Bimorph actuators

Bimorphs are designed as double layer elements. In operation, one of the layers extends while the other compresses. As a result, it courses the element to bend. Piezo bimorphs is a class of electromechanical transducers converting an electrical voltage into a mechanical displacement and vice versa. These types of actuators provide the value of a bending displacement much more than planar ones. As compared with stack actuators, bimorphs have higher stroke value but develop lower force and have lower resonance frequency.

APPLICATIONS

Scanning systems in laser technique;

Micro positioning devices for looms and Braille reading systems;

Medical sensors ;

Fans for local cooling of electronic units ;

Sensory commutating devices for ON/OFF switching electrical contacts.

Piezo bimorph design

Dimensions

Type Dimensions (mm) Mass (g)

Length (L) Width (W) Thickness (T)

40 12 0,6 1,8

55 2 0,75 6,0

35 2,5 0,6 0,5

35 2,5 0,6 0,5

100 22 1,0 17,0

Connection diagram:

a) bimorph plates are connected in parallel
b) bimorph plates are connected in series.
Piezo bimorphs connected in series are made at a customer request.

Essential characteristics of actuators connected in parallel

Type Capacitance (nF) Driving voltage (V) Free deflection (mm) Operating length (mm) Blocking force (N)

27-35 ±80 ±0,55 35 0,35

4,4-5,2 ±200 ±0,5 48 0,02

3-4 ±150 ±0,58 28,5 0,12

3-4 ±150 28,5

65-80 ±80 ±0,7 85 0,3

Bimorph capacitance is measured between the external electrodes. Characteristics for bimorph ЭП-9-47-ПлБ-002 are shown for its partial connection.
Notes:
1. Bimorphs and have no pad.

2. Bimorphs has tinned contacts areas. Free displacement and blocking force are not checked at the acceptance test for this type of bimorph.

When bimorph plates are connected in series, the actuator capacitance becomes 4 times less. In order to get the other characteristics shown in the table, the driving voltage should be increased by 2 times.

Typical relation between the force developed by piezo bimorph and the displacement.

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