GB2185599A

GB2185599A - Fuel injection pump for an internal combustion engine

Info

Publication number: GB2185599A
Application number: GB08700885A
Authority: GB
Inventors: Gerald Hofer; Max Straubel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1986-01-16
Filing date: 1987-01-15
Publication date: 1987-07-22
Also published as: JPS62195422A; GB2185599B; FR2592917A1; DE3601020A1; GB8700885D0

Abstract

A fuel injection pump for an internal combustion engine has a delivery quantity adjusting device (25) which is actuated by an adjusting lever (31), a speed governor (33) and a full-load stop (42). The full-load stop is connected to a hydraulic adjusting mechanism (41) whose control pressure, which acts on the adjusting piston (44), is controlled by a pressure control baffle plate valve (40), which is controlled by an electronic control device (38). The control pressure chamber (45) of the adjusting mechanism (41) is supplied with fuel from the pump suction chamber (11) by way of a throttle (53). The pressure control baffle plate valve has a baffle plate (58) and an inlet nozzle (59) pointing towards it, which is connected to the control pressure chamber (33) of the adjusting mechanism (41). <IMAGE>

Description

SPECIFICATION Fuel injection pump for an internal combustion engine The present invention relates to a fuel injection pump for an internal combustion engine.

Various devices are known for the speed-dependent adaptation ofthe quantity offuel to be delivered to the fuel requirement characteristic of internal combustion engines, and which control a full-load stop acting on the control lever of an injection quantity adjusting device. To do this, the full-load stop is actuated by pressure ortemperature adjusting devices by way of levers and ratchets.

Such mechanical devices are expensive and not very flexible.

In accordance with the present invention, there is provided afuel injection pumpforan internal combustion engine, the pump comprising a delivery pump for delivering fuel to a pump suction chamber in proportion to the speed, a pressure control valve for controlling the pressure in the pump suction chamber, a control lever for actuating an injection quantity control element of the injection pump, which is acted on by a speed governor and by an adjustable control spring, and an adapting device with a full-load stop forthe control elementfor adjusting a maximum permissible load-load delivery quantity, the adapting device being provided with a hydraulic adjusting mechanism having an adjusting piston for adjusting the full-load stop and an electromagneticaliy control led pressure control baffle plate valve for regulating the control pressure acting on the adjusting piston.

In contrast to the prior art, thefuel injection pump according to the present invention has the advantage of a simple and small construction.

Furthermore, the control powerto be generated for the pressure-control baffle plate valve is small, such that the electronic control device may also be of simple construction. As the adjusting piston is adjusted for the full-load stop in dependence on pressure, there is no need for revertive signalling of the position.

Byway of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawing, which is a simplified section of a distributor-type fuel injection pump.

In the distributor-type injection pump shown, a housing 10 surrounds a pump suction chamber 11, which is supplied with fuel from a supply tank 13 bya delivery pump 12. A pressure control valve 14 is connected in parallel with the delivery pump 12 and altersthe pressure in the pump suction chamber 11 in dependence on the quantity of fuel delivered. A reciprocating and simultaneously rotatingly driven pump piston 15, which defines a pump working chamber 16, serves to meterthe fuel delivery and injection quantities. During the suction stroke ofthe pump piston 15, the pump working chamber 16 is filled with fuel from the pump suction chamber 11 through a suction line 17 and control grooves 18 in the pump piston 15.During the following compression stroke of the pump piston 15, a quantity of fuel to be injected is fed, with the suction line 17 being closed, byway of a longitudinal bore 20, a delivery groove 21 connected thereto and a pressure line 22 to an injection nozzle (not shown in detail) at the engine cylinder of the internal combustion engine.

In orderto meter variable quantities of fuel to be injected, which are not dependent on the stroke of the pump piston 15, the injection pump is provided with a delivery quantity adjusting device 25. The delivery quantity adjusting device 25, which is disposed in the pump suction chamber 11, has an annular spool 26 which is displaceable on the pump piston 15 in the pump suction chamber 11 and which opens and closes a cross bore 27 connected to the longitudinal bore 20 in the pump piston 15 during the reciprocable motion of the pump piston 15, wherein, depending on the position of the annular spool 26, the cross bore 27 is opened by the annular spool 26 at an earlier or later point during the delivery stroke of the pump piston 15. The position of the annular spool 26 is adjusted by a two-armed, pivotable control lever 28, which engages in a groove 29 in the spool 26.

In order to adjust the annular spool 26, a speed governor 33 and an arbitrarily pivotablespeed adjusting lever 31 act on the control lever 28, the latter by way of a control spring 32. The speed governor 33, which is provided in a rotatable housing 34 with flyweights 35 and a sleeve 36 which is axially displaceable by said flyweights 35, is driven, as are the delivery pump 12 and the pump piston 15, by the drive shaft (not shown) ofthe injection pump. The piston of the control lever 28, and hence that of the annular spool 26, is defined by the cooperation of the force of the control spring 32 and the force exerted by the flyweights on the sleeve 36.

In order to adapt the quantity of fuel to be injected or delivered to the fuel requirement characteristic of the internal combustion engine in orderto achieve optimum torque, performance, consumption and exhaust gas, an electronic control device 38 is provided in which the family of characteristics of the internal combustion engine concerned is stored and to which signals are fed which are dependent on temperature, and ambient or load pressure. The control device 38 controls byway of a pressure control valve 40 a hydraulic adjusting mechanism 41 which is connected to the housing 10 and which acts byway of a plunger 42 on the control lever 28.The adjusting mechanism 41 is provided in an adjusting cylinder 43 connected to the housing 10 with a displaceable adjusting piston 44 whose left-hand side closes off a control pressure chamber 45 and whose right-hand sides closes off an unpressurised reference chamber 46. A pressure spring 47 in the reference cham ber 46 acts on the adjusting piston 44 against the control pressure effective in the control pressure chamber 45, so that the adjusting piston 44 takes up a position which is dependent on the control pressure and which determines the position ofthe plunger42 which is acting asthefull-load stop and which abuts atone end, against the adjusting piston 44 and, at the other end against the control lever 28.

Forthe purposes of pressure compensation and hysteresis-free adjustment, a plunger 48, which penetrates through the adjusting cylinder, also acts upon the side opposite the plunger 42 and acts by way of an extension 49 penetrating the housing 10 on a travel sensor, for example a potentiometer 50, which is connected to the control device 38.

In orderto build up a control pressure in the control pressure chamber 45 to move the full-load stop into a particular position, the pressure control chamber45 is connected ontheone hand byway of an inlet port 52 with a throttle 53 to the pump suction chamber 11 and, on the other hand, through a port 54 to the pressure control valve. The pressure control valve is in the form of a baffle plate valve 40 mounted on the adjusting mechanism 41.Such a valve is known,for example, from German Offenlegungsschrift No.31 09560. The baffle plate valve 40 is provided in a housing 56 with a two-armed baffle plate 58 which is rotatable aboutan axis 57 and towards whose left arm an inlet nozzle 59 is directed from below, to which nozzle fuel is fed from the control pressure chamber 45 byway ofthe port 54. Atthe other end, a pressure spring 60 presses on the baffle plate 52 from above. The inner chamber 61, which is kept unpressurised, of the baffle platevalve 40 is connected by way of an outlet 62 to the supplytank 13.

The baffle plate valve 40 is provided with a permanent magnet 65 which acts by way of yoke parts 66,67 on an armature 68 connected to the pivotable baffle plate 58. The armature is surrounded by a coil 69 which is triggered by the electronic control device 38 with a variable control current.

Depending on the size of the magnetic field of the coil 69,which is controlled by the control device 38 in dependence upon various operating parameters of the internal combustion engine, the baffle plate 58 opens the port of the inlet nozzle 59 to a greater or lesser extent, so that the throttle combination of the inlet nozzle 59 and the throttle 53 leading from the pump suction chamber 11 into the control pressure chamber 45 causes a control pressure to be built up in the control pressure chamber 45 which is smaller than the pressure in the pump suction chamber 11 but greater than the pressure in the inner chamber 61 of the baffle plate valve 40, which is kept unpressurised by way of the outlet 62.Furthermore, the control pressure in the control pressure chamber 45 is influenced bythespeed-dependent pressure in the pump suction chamber 11. The throttle 53, inlet nozzle 59 and baffle plate 58 are preferably selected such that a control pressure ofO to approximately 1.5 bar can be obtained in the control pressure chamber 45 during operation.

In co-operation with the unpressurised reference chamber 46 ofthe adjusting mechanism 41, which is connected bywayofa bore71 to the innerchamber 61 ofthe baffle plate valve housing 56, and with the pressure spring 47, the adjusting piston 44 takes up a position corresponding to the control pressure effective in the control pressure chamber 45 and moves the plunger 42 into a position such that said plunger42, as a full-load stopforthe control iever28, adapts the position of the control lever 28, which is influenced by the control spring 32 and the speed governor 33, to the fuel requirement characteristic of the associated internal combustion engine.

In addition, it should be noted that the position of the annular spool 26, which determines the fuel delivery quantity in each case and which is dependent on the position of the adjusting piston 44, is signalled back by way of the potentiometer 50 to the control device 38 as described above (closed loop control system). The potentiometer may be omitted, so that the control pressure set by the control device by way ofthe baffle plate valve 40 in the adjusting mechanism 41 alone determines the position of the annular spool (open loop control system).

Claims

1. Afuel injection pumpforan internal combustion engine, the pump comprising a delivery pump for delivering fuel to a pump suction chamber in proportion to the speed, a pressure control valve for controlling the pressure in the pump suction chamber, a control lever for actuating an injection quantity control element of the injection pump, which is acted on by a speed governor and by an adjustable control spring, and an adapting device with a full-load stop for the control elementfor adjusting a maximum permissible full-load delivery quantity, the adapting device being provided with a hydraulic adjusting mechanism having an adjusting piston for adjusting the full-load stop and an electromagnetically controlled pressure control baffle plate valve for regulating the control pressure acting on the adjusting piston.

2. Afuel injection pump as claimed in claim 1, wherein a control pressure chamber of the adjusting mechanism, which chamber is defined by the adjusting piston, is connected on the in let side by way of a throttle to the pump suction chamber, and, on the outlet side, to an inlet nozzle of the pressure control baffle plate valve, and wherein the throttle combination caused by the throttle and the variable throttle effect of the inlet nozzle and the deflectable baffle plate associated therewith regulate a control pressure acting on the adjusting piston which is smallerthan the pressure in the pump suction chamber.

3. Afuel injection pump as claimed in claim 2, wherein the baffle plate ofthe pressure control baffle plate valve is disposed between yoke parts of a magnetic circuit and is surrounded by a coil controlled by an electronic control device.

4. Afuel injection pump as claimed in claim 3, wherein the control device controls the coil with an electric current in dependence upon one or more of the speed, ambient air, pressure and temperature.

5. Afuel injection pump as claimed in any of claims 1 to 4, wherein on its side opposite the control pressure chamber, the adjusting piston ofthe adjusting mechanism closes off a reference pressure chamber with a relief pressure reduced in relation to the pump suction chamber and is acted upon by a return spring acting against the control pressure.

6. Afuel injection pump as claimed in claim 5, wherein the effective pressure faces of the adjusting piston facing both the control pressure chamber and the reference pressure chamber are substantially the same size.

7. Afuel injection pump as claimed in any of claims 1 to 6, wherein the adjusting piston of the adjusting mechanism is connected to a travel sensor which is connected to the control device.

8. Afuel injection pump for an internal combustion engine, substantially as herein described, with reference to, and as illustrated in, the accompanying drawing.