2. Piezo-rubber applicable to load sensors, inter alia

• A production method was developed to increase the piezoelectric performance of piezoelectric-rubber.
• Its applicability to load and force detection sensors, inter alia, was verified.

Piezoelectric materials are used in vibration reducing and sensor devices. However, existing piezoelectric-ceramics are fragile and not easily moulded. Consequently, it is expected that rubber containing particles of piezoelectric-ceramics (piezoelectric-rubber) could be applied for use in complex shape’s areas and that added impact force. However, piezoelectric performance i.e. conversion of force into electricity, of piezoelectric rubber produced by existing production methods is insufficient. Therefore, a new production method was proposed to increase the piezoelectric performance by testing different types of rubber, varying the quantity of particles of piezoelectric-ceramics, particle size and mixing methods. As a result, a new piezoelectric-rubber was developed retaining the flexibility as rubber but with a more than quadrupled piezoelectric performance (Fig 1, Table 1). The outcome of investigations into possible applications for this new piezoelectric-rubber showed that it was suited for use in sensors. Its aptness for use as a load sensor, because of the output electric charge from the piezoelectric-rubber and exerted load has high linearity. (Fig 2). Furthermore, the piezoelectric-rubber positioned under sleepers at rail joints did not break with passing trains, and produced a voltage, confirming that it can be employed in force sensors for impulsive force (Fig 3).

The improvement in piezoelectric performance indicates that in future, this piezoelectric-rubber may be utilized in vibration reducing materials.

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  Fig. 1 External aspect of the piezo-rubber
• Table 1 Piezoelectric performance of the piezo-rubber
  

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  Fig. 2 Correlation between the load and electric charge produced
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  Fig. 3 Electric charge produced in sensor under passing train