JP2023173708A - Screw fastening machine - Google Patents

Abstract

To provide a screw fastening machine which can efficiently suck and hold a screw and prevents impact torque from increasing.SOLUTION: A screw fastening machine comprises a driver bit 37 constituted to be able to rotate by receiving the drive of a rotation drive source 35 and a screw guide 33 containing the driver bit 37 to be rotatable. The screw guide 33 is constituted to be rotatable to a housing 32 to which negative pressure means is continuous and keeps a suction member 34 having a taper-shaped pad part mounted on an opening end thereof, where the suction member 34 is able to relatively rotate to the driver bit 37. This screw fastening machine comprises the suction member 34 and can efficiently suck and hold a screw S. Since the suction member 34 rotates to the driver bit 37 to prevent moment of inertia of the suction member 34 from being added to the screw S, an increase of impact torque can be prevented.SELECTED DRAWING: Figure 2

Description

The present invention relates to a screw tightening machine for tightening a screw onto a workpiece.

Conventionally, as a screw tightening machine for tightening a screw onto a workpiece, the one disclosed in Patent Document 1 is known. This screw tightening machine is equipped with a driver bit that can fit into the head of a screw, a screw guide that is arranged to enclose the driver bit, and is connected to a negative pressure mechanism, and the open end of this screw guide The structure is such that the screws are held by suction and transported to the workpiece, and then the screws are tightened. However, conventional screw tightening machines have gaps between the screw guides and the screws that allow air to pass through, making it difficult to maintain negative pressure and requiring a relatively powerful negative pressure mechanism, making them inefficient. There was a problem.

In order to solve the above problems, a screw tightening machine disclosed in Patent Document 2 has been created. This screw tightening machine is equipped with a suction part at the tip of the screw guide with a tapered lower end, and since this suction part is closed by the head of the screw, there is no gap for air to pass through, making it more efficient. It was possible to suction the screws well. In addition, the suction part is configured to be able to engage with the driver bit and rotate as a unit, and has the advantage that no friction occurs between the suction part and the screw, and the screw is less likely to be damaged. Ta.

Publication of JP-A-2002-178231 JP 2021-154463 Publication

However, in the screw tightening machine described in Patent Document 2, since the suction part and the driver bit are engaged as described above, the moment the screw seats on the workpiece and stops rotating, the driver bit is attached to the screw. Both the moment of inertia and the moment of inertia of the suction part are added. Furthermore, the suction portion has a larger outer diameter than the driver bit, and its moment of inertia tends to be larger than that of the driver bit. In other words, in the screw tightening machine described in Patent Document 2, since the suction part and the driver bit are engaged, the moment the screw is seated, a tightening torque (hereinafter referred to as impact torque) is generated due to the moment of inertia. tends to increase. As a result, the impact torque increases and exceeds the proper tightening torque, causing damage to the screws and workpieces. On the other hand, if the rotational speed is reduced in order to reduce the moment of inertia, the problem arises that the time required for tightening the screws becomes longer and the work efficiency decreases.

The present invention was created in view of the above problems, and an object of the present invention is to provide a screw tightening machine that can efficiently attract and hold screws and is configured so that the impact torque generated when the screw is seated does not increase. To achieve this object, the present invention provides a driver bit that has an engaging portion that engages with a screw and is configured to be rotatable when driven by a rotational drive source, and a screw that rotatably houses the driver bit. A screw tightening machine comprising a guide, a housing that connects the screw guide and a negative pressure means, and an adsorption member attached to an open end of the screw guide, wherein the housing rotatably holds the screw guide. The suction member is configured to be rotatable relative to the driver bit. Preferably, the portion of the suction member that comes into contact with the screw is made of an elastic member. Further, it is preferable that the hole diameter of the suction port formed through the center of the suction member is set to be equal to or smaller than the outer diameter of the driver bit. Furthermore, it is preferable that the suction member has a ring-shaped fitting part, and the screw guide has a holding groove that fits into the fitting part. Further, it is preferable that the screw guide is configured to be movable relative to the housing in the axial direction. Furthermore, it is preferable that the driver bit is connected to the rotary drive source so as to be movable relative to the rotary drive source.

According to the above invention, since the suction member is provided at the tip of the rotatably configured screw guide, it is difficult to form a gap between the screw and the suction member, thereby improving adhesion. This makes it easier to maintain negative pressure within the screw guide and housing. This has advantages such as being able to efficiently hold the screws by suction. Further, the suction member is configured to be rotatable with respect to the driver bit, and when the screw is seated, the suction member and the screw guide rotate with respect to the driver bit and the screw, so that almost no moment of inertia is transmitted to the screw. This has the advantage that impact torque does not increase and screws can be tightened with high precision. Furthermore, since the portion of the suction member that comes into contact with the screw is made of an elastic member, there is an advantage that no friction marks are generated on the surface of the screw when the suction member rotates relative to the screw. Furthermore, since the hole diameter of the suction port formed through the center of the suction member is set to be smaller than the outer diameter of the driver bit, friction also occurs between the suction member and the driver bit. Therefore, when tightening a screw, the suction member can rotate together with the driver bit and the screw, which has advantages such as suppressing wear of the portion that comes into contact with the screw. Furthermore, the suction member and the screw guide are fitted with each other through the annular fitting portion and the holding hole, and the suction member can be displaced from the screw guide in the rotational direction, further reducing impact torque. There are also advantages such as being able to Further, since the screw guide and the driver bit are configured to be movable relative to the housing and the rotational drive source in the axial direction, there are advantages such as being able to soften the impact at the moment the screw contacts the workpiece.

FIG. 1 is a side view showing a screw tightening machine according to the present invention. FIG. 1 is an enlarged partial cross-sectional side view of a main part showing the structure of a screw tightening machine according to the present invention. 2 is an enlarged partial cross-sectional side view of a main part showing the structure of a screw tightening machine according to the present invention, (a) is an enlarged view of part A in FIG. 2, and (b) is a line BB in (a). FIG. FIG. 3 is an enlarged cross-sectional side view of a main part of another embodiment of a screw tightening machine according to the present invention. FIG. 5 is an enlarged cross-sectional side view of main parts showing a state transitioned from FIG. 4 to the next state.

Embodiments of the present invention will be described below based on the drawings. In FIG. 1, 10 is a screw tightening machine that fastens a screw S, which is an example of a fastening component, to a workpiece (not shown). The screw tightening machine 10 includes an articulated robot 20 that is an example of a moving means, a driver unit 30 that moves horizontally and vertically in response to the drive of the articulated robot 20, and controls the driving of the moving means and the driver unit 30. It has a control section 40.

The articulated robot 20 includes a plurality of arm sections 21 and a plurality of joint sections 22 that connect these arm sections 21. The joint section 22 of the multi-joint robot 20 is provided with a swing drive source that swings the arm section 21 and a rotation drive source that rotates the arm section 21, and these drives are controlled by the control section 40. has been done. Therefore, during driving, the driver unit 30 can be transported to any position and in any direction.

The driver unit 30 has a connecting plate 31 connected to the tip of the articulated robot 20, as shown in FIG. 2, and a hollow cylindrical housing 32 is fixed to the connecting plate 31. . The housing 32 includes a guide holder 321 at its lower end, and a substantially hollow cylindrical screw guide 33 is rotatably held in the guide holder 321 via a ball bearing 322. This screw guide 33 has an annular holding groove 331 formed in its inner wall near its lower open end, and a substantially annular suction member with a suction port 341 passing through the center of the holding groove 331. 34 are fitted. Further, a hose joint 323 connected to the negative pressure means is attached to the housing 32, and a sealing material 324a such as a packing, The gap is hermetically sealed by the gap 324b. With these structures, when the negative pressure means is driven, the insides of the housing 32 and the screw guide 33 become negative pressure, and air can be taken in from the lower end opening of the screw guide 33.

As shown in FIG. 3(a), the suction member 34 includes an annular portion 342 that fits into the holding groove 331, and a tapered pad portion 343 continuous to the distal end side of the annular portion 342. has been done. This suction member 34 is arranged so that a pad portion 343 protrudes from the screw guide 33, and the outer diameter of the pad portion 343 is approximately the same as the outer diameter of the screw guide 33. At least the pad portion 343 of the suction member 34 is made of an elastic member such as resin, and is configured to be deformable according to the shape of the head of the screw S in contact with the suction member when the suction member 34 holds the screw S by suction. In this embodiment, the suction member 34 is a rubber seal for a rotating shaft generally called a V-ring or a V-packing, and is entirely made of rubber.

Further, an AC servo motor 35 (hereinafter referred to as a fastening motor 35), which is an example of a rotational drive source, is fixed on the housing 32 so that its output shaft 351 is inserted into the housing 32. An output shaft 351 of the fastening motor 35 is connected to a shaft joint 36 that can rotate integrally with the shaft joint 36, and a driver bit 37 is suspended from the shaft joint 36 by a pin 361. This driver bit 37 is rotatably fitted into the shaft coupling 36, and has an engaging portion 371 that can fit into the drive hole of the screw S at its tip. Further, in the driver bit 37, the diameter of the engaging portion 371 is set to be the same as or slightly larger than the hole diameter of the suction port 341 of the suction member 34 so that the engaging portion 371 is inscribed in the suction port 341 of the suction member 34. has been done. Further, the trough portion 372 of the engaging portion 371 is designed such that its upper end is above the upper surface of the pad portion 343, as shown in FIGS. 3(a) and 3(b). The gap between the portion 372 and the suction port 341 is configured to act as a ventilation path.

The articulated robot 20 and the fastening motor 35 are connected to a control section 40, and their driving is controlled by the control section 40. The control unit 40 is also connected to external devices such as a screw supply device that supplies the screw S to a predetermined screw standby position and the negative pressure means, and is configured to be able to control the driving of these external devices.

Next, the operation of the screw tightening machine 10 configured as described above will be explained. When the activation signal is input, the control unit 40 drives an external screw supply device to supply the screws S to a predetermined screw standby position. When the screw S is supplied to the screw standby position, the control unit 40 drives the articulated robot 20 to move the driver unit 30 above the screw standby position. When the driver unit 30 reaches the screw standby position, the control unit 40 drives the fastening motor 35 to rotate the driver bit 37 at low speed and raises the driver unit 30 to a height where the suction member 34 contacts the screw S. lower it. Thereby, when the lower ends of the suction member 34 and the driver bit 37 come into contact with the screw S, the engaging portion 371 of the driver bit 37 fits into the drive hole of the screw S. The control unit 40 drives the negative pressure means to attract and hold the screw S at the same time as the driver bit 37 starts rotating or after the driver bit 37 is fitted with the screw S. At this time, the pad part 343 is made of an elastic member and deforms according to the head of the screw S, so that the head and the pad part 343 come into close contact with each other, so that no gap is created through which air can pass. This makes it easier to maintain negative pressure, and even with a relatively weak negative pressure mechanism, it is possible to suction and hold the screw S sufficiently strongly, improving work efficiency.

After holding the screw S by suction as described above, the control section 40 stops the fastening motor 35 and drives the articulated robot 20 to move the driver unit 30 onto the workpiece. When the driver unit 30 reaches the workpiece, the control section 40 drives the fastening motor 35 and the moving mechanism to rotate the driver bit 37 at high speed and low torque and lower the driver unit 30 toward the workpiece. Thereby, the screw S is fastened to the workpiece. At this time, since the screw guide 33 is configured to be rotatable with respect to the guide holder 321, the frictional force generated between the suction member 34, the driver bit 37, and the screw S is applied to the suction member 34 and the screw guide. 33 becomes rotatable together with the driver bit 37 and screw S. Thereby, wear of the adsorption member 34 is suppressed. In addition, since no gap is created between the screw S and the adsorption member 34 and air is prevented from entering, the negative pressure inside the screw guide 33 can be maintained. As a result, the screw S is prevented from falling off from the suction member 34.

During the screw tightening operation as described above, the screw S stops rotating when it is seated on the workpiece. However, since the driver bit 37, screw guide 33, etc. are rotating at high speed and low torque as described above until just before the screw S is seated, they have a moment of inertia in the rotational direction and cannot be stopped immediately. . Therefore, a moment of inertia in the tightening direction is applied to the screw S in the stopped state via the driver bit 37. At this time, since the suction member 34 and the driver bit 37 are not engaged and are configured to be relatively rotatable, the pad portion 343 slides on the screw S and the driver bit 37, and the pad portion 343 is attached to the screw S. The moment of inertia of the screw guide 33 is hardly transmitted. As a result, the moment of inertia of the screw guide 33 and suction member 34, which have a larger outer diameter and a larger moment of inertia than the driver bit 37, is hardly transmitted to the screw S. Therefore, the tightening torque (hereinafter referred to as impact torque) due to the moment of inertia added to the screw S at the moment of seating does not increase, and the impact torque can be prevented from exceeding the appropriate tightening torque. As a result, the impact torque does not impede accurate screw tightening or damage the screw S or the workpiece. At the same time, since the impact torque is difficult to increase, the driver bit 37 can be rotated at high speed just before or until the screw S is seated, which has the advantage of shortening the cycle time. In addition, since the suction member 34 is made of a material such as resin that is softer than the screw S, when the suction member 34 rotates relative to the screw S, even if it rubs against the suction member 34, the head surface of the screw S No damage will occur.

Note that when the screw is seated, the adsorption member 34 has a structure in which its annular portion 342 fits into an annular holding groove 331 formed on the inner wall of the screw guide 33. It is also possible to rotate relative to each other. Therefore, although the suction member 34 normally rotates together with the screw guide 33, it can separate from the rotational movement of the screw guide 33 when an unexpectedly large force is applied and the screw guide 33 tries to rotate excessively. . As a result, even if the screw guide 33 should rotate excessively, the impact torque due to the rotation will not be transmitted to the screw S, thereby preventing damage to the screw S, the workpiece, etc.

After the screw S is seated as described above, the control unit 40 rotates the driver bit 37 at low speed and high torque to tighten the screw S with an appropriate tightening torque. At this time, since the impact torque does not exceed the appropriate tightening torque as described above, the screw S can be tightened with the appropriate tightening torque. Thereafter, the control unit 40 drives the articulated robot 20 to transport the driver unit 30 to the initial standby position.

As described above, the suction member 34 causes the screw S, driver bit 37, and screw guide 33 to rotate together due to the friction generated between them, and therefore gradually wears out when used for a long period of time. At this time, since the suction member 34 is structured to fit into the holding groove 331 of the screw guide 33, only the suction member 34 can be easily replaced. Furthermore, by using a V-ring, which is a common component, as the adsorption member 34, it can be replaced at low cost.

Further, the screw tightening machine 10 is configured such that the outer diameter of the driver bit 37 is approximately the same as the hole diameter of the suction port 341 of the suction member 34, and the trough 372 of the engaging portion 371 acts as a ventilation path. Therefore, if the screw S has a head whose outer diameter is larger than the hole diameter of the suction port 341, it is possible to suction and hold the screw guide 33 and the suction member 34 without replacing them. This eliminates the need for replacement work and improves work efficiency. Furthermore, as mentioned above, the screw S having a head outer diameter larger than the outer diameter of the screw guide 33 can also be suctioned, so if the head of the screw S is placed in a place, the screw S can be suctioned and held until the screw S is seated. It is possible to conclude the contract while Therefore, as in the conventional screw tightening machine shown in Patent Document 1, the screw guide 33, which is larger than the outer diameter of the screw S, can suction and hold the screw and tighten it even in a narrow blind hole that cannot be entered. Become. In addition, in the case of a screw tightening machine as shown in Patent Document 1, unless air can flow vigorously, the screw S cannot be held by suction, so even if the screw guide 33 can enter the blind hole, the suction will not occur in the blind hole. The force of the screw S was weakened and the screw S often fell off. However, in the present screw tightening machine, since the adsorption member 34 is sealed and there is no need for air to flow, it is possible to tighten the screw S without falling out even in a blind hole or the like. Moreover, since the screw S does not fall off, there is no need to refit the bit and the screw S, and the cycle time can be stabilized in a short period of time.

Further, during the above-mentioned fastening operation, the control section 40 may stop the negative pressure means while the screw S and the workpiece are being screwed together to release the negative pressure in the screw guide 33. In this case, when the screw S starts to be fastened, the screw S can be held by suction to stabilize its posture, but when the screw S is seated, the adhesion between the suction member 34 and the screw S is released, so the suction member 34 can easily slide. This makes it possible to further weaken the impact torque, making it possible to tighten screws with higher precision. In addition, since the negative pressure means is stopped while the lower end opening of the screw guide 33 is closed by the screw S as described above, dust accumulated on the work surface from the lower end opening of the screw guide 33 and There is no possibility of sucking up chips, etc. that are generated at times. Therefore, it is possible to prevent the screw guide 33 and the inside of the housing 32 from being contaminated by the dust and chips.

Hereinafter, a driver unit 30' which is another embodiment of the present invention will be described based on FIGS. 4 and 5. As shown in FIG. 4, this driver unit 30' is configured such that the guide holder 321' is movable up and down with respect to the housing 32. A biasing spring 325 that biases the housing 32 in a direction away from the housing 32 is contained therein. Further, the shaft joint 36 has an elongated hole extending in the vertical direction, and the pin 361 is fitted into the elongated hole. Therefore, the driver bit 37 can move up and down by an amount equivalent to the length of the elongated hole, and is always urged downward by a cushion spring 362 enclosed within the shaft joint 36. As shown in FIG. 5, the screw tightening machine 11 configured in this manner can absorb the impact generated at the moment the screw S contacts the workpiece by bending the biasing spring 324 and the cushion spring 362. It is possible to prevent damage to the thread S thread or workpiece due to impact.

Note that the screw tightening machine 10 according to the present invention is not limited to the one described above, and various changes can be made without departing from the spirit of the invention. For example, the movement mechanism is not limited to a multi-jointed robot arm as shown in Fig. 1, but may be any type of mechanism, such as a rectilinear robot that can reciprocate in the horizontal direction and a lifting mechanism that drives in the vertical direction. It's okay. Furthermore, the engaging portion 371 of the driver bit 37 is not limited to a cross shape, but may have other non-circular shapes such as a hexagonal shape or a hex lobe shape, as long as there is a gap between the engaging portion 371 and the suction port 341 to allow ventilation. There's no problem.

10... Screw tightening machine 30... Driver unit 32... Housing 321... Guide holder 33... Screw guide 331... Holding groove 34... Suction member 341... Suction port 342... Annular part 343... Pad part 35... Fastening motor 37... Driver bit 371 … Engagement part S … Screw

Claims (6)

A driver bit having an engaging portion that engages with a screw and configured to be rotatable by being driven by a rotational drive source; a screw guide rotatably containing the driver bit; the screw guide and negative pressure means; A screw tightening machine including a housing that connects the screw guide continuously, and a suction member attached to an open end of the screw guide, wherein the housing rotatably holds the screw guide, and the suction member holds the screw guide with respect to the driver bit. A screw tightening machine characterized by being configured to be able to rotate relative to each other. The screw tightening machine according to claim 1, wherein a portion of the suction member that comes into contact with the screw is made of an elastic member. 3. The screw tightening machine according to claim 2, wherein the hole diameter of the suction port formed through the center of the suction member is set to be equal to or smaller than the outer diameter of the driver bit. The screw tightening device according to claim 1, wherein the suction member has an annular fitting portion, and the screw guide has a holding groove that fits with the fitting portion. Machine. The screw tightening machine according to any one of claims 1 to 4, wherein the screw guide is configured to be movable relative to the housing in an axial direction. The screw tightening machine according to claim 5, wherein the driver bit is connected to the rotary drive source so as to be movable relative to the rotary drive source in an axial direction.

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