Valve train analysis | Optimisation of valve control ENGINEERING

Problem: Higher Efficiency requirements / Cam wear

Goal: Variable, robust valve control with optimized valve timing

Valve train analysis - optimization of valve actuation

High efficiency, reliability, and performance are key factors in the development of modern combustion engines.

A crucial factor in increasing the efficiency and wear resistance of internal combustion engines is the mechanical and thermodynamic optimization of valve actuation.

In order to reliably evaluate the opening and closing behavior, measurements and calculations of the three central variables are required:

Valve stroke

Valve velocity

Valve acceleration

Depending on the purpose of the measurement, two different measurement methods and procedures are used. The evaluation of the measurement data is independent of the measurement procedure and is performed using the same module in the Rotec software.

Measurement methods and procedures

Measurements on the motored cylinder head component

-Measurement of valve lift using simply installed optical sensors located outside the cylinder head

-Functional testing of the theoretical valve train design or individual component prototypes with regard to mechanical and kinematic aspects

Measurements on the fired engine

-Measurement of valve lift using highly integrated MR sensors on the valve guide

-Validation of valve timing and valve dynamics on a close-to-production full engine

-Measurement under actual oil and temperature conditions and torsional vibration behavior

Analysis of valve actuation

The analysis of the valve train is based on analog measured signals of the valve lift sensor (SIN, COS). These signals are evaluated in relation to the crankshaft or camshaft position. The focus is particularly on the dynamic opening and closing behavior of the valve (e.g., closing speed) in relation to engine speed.

In addition, the RAS software offers a wide range of analysis tools. For example, it is possible to automatically evaluate valve closing behavior, valve overlap, lift loss, and lift-off. Other analog measured values such as spring and cam forces can also be integrated into the valve dynamics analysis.

Advantages of testing the valve train on a fired engine

Measurements taken on a fired engine offer significant advantages over measurements taken on a motored cylinder head component:

The actual torsional vibration behavior of the engine is included in the valve dynamics analysis (e.g., excitation from combustion; function of the timing drive; control accuracy of the camshaft phasers).

Investigation of complex interactions between mechanical components, the electronic engine control system (ECU data), and peripheral conditions (e.g., charge and exhaust backpressure).

Testing under real operating conditions with actual oil and temperature conditions.

Cost savings, since there is no need to build realistic component test rigs.

“Valve Train” software module - automated analysis

Manually evaluating dynamic parameters (e.g., valve closing velocity or the cam angles of dynamic opening and closing) is very time-consuming when dealing with variable valve actuation and many engine operating points and ties up valuable development resources. The “Valve Train” software module enables the automated evaluation of measurements at constant speeds as well as during speed ramps. This reduces the need for extensive measurement series that require long test bench capacity and speeds up the evaluation process. The software module can be used to evaluate and display many application-specific parameters:

Valve lift, velocity, and acceleration

Opening intervals or specific angular positions (e.g., for dynamic opening and closing)

Lift loss or lift comparison to the kinematic lift curve

Lift area and valve overlap

Lift-off and valve bounce

Closing velocity

Mechanical stress on components (e.g., surface stress in the tappet drive)

Analog values, such as parallel measured spring and cam forces

Min./max. values from valve lift, from derived curves and from parallel measured signals

The software evaluates the behavior of all opening and closing cycles recorded in the measurement. The results can be visualized by creating 2D and 3D graph plots based on rotational speed, angular position, and time. Individual cycles with signal errors can also be automatically detected and excluded from the analysis. Using the parallel recorded speed signals from the crankshaft or camshaft, it is also possible to determine the effects of torsional vibration behavior in the timing drive and valve train on the valve dynamics.

Valve dynamics