Hybrid AWD Engine Restart Using Dual-Motor Torque Transfer
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Solution Overview
Problem
Existing hybrid vehicle systems require an oversized electric drive to restart the internal combustion engine without interrupting tractive power, leading to increased space, weight, and cost, as well as reduced efficiency.
Innovation Solution
A method involving a dual drive train system where the first electric machine builds a torque reserve by reducing its output and transferring the load to a second electric machine, allowing the internal combustion engine to be started without noticeable torque disruption, using a separating clutch and micro-slip/macro-slip operation to manage torque transfer efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric drive motor is designed with greater power to restart the internal combustion engine without interrupting traction, then the wheel torque drop is reduced and starting assistance is improved, but the installation space requirements increase, weight increases, cost increases, and efficiency decreases
Solution Approach 1:
The patent divides the drive system into two separate electric motors: a first electric motor for propulsion and a second electric motor for engine starting. This segmentation allows each motor to be optimized for its specific function, enabling the first motor to be smaller while the second motor is专门 designed for starting assistance, thereby reducing overall system weight and cost while maintaining reliable continuous traction during engine restart
Solution Approach 2:
The second electric motor serves dual purposes: it can assist the first electric motor during propulsion and simultaneously provide starting assistance for the internal combustion engine. This multi-functionality eliminates the need for an oversized single motor, reducing weight, space, and cost while ensuring reliable traction maintenance during engine restart
2Reliability
If the electric drive motor is designed with greater power to restart the internal combustion engine, then the starting assistance is improved, but the manufacturing cost increases
Solution Approach 1:
The patent segments the starting function from the propulsion function by introducing a dedicated second electric motor for engine starting. This allows the first electric motor to be designed with lower power specifications for propulsion only, reducing its manufacturing cost, while the second motor is optimized for starting assistance, making the overall system more cost-effective while maintaining reliable engine restart capability
Solution Approach 2:
The second electric motor provides partial action during normal propulsion (can assist if needed) but excessive action during engine starting (dedicated starting assistance). This partial/excessive action strategy allows cost optimization by having a smaller, cheaper second motor that only needs to provide full power during starting events, rather than continuously, thereby reducing overall manufacturing cost while ensuring reliable restart capability
3Reliability
If the electric drive motor is designed with greater power to restart the internal combustion engine, then the starting performance is improved, but the system efficiency decreases
Solution Approach 1:
The patent segments the functional requirements so that the first electric motor handles propulsion efficiency optimization while the second electric motor handles starting assistance. This allows the first motor to be sized and controlled for maximum propulsion efficiency, and the second motor to be optimized for starting events only, reducing overall energy losses compared to a single oversized motor that would operate inefficiently during normal propulsion
Solution Approach 2:
The second electric motor operates in partial action during normal driving (only assisting when needed) and provides excessive action during starting events. This ensures that the first electric motor operates in its optimal efficiency range during propulsion, while the second motor supplements only when necessary, minimizing overall energy losses while maintaining reliable engine restart capability
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 approach enables a quick and efficient start of the internal combustion engine without additional units, reducing the load on the electric machine and avoiding noticeable torque reduction, thus improving the hybrid vehicle's performance and efficiency.
Implementation Method 1
the first electric machine operating in a first operating state for a predefined period of time prior to starting the internal combustion engine... the first electric machine builds a torque reserve
Implementation Method 2
a separating clutch (7) acting between the first electric machine (3) and the internal combustion engine (2)... the separating clutch (7) is closed at a second time such that a rotational momentum of the first electric motor is transferred to the internal combustion engine
Data Source
Figure 1~2
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AI summary
The invention relates to a method for starting an internal combustion of a hybrid vehicle comprising a first powertrain (1) which comprises an internal combustion engine (2), a first electric machine (3), and a transmission (5). The first electric machine (3) can be coupled to the internal combustion engine (2) via a disconnect clutch (7) and to a first and/or second drive axle (4; 204) via a starting element (6). The hybrid vehicle also comprises a second powertrain (201) with a second electric machine (203) to which the first and/or second drive axle (4; 204) can be coupled, wherein a respective drive torque can be provided via the first and second electric machine (3, 203). The invention is characterized by the following steps: operating the first electric machine (3) and actuating the starting element (6) after a first point in time (tv) such that a first electric machine (3) torque acting via the first powertrain (1) is reduced by a torque value (R) and operating the second electric machine (203) such that a second electric machine (203) torque acting via the second powertrain (201) is increased by a value (R) in a corresponding manner; and operating the first electric machine (3) and at least partly closing the disconnect clutch (7) after a second point in time (t0) such that the rotational speed of the internal combustion engine (2) is increased until a starting criterion is reached such that the internal combustion engine (2) supports a starting process.