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Under Tension: PMI120-F90 Inductive Proximity Sensor

Monitors the correct mounting of motor chain tensioners

Numerous factors determine the life span of today's motors. In addition to light-running oils and clean-burning gas, mechanical parts like motor chains are responsible for a long life-span of modern motors. Every motor has normal mechanical wear. Keeping that mechanical wear to a minimum extends the life of the motor.

Motor control chains often serve as a link between the crankshaft and the camshaft of a drive. Motor chains that are tightened regularly work flawlessly up to a maximum abrasion elongation of two percent. If the motor chain is not tightened, the return strand starts to sag and the chain takes on an unsteady run that promotes abrasion. Damage to the motor will occur if the chain lacks the correct degree of tension.

Motor chains with a minimum wear can greatly extend motor life-span. The company iwis, a chain manufacturer in Munich, Germany produces high-precision chains and is a supplier to many automotive manufacturers.


An assembly line for 17 different types of chain tensioners must be designed (see figure 1).On this assembly line, robots assemble 17 different chain tighteners of various lengths and diameters for the automotive industry. This is a fully automated process. The testing tools for the assembly need to be flexible and must reliably detect the different sizes of motor chain tensioners.

Fig. 1: Assembly line for motor chain tensioners


The housing lengths and diameters are reliably evaluated using the PMI120-F90-IE8-V15 inductive path measurement system from Pepperl+Fuchs. The identified size is forwarded to the variable claw of the robot, which then inserts the matching spring and tappet into the sleeve and compresses everything.

During production the assembly is closely monitored and controlled. The Pepperl+Fuchs actuator is mounted to a special control unit (see figure 2). This control unit uses a defined pressure to identify the spring tension of the tappet of the motor chain tensioner. Under this pressure the tappet sinks into the housing. The offset is measured using a PMI120-F90-IE8-V15 inductive proximity sensor on the control unit.

Fig. 2: Unit for controlling the spring tension with PMI120-F90-IE8-V15 inductive path measurement system and BT-F90-W actuator

Customer benefits

With our multi-purpose path measurement systems, a variety of motor chain tensioners can be assembled within quickly. The changeover time for a new chain tensioner is minimal.