JPH0760656A - Screw fastening completion confirming method for motor-driven driver and confirming device thereof - Google Patents

Abstract

PURPOSE:To take out a screw fastening completion signal without remodeling a marketing AC motor-driven driver by confirming the completion of screw fastening by detecting variations in an effective value component of an alternating current flowing to the AC motor-driven driver and an absolute value component. CONSTITUTION:An electric current sensor 1 detects an electric current flowing to a motor-driven driver. A synchronous signal circuit 2 outputs a pulse signal in synchronism with an electric power supply frequency to a synchronous rectification circuit 4. An amplifying circuit 3 amplifies a detecting signal, and outputs it to the synchronous rectification circuit 4 and a full wave recitification circuit 7. The synchronous rectification circuit 4 takes out the electric power supply frequency and an in-phase component, and processes them by a low-pass filter 5 and a voltage comparing circuit 6, and judges the existence of an effective value component of the electric current. The full wave rectification circuit 7 converts an alternating current all into a (+) direct current, and judges the existence of an absolute value component of the electric current through a low-pass filter 8 and a voltage comparing circuit 9. The completion of screw fastening is confirmed from variations of these effective value component and absolute value component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for confirming the completion of screw tightening of a small and light AC electric screwdriver.

[0002]

2. Description of the Related Art A conventional AC electric screwdriver has a built-in control circuit for stopping the motor when the screw tightening torque reaches a certain value. Also, this AC electric driver rotates the driver driving motor by means of a start switch, and the fact that a constant torque value has been reached after the screw tightening has started is detected by both the motor and the load. Combine,
It is detected by a mechanical clutch for disengagement, and the detection signal is sent to the control circuit to stop the driving of the motor. The confirmation of the screw tightening determines that the operator has completed the screw tightening when the motor for driving the driver is stopped.

[0003]

However, when the screw tightening is left to the discretion of the operator, in rare cases an electric screwdriver is used.
If the screw is stopped early, or if the screw enters at an angle, the clutch will operate and the motor will stop before the screw is completely tightened. Was occurring. In an assembly site where a large number of screws are tightened, it is desired that the completion of tightening the screws can be signaled in order to eliminate such mistakes in the screw mounting work. This is because it is possible to input this signal to the counting device and confirm that all the screws have been tightened.

As a means for realizing this, for example, an electric driver
It is conceivable that a torque sensor may be built in or the clutch actuation signal may be taken out from an electric driver with a switch, but the structure is complicated and it is not widely used in manual tools that require small size and light weight. Is. Therefore, the object of the present invention is made in view of the above points, and the above problems are solved by taking out a screw tightening completion signal without modifying any commercially available AC electric screwdriver at present. Is.

[0005]

According to the present invention, in a method of tightening a screw with an AC electric driver, the screw is detected by detecting the amount of change in the effective value component and the absolute value component of the AC current flowing in the AC electric driver. Is a method for confirming completion of screw tightening of the electric driver for confirming that the tightening has been completed. Further, the confirmation method of the screw tightening completion of the electric driver according to the present invention is
In a method of tightening a screw with an AC electric screwdriver, a change amount of an effective value component and an absolute value component of an AC current flowing through the AC electric screwdriver is detected to confirm that the screw has been tightened and tighten the screw. The time measurement from the start to the end of attachment and the statistical processing are performed together, and the tightening confirmation of the screw is performed by comparing and calculating with the normal time.

Further, the device for confirming the completion of screw tightening of the electric driver according to the present invention is provided with a current sensor in the commercial power supply circuit for driving the electric driver, and at the same time, the effective current for separating the signal detected by the current sensor is provided. A circuit for determining the presence / absence of a value component and a circuit for determining the presence / absence of an absolute value component of current are provided.
Further, the judgment circuit of the clutch of the electric driver for judging the presence / absence signal of the effective value component and the presence / absence signal of the absolute value component under the judgment logic circuit and the time of the effective value component of the current are within the upper and lower limits. If there is a judgment circuit, the output from the judgment logic circuit is a signal with a tightening torque of a specified value, and the output side from the judgment circuit that the tightening torque is in the range of the upper limit value and the lower limit value has a proper screwing length. A circuit is provided that determines that the screw tightening is completed when both of certain signals are completed.

[0007]

The screw tightening operation of the electric screwdriver according to the present invention will be described. The current flowing through the electric driver is classified into the following four-step patterns. Step 1: Motor starting current at the start of screw tightening Since a stationary driver rotates, a large current flows. Since this changes into rotational energy, electric energy is consumed. Step 2: Current during the time when the under-neck portion of the screw is screwed into the screw hole Electric energy is consumed due to friction loss generated when tightening the screw and mechanical loss of the rotating portion inside the electric driver. An almost constant current flows.

Step 3: The period when the screw enters the screw hole and is the final tightening period. The screw head hits the upper part of the other screw hole, and the electric screwdriver
In general, the current increases because the force is applied and screwed in for fixing. This step ends in a short time. In addition, before the current value significantly increases, the motor of the electric driver is
May be stopped, so the increase may not always appear. Although the pattern does not become constant under various conditions such as the power of the electric driver and the thickness of the screw, the current is greatly reduced by stopping the motor. Step 4: Until the operator turns off the start switch after stopping the motor. There is a slight delay before the operator determines that the screws have been tightened and turns off the switch. A small amount of current is flowing through the control circuit built into the electric driver until the switch is turned off. Most of this current has no energy-consuming reactive component, and the effective component is zero. In the present invention, the time of step 4 is in principle at least 5/100
This step is recognizable for seconds. (Results from control sampling current at commercial frequency)

Considering the above steps, the fact that the screw tightening torque reaches a constant value and the clutch is disengaged and the electric driver is stopped means that steps 3 and 4 have been passed. If this is set as Condition 1, it means that the operation of the torque detecting clutch of the electric driver is detected, which means that the tightening torque has reached the set torque. Furthermore, condition 2 is an additional condition to eliminate abnormal screw tightening.
Adds the time from the start to the end of step 3.

The purpose of this is that the time from step 1 to step 3 depends on the rotational speed of the electric driver, so this time will be compared with the case where the screw is normally tightened. For example, in the following example, in the time until the clutch is disengaged, when the screwed portion is tightened again, the screw tightening time becomes shorter than the normal value. Further, in the case of a screw that is obliquely inserted, the tightening time is shortened because the neck of the screw does not completely enter the screw hole. Confirm the completion of screw tightening under these two conditions.

Regarding the detection of the operation of the electric driver according to the present invention, in the present invention, a current element such as a hall element or a current transformer is used to detect the operation step of the electric driver necessary for confirmation of screw tightening. The current is detected, and the detection signal is processed and used. That is, the detected current is divided into two elements. As the power source of the AC electric driver, an AC having a commercial frequency is used. However, the current waveform is not a sine wave, but it is an irregular waveform, although it is on the commercial frequency. In order to obtain information from the current waveform, it is separated into effective value and absolute value. Since the effective value of the alternating current corresponds to the energy consumption, the rotation of the motor can be detected by looking at it. To see the effective value of the alternating current, it can be realized by a synchronous rectification circuit or numerical operation.
When the commercial frequency component is removed from this AC current signal by a low-pass filter or the like, the energy consumed by the motor is reflected. From step 1 to step 3, the situation of the electric driver can be grasped by monitoring this alternating current. Since the motor is stopped here, the effective value component becomes zero in principle.

The absolute value of the alternating current reflects the starting switch of the electric driver. This is due to the fact that a small amount of current flows to the electric driver even after the motor is stopped, while the start switch is being pushed, as a characteristic of the electric driver. The absolute value of the current is rectified after amplifying the current signal detected by the current sensor, and the commercial frequency component is also removed through the low-pass filter. The movement of the start switch of the electric driver can be checked by monitoring the presence or absence of this current signal. Even the absolute value of the alternating current changes depending on the step, so that each step can be recognized by monitoring the value. However, by dividing the signal into two, an effective value and an absolute value, it can be converted into the presence or absence of the signal (0 or 1 signal). Therefore, the setting inside the control circuit should be adjusted according to the type of the electric driver. Escape from. It is a feature of the present invention that it contributes to improved usability and stable operation.

In the present invention, the movement of the electric driver is detected from the two signals of the effective value and the absolute value. This is the first tightening condition. The tightening condition No. 1 creates the screw tightening completion condition No. 1 depending on the presence or absence of these two kinds of currents. I The execution component has appeared and disappeared. Steps 1 to 3 have been passed. II Then, the absolute value component of the current was present for about 5/100 seconds. Step 4 passed This can be easily determined by a logic circuit or a program. Further, the tightening time is incorporated in the judgment condition in order to eliminate the double tightening that occurs when tightening the screw, and the abnormal tightening caused by the screw being caught, entering obliquely, or the like. This is the condition 2 for completion of screw tightening.

The second condition for completion of screw tightening measures the duration of the active component of the alternating current. The duration of this execution component is compared with a preset tightening time width, and if it is within that width, Condition 2 is satisfied. However, this tightening time is usually about 0.5 to 1 second, so it is meaningless if the time cannot be measured. It depends on how accurate the value can be set. The conventional problem is the setting of this time width. With an electric screwdriver, the tightening time was short and it was difficult to set the time width. On the other hand, this time is quite accurate. It is usually
When tightening the screw, the tip of the electric screwdriver (bit) is applied to the head of the screw, and the screw is already in the assembly place. Therefore, the time until the screw is tightened depends on the length under the screw and the rotation speed of the motor. The electric driver is the same,
If the tightening place and the screw are the same, this difference in time is about 0.1 seconds.

Therefore, in the present invention, since this time can be accurately measured from the current flowing through the electric driver, the following time setting method is adopted. Method of setting the tightening time width In the method of the present invention in which the AC current flowing through the electric driver is separated into the effective value component and the absolute value component, if the duration of the effective value component is measured, from the start to the completion of screw tightening. The time can be measured accurately. Statistical processing is performed based on this data. This realization can be easily performed in the device in which the microcomputer is mounted.

In order to know an appropriate screw tightening time width, test tightening is performed with an electric screwdriver, a screw and a part to be assembled which are used in advance on the assembly line. The time is statistically processed and the maximum, minimum, average, etc. are displayed so that the tightening time width of the screw can be referred to. Conventionally, this time setting reads the time from the torque waveform by mounting a torque sensor, but it requires technology and measuring equipment, and no one can easily do it. If the electric driver changes, it is necessary to measure again. Therefore, in the present invention, the tightening time width can be measured under the same condition as when the screw is actually tightened.
Therefore, even if the electric driver is replaced, it can be dealt with promptly, and this function is effective.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a circuit for extracting two signals from a motor current of an electric driver. The current sensor of No. 1 uses a hall element or a current transformer and detects the current flowing through the electric driver. The current signal detected here is decomposed into two signals through the following circuit. The synchronizing signal circuit 2 takes out a pulse signal synchronized with the power supply frequency. This is used in the synchronous rectification circuit 4 described below. The amplifier circuit 3 amplifies the signal level required for the synchronous rectification and full-wave rectification circuit 7. The amplifier circuit 3 is composed of an operational amplifier. The synchronous rectification circuit of No. 4 extracts a component in phase with the power supply frequency. Here two pulses of the sync signal circuit are used for switching to the current signal. The in-phase component corresponds to the effective value of the current. The low pass filter 5 removes the AC component contained in the output of the synchronous rectification circuit 4. The cut value is set to 1/2 or less of the power supply frequency. The effective value component of the current can be taken out by passing this. This is shown as a signal 1 in the graph of FIG.

The voltage comparison circuit 6 is a determination circuit that determines whether or not there is an effective value component. This is a general comparator circuit. This output becomes a 0, 1 digital signal.
This is shown as signal 2 in the graph of FIG. The full-wave rectifier circuit of 7 changes all the alternating current into + direct current in order to see the presence or absence of current. However, as it is, there are many pulsations and it is not possible to digitize, so a low pass filter of 8 is used to remove the AC component. This output is shown as signal 3 in the graph of FIG. This output is also connected to the voltage comparison circuit 9 for digitization. The output of the voltage comparison circuit 9 is shown as the signal 4 in the graph of FIG. This is a digital signal with or without absolute value.

Extracting the screw tightening completion signal using the digitized signal is easily realized by a microcomputer or the like. The time is a time base function of the microcomputer, the logical operation is an arithmetic function, and the memory is stored. The determination method is shown in the extraction of the tightening completion signal and its time chart shown in FIG. The conditions there are as described above. The tightening time in setting the conditions for screw tightening judgment plays an important role. Providing documentation for this time setting is important for this type of verification. However, conventionally, it was difficult to accurately detect the movement of the electric driver, so that it was difficult to provide time data, but the present invention has a resolution of 5/100 seconds, so that a time base function such as a micro computer is provided. Can be measured accurately with
The data can be statistically processed and displayed as screw tightening time information. The maximum value and the minimum value are values that can be sufficiently referred to as set values for the screw tightening condition No. 2. The method is shown in the statistical processing of screw tightening time and its display and use in FIG.

[0020]

As can be seen from the above description, the present invention knows the operation of an electric driver without altering the electric driver, knows its movement with an alternating current, detects the completion of screw tightening, and tightens the screw. By accurately measuring the time, performing data processing, and masking the screw tightening time, it is possible to confirm screw tightening more accurately. A verification device is obtained. Further, in the present invention, since the current sensor does not drop the voltage of the circuit due to its nature, there is an advantage that the performance of the electric driver is not affected at all.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing extraction of an effective value component and an absolute value of a motor current and a signal change thereof.

[Fig. 2] Extraction of screw tightening completion signal and its time chart
FIG.

FIG. 3 is an explanatory diagram showing statistical processing of screw tightening time and its display and use.

FIG. 4 is a graph showing changes in effective value of current with time.

FIG. 5 is a graph showing a change in absolute value of current with time.

[Explanation of symbols]

1 Current sensor 2 Synchronous signal circuit 3 Amplifying circuit 4 Synchronous rectifying circuit 5, 8 Low-pass filter -6 Judgment circuit for presence / absence of current effective value component 7 Full-wave rectification circuit 9 Judgment circuit for presence / absence of current absolute value

Claims (3)

[Claims] 1. A method for tightening a screw with an AC electric screwdriver, in which a change amount of an effective value component and an absolute value component of an AC current flowing through the AC electric screwdriver is detected to confirm that the screw has been tightened. A method for confirming completion of screw tightening of an electric screwdriver, characterized by: 2. A method of tightening a screw with an AC electric screwdriver, in which a change amount of an effective value component and an absolute value component of an AC current flowing through the AC electric screwdriver is detected to confirm that the screw has been tightened. In addition, the method for confirming the completion of screw tightening of the electric driver is characterized in that the time measurement from the start to the completion of screw tightening and the statistical processing are also performed and the tightening is confirmed by comparing and calculating with the normal time. 3. A commercial power supply circuit for driving an electric driver is provided with a current sensor, and a circuit for determining the presence / absence of an effective value component of the current for separating a signal detected by the current sensor and a determination for the presence / absence of an absolute value component of the current are provided. A logic circuit is provided, and a determination logic circuit for determining whether the clutch of the electric driver is off based on the presence / absence signal of the effective value component and the presence / absence signal of the absolute value component and the time when the effective value component of the current is present are the upper and lower limits. A judgment circuit for determining that the value is in the range of values is provided, and the output side from the judgment logic circuit is a signal with a specified tightening torque, and the output side of the circuit for determining that the tightening torque is within the range of the upper limit value and the lower limit value is screwed in. A device for confirming the completion of screw tightening of an electric driver, which is provided with a circuit for judging that screw tightening is completed when both of signals having an appropriate length are provided.