DE10326879A1 - Radial piston pump for fuel high pressure generation in fuel injection systems of internal combustion engines - Google Patents

Abstract

The invention relates to a radial piston pump (1) for fuel high pressure generation in fuel injection systems of internal combustion engines, in particular in a common rail injection system, with a drive shaft (4) mounted in a pump housing (2) with an eccentric shaft section (6) on which a roller ( 8) is mounted, and preferably with a plurality of relative to the drive shaft (4) radially in a respective cylinder (14) arranged piston (16), at whose the roller (8) facing ends in each case a Kolbenfußplatte (18) is arranged, which surrounds the peripheral surface (10, 12) of the roller (8) contacted. DOLLAR A The invention provides that at least a part of the roller (8), in particular at least a part of the peripheral surface (10, 12) of the roller (8), from a wear-resistant material, namely cemented carbide, from a precision casting material, cast from a carbide material, consists of a sintered tool steel or a nitriding steel.

Description

The Invention is based on a radial piston pump for fuel high pressure generation in fuel injection systems of internal combustion engines, in particular in a common rail injection system, with one in a pump housing mounted drive shaft with an eccentric shaft section, on which a roller is mounted, and preferably with several in terms of the drive shaft arranged radially in a respective cylinder Piston, at whose ends facing the roller respectively a Kolbenfußplatte is arranged, which contacts the peripheral surface of the roller, according to the genus of claim 1.

Such a radial piston pump is for example from the DE 198 09 315 A1 known. The Kolbenfußplatte and the roller of the known radial piston pump are usually made of case-hardened steel or made of tempered steel. Over time, however, these components may experience sliding wear due to adhesion, abrasion, or surface disruption. This undesirable wear can lead to a failure of the radial piston pump and thus also to a failure of the internal combustion engine.

Of the The present invention is based on the object, a Radial piston pump of the type mentioned above so on develop that their reliability elevated becomes.

According to the invention this Problem solved by the characterizing features of claim 1.

while For the first time at least part of the roller, in particular at least a part of the peripheral surface of Roller made of a wear-resistant Material, namely made of tungsten carbide, of a precision casting material, of a cast carbide Material, from a sintered tool steel or an alloyed Nitriding steel is made, the tendency of wear of the piston footplate roller-sliding pair decisively reduced. The materials mentioned have the opposite previously used steel materials have a higher modulus of elasticity, resulting in lower Deformations under load and consequently in a more even surface pressure without significant voltage spikes results. When using Above all, ceramic materials play their lesser weight a role, resulting in a low inertia of the roller.

there can the roller completely from the wear-resistant Be made of material or it is still made of case-hardened steel or tempered steel and carries on its peripheral surface at least one insert of the wear-resistant material. The usage of inserts brings the advantage of a modular construction, i. that a standardized Roller with inserts can be provided from different material and thus a variety of variants can be generated.

When using cemented carbide for the inserts or for the roller itself, a particularly wear-resistant carbide with a Vickers hardness of at least HV 1100 and a fracture toughness K _IC > = 10 MPa / m ^3/2 with binder contents of 12 to 20% comes into question , particularly preferably G20, GC37 or GC20. In particular hard metals are used here, which have low adhesion coefficients.

On suitable investment casting material forms, for example, GX-210WCr13 H, for which casting carbide material comes locally remelted, carbide SoGGH (gradient material) in question. For the sintered tool steel is suitable ASP23. One specifically by nitriding with Cr, Mo, V, or C alloyed nitriding steel is used for a variant with gradient material used. The basic elements and the nitriding process parameters lead to deep diffusion with hardships from HV 750 to 850 at the same time higher strength of the base material. The thereby forming compound layer is due to functional reasons Grind away.

Especially Preferably, the roller has at least on its peripheral surface a transverse groove extending transversely to the direction of movement. The Quernut, for example, in the center of a Nutauslauf forming Depression of the peripheral surface be arranged. In this acting as a dam cleft or transverse groove can to accumulate fuel due to the sliding movement between the peripheral surface the roller and the piston foot plate promotes the formation of a hydrodynamic sliding film, thereby the wear on the sliding surfaces is further reduced.

According to a further measure, the surface of the piston foot plate and / or the roller has a roughness R _{z of} between 0.15 μm and 2 μm. Specifically, the ceramic material has a roughness R _z between 0.15 microns and 0.5 microns, the carbide a roughness R _z between 0.3 microns and 1.0 microns and the cast carbide a roughness R _z between 0.5 microns and 2.0 μm.

embodiments The invention is illustrated in the drawings and in the following Description closer explained. In the drawings shows

1 a cross-sectional view of a radial piston pump with a Kolbenfußplatte and a drive shaft according to a first embodiment of the invention;

2 an enlarged cross-sectional view of a piston and a Kolbenfußplatte according to another embodiment;

2a an enlarged section of 2 ;

2 B another enlarged section of 2 ;

3 a bottom view of the piston foot plate of 2 ;

4 a cross-sectional view of a piston with Kolbenfußplatte and a drive shaft according to another embodiment;

5 a cross-sectional view of a drive shaft according to another embodiment;

6 a view along the line VI-VI of 5 ;

7 a view along the line VII-VII of 6 ,

In the l shown radial piston pump 1 is preferably used to generate the system pressure for the high-pressure accumulator (rail) of a common-rail injection system of a self-igniting internal combustion engine. It includes one in a pump housing 2 mounted drive shaft 4 with an eccentric shaft section 6 on which a polygonal, opposite the shaft portion 6 rotatable roller 8th is included. The polygonal roller 8th points along its peripheral surface 10 circumferentially spaced from each other, flat flat sections 12 on.

At the flat sections 12 the roller 8th each one supports itself in a cylinder 14 to the drive shaft 4 radially guided piston 16 with his piston foot plate 18 from. The piston foot plate 18 is preferably by means of a spherical bearing 20 with the to the drive shaft 4 pointing end of the piston 16 pivotally connected. The spherical bearing 20 is realized, for example, in that the piston end as a partial ball 22 is formed, which in a complementary formed spherical recess 24 in the piston foot plate 18 intervenes. In addition, the piston foot plate 18 together with the piston 16 by a spring 26 against the associated flat section 12 the roller 8th biased. The operation of such a radial piston pump 1 is for example in the DE 198 02 475 A1 described, therefore, should not be discussed further here.

At least the peripheral surface 10 the roller 8th contacting surface 28 the piston foot plate 18 consists of a wear-resistant material, namely tungsten carbide, a ceramic material, a cast carbide material or cermet. This is preferably realized in that the Kolbenfußplatte 18 on her to the caster 8th pointing surface 28 at least one example disc-shaped insert 30 made of the wear-resistant material. The use 30 Can with the remaining piston foot plate 18 be positively and / or cohesively connected, for example by gluing or by soldering. The use 30 can, as in 1 is shown over the entire contact surface 28 the piston foot plate 18 with the roller 8th or even just over part of it. Alternatively, the entire Kolbenfußplatte 18 be made of the wear-resistant material, so no additional use 30 is necessary.

When using a ceramic material for the Kolbenfußplatte 18 this preferably contains silicon nitrite Si ₃ N ₄ . Hard metals may for example consist of G20, GC37 or GC20, while the ge poured carbide material may include a shell hard casting material, in particular GGH or SoGGH.

Furthermore, the piston 16 itself be made of wear-resistant material, for example, a Si ₃ N ₄ - or a ZrO ₂ ceramic. The piston 16 can be made by extrusion and have a porosity of less than 5%, the surface being infiltrated with MoS ₂ . Alternatively, the piston 16 also isostatically pressed and sintered.

Last but not least, there is at least a part of the roller 8th , in particular the flat sections 12 of a wear-resistant material, namely of hard metal, of a precision casting material, of a cast carbide material, of a sintered tool steel or of an alloyed nitriding steel.

Analogous to the piston foot plate 18 this is preferably realized by the fact that the flat sections 12 with one use each 32 are provided from the wear-resistant material, such as

1 shows. Such an assignment 32 is in each case in a complementary shaped recess 34 in the flat section 12 positively and / or cohesively received, for example by gluing or by soldering. Alternatively, the entire roller 8th consist of the wear-resistant material.

When using carbide for the inserts 32 or for the roller 8th itself is for example G20, GC37 or GC20 in question. For example, GX-210WCr13 H forms a suitable investment casting material. For the cast carbide material, locally remelted carbide SoGGH (gradient material) may be considered. The sintered tool steel is ASP23. A nitriding steel alloyed specifically by nitriding or gas nitriding with Cr and / or Mo and / or V and / or C is used for a variant with gradient material. The basic elements and the process parameters during nitriding lead to a deep diffusion with hardnesses of HV 750 to 850 with simultaneously higher strength of the base material. The connecting layer forming in this process is removed by grinding for functional reasons.

The surfaces of the piston foot plate 18 and the roller 8th have on the sliding surfaces preferably a roughness R _z between 0.15 microns and 2 microns, depending on the materials used. The lower limit for ceramics, in particular a range from 0.15 μm to 0.5 μm, is the upper limit for metals such as SoGGH or ASP23. For carbide, a roughness R _{z of} between 0.3 μm and 1 μm is provided.

In the table below, preferable material pairings are the piston foot plate 18 on the one hand and the roller 8th on the other hand. If both in the caster 8th as well as in the piston foot plate 18 Inserts are used, any combinations of material pairings with each unchanged support bodies are possible. In particular, in the pairings in the table, in which the roller 8th preferably a total of the wear-resistant material ("solid material") alternatively also inserts 32 from the corresponding material in the area of the flat sections 12 used as it is already in 1 is shown. The roller 8th as carrier body for the inserts 32 can then be made of a different material, for example 50Cr4, 42CrV4 or 16MnCr5.

Tabelle: Bevorzugte Materialpaarungen

Table: Preferred material pairings

A special role comes to the embodiment in the 3rd line in the table. In this case, in the area of the flat sections 12 consisting of a cast steel material and in 5 separately shown roller 8th each formed a carbide zone. This carbide zone is either by a targeted solidification rate when casting the roller 8th or generated by remelting and then preferably forms the gradient material SoGGH. Result is therefore a roller 8th in which in the area of the flat sections 12 a carbidic zone 33 is formed while the remaining zones and areas of the roller 8th 5 Made of cast steel with unchanged properties.

In the area of the flat sections 12 the roller 8th can each have one or more transverse grooves 36 be trained as best by 6 you can see. How out 7 is apparent, is the transverse groove 36 in the center of a valley forming a groove outlet 29 of the flat section 12 arranged. The valley 29 is by two in relation to the flat section 12 formed angularly arranged planes, in the section line, the transverse groove 36 lies. The sink angle γ of the sink 29 For example, it is less than 15 degrees. The transition from the valley 29 and the flat section 12 is rounded with a radius R ₄ of preferably less than or equal to 1 mm. The radius R ₄ is generated, for example, by vibratory grinding. In this transverse groove acting as a stowage gap 36 or sink 29 can accumulate fuel, which due to the sliding speed between the flat sections 12 the roller 8th and the piston foot plate 18 promotes the formation of a hydrodynamic sliding film, whereby the wear on the sliding surfaces is reduced.

In the in the 2 to 4 Embodiments shown are those compared to the example of 1 constant and equivalent parts characterized by the same reference numerals. In contrast to this is the example according to 2 the piston foot plate 18 from a plate holder 38 on the associated piston 16 held. The piston foot plate 18 indicates at her the piston 16 facing surface a circular recess 40 into which the crowned end 42 of the piston 16 engages and the bottom of the recess 40 contacted. The plate holder 38 gets on the piston 16 by means of a groove 44 of the piston 16 engaging snap rings 46 countered. In a circular recess 48 in the piston foot plate 18 is a complementarily shaped insert 30 from one of the above-described wear-resistant th materials held, for example by material adhesion, in particular by soldering. How out 2a shows, is the use 30 on his to the caster 8th pointing surface 31 on the edge with an angular outlet 35 provided, wherein the outlet angle α is about 15 degrees. Furthermore, the transition between this area 31 and the spout 35 rounded with a radius Rz of about 2 mm. By means of a radius R ₁ of less than or equal to 1 mm is also the transition between the outlet 35 and the edge surface 37 of the insert 30 rounded.

Analogous to the flat sections 12 the roller 8th assign the stakes 30 the piston foot plate 18 preferably at least two intersecting grooves 50 on how best 3 shows. Due to the intersecting arrangement of the grooves 50 the likelihood is high that in terms of in relation to the plate holder 38 rotatable piston foot plate 18 one of the grooves 50 Aligned transversely to the direction of movement to promote the formation of a hydrodynamic lubricant film. The grooves 50 are preferably produced by pressing. This results in a lower notch effect compared to cutting processes, since the material fibers are not severed. How out 2 B shows are the grooves 50 each in the center of a groove forming a drain 39 the area 31 arranged. The valley is divided by two in relation to the area 31 angularly arranged planes formed in the section line, the respective groove 50 lies. The sink angle β of the sink 39 is for example 5 degrees. The transition from the valley 39 and the area 31 is rounded with a radius R ₃ of preferably less than or equal to 1 mm.

In the embodiment of 4 consists of the piston foot plate 18 completely made of one of the above-mentioned, wear-resistant materials and is in the through hole 52 a ring box 54 used, which consists of steel. The connection between the ring bush 54 and the piston foot plate 18 is preferably made by soldering. Of course, further possibilities are conceivable to wear-resistant material to the mutually associated sliding surfaces 12 . 28 the roller 8th and piston foot plate 18 to install.

Claims (11)

Radial piston pump ( 1 ) for fuel high pressure generation in fuel injection systems of internal combustion engines, in particular in a common rail injection system, with a in a pump housing ( 2 ) mounted drive shaft ( 4 ) with an eccentric shaft section ( 6 ) on which a roller ( 8th ) is mounted, and with preferably several with respect to the drive shaft ( 4 ) radially in a respective cylinder ( 14 ) arranged piston ( 16 ), at which the roller ( 8th ) facing ends in each case a piston foot plate ( 18 ) is arranged, which the peripheral surface ( 10 . 12 ) of the roller ( 8th ), characterized in that at least a part of the roller ( 8th ), in particular at least part of the peripheral surface ( 10 . 12 ) of the roller ( 8th ) consists of a wear-resistant material, namely hard metal, a precision casting material, a cast carbide material, a sintered tool steel or an alloyed nitriding steel. Radial piston pump according to claim 1, characterized in that the roller ( 8th ) on its peripheral surface ( 10 . 12 ) at least one use ( 32 ) made of the wear-resistant material. Radial piston pump according to claim 1 or 2, characterized characterized in that the cast carbide material is a shell hard casting material, especially SoGGH. Radial piston pump according to claim 1 or 2, characterized characterized in that the carbide includes G20, GC37 or GC20. Radial piston pump according to claim 4, characterized in that the hard metal has a Vickers hardness of at least HV 1100 and a fracture toughness K _IC greater than or equal to 10 MPa / m ^3/2 and a binder content of 12 to 20%. Radial piston pump according to claim 1 or 2, characterized characterized in that the investment casting material GX-210WCr13 H includes. Radial piston pump according to claim 1 or 2, characterized characterized in that the sintered tool steel includes ASP23. Radial piston pump according to claim 1 or 2, characterized in that the alloyed nitriding steel contains C and / or Cr and / or V and / or Mo, gas-nitrided and in the contact area with the Kolbenfußplatte ( 18 ) connection layer is free. Radial piston pump according to at least one of the preceding claims, characterized in that the roller ( 8th ) on its peripheral surface ( 12 ) at least one transversely extending transversely to the direction transverse groove ( 36 ) having. Radial piston pump according to claim 9, characterized in that the transverse groove ( 36 ) in the center of a groove forming a groove outlet ( 29 ) of the peripheral surface ( 12 ) is arranged. Radial piston pump according to at least one of the preceding claims, characterized in that the surface of the piston foot plate ( 18 ) and / or the roller ( 8th ) has a roughness R _z between 0.15 microns and 2 microns.