JPH0699322A - Gall detecting method in automatic screw fastening apparatus and device therefor - Google Patents

Abstract

PURPOSE:To surely detect gall caused to an automatic screw fastening apparatus by bitting foreign matters, poor screws and the like. CONSTITUTION:It is affirmed that the socket 2 of an automatic screw fastening apparatus is fitted onto the head of a bolt 1, and concurrently the tip end of the bolt 1 is engaged with the screw hole of a nut 5. Time (seating time) TMreal which has elapsed since the aforesaid affirmation was made till torque is increased up to seating torque Tseat set in advance, and/or the rotation angle thetareal of the bolt 1 are compared with the lower limit value TMmin of seating time set advance and/or the lower limit value thetamin of the seating angle. And when the seating time TMreal and/or the seating angle thetareal are found to have been lower than the lower limit value TMmin and/or the lower limit value thetamin, it is judged that gall takes place.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a galling detection method and device for tightening a screw using an automatic screw tightening machine (nut runner).

[0002]

2. Description of the Related Art FIG. 3 shows a general torque curve when a nut runner is used to tighten a screw. After fitting the nut runner socket into the bolt head,
The nut runner is started, and at the same time, measurement of the tightening time by the internal timer attached to the nut runner or the rotation angle of the bolt by the angle encoder is started. Screw the bolt at high speed to the seating point (sheeting point, SP) where the seating surface of the bolt presses against the work with a predetermined seating torque, and when the seating point (SP) is reached, apply the brake to stop the motor and screw it in. , The motor is restarted at a relatively low speed, and the screwing operation is continuously executed until the preset tightening completion point is reached.

In the automatic tightening process of such a bolt, for example, the thread of the bolt is incomplete, the bolt enters obliquely with respect to the female thread, or foreign matter is caught between the seat surface of the bolt and the workpiece to be tightened. If they get stuck (these phenomena are collectively referred to as “galling”), the torque increases even though the tightening is not actually completed, so it is erroneously judged as if the tightening was completed. I will end up. Therefore, as shown in FIG. 4, the time (seat time) until the seating point (SP) is recorded until the seating point (SP) is recorded when the tightening starts, that is, when the torque is zero, rises to the preset seating torque (Tseat) or the bolt. The rotation angle (seating angle) of is measured, and the measured value (time or angle)
Is the preset lower limit of seating time (TMmin.)
Alternatively, when the seat angle falls below the lower limit value (θmin.), It is determined that galling has occurred.

[0004]

In the above conventional method, for example, when the nut runner is started before the head of the bolt is accurately fitted in the socket of the nut runner, as shown in FIG.
As shown in Fig. 4, when the tip of the bolt engages with the screw hole and the rotation amount of the nut runner and the screwing amount of the bolt start to correspond to each other, that is, before reaching the fitting point (S), the idling area (A) of the bolt is Occur. Therefore, the measured value of the sitting time or the sitting angle includes a portion corresponding to the idling area (A), a measurement error occurs, and it becomes impossible to accurately detect galling.

An object of the present invention is therefore to ensure that galling can be reliably detected in automatic screw tightening.

[0006]

SUMMARY OF THE INVENTION As a means for solving the above problems, the present invention, when bolting a work using an automatic screw tightening machine, starts the automatic screw tightening machine so that the socket of the automatic screw tightening machine is bolted. Check that the bolt tip engages with the screw hole and that the bolt tip engages with the screw hole, and measure the time from when the above confirmation is made until the seating torque set in advance is reached, and the measured value is set in advance. When the measured value is below the lower limit value, it is determined that galling has occurred (claim 1).

According to a second aspect of the present invention, when the work is bolted by using the automatic screw tightening machine, the automatic screw tightening machine is started so that the socket of the automatic screw tightening machine fits with the head of the bolt and the bolt tip end. Is engaged with the screw hole, the rotation angle of the bolt is measured from the time when the above confirmation is made until the seating torque set in advance is reached, and the measured value is measured for the seating angle set in advance. It is characterized in that, when compared with the lower limit value, when the measured value falls below the lower limit value, it is determined that galling has occurred.

According to a third aspect of the present invention, when the work is bolted using the automatic screw tightening machine, the automatic screw tightening machine is started so that the socket of the automatic screw tightening machine fits with the head of the bolt and the tip of the bolt. Is engaged with the screw hole, the time from when the above confirmation is made until the preset seating torque is reached and the rotation angle of the bolt are measured, and both measured values are preset. It is characterized by comparing with the lower limit value of the sitting time and the lower limit value of the sitting angle, and when any of the above measured values is below the lower limit value, it is determined that galling has occurred.

The invention of claim 4 is the invention of claim 1, 2 or 3.
In the invention of, the position of the socket when the socket of the automatic screw tightening machine is fitted with the head of the bolt and the tip of the bolt is engaged with the screw hole is determined in advance, and when the socket is in this position, The socket is fitted with the head of the bolt, and it is determined that the tip of the bolt is engaged with the screw hole.

According to the invention of claim 5, there is provided a rotary driven socket capable of having an advanced position where the tip is engaged with the head of the bolt and a retracted position separated from the head of the bolt. An automatic screw tightening machine according to claim 4, wherein the automatic screw tightening machine is provided with a sensor that sends a signal when the socket at the advanced position is detected. Can be used.

[0011]

Operation: The time from when the socket is fitted with the head of the bolt and when the tip of the bolt is engaged with the screw hole until the preset seating torque is reached (seat) Start of counting seating time) and / or angle (seating angle), and determine that galling occurs when the lower limit of seating time and / or lower limit of seating angle is set in advance. By
It will be ignored while the socket or bolt is idling, and any galling will be reliably detected.

Confirmation that the socket is fitted with the head of the bolt and the tip of the bolt is engaged with the screw hole is made in the state where the socket is fitted with the head of the bolt and the tip of the bolt is engaged with the screw hole. The position of the socket, ie
This can be performed by previously determining the position where the rotation amount of the nut runner and the screwing amount start to correspond to each other and detecting that the socket is at this position. In other words,
The above confirmation is performed by the position of the socket in the advancing / retreating direction. Therefore, in the detection device, a sensor that is set to be ON or OFF when the socket at the above position is detected is arranged.

Needless to say, it should be judged that the galling has occurred even when the preset seating torque is reached before the engagement between the bolt and the nut is confirmed.

[0014]

Embodiments of the present invention will be described below with reference to FIGS. In the following description, the same contents as those in FIGS. 3 to 5 showing the prior art will be denoted by the same reference numerals or reference numerals, and the description thereof will be omitted.

In FIG. 1, a bolt (1) whose head is fitted in a shaft hole (2A) formed at the tip of a socket (2) of an automatic screw tightening machine, that is, a nut runner (10), is a workpiece to be tightened. The state is shown in which it is about to be screwed into the screw hole of the nut (5) welded and fixed to the lower surface of (4B). As shown in FIG. 1, a non-contact type detector is arranged on the side of the movement path of the socket (2) at a predetermined distance from the outer peripheral surface of the socket (2) as position detecting means in the advancing and retracting direction of the socket (2). It is set up. A proximity switch (3) is illustrated in the drawing, and this proximity switch (3) is ON while detecting the socket (2), and the socket (2) is connected to the head of the bolt (1). It is set so that it is turned off when the tip of the bolt (1) is advanced to a position where it engages with the screw hole of the nut (5) while being fitted and separated from the proximity switch (3). This allows the proximity switch (3)
The OFF signal can be used as a confirmation signal that the socket (2) is fitted with the head of the bolt (1) and the tip of the bolt (1) is engaged with the screw hole of the nut (5). As a non-contact type detector that detects the position of the socket (2) in the advancing / retreating direction, a proximity switch or a photoelectric tube may be used. You may use the displacement sensor arrange | positioned at.

Next, the operation of this embodiment will be described. First, the socket (2) of the nut runner (10) is fitted into the head of the bolt (1) and the nut runner (10) is started. At the same time, the detection of the position of the socket (2) by the proximity switch (3) and the measurement of the tightening torque by a torque measuring device (not shown) are started. As shown in FIG. 2, when the bolt (1) engages with the nut (5) past the idling region (A), a fitting confirmation signal is sent from the proximity switch (3) to the nut runner. That is, at this point, the socket (2) and the head of the bolt (1) are fitted to each other, and the socket (2) is advanced to a position where the tip of the bolt is engaged with the screw hole of the nut (5). Since the socket (2) is separated from the proximity switch (3), the proximity switch (3) is O
It becomes FF. This is used as a fitting confirmation point (S), and the time from when the seating time or seating angle starts counting until the tightening torque rises to the seating torque (Tseat) preset in the control circuit (seating time) , TMre
al) or the rotation angle of the bolt (1) (seating angle, θrea
l) is measured. When the bolt (1) continues to be tightened by the rotation of the socket (2) and reaches the seating point (SP), the measured sitting time (TMreal) or sitting angle (θreal) is set to the lower limit of the preset sitting time. Value (TMmin.) Or the lower limit of the seating angle (θmin.), The sitting time (TMreal) or the seating angle (θreal) is the lower limit of the sitting time (TMmin.) Or the lower limit of the seating angle (θmin.
min.), it is judged that galling has occurred between the bolt (1) and the nut (5).

Note that, even when the tightening torque increases and reaches the seating torque (Tseat) before reaching the fitting confirmation point (S), it is determined that the galling has occurred.

In the above embodiment, in order to eliminate the influence of the idling area (A) of the bolt (1), the seating time set from the fitting confirmation point (S) as a starting point is used as a factor for determining the occurrence of galling. Either the lower limit value (TMmin.) Or the lower limit value (θmin.) Of the seating angle is used, but the lower limit value (TMmin.) Of the sitting time and the lower limit value (θmi.
Both n.) can be used together as a judgment element of the occurrence of galling.

As can be understood from the above description, in the method of the present invention, the position of the socket (2) is detected by the proximity switch (3), and the proximity switch (3) detects the position of the socket (2).
It is determined that the bolt (1) is not held in the fitted state while the is detected. When the fitting detection signal from the proximity switch (3) is input to the control circuit of the nut runner (10) and the tightening torque reaches the seating torque (Tseat) preset in the control circuit, the socket (2) is If it can be detected, it is determined that galling has occurred in the bolt (1). Also, after the presence of the socket (2) can no longer be detected, tightening proceeds and the measured sitting time (TMreal) or sitting angle (θreal) is the lower limit of the sitting time (TMmin.) Or sitting When the angle falls below the lower limit value (θmin.), It is determined that galling has occurred in the bolt (1).

[0020]

According to the present invention, even if the bolt (1) is idling in the initial stage of tightening, the occurrence of galling can be reliably detected, so that the damage to the work due to improper tightening is greatly reduced. As a result, highly secure automatic screw tightening is possible.

[Brief description of drawings]

FIG. 1 is a front view of a galling detection device according to the present invention.

FIG. 2 is a torque curve illustrating the method of the present invention.

[Fig. 3] Typical torque curve when tightening screws using a nut runner

FIG. 4 is a torque curve for explaining a conventional galling detection method.

FIG. 5 is a torque curve for explaining a conventional galling detection method.

[Explanation of symbols]

 1 Bolt 2 Socket 3 Non-contact type detector (proximity switch) 4A Work to be tightened 4B Work to be tightened 5 Nut Teat Seating torque TMreal Seating time θreal Seating angle TMmin. Lower limit of seating time θmin. Lower limit of seating angle

Claims (5)

[Claims] 1. When bolting a workpiece using an automatic screw tightening machine, the automatic screw tightening machine is started so that the socket of the automatic screw tightening machine fits with the head of the bolt and the tip of the bolt forms a screw hole. Confirm the engagement, measure the time from the time of the above confirmation to reach the preset seating torque, compare the measured value with the lower limit of the preset sitting time, the above A method for detecting galling in an automatic screw tightening machine, characterized in that it is determined that galling has occurred when the measured value falls below the lower limit value. 2. When bolting a workpiece using an automatic screw tightening machine, the automatic screw tightening machine is started so that the socket of the automatic screw tightening machine fits with the head of the bolt and the tip of the bolt forms a screw hole. After confirming the engagement, measure the rotation angle of the bolt from the time when the above confirmation is made until the preset seating torque is reached, and compare the measured value with the preset lower limit value of the seating angle. Then, when the measured value falls below the lower limit value, it is determined that galling has occurred, and the galling detection method in the automatic screw tightening machine is characterized. 3. When bolting a workpiece using an automatic screw tightening machine, the automatic screw tightening machine is started so that the socket of the automatic screw tightening machine fits with the head of the bolt and the tip of the bolt forms a screw hole. After confirming the engagement, measure the time from the time when the above confirmation is made until the seating torque set in advance and the rotation angle of the bolt are measured, and both measured values are the lower limit of the seating time set in advance. A method for detecting galling in an automatic screw tightening machine, characterized in that, when any of the above measured values falls below the lower limit value, it is determined that galling has occurred by comparing the value and the lower limit value of the seating angle. 4. When the socket of the automatic screw tightening machine is fitted to the head of the bolt and the tip of the bolt is engaged with the screw hole, the position of the socket is previously determined, and the socket is at this position. The method for detecting galling in an automatic screw tightening machine according to claim 1, wherein the socket is fitted with the head of the bolt and the tip of the bolt is judged to be engaged with the screw hole. 5. An automatic screw tightening machine having a rotationally driven socket capable of having an advanced position where the tip of the bolt engages with the head of the bolt and a retracted position separated from the head of the bolt. 2. A galling detection device in an automatic screw tightening machine, characterized in that a sensor is provided for sending a signal when the socket at the advanced position is detected.