Electric vise

Abstract

To provide a constitution capable of preventing damage of a work by action of excessive clamp force, and capable of clamping the work by desired clamp force, in an electric vise for clamping the work between a fixed jaw and itself, by moving a movable jaw by rotating a screw shaft by a motor.SOLUTION: An electric vise has a hollow shaft connected to a screw shaft, and a rotation propulsion shaft connected to the hollow shaft by a clutch mechanism and an increasingly fastening mechanism stored in the hollow shaft, and is constituted so that an increasing fastening operation is performed by an increasing fastening mechanism in a release state. The electric vise has a torque detector detecting torque acting on a rotation propulsion shaft and a control device controlling a clutch cut detector detecting a release state of a clutch mechanism based on a torque detection value and an increasing fastening controller of controlling an increasing fastening operation based on a stopping condition.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an electric vice that includes a fixed jaw and a movable jaw, a screw shaft that moves the movable jaw in the axial direction, and a motor that rotates the screw shaft, and that moves the movable jaw by rotating the screw shaft with the motor, thereby clamping a workpiece between the fixed jaw and the movable jaw. [Background technology]

[0002] Patent Document 1 discloses the electric vice. The electric vice disclosed in Patent Document 1 is configured to measure the current supplied to the motor and control the driving of the motor based on the measured current value (supply current value). Specifically, the motor is driven to move the movable jaw toward the fixed jaw in order to clamp the workpiece, and the supply current value is compared with a preset threshold value. When it is detected that the supply current value exceeds the threshold value, the motor is controlled to stop driving. The point at which the motor drive is stopped by such control is regarded as the point at which clamping of the workpiece is completed.

[0003] Regarding the control of the motor, the measurement of the current is intended to grasp the force that the movable jaw exerts on the work (clamping force on the work). More specifically, as a result of the motor driving the movable jaw to exert a clamping force on the work, the reaction force acts on the movable jaw (motor) as a load (load torque). And since the supply current value corresponds to the load torque (the supply current value increases with an increase in the load torque), the clamping force can be grasped from the supply current value. Also, since the supply current value is proportional to the load torque (output torque of the motor), the measurement of the current substitutes for the detection of the output torque of the motor.

[0004] Patent Document 1 states that in an electric vice that continues to apply a force corresponding to the output torque of such a motor as a clamping force to the workpiece, by performing control using the threshold value as described above, clamping is completed (the motor is stopped) without the clamping force on the workpiece becoming excessive, thereby preventing damage to the workpiece, etc. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-118980 A Summary of the Invention [Problem to be solved by the invention]

[0006] In an electric vice, the clamping force actually acting on a workpiece may differ from the clamping force assumed according to the output torque of the motor due to factors such as chips getting caught between the jaws and the workpiece, the state of lubrication of the screw shaft, and the installation state of the workpiece. That is, the actual clamping force may vary above or below the assumed clamping force due to the above factors. Therefore, it is necessary to assume that the actual clamping force may be lower than the assumed clamping force, and set the threshold value to a value greater than the value determined based on the assumed clamping force so that a sufficient clamping force can be obtained even when the actual clamping force is lower.

[0007] However, the actual clamping force may be greater than the expected clamping force, so when the threshold value is set as described above, if the actual clamping force is greater than the expected clamping force, an excessive clamping force may act on the workpiece, which may result in damage to the workpiece or the vice.

[0008] Therefore, an object of the present invention is to provide an electric vice configuration that can prevent damage to the workpiece and the vice due to excessive clamping force acting on the workpiece as much as possible, while also ensuring that the workpiece is clamped with the desired clamping force. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the electric vise of the present invention comprises a fixed jaw and a movable jaw for clamping a workpiece, a screw shaft for moving the movable jaw in the axial direction, a hollow cylindrical shaft connected to one end of the screw shaft so as not to rotate relative to one another and supported rotatably on the main frame, a rotating propulsion shaft connected to the hollow shaft via a clutch mechanism, and a tightening mechanism housed within the hollow shaft, and is configured so that by rotating the rotating propulsion shaft, the hollow shaft is rotated via the clutch mechanism when the clutch mechanism is in the engaged state, and a tightening operation is performed by the tightening mechanism which applies a clamping force to the movable jaw via the screw shaft when the clutch mechanism is in the disengaged state.

[0010] Furthermore, the electric vice of the present invention is equipped with a motor that rotates and drives the rotating drive shaft, a torque detector that detects the torque acting on the rotating drive shaft, and a control device that controls the drive of the motor, and the control device is equipped with a clutch disengagement detector that detects that the clutch mechanism has been released based on the torque detection value detected by the torque detector, and a tightening controller that controls the tightening operation based on preset stop conditions.

[0011] It should be noted that the "stop condition" referred to here refers to a condition (e.g., the number of rotations, driving time, output torque threshold, etc.) that specifies the amount of motor drive corresponding to the amount of movement of the rotating propulsion shaft after the clutch mechanism is in the released state.

[0012] In the electric vice according to the present invention, the clutch disengagement detector may be configured to include a calculator for calculating a differential value of a torque detection value and a determiner for determining whether the release state has been achieved based on the differential value. Furthermore, the control device may be configured to include a calculator for calculating a distance between the fixed jaw and the movable jaw in the axial direction based on the amount of drive of the motor at the time when the release state is detected by the clutch disengagement detector, and a determiner for comparing the distance with a preset workpiece dimension to determine whether the workpiece is clamped properly. Effect of the Invention

[0013] According to the electric vice of the present invention, the clutch mechanism is in a connected state in the initial state, and when the rotation drive of the rotating propulsion shaft by the motor is started in this state, the hollow shaft is rotated via the clutch mechanism, and the screw shaft is rotated. As a result, the movable jaw moves toward the work side and abuts against the work, and the movable jaw applies a clamping force to the work. If the rotation drive of the rotating propulsion shaft by the motor is further continued, the load acting on the movable jaw as a reaction force increases, and when the load exceeds the load assumed by the clutch mechanism, the clutch mechanism is released. Then, in the released state of the clutch mechanism, even if the rotating propulsion shaft is rotated, the hollow shaft (screw shaft) does not rotate, and the rotating propulsion shaft moves toward the screw shaft side by an amount corresponding to the amount of rotation, and the screw shaft is pressed toward the work side by the force increased via the tightening mechanism.

[0014] In addition, in the electric vice of the present invention, the clutch disengagement detector detects the time when the clutch mechanism is deemed to be in a released state (release time) based on the detection value (torque detection value) of the torque acting on the rotating propulsion shaft in response to the load. After the release time, the motor is controlled in a manner different from that before the release time. Specifically, after the release time, the drive of the motor is controlled based on a preset stop condition, taking into account the rotation amount of the rotating propulsion shaft that generates the amount of movement of the rotating propulsion shaft that ultimately obtains the desired clamping force.

[0015] In this way, in the electric vice of the present invention, the control mode of the motor is switched at the time of the release, and after the time of the release, the motor is controlled based on the stop condition set based on the drive amount of the motor corresponding to the movement amount of the rotary propulsion shaft. Since the drive amount of the motor (the movement amount of the rotary propulsion shaft) can be appropriately controlled, the electric vice of the present invention can make the clamping force in the clamped state appropriate, compared to a conventional electric vice that tries to obtain the final clamping force by controlling the motor based on the output torque corresponding to an assumed clamping force that may differ from the actual clamping force. This makes it possible to make the final clamping state of the work more appropriate and to prevent damage to the work and the vice as much as possible.

[0016] Furthermore, in the electric vice of the present invention, in relation to the clutch mechanism, the torque gradually increases after the movable jaw comes into contact with the workpiece, and when the released state is reached, it changes to 0. Therefore, in such an electric vice, by configuring the clutch disengagement detector to include a calculator that calculates a differential value of the torque detection value, and a determiner that determines when the released state is reached based on the differential value, the time when the clutch mechanism is in the released state can be detected more accurately.

[0017] Furthermore, the control device is provided with a calculator for calculating the distance between the fixed jaw and the movable jaw at the time when the clutch disengagement detector detects the release state, and a determiner for comparing the calculated distance with a preset workpiece dimension to determine whether the workpiece is clamped or not, thereby determining whether the workpiece is clamped (in contact with both jaws) or not at the time of release. This makes it possible for the electric vice to automatically determine whether the workpiece is clamped or not. [Brief description of the drawings]

[0018] [Figure 1] 1 is a side cross-sectional view showing an entire electric vise according to one embodiment of the present invention. [Diagram 2] 1 is an enlarged cross-sectional view of a main portion of an electric vise according to an embodiment of the present invention in an initial state; [Diagram 3] FIG. 2 is an enlarged cross-sectional view of a main portion of the electric vise according to the embodiment of the present invention in a state where a retightening operation has been completed. [Figure 4] In comparison with FIG. 2, an outline drawing showing the portion supported by the main body frame is shown. [Diagram 5] 1 is a top view showing an entire electric vise according to one embodiment of the present invention; [Figure 6] 1 is a block diagram of an electric vise according to an embodiment of the present invention. [Figure 7] FIG. 4 is a torque waveform diagram when a workpiece is clamped by the electric vice according to the embodiment of the present invention. [Figure 8] FIG. 11 is a block diagram of an electric vise according to another embodiment of the present invention. BEST MODE FOR CARRYING OUT THEINVENTION

[0019] Hereinafter, one embodiment (example) of the electric vice of the present invention will be described with reference to Figs.

[0020] The electric vice 1 includes a housing-like main body frame 3 that is fixed onto an installation surface of a machine tool or the like, and a fixed jaw 5 and a movable jaw 7 for clamping a workpiece W. The electric vice 1 also includes a slide block 9 to which the movable jaw 7 is attached, and a screw shaft 10 for moving the slide block 9 in the longitudinal direction of the main body frame 3.

[0021] One end of the fixed jaw 5 in the longitudinal direction is fixed to the upper surface of the main body frame 3 by a screw member. The movable jaw 7 is provided on the upper surface of the main body frame 3 so as to face the fixed jaw 5 in the longitudinal direction. Furthermore, the slide block 9 is provided in the internal space of the main body frame 3 so as to be slidable in the longitudinal direction. The movable jaw 7 is connected to the slide block 9 by a screw member via a through groove formed in the upper surface of the main body frame 3.

[0022] The screw shaft 10 is provided inside the main frame 3 with its axis parallel to the longitudinal direction. The slide block 9 has a female screw hole that penetrates in the sliding direction. The slide block 9 is screwed into the female screw hole. As a result, in the electric vice 1, the slide block 9 moves in the longitudinal direction (the axial direction of the screw shaft 10) by rotating the screw shaft 10 forward / reverse, and the movable jaw 7 moves closer to / away from the fixed jaw 5.

[0023] The electric vice 1 also includes a hollow shaft 20 and a rotation drive shaft 30 for rotating the screw shaft 10. The hollow shaft 20 is provided as a shaft connected to the screw shaft 10, and the rotation drive shaft 30 is provided as a shaft connected to the hollow shaft 20 and driven to rotate by a motor described later.

[0024] Among them, the hollow shaft 20 is a hollow cylindrical shaft member having a flange portion 20a formed at the middle portion in the axial direction so as to protrude radially outward. The hollow shaft 20 is rotatably supported by the main body frame 3 at the flange portion 20a.

[0025] More specifically, the main body frame 3 has a support member 3a for supporting the hollow shaft 20 at one end side (opposite the fixed jaw 5). The support member 3a is a block-shaped member having a through hole for accommodating the hollow shaft 20. The support member 3a is provided in a direction such that the center line of the through hole coincides with the longitudinal direction, and constitutes an end portion of the main body frame 3. Regarding the relationship between the support member 3a and the hollow shaft 20, the outer diameter of the flange portion 20a of the hollow shaft 20 is slightly smaller than the inner diameter of the through hole of the support member 3a to a degree that the flange portion 20a slides against the inner peripheral surface of the through hole. The support member 3a has an annular protrusion 3b formed in the through hole so as to protrude radially inward around the entire circumference of the inner peripheral surface, and inside which the hollow shaft 20 can be disposed.

[0026] Moreover, the hollow shaft 20 is supported at the outer circumferential surface of the flange portion 20a so as to be rotatable relative to the support member 3a (main body frame 3) with the flange portion 20a disposed opposite the protruding portion 3b of the support member 3a on the fixed jaw 5 side in the longitudinal direction. A thrust metal is interposed between the flange portion 20a and the protruding portion 3b, and a retaining ring is fixed to the support member 3a on the opposite side of the thrust metal to the flange portion 20a. As a result, the hollow shaft 20 is rotatably supported as described above and positioned in the longitudinal direction with its movement restricted.

[0027] In addition, the hollow shaft 20 is a hollow cylindrical member and has a through hole, and a female thread is formed on the inner peripheral surface of one end of the through hole. An annular ring member 14 is fitted inside one end of the hollow shaft 20 and is screwed into the female thread of the through hole. The hollow shaft 20 and the ring member 14 are fixed together by a hexagon socket bolt so that they cannot rotate relative to each other.

[0028] In addition, the portion of the through hole of the ring member 14 on the screw shaft 10 side is a hexagonal hole. One end of the screw shaft 10 is formed in a hexagonal shape corresponding to the hexagonal hole of the ring member 14. In addition, one end of the screw shaft 10 is inserted into the through hole (hexagonal hole portion) of the ring member 14, thereby preventing the screw shaft 10 and the ring member 14 from rotating relative to each other. Therefore, the screw shaft 10 and the hollow shaft 20 are connected via the ring member 14 so as to prevent them from rotating relative to each other.

[0029] In addition, the biasing shaft 12 is inserted in one end of the screw shaft 10 in a slidable manner. The biasing shaft 12 is in a state where one end is inserted into the screw shaft 10 and the other end side portion protrudes from the ring member 14. The biasing shaft 12 has a flange portion at the other end side portion protruding from the ring member 14. The outer diameter of the flange portion is large enough to be in sliding contact with the inner circumferential surface of the through hole of the hollow shaft 20. Therefore, the biasing shaft 12 is in a state where the flange portion faces the ring member 14 in the longitudinal direction. In addition, a plurality of disc springs are interposed between the flange portion of the biasing shaft 12 and the ring member 14. As a result, the biasing shaft 12 is in a state where it is biased toward the opposite side to the fixed jaw 5 side by the elastic force of the disc spring.

[0030] In addition, when one end of the hollow shaft 20 is connected to the screw shaft 10 as described above, the other end of the hollow shaft 20 protrudes from the support member 3a. A round nut 22 is fitted into the other end of the hollow shaft 20. The round nut 22 is fixed to the hollow shaft 20 by a hexagon socket bolt so as not to rotate relative to the hollow shaft 20.

[0031] The rotary propulsion shaft 30 has a main body portion 31 connected to the hollow shaft 20 (round nut 22), and a small diameter portion 32 formed so as to be continuous with one end of the main body portion 31 and having a smaller diameter than the main body portion 31. The rotary propulsion shaft 30 also has a flange portion 33 formed so as to protrude from the outer circumferential surface of the main body portion 31 on the other end side (opposite side to the small diameter portion 32) of the main body portion 31 in the axial direction from the middle portion of the main body portion 31. Furthermore, a male thread is formed on the outer circumferential surface of the main body portion 31 on the small diameter portion 32 side of the flange portion 33.

[0032] The rotating propulsion shaft 30 is supported by the hollow shaft 20 via the round nut 22 by screwing the male thread of the main body 31 into the female thread hole of the round nut 22 with the small diameter portion 32 facing the fixed jaw 5 side relative to the main body 31 in the longitudinal direction. Therefore, the rotating propulsion shaft 30 is in a state where at least the flange portion 33 and the portion of the rotating propulsion shaft 30 on the other end side beyond the flange portion 33 protrude from the hollow shaft 20 (round nut 22).

[0033] In addition, a clutch mechanism 40 is provided between the hollow shaft 20 and the rotating propeller shaft 30. As a result, when the rotating propeller shaft 30 is rotated, the rotation of the rotating propeller shaft 30 is transmitted to the hollow shaft 20 via the clutch mechanism 40.

[0034] Regarding the clutch mechanism 40, in detail, a hollow cylindrical clutch ring 41 is fitted around the small diameter portion 32 of the rotary propulsion shaft 30. However, a key is interposed between the clutch ring 41 and the small diameter portion 32, and the clutch ring 41 is provided so as to be unable to rotate relative to the rotary propulsion shaft 30 and to be movable in the axial direction. The clutch ring 41 has one end (opposite the fixed jaw 5) in the axial direction formed as a (disc-shaped) clutch portion having a larger diameter than the other portions. Also, the outer diameter of the clutch portion is larger than the outer diameter of the main body portion 31 of the rotary propulsion shaft 30. Therefore, the clutch ring 41 is fitted around the rotary propulsion shaft 30 (small diameter portion 32) and faces the round nut 22 at the clutch portion.

[0035] A disk-shaped bearing holder 43 is fixed to the tip of the small diameter portion of the rotary propulsion shaft 30 by a screw member. The outer diameter of the bearing holder 43 is larger than the outer diameter of the other end side of the clutch ring 41 (a portion other than the clutch portion). Therefore, the bearing holder 43 faces the clutch portion at its outer periphery. In addition, a compression spring 42 is provided between the bearing holder 43 and the clutch portion of the clutch ring 41. As a result, the clutch ring 41 is biased toward the round nut 22 by the elastic force of the compression spring 42.

[0036] In addition, a plurality of engagement protrusions are formed at intervals in the circumferential direction on the end surface of the clutch portion of the clutch ring 41 on the round nut 22 side. On the other hand, a plurality of engagement grooves corresponding to the engagement protrusions of the clutch ring 41 (clutch portion) are formed on the end surface of the round nut 22 on the clutch ring 41 side. Therefore, in the initial state of the electric vice 1 (a state in which the workpiece W is not clamped), the clutch ring 41 is biased toward the round nut 22 side by the compression spring 42 as described above, and the engagement protrusions of the clutch ring 41 and the engagement grooves of the round nut 22 are engaged with each other, and the engagement state is maintained. As a result, the rotary drive shaft 30 and the hollow shaft 20 are connected to each other.

[0037] The rotary drive shaft 30 is rotated by the motor M as described above. That is, the electric vice 1 is provided with the motor M for driving the rotary drive shaft 30. The motor M is provided on the side of the main body frame 3 with its output shaft parallel to the rotary drive shaft 30 and facing the movable jaw 7 relative to the fixed jaw 5.

[0038] In addition, the electric vice 1 includes a drive transmission mechanism 50 for connecting the output shaft of the motor M and the rotary propulsion shaft 30. Furthermore, the electric vice 1 includes a connecting frame 60 for supporting the motor M and the drive transmission mechanism 50 relative to the main body frame 3. The connecting frame 60 includes a plate-shaped base 61 that serves as a base, and is attached to the main body frame 3 and supports the motor M and the drive transmission mechanism 50. However, the base 61 is supported by the support member 3a of the main body frame 3 with an end face in the plate thickness direction parallel to the width direction of the main body frame 3 (direction perpendicular to the axial direction of the screw shaft 10). Furthermore, the connecting frame 60 includes a cover portion that is attached to the base 61 and covers the motor M and the drive transmission mechanism 50.

[0039] The drive transmission mechanism 50 has a drive shaft 51 connected to the output shaft of the motor M via a coupling, and a driven shaft 52 connected to the rotary propulsion shaft 30 via a transmission shaft 53 and a coupling. The drive transmission mechanism 50 further has a pulley 55 attached to the drive shaft 51, a pulley 56 attached to the driven shaft 52, and a belt 57 connecting the pulleys 55 and 56. The transmission shaft 53 is connected to the rotary propulsion shaft 30 by being fitted into a receiving groove formed at the other end of the rotary propulsion shaft 30. The drive shaft 51 and the driven shaft 52 are provided so as to pass through a base 61 of the connecting frame 60, and are rotatably supported by the base 61 via a bearing (not shown). The pulleys 55 and 56 are attached to the drive shaft 51 and the driven shaft 52, respectively, on the tip side of the base 61.

[0040] Then, according to the above-mentioned configuration, when the rotating propulsion shaft 30 is rotationally driven by the motor M in the initial state, the hollow shaft 20 rotates, which in turn rotates the screw shaft 10 and moves the movable jaw 7 connected to the slide block 9 toward the fixed jaw 5. When the movable jaw 7 moves in this way and the workpiece W is clamped between the movable jaw 7 and the fixed jaw 5, the movement of the movable jaw 7 is blocked by the workpiece W, and the rotation of the screw shaft 10 (hollow shaft 20) is blocked.

[0041] When the motor M continues to rotate the rotary propulsion shaft 30, the drive torque of the motor M gradually increases as the connected hollow shaft 20 is prevented from rotating. When the drive torque exceeds the engagement force between the engagement projection of the clutch ring 41 and the engagement groove of the round nut 22, the engagement state is released (disengaged state). As a result, the rotary propulsion shaft 30 rotates relative to the hollow shaft 20 (round nut 22), and the rotary propulsion shaft 30, which is screwed into the round nut 22 by the male thread of the main body 31, moves toward the fixed jaw 5 as it rotates.

[0042] In this manner, in the electric vice 1, a state in which the hollow shaft 20 and the rotary drive shaft 30 are connected (connected state) and a state in which the connection is released (released state) are switched between the round nut 22 on the hollow shaft 20 side and the clutch ring 41 on the rotary drive shaft 30 side. Therefore, in this configuration, a combination of the round nut 22 and clutch ring 41 in the engaged state, and the compression spring 42 and bearing holder 43 that apply an elastic force to the clutch ring 41 to maintain the engaged state functions as a clutch mechanism 40.

[0043] The electric vice 1 also includes a tightening mechanism 70 that applies a clamping force to the movable jaw 7 via the screw shaft 10 when the clutch mechanism 40 is in the released state. The tightening mechanism 70 is provided between the screw shaft 10 (the biasing shaft 12) and the rotation propulsion shaft 30 in the longitudinal direction and is accommodated in the hollow shaft 20. The tightening mechanism 70 also includes a hollow cylindrical roller support 71 supported by the hollow shaft 20, an operating shaft 72 supported by the roller support 71, and a pair of large rollers 73, 73 and a pair of small rollers 74, 74 that contact the inclined surface of the operating shaft 72.

[0044] More specifically, the tightening mechanism 70 includes an operating shaft 72, which is made up of a cylindrical shaft portion 72a and a wedge-shaped portion 72b that is an isosceles triangle in side view and a rectangular shape in plan view, and is integrally formed with the shaft portion 72a in a manner that continues to one end of the shaft portion 72a. The size of the wedge-shaped portion 72b on the shaft portion 72a side in side view is slightly larger than the outer diameter of the shaft portion 72a. Therefore, a step is present between the shaft portion 72a and the wedge-shaped portion 72b on the outer surface of the operating shaft 72. The operating shaft 72 is supported by the hollow shaft 20 at its shaft portion 72a via a roller support 71.

[0045] The roller support 71 is fitted into the through hole of the hollow shaft 20 at a position between the screw shaft 10 (the biasing shaft 12) and the rotation propulsion shaft 30 in the longitudinal direction. The roller support 71 is hollow cylindrical and has a through hole. With respect to the through hole of the roller support 71, when the roller support 71 is fitted into the hollow shaft 20, a portion of the through hole on the rotation propulsion shaft 30 side in the longitudinal direction from the flange portion 20a of the hollow shaft 20 is formed as a round hole capable of accommodating the shaft portion 72a of the operating shaft 72. The diameter of the round hole is set to a size such that the shaft portion 72a of the operating shaft 72 can slide in the longitudinal direction when the shaft portion 72a is accommodated.

[0046] Furthermore, in the through hole of the roller support 71, the portion closer to the fixed jaw 5 than the round hole portion is formed as a square hole large enough to accommodate the wedge-shaped portion 72b of the operating shaft 72. The square hole is sized so that, with the wedge-shaped portion 72b of the operating shaft 72 accommodated therein, the portion of the wedge-shaped portion 72b on the shaft portion 72a side can slide in the longitudinal direction. Therefore, the through hole of the roller support 71 is a hole with a step formed on its inner surface, since the square hole is formed larger than the round hole.

[0047] The working shaft 72 is supported axially slidably relative to the roller support 71 with the shaft portion 72a inserted into the round hole of the through hole of the roller support 71 and the wedge-shaped portion 72b housed in the square hole of the through hole. As a result, the working shaft 72 is supported within the hollow shaft 20 with the side surface of the wedge-shaped portion 72b approximately parallel to the up-down direction of the electric vice 1 (main body frame 3). As described above, a step portion is present on the outer surface of the working shaft 72 and a step portion is also present on the inner surface of the through hole of the roller support 71, and therefore the two step portions come into contact with each other, restricting the movement of the working shaft 72 toward the rotation propulsion shaft 30 relative to the roller support 71.

[0048] The roller support 71 has a flange formed at one end (square hole side) thereof so as to protrude radially outward from its outer circumferential surface. The through hole of the hollow shaft 20 into which the roller support 71 is fitted has an inner diameter greater than the inner diameter of the other portion of the through hole in the axial direction at a portion closer to the one end side (fixed jaw 5 side) than the flange portion 20a. Therefore, the hollow shaft 20 has a step on the inner surface of the through hole. The outer diameter of the flange of the roller support 71 is sized so that the roller support 71 is fitted into the one end side portion of the through hole of the hollow shaft 20. The roller support 71 is fitted into the through hole of the hollow shaft 20 with the flange abutting against a step formed on the inner circumferential surface of the through hole of the hollow shaft 20.

[0049] The roller support 71 has a protruding portion 71a that protrudes from the end face of the flange toward the fixed jaw 5 in the axial direction. The protruding portions 71a are formed as a pair in the hollow shaft 20, symmetrically positioned above and below the axis of the roller support 71. The inner portions of both protruding portions 71a, 71a are cut out to form flat tapered surfaces.

[0050] A disk-shaped bearing holder 45 is fitted to the other end of the shaft portion 72a of the working shaft 72. A thrust bearing 44 is interposed between the bearing holder 45 and the bearing holder 43 attached to the rotating propulsion shaft 30. As a result, the working shaft 72 is connected to the rotating propulsion shaft 30 via the bearing holder 45, the thrust bearing 44, and the bearing holder 43 attached to the rotating propulsion shaft 30, and is rotatable relative to the rotating propulsion shaft 30. In this manner, when the working shaft 72 is connected to the rotating propulsion shaft 30, a step on its outer surface is in contact with a step on the inner surface of the through hole of the roller support 71 in the initial state.

[0051] Furthermore, when the operating shaft 72 is supported within the hollow shaft 20 as described above, the wedge-shaped portion 72b of the operating shaft 72 exists in the space between the roller support 71 and the biasing shaft 12 within the hollow shaft 20. In addition, a pair of large rollers 73, 73 and a pair of small rollers 74, 74 in the tightening mechanism 70 are provided in the space (roller accommodating space) sandwiching the wedge-shaped portion 72b from above and below, with their respective axis centers facing in the width direction.

[0052] In the initial state, the large rollers 73, 73 are in contact with one end face (the end face on the rotation propulsion shaft 30 side) of the urging shaft 12 and are opposed to each other in the vertical direction with the wedge-shaped portion 72b of the operating shaft 72 sandwiched therebetween. The small rollers 74, 74 are provided between the corresponding large roller 73 and roller support 71 in the longitudinal direction so as to sandwich the wedge-shaped portion 72b of the operating shaft 72 in the vertical direction. In the initial state, each small roller 74 is in contact with the corresponding large roller 73, the tapered surface of the protruding portion 71a of the roller support 71, and the inclined surface of the wedge-shaped portion 72b. However, the contact position between the large roller 73 and the small roller 74 is located at a position farther from the axis of the operating shaft 72 than the center of the large roller 73 in the vertical direction.

[0053] According to the tightening mechanism 70 configured as described above, when the clutch mechanism 40 is released and the rotary drive shaft 30 is further rotated and moves toward the fixed jaw 5, the rotary drive shaft 30 presses the operating shaft 72 (receives a pressing force). As a result, the operating shaft 72 moves toward the fixed jaw 5 while expanding the gap between the rollers 73, 74 vertically with the wedge-shaped portion 72b. As a result, the pressing force applied by the operating shaft 72 to the small rollers 74 is intensified and acts on the large roller 73 due to the wedge effect of the inclined surface of the wedge-shaped portion 72b with which the small rollers 74 abut and the tapered surface of the protruding portion 71a of the roller support 71, and the force acts on the screw shaft 10 via the large roller 73. Then, such a force acts on the movable jaw 7 via the screw shaft 10, and the workpiece W is clamped by the intensified force (the tightening operation is completed).

[0054] The electric vice 1 configured as above includes a control device 100 that controls the drive of the motor M. The control device 100 is connected to a main control device 90 of a machine tool or the like on which the electric vice 1 is installed. The control device 100 also includes a drive command device 101 that commands basic operations of the electric vice 1 (motor M).

[0055] The main control device 90 stores a series of machining programs for machining the workpiece W, and the machining programs include a process of clamping the workpiece W by the electric vice 1 (clamping process), and a process of releasing the clamped state of the workpiece W (unclamping process). The main control device 90 is configured to output a clamp command signal to the drive command device 101 in the control device 100 when the process reaches the clamping process as the machining program progresses. The main control device 90 is also configured to output an unclamping command signal to the drive command device 101 when the process in the machining program reaches the unclamping process.

[0056] The drive command device 101 is connected at its output end to a driver 102 that drives the motor M. The drive command device 101 is configured to output, when a clamp command signal is output from the main control device 90, a forward rotation command signal for driving the motor M in the forward direction at a set rotation speed for forward rotation (set forward rotation speed) to the driver 102. The drive command device 101 is also configured to output, when an unclamping command signal is output from the main control device 90, a reverse rotation command signal for driving the motor M in the reverse direction at a set rotation speed for reverse rotation (set reverse speed).

[0057] The driver 102 is configured to drive the motor M in the forward or reverse direction at a rotation speed (set forward speed, set reverse speed) according to the forward rotation command signal or reverse rotation command signal. Thus, when a forward rotation command signal is output from the drive command device 101, the motor M is driven in the forward direction at the corresponding set forward rotation speed, and the movable jaw 7 operates to approach the fixed jaw 5. Also, when a reverse rotation command signal is output from the drive command device 101, the motor M is driven in the reverse direction at the corresponding set reverse speed, and the movable jaw 7 operates to move away from the fixed jaw 5.

[0058] The electric vice 1 also includes a torque detector 110 that detects the torque acting on the rotary drive shaft 30. In this embodiment, the torque detector 110 detects the torque based on a measured value (drive current value) of a current (drive current) supplied to the motor M. The torque detector 110 is connected to the output end side of the driver 102. The torque detector 110 is configured to continuously output a detected torque signal corresponding to the detected value (torque detection value) for each predetermined detection period.

[0059] The control device 100 also includes a clutch disengagement detector 104 for detecting that the clutch mechanism 40 has been released based on a torque detection value detected by a torque detector 110. The clutch disengagement detector 104 is composed of a calculator 104a connected to the torque detector 110 and a determiner 104b connected to the calculator 104a. Of these, the calculator 104a is configured to determine a differential value (amount of change) of the detected torque during the detection period based on the detected torque signal output from the torque detector 110 each time the detected torque signal is input, and to output a signal indicating the differential value (differential value signal).

[0060] The judger 104b is configured to judge whether the clutch mechanism 40 is in the released state based on the differential value signal output from the calculator 104a. Specifically, in this embodiment, the judger 104b makes the judgment based on whether the differential value has changed from a positive value to 0. That is, as described above, when the rotation drive of the rotary propulsion shaft 30 by the motor M continues from the state in which the movement of the movable jaw 7 is blocked by the workpiece W, the drive torque (the drive current value) of the motor M gradually increases, but when the clutch mechanism 40 is in the released state, the drive torque starts to decrease (decrease), and the differential value becomes 0 instantaneously at the point where the torque starts to decrease. Therefore, the judger 104b is configured to judge (discriminate) the point where the differential value becomes 0. And, since the point where the differential value becomes 0 corresponds to the point where the clutch mechanism 40 is in the released state, the judger 104b is configured to output a one-shot clutch disengagement signal at the point where it is determined that the differential value becomes 0.

[0061] The control device 100 also includes a tightening controller 105 that controls the driving of the motor M based on a preset stop condition of the electric vice 1. The stop condition is determined so that the clamping force in the clamped state of the workpiece W is an appropriate magnitude. In this embodiment, the stop condition is set by the number of rotations of the rotary propulsion shaft 30. Furthermore, the number of rotations is assumed to be three in this embodiment. However, the number of rotations is not limited to three, and may be set to an appropriate number based on the clamping force that is ultimately desired to be obtained. The set value for the stop condition is input and set in an input setting device (not shown) provided in the main control device 90, and is stored in the tightening controller 105 by being transmitted from the main control device 90 to a memory device (not shown) provided in the tightening controller 105.

[0062] In the control device 100, the clutch disengagement signal from the determiner 104b is input to the retightening controller 105. When the clutch disengagement signal is input, the retightening controller 105 is configured to output, based on the number of rotations (three rotations) that is the set stop condition, a retightening drive signal for driving the motor M in the forward direction by an amount corresponding to the set number of rotations, to the driver 102. In the control device 100, the clutch disengagement signal from the determiner 104b is also input to the drive commander 101. When the clutch disengagement signal is input, the drive commander 101 is configured to stop outputting the forward rotation command signal to the driver 102.

[0063] As a result, in the control device 100, after the clutch disengagement signal is output from the determiner 104b, the driver 102 drives the motor M based on the retightening drive signal from the retightening controller 105. That is, in the control device 100, the control mode of the motor M is switched from the control mode based on the forward rotation command signal from the drive commander 101 to the control mode based on the retightening drive signal from the retightening controller 105 in response to the output of the clutch disengagement signal.

[0064] An encoder EN that detects the amount of rotation of the motor M is connected to the motor M. In the control device 100, a rotation detection signal indicating the amount of rotation detected by the encoder EN is output (feedback) to the retightening controller 105. The retightening controller 105 is configured to output a retightening drive signal based on the stop condition (set number of times) and the rotation detection signal output from the encoder EN, and to stop the output when the amount of rotation of the motor M reaches the set number of times.

[0065] Furthermore, the retightening controller 105 is configured to output a completion signal indicating that the retightening operation is completed to the main control device 90 when the amount of rotation of the motor M reaches a set number of times. Then, in response to the input of the completion signal, the main control device 90 advances the process in the machining program to the next process (e.g., a machining process).

[0066] According to the electric vice 1 equipped with the tightening mechanism 70 as described above, when a clamp command signal is issued from the main control device 90, the motor M is started to be driven and the clamping process is started. Then, as shown in FIG. 7, the driving torque of the motor M increases rapidly from the point when the fixed jaw 5 and the movable jaw 7 come into contact with the workpiece W, and starts to decrease when the clutch mechanism 40 comes into the released state (release point) as described above. Then, in the electric vice 1, the driving torque of the motor M is detected during the clamping process, and the clutch disengagement detector 104 (determining device 104b) determines (detects) the point when the differential value changes from a positive value to 0 based on the detected torque. Then, since the point when the differential value changes to 0 corresponds to the release point, the determinator 104b outputs a clutch disengagement signal at the detection point. As a result, the release point is detected.

[0067] Then, when the clutch disengagement signal is output from the judger 104b, the tightening controller 105 outputs a tightening drive signal, and the control device 100 switches from a state in which the drive of the motor M is controlled based on the forward rotation command signal from the drive commander 101 to a state in which the drive of the motor M is controlled based on the tightening drive signal. As a result, the motor M is driven in the forward direction so as to rotate and drive the rotary propulsion shaft 30 for a set number of times (three rotations) set as the stop condition from the release point as described above, and is stopped when the forward drive corresponding to the set number of times is completed. Note that the stop condition is determined so that the clamping force in the clamped state of the workpiece W is an appropriate magnitude, as described above. Therefore, when the drive of the motor M based on the tightening drive signal is completed, the workpiece W is clamped with an appropriate clamping force.

[0068] Thus, according to this embodiment, in the electric vice 1 equipped with the tightening mechanism 70, the time when the clutch mechanism 40 is released (the release time) is automatically detected based on the detected torque of the motor M, and the control mode of the motor M is switched at the detection time, and control after the detection time is performed so as to more reliably achieve clamping of the workpiece W with an appropriate clamping force based on the stop condition described above. Therefore, with such an electric vice 1, damage to the workpiece or the electric vice can be prevented as much as possible.

[0069] In this embodiment, the control device 100 includes a clamping state detector 106 for determining whether the workpiece W is clamped by the electric vice 1. The clamping state detector 106 includes a rotation amount detector 106a for detecting the amount of rotation of the motor M, a calculator 106b for calculating the amount of movement of the movable jaw 7 and the like based on the amount of rotation of the motor M detected by the rotation amount detector 106a, and a determiner 106c for determining whether the workpiece W is clamped based on the value calculated by the calculator 106b.

[0070] Of these, the rotation amount detector 106a is connected to the main control device 90, and receives a clamp command signal from the main control device 90. The rotation amount detector 106a is also connected to a determiner 104b in the clutch disengagement detector 104, and receives a clutch disengagement signal from the determiner 104b. The rotation amount detector 106a is also connected to an encoder EN, and receives a rotation detection signal (indicating the rotation amount of the motor M) from the encoder EN.

[0071] The rotation amount detector 106a is configured to detect the amount of rotation of the motor M from the point at which the motor M starts to be driven to the release point (the point at which the fixed jaw 5 and the movable jaw 7 come into contact with the workpiece W) based on the rotation detection signal from the encoder EN during the period from when the clamp command signal is input to when the clutch disengagement signal is input. The rotation amount detector 106a is configured to output a signal (rotation amount signal) indicating the amount of rotation of the motor M up to the release point in response to the input of the clutch disengagement signal.

[0072] The calculator 106b is connected to the rotation amount detector 106a, and is configured to calculate the amount of movement of the movable jaw 7 at the time of release (the amount of movement from the position of the movable jaw 7 in the initial state) based on a rotation amount signal (the amount of rotation of the motor M) output from the rotation amount detector 106a. The calculator 106b stores the interval (initial interval) between the fixed jaw 5 and the movable jaw 7 in the initial state in a built-in memory (not shown). The calculator 106b is configured to calculate the interval between the fixed jaw 5 and the movable jaw 7 at the time of release based on the amount of movement and the initial interval, and to output a signal (interval value signal) indicating the calculated interval (calculated interval).

[0073] Furthermore, the determiner 106c is connected to the calculator 106b, and is configured to compare the calculated interval with a preset dimension (workpiece dimension) of the workpiece W based on the interval value signal output from the calculator 106b to determine whether or not the workpiece W is clamped properly. In other words, if the workpiece W is clamped properly, the calculated interval and the workpiece dimension should approximately match, and the determiner 106c is configured to determine whether or not the workpiece W is clamped properly based on this.

[0074] The machining program stored in the main control device 90 includes the workpiece dimensions. The determiner 106c is connected to the main control device 90 and is configured to read out the workpiece dimensions from the main control device 90 in response to an input of an interval value signal from the calculator 106b. The determiner 106c is also configured to compare the calculated interval based on the interval value signal with the workpiece dimensions read out from the main control device 90 in response to an input of the interval value signal. Furthermore, the determiner 106c is configured to output a clamp abnormality signal to the main control device 90 indicating that the clamp state is abnormal when the difference between the two does not match and deviates from a preset error range.

[0075] Then, in response to the input of the clamp abnormality signal from the determiner 106c, the main control device 90 determines that an abnormality has occurred in the clamping state of the workpiece W, and stops the machining program. Therefore, by providing the control device 100 with such a clamping state detector 106, the appropriateness of the clamping state of the workpiece W can be automatically determined, and machining of the workpiece W in an incomplete clamping state can be effectively prevented.

[0076] The above describes one embodiment of the electric vise to which the present invention is applied (hereinafter, referred to as the "embodiment"). However, the present invention is not limited to the configuration described in the embodiment, and can be embodied in other embodiments (variations) as follows.

[0077] (1) Regarding the torque detector, in the above embodiment, the torque detector 110 detects the torque acting on the rotating propulsion shaft 30 based on a measured value (drive current value) of the current (drive current) supplied to the motor M. However, in the present invention, the torque detector is not limited to being configured to detect the torque acting on the rotating propulsion shaft based on the drive current value of the motor. For example, the torque detector may be configured to detect torque using a torque detection sensor (so-called torque sensor) that uses a strain gauge as a detection means. In that case, the torque sensor may be connected to the rotating propulsion shaft or the output shaft of the motor, and the torque acting on the rotating propulsion shaft may be detected.

[0078] (2) Regarding the clutch disengagement detector, in the above embodiment, the clutch disengagement detector 104 is configured to obtain a differential value of the detected torque and determine whether or not the clutch mechanism 40 has entered the released state based on the differential value. The clutch disengagement detector 104 is then configured to determine that the clutch mechanism 40 has entered the released state when the differential value changes from a positive value to 0. However, in the present invention, the clutch disengagement detector may be configured to determine that the clutch mechanism 40 has entered the released state when the differential value changes from 0 (or a positive value) to a negative value, for example. The clutch disengagement detector may also be configured to store a reference value (threshold value) of torque for determining that the clutch mechanism has entered the released state in an internal memory, compare the differential value (or the absolute value of the differential value) with the threshold value, and determine that the clutch mechanism has entered the released state when the differential value exceeds the threshold value.

[0079] Furthermore, the determination by the clutch disengagement detector is not limited to being based on the differential value, but may be based on the detected torque detection value. In that case, the clutch disengagement detector may be configured to make the determination based on a comparison between the detected torque detection value and a reference value (threshold value) of torque stored in the memory of the clutch disengagement detector.

[0080] (3) In the above embodiment, the stop condition used by the retightening controller is set to the number of rotations (three rotations) of the rotating propulsion shaft 30. As a result, the motor M is driven in the forward direction so as to rotate the rotating propulsion shaft 30 a set number of times (three rotations) based on the retightening drive signal from the retightening controller 105 from the time when the release time is detected. However, in the present invention, the stop condition is not limited to the number of rotations as described above, and may be set by the drive time of the motor M. In this case, the drive time is set based on the amount of movement of the rotating propulsion shaft 30 in the longitudinal direction that provides an appropriate clamping force and the preset speed of the rotating propulsion shaft 30.

[0081] When the drive time of the motor M is set as the stop condition in this way, the drive time (set time) is stored in the memory of the retightening controller, and the retightening controller is configured to include a timer that measures the drive time of the motor M from when the clutch disengagement signal is input (from the release time). Furthermore, the retightening controller is configured to start timing with the timer from when the clutch disengagement signal is input, and to output a completion signal indicating that the retightening operation is completed to the drive commander in addition to the main control device when the drive time reaches the set time. Then, the drive commander may be configured to stop outputting the forward rotation command signal to the driver in response to the input of the completion signal. As a result, the drive of the motor M is stopped when the set time has elapsed from the release time.

[0082] The stop condition can also be set as a condition related to the drive torque of the motor M after the release point in time. More specifically, the stop condition is as follows.

[0083] First, the electric vice is configured so that the rotation is stopped by engaging with the rotating propulsion shaft that rotates and moves toward the fixed jaw 5 side after the release point in time. Although not described, the electric vice 1 of the embodiment also includes a stopper mechanism 80 as a configuration for stopping the rotation by engaging with the rotating propulsion shaft 30. However, in the embodiment, the stopper mechanism 80 is set so that the engagement (stop of the rotation of the rotating propulsion shaft 30) is not performed even if the rotating propulsion shaft 30 moves toward the fixed jaw 5 side by the number of rotations set as the stop condition. In the following, since the mechanical configuration of the electric vice is the same as that of the embodiment, the mechanical configuration will be described based on the electric vice 1 of the embodiment. However, since the control configuration is different from that of the embodiment, it will be described based on FIG. 8 as described later.

[0084] The stopper mechanism 80 on which this is based comprises a hollow cylindrical adjustment ring 81 that is fitted onto the support member 3a of the main body frame 3, and a hollow cylindrical stopper ring 82 that is fitted onto the inside of the adjustment ring 81 and onto the outside of the hollow shaft 20. The stopper mechanism 80 also comprises a sleeve 83 that is generally hollow cylindrical and has a protruding portion on one end side that protrudes radially inward, and is attached to the rotary propeller shaft 30 so as to accommodate the rotary propeller shaft 30.

[0085] Of these, the adjustment ring 81 is provided so that one end side is fitted into a through hole of the support member 3a and the other end side protrudes from the support member 3a. A groove extending in the axial direction is formed on the outer circumferential surface of the adjustment ring 81, and a pin provided on the support member 3a is inserted into the groove. As a result, the adjustment ring 81 is provided in a state where it cannot rotate relative to the support member 3a but can slide in the longitudinal direction.

[0086] Moreover, the adjustment ring 81 is held in its axial position by pressing a spherical locking member on the support member 3a side against a recess formed on its outer circumferential surface. The locking member is housed in a hole formed in the support member 3a and is biased toward the adjustment ring 81 by a compression spring. Since a plurality of such recesses are formed in parallel in the axial direction, the adjustment ring 81 can have its axial position adjusted.

[0087] The stopper ring 82 has an axial dimension that is approximately half the size of the adjustment ring 81, and is fitted into the adjustment ring 81 at the one end. A groove is formed in the outer circumferential surface of the stopper ring 82 in the circumferential direction, and a pin provided on the adjustment ring 81 is inserted into the groove, so that the stopper ring 82 is provided in a state where it can rotate relatively to the adjustment ring 81 but cannot move relatively in the longitudinal direction. A key groove is formed in the inner circumferential surface of the stopper ring 82, and a key is interposed between the stopper ring 82 and the hollow shaft 20. The key groove of the stopper ring 82 is formed so as to penetrate in the axial direction, so that the stopper ring 82 is provided in a state where it cannot rotate relatively to the hollow shaft 20 but can slide in the longitudinal direction. With these configurations, the stopper ring 82 moves in the axial direction together with the adjustment ring 81 when adjusting the position of the adjustment ring 81 as described above.

[0088] The sleeve 83 is fixed to the flange 33 of the rotary drive shaft 30 by a screw member at the protruding portion, and is provided to accommodate the rotary drive shaft 30 as described above. The inner diameter of the sleeve 83, except for the protruding portion, is slightly larger than the outer diameter of the hollow shaft 20, and the sleeve 83 is provided to accommodate the other end side of the hollow shaft 20. The outer diameter of the sleeve 83 is slightly smaller than the inner diameter of the adjustment ring 81. As a result, the other end side of the sleeve 83 is inserted into the adjustment ring 81, and the sleeve 83 faces the stopper ring 82 in the longitudinal direction inside the adjustment ring 81. The distance between the sleeve 83 and the stopper ring 82 is larger than the amount of movement of the rotary drive shaft 30 when the rotary drive shaft 30 rotates three times in the initial state of the electric vice 1.

[0089] In addition, a needle bearing is interposed between the sleeve 83 and the outer peripheral surface of the hollow shaft 20. The sleeve 83 is supported by the needle bearing so as to be rotatable relative to the hollow shaft 20. The sleeve 83 is also rotatable relative to the adjustment ring 81, which is arranged so as not to be rotatable relative to the hollow shaft 20, and is able to slide in the longitudinal direction.

[0090] Since the sleeve 83 is fixed to the rotating drive shaft 30 as described above, as the rotating drive shaft 30 rotates after the release point, the sleeve 83 rotates together with the rotating drive shaft 30 and moves toward the fixed jaw 5, approaching the stopper ring 82.

[0091] In addition, the end face of the stopper ring 82 on the sleeve 83 side is provided with an engaged portion 82a formed to protrude from a part of the end face toward the sleeve 83 side. On the other hand, the end face of the sleeve 83 on the stopper ring 82 side is also provided with an engaging portion 83a formed to protrude from a part of the end face toward the stopper ring 82 side and to be able to engage with the engaged portion 82a on the stopper ring 82 side. Then, due to the rotational drive of the rotary propulsion shaft 30 after the release point, the sleeve 83 approaches the stopper ring 82 while rotating, and as the approach narrows, the engaging portion 83a on the sleeve 83 side and the engaged portion 82a on the stopper ring 82 side engage with each other. Then, due to this engagement, the rotation of the sleeve 83 (the rotation of the rotary propulsion shaft 30) is prevented (stopped).

[0092] In the electric vice equipped with the stopper mechanism 80 as described above, if the motor M continues to rotate the rotary propulsion shaft 30 after the stopper mechanism 80 has entered the engaged state as described above, the load on the motor M increases, and the drive torque (the drive current value) of the motor M rises. Therefore, by monitoring the drive torque, it is possible to determine whether the stopper mechanism 80 has entered the engaged state based on the drive torque of the motor M. Since the engaged state marks the completion of the retightening operation, the stop condition is set as a condition related to the drive torque of the motor M after the release point, and thus the drive control of the motor M until the completion of the retightening operation is realized. The control of the motor M in the electric vice in this case can be explained based on the configuration shown in FIG. 8, for example.

[0093] In the example shown in FIG. 8, similarly to the above-mentioned embodiment, the detected torque signal from the torque detector 110 is output to a calculator 104a' of the clutch disengagement detector 104'. Then, based on the detected torque signal indicating the torque detection value output from the calculator 104a', the judger 104b' judges that the clutch mechanism 40 in the electric vice has been released. In the above-mentioned embodiment, the clutch disengagement signal (signal indicating clutch disengagement) from the judger 104b is output to the drive commander 101 and the tightening controller 105, but in this example, instead, the clutch disengagement signal is output only to the calculator 104a'. In this case, since the clutch disengagement signal is not output to the drive commander 101, the drive of the motor M by the forward rotation command signal from the drive commander 101 continues even after the release point.

[0094] The calculator 104a' is configured to change the output destination of the detected torque signal from the decision unit 104b' to the retightening controller 105' in response to the input of the clutch disengagement signal. As a result, after the release point in time, the detected torque signal from the calculator 104a' is output to the retightening controller 105'.

[0095] The retightening controller 105' is configured to determine whether or not the stopper mechanism 80 has entered the engaged state based on the detected torque signal from the calculator 104a'. A torque reference value (threshold value) for determining whether the stopper mechanism 80 has entered the engaged state is stored in the retightening controller 105' as a stop condition. The retightening controller 105' is configured to compare the torque detection value with the threshold value upon input of the detected torque signal from the calculator 104a', and to output a completion signal indicating that the retightening operation has been completed to the main control device 90 and the drive command unit 101 when the detected torque signal exceeds the threshold value.

[0096] The drive command device 101 is configured to stop outputting the normal rotation command signal in response to the input of the completion signal from the tightening controller 105'. As a result, the drive of the motor M is stopped after a predetermined delay time from the time when the stopper mechanism 80 is in the engaged state.

[0097] Then, by setting the stopper mechanism 80 in the electric vice so that it is in the engaged state when the rotary propulsion shaft 30 is rotationally driven (moved toward the fixed jaw 5) to an extent that a roughly appropriate clamping force is obtained, the electric vice is in a state in which an appropriate clamping force is obtained when the driving of the motor M is stopped. In this way, in an electric vice equipped with the stopper mechanism 80, it is possible to control the driving of the motor M until the completion of the additional tightening operation that obtains an appropriate clamping force by setting the stop condition as a condition related to the driving torque of the motor M after the release point.

[0098] Incidentally, in the above embodiment, the control device 100 includes a clamp state detector 106 as a configuration for determining whether the workpiece W is clamped by the electric vice 1. However, the configuration for determining whether the workpiece W is clamped by the electric vice 1 is not essential to the present invention, and may be omitted as in the example of FIG.

[0099] (4) Regarding the electric vice equipped with a tightening mechanism, the tightening mechanism 70 of the electric vice 1 in the above embodiment is configured to include four rollers 73, 74 between the screw shaft 10 and the wedge-shaped portion 72b of the operating shaft 72, and the operating shaft 72 moves toward the fixed jaw 5 while expanding the gap between the rollers 73, 74 vertically, and the force increased by the wedge effect is applied to the movable jaw 7 via the screw shaft 10. However, the electric vice to which the present invention is applied is not limited to one equipped with a tightening mechanism of a wedge structure that increases the clamping force by such a wedge effect. For example, the present invention is also applicable to an electric vice equipped with a tightening mechanism of a lever structure or a toggle structure as disclosed in JP-A-4-240076, although detailed description will be omitted.

[0100] (5) The configuration (connection configuration) for connecting the motor M and the rotary propulsion shaft is not limited to the drive transmission mechanism 50 consisting of the pulley 55 attached to the drive shaft 51, the pulley 56 attached to the driven shaft 52, and the belt 57 connecting both pulleys 55, 56 as in the above embodiment. For example, the connection configuration may be a gear train consisting of a drive gear attached to the drive shaft 51 and a driven gear attached to the driven shaft 52. In addition, the connection configuration may be configured to directly connect the transmission shaft 53 attached to the rotary propulsion shaft 30 and the output shaft of the motor M via a coupling.

[0101] (6) The electric vice of the present invention is not limited to being installed on a machine tool as in the above embodiment, but can also be used as a standalone device. In that case, the electric vice may be provided with a manual operating device, and configured so that a command signal for starting a clamping operation, etc., is output by operating the operating device.

[0102] Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0103] 1 Electric vice 3 Main frame 3a Support member 3b Projection 5 Fixed Jaw 7 Movable Jaw 9 Slide Block 10 Screw shaft 12 Forced shaft 14 Ring member 20 hollow shaft 20a Flange part 22 Round Nut 30 Rotating propulsion shaft 31 Main body part 32 Small diameter section 33 Flange section 40 Clutch mechanism 41 Clutch ring 42 Compression spring 43 Bearing holder 44 Thrust bearing 45 Bearing holder 50 Drive transmission mechanism 51 Drive shaft 52 Driven axis 53 Transmission shaft 55 Pulley 56 Pulley 57 Belt 60 Connected Frame 61 Base 70 Tightening mechanism 71 Roller Support 71a Protrusion 72 Working shaft 72a Shaft 72b Cuneiform part 73 Big Roller 74 Small Roller 80 Stopper mechanism 81 Adjustment Ring 82 Stopper Ring 82a Engaged part 83 Sleeve 83a Engagement part 90 Main Control Unit 100 Control device 101 Drive command unit 102 Driver 104 Clutch disengagement detector 104a Arithmetic unit 104b Judgment device 105 Tightening controller 106 Clamp Status Detector 106a Rotation detector 106b Calculator 106c Determiner 110 Torque detector Medium motor EN Encoder

Claims

1. The clamping mechanism includes a fixed jaw and a movable jaw for clamping a workpiece, a screw shaft for moving the movable jaw in an axial direction, a hollow cylindrical shaft connected to one end of the screw shaft so as not to rotate relative to the main body frame, a rotary drive shaft connected to the hollow shaft via a clutch mechanism, and a tightening mechanism housed in the hollow shaft. An electric vice in which a tightening operation is performed by the tightening mechanism, which rotates the hollow shaft via the clutch mechanism in a connected state by rotating the rotary propulsion shaft, and applies a clamping force to the movable jaw via the screw shaft in a released state by the clutch mechanism, A motor that rotates the rotary propulsion shaft; A torque detector for detecting a torque acting on the rotating propulsion shaft; A control device for controlling the driving of the motor, The control device includes a clutch disengagement detector that detects that the clutch mechanism has been released based on a torque detection value detected by the torque detector, and a retightening controller that controls the retightening operation based on a preset stop condition. The electric vise is characterized by the above.

2. The clutch disengagement detector includes a calculator that calculates a differential value of the torque detection value, and a determiner that determines whether the clutch is in the released state based on the differential value.

2. The electric vice according to claim 1.

3. The control device includes a calculator that calculates a distance between the fixed jaw and the movable jaw in the axial direction based on the drive amount of the motor at the time when the clutch disengagement detector detects the release state, and a determiner that compares the distance with a preset workpiece dimension to determine whether the workpiece is clamped properly.

3. The electric vice according to claim 1 or 2.

Images