Hybrid Drive Unit Layout for Compact BEV Planetary Gear Operation
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Solution Overview
Problem
Existing drive apparatuses for vehicles with dual electric motors and a planetary gear device face challenges in reducing the axial dimension, particularly in Battery Electric Vehicle (BEV) mode, where the second electric motor drives the vehicle with the engine stopped, leading to increased space requirements and torque loads on the brake mechanism.
Innovation Solution
The drive apparatus is designed with a first drive unit that includes a first electric motor connected to the first rotary element of the planetary gear device, a second electric motor connected to the second rotary element, and a brake mechanism on a rotary shaft separate from the first axis, utilizing a power transmission mechanism with idler gears and helical gears to reduce axial dimension and torque loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the brake mechanism is placed on the first axis to enable BEV mode operation, then the vehicle can be driven by the second electric motor with the engine stopped, but the axial dimension of the first drive unit increases and torque loads on the brake mechanism increase
Solution Approach 1:
The brake mechanism is relocated from the first axis to a rotary shaft on a different axis (second axis), changing the spatial dimension where the brake is positioned. This dimensional shift allows the brake to function effectively while reducing the axial dimension along the first axis, resolving the contradiction between BEV mode capability and compact axial size.
Solution Approach 2:
A power transmission mechanism including gears is introduced as an intermediary between the rotary shaft (with brake mechanism) and the first rotary element. This intermediary system transmits torque from the second electric motor through the brake-equipped rotary shaft to the first rotary element, enabling BEV mode operation without requiring the brake to be directly on the first axis, thus reducing axial dimension while maintaining functionality.
2Adaptability or versatility
If the brake mechanism is placed on the first axis to enable BEV mode operation, then the vehicle can be driven by the second electric motor with the engine stopped, but the torque loads on the brake mechanism increase
Solution Approach 1:
The power transmission mechanism with gears acts as an intermediary that modifies the torque characteristics before they reach the brake mechanism. By positioning the brake on a rotary shaft connected through gears rather than directly on the first axis, the torque load on the brake is reduced while still enabling effective BEV mode operation.
Solution Approach 2:
The rotational speed and torque parameters are changed through the power transmission mechanism. The rotary shaft on the second axis rotates at a different speed and transmits torque through the gear system, which transforms the torque characteristics to reduce the load on the brake mechanism while maintaining the ability to stop the first rotary element during BEV mode.
3Device complexity
If the first electric motor is disposed on the first axis, then the connection to the first rotary element is direct, but the axial dimension of the first drive unit increases
Solution Approach 1:
The first electric motor is relocated from the first axis to a position on the second axis, changing its spatial arrangement. This dimensional repositioning allows the motor to connect to the first rotary element through the power transmission mechanism without increasing the axial dimension along the first axis, resolving the contradiction between connection simplicity and compact size.
Solution Approach 2:
The power transmission mechanism serves as an intermediary that connects the first electric motor (positioned on the second axis) to the first rotary element (on the first axis). This intermediary system maintains a simple and direct connection between the motor and rotary element while allowing them to be positioned on different axes, thus reducing the axial dimension without compromising connection simplicity.
Data Source
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AI summary
A vehicle drive apparatus (10;110;210;310) includes (a) an engine (18); (b) a drive shaft (14f) for driving wheels (12f, 12r); and (c) a drive unit (16f;116f;216f;316f) including (i) a first electric motor (MG1); (ii) a second electric motor (MG2), (iii) a planetary gear device (24;124;224;324) which has first through third rotary elements (RE1, RE2, RE3) that are rotatable about a first axis (CS1), (iv) a power transmission mechanism (40; 340) and (v) a brake mechanism (BR;OWC) configured to allow or stop rotation of the first rotary element (RE1). The engine (18) and the first electric motor (MG1) are connected to the first rotary element (RE1). The second electric motor (MG2) is disposed on the first axis (CS1) and is connected to the second rotary element (RE2). The drive shaft (14f) is connected to the third rotary element (RE3). The first electric motor (MG1) is disposed on a second axis (CS2) that is other than the first axis (CS1), and is connected to the first rotary element (RE1) through the power transmission mechanism (40; 340). The brake mechanism (BR;OWC) is provided on a rotary shaft (40d;40e;340d) which is rotatable about a rotary axis (CS5) other than the first axis (CS1) and which constitutes a part of the power transmission mechanism (40;340).