JPH05177463A - Automatic thread fastening machine - Google Patents

Abstract

PURPOSE:To perform thread fastening at an optimum torque by providing a recording means for recording the thread fastening information set by a setting means and a motor control means for controlling the rotation of a motor on the basis of the thread fastening information. CONSTITUTION:A torque detecting means 21 for detecting the reaction torque of a driver bit 23 rotated by receiving the rotation of a motor 5, and a setting means 29 for setting plural pieces of thread fastening information optionally selected from a main fastening torque value, the speed offset value at start of screwing, the speed offset value start of main fastening, the speed gradient and highest rotation at main fastening, a reversed torque value, the speed offset at start of reversion, and the speed gradient and highest rotation at release of biting are provided. The preset thread fastening information is recorded by a recording means 32, the rotation of the motor 5 is controlled on the basis of the thread fastening information to perform the thread fastening with high precision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic screw tightener,
In particular, the present invention relates to an automatic screw tightener that can perform screw tightening at high speed and with high accuracy.

[0002]

2. Description of the Related Art Conventionally, as a method for controlling a screw tightening torque, there are a method using no torque sensor and a method using a torque sensor. As a method that does not use a torque sensor, set the voltage applied to the motor in advance with the volume and tighten the screw by changing the rotation speed of the motor, or set the voltage corresponding to the load current flowing in the motor in advance with the volume. There is known a method of detecting a load current flowing through the screw and tightening the screw.

On the other hand, as a torque control method using a torque sensor, a driver bit is rotated by a motor,
The torque applied to the driver bit is detected by a torque detector such as a strain gauge, and when the detected value reaches a preset value, the motor is stopped as the tightening is completed, and the detected value at that time is displayed as the tightening torque value. It is common.

[0004]

However, in the above-mentioned method using the torque sensor, the motor does not stop immediately even if a stop command is immediately sent to the motor after the preset tightening torque value is reached. The tightening torque value is not the torque value when the motor stop command is issued, but the work amount of the kinetic energy of the motor at the time of the stop command transmission, that is, the torque value that also includes the torque increase due to the effect of overshoot. Will be tightened up with. As a result, the kinetic energy of the motor corresponding to this overshoot may cause a neck jump or the like after the completion of tightening.

On the other hand, the conventional method that does not use a torque sensor utilizes a static state in which the torque and the load current are in a proportional relationship, and therefore a dynamic method such as a normal screw tightening operation is used. In the state, the tightening torque cannot be set / detected accurately. Further, even if the tightening torque can be set, it has the same drawbacks as described above. Therefore, any of these methods cannot solve these drawbacks, and it is difficult to fasten the screw with high accuracy.

In view of the above problems, the present invention can perform screw tightening with an optimum torque according to the material and type of work (presence or absence of packing, etc.), type of screw (tapping screw, seat built-in screw, etc.). It is an object of the present invention to provide a high-speed and highly accurate automatic screw tightening machine.

[0007]

In order to solve the above-mentioned problems, an automatic screw tightening machine of the present invention has a torque detecting means for detecting a reaction torque of a driver bit rotated by a rotation of a motor, and a temporary tightening torque value. , Final tightening torque value, speed offset value at the start of screwing, speed gradient and maximum rotation at temporary tightening, restart command value after completion of temporary tightening, speed offset value at the start of final tightening, speed gradient at final tightening and Multiple screw tightening information (temporary tightening torque value, speed gradient when temporarily tightening, and temporary tightening torque value, which is selected from among maximum rotation, reverse rotation torque value, speed offset at start of reverse rotation, speed gradient at release of bite, and maximum rotation. Setting means for setting maximum rotation and restart command value after completion of temporary tightening), recording means for recording screw tightening information set by the setting means, and the screw tightening information Based characterized by having a motor control means for controlling the rotation of the motor.

Further, the setting means is a manual data input (MDI) system using a ten-key pad. In addition, the setting means is a communication means from the host.

[0009]

According to the present invention, screw tightening information (temporary tightening torque value, final tightening torque value, speed offset value at the time of starting screwing, speed during temporary tightening) relating to torque characteristics obtained by fast and highly accurate screw tightening Inclination and maximum rotation, restart command value after completion of temporary tightening, speed offset value at the time of final tightening start, speed gradient and maximum rotation at final tightening, reverse torque value,
A speed offset at the start of reverse rotation, a setting means for setting the speed gradient / maximum rotation when releasing the bite, a recording means for recording screw tightening information, and a motor control means for controlling the rotation of the motor based on the screw tightening information are provided. Have. Therefore, by controlling the rotation of the motor based on the preset screw tightening information, it is possible to reproduce the torque characteristic close to the torque characteristic showing the fast and highly accurate screw tightening. As a result, the screws can be tightened with high accuracy.

As described above, if the screw tightening information corresponding to the material and type of work (presence or absence of packing, etc.) and screw type (tapping screw, seat built-in screw, etc.) is set in advance, the set screw tightening information is set. By controlling the rotation of the motor based on, the screw tightening can be performed at high speed and with high accuracy.

[0011]

1 is a block diagram showing the structure of an automatic screw tightener according to an embodiment of the present invention, which is composed of an automatic screw tightener body 1 and a controller 24. The automatic screw tightener main body 1 has a driver main body 4 fixed via a gear case 3 to a driver base 2 that is moved up and down by the operation of an elevation drive source 26. Lubricating oil is contained in the driver main body 4. It is filled. A motor 5 (for example, D
C servo motor) is fixed. This motor 5
An output shaft 17 rotatably held by a part of the driver body 4 via a speed reducer (not shown) in the driver body 4,
A sun gear 19a, which will be described later, is connected to the output shaft 17 via a connecting tool 18, and the motor 5, the output shaft 17 and the sun gear 19a are configured to rotate integrally. At the lower end of the output shaft 17, the gear case 3
The sun gear 19a of the differential planetary gear mechanism 19 located inside is connected, and three planet gears 19b that mesh with the sun gear 19a at equal intervals are supported and arranged on the planetary gear base 19c. There is. Further, the planetary gear 19b meshes with the internal gear of the ring gear portion 19d having an internal gear rotatably held in the gear case 3, and the rotation of the output shaft 17 is reduced to a predetermined ratio. It is configured to be transmitted to the planetary gear base 19c. The ring gear section 1
A strain tube 20 which is an example of a torque detection unit arranged so as to include the output shaft 17 is fixed to 9d.
A strain gauge 21 for detecting the amount of strain is attached to the strain tube 20 so that the strain amount of the strain tube 20 can be detected to detect the reaction torque applied to the ring gear portion 19d. A driver bit 23 is connected to the planetary gear base 19c via a transmission mechanism 22, and the rotation of the motor 5 is transmitted to the driver bit 23.

The control unit 24 outputs a work start command, a work start unit 25, an elevating drive source drive unit 26a which starts operation in response to the work start command, and the motor 5.
And a motor drive unit 27 for driving the
A speed command section 6 for giving a speed command value of the motor 5, a setting section 29 for setting screw tightening information, and an A / D conversion section 30.
A S / H circuit 31, a control unit 45 having a RAM 32 and a ROM 33, a display unit 34, and a pass / fail judgment output unit 35.
, The motor terminal voltage detector 36, and the driver bit 23
An original position detection unit 37 for detecting whether or not
A power supply unit 38 that supplies power to the motor drive unit 27, a photocoupler 39, an input circuit 40, a battery 41, a correction unit 42, and an amplification unit that amplifies the detection value detected by the strain gauge 21. 43 and a filter section 44.

The ROM 33 stores standard data of screw tightening information in addition to a program for operating the automatic screw tightener. The RAM 32 has a predetermined area in which the standard data stored in the ROM 33 and the rewritten screw tightening information can be recorded. This screw tightening information is, as shown in FIG. 10, a small screw (M6 × 1
Torque characteristics showing fast and highly accurate screw tightening when 5) is screwed into a quenching nut with a plain washer (Fig. 1).
1 (see 1), and is configured to be recorded.

The A / D converter 30 is a high-speed A / D converter (for example, accuracy 12 bits, sampling period 25).
.mu.sec) is adopted, it is possible to accurately follow the fluctuation of the screw tightening torque. Since the motor drive unit 27 employs an H circuit using four or eight transistors so as to be suitable for driving the motor 5 in the forward and reverse directions, the motor drive unit 27 can quickly respond to the forward and reverse rotations of the motor.

The setting unit 29 has a ten key 29a for setting screw tightening information. Here, the screw tightening information includes a temporary tightening torque value, a final tightening torque value, a speed offset value at the time of starting screwing, a speed gradient and maximum rotation at the time of temporary tightening, a restart command value after temporary tightening is completed (temporary tightening torque Temporary tightening torque value to detect the value drop or the time of the operation timer from temporary tightening), the speed offset value at the time of the final tightening start, the speed gradient and the maximum rotation at the final tightening, the reverse rotation torque value,
The speed offset at the start of reverse rotation, the speed gradient at the time of releasing the bite, the maximum rotation, etc. are not necessarily set, but it is also possible to set only necessary information. If necessary, the temporary tightening torque value, the speed gradient and the maximum rotation during temporary tightening, and the restart command value after completion of temporary tightening can be excluded.

Since the quality judgment output section 35 can output a digital signal of a torque value and an analog output of the screw tightening torque in addition to the quality judgment output of the screw tightening result, it is possible to monitor the screw tightening process. Is. Further, the display unit 34 can display the torque value of the screw tightening result as well as the illumination display such as the quality judgment of the screw tightening result, so that it is responsible for the quality control of the screw tightening.

2 to 5 are flowcharts showing the operation of the automatic screw tightener according to the embodiment of the present invention, and FIG. 6 shows a time chart and an output torque waveform. First,
In # 1, the standard data in the ROM 33 is the RAM 32
It is judged whether or not it is written in a predetermined area of No. 3, and if it is not written, it waits for a write command (# 2) and ROM3
The standard data in 3 is written in a predetermined area of the RAM 32 (# 3).

If there is a standard data change command (# 4), the change process of # 5 (described later) is performed and then # 6.
If there is no change in the standard data, immediately proceed to # 6. In # 6, the original position detection unit 37 confirms that the driver bit 23 is in the original position of the predetermined work, and waits for the work start command from the work start unit 25 (#
7), the driver bit is lowered based on the driver bit lowering command from the ascending / descending drive source 26 (# 8), and the RAM3
The screw tightening information (temporary tightening torque value, speed offset value at the start of screwing, speed gradient / maximum rotation at the start of temporary tightening) is read into a predetermined area 2 (# 9).

If there is a motor forward rotation command (# 1
0), based on the screw tightening information, the motor 5 is normally rotated to start screwing (t ₀ in FIG. 6). And
When the head seat surface of the screw reaches the workpiece (t in FIG.
₁ ), the load torque for screw tightening increases, this load torque is A / D converted and read as a torque value (# 11),
It is determined whether or not a preset temporary tightening torque value has been reached (# 12). If the temporary tightening torque value is not reached, the motor 5
After waiting for the maximum rotation to be reached (# 13), the speed gradient is set to 0 (# 14). On the other hand, if the motor 5 has not reached the maximum rotation speed, the speed gradient is instructed to be read (# 15).

At # 12, when the detected value reaches the temporary tightening torque value (t ₂ in FIG. 6), a motor stop command is sent to reduce the kinetic energy of the rotary drive system such as the motor 5 (# 16), Immediately, the time is counted by the timer (# 17), and the load torque at this time is A / D converted and read as a torque value (# 18). Here, if the torque value has not reached the preset temporary tightening torque value (# 1
9), wait for # 20 time up and proceed to # 21,
When the temporary tightening torque value is reached, the process immediately proceeds to # 21.

In # 21, the screw tightening information (final tightening torque value, speed offset value at the time of final tightening, speed gradient / maximum rotation at the time of final tightening) is read in a predetermined area of the RAM 32, and the motor forward rotation command of # 22 is read. After that, the motor 5 is rotated in the normal direction based on the screw tightening information to start the final tightening (t ₃ in FIG. 6). Although the load torque increases with the final tightening, this load torque is A / D converted and read as a torque value (# 23).

If the torque value does not reach the preset final tightening torque value (# 24), wait for the motor 5 to reach the maximum rotation (# 25) and set the speed gradient to 0 (#).
26). On the other hand, if the motor 5 has not reached the maximum rotation speed, an instruction is given to make the speed gradient read (# 27). # 2
4, when the detected value reaches the final tightening torque value (see FIG.
T _4), sends a motor stop command to reduce the kinetic energy of the rotating drive system of the motor 5 and the like in (# 2
8) Then, the load torque at this time is A / D converted and read as a torque value, and the peak torque value is detected (# 29).

[0023] In # 30, check the motor 5 to stop, and displays the peak torque value containing an overshoot amount of up to (t ₅ in FIG. 6) completely stop the motor 5 (# 31). In # 32 and # 33, it is determined whether the peak torque value is within a preset allowable range (upper limit or lower limit), and if it is not within the allowable range, an upper limit or lower limit abnormality display is performed (# 34, # 35). . On the other hand, if it is within the allowable range, OK display is performed (# 36), and the quality determination output unit 35 outputs the quality determination (# 37).

In # 38, screw tightening information (reverse rotation torque value, speed offset at the start of reverse rotation, speed gradient / maximum rotation at release of bite) is read into a predetermined area of the RAM 32, and the motor reverse rotation command of # 39 is waited for. The motor 5 is reversely rotated for a short time (between t _{6 and} t ₇ in FIG. 6) to release the bite between the screw head and the driver bit 23. In # 40,
The load torque during reverse rotation is A / D converted and read as a torque value, and it is determined whether or not this torque value has reached a preset reverse rotation torque value (# 41).

If the detected value does not reach the reverse rotation torque value, it waits for the motor 5 to reach the maximum (reverse rotation) rotation (# 42), and the speed gradient is set to 0 (# 43). On the other hand, if the motor 5 has not reached the maximum rotation speed, the speed gradient is instructed to be read (# 44). At # 41, when the detected value reaches the reverse rotation torque value, the motor stop command is waited (# 45), the motor 5 is stopped, and the driver bit increase return command is waited (# 46) to raise the driver bit. Complete one cycle and wait for the next start command.

7 to 9 are flowcharts showing the standard data changing operation. When changing the standard data written in the predetermined area of RAM 32, screw tightening information (speed offset value at the start of screwing, speed gradient and maximum rotation at temporary tightening, temporary tightening torque value, restart after completion of temporary tightening) Command, speed offset value at the start of final tightening, speed gradient and maximum rotation at final tightening, final tightening torque value, lower limit torque value, upper limit torque value, speed offset at reverse rotation start,
It is possible to read out the information to be changed in the speed gradient / maximum rotation at the time of releasing the bite, the maximum torque value at the time of reverse rotation, and the display correction value, and change it to a predetermined value with the ten keys 29a (# 51 to 82). ).

According to the above embodiment, it is possible to easily rewrite the screw tightening information by the manual data input (MDI) method using the ten keys 29a. Further, for example, the screw tightening information can be set from the host via a communication means such as RS232C.

[0028]

As described above, according to the present invention, the screw tightening information corresponding to the material and type of work (presence or absence of packing, etc.), type of screw (tapping screw, seat built-in screw, etc.) is preset. Therefore, by controlling the rotation of the motor based on the set screw tightening information, the screw tightening can be performed with the optimum torque. As a result, there is an effect that screw tightening can be performed at high speed and with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an automatic screw tightening machine according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the automatic screw tightening machine according to the embodiment of the present invention.

FIG. 3 is a flowchart showing an operation of the automatic screw tightening machine according to the embodiment of the present invention.

FIG. 4 is a flowchart showing an operation of the automatic screw tightening machine according to the embodiment of the present invention.

FIG. 5 is a flowchart showing an operation of the automatic screw tightening machine according to the embodiment of the present invention.

FIG. 6 is a time chart and an output torque waveform showing the operation of the automatic screw fastening machine according to the embodiment of the present invention.

FIG. 7 is a flowchart showing a standard data changing operation of the automatic screw tightening machine according to the embodiment of the present invention.

FIG. 8 is a flowchart showing a standard data changing operation of the automatic screw tightening machine according to the embodiment of the present invention.

FIG. 9 is a flowchart showing a standard data changing operation of the automatic screw tightening machine according to the embodiment of the present invention.

FIG. 10 is a view showing a state in which a flat washer is inserted into a machine screw (M6 × 15) and screwed into a quenching nut.

11 is a torque characteristic diagram in FIG.

[Explanation of symbols]

 1 Automatic Screw Tightening Machine Main Body 5 Motor 27 Motor Driving Unit 29 Setting Unit 29a Numeric Keypad 32 RAM

Claims (4)

[Claims] 1. A torque detecting means for detecting a reaction torque of a driver bit that rotates in response to rotation of a motor, a final tightening torque value, a speed offset value at the time of starting screwing,
A plurality of values selected arbitrarily from the speed offset value at the start of final tightening, the speed gradient and the maximum rotation at the time of final tightening, the reverse rotation torque value, the speed offset at the start of reverse rotation, the speed gradient at the release of bite, and the maximum rotation. It has a setting means for setting the screw tightening information, a recording means for recording the screw tightening information set by the setting means, and a motor control means for controlling the rotation of the motor based on the screw tightening information. Automatic screw tightener. 2. A torque detecting means for detecting a reaction torque of a driver bit which rotates in response to rotation of a motor, a temporary tightening torque value, a final tightening torque value, a speed offset value at the time of starting screwing, and a speed during temporary tightening. Gradient and maximum rotation, restart command value after completion of temporary tightening, speed offset value at the time of final tightening, speed gradient and maximum rotation at the time of final tightening, reverse torque value, speed offset at the time of reverse rotation start, Setting means for setting a plurality of screw tightening information arbitrarily selected from speed gradient and maximum rotation, recording means for recording the screw tightening information set by the setting means, and a motor based on the screw tightening information. And a motor control unit for controlling the rotation of the automatic screw tightening machine. 3. The automatic screw tightener according to claim 1, wherein the setting means is a manual data input (MDI) system using a numeric keypad. 4. The automatic screw tightener according to claim 1, wherein the setting means is a communication means from a host.