JPH08229841A - Constant-tension bolt fastening device - Google Patents

Abstract

PURPOSE: To provide a constant-tension bolt fastening device that can obtain constant reflected wave regardless of a fitted state between a bolt head and a bolt fit-in part or between a nut and a bolt bottom part so as to generate no fluctuation to fastening axial force. CONSTITUTION: An output shaft 8 rotated by power transmitted from a motor is provided inside with an electrode needle 16 pressed downward by a pressure spring 17 while interlocking a socket 12 for fitting a bolt A or a nut B therein, with the rotation of the output shaft 8. The lower end of the electrode needle 16 is brought into contact with a piezoelectric ultrasonic sensor A2 provided at the top face of the head A1 of the bolt A or the bolt bottom face A3, and a tension controller is connected to the electrode needle 16 and the socket 12 to form a constant-tension bolt fastening device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention automatically stops the rotation of a motor when the torque of a drive source such as a motor is transmitted and the torque of an output shaft for fastening a bolt reaches a constant axial force. The present invention relates to a constant axial force bolt fastening device.

[0002]

2. Description of the Related Art Conventionally, it is known that when a mechanical shock is applied to a piezo element, the piezo element generates an electric pulse voltage, and conversely, when a pulse voltage is applied to the piezo element, it vibrates.

Further, when the bolt is tightened, the tightening force causes the bolt to expand, and the internal distortion caused by the expansion causes an ultrasonic pulse applied from the end surface of the bolt to be reflected at the opposite end surface, and the It has been found that the propagation time to reach the end face to which the sound wave pulse is applied becomes long.

By utilizing the fact that the propagation time of the signal in the bolt changes due to the tightening force of the bolt, the tightening force of the bolt is detected by the change in the propagation time of the ultrasonic pulse, so that a constant axial force is obtained. The tightening of bolts has started to take place.

As an example of a conventional constant axial force bolt fastening device of this type, there is a screw fastening tool disclosed in Japanese Patent Laid-Open No. 62-287981, and this screw fastening tool is an output shaft for rotating a bolt. A piezo ultrasonic sensor is installed, a pulse voltage is applied to this piezo ultrasonic sensor, the reflection of the ultrasonic pulse signal emitted from the piezo ultrasonic sensor is received by the piezo ultrasonic sensor, and this is converted into an electrical signal. By grasping the tightened state of the bolt, the output shaft is stopped by stopping the motor when a certain torque is reached.

[0006]

In such a screw tightening tool, the contact state between the output shaft provided with the piezoelectric ultrasonic sensor and the head of the bolt fitted to the output shaft is not constant. In addition, the propagation time of the ultrasonic pulse emitted from the piezo ultrasonic sensor changes due to the resistance of the contact surface, and the change in extension due to the tightening torque of the bolt cannot be accurately measured. Could not be fastened.

The present invention focuses on the fact that a bolt having a piezoelectric thin film formed on the top surface of the head of the bolt or on the bottom surface of the tip of the screw has been put into practical use, and the above-mentioned problems of the conventional screw tightening tool. In order to solve the point, by applying a pulse voltage to this piezoelectric thin film, regardless of the contact state of the bolt head and the bolt fitting portion or the bolt bottom and the nut, it is possible to propagate at a constant speed, An object of the present invention is to provide a constant axial force bolt tightening device that does not cause fluctuations in the tightening axial force.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a means for a constant axial force bolt fastening device for achieving the above-mentioned object, and claims 1
The means described is an output shaft that rotates by transmitting power from a drive source, a bolt or nut fitting socket that rotates in conjunction with the rotation of the output shaft, and an urging member provided in the output shaft. An electrode needle that is pressed downward by the head to contact the piezo ultrasonic sensor provided on the top surface of the head of the bolt or the bottom surface of the tip of the screw portion, and a constant axial force measuring means connected to the electrode needle and the socket. It is characterized by

Further, the constant axial force measuring means is inputted / outputted to / from the piezo ultrasonic sensor to measure the propagation time due to the input and the output,
It is composed of an axial force controller that determines the fastening with a constant axial force and a motor controller that is connected to the axial force controller and controls the output to the motor that is the drive source. A torque sensor may be provided therein and the rotation of the motor may be transmitted to the output shaft via a gear.

Further, the output shaft center and the motor shaft center are arranged at right angles to each other, and a bevel gear for transmitting the rotation is provided between the rotation shaft to which the rotation of the motor shaft is transmitted and the output shaft. A coupling for transmitting rotation is provided between the motor and the output shaft, and a slip ring connected to an axial force controller can be provided between the electrode needle and the output shaft.

[0011]

In the constant axial force bolt fastening device of the present invention configured as described above, when the rotation of the drive source is transmitted and the output shaft rotates, the socket also rotates with the rotation of the output shaft and is fitted into the socket. The bolt is tightened by rotating the head or nut of the bolt, but the pulse voltage from the constant axial force measuring means is applied to the piezo ultrasonic sensor on the top or bottom of the bolt head by the bias of the biasing member. The pulse voltage is transmitted to the contacting electrode needle, and this pulse voltage is applied to the piezoelectric ultrasonic sensor on the top surface or the bottom surface of the bolt.

Then, the piezoelectric ultrasonic sensor emits an ultrasonic pulse, and this signal is reflected on the bottom surface or top surface of the bolt, and this reflected wave is transmitted from the top surface or bottom surface of the bolt to the piezoelectric ultrasonic sensor to generate a pulse voltage. It is converted and transmitted to the output shaft, and the tightening axial force on the bolt is measured by measuring the propagation time from the output of this pulse voltage to the input, and when the constant axial force is reached, the output shaft rotates. Is stopped and fastening is performed with a constant axial force.

Further, the above-mentioned pulse signal is sent from the axial force controller to the electrode needle, the reflected wave is measured, and the axial force controller determines whether or not the fastening force reaches the constant axial force based on the propagation time. Then, when the constant axial force is reached, the axial force controller outputs it to the motor controller to stop the motor, and the bolt is tightened with the constant axial force.

Furthermore, the torque transmitted to the output shaft is monitored by the torque sensor provided in the power transmission path from the motor to the output shaft, and the gear of the output shaft is rotated by the gear driven by the motor. It was done like this.

Further, by arranging the motor and the output shaft at right angles to each other, the height of the constant axial force bolt fastening device can be made small, and the motor can be easily gripped, and the output shaft can be rotated by a bevel gear. This makes it easier to perform work as a hand tool having a constant axial force bolt fastening device by hand.

Further, when the motor and the output shaft are coupled to each other and the electrode needle also rotates during the rotation of the motor, a slip ring provided between the electrode needle and the output shaft causes a constant axial force. The pulse voltage of the measuring means can be transmitted to the piezoelectric ultrasonic sensor on the top or bottom of the bolt.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a constant axial force bolt fastening device such as a robot installed at a fixed place will be described below with reference to FIGS. In this embodiment, the installation plate 1 is moved to a predetermined position such as a robot or a place where a bolt to be fastened moves.
The gear box 2 is attached to the.

A torque sensor 3 for measuring and displaying the torque of the transmitted intermediate shaft is provided above the gear box 2, and a reduction gear box 5 for reducing the rotational speed of the motor 4 is provided above the torque sensor 3. The motor 4 is attached to the motor 4. The motor 4 is provided with an encoder, and the rotation speed and stop of the motor 4 are controlled according to a code output from a motor controller 6 described later.

The output shaft 8 provided with a gear 7 that meshes with the gear to which the rotation from the motor 4 is transmitted in the gear box 2 is supported by the bearing 9 of the gear box 2 at the top and bottom, and the lower portion thereof is sectioned. An engagement portion 11 is provided on the side surface of the square fitting shaft 10.

On the other hand, the hexagonal head portion A1 of the bolt A or the hexagonal hole for fitting the nut B is provided in the socket 1
2 includes a push pin 1 that engages with the engaging portion 11 of the fitting shaft 10.
3 is provided so that it can be retracted, and the push pin 13
The push pin 13 and the engaging portion 11 are engaged by being pushed inward, and the socket 12 can be fitted so as to interlock with the rotation of the fitting shaft 10.

An electrode holder 15 is housed in the output shaft 8 via an insulating tube 14, and the inside of the electrode holder 15 can be slid vertically and the output shaft 8 can be slid up and down.
The electrode spring 16 whose tip is exposed at the lower end of the spring is accommodated, and the pressing spring 1 is provided between the electrode holder 15 and the electrode needle 16.
An electrode ring 18 that slips between the electrode holder 15 and the electrode holder 15 is fixed to the housing 2a attached to the gear case.

On the other hand, a connector 20 connected to the axial force controller 19 is fitted on the top of the housing 2a. The connector 20 and the electrode ring 18,
A lead wire 21 is wired between the housing and the housing 2a, and the pulse voltage from the axial force controller 19 is transmitted to the electrode needle 16 via the electrode ring 18 and the electrode holder 15.

Further, the top surface of the head A1 of the bolt A or the bottom surface of the bottom portion A3 of the screw tip is recessed, and a piezoelectric ultrasonic sensor A2 formed of a piezoelectric thin film is formed in the recess.
Is formed and the electrode needle 16 is pressed against the piezo ultrasonic sensor A2 by the pressing force of the pressing spring 17, and when the pulse voltage transmitted to the electrode needle 16 is applied to the piezo ultrasonic sensor A2, The sound wave sensor A2 converts this into an ultrasonic wave pulse and emits it toward the bottom surface or the top surface of the bolt.

This ultrasonic pulse is reflected by the bottom surface or the top surface of the bolt A and reaches the piezoelectric ultrasonic sensor A2 again, and the piezoelectric ultrasonic sensor A2 converts this into a pulse voltage. The voltage is received and the pulse voltage is output, one terminal of the connector 20, the electrode ring 18, the electrode holder 15, the electrode needle 16, the socket 13,
A circuit configured with the output shaft 8 and the other terminal of the connector 20 can be used for transmission between the transmission / reception circuit 22.

The propagation time of the voltage A is measured by the time difference between the pulse voltage emitted from the transmitter / receiver circuit 22 and the received pulse voltage, and the measured time is input to the control circuit 23. A propagation time for a proper axial force value for the bolt A, a proper torque value, and a rotation angle range preset by the setting circuit 24 are input.

The control circuit 23 and the transmission / reception circuit 22 are composed of the axial force controller 19 and the motor controller 6 shown in FIG. 2, and operate according to the flow chart shown in FIG. 4. Steps S1 to S2 are originally bolt tightening. This is a pre-process performed prior to the attaching process.

In this process, first in step S1,
The content of the register e for recording the input in the setting circuit 24 is cleared to e = 0, and then the propagation time for obtaining the target axial force Tm set in the setting circuit 24 is input in advance in step S2. The target value is the bolt material,
Physical properties such as heat treatment and correction values depending on the temperature are taken into consideration.

After step S3, a substantial bolt tightening process is started. In step S3, the pulse voltage is transmitted from the transmission / reception circuit 22 based on the output from the control circuit 23 to the piezoelectric ultrasonic sensor A2 of voltage A. To output an ultrasonic pulse, the pulse voltage converted by the reflected wave is input to the transmission / reception circuit 22, and the propagation time T due to the time difference of transmission / reception of the pulse voltage is detected by the control circuit 23 in step S4. .

The control circuit 23 determines in step S5 whether this propagation time T is equal to the previously set target axial force Tm, and if it is smaller, repeats iteratively in step S5, but this propagation time T is Tm. When it becomes equal to or larger than, the process proceeds to step S6 and outputs to the motor controller 6, and the motor controller 6 commands the encoder of the motor to stop the rotation of the motor, and this flowchart ends and the constant axial force bolt The fastening device stops.

In this way, the bolts are tightened by the constant axial force, but T in step S4 is Tm.
If it is equal to or greater than, the propagation time measurement is continued and the converted axial force value is displayed so that the looseness of the bolt after tightening can be known. The so-called "familiar tightening" for re-tightening the bolts can also be performed while measuring the tightening torque. or,
By simultaneously measuring the values of the built-in torque sensor and rotation angle sensor, more reliable tightening management becomes possible.

In the second embodiment shown in FIG. 5, which corresponds to claim 4, the output shaft 8 and the drive shaft 30 driven by the motor 4 are arranged at right angles, and the drive shaft 30 and the output shaft 8 are arranged. Bevel gears 31 and 32 provided on the drive shaft 30
Is transmitted to the output shaft 8.

As in the previous embodiment, between the electrode holder 15 that is insulated and supported by the output shaft 8 and the electrode needle 16 that is inserted through the output shaft 8 and insulated from the output shaft 8. A pressing spring 17 for pressing the electrode needle 16 downward is installed, and a bolt A fitted in a socket 12 which is detachably attached to the lower end of the output shaft 8 and interlocks in the rotational direction.
The electrode needle 16 is brought into pressure contact with the piezo ultrasonic sensor A2 on the upper surface of the head A1 or the bottom surface A3.

The electrode needle 16 and the socket 12 are connected to the transmitting / receiving circuit 2
2, the circuit of the previous embodiment performs the same operation as the flow chart of the previous embodiment, and the constant axial force tightening of the bolt A can be performed, and the motor 4 and the output shaft 8 are at a right angle position. Therefore, the overall height can be reduced and the hand tool can be easily used.

In the third embodiment shown in FIG. 6, which corresponds to claim 5, a coupling 35 is provided on the upper end of the output shaft 8, and the lower end of the rotary shaft 36 from the motor 4 is attached to the coupling 35. Is fitted and the motor 4 is located above the output shaft 8 so that in this embodiment the overall height is high and the electrode holder 15 is rotating with the output shaft 8.

Therefore, the lead wire connected to the transmission / reception circuit 22 as in the previous embodiments cannot directly contact the electrode holder 15 to provide the non-rotating electrode ring 20, and the lead wire is twisted. For the electrode holder 1
A slip ring 38, which is insulated from the output shaft 8 by a screw 37 that is screwed into the screw 5, is attached to the output shaft 8 and a housing 39
The electrode brush 41 is attached to the slip ring 38 while being insulated and attached to the slip ring 38. The rest is the same as the first embodiment.

Thus, the output shaft 8 and the electrode holder 1
5. When the electrode needle 16 rotates and the electrode ring 20 cannot be provided in the housing 2a, the rotating slip ring 38 and the electrode brush 41 are provided to transmit the pulse signal from the transmission / reception circuit 22 to the electrode needle 16. Is something that can be done.

[0037]

As described above, according to the present invention, a pulse voltage is applied to a piezoelectric ultrasonic sensor provided in advance on the top surface or the bottom surface of a bolt to emit an ultrasonic pulse, and the reflected wave is received. Since the piezo ultrasonic sensor converts into pulse voltage, the contact state between the head or bottom of the bolt and the output shaft, as in the case where the ultrasonic sensor is installed on the conventional output shaft, and other transmission and reception propagation times change The cause disappears,
It is possible to measure the propagation time without room for inaccurate factors.

Therefore, the measurement error of the axial force of the output shaft due to the deviation of the propagation time is eliminated, and the bolt can be fastened with an accurate constant axial force. After the fastening, the measurement is continued, and It is also possible to observe the decrease in axial force after stopping tightening by displaying, and it is possible to re-tighten against the decrease in axial force at this time, and the torque and angle measurement values at that time It is possible to make a total judgment of a total of three cases in total.

Moreover, "familiar tightening" in which bolts are once loosened and then re-tightened is possible, and it is also possible to adapt the shape and size of various bolt heads by replacing the socket. And the like.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a first embodiment of the present invention.

FIG. 2 is an overall front view of the same.

FIG. 3 is a block diagram of the above circuit.

FIG. 4 is a flowchart according to the above.

FIG. 5 is a sectional view of an essential part of the second embodiment.

FIG. 6 is a front view showing a part of a third embodiment in section.

[Explanation of symbols]

 A Bolt A1 Head A2 Piezo ultrasonic sensor A3 Bottom B Nut B3 Torque sensor 4 Motor 6 Motor controller 7 Gear 8 Output shaft 12 Socket 16 Electrode needle 17 Pressing spring 19 Constant axis force controller 31, 32 Bevel gear 35 Coupling 38 Slip ring

Claims (5)

[Claims] 1. An output shaft that rotates by transmitting power from a drive source, a bolt or nut fitting socket that rotates in conjunction with rotation of the output shaft, and an urging member provided in the output shaft. An electrode needle that is pressed downward by the head to contact the piezoelectric ultrasonic sensor provided on the top surface of the head of the bolt or the bottom surface of the tip of the screw portion, and a constant axial force measuring means connected to the electrode needle and the socket. A constant axial force bolt fastening device characterized in that 2. The constant axial force measuring means inputs and outputs to and from a piezo ultrasonic sensor, measures a propagation time due to input and output, and determines an axial force controller for determining fastening with a constant axial force, and The constant axial force bolt fastening device according to claim 1, wherein the constant axial force bolt fastening device is configured with a motor controller that is connected to the axial force controller and controls an output to a motor that is a drive source. 3. The constant axial force bolt fastening device according to claim 1, wherein a torque sensor is provided in the rotation transmission path of the motor, and the rotation of the motor is transmitted to the output shaft via a gear. . 4. The output shaft center and the shaft center of the motor are arranged at right angles to each other, and a bevel gear for transmitting rotation is provided between a rotation shaft for transmitting rotation of the motor shaft and the output shaft. The constant axial force bolt fastening device according to claim 1. 5. A coupling for transmitting the rotation of the motor is provided between the motor and the output shaft, and a slip ring connected to an axial force controller is provided between the electrode needle and the output shaft. The constant axial force bolt fastening device according to claim 1.