Fuel Injection Pump Tappet Rotation Restriction via Thrust Washer
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Solution Overview
Problem
Existing fuel injection pumps face issues with assembly errors and abrasion leading to deviated contact between the cam and roller, causing tappet rotation and increased processing costs due to noncircular surfaces, which complicates the restriction of tappet rotation.
Innovation Solution
A fuel injection pump design incorporating a tappet with a tubular shape and a thrust washer with a rotation restricting part that contacts the tappet to prevent rotation relative to its center axis, allowing for easy processing of circular surfaces and reducing costs by eliminating the need for additional members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If noncircular surfaces are used to restrict tappet rotation, then tappet rotation is restricted, but processing costs increase and manufacturing complexity increases
Solution Approach 1:
A thrust washer is introduced as an intermediary component between the cam and the tappet. The thrust washer includes a rotation restricting part that protrudes toward the tappet and contacts the contact surface to prevent tappet rotation. This mediator approach allows the use of simple circular surfaces for the tappet and cylinder, eliminating the need for complex noncircular surface processing while effectively restricting rotation.
2Stability of the object's composition
If noncircular surfaces are used to restrict tappet rotation, then tappet rotation is restricted, but device complexity increases
Solution Approach 1:
The thrust washer serves as a mediator component that simplifies the overall structure. Instead of making the tappet or cylinder complex with noncircular surfaces, the thrust washer with its rotation restricting part provides the rotation restriction function. This keeps the tappet and cylinder structures simple and circular, reducing manufacturing complexity.
Solution Approach 2:
The rotation restriction function is segmented from the tappet and cylinder structures and assigned to a separate thrust washer component. This segmentation allows each component to maintain simple circular geometries while the thrust washer specifically handles the rotation restriction through its protruding rotation restricting part.
3Stability of the object's composition
If additional members are added to restrict tappet rotation, then tappet rotation is restricted, but device complexity and cost increase
Solution Approach 1:
The thrust washer is designed to perform multiple functions: it provides thrust support between the cam and casing, and simultaneously restricts tappet rotation through its rotation restricting part. By making the thrust washer multi-functional, no additional dedicated rotation restriction component is needed, reducing the total number of parts while achieving rotation restriction.
Data Source
AI summary
A fuel injection pump includes a cam rotating with a camshaft, a tappet reciprocating in response to rotation of the cam, a cylinder, a plunger, and a thrust washer. The thrust washer is located between the cam and a casing housing the camshaft at both ends of the cam in an axial direction of the cam. The tappet includes a tappet body, a roller, a supporting member, and a contact surface formed at an outer peripheral part of the tappet. The thrust washer includes a rotation restricting part that protrudes toward the tappet over a maximum lift position. The rotation restricting part restricts rotation of the tappet relative to a center axis of the tappet body by being contact with the contact surface.