JPS5840274A - Bolt clamping device through rotation-angle method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bolt tightening device using a rotation angle method that corrects the influence of inertia of a rotating part after power is cut off to an electric moving plate and enables accurate tightening.

2. Description of the Related Art In a bolt tightening device using an electric motor, a rotation angle method has conventionally been used as one method for controlling the tightening of bolts and nuts. In this rotation angle method, a bolt/nut and a member to be fastened are temporarily tightened in advance so that they come into close contact with each other, and then, starting from this fixed state, the bolt/nut is tightened by a predetermined rotation angle determined by the type of bolt, etc. However, in reality, due to variations in the coefficient of friction between bolts/nuts and fastened parts,
Since the tightening speed, that is, the angular velocity of the rotating part is different, the amount of additional tightening due to inertia after the electric motor is powered off changes. For this reason, especially when tightening a large number of bolts, there is a problem in that the tightening angles vary and the tightening accuracy decreases.

This invention was made in view of these circumstances, and calculates the final predicted tightening angle by taking into account the amount of additional tightening due to inertia, thereby eliminating variations in the final tightening angle due to inertia and enabling accurate tightening management. The first object is to provide a bolt tightening device using the rotation angle method.

In order to achieve this first object, the present invention is equipped with a digital calculation device that performs a series of calculations based on a pre-stored program and set values, and the calculation device is configured to calculate the rotation angle that is accumulated starting from the bolt tight state as the final value. A threshold determination step for determining whether a set threshold value smaller than the target tightening angle has been exceeded, and a tightening stop after determining that the angle has been exceeded based on the rotation angle and angular velocity after determining the threshold value. and a stop determination step for outputting a signal, and is configured to cut off power to the electric motor in response to the tightening stop signal.

In addition, there are cases where the screw threads of the bolts and nuts are deformed, making it difficult to screw them in smoothly, or where the bolts and nuts rotate together, making it difficult to tighten them.

A second object of the present invention is to provide a bolt tightening device using the rotation angle method, which is capable of promptly detecting an abnormality and issuing an alarm if such an abnormality occurs.

In order to achieve this second object, the present invention is provided in at least one of the threshold value determination step and the stop determination step, and the time required to satisfy the determination condition of that step is outside the set time range. Therefore, an abnormality detection step is added to detect the abnormality, generate an alarm, and output a tightening stop signal. The present invention will be described in detail below based on Examples.

First, the invention will be explained in detail. If we omit friction now,
The equation of motion during tightening is as follows.

Here, J is the inertia factor as seen from the output shaft of the electric motor, θ is the rotation angle after the start of bolt tightening, E is the spring constant of the bolt, T is the torque of the electric motor, and t is time.

Since T becomes zero after the power is cut off, at this time, d2θ J-27-r=-Eθ (2) holds true. This equation (2) is expressed as θ=θ0゜dθ/d1=ω at t=0.
If we solve under the initial condition of 0, we get Here, β-cho4.9=to' (θ.β4°). This (8)
From the formula, the maximum value θ1 of the rotation angle θ after the power is cut off is
.

becomes.

As is clear from this equation (4), the rotation angle θ immediately before the power is cut off. and the angular velocity ω at that time. If is known, it is possible to predict the maximum rotation angle θ□, that is, the final tightening angle in consideration of the amount of tightening due to inertia. This θf is the final predicted tightening angle, and this tightening angle is immediately calculated and the power is cut off when this tightening angle θf reaches the final target tightening angle θ5, which is preset according to the type of bolt. Then, the final target tightening angle θ is always achieved.

This allows for accurate tightening.

FIG. 1 is a block diagram showing an embodiment of a bolt tightening device according to the present invention. In this figure, 1 is an AC power supply, and its output voltage is supplied to a closed circuit consisting of a switch 2, a semiconductor switch 3, and a DC series motor 4. Reference numeral 6 indicates a rotation angle detector which generates an angle pulse P(θ) for each tightening rotation angle Δθ of bolts and nuts due to the rotation of the electric motor 4. Reference numeral 7 indicates a digital arithmetic unit, and this arithmetic unit operates according to the flowchart shown in FIG. 2 below. A memory 9 stores a calculation program for the calculation device to perform this predetermined calculation, and 9 indicates the final target tightening angle θ8. An input/output device sets various set values such as the threshold value θtA, data regarding bolts, and the inertia rate of the tightening device, 10 is a phase control circuit, and 11 is a gate pulse generation circuit. The phase control circuit 1° stops the generation of the gate pulse G of the gate pulse circuit 11 in response to the tightening stop signal S generated by the arithmetic unit 7, and cuts off the power to the electric motor 4 by opening the semiconductor switch 3. Also, is 12 a switch? This is a power supply voltage detector that detects the closing of - and outputs a calculation start signal to the calculation device 7.

Next, the operation will be explained based on the flowchart of FIG. 2 and the characteristic diagram of FIG. 3.

First, the bolt is temporarily tightened so that there is no gap between the bolt and the member to be tightened. This close contact state becomes the starting point of this tightening device. That is, at this time, the rotation angle θ=O. Next, the input/output device 9 inputs the spring constant E of the bolt, the inertia J of the electric motor, and a set value θ1 for determining whether the bolt tightening state has entered the elastic range A as shown in FIG. Final target tightening angle θ5. A set threshold value θth, which is slightly smaller than the final target tightening angle θ5, and various other values for detecting line abnormalities are set.

When the switch 2 is closed, the power supply voltage detector 12 detects the closing of the switch 2 and sends a calculation start signal to the calculation device 7. The arithmetic unit 7 sequentially reads programs from the memory 8 based on this arithmetic start signal and executes a series of arithmetic operations shown in FIG. First, the arithmetic unit 7 sends a tightening operation start signal to the phase control circuit 10, which causes the gate and pulse generation circuit 11 to generate a phase-controlled gate pulse G.

As a result, the semiconductor switch 3 becomes conductive with a phase synchronized with the trigger pulse G, and a drive current flows to the motor 4.
starts rotating. For this reason, the bolt is gradually tightened, and as the bolt rotates, the rotation angle detector 6 outputs an angle pulse P (ie, at every predetermined unit rotation angle Δθ).

The calculation device 7 calculates the tightening rotation angle θ by integrating the angle pulses P(θ).

The arithmetic unit 7 first determines that the tightening has progressed normally and the bolt has entered the elastic range A (FIG. 2, step 100).
). In other words, since the rotation angle θ from the starting point to entering the elastic region A is almost determined by the bolt and the object to be tightened, the rotation angle θ from the starting point to the elastic region A
Read the set value θ1 from the input/output device 9, and set the rotation angle θ.
is compared with this set value θ1°, and the rotation angle θ is compared with this set value θ1°.
Repeat this comparison operation until it reaches 1. On the other hand, the arithmetic unit 7 has a built-in clock pulse generator and integrates the required time t after the start of tightening. The time t required to satisfy the condition in step 100 is the set time 1. If this happens, it is determined in step 102 that the bolt or nut is locked due to deformation of the screw thread, etc., and a warning is issued and the tightening is stopped in step 104). Further, if this required time t is less than the set time t2, it is determined in step 106, and an alarm (
Step 104) is issued to stop tightening. That is, in steps 102, 104, and 106, the rotation angle θ is the set value θ1.
The time t required to reach 12<1<1. This is an abnormality detection step in which an abnormality is detected and an alarm is generated since it is outside the range of ing.

The arithmetic unit 7 then determines in a threshold value determination step 108 that the rotation angle θ exceeds the threshold value θth. This threshold value θth is preset as an angle smaller than the final target tightening angle θ5, and is input to the input/output device 9. Steps 110 and 112 are steps for detecting abnormalities, similar to the above-mentioned X steps 102 and 106.

When the rotation angle θ reaches the threshold value θth, the rotation angle θ at that time
is the initial value θ in equations (3) and (4) above. The angular velocity ω is determined from the time interval of the angle pulse P(θ) of the rotation angle detector 6 at that time. is calculated (step 114). That is, the angular velocity ω. is inversely proportional to the time interval of the angular pulse P(θ), and this time interval is proportional to the number N of clock pulses accumulated within this time interval, so the angular velocity ω is the result. is calculated as being inversely proportional to this clock pulse number N.

This angular velocity ω. is compared with a preset angular velocity ω1 (step 116), and if ω0>ω1, it is determined that there is rotation, and an alarm is issued (step 118), followed by outputting a tightening stop signal S to stop tightening.

That is, when co-rotation occurs, the rotational speed increases. If co-rotation has not occurred, the final predicted tightening angle θf is calculated in prediction step 120, and the calculations in steps 114, 116°120 are performed sequentially until this final predicted tightening angle exceeds the final target tightening angle θ. is repeated (stop determination step 122). The required time t at this time is set at the set value 1. ．． 1. The presence or absence of an abnormality is determined by comparing with . If an abnormality is detected in these steps 124 and 126, an alarm is issued (step 104); if there is no abnormality, the tightening is completed without issuing an alarm.

In this example, steps 102, 106, 110°11
In 2.124.126, the required tightening time l was outside the set time range, so not only was the abnormality detected,
Since the angular velocity ω0 becomes seven times greater than or equal to the set value ω1 in step 116, co-rotation is also detected, making abnormality detection more reliable. Note that step 10 of detecting co-rotation
If the alarms 6, 112, 1.26 and the alarms 102, 110, 124 for detecting abnormalities in the screw threads are provided separately, the type of abnormality can be known immediately.

Further, in this embodiment, in steps 114 to 122, the W period value ω of the angular velocity and rotation angle is sequentially determined while the condition of step 122 is satisfied. , θ. Since the final target tightening angle ~ is calculated by rereading, it becomes very accurate, but this invention
It may be configured as shown in the figure. That is, in the embodiment shown in FIG. 4, after the rotation angle θ exceeds the threshold value θth (step 108), when the tightening amount (θ-00) exceeds (θS-θf) (stop determination step 130) When the tightening is stopped and the time t required for this condition to be satisfied exceeds a set value t1, it is determined in step 132 that co-rotation occurs.

According to the embodiment shown in FIG. 4, step 120, which takes a relatively long calculation time, can be executed only once, so it is particularly suitable for an apparatus that performs fastening at high speed.

The fifth factor is a block diagram showing yet another embodiment, and FIG. 6 is a flowchart thereof. In this embodiment, the angular velocity ω is calculated based on the drive current and drive voltage of the motor, and the rotation angle θ is successively calculated based on this angular velocity ω and the clock pulses output from the clock pulse generator in the arithmetic unit. In FIG. 5, 20 is an AD converter that converts the motor voltage into a digital signal VD, 22 is a current detection resistor connected in series with the motor 4, and 24 is the motor current from the voltage across this resistor 22. Al that detects and converts it into a digital signal ID
) converter, 26 converts these digital signals■. , vo is used to calculate the angular velocity ω and rotation angle θ of the electric motor 4. Reference numeral 28 is a memory that stores a calculation program for the second digital calculation device. In this figure, the same parts as in FIG. 1 are given the same reference numerals, so their description will not be repeated.

Next, the operation of this embodiment will be explained based on FIG.

First, by closing the switch 2, the voltage detector 12 initializes the second arithmetic unit 26, which in turn initializes the memory 2.
The arithmetic program is read from 8 and the arithmetic operation is ready. - The operation unit 7 sends an operation start signal to the phase control circuit 10 based on the voltage detector 12 (7p output), and the gate pulse circuit 11 generates a gate pulse G. Therefore, the semiconductor switch 3 is synchronized with this gate pulse G. conduction, and motor current begins to flow.A[) converters 20, 22
quantizes the motor voltage and current at a cycle much shorter than the cycle of the AC power supply 1 and generates digital signals VD, I, respectively.
However, the second arithmetic unit 26 integrates these digital signals VD and ID over a half cycle or one cycle of the AC power supply 1 (step 200). These integral values ΣvD, ΣI,
correspond to the effective voltage and current of 1 series - 1 8, respectively.

Generally, the rotational speed of a series commutator motor is determined by the following speed characteristic equation.

Here, ω is the angular velocity, R is the armature resistance, Φ is the field, and K is a constant. The field Φ is generally a function of the current IM, but
It is assumed that the change characteristics are stored in the memory 28 in advance. The second arithmetic unit 26 calculates the equation (5) and outputs the angular velocity ω every half cycle or every cycle of the AC power supply 1 (step 202). Also, this second arithmetic device 2
6 calculates the minute rotation angle Δθ=ω・Δt using the clock pulses generated by the built-in clock generator, and calculates the rotation angle θ by integrating this minute rotation angle Δθ from the start of tightening.
=ΣΔθ is determined, and this rotation angle θ is output every half cycle or every cycle of the power supply 1 (step 204).

The arithmetic unit 7 appropriately reads the angular velocity ω and rotation angle θ output from the second arithmetic unit 26, and performs the same operation as in the embodiment shown in FIGS. 1 to 3 above.

In addition, in FIG. 2, the angular velocity ω is obtained from the integrated value N of the number of clock pulses in step 114, but in the embodiment of FIG. 5.6, it is sufficient to read the angular velocity ω from the second arithmetic unit 26. This step 114 is slightly different, and steps 116 and 118 for abnormality detection are omitted. As described above, the operation in the second half of FIG. 6 is substantially the same as that in FIG. 2, and the same steps are denoted by the same reference numerals, so the description thereof will not be repeated.

In the embodiments shown in FIGS. 1 to 6 below, the angular velocity ω changes as the tightening progresses, but the present invention can also be applied to those in which the angular velocity ω is controlled to be constant. Of course. For example, the armature back electromotive force is angular velocity ω
There is a device that makes the angular velocity ω constant by controlling the phase of the conduction timing of the semiconductor switch in accordance with the change in the back electromotive force. In such a case, this constant angular velocity ω is set in advance by the input/output device, the time l is measured from the clock pulse output by the clock generator built in the arithmetic unit, and the rotation is calculated from the product of the angular velocity ω and the time t. If the angle θ is calculated, the second
, 4, and 611, it is possible to perform tightening at the final target tightening angle θS.

In addition, as shown in Figure 2.4.6, in these examples, the rotation angle θ reached the set value θ1 before the rotation angle θ reached the threshold value θth, so the elastic region A (Figure 3 ), the presence or absence of a tightening abnormality is detected from the time t required to reach this set value θ1 (steps 102 and 106), so the abnormality detection is different from other steps 110 and 112. 124 and 126, the abnormality detection becomes very reliable.

However, in the present invention, an abnormality detection step may be provided in either the threshold value determination step 108 or the stop determination step 122.

As described above, this invention predicts the amount of additional tightening due to inertia after the electric motor is powered off, and makes the final predicted tightening angle match the final target tightening angle, making it possible to accurately manage tightening. , and the variation in tightening angle is eliminated. In addition, since all processing from predicting the final tightening angle to turning off the power is performed by digital signal processing, there is no phase delay during signal processing or errors due to signal holding means compared to analog signals, and tightening The attachment accuracy is significantly improved.

In addition, if an abnormality detection step is provided in the threshold value determination step or stop determination step to detect tightening abnormalities based on the time required for these determination conditions to be satisfied, it is possible to reliably detect abnormalities such as co-rotation of bolts and thread threads. Can be detected.

Furthermore, since the present invention uses a digital arithmetic unit, an abnormality detection step can be provided by simply changing the program. In addition, by changing various setting values and programs, it is possible to flexibly deal with changes in the type of bolt and tightening conditions, which has the effect of being highly versatile.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a flowchart showing its operation, Fig. 3 is a tightening characteristic diagram, Fig. 4 is a flowchart of another embodiment, and Fig. 5 is a flowchart showing its operation. FIG. 6 is a block diagram showing still another embodiment, and FIG. 6 is a flowchart thereof. 4...Electric motor, 7...Digital arithmetic unit, lO8・
. . . Threshold determination step - 120 . . . Prediction step. 122... Stop determination step, 110.112, 124.126... Abnormality detection step, θ... Rotation angle, Su... Final predicted tightening angle, 6th
...R threshold, O5...Final target tightening angle. Sea lion star

Claims (1)

[Scope of Claims] (Li) A bolt tightening device using a rotation angle method using an electric motor, comprising a digital calculation device that performs a series of calculations based on a pre-stored program and set values, the calculation device A threshold determination step for determining whether the rotation angle accumulated from the state as a starting point exceeds a set threshold value smaller than the final target tightening angle, and inertia correction based on the rotation angle and angular velocity after this threshold value determination. and a stop 4 determination step of determining that the final predicted tightening angle exceeds the final target tightening angle and outputting a tightening stop signal, A bolt tightening device using a rotation angle method, characterized in that the power supply to the electric motor is cut off in response to the tightening stop signal. (2) The rotation angle is an angle pulse output by a rotation angle detector for each predetermined unit rotation angle. The bolt tightening device according to the rotation angle method according to claim 1, wherein the angular velocity is determined by the number of clock pulses accumulated between the angular pulses. (8) Drive current and drive voltage of the motor. The bolt tightening machine according to the rotation angle method according to claim 1, which calculates the angular velocity and rotation angle based on the digital signals respectively indicating the angular velocity and the speed characteristic formula of the electric motor. The bolt tightening device according to the rotation angle method according to claim 1, in which the rotation angle is determined based on the angular velocity and the clock pulse. (5) Bolt tightening using the rotation angle method using an electric motor The attached device is equipped with a digital calculation device that performs a series of calculations based on a pre-stored program and set values, and the calculation device is configured to detect a set threshold in which the rotation angle accumulated starting from the bolt tight state is smaller than the final target tightening angle. a threshold value determination step for determining whether the value has been exceeded; a prediction step for calculating a final predicted tightening angle by performing inertia correction based on the rotation angle and angular velocity after this threshold value determination; and a prediction step for calculating the final predicted tightening angle. a stop determination step that determines that the corner has exceeded the final target tightening angle and outputs a tightening stop signal; and a stop determination step that is provided in at least one of the threshold value determination step and the stop determination step and is provided for determining that step. and an abnormality detection step of detecting an abnormality when the time required to satisfy the condition is outside the set time range, generating an alarm, and outputting a tightening stop signal, and in response to any of the tightening stop signals mentioned above. A bolt tightening device using a rotation angle method, characterized in that the electric power of the electric motor is cut off.