JPH0616990B2 - Impact wrench tightening force control device - Google Patents

Description

The present invention relates to a tightening force control device for an impact wrench, and more particularly to a device for controlling the tightening force using the rebound angle of the impact wrench.

[Prior Art] Today, impact wrenches are widely used in various fields for tightening and loosening bolts and nuts. For example, in automobile factories, one-hammer type impact wrenches are used as torsion wrenches. A bar is attached and many bolts and nuts are tightened.

However, since tightening work using such an impact wrench has been performed based on the personal experience and intuition of the worker, variations in the tightening force of bolts and nuts are likely to occur, even if the same work is performed. However, there is a problem that excessive tightening or insufficient tightening easily occurs depending on the ability of the worker, and it is difficult to perform accurate tightening work.

For this reason, conventionally, a device for controlling the tightening force of the impact wrench to a constant value has been proposed, and as such a proposal, Japanese Patent Application Nos. 51-57704 and 56-56704 have been proposed.
-82216 is known.

The control device according to the former proposal is a device that generates a signal representing the deceleration of a hammer after engaging with an anvil, and a moment applied at the same time, and a yield point or a yield point of a fastener assembly in response to the deceleration signal. A device for determining a similarly important point and a device for producing a control output signal when the clamp assembly is clamped to the yield point or a similarly important point, including a fastener for the yield point or the like. It is characterized by tightening control up to important points.

Further, the latter control device integrally mounts the detection rotary body on the rotary portion of the impact wrench, and arranges a pair of sensors facing each other with a predetermined phase difference on the detection rotary body, and based on the outputs of these sensors. It is characterized in that the rebound angle of the detected rotating body generated when the impact wrench is hit is measured, and the operation of the impact wrench is stopped when the rebound angle exceeds a predetermined value.

[Problems to be Solved by the Invention] However, in the former control device, it is necessary to provide an encoder on the rotation drive unit side as a rotation angle detection device and further to provide a dedicated detection device for detecting rebound of the impact wrench. Therefore, there is a problem that the entire device becomes large.

Furthermore, since this control device uses a one-way clutch as a part of the device for detecting rebound, even if it is possible to perform tightening work of screws and nuts, the opposite work, namely, There was a problem that the loosening work could not be performed.

Further, in this control device, the control of the tightening force of the impact wrench is not always sufficient, and there is a problem that a tightening error of about ± 30% for the general-purpose type and about ± 15% for the control type cannot be avoided.

Further, the latter control device does not need to be provided with an encoder on the rotating part side, and moreover, because the rebound is electrically detected, the entire device can be made smaller and lighter,
Further, since a one-way clutch or the like is not necessary for detecting rebound, both tightening work and loosening work can be performed.

Further, the control device according to the latter is for detecting the rebound angle and detecting the end of tightening when the detected value exceeds a predetermined value. That is, the end of tightening is determined based on the correlation between the rebound angle and the tightening torque. However, the rebound angle varies even when the same tightening torque is generated, and due to this variation, rebound may occur at an angle exceeding a predetermined value even when a sufficient tightening torque is not generated. In this case, there is a problem that the end of tightening is determined before it is sufficiently tightened.

Furthermore, in the process of tightening the bolts and nuts, the tightening torque increases less as the target value is approached, and only slightly increases near the target value. This and the variation in the rebound angle further promote the occurrence of insufficient tightening torque. In other words, just before the target tightening torque is reached, the tightening torque increases little by little, so the hammer will be hit many times, and a large value will be detected due to variations in the rebound angle. If tightened, tightening will be insufficient.

As described above, even in the control device according to the latter, it is not always possible to sufficiently control the tightening force.

Further, Japanese Utility Model Laid-Open No. 58-93472 discloses an impact wrench which detects the seating of a bolt or a nut by rebounding and determines the end of tightening by the rotation angle of the bolt and nut and the number of impacts after the seating is detected. According to this, the problem of the above-mentioned device which determines the end of tightening by the rebound angle is once solved.

However, the detection of the rebound angle is to detect the rotation angle of the anvil, that is, the socket. Therefore, the shape of the socket must be shaky with respect to the shape of the head such as a bolt. In other words, if there is no play, socket rebound does not occur and this cannot be detected. If the socket and the bolt head have such a backlash, there arises a problem that the corner of the bolt head collapses during the actual tightening work to make the bolt unusable or to reduce the impact force.

Further, since the socket constantly receives torque in the tightening direction, it cannot freely rebound, and the amount is inevitably small. Further, the rebound is also suppressed by the friction between the bolt head and the socket, and the rebound angle tends to vary due to the difference in the friction coefficient between the individual bolt heads. As described above, in this device, since the rebound angle which is small and varies is detected, the accuracy is naturally low. Therefore, even if an attempt is made to control the tightening force by the rotation angle after seating, the accuracy of seating detection is not sufficient, resulting in low accuracy.

As described above, depending on the conventional device, the tightening force cannot always be sufficiently controlled, and the tightening work cannot be performed with sufficient certainty such as not crushing the bolt head. Was wanted.

[Object of the Invention] The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a compact and lightweight impact capable of accurately controlling the tightening force of an impact wrench to a constant value. It is to provide a tightening force control device for a wrench.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an anvil that transmits a tightening force to a member to be fastened, a rotation transmission mechanism that gives a tightening force to the anvil by a hammer, and a hammer. A tightening force control device for an impact wrench, which controls driving air of an air motor in an impact wrench having an air motor for giving a rotational driving force, to control a tightening force of the tightening member, which is integrated with an impact hammer driving shaft of the impact wrench. And a disc-shaped detection rotator having an intermittent detection part at a constant interval on the outer periphery and a detection part of the detection rotator provided on the non-rotating part of the impact wrench to detect different phases. The pair of rotation detection sensors that output pulse signals, and the detection based on the phase shift of the path signals output from the pair of rotation sensors A rebound detection circuit that detects the rotation direction of the rotating body and outputs a rebound detection signal indicating whether the normal rotation operation or the rebound operation is in progress,
A rebound detection signal output from the rebound detection circuit and a pulse signal from any one of the rotation sensors are input, and a gate that outputs a pulse signal from the rotation sensor during the rebound operation, and a rebound detection signal and the gate A preset counter that outputs a pulse signal, is reset at the end of the rebound operation, counts the pulse signal, and outputs a trigger signal when the count value reaches a predetermined value, and a preset counter from the preset counter The pulse signal from either the trigger signal, the rebound detection signal from the rebound detection circuit, or the rotation sensor is input, and when the trigger signal is input, counting is started, and the pulse signal input during the forward rotation operation is input. Pulse signal that counts up and is input during rebound operation Up-down counter that counts down and outputs a drive stop command signal for the impact wrench when the count value exceeds a preset value, and stops the impact wrench when the drive stop command signal from this up-down counter is input And a stop control circuit for controlling the stop control circuit.

[Operation] The present invention is configured as described above, and the operation will be described below.

The impact hammer driving shaft of the impact wrench is provided with a disc-shaped detection rotary member having intermittent detection units at regular intervals on its outer peripheral portion. Therefore, the detection rotating body rotates as the hammer driving shaft rotates. On the other hand, the non-rotating portion of the impact wrench is provided with a pair of rotation detecting sensors that detect the detecting portion of the detecting rotating body and output pulse signals having different phases from each other. As the body rotates, two pulse signals having different phases are output. The outputs from the pair of rotation sensors are input to the rebound detection circuit. The rebound detection circuit detects the rotation direction of the detection rotor from the deviation of the two input pulse signals. Then, the rebound detection signal indicating whether the normal rotation operation or the rebound operation is in progress is output. The rebound detection signal is input to the trigger generation circuit, and the trigger detection circuit counts the pulse signal output from the rotation sensor during the rebound operation. When the count value does not exceed the preset value, the count value is erased, and when the count value exceeds the preset value, a trigger signal is output. Therefore, this trigger signal indicates that the rotation amount of the drive shaft during the rebound operation has exceeded the predetermined value, and it is possible to detect that the bolt has reached the seat surface. After the trigger signal is output from the trigger generation circuit, the rotation angle integration circuit counts the pulse signals output from the rotation sensor during the forward rotation operation and the rebound operation. Then, the value obtained by subtracting the count value during rebound operation from the count value during normal rotation operation is sequentially integrated, and when this integrated value exceeds a preset value, a drive stop command signal for the impact wrench is output. . The integrated value of this rotation angle integration circuit is
Since it corresponds to the total amount of forward rotation after the bolts reach the bearing surface, the amount of rotation of the bolts after reaching the bearing surface can be detected, and tightening will be stopped when this exceeds a certain amount. As a result, a constant tightening amount can be obtained.

Particularly, in the present invention, the pulse signal from the single rotation angle detecting means is used, the seating is detected in the trigger generating circuit, and the rotation angle after the seating is detected in the rotation angle integrating circuit. Therefore, there is an effect that a certain amount of tightening after seating can be accurately detected in a simple circuit.

Further, a conventional socket can be used as it is without using a specially shaped impact wrench socket, and a problem such as a collapse of a bolt head does not occur.

[Embodiment] Next, a preferred embodiment of the present invention will be described with reference to the drawings.

Impact Wrench Control System FIG. 2 shows a control system of the impact wrench used in this embodiment, in which the impact wrench 10 is connected to a compressed air supply source via an air supply hose 12. . Then, the controller 14 opens and closes the electromagnetic valve 16 provided in the middle of the air supply hose 12 to control the supply of the compressed air supply to the impact wrench 10.

The impact wrench 10 is formed so that the compressed air drives the air motor by pulling the starting lever 18 in the direction of the arrow in the drawing while the solenoid valve 16 is controlled to be opened and compressed air is supplied. Then, the output shaft of the wrench, that is, the anvil 20 is rotationally driven by this air motor.

Structure of Impact Wrench FIG. 3 shows a specific structure of the impact wrench 10. The impact wrench 10 of the embodiment includes an air motor 22 and an anvil 20, and the rotation of the air motor 22 is a rotation shaft 24 thereof. It is transmitted to the anvil 20 side by the hammer 26 that rotates integrally.

Then, a torsion bar (not shown) is attached to the tip of the anvil 20, and the bolts and nuts are screwed.

The structure of each part of the impact wrench 10 will be described in detail below.

First, in the impact wrench 10, the air supply valve 30 is opened by pulling the starting lever 18 in the direction of the arrow in the drawing,
The compressed air supplied through the air supply port 28 drives the air motor 22 to rotate normally or reversely.

Here, the rotation direction of the air motor 22 can be arbitrarily set to the forward rotation direction or the reverse rotation direction by operating the rotation switching lever 32.

The structure of this air motor 22 is shown in FIG. 4, which shows the impact wrench 10 shown in FIG.
It is sectional drawing cut | disconnected along the line.

In the state shown in the figure, compressed air to be supplied to the air motor 22 is supplied into the cylinder 36 in the direction indicated by the arrow 100, and the compressed air is blown to the vanes 38 so that the rotary shaft 24 is reversed. It is driven to rotate in the clockwise direction, and then discharged from the cylinder 36 as shown by an arrow 200 in the figure. Further, by switching the rotation switching lever 32 of the air motor 22, the switching valve 34 rotates 120 degrees to the right from the position shown in FIG. The shaft 24 is driven to rotate clockwise in the drawing.

The anvil 20 is rotatably supported in front of the rotation shaft 24 of the air motor 22 so that the rotation centers thereof coincide with each other. The rotation of the rotation shaft 24 is performed by the cam disc 42 and the hammer driving shaft. It is transmitted to the anvil 20 via the rotation transmission mechanism 40 including the clutch frame 44, the clutch body 56, and the hammer 26.

In the embodiment, the rotation transmission mechanism 40 has a cam disk 42 spline-fitted to the tip of the rotary shaft 24 of the air motor 22, and the clutch frame 4 is attached to the boss 42 a of the cam disk 42.
4 is fitted.

FIG. 5 shows the appearance of the clutch frame 44. The clutch frame 44 includes a pair of disk-shaped side walls 48a and 48b at the front and rear thereof, and a rear side wall 48b.
An inner circumference 58b of the cam disk 42 is formed so as to fit with the boss portion 42a of the cam disk 42.

The pair of side walls 48a and 48b are provided with a pair of pin holes 50a and 50b at positions facing each other, and a hammer pin 52 is attached and fixed between the pin holes 50a and 50b as shown in FIG. The hammer 26 is pivotally supported by the hammer 26 in a direction orthogonal to the axial direction of the hammer pin 52. Therefore, it is understood that the hammer 26 revolves with the rotation of the clutch frame 44. That is, it is understood that the clutch frame 44 is a shaft that rotationally drives the striking hammer (striking hammer driving shaft).

In the embodiment, the anvil 20 is rotatably supported by the case 54, and a clutch body portion 56 is integrally provided on the rear end side thereof.

In the embodiment, the body portion 56 is inserted into the inside of the opening portion 58a provided in the front end side wall 48a of the clutch frame 44 so as to be separated from the inside thereof, and is disposed so as to face the rotary shaft 24 of the air motor 22.

As shown in FIG. 6, the body portion 56 is provided with a pair of engagement grooves 60a and 60b which engage with the hammer 26. The hammer 26 is normally or reversely rotated according to the rotation direction of the air motor 22. It engages with either the groove 60a or 60b and transmits the rotation of the air motor 22 to the anvil 20.

With the above configuration, when tightening bolts and nuts using the impact wrench 10 of the embodiment, first, the starting lever 18 is operated to drive the air motor 22 in the clockwise direction in the figure, for example. At this time, the rotation of the air motor 22 is controlled by the rotation shaft 24, the cam disc 42, the clutch frame 4
4, transmitted to the anvil 20 via the hammer 26 and the clutch body 56, the anvil 20 rotates integrally with the socket body provided at the tip thereof, and the bolts, nuts, etc. fitted to the socket body rotate. , Progressive.

By the way, as is well known, such tightening of bolts and nuts is performed with the hammer 26 engaged with the engagement groove 60 of the anvil 20 when the bolts and nuts are floating from the seat surface. The rotating shaft 24 and the anvil 20 are integrally rotated.

However, when tightening progresses and the bolts and nuts reach the seating surface, the resistance torque from the anvil 20 side suddenly increases, and the hammer 26 starts to strike the anvil 20, and this impact action tightens the bolts and nuts. Will be performed.

FIG. 6 shows a series of striking and tightening operations by the hammer 26. First, when the bolts and nuts reach the seat surface and the resistance torque applied from the anvil 20 side reaches the motor torque, the rotation of the anvil 20 starts. As it approaches the stop, as a result, the locking force between the hammer 26 and the engagement groove 60 becomes weak,
Sliding occurs between the two and the hammer 26 is disengaged from the engagement groove 60.

As a result, the hammer 26 performs one rotation free running while accelerating integrally with the rotary shaft 24 of the air motor 22 as shown in FIG. 6 (A) without engaging with the anvil 20 side. After the free running of one rotation is completed, the hammer 26 again engages with the engagement groove 60 of the anvil body portion 56 and strikes, as shown in FIG. 6 (B).

At this time, the anvil 20 is rotated by the applied striking force to tighten the bolts and nuts.

At the same time, the hammer 26 reverses counterclockwise, that is, rebounds due to the recoil of the impact.

As shown in FIG. 6 (C), the rebound at this time is performed to a position where the rebound energy and the output torque of the air motor 22 are balanced, and then the motor output torque overcomes the rebound energy. As shown in (D), the air motor 22 starts forward rotation, and the hammer 26
After performing one rotation free running together with this air motor as described above, the next impact and rebound are similarly performed.

Therefore, by repeatedly performing such a series of striking, rebounding, and free running, the anvil 20 is gradually driven clockwise in the forward direction, and the tightening of the bolts and nuts proceeds.

A feature of the present invention is that it is possible to always tighten a screw, a nut, etc. with a constant tightening torque by utilizing such a rebound operation.

Principle of the Invention Next, the principle of the present invention will be described.

FIG. 7 shows the relationship between the rebound operation of the impact wrench 10 and the tightening torque. In the same figure (A),
The relationship between the integrated rotation angle θ of the anvil 20 and the tightening torque τ is shown, and the relationship between the hitting number I of the hammer 26 and its rebound angle β is shown in FIG. put it here,
The rebound angle β is defined as the reversal angle from the rebound start point to the rebound apex, as shown in FIG. 6 (C).

As shown in FIG. 12, the impact wrench 10 causes the hammer 26 to strike the anvil 20 with I ₀ , I ₁ , I.
_2, to each do ... and _repeatedly, θ _0, θ _1, to advance the integrated rotation angle θ of θ _{2 ...} and the anvil 20. At this time, it is understood that the tightening torque τ of the impact wrench 10 increases according to the integrated angle rotation angle θ of the anvil 20 after the striking operation is started, as shown in FIG. 7 (A). As shown in FIG. 7 (B), it is understood that the rebound angle β at each impact also increases according to the tightening torque τ at that time.

Therefore, as shown in Japanese Patent Application No. 56-83216, the rebound angle β is measured every time the hammer 26 is hit, and this rebound angle β is the target rebound angle corresponding to the desired tightening torque τ _S. It is also conceivable to form the stop command signal of the impact wrench 10 as the main force when reaching β _S. By doing so, it becomes possible to control the tightening torque of the impact wrench 10 to a desired value τ _S constantly only by detecting the rebound angle β.

However, as shown in FIG. 7 (A), in general, the target tightening torque τ _S is often set in the torque saturation region, and therefore the tightening torque τ given by the impact of the hammer 26 is τ.
Will increase only slightly as it approaches the target tightening torque τ _S.

On the other hand, as shown in FIG. 7 (B), the rebound angle β
Corresponds to the tightening torque τ with a certain variation. Therefore, when the target tightening torque τ _S set in the torque saturation region is to be detected only by the magnitude of the rebound angle β, a detection error is unavoidable, and as a result, An error of a certain width will occur in the magnitude of the tightening torque of the tightened bolt or nut.

A feature of the present invention is that such tightening torque control is performed by combining the rebound angle β and the integrated rotation angle θ of the anvil 20 described above. It is possible to tighten bolts and nuts more accurately than the above.

That is, as shown in FIG. 7 (A), when the tightening by hammering of the hammer 26 is started, the value of the tightening torque τ gradually increases until a constant snag torque τ _0, but this snag torque τ ₀ It has the characteristic of increasing sharply when it exceeds.

Therefore, the rebound angle β generated when the hammer 26 is hit
Also increases sharply around this snag torque τ ₀ ,
It is understood that the detection of the tightening torque reaching the snag torque can be accurately performed by measuring the rebound angle β.

Here, the _value of the snag torque τ ₀ varies depending on the types of bolts and nuts to be tightened,
It has been confirmed that constant values are always obtained for the same type of bolts and nuts.

Thus, previously set as the reference rebound angle beta ₀ advance the rebound angle corresponding to the magnitude of the Sunagutoruku tau _0, the measured tightening torque by the rebound angle beta is compared with the reference rebound angle beta ₀ tau is Sunagutoruku It is possible to accurately detect that τ ₀ has been reached.

By the way, as shown in FIG. 12, it is assumed that the impact rank by the hammer 26 is the snag torque τ _0, and the impact rank is I _0, and the rebound start point “a” of the anvil 20 at this time is θ = O ₁ or the origin. .., the cumulative rotation angle of the anvil 20 increases to θ ₁ , θ ₂ ... Every time the second and third hits I ₁ , I _2, ... Are performed.

At this time, as shown in FIG. 7 (A), since the magnitude of the tightening torque τ exactly corresponds to the magnitude of the integrated rotation angle θ from the origin one-to-one, it corresponds to the desired tightening torque τ _SS in advance. By setting this integrated rotation angle as the target integrated rotation angle θ _S , this integrated rotation angle θ matches the target integrated angle θ _S , so that the tightening torque of the bolts and nuts becomes the desired tightening torque τ _S. It is possible to accurately detect the arrival.

Therefore, by detecting that the tightening torque of the bolts and nuts has reached the desired tightening torque in this way, and outputting the stop command signal of the air motor 22 at the same time as this detection,
It is possible to tighten screws and nuts with a constant tightening torque with high accuracy.

A preferred embodiment of the control device of the present invention constructed according to this principle will be described below.

Tightening force control device The device of the present invention includes a detection rotator 70 provided on the drive unit side rotation shaft of the impact wrench 10 and the impact wrench 1.
And a pair of rotation detection sensors 74a and 74b which are provided on the fixed unit side of 0 and detect and output the rotation of the detection rotor 70 as pulse signals having different phases.

In the embodiment, the detection rotating body 70 is formed as a gear 72 provided along the entire outer periphery of the rear end side wall 48b of the clutch frame 44 as shown in FIG. 5, and is integral with the rotating shaft 24 of the air motor 22. Drive to rotate.

The detection rotary body 70 may be fixedly formed on the rear end side of the rotary shaft 24 of the air motor 22 as shown in FIG. It can be provided at any position.

The pair of rotation detecting sensors 74a and 74b are fixed to the inner surface of the case 54 of the impact wrench 10, and
As shown in the figure, it is arranged so as to face the outer peripheral surface of the gear 72 constituting the detection rotary body 70 so as to be close thereto and detect and output the rotation of the detection rotary body 70 as a pulse signal having a different phase.

Here, the pair of rotation detection sensors 74a, 74
It is preferable to arrange b so as to have a phase difference of 1/4 pitch of the gear, that is, a phase difference of 1/2 pitch of the convex portion 72a or the concave portion 72b. By doing so, as shown in FIG. , 74b, it is possible to obtain pulse signals having different phases by 90 degrees.

Here, when the hammer 26 is rotating in the clockwise direction, that is, in the forward rotation direction as shown in FIG. 6 (A), a pulse having a phase advanced by 90 degrees from one sensor 74a is output from the other sensor 74b. To be done. On the contrary, Fig. 6
As shown in (B) and (C), when the hammer 26 strikes and reverses in the counterclockwise direction to perform the rebound operation, the phases of both the sensors 74a and 74b are reversed, and the sensor 74b moves to the sensor 74a. A pulse whose phase is advanced by 90 degrees is output.

Therefore, by comparing the phases of the detection pulses 200a and 200b output from the two sensors 74a and 74b, the hammer 26 is rotating normally according to the output of the air motor 22 in the clockwise direction shown in FIG. By hitting against, it is possible to detect whether the vehicle is reversing due to rebound as shown in FIGS. 6 (B) and (C).

Further, by adding the pulse numbers of the detection pulses 200a and 200b output from the both sensors 74a and 74b when the anvil 20 is normally rotating, and subtracting it when the anvil 20 is rotating in reverse by the rebound, The integrated rotation angle θ of the anvil 20 generated by the impact of the hammer 26 as shown in FIG. 6 can be measured as the count value of the detection pulse of the sensor 74.

FIG. 1 shows an example of the sensor 74 and an electric circuit of a device for controlling the tightening force of the impact wrench 100 based on the detection output of the sensor 74d.
Detection outputs 200a and 200b of 4a and 74b are amplified by amplifiers 80a and 80b, and further waveform shaping circuits 82a and 82b formed by Schmitt trigger circuits.
Then, the waveform is shaped into a rectangular wave with a clear rise and fall and is output.

Then, the rebound detection circuit 84 detects the rebound operation of the hammer 26 based on the detection outputs 200a and 200b of the both sensors 74a and 74b thus output.

In the embodiment, this rebound detection circuit 84 is D-
It is formed using a flip-flop 86, and this D
The outputs of the waveform shaping circuits 82a and 82b are input to the D input terminal and the C input terminal of the flip-flop 86, respectively.

Therefore, as shown in FIG. 9, the D-flip-flop 86 outputs the normal state of the hammer 26 as Q = H, = L.
And the reverse state of the hammer 26 is Q = L,
Detect as = H.

Therefore, the detection output Q of this D-flip-flop,
And the detection outputs 200a and 20 of the sensors 74a and 74b.
By calculating 0b in combination, the rebound angle can be detected as the pulse count number each time the hammer 26 reverses.

In the present invention, from the rebound angle β, the seventh
A trigger generation circuit 88 is provided to detect the snag torque τ ₀ shown in FIG.

The trigger generation circuit 88 has a reference rebound angle β _S set in advance corresponding to a predetermined snag torque τ ₀ .
Then, the output of the D-flip-flop 86 and the sensor 7
Based on the output of 4, the rebound angle β is measured every time a rebound is detected, and when the measured rebound angle β exceeds the reference rebound angle β _S , the trigger signal 400 for starting the rotation angle detection is generated. Output.

In the embodiment, the trigger generating circuit 88 comprises an AND gate 90 and a preset counter 92, and the preset rebound angle β _S is previously stored in the preset counter 92.
The reference rebound pulse number N ₀ corresponding to is set.

The AND gate 90 integrates the output of the D-flip-flop 86 and the detection output 200b of the one sensor 74b output via the waveform shaping circuit 82b, and as shown in FIG. 9, each rebound section B, Only the detection output 200b output from the sensor 4b within the period of D ...
It is selectively taken out as 0, and its output 300 is inputted to the preset counter 92.

The preset counter 92 outputs the output 3 of the AND gate 90.
The number of 00 pulses is counted, and when the count value N exceeds the preset reference rebound pulse number N ₀ , the trigger signal 400 is output.

Here, the reference rebound pulse number N ₀ set in the preset counter 92 can be appropriately set to a desired value in accordance with the value of the snag torque τ ₀ of the bolt or nut to be tightened. The value is N ₀ =
It is set to 6.

Therefore, in the rebound section B shown in FIG. 9, since the number of detection pulses output from the AND gate 90 is 5, the trigger signal 400 is not output from the preset counter 92, but the AND gate 9 is output in the next rebound section D.
Since 0 to 6 or more detection pulses are output, the sixth detection pulse 300 is output and the trigger signal 400 is output from the preset counter 92 at the same time.

In the present invention, when the count value exceeds the preset value and the rebound angle β _S corresponding to the snag torque τ ₀ is detected, the rebound start point “a” by the impact I _{0 at} this time is next detected. With an origin θ = o
The calculation of the integrated rotation angle θ of 0 is started.

This calculation is performed by the trigger signal 400 output from the preset counter 92 and the output 2 of the sensors 74a and 74b.
This can be done by combining 00a and 200b.

Therefore, in the present invention, a rotation angle integration circuit 94 is provided, and this rotation angle integration circuit 94 is shown in FIG.
As shown in (A), the rotation angle θ _S corresponding to the target tightening torque τ _S is preset and stored as the target integrated rotation angle.

The rotation angle integrating circuit 94 outputs the output 200a of the D-flip-flop 86 and the sensor 74a or 74b.
Based on 200b, the integrated rotation angle θ from the origin “a”
When the integrated rotation angle θ exceeds the target integrated rotation angle θ _S , the impact wrench stop command signal 500 is output.

In embodiments, the rotation angle integrating circuit 96 is formed by using the up-down counter 96, previously the target integrated rotational angle θ target rotation angle pulse number is the number of pulses corresponding to _S n _S in the counter 96 It is set and stored as.

Further, the counter 96 has a reference rebound pulse number (6 in the embodiment) of the preset counter 92.
The value corresponding to is set as the initial value.

The counter 96 is the preset counter 92.
At the same time that the trigger signal 400 is output from, the counting is started from the initial value (n = 6 in the embodiment).

Here, this counting operation is performed so that the output pulse 200b of the sensor 74b is down-counted when the output of the D-flip-flop 86 is = H and up-counted when it is = L. The cumulative rotation angle θ is calculated as the pulse count value n. Therefore, the value obtained by subtracting the count value at the rebound operation from the count value at the normal rotation operation is sequentially integrated.

Then, when the count value n reaches the preset target pulse number n _S , at the same time, the stop command signal 500 is input to the stop control circuit 98.

Here, the stop control circuit 98 includes an RS flip-flop 98a, a reset switch 98b, and a solenoid valve control transistor 98c. The up-down counter 96 outputs the stop command signal 500 and at the same time, the RS flip-flop 98a. Outputs an L level signal to the transistor 98c to release the excitation of the electromagnetic relay 16a of the electromagnetic valve 16 shown in FIG.

As a result, the solenoid valve 16 is turned off and the supply of high pressure air to the impact wrench 10 is stopped, so that the impact wrench 10 is automatically stopped and controlled.

By doing so, according to the present embodiment, it is possible to always tighten the bolts and nuts using the impact wrench 10 with a constant tightening torque.

The reset switch 98b is used for the electromagnetic relay 16
It is for initializing the RS flip-flop 98a for driving a and bringing it into a high-pressure air supply state. In the embodiment, the stop command signal 500 from the up-down counter 96 is used.
Is supplied and the supply of high pressure air is interrupted, and after a lapse of a certain time by the operation of a timer, the high pressure air supply state is automatically restored.

By doing so, the worker can quickly move to the next bolt or nut tightening work after finishing the tightening of one bolt or nut.

Here, it is preferable that the timer time is formed so that it can be arbitrarily selected and set within a range of 0.1 to 9.9 seconds.

Further, in this embodiment, it is preferable that the main part of the control circuit as shown in FIG. 1 is provided in the controller 14 shown in FIG. 2, and at this time, the preset counter 92 and the up / down controller are provided on the controller 14. It is preferable to form the reference rebound angle β ₀ and the target integrated rotation angle θ _S for the counter 96 so that they can be set arbitrarily.

The present embodiment has the above configuration, and its operation will be described below.

First, when the starting lever 18 of the impact wrench 10 is operated and the air motor 22 is rotationally driven, the hammer 26 is engaged with the engaging groove 60 of the anvil 20 until the bolt and nut are attached to the seat surface.
The rotation of the air motor 22 is transmitted to the anvil 20 side as it is, and the bolts and nuts are tightened.

When the bolts and nuts reach the bearing surface and the torque resistance of the anvil 20 increases and exceeds the output torque of the air motor 22, the engagement between the hammer 26 and the engagement groove 60 is released each time, and the sixth As shown in FIGS. 7 and 7, tightening of the hammer 26 by striking the engagement groove 60 is started.

Then, the tightening torque of the bolt and the nut is sequentially increased as the tightening by such impact is repeated.

At this time, the normal rotation operation of the hammer 26 and the rebound operation due to the impact are detected by the D-flip-flop 86 based on the outputs of the sensors 74a and 74b. Then, the preset counter 92 detects whether or not the tightening torque by striking reaches a predetermined snag torque τ ₀ according to the flow chart shown in FIG.

That is, the preset counter 92 is
The engagement groove 60 is hit and the rebound is started at the same time the rebound angle β is measured. When the rebound angle β exceeds the reference rebound angle β ₀ , the retoga signal 400 is output.

In this way, when it is detected that the tightening torque τ reaches the snag torque τ ₀ , the up / down counter 96 then sequentially integrates the rotation angles of the anvil 20 according to the flowchart shown in FIG.

FIG. 12 shows an explanatory view of this integrating operation. First, the hammer 26 strikes the engaging groove 60 at the point "a".
_It is assumed that the trigger signal 400 is output when ₀ is given and the rebound is performed to the position of "b".

At this time, the preset counter 96 as described above, the rebound angle beta ₀ rebound starting point of the striking I ₀ from the "I" to end point "B", the end point "B" from the rebound starting point for the next blow I ₁ " The forward rotation angle α ₀ up to “C” and
Calculate the rotation angle γ of the anvil 20 caused by the next impact I ₁ based on the following equation: γ ₀ = (α ₀ −360 °) −β _{0 In the same} manner, the preset counter 96 performs the subsequent impact. Rotation angles γ ₁ , γ ₂ , γ ₃ ... γ of the anvil 20 caused by I ₁ , I ₂ , I ₃ ... I _n .
_n-1 ... Is calculated based on the following equation.

γ ₁ = (α ₁ -360 °) -β ₁ γ ₂ = (α ₂ -360 °) -β ₂ ... γ ₃ = (α _n -360 °) -β _n And the preset counter 96 is Then, the anvil rotation angles γ ₁ , γ ₂ , γ ₃ ... γ _n ... Produced by the respective impacts I ₁ , I ₂ , I ₃ ... I _n ... Are sequentially integrated based on the following equation, and the first impact I _{0 is obtained.} The integrated rotation angle θ of the anvil 20 with the rebound starting point “a” as the origin is sequentially calculated.

θ ₀ = γ ₀ θ ₁ = γ ₁ + θ ₀ θ ₂ = γ ₂ + θ ₁ ... θ _n = γ _n + θ _n−1 Then, this integrated rotation angle θ is preset in correspondence with the target tightening torque τ _S. At the same time when the target integrated rotation angle θ _S is reached, the counter 96 outputs a stop command signal 500 and automatically controls the impact wrench 10 to stop.

In this way, according to the present invention, as shown in FIG. 7 (A), the tightening operation of the impact wrench 10 automatically stops at the same time when the tightening torque reaches the desired target tightening torque τ _S. As long as the tightening work is performed on the same object, it is possible to perform the tightening work on the bolts, nuts and the like with a certain tightening torque without fail.

According to the bench test, the tightening accuracy of the conventional device was ± 30% for the general-purpose type and ± 15% for the control, whereas the device of this example improved the tightening accuracy to ± 10%. It is confirmed to do.

[Effect of the Invention] As described above, according to the present invention, one detection device for detecting the rotation angle of the output shaft of the impact wrench and one detection device for detecting the rebound angle of the impact hammer are provided. Since it can be detected by the method, there are effects such as cost reduction by reducing the number of parts, improvement of maintainability and reliability, and improvement of workability by reduction in size and weight.

[Brief description of drawings]

FIG. 1 is a block diagram showing a preferred embodiment of a tightening force control device for an impact wrench according to the present invention, FIG. 2 is a schematic explanatory view of an impact wrench system of this embodiment, and FIG. 3 is shown in FIG. FIG. 4 is a side sectional view of the impact wrench, FIG. 4 is a sectional view taken along line IV-IV of FIG. 3, and FIG. 5 is an explanatory view showing the mounting positions of the detection rotor and the rotation detection sensor used in this embodiment. Is an explanatory view showing the operating state of the hammer and anvil of the impact wrench of the embodiment, FIG. 7 is an explanatory view showing the relation between the rebound operation and the tightening torque of the impact wrench of the embodiment, and FIG. FIG. 9 is an explanatory view showing other mounting positions, FIG. 9 is a timing chart of the circuit shown in FIG. 1, FIG. 10 is a flow chart showing the operation of the preset counter 92 shown in FIG. 1, and FIG. 11 is FIG. Shown in FIG. 12 is a flowchart showing the operation of the down-down counter 96, FIG. 12 is an explanatory view showing the rotation angle integrating operation of the up-down counter 96 shown in FIG. 1, 10 ... Impact wrench 20 ... Anvil 22 ... Air motor 24 ... Rotation Axis 26 ... Hammer 44 ... Clutch 70 ... Detection rotor 74a, 74b ... Rotation detection sensor 84 ... Rebound detection circuit 86 ... D-flip-flop 88 ... Trigger generation circuit 90 ... And gate 92 ... Preset counter 94 ... Rotation angle integration circuit 96 ... Up / down counter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shiro Amaka Toyota-cho, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Takashi Kobayashi 3-6-15 Nonokami, Habikino-shi, Osaka Stock company Soraken (72) Inventor Masaru Mizuhara 3-6-15 Nonogami, Habikino-shi, Osaka Stock company Soraken (72) Inventor Toshihiro Fuchizaki 3-13-15 Kamikita, Hirano-ku, Osaka, Osaka In the near-meter system (56) Reference JP-A-58-22668 (JP, A) JP-A-59-196169 (JP, A) Actually developed JP-A-58-93472 (JP, U)

Claims (1)

[Claims] 1. An impact wrench having an anvil for transmitting a tightening force to a member to be fastened, a rotation transmission mechanism for applying a tightening force to the anvil by an impact hammer, and an air motor for applying a rotational driving force to the impact hammer. A tightening force control device for an impact wrench that controls the tightening force of a member to be tightened, which is provided integrally with a striking hammer drive shaft of the impact wrench and has an intermittent detection unit at an outer peripheral portion at regular intervals. A disk-shaped detection rotary body, a pair of rotation detection sensors which are provided in a non-rotating portion of the impact wrench, and which detect the detection portion of the detection rotary body and output pulse signals having mutually different phases, and the pair of rotation sensors. The direction of rotation of the detection rotor is detected from the phase shift of the pulse signal output from the A rebound detection circuit that outputs a rebound detection signal indicating whether work is in progress, and a rebound detection signal output from the rebound detection circuit and a pulse signal from one of the rotation sensors The gate for outputting the pulse signal of, the rebound detection signal, and the pulse signal output from the gate are input, reset at the end of the rebound operation, the pulse signal is counted, and the count value reaches a predetermined value. When a preset counter that outputs a trigger signal, a trigger signal from the preset counter, a rebound detection signal from the rebound detection circuit, or a pulse signal from one of the rotation sensors is input, and the trigger signal is input The pulse that starts counting and is input during forward rotation Up and down counters that up-count the pulse signals that are input during rebound operation, and output a drive stop command signal for the impact wrench when the count value exceeds a preset value. A tightening force control device for an impact wrench, comprising: a stop control circuit that stops the impact wrench when a drive stop command signal is input from the counter.