Electric gripper and its operating method

Abstract

This invention provides an electric gripper and a method for operating it. [Solution] The electric gripper includes a circuit board, a motor, a transmission mechanism, and two claw bases. The motor generates an overtorque based on an overcurrent supplied from the circuit board, and the overtorque drives the transmission mechanism. The transmission mechanism moves the two claw bases in the closing direction based on the overtorque, generating an over-gripping force to grip an object. After gripping an object, the electric gripper maintains the gripping force of the two claw bases within a predetermined range, where the upper limit is the over-gripping force, via the transmission mechanism.

Description

Technical Field

[0001] The present invention relates to an electric gripper and an operation method thereof, and particularly to an electric gripper capable of significantly improving the clamping force and an operation method thereof.

Background Art

[0002] In the prior art, as a means for increasing the clamping force of an electric gripper, a method of generally increasing the torque of the rotor of the motor as much as possible is adopted. Generally, to enhance the torque of an electric gripper, it is achieved by amplification using a gear ratio or an increase in the number of turns of the winding. However, in the technology of amplification using a gear ratio, inevitably, the closing operation speed of the electric gripper is sacrificed, and it becomes difficult to shorten the operation time. Therefore, this technology cannot be said to be an optimal means for increasing the clamping force.

[0003] On the other hand, in the technology of increasing the number of turns of the winding, the more the winding number increases in an attempt to obtain a larger torque output, and the volume of the motor also increases proportionally. For this reason, it is difficult to significantly improve the torque of the motor within the limited gripper space. Also, in order to prevent the motor from overheating during use and damaging the motor coil and driver board, generally, the current supplied to the motor is restricted so as not to exceed the rated current. Due to these constraints, to obtain the same clamping force, the volume and weight of the electric gripper become larger than those of the pneumatic gripper. As a result, it becomes a bottleneck in the development of electric grippers that require a large clamping force, and the spread in the market is hindered.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In view of such a situation, it is an issue to be solved by the present inventor to provide an electric gripper and an operation method thereof that can double the clamping force and significantly reduce the output load of the motor. <s

Means for Solving the Problems

[0005] To solve the above problems, the present invention provides an electric gripper that overcomes the problems of the prior art. The electric gripper according to the present invention is for gripping an object and includes a circuit board, a motor, a transmission mechanism, and two claw bases, wherein the circuit board supplies an overcurrent exceeding the rated current at a first time, the motor is connected to the circuit board and generates an overtorque based on the overcurrent, and the transmission mechanism includes a gear set connected to the motor, a screw rod having a rod body with a left-hand threaded portion and a right-hand threaded portion, and a linear guide positioned on one side of the screw rod, wherein the left-hand threaded portion and the right-hand threaded portion are each formed spirally toward the center of the rod body at both ends of the rod body. The rod body is rotated in conjunction with the gear set driven by the overtorque of the motor, the two claw bases are screwed onto the left-hand threaded portion and the right-hand threaded portion, respectively, and engage with the linear guide, reciprocating on the linear guide in accordance with the rotation of the rod body, the motor moves the two claw bases in the closing direction by the overtorque, the closing operation of the two claw bases generates an over-clamping force for gripping an object, and in a second time after gripping the object, the transmission mechanism maintains the clamping force of the two claw bases within a predetermined range where the upper limit is the over-clamping force.

[0006] To solve the above problems, the present invention provides an electric gripper that overcomes the problems of the prior art. The electric gripper according to the present invention is for gripping an object and includes a circuit board, a motor, a transmission mechanism, and two claw bases, wherein the circuit board supplies an overcurrent exceeding the rated current in a first time, the motor is connected to the circuit board and generates an overtorque based on the overcurrent, the transmission mechanism comprises a gear set connected to the motor and a meshing transmission mechanism connected to the gear set, the meshing transmission mechanism is controlled to rotate in conjunction with the gear set, which is driven by the overtorque of the motor, along a direction perpendicular to the output shaft of the gear set, the two claw bases each comprise a rack mechanism, the rack mechanism reciprocates in accordance with the rotation of the meshing transmission mechanism, the motor moves the two claw bases in a closing direction due to the overtorque, the closing operation of the two claw bases generates an over-gripping force for gripping an object, and in a second time after gripping the object, the meshing transmission mechanism maintains the gripping force of the two claw bases within a predetermined range where the upper limit is the over-gripping force.

[0007] To solve the above problems, the present invention provides an operating method for an electric gripper that overcomes the problems of the prior art. The operating method for an electric gripper according to the present invention is for controlling the electric gripper to grip an object, and includes the steps of: (a) supplying current to the motor of the electric gripper, the motor generating torque based on the current and driving a transmission mechanism; (b) the transmission mechanism moving two claw bases in a closing or away direction; (c) supplying an overcurrent exceeding the rated current to the motor for a first time while the two claw bases are moving; (d) the motor generating overtorque based on the overcurrent and driving the transmission mechanism, and the transmission mechanism controlling the closing operation of the two claw bases to generate an over-gripping force for gripping the object; and (e) the transmission mechanism maintaining the gripping force of the two claw bases within a predetermined range where the upper limit is the over-gripping force. [Effects of the Invention]

[0008] The main objective and effect of the present invention is to dramatically improve the gripping force of an electric gripper by combining an operating method that uses a current exceeding the rated current instantaneously with a self-locking function, thereby doubling the gripping force and significantly reducing the output load of the motor.

[0009] To further understand the techniques, means, and effects employed by this invention to achieve its intended objectives, please refer to the following detailed description of the invention and the accompanying drawings. This will provide a more specific and in-depth understanding of the objectives, structure, and features of this invention. However, the accompanying drawings are provided for reference and illustrative purposes only and do not limit the invention. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of the structure of the first embodiment of the electric gripper according to the present invention. [Figure 2A] This is a schematic diagram illustrating the principle of lead angle according to the present invention. [Figure 2B] This is a schematic diagram illustrating the principle of the friction coefficient according to the present invention. [Figure 2C] This is a schematic diagram illustrating the principle of the self-locking function according to the present invention. [Figure 3] This is a schematic diagram of the structure of a second embodiment of the electric gripper according to the present invention. [Figure 4A] This is a schematic diagram of the waveform in the first embodiment of the motor current according to the present invention. [Figure 4B] Figure 4A is a schematic diagram of the clamping force curve when using the motor current shown. [Figure 5A] This is a schematic diagram of the waveform in a second embodiment of the motor current according to the present invention. [Figure 5B] Figure 5A is a schematic diagram of the clamping force curve when using the motor current shown. [Figure 6A] This is a curve diagram showing the relationship between instantaneous current and operating time according to the present invention. [Figure 6B] This is a schematic diagram showing the arrangement of the heat-generating components according to the present invention. [Figure 7A] This is a schematic diagram of the waveform in the first operating mode of the overcurrent protection mechanism according to the present invention. [Figure 7B] This is a schematic diagram of the waveform in the second operating mode of the overcurrent protection mechanism according to the present invention. [Figure 8] This is a flowchart showing the method for operating the electric gripper according to the present invention. [Modes for carrying out the invention]

[0011] The technical content and details of the present invention will be described below with reference to the drawings.

[0012] Referring to Figure 1, a schematic diagram of the structure of a first embodiment of the electric gripper 100 according to the present invention is shown. The electric gripper 100 is for gripping an object 200 (hereinafter simply referred to as object 200) to be gripped. The electric gripper 100 includes a circuit board 1, a motor 2, a transmission mechanism 3, and two claw bases 4. The circuit board 1 is electrically connected to the motor 2, and the circuit board 1 may include a drive circuit (not shown) and a controller (not shown) for controlling the drive circuit. The controller (not shown) controls the drive circuit by receiving an external control signal and can adjust the rotational speed and torque of the motor 2 by adjusting parameters such as voltage V, current I, and frequency f supplied to the motor 2 through the drive circuit (not shown). Here, the motor 2 can preferably be a brushless DC motor (BLDC) or a permanent magnet synchronous motor (PMSM), and the rotational speed and torque of these can be controlled by the current value. However, it is not limited to these, and all types of motor 2 applicable to the electric gripper 100 are included in the technical scope of this embodiment.

[0013] In one embodiment, the circuit board 1 shown in FIG. 1 can also be arranged at a remote position and is not limited to the position shown in FIG. 1. The circuit board 1 may be arranged in the vicinity of the electric gripper 100, and parameters such as voltage V, current I, and frequency f can be transmitted by a wired or wireless method to control the motor 2. Further, the circuit board 1 may be composed of a plurality of small circuit boards. An external control signal is transmitted from a remotely arranged small circuit board to a small circuit board in the vicinity, and a drive circuit (not shown) provided on the small circuit board on the vicinity side supplies parameters such as voltage V, current I, and frequency f to control the motor 2. Therefore, the present invention is not particularly limited with respect to the configuration, installation position, and arrangement method of the circuit board

[0014] The transmission mechanism 3 is connected to the rotor of the motor 2, and the transmission mechanism 3 includes a gear set 32, a screw rod 34, and a linear guide 36. The gear set 32 may include a plurality of gears that mesh with each other. The input gear of the gear set 32 is mounted on the rotating shaft of the motor 2, and the torque of the motor 2 can be increased by the interlocking of the plurality of gears. The screw rod 34 includes a rod body 340, and left screw portions 342 and right screw portions 344 are provided at both ends of the rod body 340, respectively, which are formed spirally toward the center of the rod body 340. The output gear of the gear set 32 is mounted on the rod body 340, whereby the rotation of the motor 2 can be interlockingly controlled via the gear set 32 to rotate the rod body 340. The linear guide 36 is arranged on one side of the screw rod 34 and is provided parallel to the rod body 340.

[0015] The two claw bases 4 may each include a claw portion 40, a nut 42, and a movable part 44. The nuts 42 of the two claw bases 4 are respectively screwed onto the left threaded portion 342 and the right threaded portion 344 of the rod body 340. The movable parts 44 of the two claw bases 4 are respectively engaged with the slide grooves 360 of the linear guide 36, and the movable part 44 can perform reciprocating linear movement along the direction defined by the linear guide 36. Thereby, the two claw bases 4 can reciprocate on the linear guide 36 according to the rotation of the rod body 340. Therefore, the circuit board 1 can supply parameters such as voltage V, current I, and frequency f for controlling the motor 2, and can control the rotation of the motor 2. Then, when the motor 2 drives the gear set 32 to control the rotation of the rod body 340 in an interlocking manner, the two claw bases 4 can move in the positive direction (that is, the two claw bases 4 move in the closing direction) or the reverse direction (that is, the two claw bases 4 move in the separating direction) with respect to the defined direction. When the two claw bases 4 move in the closing direction, the electric gripper 100 can clamp the object 200 through the closing operation of the two claw bases 4. On the other hand, when the two claw bases 4 move in the separating direction, the electric gripper 100 can release the object 200 by the separating operation of the two claw bases 4.

[0016] More specifically, one of the features of the electric gripper 100 according to the present invention is that by combining an operation method using a current that instantaneously exceeds the rated current and a self-locking function, the clamping force of the electric gripper 100 is doubled. In addition, since the electric gripper 100 according to the present invention has a self-locking function, the output load of the motor 2 can be significantly reduced. Therefore, the motor 2 can achieve the target clamping force of the electric gripper 100 by only applying an instantaneous current, and the subsequent clamping force is maintained by the self-locking function. Thereby, the motor 2 can operate with an instantaneous overcurrent, and the clamping force of the electric gripper 100 can be significantly improved. <000009?

[0017] Specifically, in the electric gripper 100 according to the present invention, during the period from when the two claw bases 4 begin to move in the closing direction until the two claw bases 4 grip the object 200 (defined herein as the "first time"), the circuit board 1 controls the drive circuit based on an external control signal to supply an overcurrent Ier to the motor 2. Generally, the specifications of the motor 2 include values ​​such as rated current, rated output, and rated torque, which are clearly indicated on the nameplate. The rated current refers to the allowable current within which the motor 2 will not activate overcurrent or overtemperature protection even if it operates continuously for a long period of time (for example, 5 minutes or more) under rated environmental conditions (ambient temperature, sunlight, altitude, placement conditions, etc.). If this rated current is exceeded, the motor 2 may activate overcurrent or overtemperature protection in a short period of time (for example, within 5 minutes, but not limited to this).

[0018] Subsequently, the motor 2 outputs an overtorque Ter based on the overcurrent Ier, driving the gear set 32 ​​and the screw rod 34 to move the two claw bases 4 in the closing direction by the overtorque Ter, generating an over-gripping force Fer for gripping the object 200. Furthermore, during the period from when the two claw bases 4 grip the object 200 until the electric gripper 100 moves to an appropriate position and releases the two claw bases 4 (defined herein as the "second time"), the transmission mechanism 3 can, by mechanical operation, maintain the gripping force of the two claw bases 4 within a predetermined range where the upper limit is the over-gripping force Fer (for example, a range up to a value equivalent to 30% of the upper limit of the gripping force, but not limited to this). In this way, the electric gripper 100 according to the present invention has the effect of significantly improving the gripping force compared to conventional electric grippers.

[0019] Here, the transmission mechanism 3 can maintain the gripping force of the two claw bases 4 within a predetermined range by a locking device (not shown). In a second time after the two claw bases 4 have gripped the object 200, the transmission mechanism 3 can actively lock the two claw bases 4 using the locking device (not shown) to maintain the gripping force of the two claw bases 4 within a predetermined range. Furthermore, the transmission mechanism 3 can also be designed to have a self-locking function. Specifically, the left-hand threaded portion 342 and the right-hand threaded portion 344 of the rod body 340 according to the present invention have a lead angle α, and there is a coefficient of friction between the nuts 42 of the two claw bases 4 and the left-hand threaded portion 342 and the right-hand threaded portion 344, respectively. When the lead angle α is less than or equal to a predetermined angle (i.e., a low lead angle) and the coefficient of friction is greater than or equal to a predetermined value (i.e., a high coefficient of friction), the claw bases 4 of the electric gripper 100 will have an irreversible self-locking characteristic after displacement (i.e., a state in which the rod body 340 cannot be driven by the force from the claw bases 4). As a result, during the second time period after the two claw bases 4 have gripped the object 200, the transmission mechanism 3 can maintain the gripping force of the two claw bases 4 within a predetermined range by its self-locking function.

[0020] Furthermore, referring to Figures 2A to 2C, the reason why irreversible self-locking characteristics are achieved in the left-hand threaded portion 342 and right-hand threaded portion 344 of the rod body 340 by designing with a low lead angle and a high coefficient of friction will be explained. As shown in Figure 2A, the lead angle α of the left-hand threaded portion 342 and right-hand threaded portion 344 is defined as tanα = P / πd2. Also, in Figure 2B, the condition for the internal thread of the nut 42 of the claw base 4 to be self-locking is related to the direction of the force applied by the object. That is, in order to satisfy the self-locking condition, vector f must be greater than vector F, and as a result the object m will not be continuously displaced in the direction of vector F (i.e., the frictional force exceeds the reverse driving force). Therefore, the curve in Figure 2C can be derived by combining Figures 2A and 2B, and the transmission efficiency η is expressed as η = (1 - μ × tan × α) / (1 + μ × tan × α), and when it is 50% or less, it has a certain degree of self-locking (where α is the lead angle and μ is the coefficient of friction). Therefore, if the lead angle α is less than or equal to a predetermined angle (for example, 5° or less, but not limited thereto) and the coefficient of friction is greater than or equal to a predetermined value (for example, 0.1 or greater, but not limited thereto), the transmission mechanism 3 can have a self-locking function.

[0021] Referring to Figure 1, the transmission mechanism 3 may optionally further include a release knob 38. The release knob 38 is located at one end of the rod body 340 and is axially connected to the rod body 340. The release knob 38 rotates the rod body 340 to provide sufficient rotational force, causing the nut 42 to overcome friction and rotate, thereby releasing the self-locking function and releasing the clamping force between the two claw bases 4. This allows the lock on the claw bases 4 to be released via the release knob 38 when necessary (for example, in situations such as maintenance or removal of foreign objects). In addition, the transmission mechanism 3 may include multiple means for releasing the self-locking function (for example, release by vibration, shock, or reverse friction, etc.), but a detailed explanation of these is omitted here.

[0022] The electric gripper 100 according to the present invention has a self-locking irreversible characteristic. Therefore, after the motor 2 drives the screw rod 34 via the gear set 32 ​​to close the claw base 4 and grip the object 200, when the torque of the motor 2 increases and reaches a predetermined set value, that is, when the "second time" begins, the circuit board 1 can stop controlling the motor 2. For example, the circuit board 1 can stop the motor 2 by stopping the output of voltage V, current I, frequency f, etc. to the motor 2, or by cutting off the power supply to the motor 2 to turn off the output of the motor 2. Furthermore, because the screw rod 34 is designed with a low lead angle and a high coefficient of friction, it has a self-locking irreversible characteristic. As a result, the two claw bases 4 can maintain a gripping force slightly lower than the gripping force during closing (i.e., within a predetermined range), so that the two claw bases 4 do not easily loosen, preventing the object 200 from falling.

[0023] In addition to the safety design described above, which prevents the object 200 from falling even if the motor 2 is turned off, the present invention further enhances the maximum gripping force of the electric gripper 100 by using a method that applies a load several times the rated load to the motor 2 in a short time (i.e., a method that supplies an overcurrent Ier). Therefore, compared to conventional electric grippers, the electric gripper 100 according to the present invention can achieve the same gripping force while reducing the size of the motor 2, and as a result, advantages that contribute to miniaturization and weight reduction of the electric gripper 100 are obtained.

[0024] Referring to Figure 1, the electric gripper 100 may optionally be equipped with a position detection circuit 5. The position detection circuit 5 is located on the circuit board 1 and detects the position of the rotor of the motor 2 and outputs a position signal (not shown). The position detection circuit 5 may be composed of, for example, an encoder or a Hall element. The position detection circuit 5 allows the circuit board 1 to determine whether or not an abnormality or malfunction has occurred in the motor 2 using the position signal (not shown), and can also be used to detect the detachment of the gripped object. Specifically, in the "second time" described above, after the two claw bases 4 grip the object 200, the circuit board 1 supplies the motor 2 with a current lower than the rated current Ir (for example, 30% of the rated current Ir, but not limited to this), and the motor 2 outputs a torque less than the rated torque accordingly. As a result, the circuit board 1 can determine whether or not the rotor has been displaced based on the position signal (not shown) output from the position detection circuit 5 and detect whether or not the object 200 has detached during the gripping operation. Furthermore, during operation of the electric gripper 100, the motor 2 does not stop but continues to operate with reduced torque. Therefore, if the object 200 unexpectedly falls during the gripping operation, the claw base 4 will no longer receive a reaction force from the object, and will be driven further in the closing direction by the small torque that was maintained. As a result, the rotor of the motor 2 is displaced, and the position detection circuit 5 detects this displacement and outputs a corresponding position signal (not shown). Through this position signal (not shown), it is possible to detect the abnormality that the object 200 has fallen off, further improving the safety of the electric gripper 100 and increasing the overall efficiency during operation.

[0025] Figure 3 is a schematic diagram showing the configuration of a second embodiment of the electric gripper according to the present invention, and should be referred to in conjunction with Figures 1 to 2C. The operation methods in Figure 3 and Figure 1 are generally similar, in both cases the gear set 32 ​​is driven by the motor 2, and the closing operation of the claw base 4 is controlled to grip the object 200. The difference lies in the partially different structures of the transmission mechanism 3 and the claw base 4. Specifically, the transmission mechanism 3 shown in Figure 3 includes a gear set 32 ​​and a meshing transmission mechanism 35. The gear set 32 ​​includes a plurality of gears that mesh with each other, and the input gear is mounted on the output shaft of the motor 2. By linking the plurality of gears, the torque of the motor 2 can be amplified. The meshing transmission mechanism 35 is mounted on the output gear of the gear set 32, and the gear set 32 ​​is driven by the rotation of the motor 2, and in conjunction with this, the output shaft of the meshing transmission mechanism 35 is controlled to rotate around an axis perpendicular to the output shaft of the gear set 32. Furthermore, the output shaft of the meshing transmission mechanism 35 is axially connected to two claw bases 4.

[0026] Each of the two jaw bases 4 is equipped with a rack mechanism 46, which meshes with a movable part 44. The movable part 44 is axially connected to a meshing transmission mechanism 35 and rotates in accordance with the rotation of the meshing transmission mechanism 35, causing the rack mechanism 46 to reciprocate. Therefore, the circuit board 1 (not shown in Figure 3, but located near the end of the electric gripper 100) can rotate the motor 2 by supplying parameters such as voltage V, current I, and frequency f to control the motor 2. This causes the motor 2 to drive the gear set 32, which in turn rotates the output gear of the meshing transmission mechanism 35, and further causes the rack mechanisms 46 of the two jaw bases 4 to move in a predetermined direction, either forward (i.e., the rack mechanisms 46 of the two jaw bases 4 move in the closing direction) or reverse (i.e., the rack mechanisms 46 of the two jaw bases 4 move in the reversing direction). When the rack mechanism 46 moves in the closing direction, the electric gripper 100 grips the object 200 through the closing action of the two rack mechanisms 46. On the other hand, when the rack mechanism 46 moves away from each other, the electric gripper 100 can release the object 200 through the separating action of the two rack mechanisms 46.

[0027] The meshing transmission mechanism 35 can be configured by various orthogonal output structures. In the embodiment shown in Figure 3, the meshing transmission mechanism 35 may include a worm shaft 352 and a worm gear 354. The worm shaft 352 comprises a rod body 352A, which is provided with a first threaded portion 352B formed in a specific direction. The worm gear 354 comprises a second threaded portion 354A, which intersects perpendicularly with the axis of the rod body 352A, and the second threaded portion 354A is screwed into the first threaded portion 352B, causing it to rotate along a direction perpendicular to the output shaft of the gear set 32. A movable part 44 provided on two claw bases 4 is axially connected to the worm gear 354, and the movable part 44 rotates in conjunction with the rotation of the worm gear 354. In one embodiment, the difference between Figure 1 and Figure 3 is that the structure of the worm shaft 352 and worm gear 354 shown in Figure 3 allows for a larger reduction ratio and greater torque. However, this requires more space. Therefore, the electric gripper 100 in Figure 1 is suitable for environments where the object 200 is relatively small and the space for the electric gripper 100 is limited. On the other hand, the electric gripper 100 in Figure 3 is suitable for environments where the object 200 is relatively large and sufficient space for installation can be secured.

[0028] Similarly, the electric gripper 100 shown in Figure 3 also drives the gear set 32 ​​and the meshing transmission mechanism 35 by the overtorque Ter, so that the two jaw bases 4 move in the closing direction based on the overtorque Ter and grip the object 200 with the overgrown force Fer. Then, after the two jaw bases 4 grip the object 200, during the period (hereinafter abbreviated as the second time) when the electric gripper 100 moves to an appropriate position and releases the two jaw bases 4, the transmission mechanism 3 can maintain the gripping force of the two jaw bases 4 within a predetermined range Ra whose upper limit is the overgrown force Fer (for example, a range up to a value obtained by subtracting a value equivalent to 30% of the upper limit of the gripping force, but not limited to this).

[0029] Furthermore, the worm shaft 352 and worm gear 354 can also be designed with a large reduction ratio and a high coefficient of friction, thereby giving the pawl base 4 of the electric gripper 100 an irreversible self-locking characteristic after displacement. Specifically, the first threaded portion 352B of the worm shaft 352 has a lead angle α, and a coefficient of friction exists between the first threaded portion 352B and the second threaded portion 354A. In this case, when the lead angle α is less than or equal to a predetermined angle (i.e., a low lead angle) and the coefficient of friction is greater than or equal to a predetermined value (i.e., a high coefficient of friction), the pawl base 4 of the electric gripper 100 has an irreversible self-locking characteristic after displacement (i.e., a state in which the force from the pawl base 4 cannot drive the worm shaft 352). As a result, in the second time after the two pawl bases 4 grip the object 200, the transmission mechanism 3 can maintain the gripping force of the two pawl bases 4 within a predetermined range by the self-locking function (see Figures 2A to 2C for the detailed principle).

[0030] Furthermore, the electric gripper 100 shown in Figure 3 may also be equipped with a release knob 38. The release knob 38 is located on the gear set 32 ​​and is configured to apply sufficient torque by rotating the rod body 352A, causing the two rack mechanisms 46 to overcome frictional forces and rotate in conjunction with the rod body 352A, thereby releasing the self-locking function and releasing the gripping force of the two claw bases 4. Similarly, in the electric gripper 100 of Figure 3, the circuit board 1 may stop controlling the motor 2 when the torque of the motor 2 increases and reaches a set value (i.e., when the gripping force is within a predetermined range for a second time). The electric gripper 100 may also selectively be equipped with a position detection circuit 5 to provide a position signal (not shown) for detecting the detachment of the gripped object. In one embodiment, the circuit configuration, connections, and operating method not specifically described in Figure 3 are the same as in Figure 1, so please refer to the description of Figure 1. Repeated explanations are omitted here.

[0031] Figure 4A is a waveform diagram of the motor current in the first embodiment according to the present invention, and Figure 4B is a curve diagram of the gripping force when the motor current in Figure 4A is applied. Please also refer to Figures 1 to 3. When the electric gripper 100 uses a permanent magnet synchronous motor (or brushless DC motor), the motor 2 employs magnetic field directing control, and the torque is controlled by a current command. Therefore, based on the maximum current of the motor 2, it is possible to instantaneously output a torque N times the rated torque (i.e., overtorque Ter). Furthermore, since the electric gripper 100 has a self-locking function, the target gripping force of the two claw bases 4 can be achieved simply by instantaneously applying overtorque Ter, and the gripping force thereafter is maintained by the self-locking function. Therefore, by providing an input of N times the rated torque from the motor 2, the gripping force of the two claw bases 4 can also be increased by N times.

[0032] To elaborate further, as shown in Figure 4A, the electric gripper 100 according to the present invention mainly uses an operating method in which an overcurrent Ier is instantaneously supplied from the circuit board 1 to the motor 2 for the entire duration of the aforementioned "first time T1". Figure 4B shows the result of this operation when the electric gripper 100 is performed under the condition of the same closing speed (8 mm / s, i.e., the same rotational speed). The length of the "first time T1" varies depending on the position and size of the object, and as an example, its duration may be 50 ms, at which point the current I of the motor 2 is instantaneously increased to 120%, 160%, and 200% of the rated current Ir (i.e., overcurrent Ier). After the "first time T1" is completed with the object gripped, in the subsequent "second time T2", the current I of the motor 2 is continuously operated within a range less than the rated current Ir to provide a function for detecting loosening of the grip.

[0033] Referring to Figure 4B, it can be seen that when the current I of motor 2 instantaneously rises to 120%, 160%, and 200% of the rated current Ir, the gripping force of the electric gripper 100 also increases in accordance with the overcurrent Ier. Furthermore, because the electric gripper 100 has a self-locking function, even when the current I of motor 2 drops to 30% or less of the rated current Ir after the operating time (i.e., within the second time T2), the gripping force is still maintained within a predetermined range Ra where the upper limit is the over-gripping force Fer (for example, it may be a range up to a value obtained by subtracting a value equivalent to 30% of the upper limit of the gripping force, but is not limited to this), and a significant decrease in gripping force due to a rapid drop in current I does not occur. Therefore, in order to increase the gripping force of the electric gripper 100, in the first time T1, the circuit board 1 increases the overcurrent Ier (for example, from the conventional 120% to 200%), and the motor 2 increases the over-torque Ter, thereby improving the over-gripping force Fer through the increase in over-torque Ter.

[0034] Figure 5A is a waveform diagram of a second embodiment of the motor current according to the present invention, and Figure 5B is a curve diagram of the gripping force when the motor current in Figure 5A is applied. Furthermore, please also refer to Figures 1 to 4B. Unlike Figure 4A, Figure 5A shows the case where the same overcurrent Ier (e.g., 140% of the rated current Ir) is applied to the electric gripper 100 under conditions of different closing speeds (5 mm / s, 10 mm / s, 20 mm / s, i.e., different rotational speeds). Also, as can be seen from Figure 5B, the faster the closing speed of the electric gripper 100, the higher the gripping force of the electric gripper 100 tends to be. Therefore, in order to increase the gripping force of the electric gripper 100, it is possible to improve the over-gripping force Fer by adjusting parameters such as the voltage V, current I, and frequency f of the motor 2 (depending on the type of motor 2) using the circuit board 1 at a first time T1, and increasing the rotational speed of the motor 2 (for example, from the conventional 5 mm / s to 20 mm / s). In one embodiment, it is also possible to dramatically improve the gripping force of the electric gripper 100 by combining the increase in the overcurrent Ier shown in Figure 4A with the increase in the rotational speed of the motor 2 shown in Figure 5A.

[0035] On the other hand, the electric gripper 100 according to the present invention can improve operational stability and safety by incorporating a superior overcurrent and overtemperature protection mechanism. Specifically, the present invention makes it possible to double the gripping force of the electric gripper 100 by combining an operating method using overcurrent Ier with a self-locking function. However, in order to prevent the electric gripper 100 from experiencing unexpected failures during operation and raising safety concerns, it is necessary to provide a more appropriate protection mechanism for the operating method of overcurrent Ier. Therefore, the present invention ensures the safety of the electric gripper 100 by constructing an overcurrent and overtemperature protection mechanism specifically for the operating method using overcurrent Ier.

[0036] Figure 6A is a curve diagram showing the relationship between instantaneous current and operating time according to the present invention; please also refer to Figures 1 to 5B. Overcurrent protection is a protective function to prevent overheating of the motor 2. Through the curve between the ratio of the overcurrent Ier to the rated current and the first time (upper limit), it is possible to determine the duration of the first time at which an overcurrent Ier (ratio) is permissible. If the permissible duration is exceeded, the electric gripper 100 automatically activates the overcurrent protection mechanism to prevent damage due to overcurrent. Specifically, the electric gripper 100 according to the present invention (see Figures 1 and 3) may include a current detection circuit (not shown). The current detection circuit is located on the circuit board 1 and is used to determine whether the operating state of the circuit board 1 and the motor 2 is normal by detecting the current I supplied to the motor 2 and outputting a current signal.

[0037] Furthermore, the current detection circuit (not shown) can also be applied to the overcurrent protection mechanism during the operation of the electric gripper 100. Specifically, the current detection circuit (not shown) can detect the magnitude of the overcurrent Ier supplied from the circuit board 1 to the motor 2 during a first time period, and the circuit board 1 calculates the allowable duration of the first time period based on the overcurrent Ier. If it is determined that the actual duration of the first time period exceeds the calculated allowable duration, the electric gripper 100 switches to the overcurrent protection mechanism to prevent overheating of the motor 2. When the overcurrent protection mechanism is activated, the electric gripper 100 switches to a standby state and can resume operation after the temperature of the motor 2 drops below a predetermined temperature. As shown in Table 1 below (a schematic table showing the relationship between instantaneous current and operating time), the larger the overcurrent Ier (ratio), the shorter the allowable duration becomes, while the greater the gripping force generated. Therefore, it is desirable to set the overcurrent Ier as high as possible within the range of conditions that the electric gripper 100 can tolerate (e.g., 280%, 300%, etc.) to obtain a greater gripping force.

[0038] [Table 1]

[0039] Figure 6B is a schematic diagram showing the arrangement of heat-generating components according to the present invention, and should be referred to in conjunction with Figures 1 to 6A. In addition to the overcurrent protection mechanism shown in Figure 6A, the present invention also includes an overtemperature protection mechanism. Specifically, Figure 6B shows power components that tend to generate heat during the operation of the electric gripper 100. Power components that tend to generate heat within the electric gripper 100 generally include the position detection circuit 5 (see the subdivision (a) in the figure) and the power switch Q included in the drive circuit (see the subdivision (b) in the figure; for example, a MOSFET). Therefore, the overtemperature protection mechanism mainly targets these two types of power components. If the temperature of either one exceeds a predetermined temperature threshold, the electric gripper 100 enters an overtemperature protection state.

[0040] More specifically, the electric gripper 100 according to the present invention performs an operation that applies an overcurrent Ier in a short time, so these heat-generating components may rapidly accumulate a large amount of heat under the conditions of the overcurrent Ier. Therefore, in order to prevent burnout due to temperature rise of these heat-generating components, the present invention may provide a temperature detection circuit (not shown) in the electric gripper 100 shown in Figures 1 and 3. The temperature detection circuit (not shown) is placed around the heat-generating power components in the circuit board 1 and detects the ambient temperature around these components and outputs a temperature signal. When the circuit board 1 determines that the detected ambient temperature exceeds a preset temperature threshold, it switches the electric gripper 100 to an over-temperature protection state. This makes it possible to prevent burnout of heat-generating components.

[0041] Figure 7A is a waveform diagram of the first operating mode of the overcurrent protection mechanism according to the present invention, and Figure 7B is a waveform diagram of the second operating mode. Please refer to Figures 1 to 6B in conjunction with these. Figures 6A and 6B mainly show the protection mechanism against overcurrent and overtemperature when the electric gripper 100 performs a single gripping operation. Although protection is possible for a single gripping operation by limiting the duration of the overcurrent and detecting the temperature, when gripping operations are performed continuously at high speed and with high current, the heat generated by these heat-generating components may not be sufficiently dissipated and may gradually accumulate. This may adversely affect the motor 2. Therefore, in the present invention, I 2 By introducing a T-current limiting algorithm, a more comprehensive protection mechanism is provided.

[0042] Specifically, the electric gripper 100 according to the present invention (see also Figures 1 and 3) may include a current integration circuit (not shown). The current integration circuit (not shown) is located on the circuit board 1 and calculates an accumulated value based on the overcurrent Ier and a first time. When the circuit board 1 determines that the accumulated value exceeds a preset cumulative threshold, it transitions the electric gripper 100 to a duty cycle limit protection state. In this way, by using the current integration circuit (not shown), the gripping speed within a short time can be limited. If the overcurrent Ier is large, the next gripping time is I 2The current limiting algorithm calculates and extends the current, allowing sufficient time for energy release (i.e., cooling time for heat-generating components) in the current integration circuit (not shown), thereby realizing a speed limiting function. This prevents damage to the motor caused by continuous and high-speed high-current clamping. 2 The T-operation formula is as follows:

[0043]

number

[0044]

number

[0045] Therefore, as is clear from Equations 1 and 2, the smaller the current I, the shorter the time it takes for the accumulated value to dissipate, and the energy can be released quickly by the current integration circuit (not shown). On the other hand, when the current I is large, the time it takes for the accumulated value to dissipate becomes longer, and if sufficient energy release time cannot be secured, the accumulated value is further added, requiring an even longer time to completely release the energy.

[0046] Referring to Figure 7A, if the overcurrent Ier is 5A, 2 Based on the T formula, the cumulative value Va shown by the dashed line is formed. This cumulative value Va dissipates over time after the first time interval. Also, as shown in Figure 7A, if the interval between clamping times is sufficiently long, the energy release by the current integration circuit (not shown) is sufficient, so operation at that clamping frequency can continue and the duty cycle limit protection does not activate. On the other hand, referring to Figure 7B, if the overcurrent Ier is 10A, similarly I 2Based on the T formula, the cumulative value Va of the dashed waveform is formed. The cumulative value Va dissipates over time after the first time period has elapsed. However, because the overcurrent Ier is large, the cumulative value Va also increases, and as a result, the time it takes for the cumulative value to dissipate becomes longer. Therefore, as shown in Figure 7B, if the gripping time interval is insufficient, the energy release by the current integration circuit (not shown) is not fast enough, and the cumulative value Va is further added when the electric gripper 100 grips again. As a result, the cumulative value Va exceeds the cumulative threshold Vmax (which may be, but is not limited to, 7), and the electric gripper 100 enters a duty cycle limit protection state. At this time, a warning signal is issued to prevent damage to the motor 2 and avoid shortening its service life.

[0047] Figure 8 is a flowchart of the operation method of the electric gripper according to the present invention; please also refer to Figures 1 to 7B. The operation method shown in Figure 8 shows a control method for providing an over-gripping force Fer by the electric gripper 100, and the operation method of the electric gripper 100 includes the step (S100) of supplying current to the motor 2 of the electric gripper 100, the motor 2 generating torque based on the current, and driving the transmission mechanism 3. Here, the configuration of the transmission mechanism 3 can be referred to as the configuration of the present invention shown in Figures 1 and 3, and any configuration similar thereto is applicable, but it is not limited to the configuration of Figures 1 and 3. Next, the transmission mechanism 3 includes the step (S200) of moving the two claw bases 4 in the closing direction or the direction away from each other. The circuit board 1 outputs parameters such as voltage V, current I, and frequency f to control the motor 2, causing the motor 2 to rotate. The motor 2 drives the transmission mechanism 3, moving the two claw bases 4 in a predetermined direction, either forward (i.e., the two claw bases 4 move in the closing direction) or backward (i.e., the two claw bases 4 move away from each other). When the two claw bases 4 move in the closing direction, the electric gripper 100 can grip the object 200 by the closing action of the two claw bases 4. On the other hand, when the two claw bases 4 move away from each other, the electric gripper 100 can release the object 200 by the separating action of the two claw bases 4.

[0048] Next, while the two claw bases 4 are moving, an overcurrent exceeding the rated current is supplied to the motor 2 during a first period of time (S300). In the electric gripper 100 according to the present invention, during the period from when the two claw bases 4 start moving in the closing direction until the two claw bases 4 grip the object 200 (i.e., the first period of time), the circuit board 1 controls the drive circuit based on an external control signal and supplies an overcurrent Ier to the motor 2. Subsequently, the motor 2 generates an overtorque based on the overcurrent to drive the transmission mechanism 3, and the transmission mechanism 3 controls the closing operation of the two claw bases 4, thereby generating an over-gripping force to grip the object 200 (S400). Finally, the transmission mechanism 3 maintains the gripping force of the two claw bases 4 within a specific range where the upper limit is the over-gripping force Fer (S500). In other words, after the two claw bases 4 grip the object 200, the transmission mechanism 3 can maintain the gripping force within a predetermined range (for example, a range up to a value equivalent to 30% of the upper limit of the gripping force) via mechanical actuation until the electric gripper 100 moves to a predetermined position and releases the two claw bases 4 (i.e., a second time). In the present invention, the transmission mechanism 3 can have a self-locking function due to its structural design, thereby causing the claw bases 4 to have irreversible self-locking characteristics after movement. Although Figure 8 does not show the detailed operation method and specific implementation details of the electric gripper 100 as one embodiment, these can be understood by referring to the descriptions in Figures 1 to 7B, and are therefore not described in detail here.

[0049] The above description is merely a detailed explanation of preferred specific embodiments and drawings of the present invention, and does not limit the features of the present invention to these, nor is it intended to restrict the present invention. The technical scope of the present invention is defined by the claims described below, and all similar modifications and embodiments that are consistent with the spirit of the claims of the present invention should also be included within the technical scope of the present invention. Changes and modifications that can be easily conceived by a person skilled in the art of the present invention are also included within the claims of the present invention. [Explanation of Symbols]

[0050] 100 Electric Grippers 1 Circuit board 2 motors 3. Transmission mechanism 32 Gear Set 34 Screw Rod 340 Rod body 342 Left-hand thread section 344 Right-hand thread section 35. Meshing transmission mechanism 352 Worm shaft 352A Rod body 352B First threaded section 354 Worm Gear 354A Second threaded section 36 Linear Guide 360 sliding grooves 38 Release knob 4-prong base 40 Claw part 42 nuts 44 Moving parts 46 Rack mechanism 5. Position detection circuit Q Power switch 200, m object V Voltage I current f frequency Ier overcurrent Ir rated current Ter Overtorque Fer Excessive clamping force α Lead angle f, F vector μ coefficient of friction η Transfer efficiency T1 First period T2 Second period Ra (predetermined range) Va cumulative value

Claims

1. An electric gripper for gripping an object, The aforementioned electric gripper is A circuit board that supplies an overcurrent exceeding the rated current in the first time period, A motor connected to the circuit board and which generates overtorque based on the overcurrent, A transmission mechanism comprising a gear set connected to the motor, a screw rod having a rod body with a left-hand threaded portion and a right-hand threaded portion, and a linear guide positioned on one side of the screw rod, It includes two claw bases, each screwed into the left-hand threaded portion and the right-hand threaded portion, and engaging with the linear guide, which reciprocate along the linear guide in accordance with the rotation of the rod body, The left-hand threaded portion and the right-hand threaded portion are each formed spirally at both ends of the rod body toward the center of the rod body, and the rod body is rotated in conjunction with the gear set driven by the overtorque of the motor. An electric gripper wherein the motor moves the two claw bases in the closing direction due to the overtorque, generates an over-gripping force for gripping an object by the closing operation of the two claw bases, and during a second time after gripping the object, the transmission mechanism maintains the gripping force of the two claw bases within a predetermined range where the upper limit is the over-gripping force.

2. The left-hand threaded portion and the right-hand threaded portion have a lead angle, and there is a coefficient of friction between the two claw bases and the left-hand threaded portion and the right-hand threaded portion, respectively. The electric gripper according to claim 1, wherein, when the lead angle is less than or equal to a predetermined angle and the coefficient of friction is greater than or equal to a predetermined value, a self-locking function is provided during the second time, thereby maintaining the gripping force of the two claw bases within the predetermined range.

3. The electric gripper according to claim 2, wherein the transmission mechanism further comprises a release knob for rotating the rod body to release the self-locking function and release the gripping force of the two claw bases.

4. The circuit board further includes a position detection circuit for detecting the position of the motor rotor and outputting a position signal, In the second time, the motor outputs torque based on a current less than the rated current, and the circuit board determines whether or not the rotor is displaced based on the position signal, as described in claim 1.

5. The circuit board is further configured to include a current detection circuit for detecting the overcurrent in the first time period, The electric gripper according to claim 1, wherein the circuit board calculates the duration of the first time based on the overcurrent, and if it determines that the duration exceeds a time threshold, it transitions the electric gripper to an overcurrent protection state.

6. The circuit board is disposed on the circuit board and further includes a temperature detection circuit for detecting the ambient temperature of the circuit board, The electric gripper according to claim 1, wherein the circuit board determines that the ambient temperature exceeds a temperature threshold, and in doing so, switches the electric gripper to an over-temperature protection state.

7. The circuit board further includes a current integration circuit for calculating a cumulative value based on the overcurrent and the first time, The electric gripper according to claim 1, wherein the circuit board determines that the cumulative value exceeds a predetermined cumulative threshold, and then transitions the electric gripper to a duty cycle limit protection state.

8. An electric gripper for gripping an object, The aforementioned electric gripper is A circuit board that supplies an overcurrent exceeding the rated current in the first time period, A motor connected to the circuit board and which generates overtorque based on the overcurrent, A transmission mechanism comprising a gear set connected to the motor, and a meshing transmission mechanism connected to the gear set, It includes two claw bases, each having a rack mechanism that reciprocates in accordance with the rotation of the meshing transmission mechanism, The meshing transmission mechanism is controlled to rotate in conjunction with the gear set, which is driven by the overtorque of the motor, in a direction perpendicular to the output shaft of the gear set. An electric gripper wherein the motor moves the two claw bases in the closing direction due to the overtorque, generates an over-gripping force for gripping an object by the closing operation of the two claw bases, and in a second time after gripping the object, the meshing transmission mechanism maintains the gripping force of the two claw bases within a predetermined range where the upper limit is the over-gripping force.

9. The aforementioned meshing transmission mechanism is, A worm shaft comprising a rod body having a first threaded portion formed in a predetermined direction, A worm gear that rotates along a direction perpendicular to the output shaft, having a second threaded portion that intersects perpendicularly to the axis of the worm shaft and is screwed onto the first threaded portion, The electric gripper according to claim 8, wherein the first threaded portion has a lead angle, a coefficient of friction exists between the first threaded portion and the second threaded portion, and when the lead angle is less than or equal to a predetermined angle and the coefficient of friction is greater than or equal to a predetermined value, a self-locking function is provided in the second time, thereby maintaining the gripping force of the two claw bases within the predetermined range.

10. The circuit board further includes a current integration circuit for calculating a cumulative value based on the overcurrent and the first time, The electric gripper according to claim 9, wherein the circuit board determines that the cumulative value exceeds a predetermined cumulative threshold, and then transitions the electric gripper to a duty cycle limit protection state.

11. A method for operating an electric gripper to control the gripping of an object, (a) A step of supplying current to the motor of the electric gripper, causing the motor to generate torque based on the current and drive the transmission mechanism, (b) The step of the transmission mechanism moving the two claw bases in a closing or away direction, (c) The step of supplying an overcurrent exceeding the rated current to the motor at a first time while the two claw bases are moving, (d) The motor generates an overtorque based on the overcurrent to drive the transmission mechanism, and the transmission mechanism controls the closing operation of the two claw bases, thereby generating an over-clamping force for clamping the object; (e) A method for operating an electric gripper, comprising the step of maintaining the gripping force of the two claw bases within a predetermined range, the upper limit of which is the over-gripping force, using the transmission mechanism.

12. A method for operating an electric gripper according to claim 11, further comprising the step of increasing the motor's overtorque to increase the overgrown gripping force during the first time period.

13. The method for operating an electric gripper according to claim 11, further comprising the step of increasing the rotational speed of the motor to increase the over-gripping force during the first time period.

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