Valve Body Machining for Tolerance Control
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Solution Overview
Problem
The dimensional tolerance stack-up in valve body castings for automatic transmissions is too large to accommodate a practical integrated electromagnet, hindering accurate flow and pressure regulation, especially in high torque operating conditions.
Innovation Solution
A method involving a circular interpolation machining process using a cutting tool with pneumatic lubrication to simultaneously machine critical features like grooves and face surfaces in a valve body, ensuring precise tolerances and improved manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional casting methods are used for valve body, then manufacturing efficiency is improved, but dimensional tolerance accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by performing precision machining of critical features (grooves, face surfaces, metering edges) immediately after casting while the valve body is still in the manufacturing sequence. This ensures that the precision-machined features achieve ultra-precise dimensional tolerances (within ±0.002 inches) before any subsequent assembly or operation, preventing tolerance accumulation that would occur if machining were delayed or performed separately on assembled components.
2Device complexity
If integrated electromagnet is used in valve body, then device complexity is reduced, but manufacturing precision deteriorates due to tolerance stack-up
Solution Approach 1:
The patent merges the electromagnet assembly with the valve body by integrating the coil form, armature, and associated features directly into the cast valve body structure. This consolidation eliminates separate components and their associated tolerance stack-up, achieving the required precision for direct-acting solenoid operation while reducing overall device complexity. The integrated design allows the electromagnet to be positioned with ultra-precise tolerances relative to the spool valve features.
Solution Approach 2:
The electromagnet features (coil form, armature, mounting surfaces) are precision-machined concurrently with the valve body features in a single machining operation, establishing precise relative positions before assembly. This preliminary positioning ensures that the integrated electromagnet achieves the required tolerance accuracy without the cumulative effects of multiple separate machining and assembly operations.
3Ease of manufacture
If multiple features are machined separately in valve body, then manufacturing simplicity is improved, but manufacturing precision deteriorates due to multiple operations
Solution Approach 1:
The patent combines multiple machining operations into a single circular interpolation machining process that simultaneously machines the groove, face surface, and metering edges of the spool valve bore. This concurrent machining of multiple critical features in one operation eliminates the tolerance accumulation that would result from sequential operations, achieving ultra-precise dimensional tolerances while maintaining manufacturing simplicity through process consolidation.
Solution Approach 2:
All critical features requiring precise relative positioning are machined in a single preliminary operation before any subsequent assembly or further processing. This ensures that the dimensional tolerances between groove, face surface, and metering edges are established with maximum accuracy (within ±0.002 inches) before any potential sources of tolerance degradation occur.
4Device complexity
If conventional machining process is used, then equipment simplicity is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent employs minimum quantity lubrication (MQL) delivered through the machining tool via pneumatic or hydraulic means to achieve ultra-precise dimensional tolerances. The MQL system provides controlled lubrication at the cutting zone, enabling the machining process to achieve tolerances within ±0.002 inches while using relatively simple equipment. This pneumatic/hydraulic lubrication delivery method enhances machining precision without requiring complex specialized machinery.
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 approach enables high precision tolerances, reducing hydraulic fluid leakage and enhancing pressure regulation accuracy, allowing for independent hydraulic pressure delivery to clutches and brakes.
Implementation Method 1
supplying lubricant in a pneumatic stream through the tool to the cutting edges
Data Source
AI summary
A method for forming a valve includes forming a valve body; machining a bore by passing a tool having cutting edges along an axis into the valve body; machining a groove and face in the bore at axially spaced locations by revolving the tool about a circular circumference whose center is aligned with the bore; and supplying lubricant in a pneumatic stream through the tool to the cutting edges.