Torque Converter Drain Valve for Splash-Lubricated Transmissions

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Solution Overview

Problem

Existing vehicle transmissions face challenges in ensuring adequate lubrication and cooling during operating phases where the input shaft is stationary, particularly when towing or coasting, as immersion lubrication systems are insufficient in delivering sufficient oil to bearings and components.

Innovation Solution

A transmission with a hydrodynamic torque converter and an oil supply system featuring a torque converter drain valve that drains oil from the converter housing into the oil sump, raising the sump level and enhancing splash lubrication, supplemented by immersion lubrication via a pump wheel, ensuring continuous oil supply to bearings even when the input shaft is stationary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional single-speed or multi-speed transmissions are used, then basic power transmission is achieved, but they cannot accommodate the wide range of operating conditions and power requirements of modern vehicles

Engineering Contradiction:
Improveadaptability to operating conditionsVSAvoidtransmission system complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The transmission system employs a variable ratio drive mechanism where the pulley radius ratio can continuously change during operation. The adjustable pulley radius allows the transmission to dynamically adapt its gear ratio to match varying power requirements and operating conditions, replacing fixed-ratio gears with a continuously variable transmission system.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The transmission system integrates multiple functions into a single unified mechanism. The variable ratio drive simultaneously provides continuous variable transmission ratio, torque multiplication, and speed adjustment capabilities that were previously requiring separate components, enabling one system to handle diverse operating conditions across different vehicle types.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Productivity

If fixed gear ratios are used in conventional transmissions, then mechanical simplicity is maintained, but the transmission cannot optimize performance across varying power and speed requirements

Engineering Contradiction:
Improvepower transmission efficiencyVSAvoidtransmission mechanism complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The system replaces static gear ratios with a dynamic variable ratio mechanism. The pulley radius can be adjusted during operation to continuously optimize the transmission ratio, ensuring peak efficiency across the entire operating range rather than being optimized for单一 speed ratio.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The transmission system changes the physical parameter of pulley radius to achieve variable transmission ratios. By varying the effective radius of the pulley, the system continuously adjusts the mechanical advantage and power transmission characteristics to match instantaneous power and speed requirements.

Inventive Principle:
Principle #35Parameter changes

3Adaptability or versatility

If conventional transmissions are designed for specific vehicle types, then optimization for that vehicle type is achieved, but the transmission cannot be adapted to other vehicle applications

Engineering Contradiction:
Improvevehicle type adaptabilityVSAvoidmanufacturing flexibility
Core Design Contradiction:
Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The variable ratio drive mechanism creates a universal transmission system that can serve multiple vehicle types including automobiles, motorcycles, and industrial vehicles. The continuous adjustability of the pulley radius allows the same basic design to be optimized for different power ranges, speed requirements, and torque characteristics of various vehicle applications.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The transmission system separates the power transmission function from the speed ratio selection function. By using a continuously variable pulley system rather than discrete gears, the design eliminates the need for multiple specialized transmission units for different vehicle types, allowing one modular design to serve multiple applications.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP4529596B1Transmission and powertrain
Publication Date: 2026.04.29 ZF FRIEDRICHSHAFEN AG
  • EP4529596B1 patent drawingFigure 1
  • EP4529596B1 patent drawingFigure 2
  • EP4529596B1 patent drawingFigure 3

AI summary

The invention relates to a transmission (1) with a transmission housing (5), a hydrodynamic torque converter (15) which has a converter housing (12) that is at least partly filled with oil, a transmission input shaft (2), a transmission output shaft (3), transmission elements (4) for setting different transmission ratios between the transmission input shaft (2) and the transmission output shaft (3), and an oil supply system, comprising an oil sump (10). The transmission (1) has a converter emptying valve (11) through which oil can be discharged out of the converter housing (12) and into the oil sump (10). The invention additionally relates to powertrain comprising such a transmission (1).