Valve train analysis | Optimisation of valve control ENGINEERING

Valve train analysis - optimisation of valve control

The development of efficient and powerful combustion engines is one of the main goals of modern automotive development.

Valve control is a key element in optimising the thermodynamics and thus increasing the efficiency of combustion engines.

Measurements on the towed cylinder head

Measurement of valve lift and valve speed with laser vibrometer

Camshaft position measurement with rotary encoder

Classic measurement method with high-precision measurement signals

Measurements on the fired engine

Valve lift measurement using valve stem MR sensors

Deviation from the laser vibrometer < 20 µm

Special software solution for calculating the stroke signals from the sensor signals (SIN, COS)

Analysing the valve control

The analysis of the valve timing is based on the measured analogue signals of the valve lift (SIN, COS). These are recorded as a function of the camshaft position. The focus here is particularly on the dynamic opening and closing behaviour of the valve (e.g. closing speed) as a function of the engine speed.

In addition, a variety of analysis tools are available in the RAS software. For example, the touchdown behaviour, valve overlap, lift-off and much more can be evaluated automatically.

Advantages of valve train testing on the fuelled engine

Measurements on the fired engine offer significant advantages over measurements on the non-fired cylinder head:

Investigation of throttle force effects under real torsional vibration and thermal expansion behaviour of camshaft and cylinder head

Real operating conditions, especially with increasing charge and exhaust back pressures (e.g. due to particulate filters)

Cost savings, as there is no need to set up complex test vehicles

Valve train" software module - Automated evaluation

The manual evaluation of dynamic parameters (e.g. valve touchdown speed or times of dynamic opening and closing) is time-consuming at many operating points and ties up valuable development resources.

The Valve train software module was developed to carry out these analyses automatically.

This enables reduced evaluation time improved utilisation time of the test bench.

Instead of measurements at constant or discrete speeds, testing can be carried out with speed ramps.

Measurements on a driven or fired cylinder head

In order to be able to reliably assess the opening and closing behaviour, measurements and calculations of the three central variables are required:

Valve lift
Valve speed
Valve acceleration

Two measuring methods are used for this:

Measurement on the motorised cylinder head with a laser vibrometer
Measurement in fired operation with magnetoresistive (MR) sensor technology from Sensitec.

The variable valve lift can be determined in both types of measurement.
In addition, speed signals and angular positions on the camshaft drive system are recorded in order to derive the torsional vibration behaviour of the camshafts.

The speed and valve lift data is obtained and then analysed in the Valve train software module.

This enables automatic and graphical visualisation:

Valve speed and acceleration
Opening and closing behaviour
Stroke loss
Resonance and stress behaviour

Analysable parameters

The software module can be used to automatically analyse the following parameters, among others:

Angular position of dynamic opening and closing
Touchdown speed
Stroke loss
Lift-off and valve bounce Mechanical load on the components (e.g. surface pressure during cup drive)
Stroke area and valve overlap

The software analyses the curves of several signals - valve stroke, speed and acceleration - cyclically and displays them comparably with the associated result parameters. Predefined analysis methods are stored for specialised users (e.g. for determining the touchdown speed).

In addition, cycles with signal errors can be automatically recognised and excluded from the analysis.

Valve dynamics