Electromechanical microsystem for moving a mechanical part in two opposite directions
The disclosure relates to a microelectromechanical system comprising a support and an actuator comprising a drive module comprising: a fixed drive portion, mounted fixedly on the support, and comprising a fixed comb with fingers, and a movable drive portion, mounted movably relative to the support, and comprising a movable comb with fingers, a latching mechanism movable between an initial unlatched configuration and a final latched configuration. The movable comb is arranged facing the fixed comb so that when the latching mechanism is in the initial unlatched configuration, the fingers of the movable comb are not engaged between the fingers of the fixed comb, and when the latching mechanism is in the final latched configuration, the fingers of the movable comb are engaged between the fingers of the fixed comb and the latching mechanism prevents disengagement of the fingers of the movable comb from between the fingers of the fixed comb.
1 . A microelectromechanical system, comprising a support and an actuator, the actuator comprising a drive module comprising:
a fixed drive portion, mounted fixedly on the support, and comprising a fixed comb with fingers,
a movable drive portion mounted movably relative to the support, and comprising a movable comb with fingers,
a suspension connecting the movable drive portion to the support,
a stop, and
a latching mechanism comprising a tappet, a flexible beam connecting the tappet to the support, at least one first locking lug connected to the stop and a second locking lug connected to the support, the latching mechanism being movable between an initial unlatched configuration wherein the second locking lug is not engaged with the first locking lug and a final latched configuration wherein the second locking lug is engaged with the first locking lug,
wherein the movable drive portion is able to be moved relative to the fixed drive portion in a first direction, as a result of an electrostatic force generated by the application of a nonzero voltage between the fixed drive portion and the movable drive portion, the movement of the movable drive portion relative to the fixed drive portion causing an elastic deformation of the suspension, and the movable drive portion is able to be moved relative to the fixed drive portion in a second direction, opposite to the first direction, when the applied voltage decreases, as a result of an elastic return force generated by the suspension having been deformed elastically, the elastic return force being opposed to the electrostatic force,
wherein the tappet is arranged so that when the movable drive portion is moved for the first time relative to the fixed drive portion in the first direction, the movable drive portion pushes the tappet in the first direction, which has the effect of moving the stop in the first direction, causing an elastic deformation of the flexible beam and engaging the first locking lug with the second locking lug, and
wherein the movable comb is arranged facing the fixed comb so that when the latching mechanism is in the initial unlatched configuration, the fingers of the movable comb are not engaged between the fingers of the fixed comb, and once the latching mechanism is in the final latched configuration, the fingers of the movable comb are engaged between the fingers of the fixed comb and the stop holds the first suspension in a permanent state of deformation, preventing disengagement of the fingers of the movable comb from between the fingers of the fixed comb while allowing movement of the movable drive portion relative to the fixed drive portion throughout the subsequent operation of the actuator.
2 . The microsystem according to claim 1 , wherein when the latching mechanism is in the initial unlatched configuration, the fingers of the movable comb are spaced from the fingers of the fixed comb by a first spacing, and when the latching mechanism is in the final latched configuration, the fingers of the movable comb are spaced from the fingers of the fixed comb by a second spacing less than the first spacing.
3 . The microsystem according to one of claim 2 , wherein the second spacing is comprised between 0.1 and 5 μm, preferably comprised between 1 and 3 μm.
4 . The microsystem according to one of claim 2 , wherein a ratio between a height of the fingers and the second spacing between the fingers of the fixed comb and the fingers of the movable comb is comprised between 50 and 400, preferably comprised between 70 and 150.
5 . The microsystem according to one of claim 1 , wherein once the latching mechanism is in the final latched configuration, the stop prevents movement of the first movable portion tending to disengage the fingers of the movable comb from between the fingers of the fixed comb.
6 . The microsystem according to claim 1 , wherein once the first locking lug is engaged with the second locking lug, the first locking lug and the second locking lug prevent a return of the latching mechanism to the initial unlatched configuration.
7 . A microelectromechanical system, comprising a support and an actuator, the actuator comprising a drive module comprising:
a fixed drive portion, mounted fixedly on the support, and comprising a fixed comb with fingers,
a movable drive portion mounted movably relative to the support, and comprising a movable comb with fingers,
a suspension connecting the movable drive portion to the support,
a stop, and
a latching mechanism comprising a tappet, a flexible beam connecting the tappet to the support, at least one first locking lug connected to the stop and a second locking lug connected to the support, the latching mechanism being movable between an initial unlatched configuration wherein the second locking lug is not engaged with the first locking lug and a final latched configuration wherein the second locking lug is engaged with the first locking lug,
wherein the tappet is arranged so that when the movable drive portion is moved for the first time relative to the fixed drive portion in a first direction, the movable drive portion pushes the tappet in the first direction, which has the effect of moving the stop in the first direction, causing an elastic deformation of the flexible beam and engaging the first locking lug with the second locking lug,
wherein the movable comb is arranged facing the fixed comb so that when the latching mechanism is in the initial unlatched configuration, the fingers of the movable comb are not engaged between the fingers of the fixed comb, and once the latching mechanism is in the final latched configuration, the fingers of the movable comb are engaged between the fingers of the fixed comb and the stop holds the first suspension in a permanent state of deformation, preventing disengagement of the fingers of the movable comb from between the fingers of the fixed comb while allowing movement of the movable drive portion relative to the fixed drive portion throughout the subsequent operation of the actuator,
wherein when the latching mechanism is in the initial unlatched configuration, the fingers of the movable comb are spaced from the fingers of the fixed comb by a first spacing, and when the latching mechanism is in the final latched configuration, the fingers of the movable comb are spaced from the fingers of the fixed comb by a second spacing less than the first spacing, and
wherein a ratio between a height of the fingers and the second spacing between the fingers of the fixed comb and the fingers of the movable comb is comprised between 50 and 400, preferably comprised between 70 and 150.
8 . The microsystem according to one of claim 7 , wherein the second spacing is comprised between 0.1 and 5 μm, preferably comprised between 1 and 3 μm.
9 . The microsystem according to one of claim 7 , wherein once the latching mechanism is in the final latched configuration, the stop prevents movement of the first movable portion tending to disengage the fingers of the movable comb from between the fingers of the fixed comb.
10 . The microsystem according to claim 7 , wherein once the first locking lug is engaged with the second locking lug, the first locking lug and the second locking lug prevent a return of the latching mechanism to the initial unlatched configuration.