Title of Invention

HIGH-PRESSURE PUMP FOR A FUEL INJECTION DEVICE OF AN INTERNAL COMBUSTION ENGINE

Abstract The high-pressure pump features a drive shaft (12) that is driven in a rotary fashion, that has a shaft section (26) which is designed eccentric to its axis (13), on which a ring (28) pivots. The high-pressure pump has at least one pump element (32) that possesses a pump piston (34) that is driven at least indirectly in an elevating motion by the drive shaft through the ring (28) and that lies, at least indirectly, against the ring (28). The ring (28) is provided with a coating (56) of lubricating varnish at least on its outer surface that faces away from shaft section (26) at least in the region (29) in which the pump piston (34), of which there is at least one, lies at least indirectly at the ring (28).
Full Text

High-pressure Pump for a Fuel Injection Device of an Internal Combustion Engine
Prior Art
The invention emanates from high-pressure pump for a fuel injection device pertaining to an internal combustion engine according to the genre of Claim 1.
This kind of high-pressure pump is established through DE 198 44 272 A1. It has a drive shaft that is driven in a rotating fashion and that has a shaft section which is designed eccentric to its axis. A polygon ring pivots on the eccentric shaft section. The high-pressure pump has at least one pump element with a pump piston that is driven at least indirectly in an elevating motion by the drive shaft through the ring. The ring displays flat portions at it's periphery that correspond to the number of pump elements. The pump pistons abut these flat portions, at least indirectly, for example though a tappet rod. While operating the high-pressure pumps, the rings and the pump piston or tappet rods are subject to great strain besides resulting in surface pressures. Apart from this, sliding movements between the ring and the pump piston or tappet rods could also result. Lubrication of the contact regions between the ring and the pump piston or tappet rods takes place through fuel present in the interior of the high-pressure pump casing. Lubrication through fuel is no longer sufficient when operating at high fuel temperatures, thus resulting in a great deal of wear and tear of the rings and/or the pump pistons or tappet rod which can ultimately lead to malfunction of the high-pressure pump.

Advantages of the Invention
The high-pressure pump in accordance with the invention, with features according to Claim 1 has the advantage, when compared to prior art, of ensuring an ample resistance to wear and tear at the contact regions between the ring and at least indirectly the pump piston of which there is at least one, through the lubricating varnish coating of the ring.
Advantageous designs and other details of the high-pressure pump in accordance with the invention are specified in the dependent claims. The combination of a nitracarburised surface area layer and the coating of lubricating varnish applied on to this in accordance with Claim 3 enables particularly good resistance to wear and tear. The coating of lubricating varnish thereby helps to run in the high-pressure pump at the beginning of operation so that there is a two-way alignment of the micro topographies of the ring's surface area and at least indirectly of the pump piston. Apart from this, during high-pressure pump operation, through pressure occurring between the ring and at least indirectly the pump piston, components of the lubricating varnish are pressed into the large-pored pore seam of the nitracarburised surface area layer. Lubricant reservoirs thus develop from the lubricating varnish components and particles of solid lubricant are continuously discharged from these reservoirs when the high-pressure pump overheats at high fuel temperatures, which prevents a deficiency of lubrication.
Drawing
An exemplary embodiment of the invention is illustrated in the drawing and explained in greater detail in the subsequent description. Figure 1 illustrates a fuel injection device of an internal combustion engine with a high-pressure pump

and Figure 2 illustrates the high-pressure pump in cross-section along lines II - II in Figure 1.
Description of the Exemplary Embodiments
Figures 1 and 2 illustrate a high-pressure pump for a fuel injection device pertaining to an internal combustion engine. The high-pressure pump has a casing 10 that is composed of several parts and in which a drive shaft 12 is located. The drive shaft 12 pivots in the casing 10 at two bearing points 14 and 16 that are distanced from one another and are in the direction of the axis 13 of the drive shaft 12. The bearing points 14, 16 can be located at various parts of the casing 10.
In the area lying between the two bearing points 14, 16, the drive shaft 12 displays a shaft section 26 that is designed eccentric to its axis 13. The mechanical transmission element 28 in the form of a polygon ring pivots at the shaft section over a bearing point 30. The high-pressure pump has at least one pump element 32, preferably several, located in the casing 10 with one pump piston 34 respectively that is driven through the polygon ring 28 in an elevating motion in a direction that is at least approximately radial to the axis 13 of the drive shaft 12. The pump piston 34 can be moved in a vacuum sealed manner in the cylinder bore 36 in the casing 10 or in an element in the casing 10 and borders a pump chamber 38 in the cylinder bore 36 with its front side that faces away from the mechanical transmission element 28. The pump chamber 38 exhibits a connection to the fuel inlet through the fuel supply conduit 40 that runs in the casing 10, for example a feed pump. An inlet valve 42 that opens into the pump chamber 38 is located at the port of the fuel supply conduit 40 in the pump chamber 38 and possesses a spring-loaded valve element 43. Over and above this, the pump chamber 38 exhibits a connection to a discharge unit through a fuel discharge conduit 44 running in the casing 10 that is, for example, connected

to the accumulator. A discharge valve 46 opening from the pump chamber 38 is located at the port of the fuel discharge conduit 44 in the pump chamber 38. The discharge valve too has a spring-loaded valve element 47.
The pump piston 34 is held in contact with the polygon ring 28 directly with its piston base or through a tappet rod 52 by a pre-loaded spring 48. The polygon ring 28 does not move along with the drive shaft 12 during the rotary motion of the latter but does, however, execute a movement that is perpendicular to the axis 13 of the drive shaft 12 due to the eccentric section 26 that generates an elevating motion of the pump piston 34. In its outer cover, the polygon ring 28 exhibits a flat portion 29 for every pump element 32 against which the base of the piston 50 or the tappet rod 52 abut. During the suction stroke of the pump piston 34, which is when this moves radially inwards, the pump chamber 38 is filled with fuel through the fuel supply conduit 40 when the inlet valve 42 is open, whereby the discharge valve 46 is closed. During the discharge stroke of the pump piston 34, which is when the same moves radially outwards, fuel is supplied to the accumulator 110 through the pump piston 34 under high pressure through the fuel discharge conduit 44 when the discharge valve 46 is open, whereby the inlet valve 42 is closed.
The polygon ring 28 pivots directly at the bearing point 30 i.e. without a bearing bush or pivots though a bearing bush on the shaft section 26. The polygon ring 28 can be provided with a coating 54 of lubricating varnish on its inner surface that faces the shaft section 26. Alternatively, or in addition, the shaft section 26 can also be provided a coating 54 of lubricating varnish on its outer surface that faces the polygon ring 28. The coating 54 has a thickness of approximately 10 and 50 µm, preferably between approximately 15 and 30 µm. The coating 54 consists of a lubricating varnish having the required properties with regard to the adhesion factor, resistance to wear and tear and temperature resistance for application at the bearing point 30. Even in the case of lubrication of the bearing

point 30 with only fuel present in the interior of the casing 10, the coating 54 ensures a low adhesion factor and ample resistance to wear and tear of the bearing point 30. In the case of a pre-determined size of the external cross-section of the polygon ring 28 the same can, due to the marginal thickness of the coating 54 and of the marginal internal diameter thereby enabled, be executed with relatively large wall thickness.
At its outer side that faces away from the shaft section 26, the polygon ring 28 is provided with a coating 56 of lubricating varnish at least in the region of the flat portions 29. The polygon ring 28 can also be provided with a coating 56 of lubricating varnish on its entire surface area. The coating 56 of lubricating varnish has a thickness of between approximately 10 and 50 µm but preferably between approximately 15 and 30 µm. The lubricating varnish for the coating 56 is applied on the polygon ring 28 in a liquid or powder form and subsequently cured at heightened temperatures. The lubricating varnish thereby comprises at least essentially of a varnish with particles of a solid lubricant incorporated in it.
The polygon ring 28 is preferably provided with a nitracarburised surface area layer 58 at least in the area of the flat portions 29. The ring 28 can also exhibit the nitracarburised surface area layer 58 along its entire surface area. This surface area layer 58 is created by inserting the polygon ring 28 in a salt bath. The nitracarburised surface area layer 58 has a thickness of approximately 5 to 20 urn, preferably of approximately 10 µm. The surface area layer 58 thereby exhibits an external region with pores and an internal, pore-free region with a thickness of at least 5 µm.
The polygon ring 28 is made of steel, preferably an alloy of 16MnCrS5. The polygon ring 28 is annealed and subsequently inserted in to the salt bath where the nitracarburised surface area layer 58 is created and on which the coating 56 of lubricating varnish is applied and then cured.

The coating 56 of lubricating varnish helps to run in the high-pressure pump at the beginning of operation so that there is a two-way alignment of the micro topographies of surface areas of the flat portions 29 of the polygon ring 28 that lie next to one another and the base of the piston 50 and tappet rod 52 respectively. Apart from this, through pressure occurring between the polygon ring 28 and the base of the piston 50 and tappet rod 52 respectively during operation of the high-pressure pump, components of the lubricating varnish are pressed into the large-pored pore seam, i.e. the external region of the nitracarburised surface area layer 58 of the polygon ring 28. Lubricant reservoirs thus develop from lubricating varnish components and particles of solid lubricant are continuously discharged from these reservoirs when the high-pressure pump overheats at high fuel temperatures, which prevents a deficiency of lubrication between the polygon ring 28 and the base of the piston 50 and tappet rod 52 respectively.

Claims
1. High-pressure pump for a fuel injection device of an internal
combustion engine with a drive shaft (12) driven in a rotating fashion,
which has a shaft section (26) that is designed eccentric to its axis
(13), on which a ring (28) pivots and with at least one pump element
(32) that has a pump piston (34) which is driven at least indirectly by
the drive shaft (12) though the ring (28) in an elevating motion,
characterised in that the ring (28) is provided with a coating (56) of
lubricating varnish at least on its outer surface that faces away from
shaft section (26) at least in the region (29) in which the pump piston
(34), of which there is at least one, lies at least indirectly at the ring
(28).
2. High-pressure pump according to Claim 1, characterised in that the
ring (28) exhibits at least one flat portion (29) at its periphery against
which the pump piston (34) lies at least indirectly and which is provided
with a coating (56) of lubricating varnish.
3. High-pressure pump according to Claim 1 or 2, characterised in that
the ring (28), at least in the region in which the coating (56) of
lubricating varnish is applied, features a nitracarburised surface area
layer (58) on which the coating (56) of lubricating varnish is applied.
4. High-pressure pump according to Claim 3, characterised in that the
nitracarburised surface area layer (58) has a thickness of
approximately 5 to 20 µm, preferably of approximately 10 µm.

5. High-pressure pump according to Claims 1 to 4, characterised in that
the coating (56) of lubricating varnish has a thickness of approximately
10 to 50 µm, preferably of approximately 15 to 30 µm,
6. High-pressure pump according to one of the previous Claims,
characterised in that the ring (28) is composed of an alloy 16MnCrS5.
Dated this 20 day of February 2006

Documents:

614-CHENP-2006 AMENDED PAGES OF SPECIFICATION 15-03-2011.pdf

614-CHENP-2006 AMENDED CLAIMS 15-03-2011.pdf

614-CHENP-2006 CORRESPONDENCE OTHERS 14-11-2011.pdf

614-CHENP-2006 EXAMINATION REPORT REPLY RECEIVED 15-03-2011.pdf

614-chenp-2006 form-3 15-03-2011.pdf

614-CHENP-2006 OTHER PATENT DOCUMENT 15-03-2011.pdf

614-CHENP-2006 POWER OF ATTORNEY 15-03-2011.pdf

614-CHENP-2006 CORRESPONDENCE OTHERS 16-12-2010.pdf

614-CHENP-2006 CORRESPONDENCE OTHERS.pdf

614-CHENP-2006 CORRESPONDENCE PO.pdf

614-CHENP-2006 FORM 18.pdf

614-chenp-2006-abstract.pdf

614-chenp-2006-claims.pdf

614-chenp-2006-correspondence-others.pdf

614-chenp-2006-description(complete).pdf

614-chenp-2006-drawings.pdf

614-chenp-2006-form 1.pdf

614-chenp-2006-form 26.pdf

614-chenp-2006-form 3.pdf

614-chenp-2006-form 5.pdf

614-chenp-2006-pct.pdf


Patent Number 247549
Indian Patent Application Number 614/CHENP/2006
PG Journal Number 16/2011
Publication Date 22-Apr-2011
Grant Date 19-Apr-2011
Date of Filing 20-Feb-2006
Name of Patentee ROBERT BOSCH GmbH
Applicant Address Postfach 30 02 20, D-70442 Stuttgart, GERMANY
Inventors:
# Inventor's Name Inventor's Address
1 RITTMANNSBERGER, Wolfram Lindenspuerstrasse 23, 70716 Stuttgart
2 KLEINBECK, Thomas Suedmaehrenstrasse 2, 71665 Vaihingen/Enz-Riet, GERMANY
3 KOCH, Markus Forststrasse 82 A, 70176 Stuttgart
PCT International Classification Number F04B 1/04, F04B 1/053, F04B 9/04
PCT International Application Number PCT/DE04/01303
PCT International Filing date 2004-06-22
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 203 13 014.6 2003-08-21 Germany