Electricity: motive power systems – Positional servo systems
Reexamination Certificate
2001-12-26
2004-05-25
Duda, Rina (Department: 2837)
Electricity: motive power systems
Positional servo systems
C318S618000, C318S625000, C318S632000, C318S565000, C901S009000
Reexamination Certificate
active
06741055
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a positioning-controlling apparatus for positioning a subject by moving it to a predetermined position and a positioning-controlling method, and part-mounting equipment and a part-mounting method which comprise the positioning-controlling apparatus or employ the positioning-controlling method.
In part-mounting equipment for continuously mounting parts such as electronic parts, etc. on determined positions of a circuit-formed material such as an electronic circuit substrate or the like, a part is mounted on a determined position of a circuit-formed material by introducing the circuit-formed material into the equipment and regulating and holding it, while carrying and positioning a part at a determined position of the circuit-formed material, and mounting the part thereon. Alternatively, if a position to receive a part is specified, a circuit-formed material is carried and positioned so as to mount the part on a determined position of the circuit-formed material at the above specified position.
FIG. 7
shows an essential portion of part-mounting equipment comprising the former type positioning means which carries a part and positions it.
As seen in
FIG. 7
, part-mounting equipment (
100
) essentially consists of a part-supplying unit (
50
) for supplying parts to the part-mounting equipment (
100
), a robot (
60
) for carrying a subject on an X-Y plane, a mounting head (
75
) to be carried by the robot (
60
), a circuit-formed material-holding device (
80
) for carrying and holding a circuit-formed material, and a controller (
90
) for controlling the overall operation of the part-mounting equipment (
100
).
The robot (
60
) comprises a Y-direction driving unit which causes motors (
62
and
64
) fixed on the equipment to move a beam (
70
) along ball screws (
63
and
64
) in the direction Y, and an X-direction driving unit which causes a motor (
72
) fixed on the beam (
70
) driven by the Y-direction driving unit to move the mounting head (
75
) along a ball screw (
73
) in the direction X. In this regard, although the Y-direction driving unit may comprise a system in which driving is performed using one motor and one ball screw, Y-direction driving units of a multi-screw driving system (in this drawing, a twin-screw type using two ball screws (
63
and
65
)) have come into wide use to meet the latest demand for high-speed and high-load mounting performance, and also to achieve high rigidity and high accuracy of equipment.
As seen in
FIG. 7
, the mounting head (
75
) has
4
mounting nozzles (
76
) which are movable up and down along the direction Z and rotatable on the axis Z as the center. By this motion of the nozzles (
76
), parts are taken out and mounted. The circuit-formed material-holding device (
80
) carries a circuit-formed material such as an electronic circuit substrate (
82
) as shown in
FIG. 7
into the part-mounting equipment and regulates and holds the substrate (
82
) at a predetermined position in the course of mounting the part.
The part-mounting equipment (
100
) arranged above is operated as follows. The mounting head (
75
) with the respective mounting nozzles (
76
) which suck parts from the part-supplying unit (
50
) and hold them is carried to a mounting position by the robot (
60
), while the circuit-formed material-holding device (
80
) introduces the electronic circuit substrate (
82
) and holds it at a predetermined position. The distance which the robot (
60
) travels carrying the mounting head is computed and controlled by the controller (
90
) based on the data of a condition of the part sucked and held by the mounting nozzle (
76
), which is separately recognized, and data of a condition of the electronic circuit substrate (
82
) held. The mounting head (
75
), which is moved to the mounting position and stopped there, lowers the mounting nozzles (
76
) so as to mount the parts sucked at the ends of the nozzles (
76
) on the mounting positions of the electronic circuit substrate (
82
).
Part-mounting equipment is typically provided with a positioning-controlling apparatus for moving a subject (the mounting head (
75
) in the case of the X-direction driving unit shown in
FIG. 7
) in a predetermined direction along the ball screw which is rotated by a servo motor, and positioning it at a predetermined position and stopping it there. The system for detecting the position of the subject in this positioning-controlling apparatus is classified as a rotary encoder system in which the position of a subject is detected based on the number of rotations of a rotary encoder which rotates coaxially with a servo motor shaft, and a linear encoder system in which a position of a linear scale attached parallel to a direction along which a subject is moving is detected by a linear position-detecting device attached on the subject.
Recently, techniques for miniaturizing parts have been advanced, and hence high-density mounting of parts on an electronic circuit substrate has been realized. Therefore, accurate positioning and mounting of parts are required for part-mounting equipment. Under such circumstances, a positioning-controlling apparatus for use in part-mounting equipment tends to employ the linear encoder system capable of more accurately detecting a position of a subject than the rotary encoder system. The linear encoder is further classified as one of two types: one is an absolute type encoder which detects an absolute position by counting, and the other is an incremental type encoder which detects a relative position by counting. Of these encoders, presently, the incremental type encoder is mainly used because of its reliability and its past achievement. A positioning-controlling apparatus using this incremental type linear encoder according to the prior art is described with reference to the accompanying drawings.
FIG. 8
schematically shows the arrangement of a positioning-controlling apparatus according to the prior art which uses the incremental type linear encoder (hereinafter, simply referred to as a linear encoder). The system shown in
FIG. 8
may be considered as the essential portion of the X-direction driving unit used by the part-mounting equipment (
100
) shown in FIG.
7
. As seen in
FIG. 8
, mounted on the servo motor (
1
) is a moving mechanism comprising a ball screw (
3
) for moving a subject (an object) (
4
), and a moving member (
7
) screwed on the ball screw (
3
). The subject (
4
) (the mounting head (
75
) in the case of the X-direction driving unit shown in
FIG. 7
) is secured on the moving member (
7
), and the subject (
4
) is moved in the direction R or L via the rotation of the ball screw (
3
) by the reciprocal rotation of the servo motor (
1
). The subject (
4
) is equipped with a linear encoder (
5
) which performs position detection by detecting a linear scale (
6
) secured parallel to the ball screw (
3
). A rotary encoder (
2
) which rotates together with the servo motor (
1
) to detect a rotation amount is coaxially mounted on the servo motor (
1
).
At the time of turning on a power supply, the servo motor (
1
) using the linear encoder (
5
) as a position-detecting means cannot grasp an absolute position of the subject (
4
). Therefore, the subject (
4
) needs to be returned to an origin position which is preset as a reference position, and then a relative position from the origin position is detected by counting output signals from the linear encoder (
5
) so as to make positioning control. A detection piece (
8
) is attached to the moving member (
7
) on which the subject (
4
) is mounted, so as to detect the returning of the subject (
4
) to the origin position. Further, an origin sensor (
11
) is arranged at the origin position, and the sensor (
11
) detects the detection piece (
8
) which has been moved to the origin position.
The servo driver (
10
) controls the rotation of the servo motor (
1
) according to an instruction from the controller (
9
) which controls the overall operation of the equipment, and also according to a detection signa
Kurokawa Takahiro
Matsuo Seiichi
Tanaka Yoichi
Yanachi Seishiro
Duda Rina
Smith Tyrone
Wenderoth , Lind & Ponack, L.L.P.
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