JPH11333747A - Detecting method for deterioration of impulse wrench - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately judge that an impulse wrench deteriorates, by measuring a time change of a torque value of a oil pressure pulse, integrating it, calculating the fastening energy amount, judging that fastening capabilities of the impulse wrench is decreased when the fastening energy amount is less than a set value, and issuing a warning of deterioration. SOLUTION: A pulse output integral circuit 25 takes a change of voltage of a clearance sensor 11, changed by generation of a oil pressure pulse as a time change, and the amount of fastening energy to be generated by impact is calculated by integration. A pulse output integral circuit 26 integrates an integral value calculated by the pulse output integral circuit 25, and the total fastening energy amount after pulling of a throttle lever is calculated. A setting and inputting comparing circuit 27 generates a signal by comparing the integral value integrated by the pulse output integral circuit 26 with a set value. Therefore, decrease in fastening capabilities of the impulse wrench can be accurately detected without depending on man's senses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a torque control system of an impulse wrench for automatically stopping an air motor when a tightening torque of a bolt, a nut or the like reaches a set value. The present invention relates to a method for detecting deterioration of an impulse wrench, wherein a deterioration alarm is issued when the tightening capability of the wrench is deteriorated and the worker is notified that the wrench is deteriorated.

[0002]

2. Description of the Related Art When tightening bolts and nuts, an impulse wrench with low noise and low vibration, and when the generated torque is set in advance, does not exceed the set value and the tightening torque is stable, is applied to the impact wrench. Instead it has been used in recent years.

[0003] The impulse wrench converts a hydraulic pulse (impact pulse) generated by a hydraulic pulse generating mechanism into a tightening torque to tighten bolts and nuts. The impact received by the hand is smaller than that of an impact wrench that converts the impact of the bolt into a tightening torque and tightens bolts and nuts, so it is difficult for workers to judge when the tightening is completed because there is no response from the worker I was For this reason, even though the tightening torque has already reached the set value, the tightening is often continued further, resulting in a problem that working time is wasted.

Then, the amount of tightening energy of the generated hydraulic pulse is integrated and integrated, and when the integrated value reaches a set value,
A torque control system for closing the air supply to the air motor and stopping the impulse wrench has been invented (for example, JP-A-8-90443).

[0005] However, the oil sealed in the hydraulic pulse generating mechanism leaks from the seal, though a small amount with time. When oil starts leaking from the hydraulic pulse generation mechanism,
Although the peak value of the output tightening torque does not change much, the time during which the pulse is generated gradually becomes shorter, and the amount of tightening energy by one impact becomes smaller. If the amount of tightening energy is small, the amount of tightening per impact will be small, the number of pulses required before the impulse wrench will stop will increase, and the time to stop will increase, hindering the work of the assembly line. In addition, there is a problem that the amount of tightening energy is insufficient and the axial force of bolts and nuts is insufficient.

[0006] As a result of the experiment, the amount of oil leakage was 0.5 cc.
If it is less than this, there is not much effect, but if it leaks more, it will start to greatly affect the amount of fastening energy generated by one blow.

Conventionally, the determination of the impulse wrench deterioration depends on the feeling of the worker, and there is no device for determining the deterioration.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention
It is an object of the present invention to solve the above-mentioned problems and to provide a method for accurately determining that the fastening ability has been reduced and the impulse wrench has deteriorated without relying on human feeling.

[0009]

For this reason, according to the present invention, the time change of the torque value of the hydraulic pulse generated by the hydraulic pulse generating mechanism 13 is measured by the sensor 11 and integrated, whereby the tightening caused by one impact is performed. The amount of energy was calculated, and if the calculated amount of tightening energy generated by one impact became equal to or less than the set value, it was determined that the tightening ability of the impulse wrench 1 had decreased, and a deterioration warning was issued.

[0010] The amount of tightening energy of an arbitrary number of hydraulic pulses generated before the stop of the air motor 12 is calculated and stored, and a predetermined number is selected in descending order of the amount of tightening energy, and the average value is compared with a set value. Is preferable.

It is preferable that the amount of tightening energy of the hydraulic pulse to be stored excludes the amount of tightening energy of the last generated hydraulic pulse.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for detecting deterioration of an impulse wrench according to the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram showing the overall configuration of a torque control system having a function of issuing a deterioration alarm by the deterioration detection method of the present invention. The torque control system has an impulse wrench 1 and a controller 2, and the impulse wrench 1 Is connected to an electromagnetic valve 5 provided at an air supply port 4 by an air hose 3, the controller 2 is connected to an impulse wrench 1 and a sensor cable 6, and the controller 2 is connected to the electromagnetic valve 5 and a cable 7.

The impulse wrench 1 rotates a main shaft 10 when a throttle knob 9 provided on a handle portion 8 is pulled. The impulse wrench 1 converts generated torque into a voltage by a sensor described later. The information is transmitted to the controller 2.

Further, when the tightening torque of the bolts and nuts reaches a set value, the controller 2 issues a signal to close the solenoid valve 5 and stop the impulse wrench 1.

The details will be described below. FIG. 2 is a sectional view of the impulse wrench 1.

In this impulse wrench, when the throttle knob 9 of the handle portion 8 is pulled, air flows and the air motor 12
, And the rotor of the air motor 12 rotates the hydraulic pulse generation mechanism 13. Further, when a load is applied to the main shaft 10, a hydraulic pulse is generated in the hydraulic pulse generating mechanism 13, and the main shaft 10 of the wrench is rotated by the generated hydraulic pulse to tighten bolts and nuts. I have.

A motor case cover 14 is attached to a rear portion of the air motor 12, and includes a flywheel 15 and a linear motion conversion mechanism 17 for converting a swing angle of the flywheel 15 into a linear motion of a shaft 16. And a control bar 16a integrally attached to the rear end of the shaft 16.
, A gap sensor 11 is provided. Clearance sensor 11
Detects the amount of movement of the control bar 16a (the distance away from the gap sensor 11) and outputs it as a voltage change.

The flywheel 15 is, as shown in FIG.
It has a substantially L-shape including a weight portion 18 and an arm portion 19, and is mounted eccentrically by a shaft 20. Therefore, when a hydraulic pulse is generated and the air motor 12 is decelerated, as shown in FIG. 4, the air motor 12 swings due to inertial force, and its angle is proportional to the generated tightening torque.

Reference numeral 21 denotes a slider of the linear motion conversion mechanism 17, which moves up and down in the figure according to the swing angle of the flywheel 15, and returns to its original position by a spring 22. Has been energized. Then, the shaft 16 provided on the center axis of the impulse wrench is pressed by a ball in contact with the slope 21a of the slider 21. Therefore, a change in the swing angle of the flywheel 15 can be converted into a linear motion by the linear motion conversion mechanism 17.

This structure is substantially the same as the structure described in Japanese Patent Application Laid-Open No. Hei 8-90443 filed previously by the applicant, and a detailed description thereof will be omitted.

The output (voltage change) of the gap sensor 11 is amplified by an amplifier 23 provided in the middle of the sensor cable 6 and sent to the controller 2.

As shown in FIG. 5, the controller 2 includes a zero point position detecting circuit 24, a pulse output integrating circuit 25, a pulse output integrating circuit 26, a setting / input comparing circuit 27, a solenoid valve shutoff circuit 28, , Fastening OK display circuit 29, fastening NG display circuit 30, wrench stop detection circuit 31, deterioration measurement sample extraction circuit 32, setting / input comparison circuit 33, deterioration alarm display circuit 34, power supply circuit 35 The solenoid valve cutoff circuit 28 is connected to the solenoid valve 5.

Each circuit of the controller 2 functions as follows. The zero point position detection circuit 24 is a circuit that detects the voltage of the gap sensor 11 before the generation of the hydraulic pulse and detects the difference between the voltage of the gap sensor 11 and the voltage changed by the generation of the hydraulic pulse.

The pulse output integration circuit 25 changes the voltage (pulse) of the gap sensor 11 changed by the generation of the hydraulic pulse.
Is a circuit that calculates the amount of tightening energy generated by one blow (area when a graph is drawn with the voltage change on the vertical axis and time on the horizontal axis).

The pulse output integrating circuit 26 is a circuit that integrates the integrated value calculated by the pulse output integrating circuit 25 and integrates the total tightening energy after pulling the throttle lever 9.

The setting / input comparison circuit 27 is a circuit for comparing the integrated value obtained by the pulse output integrating circuit 26 with a set value and issuing a signal.
The electromagnetic valve 5 is closed by 28, the air motor 12 is stopped, and the indication of tightening OK is displayed by the tightening OK display circuit 29. When the air motor 12 stops before the integrated value reaches the set value, such as when the operator releases the throttle lever 9 halfway, the fastening NG display circuit 30 displays the indication of fastening NG. The wrench stop detection circuit 31 determines whether the air motor 12 has stopped.
To detect.

FIG. 6 is a timing chart when the tightening is OK. As shown in the figure, the solenoid valve 5 returns several seconds after stopping, and the indication of the tightening OK is displayed by turning the throttle lever 9 again. It disappears by pulling.

The deterioration measurement sample extraction circuit 32 determines
The integrated value of an arbitrary number of pulses (eight in this embodiment) excluding the number of pulses is stored, and if the integrated value (total tightening energy amount) integrated by the setting / input comparing circuit 27 reaches the set value. This circuit extracts a predetermined number (four in this embodiment) of the stored integrated values for each pulse and calculates the average value.

The setting / input comparison circuit 33 is a circuit that compares the average value of the integrated value of the pulse extracted by the deterioration measurement sample extraction circuit 32 with the set value to generate a signal, and the average value has reached the set value. If not, a deterioration warning is displayed by the deterioration warning display circuit 34.

FIG. 7 is a flowchart of a portion for taking out a deterioration measurement sample and displaying a deterioration warning if the set value has not been reached. The method of the present invention will be described step by step.

[Step 1] It is checked whether or not a pulse is generated in the output of the gap sensor 11 by generating a hydraulic pulse in the hydraulic pulse generating mechanism unit 13. If a pulse is generated, the process proceeds to step 2. Wait until a pulse occurs.

[Step 2] The process proceeds to step 3 except for the integrated value of the stored pulse.

[Step 3] The integrated values of the previous eight pulses except for the immediately preceding pulse are newly stored, and the routine proceeds to step 4. The reason for removing the last pulse is that the last hydraulic pulse generated when the solenoid valve 5 is shut off by the solenoid valve shutoff circuit 28 is incomplete, and accordingly, the output of the gap sensor 11 is smaller than that of a normal pulse. This is because it becomes smaller.

[Step 4] The integrated value (corresponding to the total tightening energy from the first hydraulic pulse generation to the present) obtained by the pulse output integrating circuit 26 is compared with the set value by the setting / input comparing circuit 27. If the integrated value has reached the set value, the process proceeds to step 5, and if not, the process returns to step 1.

[Step 5] Out of the eight integrated values of the stored eight pulses, four large ones are taken out and an average value is obtained. The reason why four are taken out is to prevent malfunction.

[Step 6] The average value of the four integrated values is compared with a set value for deterioration detection. If the average value is larger than the set value for deterioration detection, it is normal because it is normal, and the process returns to step 1. If it is smaller, the process proceeds to step 7, a deterioration alarm is displayed, and the process returns to step 1.

The above is the description of the embodiment. In this embodiment, the hydraulic pulse generating mechanism 13 using the flywheel 15 is used.
Adopted the method of measuring the torque value of the hydraulic pulse generated by the gap sensor, but the method of measuring other torque values,
For example, it may be measured by a strain gauge attached to the main shaft 10 or by a magnetostrictive sensor using the magnetostriction of the main shaft 10.

In this embodiment, the integral value is stored except for the integral value of the pulse immediately before the air motor 12 stops. However, the integral value may be stored. This is because even if the integral value of the last pulse is small, it is excluded in the processing of step 5 described above.

[0040]

As described above, according to the present invention, the time change of the torque value of the hydraulic pulse generated by the hydraulic pulse generating mechanism 13 is measured by a sensor and integrated, whereby the amount of tightening energy generated by one impact is obtained. It is determined that the tightening ability of the impulse wrench is reduced if the calculated amount of tightening energy generated by one impact is equal to or less than the set value,
A deterioration alarm is issued, and the amount of tightening energy generated by one blow is monitored to detect the deterioration of the wrench, so that the wrench can be accurately detected without relying on human feeling.

According to the second aspect of the present invention, the tightening energy amounts of an arbitrary number of hydraulic pulses generated before the air motor is stopped are calculated and stored, and a predetermined number is selected in descending order, and the average value and the set value are selected. By comparing with the above, it is possible to more accurately measure the amount of tightening energy generated by one impact of the impulse wrench, and to more accurately detect the deterioration of the wrench.

Still further, if the amount of tightening energy of the hydraulic pulse to be stored excludes the amount of tightening energy of the last generated hydraulic pulse as described in claim 3, the last incomplete hydraulic pulse is obtained. Since the pulse can be eliminated, the amount of tightening energy generated by one shot of the impulse wrench can be measured more accurately, and deterioration of the wrench can be detected more accurately.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the overall configuration of a torque control system using a deterioration detection method according to the present invention.

FIG. 2 is a sectional view of an impulse wrench provided with a sensor capable of measuring a tightening torque.

FIG. 3 is an enlarged explanatory view of a main part of the impulse wrench showing a state of attachment of a flywheel.

FIG. 4 is an enlarged explanatory view of a main part of the impulse wrench showing a state when the flywheel swings.

FIG. 5 is a circuit diagram of a torque control system using the deterioration detection method of the present invention.

FIG. 6 is a timing chart of a torque control system using the deterioration detection method of the present invention.

FIG. 7 is a flowchart illustrating a deterioration detection method according to the present invention.

[Explanation of symbols]

 1 Impulse wrench 2 Controller 5 Solenoid valve 10 Main shaft 11 Clearance sensor 12 Air motor 13 Hydraulic pulse generation mechanism 15 Flywheel 16 Shaft 16a Control bar 17 Linear motion conversion mechanism

Claims (3)

[Claims] A sensor (11) measures and integrates a temporal change of a torque value of a hydraulic pulse generated by a hydraulic pulse generating mechanism (13) to calculate a fastening energy amount generated by one impact, An impulse wrench characterized in that when the calculated amount of tightening energy generated by one impact falls below a set value, it is determined that the tightening ability of the impulse wrench (1) has decreased and a deterioration alarm is issued. Deterioration detection method. 2. The amount of tightening energy of an arbitrary number of hydraulic pulses generated before stopping the air motor (12) is calculated and stored, and a predetermined number is selected in descending order of the amount of tightening energy. 2. The method for detecting deterioration of an impulse wrench according to claim 1, wherein: 3. The method for detecting deterioration of an impulse wrench according to claim 2, wherein the amount of tightening energy of the hydraulic pulse to be stored excludes the amount of tightening energy of the last generated hydraulic pulse.