JP2006527330A - Radial piston pump for generating high pressure fuel in a fuel injection system of an internal combustion engine - Google Patents

Abstract

The present invention relates to a fuel injection system for an internal combustion engine, in particular a radial piston pump (1) for supplying high pressure fuel to a common rail injection system. The radial piston pump (1) includes a drive shaft (4) mounted on a pump casing (2) and having an eccentric shaft section (6) to which a roller (8) is mounted. In contrast, it is preferable to have a plurality of pistons (16) attached to the cylinder (14) in the radial direction. The end of the piston foot plate (18) is disposed toward the roller (8), and the piston foot plate contacts the circumferential surface (10, 12) of the roller (8). In the present invention, at least the surface (28) of the piston foot plate (18) in contact with the circumferential surface (10, 12) of the roller (8) has a wear-resistant material, that is, cemented carbide, ceramic material, casting. Made from carbide material or cermet.

Description

  The present invention is a radial piston pump for generating high-pressure fuel in a fuel injection system of an internal combustion engine, particularly a common rail injection system, and this radial piston pump is mounted on a pump casing and an eccentric shaft on which a drive roller is mounted. A piston foot plate having a drive shaft having a section and attached to each cylinder in a radial direction relative to the drive shaft and contacting a circumferential surface of the drive roller at an end of the piston foot plate facing the drive roller; It is based on a radial piston pump as claimed in the preceding paragraph of claim 1 which preferably has a plurality of pistons each having.

  A radial piston pump of this type is known from Patent Document 1, for example. The piston foot plates and drive rollers of known radial piston pumps are generally made of hardened or heat-treated steel. However, over time, sliding wear on these components may occur as a result of welding, wear or surface delamination. This undesired wear can lead to failure of the radial piston pump and thus also failure of the internal combustion engine.

German Patent Application Publication No. 19809315A1

  The invention aims to further develop the pump so as to improve the reliability of a radial piston pump of the type described at the outset.

  This object is achieved according to the invention by the features of claim 1.

  The sensitivity of the piston foot plate / drive roller to the pair of sliding parts is initially sensitive to wear when at least the surface of the piston foot plate in contact with the circumferential surface of the drive roller is a wear-resistant material, i.e. It is considerably reduced by comprising ceramic material, cast carbide material or cermet. The above-mentioned materials have a significantly higher elastic modulus compared to the steel materials used in the past, which reduces deformation due to loading, so there are almost no stress peaks and more surface pressure. It becomes uniform. Especially when ceramic materials are used, the ceramic material serves to reduce weight because the piston foot plate is frequently accelerated and decelerated with the piston, thus reducing the mass inertia considerably. It is.

  The entire piston foot plate can be made of wear resistant material, or otherwise made of hardened or heat treated steel and the wear resistant material on the surface of the piston foot plate facing the drive roller, as is conventional. At least one insert made of The use of inserts provides the advantage of a modular construction, i.e., standardized piston foot plates can be provided with inserts made from different materials, resulting in a number of variations.

If a ceramic material is used, this material preferably contains silicon nitride Si ₃ N ₄ and has a surface roughness R _z of 0.15 μm to 0.5 μm. The cemented carbide may for example consist of G20, GC37 or GC20 and can have a surface roughness R _z of 0.3 μm to 1.0 μm, while the cast carbide material is cold-cured. Made of cast iron material, in particular GGH or SoGGH, and has a surface roughness R _z of 0.5 μm to 2.0 μm.

  It is particularly preferred that the piston foot plate has at least two grooves intersecting each other on the surface of the piston foot plate facing the drive roller. This eliminates the area where the piston foot plate and the drive roller overlap without supplying lubricating oil. Fuel can accumulate in a groove that functions as a stagnation gap, and this fuel facilitates the formation of a hydrodynamic sliding film due to the sliding speed between the drive roller and the piston foot plate, thereby sliding. Further reduces wear on the moving surface.

  Exemplary embodiments of the invention are illustrated and described in more detail in the following description.

  The radial piston pump 1 shown in FIG. 1 is preferably used to generate system pressure for the high pressure reservoir (rail) of the common rail injection system of a compression ignition internal combustion engine. The radial piston pump 1 includes a drive shaft 4 mounted on a pump casing 2, which has an eccentric shaft section 6 on which a polygonal drive roller 8 that can rotate relative to the eccentric shaft section 6 is mounted. Polygonal drive roller 8 has flat planar sections 12 attached to it at a circumferential distance along its circumferential surface 10.

  A piston foot plate 18 of the piston 16 guided in the radial direction with respect to the drive shaft 4 of the cylinder 14 is supported by each of the planar sections 12 of the drive roller 8. The piston foot plate 18 is preferably pivotally connected to the end of the piston 16 facing the drive shaft 4 by a spherical bearing 20. The spherical bearing 20 is realized, for example, by designing the end of the piston as a partial ball 22 that engages a spherical recess 24 of a complementary design in the piston foot plate 18. Furthermore, the piston foot plate 18, together with the piston 16, prestresses on the associated planar section 12 of the drive roller 8 by means of a spring 26. The way in which this type of radial piston pump 1 functions is described, for example, in DE 198 02 475 A1, and is therefore not described in further detail here.

  At least the surface 28 of the piston foot plate 18 in contact with the circumferential surface 10 of the drive roller 8 is made of a wear resistant material, i.e. cemented carbide, ceramic material, cast carbide material or cermet. This can be achieved by the fact that the piston foot plate 18 has at least one insert 30 made of wear-resistant material, for example in the form of a disc, on the surface 28 of the piston foot plate 18 facing the drive roller 8. preferable. The insert 30 can be securely and / or closely connected to the remaining piston foot plate 18, for example by adhesive bonding or soldering. The insert 30 may extend over the entire contact surface 28 of the piston foot plate 18 that contacts the drive roller 8 or only a portion of this contact surface, as shown in FIG. Alternatively, the entire piston foot plate 18 can be made from an abrasion resistant material so that no additional insert 30 is required.

If a ceramic material is used for the piston foot plate 18, the ceramic material preferably contains silicon nitride Si ₃ N ₄ . The cemented carbide may for example consist of G20, GC37 or GC20, while the cast carbide material may contain a cold-hardened cast iron material, in particular GGH or SoGGH.

Furthermore, the piston 16 itself can be made from a wear-resistant material, for example from Si ₃ N ₄ ceramic or ZrO ₂ ceramic. The piston 16 can be produced by extrusion, also it has a porosity of less than 5%, in this case, MoS ₂ is penetrated in the piston surface. Alternatively, the piston 16 may be hydrostatically pressed and hydrostatically sintered.

  In particular, at least a part of the drive roller 8, in particular the planar section 12, may consist of a wear-resistant material, ie cemented carbide, precision casting material, cast carbide material, sintered tool steel or nitride alloy steel.

  As with the piston foot plate 18, this is preferably accomplished by the fact that each of the planar sections 12 is provided with an insert 32 of wear resistant material, as shown in FIG. This type of insert 32 is always held securely and / or in close contact with the complementary shaped recess 34 of the planar section 12, for example by adhesive bonding or soldering. Alternatively, the entire drive roller 8 may be made of a wear resistant material.

  If cemented carbide is used for the insert 32 or for the drive roller 8 itself, examples of suitable materials include G20, GC37 and GC20. A suitable precision casting material consists, for example, of GX-210WCr13 H, while a suitable casting carbide material is a locally remelted carbide SoGGH (gradient functional material). A suitable sintered tool steel is ASP23. A nitrided steel specially alloyed by nitriding or gas nitriding Cr and / or Mo and / or V and / or C is used for another form having a functionally graded material. The basic components and process parameters used in the nitriding process combine higher strength substrates simultaneously, resulting in depth diffusion with a hardness of HV750-850. The compound layer that is formed is removed by grinding for functional reasons.

Surface of the piston footplate 18 and the driving roller 8 preferably has a surface roughness R _z of 0.15μm~2μm depending on the material used for the sliding surface. A ceramic in the range of 0.15 μm to 0.5 μm is applied to the lower limit, while a metal such as SoGGH or ASP23 is applied to the upper limit. For the cemented carbide, a surface roughness R _{z of} 0.3 μm to 1 μm is provided.

  The following table describes a preferred pair of materials, one is the piston foot plate 18 and the other is the drive roller 8. If an insert is used for both the drive roller 8 and the piston foot plate 18, any desired combination of a pair of materials is always possible with an invariant support. In particular, with respect to a pair of materials in the table where the entire drive roller 8 is preferably made of an abrasion resistant material (“monolithic structure”), as already indicated in FIG. It is also possible to use an insert 32 made from In this case, the drive roller 8 as a support for the insert 32 may consist of different materials, for example 50Cr4, 42CrV4 or 16MnCr5.

  The exemplary embodiment of the third line of the table plays a specific role. In this case, the carbide zones are each formed in the region of the plane section 12 shown separately in FIG. 5 of the drive roller 8 made of cast steel material. This carbide zone is preferably formed at the target solidification rate during casting of the drive roller 8 or by remelting, and then the functionally graded material SoGGH is formed. A carbide zone 33 is thus formed in the region of the surface section 12, while the remaining zone and region of the drive roller 8 results in a drive roller 8 made of cast steel whose properties do not change.

As can be seen most clearly from FIG. 6, one or more transverse grooves 36 can each be formed in the region of the planar section 12 of the drive roller 8. As can be seen from FIG. 7, the lateral groove 36 is arranged in the center of the recess 29 that forms the outlet groove of the planar section 12. The recess 29 is formed by two surfaces arranged at an angle with respect to the planar section 12, and the transverse groove 36 is present at the intersection line of the two surfaces. The depression angle γ of the recess 29 is, for example, less than 15 degrees. The transition from the recess 29 to the planar section 12 is preferably rounded with a radius R ₄ of 1 mm or less. Radius R ₄ are formed for example by grinding. Fuel can accumulate in this transverse groove 36 or indent 29 that functions as a stay gap, and this fuel is hydrodynamically sliding due to the sliding speed between the planar section 12 of the drive roller 8 and the piston foot plate 18. Is formed, thereby reducing wear on the sliding surface.

In the embodiment shown in FIGS. 2 to 4, those parts having the same form and the same function as those in the example shown in FIG. 1 are indicated by the same reference numerals. Unlike the example shown in FIG. 1, in the example shown in FIG. 2, the piston foot plate 18 is held on the associated piston 16 by a plate holder 38. The surface of the piston foot plate 18 facing the piston 16 has a circular recess 40, and the spherical end 42 of the piston 16 engages with the circular recess to contact the base of the recess 40. The plate holder 38 is locked to the piston 16 by a snap ring 46 that engages the groove 44 of the piston 16. The circular insert 30 made from one of the above-mentioned wear-resistant materials is held in a complementary shaped recess 48 of the piston foot plate 18 by, for example, tight bonding, in particular by soldering. As can be understood from FIG. 2 a, on the edge side of the surface 31 of the insert 30 facing the drive roller 8, a lead-out portion 35 is provided in which the lead-out angle α forms an angle of about 15 degrees. Furthermore, the transition between this surface 31 and the outlet 35 is rounded with a radius R ₂ of about 2 mm. Further, the transition portion between the lead-out portion 35 and the edge surface 37 of the insert 30 is rounded with a radius R ₁ of ₁ mm or less.

Similar to the planar section 12 of the drive roller 8, the insert 30 of the piston foot plate 18 preferably has at least two grooves 50 that intersect each other, as can be seen most clearly from FIG. With respect to the piston foot plate 18 that can be rotated relative to the plate holder 38 by arranging the grooves 50 to intersect each other, one of the grooves 50 has a direction of motion to facilitate the formation of a hydrodynamic lubricating film. The probability of being oriented in the transverse direction becomes higher. The grooves 50 are preferably formed by pressing. This reduces the notch effect compared to the cutting process, because the material fibers are not cut. As can be seen from FIG. 2 b, each of the grooves 50 is arranged in the center of the recess 39, and a lead-out groove is formed in the surface 31. The recess is formed by two surfaces arranged at an angle with respect to the surface 31, and each groove 50 is disposed at the intersection of the two surfaces. The depression angle β of the recess 39 is, for example, 5 degrees. The transition between the recess 39 and the surface 31 is preferably rounded with a radius R ₃ of 1 mm or less.

  In the exemplary embodiment shown in FIG. 4, the entire piston foot plate 18 is made of one of the above-mentioned wear-resistant materials and is fitted into a passage hole 52 in an annular bushing 54 made of steel. The connection between the annular bushing 54 and the piston foot plate 18 is preferably formed by soldering. Of course, other methods for attaching the wear resistant material to the sliding surfaces 12, 28 of the drive roller 8 and piston foot plate 18 relative to each other are also conceivable.

1 is a cross-sectional view of a radial piston pump according to a first embodiment of the present invention having a piston foot plate and a drive shaft. It is an expanded sectional view of the piston and piston footplate by another embodiment. FIG. 3 is an enlarged partial sectional view of FIG. 2. FIG. 3 is another enlarged partial cross-sectional view of FIG. 2. FIG. 3 is a drawing of the piston foot plate of FIG. 2 viewed from below. FIG. 6 is a cross-sectional view of another embodiment of a piston having a piston foot plate and a drive shaft. It is sectional drawing of the drive shaft by another embodiment. FIG. 6 is a view taken along line VI-VI in FIG. 5. FIG. 7 is a view taken along line VII-VII in FIG. 6.

Claims (8)

A drive shaft (4) having an eccentric shaft section (6) mounted on the pump casing (2) and mounted with a drive roller (8);
The circumferential surface (10, 12) of the drive roller (8) is attached to each cylinder (14) provided in the radial direction with respect to the drive shaft (4), and at the end facing the drive roller (8). A plurality of pistons (16) having piston foot plates (18) in contact with
In a radial piston pump (1) for generating high-pressure fuel in a fuel injection system of an internal combustion engine having
At least the surface (28, 31) of the piston foot plate (18) in contact with the circumferential surface (10, 12) of the drive roller (8) is cemented carbide, ceramic material, cast carbide material, or cermet. A radial piston pump characterized by comprising a wear-resistant material made of   The piston foot plate (18) has at least one insert (30) made of the wear-resistant material on the surface (31) of the piston foot plate facing the drive roller (8). The radial piston pump according to claim 1. _3. The radial piston pump according to claim 1, wherein the ceramic material contains silicon nitride (Si ₃ N ₄ ) and has a surface roughness R _z of 0.15 μm to 0.5 μm. Radial piston pump according to claim 1 or 2 wherein the cemented carbide G20, contains GC37 or GC20, characterized by having a surface roughness _{R z} of 0.3Myuemu～1.0Myuemu. 3. The radial piston pump according to claim 1, wherein the cast carbide material includes a GGH or SoGGH cold-cured cast iron material and has a surface roughness R _z of 0.5 μm to 2.0 μm. 4.   The piston foot plate (18) has at least two grooves (50) intersecting each other on the surface (31) of the piston foot plate facing the drive roller (8). The radial piston pump of any one of -5.   Radial piston pump according to claim 6, characterized in that one of the grooves (50) is respectively arranged in the center of a recess (39) forming a lead-out groove on the surface (31). The surface of the piston foot plate (18) and / or the drive roller (8) has a surface roughness R _z of 0.15 μm to 2 μm, according to claim 1. Radial piston pump.

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