JP2011104669A - Driver bit used also for detecting screw floating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driver bit used also for detecting screw floating capable of deciding quality as to whether a head seat surface of a screw is surely seated on a workpiece or a part, etc when the screw is fastened. <P>SOLUTION: In the driver bit, a stopper 13 abutting on a head top surface when an engaging part 12 is engaged in a drive hole 22 is formed between a shaft 11 transmitted with a rotary drive force and the engaging part 12, a small clearance is formed between the bottom of the drive hole 22 brought into the engaged state by the abutment of the stopper 13 on the head top surface of the screw 20 and a tip of the engaging part, a diameter (D) of an outer peripheral circle of the stopper 13 is larger than a diameter (m) of a circumscribing circle of the drive hole 22, and thereby whether or not the head seat surface is seated can be exactly decided. The driver bit has a constitution in which the small clearance is formed between the drive hole and the tip of the engaging part of the drive bit, and thereby the quality decision of the screw floating is not adversely affected even if damage is generated in the drive hole or the engaging part due to a certain cause. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a screw component that is fastened to a workpiece with a predetermined fastening force, and whether or not the head seating surface of the screw is seated on the surface of the workpiece when tightened to the workpiece with a preset screw tightening torque. The present invention relates to a screw lift detection / use driver bit that enables reliable determination.

  When tightening a screw to a predetermined position on a workpiece and fixing a component, etc., if the seat surface of the screw floats without being seated on the workpiece or the component to be fixed, the component will not be fixed to the workpiece, resulting in looseness. . For this reason, this phenomenon is one of the causes of product defects. In particular, an automatic screwing machine as shown in FIG. 5 is used in the automatic assembly line, and the driver unit 5 is in a state where the screw 20 is held at the tip of the automatic screwing machine 1 with respect to the pilot hole of the workpiece. Is lowered along the guide rod 7, and the screw 20 is tightened with a predetermined fastening force via the driver bit 10. In such an automatic screw tightening machine, in order to eliminate the above-mentioned screw floating state, for example, an automatic screw tightening machine having a configuration as shown in Japanese Utility Model Publication No. 2-24587 has been used. This is because the position where the driver bit of the automatic screw tightener is lowered is detected by a sensor, and it is determined whether this position is in a preset seating state or a screw floating state. When the screw tightening is completed, it is determined whether the head is in a screw floating state or a seating state. The driver bit used for the screw tightening operation is a normal driver bit defined in JIS (Japanese Industrial Standard).

  In addition, there are many shapes of cross-recessed screws, from the general ones shown in JIS to screws with other special drive hole shapes, and the driver bits used for such screws also support drive holes. At present, it has various shapes. As a special drive hole shape, for example, there is one as shown in Japanese Patent Laid-Open No. 11-311226, and the cross hole 122 of this screw has the shape shown in FIG. This prevents the cam bit phenomenon of the driver bit 110, prevents the screw 120 from being damaged, and even if the cross hole 122 is damaged, the end portion of the cross hole 122 has a predetermined depth to achieve a quick screwing operation. This is a substantially vertical end wall portion 123. Moreover, as shown in FIG. 7, the driver bit 110 that fits in the cross hole 122 has a similar shape that fits in the vertical end wall portion 123 of the cross hole 122, and the cross hole 122 and the driver bit 110 are stabilized. The screw and the driver bit are combined so that the cam-out is eliminated when the screw is tightened.

Japanese Patent Laid-Open No. 11-311226

  In the screw shown in the prior art document, the end edge of the drive hole is a vertical end wall, and therefore the screw and bit are formed by using the driver bit having a shape corresponding to the drive hole. Are fitted so that their axes are the same, and it is possible to prevent a cam-out phenomenon or damage to a screw or the like, but it is not possible to determine whether or not a screw is floating. In addition, even in the case of a normal screw drive hole that is not a special drive hole, the driver bit that fits into this screw is also susceptible to a cam-out phenomenon, and even if the screw head seat is seated, the screw is floating The reliability is lacking because it may be judged as defective. Furthermore, the cross-shaped drive hole formed in the head of the screw is usually manufactured by forging and formed by pressing the material with a punch which is a forging tool. If it is used, it will be worn out or the depth of the drive hole will vary, and this will be affected and the screw head will be seated on the workpiece, but it will be judged as screw tightening failure. . In addition, if the depth of the drive hole is deeper than a predetermined dimension from the top surface of the head, the tip of the driver bit will enter deeply into the drive hole, so that the seat surface of the screw is not seated. Even though there is a gap between the workpiece and the workpiece, it may be judged as a good product. Such a determination is caused by various problems such as a case where a driver bit fitted into the drive hole is worn. On the other hand, since the screw drive hole is manufactured by forging as described above, the depth of the drive hole etc. changes slightly due to the adjustment method, so the shape of the screw head cross hole is always accurate. It is not formed, and the depth, shape, etc. still vary. For this reason, the accurate determination of the screw floating state cannot be obtained, and the determination is affected by such variations in the cross-hole shape of the screw, and there is a problem that the determination of the non-defective product and the defective product is inaccurate.

  The object of the present invention is to solve the above-mentioned problems, and to detect whether or not the screw head seating surface is securely seated on a work or a part during screw tightening, and a screw lift detection / use driver Is to get a bit.

  An object of the present invention is engageable when a driving force is transmitted to a shaft portion 11 to which a rotational driving force is transmitted and a driving hole 22 formed integrally with the shaft portion 11 and formed in the head portion 21 of the screw 20. In the driver bit composed of the engaging portion 12, a stopper portion 13 is formed between the shaft portion 11 and the engaging portion 12 so as to come into contact with the top surface of the head when the engaging portion 12 is engaged with the drive hole 22. In addition, a configuration is adopted in which a slight gap is provided between the bottom of the drive hole 22 in which the stopper portion 13 is brought into engagement with the top surface of the head of the screw 20 and the tip of the engagement portion, The diameter (D) of the outer circumferential circle of the stopper portion 13 is achieved by providing a screw bit detecting / driving driver bit larger than the diameter (m) of the circumscribed circle of the drive hole 22.

  In the above invention, the stopper portion is a screw lift detection / use driver bit that is a flat surface formed on a horizontal cross section orthogonal to the center line of the shaft portion 11, so that the axial centers of the screw and the driver bit coincide with each other. In this case, it is possible to accurately contact the top surface of the screw head. Further, the engaging portion has a crossing locus circle connecting the crossing corner portion 12b formed by crossing the outer peripheral wall surface 12a and the stopper portion 13 on the same plane, and the diameter (M) of the crossing locus circle is With the configuration in which there is a relationship of (M <m) with the diameter (m) of the circumscribed circle of the drive hole 22, insertion of the engagement portion of the driver bit into the drive hole is stabilized.

  According to the present invention, when a screw is tightened by an automatic screw tightening machine, whether or not the head seating surface of the screw is seated by detecting a fitting position of the drive hole and the driver bit when the screw tightening is completed. Compared to the conventional example in which the determination is made, it is based on the state in which the stopper portion of the driver bit is in contact with the top surface of the head, so it can be accurately determined whether or not the head seat is seated. In addition, since the stopper portion is in contact with the top surface of the screw head and a slight gap is formed between the drive hole and the tip of the engagement portion of the driver bit, the drive hole and the engagement portion are caused by some cause. Even if damage occurs, as long as the stopper portion is in contact with the top surface of the head, there is no adverse effect on the quality determination of screw floating. Furthermore, the standard that regulates the gauge sinking depth of the screw drive hole specifies its allowable error, and if this error is large, it has affected the quality of screw floating. Since the contact of the part with the top surface of the head is used as a condition for determining whether or not the screw is floating, the tolerance of the depth defined in the standard does not affect the determination of whether or not the screw is floating.

  In particular, the drive hole formed in the head of the screw is usually manufactured by forging and is formed by punching with a punch that is a forging tool, but repeated punching is used. Even if the drive hole becomes shallower and the drive hole becomes shallower or a slight protrusion is generated in the drive hole, resulting in variations in the drive hole size, If the driving force is applied to the screw from the engaging part while it is in contact with the top surface and the driver bit has moved to the specified position, it is determined that the head seating surface of the screw is seated and the drive hole is allowed. Even if there is a variation in depth within the error range, a screw floating state does not occur, and a specific effect such as accurate determination of non-defective products and defective products of the assembled product can be obtained.

It is a principal part front view which shows embodiment of this invention. It is a bottom view of FIG. It is a principal part fragmentary sectional front view of a screw. It is a front view which shows the use condition of this invention. It is principal part sectional drawing of the automatic screwing machine which uses this invention. It is principal part sectional drawing of the screw as a prior art example. It is a principal part front view which shows the prior art example of the driver bit used for the screw of FIG.

  The best mode for carrying out the present invention will be described below with reference to FIGS. In FIG. 5, reference numeral 10 denotes a driver bit. The driver bit 10 is integrated with the transmission shaft 2 so that a driving force for applying a predetermined screw tightening torque set in advance to the automatic screw tightening machine 1 is transmitted. Yes. This transmission shaft 2 is connected so that rotation from the rotational drive source 3 is transmitted, and the driver bit 10 has a tip positioned above the catcher 4 that holds the screw 20 supplied for each work cycle, During the screw tightening operation, the screw 20 protrudes from the catcher 4 and is tightened with a screw 20 on a work (not shown). On the other hand, the driver unit 5 including the driver bit 10 is supported by a lifting drive source 6 so as to be lifted and lowered. The driver unit 5 is lifted and lowered along a guide rod 7 arranged in the vertical direction.

  The driver bit 10 that engages with the fitting hole 22 of the head 21 of the screw 20 in this way has the shape shown in FIGS. 1 and 2, and the driver bit 10 rotates from the transmission shaft 2 to the rotational driving force. It is comprised from the axial part 11 connected so that can be transmitted, and the engaging part 12 in the front-end | tip of this axial part 11, and united. The engaging portion 12 has a shape that can be engaged when a driving force is transmitted to a driving hole 22 formed in the head portion 21 of the screw 20, and between the shaft portion 11 and the engaging portion 12. A stopper portion 13 that abuts on the top surface of the head when the engaging portion 12 is engaged with the drive hole 22 is formed. The stopper portion 13 is a flat surface formed on a horizontal cross section perpendicular to the center line of the shaft portion 11.

  Further, in this embodiment, the drive hole 22 formed in the head 21 of the screw 20 fastened by the driver bit 10 is a cross hole set in the JIS standard and has a shape as shown in FIG. ing. Then, as shown in FIG. 4, there is a slight gap between the bottom of the drive hole 22 where the stopper portion 13 is brought into engagement with the top surface of the head of the screw 20 and the tip of the engagement portion 12. It has a configuration with a large gap. In addition, the relationship (D> m) is satisfied between the diameter (D) of the outer circumferential circle of the stopper portion 13 and the diameter (m) of the circumscribed circle of the precursor driving hole 22, and (D) is ( m) is always set larger than m). Further, the engaging portion 12 has a crossing locus circle connecting the crossing corner portion 12b formed by crossing the outer peripheral wall surface 12a having the conical shape and the stopper portion 13 on the same plane. The relationship between the diameter (M) of the circle and the diameter (m) of the circumscribed circle of the drive hole 22 satisfies the relationship (M <m).

  Specifically, this cross hole is a cross-recessed pan head screw in Annex 1 specified in JIS B 1111 and its name is M4. The diameter (m) of the circumscribed circle of the cross hole is 4 The diameter (D) of the outer peripheral circle of the stopper portion 13 and the shaft portion 11 of the driver bit 10 used for this is set to 6 mm. Moreover, the diameter (M) of the cross locus circle is set to 3.5 mm, and by setting the dimensions as described above, the engagement portion of the driver bit is the drive hole 22 with respect to the cross hole. The fastening force that is applied to the screw 20 and applies a predetermined tightening torque to the screw 20 can be transmitted. The setting value of the diameter (M) of the crossing locus circle may be set to 80% or more and less than 100% of the diameter (m) of the circumscribed circle of the drive hole 22 (in this embodiment, 85% is adopted as a preferable value). However, if it is less than this, the engagement area is reduced in the transmission of the fastening force to the drive hole 22, and the drive hole 22 is crushed or the engagement portion 12 of the driver bit 10 is liable to be damaged. On the other hand, even if the center of the drive hole 22 and the center of the engaging portion 12 are slightly shifted, the diameter (D) of the outer circumferential circle of the shaft portion 11 is sufficiently larger than the diameter (m) of the circumscribed circle of the drive hole 22. Therefore, the stopper portion 13 of the driver bit 10 can stably come into contact with the head portion 21 of the screw 20.

  The outer peripheral wall surface 12a having the conical shape is a wall surface in the case where the drive hole 22 is a cross hole, and the drive hole 22 of other shapes has an upright wall, and is limited to a cross hole. Of course, the present invention can also be applied to drive holes 22 of other shapes. In that case, the outer peripheral wall surface 12a is not limited to the conical shape, but may have a cylindrical shape.

  When the screwdriver 10 configured as described above is incorporated into the automatic screwing machine 1 and screwing is performed, the driver bit 10 descends toward the cross hole-shaped drive hole 22 as shown in FIG. When the engaging portion 12 at the tip end of the driver bit 10 is engaged with the drive hole 22 by this descending, the screw 20 is tightened to the workpiece by receiving the rotation of the driver bit 10. In this screw tightening operation, as indicated by a two-dot chain line, the stopper portion 13 of the driver bit 10 comes into contact with the top surface of the head at the same time as the engagement portion 12 enters the drive hole 22. At this time, a slight gap is generated between the bottom of the drive hole 22 and the tip of the engaging portion 12.

  In this way, when the screw 20 is screwed into the workpiece and reaches a predetermined screw tightening torque, the rotational drive source 3 of the automatic screw tightening machine 1 stops and the screw tightening operation is completed. On the other hand, the head seating surface of the screw 20 in this state is seated on the workpiece, and the position of the screw 20 is not detected but a position (non-illustrated) sensor is used to detect the position of the screw. become.

  The present invention is suitable for determining whether or not the seating surface of the screw 20 is securely seated on a part (not shown) or a workpiece in the assembly work of the product, and is easy even if the type of the screw 20 changes. And can be widely applied to screw tightening work having a function of determining whether or not a screw floats.

DESCRIPTION OF SYMBOLS 1 Automatic screwing machine 2 Transmission shaft 3 Rotation drive source 4 Catcher 5 Driver unit 6 Lifting drive source 7 Guide rod 10 Driver bit 11 Shaft part 12 Engagement part 12a Outer peripheral wall surface 12b Crossing corner part 13 Stopper part 20 Screw 21 Head part 22 Drive hole

Claims (3)

Engageable when transmitting driving force to the shaft (11) to which the rotational driving force is transmitted and the driving hole (22) formed integrally with the shaft and formed in the head (21) of the screw (20). In the driver bit consisting of the engaging portion (12),
A stopper portion (13) that contacts the top surface of the head when the engaging portion is engaged with the drive hole is formed between the shaft portion and the engaging portion, and the stopper portion is formed on the top surface of the head of the screw. A gap is formed between the bottom of the drive hole brought into contact with the engagement and the front end of the engagement portion, and the diameter (D) of the outer circumference of the stopper is determined by the circumscribing of the drive hole. Screw lift detection combined use driver bit characterized by being larger than the diameter (m) of the circle.   2. The screw lift detection / use driver bit according to claim 1, wherein the stopper portion is a flat surface formed on a horizontal cross section orthogonal to the center line of the shaft portion.   The engaging portion has a crossing locus circle connecting the crossing corner portion (12b) formed by crossing the outer peripheral wall surface (12a) and the stopper portion on the same plane, and the diameter (M) of the crossing locus circle. 3. The screw lift detection / use driver bit according to claim 1, wherein a relationship of (M <m) exists between a diameter of the circumscribed circle of the drive hole and a diameter (m) of the drive hole.

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