Linear actuator
Embodiments described herein may take the form of an electromagnetic actuator that produces a haptic output during operation. Generally, an electromagnetic coil is wrapped around a central magnet array. A shaft passes through the central magnet array, such that the central array may move along the shaft when the proper force is applied. When a current passes through the electromagnetic coil, the coil generates a magnetic field. The coil is stationary with respect to a housing of the actuator, while the central magnet array may move along the shaft within the housing. Thus, excitation of the coil exerts a force on the central magnet array, which moves in response to that force. The direction of the current through the coil determines the direction of the magnetic field and thus the motion of the central magnet array.
1. A linear actuator for providing haptic output for a portable electronic device, comprising:
a housing;
a shaft affixed to the housing;
a mass moveably coupled to the shaft;
a first injector magnet affixed to a first side of the mass;
a second injector magnet affixed to a second side of the mass opposite to the first side of the mass;
a spring encircling a portion of the shaft; and
an electromagnetic structure at least partially surrounding the mass and the shaft; wherein
the electromagnetic structure is affixed to the housing and is operative to exert a motive force on the mass thereby moving the mass from a first position along the shaft to a second position along the shaft;
the spring is operative to prevent the mass from contacting the housing; and
motion of the mass from the first position along the shaft to the second position along the shaft generates the haptic output from the linear actuator.
2. The linear actuator of claim 1 , wherein the mass comprises at least two magnets.
3. The linear actuator of claim 2 , wherein
a first magnet of the at least two magnets has a first polarity; and
a second magnet of the at least two magnets has a second polarity that is opposite from the first polarity.
4. The linear actuator of claim 2 , further comprising an interface positioned between the at least two magnets.
5. The linear actuator of claim 4 , wherein the interface comprises a ferritic material.
6. The linear actuator of claim 4 , wherein the interface enhances a magnetic field generated by the at least two magnets.
7. The linear actuator of claim 1 , wherein the mass comprises:
a magnet array; and
a frame affixed to the magnet array; the frame at least partially extending around the electromagnetic structure.
8. The linear actuator of claim 1 , further comprising a bearing coupled to a portion of the mass and slidably engaging the shaft.
9. The linear actuator of claim 1 , wherein the housing contains the shaft, the mass, and the electromagnetic structure.
10. A linear actuator for providing a haptic output for a portable electronic device, comprising:
a mass assembly comprising a magnet array and a frame;
a first injector magnet affixed to a first side of the frame;
a second injector magnet affixed to a second side of the frame opposite to the first side of the frame;
a shaft extending through the mass assembly; and
a coil separated from, but at least partially encircling the magnet array, and operative to generate a force on the magnet array to cause the mass assembly to slide along the shaft to provide the haptic output for the portable electronic device.
11. The linear actuator of claim 10 , wherein the coil is stationary.
12. The linear actuator of claim 10 , further comprising a case that surrounds the mass assembly, the shaft, and the coil, wherein the shaft is affixed to the case.
13. The linear actuator of claim 12 , further comprising a bracket extending from the case, the bracket securing the actuator to a housing component of the portable electronic device.
14. The linear actuator of claim 13 , further comprising a stiffener coupled to the bracket and operative to enhance the haptic output.
15. The linear actuator of claim 10 , further comprising a convex bearing coupled to the frame and slidably engaging the shaft.
16. The linear actuator of claim 10 , further comprising a first spring positioned around a first end of the shaft and a second spring positioned around a second end of the shaft.
17. A portable electronic device, comprising:
a linear actuator operative to provide haptic output for the portable electronic device in response to a received input, comprising:
an actuator mass slidably coupled to a shaft and comprising:
at least two magnetic components; and
a frame;
an electromagnetic component at least partially contained within the frame and surrounding the at least two magnetic components, the electromagnetic component operative to generate an electromagnetic field that interacts with the at least two magnetic components and causes the actuator mass to slide along the shaft to produce the haptic output;
a first spring coupled to a first end of the shaft; and
a second spring coupled to a second end of the shaft.
18. The portable electronic device of claim 17 , wherein the portable electronic device is a wearable electronic device.
19. The portable electronic device of claim 17 , wherein at least one of the first spring and the second spring is a beehive spring.
20. The linear actuator of claim 12 , further comprising:
a first rail affixed to a first interior wall of the case and positioned adjacent the first injector magnet; and
a second rail affixed to a second interior wall of the case and positioned adjacent the second injector magnet.