Transmission Case Tubular Structure for Parking Lock Stability
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Solution Overview
Problem
Power transmission devices face challenges in preventing interference between the case and vehicle body-side constituent members while maintaining the stability of the parking gear during parking lock operations, especially when space is limited and the mounting position of these members cannot be easily changed.
Innovation Solution
A power transmission device with a multi-speed transmission system incorporating a planetary gear and a parking lock mechanism, where the planetary gear's carrier is rotatably supported by a central shaft and coupled to the output member, and the case design includes a small diameter tubular portion, an annular wall portion, and a large diameter tubular portion to accommodate the planetary gear and clutch, allowing the parking gear to be securely positioned on the carrier without tilting, thus stabilizing its orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger mount is used to suppress vibration transmission, then vibration isolation performance is improved, but the case size increases and may interfere with vehicle body-side constituent members
Solution Approach 1:
The parking lock device is nested within the case structure, with the parking gear integrated into the planetary gear mechanism. The case includes a tubular portion that rotatably supports the output member, and the parking lock device components are arranged within the case's internal space, effectively utilizing the existing structure to avoid increasing overall case size while maintaining vibration isolation performance
2Volume of stationary object
If the case is configured to avoid interfering with vehicle body-side constituent members, then spatial compatibility is improved, but the space within the case is limited and the parking gear orientation cannot be stabilized
Solution Approach 1:
The case is designed with differentiated structural zones: a tubular portion for rotatably supporting the output member, an annular wall portion for radial extension, and a large diameter tubular portion for axial extension. The parking gear is specifically positioned in the region surrounded by these structures, where the local geometric constraints naturally stabilize its orientation during parking lock operations while maintaining overall compact case dimensions
3Reliability
If the parking gear is positioned to be stable during parking lock operation, then parking lock reliability is improved, but the case structure becomes more complex
Solution Approach 1:
The case structure serves multiple functions simultaneously: it provides the overall housing for the transmission components, contains the vibration isolation mount, supports the output member through the tubular portion, and stabilizes the parking gear orientation through the annular wall and large diameter tubular portion. This multi-functionality approach avoids increasing device complexity while ensuring parking lock reliability
Data Source
AI summary
A first planetary gear and a clutch are placed between a second carrier of a second planetary gear and an output shaft in the axial direction. A transmission case has a small diameter tubular portion that rotatably supports an output shaft, an annular wall portion extended radially outward from the small diameter tubular portion, and a large diameter tubular portion extended in the axial direction from the outer periphery of the annular wall portion such that the first planetary gear and the clutch are partially surrounded. A mount is fixed to a vehicle body of a vehicle so as to at least partially overlap the small diameter tubular portion, the annular wall portion, and the large diameter tubular portion as viewed in the radial direction. A parking gear of a parking lock device is coupled to the outer periphery of the second carrier.