Fuel Pump Driving Device Layout and Timing
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Solution Overview
Problem
The existing internal combustion engine fuel pump performance is limited by the fixed arrangement of the fuel-pump-driving cam with the camshaft, leading to insufficient discharge pressure due to dependence on camshaft rotation speed, which cannot meet required performance standards.
Innovation Solution
A fuel-pump-driving device with a shaft and cam unit that allows for greater freedom in layout and sprocket configuration, including an oval-shaped cam profile and oil passage for lubrication, enabling independent operation of the fuel pump and reducing phase delay between crankshaft rotation and fuel pump operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the fuel-pump-driving cam is fixed to the camshaft together with the valve-driving cams, then the engine structure is simplified, but the fuel pump discharge pressure becomes insufficient due to dependence on camshaft rotation speed
Solution Approach 1:
The patent separates the fuel pump driving mechanism from the camshaft by introducing an independent driving shaft. The fuel-pump-driving cam is mounted on this separate shaft rather than being fixed to the camshaft, allowing the fuel pump to be driven independently from the valve train. This segmentation resolves the contradiction by enabling sufficient discharge pressure through independent optimization while maintaining overall structural simplicity.
Solution Approach 2:
The patent introduces a timing chain as an intermediary mechanism to transmit rotational force from the crankshaft to the fuel pump driving shaft. This intermediary allows the fuel pump to be driven directly from the crankshaft at the required speed, independent of camshaft rotation, thereby achieving sufficient discharge pressure while keeping the engine structure relatively simple.
2Area of stationary object
If the fuel-pump-driving cam is fixed to the camshaft, then the space arrangement is simplified, but the fuel pump cannot satisfy the required performance
Solution Approach 1:
By separating the fuel pump driving shaft from the camshaft, the patent allows independent spatial optimization of each component. The fuel pump driving shaft can be positioned and sized to optimize pump performance without being constrained by camshaft space requirements, while the camshaft can be optimized for valve train space arrangement.
Solution Approach 2:
The patent resolves the space arrangement issue by transitioning from a two-dimensional constraint (camshaft surface) to a three-dimensional solution (separate driving shaft with its own mounting space). This allows the fuel pump driving mechanism to occupy a different spatial dimension, enabling both adequate space arrangement and required pump performance.
3Device complexity
If the lifter is driven by the pump-driving cam fixed to the camshaft, then the mechanism is simplified, but phase delay occurs between crankshaft rotation and fuel pump operation
Solution Approach 1:
The patent introduces a timing chain as an intermediary that directly connects the crankshaft to the fuel pump driving shaft. This direct connection through the timing chain eliminates the phase delay that would occur with indirect camshaft-driven operation, ensuring proper timing synchronization while maintaining mechanism simplicity.
Solution Approach 2:
The timing chain provides continuous, direct transmission of rotational motion from the crankshaft to the fuel pump driving shaft without the intermittent action and phase delays associated with camshaft lobes. This ensures continuous and properly timed fuel pump operation synchronized with crankshaft rotation.
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 configuration enhances fuel pump performance by allowing greater flexibility in discharge flow rate and reducing phase delay, ensuring stable lubrication and improved operational efficiency.
Implementation Method 1
A timing chain is wrapped around a crank sprocket and a valve-driving sprocket
Implementation Method 2
A cam unit 23 is fitted onto the outer circumference of the shaft 21 via a bearing 22 so as to be free to rotate
Implementation Method 3
A cam unit 23 is fitted onto the outer circumference of the shaft 21 via a bearing 22 so as to be free to rotate
Implementation Method 4
an oil passage for supplying lubricating oil
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A fuel-pump-driving device (20) drives a plunger (31) of a fuel pump (30) to perform a reciprocating motion to supply fuel to an internal combustion engine. The fuel-pump-driving device (20) comprises a cam (27) that drives the plunger (31) according to the rotation of a fuel-pump-driving sprocket (26). The fuel-pump-driving sprocket (26) meshes with a chain (7A) which travels between a crank sprocket (3) and a valve-driving sprocket (5A) of the engine. Since the fuel-pump-driving sprocket (26) can be located in a position detached from the valve-driving sprocket (5A), the fuel-pump-driving device (20) has greater freedom of layout and the fuel pump (30) exhibits a better performance than in a case where the plunger (31) is driven by a cam that is fixed directly to the cam shaft (5) of the the valve-driving sprocket (5A).