JP5437706B2 - Temporary tightening judgment method - Google Patents

Description

  The present invention relates to a determination method when a nut (bolt) is temporarily tightened by a tightening device.

  Management of tightening force when a nut (bolt) is tightened by a tightening device such as a nut runner is generally performed using a torque sensor.

  For example, in Patent Document 1, the first reference torque, the second reference torque, and the third reference torque are set, and the first reference torque detects that the nut is in contact with a member to be tightened such as a washer in a normal state. The stop signal is output when the time until the second reference torque is reached from the time of contact or the time until the third reference torque is reached exceeds the set value.

Patent Document 2 describes that a torque rate, which is a tightening torque per tightening angle, is calculated, and a tightening failure is determined when the torque rate exceeds a set value.

In Patent Document 3, a tightening amount (rotation angle) to be further tightened after the nut is seated is set, and this rotation angle is detected by a pulse generator attached to the servo motor. It is disclosed to detect whether the torque exceeds a set value before a predetermined time elapses.

JP-A 63-237874 Japanese Utility Model Publication No. 2-33931 Japanese Unexamined Patent Publication No. 64-16379

Mistakes in tightening the nut with the tightening device include biting that the bolt axis does not coincide with the nut axis and the nut engages with the bolt diagonally, and idle rotation (whether the nut does not bite into the bolt) There is no nut in the socket).

In any of the methods disclosed in Patent Documents 1 to 3, the output of the torque sensor is compared with a set torque value, and when the set torque value is exceeded, it is determined that the nut is seated. It is difficult to distinguish both easily.

In addition, the contents disclosed in Patent Documents 1 to 3 are based on the premise that a single tightening device performs from the start of tightening to the end of tightening. However, when mounting tires on automobiles, for example, the tact time for mounting the tires must be shortened, and work efficiency can be improved by having one tightening device perform from nut mounting to tightening as in the prior art. Becomes worse. In this case, a fastening device for temporary fastening and a fastening device for final fastening are prepared. However, the above-described prior art does not show the determination about the completion of temporary fastening in the fastening device for temporary fastening.

Here, temporary tightening refers to tightening to such an extent that a tightening member such as a nut is seated against the object to be tightened, in other words, the tightening operation is completed without confirming the tightening torque after tightening. The tightening operation means that the state in which the temporary tightening has been normally performed means a state in which a tightening member such as a nut is seated on the tightening target, in other words, the tightening member is not caught or idle. A state that does not occur. The final tightening means fixing a tightening target by further applying a tightening force to the temporarily tightened tightening member. After performing the temporary tightening operation, the tightening operation is completed by applying a predetermined tightening torque by the final tightening operation.

In particular, there are usually 4 or 5 bolts in the hub to which the tire is attached, and 4 or 5 nuts are tightened at the same time. In this case, how to determine the temporary tightening, There is no indication in the prior art.

In order to solve the above problems, the present invention provides a temporary tightening determination method using a tightening device that is rotated by a servo motor, wherein the amount of rotation of the servo motor is counted by the number of pulses, and the amount of change in the pulse becomes a predetermined value or less. If the number of pulses up to this time is less than or equal to the first set value, it is determined that the bite is engaged, and the value between the first set value and the second set value is normal. It is determined that the temporary tightening has been performed, and it is determined that the servo motor is idle when the number of pulses is equal to or greater than the second set value without stopping.

In the case where a plurality of nuts (bolts) are temporarily tightened simultaneously by a tightening device, a plurality of pulses can be used as long as the number of pulses until the servo motor stops is between the first set value and the second set value. It is determined that normal temporary tightening has been performed without determining whether all of the tightening members are seated.

By doing in this way, it can be determined efficiently without waste. However, if even one of a plurality of nuts is determined to be bitten or idle, it is determined that the provisional tightening is defective, the nut is removed by rotating the tightening device in the reverse direction, and the tire is paid out of the device process. .

According to the present invention, it is possible to reliably determine whether or not temporary tightening by the tightening device has been correctly performed by a servo motor including a pulse generator without using an expensive torque sensor or rotation angle detector.

According to the present invention, when a plurality of nuts are tightened at the same time, if it is determined that at least one nut is caught and idle, a temporary fastening NG determination is made and all nuts are bitten or When it is determined that there is no idling, it is possible to make a temporary tightening OK determination even if all the nuts are not seated, so that the tightening efficiency is greatly improved.

Overall view of a robot that implements the temporary tightening determination method according to the present invention Detailed flow chart of temporary tightening determination method according to the present invention Graph showing the relationship between servo motor resolution (pulses) and biting, idling and normal tightening judgments

Embodiments of the present invention will be described below with reference to the accompanying drawings.
The robot 1 is an articulated robot composed of a plurality of arms, and a tire gripping jig 2 is provided at the tip of the arm, and a servo motor 3 having a pulse generator is attached to the back side of the tire gripping jig 2. Yes.

  A sun gear 5 is fixed to the shaft 4 of the servo motor 3, and a plurality of planetary gears 6 are engaged with the sun gear 5, and a socket 7 of the tightening device is rotated by the planetary gears 6.

  A nut 8 is held in the socket 7 by a magnet, the tire 9 held by the tire gripping jig 2 is moved with respect to the hub 10, and the hub bolt 11 is inserted into the tire wheel, and the socket 7 of the tightening device is inserted. And the nut 8 is temporarily tightened to the hub bolt 11.

  In the case of an automobile, there are usually four or five hub bolts 11, and in this embodiment, nuts 8 are temporarily tightened on the hub bolts 11 at the same time.

Next, a determination method in the temporary tightening of the nut using the articulated robot 1 will be described. FIG. 2 is a detailed flowchart of the temporary tightening determination method according to the present invention, and FIG. 3 is a graph showing the relationship between the resolution (pulse) of the servo motor and the determination of biting, idling and normal tightening.

As shown in FIG. 2, the determination method according to the present invention determines whether or not the user is seated based on the number of pulses of the servo motor. That is, the determination is performed using the function of the servo motor without using a conventional torque sensor or rotation angle sensor.

Specifically, as shown in FIG. 2 and FIG. 3, the number of pulses of the current value (A) is captured after the temporary tightening is started. Next, the number of pulses of the current value (B) after 0.02 seconds is taken in, and it is calculated whether or not B−A <50.

In the case of B−A ≧ 50 pulses, the above is repeated five times (0.1 seconds) and B−A <50 pulses, that is, 2500 pulses / second, in other words, Since the resolution (pulse) of the servo motor is 4096 pulses per rotation of the shaft, it is determined that the servo motor 3 has stopped when 2500 pulses / second = 0.61 rotations / second (36.6 rpm).

As described above, the current value (pulse) of the servo motor 3 is monitored, and if it is determined that the amount of change in the pulse has decreased five times continuously and the rotation has stopped, the current pulse value (C) at that time Capture.

When the current pulse value (C) is C <20000 (first setting value), it is determined that the bite is present, and when C ≧ 100000 (second setting value), it is determined that the rotation is idle.
In the case of 20000 ≦ C <100,000, it is determined that the temporary fastening has been normally performed.

The grounds for the numerical values of the first set value and the second set value are as follows. That is, if the separability (pulse) of the servo motor is set to 4096 pulses / rotation, the tightening length: 18 mm, and the pitch: 1.5 mm, the seat is seated at 12 rotations. Assuming 5 rotations, about 20000 pulses are the lower limit. If the upper limit is set to 24 rotations in consideration of the idling before tightening, about 100,000 pulses will be the upper limit value.

Therefore, the first set value and the second set value can be arbitrarily changed according to the tightening length and pitch.

In the embodiment, a case where the nut 8 is temporarily tightened simultaneously on a plurality (four) of hub bolts 11 is shown. In this example, if the number of pulses until the servo motor stops is less than the lower limit value or exceeds the upper limit value, it is judged that the tightening is defective, and the tightening device is rotated backward to remove all nuts. , Pay out the tires outside the equipment process.

In addition, the nut tightening can be divided into temporary and final tightening, and the respective tact time can be shortened by performing each with a different robot, but the process does not necessarily have to be divided into temporary and final tightening. .

The temporary tightening determination method according to the present invention can be effectively used in a tire mounting process of an automobile assembly line.

DESCRIPTION OF SYMBOLS 1 ... Articulated robot, 2 ... Tire holding jig, 3 ... Servo motor, 4 ... Servo motor shaft, 5 ... Sun gear, 6 ... Planetary gear, 7 ... Socket of clamping device, 8 ... Nut, 9 ... Tire, 10 ... hub, 11 ... hub bolt.

Claims (2)

In the temporary tightening determination method using a tightening device rotated by a servo motor, the amount of rotation of the servo motor is counted by the number of pulses, and the amount of change in pulses within a predetermined time is less than or equal to a predetermined value. Is determined to have stopped , and if the number of pulses up to this time is less than the first set value, which is the lower limit value, it is determined that the bite has occurred, and if the value is between the first set value and the second set value, normal A temporary tightening determination method characterized in that it is determined that a temporary tightening has been performed, and a case where the number of pulses is equal to or greater than a second set value that is an upper limit value without stopping the servomotor is determined to be idle. 2. The temporary tightening determination method according to claim 1, wherein the measurement of the change amount of the pulse within the predetermined time is performed a plurality of times, and it is determined that the servo motor has stopped on the condition that the pulse change amount has continuously decreased. Temporary fastening determination method characterized by the above.

Images