JPH0871942A - Confirming method for thread fastening completion of impact type pneumatic driver and confirming device therefor - Google Patents

Abstract

PURPOSE: To detect the inferior thread fastening of an impact type pneumatic driver by detecting the variation of the flow rate of an air flowing through the pneumatic driver for detecting the completion of thread fastening. CONSTITUTION: A throttle valve 2 is provided in an air passage to produce resistance against an air flow passing through the air passage for causing pressure drop, which is detected by an air flow rate sensor 1. Namely, pressure in the air chamber of the air flow rate sensor 1 becomes P1>P2, and the pressure drop is proportional to the air flow rate. Pressure difference P1-P2 is received and detected by a difference pressure type semiconductor pressure sensor pressure receiving section 3. The signal of the pressure difference P1-P2 is amplified to a fixed voltage level by a semiconductor pressure difference sensor amplifier 4, and set up as an air flow rate signal, and during the rotation of the driver, compared with detection reference voltage (reference voltage). When being more than the reference voltage, the signal of the driver being in rotation is outputted, and when being less than the reference voltage, a sitting point detection signal is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an impact blower capable of eliminating screw tightening defects while using an existing impact blower air screwdriver without modification such as mounting a sensor inside a small impact blower air driver. TECHNICAL FIELD The present invention relates to a confirmation method and a confirmation device of completion of screw tightening of a mold air driver.

[0002]

2. Description of the Related Art Screw tightening work using a tightening tool is used in various industries in manufacturing processes of products. Although it is a simple task, eliminating occasional screw tightening defects is important for maintaining product stability, and various measures have been taken to prevent screw tightening defects. When the tightening tool is large, the inside of the tool is modified to remove an air pressure signal for monitoring the operation of the tightening tool in order to eliminate the tightening failure of the screw. Alternatively, a tightening tool incorporating a torque sensor is used. However, in the case of small tools, this modification becomes difficult, and the present situation is that it has not been done so often. On the other hand, it is clear that it would be better if the defective tightening of the screws could be eliminated without modifying the small tightening tool.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an air flow rate sensor is attached to an air supply hose of an impact type air driver called an impact wrench or an oil pulse wrench. (EN) A method and a confirmation device for confirming completion of screw tightening of an impact type air driver for detecting a screw tightening failure by monitoring the flow rate of air sent to the impact type air driver.

[0004]

The percussion type air driver according to the present invention is used as a hit type air driver without modification. This is made possible by focusing on the change in the air flow rate of the striking air driver, which is a characteristic of this striking air driver. For this reason, it is a feature of the present invention that an air flow rate sensor which has not been used so far is adopted. As a feature of the air flow rate of the impact type air driver,
Seated when tightening the screw (when screwing in the lower part of the screw)
The difference is that the air flow rate differs greatly between hitting and hitting. For a striking type air driver, the air flow rate is large up to the seat with a light load, and the air flow rate is significantly reduced during striking.

When tightening a screw with a blow-type air screwdriver, the air flow rate changes greatly from an increase to a decrease at the time of seating the screw. Measure the time from the start of screw tightening to this inflection point,
This is to detect that the screw neck has been properly tightened by a comparison calculation with the target time.

When the screw is tightened with a striking type air driver, the striking after the screw is seated is the time required to increase the tightening torque of the screw to reach the specified torque. During this striking, the air flow rate pulsates and it can be detected from the change in the air flow rate that the striking is in progress. Therefore, when the pulsating component disappears after the air flow rate decreases, it can be detected that the thread of the screw is crushed and the tightening torque is not generated. It is a screwing failure that is generally called screw stupidity.

That is, the method for confirming the completion of screw tightening of an impact type air driver according to the present invention is a method of tightening a screw with an impact type air driver, in which a change in the flow rate of the air flowing through the air driver is detected and the screw is tightened. It is designed to detect that something has happened.

The method for confirming the completion of screw tightening of the blow-type air driver is as follows. In the method of tightening the screw with the blow-type air driver, the flow rate of the air flowing through the driver is set to the air flow rate up to the seat of the screw and the screw is tightened by striking. The air flow rate when the screw is on is detected, and the continuation time from startup to seating and its target value are compared and calculated to detect seating defects such as diagonal tightening of the screw, and the tightening torque of the screw is increased. When the pulsating component due to the impact disappears in the component of the air flow rate, it is detected as a screw stupidity due to over-tightening.

Further, in the device for confirming the completion of screw tightening of the striking type air driver, an air flow rate sensor is provided in the supply air hose of the striking type air driver, and a selection circuit for the two types of the air flow rate is provided, and the seating from start-up is performed. Is provided as a means to detect seating defects such as diagonal tightening of screws by providing a circuit for comparing and calculating the duration of time until the target value, and as a means to detect screw stupidity due to over-tightening of screws. A circuit is provided to detect the disappearance of the pulsating component due to the impact on the flow rate.

Further, the device for confirming the completion of screw tightening of the striking type air driver is provided with an air flow rate sensor in the supply air hose of the striking type air driver, and the time during which the air is flowing ends within the target time, In addition, it is provided with a confirmation means for confirming that the screw tightening is completed because the above-mentioned defective condition does not occur, and that this is used as a counting signal to count the predetermined number of tightening and that all the screws are completed. is there.

[0011]

[Operation] FIG. 1 shows an example of actual measurement of the air flow rate and screw axial force when tightening the screw of an impact type air driver. In FIG. 1, the upper graph shows the air flow rate, and the lower graph shows the screw axial force appearing on the screw. If the screw tightening process is applied in the graph shown in FIG. 1, when S1 shown in the horizontal axis is started, when S2 is screwed in,
Each can be classified when hit with S3. The movement of the air flow rate will be described for these three processes. FIG. 2 is a record of the air flow rate signal obtained by the air flow rate sensor and the air flow rate signal which is regarded as the average air flow rate by removing the pulsating component through the low pass filter.

As for the flow rate of air flowing through a normal striking type air driver, at the time of start-up, the change in the flow rate of air flowing into the air circuit inside the tool and the air motor is large, and the air flow rate is also large. When screwing in and checking the change in the air flow rate when screwing under the neck of the screw with a light load, the air flow rate after startup gradually increases in the case of idling or light load. There is almost no striking motion inside the striking type air driver, the air motor is gradually accelerated, and the air flow rate increases accordingly. At the time of striking (tightening the screw), the tightening torque of the screw of the striking type air driver increases with the striking time, so that the tightening torque value of the screw reaches a predetermined value after a certain striking time. Therefore, it requires a certain amount of time to hit. The change in the air flow rate in this case begins to include a pulsating component in the air flow rate because the air motor gives the hammer a striking force. Along with this, the average air flow rate value also decreases.

According to the present invention, the rush air flow rate at the time of starting the impact type air driver ends in about 5/100 seconds, the air flow rate at the time of screwing in gradually increases, and the air flow rate rapidly decreases after the screw is seated. This is used to detect the completion of screwing. If the air pressure is fixed and the screw is fixed, the time after starting up to this point will be a fixed time. If the target value is the time for correct screw tightening,
If the time is shorter than this time, the tightening torque is increased without screwing the screw under the entire neck, which means that the screwing length is short and the tightening is insufficient such as diagonal tightening. Further, if the time from the start to the sitting becomes longer than the target value, it means that the screw cannot be inserted or the wheel is idling.

In order to eliminate seating failure, the tightening confirmation device for a blow type air driver according to the present invention is provided with an air flow rate sensor 1 on an air hose for driving the blow type air driver, and the air detected by the sensor 1 is provided. A circuit for calculating the maximum value after masking the peak signal at start-up from the flow rate signal is provided, and a circuit for determining that the person is seated when the air flow rate signal has dropped to a predetermined value from the maximum value is set as a circuit. It is provided. This circuit is composed of a peak hold circuit and a voltage comparison circuit. Alternatively, the seating point can be recognized by calculating the time when the air flow rate signal changes from an increase to a large decrease by the AD converter and the microcomputer.

In the actual example of the air flow sensor 1, the pressure drop due to the air flow in the throttle valve 2 is taken out as a differential pressure, so that a too large pressure drop is avoided as a pressure loss. Since the sensor 1 detects the air flow rate with a small differential pressure, it is often impossible to expect the stability of the absolute value of the air flow rate. In order to avoid this, a method and a circuit for detecting a change point (inflection point) of the air flow rate are effective. In the case of the more stable sensor 1, a preset air flow rate setting value is provided, and the seating point can be detected by the passage of the air flow rate signal from the increasing value to the decreasing value. This circuit is composed of a voltage comparator.

In the period in which the tightening torque after the screw is seated in the striking type air driver is increased, the air flow rate pulsates during striking. If the pulsating component cannot be detected from the air flow rate signal even though there is an air flow rate, it means that the tightening screw does not generate tightening torque even when tightened with a striking air driver. This is because the screw thread is crushed by an excessive tightening force, and the screw is in a stupid state. Utilizing this, in the tightening confirmation device of the blow type air driver according to the present invention, the air flow sensor 1 is provided in the air hose for driving the blow type air driver in order to eliminate the screw deficient defect, and the sensor 1 detects it. A circuit that detects that there is an air flow signal even after sitting from the air flow signal that is provided, and a circuit that detects that there is a pulsating component is provided, and a circuit that determines that both of the above two conditions are satisfied is provided. If it does not hold, it is detected as a screw screw failure.

Alternatively, if the air flow rate signal that has passed through the low-pass filter decreases and then increases again, it means that the load of the striking type air driver is lightened, and the bottom value that keeps the minimum value after sitting is maintained. By providing a circuit for comparing the hold circuit with a value obtained by adding a fixed value to the minimum value, it is possible to detect that the air flow rate has increased again and to detect the occurrence of screw deficient defects. The type of hitting type air driver called oil pulse wrench with stable hitting force has stable pulsation due to hitting of the air flow rate, and the signal passing through the low pass filter reflects the movement of the driver and this detection method Works effectively.

Generally, the screw tightening of an impact type air driver is completed by tightening for a fixed time. Alternatively, in a percussion type air driver having a torque control mechanism, the tightening is stopped and the air is shut off by the set torque of the mechanism. At the same tightening point, this tightening duration is uniform. In the present invention, the use of the air flow rate sensor alone does not detect the seating failure of the screw intended by the present invention and the occurrence of screw backlash, and the screw tightening is completed at the preset target tightening time. This is a device for checking the completion of screw tightening, which makes a judgment and outputs a display. The feature of the screw tightening confirmation device of the present invention is that a screw tightening defect elimination function of the present invention is added to the general method of tightening the screw for a fixed time. The detection of fastening for a certain period of time is performed by providing a circuit for measuring the time with a pulsation and comparing the time with the target time.

Setting of the time from the start of screw tightening to the seating While the impact type air driver is small and lightweight, it is widely used in the industrial world due to its fast tightening speed. The time from starting with a striking air driver to sitting is 10 /
100 seconds to 50/100 seconds are typical times. To set this time correctly, it is necessary to measure this time. In the present invention, since it is possible to recognize from the start to the seating point,
This purpose is achieved by measuring the interval with a counter or the like. The measured values are also statistically processed by a microcomputer, and the average, maximum and minimum are calculated and displayed, and the data are supplied as data at the time of setting.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below more specifically with reference to the drawings. FIG. 3 shows an air flow rate sensor 1 for detecting the flow rate of air flowing through the impact type air driver. By providing the throttle valve 2 in the air passage, resistance is generated in the air flow and a pressure drop is generated there. This pressure drop is proportional to the air flow rate,
The pressure of the air chamber of the air flow sensor 1 is set to P1 and P2, respectively.
Then, P1> P2. This P1-P2 is received by the differential pressure type semiconductor pressure sensor pressure receiving portion 3, and by detecting this, an electric signal proportional to the air flow rate can be taken out. Since the present invention does not require absolute accuracy of the air flow rate, this type of air flow rate sensor can be easily constructed.
Since the semiconductor pressure sensor pressure receiving unit 3 is composed of a bridge circuit, the semiconductor pressure sensor amplifier 4 (constant current circuit 4-1) is used.
And a differential amplifier 4-2)). The signal obtained here is called an air flow rate signal.

FIG. 4 is a circuit configuration for detecting the signal during rotation of the driver and the average air flow rate to the percussion type air driver from the air flow rate signal. The air flow rate signal is compared with a rotation detection reference voltage of the driver by the comparator 5, and if it is equal to or higher than this rotation detection reference voltage, the percussion type air driver outputs a rotation signal as if it is rotating. The input and output of the comparator 5 are shown in FIG. This rotating signal is passed through the differentiating circuit 6 shown in FIG. 4, and the monostable multivibrator 7 is used to generate a pulse for a fixed time (about 5/100 seconds) after the percussion type air driver is activated. It is intended to mask the rush air flow rate part of. The pulse signal is shown in FIG.

The air flow rate signal passes through the low pass filter 8 shown in FIG. 4 so that the inrush air flow rate is masked by the output pulses of the analog switch 9 and the monostable multivibrator 7 so that the inflection point of the air flow rate can be detected. Is subject to signal processing. This is called the average air flow rate signal. FIG. 7 shows the average air flow rate signal.

The average air flow rate signal is used to detect a screw in the peak hold circuit 10 and the comparison circuit 11 in FIG. Inrush air flow rate is 5/100 when the impact type air driver is started
It ends in about a second, and then the air flow rate when screwing in gradually increases. The fact that the air flow rate decreases rapidly after the screw is seated is used to detect the completion of screwing. The circuit that detects this is the peak hold circuit 1.
If the output signal of 0 is divided by a resistor and used as the reference voltage of the comparison circuit 11 and the average air flow rate is input as the input of the comparison circuit 11, the average air flow rate peak value is below the divided air flow rate decrease detection level. At that time, the output of the comparison circuit 11 outputs the seating point detection. This state is shown by the signal levels shown in FIG.

Measurement of screwing time The screwing is performed until the rotation signal generated by the comparison circuit 5 is output and the seating point detection signal is output. Therefore, this time is measured by counting the clock signal with the counter. I do.
This time is compared with a preset target value, and if the time is within the range of the control deviation, the seating is determined to be normal.

The time required for this sitting is usually very short for a hitting type air driver, and it is useless at all if it is not set correctly. Therefore, in the present invention, it is possible to provide the data necessary for the setting by measuring the time during screwing, displaying the statistically processed data. Since it is possible to detect during screwing, it is easy to measure this time and perform statistical processing with a device incorporating a microcomputer, and recent devices incorporate and use an inexpensive microcomputer.

Measurement of Impact Time When a screw is screwed into the lower neck and seated, a load is applied to the anvil of the impact type air driver, and pulsation appears in the air flow rate. This reduces the average air flow rate. The pulsating component of the air flow rate is converted into an alternating component through the differentiating circuit 12, which is subjected to full-wave rectification by the full-wave rectifying circuit 13, and further converted into a continuous signal through the low-pass filter 14. This signal waveform has the AC component of the air flow rate pulsation signal as shown in FIG.
It is shown as a continuous air flow pulsation signal. The continuous air flow rate pulsation signal is compared with the pulsation detection reference voltage using the comparator 15 shown in FIG. 10 to generate a pulsation presence signal. The in-hit signal can be created by ANDing the pulsating signal and the seating point detection signal output from the comparator 11.

The striking time is related to the screw tightening force, and is an important control element in screw tightening with a striking type air driver. This time is almost constant if the place to tighten the screw, the blow type air driver and the supply air pressure are decided. An impact type air driver without torque control measures this impact time, and if the target time is within the range of the upper limit value and the lower limit value, it can be determined that the tightening is good. In addition, a striking type air driver without torque control can cut off the air supply at a target time, and a warning sound can be used to teach an operator not to perform excessive tightening.

The duration of the hitting signal is measured by counting the clock signal with a counter. Since the signal during striking can be obtained, this time measurement can be easily performed by a general circuit and method.

Detection of screw stupidity There is a defect called screw stupidity due to improper tightening that occurs during screw tightening work. This is a case where the screw thread collapses during the screw tightening process and the tightening force of the screw cannot be increased. In the case of the torque-controlled percussion air driver, in the case of this failure, the percussion air driver does not stop due to torque increase. With a striking type air screwdriver that does not control the torque, it may be overlooked without noticing even if it is overtightened and screwed up. When the screw stupidity occurs, the anvil of the driver is not loaded and the pulsation of the air flow rate to the driver is eliminated.

However, since the operator holds the trigger of the percussion type air driver, the percussion type air driver is rotating, and the signal during rotation is obtained from the air flow rate signal.
Due to this fact, there is no pulsating signal obtained from the comparator 15, there is a rotating signal obtained from the comparator 5, and there is a flip-flop 16 for storing that there is a pulsating component.
When the three conditions of the pulsating memory, which is the output of, are satisfied, it means that the screw fool has occurred. This condition judgment is AND
It can be realized with a circuit.

[0031]

As can be seen from the above description, the present invention knows the operation of the blow-type air driver without changing the blow-type air driver, and knows the movement by the change of the air flow rate, and detects the screw tightening failure. It is possible to check the screw tightening time and the hitting time of the screw correctly, process the data and mask the screw tightening time to check the screw tightening more accurately. A confirmation method and a device therefor can be obtained. Further, in the present invention, since a flow rate sensor with a small pressure drop can be used, there is an advantage that even a factory facility with a low supply air pressure can be installed without trouble.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an actual measurement example of an air flow rate and a screw axial force when a low-pass filter is not passed.

FIG. 2 is an explanatory diagram of an actual measurement example of an air flow rate signal before and after passing through a low-pass filter.

FIG. 3 is an explanatory diagram showing an air flow rate sensor.

FIG. 4 is an explanatory view showing an air flow rate signal separation circuit.

FIG. 5 is an explanatory diagram showing an air flow rate signal waveform and a rotation signal timing.

FIG. 6 is an explanatory diagram showing a pulse signal timing for a mask signal at startup.

FIG. 7 is an explanatory diagram showing an average air flow rate signal waveform.

FIG. 8 is an explanatory diagram showing detection of a seating point from an average air flow rate signal and creation of a signal during screwing.

FIG. 9 is an explanatory diagram showing seating point detection.

FIG. 10 is an explanatory diagram showing a separation circuit of a signal during hitting.

FIG. 11 is an explanatory diagram showing the relationship between each signal during pulsation, seating detection, and striking.

[Explanation of symbols]

 1 Air flow rate sensor 2 Throttle valve 3 Semiconductor pressure sensor pressure receiving part 4 Semiconductor differential pressure sensor amplifier 5 Comparator 6 Differentiating circuit 7 Monostable multivibrator 8 Low pass filter 9 Analog switch 10 Peak-hold circuit 11 Comparison circuit 12 Differentiation circuit 13 Full-wave rectifier 14 Low-pass filter 15 Comparator 16 Flip-flop

Claims (4)

[Claims] 1. A method for tightening a screw with an impact-type air driver, which is characterized in that a change in the flow rate of air flowing through the air driver is detected to detect that the screw has been tightened. How to confirm completion of attachment. 2. A method of tightening a screw with an impact type air driver, wherein the air flow rate flowing through the driver is classified into an air flow rate up to the seating of the screw and an air flow rate when the screw is tightened by striking, and starting from seating. The seating failure such as diagonal tightening of the screw is detected by comparing and calculating the continuous time to the target value, and the pulsation component due to the impact disappears in the component of the air flow rate at the time of impact that increases the tightening torque of the screw In this case, a method for confirming the completion of screw tightening of a blow-type air driver, which is characterized by detecting this as a screw stupidity caused by over-tightening. 3. A circuit for providing an air flow rate sensor in a supply air hose of a blow type air driver, providing a selection circuit for the two types of the air flow rates, and comparing and calculating a duration time from start-up to seating and a target value thereof. Is a circuit that detects the seating failure such as diagonal tightening of the screw and that detects the pulsation component due to the impact in the air flow rate at the time of impact as a means to detect the screw stupidity due to over-tightening of the screw. A device for confirming the completion of screw tightening of a blow-type air driver, characterized by being provided with. 4. A screw type air driver is provided with an air flow rate sensor in a supply air hose, and the screw is tightened by the fact that the time during which the air is flowing has ended within a target time and the above-mentioned defective condition does not occur. 4. The screw tightening of a percussion type air driver according to claim 3, further comprising a confirmation means for confirming that the completion is completed by using the count signal as a count signal and counting for a predetermined number of tightenings. Confirmation device for attachment completion.