Problem: Gear noise, transmission error (TE)
Goal: Reliable gearbox design, noise reduction

Disturbing transmission noise, vibration and roughness (NVH, Noise Vibration Harshness) seriously reduce driving comfort – especially in vehicles with low-noise electric motors. Noise can be reduced with a reliable transmission design. Therefore, it is necessary to measure and analyze the transmission error.

Gear noise
Gear whine is mainly caused by the tooth profile and tooth vibrations. In the spectrum of the transmission error and the structure or airborne noise, the tooth mesh frequencies with their harmonics and modulation sidebands (caused by the rotational harmonics; e.g. runout) show up.
Gear whine can occur at high and low load, gearbox rattle only at very low or no load (e.g. idling in an combustion engine). Then, the speed fluctuation coming from the engine (non-continuous combustion) causes the unloaded tooth flanks of the gears to lift off. The backlash is passed through with every acceleration and deceleration of the drive shaft (several times per revolution), whereby the teeth of the two gears violently strike against each other.
Other causes of gear noise can be improper gear oil or air bubbles in the oil.

Transmission Error (TE)
The main reason for gear noise are transmission errors (TE) caused by static and elastic deformation under load, unintentional manufacturing deviations and dynamic effects. The transmission error is the difference between the actual position of the output gear and the position it would occupy if the gear set transmitted the rotary motion of the input gear perfectly without error.
In addition to gear noise, the transmission error can cause wear, lower efficiency in the drive train or immediate malfunctions (more about wind turbine gearbox, rolling element gears).

Gearbox measurements
To determine the transmission error, the rotational speeds and angular positions are measured using high-resolution rotary encoders on the input and output shafts. The transmission error is calculated from the measured data. The evaluation is done in the time and order domain. At the same time, structure-borne noise signals are recorded with an accelerometer. The common time base of all measuring channels enables a correlation between transmission error and sound signals.

ROTEC ENGINEERING 
You need support with vibration analysis on engines, gearboxes, and drive trains? Our engineers consult you with extensive know-how in the areas of

• timing gear validation
• valve train optimization
• clutch design
• transmission errors (TE)
• oil supply optimization
• powertrain measurement and optimization
• current and voltage analysis
• application of measurement technology.