GB2248882A

GB2248882A - I.c. engine fuel injection pumping system

Info

Publication number: GB2248882A
Application number: GB9121027A
Authority: GB
Inventors: Werner Faupel; Edgar Goetz
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1990-10-04
Filing date: 1991-10-03
Publication date: 1992-04-22
Anticipated expiration: 2011-10-03
Also published as: GB9121027D0; DE4031232A1; DE4031232C2; GB2248882B; JPH04262052A

Abstract

The return line from the feed pump fed injection pump supply chamber contains a non-return valve 21 and a closure element 29 movable from its seat 32 by expansion of a memory metal spring 28 or an elastic element (41, Fig. 3). A closure bypass bore 37 in the element 29 or between the element and the seat 32 provides for a limited return fuel flow even at low fuel temperatures. <IMAGE>

Description

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DESCRIPTION

FUEL SUPPLY APPARATUS FOR INTERNAL COMBUSTION ENGINES This invention relates to fuel supply apparatus for internal combustion engines.

A fuel supply apparatus is knoy7 from DE-OS 27 15 587. This fuel supply apparatus has a fuel injection pump with an intake chamber, into which fuel is conveyed from a fuel supply tank by a feed pump. A relief line leads from the intake chamber by way of an overflow valve and fuel can flow back through it to the fuel supply tank. A valve, which is actuatable in dependence upon temperature, is disposed in the relief line directly downstream of the overflow valve. The temperature sensitive valve has a working element, about which fuel flows, in the form of a bimetal spring, through which the relief line can be closed in the event of low fuel temperatures. With increasing fuel temperature, the bimetal spring becomes deformed and opens the relief line. By virtue of the temperature sensitive valve, on the one hand rapid heating of the fuel in the intake chamber of the fuel injection pump is achieved, and, on the other hand, in the event of hot fuel, scavenging of the intake chamber, and hence cooling, is achieved. When the relief line is closed, however, no fuel flows to the working element, such that temperature transfer from the intake chamber to the working element is not rapid, and, in the event of increasing fuel temperature, the working element only opens the relief line with delay. Moreover, when the relief line is closed, purging of the intake chamber of the fuel injection pump is no longer possible.

In accordance with the present invention, a fuel supply apparatus for an internal combustion engine comprises a fuel injection pump, which has an intake chamber into which fuel is conveyed by a feed pump, and a relief line, which leads away from the intake chamber by way of an overflow valve and in which there is disposed immediately downstream of the overflow valve a valve, which is actuatable in dependence upon temperature and which has a working element, about which fuel flowing through the relief line flows and by means of which the opening cross section of the valve is enlargeable with increasing fuel temperature, wherein the working element acts on a closure member, which cooperates with a valve seat and changes its length in dependence upon temperature, and the temperature responsive valve has a bypass, which is in parallel with the closure member and through which fuel flows continuously out of the intake chamber and around the working element.

This has the advantage that, even when the temperature dependent valve is closed, fuel can flow through the bypass out of the intake chamber of the fuel injection pump and thus rapid temperature transport to the working element and continuous purging of the intake chamber is achieved.

In a preferred embodiment, the working element comprises a spring, which consists of a memory alloy. A simple construction of the valve is achieved, since the memory spring can act directly on the closure member.

Preferably, the working element is disposed upstream of the closure member and the closure member opens in the flow direction against a spring, which acts on the closure member. With this, only small actuating forces are required to open the valve.

Preferably the overflow valve and the temperature dependent valve, are disposed in a common housing. A compact construction of the temperature dependent valve and the overflow valve is thereby achieved.

The invention is further described, by way of example only, with reference to the accompanying drawings, in which:- Fig. 1 illustrates a fuel supply apparatus of the present invention in a simplified representation; Fig. 2 illustrates a first embodiment of an overflow valve and a temperature dependent valve of the fuel supply apparatus of Fig. 1; and Fig. 3 illustrates a second embodiment of the valves.

In Fig. 1 the fuel supply appa:atus for an internal combustion engine has a fuel injection pump 9, with an intake chamber 10, into which fuel is conveyed from a fuel supply tank 13 via an intake line 12 and a feed pump 11. A filter 14 is disposed in the intake line 12. The feed pump 11 is connected upstream of the fuel injection pump 9, but may, in another embodiment, as indicated by the dotted lines, be integrated in the fuel injection pump. The fuel in the intake chamber 10 is held in a known manner under a predetermined pressure, which, if this pressure is utilised for control purposes, is additionally regulated. Pump working chambers, which are defined by pump pistons (not shown) are supplied with fuel from the intake chamber 10 in a known way during the intake stroke of the pump pistons and, during the compression stroke of the pump pistons, fuel is conveyed to the injection points of the internal combustion engine which is operated with the fuel injection pump. The quantity of fuel not required during the pump stroke of the pump pistons, for example in the part load range, is conveyed back to the intake chamber, which leads to heating of the fuel in the intake chamber. Moreover, the fuel is heated by friction between moving components of the fuel injection pump. A part of the fuel conveyed by the feed pump 11 flows by way of an overflow valve 16 and a valve.17, which is actuatable in dependence upon temperature, through a relief line 18 back to the fuel supply tank 13. The overflow valve 16 may be a fixed or variable throttle. In the case of an in-line injection pump, in which no control operations are performed by the intake chamber pressure, the overflow valve 16 may also be in the form of a non-return valve.

In a first embodiment shown in Fig. 2, the overflow valve 16 comprises a non-return valve and is disposed in a valve housing 19. The overflow valve has a ball 21 as the closure member, which is subjected to fuel pressure in the intake chamber 10 of the fuel injection pump 9 through a bore 22 in the valve housing 19. Acting against the fuel pressuref a helical spring 24, which is supported by way of a spring abutment plate 23 on the valve housing 19r acts on the ball 21. The spring abutment plate 23 is provided with an opening 26, through which fuel may flow. The valve 17, which is actuatable in dependence upon temperature, is disposed in the valve Xhousing 19, downstream of the non-return valve 16. valve 17 has as the working element a helical spring 28, which in turn is supported by way of a spring abutment plate 27, although against the direction of flow, and consists of a memory alloy, and acts on a closure member 29, which is in the form of a disc, in the direction of flow. The spring abutment plate 27 is also provided with an opening 31 to permit the passage of fuel. The closure member 29 co-operates with a valve seat 32 formed in the valve housing 19, such that the opening movement of the closure member 29 takes place in the direction of flow. the closure member 29 is biassed in the closing direction, against the direction of flow, by a closure spring 34, which is supported by way of a spring abutment plate 33 on the valve housing 19. Since the opening movement of the closure member 29 is effected in the direction of flow, rapid and reliable opening of the valve 17 is achieved. The spring abutment plate 33 also has an opening 36.

The closure member 29 is provided with a throttle bore 37, which acts as a bypass, through which a continuous throttled flow is made possible when the non-return valve 16 is open. Alternatively, in place of the bore 37, by virtue of a corresponding embodiment of the valve seat 32 andlor the closure member 29, a deliberate leak can be achieved, even when the closure member 29 abuts against the valve seat 32, through which leak the bypass is formed.

In the event of low fuel temperature on commencement of operation of the fuel injection pump, the memory spring 28 has a short length, such that closure member 29 is held by the closure spring 34 in abutment against the valve seat 32. Fuel flows out of the intake chamber 10 of the fuel injection pump 9 through the non-return valve 16, the spring abutment plates 23, 27, 33 and the bypass 37 in the closure member 29 or between the valve seat 32 and the closure member 29. As a result of the increasing fuel temperature during operation of the fuel injection pump, the length of the memory spring 28 increases rapidly at a given temperature and lifts the closure member 29 against the force of the closure spring 34 from the valve seat 32, such that, with respect to the bypass, a substantially larger opening cross section is opened. By virtue of the valve 17 rapid heating of the fuel in the intake chamber 10 is achieved, since, in the case of low fuel temperature, only very little fuel flows back to the fuel supply tank. In the case of high fuel temperature, a greater quantity of fuel flows back to the supply tank, such that cooling of the intake chamber 10 is achieved. By virtue of the -a- continuous flow through the valve 17, it is ensured that the memory spring 28 rapidly "recognises" the fuel temperature in the intake chamber 10 and thus responds rapidly. By virtue of a corresponding matching of the volume enclosed in the valve housing 19 with the volume of the intake chamber 10, a reduction in pressure peaks in the intake chamber 10 of the fuel injection pump is possible.

In contrast to the first embodiment, in a second embodiment shown in Fig. 3, the valve 17, which is actuatable in dependence upon temperature, has as its working element, an elastic material element 40. The elastic material element 40 has a housing 41, which abuts in the direction of flow against inwardly directed projections 42 of the valve housing 19, against which it is held by a_spring 43, which is supported towards the non-return valve 16, which is unaltered with respect to the first embodiment. A pin 46, which acts on the closure member 44 of the valve 17, projects out of the housing 41 of the elastic material element 40. The elastic material element 40 is provided with a plurality of passages 47 in order to permit flow through it. The closure member 44 is provided with at least one bore 48, which forms the bypass. The elastic material element 40 increases its length as temperature increases, such that the pin 46 is displaced out of the housing 41 and the closure member is lifted from the valve seat 49 against the force of a spring 51. An expansion of the housing 41 of the elastic material element 40 against the spring 43 as a result of heating is possible. A good flow, and hence a rapid response of the valve 17, is possible through the passages 47 in the elastic material element 40.

Claims

1. Fuel supply apparatus for an internal combustion engine comprising a fuel injection pump, which has an intake chamber into which fuel is conveyed by a feed pump, and a relief line, which leads away from the intake chamber by way of an overflow valve and in which there is disposed immediately downstream of the overflow valve a valve, which is actuatable in dependence upon temperature and which has a working element, about which fuel flowing through the relief line flows and by me ans of which the opening cross section of the valve is enlargeable with increasing fuel temperature, wherein the working element acts on a closure member, which cooperates with a valve seat and changes its length in dependence upon temperature, and the temperature responsive valve has a bypass, which is in parallel with the closure member and through which fuel flows continuously out of the intake chamber and around the working element.

2. Fuel supply apparatus as claimed in claim 1, wherein the working element comprises an elastic material element.

3. Fuel supply apparatus as claimed in claim 1, wherein the working element comprises a spring, which consists of a memory alloy.

k 1

4. Fuel supply apparatus as claimed in any preceding claim, wherein the working element is disposed upstream of the closure member and the closure member opens in the flow direction against spring, which acts on the closure member.

5. Fuel supply apparatus as claimed in any preceding claim, wherein the overflow valve and the temperature dependent valve are disposed in a common housing.

6. Fuel supply apparatus as claimed in any preceding claim, wherein the overflow valve comprises a non-return valve.

7. Fuel supply apparatus as claimed in any preceding claim, wherein the bypass is formed by at least one opening in the closure member.

8. Fuel supply apparatus as claimed in any of claims 1 to 6, wherein the bypass is formed by a leakage path between the closure member and the valve seat.

9. Fuel supply apparatus constructed and adapted to operate substantially as herein described, with reference to and as illustrated in the accompanying drawings.