CVT Shift Control Actuator Diagnostic Device
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Solution Overview
Problem
Conventional diagnostic techniques for shift control actuators in continuously variable transmissions (CVTs) are inefficient in determining the ON-keeping state of upshift and downshift control actuators, often requiring prolonged time and leading to erroneous failure determinations due to repeated overshooting and feedback control capabilities.
Innovation Solution
A diagnostic device comprising a variator, chamber, upshift and downshift control valves, a fail-safe valve, and a shift controller that detects and controls the shift ratio to determine the ON-keeping state by monitoring the hydraulic fluid flow and actuator states, ensuring accurate identification of actuator failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If both upshift and downshift solenoids are turned on simultaneously to diagnose failure, then the diagnostic process can identify which solenoid is failed, but the diagnostic time becomes excessively long
Solution Approach 1:
The fail-safe valve is pre-configured to automatically close when the upshift solenoid is activated, preventing the need for simultaneous activation of both solenoids. This preliminary setup allows diagnosis to proceed by simply activating the upshift solenoid and observing whether the fail-safe valve prevents the downshift solenoid from operating, significantly reducing diagnostic time while maintaining accuracy
Solution Approach 2:
The fail-safe valve acts as an intermediary component between the upshift and downshift control systems. It mediates the interaction between the two solenoids by automatically closing when the upshift solenoid is on, thereby preventing the downshift solenoid from operating. This intermediary mechanism enables accurate failure diagnosis without requiring simultaneous solenoid activation, thus reducing diagnostic time
2Measurement precision
If feedback control is used to bring actual shift ratio close to target shift ratio, then the shift control accuracy is improved, but erroneous failure determination occurs due to repeated overshooting and hunching
Solution Approach 1:
The diagnostic method extracts the failure determination logic from the normal feedback control loop. By separately evaluating whether the fail-safe valve is functioning correctly (by checking if it closes when the upshift solenoid is activated), the system can reliably determine solenoid failures without being influenced by the oscillations and overshooting that occur during normal feedback control operation
Solution Approach 2:
The system performs a preliminary diagnostic check by activating the upshift solenoid and observing the fail-safe valve's response before making failure determinations. This preliminary action separates the diagnostic function from the continuous feedback control, preventing erroneous failure determinations caused by normal control oscillations
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
The solution enables precise determination of the ON-keeping state of upshift and downshift control actuators, reducing diagnostic time and preventing erroneous determinations by using a fail-safe valve to manage hydraulic fluid flow and a shift controller to monitor and adjust the shift ratio effectively.
Implementation Method 1
a power shift member, such as a chain or a metal belt, is bridged between a primary pulley (drive-side pulley) and a secondary pulley (driven-side pulley) of which rotational shafts are in parallel with each other, and changes the shift ratio by hydraulically changing an effective diameter of each pulley
Implementation Method 2
The fail-safe valve suspends the discharge of the hydraulic fluid from the chamber when the upshift control valve is in the filling state regardless of the state of the downshift control valve, and permits the downshift control valve to discharge the hydraulic fluid when the upshift control valve is in the non-filling state
Data Source
AI summary
A diagnostic device for a shift control actuator of a CVT includes: a variator; a chamber that is filled with and discharges hydraulic fluid for an upshift and a downshift, respectively; an upshift control valve for filling hydraulic fluid into the chamber; a downshift control valve for discharging hydraulic fluid from the chamber; a fail-safe valve for suspending the discharge of hydraulic fluid from the chamber when the upshift control valve is in a filling state; actuators for driving the upshift and downshift control valves; and a shift controller for controlling the actuators so that an actual shift ratio approaches a target ratio. The shift controller determines the state of the actuators with the information on the actual shift ratio when the controller instructs a downshift or an upshift.