DE102018204505A1 - Roller tappets, in particular for a pump and pump with roller tappet - Google Patents

Abstract

A roller tappet (20) is proposed for a pump, wherein the roller tappet (20) has a roller shoe (40) in which a roller (42) has a roller (42) in a recess (44) about its outer shaft (46) about its longitudinal axis (43). is rotatably mounted. The roller (42) has on both sides of its longitudinal center plane (61) on its outer surface (46) to its longitudinal axis (43) inclined surfaces (62). The recess (44) of the roller shoe (40) has the inclined surfaces (62) of the roller (42) opposite in the same direction inclined to the longitudinal axis (43) arranged surfaces (68). The inclined surfaces (62, 68) extend towards the end faces (64) of the roller (42) towards the longitudinal axis (43). In operation, hydrodynamic lubricating pads are formed between the inclined surfaces (62) of the roller (42) and the inclined surfaces (68) of the recess (44) and the roller (42) is inserted in the recess (44) in the direction of its longitudinal axis (43). centered.

Description

State of the art

The invention relates to a roller tappet, in particular for a pump according to the preamble of claim 1. The invention also relates to a pump with a roller tappet.

A pump with a roller tappet is through the DE 10 2010 030 498 A1 known. This pump has at least one pump element with a Rollenstö-ßel on which a pump piston is supported on a cam of a drive shaft. The roller tappet has a roller shoe in which a roller is rotatably mounted about a longitudinal axis in a recess. The roller runs on a cam of a drive shaft, which serves to drive the pump piston in a lifting movement. The roller is mounted in the manner of a sliding bearing in the recess of the roller shoe, wherein a hydrodynamic lubricating pad is formed between the roller and the recess during operation of the pump. Owing to external influences such as deviations of the orientation of the cam and the longitudinal axis of the roller relative to one another, forces acting in the direction of its longitudinal axis can act on the roller. In order to absorb these forces, supports for the roller must be provided, which are arranged in the direction of the longitudinal axis of the roller next to this. As supports, for example, serve a plunger body, in which the roller shoe is inserted. When starting the role of the supports the rotation of the roller is hindered and it can wear on the roller and / or the supports occur, whereby the life of the roller tappet and thus the pump is reduced. The supports also require increased manufacturing costs and increase manufacturing costs, especially if they are made of wear-resistant material.

Disclosure of the invention

Advantages of the invention

The roller tappet according to the invention with the features of claim 1 has the advantage that forms between the inclined surfaces of the roller and the recess, a hydrodynamic lubrication pad, whereby the roller is centered in the direction of its longitudinal axis in the recess. Starting of the roller in the direction of its longitudinal axis is thereby avoided, so that possible wear is reduced and no additional supports are required, whereby the production of the roller tappet is simplified and cheaper.

In the dependent claims advantageous refinements and developments of the roller tappet according to the invention are given. The embodiment according to claim 3 has the advantage that the roller and the recess in the roller shoe are easy to produce. The embodiment according to claim 5 has the advantage that a sufficiently large area of the roller for receiving the forces in the radial direction with respect to the longitudinal axis of the roller is available.

drawing

Several embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it 1 a pump in a simplified representation in a longitudinal section, 2 in an enlarged view a in 1 With II designated section of the roller tappet of the pump in a longitudinal section according to a first embodiment, 3 the clipping II the roller tappet according to a second embodiment and 4 the clipping II the roller tappet according to a third embodiment.

Description of the embodiments

In 1 a pump is shown, which is in particular a high-pressure fuel pump for a fuel injection device of an internal combustion engine. The pump has at least one pump element 10 on, the one in a cylinder bore 12 a housing part 14 displaceable tightly guided pump piston 16 has, hereinafter referred to as the cylinder head. The pump piston 16 limited with his in the cylinder bore 12 projecting end a pump work space 18 , That from the cylinder bore 12 projecting end of the pump piston 16 is with a roller plunger 20 connected. The roller plunger 20 rests on a cam 22 a drive shaft 24 from, by the during the rotational movement of the drive shaft 24 a stroke of the pump piston 16 in the cylinder bore 12 is effected. The drive shaft 24 may be part of the pump or part of the internal combustion engine, such as the camshaft or another shaft.

The pump workroom 18 is via an inlet valve 26 with a low pressure inlet to the pump and via an outlet valve 28 connectable with a high-pressure drain, for example, to a high-pressure accumulator 30 leads. The low-pressure inlet can be fed, for example, from a feed pump, which sucks fuel from a reservoir.

The roller plunger 20 has a roller shoe 40 in which a role 42 around its longitudinal axis 43 is rotatably mounted. The roller shoe 40 points out his the cam 22 facing side a recess 44 on, in which the role 42 is received in the manner of a plain bearing, the role 42 in the recess 44 over her outer coat 46 is stored. The roller shoe 40 is in an at least approximately hollow cylindrical plunger body 48 used in the on the cam 22 side facing away from the cylinder bore 12 outstanding end of the pump piston 16 protrudes. The pump piston 16 has a piston foot at its end 50 on, whose cross section opposite to the cross section of the cylinder bore 12 arranged portion of the pump piston 16 is enlarged. The piston foot 50 comes inside the tappet body 48 on the cam 22 opposite side of the roller shoe 40 to the plant. From the inner circumference of the plunger body 48 protrudes inside an annular shoulder 52 at whose the cam 22 facing side of the roller shoe 40 is applied.

The roller plunger 20 is by a pusher spring 54 to the cam 22 acted upon, wherein the plunger spring 54 on a spring plate 56 which supports in the ram body 48 is inserted and at its radially inner edge on the piston foot 50 of the pump piston 16 and at its radially outer edge on the cam 22 opposite side of the ring shoulder 52 of the plunger body 48 supported. By the pestle spring 54 Both the roller tappet 20 as well as the pump piston 16 to the cam 22 acted upon.

In 2 are the roller shoe 40 and the role 42 shown according to a first embodiment. The role 42 is in her in the direction of her longitudinal axis 43 seen in the middle area 60 cylindrically shaped. In their to their end faces 64 towards the axial end portions arranged has the role 42 on her outer coat 46 starting from the middle area 60 to their faces 64 towards its longitudinal axis 43 inclined surfaces 62 on. In their axial end regions, the diameter of the roll decreases 42 through the inclined surfaces 62 at least approximately frusto-conical. The on different sides of the median longitudinal plane 61 the role 42 arranged surfaces 62 the role 42 are inclined in opposite directions to each other. The front ends 64 the role 42 can be at least approximately flat and radial to the longitudinal axis 43 or curved, for example, convex, be formed.

The recess 44 in the roller shoe 40 is according to the training of the role 42 in its mid-range seen in the axial direction 66 hollow cylindrical, wherein the middle region 60 the role 42 with little radial play with respect to the longitudinal axis 43 in the middle area 66 the recess 44 is arranged. In their to the foreheads 64 the role 42 towards the axial end portions arranged has the recess 44 starting from the middle area 66 to the longitudinal axis 43 inclined surfaces 68 on. In their axial end portions, the diameter of the recess decreases 44 through the inclined surfaces 68 at least approximately frusto-conical. The on different sides of the median longitudinal plane 61 the role 42 arranged surfaces 68 are inclined in opposite directions to each other. The inclined surfaces 62 the role 42 are at a small radial distance from the inclined surfaces 66 the recess 44 arranged.

During operation of the pump, the roller rotates 42 in the recess 44 around its longitudinal axis 43 , wherein the forces resulting from the high-pressure delivery substantially through the central region 60 the role 42 on the middle area 66 the recess 44 be transmitted. Through the inclined surfaces 62 the role 42 and the inclined surfaces 68 the recess 44 act on the role 42 not only forces in the radial direction with respect to their longitudinal axis 43 but also in the direction of the longitudinal axis 43 , Between the inclined surfaces 62 the role 42 and the inclined surfaces 68 the recess 44 builds up in the operation of the pump as between the middle area 60 the role 42 and the middle area 66 the recess 44 a hydrodynamic lubrication pad on and through in the direction of the longitudinal axis 43 acting forces becomes the caster 42 in the recess 44 in the direction of its longitudinal axis 43 centered. Through the hydrodynamic lubrication pads, a direct contact of the inclined surfaces 62 the role 42 with the inclined surfaces 68 the recess 44 prevented.

The roller plunger 20 is surrounded by medium, such as the pumped by the pump fuel or lubricating oil, by the lubrication of the role 42 in the recess 44 he follows. In 2 is by arrows A the pressure distribution in the lubrication gap between the roller 42 and the recess 44 over the longitudinal extent of the roll 42 clarified. The recess 44 surrounds the role 42 in the circumferential direction about its longitudinal axis 43 over an angle which is a maximum of about 180 ° to an insertion of the roller 42 into the recess 44 transverse to the longitudinal axis 43 to enable.

In 3 are the roller shoe 40 and the role 42 according to a second embodiment, in which the basic design is the same as in the first embodiment, but the formation of the inclined surfaces is different. The inclined surfaces 162 in the axial end regions of the roll 42 are convexly curved. Correspondingly, the inclined surfaces 168 in the axial end regions of the recess 44 concave arched trained. The curvature of the inclined surfaces 162 . 168 can, for example, by a radius R be formed, with the radius of the surfaces 168 equal to or just slightly larger than the radius of the surfaces 162 , In 3 is in turn by arrows A the pressure distribution in the lubrication gap between the roller 42 and the recess 44 clarified. Also in the second embodiment is by the inclined, curved surfaces 162 . 168 a centering of the role 42 in the direction of its longitudinal axis 43 in the recess 44 causes.

In 4 are the roller shoe 40 and the role 42 illustrated according to a third embodiment. The role 42 points here over its entire extension in the direction of its longitudinal axis 43 on her outer coat 46 a convex curvature and is thus barrel-shaped. In its axially central region 260 has the role 42 while their largest diameter and the diameter of the roll 42 decreases towards the end regions lying in the axial direction. The curvature of the roll 42 is by a radius R generated. The recess 44 is correspondingly formed concavely curved over its entire extent in the axial direction, wherein the recess 44 in their middle area 266 has its largest diameter and decreases in diameter to its axial end regions. The curvature of the recess 44 is by a radius R generated equal to or only slightly larger than the radius of curvature of the roll 42 ,

Due to the convex curvature of the roll 42 and the concave curvature of the recess 44 are left and right of the median longitudinal plane 61 the role 42 lying, oppositely inclined surfaces 262 the role 42 and oppositely inclined surfaces 268 the recess 44 educated. Through the inclined surfaces 262 . 268 becomes the role 42 in the axial direction in the recess 44 centered. In 4 is the pressure distribution in the lubrication gap between the roller 42 and the recess 44 through arrows A clarified.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 102010030498 A1 [0002]

Claims (7)

Roller tappet (20), in particular for a pump, with a roller shoe (40), in which in a recess (44) a roller (42) is rotatably mounted about its outer casing (46) about its longitudinal axis (43), characterized in that the roller (42) on both sides of its longitudinal center plane (61) on its outer casing (46) inclined to its longitudinal axis (43) inclined surfaces (62; 162; 262), that the recess (44) of the roller shoe (40) the inclined surfaces ( 62; 162; 262) of the roller (42) has opposite surfaces (68; 168; 268) arranged in the same direction inclined to the longitudinal axis (43) and in that the inclined surfaces (62; 162; 262; 68; 168; End faces (64) of the roller (42) extend to the longitudinal axis (43). Roller follower to Claim 1 characterized in that said sloped surfaces (62; 162; 262; 68; 168; 268) are disposed in end portions of said roller (42) and said recess (44) towards said end faces (64) of said roller (42) , Roller follower to Claim 1 or 2 , characterized in that the inclined surfaces (62, 68) are each at least approximately frusto-conical in shape. Roller follower to Claim 1 or 2 , characterized in that the inclined arranged surfaces (162; 262) of the roller (42) are convexly curved and that the inclined arranged surfaces (168; 268) of the recess (44) are formed concave. Roller tappet after one of Claims 2 to 4 , characterized in that in the direction of its longitudinal axis (43) seen middle portion (60; 160) of the roller (42) is at least approximately cylindrical and a central region (66; 166) of the recess (44) is at least approximately hollow cylindrical , Roller follower to Claim 1 , characterized in that the outer sheath (46) of the roller (42) is convexly convex over the axial longitudinal extent of the barrel and that the recess (44) of the roller shoe (40) is concavely curved over its axial longitudinal extent. Pump, in particular a high-pressure fuel pump, having at least one pump element (10) which has a pump piston (16) driven in a reciprocating motion by a drive shaft (24), the pump piston (16) being connected to the drive shaft (24) via a roller tappet (20). supported, characterized in that the roller tappet (20) is designed according to one of the preceding claims.

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