Engine Start Control Device Hydraulic Pressure Management
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Solution Overview
Problem
Existing engine start control devices face challenges in quickly restarting a vehicle from an idling-stop state without generating shocks due to insufficient hydraulic pressure, leading to discomfort for the driver and inefficiencies in electric power consumption.
Innovation Solution
An engine start control device that includes a power transmission system with a mechanical oil pump and an electric oil pump connected in parallel, along with hydraulic pressure detection and motor control mechanisms, which drives the electric oil pump when hydraulic pressure is low and adjusts motor rotation speed to maintain clutch engagement without sudden pressure increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric oil pump is driven during the idling stop to supply hydraulic pressure, then the engaged state of the clutch can be maintained, but the line pressure increases with a time lag causing the clutch engagement to be unstable during the initial period
Solution Approach 1:
The electric oil pump is driven in advance during the idling stop period to build up hydraulic pressure before the restart is requested. This preliminary action ensures that when the restart occurs, the clutch engagement is stable without time lag, as the pressure is already sufficient.
2Reliability
If the electric oil pump is driven continuously during the idling stop to ensure sufficient line pressure, then the clutch engagement stability is improved, but the electric power consumption increases
Solution Approach 1:
Instead of continuous operation, the electric oil pump is driven periodically or intermittently during the idling stop. The control device determines appropriate driving periods based on system state, maintaining clutch engagement stability while reducing overall electric power consumption compared to continuous operation.
3Reliability
If the restart is inhibited for a predetermined period after starting the electric oil pump, then the clutch engagement stability is ensured, but the vehicle startup time is delayed causing driver discomfort
Solution Approach 1:
The electric oil pump is driven in advance during the idling stop to pre-build hydraulic pressure. This eliminates the need for a post-pump-start inhibition period, as the pressure is already sufficient when restart is requested, enabling immediate vehicle startup without compromising clutch engagement stability.
4Device complexity
If the mechanical oil pump is the sole source of hydraulic pressure, then the device complexity is reduced, but the hydraulic pressure is insufficient during the idling stop causing clutch release
Solution Approach 1:
The system merges the mechanical oil pump and electric oil pump into a hybrid hydraulic supply system. The mechanical pump provides pressure during engine operation, while the electric pump supplements during the idling stop. This combination maintains clutch engagement reliability without significantly increasing overall system complexity.
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
Enables quick vehicle startup without shocks, reduces electric power consumption, and prevents clutch release due to hydraulic pressure fluctuations, ensuring continuous engagement and minimizing energy waste.
Implementation Method 1
a mechanical oil pump, which rotates in synchronization with the engine, discharges a reduced amount when the engine rotation speed is reduced. As a result, a hydraulic pressure for bringing a forward clutch (hereinafter, referred to simply as clutch) into engagement (hereinafter, referred to as line pressure) is reduced.
Implementation Method 2
a feeling of discomfort of a driver cannot be eliminated... the clutch is suddenly brought into the engaged state with a sudden increase in line pressure
Data Source
AI summary
An engine start control device includes a mechanical pump supplying hydraulic pressure; an electric pump connected in parallel to the mechanical pump and independently driven; a device for stopping the engine when an idling stop condition is satisfied and starting the engine when a restart condition and a fuel injection condition are satisfied; a device for driving the electric pump when the hydraulic pressure is less than a first hydraulic pressure when the engine is stopped by idling stop; and a device for driving a motor at a target speed and for performing control so that the change in the target speed is small compared with the change exhibited when the hydraulic pressure is equal or higher than a second hydraulic pressure, when the hydraulic pressure is less than the second hydraulic pressure, and the restart condition is satisfied after the idling stop.