GB2174152A

GB2174152A - Fuel pump, particularly a diaphragm pump, driven by an internal combustion engine and mounted directly on the engine

Info

Publication number: GB2174152A
Application number: GB08608497A
Authority: GB
Inventors: Ernst Kuhlen
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1985-04-19
Filing date: 1986-04-08
Publication date: 1986-10-29
Also published as: FR2580727A1; GB8608497D0; IT8647629A0; DE3514165C1

Abstract

A fuel pump is described, particularly a diaphragm pump, which is driven by an internal combustion engine, the pump being mounted directly on the engine. The working chamber of the pump aspirates fuel into a working chamber (12) through a suction valve (13) and discharges it through a discharge valve (15) into a delivery chamber (30). The suction valve (13) communicates directly with an antechamber (14) which itself communicates through an inlet and an outlet channel (23,22), each containing a non-return valve (19,20), with the fuel tank of the engine. This allows evaporated fuel to be refluxed from the antechamber to the tank. <IMAGE>

Description

SPECIFICATION Fuel pump, particularly a diaphragm pump, driven by a internal combustion engine and mounted directly on the engine The invention relates to a fuel pump, particularly a diaphragm pump, driven by an internal combustion engine and mounted directly on the engine, the pump having a working chamber which receives fuel through a suction valve and delivers it through a discharge valve.

Fuel pumps of this kind occupy little space and are consequently often used for supplying fuel to the carburettor of internal combustion engines in motor vehicles.

The fuel pump is often mounted directly on the engine housing, with the consequence that the pump is subjected to engine temperatures which vary greatly in response to operating conditions. Under certain circumstances the pump can become quite hot, particularly in the confined engine space of a highly streamlined modern motor car.

Trouble arises from the fact that modern motor fuels contain increasing amounts of low-boiling fractions. When the engine becomes hot some of the fuel vaporises in the fuel system, causing uneven idling or even failure of the hot engine to start.

As described in the German Offenlegungsschrift 20 00 213, bubbles of fuel vapour form in the interior of the pump and in the delivery channel between the pump and the carburettor. To remedy the matter it is proposed, in this German Offenlegungsschrift 20 00 213, that the fuel pressure in the delivery channel be applied to a flexible diaphragm.

When the fuel pressure rises, due to vaporisation of fuel, the diaphragm responds by constricting the delivery channel, at the same time opening a reflux channel which allows fuel to flow from the delivery channel back to the suction channel through which the pump aspirates fuel. A similar proposal is made in the German Offenlegungsschrift 25 59 157. In this proposal the delivery channel between the pump and the carburettor contains a pressure controller which controls the pressure in the delivery channel and, when the pressure is too high, opens a reflux channel allowing fuel (and fuel vapour) to flow back into the fuel tank of the engine.

The remedies described in these two German Offenlegungsschrifts serve to remove the vapour bubbles, or vapour-filled spaces, in the delivery channel between the fuel pump and the carburettor. But no remedy has hitherto been proposed for removing the gas bubbles, or vapour-filled spaces, occurring upstream of the pump an which often give rise to the same uneven idling and engine starting difficulties.

The intention in the present invention is to modify the conventional fuel pump in such a way that vapour-filled spaces upsteam of the fuel pump are removed.

The problem is solved, according to the invention, by the provision of a fuel pump, particularly a diaphragm pump, driven by an internal combustion engine and mounted directly on the engine, the working chamber of the pump receiving fuel through a suction valve and delivering it through a discharge value, and in which, upstream of the suction valve, there is an antechamber which communicates through an inlet connection and a reflux connection, each equipped with a non-return valve, and through an inlet channel and a reflux channel, with the fuel tank of the engine.

The invention has the following advantages: During idling and hot operation of the engine, and in attempts to start a hot engine, the fuel pump can become strongly heated by conduction through the metal and by radiation from the engine. Under these circumstances fuel drawn from the fuel tank already evaporates to a considerable extent where it enters the hot pump. The rise in pressure produced by the evaporation has hitherto forced the fuel in the inlet channel, upstream of the pump, back into the fuel tank, temporarily starving the engine of fuel, making starting difficult and preventing the engine from responding quickly to a demand for increased power.

These faults do not occur in the fuel pump of the invention.

In the operation of the fuel pump of the present invention liquid fuel aspirated by the pump first flows into an antechamber. Evaporation here raises the pressure, closing a nonreturn valve in the inlet connection of the pump and opening a non-return valve in a reflux connection. Consequently liquid fuel containing vapour bubbles is returned from the antechamber back into the tank. The next suction stroke of the pump closes the non-return valve in the reflux connection and opens the one in the inlet connection, admitting a stream of fresh, cool fuel into the antechamber. This cools the pump rapidly, suppressing further evaporation of fuel. Consequently the engine starts easily, idling becomes steady and the engine responds without hesitation to a demand for increased power.

An example of the invention is represented diagrammatically, in the drawing and will now be described in greater detail. Although the pump illustrated is a diaphragm pump, any other kind of pump can be used without leaving the frame of the invention.

The pump has a housing 1 and a cover 2.

Clamped between the housing 1 and the cover 2 there is a flexible diaphragm 3 which flexes up and down, driven to reciprocate by a push-rod 5 fixed to a diaphragm plate 4.

The push-rod 5 is thrust downwards by a spring 6 and lifted periodically upwards by a cam 9 driven in rotation by a cam-shaft 10, itself driven by the crankshaft (not shown) of the engine, the cam 9 acting on the foot of the push-rod 5. The push-rod 5 works in an aperture 7 in the wall 8 of the engine housing.

Situated between the diaphragm 3 and a separation wall 31 there is a working chamber 12 equipped with a suction valve 13 and a discharge valve 15, both valves being located in the wall 31. The discharge valve 15 communicates through a delivery chamber 30 and a delivery connection 16 with a delivery channel 17 through which fuel is delivered to the carburettor (not shown) of the engine. The suction valve 13 communicates with an antechamber 14. A wall 11 separates the antechamber 14 from the delivery chamber 30.

The antechamber 14 communicates through an inlet connection 19 with an inlet channel 23 through which fuel is aspirated from the fuel tank (not shown) of the engine, the inlet connection 19 containing a non-return valve 18. The antechamber 14 also communicates through a reflux connection 21 with a reflux channel 22 through which fuel can, under certain circumstances, be returned to the fuel tank, the reflux connection 21 also containing a non-return valve 20.

In the operation of the fuel pump of the present invention liquid fuel aspirated by the pump first flows into the antechamber (14).

Evaporation here raises the pressure, closing the non-return valve (18) in the inlet connection (19) of the pump and opening the nonreturn valve (20) in the reflux connection (21).

Consequently liquid fuel containing vapour bubbles is returned from the antechamber (14) back into the tank. The next suction stroke of the pump closes the non-return valve (20) in the reflux connection (21) and opens the one 18 in the inlet connection (19), admitting a stream of fresh, cool fuel into the antechamber (14). This cools the pump rapidly, suppressing further evaporation of fuel. Consequently the engine starts easily, idling becomes steady and the engine responds without hesitation to a demand for increased power. The invention has the following advantages: During idling and hot operation of the engine, and in attempts to start a hot engine, the fuel pump can become strongly heated by conduction through the metal and by radiation from the engine. Under these circumstances fuel drawn from the tank already evaporates to a considerable extent where it enters the hot pump. The rise in pressure produced by the evaporation has hitherto forced the fuel in the inlet channel, upstream of the pump, back into the fuel tank, temporarily starving the engine of fuel, making starting difficult and preventing the engine from responding quickly to a demand for increased power.

These faults do not occur in the fuel pump of the invention.

Claims

1. A fuel pump, particularly a diaphragm pump, driven by an internal combustion engine and mounted directly on the engine, the working chamber (12) of the pump receiving fuel through a suction valve (13) and delivering it through a discharge valve (15), and wherein upstream of the suction valve (13) there is an antechamber (14) which has an inlet connection (19) equipped with a non-return valve (18) and a reflux connection (21) equipped with a non-return valve (20), an inlet channel (23) and a reflux channel (22) communicating respectively with the inlet and reflux connections, all whereby the antechamber (14) is directly connected to the fuel tank of the engine.

2. A fuel pump, according to claim 1 and substantially as hereibefore described with reference to the accompanying drawing.