GB2097858A

GB2097858A - A fuel injector for an internal combustion engine

Info

Publication number: GB2097858A
Application number: GB8212904A
Authority: GB
Original assignee: Sulzer AG; Gebrueder Sulzer AG
Current assignee: Sulzer AG
Priority date: 1981-05-05
Filing date: 1982-05-05
Publication date: 1982-11-10
Also published as: JPS57186054A; IT1153503B; DK105682A; IT8221046A0; DE3119050A1; GB2097858B

Abstract

A fuel injector includes a hydraulically controlled injector valve 7 controlling flow of fuel from a gallery 20 via passages 12''', 12'', 12' to the injector valve which are connected through a safety valve 19 controlled by an electromagnetic changeover valve 41. The valve 41, when operated, applies gallery pressure to a piston 44 to overcome the load of a spring 45 which keeps the safety valve normally open. The valve 19 may be closed in response to an excessive drop in pressure in the gallery 20, as detected by an electrical resistance strain gauge 48, corresponding to jamming of the valve 7 or response to excessive engine speed. The output of the pump 22 supplying the gallery may be reduced in response to a gallery pressure, as detected by the gauge 48, exceeding a value set at a controller 30 which regulates operation of the valve 7. <IMAGE>

Description

SPECIFICATION A fuel injector for an internal combustion engine The invention relates to a fuel injector for an internal combustion engine.

As an example of one type of fuel injector to which the invention may be applied there is a fuel injector for a reciprocating internal combustion engine having an injector body, the body having a gallery to receive fuel at the injection pressure, an injector valve for controlling the fuel flow from the gallery to the cylinder combustion chamber being disposed in the body, one end of the injector valve being arranged as a sealing surface and cooperating with a seat surface in the valve body, the other end of the injector valve being acted upon by way of a loading piston by a hydraulic pressure medium controlled by an electromagnetic changeover valve having a supply duct, a discharge duct and control duct for pressure medium, the ducts being adapted to be so interconnected by a valve member of the changeover valve that either the supply duct is connected to the control duct and cut off from the discharge duct or the control duct is connected to the discharge duct and cut off from the supply duct, communication between the latter and the control duct corresponding to the injector valve experiencing by way of the loading piston a hydraulic force which is greater than the opposing force near the sealing end of the injector valve and which keeps the injector valve closed, whereas communication between the control duct and the discharge duct is associated with removal of the load acting on the loading piston at the other end of the injector valve, so that the same opens.

An injector of this kind is described in Swiss Patent Specification 494,346, wherein the changeover valve member is a spool engaging at one end in the bore of a piston-like thickening of the injector valve. In this engaging or sliding zone the bore has lands which cooperate with lands in the spool. The other end of the spool, such end being outside the piston-like thickening of the injector valve, takes the form of a flange-like disc and forms the electromagnet armature. The electromagnet comprises a cylindrical winding which is disposed in an axial bore in the valve body and which has a pin extending through the winding and extending at one end to near the armature. A non-magnetic spacing coliar and a ferromagnetic pole ring are disposed between the winding and the armature, extend around the pin end near the same and are also received in the valve body.A spring is disposed between the spacer and the pole ring, on the one hand, and the pin end, on the other hand, and forces the armature away from the pole ring when the winding is in the de-energised state.

Such an injector valve may jam, and if it jams open, fuel may continue to be injected into the cylindrical combustion chamber accidentally beyond the injection phase.

Another disadvantage is that there may be an unequal load distribution over the cylinders of a multicylinder engine for instance, because the injection orifices in the fuel injector of one cylinder are enlarged more by erosion than in the other cylinders.

The fact that the electromagnet is received in the axial bore of the valve body causes severe restrictions on the construction of the device. In the event of a failure in the electromagnetic changeover valve, the complete facility including the injector valve and the seat part therefor plus the electromagnet must be replaced.

It is the object of the invention to provide a fuel injector which in the event of the injector valve jamming, does not allow fuel to reach the cylinder combustion chamber accidentally.

Accordingly the present invention provides a fuel injector for a reciprocating internal combustion engine cylinder, having a body, a fuel gallery in the body to receive fuel under pressure for injection, an injector valve operative between the gallery and an injection orifice in the body to control the injection of fuel to the cylinder from that orifice, and a safety valve arranged to cut off supply of fuel under pressure to the injection valve in response to predetermined conditions of operation in the engine.

As a further aspect the invention provides a fuel injector for a reciprocating internal combustion engine having at least one cylinder, one fuel injector body per cylinder being disposed in the cylinder head, the body having a gallery to receive fuel at the injection pressure, an injector valve for controlling the fuel flow from the gallery to the cylinder combustion chamber being disposed in the body, one end of the injector valve being arranged as a sealing surface and cooperating with a seat surface in the valve body, the other end of the injector valve being acted upon by way of a loading piston by a hydraulic pressure medium controlled by a main electromagnetic changeover valve having a supply duct, discharge duct and control duct for pressure medium, the ducts being adapted to be so interconnected by a moving member of the changeover valve that either the supply duct is connected to the control duct and cut off from the discharge duct or the control duct is connected to the discharge duct and cut off from the supply duct, communication between the latter and the control duct corresponding to the injector valve experiencing by way of the loading piston a hydraulic force which is greater than the opposing force near the sealing end of the injector valve and which keeps the injector valve closed, whereas commmunication between the control duct and the discharge duct is associated with removal of the load acting on the loading piston at the other end of the injector valve, so that the same opens, including a safety valve disposed in the body of the fuel injector operative between the gallery and the seat surface for the injector valve, and having a valve member, such safety valve member being biassed to be normally open and closable by means of an electromagnetic safety changeover valve arranged to supply gallery fuel pressure to a piston arranged to move the safety valve to its closed position and interrupt the flow of fuel to the injector valve.

The provision of the safety valve and optionally of the electromagnetic changeover valve is a simple way of preventing an accidental injection of fuel into the cylinder combustion chamber, for instance, in the event of the injector valve jamming.

The electromagnetic changeover valve is preferably operatively associated with a control device which transmits a signal to the valve electromagnet upon detecting an accidental inflow of fuel into the cylinder chamber. To this end, each cylinder can have means which detect pressure variations in the gallery of the associated fuel injector body and which produce a corresponding signal which is applied by way of a signal line to the associated control device.

A comparison of the pressure variation signals of the injectors of various cylinders can then show whether load distribution among the cylinders is uneven, as may occur if the orifices of one injector have been eroded more than the orifices of the injectors of other cylinders. The deviant-load cylinder can be determined from the comparison and the difference in load distribution compensated for by reducing the quantity of fuel injected into such cylinder.

In order to promote a fuller understanding of the above and other aspects of the present invention, an embodiment will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a view in longitudinal section of a fuel injector, and in schematic form, the elements required to control the same; and Figure 2 is an axial section through the electromagnetic changeover valve of Figure 1, to a larger scale than in Figure 1.

Figure 1 shows a fuel injector 1 which comprises a casing having three parts 2, 3 and 4 which are rigidly and sealingly interconnected in a manner not shown in greater detail. The injector 1 is received in a cylinder head 5 whose bottom surface (in the drawings) bounds a combustion chamber 6 of a cylinder of a diesel engine. The valve body part 4, which is at the bottom in Figure 1, has an injector valve 7 which is guided and sealed in a central bore in body part 4. The bottom end 8 of the injector valve 7 has a conical sealing surface which co-operates with a seat surface in the valve body part 4. The seat surface merges into an axial duct 9 which merges near its bottom end into a number of orifices 1 0 extending into the combustion chamber 6. Near the bottom end 8 of the valve 7 the valve body part 4 has a chamber 11 into which a fuel supply duct 12 extends.The duct 1 2 extends upwards towards the central body part 3 and continues therein as a duct or the like 12'.

The central body part 3 is formed with a stepped central bore 1 3 coaxial with the valve 7 and having a bottom widened portion in which a piston 1 4 for loading the valve 7 is disposed for axial movement. Near the bottom end of the piston 1 4 the body part 3 is formed with a central recess 1 5 into which a relief duct 1 6 merges. The relief duct 1 6 extends upwards through the central body part 3. The relief duct 1 6 extends at its top end into a relief duct 1 7 which is disposed in the top body part 2 and to which a line (not shown) is connected, the latter line extending away from the cylinder head 5 to a sump.Near the top end of the central part 3 the fuel supply duct or tunnel 12' extends into a chamber 18 into which a moving part 1 9 of a safety valve extends. The part 1 9 is guided and sealed in a bore coaxial of duct 12' and, by way of its bottom conical sealing surface, co-operates with the top end of the duct 12t which is formed as a seat surface of a conical shape to match the conical sealing surface of the part 1 9. A fuel supply duct 12" extends from chamber 1 8 to the top end of the central body part 3.

The duct 12" continues in the top body part 2 as a duct 12"' and terminates in a gallery 20 in the body part 2. Fuel is supplied to the gallery 20 via a line 21 which communicates with a fuel pump 22.

In the bottom right-hand portion of the part 2 (as seen in Figure 1) there is an electromagnetic changeover valve 23 whose construction is shown in greater detail in Figure 2 and which has been described in greater detail in the Applicants' copending patent application No. 8212903. The valve 23 has a supply duct 24', a control duct 25' and a discharge duct 26'. The duct 24' communicates by way of a duct 24 in the body part 2 with the gallery 20. The control duct 25' of the valve 23 communicates by way of an angled duct 25 in the body part 2 with the stepped bore 13 of the central body part 3.The discharge duct 26' of the valve 23 communicates by way of an angled duct 26 with the relief duct 1 7. The valve member 60 of the valve 23 can either connect the duct 24', 24 to the duct 25', 25 and cut the latter off from the discharge duct 26', 26, 17 or connect the duct 25', 25 to the discharge duct 26', 26, 17 and cut off the duct 25', 25 from the duct 24', 24.

Consequently, by actuation of the moving valve member 20, the pressure of the fuel in the gallery 20 can be either applied to or removed from the loading piston 14.

The changeover valve 23 is a constructional unit embodying the electromagnet device and is fitted above the cylinder head 5 laterally of the body part 2. Consequently, in the event of a fault arising in it, it can be replaced without dismantling of the fuel injector casing parts 2, 3 and 4. Another advantage of the changeover valve 23 is that its valve member 60 is so devised that the hydraulic forces acting thereon are compensated for; consequently, only reduced magnetic forces are needed to move the member 60.

The fuel pump 22 comprises a control element which is not shown in greater detail and which is operated via a linkage 27 by a control facility 28.

The control element enables the fuel pressure produced by the fuel pump to be varied as required. The fuel pump 22 can be driven by the engine crankshaft (not shown) or by a shaft rotating at the same speed as the crankshaft.

Since there is no phase relationship between injection and the fuel pump 22, pump delivery can be multiplied by means of a multiplier cam 29 on the pump drive shaft. Alternatively, the speed of the pump-driving shaft can be stepped up so that the latter shaft runs faster than the crankshaft. In another embodiment the pump drive shaft may be driven independently of the diesel engine.

The changeover valve 23 is actuated by an electric speed controller 30 which receives a signal representative of engine speed via a signal line 31. Engine speed is detected by an electromagnetic pickoff including a transducer 32 and a toothed or marked disc 33 co-operating therewith, the disc 33 rotating with the crankshaft or pump drive shaft and delivering, in addition to the pulses for determining engine speed, pulses for determining the position of the top dead centres for the various cylinders. The engine speed value signal supplied via the signal line 31 to the speed controller 30 is compared with a speed set value nS which can be preselected by means of a knob 34 on the controller 30 to produce an output signal, which is connected via a signal line 35 to the electromagnet of the valve 23.The speed controller 30 has two other knobs 36, 37 for respectively preselecting the set value for the fuel pressue Pb produced by the fuel pump 22, and for preselecting the ignition pressure Pz. The fuel pressure set value is supplied via a signal line 38 to the final-control facility 28 and is compared therein with the actual value which is detected by a pressure detector 39 connected in the line 21 and which gives a pressure signal via a signal line 40 to the control facility 28. The term "ignition pressure Pz" denotes the maximum gas pressure in the combustion chamber 6, which is related to the crank angle at which injection starts which in turn is varied by adjustment of the knob 37.

The fuel to be injected into the combustion chamber 6 by the fuel injector 1 is taken in by the fuel pump 22 via a line 21' from a tank (not shown) and pressurized to the injection pressure at which it is delivered to the gallery 20 via the line 21. The fuel goes from the gallery 20 via the duct 12"', 12" to the chamber 1 8 and - since the moving member 1 9 of the safety valve is normally in the open position -- through the duct 12', 12 into the chamber 11 in the bottom body part 4.

Consequently, the injector valve 7 is permanently subjected to the fuel pressure present in the chamber 11. However, the injector valve 7 is still kept closed by the loading piston 14 which has a greater diameter than the injector valve 7 and which, between the injection phases, also experiences the fuel pressure. Between the injection phases the electromagnet of the changeover valve 23 is in an energized state such that the valve member 60 connects the delivery duct 24', 24 to the control duct 25', 25 and cuts off the latter from the discharge duct 26', 26.

Consequently, the fuel pressure in the gallery 20 acts by way of the ducts 24', 24, 25', 25 and of the bore 1 3 on the piston 14, which as discussed above, because of its larger diameter, applies to the injector valve 7 a greater hydraulic force than the force which the fuel pressure in the chamber 11 applies upwardly to the injector valve 7. In other words, the injector valve stays closed.When the electromagnet of the changeover valve 23 receives via the line 35 a changeover signal from the speed controller 30, the valve member 60 moves to interrupt the previous communication between the supply duct or tunnel 24', 24 and the control duct 25', 25 and to initiate instead communication between the latter duct and the discharge duct 26', 26. Consequently, the pressure acting via the bore 1 3 on the piston 14 decreases and the pressure applied by the fuel in the chamber 11 to the injector valve 7 predominates. The piston 1 4 and valve 7 move upwards as seen in the drawings until the lower thickened end of piston 14 abuts the top boundary surface of recess 1 5. The way is now clear for fuel to flow through the orifices 10 into the combustion chamber 6.This injection operation ceases when the changeover valve 23 receives from speed controller 30 a signal restoring communication between the duct 24', 24 and the duct 25, so that the piston 14 is moved down by the pressure of the fuel in the bore 1 3 and moves the injector valve 7 into its closed position. The speed controller 30 therefore may affect the duration of injection. The duration of injection determines at a given fuel pressure, the quantity of fuel injected and, therefore, the engine torque.

In addition to the changeover valve 23, an exactly similar changeover valve 41 is provided on the top body part 2 of the fuel injector 1, disposed on the left-hand side of the part 2 in Figure 1. The supply duct of valve 41 communicates with the fuel supply duct 12"' and the discharge duct of the valve 41 communicates via a cross-duct 42 with the discharge duct 26 of the changeover valve 23, so that the two changeover valves 23, 41 use a common relief duct 17. The control duct of the valve 41 is connected to a duct 43 in the body part 2, the latter duct extending to a cylinder chamber in which a piston 44 is disposed. The piston is operatively connected to the valve member 19 of the saftey valve in the body part 3, such valve member normally being kept in its open position by a spring 45. The changeover valve 41, which together with its electromagnet forms a single unit, is fitted laterally to the body part 2 above the cylinder head 5 and can readily be replaced in the event of a fault arising in it, without the fuel injector 1 having to be dismantled.

The changeover valve 41 is acted upon via a signal line 46 by a control device 47 in response to the fuel pressure in the gallery 20 and the limit speed of the engine. To detect the fuel pressure in the gallery 20 an annular electrical resistance strain gauge 48 is placed near the gallery 20 around the part 2 and converts such movements of the wall of the part 2 around the gallery 20 as are caused by the pressure of the fuel therein into variations of the electrical resistance. The resulting electrical signais are supplied via a signal line 49, which divides into three branchlines 49', 49", 49"', to the device 47 which has three functions to perform in connection with fuel pressure measurement. Its first function is to cut off the flow of fuel from the gallery 20 to the orifices 10 as rapidly as possible in the event of the injector valve 7 sticking.Its second function is to detect the quantity of fuel injected per stroke so that such quantity can be compared with the quantities injected into the adjacent engine cylinders. Its third function is to detect the maximum permissible pressure in the gallery 20. A fourth function is to detect maximum engine speed, to which end an engine speed transducer 50 is connected via a signal line 51 to the detector 47.

To fulfil the first function (associated with sticking of the injector valve) the pressure variations detected by the strain gauge 48 are used. In normal operation the pressure in the gallery 20 drops during injection, then subsequently returns to its original value as fuel is supplied by the fuel pump 22.

This periodical pressure pattern is supplied via line 49" to the device 47 and recorded therein for a brief period of time-i.e., approximately 100 crank angle -- immediately following the termination of injection. This crank angle range of approximately 100 is transmitted by means of the transducer 32, via a signal line 52 to the device 47. If, during this transmission phase, it is detected that the pressure in the gallery 20 is dropping further instead of rising - as would correspond to the injector valve 7 sticking -- a signal is transmitted via the line 46 to the electromagnet of changeover valve 41.

Consequently, the valve member thereof connects the fuel supply duct 12"' to the control duct 43, so that the fuel pressure acts on the piston 44 and the same causes an abrupt downwards movement of the valve member 1 9 of the safety valve to close the same, thus cutting off the flow fuel from the chamber 18 through the ducts 12", 12' to the chamber 11. A knob 53 on the detector 47 serves to preselect the threshold value -Ap at which the step just described is triggered.

To perform the second function (detection of the quantity of fuel injected into various cylinders), the pressure variations Ap = f(EQ) occurring in the gallery 20 of each fuel injector are supplied via the particular branch line 49' concerned, over the complete revolution of the crankshaft, to the device 47 associated with each cylinder. The measured values of the various cylinders can therefore be compared with one another. If the orifices are of identical cross-sections, equal pressure variations correspond to equal injected quantities of fuel.If while the engine is operating the orifices of the nozzle of one cylinder are eroded -- i.e., their cross-section becomes larger than that of the nozzles of the other cylinders more fuel flows through the eroded nozzle at a given pressure and in a given injection time, and the increase is manifested as an increased pressure variation. This difference is indicated by the corresponding detector. It is a simple matter for the engine operating staff to shorten the injection time, by way of the speed controller 30 for the cylinder concerned, by adjustment of the knob 54 of the corresponding device, so that all the cylinders return to receiving the same quantity of fuel. To this end, the detector 47 is connected via a signal line 55 to the speed controller 30.

To perform the third function (detecting the maximum permissible pressure in the gallery 20), the signals delivered by the strain gauge 48 and supplied via the branch line 49"' are analysed not for amplitude of variation but for absolute value in the detector 47. If it then turns out that the pressure P max set by means of the knob 56 is being exceeded, a corresponding signal goes via a signal line 57 to the control facility 28, which is arranged to act on the control element of the fuel pump 22 in these circumstances so that the pump delivery pressure decreases.

To perform the fourth function (to detect if the maximum speed is exceeded), in response to a corresponding signal from the transducer 50 the changeover valve 41 of each cylinder is actuated via the signal line 46 in the same way as described above in connection with the performance of the first function. Consequently, the valve member 1 9 of the safety valve moves into the closed position, thus cutting off the supply of fuel from the gallery 20 to the injector valve chamber 11 in all the cylinders of the engine.

Claims

1. A fuel injector for a reciprocating internal combustion engine cylinder, having a body, a fuel gallery in the body to receive fuel under pressure for injection, an injector valve operative between the gallery and an injection orifice in the body to control the injection of fuel to the cylinder from that orifice, and a safety valve arranged to cut off supply of fuel under pressure to the injector valve in response to predetermined conditions of operation in the engine.

2. A fuel injector as claimed in Claim 1, in which the safety valve is biassed to an open position, and is closable against such bias by means of hydraulic pressure, and an electromagnetic safety changeover valve is provided to selectively supply such pressure from said fuel supply gallery or release the pressure.

3. A fuel injector for a reciprocating internal combustion engine having at least one cylinder, one fuel injector body per cylinder being disposed in the cylinder head, the body having a gallery to receive fuel at the injection pressure, an injector valve for controlling the fuel flow from the gallery to the cylinder combustion chamber being disposed in the body, one end of the injector valve being arranged as a sealing surface and cooperating with a seat surface in the valve body, the other end of the injector valve being acted upon by way of a loading piston by a hydraulic pressure medium controlled by a main electromagnetic changeover valve having a supply duct, discharge duct and control duct for pressure medium, the ducts being adapted to be so interconnected by a moving member of the changeover valve that either the supply duct is connected to the control duct and cut off from the discharge duct or the control duct is connected to the discharge duct and cut off from the supply duct, communication between the latter and the control duct corresponding to the injector valve experiencing by way of the loading piston a hydraulic force which is greater than the opposing force near the sealing end of the injector valve and which keeps the injector valve closed, whereas communication between the control duct and the discharge duct is associated with removal of the load acting on the loading piston at the other end of the injector valve, so that the same opens, including a safety valve disposed in the body of the fuel injector operative between the gallery and the seat surface for the injector valve, and having a valve member, such safety valve member being biassed to be normally open and closable by means of an electromagnetic safety changeover valve arranged to supply gallery fuel pressure to a piston arranged to move the safety valve to its closed position and interrupt the flow of fuel to the injector valve.

4. A fuel injector as claimed in Claim 2 or 3 in which the safety changeover valve is operatively associated with a respective control device.

5. A fuel injector as claimed in Claim 4, in which each cylinder has means for detecting pressure variations in the fuel supply gallery and producing a corresponding signal, and supplying the signal to the control device.

6. A fuel injector as claimed in Claim 5, in which the means for detecting pressure variations comprises an electrical resistance strain gauge which extends around the wall around the fuel supply gallery and detects wall movements caused by pressure variations therein.

7. A fuel injector as claimed in Claims 4, 5 or 6 in which the control device has means to compare with a pre-set value a signal representing gallery pressure variation after the end of the injection phase over only part of a crankshaft revolution and to respond to a deviation from such pre-set value by transmitting to the safety changeover valve a signal to close the safety valve.

8. A fuel injector as claimed in any one of Claims 4 to 7 in which the main changeover valve is connected by a signal line to a speed controller and to said control device by a signal line; and each control device has means arranged to receive, throughout the crankshaft revolution, a signal representative of fuel gallery pressure variation of the associated valve body, means is provided to compare such signal with the corresponding pressure-variation signal in the other control devices and in the event of an increased pressure variation in one cylinder, transmit to the speed controller a signal reducing the fuel pressure in the particular fuel gallery concerned.

9. A fuel injector as claimed in any one of Claims 4 to 8 in which the fuel gallery is connected to a fuel pressure pump having a pressure controller and the control device has means to compare the fuel gallery pressure with a critical value and in response to the same being exceeded to transmit to the fuel pump pressure controller a signal to reduce the pump delivery pressure.

10. A fuel injector as claimed in any one of Claims 4 to 9 in which the control device is connected to an engine speed transducer has means arranged to transmit in response to a signal from the transducer indicating that a critical value has been exceeded, to the safety changeover valve a signal to close the safety valve.

11. A fuel injector as claimed in any one of the preceding claims in which both the main changeover valve and the safety changeover valve are each with their respective electromagnet devices a subassembly, the subassemblies being releasably secured to the fuel injector body outside the cylinder head for removal as a separate subassembly.

12. A fuel injector substantially as described herein with reference to the accompanying drawings.