GB2377025A

GB2377025A - A valve closure detection method and means

Info

Publication number: GB2377025A
Application number: GB0116034A
Authority: GB
Inventors: Peter Miller
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2001-06-29
Filing date: 2001-06-29
Publication date: 2002-12-31
Also published as: GB0116034D0

Abstract

A valve closure detection method and means 1 comprises an armature position detection system for an electromagnetic actuator 2. The armature position detection system comprises cusp detection in which a predicted time, within which the cusp is expected, is used to enable the cusp detection signal. The cusp detection may be performed by conventional circuit arrangements 10 and the predicted time may be calculated by valve position prediction circuitry 20 using current measurements to calculate the forces and/or acceleration applied to the armature. The calculated values may then be used in predicting the time at which the valve will change state from open to closed or closed to open. The predicted time may then be compared 26 to a reference value and the output 31 used in a logic arrangement 28 to enable the output of a cusp detection signal 30. The above detection system may provide more accurate control for valve opening and closing and avoid false triggering. The above said system may be used in automotive applications such as fuel injector timing to minimise unwanted vehicle emissions.

Description

A VALVE CLOSURE DETECTION APPARATUS AND METHOD FIELD OF THE INVENTION The present invention relates generally to a valve closure detection apparatus and method. More specifically, the invention relates to electromagnetic valve closure detectors used for example in automotive applications such as with injector timing to minimise emissions from vehicles.

BACKGROUND OF THE DISCLOSURE Valve closure devices are used to detect the closure and opening of valves for systems, for example, electromagnetic valves in automotive applications such as with injector timing to minimise emissions from vehicles.

Current and near term vehicle emission regulations in Europe and the United States require detecting and checking systems that ensure that electromechanical components associated with vehicle emission system are working efficiently. In particular, the accurate detection of the electromagnetic activity in valve closure in vehicle emission systems is necessary to meet future vehicle emission regulations, such as, European Directive 1999/96/EC.

Electromagnetic valve closure devices generally use a cusp detector to detect a change of slope of the current across the solenoid injector valve over time. The change

of current over time in the solenoid is directly proportional to the distance the solenoid travels. When the slope of the current changes outside a predetermined selected range, then the solenoid is considered to have moved enough to completely close or open the valve.

However, in operation of the valve closure device with the cusp indicator in vehicles, the predetermined selected range must be set large enough to prevent false triggering or closure detection and/or even missing closures due to interference in the current signal inherent to the vehicle environment. Current signal interference in the vehicle environment may be caused by electrical that may be due to sources of interference, for example, other loads in the vehicle electrical system switching on/off. Even with the range set large enough to limit false triggering before actual change of valve condition, such valve closure devices with cusp detectors are still prone to false triggering. Additionally, as the range for identifying detection must be large enough to offset the false triggering, it is not easily possible to determine the precise point in time solenoid movement reaches the"end stop"that identifies the point in time the valve is fully closed or fully open.

Therefore, there is a need in the art for valve closure detection apparatus and method that provides greater valve open and close accuracy, improved protection from false triggering and missing closures and openings, and more accurate end stop detection.

STATEMENT OF THE INVENTION In accordance with the present invention there is provided a valve closure detection apparatus as claimed in claim 1, and a valve closure detection method as claimed in claim 5.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be more fully described, by way of example, with reference to the drawings, of which: FIG. 1 shows a schematic circuit block diagram of a valve closure detection apparatus and method according to an embodiment of the invention; and FIG. 2 shows a graph of a response of current over time across an electromagnetic solenoid of a valve according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Referring to FIG. 1 in an embodiment of the invention, a circuit block diagram of a valve closure detection apparatus and method 1 is shown. A solenoid 2 is depicted for the electromagnetic valve device, with power supply 3, for example a vehicle battery. Such electromagnetic solenoid valves and power supplies are well known.

The detection circuitry shown provides valve position prediction circuitry 20, and conventional cusp detection circuitry 10 that is commonly used in electromagnetic valve

closure detectors, for example in automotive applications such as with injector timing to minimise emissions from vehicles.

The cusp detection circuitry 10 is connected to the solenoid 2 and power supply 3 circuit for monitoring the current over the solenoid. The current over the solenoid 2 is passed through capacitor 12 that is connected in parallel with resistors 14,16 to a cusp comparator 18. The cusp comparator 18 compares the changes in slope of the current across the solenoid over time, to a predetermined selected value 19, that is stored in a memory (not shown).

If the change in slope is greater than the predetermined selected value 19, then a signal 11 is generated indicating a change in valve state, i. e. open to close, or close to open.

The valve position prediction circuitry 20 may comprises a series of squaring and integrator blocks 23,24, 25 that perform functions with the current over a sense resistor 22 to predict the approximate time in which the solenoid valve will change from a closed or open state.

For example, squaring circuit block 23 first squares the current detected over the sense resistor 22 to provide an indication of force and acceleration. Then integrator blocks 24,25 integrate the force and acceleration values to provide an indication of velocity and distance, respectively, in accordance with the following formulas: Force = jnHA, where A is area of the solenoid, H=N*I/L, where for a long solenoid N is number of turns in the solenoid, L is length of solenoid, and I is current in

solenoid, such that force is proportional to current squared (12), where F=mass*acceleration, velocity = fforce/mass dt, and distance= ffforce/mass dtdt.

Clearly, it will be understood that the function blocks, for example the squaring and integrator blocks 23,24, 25, may be implemented in software within a microcontroller (not shown). Additionally, the valve position prediction circuitry 20 may be made more complex, if required, with additional inputs, for example, fluid temperature, or with other linear or non-linear functions instead of or in addition to pure integrations to simulate mechanical losses in the sensed current. In many cases, the integrations may also be replaced with sufficient accuracy by simple RC low pas filters, which will simulate increasing losses at high accelerations and high velocities, which is typically true.

The valve position prediction circuitry 20 may also be provided with a valve position predictor comparator 26 and AND gate 28. The values generated by the function blocks 23,24, 25 are transmitted to the valve position predictor comparator that compares that value with reference value, which is a value near or close as possible to the predicted value, to limit the time in which interference may contribute to false readings. One example for the reference value may be, for example, (half) the distance the valve travels, as the acceleration is known, and thus the distance the valve mechanically travels is known.

Additionally, the time for the valve travels the second half the distance will be less, since the acceleration is

greater at the second half of the distance the valve travels. However, as analogue values may not be precise, it will be appreciated that the value used for the reference value may be a different value, chosen by other means. After a predicted position signal 31 is sent from the predictor comparator 26, the AND gate 28 then will then enable a signal 30 to be sent indicating a change of solenoid/valve condition from a closed or open state once cusp signal 11 is received from the cusp comparator 18.

In operation, referring to FIG. 2, a graph of a response of current over time across an electromagnetic solenoid of a valve according to an embodiment of the invention is shown. Specifically, the current (I) response characteristic of the current across the solenoid over time is generally divided by portions A, B, D, E, F of the graph.

Critical points of time in which the solenoid valve changes from a closed or open state is indicated by points C, E.

Portion A of the graph indicates the inductive rise of the solenoid. Portion B indicates the max current of the solenoid which is limited by the voltage. Point C is the point when the valve condition begins to change and the solenoid begins to move. Portion D indicates the change in slope of the current across the solenoid over time after the valve condition begins to change. Point E is the end stop point when the valve is completely closed or open.

Portion F indicates the time after end stop.

By calculating the approximate time in which the solenoid valve will begin to change from a closed or open state, i. e point C, the valve closure detection apparatus and method provides greater valve open and close accuracy,

improved protection from false triggering and missing closures and openings, and more accurate end stop detection. Since the approximate time a change occurs in the condition of the solenoid valve is predicted, any inaccuracies or interferences along inductive rise portion A and max current portion B that may lead to a misfiring will not be taken into consideration. Additionally, since the point C when the valve condition begins to change and the solenoid begins to move is calculated and predicted, the end stop can be calculated and predicted.

It will be appreciated that although the particular embodiments of the invention have been described above, various other modifications and improvements may be made by a person skilled in the art without departing from the scope of the present invention.

Claims

CLAIMS: 1. A valve closure detection apparatus for use with an electromagnetic solenoid valve, the apparatus comprising: cusp circuitry for detecting a change the current across the electromagnetic solenoid valve over time, the cusp circuitry having a cusp comparator for comparing the change in current to a stored predetermined selected value, and providing a cusp signal indicating the time that the current exceeds the predetermined selected value; and valve position prediction circuitry for calculating a predicted time value in which the solenoid valve changes state, the valve position prediction circuitry having a prediction comparator for comparing the predicted time value calculated by a function block, to a predetermined set reference value, and providing a predicted position signal at the calculated predicted time the solenoid valve changes open/close or close/open states, wherein said cusp signal is enabled after the predicted signal is received.
2. A valve closure detection apparatus as claimed in claim 1, wherein the function block comprises a series of squaring and integrator blocks that perform functions with the current over a sense resistor in series with the electromagnetic solenoid valve to predict the time in which the solenoid valve will change state.

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3. A valve closure detection apparatus as claimed in claim 1 or 2, wherein a end stop signal is provided at the calculated time the valve is completely closed or open.
4. A valve closure detection apparatus as claimed in any preceding claim, wherein the predetermined set reference value is calculated from half the distance in time the valve mechanically travels from open/close or close/open states.
5. A valve closure detection method for use with an electromagnetic solenoid valve, the method comprising the steps of: detecting with cusp circuitry a change in current across the electromagnetic solenoid valve over time ; comparing, in the cusp circuitry having a cusp comparator, the changes in current to a stored predetermined selected value; providing, from the cusp comparator, a cusp signal when the current exceeds the predetermined selected value ; calculating, in valve position prediction circuitry, a predicted time value in which the solenoid valve changes state; comparing, in the valve position prediction circuitry having a prediction comparator, the predicted time value calculated by a function block, to a predetermined set reference value; and

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providing, from the prediction comparator, a predicted position signal when it is predicted that the solenoid valve changes open/close or close/open state, wherein said cusp signal is enabled after the position signal is received.
6. A valve closure detection method as claimed in claim 5, wherein the calculating, in valve position prediction circuitry, step further comprises calculating with the function block comprising a series of squaring and integrator blocks that perform functions with the current over a sense resistor in series with the electromagnetic solenoid valve to predict the time in which the solenoid valve will change state.
7. A valve closure detection method as claimed in claim 4 or 5, further comprising the step of providing an end stop signal wherein the end stop signal is provided at the calculated time the valve is completely closed or open.
8. A valve closure detection method as claimed in claim 5,6, or 7, wherein in the comparing, in the valve position prediction circuitry, step the predetermined set reference value is calculated from half the distance in time the valve mechanically travels from open/close or close/open states.

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9. A valve closure detection apparatus for use with an electromagnetic solenoid valve, substantially as hereinbefore described and with reference to the drawings.
10. A valve closure detection method for use with an electromagnetic solenoid valve, substantially as hereinbefore described and with reference to the drawings.