Actuator for camera

Abstract

An actuator for a camera according to an embodiment of the present invention comprises: a housing providing an internal space; a carrier that moves in the optical axis direction with respect to the housing; a magnet provided on the carrier so as to face a coil provided on the housing; a yoke plate provided in the housing and generating an attractive force with the magnet; and a plurality of balls disposed between the housing and the carrier. In this case, the height of the yoke plate is larger than the sum of the height of the magnet and the stroke, and the stroke is the movement distance of the carrier caused by AF driving.

Description

Technical Field

[0001] This invention relates to an actuator for a camera, and more specifically, to an actuator for a camera that further improves the driving accuracy and stability of the carrier. Background Technology

[0002] With the development of hardware technology for image processing and the increasing user demand for image shooting, functions such as autofocus (AF) and optical image stabilization (OIS) have been applied to standalone camera devices and camera modules installed in mobile terminals such as mobile phones and smartphones.

[0003] The autofocus function refers to the function of adjusting the focal length of the subject by moving a carrier equipped with a lens or the like linearly along the optical axis, thereby generating a clear image in the image sensor (CMOS, CCD, etc.) located at the back of the lens.

[0004] Optical image stabilization refers to the function of improving image sharpness by adaptively moving the carrier equipped with the lens (or image sensor) in the direction of compensating for the shaking caused by hand tremors in the lens or image sensor.

[0005] One of the typical methods to achieve autofocus or OIS is as follows: a magnet (coil) is placed on the mover (carrier), and a coil (magnet) is placed on the stator (housing, base, or other form of carrier, etc.). Then, a driving force is generated between the coil and the magnet, so that the mover moves along the optical axis or in a direction perpendicular to the optical axis.

[0006] Actuators that implement AF separately, as well as actuators that integrate AF with OIS, include balls arranged between the stator (housing, etc.) and the mover (carrier, etc.).

[0007] As a carrier of the mover, it moves forward and backward along the optical axis with the housing relative to the stator as a reference, while being physically supported or guided by the balls, thereby achieving AF. In this technical field, the area or range (length) in which the mover moves along the optical axis to achieve AF is called the stroke.

[0008] When the balls are arranged in association with the AF drive, a yoke plate that attracts the magnet of the mover is provided on the stator to improve the adhesion between the balls and the mover and between the balls and the stator.

[0009] When the carrier moves along the optical axis, the movement of the yoke is fixed because it is set on the shell, which is the relative stator. Conversely, the magnet set on the carrier moves together with the carrier, so the relative positional relationship between the magnet and the yoke is time-varying.

[0010] When the AF is driven, the position of the balls arranged between the mover and the stator changes within a certain range of motion, rather than remaining in a fixed position. This change in ball position driven by the AF means that the physical position of the balls, which act as the carrier of the mover, is time-varying.

[0011] Thus, the positional relationship between the magnet and the yoke, as well as the position of the mover physically supported by the balls, are time-varying. Therefore, depending on the movable range or position of the carrier, defects such as the carrier's attitude balance being disrupted and the carrier tilting may occur. This phenomenon is particularly likely to occur in actuators equipped with long-stroke heavy lenses. Summary of the Invention

[0012] Technical problems to be solved The present invention was proposed to solve the problems described in the background art above, and its object is to provide a camera actuator that can further improve the driving accuracy of AF by precisely realizing the structural relationship between the physical support and guidance of the carrier.

[0013] Other objects and advantages of the present invention will be understood from the following description and will become clearer through embodiments of the invention. Furthermore, the objects and advantages of the present invention can be achieved through the structures and combinations thereof that appear in the claims.

[0014] Problem-solving methods A camera actuator according to an embodiment of the present invention for achieving the above-mentioned objectives may include: a housing providing an internal space; a carrier that moves along an optical axis with respect to the housing; a magnet disposed on the carrier facing a coil disposed on the housing; a yoke disposed on the housing and attracting the magnet; and ball bearings disposed between the housing and the carrier.

[0015] In this case, the height of the yoke plate of the present invention is greater than the sum of the height of the magnet and the stroke, the stroke being the distance the carrier moves caused by the AF drive.

[0016] Furthermore, the ball bearings of the present invention may be composed of a plurality of ball bearings arranged along the optical axis, and the first distance, which is the sum of the total height of the plurality of ball bearings and the stroke, may be less than the sum of the radius of the comparative ball bearing, which is one of the plurality of ball bearings, and the height of the yoke plate.

[0017] In this invention, the comparison ball can be the outermost ball among the plurality of balls, and the outermost ball can be the ball with the largest diameter among the plurality of balls.

[0018] According to an embodiment, the ball bearings of the present invention may include: a first ball bearing assembly arranged between the carrier and the housing; and a second ball bearing assembly arranged between the carrier and the housing, and arranged side by side with the first ball bearing assembly with reference to the optical axis direction.

[0019] In this case, one or more of the first ball group and the second ball group can be composed of multiple balls. Preferably, the sum of the height of the support ball group, which is the ball group with the larger total height in the first ball group and the second ball group, and the stroke can be less than the sum of the radius of the outermost ball in the ball group and the height of the yoke.

[0020] In addition, preferably, the height of the magnet of the present invention is less than the sum of the total height of the plurality of balls and the radius of the outermost ball among the plurality of balls.

[0021] Invention Effects According to the present invention, tilting phenomena that may occur during carrier movement can be effectively suppressed, and changes in the carrier's posture can be minimized, thereby improving the accuracy and operational stability of AF drive.

[0022] According to one embodiment of the present invention, the height of the yoke plate that generates attraction with the magnet is determined by taking into account the movement area (stroke) of the magnet and the carrier on which the magnet is mounted, so that the stator and mover equipped with ball bearings can be more stably and tightly attached.

[0023] In one embodiment of the present invention, the stroke is determined by considering the points where the physical support of the carrier is realized and the radius of the outermost ball, so that the carrier can be more stably supported and guided by the ball throughout the entire range of the drive AF.

[0024] According to one embodiment of the present invention, the height of the magnet in the optical axis direction is determined based on the total height of the balls and the radius of the outermost ball, thus enabling height optimization of the magnet for increasing driving force. Attached Figure Description

[0025] The following drawings, which are included with this specification, illustrate preferred embodiments of the invention and, together with the detailed description of the invention described below, serve to enable a more effective understanding of the technical concept of the invention. Therefore, the invention should not be construed as being limited to the matters described in such drawings.

[0026] Figure 1This is a diagram illustrating the structure of an actuator according to a preferred embodiment of the present invention.

[0027] Figure 2 and Figure 3 This is an explanation Figure 1 The diagram shows the ball bearings, the first track, and the second track.

[0028] Figure 4 This is a partial cross-sectional view showing the ball bearings and yoke.

[0029] Figure 5 It is a diagram illustrating the structural relationship between the yoke, balls, magnets, and stroke.

[0030] Explanation of reference numerals in the attached figures 100: Actuator 110: Carrier; 120: Shell 140: Circuit board 150: Yoke plate 160: Housing C: Coil M: Magnet; R1, R2: First track, second track D: Driver; B: Ball bearing. Detailed Implementation

[0031] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should not be construed that the terms or words used in this specification and claims have the common or dictionary-defined meanings. Based on the principle that the inventors appropriately define the concepts of the terms in order to best describe their invention, they should be interpreted as meanings and concepts consistent with the technical concept of the present invention.

[0032] Therefore, the embodiments described in this specification and the structures shown in the accompanying drawings are merely the most preferred embodiments of the present invention and do not represent the entire technical concept of the present invention. It should be understood that there are many equivalents and variations that can replace them for the purposes of this application.

[0033] Figure 1 This is a diagram illustrating the structure of a camera actuator (hereinafter referred to as "actuator") according to a preferred embodiment of the present invention. Figure 2 and Figure 3 This is an explanation Figure 1 The diagram shows the ball bearing B, the first track R1, and the second track R2, etc.

[0034] Hereinafter, the general structure of the actuator 100 of the present invention will be described first, and the specific contents of the present invention, such as the structural relationship between the ball B, the yoke 150, the magnet M and the stroke H3, will be described later.

[0035] like Figure 1As shown, the actuator 100 of the present invention may include a carrier 110, a housing 120, a circuit board 140, a magnet M and a coil C, and according to an embodiment, may include a housing 160 serving as a shield.

[0036] The actuator 100 according to the present invention is equivalent to the following device: using the electromagnetic force (magnetic force) between the coil C and the magnet M as the driving force to make the carrier 110 move forward or backward in a linear manner, so as to realize the AF or zoom function.

[0037] The figure shows an embodiment where AF is implemented alone; however, the actuator 100 of the present invention can be implemented not only as an actuator that integrates AF and OIS functions, but also as an actuator that applies a reflector, etc.

[0038] The carrier 110 of the present invention can be located in the internal space provided by the housing 120, which is equivalent to a mover that moves along the optical axis with respect to the housing 120. From the corresponding angle, the housing 120, which supports the linear movement of the carrier 110, is equivalent to a relative stator.

[0039] According to the embodiment, one or more lenses or lens assemblies (hereinafter referred to as "lenses") can be mounted in the carrier 110. As described above, when a lens is mounted on the carrier 110, the lens moves linearly by moving the carrier 110, and the relative distance between the lens and the image sensor is adjusted by such movement of the lens, thereby realizing AF or zoom function.

[0040] It goes without saying that the drive unit that makes the carrier 120 move linearly along the optical axis is a structure that uses external control signals or sensed signal systems to make the carrier 110 move in a specific direction. It can be realized by various means such as shape memory alloy (SMA), piezoelectric element, microelectromechanical system (MEMS).

[0041] However, considering the efficiency of miniaturization, power consumption, noise suppression, space utilization, linear movement characteristics, and precise control of the device, it is preferable, as illustrated in the figure, that the drive unit is implemented by a structure that utilizes the electromagnetic force (magnetic force) generated between the magnet and the coil.

[0042] Relatedly, a coil can be provided on the mover and a magnet can be provided on the stator. However, in order to improve the efficiency of electrical connection, structural design, etc., as illustrated in the figure, the magnet M is provided on the carrier 110, which serves as the mover, and the coil C is provided on the housing 120, which serves as the relative stator.

[0043] According to the implementation, it may include: a Hall sensor for sensing the position of magnet M1 or a sensing magnet; and a driver D for controlling the magnitude and direction of the current supplied to coil C1 using the signal output by the Hall sensor. The Hall sensor is typically implemented as a single electronic component (chip) integrated with the driver D, and therefore is not shown separately in the figures.

[0044] The coil C and driver D can be mounted on the circuit board 140. Preferably, the circuit board 140 is formed in a way that exposes a portion of it to the outside so as to interfacing with external modules, power supplies, external devices, etc.

[0045] Multiple balls B are arranged between the carrier 110 and the housing 120. Specifically, the multiple balls B may be a first ball group B1 arranged on a first track R1 and / or a second ball group B2 arranged on a second track R2. The first track R1 is formed in one or more of the carrier 110 and the housing 120, and the second track R2 is formed in one or more of the carrier 110 and the housing 120 and is formed side by side with the first track R1.

[0046] To effectively guide the linear movement of the carrier 110, preferably, the balls belonging to the first ball group B1 are configured such that a portion of them are housed in the first track R1. The same applies to the balls corresponding to the second ball group B2. The first ball group and the first balls belonging to the first ball group are represented by the same reference numeral B1 unless otherwise specified.

[0047] The figure shows that both the first ball group B1 and the second ball group B2 are composed of multiple balls arranged along the optical axis, but one of the ball groups can be composed of a single ball.

[0048] The figure shows an embodiment where both the carrier 110 and the housing 120 have the first track R1, but according to the implementation, the first track may be provided on only one of them. In this case, in the structure without the first track, a groove or receiving part may be provided for accommodating one or more balls (first balls) belonging to the first ball group B1 and preventing the first ball B1 from dislodging outward. The same applies to the second track R2.

[0049] Thus, with the balls B1 and B2 positioned between the carrier 110 and the housing 120, the following advantages can be achieved: by minimizing the friction caused by the rolling, moving, rotating, and point-contact of the balls with the object, the mover (carrier) can move linearly more flexibly, which can not only reduce noise and minimize driving force, but also improve driving accuracy.

[0050] Regarding the tracks R1 and R2 for arranging the ball bearings B1 and B2, one of the tracks (a horizontal cross-section based on the optical axis direction) can be configured such that the cross-section of one track R1 and the other track R2 is "V" shaped, and the cross-section of the other track is "U" shaped.

[0051] When the cross-sections of the first track R1 and the second track R2 are configured with different shape characteristics, the contact points and rotational characteristics with the balls B1 and B2 can be configured differently from each other, thereby improving the driving characteristics such as the linearity of movement and driving efficiency of the carrier 110 moving along the optical axis.

[0052] When both the carrier 110 and the housing 120 have a second track R2 with a "V" shaped cross section, the second track R2 is arranged with its open portions facing each other, and one or more balls belonging to the second ball group B2 are arranged between them. Therefore, the second ball B2 is in contact with both the second track R2 of the carrier 110 and the second track R2 of the housing 120 when a portion of it is contained within the second track R2.

[0053] Due to this physical structure, the carrier 110 moves precisely in a linear fashion by means of the physical support of the second ball bearing assembly B2 and the guidance of the second track R2.

[0054] The "V-shaped" cross-section refers not only to the V-shape of the letter itself, but also to the shape in which the inner surface of the second ball B2 and the second track R2 contact at two points.

[0055] When the cross-section of the first track R1 provided by the housing 120 is U-shaped, in order to enable the linear movement of the carrier 110, it is preferable that the cross-section of the first track R1 facing the track R1 and provided on the carrier 110 is formed into a V-shape.

[0056] The "U-shaped" cross-section refers not only to the shape of the letter U itself, but also to the fact that, as well as other shapes such as trapezoids, there can be a certain degree of free space on the inner side of the ball and the track.

[0057] As an example, the figure shows an embodiment in which the first track R1 and the second track R2 of the carrier 110 have V-shaped cross sections, and one of the first track R1 and the second track R2 of the housing 120 has a V-shaped cross section and the other track has a U-shaped cross section.

[0058] The housing 120 of the present invention has a yoke 150 made of magnetic material, which generates an attractive force with the magnet M of the carrier 110.

[0059] If an attractive force or force is generated between the magnet M and the yoke 150, then with the balls B1 and B2 arranged between the carrier 110 and the housing 120, the carrier 110 is in close contact with the housing 120 in the direction of the X-axis (based on the attached figure), thus enabling the physical contact between the balls B1 and B2 and the carrier 110, as well as between the balls B1 and B2 and the housing 120, to continue.

[0060] The axes shown in the accompanying drawings, the terms used to refer to these axes, and the terms such as upper, lower, front, rear, vertical, and horizontal used in the description based on these axes are clearly only used to indicate the relative references for illustrating embodiments of the present invention, and not to specify a certain direction or position from an absolute reference. It is self-evident that they can vary relative to the position of the object being described, the position or direction of the view, etc.

[0061] In the following description of the present invention, the Z-axis direction, which is the direction corresponding to the path of light from the subject incident on the lens and is perpendicular to the carrier 110, is defined as the optical axis direction, and the two axes on the plane (horizontal plane) perpendicular to the optical axis direction (Z-axis) are defined as the X-axis and the Y-axis.

[0062] Figure 4 This is a partial cross-sectional view showing the ball bearing B and the yoke plate 150. Figure 5 This is a diagram illustrating the structural relationship between the yoke 150, ball bearing B, magnet M, and stroke H3.

[0063] As described above, the yoke plate 150 of the present invention, as a structure provided on the housing 120 which is a relative stator, generates attraction with the magnet M provided on the carrier 110 which is a mover.

[0064] The magnet M is a permanent magnet, and the yoke 150 is made of a magnetic material, so the attraction between them is always generated regardless of the movement of the carrier 110.

[0065] Since the ball B is arranged between the carrier 110 and the housing 120, even if the magnet M set on the carrier 110 moves forward and backward along the optical axis direction by AF drive, the tight force between the housing 120 and the ball B and between the ball B and the carrier 110 must be maintained in order to make the linear movement of the carrier 110 based on AF drive continue without gaps or tilting.

[0066] Therefore, the height H1 of the yoke plate 150 is preferably designed to be greater than the height H2 of the magnet M, and is also preferably configured to be greater than the sum of the height H2 of the magnet M and the stroke H3, where the stroke H3 is the range or length region in which the carrier 110 moves along the optical axis.

[0067] The multiple balls B arranged between the housing 120 and the carrier 110 are a structure that physically supports the carrier 110 and directly guides its physical movement. As described above, the balls B can have a degree of freedom and move in the optical axis direction, but they do not have the same movement characteristics as the carrier 110, such as the direction of movement and the distance of movement.

[0068] Therefore, only by maintaining the physical support and guidance of the ball B on the carrier 110, and ensuring that the physical contact point (position of point contact) between the ball B and the carrier 110 does not detach from the attraction area formed by the magnet M and the yoke 150, can posture defects such as tilting of the carrier 110 be prevented.

[0069] Therefore, preferably, the sum of the total height (stack height) H4 of the plurality of balls B and the stroke H3 (H4+H3) (hereinafter referred to as the "first distance") is less than the sum of the radius of one of the plurality of balls B (hereinafter referred to as the "comparison ball") and the height of the yoke 150 (R+H1).

[0070] If multiple balls B are all formed with the same diameter, then it doesn't matter if the aforementioned comparison ball is any one of the multiple balls.

[0071] When the end of the carrier 110 (based on the optical axis direction) deviates from the center of the outermost ball B (based on the optical axis direction) among the plurality of balls B, the balance support of the carrier 110 may be destroyed. Therefore, if the size of the plurality of balls B is not the same, it is preferable that the aforementioned comparative ball is the outermost ball BS among the plurality of balls B.

[0072] The diameters of the multiple balls B cannot be exactly the same, and the movement and stopping of the carrier 110 during AF drive are random. Therefore, the number of balls B that are actually in contact with the carrier 110 may change at any time when the carrier 110 moves along the optical axis.

[0073] Therefore, when the diameter of the outermost ball BS (hereinafter referred to as "main ball") among the multiple balls B arranged along the optical axis is larger than the diameter of the other balls B, it is possible to guide the carrier 110 in such a way that the main ball BS is always in contact with it. Furthermore, since the relatively large-diameter main ball BS is arranged on the outermost side among the multiple balls, the possibility of the carrier 110 tilting can be relatively reduced.

[0074] The accompanying drawings show a first ball group B1 and a second ball group B2 consisting of the same number of balls. However, according to an embodiment, the first ball group B1 and the second ball group B2 may consist of different numbers of balls. As mentioned above, one of these ball groups may also consist of a single number of balls.

[0075] Thus, when multiple ball bearing groups are arranged side by side between the housing 120 and the carrier 110, preferably, the "total height H4 of the multiple ball bearings B" which is a component of the aforementioned first distance (H4+H3) is determined to be the total height of the ball bearing group with the relatively high total height among the multiple ball bearing groups (hereinafter referred to as the "support ball bearing group").

[0076] In this case, preferably, the first distance (H4+H3), that is, the sum of the height H4 and the stroke H3 of the support ball group, is less than the sum of the radius R of the outermost ball in the support ball group and the height H1 of the yoke 150 (R+H1).

[0077] If an appropriate amount and direction of power is applied to the coil C under the control of the driver D, a magnetic force (electromagnetic force) is generated between the coil C and the magnet M. As shown in the figure, preferably, the coil C that generates the driving force is designed to cover the height region of the movement range (stroke) of the magnet M disposed on the carrier 110.

[0078] Since the magnet M has weight and is a structure set on the carrier 110 that acts as a mover, the driving force generated by the coil C acts directly on the magnet M, in addition to possibly acting as a load caused by the drive. Therefore, the larger the size of the magnet M (the height relative to the optical axis direction), the greater the driving force will be.

[0079] However, since the magnet M is the object on which the driving force is directly applied, if the driving force is also applied in the area that is no longer physically supported by the ball B, the posture defects of the carrier 110 may also be relatively easy to occur.

[0080] Therefore, preferably, the height of the magnet M (based on the optical axis) is less than the sum of the total height H4 of the plurality of balls B and the radius R of the outermost ball BS among the plurality of balls (H4+R). In this case, the total height of the plurality of balls can also be the height of the supporting ball assembly, which is self-evident.

[0081] While the present invention has been described above with reference to specific embodiments and accompanying drawings, it is not limited thereto. It is self-evident that those skilled in the art to which this invention pertains can make various modifications and variations within the scope of the technical concept of the invention and the equivalents of the claims described below.

[0082] In the above description of the present invention, modifiers such as first, second, etc. are merely tool concepts used to distinguish between constituent elements, and therefore should be interpreted as not being used to indicate a specific order, priority, etc.

[0083] For the purpose of illustrating the present invention and its embodiments, the accompanying drawings and other illustrations may be shown in a slightly exaggerated form to emphasize or highlight the technical content of the present invention. However, it should be understood that various modifications and applications can be clearly made by those skilled in the art, taking into account the above content and the matters shown in the drawings.

Claims

1. An actuator for a camera, characterized in that, include: The casing provides internal space; The carrier moves along the optical axis with the shell as a reference. A magnet is disposed on the carrier so as to face a coil disposed on the housing; A yoke plate, disposed in the housing, and attracting the magnet; and Ball bearings are arranged between the housing and the carrier. The height of the yoke is greater than the sum of the height of the magnet and the stroke, where the stroke is the distance the carrier moves due to AF drive.

2. The camera actuator according to claim 1, characterized in that, The ball bearings consist of multiple balls arranged along the optical axis. The first distance, which is the sum of the total height of the plurality of balls and the stroke, is less than the sum of the radius of the comparison ball, which is one of the plurality of balls, and the height of the yoke.

3. The camera actuator according to claim 2, characterized in that, The comparison ball is the outermost ball among the plurality of balls.

4. The camera actuator according to claim 3, characterized in that, The outermost ball is the largest in diameter among the plurality of balls.

5. The camera actuator according to claim 1, characterized in that, The balls include: A first ball bearing assembly is disposed between the carrier and the housing; and The second ball bearing assembly is arranged between the carrier and the housing, and is positioned parallel to the first ball bearing assembly with reference to the optical axis direction. One or more of the first and second ball groups are composed of multiple balls. The sum of the height of the supporting ball group, which is the larger of the first and second ball groups in terms of total height, and the stroke is less than the sum of the radius of the outermost ball in the supporting ball group and the height of the yoke.

6. The camera actuator according to claim 1, characterized in that, The height of the magnet is less than the sum of the total height of the plurality of balls and the radius of the outermost ball among the plurality of balls.

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