Automatic Transmission Backward Preparation Mode
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Solution Overview
Problem
Conventional automatic transmissions experience loud switching sounds and uncomfortable vehicle operation due to sudden rotation stops during gear shifts between forward and backward movements, requiring either slow speed reduction or increased parts and costs for rpm detection.
Innovation Solution
An automatic transmission with a control unit that manages engagement mechanisms to perform a backward preparation mode, reducing the RPM of elements before shifting, and using oil-temperature and vehicle-speed detection to determine when to switch states, eliminating the need for additional rpm detection units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the switching mechanism is switched from reverse-rotation preventing state to fixed state during forward motion, then the gear shift is rapid, but a loud switching sound occurs due to sudden rotation stop
Solution Approach 1:
The control unit performs a backward preparation mode before the actual gear shift, bringing the switching mechanism to a predetermined RPM or lower in advance. This preliminary action prepares the system for a smooth transition by reducing the rotational speed beforehand, allowing the switching mechanism to be engaged without sudden stops that cause loud noises.
Solution Approach 2:
The system dynamically adjusts the rotational speed of the switching mechanism based on operational conditions. By controlling the RPM to be at or below a predetermined level before engagement, the system adapts the mechanical state to minimize harmful switching sounds while maintaining rapid shifting capability.
2Object-affected harmful factors
If the RPM is reduced slowly before switching, then the switching sound is reduced, but the shifting speed becomes slow
Solution Approach 1:
The backward preparation mode is executed in advance before the actual gear shift, separating the RPM reduction phase from the switching phase. This allows the system to reduce RPM to predetermined levels beforehand, then quickly engage the switching mechanism without the trade-off between slow reduction and fast shifting.
Solution Approach 2:
The control unit prepares the switching mechanism by reducing its RPM to predetermined levels before the actual engagement. This beforehand cushioning of the rotational energy prevents the sudden stop that would cause loud switching sounds, while the overall shifting process remains rapid due to the preparatory nature of the RPM reduction.
3Measurement precision
If an RPM detection unit is added to detect the element's RPM, then the shifting control is precise, but the parts and costs increase
Solution Approach 1:
The control unit acts as an intermediary that infers the RPM of the switching mechanism indirectly through calculations based on detectable parameters such as vehicle speed and gear ratio, rather than using a direct RPM detection unit on the element. This intermediary approach achieves precise RPM control without the complexity and cost of additional detection hardware.
Solution Approach 2:
The patent replaces a mechanical RPM detection unit with a control system that calculates RPM through software algorithms based on other measurable parameters. This substitution eliminates the need for physical sensors on the element, reducing parts and costs while maintaining measurement precision through computational methods.
Data Source
AI summary
An automatic transmission includes an input member, a planetary gear mechanism, a plurality of engagement mechanisms, an output member, a control unit, and a switching mechanism. The control unit is able to perform a backward preparation mode (step 3) which enables the rpm of an element fixed by the switching mechanism to be predetermined rpm or less by bringing the engagement mechanism into a connected state or a fixed state when the shift position is switched from a forward range to a backward range (step 1). The control unit switches the switching mechanism from a reverse-rotation preventing state to the fixed state (step 7) after the rpm of the element becomes the predetermined rpm or less (step 5) by performing the backward preparation mode.