DE102020109187A1 - Roller tappet for a pump and method of manufacturing a stroke transmission part - Google Patents

Abstract

A roller tappet for a pump, in particular a fuel pump, has a tappet housing (2) which comprises various housing sections (7, 9) which are made up of sintered materials of different compositions.

Description

The invention relates to a roller tappet suitable for use in a pump, in particular a fuel pump, according to the preamble of claim 1. Furthermore, the invention relates to a method for producing a stroke transmission part which is suitable for use in a pump.

A generic roller tappet for a fuel pump of an internal combustion engine is from DE 10 2006 057 246 B4 known. the DE 10 2006 057 246 B4 deals mainly with a mechanical plunger which has a sleeve-shaped plunger housing that is designed as a formed sheet metal part. As an alternative manufacturing process are in the DE 10 2006 057 246 B4 Extrusion, casting, sintering and plastic injection molding mentioned.

Another roller tappet for an internal combustion engine is in the DE 10 2017 120 884 A1 disclosed. In this case 100Cr6 and 16MnCr5 are mentioned as possible steel materials. Furthermore, a coating in the form of a PVD layer or DLC layer can be provided on a cam roller.

An Indian DE 10 2015 221 296 A1 The described roller tappet for a piston pump comprises a hollow cylindrical roller which is mounted on a bolt. This bolt is designed in several parts and comprises a pin-shaped part for connection to a tappet body and a bush-shaped part for mounting the roller.

One from the EP 3 221 577 B1 Known high-pressure fuel pump also comprises a roller tappet, a bearing bushing for mounting a roller being made from a plastic material, in particular PEEK.

The invention is based on the object of further developing a roller tappet for a pump compared to the prior art mentioned under manufacturing aspects, with a particularly favorable relationship between manufacturing expenditure, required installation space, moving masses and durability.

This object is achieved according to the invention by a roller tappet with the features of claim 1. The object is also achieved by a method for producing a stroke transmission part of a pump according to claim 7. The embodiments and advantages of the invention explained below in connection with the production method also apply mutatis mutandis to the device, i.e. the roller tappet, and vice versa.

The roller tappet has a tappet housing which is designed as a sintered part and which comprises various housing sections which are formed from sintered materials of different compositions.

As far as machine elements made of sintered materials are concerned, reference is made to the DE 31 51 313 C2 pointed out, which describes a rocker arm made of an iron-based sintered alloy. A positive displacement pump with sintered metal parts is, for example, from the DE 10 2015 101 490 A1 known. Here, a conveyor wheel, which has a sliding surface, is manufactured as a sintered metal part. An iron-based sintered alloy for making a synchronizer ring is shown in, for example DE 38 08 460 A1 described.

In the case of the roller tappet according to the application, a first housing section produced by sintering is preferably materially connected to a second housing section which is also produced by sintering but is composed differently. In general, the tappet housing is a stroke transmission part. Within the scope of the method according to the application, different volume areas of the stroke transmission part are sintered from different materials and connected to one another in a materially bonded manner. This does not yet contain any information about the order in which various sintering and joining processes are carried out.

A first possible variant of the method provides that initially two green compacts are formed and separate sintered parts, which are to be joined at a later point in time to form the stroke transmission part, are manufactured from these green compacts. Depending on the geometric design of the stroke transmission part, it can also be composed of more than two sintered parts. It is also possible that the stroke transmission part comprises at least one component which is not produced by sintering.

Regarding the processing of green compacts, which are to be sintered in a later process stage, reference is made to the documents WO 2016/093245 A1 , WO 2016/093244 A1 and WO 2018/146868 A1 pointed out.

If the different green compacts of the stroke transmission part, in particular the tappet housing, are first sintered and then joined, the joining can take place using an infiltrate that penetrates into the pores of the sintered parts. In this context, the EP 0 665 777 B1 pointed out.

According to an alternative procedure, a single green compact is first formed, which already has partial volumes of different Has composition. In a subsequent, single sintering process, these partial volumes are used to create the various volume regions of the stroke transmission part, each composed in accordance with the load. The powder metallurgical production takes place in this case as two-component sintering.

Regardless of the sintering and, if appropriate, joining process, a first section of the various housing sections of the stroke transmission part, in particular the tappet housing, each produced by sintering can be designed as a sliding element. Within a pump that is in operation, this sliding element of the linearly oscillating stroke transmission part makes contact with an element of the pump that is at rest. As far as the manufacture of sliding parts in the sintering process is concerned, the DE 25 50 428 A1 pointed out.

A second sintered section of the stroke transmission part can be designed as a pressure force transmission element provided for contacting a piston of a pump. Compared to the first section, the second section is mechanically much more heavily loaded during operation of the pump. On the other hand, sliding movements occur on the surface of the second section at most to a minor extent compared to the first section.

That section of the stroke transmission part which functions as a sliding element differs, for example with regard to the carbon content, from a second sintered housing section of the stroke transmission part that is not provided as a sliding element. Furthermore, the sintered housing sections that take on different functions within a pump can differ from one another with regard to their porosity. According to a possible embodiment, the housing section designed as a sliding element has both a higher carbon content and a higher porosity than the housing section designed as a pressure force transmission element.

The housing section designed as a compressive force transmission element can be designed as a hard metal part, in particular a hard metal plate. In principle, a workpiece, for example a piston or a cylinder liner, is a high-pressure pump, for example from the DE 10 2018 111 101 A1 known.

In the present case, instead of inserting a prefabricated hard metal part into the stroke transmission part, an additive manufacture of a hard metal part, which is mechanically particularly strong compared to other sintered sections of the stroke transmission part, is also possible. In this context, an example is given in the documents WO 2018/152448 A1 and DE 10 2017 101 050 A1 pointed out.

According to one possible embodiment, the housing section designed as a pressure force transmission element is to be assigned to a transverse traverse of the stroke transmission part that is oriented orthogonally to the direction of displacement of the stroke transmission part. Here, in designs with a hard metal part, which represents the compressive force transmission element, the hard metal part is inserted into the cross member, for example. In contrast to this, in designs that do not include hard metal, the entire cross member is, for example, composed uniformly and thus identical to the second housing section, which is mechanically particularly strong in comparison to the rest of the stroke transmission part.

• 1 und 2 in vereinfachten Schnittdarstellungen ein Stößelgehäuse eines Rollenstößels für eine Kolbenpumpe,
• 3 und 4 in Darstellungen analog 1 und 2 eine modifizierte Ausgestaltung eines Stößelgehäuses für einen Rollenstößel,
• 5 und 6 Schnittdarstellungen eines Rollenstößels einschließlich des Stößelgehäuses nach 1,
• 7 den Rollenstößel nach 5 in Seitenansicht,
• 8 einen das Stößelgehäuse nach 3 umfassenden Rollenstößel in perspektivischer Ansicht,
• 9 den Rollenstößel nach 8 in geschnittener perspektivischer Darstellung.

Several exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show here:

• 1 and 2 in simplified sectional views a tappet housing of a roller tappet for a piston pump,
• 3 and 4th analogous in representations 1 and 2 a modified design of a tappet housing for a roller tappet,
• 5 and 6th Sectional views of a roller tappet including the tappet housing according to 1 ,
• 7th the roller tappet 5 in side view,
• 8th one after the tappet housing 3 comprehensive roller tappet in perspective view,
• 9 the roller tappet 8th in a cut perspective view.

Unless otherwise stated, the following explanations relate to all exemplary embodiments. Corresponding parts are identified by the same reference symbols in all figures.

A total of the reference number 1 The roller tappet marked is intended for use in a piston pump not shown, namely the fuel pump of an internal combustion engine. With regard to the basic function of the roller tappet 1 reference is made to the prior art cited at the beginning.

The roller tappet 1 has a one-piece plunger housing 2 on, which is generally referred to as a stroke transmission part. In the tappet housing 2 is a bolt 3 attached, on which with the interposition of a socket 4th a role 5 is stored. When the pump is operating, the roller makes contact 5 a rotating cam.

Through a cylindrical wall 6th of the tappet housing 2 becomes a sliding surface for the linear bearing of the roller tappet 1 provided in the pump. The cylindrical wall 6th is a first housing section 7th with a hollow cylindrical basic shape. With MA designated center axis of the first, sleeve-shaped housing section 7th , i.e. sliding element, is with the longitudinal axis of the entire roller tappet 1 identical. With QA designated transverse axis represents the central axis of the bolt 3 and thus the axis of rotation of the role 5 represent.

With the first housing section 7th is a cross beam 8th integrally connected, which completely or partially as a second housing section 9 is trained. The one in the interior of the first housing section 7th arranged cross member 8th is parallel to the transverse axis QA arranged and provides a contact surface 10 ready, which is provided for contacting a pump piston, not shown. The not necessarily completely flat contact surface 10 lies in a plane to which the central axis MA represents a surface normal. When operating the with the roller tappet 1 working pump act on the contact surface 10 considerable pressure loads. In contrast, there is a sliding contact on the contact surface 10 at most to a minor extent. According to the function of the contact area 10 , which is a surface of the second housing section 9 is this housing section 9 also referred to as a pressure force transmission element.

Both housing sections 7th , 9 , that is, the sliding element 7th as well as the pressure force transmission element 9 , are made of sintered alloys, but with different compositions. This is the first housing section 7th made of an alloy, which in terms of the operation of the roller tappet 1 occurring sliding friction is optimized. The sintered alloy from which the second housing section 9 is constructed, on the other hand, is optimized in terms of load transfer and wear behavior to the pump piston.

In the embodiment according to 1 is the cross beam 8th with the second housing section 9 identical. The entire crossbeam 8th in this case thus has a uniform composition which differs from the composition of the first housing section 7th differs, with the housing sections 7th , 9 merge into one another. The tappet housing 2 after 1 can be produced, for example, by first forming a green compact which already has two sections, corresponding to the later housing sections 7th , 9 , has different composition. The entire green compact, which is optionally subjected to mechanical post-processing, is then turned into the tappet housing in a single operation 2 sintered. This can be followed by finishing steps, in particular surface processing.

In contrast to this, in the exemplary embodiment according to 3 only part of the cross member 8th , marked with dashed lines in the illustrations, as the second housing section 9 educated. In this case it is the second housing section 9 through which the contact surface 10 is formed, made of hard metal. Incidentally, the crossbar has 8th the same composition as the first, sleeve-shaped housing section 7th . The housing section designed as a hard metal plate, that is to say manufactured in a sintering process 9 can be used independently of the rest of the tappet housing 2 prefabricated and for example by soldering on the cross member 8th be attached.

The roller tappet 1 after 5 , which is the tappet housing 2 after 1 comprises, has the same external shape as the roller tappet 1 after 8th , which is the tappet housing 2 after 3 includes, on. This means that the outer shape of the roller tappet 1 does not depend on whether the second housing section 9 over the entire cross beam 8th ( 1 , 2 ) or only over part of the crossbeam 8th ( 3 , 4th ) extends. In both cases the roller tappet is 1 with inhomogeneously sintered tappet housing 2 suitable for replacing a conventional roller tappet in a piston pump.

List of reference symbols

1

Roller tappet

2

Tappet housing, stroke transmission part

3

bolt

4th

Rifle

5

role

6th

cylindrical wall, sliding surface

7th

first housing section, sliding element

8th

Cross member

9

second housing section, pressure force transmission element

10

Contact area

MA

Central axis

QA

Transverse axis

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102006057246 B4 [0002]
• DE 102017120884 A1 [0003]
• DE 102015221296 A1 [0004]
• EP 3221577 B1 [0005]
• DE 3151313 C2 [0009]
• DE 102015101490 A1 [0009]
• DE 3808460 A1 [0009]
• WO 2016/093245 A1 [0012]
• WO 2016/093244 A1 [0012]
• WO 2018/146868 A1 [0012]
• EP 0665777 B1 [0013]
• DE 2550428 A1 [0015]
• DE 102018111101 A1 [0018]
• WO 2018/152448 A1 [0019]
• DE 102017101050 A1 [0019]

Claims (10)

Roller tappet for a pump, with a tappet housing (2) which is at least partially designed as a sintered part, characterized in that the tappet housing (2) comprises different housing sections (7, 9) which are made up of sintered materials of different compositions. Roller tappet after Claim 1 , characterized in that the two housing sections (7, 9) are cohesively connected to one another. Roller tappet after Claim 1 or 2 , characterized in that one of the two housing sections (7) is designed as a sliding element and the other housing section (9) is designed as a pressure force transmission element provided for contacting a piston. Roller tappet after Claim 3 , characterized in that the two housing sections (7, 9) differ from one another with regard to at least one of the parameters carbon content and porosity. Roller tappet after Claim 4 , characterized in that the housing section (7) designed as a sliding element has both a higher carbon content and a higher porosity than the housing section (9) designed as a pressure force transmission element. Roller tappet according to claim one of Claims 3 until 5 , characterized in that the housing section (9) designed as a pressure force transmission element comprises hard metal. Method for producing a stroke transmission part (2), wherein different volume areas of the stroke transmission part (2) made of different materials are sintered and firmly connected to one another. Procedure according to Claim 7 , characterized in that first two green compacts are formed and separate sintered parts, which are to be joined to form the stroke transmission part (2), are manufactured from these green compacts. Procedure according to Claim 8 , characterized in that the sintered parts are connected to one another using an infiltrate. Procedure according to Claim 7 , characterized in that a single green compact is formed which - corresponding to the different volume areas of the stroke transmission part (2) - already has partial volumes of different composition, and the stroke transmission part (2) is sintered from this green compact.

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