EP1136694A2

EP1136694A2 - Condition sensor for a fuel injector

Info

Publication number: EP1136694A2
Application number: EP00128642A
Authority: EP
Inventors: Oliver A. Warner
Original assignee: Detroit Diesel Corp
Current assignee: Detroit Diesel Corp
Priority date: 2000-03-21
Filing date: 2000-12-28
Publication date: 2001-09-26
Also published as: CA2341047A1; AU7199700A; MXPA01000645A; BR0100501A; JP2001263207A; KR20010089129A

Abstract

The motion of a control rod in a fuel injector can be detected by an electrical sensor mounted in the fuel injector housing. The sensor includes an electrical probe, insulated from the injector housing, and having a tip located to be contacted by a shoulder on the control rod when the rod moves from the port-closed position to the port-open position. The electrical sense can be used for diagnostic purposes.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to diesel engine fuel injectors, and more particularly a sensor for determining when a fuel injector is in a fully open condition. The sensor is useful for valve timing purposes and for diagnostic information.
In one type of fuel injector a solenoid-operated valve is located in a high-pressure fuel passage for timing the flow of pressurized fuel to the fuel spray port (nozzle). The start of injection is indirectly determined by the point in time when the solenoid is energized. The duration of the fuel injection event is determined indirectly by the time interval in which the solenoid is kept energized.
The fuel injection timing can be affected by various conditions or circumstances, e.g. tolerances on mating surfaces, wear-induced leakage, fuel viscosity and supply pressure, spring force, and battery voltage. It is not possible to measure many of these factors, so as to determine whether the fuel injection process is proceeding according to design.
The present invention relates to a sensor incorporated into a fuel injector to indicate when the fuel injector has reached the full open condition. The sensor also provides information as to the duration of the full open condition. Such information, coupled with knowledge of the time at which the solenoid is initially energized, can be used to determine whether the fuel injection process conforms to permissible operational conditions. The invention can be used for fault detection purposes, engine protection purposes, or diagnostic analysis.
Specific features of the invention will be apparent from the attached drawings and description of an illustrative embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a sectional view taken through a fuel injector equipped with a sensor according to the invention.
Fig. 2 is an enlarged sectional view taken through the sensor employed in the Fig. 1 fuel injector.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Referring to Fig. 1, there is shown a conventional fuel injector that includes a housing 10 having an inlet passage 12 for receiving pressurized fuel from an engine-driven pump (not shown). Housing 10 further includes a reduced diameter nozzle 14 adapted to communicate with a combustion chamber, not shown, whereby pressurized fuel can be sprayed into the chamber through nozzle openings (ports) 16 at the nozzle tip.
A solenoid-operated control valve 18 is mounted on housing 10 for controlling the flow of pressurized fuel from inlet passage 12 to a passage 20 that leads to the nozzle ports 16. As illustratively shown in the drawings, control valve 18 includes a cup-shaped valve element 22 slidably mounted in housing 10 for movement toward a valve seat 24 interposed between passages 12 and 20.
A solenoid valve actuator 26 is located above valve element 22 to control the valve-open (or valve-close) action. A pilot valve plunger 30 is slidably positioned on the solenoid axis for movement toward or away from a pilot opening in valve element 22. As shown in Fig. 1, valve element 22 is closed by the fuel pressure existing in the space 32 above the valve element; a small opening 34 in the side of valve element 22 supplies pressurized fuel to space 32.
When solenoid 26 is electrically energized, plunger 30 is drawn upwardly so that space 32 is vented through the pilot opening. Fuel supply pressure, acting on the underside of valve element 22, lifts the valve element to the open condition. When solenoid 26 is electrically de-energized, a spring 36 returns plunger 30 downwardly to close the pilot opening, thereby allowing the fuel pressure in space 32 to build up so as to move valve element 22 to close against seat 24.
The drawings show valve 18 as a pilot-operated valve. However, a direct-acting valve could be used.
While control valve 18 is in the open condition, pressurized fuel is delivered through passage 20 to an annular chamber 38 surrounding a slidable control rod 40; the lower tip of rod 40 controls flow through the nozzle ports 16. In the absence of a high fuel pressure in chamber 38, rod 40 is maintained in a closed condition by the force of coil spring 42. When control valve 18 is opened to pressurize passage 20 and chamber 38, the increased pressure on the undersurfaces of rod 40 lift the rod, to allow pressurized fuel to be sprayed into the combustion chamber through ports 16. When solenoid 26 is de-energized to close valve 22 the pressure in chamber 38 immediately drops to allow spring 42 to move rod 40 downwardly to the port-closed position, as shown in Fig. 1.
It will be seen that solenoid 26 indirectly controls the timing and duration of the fuel injection event. The time at which the solenoid is initially energized determines the start of the fuel injection process. The duration (time interval) in which the solenoid remains energized, determines the length of the fuel injection process (i.e. the quantity of fuel injected into the combustion process). Enerigization of solenoid 26 is normally controlled by a non-illustrated electronic control module located remote from the individual injectors. The control module delivers solenoid-driver control signals to the various unit injector solenoids (one for each engine cylinder).
The present inventicn more particularly relates to an electrical sensor 44 for sensing the motion of control rod 40 during a fuel injection event. Fig. 2 shows some features of the sensor not apparent from Fig. 1. As shown in Fig. 2, the sensor includes an annular (tubular) barrel 46 having a threaded side surface, whereby the barrel can be threaded into a threaded hold machined in injector housing 10. A single rod-like electrical probe 48 extends through the barrel along the barrel axis, so that the probe remains on the barrel axis, whatever the rotated position of the barrel.
Probe 48 is electrically isolated from the barrel by an electrical insulator 50 molded around the probe so as to fill the interior space defined by the barrel. If barrel 46 were to be formed of a non-conductive plastic material, the barrel could act as the insulator.
Upper end 52 of the electrical probe is adapted to be connected to a positive voltage generated by the vehicle battery. Lower (internal) end 54 of probe 48 is adapted to contact a shoulder 56 formed on control rod 40 (Fig. 1), whereby the control rod conducts the sensor signal to ground through the fuel injector housing. As shown in Fig. 1, the internal end of probe 48 is spaced from control rod shoulder 56 so that no current is then flowing through the probe.
Sensor 44 is installed on housing 10 by screwing barrel 46 into the mating threaded hole until probe 48 is spaced a desired distance above shoulder 56 on control rod 40. A lock nut 58 is then tightened against the mouth of the threaded hole, to secure barrel 46 in the desired position of axial adjustment (i.e. along the barrel axis). The barrel axis is acutely angled to the motion axis of control rod 40 so that each unit turn of the barrel provides a specific change in the effective location of probe tip 54.
At the start of a fuel injection event, control rod 40 is shifted upwardly so that shoulder 56 contacts the internal end of probe 48 at, or near, the full-open position of the control rod. Probe 48 is preferably formed of a spring alloy, to a relatively small diameter, so that the lower end 54 of the probe can deflect slightly when shoulder 56 on the control rod forcibly strikes the probe end. As shown in Fig. 2, the probe lower end 54 is spaced from insulation 50 so that the lower section of the probe (below insulation 50) can deflect. When rod 40 returns to the port-closed position (as shown in Fig. 1) the lower section of probe 48 returns to its original condition.
Current flow generated through probe 48, by contact with shoulder 56, can provide information as to whether the fuel injection event is proceeding satisfactorily. The electrical signal generated by the probe can be detected by an inductive pick-up located in the aforementioned electronic control module. Preferably a single inductive pick-up detector is used for all of the fuel injectors in the system.
The probe 48 signal can be used to measure valve lift (by measuring the time interval between the solenoid energization signal start and the probe 48 signal start). Also, the duration of the probe 48 signal can be used to measure the duration of the fuel injection event. The probe (sensor) can be used for altering (changing) the injection timing or compensations for varying operating conditions, due to wear-driven leakage, fuel viscosity variations, frictional effects, battery voltage variations, changes in the spring 42 force, etc. The sensor can serve as a real time fault detector or as a diagnostic tool for optimizing injector performance.

Claims

A fuel injector comprising a housing having a fuel spray port means, a reciprocal fuel injection control rod for controlling the flow of pressurized fuel through said port means, a solenoid-operated valve for timing the flow of pressurized fuel to said port means, and an electrical sensor for sensing the motion of said control rod during a fuel injection event.
The fuel injection of claim 1, wherein said control rod is moveable between a port-closed position and a port-open position; said electrical sensor being oriented to sense the port-open position of said control rod.
The fuel injector of claim 2, wherein said electrical sensor is adjustably mounted in said housing, to vary the orientation of said sensor relative to the control rod.
The fuel injector of claim 2, wherein said control rod has a movement axis, and said electrical sensor has an adjustment axis that is acutely angled to the control rod movement axis.
The fuel injector of claim 2, wherein said electrical sensor comprises a threaded barrel and an electrical probe extending through said barrel on the barrel axis; said barrel being rotatably adjustable in said housing to adjust the barrel along the barrel axis.
The fuel injector of claim 5, wherein said control rod has a movement axis, said barrel axis being acutely angled to said control rod movement axis.
The fuel injector of claim 6, wherein said sensor includes an electrical insulator filling the barrel around said electrical probe.
The fuel injector of claim 7, wherein said probe extends beyond said barrel toward the control rod movement axis; said probe having a deflectable section adapted to engage the control rod as said rod nears the port-open position.
The fuel injection of claim 2, wherein said electrical sensor has a single electrical probe connectable to a positive voltage source, whereby the control rod forms a conductive path to ground when said rod contacts the probe.