Information
-
Patent Grant
-
6493927
-
Patent Number
6,493,927
-
Date Filed
Tuesday, December 26, 200023 years ago
-
Date Issued
Tuesday, December 17, 200221 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Fetsuga; Robert M.
- deVore; Peter
Agents
-
CPC
-
US Classifications
Field of Search
US
- 269 8
- 269 43
- 269 71
- 269 73
- 269 903
- 269 218
- 269 256
- 029 740
- 310 12
- 310 13
-
International Classifications
-
Abstract
A chuck for holding an object, including one or more linear motors which include one or more linear stators, two or more moving members which are movable along the linear stator or stators, independent of each other, and one or more guide members which guide each of the two or more moving members along the linear stator or stators, and two or more holding members which are supported by the two or more moving members, respectively, and which cooperate with each other to hold the object.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chuck which holds an object such as an electric component and also to an electric-component mounting system which mounts an electric component on a circuit substrate such as a printed wiring board.
2. Discussion of Related Art
There is known an electric-component (EC) mounting system which includes a chuck for holding an electric component (EC) and moves the chuck holding the EC to a circuit substrate to mount the EC on the substrate and thereby produce an electric circuit. The conventional chuck includes a pair of holding jaws, and an opening and closing device for mechanically opening and closing the jaws by moving the jaws symmetrically with respect to the center of the chuck. Thus, the chuck can hold the EC such that the center of the EC is aligned with that of the chuck.
However, the conventional chuck including the mechanical opening and closing device cannot largely change the respective positions of the holding jaws because of the mechanical structure of the opening and closing device. Therefore, the conventional chuck cannot hold different sorts of ECs having largely different sizes. In addition, the chuck cannot hold an EC having an asymmetric shape such that a desired portion of the EC is aligned with the centerline of the chuck.
While the above discussion relates to the chuck for holding the EC, the same problems as indicated above occur to other sorts of chucks for holding other sorts of objects.
SUMMARY OF THE INVENTION
The present invention provides a linear-motor-driven chuck and an electric-component mounting system which have one or more of the following technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (13). Any technical feature that includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to the latter feature. However, the following technical features and the appropriate combinations thereof are just examples to which the present invention is by no means limited. In addition, in the case where one technical feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed. That is, it is possible to select and employ only a portion (one, two, . . . , but not all) of those items.
(1) According to a first feature of the present invention, there is provided a chuck for holding an object, comprising at least one linear motor which includes at least one linear stator, two moving members which are movable along the linear stator, independent of each other, and at least one guide member which guides each of the two moving members along the linear stator; and two holding members which are supported by the two moving members, respectively, and which cooperate with each other to hold the object.
The linear motor may include a single linear stator common to the two moving members, or two linear stators for the two moving members, respectively. In the former case, each one of the two moving members may be moved over the middle or center of the single linear stator, toward the other moving member. In the latter case, the linear motor can be said as two linear motors each of which includes a corresponding one of the two linear stators and a corresponding one of the two moving members.
In the present chuck, the two holding members are supported by the two moving members of the linear motor that are movable independent of each other. Therefore, the distance between the two holding members can be largely changed more easily than the conventional chuck including the mechanical opening and closing device. Thus, the present chuck can hold various sorts of objects in a wider range. The two holding members may be two external holding members which externally engage an outer surface or surfaces of an object and thereby hold it, or two internal holding members which engage an inner surface or surfaces of an object having an inner space and thereby hold it.
(2) According to a second feature of the present invention that includes the first feature (1), the chuck further comprises a rotating device which rotates the linear motor about an axis line perpendicular to a lengthwise direction of the linear stator.
Since the present chuck includes the chuck rotating device which rotates the linear motor, the chuck can change the current angular phase of the object (e.g., electric component, EC) held by the two holding members, to any desirable angular phase. For example, the chuck can change the current angular phase of an EC to a prescribed angular phase thereof relative to a circuit board, before the EC is mounted on the board.
(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), each of the two moving members comprises an attaching member to which a corresponding one of the two holding members is detachably attached.
Since the two holding members are detachably attached to the respective attaching members of the two moving members, the current sort of holding members may be replaced with a new sort of holding members, depending upon the sort of new objects to be held next by the chuck. Thus, the present chuck can hold various sorts of objects in a wider range.
(4) According to a third feature of the present invention that includes any one of the first to third features (1) to (3), the chuck further comprises two position sensors each of which detects a current position of a corresponding one of the two moving members and produces a detection signal indicating the detected current position of the one moving member.
Since the two position sensors detect the respective current positions of the two moving members, a control device, for example, which may be employed and connected to the linear motor can more accurately control, based on the detected current positions, the respective current positions of the two moving members of the linear motor. This contributes to improving a positioning accuracy with which the chuck holds the object.
(5) According to a fifth feature of the present invention that includes any one of the first to fourth features (1) to (4), the chuck further comprises two origin sensors each of which detects a corresponding one of the two moving members which is currently positioned at an origin position thereof.
Since the two origin sensors detect the two moving members being currently positioned at their origin positions, the above control device can control, based on the detected origin positions, the respective movements of the two moving members of the linear motor. This contributes to facilitating the control to open and close the chuck.
(6) According to a sixth feature of the present invention that includes the fourth or fifth feature (4) or (5), the chuck further comprises a control device including a symmetric-movement control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members symmetrically with respect to a centerline of the chuck.
The present chuck can hold an object symmetric with respect to a plane, in a state in which the plane contains a centerline of the chuck.
(7) According to a seventh feature of the present invention that includes any one of the fourth to sixth features (4) to (6), the chuck further comprises a control device including an asymmetric-movement control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members asymmetrically with respect to a centerline of the chuck.
The present chuck is suitable for holding an asymmetric object.
(8) According to an eighth feature of the present invention that includes any one of the fourth to seventh features (4) to (7), the chuck further comprises a control device including an object-dependent control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members to respective opened positions where the two holding members supported by the two moving members are distant from each other by a distance greater than a prescribed dimension of the object by a predetermined distance and then move the two moving members toward each other at respective speeds equal to each other.
The present chuck can hold, or release, the object in a short time, and can position, and hold, the object at a desired position.
(9) According to a ninth feature of the present invention that includes any one of the first to eighth features (1) to (8), the chuck further comprises a control device including a holding-force control portion which controls a holding force with which the two holding members hold the object.
The present chuck can hold, with an appropriate holding force, an object which is easily deformable or highly fragile.
(10) According to a tenth feature of the present invention that includes any one of the first to ninth features (1) to (9), the chuck comprising two linear motors one of which includes two first moving members that are movable toward, and away from, each other in a first direction and the other of which includes two second moving members that are movable toward, and away from, each other in a second direction perpendicular to the first direction, and the first and second moving members cooperate with each other to hold the object in the first and second directions.
The present chuck can more reliably hold the object and, in particular, it is advantageous for holding an object having a shape asymmetric with respect to both of two planes which are respectively perpendicular to the first and second directions.
(11) According to an eleventh feature of the present invention, there is provided a system for mounting at least one electric component on a circuit substrate, comprising a chuck according to any one of the first to tenth features (1) to (10); a chuck moving device which moves the chuck to an arbitrary position in a movement area parallel to a substantially horizontal plane; a supplying device which is provided in the movement area and which supplies the electric component to the chuck; and a supporting device which is provided in the movement area and which supports the circuit substrate on which the electric component is to be mounted by the chuck.
Since the present EC mounting system employs the chuck which can hold various sorts of objects in a wide rage as described above, the mounting system enjoys a high degree of freedom in the meaning that it can mount various sorts of ECs on a circuit substrate.
(12) According to a twelfth feature of the present invention that includes the eleventh feature (11), the mounting system further comprises a chuck elevating and lowering device which elevates and lowers the chuck in respective directions perpendicular to the substantially horizontal plane.
Since the present EC mounting system includes the chuck elevating and lowering device which elevates and lowers the chuck, the mounting system can lower and elevate the chuck to take an EC from the EC supplying device and/or mount the EC on the circuit substrate. Therefore, the present mounting system need not lower or elevate the EC supplying device or the substrate supporting device to take out the EC from the supplying device or mount the EC on the circuit substrate supported by the supporting device. Thus, the overall construction of the EC mounting system can be simplified.
(13) According to a thirteenth feature of the present invention that includes the eleventh or twelfth feature (11) or (12), the mounting system further comprises an image taking device which takes an image of the electric component held by the chuck; and a modifying device which determines, based on image data representing the image taken by the image taking device, at least one positional error of the electric component held by the chuck and modifies, based on the determined positional error, at least one movement amount of the chuck moving device so as to move the chuck to a position where the positional error of the electric component is zero relative to the circuit substrate supported by the supporting device.
In the case where the EC held by the chuck has at least one positional error (e.g., a horizontal-position error in an X-axis direction or a Y-axis directioin, and/or an angular-phase error about a Z axis perpendicular to the X and Y axes), the present EC mounting system can mount the EC on the circuit substrate after correcting the positional error or errors. Thus, the present mounting system enjoys a high accuracy with respect to the position or positions at which the system mounts the EC on the circuit substrate. However, as described above, the chuck can enjoy a high accuracy with respect to the position or positions at which the chuck holds the EC. In the latter case, the image taking device and the modifying device may be omitted, and the chuck according to the tenth feature (10) is particularly advantageous. According to the combination of the thirteenth and tenth features (13) and (10), the EC mounting system may employ, in place of the modifying device, a correcting device which determines, based on the image data representing the image taken by the image taking device, one or more positional errors of the EC held by the two pairs of moving members and corrects, based on the determined positional error or errors, the erroneous position or positions of the EC, by correcting the respective current positions of the two pairs of moving members. In the last case, it is preferred that each pair of moving members which are moved toward, and away from, each other in first directions be moved by a small distance in each of second directions perpendicular to the first directions, and be biased toward respective neutral positions thereof by respective biasing members such as elastic members. In this case, when the respective current positions of the one or first pair of moving members are corrected by moving those members, the other or second pair of moving members follow the movement of the first pair of moving members.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features, advantages and technical and industrial significance of the present invention will be better understood by reading the following detailed description of preferred embodiments of the invention, when considered in connection with the accompanying drawings, in which:
FIG. 1
is a schematic plan view of an electric-component (EC) mounting system to which the present invention is applied;
FIG. 2
is a side elevation view of a linear-motor-driven chuck and its vicinity of the EC mounting system;
FIG. 3
is a front elevation view of the linear-motor-driven chuck and its vicinity of the EC mounting system;
FIG. 4
is a plan view of the linear-motor-driven chuck;
FIG. 5
is a front elevation view of the linear-motor-driven chuck;
FIG. 6
is a cross-sectioned, side elevation view of the linear-motor-driven chuck;
FIG. 7
is a view for explaining the manner in which two holding jaws are detached from two moving members of the linear-motor-driven chuck;
FIG. 8
is a diagrammatic view of a control device of the EC mounting system;
FIG. 9
is a flow chart representing an electric-circuit assembling routine as one of control programs according to which the control device controls the EC mounting system;
FIG. 10
is a flow chart showing detailed steps of Step S
3
of the flow chart of
FIG. 9
;
FIG. 11
is a flow chart showing detailed steps of Step S
7
of the flow chart of
FIG. 9
; and
FIG. 12
is a bottom view of a linear-motor-driven chuck as a second embodiment of the present invention.
DETAILED DESCRIPTION OF PROFFERED EMBODIMENT
FIG. 1
is a plan view of an electric-component (EC) mounting system to which the present invention is applied. The present EC mounting system includes a base
10
; and a board conveyor
12
, two EC supplying devices
16
and an EC mounting device
18
which are provided on the base
10
. The board conveyor
12
conveys a printed wiring board
14
as a circuit substrate, and positions and supports the board
14
at a predetermined EC-mount station. Thus, the board conveyor
12
also functions as a circuit-substrate supporting device. Each of the two EC supplying devices
16
includes a feeder table
20
, and a plurality of EC feeders
19
which are detachably attached to the feeder table
20
such that respective EC-supply portions of the feeders
19
are arranged along a straight line parallel to an X-axis direction. Each of the EC feeders
19
stores a number of electric components (ECs) of one sort, and supplies the ECs, one by one, from the EC-supply portion thereof. Each of the two feeder tables
20
is movable, while being guided by a pair of guide rails
22
, between an EC-supply position and a retracted position in a Y-axis direction perpendicular to the X-axis direction.
The EC mounting device
18
includes an X-Y moving device, which includes four columns
26
which stand on the base
10
; two guide rails
28
which are horizontally supported by the columns
26
such that the guide rails
28
extend parallel to the Y-axis direction; two feed screws
30
; two Y-axis motors (servomotors)
32
; a Y-axis slide
40
which is provided with two nuts (not shown) threadedly engaged with the two feed screws
30
, respectively, and is moved in the Y-axis direction by the screws
30
and the motors
32
while being guided by the guide rails
28
; a feed screw
36
; an X-axis motor (servomotor)
38
; and an X-axis slide
40
which is provided, together with the feed screw
36
and the X-axis motor
38
, on the Y-axis slide
40
and is moved in the X-axis direction by the screw
36
and the motor
38
.
The X-axis slide
40
supports an EC holding head
44
which receives an EC
134
(
FIG. 2
) from an appropriate one of the two EC supplying devices
16
, and conveys the EC
134
to a position above the printed board
14
positioned and supported by the board conveyor
12
, along an EC-convey path below which an image taking device
48
including a line image sensor
46
is provided.
As shown in
FIGS. 2 and 3
, the EC holding head
44
includes an elevator member
50
, as a main member thereof, that is supported by the X-axis slide
40
such that the elevator member
50
is movable upward and downward. The elevator member
50
is moved up and down by a feed screw
54
and a Z-axis motor (servomotor;
FIG. 8
)
56
while being guided by a pair of guide rails
52
provided on the X-axis slide
40
. Reference numeral
58
designates a timing pulley as a transmitting device which transmits the rotation of the Z-axis motor
56
to the feed screw
54
. The elevator member
50
supports a rotatable shaft
62
via bearings
60
such that the rotatable shaft
62
is rotatable about a vertical axis line thereof relative to the elevator member
50
and is not movable in directions parallel to the axis line relative to the same
50
. The rotatable shaft
62
is rotated by a θ-axis motor (servomotor)
64
via a pinion
66
and a gear (scissors gear)
68
.
A main portion of the gear
68
is integral with a lower end portion of the rotatable shaft
62
. A linear-motor-driven chuck
72
as an EC holder is detachably attached to the main portion of the gear
68
. More specifically described, an attaching member
76
is fixed to the main portion of the gear
68
via two connecting rods
74
, and a stator
82
of a linear motor
80
as a main member of the chuck
72
is detachably attached to the attaching member
76
. The linear motor
80
is a linear DC brushless motor, and includes, in addition to the above-indicated stator
82
, two moving members
84
,
86
, and two guide members
88
for guiding the moving members
84
,
86
in directions parallel to a lengthwise direction of the stator
82
.
The stator
82
includes a main portion
90
which is formed of an aluminum alloy as a non-magnetic material, and a number of permanent magnets
92
which are fixed to the main portion
90
. Each of the permanent magnets
92
has an elongate shape like a square bar, and one of opposite elongate side surfaces thereof has a north pole (N-pole) and the other long side surface has a south pole (S-pole). The main portion
90
supports the magnets
92
such that the N-poles and the S-poles are alternate with each other in the lengthwise direction of the stator
82
. The N-pole and S-pole side surfaces of each magnet
92
somewhat project from opposite side surfaces of the main portion
90
. The N-poles (or S-poles) on one of the opposite side surfaces of the main portion
90
and the N-poles (or S-poles) on the other side surface of the main portion
90
provide a zigzag pattern in a plan view.
Each of the two moving members
84
,
86
includes two iron cores
96
which face the opposite two side surfaces of the main portion
90
of the stator
82
, respectively. Respective lower end portions of the two cores
96
are connected to each other by a connecting table
98
. Thus, each of the moving members
84
,
86
has a generally U-shaped cross section. A U-phase coil, a V-phase coil, and a W-phase coil are wound around each core
96
to provide a coil unit. Each of the two coil units is designed such that under control of an electric current supplied to a corresponding one of the two moving members
84
,
86
, the each coil unit produces a force to linearly move the one moving member
84
,
86
along the stator
82
owing to the interaction between the magnetic force produced by the each coil and the respective magnetic forces of the permanent magnets
92
of the stator
82
.
The respective movements of the two moving members
84
,
86
are guided by the two guide members
88
fixed to the opposite side surfaces of the main portion
90
of the stator
82
. Two sliders
100
are fixed to opposed inner surfaces of each of the U-shaped moving members
84
,
86
, respectively, and are engaged with the two guide members
88
, respectively, via balls (not shown). Thus, each of the moving members
84
,
86
is lightly moved along the guide members
88
.
Respective origin positions of the two moving members
84
,
86
correspond to respective lengthwise opposite ends of the stator
82
. Two origin sensors
102
,
103
(
FIG. 8
) detect that the two moving members
84
,
86
are positioned, or not positioned, at their origin positions, respectively. Two position sensors
104
,
106
(
FIG. 8
) detect respective positions of the two moving members
84
,
86
as respective distances thereof as measured from the respective origin positions. In the present embodiment, each of the origin sensors
102
,
103
is provided by a transmission-type photoelectric sensor which includes a light emitting diode (LED) as a light emitter; a light receiver or detector for detecting a light emitted by the LED; and a shielding member which is provided on a corresponding one of the moving members
84
,
86
and which shields, when the one moving member
84
,
86
is positioned at its origin position, the light emitted by the LED and prevents the light from being detected by the light detector. However, the transmission-type photoelectric sensor may be replaced with a different sort of sensor, such as a reflection-type photoelectric sensor, a contact-type switch (e.g., a limit switch), or a proximity switch. In the present embodiment, each of the position sensors
104
,
106
is provided by a magnetic linear scale (“Magnescale”) including a magnetic scale having magnetic graduations and a magnetic-field detecting head which is moved on the magnetic scale while producing an electric signal indicating the current position of a corresponding one of the moving members
84
,
86
. However, the magnetic linear scale may be replaced with an optical linear scale or a different sort of position sensor. The two position sensors
104
,
106
may employ a single common magnetic scale.
A pair of holding jaws
108
,
109
which cooperate with each other to sandwich and hold the EC
134
are detachably attached to the respective tables
98
of the two moving members
84
,
86
. In the present embodiment, a jaw storing device
115
(
FIG. 1
) stores a plurality of holding jaws
108
,
109
of different sorts. The current pair of jaws
108
,
109
can be replaced with a pair of jaws
108
,
109
of a different sort, depending upon the sort of new ECs to be mounted by the EC holding head
44
. As shown in the enlarged view of
FIG. 7
, each of the two tables
98
supports an attaching member
110
and a positioning pin
111
, and each of the holding jaws
108
,
109
includes a tapered shank
112
having an annular groove
113
. In the state in which the tapered shank
112
of each jaw
108
,
109
is fitted in a tapered hole of the attaching member
110
, two arm portions of a U-shaped holding spring
114
, supported by the attaching member
110
, elastically engage the annular groove
113
of the tapered shank
112
. Thus, each jaw
108
,
109
is prevented from coming off the attaching member
110
. In addition, the positioning pin
111
fits in a positioning recess formed in each jaw
108
,
109
, thereby preventing each jaw
108
,
109
from being rotated about its tapered shank
112
. Thus, each jaw
108
,
109
is secured to the corresponding moving member
84
,
86
, such that the each jaw
108
,
109
is not movable relative to the corresponding moving member
84
,
86
.
The present EC mounting system automatically replaces the current pair of holding jaws
108
,
109
with another pair of holding jaws
108
,
109
which are stored in the jaw storing device
115
, which is provided between the EC supplying devices
16
and the board conveyor
12
, as shown in FIG.
1
. When the replacement of the current jaws
108
,
109
is needed, first, the EC holding head
44
is moved to a position above the jaw storing device
115
, then the chuck
72
is moved down toward the device
115
, subsequently a movable member of the device
115
is moved and engaged with the current jaws
108
,
109
, and the chuck
72
is moved up, so that the current jaws
108
,
109
are removed from the chuck
72
and are stored in the device
115
. The attachment of new jaws
108
,
109
is carried out in an order opposite to the order of description. Since the jaw storing device
115
is not relevant to the present invention, no detailed description and illustration are provided. In short, in the present embodiment, each jaw
108
,
109
can be attached to, and detached from, the attaching member
110
by just applying a force greater than a threshold value, to the each jaw
108
,
109
in an axial direction of the tapered shank
112
thereof. Thus, the current jaws
108
,
109
can be easily exchanged with different jaws
108
,
109
.
The present EC mounting system is controlled by a control device
116
shown in FIG.
8
. However,
FIG. 8
shows only portions of the EC mounting system that are relevant to the present invention. The control device
116
is essentially provided by a computer
118
including a processing unit (PU)
120
, a read only memory (ROM)
122
, a random access memory (RAM)
124
, an input port
126
, an output port
128
, and a bus line for connecting those elements
120
,
122
,
124
,
126
,
128
to one another. An image-data processing computer
130
which processes image data representing the image taken by the image taking device
48
, is connected to the input port
126
. In addition, the origin sensors
102
,
103
, the position sensors
104
,
106
, other sensors, and other computers are also connected to the input port
126
. The output port
128
is connected via respective drive circuits to the Y-axis motors
32
, the X-axis motor
38
, the Z-axis motor
56
, the θ-axis motor
64
, and the two moving members
84
,
86
of the chuck
72
. The ROM
122
stores various control programs including an electric-circuit assembling routine represented by the flow charts shown in
FIGS. 9
to
11
. According to the electric-circuit assembling routine, the control device
116
controls the EC mounting system to automatically mount the ECs
134
on the printed wiring board
14
and thereby assemble an electric-circuit board
14
. Hereinafter, there will be described the electric-circuit assembling operation which is carried out by the present EC mounting system.
After the board conveyor
12
positions the printed wiring board
14
at the predetermined position shown in
FIG. 1
, the control device
116
starts with Step S
1
to read out, from the RAM
124
, control data relating to a current EC
134
which is to be mounted next on the printed board
14
. This control data include identification (ID) data identifying the sort of current EC, a take-out position where the EC holding head
44
or the chuck
72
takes out the current EC
134
of that sort from one of the EC feeders
19
of the EC supplying devices
16
, and a mount position where the chuck
72
mounts the current EC
134
on the printed board
14
. Step S
1
is followed by Step S
2
where the control device
116
moves the chuck
72
to the take-out position, and then by Step S
3
where the control device
116
carries out an EC taking-out routine represented by the flow chart of FIG.
10
. First, at Step of
FIG. 10
, the control device
116
opens the chuck
72
. More specifically described, the control device
116
reads out, based on the ID data identifying the sort of current EC
134
, distance data indicating respective prescribed distances of respective portions of the EC
134
that are to be held by the two holding jaws
108
,
109
, from a reference position, i.e., the centerline of the chuck
72
. Then, the control device
116
opens each of the two moving members
84
,
86
to position a corresponding one of the two holding jaws
108
,
109
at a position which is more distant from the reference position than a corresponding one of the read-out prescribed distances by a predetermined distance.
The reference position, i.e., the centerline of the chuck
72
coincides with the axis line of rotation of the rotary shaft
62
in the state in which the chuck
72
is attached to the attaching member
76
. In the case where the EC
134
is one which has a plane-symmetric shape with respect to at least a first plane perpendicularly intersecting the direction in which the two holding jaws
108
,
109
are moved toward, and away from, each other, the two jaws
108
,
109
of the chuck
72
are opened symmetrically with respect to a second plane including the axis line of rotation of the rotatable shaft
62
. On the other hand, in the case where the EC
134
is one which has an asymmetric shape with respect to the above-indicated first plane, the two jaws
108
,
109
are opened asymmetrically with respect to the above-indicated second plane. Thus, in the present embodiment, a portion of the control device
116
that carries out Step S
11
provides an object-dependent control portion. The same portion of the control device
116
provides a symmetric-movement control portion in the case where the EC
134
is plane-symmetric, and provides an asymmetric-movement control portion in the case where the EC
134
is asymmetric.
After the chuck
72
is opened in this way, the control of the control device
116
goes to Step S
12
where the control device
116
controls the Z-axis motor
56
to move the elevator member
56
downward to a height position where the chuck
72
can hold the current EC
134
. Step S
12
is followed by Steps S
13
to S
16
to close the chuck
72
and thereby hold the EC
134
. The EC
134
indicated at two-dot chain line in
FIG. 3
is the thinnest one of a plurality of sorts of ECs which can be held by the chuck
72
. Since the chuck
72
can be largely opened, the chuck
72
can hold an EC having a thickness equal to more than several times the thickness of the EC
134
. The EC
134
can have, in a direction perpendicular to the direction in which the EC
134
is held by the chuck
72
, such a dimension as indicated at two-dot chain line in FIG.
2
. Since the elevator member
50
or the chuck
72
can be largely elevated and lowered, the EC
134
is allowed to have a height (i.e., a vertical dimension) which can change in a wide range.
The current EC
134
is fed to, and positioned at, a prescribed position by one of the EC feeders
19
of the EC supplying devices
16
. Therefore, in a state in which the chuck
72
being opened has been moved down, the two holding jaws
108
,
109
are horizontally distant from respective outer surfaces of the EC
134
by respective small distances equal to each other. Then, the chuck
72
is closed by moving the two moving members
84
,
86
at respective speeds equal to each other. When the two holding jaws
108
,
109
contact the respective outer surfaces of the EC
134
, the moving members
84
,
86
are stopped because they cannot be moved any more. The holding force with which the two jaws
108
,
109
hold the EC
134
is controlled at an appropriate force by the control device
116
by controlling, based on the ID data indicating the sort of current EC
134
read out at Step S
1
, the respective electric currents supplied to the respective coil units of the two moving members
84
,
86
. The above appropriate force is appropriate for the current EC
134
in the meaning that that force is not so great as to break the EC
134
or so small as to fail to hold the same
134
. If the two moving members
84
,
86
are thus stopped, a positive judgment is made at Step S
14
, and the control goes to Step S
15
to keep still the two moving members
84
,
86
. More specifically described, the control device
116
controls the respective electric currents supplied to the respective coil units of the two moving members
84
,
86
, such that the two holding jaws
108
,
109
hold the EC
134
with the appropriate force and such that the two moving members
84
,
86
are not moved from the respective stopped positions. For example, if the first member
84
applies, to the EC
134
, a force somewhat greater than that applied by the second member
86
, then the two members
84
,
86
holding the EC
134
move rightward in
FIG. 3
, which is detected by the position sensors
104
,
106
. Therefore, the control device
116
decreases the electric current supplied to the coil unit of the first moving member
84
, or increases the electric current supplied to the coil unit of the second moving member
86
, so that the two members
84
,
86
holding the EC
134
are moved leftward. Whether the control device
116
should decrease the first current supplied to the first member
84
or increase the second current supplied to the second member
86
depends on which one of decreasing the first current or increasing the second current is more appropriate for producing the appropriate holding force. In this way, the control device
116
controls the two moving members
84
,
86
to hold the EC
34
with the appropriate holding force and to be kept still at the respective stopped positions. In this state, the control device
116
carries out Step S
16
to move the chuck
72
upward and thus take out the EC
134
from the EC supplying devices
16
.
After the EC
134
is thus taken out, the control of the control device
116
goes to Step S
4
to move the chuck
72
to an image-take-start position, and then to Step S
5
to control the image taking device
48
to take an image of the EC
134
held by the chuck
72
. In the present embodiment, the image taking device
48
includes the line-image sensor
46
which includes an array of CCDs (charge coupled devices). Therefore, when the chuck
72
is moved at a prescribed speed from the image-take-start position in the Y-axis direction, the line-image sensor
46
iteratively takes respective line images of the EC
134
at respective predetermined intervals of time, so that image data representing an image of the entirety of EC
134
as a group of the line images are obtained by the image taking device
48
. The image-data processing computer
130
compares the thus obtained image data with correct image data, pre-stored in the RAM
124
, representing a correct image of EC
134
which is correctly held by the chuck
72
, i.e., at respective correct positions in the X-axis and Y-axis directions and at a correct angular phase (or rotation position) about the Z-axis direction. Consequently the computer
130
calculates respective positional errors, ΔX, ΔY, of a reference position of the EC
134
from the respective correct positions in the X-axis and Y-axis directions, and an angular-phase error, Δθ, of the EC
134
about a straight line which passes through the reference position, parallel to the Z-axis direction, i.e., perpendicularly to the X-axis and Y-axis directions. The image-data processing computer
130
supplies error data representing the thus calculated errors ΔX, ΔY, Δθ to the control device
116
or the computer
118
.
After the image of the EC
134
is taken at Step S
5
, the control device
116
moves the chuck
72
to the mount position indicated by the control data read out at Step S
1
. During this movement of the chuck
72
, the image-data processing computer
130
supplies the error data representing the errors ΔX, ΔY, Δθ to the control device
116
. Consequently the control device
116
stops the chuck
72
at respective X-axis-direction and Y-axis-direction positions and an angular phase which have been obtained by modifying, by the errors ΔX, ΔY, Δθ, the correct or nominal X-axis-direction and Y-axis- direction positions and the correct angular phase. Step S
6
is followed by Step S
7
to carry out an EC mounting routine represented by the flow chart of FIG.
11
. At Step S
21
of
FIG. 11
, the control device
116
moves the chuck
72
downward to press the EC
134
against the printed wiring board
14
and temporarily fix the same
134
with an adhesive which has already been applied to the board
14
. Step S
21
is followed by Step S
22
to open the chuck
72
, and then by Step S
23
to move the chuck
72
upward.
After the current EC
134
has been mounted on the printed wiring board
14
, the control goes to Step S
8
of
FIG. 9
to judge whether all the ECs
134
to be mounted on the board
14
have been mounted on the board
14
. If a negative judgment is made at Step S
8
, the control device
116
repeats Step S
1
and the following steps. Meanwhile, if a positive judgment is made at Step S
8
, the current control cycle according to the electric-circuit assembling routine of
FIG. 9
is finished.
In the EC mounting system described above, the linear-motor-driven chuck
72
includes the two holding jaws
108
,
109
for sandwiching the EC
134
in one direction and thereby holding the same
134
. However, the chuck
72
may be replaced by a different linear-motor-driven chuck
142
shown in FIG.
12
. The chuck
142
includes two linear motors
80
including four moving members
138
,
139
,
140
,
141
, two
138
,
139
of which are moved toward, and away from, each other in a first direction, the other two
140
,
141
of which are moved toward, and away from, each other in a second direction perpendicular to the first direction, and all of which cooperate with one another to hold an EC. The two linear motors include a common stator
144
having four arm portions which extend radially outward and are equiangularly spaced from one another about a vertical centerline of the chuck
142
. Since the four moving members
138
-
141
may interfere with one another around the centerline of the chuck
142
, the shapes and sizes of ECs that can be held by the chuck
142
are somewhat limited. However, in the case where each of the four moving members
138
-
141
has a shape overhanging or projecting toward the centerline, the chuck
142
can hold even an EC having a small size.
Two pairs of holding jaws
108
,
109
are detachably attached to the two pairs of moving members
138
-
141
, respectively. In this case, it is preferred that each of the four jaws
108
,
109
be supported by a corresponding one of the four moving members
128
-
141
, such that the each jaw
108
,
109
is movable relative to the one moving member
138
-
141
in directions perpendicular to the directions in which the each jaw is moved with the one moving member, and be biased by a biasing member such that the each jaw is normally biased toward a neural position thereof. More specifically described, for example, the above-described attaching member
110
is attached to each of the four tables
98
of the chuck
142
, such that the attaching member
110
is movable, owing to a stepped screw and an elongate hole, relative to the each table
98
in the directions perpendicular to the directions in which the corresponding pair of holding jaws
108
,
109
are opened and closed, and a spring member as the biasing member biases the attaching member
110
toward its neutral position. In this case, when one pair of jaws
108
,
109
hold an EC after the other pair of jaws
108
,
109
have held the EC, the EC is allowed to be moved by a small distance by elastic deformations of the two spring members associated with the other pair of jaws
108
,
109
. Thus, in this case, it is not essentially required that the EC be simultaneously held by the two pairs of jaws
108
,
109
. That is, the EC may be held first by one pair of jaws and then by the other pair of jaws. In addition, in the state in which the EC is held by the two pairs of jaws, each of respective positions of the EC relative to the chuck
142
in the first and second directions may be changed or adjusted by moving a corresponding one or ones of the four moving members
138
-
141
relative to the stator
144
.
In each of the illustrated embodiments, the control device
116
controls the respective electric currents supplied to the respective coil units of the two moving members
84
,
86
or the four moving members
138
-
141
, so that the two or four holding jaws
108
,
109
hold an EC with a holding force suitable for the sort of EC while being kept still at the respective stopped positions. However, the control device
116
may be so modified as to control the respective positions of the two or four moving members
84
,
86
,
138
-
141
in such a manner that the two or four holding jaws
108
,
109
are kept still at respective positions where the jaws
108
,
109
first contact an EC.
It is to be understood that the present invention may be embodied with various changes, modifications, and improvements, such as those described in SUMMARY OF THE INVENTION, which may occur to a person skilled in the art, without departing from the spirit and scope of the invention defined in the appended claims.
Claims
- 1. A chuck for holding an object, comprising:at least one linear motor which includes at least one linear stator, two moving members which are movable along the linear stator, independent of each other, and at least one guide member which guides each of the two moving members along the linear stator; and two holding members which are supported by the two moving members, respectively, and which cooperate with each other to hold the object.
- 2. A chuck according to claim 1, further comprising a rotating device which rotates the linear motor about an axis line perpendicular to a lengthwise direction of the linear stator.
- 3. A chuck according to claim 1, wherein each of the two moving members comprises an attaching member to which a corresponding one of the two holding members is detachably attached.
- 4. A chuck according to claim 1, further comprising two position sensors each of which detects a current position of a corresponding one of the two moving members and produces a detection signal indicating the detected current position of said one moving member.
- 5. A chuck according to claim 1, further comprising two origin sensors each of which detects a corresponding one of the two moving members which is currently positioned at an origin position thereof.
- 6. A chuck according to claim 4, further comprising a control device including a symmetric-movement control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members symmetrically with respect to a centerline of the chuck.
- 7. A chuck according to claim 4, further comprising a control device including an asymmetric-movement control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members asymmetrically with respect to a centerline of the chuck.
- 8. A chuck according to claim 4, further comprising a control device including an object-dependent control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members to respective opened positions where the two holding members supported by the two moving members are distant from each other by a distance greater than a prescribed dimension of the object by a predetermined distance and then move the two moving members toward each other at respective speeds equal to each other.
- 9. A chuck according to claim 6, further comprising a control device including an object-dependent control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members to respective opened positions where the two holding members supported by the two moving members are distant from each other by a distance greater than a prescribed dimension of the object by a predetermined distance and then move the two moving members toward each other at respective speeds equal to each other.
- 10. A chuck according to claim 7, further comprising a control device including an object-dependent control portion which controls, based on the respective detection signals produced by the two position sensors, the linear motor to move the two moving members to respective opened positions where the two holding members supported by the two moving members are distant from each other by a distance greater than a prescribed dimension of the object by a predetermined distance and then move the two moving members toward each other at respective speeds equal to each other.
- 11. A chuck according to claim 1, further comprising a control device including a holding-force control portion which controls a holding force with which the two holding members hold the object.
- 12. A chuck according to claim 1, comprising two said linear motors one of which includes two first moving members that are movable toward, and away from, each other in a first direction and the other of which includes two second moving members that are movable toward, and away from, each other in a second direction perpendicular to the first direction, wherein the first and second moving members cooperate with each other to hold the object in the first and second directions.
- 13. A system for mounting at least one electric component on a circuit substrate, comprising:a chuck according to claim 1; a chuck moving device which moves the chuck to an arbitrary position in a movement area parallel to a substantially horizontal plane; a supplying device which is provided in the movement area and which supplies the electric component to the chuck; and a supporting device which is provided in the movement area and which supports the circuit substrate on which the electric component is to be mounted by the chuck.
- 14. A system according to claim 13, further comprising a chuck elevating and lowering device which elevates and lowers the chuck in respective directions perpendicular to the substantially horizontal plane.
- 15. A system according to claim 13, further comprising:an image taking device which takes an image of the electric component held by the chuck; and a modifying device which determines, based on image data representing the image taken by the image taking device, at least one positional error of the electric component held by the chuck and modifies, based on the determined positional error, at least one movement amount of the chuck moving device so as to move the chuck to a position where the positional error of the electric component is zero relative to the circuit substrate supported by the supporting device.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-004637 |
Jan 2000 |
JP |
|
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
4817930 |
Van Deuren |
Apr 1989 |
A |
6241230 |
Kawaguchi |
Jun 2001 |
B1 |
6354580 |
Nagai et al. |
Mar 2002 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
6-93559 |
Nov 1994 |
JP |