Common-Rail Fuel Injection Pressure Control via Post-Injection

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Solution Overview

Problem

The existing common-rail fuel injection systems in diesel engines face challenges in effectively controlling operating pressure, leading to increased emissions, noise, and potential component damage due to slower pressure response and the high cost of pressure-relief valves, especially when faults occur in the pressure regulating means on the low-pressure side.

Innovation Solution

The system employs injectors as pressure-limiter valves by actuating non-effective post-injections to manage rail pressure anomalies, eliminating the need for a pressure-relief valve on the high-pressure side, using an electronic control unit to trigger retarded injections and discharge fuel back to the tank when pressure exceeds set thresholds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a pressure-relief valve is installed on the high-pressure side to control rail pressure, then pressure control reliability is improved, but system cost increases significantly

Engineering Contradiction:

Improvepressure control reliabilityVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The injection valve is made to perform dual functions: its primary function of injecting fuel into the combustion chamber, and a secondary function of acting as a pressure-relief valve when activated in reverse mode. The control unit enables the valve to switch between normal injection mode and pressure relief mode, allowing one component to serve multiple purposes in the system.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The injection valve utilizes its own internal structure and mechanism to perform pressure relief function without requiring a separate dedicated pressure-relief valve. The valve's needle and seat arrangement, originally designed for fuel injection, is leveraged to also function as a pressure relief pathway when actuated in the reverse direction, making the system self-sufficient.

Inventive Principle:

Principle #25Self-service

2Strength

If a pressure-relief valve is installed on the high-pressure side to prevent overpressure, then component safety is improved, but manufacturing cost increases

Engineering Contradiction:

Improvecomponent safetyVSAvoidmanufacturing cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The function of a separate pressure-relief valve is extracted and integrated into the existing injection valve structure. Instead of adding a new component, the invention repurposes the injection valve's existing mechanical structure to provide pressure relief capability, thereby eliminating the need for an additional safety component.

Inventive Principle:

Principle #2Taking out (Extraction)

3Device complexity

If the metering unit controls fuel pressure on the low-pressure side, then system cost is reduced, but pressure response speed deteriorates

Engineering Contradiction:

Improvesystem costVSAvoidpressure response speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The system maintains a continuously operating high-pressure pump that constantly supplies pressurized fuel to the rail, even when the engine does not require maximum pressure. This preliminary pressurization ensures that when pressure regulation is needed, the system can respond quickly by simply controlling the injection valve timing and duration, rather than having to build pressure from scratch.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control unit continuously monitors engine operating conditions and adjusts the injection valve actuation timing and duration accordingly. By using feedback from engine sensors, the system can anticipate pressure needs and adjust injection parameters in real-time, maintaining optimal pressure response without requiring a mechanically complex pressure control system.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7891342B2Method and system for controlling operating pressure in a common-rail fuel injection system, particularly for a diesel engine

Publication Date: 2011.02.22 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

In a fuel injection system of an internal combustion engine that includes, but is not limited to injectors (I1-I4), each of which is adapted to deliver a predetermined amount of pressurized fuel to a combustion chamber of a respective cylinder (C1-C4) of the engine, a high-pressure accumulator volume common to the injectors (I1-I4) and arranged to maintain the fuel at high-pressure, a pressure sensor for measuring fuel pressure in the accumulator volume, a metering unit for adjusting the fuel pressure in the accumulator volume as a function of the measured pressure, so as to maintain a predetermined target injection pressure set-point dependent on the engine operating point by returning excess fuel to a fuel tank; and an electronic control unit arranged for controlling fuel injection timing and quantity by operating injectors control valves, the operating pressure is controlled by triggering retarded injections (INJpost) of a predetermined quantity of fuel to the combustion chamber of the cylinders (C1-C4) of the engine during a respective exhaust stroke, when pressure above a predetermined threshold (THover) is detected in the accumulator volume, so as to discharge fuel from the accumulator volume without it taking part to the combustion process, thereby reducing pressure in the accumulator volume.