Patent Description:
The subject matter herein generally relates to the field of resistive torque-generating devices and systems (e.g., brakes, locks, clutches, tactile feedback devices, resistance-generating devices, motion control devices, and the like). More particularly, the subject matter herein relates to tactile feedback device (TFD) drum brakes using magnetically responsive (MR) material to generate resistive torque.

Existing magnetically responsive (MR) devices such as disk rotor brakes and drum brakes have a gap between the rotor and the coil which creates shear surfaces.

Document <CIT>, belonging to the state of the art, discloses a tactile feedback device drum brake comprising a shaft having a rotation disk rotatably connected thereto a drum rotor connected to the rotation disk, a core (<NUM>) having an integrated coil positioned radially inward from the drum rotor forming a first gap therebetween, a pole ring fixedly positioned radially outward from the drum rotor forming a second gap therebetween and a magnetically responsive material disposed within the first gap and the second gap.

Existing drum brakes do not have and cannot support more than two shear surfaces. Torque is limited to the size of the device and the available shear surface. Additionally, existing MR devices using a MR material require expensive seals to prevent the migration of the MR material from the gap into the remainder of the device. What is needed is an MR drum that is smaller than the existing devices and that provides greater torque. Also, what is needed is an MR drum brake that has improved seals to prevent migration of the MR material.

In one aspect, a tactile feedback device (TFD) drum brake according to claim <NUM> is provided. The TFD drum brake comprises a shaft, a drum rotor, a core, a pole ring, a magnetically responsive (MR) material, an upper magnetic seal, a lower magnetic seal, at least one sensor, and a housing enclosing the foregoing. The shaft has a rotation disk rotatably connected thereto. The drum rotor is connected to the rotation disk. The core has an integrated coil positioned radially inward from the drum rotor and forms a first gap therebetween. The pole ring is fixedly positioned radially outward from the drum rotor and forms a second gap therebetween. The MR material is disposed within the first gap and the second gap. The upper magnetic seal is positioned to block MR material from moving from the second gap. The lower magnetic seal is positioned to block MR material from moving from the first gap. The housing encloses the shaft, the drum rotor, the core, the upper magnetic seal, and the lower magnetic seal. The housing has a housing cap and a sensor housing secured thereto. The at least one sensor is capable of detecting rotation of the shaft.

In a preferred embodiment the drum rotor has a first brake shear surface and a second brake shear surface, wherein the first brake shear surface is on a rotor inner surface (RIS) of the drum rotor and the second brake shear surface is on a rotor outer surface (ROS) of the drum rotor. The pole ring has a pole ring shear surface on a pole ring inner surface (PRIS) fixedly and oppositely positioned from the ROS, wherein a second gap is positioned between the PRIS and the ROS. The core has an integrated coil. The core has a core shear surface on a core outer surface (COS) oppositely positioned from the RIS, wherein a first gap is positioned between the COS and the RIS. The rotation disk has an end, wherein the drum rotor is connected to the end and the rotation disk is rotatably connected to a shaft. The MR material is disposed within the first gap and the second gap. The housing includes a housing cap secured to a housing wall at housing top edge of the housing wall. The housing also includes a sensor housing secured to the housing wall at a housing bottom edge of the housing wall. The upper magnetic seal is positioned to block movement of the MR material from the first gap past an upper void between the upper magnetic seal and the housing cap. The lower magnetic seal is positioned to block movement of the MR material from the second gap past a lower void between lower magnetic seal and the core.

In yet another aspect, a method according to claim <NUM> of providing tactile feedback using TFD drum brake according to claim <NUM> is provided. The method comprises generating torque with TFD drum brake, energizing an integrated coil by applying current to the integrated coil, magnetically saturating a drum rotor, and generating a resistive torque. The drum brake includes a housing which encloses a shaft, a drum rotor, a pole ring, a core, a rotation disk, an upper magnetic seal, a lower magnetic seal, a MR material, and at least one sensor. The drum rotor has a first brake shear surface and a second brake shear surface. The first brake shear surface is on a rotor inner surface (RIS) of the drum rotor and the second brake shear surface is on a rotor outer surface (ROS) of the drum rotor. The pole ring has a pole ring shear surface on the pole ring inner surface (PRIS) fixedly and oppositely positioned from the ROS. The second gap is positioned between the PRIS and the ROS. The core has the integrated coil and a core shear surface on core outer surface (COS) that is oppositely positioned from RIS. The first gap is positioned between the COS and RIS. The rotation disk has an end. The drum rotor is connected to the end and the rotation disk is rotatably connected to the shaft. The MR material is disposed within the first gap and the second gap. The housing includes a housing cap secured to the housing wall at a housing top edge of the housing wall. The housing also includes a sensor housing secured to the housing wall at a housing bottom edge of the housing wall.

The upper magnetic seal is positioned to block movement of MR material from the first gap past an upper void between the upper magnetic seal and the housing cap. The lower magnetic seal is positioned to block movement of the MR material from the second gap past lower void between the lower magnetic seal and the core.

The TFD drum brake is controlled by a controller. The controller is in electronic communication with the at least one sensor. A power source generates a current. The power source is in electrical communication with the integrated coil. The controller is capable of controlling the current from the power source and the magnetic flux is generated as a result of the current being communicated to the integrated coil.

A circuit is provided that is capable of saturating the drum rotor with the magnetic flux. The circuit includes the core, the first gap with the MR material disposed therein, the drum rotor, the second gap with the MR material disposed therein, and the pole ring. The drum rotor saturates when the magnetic flux passes through the circuit and when the magnetic flux reaches a threshold of about <NUM> Tesla (T).

The method step of energizing the integrated coil by applying current to the integrated coil, generates the magnetic flux. The method step of magnetically saturating the drum rotor occurs with the generation of the magnetic flux. The step of magnetically saturating the drum rotor causes the first brake shear surface and the second brake shear surface of the drum rotor to shear against the MR material and each of the pole ring shear surface and the core shear surface. The method step of generating the resistive torque, includes the shearing of the MR material against the first brake shear surface, the second brake shear surface, the pole ring shear surface, and the core shear surface to create the resistive torque.

Vehicles typically have a steering column and a steering wheel to enable steering the vehicle. Many types of vehicles such as cars, trucks, off-road equipment, watercraft, etc. now use steer-by-wire technology and require the use of feedback to the operator to give the sensation of resistance as the steering wheel is turned. As used, the term steering wheel encompasses a standard wheel, or anything that rotates. The feedback is provided by a tactile feedback device (TFD). In the invention disclosed herein, the TFD is a TFD drum brake.

A typical magnetically responsive (MR) disk brake or a typical drum brake do not provide for radial compactness. A TFD drum brake as disclosed herein provides the benefits of a drum brake, but also adds a substantially increased torque provided by the MR material disposed within the TFD drum brake.

Referring to the drawings, <FIG> depict a tactile feedback device (TFD) drum brake generally designated as TFD drum brake <NUM>. TFD drum brake <NUM> comprises housing <NUM> enclosing shaft <NUM>, drum rotor <NUM>, core <NUM>, pole ring <NUM>, MR material <NUM>, upper magnetic seal <NUM>, and lower magnetic seal <NUM> within. Housing <NUM> includes housing wall <NUM>. Housing wall <NUM> includes housing top edge <NUM> and housing bottom edge <NUM>. Housing cap <NUM> is secured to housing top edge <NUM>. Housing cap <NUM> is made from a non-magnetic material (e.g., <NUM>-T6 Aluminum or similar material). Sensor housing <NUM> encloses drive electronics (not shown) for TFD drum brake <NUM> and is secured to housing bottom edge <NUM>.

Shaft <NUM> is rotatably disposed within housing <NUM>. Shaft <NUM> is rotatably supported by upper bearings <NUM> and lower bearings <NUM>. Shaft <NUM> has rotation disk <NUM> attached thereto and extending radially outward therefrom. Drum rotor <NUM> is connected to rotation disk <NUM> at end <NUM> of rotation disk <NUM> and rotates with shaft <NUM>. As illustrated in <FIG> drum rotor <NUM> extends radially outward from end <NUM> and is perpendicular to shaft <NUM> before it bends parallel to shaft <NUM> and perpendicular to rotation disk <NUM>. It is understood that rotation disk <NUM> can extend radially outward and drum rotor <NUM> can only be parallel to shaft <NUM>. Additionally, drum rotor <NUM> and rotational disk <NUM> can be a single component directly affixed to shaft <NUM>. In one embodiment, drum rotor <NUM> has a thickness between about <NUM> millimeters to about <NUM> millimeters. In another embodiment, drum rotor <NUM> has a thickness of about <NUM> millimeters to about <NUM> millimeters.

First brake shear surface <NUM> is on rotor inner surface (RIS) <NUM> of drum rotor <NUM>, and second brake shear surface <NUM> that is on rotor outer surface (ROS) <NUM> on drum rotor <NUM>. RIS <NUM> faces radially inward and ROS <NUM> faces radially outward.

Core <NUM> is disposed about shaft <NUM> and is not rotatable relative to shaft <NUM>. Core <NUM> is positioned radially inward from drum rotor <NUM>. Core <NUM> includes integrated coil <NUM>. Core <NUM> has core shear surface <NUM> on core outer surface (COS) <NUM> that is radially inward and oppositely positioned from RIS <NUM>. The space between COS <NUM> and RIS <NUM> forms first gap <NUM> therebetween. MR material <NUM> is disposed within first gap <NUM>.

Pole ring <NUM> is positioned and secured radially outward from drum rotor <NUM> and is secured between cap lower edge <NUM>, lower seat <NUM> of housing wall <NUM>, and wall inner surface <NUM>. Pole ring <NUM> is fixedly positioned radially outward from drum rotor <NUM>. Pole ring <NUM> has pole ring shear surface <NUM> on pole ring inner surface (PRIS) <NUM>. PRIS <NUM> is radially outward and oppositely positioned from ROS <NUM>. The space between ROS <NUM> and PRIS <NUM> forms second gap <NUM> therebetween. MR material <NUM> is also disposed within second gap <NUM>. Flow hole <NUM> is positioned proximate end <NUM> and is part of rotation disk <NUM>. Flow hole <NUM> allows for MR material <NUM> to flow between first gap <NUM> and second gap <NUM>.

In one embodiment, first gap <NUM> and second gap <NUM> each have a width of about <NUM> millimeters to about <NUM> millimeters. In another embodiment, first gap <NUM> and second gap <NUM> each have a width of about <NUM> millimeters to about <NUM> millimeters.

Referring to <FIG>, upper magnetic seal <NUM> is positioned between second gap <NUM>, rotation disk <NUM>, and lower edge <NUM> of housing cap <NUM>, where upper void <NUM> is formed therebetween. Upper magnetic seal <NUM> is positioned to prevent or block MR material <NUM> from moving from second gap <NUM>. Upper magnetic seal <NUM> includes permanent magnet <NUM>. Permanent magnet <NUM> is affixed to and rotates with rotation disk <NUM>. Upper opening <NUM> is positioned between upper void edge <NUM> of second gap <NUM> and permanent magnet <NUM>. Upper magnetic seal <NUM> prevents MR material <NUM> from entering upper void <NUM> through upper opening <NUM> and contaminating upper bearings <NUM>.

Lower magnetic seal <NUM> is positioned between first gap <NUM>, rotation disk <NUM>, and upper edge <NUM> of core <NUM>, where lower void <NUM> is formed therebetween. Lower magnetic seal <NUM> includes second permanent magnet <NUM>. Lower magnetic seal <NUM> is positioned to prevent or block MR material <NUM> from moving from first gap <NUM>. Second permanent magnet <NUM> is affixed to and rotates with rotation disk <NUM>. Lower opening <NUM> is positioned between lower void edge <NUM> of first gap <NUM> and second permanent magnet <NUM>. Lower magnetic seal <NUM> prevents MR material <NUM> from entering lower void <NUM> and contaminating lower bearings <NUM>.

In an alternative embodiment illustrated in <FIG>, lower magnetic seal <NUM> is positioned affixed adjacent core <NUM> with second permanent magnet <NUM> affixed to core <NUM>. Lower void <NUM> is positioned between non-magnetic washer <NUM> and lower opening <NUM>. Non-magnetic washer <NUM> is positioned affixed to and rotates with rotation disk <NUM>.

As illustrated in <FIG> and <FIG>, polarity <NUM> of lower magnetic seal <NUM> in all embodiments is opposite of polarity <NUM> of pole ring <NUM>. Rotation disk <NUM> provides the magnetic flux path for both upper magnetic seal <NUM> and lower magnetic seal <NUM>.

Referring to <FIG>, MR material <NUM> is a dry magnetically responsive powder including magnetizable particles that are not dispersed within a liquid or oil carrier. The magnetizable particles of material may include carbonyl iron, stainless steel, and/or any other magnetic material having various shapes, not limited to a spherical shape. MR material <NUM> is configured to provide smooth torque that is proportional to current, and it is independent of temperature.

As illustrated in <FIG>, <FIG>, and <FIG>, at least one sensor <NUM> is positioned to monitor rotation of shaft <NUM>.

Referring to <FIG> and <FIG>, controller <NUM> and power source <NUM> are included with TFD drum brake <NUM>. Power source <NUM> is capable of generating a current (not shown) and directly or indirectly electrically communicates the current to integrated coil <NUM>. Power source <NUM> is externally positioned from TFD drum brake <NUM>. Controller <NUM> is at least in electronic communication with at least one sensor <NUM>, integrated coil <NUM>, and power source <NUM>. Controller may include a current amplifier (not shown) and at least one temperature sensor (not shown).

Controller <NUM> is capable of controlling the current from power source <NUM> used to energize integrated coil <NUM> and generate magnetic flux <NUM>. The control is provided by using algorithms related to end-stop torque to simulate the end of travel or to torque for creating the tactile feedback based upon inputs such as steering effort, vehicle speed, and other operating functions. The control also includes processing data at least from sensor <NUM> related to the rotation of shaft <NUM>.

Controller <NUM> increases or decreases the current from power source <NUM> that is electrically communicated to integrated coil <NUM>. When the current amplifier is included, the current is controlled by the current amplifier, and it is capable of increasing or decreasing the current electrically communicated to integrated coil <NUM>. The current amplifier is used when controller <NUM> is integrally positioned within sensor housing <NUM> of TFD drum brake <NUM>. The current amplifier may be used when controller <NUM> is externally positioned from sensor housing <NUM> of TFD drum brake <NUM>.

Referring to <FIG> and <FIG>, magnetic flux <NUM> is generated when integrated coil <NUM> is energized with the current. Circuit <NUM> includes core <NUM>, first gap <NUM> with MR material <NUM> disposed therein, drum rotor <NUM>, second gap <NUM> with MR material <NUM> disposed therein, and pole ring <NUM>. Magnetic flux <NUM> passes through circuit <NUM> and saturates drum rotor <NUM>. Stated another way, controller <NUM> is capable of saturating drum rotor <NUM> with magnetic flux <NUM> generated by applying the current to integrated coil <NUM>. Magnetic flux <NUM> causes the MR material <NUM> to create shear between the core shear surface <NUM> and the first brake shear surface <NUM>, and between second brake shear surface <NUM> and pole ring shear surface <NUM>. The effect of shearing due to is the creation of torque in TFD drum brake <NUM>.

TFD drum brake <NUM> may be used on a vehicle (not shown). Vehicles typically have a steering column (not shown) and a steering wheel (not shown) to enable steering the vehicle. As discussed above, many vehicles now use steer-by-wire technology and require the use of a feedback to the operator of the vehicle to give the sensation of resistance as the steering wheel is turned. For vehicles with a steering column, TFD drum brake <NUM> enclosed therein. Shaft <NUM> of TFD drum brake <NUM> is capable of transmitting a feedback force to the operator through the steering wheel.

In an embodiment, a method of providing tactile feedback using TFD drum brake <NUM> is provided. The method comprises generating torque with TFD drum brake <NUM> described above, energizing integrated coil <NUM> by applying current to integrated coil <NUM>, magnetically saturating drum rotor <NUM>, and generating a resistive torque.

The drum brake is described above and includes housing <NUM> which encloses shaft <NUM>, drum rotor <NUM>, pole ring <NUM>, core <NUM>, rotation disk <NUM>, upper magnetic seal <NUM>, lower magnetic seal <NUM>, MR material <NUM>, and at least one sensor <NUM>. Drum rotor <NUM> has first brake shear surface <NUM> and second brake shear surface <NUM>. First brake shear surface <NUM> is on rotor inner surface (RIS) <NUM> of drum rotor <NUM> and second brake shear surface <NUM> is on rotor outer surface (ROS) <NUM> of drum rotor <NUM>. Pole ring <NUM> has pole ring shear surface <NUM> on pole ring inner surface (PRIS) <NUM> fixedly and oppositely positioned from ROS <NUM>. Second gap <NUM> is positioned between PRIS <NUM> and ROS <NUM>. Core <NUM> has integrated coil <NUM> and core shear surface <NUM> on core outer surface (COS) <NUM> oppositely positioned from RIS <NUM>. First gap <NUM> is positioned between the COS (<NUM>) and RIS <NUM>. Rotation disk <NUM> has end <NUM>. Drum rotor <NUM> is connected to end <NUM> and rotation disk <NUM> is rotatably connected to shaft <NUM>. MR material <NUM> is disposed within first gap <NUM> and second gap <NUM>. Housing <NUM> includes housing cap <NUM> secured to housing wall <NUM> at housing top edge <NUM> of housing wall <NUM>. Housing <NUM> also includes sensor housing <NUM> secured to housing wall <NUM> at housing bottom edge <NUM> of housing wall <NUM>.

Upper magnetic seal <NUM> is positioned to trap MR material in upper void <NUM> and to block movement of MR material <NUM> from first gap <NUM> past upper void <NUM> between upper magnetic seal <NUM> and housing cap <NUM>. Lower magnetic seal <NUM> is positioned to trap MR material in lower void <NUM> and to block movement of MR material <NUM> from second gap <NUM> past lower void <NUM> between lower magnetic seal <NUM> and core <NUM>. TFD drum brake <NUM> also includes at least one sensor <NUM>.

TFD drum brake <NUM> is controlled by controller <NUM>. Controller <NUM> is in electronic communication with at least one sensor. Power source <NUM> generates a current. Power source <NUM> is in electrical communication with integrated coil <NUM>. Controller <NUM> is capable of controlling the current from power source <NUM> and magnetic flux <NUM> generated as a result of current being communicated to integrated coil <NUM>.

Circuit <NUM> is capable of saturating drum rotor <NUM> with magnetic flux <NUM>. Circuit <NUM> includes core <NUM>, first gap <NUM> with MR material <NUM> disposed therein, drum rotor <NUM>, second gap <NUM> with MR material <NUM> disposed therein, and pole ring <NUM>. Drum rotor <NUM> saturates when magnetic flux <NUM> passes through circuit <NUM>.

The method step of energizing integrated coil <NUM> by applying current to integrated coil <NUM>, generates magnetic flux <NUM>.

The method step of magnetically saturating drum rotor <NUM> occurs with the generation of magnetic flux <NUM>. The step of magnetically saturating drum rotor <NUM> causes first brake shear surface <NUM> and second brake shear surface <NUM> of drum rotor <NUM> to shear against MR material <NUM> and each of pole ring shear surface <NUM> and core shear surface <NUM>.

The method step of generating the resistive torque, includes the shearing of the MR material <NUM> against first brake shear surface <NUM>, second brake shear surface <NUM>, pole ring shear surface <NUM>, and the core shear surface <NUM> to create the resistive torque.

Claim 1:
A tactile feedback device, (TFD) drum brake (<NUM>) comprising:
a shaft (<NUM>) having a rotation disk (<NUM>) rotatably connected thereto;
a drum rotor (<NUM>) connected to the rotation disk (<NUM>);
a core (<NUM>) having an integrated coil (<NUM>) positioned radially inward from the drum rotor (<NUM>) forming a first gap (<NUM>) therebetween;
a pole ring (<NUM>) fixedly positioned radially outward from the drum rotor (<NUM>) forming a second gap (<NUM>) therebetween;
a magnetically responsive (MR) material (<NUM>) disposed within the first gap (<NUM>) and the second gap (<NUM>); characterised by
an upper magnetic seal (<NUM>) positioned to block the MR material (<NUM>) moving from the second gap (<NUM>);
a lower magnetic seal (<NUM>) positioned to block the MR material (<NUM>) moving from the first gap (<NUM>);
a housing (<NUM>) enclosing the shaft (<NUM>), the drum rotor (<NUM>), the core (<NUM>), the upper magnetic seal (<NUM>), and the lower magnetic seal (<NUM>), the housing (<NUM>) having a housing cap (<NUM>) and a sensor housing (<NUM>) secured thereto; and
at least one sensor (<NUM>) capable of detecting a rotation of the shaft (<NUM>).