JP3945114B2 - Impact tightening tool - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to improvement of impact tightening tools such as impact drivers and impact wrenches.
[Prior art]
The impact driver, which is an impact tightening tool, is a tool that converts the rotation of the motor into a hammer hitting and tightening with its strong impact force. Due to its high workability of high speed rotation and high torque, it is a construction site, assembly factory, etc. Widely used in
[0003]
The present applicant has proposed a method for estimating the tightening torque from the rotational speed of the motor and the rotation of the motor between impacts as a method for controlling the tightening torque of the impact driver.
[0004]
This tightening torque estimation method is derived from the balance of kinetic energy for each impact, and the energy given to the anvil provided at the base of the output shaft by hammering is approximately equal to the energy consumed by tightening. This is a method for estimating the tightening torque from the relationship.
[0005]
As an example, it is assumed that the relationship between the screw rotation angle θ after seating determined by the member and the tightening torque T can be expressed by a function T = τ (θ) as shown in FIG. ₁ … It is assumed that it occurred at the point of θ _N. The value E ₁ obtained by integrating the function τ in the interval [θ ₁ , θ ₂ ] is the energy consumed for the tightening work, and is equal to the energy given to the anvil due to the hammer hit generated at the θ ₁ point. Therefore, the average torque <T _n > in the interval [θ _n , θ _{n + 1} ] is E _n and Θ _n = (θ _{n + 1} −θ _n ),
<T _n > = E _n / Θ _n (1)
It is obtained. In order to perform the tightening torque control, the driving of the motor may be stopped when this <T> becomes _{equal to} or greater than the set torque Tset. E _n is the rotation speed ω _n , which is the output of the rotation speed detection means, and the known moment of inertia Ja of the anvil at the time of occurrence of the hit detected by the hit detection means.
E _n = 1/2 × Ja × ω _n ² (2)
Θ can be easily obtained from the rotation angle detecting means.
[0006]
[Problems to be solved by the invention]
When obtaining the tightening torque by the method represented by the equation (1), a highly reliable impact detection means is essential. If the hit is missed, the rotation angle Θ between hits calculated at the next hit detection becomes a large value, and Equation (1) estimates a tightening torque smaller than the actual tightening torque. This means that in FIG. 8, when a hit at point θ ₂ cannot be detected,
It can also be seen from the fact that <T ₂ > is calculated not as E ₂ / (θ ₃ −θ ₂ ) but as E ₂ / (θ ₃ −θ ₁ ). For the same reason, when a hit that does not actually exist is detected by mistake, a tightening torque larger than the actual is estimated. As a result of erroneous tightening torque estimation, the member is damaged due to insufficient tightening or excessive tightening.
[0007]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an impact tightening tool that eliminates the influence of a hit detection error and improves the hit detection accuracy.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the invention of claim 1, in an impact tightening tool comprising an output shaft that is struck by a hammer and to which a rotational force is applied, and an impact detection means that detects the impact of the output shaft by the hammer , Rotation speed detection means for detecting the rotation speed of the motor that drives the hammer, and a period during which no hit can occur is obtained from the rotation speed detected by the rotation speed detection means, and the detection of hitting by the hit detection means during the period is ignored. And a striking ignore period setting means.
[0009]
According to a second aspect of the present invention, in an impact tightening tool comprising an output shaft that is struck by a hammer and to which a rotational force is applied, and a impact detection means that detects the impact of the output shaft by the hammer, the impact generation timing of the impact detection means Based on the above, the rotation angle calculation means for calculating the rotation angle of the output shaft for each hit, and the rotation angle value between the hits obtained from the rotation angle calculation means between hits is below a certain threshold value It is characterized by comprising a hit correction means for determining detection and handling invalid hits.
[0010]
In the invention of claim 3, in the invention of claim 2, the hitting correction means compares the rotation angle between previous hits obtained from the rotation angle calculation means between hits with the current rotation angle between hits, When the value is large, it is determined that the hit detection is missing, and the rotation angle between hits is corrected .
[0011]
According to a fourth aspect of the present invention, in the second aspect of the invention, the hit detection means has a hit period measuring means for measuring the detected hit period, and the hit correction means is an hit period from the hit period measuring means. based on the detection omission of shot and correcting the rotational angle interval of the strikes by determining false hit detection.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
First, before entering the description of the embodiments of the present invention, the basic principle of the present invention will be described.
[0013]
When an impact tightening tool such as the impact driver of the present invention is applied with a force of a predetermined value or more between the hammer and the anvil, the hammer freely rotates with respect to the anvil, and the hammer has a predetermined angle α [rad] (depending on the mechanism). The hammer collides with the anvil after it rotates freely more than the fixed constant). In other words, there can be no impact within the period t during which the hammer rotates freely. This period ti [sec] can be obtained by ti = α / ω, assuming that the rotation speed of the hammer 3 is ω [rad / sec].
[0014]
In addition, if the hammer does not rotate by a predetermined angle α [rad], the hit does not occur. Therefore , the hit detection result at the rotation angle between hits less than α [rad] is naturally invalid. And, when the excessive rotation angle between hits is obtained compared to the previous rotation angle, it is assumed that the hit is missed. Similarly, when the hitting cycle becomes very long compared to the previous hitting cycle. It is thought that he failed to detect the blow.
[0015]
In view of this, the present invention appropriately performs the distribution processing of the rotation angle between hits in consideration of invalid hit detection results and missed hit detection.
[0016]
Hereinafter, the present invention will be described in detail with reference to embodiments.
(Embodiment 1)
FIG. 1 shows a schematic configuration diagram of an impact tightening tool of the present embodiment. The impact tightening tool includes a motor 1 as a driving means, a speed reducer 2 as a transmission mechanism that reduces the rotation of the motor 1 at a predetermined reduction ratio, and a hammer 3 through which the rotation of the motor 1 is transmitted via the speed reducer 2. , An output shaft 5 having an anvil 4 struck by the hammer 3, and a hammer 3 hitting the anvil 4 to which a rotational force is applied impactively, and a microphone for converting an impact sound of the anvil 4 by the hammer 3 into an electric signal 6, an impact detection unit (striking detection means) 7 for detecting that the anvil 4 is struck by the hammer 3 because the output voltage of the microphone 6 exceeds a predetermined threshold, and the motor 1. A frequency generator (FG) 8 as a rotation angle detection means for generating a signal having a frequency proportional to the number of rotations, and a waveform shaping of the signal generated by the frequency generator 8, Tightening torque is calculated from the output of the waveform shaping circuit 9 that outputs a pulse signal having the number of pulses corresponding to the turning angle, and the hit detection unit 7 and the waveform shaping circuit 9, and the motor 1 is turned on when the tightening torque exceeds a specified value. A control circuit unit 10 that generates a stop signal to be stopped and a drive stop command input from the control circuit unit 10 while rotating the motor 1 in response to a trigger (speed command) St input by an operation of an operation unit (not shown). And a motor control unit 11 for stopping the rotation of the motor 1 according to the above. Here, the motor 1 and the speed reducer 2 constitute a rotational drive unit.
[0017]
The control circuit unit 10 includes a counter 12 as a rotation angle detection unit that counts the number of pulses of the pulse signal input from the waveform shaping circuit 9, a timer 13 that generates an interrupt signal at a constant time interval, and a constant A rotation speed detector (rotation speed detection means) 14 for calculating the rotation speed of the output shaft 5 by dividing the difference in counter value between interrupts by the interval of the interrupt signal from the timer 13 generated every time, and the impact An external interrupt is generated by the detection signal S of the detection unit 7, and the rotation angle of the output shaft 5 is calculated from the count value of the counter 12 until the hit detection is detected after the hit detection unit 7 detects the previous hit. Inter-blow rotation angle calculation unit (inter-blow rotation angle calculation means) 15, the rotation angle between the hits calculated by the inter-blow rotation angle calculation unit 15, and the rotation speed detection unit when the output shaft 5 is hit 14 is A torque is estimated from the rotational speed of the output shaft 5 immediately after the occurrence of the hitting, based on the above formulas (1) and (2), set by operation of a variable resistor (not shown), and an A / D converter When it is determined that the value of the set torque to be taken in after AD conversion by 16 is reached, a torque estimation unit 18 that notifies the motor control unit 11 of a drive stop command via the I / O unit 17 and stops the motor 1; In accordance with a call from the rotation angle calculation unit 15 between hits, a hit disregard period setting unit that obtains a period during which no hit can occur from the rotation speed calculated (detected) by the rotation speed detection unit 14 and ignores the hit detection for that period. 19 and a timer 20 that counts the period. The control circuit unit 10 is actually constituted by a one-chip microcomputer, for example.
[0018]
Next, the operation of the hit disregard period setting unit 19 which is a main part of the present embodiment will be described in detail based on the flowcharts of FIGS.
[0019]
First, the rotation angle calculation unit 15 between strikes is activated in the form of an external interrupt in response to the detection signal S from the strike detection unit 7, but the impact ignore period setting unit 19 is activated in response to the activation of the rotation angle calculation unit 15 between strikes. It operates in a form called from the rotation angle calculation unit 15. In the process in the impact ignoring period setting unit 19, the time required for the rotation speed ω [rad / sec] of the motor 1 to be obtained from the rotation speed detection unit 14 and the hammer 3 to rotate π [rad] at the rotation speed. A value K / ω that is slightly smaller than the count value corresponding to π / ω [sec] is set in the register of the timer 20 , and the timer 20 is allowed to be interrupted to start counting. That the period is cause counted by the timer 20 calculates the ignore time. At the same time, the rotation angle calculation unit 15 is instructed to prohibit the external interruption so as not to be activated by the external interruption by the detection signal S of the hit detection unit 7. When the count of the set count value is completed, the timer 20 outputs an interrupt signal to the strike disregard period setting unit 19 to generate an interrupt. The hit ignoring period setting unit 19 permits an external interrupt by the detection signal S of the hit detection unit 7 within the processing by this interrupt. On the other hand, after outputting the interrupt signal, the timer 20 prohibits the output of the interrupt signal thereafter.
[0020]
As described above, in this embodiment, when the hit detection unit 7 detects a hit, after the hit is detected, external interruption is prohibited during the set ignore period , and even if hit detection is detected during this period, The rotation angle calculation unit 15 is ignored.
[0021]
Here, the hit disregard period is set to a period suitable for the rotation speed, such as short when the rotation speed is high and long when the rotation speed is low.
[0022]
Thus, in this embodiment, by ignoring the wrong hit detection immediately after hit detection, the calculation of the rotation angle between hits due to the wrong hit detection is eliminated, so that the hit detection accuracy is improved and the accuracy of the rotation angle between hits is also improved. improves. Furthermore, since interruption due to hit detection is not frequently performed, the control circuit unit 10 can be constructed with a low-cost microcomputer with low processing capability.
(Embodiment 2)
In the first embodiment, the influence of wrong hit detection immediately after hit detection is eliminated by setting the hit ignore period. In the present embodiment, the hit correction unit rotates between hits as shown in FIG. There is a feature in that a hitting correction unit 21 is provided between the angle calculation unit 15 and the torque estimation unit 18 to correct an output value from the rotation angle calculation unit 15 between hits and transmit it to the torque estimation unit 18.
[0023]
In addition, the same code | symbol is attached | subjected to the same component as Embodiment 1, and description is abbreviate | omitted.
[0024]
Next, the operation of the batting correction unit 21 which is the main configuration of the present embodiment will be described based on the flowchart of FIG.
[0025]
First, the rotation angle calculation unit 15 calculates the rotation angle θ between hits by an external interruption based on the detection signal S of the hit detection unit 7, and the calculated value of the rotation angle θ between hits is taken into the hitting correction unit 21. It is.
[0026]
The hit correction unit 21 ends the interrupt process without performing the torque estimation process when the value of the rotation angle θ between hits is equal to or less than the predetermined threshold value θ _L.
[0027]
This θ _L is a count value of the frequency generator 8 corresponding to the free rotation angle π of the hammer 8 at the time of impact.
[0028]
On the other hand, when the value of the rotation angle between hits θ exceeds θ _L , after adding 1 to the number of hits Ni, the rotation angle between hits θ is 1.5 × θ _old (= the hitting rotation angle at the time of the previous hit detection) the inverted whether exceeded, the excess in which the coming to add further 1 to hit number Ni is (obtain the number of striking 2 times) to halve the rotation angle θ between the striking together. The value of θ _{old is taken as} the value of the rotation angle θ between hits. This θ _old is stored in the control circuit unit 10 as the rotation angle between hits at the time of the previous hit detection.
[0029]
In this way, when the value of the rotation angle θ between hits exceeds 1.5 × θ _old , the value of the rotation angle θ between hits is corrected to half by the processing of the hitting correction unit 21, and this corrected value is the torque estimation. The torque is estimated by being given to the unit 18.
[0030]
On the other hand, when 1.5 × θ _old is not exceeded, correction is not performed and the value of θ _old is set to the value of the rotation angle θ between hits, and then the value of the rotation angle θ between hits is given to the torque estimation unit 18 to An estimation will be made.
[0031]
Therefore, according to the present embodiment, it is possible to discriminate hits that have been mistakenly detected and hits that have been missed from the lower limit of the rotation angle θ between hits and the transition of the values, and appropriately set the rotation angle θ between hits accordingly. As a result, the accuracy of the rotation angle θ between hits is improved, and the torque estimation accuracy is improved.
(Embodiment 3)
As shown in FIG. 6, the present embodiment is different from the configuration of the second embodiment in that a timer 20 ′, which is a striking cycle measuring means, is provided and the striking cycle is taken in using the timer 20 ′. In addition, the same code | symbol is attached | subjected to the same component as Embodiment 1, 2, and description is abbreviate | omitted.
[0032]
Next, operations of the batting correction unit 21 and the timer 20 ′, which are main components of the present embodiment, will be described based on the flowchart of FIG.
[0033]
First, the external rotation angle calculation unit 15 calculates an inter-between rotation angle θ by an external interruption based on the detection signal S of the batting detection unit 7, and the calculated value of the inter-battery rotation angle θ is taken into the batting correction unit 21. It is.
[0034]
With striking correcting unit 21 calculates from the signal of a constant period outputted blow period T from the timer 20 ', the torque estimation when less than to theta _L compares the rotation angle theta between striking with a predetermined threshold serving theta _L Interrupt processing is terminated without processing. Here, θ _L is the count value of the frequency generator 8 corresponding to the hammer free rotation angle π at the time of impact, as in the case of the second embodiment.
[0035]
When the rotation angle θ between hits is larger than θ _L , 1 is added to the number of hits Ni and a determination is made that the hit period T> 1.5 × T _old . If not, the rotation angle θ between hits> 1.5 × Determine θ _old . Here, when the determination of hitting period T> 1.5 × T _old or rotation angle between hits θ> 1.5 × θ _old is satisfied, 1 is further added to the hit count Ni (the hit count is counted twice), The rotation angle θ between hits is halved. The value of θ _old is set as the value of the rotation angle θ between hits, and the value of T _old is set as the value of the hit period T.
[0036]
The theta _old batting between the rotating angle of the previous strike detection, T _old is hitting the period of time before the striking detection, Ru stored in the respective control circuit 10.
[0037]
As described above, when the determination of the striking cycle T> 1.5 × T _old or the striking rotation angle θ> 1.5 × θ _old is satisfied, the value of the striking rotation angle θ is corrected to half, and this correction is made. A value is given to the torque estimation unit 18 to perform torque estimation.
[0038]
On the other hand, if any determination is negative, correction is not performed and the value of θ _old is set as the value of the rotation angle θ between hits and the value of T _old is set as the value of the hit period T, and then the rotation angle θ between hits is changed. A value is given to the torque estimation unit 18 to perform torque estimation.
[0039]
Therefore, in the present embodiment, since the lower limit of the rotation angle θ between hits and the change of the hitting interval are considered in addition to the change in the value, the accuracy of the rotation angle θ between hits is further improved.
[0040]
【The invention's effect】
The invention according to claim 1 is an impact fastening tool comprising an output shaft that is struck by a hammer and to which a rotational force is applied, and an impact detection means that detects the impact of the output shaft by the hammer, and the rotational speed of the motor that drives the hammer A rotation speed detection means for detecting the stroke, and a hit ignore period setting means for determining a period during which no hit can occur from the rotation speed detected by the rotation speed detection means, and for ignoring hit detection by the hit detection means during the period. Because it is equipped, it is possible to ignore the wrong impact detection immediately after hit detection and eliminate the effect, so there is no calculation of the rotation angle between hits due to incorrect hit detection, and the accuracy of hit detection is improved, and the rotation angle between hits As a result, the torque estimation accuracy is improved and the hit detection interrupt is not called frequently. Therefore, there is an effect that it is possible ability to build a circuit from low-cost microcomputer low.
[0041]
According to a second aspect of the present invention, there is provided an impact tightening tool comprising an output shaft that is struck by a hammer and to which a rotational force is applied, and a impact detection means that detects the impact of the output shaft by the hammer. Based on the above, the rotation angle calculation means for calculating the rotation angle of the output shaft for each hit, and the rotation angle value between the hits obtained from the rotation angle calculation means between hits is below a certain threshold value It is equipped with a batting correction means that determines the detection and treats it as an invalid batting, so that it is possible to discriminate the batting that has been detected in error and the batting that has failed to be detected, thereby making it possible to properly correct the rotation angle between batting. The accuracy of the rotation angle between hits is improved, and as a result, the torque estimation accuracy is improved.
[0042]
According to a third aspect of the present invention, in the invention of the second aspect, the hit correction means compares the previous rotation angle between hits obtained from the rotation angle calculation means between the hits and the current rotation angle between hits. If the value is large, it is determined that the hit detection is missing, and the rotation angle between hits is corrected. Therefore, it is possible to discriminate hits that were mistakenly detected and hits that were missed from the transition of the rotation angle value between hits. Since it is possible to appropriately correct the rotation angle between hits, the accuracy of the rotation angle between hits is improved, and the torque estimation accuracy is improved.
[0043]
According to a fourth aspect of the present invention, in the second aspect of the present invention, the hit detection means includes a hit period measuring means for measuring the detected hit period, and the hit correction means receives the hit period from the hit period measuring means. Based on the above, the detection of the detection of a hit and the incorrect detection of the hit are judged and the rotation angle between hits is corrected. Therefore, in addition to the lower limit of the rotation angle between hits and the change in the value, the change in the hit interval should be considered at the same time Therefore, there is an effect that the accuracy of the rotation angle between hits is further improved, and the torque estimation accuracy is further improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a first embodiment.
FIG. 2 is a timing chart for explaining the operation of an impact ignoring period setting unit used in the above.
FIG. 3 is a timing chart for explaining the operation of a timer used in the above.
FIG. 4 is a configuration diagram of a second embodiment.
FIG. 5 is a timing chart for explaining the operation of the hitting correction unit used in the above.
FIG. 6 is a configuration diagram of the third embodiment.
FIG. 7 is a timing chart for explaining the operation of the batting correction unit used in the above.
FIG. 8 is an explanatory diagram of a problem of a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor 2 Reduction gear 3 Hammer 4 Anvil 5 Output shaft 6 Microphone 7 Impact detector 8 Frequency generator 9 Waveform shaping circuit 10 Control circuit part 11 Motor control part 12 Counter 13 Timer 14 Rotational speed detection part 15 Inter-between rotation angle calculation part 16 A / D conversion unit 17 I / O unit 18 Torque estimation unit 19 Stroke ignore period setting unit 20 Timer

Claims (4)

Rotation speed detection means for detecting the rotation speed of a motor for driving a hammer in an impact tightening tool comprising an output shaft that is struck by a hammer and to which a rotational force is applied and an impact detection means that detects the impact of the hammer by the output shaft And a hit disregard period setting means for determining a period during which no hit can occur from the rotation speed detected by the rotation speed detecting means, and ignoring hit detection by the hit detecting means during the period. Impact tightening tool. In an impact tightening tool comprising an output shaft that is struck by a hammer and to which a rotational force is applied, and a hammer detection means that detects the hammer of the output shaft by the hammer, each impact is determined based on the timing of the strike of the hammer detection means. When the rotation angle calculation means for calculating the rotation angle of the output shaft and the rotation angle value between the hits obtained from the rotation angle calculation means between the hits is less than a certain threshold value, it is determined that an incorrect hit is detected and invalid Impact tightening tool characterized in that it comprises a batting correction means for handling. The batting correction means compares the previous batting rotation angle obtained from the batting rotation angle calculating means with the current batting rotation angle, and determines that the hit detection is missing when the current value is large. The impact tightening tool according to claim 2, wherein an inter- rotation angle is corrected . The hit detection means has a hit period measuring means for measuring the detected hit period, and the hit correction means detects hit detection omission and erroneous hit detection based on the hit period from the hit period measuring means. impact tightening tool according to claim 2, wherein the determination to correct the rotation angle between the blow.

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