Normally Closed Conical Clutch Drivetrain for Electric Vehicles

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Solution Overview

Problem

Electrically driven vehicles face inefficiencies in drivetrain energy usage due to the need for energy in shifting and frictionally engaged gears, limiting their range due to the limited capacity of traction batteries.

Innovation Solution

A drivetrain with a normally closed clutch using conical friction elements that reduces friction surfaces and actuating forces, allowing for a mechanical load amplification and energy-efficient operation, particularly suitable for electric vehicles with few gears, where gear shifting is infrequent.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a normally open clutch is used in a multispeed gearbox, then gear shifting can be achieved, but energy is consumed for actuating the clutch and maintaining the closed state

Engineering Contradiction:

Improvegear shifting capabilityVSAvoidenergy consumption for clutch actuation

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent inverts the conventional clutch design by using a normally closed clutch instead of a normally open clutch. The clutch is closed by default (engaged state) and opened only when actuated, reversing the typical operation mode. This allows the drivetrain to remain in the energy-efficient closed state during normal operation, with actuation energy required only during gear shifts rather than continuously.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the operational parameters of the clutch by employing conical friction elements with specific geometric parameters (cone angle, friction surface area). These parameter changes enable mechanical load amplification, allowing the clutch to maintain the closed state with minimal holding force while still achieving effective torque transmission when engaged.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional friction elements are used in the clutch, then sufficient friction surface area is available, but large actuating forces and drag torques are required

Engineering Contradiction:

Improvefriction transmission capabilityVSAvoidactuating force

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent employs conical (curved) friction elements instead of flat friction surfaces. The conical geometry creates a mechanical load amplification effect where the axial actuating force is amplified into a larger radial clamping force through the cone angle. This curvature-based mechanism allows sufficient friction force to be generated with smaller actuating forces compared to conventional flat friction surfaces.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent optimizes the geometric parameters of the friction elements, specifically the cone angle and friction surface dimensions. By carefully selecting these parameters, the design achieves an optimal balance between friction transmission capability and actuating force requirements, reducing the force needed to actuate the clutch while maintaining reliable torque transmission.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If a multispeed gearbox is used to maximize battery capacity utilization, then operating efficiency is improved, but energy is lost during gear shifting operations

Engineering Contradiction:

Improvebattery utilization efficiencyVSAvoidenergy loss during gear shifting

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

By inverting the clutch operation mode to normally closed, the system minimizes the time the clutch disc is disengaged during gear shifts. The clutch remains engaged (closed) during normal operation, and only opens briefly when actuated for gear changes. This reduces the duration of energy loss during shifting operations compared to normally open clutches that require continuous actuation to maintain engagement.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The clutch is pre-positioned in the closed (engaged) state, which is the desired operational state for efficient power transmission. This preliminary positioning eliminates the need for continuous actuation signals and reduces the frequency and duration of actuation events during normal driving, thereby minimizing energy loss during gear shifting operations.

Inventive Principle:

Principle #10Preliminary action

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 significantly reduces energy consumption, allowing for a longer range in electric vehicles by minimizing drag torque and holding forces, and can be integrated with a gearbox for enhanced driving dynamics and comfort.

Implementation Method 1

a friction element (28, 38, 40) which is formed in a conical shape (α) and rests in a torque-transmitting fashion in an engaged state of the clutch (22) against a further friction element (38, 28, 40)

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11015658B2Drivetrain of an electrically driven vehicle and electrically driven vehicle

Publication Date: 2021.05.25 HOERBIGER ANTRIEBSTECHNIK HOLDING GMBH

AI summary

Electrically driven vehicle including a drivetrain with an electric motor which forms the drive of the vehicle, and a frictionally engaging clutch. The clutch is a normally closed clutch with conical friction elements, which rest against each other in pairs in a closed position and transmit torque.