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Transfer pump for injection of fuel at high pressure

Transfer pump for injection of fuel at high pressure description/claims

The present invention relates to improvements in pumps for the injection of fuel at high pressure, of the type comprising a piston delivering hydraulic fluid into a deformable element such as a bellows, the deformations of said bellows in a cylindrical chamber filled with fuel giving rise to a pumping effect of said fuel toward high pressure injectors.

Pumps of this type have been described in U.S. Pat. No. 2,826,068, 2,828,240 and patent application 06/02594 in the name of the applicant.

The present invention has for its object to provide a solution to two problems which arise from mounting this type of pump on motors.

The first problem arises because in certain motors it is necessary to integrate the direct injection high pressure injection pump at the end of the camshaft or on the transmission pulleys and not directly on the cylinder head. In the case of the utilization of a single piston pump an angle change is necessary, which gives rise to various drawbacks such as: the size of the pump, the requirement for an adaptation housing, lubricating means, noise, wear of the elements etc.

The second problem arises because for such a mounting, it is necessary to provide an operating play between the drive means of the pump and the latter, of the Oldham joint type, for example. When the pump is single piston, there are produced large vibrations from the resistive couple of the pump, possibly even with negative peaks, which vibrations can give rise to loosening the contact surfaces which transmit the couple, which loosening generates couple returns in the motor shaft. These couple returns constitute a disturbing element for the operation of the motor such as: coupling jolts on the camshaft or timing chain, unacceptable noise.

The solution of the first problem consists in designing the pump such that the oil portion comprises not only the pumping portion but also all the drive portion and angle change.

This has the advantages: on the one hand suppression of dynamic sealing in translation on the transfer single piston pump which is very cumbersome and remains difficult to control; on the other hand all the drive elements will be perfectly lubricated. Moreover, the increase of the closed cycle oil volume increases the resistance to oil temperature and decreases the risks of heating.

The solution of the second problem consists in providing a free wheel between the drive shaft and the cam.

By way of non-limiting example, and to facilitate understanding of the invention, there are shown the following drawings, in which:

FIG. 1 is a cross-sectional view of an embodiment of the transfer pump according to the invention,

FIG. 2 is a cross-sectional view on A-A of FIG. 1,

FIG. 3 is a fragmentary view showing a modification of FIG. 2.

Referring to these drawings, it will be seen that the pump according to the invention comprises a drive shaft 1, connected by an Oldham joint 2 to the drive member (camshaft for example) not shown.

The shaft is carried by a housing 3.

The shaft carries a cam 5, which, in the illustrated example, comprises four lugs 6.

A piston 10 comes to bear by means of a spring 11 against the cam 5, with interposition between the piston 10 and the cam 5 of roller 7, carried by a shaft 8 by means a needle bearing 9.

Preferably, a bearing member 12 is interposed between the roller 7 and the piston 10. This bearing member 12 is preferably constituted by two oppositely facing cups 12a, 12b, separated by a partition 12c provided with a plurality of openings 23.

• Provisional Patent
• Utility Patent

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