Roller tappet and method for manufacturing a housing element of a roller tappet

A roller tappet includes a housing, and the housing includes a first housing element and a second housing element. The first housing element has a receiving region configured to receive a roller of the roller tappet, and the second housing element is separate from the first housing element and is forged. The first housing element may be formed from metal sheet.

This application claims priority to German patent application no. 10 2014 218 961.6 filed on Sep. 22, 2014, the contents of which are fully incorporated herein by reference.

TECHNOLOGICAL FIELD

The invention relates to a roller tappet having a two-part housing.

BACKGROUND

A roller tappet that includes a one-piece housing made from steel plate is known from DE 10 2012 202 566 A1 (a family member of US 2013/0213333). A roller tappet is also known that includes a one-piece housing formed from a press-forged part.

SUMMARY

One aspect of the disclosure is to provide an improved roller tappet having high efficiency. The roller tappet includes a housing, and the housing includes a first housing element and at least one second housing element.

The at least one second housing element is formed separate from the first housing element. Configured “separate” from the first housing element should be understood to mean that the first housing element forms a first component and the second housing element forms a second component, and that the two components are different from each other. A high efficiency can be achieved using this design. In particular, a cost-effective construction and a simple installability can be achieved. In particular, a simple installability can be achieved in comparison to a design wherein a tappet roller is installed in a one-piece housing.

Preferably the first housing element is one-piece and/or the second housing element is one-piece. “One-piece” should be understood to mean made from one casting and/or not separable without destruction. In this way a constructively simple design can be achieved.

In addition, the first and the second housing element each form at least a significant part of an entire radial-side outer surface of the roller tappet. “Significant part” should in particular be understood to mean at least 5%, preferably at least 15%, and particularly preferably at least 25%. In this way a constructively simple design can be achieved.

The roller tappet is suitable for a high-pressure fuel pump, a valve train of an internal combustion engine, and/or for an axial- or radial-piston engine.

In addition, a method for manufacturing a housing element of the roller tappet is disclosed in which method the housing element is forged, in particular drop-forged. This forged housing element is part of the housing of the roller tappet but does not constitute the entire housing of the roller tappet. In this way a high efficiency can be achieved. A housing part or element can be manufactured entirely by forging or drop-forging, and this may allow further machining (or other material removal processes) that might follow a forging process to be omitted. The housing part can be, for example, a component that is configured to actuate a piston and/or a tappet. Under certain circumstances the housing part can include a base for this purpose, which, in the axial direction, forms an abutment surface for a tappet or a piston. Under certain circumstances an additional housing part that forms the rest of the overall housing of the roller tappet can be disposed so that it does not directly contact the piston or the tappet.

Additionally or alternatively the additional housing part can be manufactured using a manufacturing process other than forging. For example, the additional housing element can be manufactured from metal plate. Thus in some exemplary embodiments, a weight of the tappet can be reduced and/or a manufacturing can be simplified because one of the housing elements (referred to hereinafter as the first housing element) is formed in a manner other than by forging, from metal plate, for example, while the other housing element (referred to hereinafter as the second housing element) is forged.

Further advantages will become apparent from the following drawing description. An exemplary embodiment of the invention is depicted in the drawings. The drawings, the description, and the claims contain numerous features in combination. The person skilled in the art will also advantageously consider the features individually and combine them into further meaningful combinations.

DETAILED DESCRIPTION

FIG. 1shows a perspective view of a roller tappet according to the present disclosure that includes a housing10. The housing10comprises a first housing element12and a second housing element14that is attached to the first housing element12by laser welding. Alternatively the second housing element14could be press-fitted into the first housing element12. The first and the second housing elements12,14are each one-piece elements. Furthermore, the first housing element12is formed from steel plate, and the second housing element14is manufactured by forging or drop-forging.

The housing10includes an outer surface16substantially in the shape of a circular-cylindrical shell having openings. An axis of symmetry40of the circular-cylindrical shell is parallel to an axial direction of the roller tappet (FIG. 2). The surface16is an entire surface of the housing10, that is, it comprises the outer surface of the first housing element12and the outer surface of the second housing element14. The surface16is external with respect to the radial directions to the axis of symmetry40. The outer surfaces of the first housing element12and the second housing element14each form more than 10% of the surface16.

Furthermore, the first housing element12comprises a receiving region18in which a roller20of the roller tappet is disposed. The second housing element14forms an axial end region22of the roller tappet, and a base38of the roller tappet is a part of the second housing element14. In some exemplary embodiments the base38serves as a contact surface or abutment surface for a tappet or a piston (not illustrated). The base38may completely close the second housing part14in the axial direction.

The second housing element14includes an open end that faces axially away from the base38and is disposed with respect to the first housing element12so that the open end faces axially away from the first housing element12. The base38at least sectionally or even fully overlaps with the first housing part12in the axial direction40.

In the exemplary embodiment ofFIG. 3the base includes four openings.

The roller of the roller tappet abuts on a first annular region34and a second annular region36of the first housing element12. First and a second clip rings24,28each engage in a groove of the roller and thus attach the roller in an interference-fit manner with respect to an axial direction26of the roller. The roller has a circular-cylindrical shape. The grooves extend on a radial outer side of the roller along a circumferential direction of the roller. Bushings30,32of the roller tappet are rotatably supported relative to the roller. In principle the bushing30can also be rotatably supported with respect to the roller by a rolling-element bearing, such as, for example, needle roller bearings.

If the roller tappet is built into a high-pressure fuel pump, then the bushing30comes into contact with a cam, and the second housing element contacts a pump piston. In other exemplary embodiments the second housing element can also be used in other devices, for example an engine, and be in contact with a piston and/or a tappet.

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