Fuel-Pressure Controller for Direct Injection Engine Vapor Prevention
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Solution Overview
Problem
In direct injection engines, the low-pressure pump's discharge rate is excessive when fuel consumption is low, leading to battery voltage wastage and decreased fuel economy, while reducing its rate can cause vapor generation in the low-pressure fuel passage, affecting high-pressure pump efficiency and potentially causing malfunctions.
Innovation Solution
A fuel-pressure controller that includes a low-pressure fuel control mechanism, a high-fuel-pressure sensor, a learning mechanism to correct control errors, and a correction mechanism to adjust the low-pressure fuel control based on differences between detected and target pressures, ensuring the fuel pressure in the low-pressure passage matches the target pressure without generating vapor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the discharge rate of the low-pressure pump is reduced to improve fuel economy, then battery voltage wastage is reduced and fuel economy is improved, but the fuel pressure in the low-pressure fuel passage decreases causing vapor generation that deteriorates high-pressure pump discharge efficiency
Solution Approach 1:
The system uses a fuel pressure sensor to detect the fuel pressure in the low-pressure fuel passage and feeds this information back to the ECU. The ECU then adjusts the low-pressure pump's discharge rate based on the detected pressure to maintain it within a specified range, preventing vapor generation while optimizing fuel economy.
Solution Approach 2:
The low-pressure pump's discharge rate is made dynamic rather than constant. The ECU varies the discharge rate according to actual fuel pressure conditions and fuel consumption requirements, allowing the system to adapt to changing operating conditions and prevent vapor generation while minimizing energy waste.
2Reliability
If a fuel pressure sensor is provided in the low-pressure fuel passage to enable feedback control of the low-pressure pump, then the fuel pressure can be accurately controlled to prevent vapor generation, but the product cost increases
Solution Approach 1:
The system makes the existing high-pressure fuel passage's fuel pressure sensor serve a dual function: it continues to detect high-pressure fuel for injection control and additionally detects low-pressure fuel pressure when the high-pressure pump is stopped. This eliminates the need for a separate low-pressure fuel pressure sensor, reducing product cost while maintaining control accuracy.
Solution Approach 2:
The existing fuel pressure sensing capability of the system is utilized to serve the additional function of monitoring low-pressure fuel passage pressure. The system uses its own existing sensor and control mechanisms to achieve low-pressure control without requiring external additional components.
3Ease of operation
If the low-pressure pump is driven under constant condition to simplify control, then the control system is simple, but the discharge rate is excessive when fuel consumption is low causing energy waste
Solution Approach 1:
The control system transitions from constant-speed control to variable-speed control. The ECU dynamically adjusts the low-pressure pump's discharge rate based on detected fuel pressure and fuel consumption conditions, enabling the system to adapt to varying operational requirements and eliminate energy waste during low fuel consumption periods.
Solution Approach 2:
The system implements feedback control where the ECU continuously monitors fuel pressure via the sensor and adjusts the low-pressure pump's discharge rate accordingly. This closed-loop control maintains fuel pressure within the specified range while optimizing energy consumption based on actual fuel injection requirements.
Data Source
AI summary
When a specified learning execute condition is established, the high-pressure pump is stopped so that the fuel pressure in the high pressure fuel passage is made equal to the fuel pressure in the low pressure fuel passage. A low pressure fuel control is executed to control a driving voltage of the low-pressure pump based on the operational characteristic of the low-pressure pump. A driving voltage of the low-pressure pump is gradually corrected so that the difference between the detected high fuel pressure and a target low fuel pressure becomes small. A driving voltage correcting amount is learned as the control error of the low pressure fuel control. The driving voltage correction amount is stored as the learning correction amount, and the driving voltage of the low-pressure pump is corrected by means of the learning correction amount.