Piston Pump Varying Pairing Clearances Heat Expansion
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Solution Overview
Problem
Piston seizure or plunger seizure occurs in fuel pumps due to the reduction of pairing clearance caused by differential heat expansion between the pump cylinder and piston, leading to fuel leakage and pump failure.
Innovation Solution
A piston pump design with varying pairing clearances between the pump cylinder and piston, with a larger clearance over the leakage groove to accommodate heat expansion differences, reducing the risk of piston seizure while maintaining low fuel leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a very small pairing clearance is used between the pump cylinder and pump piston, then fuel leakage is reduced, but the risk of piston seizure increases due to differential heat expansion
Solution Approach 1:
The patent applies local quality by creating different pairing clearances in different portions of the pump piston. The first portion (over the leakage groove) has a larger pairing clearance to accommodate heat expansion and prevent seizure, while the second portion (away from the leakage groove) has a smaller pairing clearance to minimize fuel leakage. This localized differentiation resolves the contradiction by addressing each region's specific requirements.
2Ease of manufacture
If a uniform pairing clearance is used throughout the pump piston, then manufacturing is simpler, but piston seizure occurs in the leakage groove region due to heat expansion differences
Solution Approach 1:
The patent divides the pump piston into different portions with different pairing clearances. The first portion over the leakage groove has a larger clearance to prevent seizure, while the second portion has a smaller clearance for optimal performance. This local differentiation resolves the contradiction by prioritizing reliability in the critical leakage groove region while maintaining manufacturing feasibility through structured variation.
3Productivity
If the pairing clearance is reduced to minimize fuel leakage, then pump efficiency improves, but the differential heat expansion causes the clearance to reduce further leading to seizure
Solution Approach 1:
The patent implements local quality by providing different pairing clearances in different portions of the pump piston. In the first portion over the leakage groove, a larger pairing clearance is provided to compensate for differential heat expansion and prevent seizure. In the second portion away from the leakage groove, a smaller pairing clearance is provided to minimize fuel leakage and maximize pump efficiency. This localized approach resolves the contradiction by addressing the specific needs of each region.
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
The design effectively reduces the risk of piston seizure and maintains low fuel leakage by adjusting the clearance to account for heat expansion, enhancing the operational safety and efficiency of the fuel pump.
Implementation Method 1
In particular when in FIG. 1 the pump piston 12 is moved upwards in the recess 13, a compression of the fuel takes place
Implementation Method 2
the leakage groove 14 is coupled to a leakage line 15, via which ultimately a fuel leakage is dischargeable into a leakage tank, in which a low pressure, in particular ambient pressure, is present
Implementation Method 3
the risk of a so-called piston seizure or plunger seizure is primarily caused in that the pump cylinder, in the region of the leakage groove, is subject to a lower heat expansion than the pump piston
Data Source
AI summary
A piston pump as a high-pressure fuel pump of a common rail system includes: a pump cylinder; a pump piston moveably mounted in a recess of the pump cylinder, the pump piston being moveable up and down in the recess; and a leakage groove arranged in the pump cylinder in a region of the recess, the leakage groove being coupled with a leakage line configured to discharge a fuel leakage. Between the pump cylinder and the pump piston a different size pairing clearance is formed in first and second portions of the pump cylinder.