Piezo Actuator Stroke Control for Fuel Injection Hardware
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Solution Overview
Problem
Existing fuel injection systems face challenges in efficiently managing needle stroke and fuel flow across varying temperatures, leading to high hardware costs due to the need for consistent actuation voltage and maximum needle stroke, especially at low temperatures, which limits the ability to achieve maximum rail pressure and increases hardware demands.
Innovation Solution
The method adjusts the actuation of the piezo actuator based on injector temperature, reducing the needle stroke at low temperatures to lower the actuation voltage and increase duration, while maintaining maximum stroke at high temperatures for complete dethrottling and maximum fuel flow, thereby reducing electrical demands on the actuation hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the piezo actuator is actuated with maximum needle stroke at all times, then maximum fuel flow is achieved at high temperatures, but the actuation voltage and hardware requirements increase significantly at low temperatures
Solution Approach 1:
The patent applies dynamics by making the needle stroke variable rather than fixed. The control unit dynamically adjusts the needle stroke based on detected temperature conditions - using maximum stroke at high temperatures for maximum fuel flow, and reduced stroke at low temperatures to prevent excessive actuation voltage and hardware stress. This dynamic adaptation resolves the contradiction between maintaining maximum productivity and reducing device complexity requirements.
Solution Approach 2:
The patent changes the physical parameter of needle stroke based on temperature conditions. At high temperatures, the system uses maximum needle stroke to achieve maximum fuel flow. At low temperatures, the system reduces the needle stroke parameter to prevent excessive actuation voltage and hardware requirements. This parameter change strategy allows the system to optimize fuel flow when needed while reducing hardware demands during cold operation.
2Device complexity
If the needle stroke is reduced at low temperatures, then actuation voltage and hardware demands are lowered, but fuel flow is reduced
Solution Approach 1:
The system dynamically adjusts needle stroke based on temperature conditions, using reduced stroke at low temperatures to lower hardware demands while maintaining adequate fuel flow for cold-start operation. At high temperatures, it switches to maximum stroke to maximize fuel flow. This dynamic behavior allows the system to accept reduced productivity during cold operation in exchange for significantly reduced hardware demands.
Solution Approach 2:
The patent changes the needle stroke parameter based on temperature to resolve the contradiction. At low temperatures, reducing the stroke parameter lowers actuation voltage and hardware demands, which is acceptable during cold operation. At high temperatures, the parameter is increased to maximum to achieve maximum fuel flow. This parameter adaptation allows the system to prioritize hardware protection during cold operation.
3Reliability
If maximum needle stroke is maintained across all temperatures, then complete dethrottling is achieved at high temperatures, but the piezo actuator experiences excessive electrical stress at low temperatures
Solution Approach 1:
The patent applies dynamics by making the needle stroke variable based on temperature conditions. The control unit detects temperature and dynamically adjusts the stroke accordingly - using maximum stroke at high temperatures to ensure complete dethrottling and reliability, while reducing stroke at low temperatures to prevent excessive actuation voltage and electrical stress on the piezo actuator.
Solution Approach 2:
The patent changes the needle stroke parameter based on temperature to protect the piezo actuator from excessive electrical stress. At high temperatures, the parameter is set to maximum to ensure complete dethrottling and system reliability. At low temperatures, the parameter is reduced to lower actuation voltage and prevent electrical stress, accepting that dethrottling may not be complete during cold operation.
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 allows for the use of lower-cost actuation hardware by optimizing fuel flow and reducing hardware requirements, with minimal impact on the combustion process, especially at low temperatures, and ensuring maximum fuel flow at normal operating temperatures.
Implementation Method 1
The drive of the injector comprises, for moving the closure element, an actuator which is designed to, in a manner dependent on a control signal, lift the closure element out of the closed position to a stroke height, hold said closure element at said stroke height, and/or move the closure element back into the closed position. For example, said actuator may be provided by a piezo element, which expands or contracts owing to electrical charging or discharging processes and thereby initiates a stroke or closing movement of the closure element.
Data Source
AI summary
The invention relates to a method and a device for actuating an injection valve, which has a piezo actuator and a nozzle needle, of a fuel injection system of an internal combustion engine, in which method a control unit, in a manner dependent on a setpoint stroke height of the piezo actuator in successive injection cycles, outputs a control signal for changing the actual stroke height of the piezo actuator, characterized in that the control unit changes the setpoint stroke height of the piezo actuator, for compensation of the temperature dependency of the capacitance of the piezo actuator, in a manner dependent on the temperature of said piezo actuator.