EV Gear Shifting Speed Matching Without Synchronizer Rings
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Solution Overview
Problem
Current electric vehicle transmissions have a limited success rate of gear shifting, often leading to gear shifting failures due to inconsistent rotational speeds between engagement components.
Innovation Solution
A gear shifting method that adjusts the rotational speed difference between the input-side and output-side engagement components to a precise preset value within the range of 10-30 rpm, particularly 15 rpm, using a transmission control unit (TCU) to control the drive motor, eliminating the need for synchronizer rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotational speed difference between engagement components is not precisely controlled, then the gear shifting process is simpler, but the gear shifting success rate is low
Solution Approach 1:
The system performs preliminary speed adjustment of the drive motor before gear engagement occurs. The TCU calculates a target rotational speed for the input-side engagement component and controls the drive motor to reach this target speed in advance, ensuring the rotational speed difference is within the preset range (10-30 rpm) before the engagement command is executed. This preliminary action prevents gear shifting failure without requiring complex additional hardware.
Solution Approach 2:
The system implements a feedback control mechanism where the TCU continuously monitors the actual rotational speed of the input-side engagement component and compares it with the target rotational speed. Based on this feedback, the TCU adjusts the drive motor's rotational speed in real-time to ensure the rotational speed difference remains within the acceptable range. This closed-loop feedback ensures high gear shifting success rate while keeping the control system manageable.
2Reliability
If synchronizer rings are used to assist gear engagement, then the gear shifting success rate improves, but the device complexity and cost increase
Solution Approach 1:
The invention extracts and removes the synchronizer ring from the transmission system by relying solely on precise speed control of the drive motor. The TCU controls the rotational speed difference between input-side and output-side engagement components to be within 10-30 rpm, which eliminates the need for synchronizer rings to equalize speeds. This simplifies the transmission structure while maintaining high gear shifting success rate.
Solution Approach 2:
The invention replaces the mechanical synchronizer ring system with an electronic control system. Instead of using a mechanical device (synchronizer ring) to assist gear engagement, the system uses the TCU to electronically control the drive motor's rotational speed, creating a speed difference within the optimal range that enables successful engagement without mechanical assistance.
3Reliability
If the rotational speed difference is kept very small (near zero), then the engagement is smoother, but the gear shifting success rate decreases
Solution Approach 1:
The invention changes the optimal parameter range for rotational speed difference from near-zero (conventional wisdom) to 10-30 rpm. Research and testing revealed that a small but non-zero speed difference actually improves gear shifting success rate by preventing tooth collision and facilitating smoother engagement. The TCU is configured to maintain this specific parameter range, optimizing both success rate and engagement smoothness.
Data Source
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AI summary
The present application proposes a gear shifting method for use in electric vehicles, wherein the gear shifting method at least comprises: a speed adjustment process, wherein a speed adjustment request is issued to adjust the rotational speed of the drive motor of the electric vehicle, ensuring that the absolute rotational speed difference between the output-side engagement component and the input-side engagement component remains within the range of 10 rpm to 30 rpm when the input-side engagement component and the output-side engagement component of the transmission, driven by the drive motor, are disengaged; and an engagement process, wherein an engagement command is issued after the completion of the speed adjustment process, so as to engage the input-side engagement component with the output-side engagement component for gear engagement. The positive effects of the present application are as follows: it can greatly increase the success rate of gear shifting; it eliminates the need for synchronizer rings used in a conventional transmission for assisting in gear engagement.