Control Device for Engine Start Assist with Slip Engagement
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Solution Overview
Problem
Internal combustion engine startability is compromised in cold environments due to increased oil viscosity, leading to failed starts and deceleration feel when traditional start assist control methods are insufficient, as they either fail to provide sufficient torque or result in reduced output torque at the wheels.
Innovation Solution
A control device that implements a two-stage start assist process: initially bringing the first engagement device into slip engagement at a first pressure while increasing torque, and if that fails, increasing the engagement pressure to a second pressure based on the rotational speed of the engine, while also boosting torque generation by the rotating electrical machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transfer torque capacity of the first engagement device is increased to improve startability, then the internal combustion engine can be started more reliably, but output torque at wheels is reduced causing deceleration feel
Solution Approach 1:
The patent applies dynamics by making the engagement pressure adjustable based on operating conditions. The control device dynamically determines the engagement pressure of the first engagement device according to the rotational speed of the internal combustion engine and torque requirements, rather than using a fixed high pressure. This allows the system to provide sufficient torque for starting while minimizing unnecessary torque transfer that would cause deceleration feel during normal operation.
Solution Approach 2:
The patent changes the parameter of engagement pressure from a fixed value to a variable parameter that is adjusted based on engine rotational speed and torque requirements. The control device modifies the engagement pressure parameter in real-time during the starting process, increasing it only when necessary to provide sufficient starting torque, and reducing it when the engine is running smoothly, thereby resolving the contradiction between startability and deceleration feel.
2Reliability
If the engagement pressure is increased to provide sufficient torque for starting, then the internal combustion engine can start reliably in cold environments, but the output torque at wheels is reduced
Solution Approach 1:
The system dynamically adjusts engagement pressure based on real-time engine rotational speed and torque requirements rather than maintaining a constantly high pressure. During cold starting when high torque is needed, the engagement pressure is increased temporarily. Once the engine starts and rotational speed increases, the pressure is reduced, thereby maintaining power output at the wheels while ensuring reliable starting in cold conditions.
Solution Approach 2:
The engagement pressure is applied periodically or temporarily only during the critical starting phase when high torque is required, rather than continuously. The control device increases engagement pressure at the beginning of the starting process to ensure reliable ignition in cold environments, then reduces or releases the pressure once the engine is running, thus preventing continuous power loss at the wheels.
3Object-generated harmful factors
If the motor torque is increased to compensate for reduced output torque, then the deceleration feel can be minimized, but the motor may be unable to generate sufficient torque when at maximum capacity
Solution Approach 1:
The patent applies preliminary action by bringing the first engagement device into slip engagement before full engagement. This preliminary slip engagement phase allows the motor to gradually transfer torque to the engine while minimizing sudden torque changes that would cause deceleration feel. The control device carefully manages the transition from disengaged to engaged state, preparing the system in advance to avoid abrupt torque transfers that the motor cannot compensate for.
Solution Approach 2:
The patent uses partial engagement (slip engagement) rather than full engagement initially. The first engagement device is brought into slip engagement at a controlled pressure that provides sufficient torque for starting without fully engaging the clutch. This partial action allows the motor to provide torque compensation gradually, and only when necessary does the system increase to full engagement pressure, avoiding unnecessary motor torque demands.
Data Source
AI summary
A control device for performing start assist control for an internal combustion engine includes: a first start assist processing unit that executes a first start assist process that brings a first engagement device into slip engagement at a first engagement pressure while increasing a torque generated by a rotating electrical machine; and a second start assist processing unit that increases, when the first start assist process fails to start the internal combustion engine, an engagement pressure of the first engagement device to a second engagement pressure higher than the first engagement pressure while increasing the torque generated by the rotating electrical machine. The second start assist processing unit determines the second engagement pressure on the basis of a rotational speed of the internal combustion engine in the first start assist process.