Variable Compression Ratio Engine Control for Chain Tension
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Solution Overview
Problem
In internal combustion engines with a common rail type fuel injection system, excessive fuel pressure variations due to abnormal states like malfunctioning spill valves cause significant tension variations in the chain drive, leading to reduced durability and potential engine shutdown, which is undesirable for continuous vehicle operation.
Innovation Solution
A control device with a variable compression ratio mechanism that senses abnormal fuel pressure states and decreases the mechanical compression ratio to mitigate chain tension variations, allowing continuous engine operation while protecting the chain from excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the high pressure fuel pump is mechanically driven through the chain by the crank shaft, then the fuel injection system can operate, but the chain tension becomes excessive when fuel pressure is extraordinarily increased
Solution Approach 1:
The invention changes the compression ratio parameter of the engine to control the chain tension. When abnormal fuel pressure is detected, the control device adjusts the compression ratio to a lower value, which reduces the tension variation and peak tension of the chain drive system, thereby protecting the chain from excessive stress while maintaining fuel injection operation.
2Duration of action of stationary object
If the compression ratio is decreased to reduce chain tension, then the chain durability is improved, but the thermal efficiency of the engine is reduced
Solution Approach 1:
The invention applies periodic or conditional action by only decreasing the compression ratio when abnormal fuel pressure conditions are detected. During normal operation, the compression ratio remains at its optimal value for thermal efficiency. When abnormal pressure is sensed, the compression ratio is temporarily adjusted to protect the chain, and can be restored when normal conditions return.
3Reliability
If the fuel injection is immediately stopped to protect the engine from abnormal fuel pressure, then the engine is protected, but the vehicle cannot continue to run
Solution Approach 1:
The invention converts the harmful effect of abnormal fuel pressure into a controllable parameter by using it as a signal to adjust the compression ratio. Instead of stopping fuel injection, the system uses the abnormal pressure condition to trigger a compression ratio adjustment that protects the chain while allowing the engine to continue operating, thus turning a potentially harmful situation into a manageable operational state.
Data Source
AI summary
An internal combustion engine (1) includes a variable compression ratio mechanism (2), and a common rail type fuel injection device using a high pressure fuel pump (46) which is mechanically driven. A fuel pressure P within the common rail (45) is read (step 1). When the fuel pressure P exceeds an upper limit fuel pressure Pmax (step 4), an abnormal increase of the fuel pressure P is judged. A target compression ratio by the variable compression ratio mechanism is set to a minimum compression ratio Emin (step 6). With this, a rotation variation of a crank shaft (21) becomes small. A tension variation of a chain (43) is relieved. A reduction of durability of the chain (43) is suppressed.