Bi-stable voice coil park brake
The present disclosure provides devices and methods related to park brake systems and methods. In various embodiments, a park brake system may comprise a motor shaft having a first diameter portion and a second diameter portion, the second diameter portion having a greater diameter than the first diameter portion. A park brake system may further comprise a spring disposed at least partially around a circumference of the motor shaft, a wire coil disposed at least partially around a circumference of a bobbin, a one-way clutch disposed at least partially within the bobbin and coaxial to the motor shaft, an annular magnet disposed coaxial to the motor shaft and distal to at least a portion of the bobbin, and a clutch release mechanism disposed coaxial to the motor shaft and around the first diameter portion. In response to a first voltage being applied to the wire coil, the one-way clutch may translate axially in a first direction relative to the motor shaft and engage with the second diameter portion; in response to a second voltage applied to the wire coil, the one-way clutch may translate axially in a second direction relative to the motor shaft and engage with the clutch release mechanism.
1. A park brake system, comprising:
a motor shaft having a first diameter portion and a second diameter portion, the second diameter portion having a greater diameter than the first diameter portion,
a spring disposed at least partially around a circumference of the motor shaft,
a wire coil disposed at least partially around a circumference of a bobbin,
a one-way clutch disposed at least partially within the bobbin and coaxial to the motor shaft,
an annular magnet disposed coaxial to the motor shaft and distal to at least a portion of the bobbin, and
a clutch release mechanism disposed coaxial to the motor shaft and around the first diameter portion,
wherein, in response to a first voltage applied to the wire coil, the one-way clutch translates axially in a first direction relative to the motor shaft and engages with the second diameter portion, and
wherein, in response to a second voltage applied to the wire coil, the one-way clutch translates axially in a second direction relative to the motor shaft and engages with the clutch release mechanism.
2. The park brake system of claim 1 , wherein the clutch release mechanism further comprises:
a clutch release bearing disposed coaxial to the motor shaft and around the first diameter portion,
a clutch release bearing support disposed coaxial to the motor shaft and between the clutch release bearing and the first diameter portion, and
a clutch release bearing nut disposed coaxial to the motor shaft, around the first diameter portion, and proximal to the clutch release bearing support.
3. The park brake system of claim 2 , wherein the one-way clutch is disposed to prevent rotation of the motor shaft in a first rotational direction in response to engagement with the second diameter portion.
4. The park brake system of claim 3 , further comprising an annular bobbin washer disposed coaxial to the motor shaft, proximal to the annular magnet, and distal to at least a portion of the bobbin.
5. The park brake system of claim 3 , wherein the bobbin comprises a ferromagnetic insert.
6. The park brake system of claim 3 , wherein the second voltage is reversed relative to the first voltage.
7. The park brake system of claim 3 , wherein the spring exerts a proximal force on the bobbin.
8. The park brake system of claim 3 , further comprising:
an anti-rotation stop disposed on a voice coil housing, and
an anti-rotation guide disposed on the bobbin and having an anti-rotation face,
wherein, in response to the one-way clutch engaging with the second diameter portion, the anti-rotation stop and the anti-rotation face are disposed adjacent to one another.
9. The park brake system of claim 3 , further comprising a damper mechanism disposed coaxial to the motor shaft and proximal to the bobbin.
10. An electromechanical actuator (“EMA”), comprising the park brake system of claim 1 .
11. A method comprising:
applying a first voltage to a wire coil disposed at least partially around a circumference of a bobbin, wherein a one-way clutch is disposed at least partially within the bobbin and coaxial to a motor shaft having a first diameter portion and a second diameter portion, the second diameter portion having a greater diameter than the first diameter portion,
translating the one-way clutch axially in a first direction with respect to the motor shaft, and
engaging the one-way clutch to the second diameter portion, wherein rotation of the motor shaft is prevented in a first rotational direction in response to engagement of the one-way clutch with the motor shaft.
12. The method of claim 11 , further comprising:
applying a second voltage to the wire coil,
translating the one-way clutch axially in a second direction,
disposing the one-way clutch around the first diameter portion, and
engaging the one-way clutch to a clutch release mechanism disposed coaxial to the motor shaft and around the first diameter portion.
13. The method of claim 12 , further comprising:
dissipating a kinetic energy of the one-way clutch as it translates in the second direction by a damper mechanism disposed coaxial to the motor shaft and proximal to the bobbin.
14. The method of claim 12 ,
wherein, in response to engagement of the one-way clutch with the second diameter portion, rotation of the motor shaft is prevented in a first rotational direction, and
wherein, in response to engagement of the one-way clutch with the clutch release mechanism, rotation of the motor shaft is not prevented in the first rotational direction.
15. The method of claim 12 , wherein the first voltage is applied by an electromechanical actuator controller (“EMAC”).