GB2361048A

GB2361048A - Distributor injection pump

Info

Publication number: GB2361048A
Application number: GB0105334A
Authority: GB
Inventors: Andreas Dutt
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-03-14
Filing date: 2001-03-05
Publication date: 2001-10-10
Anticipated expiration: 2021-03-05
Also published as: GB0105334D0; DE10012306A1; JP2001263190A; DE10012306C2; GB2361048B

Abstract

A distributor injection pump comprises a distributor shaft 10 which rotates in a bearing (14) and comprises a distributor groove 22. The distributor shaft is provided on its outer surface with an axially extending lubricant groove 24, 26 which issues at an end face of the distributor shaft and extends as far as to an annular chamber (16, figure 1) which is formed in the bearing and is supplied with fuel subjected to delivery pressure. Groove 22 preferably has a first portion 24 extending between the end face and a back-fill groove 28 and of smaller cross-section than a second protion 26 extending between back-fill groove 28 and chamber (16). The lubrication groove 24,25 preferably trails distribution groove 22 by 90 { in use and preferably has sharp edges to aid carrying away of dirt particles. The arrangement improves hydrodynamic lubrication and provides a cooling and flushing function. The distributor injection pump is used for fuel injection in internal combustion engines.

Description

2361048 1

DESCRIPTION

Distributor injection 12muM The invention relates to a distributor injection pump having a distributor shaft which rotates in a bearing and comprises a distributor groove.

Distributor injection pumps of this type are generally known in prior art. They are used for the purpose of supplying pressurized fuel selectively to an injection nozzle of an internal combustion engine. During each injection process, a pressure field builds up owing to the pressure prevailing in the distributor groove and in conjunction with the rotation of the distributor shaft this pressure field serves to produce a circulating transverse force. As a consequence, the distributor shaft is deflected outwards. The respective counterforce is generated by a hydrodynamic sliding bearing which is attached to the side of the distributor shaft lying opposite the distributor groove. This sliding bearing is hitherto supplied by a leakage flow between the distributor shaft and the bearing thereof, so that the influx of lubricant is dependent upon the clearance between the bearing and the distributor shaft. In each case, the leakage current must be dimensioned so as to provide a sufficient through-flow of lubricant, which in the case of pulsating loads guarantees cooling on the one hand and sufficient liquid padding between the distributor shaft and the bearing on the other hand.

An object of the present invention is to develop farther a distributor injection pump of the type stated in the introduction such that lubrication of the hydrodynamic sliding bearing is improved so as to afford a greater degree of protection to prevent the distributor shaft from seizing up.

1 2 In accordance with the present invention, the distributor shaft is provided on its outer surface with an axially extending lubricant groove which issues at an end face of the distributor shaft and extends as far as to an annular chamber which is formed in the bearing and is supplied with fuel subjected to delivery pressure.

A distributor injection pump in accordance with the invention can have the advantage that, irrespective of the bearing clearance, the axially extending lubricant groove guarantees a sufficient influx of lubricant for the sliding bearing. In accordance with a preferred embodiment, the lubricant groove can comprise a first portion and a second portion, wherein the first portion issues at the end face, extends as far as to a back fill groove and comprises a smaller cross-section than the second portion which extends from the back fill groove as far tq as the annular chamber. The cross-section of the second portion of the lubricant groove is designed in such a manner that sufficient quantities of fuel can flow through for the purpose of the back-filling procedure. Between the back fill groove and the end face of the distributor shaf which leads to a magnet chamber, the cross-section is optimized for a sufficient influx of lubricant for the hydrodynamic sliding bearing and the correct throughflow of coolant for the magnet chamber. A further advantage is that it is possible to omit the back fill bore which is typically provided. It is also possible to dispense with the typical suction pump effect during back-filling from the annular chamber.

The lubricant groove is preferably arranged in such a manner that in relation to the normal direction of rotation of the distributor shaft it trails the distributor groove. Therefore, it lies in a region of the hydrodynamic sliding bearing, in which negative pressure prevails, so that the fuel which serves as a lubricant is drawn by suction out of the axially extending lubricant groove into the sliding bearing. Preferably, the lubricant groove trails the distributor groove by approximately 90'.

In accordance with a preferred embodiment of the invention, the lubricant groove can be formed with sharp edges. In this manner, any particles of dirt located in the bearing gap Of the hydrodynamic sliding bearing are carried away.

3 The invention will be described further hereinafter with reference to a preferred embodiment which is illustrated in the accompanying drawings, in which Figure 1 shows a partially cut view of a distributor injection pump; Figure 2 shows a plan view of a distributor shaft which is used in the distributor injection pump of Figure 1; Figure 3 shows a schematic sectional view of the hydrodynamic sliding bearing being formed on the distributor shaft; Figure 4 shows a truncated sectional view along the plane IV of Figure 2; and Figure 5 shows, with respect to Figure 4, an enlarged scale, truncated sectional view along the plane V of Figure 2.

The distributor injection pump illustrated in Figure 1 contains a distributor shaft 10 which is disposed in a bearing bush 12 whose inner surface forms a bearing 14 for the distributor shaft 10. Forined in the bearing bush 12 is an annular chamber 16 which serves to supply the fuel which is subjected to a delivery pressure and is to be injected. The bearing bush 12 is positioned in a housing 18, in which there is formed a solenoid valve chamber 20 which contains a solenoid valve which is provided for the purpose of switching the injection procedure. The fuel is ultimately carried away via a distributor groove 22 of the distributor shaft 10.

The distributor shaft 10 comprises a lubricant groove which extends in the axial direction on its outer surface and which consists of a first portion 24 and a second portion 26. Starting 4 from the end face of the distributor shaft on the right-hand side in the Figures, the first portion of the lubricant groove extends as far as to a backfill groove 28, and starting from the back fill groove 28, the second portion 26 of the lubricant groove extends as far as to a point on the distributor shaft which is connected to the annular chamber 16 in the bearing bush 12. The cross-section of the first portion is smaller than the cross-section of the second portion of the lubricant groove. A value of 0.5 mm can be taken as a reference value for the width of the lubricant groove in the first portion, whereas a value of about 1.5 mm. can be assumed for the width in the second portion. Since the lubricant groove extends as far as to the solenoid valve chamber, the quantity of fluid, which is required for flushing and cooling purposes, in the region of the valve seat is taken from the distributor injection pump so that a greater degree of hydraulic efficiency is achieved- As shown in Figure 3, the lubricant groove is arranged in relation to the direction of rotation of the distributor shaft 10 such that it trails the distributor groove 22 by approximately 9T. The lubricant groove is thus arranged in a region, in which negative pressure prevails. This is evident in Figure 3 which illustrates the pressure progression in the hydrodynamic sliding bearing which prevails in the bearing 14 as the distributor shaft 10is rotated, which bearing is filled with fuel serving as a lubricant The pressure prevailing in the distributor groove 22 serves to generate a transverse force, illustrated in this case by the arrow F, which acts upon the distributor shaft and circulates with the distributor shaft. This transverse force is counteracted by the pressure resulting from the fuel banking up in the narrowing bearing gap. The illustrated pressure distribution circulates with the distributor shaft, so that the lubricant groove is always arranged in the same position in relation to the area in which negative pressure prevails.

Since the lubricant groove is connected to the annular chamber 16, the hydrodynamic sliding bearing being formed is guaranteed to be supplied with lubricant in a uniform manner irrespective of bearing clearance tolerances.

Claims

A distributor injection pump having a distributor shaft which rotates in a bearing and comprises a distributor groove, and wherein the distributor shaft is provided on its outer surface with an axially extending lubricant groove which issues at an end face of the distributor shaft and extends as far as to an annular chamber which is formed in the bearing and is supplied with fuel subjected to delivery pressure.
2. A distributor injection pump according to claim 1, wherein the lubricant groove comprises a first portion and a second portion, and wherein the first portion issues at the end face, extends as far as to a back fill groove and comprises a smaller cross-section than the second portion which extends ftom the back fill groove as far as to the annular chamber.
3. A distributor injection pump according to any of the preceding claims, wherein the lubricant groove is arranged in such a manner that in relation to the normal direction of rotation of the distributor shaft it trails the distributor groove.
4. A distributor injection pump according to claim 3, wherein the lubricant groove trails the distributor groove by approximately 90'.
5. A distributor injection pump according to any of the preceding claims, wherein the lubricant groove is formed with sharp edges.
6. A distributor injection pump substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.