Acoustics of gearboxes: only a quiet transmission is a good transmission

A key to quieter gearboxes: the interaction of all components

Gearboxes are complex systems in which many components influence noise behavior. In gear drives, tooth engagement plays a decisive role in acoustics. Take advantage of our expertise in the acoustic design of gear teeth and gearboxes!

This is where our expertise comes into play

We have extensive capabilities for simulation (Simpack, Romax, Ansys) and experimental analysis (modal and operational vibration mode analyses), for example using optical measurement methods (3D scanning laser vibrometry) to record surface accelerations.

How you benefit

We support you in reducing excitation in the tooth engagement of gearboxes. In doing so, we focus not only on the gear teeth, but also on the interaction of all individual parts. We help you to comply with the legally prescribed and customer-specified acoustic limit values for both airborne and structure-borne noise.

How to efficiently evaluate the acoustic behavior of a transmission: Transmission substructuring

Using the substructuring approach, we work with you to analyze the complex structure of the transmission – component by component. With the help of special methods, we can combine simulated (calculated) and experimental (measured) components to achieve a higher quality of prediction.

Our toolbox of methods also allows us to determine critical paths for sound and vibration transmission (transfer path analysis). Our goal is always to identify noise and unwanted vibrations at an early stage and reduce noise to a minimum.

This is where our expertise comes into play

We have detailed knowledge in the field of transfer path analysis and gearbox acoustics. For example, frequency-based substructuring as a method of transfer path analysis enables us to map the dynamic properties of gearboxes using numerical and experimental data.

How you benefit

We optimize the acoustic properties of your product. With our variant analysis, we help you reduce costs and shorten development times. We support you in the development and implementation of digitalization concepts through simple data exchange and data storage. We work with you to create the conditions for developing hybrid models for the use of experimental and numerical data. 

Measurements

• Analysis of gearboxes by extensive vibro-acoustic measurements, for example analysis of operating deflection shapes (ODS)
• Detection of surfaces relevant for noise radiation
• Experimental modal analysis (EMA)
• Model updating

Simulation

• Analysis of gearboxes by multi-physical simulation (finite element simulation – FEM, multibody simulation – MBS, analytical approaches)
• Acoustical optimization considering degree of efficiency and strength
• Excitation prediction and calculations of load distribution considering the elastic behavior of shafts, bearings and gearboxes
• Optimization of gear flank topology for noise reduction and increase of load capacity
• Acoustical optimization of the gear body geometry
• Simulation-based analysis of deviations due to manufacturing and assembly processes
• Calculation of noise radiation of gearboxes
• Development of measures for reducing vibration / noise
• Design of active systems for vibration control (AVC) on relevant transfer paths

Testing options

• Fundamental investigations on high-speed gearboxes for vehicles and industrial applications (spur and helical gears) with arbitrary profiles regarding load and rotational speed
• Quasi-static measurement of transmission errors caused by gear mesh
• Investigation of efficiency by high-precision torque measurement at the input and output sides (power loss)
• Analysis of airborne noise and structure-borne noise at various points of operation (for example by using laser vibrometry or sound intensity mapping with microphone array technologies)

Technical data of test rig for gearboxes

• Maximum rotational speed: 10,000 rpm
• Permanent maximum torque: 1,100 Nm (up to 1,650 rpm)
• Maximum power: approx. 190 kW
• High-precision measuring of angle of rotation
• Flexible setups:
  • Setup 1: test housing with variable center distances for supporting various spur gears with tempered injection lubrication
  • Setup 2: support of an external gearbox
  • Setup 3: support of an entire E-powertrain, including vehicle engine and application of the respective wheel driving torque
• Vehicle energy system for 3-E operation (Setup 3) with battery simulation capacity (200 kW, 8-800 VDC)
• Optional location: semi-anechoic chamber

Gear excitation

The acoustical evaluation of power transmissions requires the detailed analysis of the gear mesh relations considering the dynamic behavior of the surrounding components like bearings, shafts and the gearbox housing. We use modern computing approaches to estimate the impact of these influencing parameters on gear mesh excitation. The objective is the minimization of excitation which, for example, can be achieved by micro geometry optimization of the tooth flanks.

Simulation of manufacturing in gear grinding

Especially in the case of vehicle transmissions, the requirements continuously increase for load capacity and dynamic behavior. A reason for the increasing demands can be found in the use of new electrical drives where no combustion engine exists, i.e. no masking effects occur. Nowadays, the specific application of tooth flank micro geometries is used to improve the load capacity of gears and the acoustic behavior of the gearbox. However, deviations of the target flank form can lead to significant changes in the predicted behavior. These deviations can be caused by the manufacturing process, for example the bias which occurs during the gear grinding process of gears with lead crowning. The use of manufacturing simulations enables the consideration of these deviations to improve the corresponding prediction models.

Numerical calculation of noise radiation

The acoustical properties of transmissions are important quality criteria. For evaluation of the acoustical behavior even within the development process, we use simulation methods considering the dynamic properties of the entire system which includes the excitation and transfer behavior as well as the simulation of the radiated sound. Our objectives are the identification of critical operation points and the structural optimization of the gearbox housing.

End-of-line vehicle correlation

In most cases, the acoustical behavior of vehicle components differs in the final implementation inside the vehicle structure and the end-of-line test rig in production. The differences are caused by the changing mounting conditions. Based on correlation analysis, we develop mathematical methods to characterize the component’s acoustical behavior between test bench and vehicle. By applying specific and statistically verified end-of-line analyses (EOL), we can ensure constant high acoustical quality of gearboxes in various car body variants.