GB2329223A - Control arrangement for a fuel pump - Google Patents

Abstract

A control arrangement for controlling, for example, the timing of a rotary fuel pump 10,20,22,24 comprises an electrical generator 38,40 located within the housing of the fuel pump and driven by the rotary distributor member 10 thereof. The electrical power supply generated by the generator is used to drive a controller 46 which controls the operation of an electromagnetically operated variable orifice 36. The variable orifice 36 controls the pressure in a chamber 34 to determine the position of a timing piston 28 coupled to the cam ring 24 of the fuel pump.

Description

CONTROL ARRANGEMENT This invention relates to an arrangement for controlling the operation of, for example, a fuel pump. It is desirable to control the operation of a fuel pump for a compression ignition internal combustion engine so that the timing of the fuel delivery by the fuel pump is dependent upon, for example, the speed or temperature of the associated engine.

It is known to control the timing of fuel delivery by a rotary fuel pump by controlling the angular position of a cam ring. The cam ring may include a peg or tooth located within a recess formed in an advance piston so that movement of the advance piston causes angular movement of the cam ring to adjust the timing of fuel delivery. Such movement of the advance piston can be controlled by controlling the fuel pressure applied to the piston, for example using an electromagnetically controlled valve. It will be appreciated, however, that such an arrangement requires the provision of an external electrical supply to permit control and actuation of the valve, and the provision of such an external electrical supply may be disadvantageous.

According to the present invention there is provided a control arrangement for a fuel pump of the type including a rotary component and a housing, the control arrangement comprising an electrical generator located within the housing of the pump and driven by the rotary component, control means arranged to receive electrical power from the electrical generator, and actuator means controlled by the control means.

The actuator means may take the form of the electromagnetic actuator of a valve, the control means controlling operation of the valve to control the fuel pressure applied to an advance piston.

The control arrangement may further comprise sensor means arranged to supply signals to the control means. The sensor means may be arranged to output a signal indicative of the angular position of the rotary component relative to the cam ring of the pump.

The invention further relates to a fuel pump incorporating such a control arrangement.

The control arrangement is advantageous in that no external power supply is required.

The invention will further be described, by way of example, with reference to the accompanying drawing which is a diagrammatic representation of a fuel pump incorporating a control arrangement in accordance with an embodiment of the invention.

The accompanying drawing illustrates, in diagrammatic form, a rotary fuel pump which comprises a rotary distributor member 10 which is rotatable within a sleeve. The rotary distributor member 10 is driven by a drive shaft 12 which, in turn, is rotated at a speed associated with the speed of rotation of an associated engine. The drive shaft 12 further drives a low pressure fuel pump 14, for example, in the form of a rotary vane pump which is arranged to draw fuel from a fuel reservoir 16 through appropriate filter devices 18, and to supply fuel through a passage (not shown) to a high pressure part of the fuel pump. The high pressure part of the fuel pump is composed of bores provided in the rotary distributor member 10 within which pumping plungers 20 are reciprocable. The pumping plungers 20 each carry shoe and roller arrangements 22 the rollers of which are arranged to engage the cam surface of a cam ring 24. In use, in the position shown, the bores within which the plungers 20 are reciprocable are charged with fuel at relatively low pressure by the low pressure fuel pump 14. The plungers 20 occupy their radially outermost positions. Rotation of the distributor member 10 from the position shown results in the rollers of the shoe and roller arrangements 22 engaging cam lobes 26 provided on the cam ring 24, causing the plungers 20 to be pushed radially inward. Such movement of the plungers 20 pressurizes the fuel located within the plunger bores and results in fuel being supplied at high pressure from the fuel pump.

The timing at which fuel compression and delivery commences depends upon the relative angular position of the cam ring 24 with respect to the distributor member 10. With the distributor member 10 rotating in a clockwise direction, it will be appreciated that angular movement of the cam ring 24 in the clockwise direction delays or retards the time at which fuel compression and delivery takes place, angular movement of the cam ring 24 in the opposite direction advancing the timing of fuel compression and delivery. Angular movement of the cam ring 24 is achieved using a conventional advance piston arrangement.

The advance piston arrangement comprises an advance piston 28 which is slidable within a bore, and biased by means of a spring 30 towards an end of the bore. A peg 32 secured to the cam ring 24 is engaged within a recess formed in the advance piston 28 such that linear, sliding movement of the piston 28 within the bore is transmitted through the peg 32 to move the cam ring 24 angularly and hence adjust the timing of commencement of fuel compression and fuel delivery by the pump.

The position of the piston 28 within the bore is dependent upon the pressure of fuel applied to the end of the piston 28 remote from the spring 30. In the illustrated embodiment, fuel from the low pressure pump 14 is supplied to a chamber 34 defined, in part, by the end face of the piston 28 remote from the spring 30. A pressure controller in the form of an electromagnetically controlled variable orifice 36 controls communication between the chamber 34 and the low pressure side of the pump 14. Further, a restricted flow passage 38 provides communication between the chamber 34 and a suitable low pressure reservoir, such communication being permitted oniy at a restricted rate.

It will be appreciated that when the electromagnetically controlled variable orifice 36 forms a large restriction to fuel flow from the chamber 34 to the low pressure side of the pump 14, the pressure of fuel within the chamber 34 is relatively high, adjustment of the electromagnetically controlled variable orifice 36 to allow fuel to escape from the chamber 34 to the low pressure side of the pump 14 at a relatively high rate permitting the fuel pressure within the chamber 34 to fall. In general terms, when the electromagnetically controlled variable orifice 36 allows fuel to flow at a high rate, the piston 28 moves under the action of the spring 30 moving the cam ring 24 to retard the timing of fuel compression and delivery, the movement of the piston 28 displacing fuel from the chamber 34 past the restriction 38 to the low pressure drain.

Whilst the electromagnetically controlled variable orifice 36 forms a large restriction to flow, the fuel pressure within the chamber 34 increases and the piston 28 moves against the action of the spring 30, moving the cam ring 24 to advance the timing of fuel delivery.

The rotary distributor member 10 carries the rotary part of an electrical generator, and in the illustrated embodiment, the rotary parts takes the form of magnets 38. The stator of the generator, which in the illustrated embodiment comprises the windings 40, is located within the housing 42 of the pump and is linked by a link member 44 to the cam ring 24 to be moveable therewith. The generator is arranged to supply electrical power to a controller 46. The controller is arranged to receive an input signal from a sensor 48 which is arranged to sense the movement of a particular part of the distributor member past the sensor. The signal produced by the sensor 48 is therefore indicative of the angular position of the plungers 20 relative to the cam ring 24. The controller 46 uses the signal provided by the position sensor 48 to control the operation of the electromagnetically controlled variable orifice 36, and hence to control the angular position of the cam ring 24. For example, if the position sensor 48 indicates that the cam ring 24 occupies a position in which the timing of fuel compression and delivery is advanced relative to the desired timing of fuel compression and delivery, the controller 46 supplies a signal to the electromagnetically controlled variable orifice 36 to allow the fuel pressure within the chamber 34 to fall hence allowing the piston 28 to move under the action of the spring 30 resulting in movement of the cam ring 24 in the clockwise direction to retard the timing of fuel compression and delivery until the desired position of the cam ring 24 is achieved, this being determined using the output of the sensor 48. Once the cam ring 24 occupies the desired position, the electromagnetically controlled variable orifice 36 is controlled to maintain the cam ring 24 in the desired position.

It will be appreciated that the generator generates an alternating current output the frequency of which may be used to derive a signal indicative of the speed of rotation of the drive shaft 12. As the drive shaft 12 is rotated in timed relation with the engine, the alternating current signal is indicative of the operating speed of the engine, and the controller 46 uses the speed signal to determine the desired timing of fuel delivery.

The controller 46 may additionally use the output of other sensors relating to other engine parameters, for example engine temperature, in determining the desired timing of fuel delivery.

Although in the embodiment described hereinbefore, the pressure controller takes the form of a variable orifice, it will be appreciated that an electromagnetically controlled valve could be used to control the fuel pressure applied to the advance piston.

Further, although the description hereinbefore is of the control arrangement being used in controlling the operation of a rotary fuel pump, the invention is suitable for use in other applications.

Claims (7)

1. A control arrangement for use with a pump including a rotary component located within a pump housing, the control arrangement comprising an electrical generator located within the pump housing and driven by the rotary component, control means arranged to be supplied with electrical power by the electrical generator, and actuator means operable under the influence of the control means.

2. A control arrangement as claimed in Claim 1, wherein the actuator means comprises an electromagnetically actuable fuel pressure controller.

3. A control arrangement as claimed in Claim 2, wherein the control means controls operation of the electromagnetically actuable pressure controller to control the fuel pressure applied to an advance piston.

4. A control arrangement as claimed in any one of Claims 1 to 3, further comprising sensor means arranged to supply a signal to the control means.

5. A control arrangement as claimed in Claim 4, wherein the sensor means is arranged to generate a signal indicative of the position of the pumping plungers of the pump relative to the cam lobes of a cam surface thereof.

6. A fuel pump comprising a rotary component located within a pump housing and a control arrangement as claimed in any one of the preceding claims.

7. A control arrangement substantially as hereinbefore described with reference to the accompanying drawing.