JPH0248182A - Tightening with nut runner - Google Patents

Abstract

PURPOSE:To accurately set the seating point, prevent excessive tightening and greatly improve the tightening accuracy by applying the braking torque as it cancells the inertia force of a nut runner at the point of seating and the completion of the tightening. CONSTITUTION:With a joint part 5 caught by a tightening attachment 3 stuck to the end of the turning shaft of a motor 1, the attachment 3 is turned by the driving force of a motor 1 and then stopped. At this time the braking torque calculated from the expression of T=Id<2>theta/dt<2> (where T standing for braking torque, I for inertia moment of the turning shaft of the motor and theta for the angle of turning) is applied to said shaft in the direction reverse to the turning moment simultaneously with the stop point of current supply to the motor 1 so that the turning shaft 1 of the motor 1 is stopped instantly. As a result, at the time of seating or completion of the seating of the nut runner 9, the turning action thereof is stopped simultaneously when the current supply to the motor is stopped, whereby preventing the excessive tightening.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for tightening a Nando lunch used for automatically tightening bolts, nuts, etc.

Conventionally, automatic assembly technology has been widely used in the assembly work of automobiles, etc., and joining is particularly important work, of which tightening with screws is the most frequently used. A nut runner is used for tightening screws in the above automatic assembly technique, and a specific example thereof will be shown below with reference to FIG. In the figure, (
1) is the motor, (2) is the reducer, (3) is the bolt tightening attachment, (4) is the angle detector, (5) is the bolt, (6) is the NAND, (7) is the washer, ( 8a)
(8b) is two members to be coupled, and the nut runner (9) includes a motor (1), a reduction gear (2), an attachment (3), and an angle detector (4). The motor (1) is the source of force for bolt tightening, and the reducer (2) contains lubricating oil.
A gearbox that smoothly reduces motor rotation and generates large torque, and has a bolt tightening attachment (8) fixed to the tip of its main shaft. The angle detector (4) is
As shown in Figure 3, there are three pairs of N on the rotating shaft of the motor (1).
A cylindrical magnet (4a) consisting of an S pole is connected with its central axis aligned with the upper rotating shaft, and three magnetoresistive elements (4b) (4c) (4d) are arranged around it at a constant pinch angle. When the cylindrical magnet (4a) is rotated,
The surrounding magnetic flux density changes and the magnetoresistive element (4b) (
4c) Since the resistance value of (4d) changes, this is used to output six pulses per rotation and detect the phase. The bolt (5) is threadedly engaged with the NAND (6) via the washer (7) to connect the members (8a) and (8b) to be connected.

In order to tighten the bolt (5) using the nut runner (9), first, as shown in Fig.
a) Overlap (8b) and connect each mounting hole (8ax)
A bolt (5) is inserted through (8b1) through a washer (7) and screwed onto the nand (6). Then, the axotiment (3) of the nut runner (9) is fitted into the head of the bolt (5) to rotate the motor (1). Then,
The bolt (5) is in an unloaded state until the connected members (8a) (8b) are tightened, and the angle detector (4) outputs 6 pulses per rotation as shown in Fig. 4. As shown, it rotates at high speed with a constant current (11). Therefore, when the rotation angle (θ) of the bolt (5) reaches (θ1) and the tightening state is entered, the current (i) increases and (12
), and this moment is taken as the seating point when the bolt (5) enters the tightening state. From this point on, the bolt (5) is rotated at a constant low speed and the preset tightening is completed with the current (
When the current (+) reaches i3), the rotation is stopped.

By the way, according to the above-mentioned Natsutranna (9), Revol 11
5), when the current (i) reaches (i3) and the tightening is completed, even if the rotation of the motor (1) is stopped, inertia acts and the bolt ( 5) could be over-tightened and break. Also, bolt (
5) In order to accurately set the tightening from this point until the end even when the person is seated, the power supply to the motor (1) is stopped at the moment the person is seated, as shown in Figure 5. However, even at this time, the rotation does not stop immediately due to the influence of inertia, resulting in an error in the accuracy of tightening.

In the present invention, a fastening attachment fixed to the tip of a rotating shaft of a motor grips a coupling member, rotates it by motor drive, and then stops it, as described below with reference to Figure 1. do. First, as before, the second
When tightening the bolt (5) with the nut runner (9) shown in the figure, as shown in Fig. 1, when a predetermined input voltage is applied to the motor (1) at the time of starting the nut runner, the angular velocity (ω) does not respond immediately. , gradually rises and reaches a constant value (ωS). Therefore, from the above transient response, the braking torque calculated from the rotational angular acceleration of the motor (1) at startup ((Zo)■: moment of inertia of the motor's rotating shaft, θ: rotational angle) is used to stop power supply to the motor. It is characterized in that it simultaneously applies rotational force in the opposite direction and instantly stops the rotating shaft of the motor.

According to the above-mentioned technical means, when the nut runner (9) is seated or when tightening is finished, the rotation of the nut runner (9) is immediately stopped at the same time as the power supply to the motor (1) is stopped.

The tightening method of the nut runner according to the present invention is calculated using the angular velocity. Then, when the motor (1) is further rotated and the bolt (5) starts to come into contact with the member to be connected and the seating point has arrived, and the power supply to the motor (1) is stopped,
To = I (1, o (However, ■: Moment of inertia of the motor's rotating shaft) Braking l・Luke (To)
is added in the opposite direction to the rotation direction. At this time, the braking torque (
The application time (t) of To) is given by t=kI (where k: externally set constant, ■=the above moment of inertia).

Then, the above-mentioned braking torque (To) is added to the frictional force (C) between the bolt (5) and the seat surface of the coupled member, canceling out the inertial force of the nut runner (9), and the nut runner (9)
will stop immediately and the seating point will be precisely set. next,
From this point on, the nut runner (9) is rotated again to begin tightening the bolt (5), and when the bolt (5) has been tightened by rotating it by the set angle, the power supply to the motor (1) is stopped and the braking torque ( 'l'o) Natsutranna (9)
, the inertial force is canceled out and Natsutranna (
9) can be stopped immediately to prevent the bolt (5) from passing through the line.

Since the present invention automatically tightens bolts and nuts using a nut runner, braking torque is applied to cancel the inertia of the nut runner when seating and when tightening is completed, so that the timing of seating is accurate. It is also possible to prevent wires from running through the wire, greatly improving the tightening accuracy.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the temporal change in rotational angular velocity when starting the Natsu runner, Fig. 2 is a schematic side sectional view showing a conventional Natsu runner, and Fig. 3 is a plan view of the angle detector included in the Natsu runner shown in Fig. 2. , FIG. 4 is a graph showing the change in motor current value with respect to the rotation angle of the nut runner shown in FIG.
The figure is a graph showing changes in the rotational speed of the NAND runner shown in FIG. 2 with respect to the rotational angle. (1) - Motor, (3) - Attachment, (
5)(6)--Connecting member. Patent applicant Sanyo Kiko Co., Ltd.

Claims (1)

[Claims] (1) After gripping the coupling member with a tightening attachment fixed to the tip of the motor's rotating shaft and rotating it by motor drive, when stopping it, T=I(d^2θ/dt^
2) (T: braking torque, I: moment of inertia of the motor's rotating shaft, θ: rotation angle) is applied in the opposite direction to the rotational force at the same time as the power supply to the motor is stopped. A method for tightening a nut runner, which is characterized by instantaneously stopping a rotating shaft.