JP2006505957A - Improved MR device - Google Patents

Abstract

Disclosed are damper devices, magnetic viscous devices including rotary devices, and haptic systems comprised of these devices. These devices include dry magnetically responsive particles, or MR fluid containing the magnetically responsive particles. Soft magnetic particles have a cumulative volume fraction of 10%, 50%, and 90% by volume (ie, 2 μm D ₁₀ to 5 μm D ₁₀ or less, 8 μm D ₅₀ to 15 μm D). ₅₀ or less, having from 25μm of _{D 90} 40 [mu] m of _{D 90} or less), characterized by a single process output product population of atomized particles, and, of 0.77 or more, the smallest log-normal particle size against cumulative volume% fraction Characterized by square regression.

Description

(Background of the Invention)
Magnetorheological (MR) devices (eg, linear dampers, rotary brakes, and rotary clutches) with “rotary-acting” changes or “linear-acting” changes, such as working gaps in the device Magnetorheological materials are used as dry particles occupying the working gap or as particles dispersed in the fluid. These particles are composed of magneto-soft particles. The higher the strength of the applied magnetic field, the greater the damping or resistance or torque required to overcome the grain structure aligned in the magnetic field.

  The MR device is entitled “Portable Controllable Fluid Rehabilitation Devices”, US Pat. No. 5,816,372, entitled “Magnetorheological Fluid Devices And Process Of Controlling Force In Exercise Equipment Utilizing Same” U.S. Pat. No. 5,711,746; U.S. Pat. No. 5,842,547 entitled "Controllable Brake"; U.S. Pat. No. 5,878, titled "Controllable Vibration Apparatus" 871, and U.S. Pat. Nos. 5,547,049, 5,492,312, 5,398,917, 5,284,330, and 5,277,281. (All of which are assigned to the assignee of the present invention).

  The present invention comprises a housing or chamber containing a magnetically controllable fluid as disclosed herein below, and comprises a movable member (piston or rotor) attached for movement through the fluid in the housing. Regarding dampers. Both the housing and the movable member comprise magnetically permeable pole pieces. The magnetic field generator generates a magnetic field across both pole pieces to direct the magnetic flux to the desired region of the controllable fluid. Such devices require precise tolerance components, expensive seals, expensive bearings, and relatively small volumes of magnetically controllable fluid. MR devices designed so far are relatively expensive to manufacture. There is a continuing need to reduce the cost of controllable MR devices to provide variable force and / or variable torque.

  Conventional MR fluids containing magnetically active microparticles with an average diameter on the order of approximately 1-100 μm use conventional iron particles produced by the carbonyl method (by which the particles are enlarged by the deposition of pentacarbonyl salts). . Carbonyl powder is famous for its high cost. The magnetorheological fluid is manufactured using magnetically active particles manufactured by an atomization method. Atomization is a reductive process that breaks a molten metal stream into small particles. The molten metal stream is delivered to a high-pressure, high-speed stream and divided by high shear and turbulence (hereinafter collectively referred to as “atomized particles”).

  Due to performance and cost issues, so far, a suitable alternative to expensive carbonyl iron with atomized particles has not been a simple alternative. In conventional particles, atomized particles in a single process stream have been sieved to eliminate a significant fraction of 10-20% of particles over 74 μm. In other examples, even larger fractions of 20-30 +% of the single process yield of atomized particles larger than 45 μm in size must be excluded. The removal of such unusable volume fractions, which represent indeed less than 90% yield, is currently considered uneconomical.

  Attempts have been made to blend atomized particles with carbonyl iron particles to achieve a particle size distribution suitable for use in MR dry powders and MR fluids. To date, attempts to provide 100% conventional atomized particles through a 74 μm sieve and approaching a Gaussian distribution have been achieved by blending the particles from more than one process stream. One example is a blend of carbonyl iron and atomized particles. US Pat. No. 6,027,664 (Lord Corporation) teaches a blend of a first population having an average particle diameter that is 3 to 15 times greater than the second population. The smaller average size particles are carbonyl iron and the larger size particles are atomized iron. Such mixtures suffer from economic losses due to the loss of output that continues from classification or sieving and the costs associated with the blending itself.

The suitability of any particulate metal for use in MR fluids is, in one aspect, determined by analyzing deviations from the Gaussian distribution and can be illustrated by regression analysis. The mixture of the two different populations taught so far in the art gave some degree of compatibility with the Gaussian distribution approaching that of the carbonyl iron-based particles. For example, a 50:50 (weight) mixture of carbonyl iron and water-atomized particles (available at the filing date of the '664 patent) has a log normal size distribution of 0.82 (R ² ). Although technically feasible, previously available particle blends suffer from the same economic disadvantages. Thus, to overcome this economic drawback, MR devices that utilize controllable powders or MR fluids that utilize lower cost single process flow particles are required. To improve economic factors in controllable devices, including particle components derived from a single process output population of magnetically responsive particles that exhibit an appropriate size population and size distribution It is advantageous to provide an MR fluid.

(Summary of the Invention)
In accordance with the present invention, a magnetorheological fluid is provided. In another aspect of the invention, linear or rotary magnetically controllable devices (e.g. dampers, clutches, brakes) and haptics using such devices and the magnetorheological fluids or powders according to the invention Interface systems are provided. These devices range from 2 μm, 3 μm, or 4 μm 10% volume fraction (D ₁₀ ) to 5 μm D ₁₀ or less; 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, or 14 μm 50% volume fraction (D ₅₀ diameter) ) To 15 μm of D ₅₀ or less; 25 μm of 90% volume fraction (D ₉₀ ) to particles having a D _{90 of} 40 μm or less of magnetically responsive particles (ie non-mixed) Characterized by including magnetically-soft particles in the working gap or space; and this single-process population of atomized particles is lognormal to a cumulative volume% of 0.77 or higher Further characterized by least squares regression (R ² ) from particle size. A rotary device according to the present invention may use magnetizable fluids or magnetizable particles of a single atomization process flow population without a fluid carrier.

Magnetorheological damper device (which includes an MR fluid containing a volume% of carrier fluid and a volume% of particles derived from a single atomization process stream, and optionally additives that reduce friction between particles) Within the working gap, where the magnetically responsive particles exhibit 2 μm D ₁₀ to 5 μm D ₁₀ or less, 8 μm D ₅₀ to 15 μm D ₅₀ or less, and 25 μm D ₉₀ to 40 μm D ₉₀ or less In one embodiment of the device for), the atomized particle population is also characterized by a least squares regression (R ² ) from log-normal particle size for cumulative volume% greater than or equal to 0.77.

  The invention further relates to a magnetorheological rotary device comprising such particles in a working gap with or without a carrier fluid. The invention further relates to a user operated haptic interface system that provides resistance to the haptic interface device. The system includes a controller for receiving a variable input signal and providing a variable output signal. The controller is adapted to process a variable input signal and execute a program that produces a variable output signal accordingly. The haptic interface device is in communication with at least one magnetically controllable device disclosed herein.

(Detailed description of the invention)
Linear or rotary controllable devices include brakes, pistons, clutches, and dampers known in the art. Examples of dampers that include a magnetorheological fluid are disclosed in US Pat. Nos. 5,390,121 and 5,277,281.

A linear controllable damping device for variable damping motion uses the magnetorheological fluid specified herein and comprises the following elements:
a) a housing for containing a volume of magnetorheological fluid;
b) a piston adapted for movement in a housing containing a fluid, wherein the piston is made of iron-containing metal and defines a number of turns of conductive wire defining coils that generate magnetic flux in and around the piston. Valve means having a working gap associated with the housing and the piston for controlling the movement of the magnetorheological fluid;

  Examples of devices herein include fluid valves, composite structures and composite structural elements, shock absorbers, haptic devices, exercise equipment, electrical switches, prosthetic devices including fast-cure casts, elastic mounts, vibration mounts, and To contain an excess of the magnetorheological fluid of the present invention required to occupy the working gap via a reservoir of magnetorheological fluid outside the working gap, from which particles can move into the working gap. Other similar devices built on the

  In the exemplary particle example of the present invention, the first portion of the magnetorheological fluid is positioned within the working gap while the second portion of the magnetorheological fluid is located outside the working gap and within the working gap. Positioned in communication with the magnetorheological fluid (ie, within the fluid-filled compartment). Upon polarization of the particles in the magnetorheological fluid by application of an external magnetic field, the particles from the second part move into the working gap, which results in an increase in the particle concentration of the magnetorheological fluid in the working gap. As a result, the force output of the magnetorheological fluid device increases. During application of the external magnetic field, the particle volume concentration in the first portion of the magnetorheological fluid is higher than the total particle volume concentration at rest or in the off state. The stationary or off-state particle volume concentration is the average particle volume concentration indicated by the combination of the magnetorheological fluid in the first part and the controllable fluid in the second part when no magnetic field is applied. means.

(Controllable damper)
The magnetorheological fluid controllable damper has the essential components of a fixed housing, a movable piston, and a magnetic field generator. The housing contains a predetermined volume of the MR fluid described herein. The damper has two principle modes of operation: a sliding plate mode and a flow (or valve) mode. Both mode components exist for each MR damper, with the force component governing the flow mode or valve mode.

  The damper functions as a Coulomb damper or a Bingham damper, where the force generated can be controlled independently of the piston speed, and a large force can be generated at low or zero speed. This independence improves the controllability of the damper and makes the force a function of a precisely tuned magnetic field strength (which is a function of the current flow in the circuit).

  Referring to FIG. 10, a simplified structural diagram of a cross-section of a piston portion of an MR device, well known in the art, is illustrated (US Pat. No. 5,277, issued January 11, 1994). 281 is more fully illustrated). The piston is disposed within the housing (not shown). The piston head 30 on the piston rod 32 is formed with a maximum diameter smaller than the inner diameter of the housing. In FIG. 10, the illustrated piston embodiment comprises a coil 40 wound on a core element 43 and residing in a cup member 53. A lead wire (one of which is connected to a first end of a conductive rod extending through the piston rod 32; one is a lead connected to the first end of the coil winding; and One is the ground wire from the other end of this coil winding) and the electrical connection to the coil through the piston rod is not shown. The upper end (not shown) of the piston rod 32 has a groove formed thereon to allow attachment to the damper. Depending on the application, an external power supply that supplies current in the range of 0-4 amps at a voltage of 12-24 volts is connected to these leads.

  The cup member 53 has a plurality of passages 56, each of which has a predetermined gap formed therein. In other exemplary embodiments, this gap is provided annularly. One or more seals as at 54 extend around the circumference of the cup member 53. The cup member 53 is attached to the core element 43 by any fastening means (not shown), such as by screw parts. Alternatively, the coil may be associated with the housing, if desired, giving the possibility of a more fixed coil. The device of the present invention utilizes a predetermined annular flow gap in the range of 0.1 to 0.90 mm, and preferably 0.4 to 0.6 mm. This gap is desirably small to provide a compact MR fluid device that generates relatively high on-state forces. Magnetically responsive particles obtained from the carrier and the single atomization process flow disclosed above within a device gap of 0.08 mm to 0.9 mm, and more particularly within a working gap of 0.08 to 0.75 mm. There are MR fluids, including

(Controllable clutch or controllable brake)
The term “clutch” is used when acceleration torque is transmitted. The term “brake” is used when deceleration torque is transmitted. The clutch according to the invention can also be used as a brake. A typical MR fluid clutch or MR fluid brake comprises: a housing (preferably having a first half and a second half having substantially similar internal dimensions), preferably a disk-type rotor, Rotating shaft (preferably made of soft magnetic material, with optional key slots therein), soft magnetic yoke (preferably substantially identical, first pole piece half and second pole piece A nonmagnetic bushing impregnated with grease or oil, which supports the shaft in the radial direction; an elastomer seal (preferably an elastomer quad-ring type of elastomer) Seal); disc spring for centering the rotor, coil assembly for generating variable magnetic field ( Re is, polymers bobbin (e.g., nylon), and a plurality of hoops winding a wire coil), as well as electrical connectors and electrical fastener. Half of each pole piece has a groove formed therein that forms a groove that interacts with each other to receive the working portion of the rotor. Receiving the rotor in this groove creates a first gap and a second gap adjacent to the working surface containing a sufficient volume of MR fluid as specified herein. The clutch is a barrel rotor type clutch or a multi-plate clutch. These clutches are well known and are described, for example, in US Pat. No. 5,988,366 (incorporated herein by reference). The MR fluid contained in the groove is of the dry powder type (without fluid carrier) or of the MR fluid type. The particles responsive to the magnetic field contained in the working gap are single-processed products of atomized particles with populations exhibiting R ² greater than or equal to 0.77, and also from 2 μm D ₁₀ to 5 μm D ₁₀ or less, Characterized by a volume fraction of 8 μm D ₅₀ to 15 μm D ₅₀ or less, and 25 μm D ₉₀ to 40 μm D ₉₀ or less.

An exemplary controllable brake according to the present invention comprises:
(A) shaft;
(B) a rotor made of a highly magnetically permeable material (the rotor is connected to the shaft by the first and second rotor surfaces, the working part, and the outer periphery). To prevent relative rotation between them));
(C) A housing with a soft magnetic yoke manufactured from a highly magnetically permeable powdered metal material, the soft magnetic yoke having a groove formed therein, which receives the working part of the rotor And forming a first gap adjacent to the first rotor surface and a second gap adjacent to the second rotor surface, wherein the housing is compared to a part of the housing comprising a yoke; Including a relatively thin molded portion, which is formed adjacent to the shaft to prevent the magnetic field from increasing in the seal area of the shaft);
(D) soft magnetic particles, either as dry powder or dispersed in a carrier fluid (the particles are contained within the first gap and the second gap and at least partially fill these gaps) The particles are characterized by being obtained from a single process output of atomized particles having a population exhibiting an R ² of 0.77 or more, and also from 2 μm D ₁₀ to 5 μm D ₁₀ or less, 8 μm Characterized by a volume fraction of D ₅₀ to 15 μm of D ₅₀ or less, and 25 μm of D ₉₀ to 40 μm of D ₉₀ or less); and (e) variable, for example provided by a coil and adjacent to a soft magnetic yoke A magnetic field generating device that generates a magnetic field (when a voltage is applied to a means for generating a variable magnetic field, the softness in the first gap and the second gap is Changing sex particles rheology, whereby the variable magnetic field is oriented to produce a change in the torsional resistance of the controllable brake).

  More specifically, half of the controllable brake housing is manufactured from wrought steel, stamped steel, cast or machined aluminum, aluminum alloys, powdered metal, and the like. The most preferred housing material is cast aluminum or zinc / aluminum alloy. Each housing half preferably has pole pockets formed therein and spaced radially outward from the shaft axis. This pocket is formed near the outermost portion of its radial portion to receive half of the ring-like pole piece of the soft magnetic yoke therein. It is customarily taught to prevent or minimize stray magnetic field build-up in the area adjacent to the shaft by spacing it away from the shaft with the soft magnetic yoke.

When aluminum or other non-magnetic material is used in the housing, spacing the soft magnetic yoke radially outward from the shaft limits the magnetic field at or near the shaft seal. Acts as a means. Similarly, when steel or other similar magnetic material is used for the housing, a magnetic flux saturation zone having a certain thickness is combined with spacing the soft magnetic yoke radially outward from the shaft. Limiting the amount of stray field present in the region adjacent to the shaft. The housing functions to support the shaft and form part of the MR fluid enclosure. The housing also includes a projecting flange portion, preferably there are three or four pairs of this flange portion, which are equally spaced and via fasteners to secure the assembly together. (For example, using a socket head cap screw and nut) and bolted together. The housing also comprises means for preventing rotation of the pole pieces half relative to each other and half of the housing. One such prevention means is a nub and receiving groove to prevent rotation. Further, the fastener can interact with a local cutout or groove formed on the radial outer periphery of the pole piece to limit its rotation. Inducing a magnetic field between the poles results in the structuring of a magnetically responsive particle that polarizes and aligns into a chain acting across the first gap and the second gap. The metal particles have a density range of about 6.4 gm / cm ³ to about 7.8 gm / cm ³ . A change in rheology as a function of the magnitude of the magnetic field results in an increase in torsional resistance between the housing and the rotor in its working section, and an increase in resistance to torsional rotation of the shaft relative to the housing. This provides a controllable resistance in systems where MR brakes are used, which for the exemplary embodiment is about 220 in. -Lb. It can be a range up to the torque output.

(Haptic interface system)
The controllable damper and / or controllable brake can also be incorporated as part of a haptic interface system according to the present invention. In accordance with another embodiment of the present invention, a haptic interface system is disclosed that comprises a haptic interface device that can be moved by an operator in at least one direction of rotation or movement, the haptic interface system comprising: Provides resistance to the device. The system includes a controller for receiving a variable input signal and providing a variable output signal. The controller is adapted to process a variable input signal and correspondingly execute a program that produces a variable output signal. The haptic interface device is in communication with at least one magnetically controllable device, such as a damper. There may be more than one similar or different controllable device in the haptic interface system. The at least one controllable damper device or controllable brake device has a plurality of positions, wherein the haptic interface device motion ease between the plurality of positions is MR fluid (damper And a variable resistance of a controllable device comprising a powdered soft magnetic material, or soft magnetic particles dispersed in a carrier fluid (MR fluid). Soft magnetic (magnetically responsive) particles have a single atomization process with 2 μm D ₁₀ to 5 μm D ₁₀ or less; 8 μm D ₅₀ to 15 μm D ₅₀ ; and 25 μm D ₉₀ to 40 μm D ₉₀ And where the single process population shows a least squares regression (R ² ) from a lognormal distribution of 0.77 or greater. The powder or MR fluid receives a variable output signal and provides a variable resistance as a function of the variable output signal. This resistance function can be directly proportional to the variable output signal provided by the computer data algorithm, or can be a derivative from the variable output signal. Variable resistance force, depending on the output signal that directly controls the relaxation of movement, simulates the resulting force, and / or simulates the boundary limit of the haptic interface device, among force types , Provided by changing the rheology of the MR powder or MR fluid. The variable resistance force provides resistance to movement of the haptic interface device that is guided by the operator in at least one direction of movement.

  Examples of vehicles and machines that can incorporate the haptic interface system of the present invention include industrial vehicles, ships, overhead cranes, trucks, automobiles, and robots. A haptic interface device may include, but is not limited to, a steering wheel, crank, foot pedal, knob, mouse, joystick, or lever.

  In particular, the haptic interface system according to the present invention comprises one or more motors connected to the interface device to provide a force feedback sensation. Typical motors include direct current (DC) stepper motors and servo motors. If the interface device is a joystick, a motor is used to provide force in the x-axis direction, y-axis direction, or a combination of these to provide force in any direction in which the joystick can be moved. Similarly, if the interface device is a steering wheel, a motor is used to provide rotational force in the clockwise and counterclockwise directions. Thus, the motor is used to apply a force in any direction in which the interface device can be moved.

  In a system using a single motor, the motor can be connected to the interface device through a gear train, or other similar energy transfer device, to apply force in one or more directions. In order to be able to use one motor in the system, typically a reversible motor is utilized to provide forces in two different directions. In addition, the mechanism is required to engage and disengage various gears or other energy transfer devices in order to provide force in the appropriate direction at the appropriate time. Conversely, other typical systems use one or more motors to provide force in the required direction. Thus, current systems utilize a number of different approaches to deal with force feedback sense delivery.

  In addition, the controller may send signals to the vehicle, machine, or computer simulation in response to information obtained from sensors and other inputs to control the operation of the vehicle, machine, or computer simulation. Once operator input and other inputs are processed by the microprocessor, a force feedback signal is sent to the magnetically controllable device, which then reflects the control of the vehicle, machine, or computer simulation. Control an interface (eg, joystick, steering wheel, mouse, etc.).

  The system further comprises a controller (eg, a computer system) adapted to execute the interactive program, and a sensor that detects the position of the haptic interface device and provides a variable input signal corresponding to the controller. This controller processes variable input signals from interactive programs and sensors, and provides variable output signals that correspond to semi-active variable resistance forces that provide the operator with a tactile sensation calculated by the interactive program To do. The variable output signal applies a voltage to the magnetic field generating device disposed adjacent to the first and second members to generate a magnetic field having a strength proportional to the variable resistance force. This magnetic field is applied across the MR fluid disclosed herein that is disposed in the working gap or working space between the first member and the second member. The applied magnetic field is associated with the relative fluid movement (eg, linear motion, rotational motion, or curvilinear motion) between the first member and the second member in communication with the haptic interface device. Change the resistance. A variable output signal from the controller controls the strength of the applied magnetic field (and thus the variable resistance of the MR fluid). The resistance provided by energizing the MR fluid controls the relaxation of the haptic interface device motion between multiple locations. Thus, the haptic interface system provides a vehicle, machine, or computer simulation operator with a force feedback sensation via a magnetically controllable device that opposes the movement of the haptic interface device.

  The haptic interface device is in operative contact with a vehicle, machine, or computer system operator. The magnetically controllable device advantageously includes an MR fluid between the first member and the second member, wherein the second member is in communication with the haptic interface device. The haptic interface system of the present invention can be used to control vehicle steering, throttle, clutch, and brake; computer simulation; machine motion and function. Examples of vehicles and machines that may comprise the haptic interface system of the present invention include industrial vehicles and ships, overhead cranes, trucks, automobiles, and robots. Haptic interface devices can include, but are not limited to, steering wheels, cranks, foot pedals, knobs, mice, joysticks, and levers.

  In a preferred controllable device, the MR fluid described herein is distributed around an absorbent element that is disposed between the first member and the second member. A preferred absorbent element is a reticulated porous polymer matrix and is elastic. The elastic element is preferably positioned within the device in a partially compressed state from a stationary state (preferably in an amount of about 30-70% compression from the stationary state). The absorbent element can be formed as a matrix structure having an open space to hold the MR fluid. Suitable materials for the absorbent element include open-celled foam, derived from polyurethane materials and the like, among others. A preferred haptic interface system is disclosed in US Pat. No. 6,373,465 (incorporated herein by reference).

(Particle component)
Removal of microfractions representing particles containing oversized sizes with particles less than 5% by volume, more typically less than 2% by volume, and more preferably less than 1% by volume (200 mesh, 170 mesh, or Magnetic responsiveness due to the fact that there is no classification other than a single coarse screening, such as passing through a 140 mesh sieve (74, 88 and 105 micrometers, respectively) The MR fluid comprising particles, or carriers and responsive particles, is obtained from a single atomization process stream having an inherent particle distribution. As used herein, the term “unclassified” is taken to mean that there is no further classification other than a single coarse sieving step. Single process stream particle populations are distinguished based on cumulative volume fractions below a particular micrometer (micron) size. Instrumental analysis methods known in the art can report cumulative volume percentages below a certain particle size at 10%, 50%, and 90%, and D ₁₀ , D ₅₀ , and D ₉₀ , respectively. , Said in the field. Magnetically responsive particles operating within the working gap are characterized by 2 μm D ₁₀ to 5 μm D ₁₀ or less; 8 μm D ₅₀ to 15 μm D ₅₀ or less; and 25 μm D ₉₀ to 40 μm D ₉₀ . Particle populations from a single atomization process stream are further characterized by a least squares regression (R ² ) of log-normal particle size in microns for a cumulative volume% fraction greater than 0.77.

The determination of D ₁₀ , D ₅₀ , and D ₉₀ is accurately measured using equipment available in the art. Malvern Instruments, Ltd. (Malvern, UK) model Mastersizer® S, Version 2.18 analyzes particle volume distribution and analyzes cumulative volume% fraction μm size at D ₁₀ , D ₅₀ , and D ₉₀ In order to do this, the manufacturer is provided with appropriate functions. Particle fraction data, for the determination of R ^2, such as Excel (registered trademark), is input to a typical built in statistical software under normal regression analysis techniques.

Referring to FIG. 1, FIG. 1 illustrates the following to illustrate the consistency of carbonyl iron (C-1) compared to the atomized particle population and the mixture of atomized particles and carbonyl iron (Control 7): 1 includes lognormal plots of data obtained from each of the examples. For each example analyzed for volume% distribution, cumulative volume fraction data for log-normal particle size (μm) was input into Microsoft® Excel regression analysis software and a least squares regression function was calculated. The R ² values obtained for the examples characterize the degree of agreement with the lognormal distribution.

  Referring to FIG. 2, the graph shows the log normal of the particle size distribution from the data in Table 1 using Malvern Mastersizer® S for control 1-carbonyl iron particles (R-2430, eg, ISP Corp.). Represents a plot.

  Referring to FIG. 3, the graph shows a log-normal plot of the particle size distribution from the data in Table 2 using Malvern Mastersizer® S for atomized particles (FPI (-325 mesh), eg Hoeganes). To express.

  Referring to FIG. 4, the graph shows the log of the particle size distribution from the data in Table 3 using Malvern Mastersizer® S for Control 3 atomized particles (FPI Grade II (2), eg, Hoeganes). Represents a normal plot.

  Referring to FIG. 5, the graph is a lognormal plot of the particle size distribution from the data in Table 4 using Malvern Mastersizer® S for control 4 atomized particles (FPI Grade II GAF, eg, Hoeganes). Represents.

  Referring to FIG. 6, the graph shows the particle size distribution from the data in Table 5 using Malvern Mastersizer® S for control 5 atomized particles (Atomet® PD3871, eg, Quebec Metal Powders). Represents a lognormal plot of.

  Referring to FIG. 7, the graph shows the particle size distribution from the data in Table 6 using Malvern Mastersizer® S for control 6 atomized particles (Atomet® PD4155, eg, Quebec Metal Powders). Represents a lognormal plot of.

  Referring to FIG. 8, the graph shows the particle size distribution from the data in Table 7 using Malvern Mastersizer® S for Control 7 (50:50 wt% mixture of carbonyl iron 2430 and FPI Grade II). Represents a lognormal plot.

  Referring to FIG. 9, a graph represents the log normal plot cumulative volume% of particles from the data in Table 8 for atomized particles used in accordance with the present invention.

The calculated R ² values obtained from the above are listed below in descending order.

In accordance with a controllable device that includes a dry powder or MR fluid within the working gap, a single process yield atomized particle population is achieved that exhibits an R ² of 0.77 or greater, with improved cost performance. This single process atomized particle is also characterized by a particle diameter size within the _10th , _50th , and _90th cumulative volume percentages (D10, D50, and D90, respectively). The MR responsive magnetically responsive particles of the present invention exhibit 2 μm D ₁₀ to 5 μm D ₁₀ or less; 8 μm D ₅₀ to 15 μm D ₅₀ or less; and 25 μm D ₉₀ to 40 μm D ₉₀ or less. More preferred single process atomized particles are characterized by 2 μm D ₁₀ to 5 μm D ₁₀ or less; 10 μm D ₅₀ to 13 μm D ₅₀ or less; and 28 μm D ₉₀ to 35 μm D ₉₀ or less.

The particle population utilized herein utilizes a process output from a single process stream that is distinguished from a blend of one or more lots or blends of particles from different process streams. Improvements are provided in which a single process population exhibits an R ^{2 of} 0.77 or more, a D _{10 of} ² to 5 μm or less, a D _{50 of} 8 to 15 μm or less, and a D ₉₀ of 25 to 40 μm or less. A method for making particles of a single atomization process product having the above properties is described in WO 99/11407. The process of WO 99/11407 is a hybrid gas-water atomization process whereby gas (eg, air) flows as a laminar flow to the inlet of a tapered inlet nozzle and near the outlet of the nozzle. It flows out of the nozzle almost at the speed of sound. The nozzle assembly has an orifice in its center, an inverted conical shape, a slit surrounding the lower side of the nozzle for water injection, and an ejector tube that is perpendicular to the lower surface of the nozzle and coaxial with the orifice. Prepare. The nozzle shape is such that the gas is drawn in a laminar flow from the upper side of the orifice, and the velocity of the gas increases as the gas passes through the narrowed area of the orifice, resulting in a speed of sound as the gas exits the orifice. Constructed to be near or equal to the speed of sound. The nozzle device comprises a baffle plate / annular ring at the orifice outlet, which has an aperture having a smaller diameter than the orifice outlet aperture.

The gas pressure drops along the nozzle from the inlet to the outlet, rises as it exits the nozzle outlet, and the increased pressure of the gas reaches the converging point of the inverted-cone shaped flow liquid jet To fall. The gas emerging from the orifice expands rapidly and impinges on the walls of the liquid jet, and reflections of the impinging gas produce expansion and compression waves. Due to repeated reflections on the wall of the liquid, the expansion and compression waves cause a splitting action on the flow of molten metal when the atomization phenomenon occurs. A single process product and a commercial product providing the specific D ₁₀ , D ₅₀ , and D ₉₀ described above are sold by Atmix Corp under the name PF-20E. US Pat. No. 6,254,661 is hereby incorporated by reference as if fully set forth herein.

The atomized soft magnetic particle composition prepared in the above hybrid method includes iron alone or alloy level aluminum, silicon, cobalt, nickel, vanadium, molybdenum, chromium, silicone, tungsten, boron, manganese, and / or Or of iron combined with copper or the like (eg, iron: cobalt alloy and iron: nickel alloy in the range of about 30:70 W / W to 95: 5 W / W (preferably about 50:50 to 85:15)) Consists of such elements. Exemplary iron-nickel alloys have a typical iron-nickel weight ratio in the range of about 90:10 to 99: 1, preferably 94: 6 to 97: 3. The alloy may advantageously contain small amounts of other elements (eg, vanadium, chromium, etc.) up to 3% by weight to improve the ductility and mechanical properties of the alloy. Exemplary particles also include iron oxide and / or iron nitride and / or iron carbide. Iron oxide includes all known pure iron oxides (eg, Fe ₂ O ₃ and Fe ₃ O ₄ ), as well as iron oxides containing small amounts of other elements (eg, manganese, zinc, or barium). Specific examples of iron oxide include ferrite and magnetite. Preferably, the magnetically responsive particles used have less than about 0.01% carbon. In particularly preferred embodiments, the magnetically responsive particles comprise 97% to 99% iron and less than about 1% oxygen and nitrogen.

In devices using MR fluids, the particulate component represents from about 5 to about 50 volume percent, preferably from about 15 to 40 volume percent of the total volume of the magnetorheological fluid. The volume percent of the particle component is selected within a specific range depending on the desired magnetic yield stress, the desired MR fluid viscosity, and other design criteria desired. The density of the magnetically responsive particles typically ranges from about 6.4 gm / cm ³ to about 7.8 gm / cm ³ . With respect to the weight percent corresponding to the above volume fraction of particles, the carrier fluid and magnetorheological fluid particles have a specific gravity of about 0.80 and 7.8, respectively, 30 to 89 weight percent, preferably about 59 to There are 85% by weight of particles.

  Embodiments of a magnetorheological fluid included in a controllable device of the present invention are dispersed in a carrier fluid to provide a magnetorheological fluid composition. This carrier component is typically present in an amount of about 50 to about 95 volume percent of the magnetorheological fluid. The volume percentage of particulate component in the magnetorheological fluid embodiment is the designed yield stress level, off-state viscosity, and other fluid or device designs that are readily understood by those skilled in the art and that are beyond the scope of this disclosure. Depending on the factor, it is an arbitrary range preselected. The carrier component forms a continuous phase of the magnetorheological fluid. The carrier fluid used to form the magnetorheological fluid from the magnetorheological composition of the present invention can be any known vehicle or carrier fluid for use with the magnetorheological fluid. If the magnetorheological fluid is designed as an aqueous MR fluid, those skilled in the art will understand which additives disclosed herein are suitable for such aqueous systems according to the teachings in the published art. An aqueous carrier system is described, for example, in US Pat. No. 5,670,077, which is hereby incorporated by reference in its entirety. If a water-based system is used, the formed magnetorheological fluid may optionally include one or more suitable thixotropic agents, antifreeze components, or rust inhibitors as typical conventional optional additives. May be included.

In a preferred aspect, the devices disclosed herein using MR fluids utilize a carrier fluid that is an organic liquid. Suitable carrier fluid that may be used include natural fatty oils, mineral oils, polyphenyl ethers, dibasic acid _esters, C 3 -C ₈ aliphatic _alcohols, C 3 -C ₈ aliphatic _glycol, C 3 -C ₈ aliphatic diols, and C ₃ -C ₈ aliphatic higher polyols than, neopentyl polyol esters, phosphoric acid esters, synthetic cycloparaffins and synthetic poly α- olefins, unsaturated hydrocarbon oils, monobasic acid esters, glycol Esters and glycol ethers, silicate esters, silicone oils, silicone copolymers, synthetic hydrocarbons, perfluorinated polyethers and perfluorinated polyesters, and halogenated hydrocarbons, and mixtures or blends thereof. Water, as well as water mixed with miscible organic compounds, are useful carrier fluids. Preferred aqueous carriers include a mixture of water and one of C ₃ -C ₈ diols such as ethylene glycol, propylene glycol, and butanediol.

  Hydrocarbons such as mineral oils, paraffins, cycloparaffins (also known as naphthenic oils), and synthetic hydrocarbons are a preferred class of organic carrier fluids. Synthetic hydrocarbon oils include oils obtained from oligomerization of olefins such as polybutenes, and alpha-olefins having 8 to 20 carbon atoms, by acid-catalyzed dimerization and as catalysts for trialuminum alkyls. Mention may be made of oils obtained by oligomerization using (trialuminium alkyls). Poly-α-olefin oil is a particularly preferred carrier fluid. The carrier fluids referred to herein are prepared by methods well known in the art and such fluids are commercially available. Preferred poly-α-olefins include products such as Durasyn® PAO and Chevron Synfluid® PAO. Preferred poly-α-olefin carrier fluids exhibit a viscosity of 1 to 50 centistokes at 100 ° C., and more preferably have a viscosity of 1 to 10 centistokes at 100 ° C.

  The magnetorheological fluid may optionally include other components such as thixotropic agents or viscosity modifiers, dispersants or surfactants, antioxidants, corrosion inhibitors, and one or more lubricants. Such optional ingredients are known to those skilled in the art. For example, as the dispersant, lithium stearate, lithium hydroxystearate, calcium stearate, aluminum stearate, ferrous oleate, ferrous naphthenate, zinc stearate, aluminum tristearate and aluminum distearate, stearic acid And carboxylate soaps such as sodium, strontium stearate, and mixtures thereof.

  Examples of optional additives that provide an antioxidant function include zinc dithiophosphate, hindered phenols, aromatic amines, and sulfurized phenols. Examples of lubricants include organic fatty acids and amides, lard oil, and high molecular weight organic phosphorus compounds, phosphate esters. Exemplary synthetic viscosity modifiers include olefin polymers and copolymers, methacrylates, dienes or alkylated styrenes. In addition, other optional additives that provide steric stabilization include fluoroaliphatic polymeric esters, and organic titanates, organic aluminates, organic silicones, and organic zirconates as coupling agents. Included are compounds that provide chemical coupling.

  One skilled in the art can readily select any additive component desired in a particular formulation. When present, the amounts of these optional components can typically range from about 0.1 to about 12 volume percent each, based on the total volume of the magnetorheological fluid. Preferably, any components utilized are each present in the range of about 0.5 to about 7.5% by volume, based on the total volume of the magnetorheological fluid.

  Optional but preferred uses of thixotropic agents include any such agent that provides thixotropic rheology. The thixotropic agent is selected in view of the selected carrier fluid. If the magnetorheological fluid is formed using a carrier fluid that is an organic fluid, a thixotropic agent compatible with such a system can be selected. Thixotropic agents useful for such organic fluid systems are described in US Pat. No. 5,645,752, which is hereby incorporated by reference in its entirety. Preferably, oil-soluble metal carboxylates and the like (collectively referred to as soap, for example, the above-mentioned carboxylate soaps listed above) are preferably used. When utilized, thixotropic agents are typically used in an amount in the range of about 0.1-5.0%, preferably about 0.5-3.0% by volume of the magnetorheological fluid. . Examples of preferred thixotropic agents include soap, colloidal silica, and organoclay. Preferred embodiments include organoclay thixotropic agents, such as bentonite. Bentonite clays tend to be thixotropic and shear thinning (ie, they are easily broken by the application of shear and form a network that reforms when shear is stopped). Bentonite clay material is organic-modified by treatment with a hydrophobic organic material. The material referred to as bentonite is sometimes referred to interchangeably with the terms smectite and montmorillonite. Montmorillonite clay typically constitutes the majority of bentonite clay. Montmorillonite clay contains a large fraction of aluminum silicate. Hectorite clay contains a large fraction of magnesium silicate. Commercially available organically modified clays include, for example, Claytone AF from Southern Clay Products, and Bentone®, Baragel®, and Nykon®, a family of organic clays from RHEOX. . Other suitable clays are those disclosed in US Pat. No. 5,634,969 to Cody et al. A preferred organoclay is Claytone EM.

  The off-state viscosity of a magnetorheological fluid comprising the magnetorheological composition of the present invention depends primarily on the volume of the particle component and the type of carrier fluid. Those skilled in the art will determine the desired required viscosity according to the application specified for the magnetorheological fluid.

  The magnetorheological fluids of the present invention may also contain other optional additives such as dyes or pigments, abrasive particles, lubricants, antioxidants, pH shifters, salts, deoxidizers, and / or corrosion inhibitors. . These optional additives can be in the form of a dispersion, suspension, or material that is soluble in the carrier vehicle.

  The organoclay is used at a concentration between about 0.1-12% by weight, preferably between 0.3-5.0% by weight, based on the weight of the MR fluid composition. In a preferred embodiment, the only thixotropic agent present is bentonite, except for other types of thickeners.

  Preferred embodiments include, but are not limited to, colloidal sized silica particles, molybdenum compounds (eg, organic molybdenum, molybdenum sulfide or molybdenum disulfide, and molybdenum phosphate); and fluorocarbon polymers ( For example, polytetrafluoroethylene), as well as compounds that reduce friction between particles (friction reducing additive), such as mixtures thereof. In a preferred embodiment, an extreme pressure additive is also included along with the friction reducing additive. Extreme pressure additives are known in the field of lubricants and are known derivatives such as organophosphorus compounds, phosphonate compounds, phosphonites, phosphates, phosphinates, phosphinites, phosphites, and their amide or imide derivatives, Mention may be made of thiophosphorus compounds, as well as thiocarbamates. An exemplary useful organophosphorus extreme pressure additive for inclusion with the magnetically responsive particles herein has a structure represented by the following formula:

Where R ¹ and R ² are each independently hydrogen, an amino group, or an alkyl group having 1 to 22 carbon atoms; X, Y, and Z are each independently —CH _2- , a nitrogen heteroatom, or an oxygen heteroatom, wherein at least one of X, Y, or Z is an oxygen heteroatom; a is 0 or 1; and n is a valence of M Yes; provided that when X, Y, and Z are each an oxygen heteroatom, M is a metal ion or a salt moiety formed from an amine of formula B:

Wherein R ³ , R ⁴ , and R ⁵ are each independently hydrogen or an aliphatic group having 1 to 18 carbon atoms; at least one of X, Y, or Z is an oxygen heteroatom If not, M is selected from the group consisting of a metal ion, a non-metal moiety, and a divalent moiety; in addition, when Z is —CH ₂ —, M is a divalent moiety and Z is When it is a nitrogen heteroatom, M is not an amine of formula B.

  A typical thioline extreme pressure additive has a structure represented by the following Formula A:

Here, R ¹ and R ² are each independently
Y-((C) (R ⁴ ) (R ⁵ )) _n- (O) _w-
Having a structure represented by
Where Y is hydrogen or a moiety containing a functional group such as amino, amide, imide, carboxyl, hydroxyl, carbonyl, oxo or aryl; n is an integer from 2 to 17, so that C (R ⁴ ) (R ⁵ ) is a divalent group having a structure such as a linear aliphatic, branched aliphatic, heterocyclic, or aromatic ring; R ⁴ and R ⁵ are each independently And can be hydrogen, alkyl, or alkoxy; and w is 0 or 1.

  A preferred number of thiocarbamate extreme pressure additives have the structure represented by the following formula B:

Here, R ¹ and R ² are each independently
Y-((C) (R ⁴ ) (R ⁵ )) _n −
Having a structure represented by
Where Y is hydrogen or a moiety containing a functional group such as amino, amide, imide, carboxyl, hydroxyl, carbonyl, oxo or aryl; n is an integer from 2 to 17, and consequently , C (R ₄ ) (R ₅ ) is a divalent group having a structure such as a linear aliphatic, branched aliphatic, heterocyclic, or aromatic ring; and R ⁴ and R ⁵ are Each can independently be hydrogen, alkyl, or alkoxy. R ^{3 in} Formula A or B can be a metal ion (eg, molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium, or lead) or a non-metallic moiety (eg, hydrogen, sulfur-containing) Group, alkyl, alkylaryl, arylalkyl, hydroxyalkyl, oxy-containing group, amide, or amine). The subscripts a and b of formula A or B are each independently 0 or 1, where a + b is at least equal to 1 and x in formula A or B is the valence of R ³ Depending on the number, it is an integer from 1 to 5.

  Known organomolybdenum compounds are described in US-A-4,889,647 and US-A-5,412,130, both of which are incorporated herein by reference. A suitable organomolybdenum complex is prepared by reacting a fatty oil, diethanolamine and a molybdenum source. Suitable heterocyclic organomolybdates are prepared by reacting a diol, diamino-thiol-alcohol, and amino alcohol compound with a molybdenum source in the presence of a phase transfer agent. Other suitable organomolybdenum are described in US-A-5,137,647 (incorporated herein by reference) (eg, prepared by reacting an amine-amide with a molybdenum source). Organic molybdenum compounds). Molybdenum thiadiazole is a preferred molybdenum compound and is described in US Pat. No. 5,627,146, incorporated herein by reference. Commercially available molybdenum thiadiazoles are the names of Polyvan® 822 and Polyvan® 2000, R.I. T.A. Available from the Vanderbilt Company. Another example is molybdenum hexacarbonyl dicanthogen. Organic, as disclosed in US-A-4,164,473 (incorporated herein by reference), prepared by reacting a hydrocarbyl-substituted hydroxyalkylated amine with a molybdenum source. Molybdenum; and alkyl esters of molybdic acid as disclosed in US-A-2,805,997 (incorporated herein by reference). Preferred organomolybdenum compounds are prepared according to US-A-4,889,647 and US-A-5,412,130 (incorporated herein by reference), and in particular one of them is Polyvan ( Registered trademark) 855, R.I. T.A. Vanderbilt Inc. Commercially available.

  When using organomolybdenum compounds, they are available in the liquid state at ambient temperature and are 0.1-12% by volume, preferably 0.25-10, based on the total volume of the magnetorheological fluid. It can be introduced into the MR fluid at an effective use level in the range of volume%.

  Embodiments of a magnetorheological fluid used in a device according to the present invention first mix the ingredients by hand with a relatively low shear force using a spatula or the like and then using a homogenizer, mechanical mixer or shaker Mix more thoroughly with relatively higher shear forces, or use a suitable one such as a ball mill, sand mill, attritor mill, paint mill, colloid mill, etc. (these are well known) It can be prepared by dispersing the components using a milling device.

  Testing a variety of special purpose devices, such as dampers, mounts, brakes, and clutches, that utilize the magnetorheological fluid of the present invention is a second method of evaluating the mechanical performance of these materials. The controllable fluid containing device is simply placed alongside the mechanical actuator and is operated with specific displacement and amplitude and frequency. A magnetic field is suitably applied to the device and the output is determined from the resulting expansion / compression waveform plotted as a function of time. The methodology utilized to test dampers, mounts, and clutches is well known to those skilled in the art of vibration control.

  The particle component used in accordance with embodiments of the present invention exhibits a relatively low dry powder flow rate compared to prior art magnetically responsive particles. A method for determining the relative powder flow rates of various particle types using scintillation vials is described below.

  Examples of magnetically responsive particles are listed below for comparison. In each example, the percentage obtained for each group of particles representing the particle mixture is expressed as a weight percent based on the total weight of the mixture of the different populations of particles.

(Powder flow test)
35 g of metal powder was placed in a 20 ml scintillation vial. The vial was tapped several times to flatten and stabilize the powder. The vial was passed through a tapered funnel with a 15 mm opening and a 60 ° taper angle (which was attached to a 6V vibration motor modified from a telephone paging device). The time recorded until the contents were empty was recorded. Repeated 2-3 times with a new sample and averaged. Various grades of iron particles were measured and the powder flow rates were compared.

  The particles used according to the invention (Example 1) are slower in dry powder flow properties and surprisingly this is an improved magnetoviscous response from the particle flow through the orifice in the controllable device. Correlate with

(Example of MR fluid)
Magnetorheological fluid is 20% Atmix® PF20 E atomized iron powder ((D ₁₀ = 3.14 μm; D ₅₀ = 11.89; D ₉₀ = 31.34 μm) (R ² = 0.77), 1% by weight lithium hydroxystearate, 1% by weight molybdenum disulfide, and 99% iron, less than 1% oxygen, less than 1% nitrogen, and less than 0.01% carbon), and Prepared by mixing with residual volume (78% -100%) composed of a synthetic hydrocarbon oil carrier fluid, obtained from poly-α-olefins and sold under the name Durasyn® 162 Is done.

FIG. 1 shows (cumulative volume%) versus (particle size) for iron particles, obtained from the data in Tables 1-8, measured using Malvern Instruments, Ltd, Mastersizer® S, Version 2.18. (Μm)) is a lognormal regression plot by Excel® of the curve. FIG. 2 shows (cumulative volume%) vs. prior art carbonyl iron particles obtained from the data in Table 1, measured using Malvern Instruments, Ltd., Mastersizer® S, Version 2.18. 2 is a lognormal regression plot by Excel® of particle size (μm). FIG. 3 shows (cumulative volume%) versus (particles) for conventional atomized particles, obtained from the data in Table 2, measured using Malvern Instruments, Ltd, Mastersizer® S, Version 2.18. 2 is a lognormal regression plot with Excel® of size (μm). FIG. 4 shows (cumulative volume%) versus (particles) for conventional atomized iron particles, obtained from the data in Table 3, measured using Malvern Instruments, Ltd, Mastersizer® S, Version 2.18. 2 is a lognormal regression plot with Excel® of size (μm). FIG. 5 shows (cumulative volume%) versus (particles) for conventional atomized particles obtained from the data in Table 4, measured using Malvern Instruments, Ltd, Mastersizer® S, Version 2.18. 2 is a lognormal regression plot with Excel® of size (μm). FIG. 6 shows (cumulative volume%) versus (particles) for conventional atomized particles obtained from the data in Table 5 measured using Malvern Instruments, Ltd, Mastersizer® S, Version 2.18. 2 is a lognormal regression plot with Excel® of size (μm). FIG. 7 shows (cumulative volume%) versus (particles) for conventional atomized particles, obtained from the data in Table 6, measured using Malvern Instruments, Ltd., Mastersizer® S, Version 2.18. 2 is a lognormal regression plot with Excel® of size (μm). FIG. 8 shows (cumulative volume%) versus (particles) for conventional atomized particles, obtained from the data in Table 7, measured using Malvern Instruments, Ltd, Mastersizer® S, Version 2.18. 2 is a lognormal regression plot with Excel® of size (μm). FIG. 9 shows (cumulative volume%) versus atomized particles of Example 1 obtained from the data in Table 8 measured using Malvern Instruments, Ltd, Mastersizer® S, Version 2.18. It is a lognormal regression plot by Excel (particle size (μm)). FIG. 10 is a simple structural view of the transverse section of the piston portion of the MR damper device.

Claims (26)

A magnetorheological fluid comprising a carrier fluid component and a magnetizable particle component, wherein the magnetizable particle component is 2 μm D ₁₀ to 5 μm D ₁₀ or less; 8 μm D ₅₀ to 15 μm D ₅₀ or less; 25 μm characterized from D ₉₀ by 40μm of D ₉₀ or less; and 0.77 or more, further characterized by the least squares regression of the particle size versus log normal cumulative volume% ^{(R 2),} magnetorheological fluid.   The magnetorheological fluid of claim 1, wherein the carrier component has a viscosity of between about 1 centistoke and about 500 centistoke at 100 degrees Celsius.   The magnetorheological fluid of claim 2, wherein the carrier component has a viscosity at 100 ° C. of less than about 10 centistokes.   The carrier component is present in an amount of about 50 to about 95 volume percent of the magnetorheological fluid and the particulate component is present in an amount of about 5 to about 50 volume percent of the magnetorheological fluid. Magnetorheological fluid.   The carrier component is natural fatty oil, mineral oil, polyphenyl ether, dibasic acid ester, neopentyl polyol ester, phosphite ester, synthetic cycloparaffin, synthetic paraffin, unsaturated hydrocarbon oil, monobasic acid ester, Glycol esters and glycol ethers, fluorinated esters and fluorinated ethers, silicate esters, silicone oils, silicone copolymers, synthetic hydrocarbons, perfluorinated polyethers and perfluorinated polyesters, halogenated hydrocarbons, and mixtures and derivatives thereof The magnetorheological fluid of claim 2, wherein the magnetorheological fluid is selected from the group consisting of:   The magnetorheological fluid of claim 2, wherein the carrier component is selected from the group consisting of water, glycols, glycol esters, and mixtures thereof.   The magnetorheological fluid of claim 1, wherein the carrier component further comprises a dispersant.   The magnetorheological fluid of claim 1, further comprising a thixotropic agent selected from the group consisting of soap, colloidal silica, and organoclay.   The magnetorheological fluid according to claim 8, wherein the thixotropic agent is an organoclay selected from organically modified bentonite.   The magnetorheological fluid of claim 1, further comprising an extreme pressure additive.   The magnetorheological fluid according to claim 10, wherein the extreme pressure additive is selected from the group consisting of a thiophosphorus compound and a thiocarbamate. 12. The magnetorheological fluid of claim 11, wherein the extreme pressure additive is an organophosphorus compound having the following formula:

Where R ¹ and R ² are each independently hydrogen, an amino group, or an alkyl group having 1 to 22 carbon atoms; X, Y, and Z are each independently —CH _2- , a nitrogen heteroatom, or an oxygen heteroatom, wherein at least one of X, Y, or Z is an oxygen heteroatom; a is 0 or 1; and n is a valence of M Yes; provided that when X, Y, and Z are each an oxygen heteroatom, M is a salt moiety formed from an amine of formula B:

Where R ³ , R ⁴ , and R ⁵ are each independently hydrogen or an aliphatic group having 1 to 18 carbon atoms; and at least one of X, Y, or Z is When not an oxygen heteroatom, M is selected from the group consisting of a metal ion, a non-metal moiety, and a divalent moiety, and when Z is a nitrogen heteroatom, M is not an amine of formula B. The magnetorheological fluid of claim 11, wherein the extreme pressure additive is a thiophosphorus compound having the following structure:

Here, R ¹ and R ² are each independently
Y-((C) (R ⁴ ) (R ⁵ )) _n- (O) _w-
Having a structure represented by
Where Y is hydrogen or a moiety containing a functional group such as amino, amide, imide, carboxyl, hydroxyl, carbonyl, oxo, or aryl;
n is an integer of 2 to ¹⁷ , and as a result, C (R ⁴ ) (R ⁵ ) is a divalent group having a structure such as a linear aliphatic, branched aliphatic, heterocyclic, or aromatic ring Is;
R ⁴ and R ⁵ can each independently be hydrogen, alkyl, or alkoxy; and w is 0 or 1. The magnetorheological fluid of claim 11, wherein the extreme pressure additive is a thiocarbamate represented by the following formula B:

Here, R ¹ and R ² are each independently
Y-((C) (R ⁴ ) (R ⁵ )) _n −
Having a structure represented by
Wherein Y is selected from hydrogen, amino group, amide group, imide group, carboxyl group, hydroxyl group, carbonyl group, oxo group, or aryl group; n is an integer from 2 to 17; R ⁴ and R ⁵ is independently hydrogen, an alkyl group, or an alkoxy group; and R ³ is selected from the group consisting of a metal ion, a non-metal moiety, and a divalent moiety; a and b are each independently And a + b is at least equal to 1 and x is an integer from 1 to 5, depending on the valence of R ³ .   The particle component is selected from the group consisting of iron, iron manganese, iron boron, iron oxide, iron nitride, iron carbide, iron chromium, low carbon steel, iron silicon, iron nickel, iron cobalt, and mixtures thereof; The magnetorheological fluid according to claim 1.   16. The magnetorheological fluid of claim 15, wherein the particle component is selected from the group consisting of iron, iron oxide, iron nickel, iron cobalt, iron manganese, iron silicon, and iron boron.   8. Magnetic according to claim 7, wherein the dispersant is selected from oleate, naphthenate, sulfonate, phosphate ester, stearic acid, stearate, glycerol monooleate, sorbitan sesquioleate, laurate, fatty acid and fatty alcohol. Viscous fluid.   The magnetorheological fluid of claim 17, wherein the dispersant comprises stearate.   The magnetorheological fluid of claim 1 further comprising a molybdenum compound.   The magnetorheological fluid according to claim 19, wherein the molybdenum compound is organic molybdenum.   21. A magnetorheological fluid according to claim 20, wherein the organomolybdenum compound is selected from Polyvan (R) 822, Polyvan (R) 2000, and Polyvan (R) 855.   The magnetorheological fluid according to claim 19, wherein the molybdenum compound is molybdenum disulfide.   A linear damper device characterized by a design (working) gap of 0.08 mm to 0.90 mm, comprising the magnetorheological fluid of claim 1. Haptic interface system with:
A haptic interface device movable by an operator in at least one direction of rotation or movement, wherein the haptic interface system provides resistance to the haptic interface device;
A controller for receiving a variable input signal and providing a variable output signal, executing a program that processes the variable input signal and derives the variable output signal in response to the input variable And a magnetically controllable device adapted to receive the variable output signal and provide a resistive force as a function of the variable output signal, the device comprising: Wherein the magnetizable fluid component provides a variable resistance force by ordering of the particle component in response to the output signal, thereby resisting displacement of the haptic interface device, thereby Magnetically controllable device that directly controls the relaxation of the movement of the interface device.   The magnetically controllable device is a damper, and the particles are water, glycol, natural fatty oil, mineral oil, polyphenyl ether, dibasic acid ester, neopentyl polyol ester, phosphite ester, synthetic cyclohexane Paraffin, synthetic paraffin, unsaturated hydrocarbon oil, monobasic acid ester, glycol ester, glycol ether, fluorinated ester, fluorinated ether, silicate ester, silicone oil, silicone copolymer, poly-α-olefin, perfluorinated poly 25. The haptic interface system of claim 24, dispersed in a carrier component selected from the group consisting of ethers, perfluorinated polyesters, halogenated hydrocarbons, and mixtures and derivatives thereof. Rotary magneto-rheological fluid device comprising:
(A) shaft;
(B) a rotor made of a magnetically permeable material, the rotor having first and second rotor surfaces, an actuating portion, and an outer periphery, by which the rotor is the shaft Interconnected to the rotor to prevent relative rotation between them;
(C) a housing comprising a soft magnetic yoke manufactured from a highly magnetically permeable powder metal material, the soft magnetic yoke having a groove formed therein, the groove being formed on the rotor; Receiving a working portion and forming a first gap adjacent to the first rotor surface and a second gap adjacent to the second rotor surface, the housing comprising a portion of the housing comprising a yoke; A relatively thin molded portion that is formed adjacent to the shaft to prevent the magnetic field from increasing in the seal area of the shaft;
(D) Magnetorheological fluid according to claim 1 or powder magnetizable particles without carrier fluid, wherein the particles without fluid or carrier fluid are contained within the first gap and the second gap And at least partially filling the first gap and the second gap, the magnetizable particle component of the fluid, and the powder magnetizable particles having a population exhibiting an R ² of 0.77 or greater 2 μm D ₁₀ to 5 μm D ₁₀ or less, 8 μm D ₅₀ to 15 μm D ₅₀ or less, and 25 μm D ₉₀ to 40 μm D ₉₀ or less volume fraction The magnetorheological fluid of claim 1, or powder magnetizable particles without a carrier fluid, further characterized by: and (e) the soft magnetic fluid A magnetic field generator that provides a variable magnetic field adjacent to the magnetic field, and when a voltage is applied to the magnetic field generator, the soft magnetic particles in the first gap and the second gap change rheology; Thereby, a magnetic field generator in which the variable magnetic field acts to cause a change in torsional resistance of the rotary device.

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