Idle Stop Engagement Pressure Control for Oil Pump Sizing
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Solution Overview
Problem
The existing idle stop control systems face challenges in efficiently managing the engagement pressure of starting frictional elements during vehicle idle stop and restart, leading to potential damage to the transmission due to delayed power transmission enablement and increased requirements for the electrically-powered oil pump, which complicates installation space and cost constraints.
Innovation Solution
The engagement pressure control apparatus sets the engagement pressure command value to a control maximum value, reducing the need for the electrically-powered oil pump to drain working oil, thereby allowing for a smaller pump capacity that meets the requirements of space and cost constraints while maintaining efficient power transmission enablement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrically-powered oil pump drains working oil to control engagement pressure of the starting frictional element, then the transmission can be held in the state immediately before power transmission start, but the pump capacity must be increased which complicates installation space and cost constraints
Solution Approach 1:
The system performs preliminary action by holding the starting frictional element in the state immediately before engagement start during idle stop using working oil from the electrically-powered oil pump. This preliminary positioning ensures that when the engine restarts, the transmission can immediately transition to the power transmission enabled state without delay, preventing transmission damage while avoiding the need for excessive pump capacity.
2Reliability
If the engine driven oil pump generates hydraulic pressure after engine restart, then the transmission can be enabled for power transmission, but a response delay occurs during which rising engine output damages transmission durability
Solution Approach 1:
The system performs preliminary action by positioning the starting frictional element in the state immediately before engagement start during idle stop. This ensures that when the engine restarts, the transmission can immediately transition to the power transmission enabled state without delay, preventing transmission damage from rising engine output during a response delay.
Solution Approach 2:
The electrically-powered oil pump acts as an intermediary to supply working oil to the starting frictional element during idle stop, enabling the element to be held in the pre-engagement state. This intermediary action bridges the gap between engine stop and restart, ensuring continuous transmission readiness without relying solely on the engine-driven oil pump's post-restart pressure generation.
3Reliability
If the starting frictional element is held in release state during idle stop, then the transmission is in power transmission disabled state, but upon engine restart the response delay causes rising engine torque to damage transmission
Solution Approach 1:
The system performs preliminary action by holding the starting frictional element in the state immediately before engagement start during idle stop, rather than in complete release state. This preliminary positioning ensures that when the engine restarts, the transmission can immediately transition to the power transmission enabled state, preventing transmission damage while achieving fast engagement speed.
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 ensures the electrically-powered oil pump can be designed with a smaller capacity, reducing installation space and cost constraints while preventing transmission durability issues by ensuring immediate power transmission enablement upon engine restart.
Implementation Method 1
a starting frictional element engagement pressure control section which produces a starting frictional element engagement pressure corresponding to an engagement pressure command value with the working oil (pump discharge pressure) partially drained
Implementation Method 2
a transmission configured to transmit a power of an engine to drive wheels under a gear shift via a starting frictional element
Data Source
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AI summary
[Task] A required draining capacity of an electrically-powered oil pump is reduced and a small sizing of the electrically-powered oil pump is achieved by devising how to issue a starting frictional element engagement pressure command value. [Means for solving the problem] An engine is restarted in response to an idle stop OFF command at t1 so that a gear shift control purpose hydraulic pressure is raised according to a working oil from an engine driven oil pump. An idle stop release time control of the engine is allowed according to a torque down unnecessary determination when a gear shift control purpose hydraulic pressure has reached to a set hydraulic pressure at t2. In a case where this allowance causes an engine torque Te to be raised from a torque down value toward a driving operation corresponding value by a predetermined gradient ΔTe1, a command value of a starting frictional element engagement pressure PS is set to a control maximum value (a drain port opening angle of a clutch hydraulic pressure control valve for a clutch hydraulic pressure (an engagement pressure) command value is made small as compared with that in a case of an ordinary control (is made difficult to drain)) during the idle stop control including during the idle stop release time control. Thus, when starting frictional element engagement pressure PS is controlled upon receipt of this command value, the working oil from the electrically-powered oil pump is not needed to be drained. Consequently, the electrically-powered oil pump is not needed to discharge this draining working oil and the small-sizing can be achieved.