The document discusses using eddy-current displacement sensors to measure the thickness of the oil film between a cylinder wall and piston rings in an internal combustion engine. The sensors are installed behind a protective layer in the cylinder wall and can measure the spacing between the piston rings and cylinder wall with high temporal and spatial resolution while withstanding the high temperatures and harsh environment of the engine compartment. The selected eddy-current sensor system includes temperature monitoring and compensation to reliably collect oil film thickness measurements under realistic engine operating conditions.

1. A133_d
Eddy-current displacement sensors
eddyNCDT
Oil film thickness measurement in an internal combustion engine
Included in the objectives of current engine The sensors are built into the cylinder wall behind a
development are minimization of pollutants and the protective layer. The protective layer both thermally
reduction of oil consumption. In order to be able to insulates the sensor and also replicates the contour
take measures in achieving these objectives, then of the cylinder wall. The spacing of the piston rings to
along with a number of other factors, it is very the cylinder wall is measured. For the measurement it
important to obtain knowledge of the behavior and is assumed that the gap between the cylinder wall
the thickness of the oil film between the cylinder wall and the piston rings is completely filled with oil.
and piston or piston rings In this respect the upper A measurement system with a high temporal
third of the cylinder bore is of particular interest. To resolution (0.1° / crankshaft rotation) and a very high
obtain reliable measurement results which can be of spatial resolution (~ 1 µm) is required for the
use in development for large-scale production, tests measurements. It must not be affected by oil and
must be conducted on real engines and under must be tolerant of contamination.
realistic operation conditions. The sensors are subjected to high temperatures
(short-term up to 200°C) and, to prevent damage, are
temperature-monitored. Due to their very small
construction, the effect on the tribological system
between the piston ring and cylinder wall is very
slight.
The subminiature displacement sensor EU05/65
can be integrated even under the most arduous
of conditions - here in the running engine compartment
and it supplies highly accurate measurement results.

2. Applikation
Measurement system performance data
- Measurement range: 0.5 mm
- Resolution: better than 1 µm
- Bandwidth: 100 kHz
Ambient conditions
- Temperatures up to 200°C on the sensor
- Oil, fuel, air mixture
- Combustion gases
- Vibration, high pressures
System configuration
3 x DT3300 multifunction controller
3 x additional temperature output
3 x miniature sensor EU05/180(65)
3 x EA3200-EU05/180(65)M-EC3,25 adaptation board
3 x E3000 TCS/20°C/180°C/TA special temperature
compensation
1 x PS300/12/5 power supply
3 x EC3/2 sensor cable
2 x PSC30 supply/synchronisation cable
3 x SCA3/5 signal cablekabel
Reasons for the system selection
- Non-contacting
- Free of wear With its rugged ceramic cap
- Not affected by fuel, oil and exhaust fumes the subminiature displacement
- High temperature resistance sensor EU05/65 is predestined for
- Pressure-proof applications in the engine compartment.
- Very small sensor design
- Very accurate
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