Screw tightening system, controller, and non-transitory storage medium

Patent metadata

Field	Value
Publication number	US-2023271282-A1
Application number	US-202318163395-A
Country	US
Kind code	A1
Filing date	Feb 2, 2023
Priority date	Feb 28, 2022
Publication date	Aug 31, 2023
Grant date	—

Abstract

A screw tightening system includes an actuator including a driver bit that rotationally drives a screw and a motor coupled with driver bit, and a controller that controls actuator. Controller includes an acquirer that acquires torque values of a torque generated in a motor, a calculator that calculates a standard deviation of the torque values in a temporary tightening period, and a determiner that determines that there is an abnormality when a ratio of the standard deviation to a reference standard deviation exceeds a first threshold value.

First claim

What is claimed is:

1 . A screw tightening system comprising:
an actuator including a driver bit configured to rotationally drive a screw and a motor coupled with the driver bit; and a controller configured to control the actuator, wherein the controller includes an acquirer configured to acquire torque values of a torque generated in the motor, a calculator configured to calculate a standard deviation of the torque values acquired in a temporary tightening period from when the screw engages with a screw hole until when the screw is seated in the screw hole, and a determiner configured to determine that there is an abnormality when a ratio of the standard deviation to a reference standard deviation exceeds a first threshold value.

2 . The screw tightening system according to claim 1 , wherein the controller further includes a commander that commands the motor to stop when it is determined that there is an abnormality.

3 . The screw tightening system according to claim 1 , wherein
the acquirer acquires each of the torque values at a predetermined cycle, and the calculator starts calculation of the standard deviation when the torque value is acquired a first predetermined number of times or more in the temporary tightening period.

4 . The screw tightening system according to claim 3 , wherein the calculator calculates the standard deviation by using the torque values acquired for all number of times from a start of the temporary tightening period to a present time.

5 . The screw tightening system according to claim 3 , wherein the calculator calculates the standard deviation by using the torque values for a latest second predetermined number of times.

6 . The screw tightening system according to claim 1 , wherein the reference standard deviation is calculated based on the torque values acquired for all number of times in the temporary tightening period when the screw is considered to be normally tightened to the screw hole.

7 . The screw tightening system according to claim 1 , wherein the reference standard deviation is an average value of standard deviations each of which is calculated based on the torque values acquired for a third predetermined number of times in the temporary tightening period when the screw is considered to be normally tightened to the screw hole.

8 . The screw tightening system according to claim 1 , wherein the determiner selects one from a plurality of reference standard deviations prepared in advance depending on at least one of a size of the screw, a material of the screw, and a material of the screw hole.

9 . The screw tightening system according to claim 1 , wherein the determiner selects one from a plurality of first threshold values prepared in advance depending on at least one of the size of the screw, the material of the screw, and the material of the screw hole.

10 . The screw tightening system according to claim 1 , wherein
the actuator further includes a load sensor configured to detect a load generated in the driver bit, and the determiner determines that there is an abnormality when the load detected by the load sensor exceeds a second threshold value.

11 . A controller configured to control an actuator including a driver bit configured to rotationally drive a screw and a motor coupled with the driver bit, the controller comprising:
an acquirer configured to acquire torque values of a torque generated in the motor; a calculator configured to calculate a standard deviation of the torque values acquired in a temporary tightening period from when the screw engages with a screw hole until when the screw is seated in the screw hole; and a determiner configured to determine that there is an abnormality when a ratio of the standard deviation to a reference standard deviation exceeds a first threshold value.

12 . A non-transitory storage medium configured to store a control program causing one or more processors of a computer connected to an actuator including a driver bit configured to rotationally drive a screw and a motor coupled with the driver bit, when executed by the one or more processors,
to acquire torque values of a torque generated in the motor, to calculate a standard deviation of the torque values acquired in a temporary tightening period from when the screw engages with a screw hole until when the screw is seated in the screw hole, and to determine that there is an abnormality when a ratio of the standard deviation to a reference standard deviation exceeds a first threshold value.

Assignees

• Omron Tateisi Electronics Co

Inventors

• Biwaki Shu
• Liu Zhiqiang
• Murai Masahiro
• Tsuchihashi Yuki

Classifications

• B23P19/06 Primary

  Screw or nut setting or loosening machines · CPC title

• B23P19/00

  Machines for simply fitting together or separating metal parts or objects, or metal and non-metal parts, whether or not involving some deformation {(connecting metal parts or objects by metal-working procedures B21J, B23K)}; Tools or devices therefor so far as not provided for in other classes (hand tools in general B25) · CPC title

• G05D17/02

  characterised by the use of electric means · CPC title

• B23P19/066 Primary

  by electrical means · CPC title

• B25J9/1674 Primary

  characterised by safety, monitoring, diagnostic · CPC title