CVT Hydraulic Control Torque Point Estimation
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Solution Overview
Problem
Conventional idle neutral control in continuously variable transmissions requires a sensor to detect input rotational speed, increasing costs and weight, and limiting layout flexibility, while also being prone to variations in clutch pressure control leading to reduced start-up performance and fuel consumption issues.
Innovation Solution
A hydraulic pressure control device comprising a hydraulic pressure regulating section, a rotational movement detecting section, and a control section that estimates the torque transmission point without a sensor for input rotational speed detection, using the primary pulley rotational speed sensor to detect the torque transmission point and control clutch engagement hydraulic pressure, allowing accurate clutch disengagement and reducing system variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor for detecting input rotational speed is added to achieve accurate torque transmission point detection, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary element (the primary pulley rotational speed sensor) to indirectly detect the torque transmission point. Instead of directly sensing clutch input rotational speed, the system uses the rotational speed of the primary pulley as a mediator to infer the clutch engagement state and determine the torque transmission point, thereby avoiding the need for additional sensors on the clutch.
Solution Approach 2:
The system utilizes existing sensors and components (primary pulley rotational speed sensor, hydraulic pressure regulator) to achieve the detection function. The primary pulley rotational speed sensor serves dual purposes: monitoring primary pulley speed and enabling torque transmission point detection through control unit analysis, making the existing sensor system work harder rather than adding new sensors.
2Reliability
If clutch pressure is increased to ensure reliable engagement, then reliability is improved, but start-up performance deteriorates due to delayed clutch engagement
Solution Approach 1:
The control unit performs preliminary analysis of primary pulley rotational speed data before full clutch engagement to predict the torque transmission point. By anticipating when torque transmission will occur based on rotational speed trends, the system can prepare optimal pressure levels in advance, ensuring smooth engagement without delay or excessive pressure.
Solution Approach 2:
The hydraulic pressure regulator dynamically adjusts clutch pressure based on real-time rotational speed feedback from the primary pulley sensor. Rather than using fixed pressure levels, the system continuously adapts pressure according to the actual engagement progress and torque transmission characteristics, optimizing both reliability and response time.
Data Source
AI summary
A hydraulic pressure control device is provided that that controls hydraulic pressure of a clutch supplying torque to a continuously variable transmission while the vehicle is stopped and in a running range. The hydraulic pressure control device has an control section that estimates a clutch engagement hydraulic pressure for changing the clutch from an engaged state to a disengaged state based the hydraulic fluid pressure acting on the clutch during the stopping of the rotational movement of a primary pulley of the continuously variable transmission, and then controls regulation of the hydraulic pressure to the clutch from an engaged state to a disengaged state, when the vehicle is stopped and in the running range, so that the torque from the engine does not rotate a secondary pulley of the continuously variable transmission.