Information
-
Patent Grant
-
6497221
-
Patent Number
6,497,221
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Date Filed
Monday, November 6, 200023 years ago
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Date Issued
Tuesday, December 24, 200221 years ago
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Inventors
-
Original Assignees
-
Examiners
- Wolfe; Willis R.
- Hoang; Johnny H.
Agents
- Michael Best & Friedrich LLP
-
CPC
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US Classifications
Field of Search
US
- 123 478
- 123 490
- 123 494
- 073 119 A
- 361 152
- 361 153
- 361 154
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International Classifications
-
Abstract
A method and system of adjusting a drive signal to a fuel injector or other electromagnetic device having an electromagnetic coil and an armature. The system includes an amplifier coupled to the electromagnetic coil by a link. A sensor is coupled to the link to measure the electric signal travelling through the link and produces an output signal based on the sensed electric signal. A controller coupled to the amplifier and to the sensor produces a drive signal for the electromagnetic coil. The controller determines the position of the armature based on the output signal of the sensor, and modifies the drive signal based on the position of the armature. The method includes sending a drive signal to a fuel injector, sensing whether the armature contacts the body of the fuel injector, running the injector with the drive signal if no contact is detected, and upon sensing contact between the armature and the body, modifying the drive signal. If the armature contacts the body of the fuel injector when driven by the modified drive signal, the controller modifies the modified drive signal until no contact between the armature and the body is detected. Then, the injector is run using the modified signal. The drive signal if preferably modified by notching the drive signal or stepping the drive signal.
Description
BACKGROUND OF THE INVENTION
The present invention relates to fuel injectors. More particularly, the invention relates to methods and devices used to control the actuation of fuel injectors.
Modem internal combustion engines rely on electronically controlled fuel injection systems. Mechanical injectors spray or otherwise dispense fuel within the combustion chamber(s) of the engine at specific times. The timing of fuel dispensing and the amount of fuel dispensed affects engine performance in a myriad of ways. While systems have been developed to control fuel injectors, these systems suffer from several deficiencies.
As is known, a fuel injector has an electromagnetic coil that is used to open and close a fuel-metering valve to control the flow of fuel into the engine. In most conventional fuel systems, the drive signal delivered to the coil is an amplified square wave. The square wave deteriorates slightly as it is amplified and run through the coil. Thus, the signal delivered to the fuel injector is not a true square wave. One deficiency in modem systems is that distorted square wave signals cause the armature to forcefully drive the valve into end stops positioned at either end of the path of travel of the valve. When the valve contacts the stops, the valve bounces. This generates an unpleasant noise and excessive wear of the valve and stops.
SUMMARY OF THE INVENTION
In light of the noted noise and wear problems of present fuel injection systems, there is a need for an improved fuel injection system that eliminates or reduces valve or armature bounce.
The present invention includes a fuel injector control system that modifies the control signal sent to the electromagnetic coil of a fuel injector. The control system has a microprocessor or other programmable device that delivers an output signal to an amplifying circuit such as a power transistor. The microprocessor modifies the control signal by notching or stepping the signal at times that correspond to the opening and closing of the injector valve. The notches in the signal help eliminate vibrations in the fuel injector caused by the impact of the valve contacting the stops within the injector. The microprocessor adjusts the notching of the drive signal by monitoring the electromagnetic characteristics of the fuel injector.
The invention also provides a method of driving a fuel injector that includes, sending a drive signal to a fuel injector, sensing whether the armature contacts the body of the fuel injector, running the injector with the drive signal if no contact is detected, and upon sensing contact between the armature and the body, modifying the drive signal. As noted, the drive signal is modified by notching or stepping the drive signal. The modified drive signal is reapplied to the fuel injector and the system then senses whether the armature contacts the body of the fuel injector when driven by the modified drive signal. The system continues to modify the signal until no contact between the armature and the body is detected. The injector is then run with the modified signal.
As is apparent from the above, it is an advantage of the present invention to provide a method and system for controlling a fuel injector. Other features and advantages of the present invention will become apparent by consideration of the detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a cross sectional diagram of an exemplary fuel injector.
FIG. 2
is a waveform diagram illustrating the movement of an armature in a fuel injector when driven by a square wave drive signal.
FIG. 3
is a waveform diagram illustrating the movement of an armature in a fuel injector when driven by a notched-wave drive signal.
FIG. 4
is a schematic diagram of an injector control system of the invention.
FIG. 5
is a waveform diagram illustrating the modification of a drive signal by notching.
FIG. 6
is a waveform diagram illustrating the modification of a drive signal by stepping.
FIG. 7
is a flowchart of the control and signal modification process of the invention.
DETAILED DESCRIPTION
Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. In particular, although the invention is described in relation to a fuel injector, the control techniques described herein are applicable to similar devices such as antilock braking system valves, intake, and exhaust valves, and other electromagnetically operated devices.
A fuel injector
10
is shown in FIG.
1
. The fuel injector
10
includes a housing or molding
12
. The molding
12
has an opening
13
for receiving a fuel line (not shown). A coil assembly
14
with an electromagnetic coil
16
is positioned in the molding
12
. The electromagnetic coil
16
interacts with a magnetic armature
18
that is connected to a needle assembly
20
. The needle assembly
20
includes a ball
22
and a needle
24
. The needle
24
is biased in a closed position by a spring
26
such that the ball
22
is seated in a seat
28
. When the electromagnetic coil
16
is energized, the armature
18
is drawn upwards to contact a stop
30
. The needle
24
, which is attached to the armature
18
is also drawn upwards resulting in the ball
22
leaving the seat
28
and the forceful ejection of fuel out of a metering plate
32
positioned at the bottom of the fuel injector
10
.
The fuel injector
10
is actuated by applying an electric signal to the electromagnetic coil. As shown in
FIG. 2
, known fuel injector systems apply a square wave drive signal, such as the signal
35
, to the electromagnetic coil. When the signal
35
is initially applied to the electromagnetic coil
16
, the armature
18
moves between a first position
37
, where the ball
22
is seated in the seat
28
, i.e., the injector is closed, to a second position
39
, where the ball
22
is unseated, i.e., the injector is open. The injector is held open for a predetermined period of time depending on the amount of fuel that is to be dispensed and then the drive signal is removed or reduced to zero amplitude. As can be seen by reference to the waveform
40
, in response to the drive signal, the armature
18
moves from the position
37
to the position
39
, but strikes the stop
30
with such force that the armature
18
oscillates for a period of time, as shown in portion
42
of the waveform
40
. The armature
18
then remains in a static open position, as is shown by portion
44
of the waveform
40
. When the drive signal is removed, the armature
18
then moves back to the position
37
. The ball
22
strikes the seat
28
such that the armature
18
oscillates for a second period of time, as is shown by portion
46
of the waveform
40
. The oscillation of the armature
18
and ball
22
against the stop
30
and seat
28
causes noise and wear in the injector
10
.
The inventors have discovered that the oscillation of the armature can be reduced by modifying the drive signal. A fuel injector control system
50
of the invention is shown in FIG.
4
. The system includes an engine control unit
52
, which includes a programmable processor (not shown). The engine control unit
52
generates an output signal that is sent to an amplifier
54
over a link
56
. The amplifier
54
may take the form of a power transistor. The amplifier
54
provides a drive signal to a fuel injector
58
over a link
60
. The fuel injector
58
may be almost any type of fuel injector that operates under substantially the same operating principles of the fuel injector
10
. For purposes of discussion, it is assumed that the fuel injector
58
has an armature and electromagnetic coil that are the same or equivalent to those described with respect to the injector
10
. Furthermore, component parts of the injector
10
will be used in the discussion below, although its should be understood that it is immaterial whether the injector
10
,
58
, or other injector is used in the invention.
A sensor
62
, which may take the form of a voltmeter (shown) or an ammeter (not shown) samples a feedback signal from the link
60
and delivers that feedback signal over a link
64
to the engine control unit
52
.
The engine control unit
52
modifies the drive signal sent to the fuel injector
58
based on the feedback signal received from the sensor
62
. In particular, the engine control unit
52
determines the position of the armature
18
based on the output signal of the sensor
62
and modifies the drive signal to prevent oscillation of the armature
18
.
FIGS. 3 and 5
illustrate one embodiment of the invention where the drive signal is modified by notching.
As shown in
FIG. 5
, an exemplary drive signal
75
includes an opening notch
77
and a closing notch
79
. The effect of these notches on the movement of the armature
18
is illustrated in FIG.
3
. As shown, applying a notched drive signal
90
having a trough
92
and an impulse
94
results in an armature waveform
98
with little or no oscillation. The engine control unit
52
controls the location and duration of the notches such that oscillation of the armature
18
is controlled during opening of the fuel injector by momentarily reducing the amount of energy applied to the electromagnetic coil. Conversely, oscillation of the armature
18
during closing is controlled by applying an impulse of energy.
In addition to modifying the drive signal by notching, stepping the drive signal is also effective in reducing oscillation of the armature
18
.
FIG. 6
illustrates a drive signal
110
having an opening step
112
and a closing step
114
. The engine control unit controls the height and duration of the opening and closing steps
112
and
114
.
The algorithm implemented via software installed on the engine control unit
52
is illustrated in the flow chart of FIG.
7
. As shown at step
200
, the engine control unit
52
generates and sends an unmodified drive signal to the fuel injector
58
. At step
204
, the engine control unit
52
senses whether the armature contacts the body of the fuel injector using the feedback signal from the sensor
62
. If no contact is sensed, then the fuel injector is run with the original drive signal. If contact is detected, the drive signal is modified as shown in step
208
. The engine control unit
52
then rechecks whether the armature contacts the body of the fuel injector when driven by the modified drive signal, as shown at step
212
. If contact is detected, the signal is modified further. The armature contact is continually checked and the drive signal modified until an acceptable level of vibration is detected. The multiple modified drive signal is then used to run the fuel injector, as shown at step
216
.
As can be seen from the above, the present invention provides a fuel injector control system that reduces meter-valve bounce and the wear associated with that bounce. Various features and advantages of the invention are set forth in the following claims.
Claims
- 1. A system for controlling an electromagnetic coil and an armature, the system comprising:an amplifier coupled to the electromagnetic coil by a link; a sensor coupled to the link to measure an electric signal travelling through the link and operable to produce an output signal; and a controller coupled to the amplifier and to the sensor and operable to produce a drive signal for the electromagnetic coil, the controller further operable to determine a position of the armature based on the output signal of the sensor, wherein the drive signal is modified based on the position of the armature and the drive signal is notched such that it has an opening notch and a closing notch.
- 2. A system as claimed in claim 1, wherein the amplifier is a transistor.
- 3. A system as claimed in claim 1, wherein the sensor is a voltage sensor.
- 4. A system as claimed in claim 1, wherein the sensor is a current sensor.
- 5. A system as claimed in claim 4, wherein a location and duration of the opening and closing notches are controlled by the controller.
- 6. A system as claimed in claim 1, wherein the drive signal is modified to have an opening step and a closing step.
- 7. A system as claimed in claim 6, wherein a height and duration of the opening and closing steps are controlled by the controller.
- 8. A system as claimed in claim 1, wherein the controller is an engine control unit.
- 9. A method of modifying a drive signal to a fuel injector having an armature and a body, the method comprising:sending the drive signal to a fuel injector; sensing whether the armature contacts the body of the fuel injector; running the fuel injector with the drive signal if no contact is detected; upon sensing contact between the armature and the body, modifying the drive signal; repeating the acts of sensing contact and modifying the drive signal until no contact between the armature and the body is detected; and running the fuel injector with the modified drive signal.
- 10. A method as claimed in claim 9, wherein the act of modifying the drive signal includes notching the drive signal.
- 11. A method as claimed in claim 10, wherein notching the drive signal includes creating an opening notch and a closing notch.
- 12. A method as claimed in claim 11, wherein notching the drive signal includes controlling a location and duration of the opening and closing notches.
- 13. A method as claimed in claim 9, wherein the act of modifying the drive signal includes stepping the drive signal.
- 14. A method as claimed in claim 13, wherein stepping the drive signal includes creating an opening step and a closing step.
- 15. A method as claimed in claim 14, wherein stepping the drive signal includes controlling a height and duration of the opening and closing steps.
- 16. A method as claimed in claim 9, wherein the act of sensing whether the armature contacts the body of the fuel injector includes sensing a current of the drive signal.
- 17. A method as claimed in claim 9, wherein the act of sensing whether the armature contacts the body of the fuel injector includes sensing a voltage of the drive signal.
- 18. A method as claimed in claim 9, wherein the act of sending the drive signal to the fuel injector involves generating a square wave.
- 19. A system for controlling an electromagnetic coil and an armature, the system comprising:an amplifier coupled to the electromagnetic coil by a link; a sensor coupled to the link to measure a signal travelling through the link and operable to produce an output signal; a controller coupled to the amplifier and to the sensor and operable to produce a drive signal for the electromagnetic coil, the controller further operable to determine a position of the armature based on the output signal of the sensor, wherein the drive signal is modified by being either notched or stepped based on the position of the armature and the drive signal is notched such that it has an opening notch and a closing notch.
- 20. A system as claimed in claim 19, wherein the amplifier is a transistor.
- 21. A system as claimed in claim 19, wherein the sensor is a voltage sensor.
- 22. A system as claimed in claim 19, wherein the sensor is a current sensor.
- 23. A system as claimed in claim 19, wherein a location and duration of the opening and closing notches are controlled by the controller.
- 24. A system as claimed in claim 19, wherein the drive signal is modified to have an opening step and a closing step.
- 25. A system as claimed in claim 19, wherein a height and duration of the opening and closing steps are controlled by the controller.
- 26. A system as claimed in claim 19, wherein the controller is an engine control unit.
- 27. A system for controlling an electromagnetic coil and an armature, the system comprising:an amplifier operable to be coupled to the electromagnetic coil by a link; a sensor operable to be coupled to the link to sense an electric signal travelling through the link and operable to produce an output signal; and a controller operable to be coupled to the amplifier and to the sensor and operable to produce a drive signal for the electromagnetic coil, the controller further operable to determine a position of the armature based on the output signal of the sensor, wherein the drive signal is modified based on the position of the armature and the drive signal is notched such that it has an opening notch and a closing notch.
US Referenced Citations (29)