High-Pressure Pump Plunger Assembly with Thermal Expansion
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Solution Overview
Problem
Existing high-pressure pumps for internal combustion engines face challenges in preventing plunger separation from the cylinder during assembly, especially when the suction valve unit is positioned radially and the pressure chamber opposite to the plunger is closed, making it difficult to insert the plunger from the opposite opening.
Innovation Solution
A high-pressure pump design featuring a large-diameter portion at the end of the plunger with an outside diameter larger than the cylinder's inside diameter but smaller than the pressure chamber's inside diameter, which engages with a step portion between the cylinder and pressure chamber, combined with a temperature control process that adjusts the diameters to facilitate insertion and prevent separation, allowing the plunger to be inserted even when the pressure chamber is closed by the pump body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the suction valve unit is positioned radially and the pressure chamber is closed by the pump body, then the axial size of the pump is reduced, but the plunger cannot be inserted from the opening of the cylinder on the side opposite to the pressure chamber
Solution Approach 1:
The plunger is segmented into two parts: a small-diameter portion that fits inside the cylinder and a large-diameter portion that protrudes into the pressure chamber. This segmentation allows the plunger to be inserted from the side opposite the pressure chamber while the large-diameter portion engages with the step portion to prevent separation.
Solution Approach 2:
The solution moves the engagement interface from the axial dimension to the radial dimension by creating a step portion in the radial direction between the cylinder and pressure chamber. The large-diameter portion of the plunger engages with this radial step, allowing insertion from the opposite side while maintaining axial compactness.
2Reliability
If the large-diameter portion of the plunger has an outside diameter larger than the inside diameter of the cylinder, then separation of the plunger from the cylinder is prevented, but insertion of the plunger into the cylinder becomes difficult
Solution Approach 1:
The diameter parameter of the plunger is changed along its length, creating a large-diameter portion and a small-diameter portion. The large-diameter portion engages with the step portion to prevent separation, while the small-diameter portion allows easy insertion into the cylinder.
Solution Approach 2:
Different portions of the plunger have different diameters tailored to their specific functions: the large-diameter portion provides engagement and prevention of separation, while the small-diameter portion facilitates insertion. This local differentiation of quality resolves the contradiction between secure engagement and ease of assembly.
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 prevents plunger separation and reduces the axial size of the cylinder, improving assembly efficiency and reducing the number of parts by forming the cylinder and pump body integrally, while allowing for easier insertion of the plunger into the pressure chamber, even when it is closed by the pump body.
Implementation Method 1
at least either 'heating the cylinder' or 'cooling the large-diameter portion' is performed to allow the inside diameter of the cylinder to become larger than the outside diameter of the large-diameter portion
Data Source
AI summary
A pump body of a high-pressure pump includes a pressure chamber formed in a deep portion of a cylinder. The pump body closes the pressure chamber on a side opposite to a plunger. The plunger reciprocates within the cylinder to vary a volume of the pressure chamber. The large-diameter portion provided at an end of the plunger on a side protruding to the pressure chamber has an outside diameter larger than an inside diameter of the cylinder and smaller than an inside diameter of the pressure chamber. In this case, the large-diameter portion is engaged with a step portion between the cylinder and the pressure chamber in a state before attachment of the high-pressure pump to an internal combustion engine. Accordingly, separation of the plunger from the cylinder is avoidable.