GB2170554A - I.C. engine fuel injection nozzle lift sensors - Google Patents

Abstract

A piezo electric crystal 28 mounted in the valve spring abutment 21 or supported from the spring housing within the spring 22 (Figs. 4 and 5) is subject to compression due to the inertia of a plunger 31 or sleeve (38, Fig. 3) when the fuel pressure actuated nozzle valve moves from or into engagement with the valve seat to provide voltage signals at an output terminal (35, Fig. 1). <IMAGE>

Description

SPECIFICATION Fuel injection nozzles This invention relates to fuel injection nozzles for supplying fuel to an internal combustion engine of the kind comprising a nozzle body and a fuel pressure actuated valve member slidable within a bore formed in the body, a coiled compression spring acting to bias the valve member into contact with the seating, the arrangement being such that when fuel under pressure is applied to the valve mem ber, --the valve member will lift from its seating against the action of the spring to allow fuel flow through an outlet, the valve member being returned by the action of the spring into contact with the seating when the supply of fuel is halted.

It is necessary with modern fuel systems of which the aforesaid nozzle forms part, to provide an indication of when fuel delivery to the associated engine takes place and when the supply of fuel ceases. This is to enable timing of fuel delivery to be adjusted accurately. The object of the present invention is to provide a nozzle of the kind specified in a simple and convenient form.

Examples of nozzle in accordance with the invention will- now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of a nozzle, Figure 2 is a view to an enlarged scale of a portion of the nozzle seen in Figure 1, Figure 3 is a view similar to Figure 2 showing a modification,.

Figure 4 is a view similar to Figure 1 showing a further modification, and Figure 5 is a view to an enlarged scale of a portion of the nozzle seen in Figure -1.

Referring to Figure 1 of the drawings the fuel injection nozzle is of the so-called inwardly opening type and includes a nozzle body 9 which is secured by a cap nut 10 to a tubular holder 11, there being located between the holder 11 and the body 10, a distance member 12. Formed in the nozzle body is a stepped -blind bore 13 which has an enlargement 14 defined intermediate. its ends. The enlargement is connected by way of an inlet passage 1 5 extending within the body, the distance member and the holder, to a fuel inlet 16 which is connected in use to an outlet of a high pressure injection pump.

At the blind end of the bore there is a defined a seating 1 7 which surrounds an outlet orifice 18 and slidable within the bore 13 is a valve member 19 having its end adjacent the seating shaped for co-operation' therewith.

The valve member at this end defines a projection which extends through the outlet orifice 18 for the purpose of shaping the resulting fuel spray through the outlet orifice. Moreover, the portion of the valve member which extends between the enlargement and the seating is of reduced diameter.

The opposite end of the valve member mounts a pin 20 which extends with clearance through a hole formed in the distance member 12. The pin carries a spring abutment 21 against which is located one end of a coiled compression spring 22 the other end of which engages a shim 23 which engages a step defined in the tubular holder.

In operation when fuel under pressure is supplied to the inlet the pressure in the enlargement 14 acts upon the valve member to lift the valve member against the action of the spring 22 in a direction away from the seating 17. As soon as the valve member is lifted from the seating fuel can flow between the valve member and seating and through the outlet orifice, the fuel flowing from the enlargement by way of the annular clearance defined between the valve member and wall of the bore. The extent of movement of the valve member is limited by its engagement with a surface 24 defined by the distance member 12 and the force which is exerted by the spring 22 can be varied during the assembly of the nozzle by suitable selection of the thickness of the shim 23. When the supply of fuel to the inlet ceases, the valve member will return to the closed position in which it is shown in Figure 1.

In order to control the timing of delivery of fuel to the engine associated with the nozzle it is desirable to know the instants of the start of delivery of fuel and the cessation of delivery of fuel and the best indication of when delivery of fuel starts is obtained by sensing the lifting of the valve member from the seating. To provide an indication of the cessation of fuel delivery, the movement of the valve member into contact with the seating can be sensed.

Turning now to Figure 2. The pin 20 and the spring abutment 21 are illustrated and it will be noted that the spring abutment defines a portion 25 which extends partly within the spring 22. The portion 25 of the spring abutment is provided with a cross drilling 26 and an axial drilling 27 which opens into the cross drilling. Located within the cross drilling is a piezo-electric crystal 28 which is surrounded by a body 29 of electrically insulating material.

The face of the crystal directed towards the pin, is engaged by a resilient element 30 which effects electrical connection between the aforesaid face and the spring abutment.

The opposite face of the crystal is engaged by a plunger 31 which beyond a retaining member to be described, is provided with a flange 32 which is engaged by a light coiled compression spring 33, the spring as seen in Figure 1, being carried upon an electrically insulated stem 34 which is connected to a ter minal 35 on the exterior of the holder.

The retainer member 36 is of annular form and has an outside diameter such that it can be assembled within- the drilling 27 such that the plunger can move therein. At its inner end i.e. that portion which lies within the drilling 26, the retainer member is flanged on its external and its internal surfaces and when the retainer member is pushed into position fol lowed by the plunger, the latter will engage the internal flange and deform the portion of the member which lies within the drilling, outwardly so as to prevent the member being withdrawn from the drilling. At its opposite end the retaining member is of enlarged section and it defines an internal projection 37 which can engage with a step defined on the periphery of the plunger.The arrangement is such that when the plunger is pushed into position the projection 37 will engage behind the step after the crystal 28 has been subjected to a predetermined loading, such load ing being derived from the resilient member 30. Once in position therefore the plunger is retained. 8ince the plunger makes electrical connection with the face of the crystal opposite to that engaged by the spring means, the signal generated when the crystal is stressed, will be available between the terminal 35 and the body of the injection nozzle.

In use, when the valve member is suddenly lifted from its seating by the action of fuel under pressure, the inertia of the plunger 31 causes the crystal to be subject to an additional compressive stress so that a signal is available at the output terminal. As the valve member continues to lift from its seating it will be halted by its engagement with the surface 24 on the distance member. However, since the spring abutment 21 is not itself halted the variation of stress applied to the crystal will be comparatively small. When the valve member returns into contact with its seating, and when it engages the seating, the inertia of the plunger 31 again causes an increase in the stress applied-to the crystal and once again this variation of stress is reflected in the signal at the output terminal.With the arrangement described therefore two comparatively large amplitude signals of the same polarity are obtain-ed indicating lifting of the valve member from the seating and closure of the valve member onto its seating respectively.

There may be a small variation in the signal when the valve member engages the surface 24. However, because it will be of smaller amplitude, this can be recognized and ignored by the signal processing apparatus.

In the modification which is seen in Figure 3, identical reference numerals are utilized wherever possible. In this example the plunger 31 is replaced by a metallic sleeve 38 which is retained in position by the retaining member 36. The electrical connection to the terminal 35 from the sleeve 36 is effected by means of a flexible foil 39 the foil being connected to the conductor 34. In this example it is the.

inertia of the sleeve 38 which results in an increased stress being applied to the crystal when the valve member is lifted from its sea ting and when it returns into contact with its seating.

Turning now to the examples shown in Fig ures 4 and 5, the general structure of the injection nozzle is the same as seen in Figure 1 and identical: reference numerals have been applied. The difference lies in the way in which the lifting of the valve member 19 from the seating 17 is detected.

In this example a transducer generaliy indi cated at 40 in Figure 4, is provided and this is located within the confines of the spring 22. As seen in Figure 5, the transducer in cludes a- support member 41 which is adapted to be supported in the holder 11 so as to extend within the spring 22. The support member has hollow portion at its end di rected towards the valve member and mounted within the hollow portion is a piezo electric crystal 42. One end face of-the-crystal is engaged by a metallic plate 43 which is connected to an insulated lead 44 leading to the terminal 35. The plate 43 is housed within an electrically insulating housing 45.The op posite end face of the crystal is engaged. by a further metallic plate 46 and located within the support member is an annular clamping mem ber 47 which engages the plate 46 to impart a small compressive stress tithe crystal 42.

Slidable within the clamping member is push piece 48 which is engaged by an abutment member 49 slidable- within the support mem ber.41. The abutment member is engaged by one end of a rod 50 formed from resilient material and which at its end remote from the abutment member can engage with the spring abutment 21. The dimensions of the rod are such that following assembly, the rod is in a slightly compressed state so that the com- pressive stress which is applied to the crystal by the -clamping member 47 is slightly en hanced, Although the rod 50 can engage the abut ment it is preferable to provide a spring 51 intermediate the rod and the abutment. The spring is enclosed except for its end portion remote from the rod, within the hollow portion of the support member The spring acts to prevent wear and distortion of the end of the rod.

The crystal is polarized so that when com pressive stress is applied to it, a potential difference will exist across the end faces which are contacted by the metallic. plates 43 and 46. The magnitude of the potential differ-.

ence will- dependupon the thy~ degree of compres- sive strength. Following assembly -however leakage of the electrical charge will occur so that the voltage difference between the -afore said plates will be substantially zero. When the valve member is lifted from its seating there is an increase in the compressive stress applied to the crystal and a voltage is deveioped which can be sensed between the body of the injection nozzle and the terminal 35. In this case the stress will increase as the valve inember moves towards its fully open position and so it is possible to monitor the signal so as to provide an indication of the degree of lift of the valve member as well as being able to detect opening of the valve member and its closure onto the seat.

The injection nozzles illustrated are of the inwardly opening type which have a pintle or projection 18 integral with the valve member and extending through the outlet orifices. The transducer can be applied to other known forms of inwardly opening injection nozzles without such projections.

It is-preferable to provide an impedance transforming circuit on or adjacent the nozzle holder in order to reduce the risk of electrical interference of the signal provided by the transducer.

The nozzles described together with the forms of transducer described have the substantial advantage that they can cope with variation in- dimensions in the various components due to manufacturing tolerances and due to wear which may take place when the nozzle is in service.

Claims (6)

1. A fuel injection nozzle of the kind specified including a piezo electric crystal mounted so that a compressive stress is applied to the crystal as the valve member is lifted from the seating, the nozzle including electrical connector means whereby the voltage change between two faces of the crystal as a result of the change in stress in the crystal, can be monitored from the exterior of the nozzle.

2. A nozzle according to Claim 1 in which said crystal dismounted on a spring abutment carried by said valve member, the nozzle including a mass engaging one face of the crystal whereby as the valve member is lifted from the seating the inertia of the mass will cause a change in the compressive stress applied to the crystal.

3. A nozzle according to Claim 1 in which said crystal is mounted in a part secured to the housing of the nozzle, the nozzle including a rod through which stress is applied to the crystal during the movement of the valve member to its open position.

4. A fuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

5. A fuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 1 and 3 of the accompanying drawings.

6. A fuel injection nozzle comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 4 and 5 of the accompanying drawings.