Variable Valve Actuator Low-Pressure Relief Cold Start

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Solution Overview

Problem

Conventional variable valve actuation systems in internal combustion engines face challenges with high viscosity fluids during cold start-ups, leading to delayed engine starting and reduced efficiency due to extended valve timing, and existing solutions like disabling the system result in undesirable emissions and suboptimal efficiency.

Innovation Solution

A valve actuation system with a cam follower, rocker arm, and a variable valve actuator that includes a housing with a plunger, control valve, and low-pressure relief valve, where the control valve is cycled prior to start-up and fluid is released when pressure falls below a predetermined value, allowing the actuator to hold valves open independently of cam lobe motion and improving engine efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the valve actuation system is disabled during cold start-up to prevent timing variations, then valve timing control is maintained, but engine emissions increase and efficiency decreases

Engineering Contradiction:

Improvevalve timing controlVSAvoidemissions

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The system applies preliminary action by cycling the control valve before cold start-up to pre-condition the hydraulic fluid and reduce its viscosity. This preparatory step prevents the harmful effect of high viscosity during actual operation, allowing the VVA system to function properly from cold start-up without disabling it, thereby maintaining valve timing control and reducing emissions simultaneously

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If the control valve is cycled prior to start-up, then fluid viscosity is reduced and valve timing is improved, but system complexity increases

Engineering Contradiction:

Improvevalve timingVSAvoidcontrol valve operation

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The control valve is cycled a predetermined number of times before cold start-up to pre-condition the hydraulic fluid. This preliminary action reduces fluid viscosity in advance, ensuring proper valve timing during engine operation without requiring complex real-time adjustments during cold start-up

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control valve undergoes periodic cycling at a predetermined frequency before start-up to effectively reduce fluid viscosity through repeated motion. This periodic action conditions the hydraulic fluid systematically, improving valve timing reliability while using a simple, repeatable control sequence rather than complex continuous control

Inventive Principle:

Principle #19Periodic action

3Stability of the object's composition

If fluid pressure is maintained during cold start-up, then system stability is improved, but valve timing accuracy deteriorates due to high viscosity

Engineering Contradiction:

Improvefluid pressureVSAvoidvalve timing accuracy

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The control valve is cycled before cold start-up to pre-condition the hydraulic fluid and reduce its viscosity. This preliminary action ensures that when the engine starts, the fluid has already been conditioned and will not cause timing inaccuracies, allowing both pressure stability and timing accuracy to be maintained

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system transitions from a static control valve position to dynamic cycling before start-up, and then returns to controlled operation. This dynamic phase temporarily alters fluid conditions to reduce viscosity, enabling the system to achieve both pressure stability and timing accuracy during subsequent operation

Inventive Principle:

Principle #15Dynamics

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

Facilitates reliable and efficient engine start-up by managing fluid viscosity and valve timing, reducing emissions and improving engine performance by ensuring proper valve closure and compression, even at cold temperatures.

Implementation Method 1

a relief valve configured to automatically open and release fluid from the housing when a pressure inside the chamber is below a predetermined pressure value

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

the operating fluid may have a cold temperature and, thus, a high viscosity. The high viscosity of the fluid increases the amount of time required for the system to operate

Methodology Applied

Scientific EffectFluid viscosity:

Data Source

PatentUS10323579B2Variable valve actuator having low-pressure relief

Publication Date: 2019.06.18 CATERPILLAR INC

AI summary

A valve actuation system is disclosed for an engine. The valve actuation system may have a variable valve actuator that is configured to engage a rocker arm and hold the valve at an open position regardless of motion of a cam lobe. The variable valve actuator may have a housing forming a chamber, a plunger disposed in the chamber, a control valve movable to control a flow of fluid into the chamber, and a relief valve configured to automatically open and release fluid from the housing when a pressure inside the chamber is below a predetermined pressure. The valve actuation system may further have a controller configured to cycle the control valve prior to start-up of the engine and to selectively move the control valve after start-up.