Hydraulic Control Apparatus for Sequential Shifts in Automatic Transmissions
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Solution Overview
Problem
Sequential shifts in automatic transmissions often result in engine idle revving and delayed achievement of final speed due to delays in hydraulic pressure rise and drop between engagement and release friction elements, particularly when the shift determination occurs during the inertia phase.
Innovation Solution
A hydraulic control apparatus with a selector valve that switches positions based on the operating pressure of the release-side friction element, allowing fluid communication to the engagement-side friction element only when necessary, and controlling hydraulic pressure to facilitate simultaneous piston stroke and pressure regulation, ensuring timely engagement and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the second shift is performed after termination of the first shift, then the sequential shift can be completed, but the time required to achieve final speed increases
Solution Approach 1:
The selector valve is switched to the first position in advance when the first friction element is released, preparing the hydraulic supply path for the second friction element before the engagement command is issued. This preliminary action ensures that hydraulic pressure can be supplied immediately when needed, reducing the time delay in achieving final speed during sequential shifts
2Loss of time
If the hydraulic command is outputted immediately after sequential shift determination, then the shift time is reduced, but hydraulic pressure rise in the engagement-side friction element is delayed causing engine idle revving
Solution Approach 1:
The selector valve is switched to the first position in advance when the first friction element is released, preparing the hydraulic supply path for the second friction element before the engagement command is issued. This ensures that when the engagement command is given, hydraulic pressure can rise immediately without delay, preventing engine idle revving while maintaining reduced shift time
Solution Approach 2:
The selector valve acts as an intermediary component that controls the connection between the hydraulic supply source and the second friction element. By switching the selector valve to the first position in advance, the hydraulic path is prepared as an intermediary step, ensuring that pressure can be transmitted immediately when the engagement command is issued, thus synchronizing pressure rise with the engagement timing
3Reliability
If the selector valve is switched after hydraulic pressure drop in the release-side friction element, then interlock between friction elements is prevented, but pressure regulator valve is not supplied with source pressure causing delay in engagement
Solution Approach 1:
The selector valve is switched to the first position in advance when the first friction element is released, before the hydraulic pressure has fully dropped. This preliminary switching prepares the hydraulic supply path for the second friction element while the first element is still maintaining pressure, ensuring that when the engagement command is issued, the pressure regulator valve already has source pressure available, eliminating engagement delay while the interlock prevention is maintained through proper timing
4Object-generated harmful factors
If the following shift is performed after changeover of the selector valve, then hydraulic pressure synchronization is achieved, but the final speed is accomplished with delay
Solution Approach 1:
The selector valve is switched to the first position in advance when the first friction element is released, preparing the hydraulic supply path before the engagement command for the second friction element is issued. This timing ensures that when the engagement command is given, the hydraulic path is already prepared and pressure can be supplied immediately, achieving both pressure synchronization and reduced time to final 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 solution minimizes engine idle revving and reduces the time required to achieve final speed by ensuring synchronized hydraulic pressure management across friction elements, preventing delays and shocks during sequential shifts.
Implementation Method 1
a selector valve that is switchable between a first position where fluid communication between the pressure regulator valve and the second friction element is allowed, and a second position where the fluid communication between the pressure regulator valve and the second friction element is blocked
Implementation Method 2
a pressure regulator valve regulating a hydraulic fluid pressure that is supplied to the second friction element
Implementation Method 3
a plurality of friction elements and establishes a plurality of speeds by changeover of the plurality of friction elements between engagement and release
Data Source
AI summary
A hydraulic control apparatus for an automatic transmission, including a sequential shift control means for performing sequential shift control in a case where it is necessary to execute the second shift during execution of the first shift. The sequential shift control includes starting reduction of hydraulic fluid pressure in the third friction element when a parameter that varies in accordance with a degree of progress of the first shift has reached a predetermined value, and performing piston stroke control that includes outputting a high hydraulic pressure command as a hydraulic fluid pressure to the second friction element when the selector valve is switched from the second position to the first position, and subsequent to completion of outputting of the high hydraulic pressure command, outputting a low hydraulic pressure command that is lower than the high hydraulic pressure command.