Title of Invention

FUEL HIGH-PRESURE ACCUMULATOR

Abstract

Afuel high-pressure accumulator for a common rail fuel injection system of an internal combustion engine, with a basic tubular body, which has an essentially cylindrical interior chamber arranged concentrically with the longitudinal axis of the basic tubular body, the chamber being connected to a plurality of connection apertures, characterized in that the cross section of the basic tublar body is of weakened construction in the sectional areas iin which the connection apertures are arranged, the weakenings of the basic tubular body are formed on the outer surface of the basic tubular body.

Full Text

R.35873 PCT/DE00/03695 20.08.1999 Robert Bosch GmbH, 70469 Stuttgart Fuel high-pressure accumulator Prior art The invention relates to a fuel high-pressure accumulator for a common rail fuel injection system of an internal combustion engine, with a basic tubular body, which has an essentially cylindrical interior chamber arranged concentrically with the longitudinal axis of the basic tubular body, the chamber being connected to a plurality of connection apertures. In common rail injection systems a high-pressure pump, which may be assisted by a pre-supply pump, delivers the fuel to be injected from a tank into the central fuel high-pressure accumulator, which is known as a common rail. From the rail, fuel lines lead to the individual injectors, which are assigned to the cylinders of the internal combustion engine. The injectors are actuated individually by the engine electronics as a function of the operating parameters of the internal combustion engine, in order to inject fuel into the combustion chamber of the internal combustion engine. The fuel high-pressure accumulator isolates the pressurization and injection functions from one another. A conventional fuel high-pressure accumulator is described, for example, in DE 195 48 611. The known fuel high-pressure accumulator can withstand pressures of up to approximately 1100 bar. The object of the invention is to increase the high-pressure resistance of the known fuel high-pressure accumulator by means of simple measures. The object is achieved in a fuel high-pressure accumulator for a common rail fuel injection system of an internal combustion engine, with a basic tubular body, which has an essentially cylindrical interior chamber arranged concentrically with the longitudinal axis of the basic tubular body, the chamber being connected to a plurality of connection apertures, in that the cross section of the basic tubular body is of weakened construction in the sectional areas in which the connection apertures are arranged. It has emerged in the course of the present invention that under internal pressure critical tensile stresses occur in the area of the intersections between the connection apertures. Purposely weakening the basic tubular body increases the high-pressure resistance of the fuel high-pressure accumulator according to the invention. A particular embodiment of the invention is characterized in that the connection apertures essentially open tangentially into the interior chamber of the basic body, and that a weakening of the basic tubular body is provided in the area of each of the connection apertures. In operation of the fuel high-pressure accumulator according to the invention the interior chamber of the basic tubular body expands under the high pressure prevailing there. Purposely weakening the basic tubular body causes the circular cross section of the interior chamber to deform to an elliptical shape in the unstressed state, which is known as ovalization of the diameter. In this a major vertex of the ellipse is arranged in the area of each connection aperture. This induces a compressive stress in the circumferential direction of the basic tubular body in the area of intersection between the basic tubular body and the connection aperture. The said compressive stress partially compensates for the critical tensile stress. This reduces the stress loading in the areas of the intersections most at risk. A further particular embodiment of the invention is characterized in that, viewed in cross section, a further weakening of the basic tubular body is provided opposite each of the connection apertures. This enhances the effect, already described, of ovalization of the interior chamber of the basic tubular body. This leads to a further increase in the high-pressure resistance of the fuel high-pressure accumulator according to the invention. A further particular embodiment of the invention is characterized in that the connection apertures essentially open radially into the interior chamber of the basic body, and that, viewed in cross section, a weakening of the basic tubular body is provided opposite each of the connection apertures. As a result, the effect, already described, of ovalization of the interior chamber of the basic tubular body is obtained even in the case of a radial connection aperture. A further particular embodiment of the invention is characterized in that the weakening of the basic tubular body is formed by a grind, an undercut or a flat surface. These methods of weakening the cross section have the advantage that they are easy to produce. As a result, the high stresses occurring under internal pressure in the area of intersection can be reduced even in conventional fuel high-pressure accumulators. Further advantages, features and details of the invention are revealed in the description below, in which two exemplary embodiments of the invention are described in detail with reference to the drawing. In these the features mentioned in the claims and in the description may each be essential for the invention either separately or in any combination. In the drawing: Figure 1 shows a cross section through a first exemplary embodiment of the invention with a tangential connection bore and Figure 2 shows a further exemplary embodiment of the invention with a radial connection bore. The first exemplary embodiment of a fuel high-pressure accumulator represented in Figure 1 comprises a basic tubular body 1. The basic tubular body 1 takes the shape of a hollow cylinder ♦ A longitudinal bore 2 is hollowed out inside the basic tubular body 1. The longitudinal bore 2 is arranged concentrically in the basic tubular body 1 and forms the accumulator volume of the fuel high-pressure accumulator according to the invention. A connection bore 3 runs transversely to the longitudinal axis of the basic tubular body and opens tangentially into the longitudinal bore 2. The bore intersection between the connection bore 3 and the longitudinal bore 2 is indicated at 4. In the area of the connection bore 3 a recess 5 is provided in the outer circumferential surface of the basic tubular body 1. The recess 5 is of circular cross section and extends in the longitudinal direction of the basic tubular body 1 only in the area of the connection bore 3. A flattening is indicated at 6 opposite the recess 5. The high pressure prevailing inside the basic tubular body 1 during operation is represented by a plurality of arrows in a radial direction on the circumference of the longitudinal bore 2. The deformation of the basic tubular body 1 under high pressure is indicated by an ellipse 7 represented by dashed lines. As a result of the cross-sectional weakenings at the points 5 and 6, additional compressive stresses occur in a circumferential direction at the critical point 8. The second exemplary embodiment of a fuel high-pressure accumulator represented in Figure 2 comprises a basic tubular body 11. A longitudinal bore 12 is hollowed out of the basic tubular body 11. A connection bore 13 opens radially into the longitudinal bore 12* The bore intersection between the connection bore 13 and the longitudinal bore 12 is indicated at 14. The internal pressure occurring during operation is represented by a plurality of arrows in a radial direction on the circumference of the longitudinal bore 2, Owing to a flattening 16 arranged opposite the connection bore 13 the basic tubular body 11 is deformed in the shape of an ellipse 17 represented by dashed lines. This relieves the critical point 18 in the area of the bore intersection 14. The solution according to the invention reduces the high stresses in the area of the bore intersections. Under load, an ovalization of the diameter is achieved owing to the cross-sectional weakenings. This induces compressive stresses in the circumferential direction in the area of intersections and partially compensates for the critical tensile stresses. The stress loading in the bore intersections is consequently reduced. The invention can be arranged not only on fuel high-pressure accumulators, but also on injectors and pump nozzle bodies. According to the present invention the weakenings 5, 6; 16 of the basic tubular body are formed on the outer surface of the basic tubular body* 20.08.1999 Robert Bosch GmbH, 70469 Stuttgart NEW Claims 1. A fuel high-pressure accumulator for a common rail fuel injection system of an internal combustion engine, with a basic tubular body (1; 11), which has an essentially cylindrical interior chamber (2; 12) arranged concentrically with the longitudinal axis of the basic tubular body, the chamber being connected to a plurality of connection apertures (3; 13), characterized in that the cross section of the basic tubular body (1; 11) is of weakened construction in the sectional areas in which the connection apertures (3; 13) are arranged. 2. The fuel high-pressure accumulator as claimed in Claim 1, characterized in that the connection apertures (3) essentially open tangentially into the interior chamber of the basic body (1), and that a weakening (5) of the basic tubular body (1) is provided in the area of each of the connection apertures (3). 3. The fuel high-pressure accumulator as claimed in Claim 2, characterized in that, viewed in cross section, a further weakening (6) of the basic tubular body (1) is provided opposi te each of the connection apertures (3). 4. The fuel high-pressure accumulator as claimed in Claim 1, characterized in that the connection apertures (13) essentially open radially into the interior chamber of the basic body (11) and that, viewed in cross section, a weakening' (16) of the basic tubular body (1) is provided opposite each of the connection apertures (13). 5. The fuel high-pressure accumulator as claimed in any of the preceding Claims, characterized in that the weakening (5, 6; 16) of the basic tubular body (1; 11) is formed by a grind, an undercut or a flat surface. 6. A fuel high-pressure accumulator, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

in-pct-2001-1117-che-abstract.pdf

in-pct-2001-1117-che-claims filed.pdf

in-pct-2001-1117-che-claims granted.pdf

in-pct-2001-1117-che-correspondnece-others.pdf

in-pct-2001-1117-che-correspondnece-po.pdf

in-pct-2001-1117-che-description(complete)filed.pdf

in-pct-2001-1117-che-description(complete)granted.pdf

in-pct-2001-1117-che-drawings.pdf

in-pct-2001-1117-che-form 1.pdf

in-pct-2001-1117-che-form 26.pdf

in-pct-2001-1117-che-form 3.pdf

in-pct-2001-1117-che-form 5.pdf

in-pct-2001-1117-che-other documents.pdf

in-pct-2001-1117-che-pct.pdf