JPH08267369A - Torque control type pulse tool - Google Patents

Abstract

(57) [Summary] [Purpose] To make it possible to easily perform the required zero reset in a torque-controlled pulse tool. [Structure] The electric motor 15, an on / off switch 34 for starting the electric motor 15, and the electric motor 1
And a tool output shaft 19 which is generated by the pulse force generator 16 and is driven by the pulse force generator 16.
Within a fixed time period between the torque sensor 21 that detects the pulsed torque transmitted to the motor and the first pulsed torque generated after the on / off switch 34 is operated to start the electric motor 15. Torque sensor 21
And a first CPU 50 for resetting the zero point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque-controlled pulse tool such as a screw tightening tool having a torque sensor.

[0002]

2. Description of the Related Art As a conventional screw tightening tool for generating a pulse force, an air tool using an air motor as a rotary drive source and an electric tool using an electric motor as a rotary drive source are known. As a tool for screw tightening of this kind, there is known a tool for accurately detecting a pulsed torque applied to an object by incorporating a torque sensor for detecting the screw tightening torque. . This torque is applied in the form of a plurality of pulses spaced apart from each other in time. As a torque sensor, a magnetic anisotropy portion is formed on the outer circumference of the torque detection shaft, and changes in the magnetic characteristics of the magnetic anisotropy portion when torque is applied to this shaft are measured in the vicinity of this magnetic anisotropy portion. It was made to detect with the coil provided in
A so-called magnetostrictive torque sensor is used.

In this magnetostrictive torque sensor, the sensor portion having a magnetic anisotropy portion formed on its axis, the exciting circuit for exciting the coil, the detecting circuit for processing the signal from the coil, and the like A change in the atmosphere causes a zero point error in the torque signal value.

Therefore, as a conventional screw tightening tool having a torque sensor, there has been proposed one in which the zero point is reset while the tool is continuously used. For example, there has been proposed one in which a predetermined zero point reset is performed after a certain pulsed torque is generated and before the next pulsed torque is generated.

[0005]

However, in such a configuration, since the accurate zero reset cannot be expected until the generated pulsed torque is completely extinguished, the extinction of the pulsed torque is eliminated. There is a problem in that the detection must be performed reliably, the detection work is troublesome, and complicated control is required to reset the zero point.

Therefore, an object of the present invention is to solve such a problem and to easily perform a required zero point reset.

[0007]

To achieve this object, the present invention provides a rotary drive source, a switch for activating the rotary drive source, and a pulse force generating means driven by the rotary drive source. A torque sensor for detecting a pulsed torque generated by the pulse force generating means and transmitted to the tool output shaft, and a first pulsed torque after the switch is operated to start the rotary drive source. And means for resetting the torque sensor to the zero point within a fixed time until the occurrence of.

[0008]

In such a structure, the rotary drive source such as the electric motor and the pulse force generating means such as the hydraulic pulse unit generate the first pulse-shaped torque during the rising within a fixed time immediately after the start-up. Within a certain period of time until the above, the load is not substantially applied. Therefore, if the zero point of the torque sensor is reset within the above-mentioned fixed time by using the timing at which the switch for starting the rotary drive source is operated, it is a simple operation, but no load is reliably generated. Accurately reset the zero point in time. In addition, since pulse tools such as screw tightening tools operate for a few seconds at most, it is unlikely that a substantial zero point change will occur during operation, and it is only necessary to reset the zero point once immediately after startup. There is no problem with the simple process of.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 3 to 5 show a screw tightening tool 11 as an example of a pulse tool. The screw tightening tool 11 is configured as a handheld tool, and its casing 12 includes a main body portion 13 and a handle portion 14. An electric motor 15 as a rotary drive source and a hydraulic pulse force generator 16 driven by the electric motor 15 are provided inside the main body 13. An angle sensor 17 is mechanically connected to the electric motor 15. The pulse force generator 16 converts continuous torque supplied from the electric motor 15 into impulse-shaped torque, and can amplify the torque value of the electric motor 15 by 50 to 100 times as a peak value. A DC motor that generates a large torque is often used as the electric motor 15, but a high-speed AC servo motor or DC servo motor can also be used. It is also possible to install a reduction mechanism for amplifying the torque between the electric motor 15 and the pulse generator 16. Further, as the pulse force generation device 16, instead of the above-mentioned hydraulic type, a device that generates a mechanical impact force can be used.

A magnetostrictive torque sensor shaft 18 is coaxially connected to the output side of the pulse force generator 16, and a tool output shaft 19 is coaxially connected to the tip of the torque sensor shaft 18. The tool output shaft 19 has a casing 12 at its tip.
It is possible to perform the required screw tightening operation by projecting from.

The torque sensor shaft 18 constitutes a non-contact magnetostrictive torque sensor 21. That is, on the outer circumference of the torque sensor shaft 18, a pair of magnetic anisotropic portions 2 formed by knurling grooves are provided at intervals in the axial direction.
2 and 23 are formed, and a coil portion including an exciting coil and a detection coil is provided around these magnetic anisotropic portions 22 and 23.
24 are arranged in a non-contact state. Therefore, when the pulsed torque generated by the electric motor 15 and the pulse force generator 16 is transmitted to the screw or the like to be tightened through the output shaft 19, the magnetic anisotropy is generated according to the magnitude of the torque. The magnetic characteristics of the elastic portions 22 and 23 change, and an electric signal corresponding thereto is output from the coil portion 24, whereby the magnitude of the torque is obtained. The coil portion 24 is arranged inside the magnetic shield case 25 in order to avoid the influence of magnetic leakage from the motor 15. In addition, in order to surely prevent the influence of such magnetism, the motor 15 and the pulse force generator 16
Parts made of non-magnetic material are used in. Further, as the torque sensor, instead of such a magnetostrictive type, a strain gauge type using a rotary transformer may be used. And in that case, the same measure is taken against the magnetic leakage.

By providing the pair of magnetic anisotropy portions 22 and 23 in this manner and setting the directions of the magnetic anisotropy to be opposite to each other as shown in the figure, the environment such as the ambient temperature of the torque sensor can be improved. Even if there is a change, the effect is canceled out and the occurrence of an error is prevented. If it is possible to allow a slight decrease in sensor performance, the magnetic anisotropy can be limited to one location. In that case, the torque sensor shaft 18 can be configured to be short, and the tool 11 can be downsized. Can be achieved.

Inside the main body 13 of the casing 12 near the torque sensor shaft 18, a sensor board 26 on which electronic components for controlling the torque sensor 21 are mounted is provided. Further, inside the handle portion 14 of the casing 12, there is provided a main board 27 on which electronic components for controlling the electric motor 15 and processing a signal sent from the sensor board 26 are mounted. These substrates 26 and 27 are provided with an appropriate shock absorbing structure so as not to receive vibration from the pulse force generator 16 and the like.

A torque display / setting board 30 is provided inside the rear surface of the main body 13 of the casing 12. And, on the back surface of the main body portion 13, using the substrate 30,
A torque setting unit 31, a torque display unit 32, and a torque abnormality / normality display unit 33 are provided. Further, the handle portion 14 includes an on / off switch 34 for starting / stopping the electric motor 15 by a manual operation, a motor 15, that is, an output shaft.
A changeover switch 35 for changing the rotation direction of 19 is provided.

A cable 36 from the outside of the casing 12 is connected to the main board 27, and this cable 36 is used for the tool 11
It is used for supplying power to and transmitting data from the tool 11 to the outside. That is, as shown in FIG. 4, the cable 36 is led to an AC / DC adapter 37 for power supply, and the communication line 38 from the adapter 37 is further led to a data processor 39 using a computer. ing. The data processing device 39 is of a separate type, and a commercially available general-purpose computer can be used. A detachable communication line 38 is used.
40 is a printer. Instead of supplying power by the AC / DC adapter 37, a battery built-in system can be adopted.

FIG. 2 shows a block diagram of the device. In the torque sensor 21, the coil section 24 is composed of the exciting coil 42 and the detecting coils 43 and 44 as described above, and the exciting coil 42 is connected to the AC power supply section 45. Detection coils 43 provided corresponding to the magnetic anisotropy portions 22 and 23,
The output side of 44 is connected to a differential amplifier 48 via low-pass filters 46 and 47. The output side of the differential amplifier 48 is connected to the compensation circuit 49. The sensor board 26 is provided with a first CPU 50 for controlling the torque sensor 21, and the first CPU 50 has a torque sensor 21.
The signal line from the temperature sensor 51 for detecting the temperature of is connected.

Therefore, the screw is tightened by the tool output shaft 19, and the torque based on the screw tightening is applied to the torque sensor shaft 18.
When applied to the detector, a signal appears in the detection coils 43 and 44 corresponding to the magnitude of the torque. Then, these signals are sent to the differential amplifier 48 through the low-pass filters 46 and 47, so that a torque signal corresponding to the magnitude of the torque appears on the output side of the differential amplifier 48. . In addition, depending on the temperature detection result of the temperature sensor 51, the compensation circuit
The torque signal whose temperature has been compensated by 49 is finally output.

A second CPU 53 is provided on the main board 27, and a signal line from the compensation circuit 49 is connected to the second CPU 53 via an A / D converter 54.
A signal line from the torque setting unit 31 is connected to the second CPU 53 via a set torque storage device 55.
Further, the second CPU 53 can control the electric motor 15 via the motor control circuit 56, and the display control circuit 57.
Display contents can be output to each of the display units 32 and 33 via.
Further, via the communication control circuit 58, data can be exchanged with the data processing device 39 by the cable 36 and the communication line 38.

Further, the main board 27 is provided with a tightening torque storage device 60 constituted by an electrically rewritable ROM (EEPROM).
Is capable of receiving and storing data from the compensating circuit 49 and capable of exchanging data with the second CPU 53. The aforementioned on / off switch 34 is connected to the first and second CPUs 50 and 53, and the changeover switch 35 is connected to the second CPU 53. Angle sensor 17
The signal from is input to the second CPU 53.

In such a structure, when the on / off switch 34 is operated to operate the electric motor 15, an impulse force is correspondingly generated by the pulse force generator 16, and the output shaft 19 is rotated by the impulse force. Therefore, it becomes possible to perform a predetermined screw tightening operation. The applied torque at that time is detected by the torque sensor 21.

In the concrete screw tightening work, first, the torque setting section 31 manually sets the torque to be applied to the object. The set value is stored in the storage device 55 and is displayed on the torque display unit 32 via the display control circuit 57 by the action of the second CPU 53.

When the on / off switch 34 is manually operated in this state, a zero point reset described later is first performed,
Then, the actual screw tightening is performed. Then, the tightening torque at that time is detected by the torque sensor 21, and the torque signal during the tightening work based on the torque is detected by the compensation circuit.
After being subjected to temperature compensation by 49, it is sent to the second CPU 53 via the A / D converter 54. This second CPU 53
The torque data temperature-compensated by the compensating circuit 49 is compared with the data from the set torque storage device 55, and the electric motor 15 is stopped when the torque applied to the object reaches the set target torque value.

This completes the screw tightening operation for one object, and the tightening torque value at that time is stored in the tightening torque storage device 60 and displayed by the torque display unit 32. The storage device 60 can store tightening torque values for a large number of objects, and the stored data is transmitted to the data processing device 39 via the cable 36 and the communication line 38 at an appropriate time.
Then, the data processing device 39 performs quality control data processing on the tightening torque of the object and the like.

Since the target setting torque value is directly set by the torque setting unit 31 in this way, the screw tightening can be performed with a flexible and accurate torque value. Moreover, since the final tightening torque value is stored and the data can be processed, the screw tightening torque quality control can be easily performed. Furthermore, if the shaft coupling system is devised and the motor 15, the pulse generator 16, and the torque sensor 21 are of the build block system, they can be easily replaced during maintenance. In addition, by using the storage device 60 of the main board 27,
It is also possible to add a function to prevent forgetting to tighten a plurality of screws.

The angle sensor 17 may be used to control the speed of the motor 15. Further, instead of the electric motor 15, another rotation drive source such as an air motor can be used. Further, the heat generated by the motor 15, the pulse force generator 16 and the torque sensor 21 can be cooled by the air flow generated based on the rotation of the motor 15.

FIG. 1 shows the details of the pulsed torque applied to the object. The horizontal axis represents time, and the vertical axis represents the torque signal V _T.
Respectively. Here, when the on / off switch 34 is turned on, the zero point reset of the torque sensor 21 is performed during the time t ₁ by using it as a trigger signal. That is, immediately after the on / off switch 34 is turned on, and within the short time t ₁ when the first pulsed torque is not yet generated, the electric motor 15 and the pulse force generation device 16 are still in the rising state. , The actual load is not working. Therefore, during this time t ₁ , the first CPU 50 sets the output of the compensation circuit 49 at that time to zero torque.
The compensation circuit 49 is reset to zero.

As a result, when the pulsed torque is applied to the object as shown in the figure, the zero point is reset at the start of the screw tightening work, so that the torque can be accurately measured. . Since the screw tightening tool 11 operates for only a few seconds at most, it is unlikely that a substantial zero change will occur during its operation. Even with this simple process, there is no practical error in the torque measurement.

Then, a pulsed torque is applied to the object by the rotation of the electric motor 15 thereafter, and this pulsed torque is applied so that the peak value gradually increases as shown in the figure. The second CPU 53 measures the peak torque value of each of these pulse torques.

If the above set target torque value is V _TO ,
When the measured peak torque value reaches the value V _TF that exceeds the target torque value V _TO , it is determined that the screw tightening work is completed as described above, and the motor 15 is stopped.

Further, here, a start level V _TS for torque measurement is set. Then, from the time when the torque peak value exceeds the start level V _TS , the second CP
Whether time screwing does not exceed the set target time T ₃ is diagnosed by U53. Then, when the screw tightening time exceeds the set target time T ₃ , it is displayed on the display unit 33 as an abnormality of the pulse force generator 16 or the object. When there is no abnormality, the display unit 33 displays that it is normal.

The tightening torque storage device 60 stores the peak torque value V _TF at the time when the screw tightening work is completed. Then, the torque value, that is, the final tightening torque value of the object is displayed on the torque display unit 32 only for the time t ₂ after the motor 15 is stopped and before the switch 34 is turned on again. That is, the torque display unit 32 normally displays the above-mentioned set target torque value, but displays the final tightening torque value after the screw tightening is completed.

After that, when the on / off switch 34 is turned on again for the next screw tightening work, the zero point reset of the torque sensor 21 is similarly performed during the time t ₁ . The tightening torque storage device 60 stores peak torque values V _TF at the completion of screw tightening for a large number of screw tightening operations. When processing the stored data, the tool 11 is connected to the data processing device 39 by the cable 36 and the communication line 38, and then the data is transmitted.
The processing device 39 performs quality control data processing on the final tightening torque of the object. After transmitting the data, the tool 11 can be used in the original state by removing the communication line 38 again. Further, one processing device 39 can perform data processing for a plurality of tools,
Moreover, a commercially available computer can be used as the processing device 39. Therefore, the entire system can be constructed at a lower cost than in the case where each tool is equipped with a special data processing device.

Since the angle sensor 17 is built in the casing 12, the first and second CPUs 50 and 53 can perform screw tightening control based on both the applied torque and the angle.

The main board 27 may be separately mounted outside the casing 12. In that case, the circuit for data processing can be built in the board,
In that case, the separate data processing device 39 becomes unnecessary.

[0035]

As described above, according to the present invention, the torque sensor is generated within a certain period of time until the first pulsed torque is generated after the switch is operated to activate the rotary drive source. Since there is a means for resetting the zero point, that is, the torque sensor is reset to the zero point when the substantial load is not acting during the rising immediately after the start-up, it is certain that no load is generated. The zero point can be reset easily and accurately.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an output of a torque control type pulse tool according to an embodiment of the present invention.

FIG. 2 is a block diagram of the pulse tool.

FIG. 3 is a sectional view of the pulse tool.

FIG. 4 is a partially cutaway perspective view of the pulse tool.

FIG. 5 is a rear view of the pulse tool.

[Explanation of symbols]

 15 Electric motor 16 Pulse force generator 19 Tool output shaft 21 Torque sensor 34 ON / OFF switch 50 First CPU

Claims (1)

[Claims] 1. A rotary drive source, a switch for activating the rotary drive source, pulse force generating means driven by the rotary drive source, and transmission to a tool output shaft generated by the pulse force generating means. A torque sensor for detecting a pulsed torque, and the torque within a fixed time between generation of the first pulsed torque after the switch is operated to activate the rotary drive source. And a means for resetting a sensor to a zero point.