Small actuator

Abstract

A small actuator is provided. A small actuator according to an aspect of the present invention comprises: a housing; a motor including a motor gear and disposed in the housing; a first transmission gear including a first gear unit which is in outer contact with the motor gear and a second gear unit integrally formed with the first gear unit; a second transmission gear including a third gear unit which is in outer contact with the second gear unit and a fourth gear unit integrally formed with the third gear unit; a third transmission gear including a fifth gear unit which is in outer contact with the fourth gear unit and a sixth gear unit integrally formed with the fifth gear unit; a fourth transmission gear including a seventh gear unit which is in outer contact with the sixth gear unit and an eighth gear unit integrally formed with the seventh gear unit; and an output shaft including an output gear which is in outer contact with the eighth gear unit.

Description

miniature actuators

[0001] The present invention relates to a miniature actuator.

[0002] Robots come in a variety of forms, but their mechanical configuration consists of multiple rotary joints, each equipped with an actuator that enables rotational movement.

[0003] With recent advances in factory automation and the advancement of unmanned, advanced industrial facilities, demand for collaborative robots, such as manipulator-type robots, is increasing. Miniaturization, high output, and precision are performance factors that require continuous improvement.

[0004] For this purpose, a compact, high-power, and precise miniature actuator is required.

[0005] Small actuators applied to the rotary joints or ends of robots include the small actuator from ROBOTIS and the AK10-9 model from CubeMars.

[0006] Robotis' small actuators can be used by connecting the actuators with 3 or 4 wires and installing them on the joints or ends of the robot, but they have limitations in size, making it difficult to attach them to the joints as a direct drive type, and there are problems such as making it difficult to reflect the force or position measured from the robot in real time for control and making it difficult to predict the force generated by interaction.

[0007] In addition, the AK10-9 model from Cubemas had a problem in that it was difficult to attach it to the joints or ends of the robot due to its size, as the actuator structure required a low reduction ratio to generate a large torque.

[0008] The problem to be solved by the present invention is to provide a small actuator having a low inertia and high gear ratio.

[0009] In addition, a problem to be solved by the present invention is to provide a miniature actuator capable of detecting the rotation angle of an output shaft.

[0010] In addition, the problem to be solved by the present invention is to provide a small actuator capable of detecting torque by detecting current flowing in a motor.

[0011] In addition, the problem that the present invention seeks to solve is to provide a compact actuator that can improve space efficiency.

[0012] According to an aspect of the present invention for achieving the above object, a miniature actuator comprises: a housing; a motor including a motor gear and disposed in the housing; a first transmission gear including a first gear unit externally contacting the motor gear and a second gear unit integrally formed with the first gear unit; a second transmission gear including a third gear unit externally contacting the second gear unit and a fourth gear unit integrally formed with the third gear unit; a third transmission gear including a fifth gear unit externally contacting the fourth gear unit and a sixth gear unit integrally formed with the fifth gear unit; a fourth transmission gear including a seventh gear unit externally contacting the sixth gear unit and an eighth gear unit integrally formed with the seventh gear unit; and an output shaft including an output gear externally contacting the eighth gear unit.

[0013] In this case, the second transmission gear and the fourth transmission gear may overlap in the vertical direction, and the third transmission gear and the output shaft may overlap in the vertical direction.

[0014] Specifically, the second transmission gear, the third transmission gear, the fourth transmission gear, and the output gear can be sequentially arranged in a zigzag pattern.

[0015] Additionally, the third gear unit may be vertically overlapped with the seventh gear unit as a whole, and the output gear may be vertically overlapped with the fifth gear unit as a whole.

[0016] In addition, the diameter of the third gear unit may be formed to be larger than the diameter of the fourth gear unit, the diameter of the seventh gear unit may be formed to be larger than the diameter of the eighth gear unit, and the diameter of the fifth gear unit may be formed to be larger than the diameter of the sixth gear unit.

[0017] Through this, a small actuator with low inertia and high gear ratio can be implemented.

[0018] Additionally, the motor may be a coreless DC motor having low inertia.

[0019] In addition, it may further include a magnet disposed on the output shaft and disposed below the third transmission gear, a substrate disposed in the housing, and a magnet sensor disposed on the substrate and facing the magnet.

[0020] Through this, the rotation angle of the output shaft can be detected.

[0021] In addition, the housing includes a first housing, a second housing disposed below the first housing, and a third housing connecting the first housing and the second housing, and the output shaft can be rotatably coupled to the third housing via a bearing.

[0022] In addition, the substrate further includes a current sensor disposed thereon, and the current sensor can detect current flowing to the motor.

[0023] Through this, the torque of a small actuator can be detected by detecting the current flowing through the motor.

[0024] In addition, the substrate may include an inner substrate coupled to the second housing, and an outer substrate electrically connected to the inner substrate and disposed on the outside of the housing, and the magnet sensor, the current sensor, and the motor drive may be disposed on the inner substrate, and a control unit may be disposed on the outer substrate.

[0025] In addition, the device further includes a motor drive disposed on the substrate and controlling the operation of the motor; and a control unit disposed on the substrate and electrically connected to the current sensor and the motor drive, wherein the control unit can predict the torque of the small actuator through the current flowing in the motor detected by the current sensor, and control the operation of the motor through the motor drive according to the predicted torque of the small actuator.

[0026] Additionally, the third transmission gear may be rotatably coupled to the output shaft.

[0027] In addition, the housing includes a first housing, a second housing disposed below the first housing, and a third housing connecting the first housing and the second housing, and includes a rotation shaft disposed inside the first transmission gear and formed integrally with the first transmission gear, and the rotation shaft can be rotatably coupled to the third housing.

[0028] Additionally, the device includes a fixed shaft having an upper portion coupled to the first housing and a lower portion coupled to the third housing, and the second transmission gear and the fourth transmission gear can each be rotatably coupled to the fixed shaft.

[0029] This can improve space efficiency.

[0030] Through this embodiment, a small actuator having a low inertia gear ratio can be provided.

[0031] Additionally, the present embodiment can provide a miniature actuator capable of detecting the rotation angle of an output shaft.

[0032] Additionally, the present embodiment can provide a small actuator capable of detecting torque by detecting current flowing through a motor.

[0033] Additionally, the present embodiment can provide a compact actuator that can improve space efficiency.

[0034] FIG. 1 is a perspective view of a miniature actuator according to one embodiment of the present invention.

[0035] Figure 2 is an exploded perspective view of a miniature actuator according to one embodiment of the present invention.

[0036] FIG. 3 is a front view of a portion of a miniature actuator according to one embodiment of the present invention.

[0037] FIG. 4 and FIG. 5 are diagrams showing the distribution of normalized logarithmic values ​​of inertia of a small actuator according to one embodiment of the present invention.

[0038] FIG. 6 is a graph showing the reverse driving torque generated over time of a small actuator according to a prior art and an embodiment of the present invention.

[0039] FIG. 7 and FIG. 8 are drawings showing a substrate of a small actuator according to one embodiment of the present invention.

[0040] Fig. 9 is a circuit diagram of a miniature actuator according to one embodiment of the present invention.

[0041] FIG. 10 is a part of a circuit diagram of a miniature actuator according to one embodiment of the present invention.

[0042] FIG. 11 is a graph showing voltage and current over time of a small actuator according to one embodiment of the present specification.

[0043] FIG. 12 is a graph showing the rotation angle of a magnet over time of a small actuator according to one embodiment of the present specification.

[0044] FIG. 13 is a graph showing the relationship between the actual rotation angle and the reference rotation angle of the magnet of a small actuator according to one embodiment of the present specification.

[0045] FIG. 14 is a graph showing the relationship between the input voltage and the measured current of a small actuator according to one embodiment of the present specification.

[0046] FIG. 15 is a graph showing the relationship between the measured current and torque of a small actuator according to one embodiment of the present specification.

[0047] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0048] However, the technical idea of ​​the present invention is not limited to some of the embodiments described, but can be implemented in various different forms, and within the scope of the technical idea of ​​the present invention, one or more of the components between the embodiments can be selectively combined or substituted for use.

[0049] In addition, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as having a meaning that can be generally understood by a person of ordinary skill in the technical field to which the present invention belongs, unless explicitly and specifically defined and described, and terms that are commonly used, such as terms defined in a dictionary, may be interpreted in consideration of the contextual meaning of the relevant technology.

[0050] Additionally, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0051] In this specification, the singular may also include the plural unless specifically stated otherwise in the phrase, and when it is described as “A and / or at least one (or more) of B, C”, it may include one or more of all combinations that can be combined with A, B, C.

[0052] Additionally, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and are not intended to limit the nature, order, or sequence of the components.

[0053] And, when a component is described as being 'connected', 'coupled', or 'connected' to another component, it may include not only cases where the component is 'connected', 'coupled', or 'connected' directly to the other component, but also cases where the component is 'connected', 'coupled', or 'connected' by another component between the component and the other component.

[0054] Additionally, when described as being formed or arranged "above" or "below" each component, "above" or "below" includes not only cases where the two components are in direct contact with each other, but also cases where one or more other components are formed or arranged between the two components. Furthermore, when expressed as "above" or "below," the meaning may include not only the upward direction but also the downward direction based on one component.

[0055] Hereinafter, the present invention will be described in more detail with reference to the attached drawings.

[0056] Fig. 1 is a perspective view of a miniature actuator according to one embodiment of the present invention. Fig. 2 is an exploded perspective view of a miniature actuator according to one embodiment of the present invention. Fig. 3 is a front view of a portion of a miniature actuator according to one embodiment of the present invention.

[0057] Referring to FIGS. 1 to 3, a miniature actuator (10) according to one embodiment of the present invention may include a housing (100), a motor (200), a transmission gear (300), an output shaft (400), a magnet (500), a substrate (600), a fixing member (700), and a bearing (800), but may be implemented excluding some of these configurations, and additional configurations are not excluded.

[0058] The miniature actuator (10) is a miniature actuator that can be applied to the terminal devices or joints of robots in confined spaces, but is not limited thereto and can be utilized in various fields. For example, the terminal devices of the robot may include a gripper for grasping an object or a robot hand. The miniature actuator (10) utilizes a modular structure with a built-in signal processing device, sensor, and driver, so that a separate signal processing device is not required and maintenance is easy. The miniature actuator (10) utilizes a low-inertia gear and a low-inertia motor, so that it is light in weight and has excellent reverse drivability. The miniature actuator (10) can communicate with the outside. The miniature actuator (10) can predict torque based on a current signal, so that fast torque feedback and control are possible.

[0059] A housing (100) can form the exterior of a small actuator (10). A motor (200), a transmission gear (300), an output shaft (400), a magnet (500), a substrate (600), a fixing member (700), and a bearing (800) can be arranged inside the housing (100). A portion of the substrate (600) can be arranged on the exterior of the housing (100). The housing (100) can be formed in an overall hexahedral shape.

[0060] The housing (100) may include a first housing (110), a second housing (130) positioned below the first housing (110), and a third housing (120) connecting the first housing (110) and the second housing (130).

[0061] A first coupling hole may be formed on the upper surface of the third housing (120), and a first coupling protrusion may be formed on the lower surface of the first housing (110) to be inserted into the first coupling hole of the third housing (120). A second coupling hole may be formed on the upper surface of the second housing (130), and a second coupling protrusion may be formed on the lower surface of the third housing (120) to be inserted into the second coupling hole of the second housing.

[0062] A motor (200), a transmission gear (300), and an output shaft (400) may be placed in the space between the first housing (110) and the third housing (120). The first housing (110) may include an output hole (112) penetrated by the output shaft (400).

[0063] A fixing member (700), an internal substrate (610), and a magnet (500) can be placed in the space between the third housing (120) and the second housing (130).

[0064] The third housing (120) may include a bearing mounting hole (124) through which the output shaft (400) passes and to which a bearing (800) is coupled. The third housing may include a motor hole (122) through which a lower region of the motor (200) is mounted and through which a portion of the lower region of the motor (200) is coupled. The third housing (120) may include a rotation hole (126) through which a rotation shaft (320) disposed within the first transmission gear (310) is rotatably coupled. The third housing (120) may include a fixed hole (128) through which a fixed shaft (330) disposed within the second transmission gear (340) and the fourth transmission gear (360) passes.

[0065] The motor (200) may be placed in the housing (100). Specifically, the motor (200) may be placed in a space between the first housing (110) and the third housing (120). The lower region of the motor (200) may be mounted in the upper region of the motor hole (122) of the third housing (120). The lower region of the motor (200) may penetrate the motor hole (122) of the third housing (120). The motor (200) may be a coreless direct current (DC) motor having low inertia.

[0066] The motor (200) may include a motor gear (210). The motor gear (210) may be disposed in a lower region of the motor (200). The motor gear (210) may rotate clockwise or counterclockwise depending on the rotation of the motor shaft of the motor (200). The motor gear (210) may be in external contact with the first transmission gear (310). The motor gear (210) may be disposed below the third housing (120). The motor gear (210) may penetrate a portion of the fixing member (700).

[0067] The transmission gear (300) can be externally connected to the motor gear (210) of the motor (200). The transmission gear (300) can be externally connected to the output shaft (400). The transmission gear (300) can have a high gear ratio. Through this, the transmission gear (300) can reduce the output of the motor (200) and transmit it to the output shaft (400).

[0068] The transmission gear (300) may include a first transmission gear (310). The first transmission gear (310) may be externally connected to the motor gear (210). The first transmission gear (310) may include a first gear unit (312) externally connected to the motor gear (210) and a second gear unit (314) formed integrally with the first gear unit (312).

[0069] The first gear unit (312) may be horizontally overlapped with the motor gear (210). The diameter of the first gear unit (312) may be larger than the diameter of the motor gear (210). The number of teeth of the first gear unit (312) may be greater than the number of teeth of the motor gear (210). The vertical length of the first gear unit (312) may be shorter than the vertical length of the motor gear (210).

[0070] The second gear unit (314) may be disposed above the first gear unit (312). The vertical length of the second gear unit (314) may be longer than the vertical length of the first gear unit (312). The diameter of the second gear unit (314) may be smaller than the diameter of the first gear unit (312). The number of teeth of the second gear unit (314) may be smaller than the number of teeth of the first gear unit (312). The second gear unit (314) may be externally connected to the second transmission gear (340). The second gear unit (314) may be externally connected to the third gear unit (342). The second gear unit (314) may overlap the bearing (800) in the horizontal direction. The second gear unit (314) may be disposed below the third housing (120). The second gear unit (314) can be placed between the third housing (120) and the fixed member (700).

[0071] The rotation shaft (320) may be disposed inside the first transmission gear (310). The rotation shaft (320) may rotate integrally with the first transmission gear (310). The rotation shaft (320) may penetrate the first transmission gear (310). The rotation shaft (320) may be formed integrally with the first transmission gear (310). The rotation shaft (320) may be rotatably coupled to the third housing (120). Specifically, an upper region of the rotation shaft (320) may be rotatably coupled to a rotation hole (126) of the third housing (120), and a lower region of the rotation shaft (320) may be rotatably coupled to a fixing member (700). Oil may be provided between the rotation shaft (320) and the rotation hole (126), and between the rotation shaft (320) and the fixing member (700) to provide low friction.

[0072] The transmission gear (300) may include a second transmission gear (340). The second transmission gear (340) may be externally connected to the first transmission gear (310). The second transmission gear (340) may include a third gear unit (342) externally connected to the second gear unit (314) of the first transmission gear (310), and a fourth gear unit (344) integrally formed with the third gear unit (342). The second transmission gear (340) may be rotatably connected to a fixed shaft (330). The second transmission gear (340) may be penetrated by the fixed shaft (330). Oil may be provided between the second transmission gear (340) and the fixed shaft (330) to reduce friction.

[0073] The third gear unit (342) may be horizontally overlapped with the second gear unit (314). The diameter of the third gear unit (342) may be larger than the diameter of the second gear unit (314). The number of teeth of the third gear unit (342) may be greater than the number of teeth of the second gear unit (314). The vertical length of the third gear unit (342) may be shorter than the vertical length of the second gear unit (314). The third gear unit (342) may be disposed in the space between the first housing (110) and the third housing (120). The third gear unit (342) may be vertically overlapped with the seventh gear unit (362) as a whole.

[0074] The fourth gear unit (344) may be disposed above the third gear unit (342). The vertical length of the fourth gear unit (344) may be longer than the vertical length of the third gear unit (342). The diameter of the fourth gear unit (344) may be smaller than the diameter of the third gear unit (342). The number of teeth of the fourth gear unit (344) may be smaller than the number of teeth of the third gear unit (342). The fourth gear unit (344) may be externally connected to the third transmission gear (350). The fourth gear unit (344) may be externally connected to the fifth gear unit (352). The fourth gear unit (344) may be disposed in a space between the first housing (110) and the third housing (120).

[0075] The fixed shaft (330) can be arranged inside the second transmission gear (340) and the fourth transmission gear (360). The fixed shaft (330) can penetrate the second transmission gear (340) and the fourth transmission gear (360). The fixed shaft (330) can be coupled to and fixed in the housing (100). An upper region of the fixed shaft (330) can be coupled to and fixed in the first housing (110). A lower region of the fixed shaft (330) can be coupled to and fixed in the third housing (120). A lower region of the fixed shaft (330) can be inserted into and fixed in the fixing hole (128) of the third housing (120).

[0076] The transmission gear (300) may include a third transmission gear (350). The third transmission gear (350) may be externally connected to the second transmission gear (340). The third transmission gear (350) may include a fifth gear unit (352) externally connected to the fourth gear unit (344), and a sixth gear unit (354) integrally formed with the fifth gear unit (352). The third transmission gear (350) may be rotatably coupled to the output shaft (400). The third transmission gear (350) may be disposed on a bearing (800).

[0077] The fifth gear unit (352) may be horizontally overlapped with the fourth gear unit (344). The diameter of the fifth gear unit (352) may be larger than the diameter of the fourth gear unit (344). The number of teeth of the fifth gear unit (352) may be greater than the number of teeth of the fourth gear unit (344). The vertical length of the fifth gear unit (352) may be shorter than the vertical length of the fourth gear unit (344). The fifth gear unit (352) may be penetrated by the output shaft (400). A portion of the fifth gear unit (352) may be vertically disposed between the third gear unit (342) and the seventh gear unit (362).

[0078] The sixth gear unit (354) may be disposed above the fifth gear unit (352). The vertical length of the sixth gear unit (354) may be longer than the vertical length of the fifth gear unit (352). The diameter of the sixth gear unit (354) may be smaller than the diameter of the fifth gear unit (352). The number of teeth of the sixth gear unit (354) may be smaller than the number of teeth of the fifth gear unit (352). The sixth gear unit (354) may be externally connected to the fourth transmission gear (360). The sixth gear unit (354) may be externally connected to the seventh gear unit (362). The sixth gear unit (354) may be penetrated by the output shaft (400).

[0079] The transmission gear (300) may include a fourth transmission gear (360). The fourth transmission gear (360) may be externally connected to the third transmission gear (350). The fourth transmission gear (360) may include a seventh gear unit (362) externally connected to the sixth gear unit (354), and an eighth gear unit (364) integrally formed with the seventh gear unit (362). The fourth transmission gear (360) may be rotatably connected to a fixed shaft (330). The fourth transmission gear (360) may be penetrated by the fixed shaft (330). The fourth transmission gear (360) may be disposed above the second transmission gear (340). The fourth transmission gear (360) may be vertically spaced apart from the second transmission gear (340). Oil may be provided between the fourth transmission gear (360) and the fixed shaft (330) to reduce friction.

[0080] The seventh gear unit (362) may be horizontally overlapped with the sixth gear unit (354). The diameter of the seventh gear unit (362) may be larger than the diameter of the sixth gear unit (354). The number of teeth of the seventh gear unit (362) may be greater than the number of teeth of the sixth gear unit (354). The vertical length of the seventh gear unit (362) may be shorter than the vertical length of the sixth gear unit (354). The seventh gear unit (362) may be disposed in a space between the first housing (110) and the third housing (120). A portion of the seventh gear unit (362) may be disposed vertically between the fifth gear unit (352) and the output gear (410).

[0081] The eighth gear unit (364) may be disposed above the seventh gear unit (362). The vertical length of the eighth gear unit (364) may be longer than the vertical length of the seventh gear unit (362). The diameter of the eighth gear unit (364) may be smaller than the diameter of the seventh gear unit (362). The number of teeth of the eighth gear unit (364) may be smaller than the number of teeth of the seventh gear unit (362). The eighth gear unit (364) may be externally connected to the output gear (410). The eighth gear unit (364) may be disposed in a space between the first housing (110) and the third housing (120).

[0082] The output shaft (400) may extend vertically. The output shaft (400) may be externally connected to the transmission gear (300). Specifically, the output shaft (400) may include an output gear (410) externally connected to the fourth transmission gear (360) of the transmission gear (300). The output gear (410) is formed integrally with the output shaft (400) and may rotate integrally with the output shaft (400). The output gear (410) may be externally connected to the eighth gear unit (364) of the fourth transmission gear (360). The output gear (410) may be disposed above the third transmission gear (350). The output gear (410) may be spaced apart from the third transmission gear (350) in the vertical direction. The diameter of the output gear (410) may be larger than the diameter of the eighth gear unit (364). The number of teeth of the output gear (410) may be greater than the number of teeth of the eighth gear unit (364). The vertical length of the output gear (410) may be shorter than the vertical length of the eighth gear unit (364). The output gear (410) may be vertically overlapped with the fifth gear unit (352) as a whole.

[0083] A bearing (800) may be coupled to the output shaft (400). The bearing (800) may be coupled to a lower region of the output shaft (400). The output shaft (400) may penetrate the bearing (800). The output shaft (400) may be rotatably coupled to the third housing (120) through the bearing (800). Specifically, the output shaft (400) may be rotatably coupled to a bearing mounting hole (124) of the third housing (120) through the bearing (800). The lower region of the output shaft (400) may penetrate the bearing mounting hole (124) of the third housing (120). An upper region of the output shaft (400) may protrude above the first housing (110). The upper region of the output shaft (400) may be connected to an external device.

[0084] The second transmission gear (340) and the fourth transmission gear (360) can be vertically overlapped. The third transmission gear (350) and the output shaft (400) can be vertically overlapped. Specifically, the second transmission gear (340), the third transmission gear (350), the fourth transmission gear (360), and the output gear (410) can be sequentially arranged in a zigzag pattern. Through this, a compact actuator (10) having a low inertia and high gear ratio can be implemented.

[0085] The magnet (500) can be placed on the output shaft (400). The magnet (500) can be coupled to the lower region of the output shaft (400). The magnet (500) can rotate integrally with the rotation of the output shaft (400). The magnet (500) can be placed in the space between the second housing (130) and the third housing (120). The magnet (500) can be formed in a cylindrical shape, but is not limited thereto, and the shape of the magnet (500) can be variously changed. The magnet (500) can be placed below the bearing (800). A portion (402) of the output shaft (400) placed between the magnet (500) and the bearing (800) can overlap with the first gear unit (312) in a horizontal direction.

[0086] The fixing member (700) can be placed in the housing (100). The fixing member (700) can be coupled to the third housing (120). The fixing member (700) can be placed below the third housing (120). The fixing member (700) can be penetrated by the lower region of the motor gear (210). The fixing member (700) can be rotatably coupled to the lower region of the rotational axis (320).

[0087] The bearing (800) can be coupled to the output shaft (400). The bearing (800) can be placed in the housing (100). The bearing (800) can be coupled to the third housing (120). The bearing (800) can be placed in the bearing mounting hole (124) of the third housing (120). The bearing (800) can be penetrated by the output shaft (400). The bearing (800) can be coupled to the third housing (120) to allow the output shaft (400) to rotate with respect to the third housing (120). The bearing (800) can be placed between the magnet (500) and the third transmission gear (350).

[0088] The substrate (600) may be placed in the housing (100). Specifically, the substrate (600) may be placed in a space between the second housing (130) and the third housing (120). The substrate (600) may include an inner substrate (610) placed below the motor (200), the transmission gear (300), and the output shaft (400), and an outer substrate (620) electrically connected to the inner substrate (610) and placed on the outside of the housing (100). The inner substrate (610) may be coupled to the second housing (130).

[0089] FIG. 4 and FIG. 5 are diagrams showing the distribution of normalized logarithmic values ​​of inertia of a small actuator according to one embodiment of the present invention.

[0090] Referring to FIG. 4, it can be seen that the transmission gear (300) of the small actuator (10) according to one embodiment of the present invention has a high gear ratio and a low gear module, so that the normalized logarithm value of the inertia of the small actuator (10) is low.

[0091] Referring to FIG. 5, it can be seen that the motor (200) of the small actuator (10) according to one embodiment of the present invention is a low-inertia DC motor, so the motor inertia is small and the normalized logarithm value of the inertia of the small actuator (10) is low.

[0092] That is, the miniature actuator (10) according to one embodiment of the present invention has a small gear module and low motor inertia, and thus has a low normalized logarithmic value of inertia, resulting in a light weight and high reverse drivability. At the same time, it has a high gear ratio, thereby increasing usability.

[0093] FIG. 6 is a graph showing the reverse driving torque generated over time of a small actuator according to a prior art and an embodiment of the present invention.

[0094] Referring to FIG. 6, it can be seen that the time-dependent reverse driving torque of the small actuator (10) according to one embodiment of the present invention is lower than that of the prior art A and the prior art B. Specifically, it can be seen that the time-dependent reverse driving torque of the small actuator (10) according to one embodiment of the present invention is 6 times lower than that of the prior art A and 4.6 times lower than that of the prior art B. In this case, when power was not applied to the small actuator (10), a thread and a pulley were connected to the small actuator (10) and an external stage was moved, the force transmitted through the thread was measured.

[0095] In summary, the small actuator (10) according to one embodiment of the present invention has high reverse drivability, so that it can precisely measure the current transmitted to the motor even at low torque.

[0096] Figures 7 and 8 are drawings showing the substrate of a miniature actuator according to one embodiment of the present invention. Figure 9 is a circuit diagram of a miniature actuator according to one embodiment of the present invention. Figure 10 is a part of a circuit diagram of a miniature actuator according to one embodiment of the present invention.

[0097] Referring to FIGS. 7 to 10, the substrate (600) may include a magnet sensor (6122), a first cable connector (6124), a second cable connector (6222), a third cable connector (6224), a motor drive (6142), a current sensor (6144, 6146), an external connector (6244), and a control unit (6242), but additional configurations are not excluded.

[0098] Specifically, a magnet sensor (6122) and a first cable connector (6124) may be arranged on the upper surface (612) of the inner substrate (610). A motor drive (6142) and current sensors (6144, 6146) may be arranged on the lower surface (614) of the inner substrate (610). An external connector (6244) and a control unit (6242) may be arranged on the outer surface (624) of the outer substrate (620). A second cable connector (6222) and a third cable connector (6224) may be arranged on the inner surface (622) of the outer substrate (620).

[0099] The magnet sensor (6122) may be disposed on the substrate (600). Specifically, the magnet sensor (6122) may be disposed on the upper surface (612) of the inner substrate (610). The magnet sensor (6122) may face the magnet (500). The magnet sensor (6122) may detect the rotation of the magnet (500). Specifically, the magnet sensor (6122) may detect the rotation angle and rotation speed of the magnet (500). Through this, the magnet sensor (6122) may detect the rotation angle and rotation speed of the output shaft (400).

[0100] The first cable connector (6124) may be disposed on the substrate (600). Specifically, the first cable connector (6124) may be disposed on the upper surface (612) of the inner substrate (610). The first cable connector (6124) may be electrically connected to the second cable connector (6222) of the outer substrate (620) via a cable. In this case, the cable connecting the first cable connector (6124) and the second cable connector (6222) may pass through the second housing (130).

[0101] The motor drive (6142) may be disposed on the substrate (600). Specifically, the motor drive (6142) may be disposed on the lower surface (614) of the inner substrate (610). The motor drive (6142) may be electrically connected to the motor (200). The motor drive (6142) may control the voltage or current applied to the motor (200). That is, the motor drive (6142) may control the driving of the motor (200).

[0102] Current sensors (6144, 6146) may be placed on the substrate (600). Specifically, current sensors (6144, 6146) may be placed on the lower surface (614) of the inner substrate (610). Current sensors (6144, 6146) may be electrically connected to the motor (200). Current sensors (6144, 6146) may measure or detect current flowing in the motor (200). Through this, torque of the small actuator (10) may be detected by detecting current flowing in the motor (200).

[0103] The current sensor (6144, 6146) may include a current amplifier (6146) and a current meter (4144). The current meter (4144) may be a shunt resistor. A shunt resistor is a type of shunt resistor used to measure current and may be referred to as a shunt resistor. Through this, the current sensor (6144, 6146) can be configured in a small and lightweight form.

[0104] An external connector (6244) may be placed on the substrate (600). Specifically, the external connector (6244) may be placed on the outer surface (624) of the external substrate (620). A cable for electrically connecting to devices placed externally may be connected to the external connector (6244).

[0105] The control unit (6242) may be disposed on the substrate (600). Specifically, the control unit (6242) may be disposed on the outer surface (624) of the external substrate (620). The control unit (6242) may be electrically connected to the magnet sensor (6122), the motor drive (6142), and the current sensors (6144, 6146). The control unit (6242) may control the operation of the motor (200) through the motor drive (6142). The control unit (6242) may detect the rotation speed and rotation angle of the output shaft (400) through the magnet sensor (6122), and measure the current flowing in the motor (200) through the current sensors (6144, 6146). That is, the control unit (6242) can predict the torque of the small actuator (10) through the current flowing in the motor (200) detected by the current sensor (6144, 6146), and control the operation of the motor (200) through the motor drive (6142) according to the predicted torque of the small actuator (10). Through this, the control unit (6242) can perform fast torque feedback control. The control unit (6242) can communicate with an external device. The control unit (6242) can perform high-speed communication of 10 KHz or more with the external device. The control unit (6242) can be referred to as a 'MCU (Micro Controller Unit)'.

[0106] A second cable connector (6222) may be disposed on the substrate (600). The second cable connector (6222) may be disposed on the inner surface (622) of the outer substrate (620). The second cable connector (6222) may be electrically connected to the first cable connector (6124) of the inner substrate (610) via a cable. In this case, the cable connecting the second cable connector (6222) and the first cable connector (6124) may be a flat cable.

[0107] A third cable connector (6224) may be disposed on the substrate (600). The third cable connector (6224) may be disposed on the inner surface (622) of the outer substrate (620). The third cable connector (6224) may be electrically connected to a cable for electrically connecting to another sensor installed on the inner substrate (610), the outer substrate (620), or another substrate.

[0108] Through this, since the signal processing device, the sensor, and the motor driver are configured as an integrated unit, maintenance of the small actuator (10) is easy, and data can be exchanged at high speed when connected to an external device. In addition, since an external connection method that allows bidirectional connection is provided, there is an advantage that there is no need to consider the direction of the connector when connecting. In addition, since the board on which the signal processing device is installed and the board on which the sensor and driver are installed are manufactured as separate types and can be easily connected with a commercial flat cable, replacement is easy in the event of a failure.

[0109] FIG. 11 is a graph showing voltage and current over time of a small actuator according to one embodiment of the present specification.

[0110] Referring to FIG. 9 and FIG. 11, the voltage (V) going from the control unit (6424) to the motor drive (6142) over time GS ) and the voltage (V) applied from the motor drive (6142) to the motor (200) DS ) and the current (I) actually flowing in the motor (200) DS ) can be known. Here, DAQ (Data acquisition) can be interpreted to mean a point where data is measured.

[0111] That is, since the measurement is synchronized to the digital signal that applies the current, it can be seen that current measurement is possible at a fast speed of 20 kHz. This can obtain more accurate current information than the method of detecting the current using a passive low-pass filter that utilizes a resistor and capacitor.

[0112] Fig. 12 is a graph showing the rotation angle of a magnet over time of a small actuator according to one embodiment of the present specification. Fig. 13 is a graph showing the relationship between the actual rotation angle of a magnet of a small actuator according to one embodiment of the present specification and a reference rotation angle. Fig. 14 is a graph showing the relationship between an input voltage and a measured current of a small actuator according to one embodiment of the present specification. Fig. 15 is a graph showing the relationship between a measured current and a torque of a small actuator according to one embodiment of the present specification.

[0113] A miniature actuator (10) according to one embodiment of the present invention detects the magnetic field of a magnet (500) by utilizing a magnetic sensor (6122), which is a rotary position detection sensor, and thus has a high precision characteristic. In order to experimentally verify these characteristics through FIGS. 12 to 15, the performance was compared with that of a potentiometer, which is mainly used in conventional miniature actuators.

[0114] Specifically, referring to FIGS. 12 and 13, it can be experimentally confirmed that the potentiometer has a root mean square error (RMSE) of 0.66°, and the magnet (500)-based magnetic sensor (6122) has a root mean square error of 0.33°, which is approximately twice the position detection performance.

[0115] According to one embodiment of the present invention, a miniature actuator (10) can calculate the torque that the miniature actuator (10) applies to the outside by applying voltage to the motor (200) and measuring the current generated thereby. In order to experimentally verify this, voltage was applied to the miniature actuator (10), and the relationship between the input voltage and the measured current, and the relationship between the measured current and the generated torque were analyzed. Specifically, referring to FIGS. 14 and 15, it can be seen that the experimental results show a linear relationship between the input voltage and the measured current. That is, it can be seen that the miniature actuator (10) according to one embodiment of the present invention can control by measuring the generated current and converting it into an external torque.

[0116] Although the embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical concept or essential features thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. Housing; A motor comprising a motor gear and disposed in the housing; A first transmission gear including a first gear unit external to the motor gear and a second gear unit formed integrally with the first gear unit; A second transmission gear including a third gear unit external to the second gear unit and a fourth gear unit formed integrally with the third gear unit; A third transmission gear including a fifth gear unit external to the fourth gear unit and a sixth gear unit formed integrally with the fifth gear unit; A fourth transmission gear including a seventh gear unit external to the sixth gear unit and an eighth gear unit integrally formed with the seventh gear unit; and An output shaft including an output gear externally connected to the above eighth gear unit, The second transmission gear and the fourth transmission gear are vertically overlapped, A small actuator in which the third transmission gear and the output shaft overlap in a vertical direction.

2. In paragraph 1, A small actuator in which the second transmission gear, the third transmission gear, the fourth transmission gear, and the output gear are sequentially arranged in a zigzag pattern.

3. In paragraph 1, The above third gear unit is vertically overlapped with the above seventh gear unit as a whole, The above output gear is a small actuator that is vertically overlapped with the fifth gear unit as a whole.

4. In paragraph 3, The diameter of the third gear unit is formed to be larger than the diameter of the fourth gear unit, The diameter of the above 7th gear unit is formed to be larger than the diameter of the above 8th gear unit, A small actuator in which the diameter of the fifth gear unit is formed larger than the diameter of the sixth gear unit.

5. In paragraph 1, The above motor is a compact actuator that is a coreless DC motor with low inertia.

6. In paragraph 1, A magnet disposed on the output shaft and below the third transmission gear; a substrate placed in the housing; and A miniature actuator further comprising a magnetic sensor disposed on the substrate and facing the magnet.

7. In paragraph 6, The housing includes a first housing, a second housing disposed below the first housing, and a third housing connecting the first housing and the second housing. A miniature actuator in which the output shaft is rotatably coupled to the third housing via a bearing.

8. In paragraph 6, Further comprising a current sensor disposed on the above substrate, The above current sensor is a small actuator that detects the current flowing to the motor.

9. In paragraph 8, The substrate includes an inner substrate coupled to the second housing, and an outer substrate electrically connected to the inner substrate and disposed on the outside of the housing. The magnetic sensor, the current sensor, and the motor drive are arranged on the internal substrate. A small actuator having a control unit arranged on the above external substrate.

10. In paragraph 8, A motor drive disposed on the substrate and controlling the operation of the motor; and Further comprising a control unit disposed on the substrate and electrically connected to the current sensor and the motor drive, A small actuator in which the control unit predicts the torque of the small actuator through the current flowing in the motor detected by the current sensor, and controls the operation of the motor through the motor drive according to the predicted torque of the small actuator.

11. In paragraph 6, The third transmission gear is a small actuator rotatably coupled to the output shaft.

12. In paragraph 1, The housing includes a first housing, a second housing disposed below the first housing, and a third housing connecting the first housing and the second housing. It includes a rotation shaft arranged inside the first transmission gear and formed integrally with the first transmission gear, The above rotation axis is a small actuator rotatably coupled to the third housing.

13. In paragraph 12, It includes a fixed shaft whose upper part is coupled to the first housing and whose lower part is coupled to the third housing, A small actuator in which the second transmission gear and the fourth transmission gear are each rotatably coupled to the fixed shaft.

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