JPH04771B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic tracking method for a workpiece assembly device, and more specifically, the invention relates to an automatic tracking method for a workpiece assembly device, and more specifically, a method for automatically following a workpiece being transported by the assembly section of the workpiece assembly device, and performing an assembly operation for the workpiece while the workpiece is being transported. This is related to how to do this.

B. Prior Art For example, a part of a workpiece assembly apparatus that performs assembly work on transported workpieces is shown in FIG. 1 and will be described. In the figure, 1 is a conveyor equipped in the work assembly process, 2 is a transfer section (hereinafter referred to as pallet) fixed on the conveyor 1,
This pallet 2 has positioning holes 2a, 2a into which positioning pins to be described later are inserted. 3
Reference numeral 4 indicates a workpiece placed on the pallet 2 to undergo a predetermined assembly process; 4 indicates a stopper mechanism for stopping the pallet 2 conveyed by the drive of the conveyor 1; It consists of a cylinder 4a disposed below the conveyor 1 at a predetermined position, and a stopper 4b fixed to the tip of the rod of the cylinder 4a. Reference numerals 5 and 5 indicate positioning mechanisms for positioning the pallet 2 that is conveyed by the drive of the conveyor 1 and stopped by the stopper mechanism 4;
The cylinders 5a, 5a are arranged below the conveyor 1 at a predetermined position, and the positioning pins 5b, 5b are fixed to the rod tips of the cylinders 5a, 5a.
It consists of In addition, the positioning mechanisms 5, 5 are arranged so that the pallet 2
It is installed in two places, front and rear.

Therefore, conventionally, during workpiece assembly work, when the pallet 2 on which the workpiece 3 is placed is conveyed in a fixed direction by the drive of the conveyor position and reaches a predetermined position, the cylinder 4a of the stopper mechanism 4 is operated. As a result, the stopper 4b rises and comes into contact with the front end surface of the pallet 2, thereby stopping the pallet 2. When the pallet 2 is stopped, the cylinders 5a, 5a of the positioning mechanisms 5, 5 are activated, so that the positioning pins 5b, 5b are raised, and the pallet 2 is moved upward.
into the positioning holes 2a, 2a of the pallet 2.
position. After the pallet 2 is automatically positioned by the stopper and the positioning mechanisms 4, 5, 5, assembly processing such as screw tightening and parts supply is performed on the workpiece 3 on the pallet 2. After completing this assembly process, each cylinder 4a, 5a, 5a of the stopper and positioning mechanism 4, 5, 5,
is reversely operated and the stopper and positioning pin 4b,
5b and 5b move back and forth, automatic positioning of the pallet 2 is canceled, and the conveyor 1 starts driving again to convey the next pallet 2 to a predetermined position.

By the way, in the above-mentioned conventional method, since the pallet 2 is mechanically positioned by the stopper and the positioning mechanisms 4, 5, 5, it is possible to carry out a stable assembly operation. 5, 5 and a control section for controlling these mechanisms, the structure becomes complicated. In addition, the working time in the work assembly processing mentioned above includes the stopping time during the work, the stopper and the positioning mechanism 4, 5, 5.
Another problem was that it required a lot of work time and the efficiency of the assembly work was significantly reduced.

B. Purpose of the invention The present invention was proposed in view of the above problems, and
It is an object of the present invention to provide a method that allows an assembly section of a workpiece assembly device to automatically follow a workpiece being transported so that the workpiece assembly work can be performed while the workpiece is being transported.

C. Structure of the Invention The present invention provides a workpiece assembly device 6 having an assembly section 6a for assembling the workpiece 3, in which the workpiece 3 is placed and the assembly section 6a is used to move the transfer section 2 that transports the workpiece 3 in a fixed direction. In this automatic tracking method, a detector 8 for detecting a part of the moving transfer section 2 in a non-contact manner is provided in the assembly section 6a.
Transfer section detection time t obtained from detection signal A by
is accumulated every fixed time T, and the accumulated time is fixed time T
The speed of the assembling section 6a is controlled so that the speed of the assembling section 6a becomes 1/2 of that of the transfer section 2, so that the assembling section 6a automatically follows the transfer section 2.

D. Embodiment An embodiment of the automatic tracking method of a workpiece assembly apparatus according to the present invention will be described below with reference to FIGS. 2 to 7. The same reference numerals as in FIG. 1 indicate the same parts, and the explanation thereof will be omitted. In FIG. 2, reference numeral 6 denotes a work assembly device, which is installed parallel to the assembly section 6a and the conveyance direction of the pallet 2 by the conveyor 1, and moves the assembly section 6a in the square direction. It consists of a feeding mechanism 6b for causing 7 is an assembly head that performs predetermined assembly processing on the workpiece 3;
The assembly head 7 faces the workpiece 3 on the pallet 2 and is mounted on the assembly section 6a so as to be movable in a direction perpendicular to the conveyance direction of the pallet 2. Reference numeral 8 denotes a detector such as a photoelectric switch or a nearby switch that is fixed at a position facing the end of the pallet 2 in the assembly section 6a, and this detector 8 detects the presence or absence of the tip of the pallet 2 in a non-contact manner. .

FIG. 3 shows a block diagram of the structure of the workpiece assembly apparatus, in which numeral 9 represents a detection waveform shaping section connected to the detector 8 of the assembly section 6a; The detection signal A detected as an analog signal by 8 is compared with a constant level value and converted into a predetermined pulse signal B. Reference numeral 10 denotes a pulse width integration section connected to the detection waveform shaping section 9. This pulse width integration section 10 measures the time of the pulse signal B obtained as the output of the detection waveform shaping section 9 and calculates the pulse width (ON). time), that is, the transfer portion detection time is integrated. Reference numeral 11 denotes a deviation time calculation unit connected to the pulse width integration unit 10, and this deviation time calculation unit 11 sets the integration signal C obtained as the output of the pulse width integration unit 10 by a sampling timing control unit to be described later. It is compared with a set time of 1/2 of the sampling time, which is a fixed time, and converted into a speed deviation signal D as a deviation time output. 12
is a speed signal calculation output section connected to the deviation time calculation section 11, and this speed signal calculation output section 12 is
The speed deviation signal D obtained as the output of the deviation time calculating section 11 is converted into a speed signal E which is added to the current speed of the assembly head 7. 13 sends a timing signal F to the pulse width integration section 10, deviation time calculation section 11, and speed signal calculation output section 12 at every sampling time T. 14 is a DC motor speed control section connected to the speed signal calculation output section 12;
The DC motor speed control section 14 converts the speed signal E obtained as the output of the speed signal calculation output section 12 into a DC motor.
It is converted into a drive signal G for the motor 15. The DC motor 15 is driven to rotate at a desired number of rotations by the drive signal G, and moves the assembly head 7 at a speed corresponding to the number of rotations.

Therefore, when the assembly head 7 of the workpiece assembly device 6 is made to automatically follow the pallet 2 being transported, if the assembly head 7 is completely following the pallet 2 (see Fig. 4), the detector 8 The end of the pallet 2 on the conveyor 1 is detected, and the detection signal A is converted by the detection waveform shaping section 9 into a pulse signal B corresponding to whether or not the end of the pallet 2 is detected. This pulse signal B is inputted to a pulse width integrating section 10, time is measured, and the pulse width t of the pulse signal B is integrated. Then, based on the integration signal C outputted from the pulse width integration section 10, the integration time is compared with a set time of 1/2 of the sampling time T in the deviation time calculation section 11. At this time, since the cumulative time at the sampling time T is substantially constant and coincides with the set time of 1/2 of the sampling time T, the speed deviation signal D output from the deviation time calculation section 11 is 0. becomes. As a result, the speed signal calculation output unit 12 outputs a speed signal E corresponding to the current speed of the assembly head 7, and the CD motor speed control unit 14 rotates the DC motor 15 using the drive signal G to move the assembly head 7 to the current speed. Move it as it is.

Furthermore, if the assembly head 7 is behind the pallet 2 (see Fig. 5), the pulse signal B output from the detection waveform shaping section 9 at the first sampling time T continues to be in the ON state, and the pulse signal The integration time of the pulse width t of the pulse signal B based on the integration signal C output from the width integration section 10 is 1/ of the sampling time T in the deviation time calculation section 11.
2, the deviation time calculation unit 1
The speed deviation signal D output from 1 has a positive value, and the speed signal E is obtained by adding that value to the current speed at the speed signal integration output section 12. Based on this speed signal E, the DC motor speed control section 14 controls the DC motor 1.
Send the drive signal G to increase the rotation speed of 5, and
Due to the increase in the rotation speed of the DC motor 15, the assembly head 7
is accelerated. Therefore, the subsequent sampling time T
, the pulse width t of the pulse signal B output from the detection waveform shaping section 9 decreases, and the pulse width t of the pulse signal B output from the detection waveform shaping section 9 decreases.
The cumulative time output from 0 is the deviation time calculation section 11.
The speed deviation signal D outputted from the deviation time calculating section 11 finally becomes 0, and the assembly head 7 asymptotically approaches the setting time of 1/2 of the sampling time T in . Follows palette 2 perfectly.

Furthermore, when the assembly head 7 is advancing relative to the pallet 2 (see Fig. 6), the pulse signal B output from the detection waveform shaping section 9 at the first sampling time T continues to be in the OFF state, and the pulse width The integration time output from the integration section 10 is less than the set time of 1/2 of the sampling time T, and the speed deviation signal D output from the deviation time calculation section 11 becomes a negative value, and that value is subtracted from the current speed. A speed signal E is obtained at the speed signal calculation output section 12. In response to this speed signal E, the DC motor speed control section 14 sends out a drive signal G that lowers the rotational speed of the DC motor 15, and as the rotational speed of the DC motor 15 decreases, the assembly head 7 is decelerated. Therefore, in the subsequent sampling time T, the pulse width t of the pulse signal B output from the detection waveform shaping section 9 increases,
The integrated time asymptotically approaches the set time of 1/2 of the sampling time T, and the speed deviation signal D output from the deviation time calculating section 11 finally becomes 0, and the assembly head is started as in the case shown in FIG. 7 follows palette 2 perfectly.

By the way, when the assembly head 7 is following the pallet 2, the pulse signal B output from the detection wave shaping section 9 due to the detection signal A of the detector 8 has an irregular waveform because the detector 8 has an irregular waveform. This is because the input signal level is very close to the comparison signal level of the detection waveform shaping section 9. If the detection waveform shaping section 9 is provided with a hysteresis characteristic, the pulse signal B obtained as its output will be the same as the seventh pulse signal. As shown in the figure, the ON-OFF signal has a large period, and the speed deviation signal D does not converge to 0 but constantly repeats increases and decreases. This also applies when the sampling time T is lengthened. However, when viewed macroscopically, the above phenomenon means that the assembly head 7 follows the pallet 2 within a certain error, and the error does not pose a practical problem.

Therefore, during workpiece assembly work, the assembly section 6a of the workpiece assembly device 6 is first located at one end of the moving range and waits for the pallet 2 to be conveyed by the conveyor 1. Therefore, the initial speed of the assembly head 7 of the assembly section 6a is 0, but when the end of the pallet 2 being conveyed is detected by the detector 8, the speed deviation signal D becomes maximum, and the assembly head 7 is moved by the feeding mechanism. 6b, and as time elapses, the tracking of the pallet 2 is completed as described above, and the speed deviation signal D finally becomes one. Therefore, this speed deviation signal D is constantly monitored, and when the value reaches a predetermined value or less, work assembly work is started. When this work assembly operation is completed, the assembly head 7 retreats to the initial position and waits for the next pallet 2 to be transported. The working time for this workpiece assembly is determined by the conveyance speed of the conveyor 1 and the movable distance of the assembly head 7. In addition, if the above-mentioned work is not completed within the movement range of the assembly head 7, it is possible to stop the conveyor 1 and carry out the work. Even in this case, the assembly head 7 constantly monitors and follows the end of the pallet 2. do.

In the above embodiment, the tip of the pallet 2 being conveyed is detected by the detector 8 in a direction parallel to the conveyance direction, but the present invention is not limited to this, and for example, the tip of the pallet 2 If the pallet 2 is detected also in the direction perpendicular to the transport direction, highly accurate position tracking control is possible, and if the detector 8 is also placed at a position corresponding to the front and rear ends of the pallet, Reliability is also improved.
Furthermore, the above position tracking control can also be realized by software control using a microcomputer.

E. Effects of the Invention According to the present invention, the assembly head automatically follows the work being transported and the assembly work is executed while the work is being transported, so that the work time can be significantly shortened and the assembly work can be completed. It becomes possible to improve efficiency. Further, since there is no need to provide a stopper, a positioning mechanism, etc. as in the prior art, the structure can be simplified and a low-cost work assembly device can be realized.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view for explaining conventional work assembly work, FIGS. 2 and 3 are schematic plan views and configuration block diagrams for explaining the automatic tracking method of the work assembly apparatus according to the present invention, 4 to 7 are explanatory diagrams showing output signals from each block in FIG. 3. 2... Transfer section (pallet), 3... Work, 6
. . . Work assembly device, 6a . . . Assembly section, 8 . . . Detector, A . . . detection signal, t .

Claims (1)

[Claims] 1. A method for automatically following the movement of a transfer section on which the work is placed and conveyed in a fixed direction in a work assembly device having an assembly section for performing work assembly work, the method comprising: a moving transfer section; A detector for non-contact detection of a portion of An automatic tracking method for a workpiece assembly apparatus, characterized in that the speed of the assembly section is controlled so that the assembly section automatically follows the transfer section.