Common Rail Pressure Control Gradient Threshold
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Solution Overview
Problem
Existing methods for controlling rail pressure in common rail systems during partial load reductions in internal combustion engines experience pressure oscillations due to frequent changes from closed-loop to open-loop control, leading to unstable rail pressure and potential unintended valve openings.
Innovation Solution
The method computes a limiting value for temporary PWM assignment based on the gradient of a power-determining signal, such as set speed or torque, to differentiate between complete and partial load rejections, preventing unnecessary transitions and maintaining stable rail pressure without additional sensors or hardware changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control operation is changed from closed-loop control to open-loop control after a load reduction is detected, then the rail pressure can be controlled more effectively during complete load rejection, but pressure oscillations occur during partial load reduction due to frequent transitions
Solution Approach 1:
The patent changes the threshold parameter dynamically based on the gradient of the power-determining signal. Instead of using a fixed pressure threshold for switching between control modes, the threshold is adjusted according to how rapidly the load is changing. This allows the system to tolerate higher pressure excursions during rapid complete load rejection while maintaining strict pressure control during slower partial load reductions, thereby preventing oscillations while maintaining reliability.
Solution Approach 2:
The patent introduces dynamic adaptation of the control threshold based on the rate of change of the power-determining signal. The threshold is not static but evolves with the operating conditions, specifically with the gradient of the power-determining signal. This dynamic approach allows the control system to adapt its behavior to the severity and speed of load changes, switching between closed-loop and open-loop control modes more intelligently to avoid unnecessary transitions during partial load reductions.
2Device complexity
If a fixed limiting value is used for temporary PWM assignment activation, then the control logic is simple, but it causes unintended valve openings and pressure oscillations during partial load reduction
Solution Approach 1:
The patent transforms the fixed limiting value into a dynamic parameter that changes based on the gradient of the power-determining signal. The limiting value is no longer a constant but varies according to the rate of change of the power-determining signal. This dynamic parameter adjustment prevents the premature activation of temporary PWM assignment during partial load reductions, eliminating unintended valve openings and pressure oscillations while maintaining appropriate response during complete load rejection.
3Speed
If the PWM signal is temporarily set to a higher value during open-loop control, then the suction throttle closes faster and less fuel is delivered to the rail, but frequent transitions cause pressure oscillations during partial load reduction
Solution Approach 1:
The patent introduces a gradient-based threshold that changes the activation condition for temporary PWM assignment. By considering the rate of change of the power-determining signal, the system determines whether a load reduction is severe enough to warrant aggressive throttle closing. During partial load reductions with low gradients, the threshold is not exceeded, preventing unnecessary PWM increases and subsequent pressure oscillations, while still enabling fast throttle response during complete load rejection.
Data Source
AI summary
The invention relates to a control and regulation method for an internal combustion engine (1) having a common rail system wherein the rail pressure (pCR) is regulated in normal operation in that an offset of the rail pressure (pCR) is calculated and a PWM signal (PWM) is determined for activating the control process via a pressure controller based on the offset, wherein a load rejection when the rail pressure (pCR) exceeds a limit and wherein upon recognition of the load rejection, the rail pressure (pCR) is controlled in that the PWM signal (PWM) is temporarily set to a PWM value that is higher compared to normal operation via a PWM parameter. The invention is characterized in that the threshold for activation of the temporary PWM parameter is calculated in dependence on the gradient of a power-determining signal.