Exhaust Valve Phase Control for Engine Braking Torque

Solution Overview

Problem

Existing combustion engine technologies face challenges in efficiently engine-braking vehicles using compression during the exhaust stroke while minimizing the risk of engine failure and achieving stepless control of braking torque.

Innovation Solution

The solution involves phase-shifting the opening and closing times of the exhaust valves, using a decompression device to open and close them in the transition area between the exhaust and inlet strokes, and controlling the phase shift of the second camshaft to manage compression during the exhaust stroke, thereby reducing the risk of engine failure and allowing stepless control of braking torque.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the exhaust valves are deactivated during the exhaust stroke to reinforce engine braking, then the braking torque is improved, but the pressure in the cylinders becomes excessively high which may cause engine failure

Engineering Contradiction:

Improvebraking torqueVSAvoidengine failure risk

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The exhaust valves are opened periodically during the exhaust stroke at controlled intervals rather than remaining continuously closed. This periodic opening allows pressure relief while maintaining compression during other phases, resolving the contradiction between achieving high braking torque and preventing excessive pressure buildup that could cause engine failure

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The valve timing is made dynamic and adjustable rather than fixed. The control system can vary the opening and closing times of exhaust valves based on operating conditions, allowing optimization of braking torque while preventing excessive pressure buildup that would compromise engine reliability

Inventive Principle:

Principle #15Dynamics

2Reliability

If the exhaust valves are opened frequently during engine braking to reduce cylinder pressure, then the risk of engine failure is reduced, but the braking torque effect is weakened

Engineering Contradiction:

Improveengine failure riskVSAvoidbraking torque

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The exhaust valves are opened periodically during the exhaust stroke at controlled intervals rather than remaining continuously closed. This periodic opening allows pressure relief while maintaining compression during other phases, resolving the contradiction between achieving high braking torque and preventing excessive pressure buildup that could cause engine failure

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

Instead of fully opening exhaust valves continuously (excessive action), the system applies partial opening at specific intervals during the exhaust stroke. This provides sufficient pressure relief to prevent engine failure while maintaining enough compression to preserve effective braking torque

Inventive Principle:

Principle #16Partial or excessive action

3Force

If the number of cylinders with deactivated exhaust valves is increased to control braking torque, then the braking torque control is improved, but the control becomes stepped rather than stepless

Engineering Contradiction:

Improvebraking torque controlVSAvoidstepless control capability

Core Design Contradiction:

ForceVSEase of operation

Solution Approach 1:

The valve timing is made dynamic and adjustable rather than fixed. The control system can vary the opening and closing times of exhaust valves based on operating conditions, allowing optimization of braking torque while preventing excessive pressure buildup that would compromise engine reliability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Instead of changing the number of affected cylinders (discrete steps), the system changes the timing parameters (phase angles) of valve opening and closing. This continuous parameter adjustment enables stepless control of braking torque while maintaining precise control capability

Inventive Principle:

Principle #35Parameter changes

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 approach effectively reduces the risk of engine failure and enables stepless control of braking torque during engine braking, enhancing driving comfort by utilizing compression during the exhaust stroke.

Implementation Method 1

the pressure of the air compressed in the cylinders must be reduced at the end of each compression. This is carried out with a decompression device that controls the exhaust valves, so that they are opened at the end of the compression stroke and at the end of the expansion stroke

Methodology Applied

Scientific EffectPressure reduction: Depressurisation

Implementation Method 2

When the air in the cylinders is compressed during the compression stroke, the pistons will, via the rods, exert a braking torque on the crankshaft

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS10323551B2Combustion engine, vehicle comprising the combustion engine and method for controlling the combustion engine

Publication Date: 2019.06.18 SCANIA CV AB

AI summary

A method to control a four-stroke combustion engine, comprising at least one cylinder; a piston arranged in each cylinder; at least one inlet valve arranged in each cylinder which is connected with an inlet system; at least one first camshaft which controls each inlet valve; at least one exhaust valve arranged in each cylinder which is connected with an exhaust system; at least one second camshaft which controls each exhaust valve; and a crankshaft which controls each camshaft. At least one phase-shifting device is arranged between the crankshaft and the second camshaft, to phase-shift the second camshaft in relation to the crankshaft to a state, where the exhaust valve is controlled in such a way, that it is opened during the expansion stroke of the engine and closed during the exhaust stroke of the engine, to achieve engine braking through compression in the cylinders during the exhaust stroke.