Electrically Variable Transmission Clutch Brake Dynamics
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Solution Overview
Problem
Conventional single mode electrically variable transmissions (EVTs) for hybrid electric vehicles lack efficiency and expanded operating capabilities, particularly in electric drive modes, as they can only utilize one electric motor for propulsive force, leading to increased operating temperatures and reduced performance on grades.
Innovation Solution
Incorporating a selectively engagable torque transmitting device, such as a controlled clutch brake, which allows both electric motors to provide propulsive force in electric drive mode, enabling load sharing and regenerative braking, and aiding in engine startup and shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single mode EVT is used with only one e-motor as traction motor, then the structure is simple, but the power output is limited and motor temperature increases
Solution Approach 1:
The patent applies dynamics by enabling the first e-motor to switch between operating as a generator and operating as a motor. The clutch brake dynamically engages and disengages based on operating conditions. This dynamic reconfiguration allows both e-motors to provide propulsive force when needed, increasing power output while maintaining a relatively simple single-mode transmission structure.
2Device complexity
If a conventional single mode EVT is used with only one e-motor as traction motor, then the structure is simple, but operating temperature increases due to concentrated load
Solution Approach 1:
The clutch brake enables dynamic load distribution between the two e-motors. When engaged, it allows the first e-motor to assist as a motor, spreading the load and reducing operating temperatures. The system can adaptively switch between single-motor and dual-motor modes based on thermal conditions and power demands.
Solution Approach 2:
The first e-motor can be discarded as a motor when not needed and recovered as a motor when dual-propulsion is required. This flexible role switching allows the system to use both motors for propulsive force when temperature management is critical, preventing thermal overload while maintaining structural simplicity.
3Power
If the clutch brake is selectively engaged to ground the input member, then both e-motors can provide propulsive force, but the device complexity increases
Solution Approach 1:
The clutch brake serves multiple functions: it grounds the input member to enable dual-motor propulsion, it allows the first e-motor to operate as a generator, and it enables regenerative braking. This multi-functional component increases power capability while adding minimal structural complexity compared to more elaborate transmission systems.
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 configuration enhances operational efficiencies by reducing motor temperatures, improving drive and regenerative braking efficiency, and enabling vehicle launch on grades without engine assistance, while simplifying engine transitions and reducing system losses.
Implementation Method 1
the clutch brake can comprise a friction clutch that can be selectively slipped to slow down rotation of the engine adapted to be coupled to the input member before grounding the input member
Implementation Method 2
the first motor-generator can provide driving torque to assist the second-motor generator in the electric drive mode
Implementation Method 3
The first motor-generator can also function as a generator to aid the second motor-generator with regenerative braking
Data Source
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AI summary
An electrically variable transmission includes an input member (22), first and second motor-generators (46, 50) and a gear reduction arrangement (42) including at least a first gear (78) coupled to at least one second gear (86). A first planetary gear set (38) includes a first sun gear (60), a first ring gear (64) and a first carrier (68) rotatably supporting a plurality of pinion gears (72) in meshing engagement with the first sun gear (60) and the first ring gear (64) The first carrier (68) is nonrotatably coupled to the input member. (22) and the first ring gear (64) is coupled to the at least one second gear (86). The first sun gear (60) is nonrotatably coupled to the first motor-generator (46) and the first gear (78) is nonrotatably coupled to the second motor-generator (50). A torque transmitting device (34) is configured to selectively fix rotation of the input member (22) in at least one of a first rotational direction and a second opposite rotational direction.