GB2048373A

GB2048373A - A fuel injection pump for an internal combustion engine

Info

Publication number: GB2048373A
Application number: GB8011024A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1979-04-06
Filing date: 1980-04-02
Publication date: 1980-12-10
Also published as: GB2048373B; DE2913909C2; JPH0310032B2; JPS55139965A; DE2913909A1

Abstract

A fuel injection pump for an internal combustion engine having a pump piston (8) received in a bore (10) and reciprocally and rotatably driven by cam drive means (3). A working chamber (11) is defined between an end of the bore (10) and an end of the pump piston (8). In order to stop the engine or to achieve quiet running a passage (16) is connectible with the working chamber (11) by means of an electro- magnetically operated valve (17). The passage leads to a suction chamber (25) of the injection pump. Alternatively to achieve quiet running the passage (16) communicates with an accumulator. <IMAGE>

Description

SPECIFICATION A fuel injection pump for an internal combustion engine This invention concerns fuel injection pump for an internal combustion engine.

In a known fuel injection pump having a passage which connects a pump working chamber to a relief chamber, the relief passage for determining the termination of injection is controlled by distributor grooves and is additionally controlled by a solenoid valve. It is impossible, by this means, to stop the internal combustion engine by shutting off the quantity of fuel injected. In another proposed fuel injection pump, the fuel supply to the pump working chamber can be interrupted to stop the internal combustion engines by means of a solenoid valve disposed in the passage leading from the suction chamber of the pump to the pump working chamber.In both these known cases, the distributor having the distributor grooves chiefly serves as a pressure block between the pump working chamber and the valve, so that the closure springs of the valve or the strength of the magnet do not have to be matched to the pump working pressure.

According to the present invention there is provided a fuel injection pump for an internal combustion engine, having at least one passage leading from a pump working chamber to a relief chamber, such as the pump suction chamber or a hydraulic accumulator, the or each passage being controllable by at last one valve which is operable electro-magnetically, the or each valve having a movable valve member which is subjected in the closing direction to the pressure prevailing in the pump working chamber.

In contrast to the prior art, the fuel injection pump in accordance with the invention, renders it possible to open the relief passage before the commencement of the pressure stroke when it is necessary to open this passage and absolute tightness is achieved during the pressure stroke for as long as the valve is closed.

The valve of the fuel injection pump in accordance with the invention can be opened by the electro-magnet when the latter is nonenergised, the valve being opened in one case by means of an opening spring whose force is overcome by the electro-magnet, and, in the other case, the valve being opened by the electro-magnet itself. The use of the electomagnetically controlled valve can serve either to stop the internal combustion engine, or to operate a quiet-running device in which a portion of the fuel flows out of the pump working chamber and thus prolongs the period of injection, so that a smaller quantity of fuel per unit of time is injected.

The present invention will now be described further, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary sectional view of a first embodiment of a fuel injection pump having an electo-magnetically operated valve, Figure 2 is a sectional view of a second embodiment of the invention having a modified electro-magneticially operated valve, Figure 3 is a fragmentary sectional view of a third embodiment of a fuel injection pump in accordance with the invention, Figure 4 is a fragmentary sectional view of a further embodiment of an injection pump, Figure 5 is a sectional detail view showing the connection between the electro-magnet housing and the valve body; and Figure 6 is a fragmentary sectional view of a still further embodiment of an injection pump in accordance with the invention.

Referring to Fig. 1 a drive shaft 2 is jour nalled in a housing 1 of a fuel injection pump for multicylinder internal combustion engines.

An end cam plate 3 is coupled to the drive shaft and is rotatably driven thereby. The end cam plate 3 is provided with four cams, corresponding to the four cylinders of an internal combustion engine to be supplied with fuel, which engage fixed rollers 5 which generate reciprocating movement upon rotation of the drive shaft. A pump piston 8 which is coupled to the end cam plate 3 by a coupling member 6, and which is pressed against the cam plate by at least one spring, is thereby reciprocated and simultaneously rotated.

The pump piston 8 operates in a cylindrical sleeve 9 which has a cylindrical bore 10 and which is fitted in the housing 1. A closed end, at the top, of the bore 10 and the piston 8 define a working chamber 11 in the cylinder bore 1 0. A valve body 1 2 serves as a closure for the cylindrical sleeve 9 and, together with a movable valve member 13, constitutes a relief valve for the pump working chamber. The movable valve member 1 3 is loaded by means of a closure spring 14 which presses a head 1 5 of the movable valve member 1 3 onto a seat in the valve body 1 2.

The head 1 5 is additionally pressed against its seat by the pressure prevailing in the pump working chamber 11. This valve controls a relief passage 1 6 which leads to a chamber in which a pressure prevails which is lower than the pressure prevailing in the pump working chamber 11 during the pressure stroke.

The movable valve member 1 3 is actuated by means of a solenoid 1 7 having a coil 18, an armature 19, and a core 20. A housing 21 of the solenoid 1 7 is screwed into the housing 1 of the fuel injection pump and a shoulder of the solenoid housing clamps the valve body 1 2 rigidly against the cylinder barrel 9 by way of a sleeve 22, wherein certain differing expansions upon changes in temperature are compensated for.

The pump working chamber 11 is supplied with fuel by way of a suction passage 23 which is controlled by suction grooves 24 disposed in the surface of the piston 8. The suction grooves 24 open the suction passage 23 during each suction stroke of the pump piston 8. Fuel is supplied from a suction chamber 25 which is disposed in the housing 1 and in which a slight over-pressure prevails.

In order to regu)ate-the quantity of fuel delivered, the working chamber 11 is connectible to the pump suction chamber 25 by way of an axial blind bore 26 in the pump piston 8 and a transverse bore 27 which intersects the blind bore. A delivery quantity regulating member 28 for the fuel cooperates with the transverse bore 27 and is in the form of an annular valve slide which is displaceable on the pump piston and whose position determines the instant at which the transverse bore 27 opens during the upward movement of the piston 8 (pressure stroke) and at which communication is established between the working chamber 11 and the pump suction chamber 25. Thus, an adjustment of the annular valve slide 28 can vary the quantity of fuel which is not injected.For the purpose of varying the quantity of fuel injected, the annular valve slide 28 is adjusted by means of a regulating lever 30 having a ball head 31 which engages a recess 32 in the annular valve slide 28. The regulating lever is pivotable about a spindle 34 which is adjustable by means of an eccentric 35. A governing spring (not illustrated) acts upon the other end of the regulating lever 30 against the force of a rotational-speed dependent sensor. The initial stress of the governing spring can be varied by, for example, an adjusting lever which can be arbitrarily adjusted.The rotational-speed dependent sensor acts in a direction to reduce the quantity of fuel injected as the rotational speed increases, while the governing spring acts in a direction to increase the quantity of fuel injected, wherein a centrifugal sensor or, alternatively, a hydraulic sensor can serve as the rotational-speed dependent sensor. The prevailing position of equilibrium, corresponding to a specific quantity of fuel injected, can be correspondingly varied by the adjusting lever.

The internal combustion engine is supplied with fuel from the pump working chamber 11 during the pressure stroke, for as long as the transverse bore 27 is closed, by way of the blind bore 26 which communicates by way of a transverse bore 36 with an annular groove 37 from which a distributor groove 38 branches, a pressure line 39 being opened by the distributor groove 38. Pressure conduits 39 (only one of which is illustrated) equal in number to the number of engine cylinders to be supplied with fuel are provided around the distributor piston 8.During rotation of the pump piston 8, the pressure conduits 39 are successively opened by the longitudinal distributor groove 38 and are correspondingly supplied with fuel from the pump working chamber 11 until the transverse bore 27 is opened by the annular valve slide 28 and the fuel can flow back, non-utilised, from the pump working chamber 11 into the suction chamber 25.

In the embodiments illustrated in Figs. 1 and 2, the relief passage 16 leads into a passage 40 which terminates in the suction chamber 25. Thus, with the valve 12, 1 3 open, the fuel may flow, non-utilised, back into the suction chamber 25 from the pump working chamber 11, so that the internal combustion engine is stopped.

In the first embodment illustrated in Fig. 1, the armature 1 9 is pulled downwardly against the core 20 when the coil 1 8 of the solenoid 1 7 is energised, and thus abuts against the movable valve member 1 3. During the pressure stroke of the pump piston 8, the solenoid cannot overcome the force in the pressure chamber 11 acting upon the valve 12, 13 in the closing direction. However, as soon as the pump piston 8 commences the suction stroke, the solenoid overcomes the force of the closure spring 14 of the valve and opens the latter.With the valve open pressure cannot build up in the pump working chamber 11 during the subsequent pressure stroke of the pump piston 8, so that the valve 12, 1 3 remains in its open position and the entire quantity of fuel delivered by the pump piston 8 flows back, non-utilised, into the suction chamber 25 by way of the passages 1 6 and 40. Even when strong forces act upon the movable valve member 1 3 in the closing direction as a result of dynamic throttling conditions between the head 1 5 and the valve body 12, and overcome the force of the solenoid, the valve is opened again during the next suction stroke, so that there is a considerable reduction in the engine speed and the engine is finally stopped.

In the further three embodiments illustrated in Figs. 2 to 4, the corresponding components are provided with the same reference numerals as in the first embodiment, the reference numerals being provided with an index mark in the case of structural differences.

In the second embodiment illustrated in Fig.

2 only the solenoid and the triggered valve are shown. In contrast to the first embodiment, the core 20' of the magnet is disposed at the top and the armature 19' is disposed at the bottom facing the valve. When the coil 1 8 is energised, the armature 19' is thus pulled upwardly towards the core 20'. The armature 19' has an interior bore which is closed at the bottom by means of a base 41 which incorporates openings 42 for pressure equalisation.

An opening spring 43 is disposed between the base 41 and the core 20' and, when the magnet is non-energised, displaces the armature 19' onto the movable valve member 13', thereby overcoming the force of the closure spring 14' and opening the valve 12', 1 3'.

The stroke of the armature 19' is limited by an annular stop 44. Here also, the opening spring 43 can only open the valve when the pump piston has completed a suction stroke.

As soon as the coil 1 8 is energised, the armature 19', overcoming the force of the spring 43, is pulled upwardly, so that the closure spring 14' pulls the movable valve member 13' onto its seat and prevents fuel from flowing off by way of the passage 1 6.

By way of example, the coil 1 8 is switched on by the ignition key of the internal combustion engine, so that the solenoid is energised for the starting operation and thus fuel is prevented from flowing through the relief passage 16, and the internal combustion engine can start. The internal combustion engine is then stopped by de-energising the solenoid 1 8 by switching off the electrical circuit by means of the ignition key, whereupon the valve 12', 13' is opened by the spring 43 and the fuel delivered by the piston 1 8 flows back, non-utilised, into the suction chamber 25 with the result that the internal combustion engine stops.

In the third embodiment illustrated in Fig.

3, 3, the valve 12, 1 3 and the solenoid 17 are constructed in the same manner as in the embodiment illustrated in Fig. 1. However, in contrast to the embodiment of Fig. 1, the fuel shut off by the valve is conducted through the throttling gap x and by way of a passage 45 into an accumulator 46. The valve 12, 1 3 is opened only during idling and, possibly, lower part load, so that a portion of the fuel delivered by the pump flows into the accumulator 46, thus prolonging the injection time in the engine. This prolongation of the duration of injection causes a great reduction in the sound produced by the engine and thus produces so-called quiet-running of the internal combustion engine. During the suction stroke of the pump piston 8, a portion of the fuel located in the reservoir 46 flows back into the pump working chamber 11.This return flow can be effected either by way of the relief passage 45 and the valve 12, 13, or by way of one of the suction grooves 24. In the latter case, the passage 45 has to be provided with a corresponding extension 47 leading to the bore 1 0. By way of example, the solenoid 1 7 can be controlled by means of a switch actuated by the accelerator pedal, so that the solenoid 1 7 is correspondingly energised when the accelerator pedal is in its idling and full load positons. The fourth embodiment illustrated in Fig. 4 differs from the third embodiment illustrated in Fig. 3, in that the accumulator is in the form of a spring-loaded device 46'. The spring-loaded device 46' operates with a spring-loaded piston 48 loaded by means of a spring 49.Whilst the accumulator capacity is largely derived from the compressibility of the fuel in the embodiment of Fig. 3, in the embodiment of Fig. 4 the accumulator capacity is additionally determined by the stroke of the spring-loaded piston 48.

Fig. 5 shows an arrangement for facilitating assembly of the valve body 12' so that the valve body 12' and the sleeve 22 thereby remain assembled with the solenoid housing 21' during assembly or disassembly of the solenoid. The outer surface of the valve body 12' has a screw-thread having only a few threads and which, when in its illustrated state which also corresponds to the fitted state, extends into an annular groove 51 disposed in the interior bore of the solenoid 21'. A screw-thread 52 is contiguous with the annular groove 51 towards the end of the bore, the valve body 12' being screwed into the solenoid housing 21' by means of the screw thread 52 until the thread 50 of the valve body turns loosely in the groove 51.

In the embodiment illustrated in Fig. 6, respective controlled valves are provided for stopping the engine and for prolonging the period of injection. The movable valve member 13" for prolonging the duration of injection is disposed in a valve member 54 for stopping the engine, and the valve member 54 is disposed in the valve body 12'. The quantity of fuel which is diverted for quiet running flows off by way of a passage 45", and the quantity of fuel for stopping the engine flows off by way of a relief passage 16". In the same time manner as in the embodiments described above, the passage 45" can open either into an accululator, or, in a throttled manner, into a chamber of lower pressure. In each case, it must first be possible to initiate quiet running before the engine is stopped.The solenoid (of which only the armature 20" is indicated) is in the form of a two-stage solenoid which opens the quietrunning passage 45" in the first stage h1, and then opens the relief passage 16" in the second stage h2.

The valve member 13" is loaded in the closing direction by means of a spring 14", one end of which spring abuts against a spring plate 55 connected to the valve member 13", and the other end of which abuts against the valve member 54. The valve member 54 is in turn loaded by a spring 56 which abuts against the valve body 12" and against a spring plate 57. Only the spring 14" is compressed when the solenoid is in its first stage h1. The valve member 54 is displaced against the force of the spring 56 by the spring plate 55 when the solenoid is in its second stage h2.

It is also conceivable for the valve member to be arranged adjacent to one another to operate for stopping the engine and for quiet running, the solenoid acting only upon one valve member for the first stage, and both valve members for the second stage.

Preferably the valve seat and the valve closure member have conical or spherical surfaces.

Claims

1. A fuel injection pump for an internal combustion engine, having at least one passage leading from a pump working chamber to a relief chamber, such as the pump suction chamber or a hydraulic accumulator, the or each passage being controllable by at least one valve which is operable electro-magnetically, the or each valve having a movable valve member which is subjected in the-clos ing direction to the pressure prevailing in the pump working chamber.

2. A fuel injection pump as claimed in claim 1, in which the movable valve member is biassed in the closing direction by means of a closure spring.

3. A fuel injection pump as claimed in claim 1 or 2, in which the valve seat and/or the movable valve member of the seat valve are of spherical and/or conical construction.

4. A fuel injection pump as claimed in one of the preceding claims, in which the armature of the electro-magnet acts at least indirectly upon the movable valve member.

5. A fuel injection pump as claimed in any one of the preceding claims, in which the valve is openable when the electro-magnet is energised.

6. A fuel injection pump as claimed in claim 5, when appendent to claim 2 in which the force exerted by the electro magnet is greater than the sum of the forces exerted by the closure spring and the flow force which acts upon the movable valve member as a result of the pressure difference when the valve is open.

7. A fuel injection pump as claimed in any of the claims 1 to 4, in which, when the electro-magnet is de-energised, the valve is openable by means of an opening spring.

8. A fuel injection pump as claimed in claim 7, when appendent to claim 2 in which the force of the opening spring is greater than the sum of the forces of the opposing closure spring and the flow force which acts upon the movable valve member as a result of the pressure difference when the valve is open.

9. A fuel injection pump as claimed in claim 7 or 8, in which the force of the electromagnet is greater than the force of the opening spring.

10. A fuel injection pump as claimed in any one of the preceding claims, in which fuel flows around the electro-magnet at least in the region of the armature.

11. A fuel injection pump as claimed in any one of the preceding claims, in which a housing of the electro-magnet is screwable into the housing of the injection pump and, by means of a shoulder in an interior bore, thereby clamps a valve seat and a valve body, accommodating the movable valve member, onto the pump housing.

1 2. A fuel injection pump as claimed in claim 11, in which an expansible sleeve is arranged between the valve body and the electro-magnet housing and has radial bores serving as a portion of the passage.

1 3. A fuel injection pump as claimed in claim 11 or 12, in which, in order to facilitate assembly, the interior bore electro-magnet, houses a screw-thread which merges into an annular groove and through which a screwthread, having only a few threads, of the valve body is screwable, so that the screwthread of the valve body is accommodated with axial play in the annular groove.

14. A fuel injection pump as claimed in any one of the preceding claims, in which the passage leads to a low pressure chamber.

1 5. A fuel injection pump as claimed in claim 14, in which the low pressure chamber is the suction chamber of the injection pump.

1 6. A fuel injection pump as claimed in any one of the claims 1 to 13, in which the passage leads into an accumulator chamber which is otherwise closed.

1 7. A fuel injection pump as claimed in claim 16, in which the accumulator has a spring-loaded piston which acts as a movable wall.

1 8. A fuel injection pump as claimed in any one of the claims 14 to 17, in which a throttle is disposed in the passage.

1 9. A fuel injection pump as claimed in any one of the preceding claims, in which two valves are provided for controlling respective passages for stopping the engine and for quiet running.

20. A fuel injection pump as claimed in claim 19, in which the two valves are controllable by an electro-magnet.

21. A fuel injection pump as claimed in claim 20, in which the electro-magnet is a two stage magnet, the first stage operating a first valve member for quiet running and the second stage operating a second valve member for stopping the engine.

22. A fuel injection pump as claimed in claim 21, in which the movable valve members of the respective valves are arranged coaxially one within the other.

23. A fuel injection pump as claimed in claim 22, in which the first valve member is disposed within the second valve member and after displacement of the first valve member during the first stage the second member is displaced with the first member during the second stage.

24. A fuel injection pump as claimed in claim 21, in which the valve members are arranged adjacent to one another.

25. A fuel injection pump constructed and arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in any one of Figs. 1 to 5 of the accompanying drawings.

26. A fuel injection pump constructed and arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in Fig. 6 of the accompanying drawings.