EP0290855A2

EP0290855A2 - Pump with a self-contained casing comprising separate pumping and drive sections, for high-pressure fuel injection in internal combustion engines

Info

Publication number: EP0290855A2
Application number: EP88106652A
Authority: EP
Inventors: Nedo Ferrucci
Original assignee: OMAP SpA
Current assignee: OMAP SpA
Priority date: 1987-05-12
Filing date: 1988-04-26
Publication date: 1988-11-17
Also published as: IT8702917A0; EP0290855A3; IT1206949B

Abstract

This reciprocating pump for high-pressure fuel injection in internal combustion engines is characterised by a self-contained casing (1) provided with separate pumping (15, 16) and drive sections (3) to allow their overhaul and/or replacement by particularly advantageous procedures.

Description

This invention relates to the field of fuel pumps used for fuel injection in internal combustion engines of the diesel or otto cycle type, and in particular to a reciprocating pump.
The injection of fuel into the combustion chambers of internal combustion engines is known to require very high pressures and very short times of action. This requirement has lead to specific construction methods for such reciprocating pumps, but these have resulted in various problems. One of these is connected with the thermal expansion of the metallic structures, which influence such pumps because they are usually integral with the crankcase. In this respect as the pumping plungers operate with lapped surfaces and with a degree of play which generally does not exceed three thousandths of a millimetre, the temperature rise which the engine structure undergoes (in passing from ambient temperature to normal working temperature, or even higher under certain limiting conditions), creates expansion such as to cause excessive wear. This obviously results in abnormal engine operation. The usual integral construction of reciprocating pumps with the crankcase of certain engines, particularly of the diesel type, can create certain difficulties when they have to be maintained or repaired in industrially underdeveloped countries in which repair mechanics are poorly competent or insufficiently capable.
An object of the present invention is to provide a reciprocating pump which is thermally insulated to a certain extent from the engine structure so as to reduce the degree of temperature rise during operation.
A further object is to provide a reciprocating pump having a self-contained casing comprising a drive part and pumping part which are separate and themselves self-contained, so as to facilitate replacement of an individual damaged element.
A further object is to provide a reciprocating pump which still retains the typical operating characteristics of conventional pumps integral with the crankcase.
These and further objects are attained, as will be apparent to experts of the art on reading the following description, by a reciprocating pump for high-pressure fuel injection in internal combustion engines, characterised by a self-contained casing provided with pumping and drive sections which are separate from each other to allow their overhaul and/or replacement by particularly advantageous procedures.
The invention is illustrated by way of non-limiting example on the accompanying drawing, in which:
Figure 1 is a complete side sectional view of the casing of a three-plunger reciprocating pump, and showing a specific pumping unit in partial section;
Figure 2 is a side view taken perpendicular to Figure 1.
With reference to the said figures, an outer box casing 1 is provided with a hole 2 for supporting a cylindrical portion 3T of a camshaft 3 supported at its other end 3E by a seat 4S in a cover 4 fixed by usual screws 5.
The camshaft 3 is retained in its working seat by a split ring 6 operating in an outward direction. Inward retention is provided by a shoulder 3P formed on the end 3F which is rotated by specific members of the engine by way of pins or bolts engaged in bores 7 with the assistance of a locating seat 8.
The box casing 1 is provided with a flange 1G having slotted holes 9 to enable the casing 1 to be fixed to the engine (not shown) on the plane Z, using normal bolts.
On the end 3E of the shaft 3 there is fixed a normal centrifugal regulator 13 which with the aid of lever systems 19 controls the sliding of normal flow regulator racks 10 which drive pinions 11 effecting the normal rotation of pumping plungers 12.
The cams are indicated by 3B, 3C, 3D, and on them there rotate the rollers 14 of the tappets which comprise the individual pumping plungers 12. The box casing 1 is provided upperly with an aperture into which a housing for the various pumping units 16 is inserted. The drawing shows a type comprising three pumping units for feeding a three-cylinder engine, however the pump of the present invention can be provided with any number of pumping units, and is therefore suitable for any multi-cylinder engine.
The housing 15 is shown sectioned only to the extent necessary to show the arrangement of the various pumping units 16 in its interior. The housing 15 is fixed to the box casing 1 by normal bolts 17.
The described embodiment advantageously enables those parts of the pump most subject to wear or damage (ie the elements which undergo reciprocating movement and are subjected to the flowing fuel) to be replaced by merely unscrewing a few fixing bolts 17 and removing the delivery pipes from their connectors 18.
This is an advantage not only in terms of servicing speed which in certain situations can be invaluable, but also in terms of the possibility of service by personnel who do not have specific equipment available or who are not sufficiently trained to carry out the setting, overhaul or replacement of internal components. This applies in the case of damage in technologically underdeveloped countries. A further advantage of the present invention is the considerable area of its radiant surface compared with the small area of the surface 1G by which it is connected to the engine and through which it absorbs heat.

Claims

1. A reciprocating pump for high-pressure fuel injection in internal combustion engines, characterised by a self-contained casing provided with a pumping section (15, 16) and drive section (1, 3) which are separate from each other to allow their overhaul and/or replacement by particularly advantageous procedures.

2. A reciprocating pump for high-pressure fuel injection as claimed in the preceding claim, characterised by being fixed to the engine by a flange (1G), the connection surface of which is perpendicular to the camshaft (3) of the drive section (1, 3) so as to limit the area of the heat conducting surface.