Task:
This Gearbox test bench is used to determine and test the control characteristics of automatic transmissions with hydraulic and electronic control. For this purpose, the test transmissions are accelerated at ambient temperatures of -40 °C to +50 °C under partial load and dynamically run through certain areas of the entire control or shift characteristic map within the test program in order to assess the function of the transmission's control system.
Both continuously variable automatic transmissions as well as stepped automatic transmissions for front and rear-wheel drive and special transmissions are tested.
The test stand should be able to be operated in the following modes:
- Manual operation
- Static automatic mode
- Dynamic automatic mode
- Driving simulation
Static and dynamic test sequences of the transmission test bench
In the static operating modes, the test stand can be operated with torque and speed control on both the drive and the output.
In the "Driving simulation" operating mode, the motor torques are specified to the drive system by the process computer. The parameters for the output system (rolling resistance, air resistance, acceleration resistance, gradient resistance, additional static resistance) are calculated by the driving simulation computer.
Road data and environmental data in the form of speed and torque values are transferred from the test bench to the test specimen. Reproducible tests with uphill and downhill driving, kick-down acceleration, shifting cycles at different transmission temperatures etc. can thus be simulated on the test bench without having to install the test specimen in a car for the otherwise necessary road test.
The test stand also has a start-up and shutdown routine to protect the test specimen from damage.
Solution:
Drive unit
In order to achieve the high speed/torque dynamics with low inertia, the drive is equipped with secondary controlled hydraulic drives. The speed of the hydraulic motor is translated to the required test bench speed by means of a backlash-free high-performance chain drive.
Output unit
The output unit has the same basic design as the drive unit, but the output torque is max. 360 Nm. In order to be able to compensate for the offset of the output shafts for the different gearboxes, the output unit is mounted on a stable lifting table with cross slide.
A safety toothed clutch is installed in the drive and output train to ensure that the test stand is switched off quickly in the event of an EMERGENCY STOP or test specimen defect.
The drive torque is determined using a type T 32 torque measuring shaft (HBM). In order to achieve the greatest possible rigidity with low inertia of the drive, the connection between the drive unit and the test specimen is made with a carbon fiber reinforced plastic tube.
For testing test specimens with front-wheel drive, the two side shafts are each routed via an intermediate gearbox back to a common drive shaft to the output drive train.
