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Measurements on the valve train / of valve train dynamics

Problem: Increased pollutant emissions

Goal: Efficient and powerful combustion engine

The development of efficient and powerful combustion engines is one of the main goals of automotive development. In this context, valve timing is a decisive element in the optimization of thermodynamics and thus in the efficiency of combustion engines.

The analysis of valve timing is carried out based on the measured, analog variables valve lift or valve speed in relation to the camshaft position. Here, the focus is particularly on the dynamic opening and closing behavior of the valve (e.g. closing velocity) as a function of the engine speed.

MEASUREMENT ON THE MOTORED CYLINDER HEAD AND FIRED ENGINE

To be able to reliably assess the opening and closing behavior, measurements and calculations of the three measured variables valve lift, valve speed and valve acceleration are necessary. Two different measuring methods can be used for this purpose: measurement on the motored cylinder head using a laser vibrometer and in fired operation using magneto resistive (MR) sensor technology. The measured variable valve lift can be determined both on the motored cylinder head and in fired operation using MR sensors. For this purpose, the speed signals and angular positions at the camshaft drive system are recorded. In the first step, the torsional vibration behavior of the camshafts can be derived from this. The measured data from speeds and valve lift can then be evaluated in the valve train software module. This allows variables such as valve speed and acceleration, opening and closing behavior, lift loss, resonance, and stress behavior to be automatically evaluated and graphically displayed

ADVANTAGES OF VALVE TRAIN TESTS ON THE FIRED ENGINE

Measurements on the fired engine have advantages over those on the towed cylinder head. For example, you can also investigate the effects of the gas forces under real torsional vibration and thermal expansion behaviour of the camshafts or the cylinder head on the fired engine. These effects are becoming more and more important with increasing charging and exhaust gas backpressures (particle filters).

Another advantage is that the costs for the construction of a sometimes very complex test part carrier can be saved.

SOFTWARE MODULE FOR AUTOMATED EVALUATION OF DYNAMIC PARAMETERS

The manual evaluation of dynamic parameters, such as the valve touchdown speed or the time of dynamic opening and closing, is very laborious with a large number of different operating points and takes up a lot of your working time.

The software module “Valve Train” was developed with the aim of performing these evaluations automatically. This not only reduces the evaluation time, but also the size of the test matrix and, accordingly, the utilisation time of the test bench. Instead of performing measurements at constant, discrete speeds, you can now perform speed ramps.

With the software module, the following parameters, among others, can be evaluated: Angular position of dynamic opening and closing, touchdown speed, stroke loss, lift-off, valve bounce, mechanical load on the components (surface pressure during cup drive), stroke area and valve overlap.

The software evaluates progressions of several signals (stroke, speed and acceleration) and automatically displays them comparably for each cycle with the corresponding result parameters. For some analyses, additional evaluation methods are stored that are ready-made for the specialised user (e.g. touchdown speed).

In addition to the multitude of analysis options, you can automatically record cycles with signal errors and remove them from the evaluations.

The application of the measurement technology as well as on-site measurements, analysis and evaluation can be completely provided and carried out by ROTEC ENGINEERING.

ROTEC ENGINEERING carries out tests on electric as well as hydraulic camshaft phasers. Thus, interactions between valve actuation and timing are recorded or the functional behaviour of the camshaft phasers is explicitly analysed.

Measurement on
motored cylinder head

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  • Measurement of valve stroke and valve speed with laser vibrometer
  • Camshaft position measurement with rotary encoder
  • Classic measuring method with high-precision measurement signals

Measurement on
fired engine

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  • Valve stroke measurement with prepared valve stem and MR sensor technology
  • Deviation from the laser vibrometer < 20 µm
  • Special software solution for calculating the stroke signals from the sensor signals (SIN, COS)

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