KR20220160267A - Linear actuator based on magneto-rheological elastomer - Google Patents

Abstract

The present invention provides a magnetorheological elastomer-based linear actuator. According to the present invention, the linear actuator comprises: a vibration member made of a magnetorheological elastomer material; a motion shaft having a lower end coupled to the vibration member; a mover which is coupled to have a frictional force on the motion shaft and moves with respect to the motion shaft when an inertia force is greater than the frictional force with motion shaft when the motion shaft moves by the vibration member; and a magnetic field generating unit configured to generate a magnetic field to be applied to the vibration member. According to the present invention, a position of the mover can be precisely controlled by using the vibration member made of a magnetorheological elastomer material so as to provide the linear actuator which increases durability more than a case in which a piezoelectric element is used.

Description

Linear actuator based on magneto-rheological elastomer}

The present invention relates to a linear actuator, and more particularly, to a linear actuator that moves a mover along a motion axis using a vibrating member made of a magnetorheological elastomer.

Conventionally, a voice coil motor (VCM) has been mainly used in the field of lens driving or precise positioning, but recently, piezoelectric linear actuators that do not require magnets or windings and have high torque and low noise have attracted much attention.

For example, cases in which piezoelectric linear actuators are used for autofocusing (AF) actuators or OIS (Optical Image Stabilizer) actuators of small camera modules mounted on smartphones are increasing.

Referring to FIG. 1 , the piezoelectric linear actuator 10 includes a vibrating unit 40 in which a piezoelectric layer 30 is formed on one or both surfaces of an elastic body 20, and an upper portion in a state where the lower end is coupled to the vibrating unit 40 It includes a movement shaft 50 protruding into and a mover 60 coupled to the movement shaft 50 to have a predetermined frictional force.

When an electric field is applied, the piezoelectric layer 30 expands or contracts in response to the direction of the electric field, and in a state where the edges are constrained, the central portion rises or falls according to the direction of the electric field. Therefore, when AC power or pulse power is applied to the piezoelectric layer 30, the piezoelectric layer 30 vibrates up and down.

The piezoelectric linear actuator 10 uses this property of the piezoelectric layer 30. For example, when the driving voltage applied to the piezoelectric layer 30 is slowly increased or decreased, the central portion of the piezoelectric layer 30 slowly rises or Since it descends, the movement shaft 50 and the movement element 60 move together.

On the other hand, if the driving voltage is rapidly increased or decreased, the movement speed of the piezoelectric layer 30 and the motion shaft 50 becomes very fast. At this time, if the inertial force of the mover 60 is greater than the frictional force, the mover 60 stays in place Since only the movement shaft 50 moves, the coupling position of the exerciser 50 is changed.

The piezoelectric linear actuator 10 can precisely control the position of the mover by adjusting the frequency of the driving voltage and the rising or falling speed of the voltage using this principle. Also called actuator.

However, since the piezoelectric element used in the piezoelectric linear actuator 10 is vulnerable to impact, there is a disadvantage in that the possibility of damage or failure increases during long-term use, so it is necessary to prepare a supplementary measure for this.

Republic of Korea Patent Registration No. 10-0443638 (Announced on August 11, 2004)

The present invention has been conceived against this background, and an object of the present invention is to provide a linear actuator that can be used in the field of lens driving or precise positioning without using a piezoelectric element that is vulnerable to impact.

In order to achieve this object, one aspect of the present invention, a vibrating member made of a magnetorheological elastomer material; A motion shaft having a lower end coupled to the vibrating member; a mover that is coupled to have a frictional force on the movement axis and moves with respect to the movement axis when the inertia force is greater than the frictional force with the movement axis when the movement axis moves by the vibrating member; A linear actuator including a magnetic field generating unit generating a magnetic field to be applied to a vibrating member is provided.

In the linear actuator according to one aspect of the present invention, the magnetorheological elastomer may be a porous magnetorheological elastomer in which a plurality of pores are formed inside an elastic substrate.

Further, in the linear actuator according to one aspect of the present invention, the mover is made of a magnetorheological elastic material, and a magnetic field generating unit for adjusting frictional force may be installed around the mover.

In addition, in the linear actuator according to an aspect of the present invention, the magnetic field generating unit is installed inside a housing with an open top, the vibrating member is installed on top of the magnetic field generating unit, and the vibrating member is installed on top of the vibrating member. A support member coupled to an upper end of the housing may be installed while pressing the upper surface of the periphery.

According to the present invention, since the position of the mover can be precisely controlled using the vibrating member made of magnetorheological elastomer, it is possible to provide a linear actuator with much improved durability compared to the case of using a piezoelectric element.

1 is a view illustrating a conventional piezoelectric linear actuator
2 is a perspective view of a magnetorheological elastomer-based linear actuator according to a first embodiment of the present invention;
3 is an exploded perspective view of a magnetorheological elastomer-based linear actuator according to a first embodiment of the present invention;
4 is a view showing a control system of a magnetorheological elastomer-based linear actuator according to a first embodiment of the present invention;
5 is a cross-sectional view of a vibrating member made of magnetorheological elastomer
6 is a diagram illustrating a deformation cycle by a magnetic field of a vibrating member made of magnetorheological elastomer;
Figure 7 is a graph showing the magnetic field strength and movement axis displacement for the mover descent
8 is a view showing a state in which the exerciser descends
Figure 9 is a graph showing the magnetic field strength and displacement of the movement axis for the lifter
10 is a view showing a state in which the exerciser rises
11 is a diagram showing a magnetorheological elastomer-based linear actuator and a control system according to a second embodiment of the present invention;
12 is a view showing a modified example of an actuator according to a second embodiment of the present invention;
13 is a cross-sectional view of a magnetorheological elastomer-based linear actuator according to a third embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

For reference, there are parts shown in dimensions or ratios different from actual ones in the drawings attached to this specification, but this is for convenience of description and understanding, so it should be noted in advance that the scope of the present invention should not be construed as being limited due to this. In addition, in the present specification, when one element is connected, coupled, or electrically connected to another element, not only when one element is directly connected, coupled, or electrically connected to another element, but also between other elements in the middle. and indirectly connected, bonded or electrically connected. In addition, when one element is directly connected or combined with another element, it means that it is connected or combined without another element in the middle. In addition, the fact that a part includes a certain component means that it may further include other components rather than excluding other components unless otherwise stated. In addition, since expressions such as front, back, left, right, up, and down in this specification are relative concepts that may vary depending on the viewing position, the scope of the present invention is not necessarily limited to the corresponding expressions.

<First Embodiment>

2, 3, and 4 are a perspective view, an exploded perspective view, and a view showing a control system of the linear actuator 100 according to the first embodiment of the present invention, respectively.

As shown in the drawing, the linear actuator 100 according to the first embodiment of the present invention includes a cylindrical housing 110 with an open top, a magnetic field generator 140 installed inside the housing 110, and , a vibrating member 130 made of a magneto-rheological elastomer (MRE) material installed on the upper portion of the magnetic field generating unit 140, and a support member 120 for pressing and supporting the periphery of the upper surface of the vibrating member 130, The movement shaft 150 protruding upward in a state where the lower end is coupled to the central portion of the vibrating member 130, the movement shaft 150 coupled to have a predetermined frictional force, and the movement element 160, and the frictional force of the movement element 160 In order to maintain the tightening member 170 coupled to the circumference of the exerciser 160, the power supply unit 180 for supplying power to the magnetic field generator 140, and the control unit for controlling the operation of the power supply unit 180 ( 190).

The shape of the housing 110 is not particularly limited, and as shown in the drawings, the planar shape may be circular or other shapes such as elliptical or polygonal shapes.

The support member 120 is for fixing the periphery of the vibrating member 130 to the housing 110, and may be coupled to the sidewall of the housing 110 while pressing the peripheral portion of the upper surface of the vibrating member 130. It is preferable that the supporting member 120 has a ring shape, but may have other shapes as long as the edge of the vibrating member 130 can be stably fixed.

The vibration member 130 may be a plate having a shape corresponding to the inner wall of the housing 110 .

As illustrated in the cross-sectional view of FIG. 5, the magneto-rheological elastomer used as a material for the vibrating member 130 contains magnetic particles 134 in an elastic base 132 such as natural rubber or silicone rubber. It is relatively flexible in an unapplied state, but when a magnetic field is applied, it has a characteristic of shrinking due to attraction between the magnetic particles 134 .

Therefore, when an alternating magnetic field is generated from the magnetic field generating unit 140 installed at the bottom, as shown in FIG. 6, vibration occurs while the vibrating member 130 repeats contraction and restoration.

As such, since the vibrating member 130 made of magnetorheological elastomer vibrates due to the magnetic field, the power supply unit 180 controls the frequency and waveform of the alternating magnetic field applied from the magnetic field generating unit 140 to control the vibration frequency of the vibrating member 130. and can control the waveform.

The magnetic field generator 140 may be an electromagnet including a core ( 141 in FIG. 11 ) and a coil ( 142 in FIG. 11 ) connected to the power supply unit 180 . In addition, the magnetic field generator 140 may be an electro-permanent magnet (EPM) capable of controlling an external magnetic field by winding a coil around two permanent magnets.

The magnetic field generator 140 is preferably installed below the vibrating member 130, but is not necessarily limited thereto, and may be installed near the edge of the vibrating member 130 or above the vibrating member 130.

The lower end of the movement shaft 150 may be coupled to the upper surface of the vibrating member 130 or may be coupled through the central portion of the vibrating member 130 . Although not shown in the drawing, a flange having a relatively large diameter may be formed at the lower end of the motion shaft 150 and the flange may be coupled to the upper or lower surface of the vibrating member 130 .

In the drawings, the movement shaft 150 is shown as having a cylindrical shape, but may have various shapes such as an elliptical column, a polygonal column, and the like.

The mover 160 has a penetrating portion into which the motion shaft 150 is inserted, and is coupled to the motion shaft 150 to have a constant frictional force. That is, when there is no external force while the movement shaft 150 is inserted into the penetrating portion, the mover 160 maintains its position due to frictional force, and when an external force greater than the frictional force is applied, the mover 160 is coupled so that it can move.

The mover 160 moves up and down along the movement shaft 150 by the vibration of the vibrating member 130 . Therefore, when a position adjustment target (eg, lens barrel) is coupled to the mover 160, the position of the position adjustment target can be controlled by moving the mover 160.

Since the inner wall of the penetrating part of the mover 160 can be easily worn due to continuous friction with the moving shaft 150, the mover 160 is made of a material having excellent wear resistance or the inner wall of the penetrating part of the mover 160 is made of a material having excellent wear resistance. It is desirable to reinforce with

In addition, in order to maintain a constant friction force between the exerciser 160 and the motion shaft 150, a tightening member 170 capable of applying pressure toward the motion shaft 150 may be installed around the exerciser 160. The type of tightening member 170 is not particularly limited, and various materials and shapes such as a rubber ring, a metal ring, a C-ring, and an O-ring may be used.

The power supply unit 180 may include a battery and a control circuit for controlling an input to the magnetic field generator 140 under the control of the control unit 190 . The power supply unit 180 may include an AC-DC conversion circuit instead of a battery.

Hereinafter, a case in which the mover 160 descends along the motion shaft 150 in the linear actuator 100 according to the first embodiment of the present invention will be described with reference to FIGS. 7 and 8 .

First, as shown in FIG. 7(a), when the strength of the magnetic field generated by the magnetic field generator 140 is slowly increased by controlling the power supply unit 180 connected to the magnetic field generator 140, the magneto-rheological material vibrates. Member 130 contracts slowly.

As such, when the vibrating member 130 slowly contracts, as shown in FIG. 160) also descends along with the motion shaft 150.

Subsequently, when the power supply connection to the magnetic field generator 140 is cut off or the current intensity is rapidly reduced, the intensity of the magnetic field is rapidly reduced, and thus the contracted vibrating member 130 rapidly expands to its original shape.

As such, when the vibrating member 130 rapidly expands, the motion shaft 150 also rises rapidly. At this time, if the inertial force of the mover 160 is greater than the frictional force, only the motion shaft 150 rises while the mover 160 remains in place. As a result, the position where the exerciser 160 is coupled to the motion shaft 150 becomes lower than before.

In this way, when the magnetic field is turned off after applying the magnetic field pulse of the slow increasing high speed decreasing method for a predetermined time, the position where the mover 160 is coupled to the motion shaft 150 is lowered than before. At this time, the descending distance of the mover 160 is proportional to the frequency and application time of the magnetic field pulse.

Next, with reference to FIGS. 9 and 10 , a case in which the mover 160 ascends along the motion axis 150 in the linear actuator 100 according to the first embodiment of the present invention will be described.

First, as shown in FIG. 9(a), when the strength of the magnetic field is slowly decreased by controlling the power supply unit 180 in a state in which a magnetic field is generated in the magnetic field generating unit 140, the vibrating member 130 made of magneto-rheological elastic material expands slowly

In this way, when the vibrating member 130 expands slowly, as shown in FIG. 9 (b), the movement shaft 150 coupled to the vibrating member 130 also slowly rises, and thereby the mover coupled to the movement shaft 150 ( 160) also rises along with the motion shaft 150.

Subsequently, when the intensity of the current supplied to the magnetic field generating unit 140 is rapidly increased, the intensity of the magnetic field increases rapidly, and the vibrating member 130, which has been inflated due to this, rapidly contracts due to the influence of the magnetic field.

As such, when the vibrating member 130 rapidly contracts, the motion shaft 150 also rapidly descends. At this time, when the inertial force of the mover 160 is greater than the frictional force, only the motion shaft 150 descends while the mover 160 remains in place. As a result, the position where the exerciser 160 is coupled to the motion shaft 150 becomes higher than before.

In this way, when the magnetic field is turned off after applying the magnetic field pulse of the high-speed increase and low-speed decrease method for a predetermined time, the position where the mover 160 is coupled to the motion shaft 150 rises more than before. At this time, the rising distance of the mover 160 is proportional to the frequency and application time of the magnetic field pulse.

<Second Embodiment>

As shown in the cross-sectional view of FIG. 11, the linear actuator 100a according to the second embodiment of the present invention includes a first magnetic field generator 140 installed inside the housing 110 and a first magnetic field generator 140 In a state in which the vibration member 130 made of a magnetorheological elastomer installed on the upper part of the vibration member 130, the support member 120 for pressing and supporting the periphery of the upper surface of the vibration member 130, and the lower end coupled to the central portion of the vibration member 130 A motion shaft 150 protruding upward, a motion element 160a coupled to the motion shaft 150 to have a predetermined frictional force and made of magnetorheological elastic material, and a second magnetic field generator 162 installed around the motion element 160a. ), a power supply unit 180 for supplying power to the first and second magnetic field generators 140 and 162, and a control unit 190 for controlling the operation of the power supply unit 180.

That is, in the linear actuator 100a according to the second embodiment of the present invention, the motion element 160a is made of a magnetorheological elastic material and the second magnetic field generator 162 is installed around the motion element 160a. There is a difference from the embodiment.

Since the mover 160a is made of a magnetorheological elastomer, when a magnetic field is applied from the second magnetic field generator 162, the mover 160a contracts and the frictional force with the motion shaft 150 increases. Therefore, according to the second embodiment of the present invention, there is an advantage in that the frictional force between the mover 160a and the motion shaft 150 can be adjusted by controlling the second magnetic field generator 162 .

Meanwhile, the second magnetic field generator 162 installed to control the frictional force of the mover 160a may be coupled to the mover 160a as shown in FIG. 12 .

<Third Embodiment>

As shown in the cross-sectional view of FIG. 13, the linear actuator 100c according to the fourth embodiment of the present invention is different from the first embodiment in that the vibrating member 130a is made of a porous magnetorheological elastomer, and the rest of the configuration is the same as that of the linear actuator 100 according to the first embodiment.

The porous magnetorheological elastomer is prepared by mixing, for example, silicone rubber material, silicone oil, carbonyl iron powder, ethanol, etc. in a predetermined weight ratio, and going through a homogenization and curing process, while ethanol evaporates during the curing process. A large number of pores are formed inside.

As shown in the figure, when the vibrating member 130a is made of a porous magnetorheological elastomer in which a plurality of pores 136 are formed inside the elastic substrate 132, flexibility and flexibility compared to the case of using a magnetorheological elastomer without pores Since the elasticity is improved, the vibration width is increased, so there is an advantage in that the displacement of the exerciser 160 can be increased.

Even in this case, it goes without saying that the mover 160 may be replaced with a mover 160a made of a magnetorheological elastic material, and the second magnetic field generator 162 may be installed around the mover 160a.

In the above, preferred embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments and may be variously modified or modified in a specific application process, and the modified or modified embodiments are also covered by the claims described later. If it includes the technical idea of the present invention disclosed, it will be taken for granted that it belongs to the scope of the present invention.

100: linear actuator 110: housing
120: support member 130: vibration member 132: elastic substrate
134: magnetic particles 136: pores 140: magnetic field generating unit
141: core 142: coil 150: movement axis
160, 160a: exerciser 162: magnetic field generator 170: tightening member
180: power supply unit 190: control unit

Claims (4)

Vibration member made of magneto-rheological elastomer;
A motion shaft having a lower end coupled to the vibrating member;
a mover that is coupled to have a frictional force on the movement axis and moves with respect to the movement axis when the inertia force is greater than the frictional force with the movement axis when the movement axis moves by the vibrating member;
Magnetic field generating unit for generating a magnetic field to be applied to the vibrating member
Linear actuator including According to claim 1,
The magnetorheological elastomer is a linear actuator, characterized in that a porous magnetorheological elastomer in which a plurality of pores are formed inside the elastic substrate According to claim 1,
The actuator is made of a magnetorheological elastic material, and a magnetic field generator for adjusting frictional force is installed around the actuator. According to claim 1,
The magnetic field generator is installed inside a housing with an open top,
The vibrating member is installed above the magnetic field generating unit,
A linear actuator, characterized in that a support member coupled to the upper end of the housing while pressing the upper surface of the periphery of the vibrating member is installed on the upper part of the vibrating member.

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