Measurements on the valve train / of valve train dynamics

Goal: economical and powerful combustion engine

The analysis of the valve train is carried out on the basis of the measured, analogue variables valve lift or valve speed in relation to the camshaft position. Due to the increasing complexity of valve actuation, it is a decisive element in the optimisation of thermodynamics and thus in the development of economical and powerful combustion engines. In particular, the dynamic opening and closing behaviour of the valve (e.g. touchdown speed) as a function of the engine speed is the focus here.

MEASUREMENTS ON THE MOTORED CYLINDER HEAD AND FIRED ENGINE

In order to be able to reliably assess the opening and closing behaviour, the measurements and calculations of the three measured variables valve lift, speed and acceleration are necessary. For this purpose, you can use two different measuring methods: measurement on the towed cylinder head by means of a laser vibrometer and in fired operation by means of magnetoresistive sensor technology. The measured variable valve lift can be determined both on the towed cylinder head and in fired operation using magnetoresistive sensors. For this purpose, the speed signals and angular positions on the camshaft drive system are recorded. In the first step, the torsional vibration behaviour of the camshafts can be derived from this. The measured data from speeds and valve lift can then be fed into a special software tool for valve trains. This allows variables such as valve speed and acceleration, opening and closing behaviour, stroke loss, resonance and stress behaviour 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.

Keywords: Valve lift, valve speed, valve acceleration, motored cylinder head, fired engine, gas forces, valve touchdown speed, dynamic opening and closing, touchdown speed, stroke loss, lift-off, valve bounce, mechanical load, stroke area, valve overlap

Measurements on mo-
tored cylinder head

Akkordeon Nr. 1

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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

Comparison Valve train MR sensor/laser sensor

Measurements on
fired engine

Akkordeon Nr. 1

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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)