JP2004082303A - Rotating fastening device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fasten a fastened tool at a high speed with high accuracy by using a rotating fastening device. <P>SOLUTION: High-speed fastening is performed by driving the rotating fastening device with high driving energy in starting the fastening. The driving energy is inhibited when fastening torque reaches driving energy switching torque Te. Whereby the over-chute of the fastening torque after the fastening torque reaches cut-off torque Tc and the driving energy is cut off, can be reduced, and final torque can be controlled to be close to target fastening torque Tt. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rotary tightening device, and more particularly to a rotary tightening device that performs stable tightening.
[0002]
[Prior art]
Tightening of a fastener such as a nut or bolt is generally performed by a rotary tightening device such as an impact wrench or a nut runner. In particular, a rotary tightening device driven by an air motor, an electric motor, or the like can efficiently tighten a tool to be tightened, and is widely used in fields such as machine production.
[0003]
The impact wrench is a device for temporarily storing rotational energy output from an air motor or an electric motor, and then releasing the rotational energy as discontinuous pulse-like tightening energy to tighten the fastener. In addition to the conventional air impact wrench, recently, an impact wrench called an oil pulse wrench using an oil pulse mechanism has become widespread. On the other hand, the nut runner is a device that continuously transmits the energy output of the rotation of the air motor or the electric motor to a tool to be tightened such as a nut or a bolt to perform tightening. In addition, a driver that operates on the same principle as the nut runner and specializes in bolt tightening is one of the rotary tightening devices.
[0004]
In the tightening of a tool to be tightened using such a rotary tightening device, first, the tool to be tightened is rotated to a position called a seating position where a load is applied, and from there, tightening utilizing deformation of the tool to be tightened is performed. Done. As a guide for tightening, it is desirable to make the axial force due to the elasticity of the tool to be tightened an appropriate magnitude, but it is generally difficult to measure the axial force, so tightening torque, tightening time, or tightening rotation Angles and the like are often used as target values.
[0005]
However, when tightening is performed quickly, it is difficult to properly tighten to these target values. The main reason for this is that, due to the inertia of the rotary fastening device, the fastening proceeds even after the supply of the driving energy for driving the device is stopped. Since it is difficult to predict the progress of the tightening, the final value will deviate from the target value with some variation.
[0006]
As an example, a description will be given of a state in which tightening is performed by using an oil pulse wrench to achieve a target tightening torque. FIG. 4 is a schematic diagram showing a temporal change of the tightening torque acting on the shaft of the oil pulse wrench. After confirming the seating of the tool to be tightened in a pre-stage (not shown), the operator issues a command to execute tightening to the oil pulse wrench. Thereby, the tightening of the tool to be tightened progresses, and at the same time, the tightening torque increases as shown in the figure. To be precise, in the case of an oil pulse wrench, the increase in the tightening torque is stepwise, but here, it is schematically shown as a straight line. Eventually, when the tightening torque reaches the cutoff torque _Tc , the energy for driving the oil pulse wrench is cut off. However, even after the drive energy is cut off, some tightening energy is released due to inertia, so that the tightening torque slightly increases. Since it is difficult to predict the overshoot, the final tightening torque generally is irregularly deviated from the target tightening torque _Tt . In particular, this tendency is observed in an impact wrench such as an oil pulse wrench.
[0007]
Conventionally, in order to solve this problem, measures have been taken to reduce the driving energy and thus the tightening energy. FIG. 5 is a schematic diagram when the increase in the tightening torque is reduced to about half. In this case, after the tightening torque reaches the cutoff torque _Tc and the driving energy is cut off, the tightening torque does not overshoot much. For this reason, variation in overshoot is reduced, and the final torque can be made closer to the target tightening torque _Tt . However, as described above, when the supply of the driving energy is reduced to suppress the excess tightening energy output after the driving energy is cut off, the time required for completing the tightening increases. For example, compared with the example clamping time t ₁ in FIG. 4, the tightening time t ₂ in the example of FIG. 5 is about twice, they've invited redundant working time.
[0008]
The method of controlling the driving energy is described in JP-A-2000-326250. Here, in order to suppress the variation of the tightening end time of the nut runner, a method is described in which the rotation speed (drive energy) of the motor is increased when the work is slow, and the rotation speed of the motor is reduced when the work is fast. I have. However, with this method, it is not possible to control the variation after the drive energy is cut off.
[0009]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to suppress the deviation between the target value and the final value without unnecessarily extending the time required for completing the fastening.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, a rotary tightening device according to the present invention includes a control unit that controls the amount of tightening energy supplied to a tightening unit, and a torque meter that measures a tightening torque. This is a rotary tightening device that rotates a fixture and tightens with a target tightening torque. After the tightening torque reaches a predetermined value equal to or less than the target tightening torque, the tightening energy is reduced compared to before. Tighten.
[0011]
Further, the rotary tightening device of the present invention includes a control unit that controls the magnitude of the tightening energy supplied to the tightening unit, and a clock that measures the tightening time, and rotates the tool to be tightened, A rotary tightening device for tightening a target tightening time, wherein after the tightening time reaches a predetermined value equal to or less than the target tightening time, the tightening can be performed with a smaller tightening energy than before.
[0012]
In addition, the rotary tightening device of the present invention includes a control unit that controls the amount of tightening energy supplied to the tightening unit, and a unit that measures a tightening rotation angle, and rotates the tool to be tightened. A rotation tightening device for tightening a target tightening rotation angle, wherein after the tightening rotation angle reaches a predetermined value equal to or less than the target tightening rotation angle, tightening is performed with a smaller tightening energy than before. be able to.
[0013]
Further, the rotary tightening device of the present invention may be an impact wrench.
[0014]
Further, the rotary tightening device of the present invention may be a nut runner.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a schematic diagram in which the configuration of the present embodiment is applied to an oil pulse wrench. The oil pulse wrench 10 can be divided into a main body 12 that performs tightening, and a drive energy controller 14 that drives the main body 12. This classification is based on the difference in the functions. In practice, the control unit 14 may be provided on the main unit 12 or both may be physically separated. The main body 12 has a driving motor unit 16 for converting the driving energy into continuous rotation energy by a motor, and temporarily stores the energy output from the driving motor unit 16 therein, thereby forming a discontinuous pulse-type fastening energy. The oil pulse unit 18 is provided to be released. Then, the tightening energy output in a pulse shape is transmitted to the shaft 20 and further transmitted to the tool to be tightened through the tightening portion 21 at the tip of the shaft 20. From the viewpoint of torque, it can be said that the shaft 20 receives the torque from the oil pulse 18 and transmits the torque to the fastener through the fastening portion 21. The torque acting on the shaft 20 is called a tightening torque and can be measured by a torque meter 22 installed on the shaft 20. The tightening torque increases as the tightening proceeds.
[0017]
The output of the torque meter 22 is passed through a cable 24a to a signal processing unit 26 in the control unit 14 where the output is processed, and further sent to a storage / calculation unit 28 for storing and calculating data. The storage / arithmetic unit 28 is connected to a display unit 30 having a liquid crystal display and the like, an input / output instruction unit 32 having input keys and the like, and a motor control unit 34 for instructing the amount of electric power input to the motor. From the input / output instructing unit 32, a driving energy switching torque _Te , a cutoff torque _Tc , and a target tightening torque _Tt are input for controlling driving energy described later. The cutoff torque _Tc is smaller than the target tightening torque _Tt , and the drive energy switching torque _Te is smaller than the cutoff torque _Tc . The storage / arithmetic unit 28 stores these input values and instructs the motor control unit 34 on appropriate control contents. For example, during the tightening operation, the torque value sent from the signal processing unit 26 is compared with these predetermined torque values, and the method of controlling the driving energy is calculated. The motor control unit 34 specifically adjusts the input power according to the command, and controls the driving motor unit 16 connected by the cable 24b. The display unit 30 sequentially displays the execution contents of the series of processes to notify the operator. The control unit 14 may have a function other than the drive energy control described above. For example, the control unit 14 may perform tightening control of a plurality of different fasteners.
[0018]
Next, the tightening of the tool to be tightened will be described with reference to the flowchart of FIG. First, the worker performs an operation of installing the tightened device at the sitting position (S1). Here, the term “seating” refers to a point in time when tightening using the elasticity of the fastener is started, and the fastener can be rotated with small energy (torque) until seating. When the seating is confirmed by the value of the tightening torque or the like, the storage / calculation unit 28 instructs the motor control unit 34 to increase the drive energy for driving the drive motor unit 16 and starts the tightening ( S2). During the tightening, the torque meter 22 constantly measures the tightening torque, and a comparison between the torque value and the drive energy switching torque _Te is frequently executed in the storage / calculation unit 28 (S3). . When the torque value tightening reaches driving energy switching torque T _e, storage and computing unit 28 instructs to reduce the driving energy to the motor controller 34, as a result, through the driving motor 16 The transmitted fastening energy is reduced (S4). At this stage, the storage / calculation unit 28 compares the tightening torque value with the cutoff torque _Tc . Then, when the cutoff torque _Tc is reached, the motor control unit 34 is instructed to cut off the drive energy, and the movement of the drive motor unit 16 is stopped (S6). Further, when the movement of the drive motor unit 16 stops, the tightening torque is compared with the target tightening torque _Tt, and it is calculated whether the difference is within a predetermined upper and lower limit tolerance (S7). If the tolerance is within the tolerance, the fastening is finished. If the tolerance is out of the tolerance, a display indicating the failure of the fastening is displayed on the display unit 30 and the fastening is performed again.
[0019]
FIG. 3 is a schematic diagram showing a state of a temporal change of the tightening torque in the process described here. The tightening torque starts from the torque at the time of completion of seating and increases almost linearly with time. This situation is the same as that shown in the conventional example. However, in the present embodiment, the drive energy is suppressed when the drive energy switching torque _Tc is reached. For this reason, the tightening energy is also suppressed, so that the increase in the tightening torque is half that in the illustrated example. When the tightening torque reaches the cutoff torque, the supply of the driving energy is stopped. However, because of the excess tightening energy released thereafter, the tightening torque exhibits a slight overshoot until it stops, as described in the conventional example. However, since the magnitude is smaller than that of the conventional example, the final torque can be controlled to a value close to the target tightening torque _Tt . The time t ₃ when required for this task, as long as appropriately select the setting value of the driving energy switching torque T _c, sufficiently smaller than the conventional example of t ₂ shown in FIG. 5, prior art shown in FIG. 4 and it showed a value close to t ₁ of the example. In other words, it can be seen that this makes it possible to realize stable fastening without unnecessarily extending the fastening time. In the example shown in FIG. 3, the drive energy switching torque _Tc is set to be about ／ of the target tightening torque _Tt . Although this ratio depends on the strength of tightening, etc., if it is larger than about 1/2, a sufficient effect of shortening the tightening time will be obtained.
[0020]
Similar to the control based on the tightening torque shown here, it is also possible to perform the control based on the tightening time and the tightening rotation angle. In this case, instead of the torque meter 22, an output of a clock for measuring a tightening time or an output of a measuring means for measuring a rotation angle may be input to the signal processing unit 26 to perform similar control. For example, when performing control based on the tightening time, when the tightening energy is set to a predetermined value, the energy is reduced when the predetermined tightening time has elapsed, and the tightening is further performed for a predetermined time. What should I do? The end of the tightening can also be determined based on the measurement result of the torque meter 22. Similarly, in the case of the control based on the tightening rotation angle, the energy used for the tightening may be reduced when the motor is rotated by the predetermined tightening rotation angle. Also in this case, the end of the tightening may be determined based on the tightening rotation angle, or may be determined based on the measurement result of the torque meter 22.
[0021]
In addition to the oil pulse wrench shown here, similar control can be performed not only by using a general impact wrench, but also by using a rotary tightening device such as a nut runner that performs continuous tightening. It is also possible to do.
[0022]
In the above-described embodiment, the magnitude of the drive energy is switched only in one step. However, a plurality of drive energy switching torques are provided, and the drive energy is suppressed stepwise each time the torque is reached. May be. In addition, the suppression of the driving energy is not performed instantaneously, but can be gradually reduced with time.
[0023]
Further, by controlling the process until the energy output from the driving motor unit 16 is transmitted to the tightening unit 21 instead of the driving energy for driving the driving motor unit 16, the tightening energy is increased. It is also possible to switch between them.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing the configuration of the present embodiment.
FIG. 2 is a flowchart illustrating an outline of control according to the present embodiment.
FIG. 3 is a diagram illustrating a temporal change of a tightening torque in the embodiment.
FIG. 4 is a diagram showing a temporal change of a tightening torque in a conventional example.
FIG. 5 is a diagram showing a temporal change of a tightening torque in another conventional example.
[Description of Signs] 10 oil pulse wrench, 12 main unit, 14 control unit, 16 drive motor unit, 18 oil pulse unit unit, 20 axes, 21 tightening unit, 22 torque meter, 26 signal processing unit, 28 storage / Arithmetic unit, 34 Motor control unit.

Claims (5)

A control unit for controlling the amount of tightening energy supplied to the tightening unit;
Equipped with a torque meter to measure the tightening torque,
A rotary tightening device that rotates a tool to be tightened and tightens with a target tightening torque,
After the tightening torque reaches a predetermined value equal to or less than the target tightening torque, the rotary tightening device performs tightening with a smaller tightening energy than before. A control unit for controlling the amount of tightening energy supplied to the tightening unit;
Equipped with a clock to measure the tightening time,
A rotary tightening device for rotating a tool to be tightened and tightening for a target tightening time,
After the tightening time reaches a predetermined value equal to or less than the target tightening time, the rotary tightening device performs tightening with a smaller tightening energy than before. A control unit for controlling the amount of tightening energy supplied to the tightening unit;
Equipped with a means for measuring the tightening rotation angle,
A rotary tightening device that rotates a tool to be tightened and tightens a target tightening rotation angle,
After the tightening rotation angle reaches a predetermined value equal to or less than the target tightening rotation angle, a rotation tightening device that performs tightening with smaller tightening energy than before. The rotary tightening device according to any one of claims 1 to 3, wherein the rotary tightening device is an impact wrench. The rotary tightening device according to any one of claims 1 to 3, wherein the rotary tightening device is a nut runner.

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