Fluid Injector Coil Energy Dissipation via External Voltage Suppressor
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Solution Overview
Problem
Existing fluid injectors, particularly selective catalytic reduction (SCR) dosing injectors, face compatibility issues with various engine control units (ECUs) due to energy dissipation challenges during coil discharge, leading to reliability concerns and potential ECU overheating.
Innovation Solution
Incorporating a voltage suppressor, such as a transient-voltage-suppression diode with a PN junction, directly connected to the coil and cooled by the same liquid-cooling system, to quickly and reliably discharge stored energy when the drive signal is turned off, thereby alleviating energy dissipation stress on ECUs and enhancing compatibility with a broader range of control units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the coil energy is discharged through internal ECU components (such as low-side FET switch), then the ECU can control the injector operation, but the ECU components overheat and fail due to large energy dissipation
Solution Approach 1:
The energy dissipation function is extracted from the ECU and transferred to an external voltage suppressor diode. The diode is connected in parallel with the coil and provides a dedicated path for discharge current, removing the harmful thermal load from the ECU's internal switching components while preserving the ECU's control capability.
Solution Approach 2:
The voltage suppressor diode acts as an intermediary component between the coil and the ECU. It mediates the energy transfer by providing a controlled discharge path that protects the ECU from direct exposure to high energy dissipation, allowing the ECU to maintain control without suffering thermal damage.
2Reliability
If a voltage suppressor is added to discharge coil energy externally, then ECU reliability is improved and compatibility is increased, but the device complexity increases
Solution Approach 1:
A simple, inexpensive voltage suppressor diode is added to the circuit. This low-cost component provides reliable energy dissipation and protects the expensive ECU, offering high reliability improvement at minimal cost and complexity increase. The diode is a basic electronic component that is easy to integrate.
3Productivity
If the voltage suppressor operates at high frequencies typical of SCR dosing injectors, then the injector can meet performance requirements, but the voltage suppressor must withstand harsh engine bay environment and high frequency operation
Solution Approach 1:
The voltage suppressor diode is selected with specific electrical parameters (breakdown voltage, reverse recovery time, power rating) that are optimized for high-frequency operation. By carefully choosing components with appropriate parameters, the system achieves the required productivity while maintaining reliability in the harsh engine environment.
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 solution improves the reliability of fluid injectors by allowing them to operate with a wider range of ECUs, reducing the risk of ECU overheating and increasing engine reliability, while also providing a diagnostic circuit to detect faults in the voltage suppressor.
Implementation Method 1
The voltage suppressor preferably comprises a transient-voltage-suppression diode. According to the present invention a PN junction is used. The PN junction is arranged to breakdown and discharge energy stored within the coil when a drive voltage is removed from the coil.
Implementation Method 2
The coil is cooled and the voltage suppressor is arranged to be cooled by the same cooling means. The voltage suppressor is sealed within the same liquid-cooled jacket of the coil.
Data Source
Figure 1
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AI summary
A fluid injector comprising a coil (110) arranged to drive a pump (120) from a first state to a second state when energized, so as to pump a dosing fluid; a PN junction (130) electrically arranged across the coil to discharge energy stored in the coil (110) when the voltage across the coil is above a threshold. In one particular embodiment, the fluid injector is a selective catalytic reduction dosing fluid injector.