. Alternatively, they can also be created, in particular, by milling.

[0019] The proposed roller tappet can also be used as a bucket tappet for a pump or valve train of an internal combustion engine. It is particularly advantageous for use in passenger cars or trucks.

[0020] Further claimed features of the invention will become apparent from the following description and the drawings, which further explain the present invention. They show: Fig. 1 a roller tappet according to the invention in a first embodiment, Fig. 2 the roller tappet in a longitudinal section, Fig. 3 a plan view of the cam roller arranged in the roller tappet, Fig. 4 a cross-section of the roller tappet at the level of the roller axis of the cam roller, Fig. 5 a roller tappet according to the invention in a second embodiment, Fig. 6 the roller tappet Fig. 5 in a longitudinal section, Fig. 7 the roller tappet Fig. 5 a cross-section at the level of the roller axis of the cam roller, Fig. 8 a perspective view of the roller tappet housing from Fig. 5, Fig. 9 a cross-section of the roller tappet housing Fig. 4 at the level of the roller axis.

[0021] The figures show various views and embodiments of a roller tappet according to the invention for a pump or valve train of an internal combustion engine by way of example.

[0022] The Fig. The roller tappet shown in Figures 1 to 4 in a first exemplary embodiment has an elongated cylindrical housing 1, into which a cam roller 2 is accommodated from one axial end for tapping a cam lift movement from a camshaft (not shown) of the internal combustion engine. The housing 1 serves to guide the roller tappet longitudinally along an imaginary cylindrical or longitudinal axis 3 of the housing 1 in a tappet guide (not shown), in particular a bore, in a stationary component in the internal combustion engine. The cylindrical or longitudinal axis 3 simultaneously forms the central axis of the housing 1.

[0023] Starting from a drive-side axial end, the housing 1 is designed with a receptacle 4 in which the cam roller 2 is arranged in the housing 1. The receptacle 4 has a quadrangular shape in the axial plan view, adapted to the shape of the cam roller 2. The cam roller 2 is rotatably mounted on a cam roller pin 5 about a cam roller axis 6, wherein the cam roller pin 5 is supported with its ends in aligned opposite receiving bores 7, 8 on the housing 1 ( Fig. 1 and Fig. 2). The cam roller 2 protrudes slightly from the housing 1 for cam contact with the camshaft. A plain bearing is provided as the cam roller bearing. The roller tappet serves to pick up a cam stroke movement on the cam roller 2 and to transmit this at the output-side end 9 of the housing 1, for example, to a high-pressure pump piston (not shown) in a pump drive. The housing 1 is constructed in one piece.

[0024] The receptacle 4 forms four corners on the inside or inner shell of the housing 1. The four corners are each radially widened by a recess 10, 11, 12, 13 on the inside of the housing 1. The latter are designed such that the cam roller 2 is rotatable about the cam roller axis 6 with the roller edges or edges 14, 15 formed at its axial ends, receiving it in the recess 10, 11, 12, 13 without contact or protruding into the latter ( Fig. 3 and Fig. 4). Fig. 4 shows the roller tappet in cross-section with a cutting plane at the axial height of the cam roller axis 6 or the cam roller pin 5. There, the cam roller 2 projects into the housing 1 with the greatest radial width and thus requires the greatest space in the housing 1. After Fig. 4, the cam roller 2 with the roller edges 14, 15 projects into the clearances 10, 11, 12, 13 without contact.

[0025] The reliefs 10, 11, 12, 13 are each designed as a radial recess or bulge on the inside of the housing 1, which forms a circular arc-shaped cross-sectional profile and runs axially in the direction of the cylinder and longitudinal axis 3 in the area of ​​the cam roller 2 as a groove ( Fig. 2). Thus, the reliefs 10, 11, 12, 13 can be easily and cost-effectively produced by drilling. The receptacle 4 is axially limited in the direction of the cylinder and longitudinal axis 3 by a base 16, adapted to the space requirements of the cam roller 2. The reliefs 10, 11, 12, 13 are axially limited inwardly above the base 16 by a blind hole.

[0026] The additional clearances 10, 11, 12, 13 create additional space at the corners of the housing 1 to accommodate the cam roller 2. Accordingly, for given external dimensions of the housing, a cam roller 2 with a larger outer diameter and / or axially wider in the direction of the cylinder or longitudinal axis 3 can be arranged in the housing 1 in a space-saving manner. This enables the absorption of larger radial forces while maintaining the maximum permissible Hertzian pressure at the line contact on the outer diameter of the cam roller 2 between the latter and the cam of the driving camshaft, and increases the power density at the roller tappet.

[0027] In addition, a larger outer diameter of the cam roller 2 can reduce the cam roller speed under the same drive conditions on the camshaft, thus increasing the service life. Furthermore, an enlarged chamfer 17 on the edges formed on the roller edges 14, 15 of the cam roller 2 can prevent or minimize any damage caused by impact points during transport. To avoid stress peaks during operation on the edges 14, 15 of the cam roller 2 and the resulting damage caused by edge supports, it is possible to form and optimize an appropriate profile on the outer circumference of the cam roller 2, for example a slightly crowned design for contact with the camshaft, over a larger width of the cam roller 2.

[0028] It is also conceivable to reduce the external dimensions of the housing 1 while keeping the same dimensions of the cam roller 2 and thus to reduce the installation space required for the roller tappet in the internal combustion engine.

[0029] In Fig. Figures 5 to 9 show a second embodiment of a roller tappet according to the invention, in which the design of the housing 1 is further optimized with regard to the installation space requirement and the clearance of the cam roller 2 in the housing 1. For this purpose, a radial through-opening 18, 19, 20, 21 is provided on the housing 1 in the region of the recesses 10, 11, 12, 13 at the level of the cam roller axis 6. In this way, the through-openings 18, 19, 20, 21 are arranged in the area where the cam roller 2 requires the greatest space and can additionally accommodate the roller edges 14, 15.

[0030] The axial height of the cam roller axis 6 is indicated by a dashed line and refers to the direction of the cylinder and longitudinal axis 3 ( Fig. 5 and Fig. 8). For further clarification, the cross sections of the roller tappet and the housing 1 are shown in Fig. 7 and Fig. 9 each with the cutting plane exactly at the axial height of the cam roller axis 6.

[0031] Due to the arrangement of the additional radial through-openings 18, 19, 20, 21, the cam roller 2 can be connected to the roller edge 14 as in Fig. 7, shown as an example, with maximum axial play X along the cam roller axis 6 and with maximum radial play R, each protruding from the radial bearing into the through-hole 20 without contact. In this way, the axial and radial play X, R of the cam roller 2 in the through-holes 18, 19, 20, 21 can be easily compensated in the housing 1 in a space-saving manner. In addition, symmetry errors, in particular at the through-holes 7, 8 for receiving the cam roller pin 5, and coaxial deviations can be compensated at the through-holes 18, 19, 20, 21 in the housing 1.

[0032] This also allows for optimized manufacturing tolerances and reduced production costs. The through-holes 18, 19, 20, and 21 can be manufactured particularly easily and cost-effectively from the outside of the housing 1. They are preferably produced by drilling. Milling is also conceivable.

[0033] The cam roller bolt 22 is a particularly lightweight hollow bolt and the plain bearing of the cam roller 2 is designed with an intermediate ring 23. For further information, please refer to the description of Fig. 1 to 4.

[0034] The housing 1 is essentially thin-walled with reduced mass and a lightweight construction, manufactured simply and cost-effectively by cold extrusion. Wall thicknesses of 1 to 1.5 mm are preferably achieved. The lightweight construction increases the dynamics of the roller tappet during operation. The previously described through openings 18, 19, 20, 21 on the housing 1 also improve the extrusion properties of the material in the thin-walled area during production. List of reference symbols 1 housing 2 cam roller 3 cylinder or longitudinal axis 4 Recording 5 cam roller bolts 6 Cam roller axis 7 mounting hole 8 mounting hole 9 output end 10 Release, recess, groove 11 Release, recess, groove 12 Release, recess, groove 13 Release, recess, groove 14 Roll edge, edge 15 Roll edge, edge 16 Floor 17th phase 18 Exemption, passage opening 19 Exemption, passage opening 20 Exemption, passage opening 21 Exemption, passage opening 22 cam roller bolts 23 intermediate ring X Axial play R radial clearance QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2017 107 100 B3

[0002]

Claims

[1] Roller tappet for a pump or valve train of an internal combustion engine, comprising a cylindrical housing (1) in which a cam roller (2) for taking off a cam stroke movement from a camshaft of the internal combustion engine is at least partially received starting from an axial end, characterized by , that for the arrangement of the cam roller (2) in the housing (1) the housing (1) is adapted to the square shape of the cam roller (2) in the top view by means of a recess (10 to 13, 17 to 20) on the inside of the housing (1) such that the cam roller (2) is rotatably received about a roller axis (6) with the roller edges (14, 15) formed at its axial ends in the recesses (10 to 13, 17 to 20) without contact. [2] Roller plunger according to claim 1, characterized by, that the cutouts (10, 11, 12, 13) starting from the end of the housing (1) each form a radial recess on the inside of the same, which runs as a groove in the axial direction. [3] Roller plunger according to one of claims 1 or 2, characterized by , that the clearances (17, 18, 19, 20) each form a radial through-opening on the housing (1) in the area of ​​the greatest space requirement of the cam roller (2) to accommodate it at the roller edges (14, 15). [4] Roller plunger according to one of claims 2 or 3, characterized by , that in the area of ​​the recesses (10, 11, 12, 13) in the area of ​​the greatest space requirement of the cam roller (2) a radial through-opening (17, 18, 19, 20) is provided on the housing (1) for receiving the cam roller (2) at the roller edges (14, 15). [5] Roller plunger according to one of claims 3 or 4, characterized by, that the radial through-openings (17, 18, 19, 20) are each arranged at the level of the cam roller axis (6). [6] Roller plunger according to any one of claims 2 to 5, characterized by , that the depressions (10, 11, 12, 13) form a circular arc cross-sectional profile in the axial plan view. [7] Roller plunger according to any one of claims 1 to 6, characterized by , that for the arrangement of the cam roller (2) in the housing (1) the housing forms a receptacle (4) starting from the axial end with a square shape adapted to the cam roller (2) in the axial top view and a clearance (10 to 13, 17 to 20) is provided in the corners on the inside of the housing (1). [8] Roller plunger according to any one of claims 1 to 6, characterized by , that the cutouts (10 to 13, 17 to 20) are produced by drilling or milling.

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