Starter Solenoid Bypass Layout for Cold-Start Reliability
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Solution Overview
Problem
Existing solenoid drives for internal combustion engine starters face challenges in reliability, especially in cold ambient conditions, and increased wear of the pinion and gearwheel due to high initial magnetic forces required for engagement, which can be insufficient to overcome resistance and lead to failure.
Innovation Solution
The bypass device is axially spaced from both face side walls of the coil receiving chamber, allowing magnetic flux to bypass the axial gap between the plunger and plunger stop, providing high initial forces that reduce to a minimum and then increase, optimizing magnetic attraction forces throughout the plunger movement to ensure reliable operation and reduce wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high magnetic forces are applied to the plunger to ensure reliable engagement in cold conditions, then the reliability of the starter is improved, but the wear of the pinion and gearwheel increases
Solution Approach 1:
The magnetic force is made dynamic rather than static by using a bypass device that automatically modulates its strength during plunger movement. The bypass device creates a time-varying magnetic circuit that provides high initial force when needed and reduces force during engagement, resolving the contradiction between reliability and wear prevention.
Solution Approach 2:
The bypass device acts as an intermediary magnetic path that controls the flow of magnetic flux between the coil, plunger, and plunger stop. By providing an alternative magnetic pathway, it mediates the magnetic force transmission to achieve both high initial force and reduced engagement force, solving the contradiction.
2Reliability
If high magnetic forces are used to overcome resistance in cold and moist environments, then the plunger can be reliably moved into engagement position, but the initial magnetic force causes excessive wear during engagement
Solution Approach 1:
The magnetic force is applied periodically with varying intensity during the plunger movement. The bypass device creates distinct phases: high force at the beginning to overcome static resistance, and reduced force during the engagement process, matching the periodic nature of the plunger's movement and resolving the wear contradiction.
Solution Approach 2:
The magnetic circuit parameters are changed during operation by the bypass device's geometric configuration. The magnetic permeability and flux path length vary as the plunger moves, automatically adjusting the magnetic force parameter to provide high initial force then reduce it, solving both reliability and wear requirements.
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 arrangement ensures sufficient force to initiate movement in all conditions, particularly cold and moist environments, while minimizing magnetic forces during the engagement process to prevent wear on the pinion and gearwheel.
Implementation Method 1
the coil arrangement has to transmit comparatively large electromagnetic forces to the plunger in order to draw the latter into the coil interior space
Implementation Method 2
the coil arrangement has to transmit comparatively large electromagnetic forces to the plunger
Implementation Method 3
allows magnetic flux to bypass the axial gap between the plunger and plunger stop
Implementation Method 4
the bypass device is arranged and dimensioned in such a manner that, when the plunger is adjusted into the active position, magnetic field lines are deflected by the bypass device
Data Source
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AI summary
The present invention relates to a solenoid drive (6) for a starter (1), comprising a ferromagnetic housing (19) which comprises a coil receiving chamber (64) axially limited by a first face side wall (65) and an opposing second face side wall (66), a cylindrical coil arrangement (22) which has at least one electric coil (40, 41) and which is arranged in the coil receiving chamber (64) and which coaxially surrounds a cylindrical coil interior space (25), a ferromagnetic plunger stop (20) which has a central region (43) projecting axially in the coil interior space (25), a ferromagnetic plunger (21) which is arranged at the housing (19) axially opposing the plunger stop (20), which projects axially into the coil interior space (25), and which is arranged so as to be adjustable axially bi-directionally relative to the housing (19) between an active position (AS) which is proximal with respect to the central region (43) and a passive position (PS) which is distal with respect to the central region (43), and a ferromagnetic bypass device (45) which is arranged coaxially with respect to the coil arrangement (22) and radially within the at least one coil (40, 41). Simplified production capability is produced, for example, by the bypass device (45) being spaced apart axially from the two face side walls (65, 66).