GB2269950A - Fuel injector controller with fault monitoring - Google Patents
Fuel injector controller with fault monitoring Download PDFInfo
- Publication number
- GB2269950A GB2269950A GB9315167A GB9315167A GB2269950A GB 2269950 A GB2269950 A GB 2269950A GB 9315167 A GB9315167 A GB 9315167A GB 9315167 A GB9315167 A GB 9315167A GB 2269950 A GB2269950 A GB 2269950A
- Authority
- GB
- United Kingdom
- Prior art keywords
- current
- circuit
- recirculation
- charge
- solenoid actuator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/045—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage adapted to a particular application and not provided for elsewhere
- H02H9/047—Free-wheeling circuits
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H47/00—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
- H01H47/22—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current for supplying energising current for relay coil
- H01H47/32—Energising current supplied by semiconductor device
- H01H47/325—Energising current supplied by semiconductor device by switching regulator
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Fuel-Injection Apparatus (AREA)
Abstract
A switch mode injector control system comprises a charge switch MOSFET 14, an injector coil 16, a current sensor 18, and a recirculation switch 20 and diode 22. Current flows alternately through the charge circuit 10 and through the recirculation circuit 12 in response to signals from the current sensor 18. The control circuit 24 detects if the coil current reaches too great a level, or does not reach a given level within a given time, and turns off switches 14 or 20, or both. <IMAGE>
Description
Fuel Injector Control
The present invention relates to solenoid actuation systems which include switch mode circuits to control the current level in the actuation means, and has particular application in fuel injector control systems.
The present invention provides a solenoid actuator control system having a charge circuit and a recirculation circuit with a common section forming part of each, a power supply for creating a potential difference across the charge circuit, solenoid actuation means in the common section, charge switch means for opening and closing the charge circuit and a control means for controlling the charge switch means wherein the control unit is arranged to time certain operations of the system to check for correct operation.
The solenoid actuator control system may further comprise recirculation switch means for opening and closing the recirculation circuit.
Preferably the control means is arranged to open the, or at least one of the, switch means if the current measured by the current measuring means remains at or above a predetermined level for a predetermined period of time.
More preferably the control means is arranged to open the charge switch means if, after a predetermined period from initiation of the actuation pulse, the current measuring means does not measure a current greater than a predetermined value.
Still more preferably the control means is arranged to open the, or at least one of the, switches if the current measuring means detects a predetermined current within a predetermined period of time.
Conveniently said predetermined period of time is measured from the initiation of an actuation pulse.
The present invention also provides a solenoid actuator control system having a charge circuit and a recirculation circuit with a common section forming part of each, a power supply for creating a potential difference across the charge circuit, solenoid actuation means in the common section, charge switch means for opening and closing the charge circuit, current measuring means for measuring the current in the charging circuit and in the recirculation circuit, and control means for switching the system from a charge mode to a recirculation mode and back in reponse to signals from the current measuring means to regulate the current through the actuation means, the control means being arranged to adopt a peak mode holding the current in the solenoid actuation means between a peak high level and a peak low level during an initial period and then to adopt a hold mode holding the current in the actuation means between a hold high level and a hold low level, wherein the control means is arranged to enter hold mode after a predetermined period from initiation of an actuator pulse.
The circuit may also comprise recirculation switch means for opening and closing the recirculation circuit.
Preferably the control means is arranged to enter hold.
mode on expiry of a first predetermined period if the current in the actuation means has reached a predetermined level within that period, and to enter hold mode on expiry of a second predetermined period if the said predetermined level has not been reached within one of said periods.
More preferably the control means is arranged to enter hold mode immediately if the said predetermined level is reached during the second time period.
Desirably the recirculation switch is arranged to be closed before the charge switch after the control means has switched from peak mode to hold mode thereby to slow down the current decay rate.
The switch means may each comprise a transistor, and preferably a MOS-E'ET.
Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:
Fig 1 is a diagram of a fuel injector control system according to a first embodiment of the invention;
Fig 2 is a graph showing the current through the injector actuation means of the system of Fig 1 as a function of time during nominal operation;
Fig 3 is a graph similar to Fig 2 showing the current during different operation when the current in the injector actuation means rises less quickly;
Fig 4 is-a graph similar to Fig 3 showing the current during different operation when the current in the injector actuation means rises still less quickly; and
Fig 5 is a diagram of a fuel injector control system according to a second embodiment of the invention.
Referring to Fig 1, in the first embodiment of the invention the fuel injector supply system comprises a charge circuit 10 and a recirculation circuit 12.The charge circuit 10 comprises a power supply, a charge switch 14 in the form of a MOS-FET, a fuel injector actuation means in the form of an injector coil 16, a current sensor 18 and an earth connection connected in series in that order.
A recirculation switch 20 in the form of a MOS-FET and a diode 22 are connected in series across the injector coil 16 and the current sensor 18. The diode prevents current flow from the supply through the recirculation switch 20 to earth so current can therefore only flow through the recirculation switch 20 by flowing around the loop comprising the recirculation switch 20 the diode 22 the injector coil 16 and the current sensor 18.
That loop forms the recirculation circuit 12, and the injector coil 16 and current sensor 18 are in a common section 17 forming part of the charge circuit 10 and the recirculation circuit 12.
A control circuit 24 including a clock 26 is connected to the charge switch 14, the recirculation switch 20 and the current sensor 18 and is arranged to operate the switches to control the current in the injector coil in response to the current sensor 18 and the clock 26.
The current passed through the injector coil 16 will now be described with reference to Figure 2 in which the current through an injector in normal operation is shown as a function of time. The current pattern shown is that required for a low impedence injector which requires an initial peak current to open the injector and then a lower hold current to hold the injector open for as long as is required.
When the injector is closed the charge switch 14 and the recirculation switch 20 are both open and no current flows in the injector coil 16. When it is desired to initiate an injector pulse a command signal is produced in the engine management system which closes both the switches 14, 20 and triggers the clock 26 at time to and the current I through the injector coil 16 rises rapidly.
When the current sensor 18 detects that the current reaches a peak high level 14 the control circuit 24 opens the charge switch 14. That prevents any further current from flowing through the charge circuit 10 but a current does continue to flow through the injector coil 16 and current sensor 18 round the recirculation circuit 12.
The current in the recirculation circuit falls off because there is no power supply to maintain it. When the current falls to a peak low level I3 the charge switch is closed again and the current I rises again.
The charge switch 14 keeps switching on and off to maintain the current I between the peak high and peak low levels I4, I3 until a time td at the expiry of a period T-peak from the initial closing of the charge switch 14, when it is assumed that the injector is fully open. At that point the charge switch and the recirculation switch are both opened and the current I drops rapidly until the current sensor detects that it has reached a hold high level I2. 2 The recirculation switch then closes so that the current I drops less rapidly until it reaches I1. Then -he charge switch 14 and recirculation switch 15 are both closed until the current rises to the hold high level I2.The current is held between Il and I2 by the control unit 24 switching the charge switch 14 on and off for a hold period T-hold, which expires at time tp The complete length of the pulse from to to tp is p determined by the engine management system and is dependent on the speed of the engine and the amount of fuel required.
At time t both switches 14, 20 are opened and the p current I falls rapidly to zero, allowing the injector to close and ending the injection pulse.
If the current reaches 13 before the desired injector opening time td then the injector is functioning normally and the control circuit operates as described above. If the current reaches I3 at a time tl after the expiry of the desired peak current time at td but before expiry of a maximum injector opening time at tm as shown in Figure 3 then the control circuit 24 opens both of the switches on the expiry of that time period and enters hold mode, which is maintained until the end of the injector-pulse period at tp when both of the switches 14, 20 are opened.
Referring to Figure 4, if at time tm the peak high current 14 has not been reached the control circuit goes to hold mode at t and this is maintained until the end
m of the injector pulse at tp.
Because the required injector pulse can sometimes be very short it is possible that t is before the expiry of
T-peak, or before the peak high current 14 has been reached. In that case the switches 14, 20 still both open at t
p
Referring to Figure 5 in a preferred embodiment of the invention all of the components which are the same as those in Figure 1 are indicated by the same reference numeral preceeded by 1. The only difference is that the recirculation switch 120 is in the common section 117 of the circuit between the injector coil 116 and the current measurer 118. This enables the inclusion of additional safety features to protect the circuit.
Because the injector coil 116 is remote from the rest of the circuit there is a length of wire from the top of the injector coil, ie the side thereof nearest the supply, to the charge switch 114 and another length of wire from the bottom of the injector coil, ie the side thereof nearest to earth, to the recirculation switch 120 which can be shorted causing damage to the circuit, in particular to the current measurer 118, or cause the injector to be held on for long periods which is obviously undesirable for example after an accident.
The control circuit 124 is therefore arranged to detect certain irregularities in the current measured by the current measurer 118 and operate at least one of the switches 114, 120 to break any short circuit which may have been created.
The clock 126 and the current measurer 118 can be used to monitor the generation of the system to check for its correct operation and take precautionary measures such as switching off the current to the injector coil 116 if any problems are detected.
If the bottom of the injector coil 116 is shorted to ground the current sensor 118 will not sense an increase in current after the switches 114, 120 are closed at the start of an injection pulse. The control circuit 124 is therefore arranged to measure the time taken from to for the current to reach I2. If this exceeds a predetermined period the control circuit opens the charge switch 114. Although I2 is used as the measured current in this case, I3, or another suitable current level could equally be used.
If the top of the injector coil is shorted to ground the current sensor would not detect a rise in current after to. However the current in the charge switch would rise very quickly because there would be little impedence in the circuit. Therefore a current limiting device 128 is connected between the charge switch 114 and the supply to cut off the circuit if the current through it is high enough to damage the recirculation switch 114.
If the bottom of the injector coil 116 is shorted to the supply the current will rise much more quickly after to than usual because of the low impedence in the circuit.
The control circuit is therefore arranged to turn off the recirculation switch 120 if the current reaches I3 before a-predetermined time t . Again, current levels
x other than I3 could be used in this check.
Finally, if the top of the injector coil 116 is short to the supply, the current will rise in the normal way, but will not fall again when the charge switch 114 is opened when the current reaches I The control circuit is therefore arranged to check the time taken for the current to fall from 14 to I3 in peak mode and, if that time exceeds a predetermined period, the recirculation switch 120 is opened.
The control circuit 124 is also arranged to check the current I in both peak mode and hold mode to determine whether it reaches any of a number of check levels which would indicate a malfunction. In peak mode the check current levels are set above the peak high current 14 and below the peak low current 13. In hold mode the check levels are set above the hold high level I2 and below the hold low level I1. If any of the check levels are reached the current to the injector coil 116 is cut off or some other precantionary action taken.
Alternatively only one check level may be used in each mode.
Claims (12)
1. A solenoid actuator control system having a charge
circuit and a recirculation circuit with a common
section forming part of each, a power supply for
creating a potential difference across the charge
circuit, solenoid actuation means in the common
section, charge switch means for opening and closing
the charge circuit and a control means for
controlling the charge switch means wherein the
control unit is arranged to time certain operations
of the system to check for correct operation.
2. A solenoid actuator control system according to
claim 1 further comprising recirculation switch
means for opening and closing the recirculation
circuit.
3. A solenoid actuator control system according to
claim 1 or claim 2 wherein the control means is
arranged to open the, or at least one of the, switch
means if the current measured by the current
measuring means remains at or above a predetermined
level for a predetermined period of time.
4. A solenoid actuator control system according to any
one of claims 1 to 3 wherein the control means is
arranged to open the charge switch means if, after a
predetermined period from initiation of an actuator
pulse, the current measuring means does not measure
a current greater than a predetermined value.
5. A solenoid actuator control system according to any
one of claims 1 to 4 wherein the control means is
arranged to open the, or at least one of the,
switches if the current measuring means detects a
predetermined current within a predetermined period
of time.
6. A solenoid actuator system according to claim 5
wherein said predetermined period of time is
measured from the initiation of an injector pulse.
7. A solenoid actuator control system having a charge
circuit and a recirculation circuit with a common
section forming part of each, a power supply for
creating a potential difference across the charge
circuit, solenoid actuation means in the common
section, charge switch means for opening and closing
the charge circuit, current measuring means for
measuring the current in the charging circuit and in
the recirculation circuit, and control means for
switching the system from a charge mode to a
recirculation mode and back in reponse to signals
from the current measuring means to regulate the
current through the solenoid actuation means, the
control means being arranged to adopt a peak mode
holding the current in the solenoid actuation means
between a peak high level and a peak low level
during an initial period and then to adopt a hold
mode holding the current in the actuation means
between a hold high level and a hold low level,
wherein the control means is arranged to enter hold
mode after a predetermined period from initiation of
an actuator pulse.
8. A solenoid actuator control circuit according to
claim 7 further comprising recirculation switch
means for opening and closing the recirculation
circuit.
9. A solenoid actuator control system according to
claim 7 or claim 8 wherein the control means is
arranged to enter hold mode on expiry of a first
predetermined period if the current in the actuation
means has reached a predetermined level within that
period, and to enter hold mode on expiry of a second
predetermined period if the said predetermineci level
has not been reached within one of saia periods.
10. A solenoid actuator control system according to
claim 9 wherein the control means is arranged to
enter hold mode immediately if the said
predetermined level is reached during the second
time period.
11. A solenoid actuator control system according to
claim 8, or either of claims 9 or 10 when dependent
thereon, wherein the recirculation switch is
arranged to be closed before the charge switch after
the control means has switched from peek mode to
hold mode thereby to slow down the current decay
rate.
12. A solenoid actuator control system substantially as
hereinbefore described with reference to the
accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9603567A GB2295931B (en) | 1992-08-22 | 1993-07-22 | Fuel injector control |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB929217921A GB9217921D0 (en) | 1992-08-22 | 1992-08-22 | Fuel injector control |
| GB9226904A GB2273836A (en) | 1992-12-24 | 1992-12-24 | Fuel injector control circuit with voltage boost |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9315167D0 GB9315167D0 (en) | 1993-09-08 |
| GB2269950A true GB2269950A (en) | 1994-02-23 |
Family
ID=26301484
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9315167A Withdrawn GB2269950A (en) | 1992-08-22 | 1993-07-22 | Fuel injector controller with fault monitoring |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2269950A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2289584A (en) * | 1994-05-19 | 1995-11-22 | Fuji Heavy Ind Ltd | Fuel injector driver circuit |
| US7433171B2 (en) * | 2000-10-21 | 2008-10-07 | Trw Limited | Fast current control of inductive loads |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3909681A (en) * | 1973-11-28 | 1975-09-30 | Honeywell Inf Systems | Driving circuit for printing electromagnet |
| GB2152305A (en) * | 1983-12-22 | 1985-07-31 | Bosch Gmbh Robert | Circuit arrangement for controlling and monitoring electrical loads |
| WO1988002544A1 (en) * | 1986-10-02 | 1988-04-07 | Motorola, Inc. | Solenoid driver control circuit with initial boost voltage |
| US4964014A (en) * | 1989-01-06 | 1990-10-16 | Deere & Company | Solenoid valve driver |
-
1993
- 1993-07-22 GB GB9315167A patent/GB2269950A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3909681A (en) * | 1973-11-28 | 1975-09-30 | Honeywell Inf Systems | Driving circuit for printing electromagnet |
| GB2152305A (en) * | 1983-12-22 | 1985-07-31 | Bosch Gmbh Robert | Circuit arrangement for controlling and monitoring electrical loads |
| WO1988002544A1 (en) * | 1986-10-02 | 1988-04-07 | Motorola, Inc. | Solenoid driver control circuit with initial boost voltage |
| US4964014A (en) * | 1989-01-06 | 1990-10-16 | Deere & Company | Solenoid valve driver |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2289584A (en) * | 1994-05-19 | 1995-11-22 | Fuji Heavy Ind Ltd | Fuel injector driver circuit |
| GB2289584B (en) * | 1994-05-19 | 1998-11-18 | Fuji Heavy Ind Ltd | Fuel injection control system for automobile engine |
| US7433171B2 (en) * | 2000-10-21 | 2008-10-07 | Trw Limited | Fast current control of inductive loads |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9315167D0 (en) | 1993-09-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |