Valve Actuation Mechanism with Reset Cam Profile for Engine Brake

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Solution Overview

Problem

Existing engine brake systems for internal combustion engines in automotive vehicles face challenges in efficiently resetting the activation piston to its initial position, particularly when using single valve brake technology, leading to valve overlapping and reduced engine brake function efficiency.

Innovation Solution

A valve actuation mechanism that incorporates a reset cam profile and reset valve, allowing independent control of the reset valve movement via a cam follower, ensuring the fluid circuit is opened when the piston is pushed back by the spring force, reducing valve overlapping and improving reset functionality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single control valve is used for multiple cylinders to direct pressurized control fluid, then the device complexity is reduced, but the reliability of the reset function deteriorates when retraction is needed for a period inferior to one revolution of the camshaft

Engineering Contradiction:

Improvecontrol valve quantityVSAvoidreset function reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The invention divides the control system into individual control valves for each rocker/cylinder, allowing independent control of the activation piston in each cylinder. This segmentation enables reliable reset timing for each cylinder independently, solving the problem where a single shared control valve cannot provide timely reset for multiple cylinders operating at different phases.

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If the check valve is forced open to allow control fluid escape, then the piston can be reset, but valve overlapping occurs causing negative airflow

Engineering Contradiction:

Improvepiston reset capabilityVSAvoidvalve overlapping and negative airflow

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The invention opens the reset valve in advance during the valve closing phase, before the piston needs to retract. This preliminary action ensures that control fluid can escape gradually, allowing the piston to reset at the precise moment when valves are closing, thereby preventing valve overlapping while maintaining reliable reset functionality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The reset valve operation is synchronized with the camshaft position and valve cycle through a feedback mechanism. The control system monitors the valve phase and timing, automatically opening the reset valve at the optimal moment when valves are closing, thus coordinating piston retraction with valve events to prevent harmful overlapping while ensuring timely reset.

Inventive Principle:

Principle #23Feedback

3Duration of action of stationary object

If the activation piston remains in the second position for extended periods, then the engine brake function is maintained, but the risk of valve overlapping increases during reset

Engineering Contradiction:

Improveengine brake durationVSAvoidvalve timing precision

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The reset valve is opened in advance during the valve closing phase, preparing the control fluid path for piston retraction. This preliminary action ensures that when the piston needs to reset after prolonged engine brake operation, the control fluid can escape immediately without delay, maintaining precise valve timing even after extended periods in the second position.

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

The mechanism effectively reduces valve overlapping between intake and exhaust valves, enhancing the engine brake function by ensuring precise timing and synchronization of valve closures, thereby improving the engine's efficiency and reliability.

Implementation Method 1

each reset valve comprises a cam follower, adapted to drive the reset valve as a function of the movement of the reset profile

Methodology Applied

Scientific EffectCam mechanism: Cam

Implementation Method 2

movable with respect to the rocker under action of a fluid pressure raise in a chamber

Methodology Applied

Scientific EffectFluid pressure: Pressure Increase

Implementation Method 3

when the piston is pushed back by the spring force

Methodology Applied

Scientific EffectSpring force: Spring

Data Source

PatentUS9163566B2Valve actuation mechanism and automotive vehicle comprising such a valve actuation mechanism

Publication Date: 2015.10.20 VOLVO TRUCK CORP

AI summary

A valve actuation mechanism includes rockers moved by a camshaft, each rocker being adapted to exert a valve opening force on at least a portion of a valve opening actuator of each cylinder, via an activation piston, housed in a bore of the rocker and movable with respect to the rocker under action of a fluid pressure raise in a chamber fluidly linked to the bore, from a first position to a second position, in which a cam follower of the rocker reads at least one auxiliary cam sector of a cam of the camshaft so as to perform an engine operating function. Each rocker includes a reset valve adapted to reduce fluid pressure in the chamber. The valve actuation mechanism includes, for each rocker, a reset cam profile adapted to open the reset valve when the activation piston has to be moved from its second position to its first position, and each reset valve includes a cam follower adapted to drive the reset valve as a function of the movement of the reset profile.