Capacitive Actuator Charging Circuit with Time-Controlled Shutdown
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Solution Overview
Problem
The existing method for charging capacitive actuators in fuel injection valves results in uneven charging profiles due to decreasing current gradients, leading to reduced actuator voltages and inefficient fuel injection, as the charging current fails to reach the prescribed threshold values consistently, causing inconsistent movement in the jet needle.
Innovation Solution
Implementing a time-controlled shutdown of the charging current based on the maximum current reached, where the first power transistor is turned off after a period corresponding to the maximum current value, ensuring consistent charge application with each pulse, or using a fixed period or a period-dependent on the maximum value and threshold, to maintain efficient charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the charging current is allowed to decrease naturally without time-controlled shutdown, then the circuit operation is simple, but the charging profile becomes uneven and actuator voltage becomes inconsistent
Solution Approach 1:
The patent applies periodic pulsed actuation of the power transistor to charge the capacitive actuator. The control circuit periodically switches the power transistor on and off, creating controlled charging pulses rather than continuous charging. This periodic action ensures consistent charge application with each pulse while maintaining simple circuit operation, resolving the contradiction between charging consistency and control complexity.
2Speed
If the first power transistor is turned off when the current reaches the first threshold value, then the charging speed is high, but the charging current fails to reach threshold values consistently leading to uneven charging profiles
Solution Approach 1:
The patent employs feedback control where the control circuit continuously monitors the actuator current and compares it against reference values. Based on this feedback, the control circuit adjusts the switching timing of the power transistor to ensure the charging current reaches the first threshold value consistently. This feedback mechanism maintains high charging speed while ensuring charging profile consistency by preventing premature or delayed shutdown.
3Manufacturing precision
If the charging period is extended to allow current to reach threshold values, then the charging profile becomes more consistent, but the charging efficiency decreases and actuator response time increases
Solution Approach 1:
The patent uses dynamic control of the charging period based on real-time current measurements. The control circuit adjusts the charging duration dynamically - extending it when needed to ensure threshold values are reached, but cutting it short when the threshold is achieved early. This dynamic adjustment maintains charging profile consistency while optimizing charging efficiency and preventing unnecessary extension of charging time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures approximately equal charge application with each charging pulse, maintaining consistent actuator voltage and movement, thereby improving the precision and efficiency of fuel injection.
Implementation Method 1
Owing to the inductance of the coil LMAIN, the current rise is admittedly restricted, but the initially still low voltage UP1 on the capacitive actuator P1 means that the rise will nevertheless still be relatively steep.
Implementation Method 2
The magnetic field stored in the coil LMAIN is then reduced again, since a current flows via the diode D2 connected in parallel with the second power transistor T2
Data Source
AI summary
A method for operating a circuit for charging and discharging a capacitive actuator. The circuit has a series circuit of first and second power transistors with respective parallel-connected diodes connected between the potentials of a supply voltage source. The node between the power transistors is connected via a coil to the capacitive actuator. For charging the actuator, the first power transistor, which connects the capacitive actuator to the positive potential, is periodically turned on during a prescribed time and turned off when a first prescribed threshold value is reached by the current through the actuator, until a lower threshold value is reached by the current. If the actuator current no longer reaches the first prescribed threshold value then the first power transistor is turned off after a time that corresponds to the maximum value reached by the actuator current.