JPH04310327A - Positioning method for work in automatic assembling machine - 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]

0001

[Industrial Application Field] The present invention is a method for automatically detecting screw holes, etc. arranged on the circumference of a workpiece, and positioning the screw holes, etc. at predetermined positions to enable automatic assembly. This invention relates to a method for positioning a workpiece in an automatic assembly machine.

0002

[Prior Art] Conventionally, when assembling several mechanical parts (workpieces) to provide a certain function, it is often necessary to align a hole with a protrusion that fits into the hole, or with a screw hole. A method of fixing using screws, etc. is used. Generally, in these methods, the positions of screw holes, etc. are determined by setting the workpiece in a predetermined direction or posture and mounting it on the assembly machine, so a mechanism for detecting and positioning the screw hole positions is required. is not necessary.

However, in the case of a workpiece a having a rotationally symmetrical shape as shown in FIGS. 4 and 5, its outer shape is circular and has screw holes b, ... on one side in the axial direction, and a center part on the other side. It has a circular fitting hole c, but when setting it on the assembly machine,
Some do not have protrusions or marks d that are used for positioning, and it is not possible to perform positioning by mechanically fitting irregularities. Therefore, it is considered to provide marks such as protrusions or grooves by post-processing, but this not only increases cost but also makes it impossible to provide marks on some workpieces.

[0004] It is difficult to set such workpieces in a predetermined direction or posture, and the operator has to rely on visual judgment, and the positioning work requires a considerable amount of effort. This is one of the obstacles to automatic assembly.

[0005]

[Problems to be Solved by the Invention] In view of the above-mentioned situation, the present invention aims to solve the problem by changing the direction of a workpiece where there is no mark such as a projection conventionally used for positioning, or where a mark cannot be attached. An object of the present invention is to provide a method for positioning a workpiece in an automatic assembly machine, which can maintain a constant posture and accurately position screw holes, etc. used for assembly.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a workpiece having a shape changing part such as a screw hole at a predetermined position with respect to the central axis, and makes the workpiece coaxial with the shaft of a control motor. The detection sensor is placed facing the surface of the workpiece having the shape-changing part, and the workpiece is rotated with the distance from the central axis to the target shape-changing part and the distance to the detection sensor matched. , Workpiece positioning in an automatic assembly machine in which the rotation of the control motor is stopped when the detection sensor detects the desired shape-changing part, and the positions of other screw holes, etc. are determined using the detected shape-changing part as the origin. A method was established.

[0007] Furthermore, the detection sensor detects the shape changing portion in two
It is preferable to stop the rotation of the control motor when a set number of times or more is detected.

[0008]

[Operation] The workpiece positioning method in the automatic assembly machine of the present invention, which has the above-mentioned contents, is such that the shape-changing parts such as screw holes used when assembling several workpieces are determined with respect to the central axis of the workpieces. By utilizing the fact that the sensor is formed at a certain position and that its position is accurately recognized with respect to the central axis and with respect to any shape-changing part, the position of the detection sensor can be adjusted from the central axis to the desired shape-changing part. Taking advantage of the fact that it is easy to set the distance and the distance to the detection sensor to match, the workpiece is rotated by the control motor after the workpiece is mounted so that its center axis and the axis of the control motor are coaxial. When the detection sensor placed facing the surface with the shape-changing part detects the target shape-changing part, the control motor stops rotating, so that the target shape-changing part is always located at the same position. The coordinates of other screw holes, etc., are determined accurately using the detected shape change portion as the origin.

[0009] Furthermore, when the distance from the central axis of the workpiece to the shape changing part and the distance to the detection sensor are set, and the detection sensor is set to face the surface having the shape changing part, the position of the detection sensor is may almost coincide with the shape-changing part by chance, and in such a situation, the relative position of the shape-changing part and the detection sensor may change back and forth depending on the size of the shape-changing part, the sensitivity and accuracy of the detection sensor, and the spread of the detection area. Even if they are misaligned or perfectly matched, the detection sensor may detect the presence of the shape change portion and issue a stop signal to the control motor before the workpiece rotates. In this case, even if the positions of the shape-changing part and the detection sensor almost match, they may be slightly shifted back and forth from each other, or the stop position may be different from the one in which the detection sensor detects the shape-changing part and stops after the work has rotated. However, it is not possible to position the screw holes etc. in a constant manner. Therefore, by stopping the rotation of the control motor when the detection sensor detects the shape-changing part a set number of times, the workpiece is always stopped under the same conditions, and the position of the screw hole can be reproducibly changed. Position it well and accurately.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be further explained in detail based on embodiments shown in the accompanying drawings.

FIGS. 1 and 2 show typical embodiments in which positioning is performed by the method of the present invention, in which 1 is a workpiece such as a mechanical part to be assembled, 2 is a rotation device, and 3 is a detection sensor. are shown respectively. The workpiece 1 is mounted on a rotating device 2 and rotated, and a predetermined target is detected in a non-contact manner by a detection sensor 3 disposed facing the detection surface of the workpiece 1, and the rotating device 2 is rotated based on the detected signal. A stop signal is sent to stop the workpiece 1 at a predetermined position.

The workpiece 1 used in this embodiment has a rotationally symmetrical outer shape with a central axis 4, and a screw hole whose distance and relative position from the central axis 4 are determined on one side perpendicular to the central axis 4. 5,... are formed at a plurality of locations, and a circular recess 6 is formed in the center of the other side, and there is no other mark such as a protrusion. Here, the shape of the screw hole 5 has changed sharply with respect to the surface having the screw hole 5, and in this embodiment, it is assumed to be a typical shape changing part, and will be described below with the same reference numerals. . but,
As is clear from the gist of the present invention, the shape changing portion is not limited to a screw hole, but when rotated around the central axis 4, the shape changes sharply in the direction of rotation, and the shape changes sharply in the direction of rotation. For example, a stepped portion may be used as long as the distance from 4 is determined. Further, even the illustrated screw holes 5 do not need to be located on the same circumference, and may be located at arbitrary positions.

The rotating device 2 has a fixing jig 7 such as a rotary table on which the workpiece 1 is mounted, and the fixing jig 7 is equipped with a control device attached to a motor fixing plate 8 that can accurately control the rotation angle and stoppage thereof. It is fixed to the rotating shaft 10 of the motor 9. Here, the fixing jig 7 has a circular receiving part 12 protruding from the center of the flange 11 and coaxial with the rotating shaft 10,
When the recess 6 of the work 1 is fitted into the receiving part 12 and mounted, the central axis 4 of the work 1 and the rotating shaft 10 are coaxial. Furthermore, the control motor 9 employs an ultrasonic motor in this embodiment. This ultrasonic motor has a brake mechanism when it stops, and when it stops, its rotating shaft 1
0 is completely fixed, which is most suitable for the present invention. However, if the workpiece 1 is large and heavy, it is also possible to use a servo motor such as a pulse motor as the control motor 9. Furthermore, it is also preferable to interpose a roller, a bearing, or the like between the flange 11 of the fixture 7 and the motor fixing plate 8. In addition, the control motor 9
It is not necessary for the motor to suddenly stop at that position when it receives a stop signal, but it is required to always rotate by a certain rotation angle and then stop when it receives a stop signal.

The detection sensor 3 is disposed facing the surface of the workpiece 1 having the shape-changing portion 5, and has a function of detecting the presence of the shape-changing portion 5. The detection sensor 3 is attached to a drive unit such as a robot arm that can be positioned three-dimensionally, so that the distance from the central axis 4 of the workpiece 1 and the distance from the workpiece 1 can be set as appropriate. Here, the detection sensor 3 has a structure that generates a laser beam, detects the reflected light from the workpiece 1, and detects the shape changing part 5 from the difference in reflectance, or a structure that detects the shape change part 5 from the difference in reflectance. those with structures that directly measure distance;
In addition, if the workpiece 1 is a conductor, a fluctuating magnetic field is generated,
A non-contact detector such as an eddy current detector that has a structure that detects the magnetic field generated by the eddy current induced on the surface of the workpiece 1 and detects the shape changing part 5 based on the magnitude of the signal can be used, and the selection thereof is is determined depending on the material of the workpiece 1, the surface characteristics, and the state of the shape-changing portion 5. In this case, the accuracy of the detection sensor 3 is not necessarily required to be smaller than the diameter of the screw hole 5, but it is necessary to always output the same signal when the relative positions of the detection sensor 3 and the screw hole 5 are the same. is required.

Therefore, in order to always set the direction or posture of the workpiece 1 constant and to accurately position the screw holes 5 etc. using the method of the present invention, first, the recess 6 of the workpiece 1 is placed in the receiving position of the fixing jig 7. At the same time, the lower surface of the workpiece 1 is brought into contact with the flange 11 and fixed by the friction, or the workpiece 1 is fixed with a vacuum chuck provided at an appropriate position on the fixing jig 7, and the control motor 9 is rotated. The shaft 10 and the central axis 4 of the workpiece 1 are made to coincide. Next, the detection sensor 3 is connected to the workpiece 1.
The shape changing portion 5 is disposed facing the surface on which the shape changing portion 5 is formed, and the distance from the central axis 4 to the shape changing portion 5 is set to match the distance to the detection sensor 3. Finally, the workpiece 1 is rotated in a fixed direction by the control motor 9, and when the detection sensor 3 detects the shape changing part 5, a stop signal is output to the control motor 9 to promptly stop the rotation. At this time, the relative positions of the detection sensor 3 and the shape changing part 5 are always the same, and if the coordinates of the detected shape changing part 5 are determined experimentally from the coordinates of the detection sensor 3,
The coordinates of the other shape changing portions 5 can be calculated from the design values, so that all the screw holes 5 can be positioned with high accuracy, and their coordinates can also be calculated accurately.

In this positioning method, the factors that affect the positioning accuracy of the screw holes 5, etc. are: (1) the control motor 9;
ON/OFF characteristics (rise and fall time accuracy),■
At the same time as the control motor 9 is operated, the detection sensor 3 is activated as shown in FIG.
The moment you move to the position shown in
There is a precision in stopping the control motor 9 when detecting the screw hole 5, etc. (i.e., positioning accuracy of the screw hole 5, etc.), and in order to eliminate these factors, in the present invention, the sensor 3 detecting the shape changing part 5 has to stop the sensor 3 more than once. When the set number of times is detected,
The control motor 9 is stopped.

That is, when the position of the detection sensor 3 is set with respect to the workpiece 1, the positional relationship is such that the screw hole 5 and the detection area 13 of the detection sensor 3 substantially coincide with each other, as shown in FIG. There is. The arrow in the figure indicates the rotation direction of the workpiece 1, and FIG. 3(a) shows a state where the detection area 13 overlaps the front edge of the screw hole 5 in the rotation direction, and FIG. 3(b) shows the state where the detection area 13 overlaps the front edge of the screw hole 5.
A state in which the detection area 13 and the center are aligned, FIG. 3(c)
shows a state in which the detection region 13 overlaps the rear edge of the screw hole 5 in the rotational direction, and in any of these cases, the detection sensor 3 cannot detect the presence of the screw hole 5 due to the limit of the accuracy of the detection sensor 3. do. In either case, the control motor 9 remains stopped at that position, or starts rotating and stops immediately. Therefore, the stopping position of the work 1 may not be constant.

However, in the present invention, the shape changing portion 5
Since the control motor 9 is stopped when the detection sensor 3 detects the set number of times or more, the detection sensor 3 always sends a stop signal to the control motor in the positional relationship shown in Fig. 3(a). After that, the control motor 9 rotates by a certain angle and then stops. Therefore, this stopping position is always constant for each workpiece 1.

In this way, when the workpiece 1 always stops at a constant position, the relationship between the detection sensor 3 and the detected specific position of the shape-changing portion 5 is determined experimentally, and thereby the shape-changing portion 5 is set as the origin. As a result, the position coordinates of the other screw holes 5, etc. can be calculated accurately. Based on this result, it becomes possible to accurately fix other parts to the workpiece 1 with screws or the like.

[0020]

Effects of the Invention According to the method for positioning workpieces in an automatic assembly machine of the present invention as described above, the shape-changing portions such as screw holes used when assembling several workpieces are aligned with respect to the central axis of the workpieces. The position of the detection sensor can be adjusted from the central axis to the desired shape-changing part by utilizing the fact that the position is accurately recognized with respect to the central axis and with respect to the desired shape-changing part. Taking advantage of the fact that it is easy to set the distance between When the detection sensor, which is placed facing the surface of the workpiece that has the shape-changing part, detects the target shape-changing part, the control motor stops rotating, so that the target shape-changing part is always located at the same position. Based on this, the position coordinates of other screw holes, etc. can be determined accurately using this detected shape change part as the origin, making it possible to automatically assemble even workpieces that do not have protrusions that serve as landmarks. became.

Furthermore, by stopping the rotation of the control motor when the detection sensor detects the shape changing portion a set number of times or more, the accuracy of the detection sensor and the operating characteristics of the control motor are not so good. However, if the reproducibility is good, the workpiece can always be stopped under the same conditions, and the position of the screw hole etc. can be accurately positioned with good reproducibility.

[Brief explanation of drawings]

[Figure 1] A simplified plan view showing the relationship between the workpiece attached to the rotating device and the detection sensor.

[Figure 2] Cross-sectional view taken along line A-A in Figure 1

[Fig. 3] Shows the positional relationship between a shape-changing part such as a screw hole and the detection area of a detection sensor, where (a) is a simplified plan view of the shape-changing part overlapped with the front edge in the rotational direction, and (b) is a simplified plan view. A simplified plan view with the centers completely aligned; (c) is a simplified plan view with the parts overlapping the rear edge of the shape changing part in the rotational direction.

[Fig. 4] Plan view showing a conventional example of a workpiece with marks

[Figure 5] Similarly, central longitudinal front view

[Explanation of symbols]

1 Work
2 Rotating device 3 Detection sensor
4 Central axis 5 Shape changing part (screw hole) 6 Recessed part 7
fixing jig
8 Motor fixing plate 9 Control motor
10 Rotating shaft 11
flange
12 Receiving part 13 Detection area

Claims (2)

[Claims] Claim 1: A workpiece having a shape-changeable part such as a screw hole at a predetermined position with respect to a central axis is installed coaxially with the shaft of a control motor, and the workpiece is faced to a surface having a shape-changeable part. The workpiece is rotated with the distance from the center axis to the target shape-changing part matched with the distance to the detection sensor, and when the detection sensor detects the target shape-changing part, the control motor is activated. A method for positioning a workpiece in an automatic assembly machine, characterized in that the rotation of the workpiece is stopped, and the positions of other screw holes, etc. are determined using the detected shape-changing portion as the origin. 2. The method for positioning a workpiece in an automatic assembly machine according to claim 1, wherein the control motor stops rotating when the detection sensor detects the shape changing portion a set number of times or more.