Box bit and automatic fastening machine equipped with the same

Abstract

To provide a box bit which easily fits to a fastening component.SOLUTION: A box bit 10 has a fitting hole 11 which can fit to a polygonal fitting part formed on a fastening component B. The fitting hole 11 is configured into a petal-like shape in which a prescribed number of fitting recesses 12 positioned on a radial direction outer side with respect to an apex of the fitting part of the fastening component B and fitting protrusions 13 continuous with the fitting recess 12 and projecting to a radial direction inner side, are alternately formed in a circumferential direction. In the fitting hole 11, a relief surface 142 which gradually tilts toward the depth of the fitting hole as approaching the radial direction inner side or a rotation direction upstream side, is formed on an opening edge part of the fitting protrusion 13.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a box bit that is fitted into a fitting portion of a fastening part such as a hexagonal bolt or nut to tighten the fastening, and to an automatic fastening machine equipped with the box bit. [Background technology]

[0002] Conventionally, a box bit having a hexagonal column-shaped fitting hole at one end is known as a fastening tool used in a bolt tightening machine for tightening a hexagonal bolt or the like. This box bit can fit the head of the bolt into the fitting hole by rotating and moving forward toward the bolt, and the bolt tightening machine is configured to be able to transport the box bit with the bolt fitted to a predetermined fastening position, and to apply a rotational driving force to the box bit to tighten the bolt to the workpiece. However, in the conventional box bit, the fitting hole is hexagonal column-shaped and the open end face is flat, so that if the phase of the box bit and the phase of the bolt are slightly misaligned during fitting, the end face of the box bit and the head end face of the bolt come into surface contact. In this way, when the end face of the box bit and the head end face of the bolt come into surface contact, the box bit may rotate the bolt together due to frictional resistance generated on these contact surfaces. In other words, the above-mentioned box bit has a problem that the fitting hole and the bolt do not match in phase, and fitting failure frequently occurs. Furthermore, when such a poor fitting occurs, it is necessary to once retract the box bit and then perform the fitting operation again, which causes the cycle time of the bolt tightening machine to be extended.

[0003] In order to solve such a problem of poor fitting, a box bit as shown in Prior Patent 1 has been created. The box bit of Prior Patent 1 has an arc-shaped fitting recess centered on the axis of the box bit arranged on the opening surface of the fitting hole, and the fitting recess is formed so as to incline toward the back of the fitting hole. Six of these fitting recesses are arranged radially, and between these fitting recesses and the adjacent fitting recesses, a fitting protrusion that can abut against the side surface of the bolt head and transmit torque is formed. The conventional box bit configured in this way can guide the corner of the head from the fitting recess to the fitting protrusion even if the phase with the bolt head is slightly shifted, making it possible to reduce the occurrence of poor fitting. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Publication No. 61-016276 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even in the box bit described in Prior Patent 1, when the fitting convex portion and the head end face of the bolt come into contact with each other under the condition that a high thrust is applied to the head of the bolt, the bolt may rotate co-rotating due to the frictional force generated between the fitting convex portion and the bolt, or the engagement between the apex of the bolt head and the inner pointed end of the bolt. Therefore, even in the box bit described in Prior Patent 1, there is still a problem that the fitting failure is likely to occur. In addition, as a countermeasure against the co-rotation of the bolt, there is a method of fixing the bolt so that it does not rotate by clamping the shaft portion of the waiting bolt with a predetermined holding mechanism, but in this case, another problem occurs in that the structure and control of the bolt tightening machine become complicated by providing a holding mechanism. [Means for solving the problem]

[0006] The present invention has been created in view of the above problems, and aims to provide a box bit that can be easily fitted with a fastening part. In order to achieve this object, the present invention provides a box bit having a fitting hole that can be fitted with a polygonal column-shaped fitting part formed in a fastening part, and the fitting hole is configured in a petal shape in which a predetermined number of fitting recesses located radially outward from the apex of the fitting part of the fastening part and fitting protrusions that are continuous with the fitting recesses and protrude radially inward are formed alternately in the circumferential direction, the box bit being characterized in that an escape surface is formed on the end face of the fitting protrusion, which gradually inclines toward the inner side in the radial direction or toward the upstream side in the rotation direction so as to move toward the depth of the fitting hole. It is preferable that the escape surface is configured in a substantially conical shape formed so that the center point is located radially inward and upstream in the rotation direction from the inner pointed end of the fitting protrusion, or that the escape surface is configured in a substantially spherical shape. It is also preferable that a lead-in surface is formed on the opening edge of the fitting hole, which gradually inclines toward the inner side in the radial direction so as to move toward the depth of the fitting hole.

[0007] In addition, a second object of the present invention is to provide an automatic fastening machine equipped with the above-mentioned box bit, which is characterized in that it is equipped with the box bit, a rotational drive source that rotates the box bit, and a moving means that moves the box bit. Effect of the Invention

[0008] According to the box bit of the present invention, the escape surface formed at one end of the fitting protrusion allows the fitting hole and the fastening part to rotate relative to each other without co-rotating the fastening part, regardless of the phase in which the fitting hole and the fastening part abut, so that the fitting hole and the fastening part can be easily fitted together. In addition, since the escape surface is configured to be approximately conical or approximately spherical, it has the advantage of being relatively inexpensive and easy to manufacture. Furthermore, since the lead-in surface is formed, the contact area is further reduced, making it easier to rotate relative to each other, so that the bolt can be fitted more easily. Moreover, when the box bit is applied to an automatic fastening machine equipped with a rotary drive source and a moving means, it is not necessary to perform the fitting operation of fitting the bolt into the box bit multiple times, and there is also the advantage of improving the cycle time. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a structure of an automatic fastening machine according to the present invention. [Diagram 2] FIG. 2 is an enlarged perspective view of a main portion showing the structure of a box bit according to the present invention. [Diagram 3] FIG. 2 is an enlarged bottom view of a main portion showing the structure of the box bit according to the present invention. [Figure 4] 10A and 10B are explanatory diagrams showing the state of the box bit and the bolt, in which (a) shows the state where the bolt is engaged with the engagement hole, (b) shows the state where the bolt is abutting against the lead-in surface, and (c) shows the state where the bolt is abutting against the relief surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In Fig. 1, 1 denotes a bolt tightening machine for tightening a bolt B having a hexagonal column-shaped head, which is an example of a fastening part, and includes a box bit 10 that fits with the bolt B, a connecting shaft 20 connected to the box bit 10, a rotary drive source 30 that rotates the connecting shaft 20, and a moving means 40 that reciprocates the rotary drive source 30 in the axial direction of the connecting shaft 20. Therefore, the box bit 10 is rotatable when driven by the rotary drive source 30, and is movable when driven by the moving means 40. The bolt tightening machine 1 is supported by a horizontal articulated robot (not shown), which is an example of a moving operation mechanism to which the moving means 40 is separately provided, and is configured to be movable in the horizontal direction when driven by the horizontal articulated robot.

[0011] As shown in FIG. 2, the box bit 10 has a fitting hole 11 at one end that can fit with the head of the bolt B, and a connecting portion 16 that is connected to the connecting shaft 20 at the other end. The fitting hole 11 of the box bit 10 has six arc-shaped fitting recesses 12 centered on the axis of the box bit 10 and six fitting protrusions 13 that are continuous with the fitting recesses 12 and protrude radially inward, which are alternately formed in the circumferential direction, and are configured to be approximately petal-shaped. The fitting recesses 12 of the fitting hole 11 are configured to have a diameter slightly larger than the circumscribing circle of the head of the hexagonal bolt B. On the other hand, the fitting protrusions 13 have an inner pointed end 131 set at a position slightly outside the inscribing circle of the bolt B, and have an upstream wall surface 132 and a downstream wall surface 133 that extend from the inner pointed end 131 toward the fitting recesses 12 on the upstream and downstream sides of the rotation direction of the box bit 10. A magnet (not shown) is fixed to the back of the fitting hole 11, and this magnet is configured to be able to attract and hold the bolt B accommodated in the fitting hole 11. In this embodiment, the fitting recess 12 is configured in an arc shape with a central angle set to 24 degrees, and the angle of the inner pointed end 131 (the angle between the upstream wall surface 132 and the downstream wall surface 133) is set to 150 degrees.

[0012] 3, a lead-in surface 141 and an escape surface 142 are formed at one end of the box bit 10. First, the lead-in surface 141 is a tapered surface having a substantially conical shape formed so as to be inclined while decreasing in diameter as it goes from the opening edge of the fitting hole 11 toward the back, and its maximum diameter is set to the same diameter as the arc shape of the fitting recess 12. On the other hand, the escape surface 142 is an inclined surface formed at one end of the fitting protrusion 13, and is set so as to be steeper inclined than the lead-in surface 141. This escape surface 142 is inclined so as to gradually go toward the back of the fitting hole 11 as it goes toward the radial inside of the box bit 10 and the upstream side of the rotation direction of the box bit 10 (the opposite direction to the arrow R), and is set so that the head of the bolt B that abuts against the escape surface 142 slides along the inclination. In this embodiment, the relief surface 142 is a tapered surface having a substantially conical shape formed to overlap the lead-in surface 141, and its center point 143 is set at a position radially inward from the inner tip 131 and shifted by a predetermined angle upstream in the rotation direction of the box bit 10. The relief surface 142 is dimensioned so that its maximum diameter portion includes the boundary point 15 between the upstream wall surface 132 and the fitting recess 12. The lead-in surface 141 has an inclination angle of 45 degrees, and the relief surface 142 has an inclination angle of 60 degrees. Furthermore, the center point 143 is shifted 10 degrees upstream in the rotation direction from the inner tip 131.

[0013] The rotary drive source 30 is configured to rotate the box bit 10 in the direction of arrow R (counterclockwise as viewed from the bottom) shown in Figs. 3 and 4 when fastening the bolt B described later. The moving means 40 has an AC servo motor 41, which is an example of a driving source, a ball screw 42 that rotates by receiving the drive of the AC servo motor 41, and a driving nut 43 that is screwed with the ball screw 42 and moves up and down by the rotation of the ball screw 42, and the rotary drive source 30 is connected to the driving nut 43. As a result, the rotary drive source 30 and the box bit 10 can be reciprocated in the axial direction of the connecting shaft 20 by driving the AC servo motor 41 of the moving means 40. The rotary drive source 30, the moving means 40, and the horizontal articulated robot are controlled by a control device (not shown), and are configured to move the box bit 10 between a predetermined waiting position, a receiving position set on the axis of the bolt B, and a fastening position by driving the horizontal articulated robot.

[0014] Next, the operation of the bolt fastening machine 1 configured as above will be described. When a drive signal is input, the horizontal articulated robot moves the box bit 10 from a predetermined standby position toward a receiving position that is set on the axis of the bolt B held by a predetermined jig (not shown). When the box bit 10 reaches the receiving position, the horizontal articulated robot stops. After the horizontal articulated robot stops, the rotation drive source 30 is actuated to rotate the box bit 10 in the direction of arrow R, and the moving means 40 is actuated to move the box bit 10 toward the bolt B.

[0015] When one end of the box bit 10 moving while rotating as described above reaches the head end face of bolt B, if the fitting recess 12 of the fitting hole 11 overlaps with the apex of the head of bolt B as shown in Figure 4(a), the box bit 10 will be accommodated in the fitting hole 11 without the head end face of bolt B abutting against its end face. At this time, the fitting recess 12 is configured in an arc shape as described above, and even if it is slightly out of phase with the box bit 10 as shown by the two-dot chain line in Figure 4(a), the fitting recess 12 can be overlapped with the apex of the head of bolt B, allowing it to fit into bolt B relatively smoothly.

[0016] However, as shown in (b) and (c) of FIG. 4, when the fitting protrusion 13 of the fitting hole 11 overlaps with the apex of the head of the bolt B, the lead-in surface 141 or the relief surface 142 comes into contact with the head end surface of the bolt B. First, as shown in (b) of FIG. 4, when the lead-in surface 141 comes into contact with the bolt B, the lead-in surface 141 is inclined so as to gradually move toward the back of the fitting hole 11 as it moves radially inward, as described above, so that the lead-in surface 141 can come into contact only with the apex of the head of the bolt B or its vicinity. As a result, the contact area between the lead-in surface 141 and the bolt B becomes relatively small, so that the frictional resistance generated between them becomes small, and the lead-in surface 141 can rotate smoothly relative to the bolt B. Therefore, before the bolt B starts to rotate together due to friction, the lead-in surface 141 comes out of the head of the bolt B, and at the same time, the relief surface 142 located upstream of the lead-in surface 141 comes into contact with the bolt B.

[0017] When the relief surface 142 abuts against the bolt B, the relief surface 142 is gradually inclined toward the back of the fitting hole 11 as it moves toward the upstream side in the rotation direction of the box bit 10, and since the relief surface 142 can rotate relative to the head of the bolt B while following the inclination, co-rotation of the bolt B is prevented. At this time, since the relief surface 142 is gradually inclined toward the back of the fitting hole 11 as it moves toward the radially inward side, the relief surface 142 can abut only against the apex of the head of the bolt B or its vicinity, as with the lead-in surface 141, and smoothly slides against the bolt B. In addition, since the inner pointed end 131 is also inclined, even if the apex of the head of the bolt B and the inner pointed end 131 overlap, they do not engage with each other. As a result, the relief surface 142 also comes off the bolt B without co-rotating. At this time, the maximum diameter portion of the relief surface 142 is sized to include the boundary point 15 between the upstream wall surface 132 and the upstream fitting recess 12, thereby preventing the boundary point 15 from getting caught on the apex of the head of the bolt B. As the relief surface 142 disengages from the bolt B in this way, the fitting recess 12 located upstream of the relief surface 142 in the rotation direction overlaps with the apex of the head of the bolt B, so that the box bit 10 accommodates the bolt B in the fitting hole 11.

[0018] As described above, the relief surface 142 and the like are formed, so that the box bit 10 can rotate relative to the bolt B until the fitting recess 12 overlaps with the bolt B without rotating the bolt B together, regardless of the phase in which the box bit 10 contacts the bolt B, and the bolt B can be accommodated in the fitting hole 11. Therefore, it is not necessary to perform the fitting operation multiple times, and the cycle time of the bolt tightening machine 1 is shortened. In addition, the bolt B accommodated in the fitting hole 11 is magnetized and held by the magnet provided at the back of the fitting hole 11, and rotates together with the box bit 10 with the upstream wall surface 132 of the fitting protrusion 13 abutting against the head side of the bolt B. When the bolt is accommodated in the fitting hole, the rotary drive source 30 stops, and then the horizontal articulated robot moves the box bit 10 and the bolt B from the receiving position to the fastening position. When the bolt reaches the fastening position, the horizontal articulated robot stops. After the horizontal articulated robot stops, the rotational drive source 30 is activated to rotate the box bit 10 in the direction of arrow R, and the moving means 40 is driven to move the box bit 10 toward the specified workpiece and tighten the bolt B.

[0019] In the box bit 10 of this embodiment, since the relief surface 142 is configured to be substantially conical as described above, it can be easily manufactured by arranging a drill with a cone-shaped tip on the center point 143 and transferring the cone-shaped tip by cutting. Therefore, it can be manufactured cheaply and in a short time compared to cutting out a predetermined inclined surface using a milling machine or a multi-function machine. In addition, since the relief surface 142 is formed on the upstream side of the rotation direction, the area of ​​the downstream wall surface 133 that abuts against and presses the side surface of the bolt B during the fastening process is not significantly reduced. Therefore, in the fastening process, the pressure applied to the downstream wall surface 133 and the side surface of the bolt B does not increase, and damage to these abutting points is prevented. In addition, since the relief surface 142 is formed, it is not necessary to make the fitting recess 12 extremely large. Therefore, the fitting protrusion 13 that abuts against the bolt B during fastening is extremely small, and it is prevented from being damaged by the fastening torque, or the bolt comes off the fitting protrusion during fastening, causing the box bit to spin freely. At the same time, since the guide surface 141 is formed, the amount of the fitting protrusion 13 that is cut is reduced compared to when the entire end face of the fitting protrusion 13 is formed with the relief surface 142. This improves the strength of the box bit 10, making it less susceptible to breakage. Furthermore, by making fitting easier with the relief surface 142, etc., there is no need for a mechanism for holding the shaft portion of the bolt B, etc. Therefore, the configuration of the control device that controls the moving means 40, etc. may be simple, and the bolt tightening machine 1 can be manufactured relatively easily and at low cost.

[0020] The box bit 10 according to the present invention is not limited to the above, and various modifications are possible within the scope of the invention. For example, the box bit 10 in the above embodiment is a magnetized type having a magnet in the fitting hole 11, but is not limited to this, and may be an air-intake type box bit having an air intake hole on the bottom surface of the fitting hole 11 and capable of adsorbing and holding the head end surface of the bolt B, a box bit for tightening a temporarily fastened bolt B, or a box bit for fastening a nut having a recess for a male thread on the bottom surface of the fitting hole 11. In addition, the relief surface 142 is not limited to a substantially conical shape, and may be a substantially spherical shape whose central axis is set coaxially with the center point 143, or other shapes. Furthermore, the inclination angle of the introduction surface 141, the inclination angle of the relief surface 142, and the angle difference between the center point 143 and the inner pointed end 131 can be appropriately set according to the head shape of the bolt B used and the outer shape of the nut. Moreover, the configurations of the rotary drive source 30, the moving mechanism 40, and the horizontal articulated robot are not limited to those described above, and other configurations may also be used without any problem. [Explanation of symbols]

[0021] 1 … Automatic fastening machine 10 … Boxbit 11 ... Fitting hole 12 ... Fitting recess 13 ... Fitting protrusion 141 ... Call-in surface 142 ... Relief surface 143 … center point B … Fastening parts

Claims

1. The fastening part has a fitting hole that can be fitted with a polygonal column-shaped fitting portion formed in the fastening part, In the box bit, the fitting hole is configured in a petal shape with a predetermined number of fitting recesses located radially outward from the apex of the fitting portion of the fastening component and fitting protrusions continuing from the fitting recesses and protruding radially inward, alternately formed in the circumferential direction, An end face of the fitting protrusion is formed with a relief surface that is gradually inclined toward the inside in the radial direction or toward the upstream side in the rotation direction so as to gradually approach the depth of the fitting hole, The escape surface is configured in a generally conical shape with its center point located radially inward from the inner pointed end of the mating protrusion and upstream in the direction of rotation, and the maximum diameter portion on the opening edge side is set to a dimension that includes the boundary point between the upstream mating recess and the mating protrusion.

2. The box bit according to claim 1, characterized in that the fitting hole is provided with a lead-in surface that is formed so as to taper in diameter as it extends from the opening edge of the fitting hole toward the back.

3. A box bit according to claim 1 or 2; An automatic fastening machine comprising a rotary drive source for rotary driving the box bit and a moving means for moving the box bit.

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