PATENT DOCUMENT

Publication Number: US-10381144-B1
Application Number: US-201615343177-A
Country: US
Kind Code: B1

Title: Haptic actuator with ferritic core

Abstract:
Disclosed herein are linear actuators and haptic actuators for providing haptic output on an electronic device. In some embodiments, the linear actuator comprises two linear arrays of permanent magnets within and fixed to a housing. The linear arrays are arranged in parallel planes oriented toward, and located on opposites sides of, a moveable assembly comprising a shaft having a ferritic core. The shaft comprises a set of conducting coils, each conducting coil being located between a magnet from each of the two linear arrays. The linear actuator comprises a support mechanism that is attached to both the housing and to the moveable assembly and is configured to pivot. An electromagnetic force can arise from a current in the coils to cause the moveable assembly to move linearly between the two linear arrays.

Claims:
What is claimed is: 
     
       1. A linear actuator, comprising:
 a housing composed of a first ferritic material; 
 a first set of permanent magnets within, and fixed to, the housing to form a first linear array; 
 a second set of permanent magnets within, and fixed to, the housing to form a second linear array; 
 a moveable assembly contained within the housing and comprising:
 a shaft comprising a second ferritic material positioned between the first and second sets of permanent magnets; and 
 a set of conducting coils wound around the shaft, a conducting coil of the set of conducting coils being wound around a coil axis and positioned between:
 a first permanent magnet, of the first linear array, having a first magnetic axis that extends through and is perpendicular to pole faces of the first permanent magnet, the first magnetic axis being substantially perpendicular to the coil axis; and 
 a second permanent magnet, of the second linear array, having a second magnetic axis that extends through and is perpendicular to pole faces of the second permanent magnet, the second magnetic axis being substantially perpendicular to the coil axis; and 
 
 
 a support mechanism within the housing that is attached to the housing and to the moveable assembly, the support mechanism operative to pivot; wherein 
 in response to an electromagnetic force, the moveable assembly moves within the housing while the support mechanism pivots. 
 
     
     
       2. The linear actuator of  claim 1 , wherein:
 the first and second magnetic axes have a same magnetic polarity; and 
 the coil axis of the conducting coil is parallel to a longitudinal axis of the housing. 
 
     
     
       3. The linear actuator of  claim 1 , wherein the second set of permanent magnets has as many permanent magnets as the first set of permanent magnets. 
     
     
       4. The linear actuator of  claim 1 , wherein the set of conducting coils has as many conducting coils as there are permanent magnets in the first set of permanent magnets. 
     
     
       5. The linear actuator of  claim 1 , wherein the permanent magnets of the first set of permanent magnets are flat in shape and are positioned along the first linear array so that the first linear array forms a plane. 
     
     
       6. The linear actuator of  claim 5 , wherein:
 the plane is a first plane; 
 the permanent magnets of the second set of permanent magnets are flat in shape and are positioned along the second linear array so that the second linear array forms a second plane; and 
 the second plane of the second linear array is opposite, and parallel to, the first plane of the first linear array. 
 
     
     
       7. The linear actuator of  claim 6 , wherein:
 each permanent magnet of the first linear array has a respective magnetic pole face with a magnetic polarity that is oriented perpendicular to the plane of the first linear array; 
 the magnetic polarities of the respective magnetic pole faces of the permanent magnets of the first linear array alternate along the first linear array; 
 each permanent magnet of the second linear array has a respective magnetic pole face with a magnetic polarity that is oriented perpendicular to the second plane of the second linear array; and 
 the magnetic polarities of the respective magnetic pole faces of the permanent magnets of the second linear array alternate along the second linear array. 
 
     
     
       8. The linear actuator of  claim 1 , wherein the shaft is thinner in cross-section than a permanent magnet of the first linear array. 
     
     
       9. The linear actuator of  claim 1 , wherein the moveable assembly comprises a first non-ferritic component attached to the shaft at a first end of the shaft, and a second non-ferritic component attached to the shaft at a second end of the shaft. 
     
     
       10. The linear actuator of  claim 9 , wherein the support mechanism comprises:
 a first pivot arm that pivots about a first axis; and 
 a second pivot arm that pivots about a second axis; 
 
       wherein
 the first pivot arm is attached to the first non-ferritic component of the moveable assembly with a first pin joint; and 
 the second pivot arm is attached to the second non-ferritic component of the moveable assembly with a second pin joint. 
 
     
     
       11. The linear actuator of  claim 1 , wherein a current flowing in the set of conducting coils generates a Lorentz force that contributes to the electromagnetic force. 
     
     
       12. The linear actuator of  claim 1 , wherein:
 a first current flowing in a first conducting coil of the set of conducting coils generates a first Lorentz force that contributes to the electromagnetic force; 
 a second current flowing in a second conducting coil of the set of conducting coils generates a second Lorentz force; and 
 the first Lorentz force and the second Lorentz force are aligned. 
 
     
     
       13. The linear actuator of  claim 12 , wherein an alternating current is induced in the set of conducting coils so that the electromagnetic force causes the moveable assembly to move alternately in a first direction along a longitudinal axis of the housing and in a second direction opposite to the first direction. 
     
     
       14. A haptic actuator for an electronic device, comprising:
 a housing enclosing an interior volume and comprising an exterior attachment component by which the haptic actuator can be attached to the electronic device; 
 a linear actuator, operative to provide haptic output to the haptic actuator in response to a received input from the electronic device, comprising:
 a set of magnets positioned within the interior volume and fixed to one or more interior surfaces of the housing and having magnetic axes that extend through and are perpendicular to pole faces of the set of magnets; 
 a moveable assembly contained within the interior volume comprising:
 a shaft positioned adjacent to the set of magnets; and 
 a set of conducting coils, each respective conducting coil being wound around the shaft and positioned adjacent to a respective magnet of the set of magnets; and 
 
 a support mechanism within the interior volume that is attached to the housing and to the moveable assembly; 
 
 wherein:
 each conducting coil is wound around a coil axis that is transverse to the magnetic axes; 
 the received input from the electronic device causes current to flow in at least one conducting coil; 
 current flowing in any one of the set of conducting coils generates an electromagnetic force on the shaft directed along an axis of the shaft to cause the moveable assembly to move within the housing as the support mechanism pivots; and 
 the support mechanism applies a restoring force. 
 
 
     
     
       15. The haptic actuator of  claim 14 , wherein:
 the set of magnets comprises more than one magnet; 
 the magnets of the set of magnets are positioned in a sequence with respect to the axis of the shaft; and 
 the polarities of the magnets alternate along the sequence. 
 
     
     
       16. The haptic actuator of  claim 15 , wherein the set of conducting coils has as many conducting coils as there are magnets in the set of magnets, and the conducting coils of the set of conducting coils are positioned along the shaft so that each conducting coil is adjacent to one of the magnets of the set of magnets. 
     
     
       17. The haptic of  claim 14 , wherein the received input from the electronic device causes current to flow in each conducting coil so that the generated electromagnetic forces are parallel. 
     
     
       18. The haptic actuator of  claim 16 , wherein the set of magnets comprises:
 a first subset of permanent magnets that are positioned to form a first linear array; and 
 a second subset of permanent magnets that are positioned to form a second linear array that is opposite to the first linear array; 
 wherein the shaft is positioned between the first linear array and the second linear array. 
 
     
     
       19. A system for providing haptic output in an electronic device, the system comprising:
 a haptic actuator comprising:
 an attachment component connecting the haptic actuator to the electronic device; 
 a housing enclosing an interior volume; and 
 a linear actuator comprising:
 a set of magnets positioned within the interior volume, each respective magnet of the set of magnets having a respective magnetic axis that extends through and is perpendicular to pole faces of the respective magnet; 
 a moveable assembly contained within the interior volume comprising: 
 a shaft defining a longitudinal axis that is transverse to the magnetic axes of the magnets of th set of magnets; and 
 a set of conducting coils wound around the shaft, each respective conducting coil at least partially encircling a coil axis substantially coincident with the longitudinal axis of the shaft and positioned adjacent to a respective magnet of the set of magnets; and 
 a support mechanism within the interior volume that is attached to the housing and to the moveable assembly; 
 
 
 wherein:
 the electronic device is operative to send a signal to the haptic actuator; and 
 in response to the signal sent from the electronic device being received at the haptic actuator, the haptic actuator is operative to induce a current in the set of conducting coils sufficient to cause the moveable assembly to move linearly. 
 
 
     
     
       20. The system of  claim 19 , wherein the induced current is an alternating current.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a nonprovisional patent application of and claims the benefit of U.S. Provisional Patent Application No. 62/397,649, filed Sep. 21, 2016 and titled “Haptic Actuator with Ferritic Core,” the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present disclosure generally relates to linear actuators that can be used to provide haptic output for an electronic device. More specifically, the present disclosure is directed to a bidirectional linear actuator having a coil architecture on a ferritic shaft and stationary magnet arrays that can provide haptic output for an electronic device in response to an electromagnetic force. 
     BACKGROUND 
     Electronic devices are commonplace in today&#39;s society. Example electronic devices include cell phones, tablet computers, personal digital assistants, and the like. Some of these electronic devices include a haptic actuator that provides haptic (touch) output to a user. The haptic output may be provided by an actuator that utilizes a vibratory motor or an oscillating motor. The vibration may alert a user to an incoming telephone call when the cell phone is muted, for example. The vibration takes the place of the standard audio alert and may be felt by the user if he or she is touching the phone. However, the vibration may still be noisy in certain environments and this may be undesirable. 
     Further, many rotary mass actuators not only create an audible buzz, but also an undesirable feel. Because rotary mass actuators spin up to an operating state and then wind down to a rest state, they constantly shake the enclosure of the electronic device. This feels “buzzy” to a user and there is little, if any, control over the haptic output of such a device other than to control the amplitude of the output or to provide discrete outputs with an unacceptably long time between the outputs. 
     Certain linear actuators are used instead of rotary mass actuators in some electronic devices. Linear actuators may deliver a more crisp haptic output and are quieter in certain cases. However, many such linear actuators are relatively large and some may move a mass only in a single direction. Accordingly, an improved linear actuator, such as one with a narrow profile, may be advantageous. 
     SUMMARY 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     Disclosed herein are linear actuators, haptic actuators, and devices for providing haptic output or other tactile sensations for an electronic device. The haptic devices may make use of a linear actuator s that causes bidirectional linear motion of a moveable assembly by applying electromagnetic force. The haptic devices are connected to the electronic device through attachment components so that the bidirectional linear motion of the linear actuator is a transmitted to the electronic device. In some embodiments, arrays of magnets that are fixed to a housing of the linear actuator are configured on opposite sides of a shaft, and a sequence of conducting coils is wound around the shaft. Current in the conducting coils induces electromagnetic forces on the shaft, causing it to move linearly. 
     More specifically, an embodiment described herein is a linear actuator having a housing that includes a ferritic material. Within and fixed to the housing are a first set of permanent magnets that form a first linear array and a second set of permanent magnets that form a second linear array. The linear actuator further includes a moveable assembly having a shaft positioned between the first and second linear arrays of magnets. Wound around the shaft is a set of conducting coils, with each conducting coil located between a permanent magnet of the first linear array and a permanent magnet of the second linear array. The moveable assembly is attached to a support mechanism that is attached to the housing. The support mechanism is configured to pivot as the moveable assembly moves linearly along an axis of the housing. 
     In additional or alternative embodiments, the magnets have a flat shape having two faces, with the faces being the magnetic poles of the magnet and so of opposite polarity. A first face is attached to the housing to channel the magnet&#39;s magnetic flux into the housing. The second face is oriented directly toward a conducting coil on the shaft. The shaft can have a wide thin cross section with respect to an axis of a long dimension of the shaft. The axis of the shaft is configured to be parallel to an axis of the housing. Magnetic fields from the second faces of the magnets are thus perpendicular to the axis of the shaft and so also of the axis of the conducting coils. 
     As current is induced in the conducting coils, Lorenz forces arise from the vector cross products of the current directions with the magnetic fields from the two faces of the permanent magnets. These Lorenz forces are applied to the shaft and directed along the axis of the shaft. The Lorenz forces may cause the moveable assembly to move linearly along the direction of the shaft. Applying alternating current causes the moveable assembly to alternate directions of movement. The support mechanism can support the moveable assembly so that it does not contact the magnets. As the direction of movement of the moveable assembly alternates, a change in momentum is transferred to the housing, causing a haptic output. 
     Also described is an electronic device that includes a haptic actuator. The haptic actuator provides a vibratory tactile output from the electronic device. The haptic actuator uses a linear actuator contained within an interior volume of a housing. Electromagnetic forces are applied by the linear actuator to induce linear motion in a moveable assembly in the interior volume. The moveable assembly is attached to a support mechanism within the interior volume that can pivot as the moveable assembly moves linearly. The support mechanism is fixed to the housing so that motion of the moveable assembly is transferred through the housing to electronic device. 
     More specifically, an embodiment described herein is haptic actuator for an electronic device that is operative to provide haptic output to electronic device in response to an input received from the electronic device. The haptic actuator includes a linear actuator, a housing that encloses an interior volume and that has exterior attachment components by which it can be attached to the electronic device. A set of magnets is positioned in the interior volume to form a linear array; the magnets are fixed to one or more internal surfaces of the housing. The linear actuator also includes a moveable assembly that in turn includes a shaft positioned adjacent to the linear array of magnets. Wound around the shaft is a set of conducting coils, with each conducting coil positioned adjacent to a respective magnet of the linear array of magnets. The linear actuator also includes a support mechanism within the interior volume that is attached to the housing and to the moveable assembly. The support mechanism is operative to pivot. A received input from the electronic device causes a current to flow in at least one conducting coil. The flowing current generates an electromagnetic force that is applied to the shaft along an axis of the shaft and so causes the moveable assembly to move linearly in the direction of the axis of the shaft as the support mechanism pivots. 
     In additional or alternative embodiments the linear array of magnets have magnetic pole faces directed toward the conducting coils, with the magnetic polarity of the magnetic pole faces alternating sequentially along the linear array. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements. 
         FIG. 1A  illustrates a first electronic device that may incorporate an embodiment. 
         FIG. 1B  illustrates second electronic device that may incorporate an embodiment. 
         FIG. 2A  illustrates a haptic actuator, according to an embodiment. 
         FIG. 2B  illustrates a configuration of a first array of magnets on a first housing component of a haptic actuator, according to an embodiment. 
         FIG. 2C  illustrates a configuration of a second array of magnets on a second housing component of a haptic actuator, according to an embodiment. 
         FIG. 3A  illustrates certain internal components of a haptic actuator, according to an embodiment. 
         FIG. 3B  illustrates details of a first flexible coupling of certain internal components of the embodiment of  FIG. 3A . 
         FIG. 3C  illustrates details of a second flexible coupling of certain internal components, according to an embodiment. 
         FIG. 4  shows a cross section showing certain internal components of a linear actuator, according to an embodiment. 
         FIG. 5A  illustrates details of windings on a ferritic core of a linear actuator, according to an embodiment. 
         FIG. 5B  shows an cross section of the configuration of windings on the ferritic core of the linear actuator of  FIG. 5A , according to an embodiment. 
         FIG. 5C  illustrates vectors of current and forces acting on components of a linear actuator, according to an embodiment. 
         FIG. 5D  shows a cross section of components of a linear actuator and directions of magnetic flux, according to an embodiment. 
         FIG. 6A  illustrates a top view of a first alternative mounting of certain internal components of a haptic actuator, according to an embodiment. 
         FIG. 6B  illustrates a perspective view of the first alternative mounting of certain internal components of the haptic actuator shown in  FIG. 6A , according to an embodiment. 
         FIG. 6C  illustrates a second alternative mounting of certain internal components of a the haptic actuator of  FIG. 6A , according to an embodiment. 
         FIG. 6D  shows a cross section of an alternative configuration of a shaft and magnet array for a linear actuator of a haptic actuator, according to an embodiment. 
         FIG. 7A  shows an exploded view of an alternative configuration for a linear actuator having a fixed array of magnets about a moveable shaft with conducting coils, according to an embodiment. 
         FIG. 7B  shows a bottom half of a cylindrical housing composed of a ferritic material. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The embodiments disclosed herein are directed to haptic actuators for use as part of an electronic device. It is sometimes desired for an electronic device to transmit a signal to a user in the form of a haptic output, i.e., a tactile output. Examples include a smart watch that vibrates at a scheduled time, and a cell phone that vibrates for an incoming call. 
     Haptic actuators often include a support mechanism for attachment to an electronic device and a linear actuator that moves a mass in varying directions; changes in momentum of the mass are transmitted through the support mechanism to the electronic device. In particular, linear actuators work by moving a mass in one or both directions along a single line or axis. Embodiments disclosed herein are directed to linear haptic actuators for electronic devices. 
     Although specific electronic devices are shown in the figures and described below, the haptic actuators described herein may be used with various electronic devices, mechanical devices, electromechanical devices and so on. Examples of such include, but are not limited to, mobile phones, personal digital assistants, time keeping devices, health monitoring devices, wearable electronic devices, input devices (e.g., a stylus, trackpads, buttons, switches, and so on), a desktop computer, electronic glasses, steering wheels, dashboards, bands for a wearable electronic devices, and so on. Although various electronic devices are mentioned, the haptic actuators and linear actuators disclosed herein may also be used in conjunction with other products and combined with various materials. 
     The linear actuators described herein operate to produce haptic output by moving a mass bilinearly, that is, in both directions along a single line. For brevity of this disclosure such bilinear motion will simply be termed “linear motion” and objects exhibiting such bilinear motion will be said to be moving “linearly.” By conservation of momentum, changes in the direction of motion of the mass are transferred to support mechanisms of the mass. When the support mechanisms are connected to an electronic device, either directly or through intermediate components such as a housing for the actuator, the changed momentum of the mass is transferred to the electronic device and so produces a haptic output. 
     Some forms of linear actuators are configured to have one or more current carrying coils of wires that are stationary within a housing. In those forms, a movable mass then may include one or more magnets, either permanent magnets or electromagnets. Alternating current induced in the current carrying coils generates magnetic fields that in turn exert electromagnetic forces on the magnets of the movable mass. As used herein, an “electromagnetic force” denotes an electric force, a magnetic force, or a combination thereof. 
     In contrast, some linear actuators described herein make use stationary magnets attached to a housing of the linear actuator. In some embodiments a moveable assembly within the housing has a shaft about which conducting coils are wound. Currents induced in the conducting coils are subject to a Lorentz force that can cause the moveable assembly to move. Some embodiments include permanent magnets in planar arrays and have a shaft with a wide, thin cross section so that the wires in the conducting coils about the shaft form, in cross section, two approximately parallel lines, with comparatively small perpendicular connections. This is termed a “flat coil architecture.” This can allow for a slimmer and smaller profile for the haptic actuator. 
     Further, magnetic fields from the stationary magnets can be oriented to pass into a housing made of a ferritic material. Typically, but not necessarily, a ferritic material has a high magnetic permeability. When the stationary magnets are arranged in a linear array and adjacent magnets of the array have alternating polarities, the magnetic flux from the permanent magnets may be mostly confined to the housing and so shield components outside the haptic actuator from magnetic fields. Further, a ferritic housing can shield the internal components of the haptic actuator from electromagnetic fields originating outside the haptic actuator. 
     When the shaft is made, at least in part, of a ferritic material, the magnetic fields produced by the magnets can then be channeled into the shaft and so reduce fringing effects of the magnetic fields. This can increase the strength of the magnetic fields that contribute to the Lorentz force, and so produce a stronger haptic output from less current. 
     Detailed embodiments of these general considerations will now be disclosed in relation to the accompanying figures. 
       FIG. 1A  illustrates a first example electronic device  100  that may incorporate a haptic actuator according to one or more embodiments presented herein. In the example shown, the electronic device is an electronic watch  100 . The haptic actuator may be mounted internally to provide a haptic output through either a case  102  or a surface  104  of the electronic watch  100 . The electronic watch  100  may include a stem input  106  and a button  108  by which a user may control operations of the electronic watch, including behaviors of the haptic actuator. As the electronic watch  100  is relatively small, the associated haptic actuator may be similarly compact. 
       FIG. 1B  illustrates a second electronic device  120  that may incorporate a haptic actuator according to one or more embodiments of the presented herein. In this example the electronic device is a smart phone having a case  121 , a surface display  122 , and an user input button  124 . The smart phone  120  may have a program that, when run, allows a user to modify the behavior of the haptic actuator. 
     Haptic actuators that use one of the linear actuators described herein may replace rotary or conventional linear actuators in the electronic devices described above. As a result, the profile of the electronic devices may be smaller or thinner. 
       FIG. 2A  illustrates components of an embodiment of a haptic actuator  200  that may be used to provided haptic output in an electronic device. The haptic actuator  200  comprises a connection mechanism to link it to electronic device, a housing and a linear actuator within the housing. The linear actuator for the haptic actuator  200  is shown within an interior volume formed by a first housing component  202  and a top component  203 ; the top component  203  is detached in  FIG. 2A  to show internal components within the interior volume. The first housing component  202 , together with the top component  203 , is referred to collectively as the “housing.” The first housing component  202  and top component  203  may be made from a ferritic material, (e.g., a cobalt-iron soft magnetic alloy such as Hiperco27, Hiperco 50 or others), to provide magnetic shielding of components within the interior volume of the housing from outside electromagnetic forces, and to provide a channel for magnet flux from magnets within the interior volume, as described below. 
     The first housing component  202  includes attachment tabs  204 A and  204 B. These tabs may secure the haptic actuator  200  to an electronic device (or other structure) so that linear movements of the linear actuator are transmitted to the electronic device. Other embodiments may have alternative attachment components by which the haptic actuator can be attached to an electronic device. 
     The embodiment shown in  FIG. 2A  has a longest dimension, L, indicated by the axis  206 . Also, this embodiment has a second longest dimension, W, shown by axis  207 , that is perpendicular axis  206 . Finally, this embodiment has a smallest dimension, V, indicated by axis  208 , that is perpendicular to both axes  206  and  207 . 
     Pivots  230 A,  230 B are affixed to interior surfaces of the housing but are free to rotate about respective axes. In the embodiment shown, the pivots  230 A,  230 B are at opposing ends of the longest axis  206  of the linear actuator. Respective pivot arms  232 A,  232 B are attached to the pivots  230 A,  230 B. These pivot arms are configured to rotate in both directions within the interior of the linear actuator about respective axes of the pivots  230 A,  230 B. Pivot  230 A and pivot arm  232 A may be formed as a single component. In some embodiments pivots  230 A,  230 B may include internal restoring springs that counteract rotations of pivot arms  232 A,  232 B from a neutral or equilibrium angle. 
     External ends  220 A,  220 B are flexibly coupled to respective pivot arms  232 A,  232 B. The external ends  220 A,  220 B are at opposing ends of a shaft (not shown in  FIG. 2A , but shown and discussed below with respect to  FIG. 3 ). The external ends  220 A,  220 B of the shaft may be composed of a non-ferritic metal, such as tungsten, to provide increased mass to be moved by the linear actuator to provide increased haptic output. In alternative embodiments, one or more of the external ends may include ferritic material. As pivot arm  232 A rotates about pivot  230 A, its flexible coupling with external end  220 A allows external end  220 A to move primarily linearly along the axis  206  of the housing. Further details of the configuration and motions of the external ends  220 A,  220 B, the pivots  230 A,  230 B, and the pivot arms  232 A and  232 B, will be provided below in relation to  FIGS. 3A-C . 
     A first linear array of magnets  210 A-N is configured sequentially within the interior volume of the haptic actuator  200  along the axis  206 . In the embodiment shown, the magnets have longest dimensions that are oriented across the horizontal axis  207  of the housing. The particular embodiment shown uses five planar magnets (i.e., N=5), though other embodiments may use either more or fewer magnets. The planar magnets are oriented to lie in a plane parallel to the plane defined by axes  206  and  207 . Each of the magnets  210 A-N in the first linear array has one of its magnetic pole faces oriented along the axis  208  of the linear actuator. In the embodiment shown, when the top component  203  is attached to the first housing component  202 , the magnetic poles of the magnets  210 A-N are directed perpendicular into the top component  203 . The magnetic poles of the magnets  210 A-N alternate sequentially along the first linear array, as will be explained further below. 
     In some embodiments, the first linear array of magnets  210 A-N is fixed in position with respect to the housing. In one embodiment the magnets  210 A-N are attached at their horizontal edges to the first housing component  202 . In an alternative embodiment, shown in  FIG. 2B , the planar magnetic pole faces of the magnets  210 A-N are attached directly to, and are flush with, the top component  203  of the housing. Note that in  FIG. 2B  the shown magnetic pole faces are on the opposite sides of the planar magnets  210 A-N as shown in  FIG. 2A , and so have opposite magnetic polarity. The magnets  210 A-N may be made with a material of high magnetic strength, e.g., N48H, another neodymium-iron-boron alloy or other magnetic material. 
       FIG. 2C  illustrates a configuration for a second linear array of magnets,  212 A-N, with N=5 as for the first linear array. In the embodiment shown, the magnets of the second linear array are also planar magnets, and are affixed sequentially to an interior surface of the first housing component  202 . The shown magnetic pole faces of the magnets in the second linear array are directed perpendicular to the surface of the housing component  202  into the interior volume. In the embodiment shown, when the top component of the housing  203  is attached the first component of the housing  202 , each magnet of the first linear array is directly opposite a respective magnet of the second linear array to form a sequence of magnet pairs. Further, the magnetic pole faces of the two magnets in each such magnet pair have the same magnetic polarity. That is, either both have “North” (N) magnetic polarity, or both have “South” magnetic polarity (S). The magnetic pole faces of the magnets in the second linear array also have sequentially alternating magnetic polarity.  FIG. 2C  also shows attachment sites  240 A,  240 B at which pivots  230 A,  230 B may be affixed to the housing. 
     While in the embodiments shown and discussed the magnets  210 A-N and  212 A-N are permanent magnets, in some embodiments the magnets  210 A-N and  212 A-N may be implemented as electromagnets. 
       FIG. 3A  illustrates the internal components of the linear actuator within the haptic actuator  200  without showing the housing. In the embodiment shown, the pivots  230 A,  230 B have respective internal axes  234 A,  234 B about which the pivot arms  234 A,  234 B can rotate in both directions.  FIG. 3A  shows the first and second linear arrays of magnets,  210 A-N and  212 A-N, configured opposite to each other in parallel planes. A shaft  360  extends between the two parallel planes. A more complete view of the shaft  360  is shown in  FIG. 4  and discussed below. The shaft  360 , external ends  220 A,  220 B, pivots  230 A,  230 B, and pivot arms  234 A,  234 B form a moveable assembly on which electromagnetic forces induce linear motion, as discussed below. 
     Embodiments may implement the flexible coupling of pivot arm  232 A to external end  220 A in a variety of ways to ensure linear, or very nearly linear, motion of the shaft discussed below along the direction of axis  206 . In some embodiments the flexible coupling of pivot arms  232 A,  232 B is configured so that at least the shaft is suspended between the first and second linear array of magnets  210 A-N and  212 A-N without contacting either array. 
     In a first embodiment, the pivot arm  232 A is flexibly coupled to external end  220 A by a pin joint. The external end  220 A is rigidly affixed to the shaft  360 . As will be discussed below, electromagnetic forces are induced on the shaft  360  between the magnet arrays, with the forces directed along the axis  206 . As the shaft  360  moves in response to the forces, the external end  220 A exerts a force on the pivot arm  232 A at the pin  342 A, inducing a torque about the axis  234 A of the pivot  230 A, inducing the pivot arm to rotate. The rotation of the pivot arm then induces a location of the pin joint  342 A to move in along a circular arc. An effect of the such a circular motion of the pin joint is to induce a sideways motion of the external end, and the shaft to which it is rigidly attached, in a direction along the axis  207 . However, the amount of such sideways motion can be kept small if: (i) a neutral or equilibrium position of the pivot arm  232 A about pivot  230 A is along the axis  207 , and (ii) rotations from neutral position are through small angles only. The small amount of movement of the external end  220 A and shaft  360  along the direction of axis  207  may add to the haptic output produced. 
     In this embodiment, an analogous configuration for the flexible coupling of pivot arm  232 B to external end  220 B also is used. In this embodiment, a neutral or equilibrium configuration for both sets of pivot arms  232 A,  232 B and pivots  230 A,  230 B is such that the directions from the pin joints  342 A, and  342 B are toward the respective pivot axes  234 A,  234 B, i.e., both directions are in the direction of axis  207  of the housing. Thus when the externals ends  220 A,  220 B and shaft  360  move in the positive direction of long axis  206  of the housing, the rotation of both pivots  230 A,  230 B is clockwise with respect to the orientation shown in  FIG. 3A , with the pivot arms  232 A,  232 B retaining a mostly parallel orientation. The sideways motion induced in the external ends  220 A,  220 B, and shaft  360  is then in the positive direction of axis  207  of the housing. 
       FIG. 3B  shows a second embodiment for an flexible coupling of pivot arm  232 A to external end  220 A configured to reduce the sideways motion described for the previous embodiments. In this embodiment, the pivot arm  232 A is not connected directly to the external end  220 , but to a connector  226 A. Pivot arm  232 A comprises an end section  233 A that extends between two extensions,  227 A and  228 A of the connector  226 A. Connector  226 A is connected to pivot arm  232 A by a pin joint  342 A that extends through extension  227 A and end section  233 A. Connector  226 A is then connected to the external end  220 A at a second pin joint  330 A. The external end  220 A is then connected rigidly to the shaft  360 . When electromagnetic forces are induced to cause external end  220 A and shaft  360  to move along axis  206 , the connector  226 A may pivot about both pin joints  342 A and  330 A to allow external end  220 A and shaft  360  to move along axis  206  without needing to move along axis  207 . 
     This embodiment may also use an optional slider bearing  224 A affixed to the side of external end  220 A and positioned to be near, or in contact with, an interior surface of the housing to reduce further sideways motion of the external end  220 A and shaft  360  along the axis  207 . It would be clear to one of skill in the art that a similar connector (not shown) could be attached on the opposite end of the shaft  360  to connect pivot arm  232 B to external end  220 B. 
       FIG. 3C  illustrates a third embodiment for a flexible coupling of pivot arm  232 A to external end  220 A that can also reduce the sideways motion for the external end  220 A and shaft  360 . As in the first described embodiment, the external end  220 A is rigidly attached to the shaft  360 . The pivot arm  232 A includes an end extension  233 A that extends between extensions  223 A and  222 A of external end  220 A. But instead of the pin joint  342 A shown in  FIGS. 3A and 3B , there is a pin  343 A extending from the end extension  233 A of pivot arm  232 A into a circular gap  344 A of an extension  223 A of the external end  220 A. The extension  223 A extends about one side of the end section  233 A of pivot arm  232 A. External end  220 A may also comprise a second extension  222 A that extends from external end  220 A about an opposite side of the end section  233 A of pivot arm  232 A. The extension  222 A may also have a circular gap to receive an opposite end of pin  343 A. 
     When an electromagnetic force is induced on external end  220 A and/or shaft  360  causing them to move in the direction of axis  206 , a corresponding force is induced on the pin  343 A also in the direction of axis  206 . The shape of the gap  344 A allows the pin  343 A to move along a circular arc as pivot arm  232 A rotates, while allowing external end  220 A and shaft  360  to move along axis  206  without needing to move along axis  207 . Optional jewel bearing  224 A may be used as described above. A corresponding connection may be used between external end  220 B and pivot arm  232 B. 
     Other embodiments may use variations of these connections, or alternative connection configurations, so that linear motion of the shaft from an equilibrium position is opposed by a restoring force. Examples of such alternative connection configurations are discussed below with respect to  FIGS. 6A, 6B, and 6C . Alternative connection configurations than those disclosed above, or those discussed below with respect to  FIGS. 6A, 6B, and 6C , may also be used in other embodiments. 
       FIG. 4  shows a cross section of the embodiments shown in  FIG. 2A  and  FIG. 3A , without the top component  203  of the housing and without the first linear array of magnets  210 A-N. The shaft  360  is shown extending from external end  220 A to external end  220 B above the second linear array of magnets  212 A-N. 
     Within pivot  230 A is the axis  234 A about which pivot  230 A rotates. Internal to pivot  230 A is a restoring spring, such as a torsion spring, configured to opposes rotation about axis  234 A. In one embodiment, a neutral or equilibrium position for the restoring springs of pivots  230 A,  230 B, and for the moving assembly as a whole, is when the pivot arms  232 A is parallel to direction  207  of the housing. The restoring springs may be chosen strong enough to prevent motion of the shaft  360  and its external ends  220 A-B from contacting the housing or the pivot arms  232 A,  232 B, under the maximum electromagnetic force that may be applied to the shaft  360 . 
     In one set of embodiments the shaft  360  may be made of a ferritic material (i.e., one with a high magnetic permeability, e.g., Hiperco 50). Other embodiments may use other ferritic materials. 
     Along the shaft  360  is a sequence of wire windings forming conducting coils  450 A-N around the shaft  360 . In the embodiment shown there is one conducting coil for each opposing magnet pair, e.g. coil  450 A is between magnets  210 A and  212 A from the first and second linear arrays of magnets. These conducting coils are positioned along the shaft  360  so as to lie between the faces of the two magnets of each magnet pair. There may be gaps between the conducting coils  450 A-N. The planes formed by the first and second linear arrays of magnets are spaced apart sufficiently that the conducting coils do not contact either linear array of magnets. 
     The conducting coils  450 A-N may each have separate connections to an exterior power source. Alternatively, the conducting coils  450 A-N may be part of one circuit, with a connection wire linking each conducting coil to the next conducting coil in the sequence of conducting coils. As will be discussed below, in some embodiments the direction of electrical current in the sequence of conducting coils reverses from one conducting coil to its successor in the sequence. For a sequence of conducting coils that are linked as one wire, this current reversal can be implemented by winding the wire in the conducting coils with alternating orientations (e.g., clockwise versus counterclockwise) with respect to the axis of the shaft  360 . The connection of the conducting coils to an exterior power source may be through a wire or wires embedded in the shaft  360 . Other embodiments may use alternative means of connection to an external source for the current. 
     The operation of the embodiments of linear actuators shown in  FIG. 4  for producing haptic output is more easily understood in conjunction with  FIGS. 5A-D . 
       FIG. 5A  shows a perspective view of a section of the shaft  360  with the conducting coil  450 B that is between the magnets  210 B and  212 B (not shown).  FIG. 5A  is a conceptual rendering only, actual details of the cross sectional shape of the shaft  360  and of the configuration of wire windings in the conducting coil may differ. An axis  530  of shaft  360  is shown for orientation and explanatory purposes. 
       FIG. 5B  illustrates a cross sectional view across the horizontal axis of the linear actuator at the position of magnet  210 B of the first linear array of magnets so that the view is into the axis  530  of the shaft  360 . Magnet  210 B has a magnetic pole face oriented directly toward the shaft  360 , about which are the windings of the conducting coil  450 B. On the opposite side of shaft  360  from magnet  210 B is magnet  212 B, also having a magnetic pole face oriented toward the shaft  360 . These two magnetic pole faces both have the same magnetic polarity. The directions of the magnetic fields of magnet  210 A and magnet  212 B are respectively indicated by the vectors  510 B and  512 B. 
     In the embodiment shown, the shaft  360  has a wide, thin planar configuration. As a result, the shown wire windings of conducting coil  450 B have wide straight profiles in the shown cross section of  FIG. 5B , with two straight lengths on opposite sides of the shaft  360 . 
     Current may be made to flow in the conducting coils  450 A-N. If the conducting coils  450 A-N are wired together in series, the same current value will flow in each conduction coil. Alternatively, the conducting coils  450 A-N may have subsets wired separately to outside power (or voltage or current) sources so that different conducting coils can simultaneously carry different current values. Such variability may be used by the electronic device to control the intensity of the haptic output. 
     When current flows in a wire that is in a magnetic field B, the flowing charges are subject to the Lorentz force given by the vector cross product F=qν×B, where q is the charge on the particle and ν is the velocity of the particle. In the case of current flowing in a wire, the force is felt on the wire. 
       FIG. 5C  shows, for the configuration of  FIG. 5B , vectors for the current, I, flowing in the conducting coil  450 B, and the magnetic field vector  510 B that arises from magnet  210 B. In this embodiment the width and flatness of the top wire shown in  FIG. 5B , and the width and flatness of the magnet  210 B, ensure that ν and B are orthogonal so that the cross product is maximized.  FIG. 5C  also shows a second, slightly rotated view of the vectors for the current in the conducting coil  450 B and the magnetic field  510 B to show the resulting Lorentz force vector {right arrow over (F)}  520  on a wire of the conducting coil  450 B. 
     As the current in conducting coil  450 B traverses the bottom straight section below shaft  360 , the signs of both by ν and B are reversed, where the magnetic field  512 B now arises from the opposite magnet  212 B of the magnet pair  210 B,  212 B. Consequently, the resulting Lorentz force on the bottom straight section is aligned (in the same direction) as the Lorentz force on the top straight section. 
     Because the shaft  360  is made with a ferritic material, the two magnetic fields  510 B and  512 B are channeled into the shaft  360  and cancel each other therein. Thus the shaft  360  shields the wires in the bottom straight section from the top magnetic field  510 B so that magnetic field  510 B does not contribute a canceling effect in the calculation of the Lorentz force on the bottom wires in the bottom straight section. Similarly, the shaft  360  shields the wires on the top section of conducting coil  450 B from the bottom magnetic field  512 B produced by magnet  212 B. The result can be a significant total force on the conducting coil  450 B, which is imparted to the shaft  360  causing the shaft  360  to move in the direction of its axis  530 , which is nearly parallel with the long axis  206  of the housing. 
     To prevent the shaft from extending so far that it contacts the housing, the springs in pivots  230 A-B can be chosen so that their applied restoring force against displacement of the moveable assembly from its equilibrium position at a maximum desired displacement matches the maximum Lorentz force. The Lorentz force depends directly on the induced current so the maximum Lorentz force can be controlled by regulation of the current. 
     Since haptic output involves a vibratory feel, the motion induced on shaft  360  by the Lorentz force as just described needs to be reversed so that the moveable assembly subsequently moves in the opposite direction. One method for reversing direction of motion of the moveable assembly is to apply an alternating current through the conducting coils. Reversing the direction of the current flow then reverses the sign of the Lorentz force and reverses the direction of motion of the moveable assembly. 
       FIG. 5D  shows a cross-sectional view along a cut along the long axis  206  of linear actuator as shown in  FIG. 2A . The view is thus directly into the width axis  207  of linear actuator as shown in  FIG. 2A . Sections of the housing&#39;s top component  203  and a bottom surface of the first housing component  202  are shown. Shown attached to the top component  203  are two magnets  210 B,  210 C from the first linear array of magnets. Shown attached to a bottom section of the first housing component  202  are two magnets  212 B and  212 C. Also shown is the shaft  360  with two conducting coils. 
     As discussed previously, the magnets  210 B,  210 C have magnetic pole faces directed toward respective conducting coils, producing respective magnetic fields  510 B and  510 C toward or way from the shaft. Since the magnetic polarities of the magnets  210 A-N of the first linear array alternate, the magnetic fields  510 B and  510 C produced by magnets  210 B and  210 C are reversed. This alternation has a first advantage when the housing is made with a ferritic material. Since each of magnets  210 B,  210 C has a first of its two magnetic pole faces attached directly to the housing, and since the magnetic polarities of those two first magnetic pole faces are opposite, the ferritic housing creates a magnetic circuit to channel and contain the magnetic flux  514  between those two first magnetic pole faces. Thus the magnetic fields produced by magnets  210 B,  210 C can have greatly reduced effect outside of the linear actuator. 
     Since the shaft  360  is also made with a ferritic material, the magnetic fields  510 B and  510 C from the second magnetic pole faces of magnets  210 B-C have reduced divergence (i.e., fringing or flaring field lines) as they emerge. That is, the shaft  360  also provides a partial magnetic circuit that works to maintain the orientation of the magnetic fields  510 B and  510 C directly toward the shaft  360  (i.e., perpendicularly to the axis  530  of the shaft  360 ). This helps maximize the Lorentz force across the extent of the conducting coils. 
     However, as the directions of the magnetic fields  510 B and  510 C reverse along the first linear array, to have the Lorentz force generated by each conducting coil have the same direction, the directions of the currents in the conducting coils must also reverse from one conducting coil to the next conducting coil. One way this can be achieved is to alternate the orientation of the windings (with respect to the axis of the shaft) of the conducting coils. An alternate way to achieve the reversal of the current direction between conducting coils is reverse how the ends of a following conducting coil are connected to the source that induces the current. 
       FIG. 5D  also shows magnets  212 B,  212 C from the second linear array of magnets affixed to an interior surface of the first housing component  202  and located on the opposite side of the shaft  360 . A similar magnetic circuit is provided by the first housing component  202  to contain the magnetic fluxes from magnets  212 B,  212 C. Similarly, the shaft  360  provides a magnetic circuit for the fields  512 B and  512 C from the magnets  212 B,  212 C.  FIG. 5D  illustrates how the shaft  360  shields the magnetic fields  512 B and  512 C from contributing to Lorentz force calculations on the wire components across the top of conducting coil  450 B. 
     The discussion just provided also applies to other conducting coils and magnet pairs in the sequence along the shaft  360 . The wire sections across the top and bottom of conducting coil  450 C are respectively subjected to Lorentz forces from magnetic fields  510 C and  512 C from respective magnets  210 C and  212 C. The current in conducting coil  450 C must be reversed in orientation from the current in conducting coil  450 B to have the Lorentz force applied on conducting coil  450 C be in the same direction as the Lorentz force applied on conducting coil  450 B. This can be accomplished by reversing the direction of the windings from one conducting coil to the next (not shown in  FIG. 5D ) or by reversing the current flow direction between conducting coils  450 B and  450 C. 
     When alternating current (AC) is applied to each conducting coil, over a half period of the current the Lorentz force applied to conducting coil  450 B will reverse. The form of the applied AC current can be sinusoidal or be the current induced by alternating polarity step voltages. The period of the applied AC current may be selected to limit the total displacement of the moveable assembly, and/or to control the haptic output produced in the electronic device. 
     An applied AC causes the moveable assembly to oscillate linearly (in both directions) mostly along the axis  206  of the housing. The resulting change in momentum of the moveable assembly is then transferred through the connections of the moveable assembly to the housing to the haptic actuator  200  as a whole. The haptic actuator  200  then transmits the haptic output to the electronic device. 
     Additional and/or alternative embodiments to those described above are within the scope and spirit of the disclosure, and will now be discussed. 
       FIGS. 6A-6C  disclose further embodiments that use alternative support mechanisms that suspend the moveable assembly.  FIGS. 6A-6C  shows embodiments in which the displacement restoring force applied to the moveable assembly is provided by springs rather than by pivots  230 A-B and pivot arms  232 A-B.  FIG. 6D  shows embodiments that may use an alternate form of a stationary magnet array about a shaft with conducting coils.  FIGS. 7A-B  show embodiments that use a cylindrical housing to which is attached a linear array of circular toroidal magnets about a cylindrical shaft. 
       FIG. 6A  shows a top view of an embodiment for a linear actuator for the haptic actuator  200  that uses an alternative set of components for providing a restoring force on the shaft  360 . For simplicity of description, the top component  203  of is not shown, nor are the first and second linear arrays of magnets, nor the conducting coils on shaft  360 . Instead of the pivots  230 A,  232 B and pivot arms  232 A,  232 B described above, leaf springs  610 A,  610 B are configured on interior surfaces of the first housing component  202  at opposite ends of the long axis  206  of the linear actuator. In order to suspend the shaft  360  between the two linear arrays of magnets, the external ends  220 A,  220 B may be supported by rods  612 A,  612 B that are rigidly fixed to interior surfaces of the housing. In another embodiment the support rods  612 A,  612 B may be one unit extending through the shaft  360 . In another embodiment the external ends  220 A-B may slide over low friction interior surfaces of the housing. The jewel bearings  224 A,  224 B,  225 A, and  225 B may be used to restrict sideways motion of the moveable assembly (now comprising shaft  360  and the external ends  220 A,  220 B) so that the motion of the moveable assembly is linear along the axis  206 . 
       FIG. 6B  shows a perspective view of the embodiment discussed in relation to  FIG. 6A . A physical limit to how much the leaf springs  610 A-B can deflect can prevent the moving assembly from impacting the housing. 
       FIG. 6C  shows another embodiment of the linear actuator that uses coil springs  620 A,  620 B configured on at least one interior surface of the first housing component  202 . In the embodiment shown, the interior surface is at one end of the long axis  206 . The coil springs further contact the external end  220 A of the shaft  360  to apply a restoring force to the shaft  360 . The coil springs may have rest length chosen as the distance from the external end  220 A to the interior when the shaft  360  is in a neutral position. 
       FIG. 6D  illustrates an alternative configuration for a permanent magnet, according to some embodiments. A sequence of toroidal magnets, such as magnet  610 , could be used around the shaft  360  in place of a sequence of magnet pairs, such as  210 A and  212 A, from two opposed linear arrays of magnets. The interior face of toroidal magnet  610  that is directed toward the shaft would be a single magnetic pole face. The exterior face of toroidal magnet  610  would be the opposite magnetic pole face and would be directed into the housing that includes ferritic material to form a magnetic circuit for the flux from the toroidal magnets in the sequence. 
       FIGS. 7A-B  shows an expanded view of an embodiment of a linear actuator that uses an alternative configuration for a linear array of stationary permanent magnets and a movable ferritic shaft containing conducting coils.  FIG. 7A  shows a cylindrical shaft  760  about which are wound conducting coils  750 A and  750 B. As described above, the shaft  760  may be made with a ferritic material. 
       FIG. 7B  shows a bottom half of cylindrical housing  702  composed of a ferritic material. It will be clear to one of skill in the art how the symmetrical top half of the cylindrical housing is configured. The ferritic materials of the cylindrical housing  702  and the cylindrical shaft  760  may be the same or different. Shown attached to the interior surface of the cylindrical shaft  702  are permanent magnets  710  and  712 . Permanent magnets  710  and  712  may be configured as cylindrical shells, may extend completely around the internal surface of cylindrical housing  702 , and be attached to the internal surface of the cylindrical housing  702  along the exterior face of the cylindrical shell. The exterior face of the cylindrical shell magnet  710  may be one magnetic pole face with magnetic field oriented radially into or from the cylindrical housing  702  with respect to the axis of the cylindrical housing  702 . The interior faces of the cylindrical shell of permanent magnets  710  and  712  may then be the opposite magnetic pole face so that the emanating magnetic field is directed radially toward the cylindrical shaft  760 . The conducting coils  750  and  760  are configured to lie within the cylindrical shells formed by permanent magnets  710  and  712 , respectively. 
     Some embodiments may combine the configurations shown in  FIGS. 7A-B  with elements described previously to complete a linear actuator for a haptic actuator, as would be clear to one of skill in the art. The operation of such a haptic actuator would be as described previously. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20161103
Publication Date: 20190813
Grant Date: 20190813
Priority Date: 20160921
Inventors: DEGNER, BRETT W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01F7/1607", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F7/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F7/10", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 67543688