EP1400676B1 - Injector system - Google Patents
Injector system Download PDFInfo
- Publication number
- EP1400676B1 EP1400676B1 EP20030255966 EP03255966A EP1400676B1 EP 1400676 B1 EP1400676 B1 EP 1400676B1 EP 20030255966 EP20030255966 EP 20030255966 EP 03255966 A EP03255966 A EP 03255966A EP 1400676 B1 EP1400676 B1 EP 1400676B1
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- European Patent Office
- Prior art keywords
- current
- discharge
- charge
- injector
- drive circuit
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- 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.)
- Expired - Lifetime
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- 239000003990 capacitor Substances 0.000 claims description 90
- 238000004146 energy storage Methods 0.000 claims description 34
- 239000007924 injection Substances 0.000 claims description 31
- 238000002347 injection Methods 0.000 claims description 31
- 230000002457 bidirectional effect Effects 0.000 claims description 26
- 230000007423 decrease Effects 0.000 claims description 2
- 239000000446 fuel Substances 0.000 description 125
- 230000004913 activation Effects 0.000 description 9
- 230000003247 decreasing effect Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 9
- 238000007599 discharging Methods 0.000 description 9
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- 238000013459 approach Methods 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 239000002283 diesel fuel Substances 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- KJLLKLRVCJAFRY-UHFFFAOYSA-N mebutizide Chemical compound ClC1=C(S(N)(=O)=O)C=C2S(=O)(=O)NC(C(C)C(C)CC)NC2=C1 KJLLKLRVCJAFRY-UHFFFAOYSA-N 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000003134 recirculating effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/20—Output circuits, e.g. for controlling currents in command coils
- F02D41/2096—Output circuits, e.g. for controlling currents in command coils for controlling piezoelectric injectors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/20—Output circuits, e.g. for controlling currents in command coils
- F02D2041/202—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit
- F02D2041/2051—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit using voltage control
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/20—Output circuits, e.g. for controlling currents in command coils
- F02D2041/202—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit
- F02D2041/2058—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit using information of the actual current value
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/20—Output circuits, e.g. for controlling currents in command coils
- F02D2041/2068—Output circuits, e.g. for controlling currents in command coils characterised by the circuit design or special circuit elements
- F02D2041/2072—Bridge circuits, i.e. the load being placed in the diagonal of a bridge to be controlled in both directions
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/20—Output circuits, e.g. for controlling currents in command coils
- F02D2041/2068—Output circuits, e.g. for controlling currents in command coils characterised by the circuit design or special circuit elements
- F02D2041/2082—Output circuits, e.g. for controlling currents in command coils characterised by the circuit design or special circuit elements the circuit being adapted to distribute current between different actuators or recuperate energy from actuators
Description
- The present invention generally relates to fuel injector drive circuitry and, more particularly, relates to a drive circuit for controlling one ore more piezoelectric fuel injectors. The present invention also relates to a method of controlling such a drive circuit.
- Automotive vehicle engines are generally equipped with fuel injectors for injecting fuel (e.g., gasoline or diesel fuel) into the individual cylinders or intake manifold of the engine. The engine fuel injectors are coupled to a fuel rail which contains high pressure fuel that is delivered by way of a fuel delivery system. The injectors typically employ a valve needle that is actuated to open and close so as to control the amount of high pressure fuel metered from the fuel rail and injected into the corresponding engine cylinder or intake manifold.
- One type of fuel injector that offers precise metering of fuel is the piezoelectric fuel injector. Piezoelectric fuel injectors employ piezoelectric actuators made of a stack of piezoelectric elements arranged mechanically in series for opening and closing an injection valve to meter fuel injected into the engine. Examples of piezoelectric fuel injectors are disclosed in
U.S. Patent Nos. 4,101,076 and4,635,849 . Piezoelectric fuel injectors are well-known for use in automotive engines. - The metering of fuel with a piezoelectric fuel injector is generally achieved by controlling the electrical voltage potential applied to the piezoelectric elements to thereby vary the amount of expansion and contraction of the piezoelectric elements. The amount of expansion and contraction of the piezoelectric elements varies the travel distance of a valve piston and, thus, the amount of fuel that is passed through the fuel injector. Control of the piezoelectric actuator thus controls fuel delivery.
- Piezoelectric fuel injectors offer the ability to precisely meter a small amount of fuel. However, piezoelectric fuel injectors also require relatively high voltages (in the hundreds of volts) and high currents (tens of amps) in order to function properly. Known conventional drive circuitry for controlling piezoelectric fuel injectors is generally complicated and usually requires extensive energy. Additionally, many prior piezoelectric injector drive circuits generally do not optimize injector performance over a wide operating range of the engine.
- Accordingly, it is therefore desirable to provide for a less complicated and more energy efficient drive circuit for driving a piezoelectric injector, such as a fuel injector for injecting fuel into an engine. It is also desirable to provide a drive circuit that offers enhanced operation of the piezoelectric injector over a wide range of engine operating points (e.g., engine speed, load, etc.).
- In order to inject fuel so as to provide an "injection event", the piezoelectric actuator undergoes a discharge and a charge mode. In one type of piezoelectric injector (known as positive-charge displacement injectors), the injector is configured such that charging of the actuator stack causes the needle to lift away from the valve needle seating to start the injection event, with discharging of the actuator stack causing the needle to seat to end the injection event. In another type of piezoelectric injector (known as negative-charge displacement injectors) it is discharging of the actuator stack that causes the needle to lift, with charging of the stack causing the valve needle to seat. The injector is said to be "opened" when injection occurs, and "closed" when injection does not occur.
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GB2334164 - One problem which has been encountered in negative-charge displacement injectors is that, at the end of an injection event when the piezoelectric actuator is re-charged to close the injector, a degree of voltage overshoot occurs. The re-charging voltage is applied to the actuator for a pre-determined duration, to ensure the voltage across the actuator reaches a threshold voltage level, VCHARGE, at which the actuator causes the injector to close. However, in practice, certain system factors may cause continued extension of the piezoelectric stack for a short period of time after this calculated duration. This leads to a fluctuation of the voltage across the stack about the desired voltage level, VCHARGE, an effect referred to as "voltage ringing". Positive voltage ringing occurs where the voltage across the stack is caused to exceed the threshold level, VCHARGE, and negative voltage ringing occurs where the voltage across the stack is caused to fall below the threshold level, VCHARGE. A similar problem arises during the discharge mode where the voltage across the piezoelectric stack is not maintained at the desired negative voltage threshold, VDISCHARGE, during the injection event. The effects of voltage ringing are disadvantageous as it reduces the accuracy with which the injector can be controlled and thus compromises injector efficiency.
- It is thus a further object of the present invention to provide an improved drive circuit and method for controlling fuel injection with a negative-charge displacement piezoelectric injector, which addresses the aforementioned problem of voltage ringing.
- According to a first aspect of the present invention there is provided a drive circuit as claimed in
claim 1. - By recovering energy stored in the injector in a recirculation mode, an enhanced energy efficient injector drive circuit is provided, as the voltage across the injector element changes for every inductor charge and recirculation cycle.
- A benefit of the invention is that the operation of the injector(s) may be varied over a wide range of engine operating points by controlling the current as a function of the first and second current thresholds. The first and second current thresholds may be controlled either dynamically or retroactively in time for the next injection event. Alternatively, the control means may comprise logic circuitry responsive to a frequency control signal.
- A further advantage of the present invention is that the discharging/charging modes may be terminated at any time to allow intermediate voltages (i.e. between VCHARGE and VDISCHARGE) to be achieved. This allows the injection characteristic of the injected fuel spray to be varied to give, for example, a so-called "boot-shaped" injection.
- In one embodiment of the present invention, the drive circuit is substantially configured as an H-bridge circuit and the inductor is preferably coupled in series with the injector(s) in the bidirectional current path.
- Where the drive circuit is configured as an H-bridge circuit, the energy storage device preferably comprises a capacitor, and the switching means preferably includes first and second switch means which are controllable to charge the injector(s), and third and fourth switch means which are controllable to discharge the injector(s).
- In other embodiments of the present invention, the drive circuit is substantially configured as a half H-bridge circuit. An advantage of configuring the drive circuit in this manner is that fewer components are required, and therefore the circuit is cheaper to manufacture (and more reliable and efficient) than the full H-bridge circuit. Furthermore, the half H-bridge circuit provides for the voltage across the injectors to be limited so that the injector actuators are not damaged during charging and discharging.
- The half H-bridge drive circuit may have a single inductor coupled in series with the injector(s) in the bi-directional current path. Alternatively, the half H-bridge drive circuit may have a first inductor disposed in the charge current path, and a second inductor disposed in the discharge current path. The inductance of the first inductor may be different to the inductance of the second inductor.
- In the half H-bridge circuit, the at least one energy storage device preferably comprises first and second capacitors, wherein the first capacitor preferably stores energy for use in the charge mode, and the second capacitor preferably stores energy for use in the discharge mode. The switching means in this arrangement preferably comprises a first switch means (such as a "charge" switch) which is controllable to charge the injector(s), and a second switch means (such as a "discharge" switch) which is controllable to discharge the injector(s). The advantage of providing only two switch means (i.e. the charge and discharge switches) in the half H-bridge drive circuit embodiments is that only minimal losses occur due to the reduced number of circuit components in comparison to the full H-bridge circuit.
- The drive circuits of the embodiments of the present invention may control at least first and second injectors, and may further comprise selector means (such as selector circuitry, for example) for selecting one of the at least first and second injectors. Conveniently, the selector means may be controlled so as to ensure that all the injectors are brought up to the same voltage during the charge mode. Only a selected one of the piezoelectric injectors may be discharged during the discharge mode.
- The at least first and second injectors may conveniently be arranged electrically in parallel. The advantage of arranging the injectors in parallel is that, at the end of the charging mode upon termination of the injection event by a selected injector, any voltage across the selected injector in excess of a predetermined voltage charge threshold tends to equalise with the voltage across the unselected injector(s). Thus, positive voltage ringing is damped due to excess energy being shared between the injectors. Accuracy of control of the injector and injector efficiency is thus improved.
- Advantageously, additional diodes may be provided in the half H-bridge circuit arrangement. A first additional diode may be connected in parallel with the charge current path to prevent a selected injector from being driven to a voltage higher than the highest voltage, VC1, applied to the first energy storage means during operation of the drive circuit. A second additional diode may be connected in parallel with the discharge current path so as to provide an additional current path for the recirculation current at the end of the discharge mode. The first and/or second additional diodes are advantageously provided when the first or second inductor has a large inductance of, for example, approximately 110 microHenrys or higher.
- In one embodiment, the current sensing means preferably comprises a sense resistor. In another embodiment, the current sensing means preferably comprises a first current sensing means (such as a transformer) in series with the first inductor for sensing the current flowing in the charge current path, and a second current sensing means (again, such as a transformer) in series with the second inductor for sensing the current flowing in the discharge current path. An advantage of using a transformer in place of a sense resistor is that a transformer can measure current directly (and is thus more efficient due to minimal losses), whereas a sense resistor requires additional electronics to give a current reading.
- The drive circuit may further comprise voltage sensing means for monitoring voltage across the selected injector, and the control means may be arranged to receive a signal indicative of the sensed voltage and provide a terminate control signal to the switch means to terminate the charging mode once a threshold charge voltage, VCHARGE, is sensed. The control means may also be arranged to provide an initiate signal to the charge (or discharge) switch means to initiate the charging (or discharging) mode of the selected injector. The control means may also be arranged to provide a terminate signal to the switch means to terminate the discharging means.
- The control means may be further arranged to control the activation and deactivation of the charge and discharge switch means to reduce voltage ringing in the drive circuit.
- It will be appreciated that although the present invention is particularly applicable to an injector system in which the injectors have piezoelectric actuators, it is equally applicable to any system in which the injectors have capacitive-like properties, for example motor-driven injectors.
- Preferred embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
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Figure 1 is a block diagram illustrating a first embodiment of a drive circuit according to the present invention for controlling a piezoelectric fuel injector in an engine; -
Figure 2 is a block/circuit diagram illustrating the piezoelectric drive circuit according to the first embodiment of the present invention; -
Figures 3a and3b are flow diagrams illustrating a control routine for operating the drive circuit ofFigure 2 ; -
Figures 4a to 4c are graphs which illustrate voltage and current levels during operation of the drive circuit ofFigure 2 , according to one example; -
Figure 5 is a block diagram illustrating second and third embodiments of a drive circuit according to the present invention for controlling two piezoelectric fuel injectors in an engine; -
Figure 6a is a block/circuit diagram illustrating the piezoelectric drive circuit according to the second embodiment of the present invention; -
Figure 6b illustrates the enabling/disabling and activation/deactivation of a switch during operation of the drive circuit ofFigure 6a ; -
Figures 7a and7b are flow diagrams illustrating a control routine for operating the drive circuit ofFigure 6a ; -
Figures 8a to 8d are graphs which illustrate voltage and current levels during operation of the drive circuit ofFigure 6a , according to one example; -
Figure 9 is a block/circuit diagram illustrating the piezoelectric drive circuit according to a third embodiment of the present invention; -
Figures 10a to 10e are graphs which illustrate energy, current and voltage levels during operation of the drive circuit ofFigure 9 , according to one example; and -
Figure 11 illustrates the enabling and disabling of switches during operation of the drive circuit of the present invention. - Referring to
Figure 1 , anengine 10, such as an automotive vehicle engine, is generally shown having apiezoelectric fuel injector 12 for metering and injecting fuel into an individual cylinder or intake manifold of theengine 10. Thepiezoelectric fuel injector 12 controls the amount of fluid (e.g., liquid) fuel injected from a fuel rail of a fuel delivery system into an engine during each fuel injection stroke of theengine 10. Thepiezoelectric fuel injector 12 may be employed in a diesel engine to inject diesel fuel into the engine or may be employed in a spark ignited internal combustion engine to inject combustible gasoline into the engine. While onepiezoelectric fuel injector 12 is shown and described in the embodiment ofFigure 1 , it should be appreciated that theengine 10 may include two or more piezoelectric fuel injectors, all of which could be controlled by a common drive circuit. - The
engine 10 is generally controlled by an engine control module (ECM) 14. TheECM 14 generally includes a microprocessor andmemory 16 for performing various control routines for controlling the operation of theengine 10, including control of the fuel injection. TheECM 14 may monitor engine speed and load and control the amount of fuel and injection timing for injecting fuel into the engine cylinder. According to a first embodiment, a piezoelectric full H-bridge drive circuit 20a is shown integrated into theengine control module 14 monitoring and controlling the injector high side voltage INJHI and injector low side voltage INJLO to control actuation of thepiezoelectric fuel injector 12 to open and close theinjector 12. Thepiezoelectric drive circuit 20a may be integrated in theengine control module 14 as shown or may be provided separate therefrom. The microprocessor andmemory 16 providevarious control signals 18 to thedrive circuit 20a. - The
piezoelectric drive circuit 20a controls the opening and closing of thepiezoelectric fuel injector 12 to meter and inject precise amounts of fuel into an individual cylinder or intake manifold of theengine 10. Thepiezoelectric drive circuit 20a as shown and described herein operates in a discharge mode which discharges theinjector 12 to open the injector valve to inject fuel, and further operates in a charge mode which charges theinjector 12 to close the injector valve to prevent injection of fuel. However, thedrive circuit 20a andinjector 12 could be otherwise configured to open during a charge mode and close during a discharge mode. It should be appreciated that thedrive circuit 20a of the present invention advantageously provides simplified injector control circuitry which offers enhanced energy efficiency. - The first embodiment of the
piezoelectric drive circuit 20a is further illustrated in detail in the block/circuit diagram ofFigure 2 . Thedrive circuit 20a in the first embodiment generally is configured as a full H-bridge having amiddle circuit branch 26 that serves as a bidirectional current path coupled to positive (+) and negative (-) terminals of thepiezoelectric fuel injector 12. Thedrive circuit 20a includes avoltage input 22 for receiving a voltage VS (e.g., 12 volts) from a voltage source (e.g., vehicle battery). The voltage VS is increased to a higher step-up voltage VC1 (e.g., 230 volts) via a step-up transformer (DC-to-DC converter) 24. The step-up voltage VC1 is applied to an energy storage capacitor C1 via a diode D5. The step-up voltage VC1 applied to capacitor C1 may provide a high voltage such as 230 volts, according to one example. - The
drive circuit 20a includes four switches Q1 to Q4 positioned at opposite comers of the H-bridge circuit configuration. According to one embodiment, switches Q1 to Q4 may each include an n-channel insulated gate bipolar transistor (IGBT) having a gate controlling current flow from the collector to the emitter. Each of the switches Q1 to Q4 allows for unidirectional current flow from the collector to the emitter when turned on, and prevents current flow when turned off. Connected in parallel to the switches Q1 to Q4 are four recirculation diodes D1 to D4, respectively, for providing unidirectional current flow opposite to the direction of current flow in the corresponding switches Q1 to Q4. The recirculation diodes D1 to D4 allow recirculation current to return to the capacitor C1 during an energy recovery mode. - The
piezoelectric fuel injector 12 is shown connected in the bidirectionalcurrent path 26 across charge (+) and discharge (-) terminals. Thepiezoelectric fuel injector 12 has the electrical characteristics of a capacitor and, thus, is shown represented as a capacitor labeled INJ. Theinjector 12 is chargeable to hold a voltage VINJ which is the voltage potential between voltages INJHI and INJLO across the charge (+) and discharge (-) terminals. It should be appreciated that thepiezoelectric fuel injector 12 is charged and discharged by controlling the current flow ICHARGE and IDISCHARGE through the bidirectionalcurrent path 26 as explained herein. - The
drive circuit 20a includes an inductor L1 connected in series with thepiezoelectric fuel injector 12 as part of the bidirectionalcurrent path 26. The inductor L1 operates as a current-limiting inductor that controls current flowing through the bidirectionalcurrent path 26. Thedrive circuit 20a advantageously employs the current-limiting inductor L1 in series with thepiezoelectric fuel injector 12 in a bridge arrangement to charge and discharge theinjector 12. The H-bridge drive circuit structure results in energy recovery due to the use of the current-limiting inductor L1 in conjunction with the recirculation diodes D1 to D4. Additionally, the current-limiting inductor L1 limits the maximum current applied to thepiezoelectric fuel injector 12 which prevents damage to the stack of piezoelectric elements inside of theinjector 12. - The
drive circuit 20a also includes a sense resistor R1 coupled between ground and the emitter of each of the transistors Q2 and Q4. A differential amplifier U2 senses the voltage potential drop across the sense resistor R1 so as to monitor the current flowing to or from ground through the sense resistor R1. The differential amplifier U2 generates a voltage proportional to the amount of current flowing between the capacitor C1 and ground, and thus the current flow through thecurrent path 26. The output of the differential amplifier U2 is applied as an input to both of the comparators U3 and U4. The comparator U3 compares the sensed current to a peak current threshold IP, while the comparator U4 compares the sensed current to a recirculation current threshold IR. The peak current threshold IP and recirculation current threshold IR are stored and processed via the microprocessor andmemory 16, or alternately may be provided in discrete circuitry. The peak current threshold IP and recirculation current threshold IR define a range limiting the current flow through thecurrent path 26. Whenever the absolute value of the sensed current exceeds the peak current threshold IP, the current supplied from capacitor C1 is interrupted by turning switches Q1 to Q4 off. The inductor L1 causes current to continue to flow in the same direction in thecurrent path 26 by drawing current from ground and applying the current to the capacitor C1 through selected pairs of recirculation diodes D1 to D4 so as to transfer energy stored in the inductor L1 and theinjector 12 into the capacitor C1. - The
drive circuit 20a monitors and controls the current flow ICHARGE and IDISCHARGE as follows. Comparator U4 determines when the absolute value of the sensed current drops below the recirculation current threshold IR and generates an output signal provided as an input to an AND logic gate U7. Comparator U3 determines when the absolute value of the sensed current exceeds the peak current threshold IP and generates an output signal which, in turn, is input to both a one shot circuit U6 and a flip-flop U5. The one shot circuit U6 generates an output signal as an input to the AND logic gate U7 when the absolute value of the sensed current exceeds the peak current threshold IP. Flip-flop U5 generates an output signal, depending upon a frequency control input, which is provided as an input to the AND logic gate U7. Accordingly, the AND logic gate U7 provides a high logic output whenever the absolute value of the sensed current is within the limited current range between the peak current threshold IP and the recirculation current threshold IR, and thecircuit 20a is not in the recirculation mode. - The opening and closing characteristics of the
piezoelectric fuel injector 12 are generally influenced by the voltage slew rate applied to theinjector 12 during the discharge and charge cycles, respectively. In order to vary the voltage slew rate, thedrive circuit 20a of the present invention varies the average current ICHARGE or IDISCHARGE flowing through theinjector 12. As a consequence, a lower average current flowing through theinjector 12 results in a reduced voltage slew rate. The average current flowing throughinjector 12 is controlled by changing the peak current threshold IP and/or the recirculation current threshold IR. - The frequency control signal provides an optional means to vary the charge and discharge voltage slew rate by varying the frequency of the frequency control signal. It should be appreciated that the flip-flop U5 generates an output on line Q at a predetermined point of each cycle of the frequency control signal. According to one embodiment, an active edge of the frequency control signal may be used to control timing for starting each cycle of the charge and discharge modes in order to control the average current and, thus, the voltage slew rate.
- The
drive circuit 20a further includescontrol logic 30 for receiving the output of the AND logic gate U7. Thecontrol logic 30 may include software executed by the microprocessor andmemory 16. In addition, thecontrol logic 30 receives various inputs from the microprocessor andmemory 16, or alternately from discrete circuitry. These inputs include a charge voltage threshold VCHARGE, a discharge voltage threshold VDISCHARGE, and a charge/discharge signal C/D. Thecontrol logic 30 further receives an output of a differential amplifier U1 which senses the voltage potential across the charge and discharge terminals (+) and (-) of theinjector 12 so as to determine the voltage difference VINJ across thepiezoelectric fuel injector 12. Thecontrol logic 30 processes the inputs as described herein and generates control signals to control each of the switches Q1 to Q4. - The
drive circuit 20a operates in a discharge mode to open thefuel injector 12 and in a charge mode to close thefuel injector 12. In order to discharge theinjector 12, switches Q3 and Q2 are activated to allow current to flow from the high voltage supply across the capacitor C1 through switch Q3, inductor L1,injector 12, switch Q2, and sense resistor R1 to ground. The current ICHARGE or IDISCHARGE flowing through thedrive circuit 20a is monitored by the differential amplifier U2 and, as soon as the peak current threshold IP is reached, the comparator U3 triggers the one shot circuit U6 to initiate a forced off time. At this point, switches Q2 and Q3 are turned off and the current buildup IL1 in inductor L1 is recirculated through the recirculation diodes D1 and D4 in a recirculation mode. - The direction of the current flow through the inductor L1 and the
injector 12 does not change with the recirculation mode. However, during the recirculation mode in the discharge mode, current flows from ground through the sense resistor R1, recirculation diode D4, inductor L1,injector 12, recirculation diode D1 and into the capacitor C1 where energy in the inductor L1 is transferred to the capacitor C1 and made available for the next charge or discharge cycle. Because theinjector 12 is in series with the inductor L1 in the bidirectionalcurrent path 26, energy is also transferred from theinjector 12 to the capacitor C1 during the recirculation mode. This recirculation mode represents the energy recovery portion of the discharge and charge events, and serves to recover energy from theinjector 12 for storage in the capacitor C1. The forced off time generated by the one shot circuit U6 allows the current sensing circuitry time to adjust to the current reversal occurring in the sense resistor R1 during the transition from current buildup to current recirculation. The current sensing circuitry monitors the recirculation current and, when the absolute value of the recirculation current drops below the recirculation current threshold IR, the comparator U4 turns switches Q2 and Q3 on to continue the discharge process. - The differential amplifier U1 monitors the voltage VINJ across the
injector 12, and the cycling of current buildup and recirculation proceeds until the H-bridge control logic 30 detects that the appropriate discharge voltage threshold VDISCHARGE has been achieved. The monitored voltage VINJ across theinjector 12 is compared to the charge voltage threshold VCHARGE or discharge voltage threshold VDISCHARGE. It should be appreciated that the charge voltage threshold VCHARGE and discharge voltage threshold VDISCHARGE can be varied to optimize operation over a wide range of engine operating points. - In lieu of the differential amplifier circuitry U1 and U2, it should be appreciated that the
microprocessor 16 could monitor the injector voltage and current directly. It should also be appreciated that the charge cycle operation, which causes theinjector 12 to close, is similar to the discharge operation as explained above, except that during the charge mode current flows through the switches Q1 and Q4 during current buildup, and through the recirculation diodes D2 and D3 during the recirculation mode. - Referring to
Figures 3a and3b , acontrol routine 100 for performing control logic is illustrated for controlling operation of thepiezoelectric fuel injector 12 in accordance with the first embodiment of the present invention. Thecontrol routine 100 begins atstep 102 and checks indecision step 104 if there is a request by theengine control module 14 to turn on thepiezoelectric fuel injector 12. If there is a request to turn on theinjector 12, routine 100 proceeds to decision step 140 to operate thedrive circuit 20a in the discharge mode. If not, routine 100 checks if there is a request by theengine control module 14 to turn off theinjector 12 indecision step 106 and, if not, returns to the beginning instep 102. If there is a request to turn theinjector 12 off, routine 100 proceeds todecision step 108 to operate thedrive circuit 20a in the charge mode. - In the charge mode,
decision step 108 checks if the charge voltage limit (threshold VCHARGE) across thepiezoelectric fuel injector 12 has been met. This is determined by comparing the output of differential amplifier U1 with the charge voltage threshold VCHARGE. If the charge voltage limit has been met, indicative of theinjector 12 being closed, all switches Q1 to Q4 are turned off instep 110, before returning to the beginning of the routine 100 instep 120. If the charge voltage limit has not yet been met, routine 100 proceeds todecision step 114 to check if the absolute value of the current sensed across the sense resistor R1 is greater than the peak current threshold IP, as determined by the comparator U3. - If the absolute value of the sensed current is greater than the peak current threshold IP, switches Q1 and Q4 are turned off in
step 116 before returning to the beginning of the routine 100 instep 120. Once the absolute value of the sensed current exceeds the peak current threshold IP, the switches Q1 and Q4 are turned off and the current flowing through the inductor L1 causes energy in the inductor and theinjector 12 to be transferred into the capacitor C1 until the absolute value of the sensed current drops below the recirculation current threshold IR. This is achieved by the inductor L1 causing current to flow through theinjector 12 in a recirculation path by forcing current from ground through the sense resistor R1, diode D2,injector 12, inductor L1, diode D3 to the positive terminal of the capacitor C1. Thus, energy is recovered during the recirculation mode. - If the absolute value of the sensed current does not exceed the peak current threshold IP, routine 100 proceeds to
decision step 122 to check if the switches Q1 and Q4 are already turned on and, if so, returns to the beginning of the routine 100 instep 120. If both switches Q1 and Q4 are determined not to be already turned on instep 122, routine 100 determines, indecision step 124, if the absolute value of the current sensed across the sense resistor R1 is less than the recirculation current threshold IR as determined by comparator U4 and, if not, returns to the beginning instep 120. - If the absolute value of the sensed current is less than the recirculation current threshold IR, the
control routine 100 proceeds todecision step 126 to determine if thedrive circuit 20a is in a frequency control mode in which the frequency control signal is adjusted to set the charge and discharge voltage slew rate. If the frequency control mode is not in operation, switches Q1 and Q4 are turned on instep 128 before returning to the beginning of the routine 100 instep 120. By turning on switches Q1 and Q4, thecontrol routine 100 causes charge current ICHARGE to continue to flow from the high voltage energy storage capacitor C1 through switch Q1,injector 12, inductor L1, switch Q4, and through sense resistor R1 to ground. In thedrive circuit 20a, by closing the switches Q1 and Q4, a charge current ICHARGE flows through the inductor L1 and theinjector 12 in the bidirectionalcurrent path 26 to cause thepiezoelectric fuel injector 12 to close to prevent the injection of fuel into theengine 10. Once thefuel injector 12 is closed, it remains closed until thedrive circuit 20a is controlled to generate a discharge current IDISCHARGE when the fuel injector is requested to be open to inject fuel into theengine 10. It should be appreciated that switches Q1 and Q4 will be cycled on and off simultaneously for as long as it takes to close thefuel injector 12, and that multiple cycles of turning switches Q1 and Q4 on and off simultaneously may be performed to achieve this function. - In the frequency control mode of operation, the
control routine 100 determines if an active edge of the frequency cycle is received indecision step 132 and, if not, returns instep 120. If an active edge is detected indecision step 132, routine 100 proceeds to turn switches Q1 and Q4 on at that time instep 134, before returning instep 120. Accordingly, the frequency control mode waits for an active edge before turning the switches Q1 and Q4 on. By selecting the appropriate frequency of the frequency control signal, changes in the charge and discharge voltage slew rate can be effected. It should also be appreciated that changes in the charge and discharge voltage slew rate may also be achieved by varying the recirculation current threshold IR and peak current threshold IP. - Returning to
decision step 104, thecontrol routine 100 proceeds to decision step 140 if theinjector 12 is requested to be on, and checks for whether the discharge voltage limit (threshold VDISCHARGE) has been met. If the discharge voltage limit VDISCHARGE has been met, indicative of theinjector 12 being open, routine 100 proceeds to turn off all switches Q1 to Q4 instep 142 before returning instep 120. - If the discharge voltage limit VDISCHARGE has not been met in step 140, the
control routine 100 checks indecision step 146 if the absolute value of the current sensed at the sensing resistor R1 is greater than the peak current threshold IP, as determined by the comparator U3. If the absolute value of the sensed current is greater than the peak current threshold IP, switches Q2 and Q3 are turned off instep 150 before returning to the beginning of the routine 100 instep 120. If the absolute value of the sensed current is not greater than the peak current threshold IP,decision step 148 checks whether switches Q2 and Q3 are already on and, if so, returns to the beginning instep 120. If switches Q2 and Q3 are not on, the routine 100 proceeds todecision step 154 to check if the absolute value of the sensed current is less than the recirculation current threshold IR, as determined by comparator U4 and, if not, returns to the beginning instep 120. - If the absolute value of the sensed current is less than the recirculation current threshold IR, the
control routine 100 proceeds todecision step 156 to determine if the frequency control mode is in effect. If the frequency control mode is in operation,decision step 162 checks if an active edge of the frequency control signal has been received and, if not, returns instep 120. If an active edge has been received, switches Q2 and Q3 are turned on instep 164 before returning instep 120. Absent the frequency control mode, the routine 100 turns switches Q2 and Q3 on instep 158 before returning instep 120. It should be appreciated that the frequency control mode allows for the charge and discharge voltage slew rate to be varied by varying the frequency of the frequency control signal. - By turning switches Q2 and Q3 on, current is caused to flow from the high voltage energy storage capacitor C1 through switch Q3, inductor L1,
injector 12, switch Q2, and sense resistor R1 to ground. This provides for a discharge current IDISCHARGE flowing through theinjector 12 and the inductor L1 in the bidirectionalcurrent path 26. The discharge current IDISCHARGE causes thefuel injector 12 to open to allow fuel to be injected into theengine 10. - In the discharge mode, the
drive circuit 20a is controlled to apply voltage to the negative terminal of thefuel injector 12 in a manner that limits the current flow through the injector by way of the current-limiting inductor L1. When the absolute value of the sensed current exceeds the peak current threshold IP, switches Q2 and Q3 are turned off until the absolute value of the sensed current drops below the recirculation current threshold IR. During this time period, current is allowed to flow back into the capacitor C1 during a recirculation mode to transfer energy in the inductor L1 and theinjector 12 to the capacitor C1. When the absolute value of the sensed current drops below the recirculation current threshold IR, switches Q2 and Q3 are turned on to allow discharge current to again flow to the negative terminal of theinjector 12. This cycling of the discharge current IDISCHARGE and the recirculation current is repeated until the discharge voltage limit VDISCHARGE is met, at which time theinjector 12 is fully open. Thefuel injector 12 remains fully open, until thedrive circuit 20a charges thefuel injector 12, when a request for closing the fuel injector is made. - Referring to
Figures 4a to 4c , the voltage VC1 across the capacitor C1, the current IL1 through the inductor L1, and the charge/discharge voltage VINJ across theinjector 12 are illustrated during both discharge and charge modes to open and close thepiezoelectric fuel injector 12, according to one example. - The voltage VC1 across the capacitor C1, shown by
line 40 inFigure 4a , is shown increasing viawaveform 42 havingspikes 46 during the discharge mode, and decreasing viawaveform 44 havingspikes 48 during the charge mode. - The inductor current IL1, shown by
line 50 inFigure 4b , is shown ramping down to approximately minus twenty amps (-20 A) during current buildup, and decaying back to about zero amps during the recirculation mode as shown byspikes 56 ofwaveform 52 during the discharge mode. During the charge mode, current IL1 increases from about zero amps to approximately twenty amps (+20 A) during current buildup, and then ramps back down to approximately zero amps during the recirculation mode, as shown byspikes 58 ofwaveform 54. Thespikes Figure 4c . - The injector voltage VINJ shown by
line 60 inFigure 4c , shows the voltage of theinjector 12 decreasing inwaveform 62 during a discharge mode, and increasing inwaveform 64 during a charge mode. The voltage slew rate (i.e. slope) ofwaveform fuel injector 12 will be opened and closed. However, it should be appreciated that the rate of opening and closing thefuel injector 12 may be varied to enhance engine operation over a wide range of engine speed/load points. - Accordingly, the
drive circuit 20a of the present invention advantageously controls the operation of apiezoelectric fuel injector 12 by controlling the current through thefuel injector 12 via a current-limiting inductor L1 in series with theinjector 12. Thedrive circuit 20a recirculates energy stored in theinjector 12 back into the energy storage capacitor C1 so as to provide for an enhanced circuit arrangement. In addition, thedrive circuit 20a allows for adjustment of the voltage slew rate for charging and discharging theinjector 12 which allows for enhanced operation over a wide range of engine operating characteristics (e.g., engine speed, load, etc.). Further, the charge voltage threshold VCHARGE and discharge voltage threshold VDISCHARGE can also be varied to optimize engine operation. - Referring to
Figures 5 and6a , apiezoelectric drive circuit 20b is shown according to a second embodiment of the present invention. Thepiezoelectric drive circuit 20b employs a half H-bridge configuration, in contrast to the full H-bridge configuration of thedrive circuit 20a described above in the first embodiment. Thedrive circuit 20b is shown as part of theengine control module 14 and receives control signals 18 from microprocessor andmemory 16. With particular reference toFigure 5 , thedrive circuit 20b controls the opening and closing of twopiezoelectric fuel injectors engine 10. - While two
piezoelectric fuel injectors drive circuit 20b according to the second embodiment, it should be appreciated that theengine 10 may include one or morepiezoelectric fuel injectors 12a,...,12n, all of which could be controlled by thedrive circuit 20b. - The second embodiment of the
piezoelectric drive circuit 20b is illustrated in detail in the block/circuit diagram ofFigure 6a . Thedrive circuit 20b in the second embodiment generally is configured as a half H-bridge having amiddle circuit branch 26 that serves as a bidirectional current path. Themiddle circuit branch 26 includes an inductor L11 coupled in series with a parallel connection ofpiezoelectric fuel injectors drive circuit 20b includes avoltage input 22 for receiving a voltage VS (e.g., 12 volts) from a voltage source (e.g., vehicle battery). The voltage VS is increased to a higher step-up voltage VC11 (e.g., 200 volts) via a step-up transformer (DC-to-DC converter) 24. The step-up voltage VC11 is applied to a first energy storage capacitor C11 via a diode D15. The step-up voltage VC11 applied to the first capacitor C11 may provide a high voltage such as 200 volts, according to one example. The step-uptransformer 24 also provides a voltage VC12 to a second energy storage capacitor C12 of about 100 volts, according to one example. The step-uptransformer 24 has a return line coupled to a diode D16. - The
drive circuit 20b includes switches Q11 and Q12 for controlling respective charge and discharge operations of theinjectors - Connected in series with each of the
piezoelectric fuel injectors piezoelectric fuel injectors injector 12a includes a unidirectional switch Q13 having a gate coupled to a gate drive 34a which is powered at a bias supply input 32a by 125 volts, according to one example. The unidirectional switch Q13 may include an N-channel insulated gate bi-polar transistor (IGBT) which, when turned on, allows current flow only in the discharge direction. A diode D13 is connected in parallel with switch Q13 to allow current flow in the charge direction. - The switching circuitry associated with the
piezoelectric fuel injector 12b likewise includes a unidirectional switch Q14 having a gate coupled to a gate driver 34b and a bias supply input 32b for receiving 125 volts, according to one example. The unidirectional switch Q14 likewise may include an N-channel insulated gate bi-polar transistor (IGBT) which, when turned on, allows current flow only in the discharge direction. A diode D14 is coupled in parallel with switch Q14 to allow current flow in the charge direction. - The sense resistor R11 is connected within the bidirectional
current path 26. Coupled to both terminals of the sense resistor R11 is acurrent monitor 36 for monitoring the current flow through the sense resistor R11 and, thus, the current flow through the bidirectionalcurrent path 26. The output of thecurrent monitor 36 is supplied to a comparator U11 which compares the sensed current with current thresholds IP and IR and generates output signals. - The microprocessor and
memory 16 provides the current thresholds including the peak current threshold IP and the recirculation current threshold IR. In addition, the microprocessor andmemory 16 also provides a charge voltage threshold VCHARGE and a discharge voltage threshold VDISCHARGE. The microprocessor andmemory 16 further provides a charge/discharge signal C/D, and an injector selector for selecting one of the injectors during the discharge operation. While various thresholds are shown provided by the microprocessor andmemory 16, it should be appreciated that such signals may alternately be provided with discrete circuitry. - The
drive control circuit 20b includescontrol logic 30 for receiving the output of the comparator U11, a sensed voltage from the positive terminal (+) of theinjectors memory 16. Thecontrol logic 30 may include software executed by the microprocessor andmemory 16. Thecontrol logic 30 processes the various inputs as described herein and generates control signals to control each of the switches Q11 to Q14. - The
drive circuit 20b of the second embodiment operates in a discharge mode to open a select one of thefuel injectors fuel injectors injectors injector injectors - During the recirculation mode, current flows from the negative side of the 200 volt power supply across the first capacitor C11, through the current sense resistor R11, through the selected one of switches Q13 and Q14, through the selected
injector load piezoelectric injectors injector bridge drive circuit 20b is deactivated until a charge cycle is initiated, or until it is determined that additional discharge pulses are required to maintain the desired injector voltage. - In order to charge (close) the
injectors injectors injectors injectors - During the recirculation mode, current flows from the negative side of the 100 volt power supply across the second capacitor C12, through diode D12, through the inductor L11 and the
injectors piezoelectric injectors injectors bridge drive circuit 20b is deactivated until a discharge cycle is initiated, or until it is determined that additional charge pulses are required to maintain the desired injector voltage. - Although the operation of the
circuit 20b in the charge and discharge modes has been explained with reference to the activation of the charge and discharge switches Q11 and Q12, in practice charge and discharge of theinjectors microprocessor 16 by pulsing the charge enable/discharge enable signal C/D (mode 2). Alternatively, the enabling of the charge switch Q11 or discharge switch Q21 can be carried out under the direct control of themicroprocessor 16, and the deactivation of the charge switch or discharge switch can occur when the current flowing in thebidirectional path 26 falls below a reduced recirculation current threshold IR (mode 3). - The aforedescribed modes are illustrated in
Figure 6b , where plot (a) firstly illustrates the current IINJ1 flowing in thefirst injector 12a during a discharge mode (although the plot is equally applicable to the charge mode of operation). It can be seen that the current in thebidirectional path 26 is oscillating between the peak current threshold IP and the recirculation current threshold IR. Plot (b) illustrates the C/D signal (as inFigure 2 ) changing from low (disable) to high (enable) to enable the discharge switch Q12 during the discharge mode. Plot (c) shows the discharge switch Q21 switching on as the current reaches IP, and switching off when the current falls to below IR. Mode 2 is illustrated in plots (d) and (e) where the C/D signal (shown in plot (d)) is pulsed to enable and disable the discharge switch Q21 (shown in plot (e)). - The opening and closing characteristics of the
piezoelectric injectors injector Figure 6b shows the deactivation of the discharge switch Q12 occurring when either IP and or IR has been reduced. - Additionally, a microprocessor analog-to-digital (A/D) channel can be used to monitor the voltage at the
injectors current monitor 36 and comparator U11, it should be appreciated that the microprocessor andmemory 16 could monitor the injector current, as well as injector voltage, directly. - Referring to
Figures 7a and7b , acontrol routine 200 for performing control logic is illustrated for controlling operation of thepiezoelectric fuel injectors drive circuit 20b according to the second embodiment of the present invention. Thecontrol routine 200 begins atstep 202 and checks indecision step 204 if there is a request by theengine control module 14 to turn on one of the fuel injectors. If there is a request to turn on one of the injectors, the routine 200 proceeds todecision step 240 to operate thedrive circuit 20b in the discharge mode. If not, the routine 200 checks if there is a request by theengine control module 14 to turn off thefuel injectors decision step 206 and, if not, returns to the beginning instep 202. If there is a request to turn thefuel injectors decision step 208 to operate thedrive circuit 20b in the charge mode. - In the charge mode, the routine 200 in
decision step 208 checks if the charge voltage limit (threshold VCHARGE) across each of thefuel injectors injectors injectors step 210 before returning to the beginning of the routine 200 instep 220. If the charge voltage limit has not yet been met, the routine 200 proceeds todecision step 214 to check if the absolute value of the current sensed across the sense resistor R11 is greater than the current threshold IP, as determined by comparator U11. - If the absolute value of the sensed current is greater than the peak current threshold IP, switch Q11 is turned off in
step 216 before returning to the beginning of the routine 200 instep 220. Once the absolute value of the sensed current exceeds the peak current threshold IP, switch Q11 is turned off and the current flowing through the inductor L11 causes energy in the inductor and theinjectors injectors injectors - If the absolute value of the sensed current does not exceed the peak current threshold IP, the routine 200 proceeds to
decision step 222 to check if switch Q11 is already on and, if so, returns to the beginning of the routine 200 instep 220. If switch Q11 is determined not to be already turned on instep 222, routine 200 determines, indecision step 224, if the absolute value of the current sensed across the sense resistor R11 is less than the recirculation current threshold IR as determined by the comparator U11 and, if not, returns to the beginning instep 220. If the absolute value of the sensed current is less than the recirculation current threshold IR, thecontrol routine 200 proceeds to turn switch Q11 on instep 234, before returning instep 220. - By turning switch Q11 on, current is caused to flow from the first energy storage capacitor C11 through switch Q11, inductor L11,
injectors D 14, sense resistor R11 and returning to the negative terminal of the first capacitor C11. This provides for a charge current ICHARGE flowing through theinjectors current path 26. The charge current ICHARGE causes the fuel injector previously discharged to charge (close) and the remaining fuel injector(s) to remain charged (closed). - In the charge mode, the
drive circuit 20b is controlled to apply voltage to the positive terminal of thefuel injectors injectors injectors injectors injectors fuel injectors drive circuit 20b discharges a selected one of thefuel injectors fuel injectors - Returning to
decision step 204, thecontrol routine 200 proceeds todecision step 240 during the discharge mode when one of theinjectors Q 14 instep 242 before returning instep 220. - If the discharge voltage threshold VDISCHARGE has not been met in
step 240, thecontrol routine 200 checks indecision step 244 if thefirst fuel injector 12a is in an active state to be turned on and, if so, switch Q13 is turned on instep 256. If it is determined that thefirst injector 12a is not in an active state, it is assumed that thesecond injector 12b is in the active state and, thus, the routine 200 turns on switch Q14 instep 252. With one of the switches Q13 and Q14 turned on, the routine 200 proceeds todecision step 246 to check if the absolute value of the current sensed at the resistor R11 is greater than the peak current threshold IP, as determined by the comparator U11. If the absolute value of the sensed current is greater than the peak current threshold IP, switch Q12 is turned off instep 250 before returning to the beginning of the routine 200 instep 220. Once the absolute value of the sensed current exceeds the peak current threshold IP, switch Q12 is turned off and the current flowing through the inductor L11 causes energy in inductor L11 and the selected one ofinjectors injectors injectors - If the absolute value of the sensed current is not greater than the peak current threshold IP,
decision step 248 checks whether switch Q12 is already on and, if so, returns to the beginning instep 220. If switch Q12 is not on, the routine 200 proceeds todecision step 254 to check if the absolute value of the sensed current is less than the recirculation current threshold IR, as determined by comparator U11 and, if not, returns to the beginning instep 220. If the absolute value of the sensed current is less than the recirculation current threshold IR, thecontrol routine 200 proceeds to turn switch Q12 on instep 264 before returning instep 220. - By turning switch Q12 on, current is caused to flow from the second energy storage capacitor C12 through sense resistor R11, the selected one of the transistors Q13 and Q14 and
corresponding injectors injector current path 26. The discharge current IDISCHARGE causes the selected one of thefuel injectors engine 10. - In the discharge mode, the
drive circuit 20b is controlled to apply voltage to the negative terminal of the selected one offuel injectors injectors injectors injectors injectors fuel injectors drive circuit 20b charges thefuel injectors fuel injectors - Referring to
Figures 8a to 8d , the voltage VC11 and VC12 across the first and second capacitors C11 and C12, the current IL11 through the inductor L11, and the charge/discharge voltage VINJ1 across theinjector 12a are illustrated during both discharge and charge modes to open and close thepiezoelectric fuel injector 12a, according to one example. - The voltage VC11 across the first capacitor C11, shown by line 40a in
Figure 8a , is shown increasing viawaveform 42a having spikes 46a during the discharge mode, and decreasing via waveform 44a having spikes 48a during the charge mode. - The voltage VC12 across the second capacitor C12 shown by
line 40b inFigure 8b , is shown decreasing viawaveform 42b having spikes 46b during the discharge mode, and increasing via waveform44b having spikes 48b during the charge mode. - The inductor current IL11, shown by
line 50a inFigure 8c , is shown ramping down to approximately minus twenty amps (-20 A) during current buildup and decaying back to about minus ten amps (-10 A) during the recirculation mode as shown by spikes 56a ofwaveform 52a during the discharge mode. During the charge mode, current IL11 increases from about zero amps to approximately twenty amps (+20 A) during current buildup and ramps back down to approximately ten amps (+10 A) during the recirculation mode, as shown byspikes 58a ofwaveform 54a. Thespikes 56a and 58a of current IL11 occur for as long as the voltage VC12 or VC11 is applied to discharge or charge the injector voltage VINJ1 as shown inFigure 8d . - The injector voltage VINJ1, shown by
line 60a inFigure 8d , shows the voltage VINJ1 of theinjector 12a decreasing inwaveform 62a during a discharge mode, and increasing in waveform 64a during a charge mode. The voltage slew rate (slope) ofwaveform 62a or 64a can be adjusted by varying the peak and/or recirculation current thresholds IP and IR. The higher the voltage slew rate, generally the faster thefuel injector fuel injector - Accordingly, the half H-
bridge drive circuit 20b according to the second embodiment of the present invention advantageously controls operation of one or a plurality of piezoelectric fuel injectors (e.g., 12a and 12b) by controlling current through thefuel injectors current path 26. Thedrive circuit 20b recirculates energy stored in theinjectors drive circuit 20b incorporates selector switching circuitry to advantageously control multiple injectors in a single drive circuit by employing a single bridge structure including a single charge/discharge inductor L11 and switches Q11 and Q12. The topology of the half H-bridge drive circuit 20b may reduce input power draw and lessen the silicon content required for the circuitry, however, the half H-bridge drive circuit 20b may require the use of multiple high voltage supplies. It should be appreciated that thedrive circuit 20b may be further adjusted by adjusting voltage slew rate, the charge voltage threshold VCHARGE, and the discharge voltage threshold VDISCHARGE, to optimize engine operation. - Referring to
Figure 9 , apiezoelectric drive circuit 20c is shown according to a third embodiment of the present invention. As for the previous embodiments, thedrive circuit 20c is part of theengine control module 14 and receives control signals 18 from microprocessor andmemory 16. Thedrive circuit 20c controls the opening and closing ofpiezoelectric fuel injectors engine 10. - The
piezoelectric drive circuit 20c generally is configured as a half H-bridge having amiddle circuit branch 26 that serves as a bidirectional current path, as illustrated inFigure 9 . Thedrive circuit 20c includes avoltage input 22 for receiving a voltage Vs (e.g., 12 volts) from a voltage source (e.g., vehicle battery). The voltage Vs is increased to a higher step-up voltage VC21 (e.g., 230 Volts) via a step-up transformer (DC-to-DC converter) 24. The step-up voltage is applied to a first energy storage capacitor C21 via a diode D25. The step-up voltage VC21 applied to the first capacitor C21 may provide a high voltage such as 200 Volts. The step-uptransformer 24 also provides a voltage VC22 of about 100 Volts to a second energy storage capacitor C22. The step-uptransformer 24 also has a return line coupled to a diode D26. - The
drive circuit 20c further includes first and second switches Q21 and Q22 positioned at opposite comers of the half H-bridge configuration, for controlling the charge and discharge operations respectively of theinjectors - A charge
current path 4 is provided in thedrive circuit 20c between the bi-directionalcurrent path 26 and the high voltage rail V1. Situated in the chargecurrent path 4 is a first transformer T1 in series with a first inductor L21 and the first (charge) switch Q21. A dischargecurrent path 6 is provided in thecircuit 20c between the bi-directionalcurrent path 26 and ground. Situated in the dischargecurrent path 6 is a second transformer T2 in series with a second inductor L22 and the second switch Q22. Coupled to the first T1 and second T2 transformers is a current monitor (not shown) for monitoring current flowing through the inductors in the chargecurrent path 4 and the dischargecurrent path 6. The output of the current monitor is supplied to a comparator means (not shown) which compares the sensed current with the current thresholds IP and IR and generates output signals. - The
drive circuit 20c further includes first D21 and second D22 recirculation diodes. The first recirculation diode D21 is connected across the second switch Q22, the second inductor L22, the first and second transformers T1 and T2, and the first inductor L21. The second recirculation diode D22 is connected across the second inductor L22, the first and second transformers T1 and T2, the first inductor L21 and the first switch Q21. The recirculation diodes D21 and D22 allow a recirculation current to return to the first C21 and second C22 energy storage capacitors during an energy recovery or recirculation mode of operation of thecircuit 20c. - Each of the
injectors first injector 12a, for example, is activated (i.e. switched on), current flow IDISCHARGE is permitted in a discharge direction through the selected injector. A diode D23 is connected in parallel with the selector switch Q23 to allow current ICHARGE to flow in the charge direction during the charging mode of operation of the circuit. Similarly, a diode D24 is connected in parallel with the selector switch Q24 for thesecond injector 12b. - Predetermined values for IP and IR are stored in the
microprocessor 16, along with a charge voltage threshold VCHARGE, and a discharge voltage threshold VDISCHARGE. If required, and preferably so, the current thresholds IP and IR, the voltage thresholds, VCHARGE and VDISCHARGE, may be adjustable. - A voltage sensing means (not shown) may also be provided to sense the voltage, VSENSE, across the
injector microprocessor 16 further provides a charge/discharge signal C/D and an injector selector for selecting one of theinjectors - The
drive circuit 20c also includescontrol logic 30 for receiving: 1) the output of transformers T1 and T2; 2) the sensed voltage, VSENSE, from the positive terminal (+) of theinjectors microprocessor 16. Thecontrol logic 30 may include software executed by themicroprocessor 16 for processing the various inputs so as to generate control signals for each of the charge and discharge switches Q21, Q22, and the selector switches Q23 and Q24. - During operation of the
drive circuit 20c, a drive pulse (or voltage waveform) is applied to the piezoelectric actuator of thefuel injectors injector 12a is in a non-injecting state, prior to injection, the drive pulse is at VCHARGE so that a relatively high voltage is applied to the piezoelectric actuator. Typically, VCHARGE is around 200 to 300 V. When it is required to initiate an injection event, the drive pulse is reduced to VDlSCHARGE, which is typically around -100 V. To terminate injection, the voltage of the drive pulse is increased to its charging voltage level, VCHARGE, once again. - During the discharge mode, the discharge switch Q22 is activated (i.e. closed) and one of the selector switches Q23 and Q24 is then activated to select one of
injectors first injector 12a, the selector switch Q23 is closed. The other selector switch Q24 for thesecond injector 12b remains deactivated as thesecond injector 12b is not required to inject. - Assuming that it is desired to inject using the
first injector 12a, upon activation of the discharge switch Q22, current is allowed to flow from the 100 V power supply across the capacitor C22, through the selector switch Q23, and into the corresponding negative side of the selectedinjector 12a. A discharge current IDISCHARGE flows from the injector load forinjector 12a, through the second transformer T2, through the second inductor L22, through the closed discharge switch Q22, and back to the negative terminal of the second capacitor C22. As the selector switch Q24 remains open, and due to the presence of the diode D24, substantially no current is able to flow through thesecond injector 12b into the negative side of theinjector 12b. - The second transformer T2 senses the current flow through the discharge
current path 6 as it builds up in thedrive circuit 20c and, as soon as the peak current threshold IP is reached, thecontrol logic 30 generates an output signal to initiate de-activation (i.e. opening) of the discharge switch Q22. At this point, the current that has built-up in the second inductor L22 recirculates through the recirculation diode D22. As a consequence, the direction of current flow along the bidirectionalcurrent path 26 and the selected one of theinjectors drive circuit 20c. - During the recirculation mode, current flows from the negative side of the 200 volt power supply across the first capacitor C21, through the selected switch Q23, through the selected
injector 12a, through the second transformer T2, through the second inductor L22, through the recirculation diode D22, and finally into the positive side of the first capacitor C21. During this recirculation mode, energy from the second inductor L22 and the selected one of thepiezoelectric injectors - The current sense circuitry monitors the recirculation current, and when the recirculation current has fallen below the recirculation current threshold IR (which is zero amps for this circuit) a signal is generated to reactivate the discharge switch Q22, thereby continuing the discharge operation. The voltage VINJ1 or VINJ2 across the selected
injector - In this discharge cycle, the second capacitor C22 provides energy, while the first capacitor C21 receives energy for storage. Once the appropriate discharge voltage threshold VDISCHARGE is achieved, the half H-
bridge drive circuit 20c is deactivated until a charge cycle is initiated, or until it is determined that additional discharge pulses are required to maintain the desired injector voltage. The provision of additional discharge pulses will be described in detail later. - In order to charge (i.e. close) the
first injector 12a, the charge switch Q21 is activated, thus allowing a charge current ICHARGE to flow from the 200 V power supply across the first capacitor C21, through the charge switch Q21, through the first inductor L21, through the first transformer T1, through theinjector 12a (and optionally throughinjector 12b depending on the voltage drop across this injector), and back to the energy storage capacitor C21. This is the charging mode of operation of thedrive circuit 20c. During the charging mode, the majority of the charge current ICHARGE will flow through the previously discharged injector (i.e. thefirst injector 12a). Thesecond injector 12b that was not previously discharged will receive current if the corresponding voltage VINJ2 across it has dropped below the charge voltage threshold VCHARGE. - The first transformer T1 senses the current flow through the charge
current path 4 as it builds up in thedrive circuit 20c and, as soon as the peak current threshold IP is reached, thecontrol logic 30 generates a control signal to open the charge switch Q21. At this point, the current that is built up in the first inductor L21 recirculates through the recirculation diode D21. This is the recirculation mode of the charging mode of operation of thedrive circuit 20c. Thus, the direction of current flow through the first inductor L21 andinjectors - During the recirculation mode, current flows from the negative side of the 100 volt power supply across the second capacitor C22, through the first recirculation diode D21, through the first inductor L21 and the first transformer T1, through the
injectors piezoelectric injectors injector 12a is monitored, and the cycle of current buildup and recirculation continues until the appropriate charge voltage level (threshold VCHARGE) has been achieved. In this charging mode, the first capacitor C21 provides energy, and the second capacitor C22 receives energy for storage. Once the appropriate charge voltage threshold VCHARGE is achieved, the half H-bridge drive circuit 20c is deactivated until a discharge cycle is initiated. - Optional further diodes D27 and D28 may be provided in the
drive circuit 20c, as indicated by the dashed lines inFigure 9 . Optional diode D27 may be situated between the bi-directionalcurrent path 26 and the positive terminal of the first energy storage capacitor C21. Optional diode D28 may be situated between the negative terminal of the second energy storage capacitor C22 and the bi-directionalcurrent path 26. - Diode D27 provides a 'voltage clamping effect' for a selected
injector injector 12a that is injecting is opened at the end of the discharge mode approximately simultaneously with the discharge switch Q22 being deactivated i.e. opened). The provision of the diode D28 is important as it provides a recirculation path for residual energy in the second inductor L22 at the end of the discharge mode to recirculate to the first energy storage capacitor C21. However, if the switch Q23 for the selectedinjector 12a is not deactivated (i.e. opened) at the end of the discharge mode (i.e. it is kept closed), then diode D28 will generally not be required. - Referring now to
Figures 10a and 10b , the energy EC21 and EC22 stored on the first C21 and second C22 capacitors, respectively, is shown during discharge and charge modes. - The energy EC21 stored on the first capacitor C21 (given by
line 70a inFigure 10a ) is shown increasing viawaveform 72a having spikes 76a during the discharge mode, and decreasing viawaveform 74a having spikes 78a during the charge mode. - The energy EC22 stored on the second capacitor C22 (given by
line 70b inFigure 10b ) is shown decreasing viawaveform 72b having spikes 76b during the discharge mode, and increasing viawaveform 74b having spikes 78b during the charge mode. -
Figure 10c shows the charge/discharge voltage VINJ1 across thefirst injector 12a during the charge and discharge modes. The injector voltage VINJ1 (shown byline 80 inFigure 10c ) shows the voltage across thefirst injector 12a decreasing inwaveform 82 during the discharge mode, and increasing inwaveform 84 during the charge mode.Figure 10c also shows the current, IINJ1, through thefirst injector 12a. -
Figures 10d and 10e respectively illustrate the current IL21 and IL22 through the first L21 and second L22 inductors. - Referring now to
Figure 10d , the first inductor current IL21 is given byline 80a. During the charge mode, IL21 decreases from about zero amps to approximately minus twenty five amps (-25 A) during current buildup, and ramps back up to approximately zero amps during the recirculation mode, as shown byspike 84a of thewaveform 80a. Thespikes 84a of current IL21 occur for as long as the voltage VC1 or VC2 is applied to discharge or charge thefirst injector 12a, as shown inFigure 10c . - With reference to
Figure 10e , the second inductor current IL22 (given byline 80b) is shown increasing to approximately twenty five amps (+25 A) and decaying back to about zero amps during the recirculation mode of the discharge mode, as shown by spikes 82b of thewaveform 80b. - In summary, when it is required to inject with a selected injector (e.g. the
first injector 12a), the discharge switch Q22 and the selector switch Q23 of the first injector are both closed. During the discharge and recirculation modes that follow, the discharge switch Q22 is automatically opened and closed until the voltage across the selectedinjector 12a is reduced to the appropriate voltage discharge level (i.e. VDISCHARGE, as shown inFigure 10c ) to initiate injection. After a predetermined time for which injection is required, closing of theinjector 12a is achieved by closing the charge switch Q21, causing a charging current to flow through the first 12a andsecond injectors 12b. During the subsequent charging and recirculation modes, the charge switch Q21 is continually opened and closed until the appropriate charge voltage level is achieved (i.e. VCHARGE, as shown inFigure 10c ). - The
control routine 200 described previously (and illustrated inFigures 7a and7b ) for controlling operation of thedrive circuit 20b of the second embodiment of the present invention may also be used to control the operation of thedrive circuit 20c of the third embodiment of the present invention. Furthermore, the charge Q21 and discharge switches Q22 may be operated in a number of different ways to charge/discharge the injectors (seeFigure 6b ), as described previously. - The
drive circuits microprocessor 16 control, or may be implemented in hardware. Referring now toFigure 11 , plot (a) illustrates schematically the charge/discharge voltage VINJ1 across thefirst injector 12a during the charge and discharge modes. Plot (a) shows the voltage decreasing during the discharge mode P1, increasing slightly during the injection event, and increasing further during the charge mode P3, as described previously. However, in practice, when VDlSCHARGE has been reached and an injection event is underway, the voltage across the piezoelectric actuator becomes more positive than is required (known as positive ringing) thereby reducing efficiency and accuracy of control of fuel injection. It can also be seen from plot (a) that when VCHARGE is reached, the voltage VINJ1 becomes more negative than is required (known as negative ringing), again reducing efficiency and accuracy of control. - In order to overcome the disadvantageous effects of positive ringing at the end of the discharge mode P1, the
microprocessor 16 can be programmed to maintain the discharge switch Q22 in an enabled state for a period of time, t1, after the discharge voltage VDISCHARGE has been reached (as shown in plot (c)). During this time period t1, the second transformer T2 monitors the current buildup in the dischargecurrent path 6 and, as soon as the peak current threshold IP is reached, the discharge switch Q22 is switched off. The current that has built up in the second inductor L2 then recirculates in the manner previously described, and subsequently falls. When the current flowing in the circuit during the recirculation mode falls below the recirculation current threshold IR, switch Q22 is reactivated to continue the discharge operation. Thus additional discharge pulses are produced during a damping mode P2 in which the voltage VINJ1 across the injector is damped so as to reduce positive ringing in thecircuit 20c. The damped voltage VINJ1 is illustrated by the dashedline 160 in plot (a) ofFigure 11 . - As illustrated in plot (c), the discharge switch Q22 is enabled continuously during the discharge mode P1 and the time period t1. However, in an alternative mode of operation, the discharge switch Q22 can be disabled for a short period after VDISCHARGE has been reached, and then enabled for the time period t1 (as shown in plot (b)).
- Depending on the voltage drop across the
injector 12a, the current flowing in thecircuit 20c may never reach the peak current threshold IP. In this case, another alternative approach may be adopted in which the discharge switch Q22 is alternately enabled and disabled under the direct control of themicroprocessor 16 via the charge/discharge signal C/D. Thus, the discharge switch Q22 is deactivated for a short period after VDISCHARGE has been reached, and then alternately reactivated and deactivated during the time period t1 (as shown in plot (d)). In another modification of the method of the present invention, the period of activation of the discharge switch Q22 (and therefore the degree of damping) may be varied by reducing the peak current threshold IP to IREDUCED such that the discharge switch Q22 is deactivated when IREDUCED is reached, rather than being directly controlled by themicroprocessor 16. - The
microprocessor 16 can also be programmed so as to maintain the injector selector switch Q23 closed for a short period after the discharge voltage VDISCHARGE has been reached, as illustrated in plot (i). The injector selector switch Q23 is then switched on again for the time period t1, prior to the subsequent charging mode P3. - To overcome the disadvantageous effects of negative ringing at the end of the charge mode P3, the
microprocessor 16 can be programmed to enable the charge switch Q21 for a period of time t2 at the end of the charge mode (as shown in plot (g) ofFigure 11 ). During this time period, t2, the first transformer T1 monitors the current buildup in thecircuit 20c and, as soon as the peak current threshold Ip is reached, the charge switch Q21 is switched off. The current that has built up in the first inductor L21 recirculates, and the current in thecircuit 20c falls. When the current recirculating in the circuit falls below the recirculation current threshold IR, the charge switch Q21 is reactivated. Thus, additional charge pulses are produced during a damping mode P4 in which the voltage VINJ1 is damped so as to reduce negative ringing in the drive circuit. The damped voltage VINJ1 is illustrated by the dashedline 162 in plot (a). - As illustrated in plot (g) of
Figure 11 , the charge switch Q21 is enabled continuously during the charge mode P3 and the time period t2. However, in an alternative mode of operation, the charge switch Q21 can be disabled briefly after VCHARGE has been reached, and then enabled for the time period t2 (as shown in plot (f)). - Depending on the voltage drop across the
injector 12a, the current in the circuit may never reach the peak current threshold IP. In this case, another alternative approach may be adopted in which the charge switch Q21 is alternately enabled and disabled under the direct control of themicroprocessor 16 via the charge/discharge signal C/D. Thus the charge switch Q21 is deactivated briefly after VCHARGE has been reached, and then alternately reactivated and deactivated during the time period t2 (as shown in plot (h) ofFigure 11 ). In another modification, the period of activation of the charge switch Q21 may be varied by reducing the peak current threshold IP to IREDUCED such that the charge switch Q21 is deactivated when IREDUCED is reached, rather than under the direct control of the charge/discharge signal C/D from themicroprocessor 16. - The
microprocessor 16 can also be programmed to maintain the injector selector switch Q23 of the previously selectedinjector 12a closed for a short period after the charge voltage VCHARGE has been reached, as illustrated in plot (i). - The
microprocessor 16 may use pre-calibrated data to determined the appropriate time periods t1 and t2 for which the injector select switch Q23 and the charge Q21 and discharge Q22 switches are enabled and disabled. Alternatively, the time periods t1 and t2 could be varied after each injection event to enable more accurate control of the injectors. - Having described particular preferred embodiments of the present invention, it is to be appreciated that the embodiments in question are exemplary only and that variations and modifications such as will occur to those possessed of the appropriate knowledge and skill may be made without departure from the scope of the invention as set forth in the appended claims.
- For example, the
piezoelectric injectors drive circuits injectors - While two
piezoelectric fuel injectors engine 10 may include one or more piezoelectric fuel injectors, all of which could be controlled by thedrive circuits piezoelectric fuel injector 12 is shown and described in connection with thedrive circuit 20a of the first embodiment, multiple fuel injectors could be controlled using this drive circuit. - The
drive circuits engine control module 14, or may be provided separate therefrom.
Claims (21)
- A drive circuit (20a,20b,20c) for at least one injector (12;12a,12b) having capacitive-like properties, said drive circuit comprising:a voltage input (22) for receiving a voltage signal;at least one energy storage device (C1,C2;C11,C12;C21,C22) coupled to the voltage input for storing an electrical charge;a bidirectional current path (26) coupled to the at least one injector (12,12a,12b), and current sensing means for sensing the current flowing through the bidirectional current path (26);at least one inductor (L1;L11;L21,L22) coupled to the at least one injector (12;12a,12b); andswitching means for controlling current flow through the at least one injector (12;12a,12b) and the at least one inductor (L1;L11;L21,L22) to open and close the at least one injector(s), wherein the switching means is controllable to cause a charging current (ICHARGE) to flow through the bidirectional current path (26) during a charge mode so as to charge the at least one injector (12; 12a, 12b), and to cause a discharge current (IDISCHARGE) to flow through the bidirectional current path (26) during a discharge mode so as to discharge the injector(s) (12; 12a, 12b); andcontrol means (14) configured to control the switching means such that current flow through the bidirectional current path (26) increases during a current buildup phase to a first predetermined current threshold (IP) and decreases during a current recirculation phase to a second predetermined current threshold, thereby providing a recirculation current to recover energy stored in the at least one injector (12;12a,12b) for storage in the at least one energy storage device (C1,C2;C11,C12;C21,C22), and wherein the control means (14) is configured to monitor the current sensing means and, in response thereto, to control the average current flowing through the at least one injector (12; 12a, 12b) by changing the first predetermined current threshold (IP) and/or the second predetermined current threshold (IR)
- The drive circuit (20a) as claimed in claim 1, wherein the drive circuit is substantially configured as an H-bridge circuit.
- The drive circuit (20a,20b) as claimed in any preceding claim, wherein a first inductor (L1;L11) is coupled in series with the at least one injector (12;12a,12b) in the bidirectional current path (26).
- The drive circuit (20a) as claimed in any preceding claim, wherein the at least one energy storage device comprises a capacitor (C1).
- The drive circuit (20a) as claimed in any preceding claim, wherein the switching means comprises first (Q1) and second switches (Q4) which are controllable to charge the at least one injector (12), and third (Q2) and fourth (Q3) switches which are controllable to discharge the at least one injector (12) selected for injection.
- The drive circuit (20b,20c) as claimed in claim 1, wherein the drive circuit is substantially configured as a half H-bridge circuit comprising a charge current path (4) for receiving the charging current (ICHARGE), and a discharge current path (6) for receiving the discharge current (IDISCHARGE).
- The drive circuit (20b) as claimed in claim 6, wherein a first inductor (L11) is disposed in the bidirectional current path (26).
- The drive circuit (20c) as claimed in claim 6, wherein a first inductor (L21) is disposed in the charge current path (4), and a second inductor (L22) is disposed in the discharge current path (6).
- The drive circuit (20b,20c) as claimed in any of claims 6 to 8, wherein the switching means comprises a first switch (Q11;Q21) that is controllable to charge the at least one injector (12a,12b), and a second switch (Q12;Q22) that is controllable to discharge the at least one injector (12a,12b).
- The drive circuit (20b,20c) as claimed in any of claims 6 to 9, wherein the drive circuit is arranged to control at least first (12a) and second (12b) injectors, said drive circuit further comprising selector means (Q13,Q14;Q23,Q24) for selecting one of said first (12a) and second (12b) injectors.
- The drive circuit (20b,20c) as claimed in claim 10, wherein the at least first (12a) and second (12b) injectors are coupled in parallel.
- The drive circuit (20b,20c) as claimed in claim 10 or claim 11, wherein the drive circuit is arranged to charge all of said injectors (12a,12b) during the charge mode, and to discharge a selected one of the injectors (12a,12b) during the discharge mode.
- The drive circuit (20b,20c) as claimed in any of claims 6 to 12, wherein the at least one energy storage device comprises first (C11,C21) and second (C12,C22) capacitors, wherein the first capacitor (C11,C21) stores energy for use in the charge mode, and the second capacitor (C12,C22) stores energy for use in the discharge mode.
- The drive circuit (20b,20c) as claimed in any of claims 10 to 13, further comprising a first further diode (D27) connected in parallel with the charge current path (4) for limiting the voltage across the selected injector (12a,12b).
- The drive circuit (20c) as claimed in any of claims 8 to 14, further comprising a second further diode (D28) connected in parallel with the discharge current path (6) so as to provide another path for current at the end of the discharge mode.
- The drive circuit (20c) as claimed in any of claims 6 to 15, wherein the current sensing means comprises a first transformer (T1) in series with the first inductor (L21) for sensing the current flowing in the charge current path (4), and a second transformer (T2) in series with the second inductor (L22) for sensing the current flowing in the discharge current path (6).
- The drive circuit (20a,20b,20c) as claimed in any preceding claim, further comprising voltage sensing means for sensing the voltage across the selected injector (12;12a,12b), and wherein the control means (14) is arranged to receive a signal indicative of the sensed voltage from the voltage sensing means.
- The drive circuit (20a,20b,20c) as claimed in claim 17, wherein the control means (14) is arranged to provide a terminate control signal to the switch means (Q1;Q11;Q21) to terminate the charge mode once a threshold charge voltage (VCHARGE) is sensed.
- The drive circuit (20a,20b,20c) as claimed in claim 17 or claim 18, wherein the control means (14) is arranged to provide an initiate control signal to the switch means (Q1;Q11;Q21) to initiate the charge mode of the selected injector (12;12a,12b).
- The drive circuit (20a,20b,20c) as claimed in any of claims 17 to 19, wherein the control means (14) is arranged to provide an initiate control signal to the switch means (Q2;Q12;Q22) to initiate the discharge mode of the selected injector (12;12a,12b).
- The drive circuit (20a,20b,20c) as claimed in any of claims 17 to 20, wherein the control means (14) is arranged to provide a terminate control signal to the switch means (Q2;Q12;Q22) to terminate the discharge mode once a threshold discharge voltage (VDISCHARGE) is sensed.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP09175047A EP2149695A3 (en) | 2002-09-23 | 2003-09-23 | Injector drive circuit |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US25223702A | 2002-09-23 | 2002-09-23 | |
US252237 | 2002-09-23 | ||
US10/403,713 US6760212B2 (en) | 2002-09-23 | 2003-03-31 | Piezoelectric injector drive circuit |
US403713 | 2003-03-31 |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP09175047A Division EP2149695A3 (en) | 2002-09-23 | 2003-09-23 | Injector drive circuit |
Publications (3)
Publication Number | Publication Date |
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EP1400676A2 EP1400676A2 (en) | 2004-03-24 |
EP1400676A3 EP1400676A3 (en) | 2006-03-22 |
EP1400676B1 true EP1400676B1 (en) | 2009-12-16 |
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ID=31949805
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
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EP20030255969 Expired - Lifetime EP1400677B1 (en) | 2002-09-23 | 2003-09-23 | Injector system |
EP20030255966 Expired - Lifetime EP1400676B1 (en) | 2002-09-23 | 2003-09-23 | Injector system |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
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EP20030255969 Expired - Lifetime EP1400677B1 (en) | 2002-09-23 | 2003-09-23 | Injector system |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9048775B2 (en) | 2012-10-30 | 2015-06-02 | National Instruments Corporation | H-bridge for combined solenoid and piezo injection control |
US9611797B2 (en) | 2012-10-30 | 2017-04-04 | National Instruments Corporation | Direct injection flexible multiplexing scheme |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1574696A3 (en) | 2004-03-10 | 2006-01-04 | Delphi Technologies, Inc. | Power supply arrangement for a fuel injector drive circuit |
EP1843027B1 (en) | 2006-04-03 | 2018-12-19 | Delphi International Operations Luxembourg S.Ã r.l. | Drive circuit for an injector arrangement and diagnostic method |
DE102006018957A1 (en) * | 2006-04-24 | 2007-10-25 | Robert Bosch Gmbh | Method for operating an injection system |
GB0610233D0 (en) * | 2006-05-23 | 2006-07-05 | Delphi Tech Inc | A method of operating a fuel injector |
GB0610226D0 (en) | 2006-05-23 | 2006-07-05 | Delphi Tech Inc | Drive circuit for an injector arrangement and a diagnostic method |
EP1927742A1 (en) * | 2006-11-23 | 2008-06-04 | Delphi Technologies, Inc. | A method of operating a piezoelectric device |
ATE450705T1 (en) | 2007-02-02 | 2009-12-15 | Delphi Tech Inc | METHOD FOR OPERATING A PIEZOELECTRIC ACTUATOR |
DE102007014331A1 (en) * | 2007-03-26 | 2008-10-02 | Robert Bosch Gmbh | Drive circuit and driving method for a piezoelectric element |
EP2006518B1 (en) | 2007-06-22 | 2011-11-02 | Delphi Technologies Holding S.Ã .r.l. | Detection of faults in an injector arrangement |
DE102009025478A1 (en) * | 2009-06-18 | 2011-01-05 | Austriamicrosystems Ag | Circuit arrangement for switching capacitor in e.g. switching power supply, has switching element controlling switch device, such that switch device cancels short-circuit of capacitor when preset charge state of capacitor is reached |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19632837A1 (en) * | 1996-08-14 | 1998-02-19 | Siemens Ag | Device and method for controlling at least one capacitive actuator |
DE19652809C1 (en) * | 1996-12-18 | 1998-06-10 | Siemens Ag | Method and device for controlling at least one capacitive actuator |
DE19854789A1 (en) * | 1998-02-10 | 1999-08-12 | Bosch Gmbh Robert | Method and device for loading and unloading a piezoelectric element |
DE19944734B4 (en) * | 1999-09-17 | 2007-02-15 | Siemens Ag | Method and device for charging at least one capacitive actuator |
DE10120143A1 (en) * | 2001-04-25 | 2002-10-31 | Conti Temic Microelectronic | Capacitive setting element control method for fuel injection valve of IC engine, involves charging and discharging of capacitive setting element via inductive element and charging or discharging switch |
JP2003111448A (en) * | 2001-09-28 | 2003-04-11 | Denso Corp | Piezoelectric actuator drive circuit |
-
2003
- 2003-09-23 EP EP20030255969 patent/EP1400677B1/en not_active Expired - Lifetime
- 2003-09-23 EP EP20030255966 patent/EP1400676B1/en not_active Expired - Lifetime
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9048775B2 (en) | 2012-10-30 | 2015-06-02 | National Instruments Corporation | H-bridge for combined solenoid and piezo injection control |
US9611797B2 (en) | 2012-10-30 | 2017-04-04 | National Instruments Corporation | Direct injection flexible multiplexing scheme |
Also Published As
Publication number | Publication date |
---|---|
EP1400677A3 (en) | 2006-03-22 |
EP1400677B1 (en) | 2009-11-18 |
EP1400676A3 (en) | 2006-03-22 |
EP1400676A2 (en) | 2004-03-24 |
EP1400677A2 (en) | 2004-03-24 |
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