Multi-shaft linear motor and component transfer apparatus

A multi-shaft linear motor formed by a plurality of single-shaft linear motors is disclosed. Each of the single-shaft linear motors is provided with a magnetic body and an armature. Each of the single-shaft linear motors includes a base plate. The base plate has a base surface defining the moving direction, wherein the stator is fixed onto the base surface along the moving direction, and the mover is attached onto the base surface in a movable manner reciprocating along the moving direction and in opposed relation to the stator. The single-shaft linear motors are stacked in a stacking direction perpendicular to the base surface in such a way that the single-shaft linear motors are individually detachable as a unit, the base plate thereof contains the stator and the mover.

TECHNICAL FIELD

The present invention relates to a multi-shaft linear motor and a component transfer apparatus, and more particularly, to a multi-shaft linear motor formed by assembling a plurality of single-shaft linear motors each adapted to linearly move a movable section, and a component transfer apparatus using the multi-shaft linear motor.

BACKGROUND ART

A driving mechanism designed to drive in an upward-downward direction a suction nozzle for suction-holding a component is provided in, for example, component transfer apparatuses for handling components such as an electronic component, or manufacturing apparatuses for manufacturing a semiconductor device, a liquid-crystal display device, and others. A linear motor is employed as an element of such the driving mechanism. Demands for this type of linear motor have been increasing year by year. Particularly, there has been a growing need for a high-performance linear motor. To meet such a need, a linear motor, which is suitable for a component transfer apparatus, for example, has been proposed (see, for example, the following Patent Document 1).

Generally, a conventional linear motor has a cuboid housing with a wall thickness sufficient for mechanical strength. The housing contains a plurality of annular-shaped coils each having a hollow hole. These coils are arranged such that central axes of the hollow holes thereof align along a longitudinal direction of the housing to form a stator as a whole. Also, through-holes are formed in each of upper and lower walls of the housing to have a size slightly greater than that a diameter of a driving shaft so as to movably receive the driving shaft. Aligned coils as a stator are fixed to position hollow holes thereof to be concentric to each of the through-holes. The driving shaft as a mover, which is composed of a permanent magnet, is inserted into the through-holes and the hollow holes of the aligned coils to penetrate through the aligned coils concentrically.Patent Document 1: JP 2006-180645A (FIGS. 5 and 8)

DISCLOSURE OF THE INVENTION

To obtain a high-performance, linear motor is required to adjust relative position (alignment) between a driving shaft (mover) and a coil (stator) with a high degree of accuracy. It is also required to improve not only ease of assemble but also maintenance serviceability.

However, the conventional technique described in the above prior art document requires an operation of adjusting positions of a large number of coils relative to a common housing, in advance of position adjustment between a driving shaft and aligned coils. Specifically, it is necessary to form a plurality pairs of upper and lower through-holes in upper and lower wall members of a housing with a high-degree of positional accuracy. Also, an aligned coils inside the housing should be arranged in such a manner that relative positions between each coil and a corresponding one of the upper and lower through-holes pair of the housing are maintained with a high-degree of positional accuracy so that the aligned coils are aligned with the corresponding pair of the upper and lower through-holes in an upward-downward direction. Furthermore, it is necessary to insert the driving shafts into the respective upper and lower through-holes pair and the hollow hole of the aligned coils, while maintaining the positioning of the driving shaft relative to the housing. As stated above, the conventional technique requires an assembling operation of the aligned coils and the driving shafts into the linear motor while maintaining the positioning of them relative to the common housing. Such an assembling operation of the driving shafts maintaining relative positioning accuracy is anything but easy, and thereby it is difficult to produce a high-performance multi-shaft linear motor.

It is a primary object of the present invention to provide a high-performance linear motor which is excellent in ease of assemble and maintenance serviceability.

It is another object of the present invention to provide a component transfer apparatus using the above linear motor.

In order to solve above problem, according to one aspect of the present invention, there is provided a multi-shaft linear motor which comprises a plurality of single-shaft linear motors each provided with a magnetic body and an armature, and the single-shaft linear motor is adapted to produce a force which causes the magnetic body and the armature to be relatively displaced along a given linear moving direction by interaction of magnetic fluxes generated between the magnetic body and the armature during an operation of supplying electric power to the armature. The single-shaft linear motor includes: a stator formed as one of the magnetic body and the armature; a mover formed as the other of the magnetic body and the armature and adapted to be movable relative to the stator; and a base plate having a base surface defining the moving direction. The stator is fixed onto the base surface along the moving direction, and the mover is attached onto the base surface in a movable manner reciprocating along the moving direction and in opposed relation to the stator. Also, the single-shaft linear motors are stacked in a stacking direction perpendicular to the base surface in such a way that the single-shaft linear motors are individually detachable as a unit. Each the base plate of the units contains the stator and the mover.

In this aspect, each of the single-shaft linear motors in which the stator and the mover formed as one and the other of the magnetic body and the armature are provided on the base plate can be handled as a separate unit, so that it is not necessary to disassemble the stator and the mover during assembling or maintenance of the multi-shaft linear motor. Thus, it becomes possible to guarantee relative positioning accuracy of each of the movable sections of the multi-shaft linear motor based on assembling accuracy of each of the single-shaft linear motors.

Also, in the present invention, the multi-shaft linear motor is formed by arranging the plurality of single-shaft linear motors in a stacking manner. Thus, the number of the movable sections in the multi-shaft linear motor can be easily changed by changing the number of the single-shaft linear motors to be stacked, so that the multi-shaft linear motor is excellent in versatility. In addition, a maintenance operation, such as inspection or repair, can be performed with respect to each of the single-shaft linear motors constituting the multi-shaft linear motor, so that the multi-shaft linear motor is also excellent in terms of maintenance serviceability.

According to another aspect of the present invention, there is provided a component transfer apparatus having the above the multi-shaft linear motor as an upward/downward driving mechanism.

These and other features and advantages of the present invention will become more apparent from embodiments thereof which will be described with reference to the accompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the drawings, the best mode for carrying out the present invention will now be specifically described.

The present invention relates to a multi-shaft linear motor MLM formed by assembling a plurality of single-shaft linear motors LM each adapted to linearly move a movable section with respect to a base plate, and a component transfer apparatus using the multi-shaft linear motor MLM. In the following description, after describing a single-shaft linear motor LM suited to constitute a multi-shaft linear motor MLM according to the present invention, it will be separately described in detail with respect to a multi-shaft linear motor MLM according to the present invention and a surface mounter MT which is one example of a component transfer apparatus using the multi-shaft linear motor MLM. To clarify a directional relationship in each of the following illustrative figures, XYZ rectangular coordinate axes on the basis of a linear motor LM and MLM are shown therein. Among the three directions X, Y, and Z, a moving direction to be set for the linear motor LM and MLM, a widthwise direction of the linear motor LM and MLM, and a frontward-rearward direction of the linear motor LM and MLM, are indicated by Z, Y, and X, respectively. Also, the signs (+, −) in each of the rectangular coordinate axes designate a frontward side (+X side), a rearward side (−X side), one edge side (−Y side), the other edge side (+Y side), a forward side (−Z side) and a backward side (+Z side), in the directions X, Y, AND Z, for descriptive purposes.

<Single-Shaft Linear Motor Preferable for Multi-Shaft Linear Motor>

Referring toFIGS. 1 to 5, this single-shaft linear motor LM has a thin tray-shaped base plate1. The base plate1is designed such that a longitudinal direction thereof defines a given moving direction Z. As shown inFIG. 5, an inner bottom surface of the base plate1is formed as a base surface1a, and three standing walls1bto1deach standing toward the frontward side (+X side) are continuously provided along two edges of the base plate1on respective opposite sides (+Y and −Y sides) in the widthwise direction Y and one edge of the base plate1on the backward side (+Z side) in the moving direction Z, wherein the standing walls1bto1dand the base surface1amake up a bottomed recess portion1eopened toward the frontward side (+X side). The recess portion1eis one example of a containing space for containing therein elements of the single-shaft linear motor LM in an after-mentioned manner. Numeral1hinFIGS. 1 and 2designates a spring engagement portion for allowing one of opposite ends of a return spring15(seeFIG. 20) for biasing a movable base4toward the backward side (+Z side) to be attached thereto, as described later. In this mode of implementation, the base surface1aand the standing walls1bto1dare integrally molded using an aluminum alloy or the like to form the base plate1as a non-magnetic member. Alternatively, the base plate1may be formed by producing the base surface1aand the standing walls1bto1dseparately and then assembling these components together. Although the base plate1is made of such a non-magnetic material, it is understood that the base plate1may be made of a resin material.

As mentioned above, in the single-shaft linear motor LM, the frontward-rearward direction X corresponds to a direction perpendicular to the base surface1a. A space or the recess portion1e, which are surrounded by standing walls1bto1dextending along the frontward direction and the base surface1a, corresponds to a “containing space” in the appended claims. In this mode of implementation, a forward-side (−Z side) of the base plate1in the moving direction Z is open so that the standing walls1bto1ddefine an open zone1jcommunicating between the internal space (containing space) of the recess portion1eand an outside of the internal space. In this mode of implementation, the formation of the open zone1jallows an after-mentioned movable base4and an after-mentioned block member164to be partly moved in and out of the internal space of the recess portion1eaccording to driving of the after-mentioned movable base in the moving direction Z.

A linear guide2is provided on the base surface1ato extend along the moving direction Z. The linear guide2comprises a linear-shaped rail2afixed to the base plate1along the moving direction Z, and two sliders2b1and2b2each attached to the rail2aslidably only in the moving direction Z. Also, in order to prevent the sliders2b1and2b2from leaving the rail2a, two linear guide stoppers2c1and2c2are attached to the base surface1aof the base plate1at positions opposed to respective opposite longitudinal ends of the linear guide2.

A movable base4is attached to the sliders2b1and2b2to extend along the moving direction Z. The movable base4has an internal space having a reverse U shape in transverse section (section taken along an X-Y plane). The movable base4is fixed to the sliders2b1and2b2so that a ceiling surface of the internal space seat on respective upper surfaces of the sliders2b1and2b2. In this single-shaft linear motor LM, a plurality of through-holes4aare formed in the ceiling surface of the movable base4to facilitate a reduction in weight of the movable base4. As mentioned above, in the single-shaft linear motor LM, the movable base4and the sliders2b1and2b2are adapted to be integrally movable in the moving direction Z, to serve as a component equivalent to a “movable section” in the appended claims. As described later, the movable base4is provided with a mover which is attached to a lateral surface of an end of the movable base4on the one edge side (−Y side) in the widthwise direction Y, and a linear scale7bwhich is attached to a lateral surface of an end of the movable base4on the other edge side (+Y side) in the widthwise direction Y.

Referring next toFIGS. 6 to 8, a yoke5made of a ferromagnetic material is attached to a lateral surface of the movable base4on the one edge side (−Y side) in the widthwise direction Y. A permanent magnet array6is attached to a surface of the yoke5in a line, in such a manner that a permanent magnet of which an N-pole is opposed to the surface and a permanent magnet of which an S-pole is opposed to the surface are alternately arranged along the moving direction Z (in the single-shaft linear motor LM, total fourteen permanent magnets). A mover10of the single-shaft linear motor LM is made up of the permanent magnet array6and the yoke5. In the single-shaft linear motor LM, the permanent magnet array6is molded within a resin layer constituting an outer shell of the mover10, to protect a surface thereof, which makes it possible to effectively prevent damage or the like of the permanent magnet array6. The resin layer covers the permanent magnet array6, leaving a space on the forward side (−Z side) in the moving direction Z with respect to the mover10, so that a portion of the lateral surface of the movable base4on the forward side with respect to the mover10is exposed.

Two female screw portions4bare formed in the exposed region of the movable base4along the moving direction Z. The female screw portions4bare one example of coupling means for attaching a driven object to an end of the movable base4on the one edge side directly or through a coupling unit164(seeFIG. 20). For example, in an after-mentioned surface mounter, the coupling unit164(seeFIG. 20) is coupled to the movable base4using the female screw portions4b, and then a nozzle shaft as a driven object is connected to the coupling unit164. Namely, a driven object can be attached to the movable base4through the coupling unit164coupled to the end of the movable base4using the female screw portions4b. This point will be more specifically described in the following “SURFACE MOUNTER” Section.

Referring next toFIG. 2, an armature3as one example of a “stator” in the appended claims is, disposed on the one edge side in the widthwise direction Y with respect to the mover10made up of the yoke5and the permanent magnet array6as described above, and fixed to the base surface1aof the base plate1. The armature3comprises a core3a, a plurality of hollow-shaped bobbins3b, and a plurality of coils3ceach of which is formed by winding an electric wire around respective outer peripheries of the bobbins3b. The core3ais formed by stacking, in a frontward-rearward direction X, a plurality of comb-shaped silicon steel plates (unit plates) each having a longitudinal direction extending on a Y-Z plane and along the moving direction Z. The pile of silicon steel plate forms teeth on the other edge side (+Y side) in the widthwise direction Y, at regular intervals along the moving direction Z. In the core3adesigned in this manner, the teeth are arranged side by side in a line at regular intervals in the moving direction Z to form a tooth array. Then, the bobbins3beach pre-wound with the coil3care mounted to respective ones of the teeth. In this manner, an array of a plurality of (in the single-shaft linear motor LM, nine) teeth of the core3aand a plurality of coils3cwound around the tooth array are provided at the same intervals along the moving direction Z to form the armature3, which is disposed opposed to the mover10. In the single-shaft linear motor LM, as shown inFIG. 3, the armature3is formed such that each of a distal end surface8(surface on the +Y side) of the teeth of the core3awound with the coils3c, and a counter surface8′ of the permanent magnet array6of the mover10opposed to the distal end surface8, becomes parallel to an X-Z plane including the frontward-rearward direction X and the moving direction Z. When a current is applied to respective ones of the coils3cin a given sequence from a motor controller whose illustration is omitted, a propulsion force in the moving direction Z is generated in the mover10by interaction between the magnetic pole of the distal end surface8and the magnetic pole of the counter surface8′ arranged as described above, so that the movable base4is driven in the moving direction Z.

In the single-shaft linear motor LM, the permanent magnet array6is used in the mover10, and the core3amade of a magnetic material is used in the armature3serving as the stator. Thus, a cogging force is generated between the tooth array of the core3aand the permanent magnet array6of the mover10. As is well known, the “generation of a cogging force” is a phenomenon that a magnetic flux density of the permanent magnet array6is changed depending on a position of the teeth of the core3a, and thereby magnetic energy is changed to cause a pulsation of an electromagnetic force acting on the armature3. Therefore, in order to reduce a cogging force, two sub-teeth9aand9beach made of a magnetic material are provided at respective opposite ends of the tooth array of the armature3, as shown inFIG. 9. Specifically, the sub-tooth9aand the sub-tooth9bare detachably provided on the base surface1aof the base plate1, respectively, at a desired position identical to or different from a tooth array pitch, in a backward-side (+Z-side) portion of the tooth array, and a desired position identical to or different from the tooth array pitch, in a forward-side (−Z-side) portion of the tooth array, in such a manner that a distance from the permanent magnet array6becomes a desired value.

In the single-shaft linear motor LM designed as described above, a region of the base plate connected to the core3aextends to a vicinity of the sub-teeth9aand9b, so that a magnetic coupling between the core3aof the armature3and each of the sub-teeth9aand9boccurs to cause unevenness in magnetic flux density distribution. Thus, it is likely that a stable cogging-force reducing function cannot be obtained simply by arranging the sub-teeth9aand9bat given positions. In particular, during acceleration, deceleration, or the like, or in a situation where an operating condition (a constant movement speed after acceleration) itself changes, an amount of current flowing through the coils3cis likely to change and deviate from an assumed value to cause difficulty in desirably forming a magnetic pole of a counter surface of the sub-teeth9aand9bopposed to the permanent magnet array6or an intensity of the magnet pole, so that a cogging-force reducing effect based on the sub-teeth9aand9bis not always obtained. Therefore, in this mode of implementation, a magnetic plate11is provided between the base plate1and each of the sub-teeth9aand9bto supplement the cogging-force reducing effect based on the sub-teeth9aand9b. More specifically, the single-shaft linear motor is designed as follows.

Referring toFIGS. 5 and 9, a plate-fitting portion1gis formed on the base surface1aof the base plate1to have a shape approximately equal to a planar shape of the magnetic plate11(seeFIG. 5). The plate-fitting portion1gis formed in a position where the magnetic plate11is disposed opposed to both the mover10and the armature3in the frontward-rearward direction X. Also, as shown inFIG. 2, when the magnetic plate11is fitted in the plate-fitting portion1g, a front surface of the magnetic plate11is flush with the base surface1a. Based on providing the magnet plate11, it becomes possible to generate a magnet flux passing through the sub-tooth9a, one permanent magnet in the permanent magnet array6, the yoke5and the magnetic plate11, and reaching the sub-tooth9a, on the X-Y plane, in addition to a magnetic flux passing through the core3a, the sub-tooth9a, one permanent magnet in the permanent magnet array6, the yoke5, an adjacent permanent magnet in the permanent magnet array6, and an adjacent one of the teeth and reaching the core3a, on the Y-Z plane, so as to effectively reduce the cogging force.

As mentioned above, the movable base4is driven in the moving direction Z by interaction of magnetic fluxes generated between the mover10and the armature3. In this connection, two movement restriction stoppers12aand12bare detachably fixed to the base surface1aof the base plate1to prevent the movable base4from being moved beyond a given moving range.

To detect accurately a position of the movable base4, a detector unit7having a sensor7aand a linear scale7bto serve as detection means is provided on a side opposite to the armature (i.e., on the +Y side) with respect to the movable base4.

Referring toFIGS. 2 and 5, the sensor7aof the detector unit7is integrally assembled to a sensor control unit7c. This assembly (the sensor7a+the sensor control unit7c) is adapted to be detachable relative to the recess portion1ethrough a cutout1fformed in the standing wall1b, as shown inFIG. 5. In an operation of mounting the assembly, the assembly is fixed to the base plate1in such a manner as to allow the sensor7ato face inside the recess portion1eof the base plate1and allow the sensor control unit7cto be disposed on a side opposite to the linear scale, i.e., on the other edge side (+Y side) in the widthwise direction Y, with respect to the sensor7a.

The linear scale7bon the other hand is provided on a lateral surface of the movable base4on the other edge side (+Y side) to extend along the moving direction Z. The sensor7ais disposed opposed to the linear scale7bin the widthwise direction Y during the operation of mounting the assembly (the sensor7a+the sensor control unit7c). Particularly, in this mode of implementation, respective mounting positions of the sensor7aand the linear scale7bare set such that each of a surface7eof the linear scale7band a sensing surface7e′ of the sensor7aopposed to the surface7ebecomes parallel to the X-Z plane including the frontward-rearward direction X and the moving direction Z, as shown inFIG. 4. This makes it possible to allow a region of the linear scale7bopposed to the sensor7ato be displaced in response to a displacement of the movable base4along the moving direction Z, and to accurately detect a position of the movable base4in the moving direction Z based on the displacement of the region of the linear scale7b.

Also, in order to prevent foreign substances, such as dust or foreign particles, from getting into the sensor control unit7c, a sensor cover7d(seeFIG. 2) is attached to the standing wall1bof the base plate1after the mounting of the assembly to cover the sensor control unit7c.

In the single-shaft linear motor LM, the linear scale7bis attached to the movable base4, and the sensor7ais disposed on the base plate1. Alternatively, the sensor7aand the linear scale7bmay be arranged in the reverse relation. Also, the detector unit7may be designed such that one of the components (the sensor7aand the linear scale7b) thereof is attached to the sliders2b1and2b2, instead of attaching it to the movable base4. A detection scheme of the detector unit7may be a magnetic scheme using magnetism, or an optical scheme.

In order to constitute a multi-shaft linear motor MLM by positioning and connecting a plurality of the single-shaft linear motors LM with each other, the single-shaft linear motor LM has following structures. That is, the base plate1is formed with a set of two through-holes21(seeFIG. 5) which open in the frontward-rearward direction X. A positioning pin20is fixed to each of the two through-holes21leaving some space on a bottom side of the through-hole21. The positioning pin20is fixed to allow a frontward side (+X side) portion to protrude from the through-hole21, so that, in an assembling operation of two single-shaft linear motors LM1and LM2, each of the positioning pins20of the single-shaft linear motor LM1on a bottom side thereof is fitted into a corresponding one of the through-holes21of the single-shaft linear motor LM2on a top side thereof to establish positioning. Thus, in this mode of implementation, the “positioning pins20” and the “through-holes21” serve as a “bottom-side engagement section” and a “top-side engagement section” in the appended claims, respectively. It is understood that the positioning pin20may also be fixed to the through-hole21in each of the single-shaft linear motors LM leaving some space on a top side of the through-hole21, so as to allow a portion of the positioning pin21on the rearward side (−X side in the frontward-rearward direction X) to protrude from the through-hole21. As shown inFIGS. 1 to 5, three through-holes1pto1rare formed in the base plate1of the single-shaft linear motor LM to be penetrated therethrough in the frontward-rearward direction X. Specifically, two1p,1qof the three through-holes are formed in the standing wall1bat positions across the armature3in the moving direction Z, and the remaining through-hole1ris formed in the standing wall1bon the other edge side (+Y side) in the widthwise direction Y. The three through-holes1pto1rformed in this manner are located at positions across the mover10as shown inFIG. 1, and arranged in a generally isosceles triangle shape when viewed from the frontward side.

FIG. 10andFIG. 11are, respectively, a perspective view and a sectional view showing a multi-shaft linear motor according to a first embodiment of the present invention. In the first embodiment, a multi-shaft linear motor MLM is formed by preparing two single-shaft linear motors LM1and LM2, each having the same structure as that of the afore-mentioned single-shaft linear motor LM. These single-shaft linear motors LM1and LM2are stacked in such a manner that tops (front surfaces) of the standing walls1bto1dof one single-shaft linear motor LM1are piled with a rear surface of the base plate1of the single-shaft linear motor LM2along the frontward-rearward direction X. More specifically, the base plate1of each of the single-shaft linear motors LM1and LM2are formed with the three through-holes1pto1reach one of a pair of through-holes opposed in the frontward-rearward direction X. A bolt13pis inserted from the frontward side (+X side) of the single-shaft linear motor LM2to penetrate through the through-holes1pof the single-shaft linear motors LM1and LM2, and a nut14pis screwed on a distal end of the bolt13pfrom the rearward side (−X side) of the single-shaft linear motor LM1. In the same manner as that for the through-holes1p, two bolts13and13rare inserted into the through-holes1qand1r, respectively, and a nut14qis screwed on each of the bolts13and13r. In this manner, the single-shaft linear motors LM1and LM2are fixedly fastened at three positions and integrated together to form a two-shaft linear motor MLM. Thus, the bolts13pto13rand the nuts14pto14qserve as a “fastener member” in the appended claims.

As mentioned above, in the first embodiment, the multi-shaft linear motor MLM is formed by stacking the two single-shaft linear motors LM1and LM2. The two movable bases4in the multi-shaft linear motor MLM are positioned in a relative positional relationship which corresponds to a stacked arrangement of the single-shaft linear motors LM1and LM2. In the first embodiment, each of the single-shaft linear motors LM1and LM2has the same structure (FIG. 1), and the multi-shaft linear motor MLM has a stacked structure where the two base plates1of the single-shaft linear motors LM1and LM2are directly stacked each other, so that a pitch PT between the movable bases4in a stacking direction (frontward-rearward direction X) becomes equal to a depth dimension of each of the single-shaft linear motors LM1and LM2. In this way, the stacked arrangement of the single-shaft linear motors LM1and LM2enables the movable bases4to be arranged with excellent relative positional accuracy in the stacking direction (frontward-rearward direction X), and to be driven independently. Also, the positioning of the single-shaft linear motors LM1and LM2are secured, at the boundary between the single-shaft linear motors LM1and LM2which are located adjacent to each other in the stacking direction (frontward-rearward direction X), by engaging the positioning pins (bottom-side engagement section)20provided in the bottom-side single-shaft linear motor LM1located on a bottom side in the stacking direction (frontward-rearward direction X) (a lower side inFIG. 11) with the corresponding through-holes (top-side engagement section)21provided in the top-side single-shaft linear motor LM2located on a top side in the stacking direction (frontward-rearward direction X) (an upper side inFIG. 11). This makes it possible to further enhance the relative positional accuracy.

Also, the multi-shaft linear motor MLM is formed by stacking the single-shaft linear motors LM1and LM2each having the same structure as that of the single-shaft linear motor LM illustrated inFIG. 1, so that the pitch PT can be shortened. Specifically, in the single-shaft linear motor LM (LM1and LM2) illustrated inFIG. 1, the coils3cof the armature3, which forms the stator, and the mover10are disposed side by side in the widthwise direction Y. Thus, as compared with a structure where an armature, a permanent magnet array, a yoke, and a movable base are arranged in the stacking direction (frontward-rearward direction X) with respect to the base plate1, a thickness of the linear motor LM can be reduced, and thereby the pitch PT can be shortened.

In the single-shaft linear motor LM (LM1and LM2), an attachment position of the mover10to the movable base4is the lateral surface of movable base4on the one edge side (−Y side) in the widthwise direction Y, and the armature3is provided in opposed relation to the mover10attached to the lateral surface. Thus, as compared with a structure where a mover is disposed on an upper surface of the movable base4, the thickness of the linear motor LM can be further reduced, and thereby the pitch PT can be further shortened.

Also, as shown inFIG. 11, the tops of the standing walls of the bottom-side single-shaft linear motor LM1located on the bottom side in the stacking direction is in contact with the rear surface1kof the base plate1of the top-side single-shaft linear motor LM2located on the top side of and adjacent to the bottom-side single-shaft linear motor LM1, so that the containing space (internal space of the recess portion1e) of the bottom-side single-shaft linear motor LM1is covered by the surface1kof the base plate1of the top-side single-shaft linear motor LM2on the side opposite to the base surface. Thus, the base plate1of the top-side single-shaft linear motor LM2serves as a cover member for the bottom-side single-shaft linear motor LM1. This enables not only to effectively prevent foreign substances from getting in, but also to shorten the thickness of the single-shaft linear motor in the stacking direction (frontward-rearward direction X) to be suppressed, which results in further shortening the pitch PT between the single-shaft linear motors LM1and LM2.

While the two single-shaft linear motors LM1and LM2are stacked to form the two-shaft linear motor MLM in the first embodiment, the multi-shaft linear motor may consist of three or more single-shaft linear motors (ten-shaft linear motor is used in an after-mentioned surface mounter). In fact, the number of single-shaft linear motors to be stacked can be variously set to readily change the number of the movable bases4. Thus, the first embodiment is excellent in versatility. Also, each of the single-shaft linear motors LM1and LM2(the base plate1) can be handled as a separate unit, so that it is not necessary to disassemble the stator and the mover in assembling or maintenance of the multi-shaft linear motor MLM. Thus, in a maintenance operation, such as inspection or repair, which is performed with respect to each of the single-shaft linear motors LM1and LM2constituting the multi-shaft linear motor MLM, a target one of the single-shaft linear motors can be selectively taken out from the multi-shaft linear motor MLM to perform inspection, repair or the like. Thus, the first embodiment is also excellent in terms of maintenance serviceability.

Also, because of the common bolts13pto13r, which are inserted into the corresponding through-holes1pto1rin the respective single-shaft linear motors LM1and LM2to fasten these motors, the operations for fastening the linear motors can be efficient. Furthermore, the number of fastening members can be reduced as compare with a case where single-shaft linear motors are individually connected one by one. This facilitates a reduction in production cost of the multi-shaft linear motor MLM.

The multi-shaft linear motor MLM, which is formed by using the single-shaft linear motors LM1and LM2which are the same structure as that of the single-shaft linear motor LM illustrated inFIG. 1, also has the following advantages. In the single-shaft linear motor LM, each of the standing walls1band1cextends from a respective one of the opposite edges of the base plate1in the widthwise direction Y toward the frontward side with respect to the base surface1a, as shown inFIG. 5. The recess portion1e, which is surrounded by the standing walls1band1cand the base surface1a, defines the containing space opened toward the frontward side with respect to the base surface1a. Accordingly, because the opening of the base plate1defined in this manner has broadening in the moving direction Z and the widthwise direction Y, an operator can access the recess portion1e(containing space) from the frontward side through the opening. This also facilitates visual check during assembling to allow an operator to readily check a positional relationship between the stator and the mover. Therefore, as is clear fromFIG. 5, any elements of the linear motor LM can be readily inserted into the recess portion1ethrough the opening. Thus, in the first embodiment, a production/assembling operation of the linear motor LM can be facilitated. Similarly, in an operation, such as maintenance or repair, for the single-shaft linear motor, the movable section and the mover can be dealt as a single unit to be disassembled from or re-assembled to the linear motor, making it possible to reduce time and effort for the disassembling and re-assembling.

In the embodiment, the plurality of standing walls1bto1dincluding the standing walls1band1care integrally formed with the base plate1, so that the rigidity of the base plate1is improved. Also, all of the movable section (sliders2b1and2b2), the stator (armature3) and the mover10are set up in the internal space (containing space) of the recess portion1e. Based on employing these structures, the strength of the single-shaft linear motor LM is improved. In addition to the advantage in terms of strength, the formation of the standing walls1bto1dalso contributes to effectively preventing foreign substances outside the motor from getting in.

A standing wall may be formed on the entire peripheral edge of the base plate1. However, in this case, design factors, such as sizes of the linear guide2and the movable base4in the moving direction; a moving range of the movable section; or the like will be significantly restricted by the presence of two walls located on the forward and backward sides in the moving direction Z in opposed relation. Moreover, a position for coupling a driven object to the movable base4will be limited to the frontward side. In contract, in the single-shaft linear motor LM, the open zone1jis defined at the forward-side (−Z side) end of the base plate1, so that the internal space (containing space) of the recess portion1eis opened through the open zone1j. Based on providing the open zone1jin this manner, a driven object (such as an after-mentioned nozzle shaft) coupled by the forward-side (−Z side) end or the female screw portions4bcan be moved to get in and out of the internal space of the recess portion1eaccording to driving of the movable base4in the moving direction Z. This makes it possible to expand the moving range of not only the movable base4provided in the single-shaft linear motor but also each of the movable bases4provided in the multi-shaft linear motor MLM (and the driven object coupled to the movable base4), to obtain a single-shaft linear motor LM having high versatility.

The multi-shaft linear motor of the present invention is not limited to the above embodiment, but various changes and modifications other than those described above may be made therein without departing from the spirits and scope of the invention. For example, although each of the single-shaft linear motors constituting the multi-shaft linear motor MLM according to the first embodiment has the same structure, a different type of single-shaft linear motor may be combined therewith.

In the multi-shaft linear motor MLM according to the first embodiment, the pitch PT between the movable bases4in the stacking direction is automatically determined in unique by the size of the single-shaft linear motors LM1and LM2in the frontward-rearward direction. Alternatively, as shown in a second embodiment illustrated inFIGS. 12 and 13, a pitch adjustment plate SC may be interposed at a boundary position where the single-shaft linear motors LM1and LM2are located adjacent to each other in the stacking direction (frontward-rearward direction X). Because of the interposition of the pitch adjustment plate SC, the pitch PT between the single-shaft linear motors LM1and LM2is increased by a thickness of the pitch adjustment plate SC. A distance between the single-shaft linear motors LM1and LM2in the stacking direction (frontward-rearward direction X) can be adjusted by interposing the pitch adjustment plate SC therebetween, so that the pitch PT between the movable bases4in the stacking direction (frontward-rearward direction X) can be adjusted easily and with a high degree of accuracy. If the multi-shaft linear motor MLM contains three or more single-shaft linear motors, the number of the boundaries where two of the single-shaft linear motors are located adjacent to each other in the stacking direction (frontward-rearward direction X) will be increased up to two or more. In such a multi-shaft linear motor MLM having the plurality of boundary positions, the pitch adjustment plate SC may be inserted into each of the boundary positions or may be inserted into a part of the boundary positions, depending on design of the multi-shaft linear motor MLM.

In the multi-shaft linear motor MLM according to the first embodiment, a plurality of the single-shaft linear motors LM illustrated inFIG. 1are assembled together. Alternatively, each of the single-shaft linear motors LM may be designed as follows. In the single-shaft linear motor LM illustrated inFIG. 1, the mover and the armature (stator)3are disposed on the only one edge side (−Y side) in the widthwise direction Y with respect to the movable base4to drive the movable base4. Alternatively, the mover and the armature (stator)3may be additionally disposed on the other edge side (+Y side) in the widthwise direction Y with respect to the movable base4. This makes it possible to further increase a propulsion force for driving the movable base4. Also, the single-shaft linear motor LM constituting the multi-shaft linear motor MLM may be designed to form a magnetic circuit in such a manner that the movable base4is made of a ferromagnetic material, and the permanent magnet array6is provided directly on the lateral surface of the movable base4on the one or other edge side in the widthwise direction Y to extend in the moving direction Z. In the single-shaft linear motor LM, the yoke5may be attached to respective lateral surfaces of the sliders2b1and2b2on the one or other edge side in the widthwise direction Y, and then the permanent magnet array6may be attached to the yoke5. In this case, the sliders2b1and2b2are equivalent to the “movable section” in the appended claims. Also, a magnetic circuit may be formed in such a manner that the sliders are made of a ferromagnetic material, and the permanent magnet array6is provided directly on respective lateral surfaces of the sliders on the one or other edge side in the widthwise direction Y to extend in the direction Z. In the single-shaft linear motor LM illustrated inFIG. 1, the mover is made up using the permanent magnet array6, and the stator is made up using the armature3. Alternatively, the multi-shaft linear motor may be formed using a single-shaft linear motor comprising a mover made up using an armature, and a stator made up using a permanent magnet array.

The sectional shape of the movable base4may be an H shape.

Also, a plurality of single-shaft linear motors each different from the single-shaft linear motor illustrated inFIG. 1, for example, a plurality of single-shaft linear motors illustrated inFIG. 14in another mode of implementation of the present invention, may be assembled together, or the single-shaft linear motor illustrated inFIG. 1and the single-shaft linear motor illustrated inFIG. 14may be assembled in combination.

Referring toFIG. 14, in the single-shaft linear motor illustrated inFIG. 14, three standing walls1bto1deach standing in the frontward-rearward direction X are provided as a member integral with or separated from a base plate1to partially extend in the moving direction Z along opposite edges of the base plate1in the widthwise direction Y. A cover member SP is attached to tops of the standing walls1bto1din spaced-apart and opposed relation to a base surface1aof the base plate1, and a space surrounding the standing walls1bto1dand the base surface1ais defined as a containing space. A movable base4is provided in the containing space movably in the moving direction Z. An armature (stator)3is provided on the base surface1aof the base plate1to extend in the moving direction Z, and a mover (a yoke5and a permanent magnet array (not shown)) is provided to extend in the moving direction Z in opposed relation to an array of coils2c(coil array) of the armature3.

FIG. 15is a top plan view showing a general structure of a surface mounter which is one example of a component transfer apparatus, according to one embodiment of the present invention.FIGS. 16 and 17are front and side views of a head unit, respectively.FIG. 18is a block diagram showing an electrical configuration of the surface mounter illustrated inFIG. 15. In these figures and subsequent illustrative figures, a three-dimensional-XYZ coordinate system is employed in which a vertical direction is defined as the Z-axis. In a state after a multi-shaft linear motor MLM is set up in the surface mounter, the directions X, Y, and Z are aligned with the X-, Y-, and Z-axes, respectively.

In this surface mounter MT, a board carrying mechanism102is installed on a base111to allow a board103to be carried in a given carrying direction. In the illustrated example, the carrying direction is along the X-axis direction. More specifically, the board carrying mechanism102comprises a pair of conveyers121,121adapted to carry the board103in a direction from a right side to a left side inFIG. 15, on the base111. These conveyers121,121are controlled by a drive control section141of a control unit104which is adapted to control the entire surface mounter MT. Specifically, the conveyers121,121are operable, in response to a drive instruction from the drive control section141, to carry in the board103and to stop the carried-in board103at a given mounting-operation position (a position of the board103indicated by the two-dot chain line inFIG. 15). The board103carried in this manner is fixedly held by a holding device whose illustration is omitted. Then, an electronic component (not shown) supplied from a component containing section105is transferred to the board103by a suction nozzle161equipped in a head unit106. After completion of a mounting operation for all of a plurality of components to be mounted on the board103, the board carrying mechanism102is operable, in response to a drive instruction from the drive control section141, to carry out the board103.

The component containing section105is disposed on opposite sides of the board carrying mechanism102. Each of the component containing sections105comprises a large number of tape feeders151. The tape feeder151is provided with a reel (not shown) wound with a tape which receives/holds therein a plurality of electronic components, and adapted to supply the electronic components. Specifically, a plurality of small-piece chip electronic components, such as integrated circuits (ICs), transistors, resistors, or capacitors are received and held in each of the tapes at given intervals. When the tape feeder151reels the tape out from the reel toward the head unit106along the Y-axis direction, the electronic components in the tape are intermittently fed out to allow the suction nozzle161of the head unit106to perform an operation of picking up the electronic component.

In this embodiment, in addition to the board carrying mechanism102, a head driving mechanism107is provided. The head driving mechanism107is designed to move the head unit106in the X-axis and Y-axis directions over a given range of the base111. An electronic component sucked by the suction nozzle161is carried from a position just above the component containing section105to a position just above the board103by the movement of the head unit106. The head driving mechanism107comprises a mounting head-support member171extending along the X-axis direction. The mounting head-support member171supports the head unit106in a movable manner in the X-axis direction. Also, the mounting head-support member171is supported by a fixed rail172extending in the Y-axis direction, at opposite ends thereof in the X-axis direction, so that it can be moved in the Y-axis direction along the fixed rail172. The head driving mechanism107further comprises an X-axis servomotor173serving as a driving source for driving the head unit106in the X-axis direction, and a Y-axis servomotor174serving as a driving source for driving the head unit106in the Y-axis direction. The servomotor173is coupled to a ball screw175, so that, when the servomotor173operates in response to an operation instruction from the drive control section141, the head unit106is driven back and force along the X-axis direction through the ball screw175. The servomotor174is coupled to a ball screw176, so that, when the servomotor174operates in response to an operation instruction from the drive control section141, the mounting head-support member171is driven back and force along the Y-axis direction through the ball screw176.

The head driving mechanism107drives the head unit106so that it carries the electronic component to the board103and transfer the electronic component to a given position while the suction nozzles161suck and hold the electronic components (a component transfer operation). More specifically, the head unit106is designed as follows. That is, ten mounting heads each extending in the vertical direction Z are arranged in a line at even intervals in the X-axis direction (the carrying direction of the board103by the board carrying mechanism102). The suction nozzle161is attached to a distal end of each of the mounting heads. Specifically, as shown inFIGS. 16 and 17, each of the mounting heads comprises a nozzle shaft163extending in the Z-axis direction. The shaft nozzle163has an air passage formed to extend in an upward direction (+Z side) along an axis thereof. The shaft nozzle163has a lower end which communicates through the suction nozzle161with the air passage. The suction nozzle163also has an upper end which is opened and connected through a coupling unit164, a connection member165, an air pipe166, and a vacuum switching valve mechanism167to a vacuum suction source and a positive pressure source.

In the head unit106, an upward/downward driving mechanism168is provided to move the nozzle shaft163up and down in the Z-axis direction. A motor controller142of the drive control section141controls the upward/downward driving mechanism168to move the nozzle shaft163up and down along the Z-axis direction to move the suction nozzle161in the Z-axis direction, thereby setting the suction nozzle161at a given position. In this embodiment, a multi-shaft linear motor MLM comprising ten single-shaft linear motors LM1to LM10assembled together is used as the upward/downward driving mechanism168. Details of this structure will be described later.

Also, a rotation servomotor169is provided to rotate the suction nozzle161around an R direction (two-way) in the X-Y plane (about the Z-axis). The rotation servomotor169is operable, based on an operation instruction from the drive control section141of the control unit104, to rotate the suction nozzle161in the R direction. Thus, the head unit106is moved to the component containing section105by the head driving mechanism107in the above manner, and then the upward/downward driving mechanism168and the rotation servomotor169are driven to bring a distal end of the suction nozzle161into contact with the electronic component supplied from the component containing section105, in an adequate posture.

Referring toFIGS. 19 and 20, the multi-shaft linear motor MLM used as the upward/downward driving mechanism168comprises ten single-shaft linear motors LM1to LM10, and two side plates SPa and SPb. Each of the single-shaft linear motors LM1to LM10is the equivalent of the single-shaft linear motor LM described in connection withFIG. 1, and the single-shaft linear motors LM1to LM10are arranged by stacking in the X-axis direction in the manner described in connection withFIGS. 10 and 11. The side plate SPb provided on a topmost side (+X side) in a stacking direction also functions as a cover covering a recess portion1e(seeFIG. 5) of the topmost single-shaft linear motor LM10.

The single-shaft linear motors LM1to LM10arranged side by side along the X-axis are sandwiched between the two side plates SPa and SPb. Three fastening through-holes are formed in each of the side plates SPa and SPb. The single-shaft linear motors LM1to LM10at given positions penetrate the through-holes in the X-axis direction. Three bolts13pto13rare inserted into respective ones the fastening through-holes from the side of the side plate SPb to penetrate therethrough in the X-axis direction, and fastened with respective ones of three nuts14pto14qscrewed thereon from the side of the side plate Spa. The side plate SPa, the single-shaft linear motors LM1to LM10, and the side plate SPb are thus integrated together to form the multi-shaft linear motor MLM. The cover member SPa is disposed, and the cover member SPb is disposed on a topmost (+X side) one LM10of the single-shaft linear motors.

As shown inFIGS. 16 and 17, the multi-shaft linear motor MLM is attached to a base frame160of the head unit106.

As mentioned above, in this embodiment, the ten single-shaft linear motors LM1to LM10are stacked. Among them, the single-shaft linear motor LM1located on the bottommost side (−X side) is equivalent to a “bottommost single-shaft linear motor” in the appended claims, and the side plate SPa located on a rear surface of the bottommost single-shaft linear motor is equivalent to a “bottom-side holding member” in the appended claims. Also, the single-shaft linear motor LM10located on the topmost side (+X side) is equivalent to a “topmost single-shaft linear motor” in the appended claims, and the side plate SPb located on a front surface of the topmost single-shaft linear motor is equivalent to a “top-side holding member” in the appended claims. Also, the base frame160of the head unit106is equivalent to a “base member” in the appended claims.

A coupling unit164is fixed to each of the movable bases4of the multi-shaft linear motor MLM to allow the nozzle shaft163to be coupled to a respective one of the movable bases4.

As shown inFIGS. 16 and 17, the coupling unit164comprises an L-shaped block member164afixed to an end of the movable base4on the forward side (−Z side) in the moving direction Z, and a shaft holder164bfixed to the block member164a. In this embodiment, each of the members164aand164bis one example of a coupling member for coupling the nozzle shaft163as a driven object and the movable base4as a main component of the movable section.

The block member164ahas integrally a vertical portion extending upwardly along the Z-axis direction, and a horizontal portion extending from a lower end of the vertical portion (the forward side (−Z side) in the moving direction Z) toward the one edge side (−Y side) in the widthwise direction Y. The vertical portion of the block member164ais fixed to the movable base4by a screw. The shaft holder164bis attached to a lower surface (−Z side) of the horizontal portion of the block member164a. Thus, the nozzle shaft163is integrally coupled to the movable base4of a corresponding one of the single-shaft linear motors LM1to LM10through the coupling unit164, in an upwardly and downwardly movable manner along the Z-axis direction.

In this embodiment, the multi-shaft linear motor MLM is used as the upward/downward driving mechanism168, and the moving direction Z of each of the movable bases4is set to be parallel to a vertical direction. Therefore, each of the movable bases4is constantly biased toward the forward side (−Z side) by gravity. For this reason, in each of the single-shaft linear motors LM1to LM10, an upper end of a return spring15is engaged with a spring engagement portion1hof the base plate1, and a lower end of the return spring15is engaged with a spring engagement portion164cprovided on the horizontal portion of the block member164a. The movable base4is thus biased toward the backward side (+Z side), i.e., upwardly, by the return spring15. Therefore, during stop of a current supply to the coils3cof each of the single-shaft linear motors LM1to LM10, the movable base4is received inside the base plate1. Consequently, each of the suction nozzles161is located at an upper position. This prevents each of the suction nozzles161or the electronic component sucked by the suction nozzle161from causing an accident of interference with the board103, the conveyer121or the like, even if, for example, the X-axis servomotor173or the Y-axis servomotor174is activated under a condition that the upward/downward driving mechanism168is nonfunctional due to stop of a current supply.

As shown inFIG. 17, the connection member165is attached to a front surface (the −Y side in the widthwise direction Y) of the shaft holder164b. One end of the air pipe166is connected to the connection member165, to allow the air sent from the vacuum switching valve mechanism167through the air pipe166to be sent to the shaft holder164b, or reversely allow the air from the shaft holder164bto be sucked toward the vacuum switching valve mechanism167through the air pipe166. As mentioned above, the vacuum switching valve mechanism167and each of the suction nozzles161are connected to each other by the following path: the air pipe166—an air path (not shown) inside the shaft holder164b—the nozzle shaft163, to allow a positive pressure to be supplied to the suction nozzle161, or to allow a negative pressure to be supplied to the suction nozzle161.

In the surface mounter having the above structure, exerting a program pre-stored in a memory (whose illustration is omitted) of the control unit104, a main control section143of the control unit104operates to control each section of the surface mounter to move the head unit106between a position just above the component containing section105and a position just above the board103in a reciprocating manner. Also, under a condition that the head unit106is stopped at the position just above the component containing section105, the upward/downward driving mechanism168and the rotation servomotor169are drive-controlled to bring the distal end of the suction nozzle161into contact with the electronic component supplied from the component containing section105, in an adequate posture, and provide a negative-pressure suction force to the suction nozzle161to allow the electronic component to be held by the suction nozzle161. Then, suction-holding the electronic component, the head unit106moves to the position just above the board103and transfers the electronic component to a given position. In this manner, the component transfer operation of transferring the electronic component from the component containing section105to a component mounting region of the board103is repeatedly performed.

As mentioned above, the surface mounter according to this embodiment is adapted to drive the nozzle shaft163up and down in the Z-axis direction using the multi-shaft linear motor MLM. The multi-shaft linear motor MLM comprises the ten single-shaft linear motors LM1to LM10, each of which has the same structure as that of the single-shaft linear motor LM illustrated inFIG. 1. Because the ten single-shaft linear motors LM1to LM10are arranged by stacking in the frontward-rearward direction X (i.e., in a direction perpendicular to the base surface1a), the following functions/effects can be obtained. The plurality of movable bases4can be arranged in the stacking direction (frontward-rearward direction X) with excellent relative positional accuracy, so that the nozzle shafts coupled to the respective movable bases4can also be arranged in the stacking direction (frontward-rearward direction X) with excellent relative positional accuracy. Then, each of the single-shaft linear motors LM1to LM10can be driven independently to accurately position each of the suction nozzles161in the upward-downward direction Z.

In the multi-shaft linear motor MLM having the above structure, the pitch PT between the movable bases4in the stacking direction is shortened, so that a pitch PT, between the nozzle shafts coupled to the respective movable bases4in the stacking direction, can be shortened to allow the suction nozzles161to hold components at a pitch PT narrower than ever before, e.g., 12 mm pitch, in the stacking direction. In cases where it is necessary to change the pitch PT in the stacking direction, a depth dimension of the single-shaft linear motor constituting the multi-shaft linear motor MLM may be changed. Alternatively, as shown inFIG. 21, a pitch adjustment plate SC may be inserted into a boundary position where two of the single-shaft linear motors LM5to LM10are located adjacent to each other, to adjust pitches PT1, PT2, - - - , between adjacent ones of the single-shaft linear motors LM5to LM10in the stacking direction. In this case, a pitch PT1between adjacent ones of the linear motors LM1to LM5and a pitch PT2between adjacent ones of the linear motors LM5to LM10can be set to become different from each other. This makes it possible to adjust the pitch in the stacking direction flexibly and with a high degree of accuracy without changing the structure of each of the single-shaft linear motors LM5to LM10.

In the upward/downward driving mechanism168(multi-shaft linear motor MLM) in this embodiment, the side plate SPa is disposed on the side of the rear surface (−X side) of the bottommost single-shaft linear motor LM1, and the side plate SPb is disposed on the side of the front surface (+X side) of the topmost single-shaft linear motor LM10. In fact, the ten single-shaft linear motors LM1to LM10are sandwiched between the side plates SPa and SPb which integrally hold the motors. In addition, the side plates SPa and SPb of the upward/downward driving mechanism168(multi-shaft linear motor MLM) formed in this manner are detachably attached to the base frame160of the head unit106. Thus, as compared with an operation of attaching the ten single-shaft linear motors LM1to LM10to the base frame160individually, an attaching operation can be facilitated. In addition, an operation of detaching the upward/downward driving mechanism168from the base frame160of the head unit106to perform a maintenance operation, such as inspection or repair of the upward/downward driving mechanism168can also be facilitated. This provides improved maintenance serviceability of the upward/downward driving mechanism.

In the above embodiment, the multi-shaft linear motor MLM formed by stacking a plurality of the single-shaft linear motors LM illustrated inFIG. 1is used as the upward/downward driving mechanism168. Alternatively, a multi-shaft linear motor formed by stacking a plurality of single-shaft linear motors different from the single-shaft linear motors LM illustrated inFIG. 1, for example a plurality of the single-shaft linear motors LM illustrated inFIG. 14, or a combination of a plurality of types of single-shaft linear motors each having a different structure, may also be used.

In the above embodiment, the present invention is applied to a surface mounter MT functioning as a component transfer apparatus. However, an apparatus suited to use the present invention is not limited thereto, but the present invention may be applied to any other suitable type of component transfer apparatus, such as an IC handler.

As described above, according to one aspect of the present invention, there is provided a multi-shaft linear motor which comprises a plurality of single-shaft linear motors each provided with a magnetic body and an armature and adapted to produce a force causing the magnetic body and the armature to be relatively displaced along a given linear moving direction by interaction of magnetic fluxes generated between the magnetic body and the armature during an operation of supplying electric power to the armature. In the multi-shaft linear motor, each of the single-shaft linear motors includes a stator formed as one of the magnetic body and the armature, a mover formed as the other of the magnetic body and the armature and adapted to be movable relative to the stator, and a base plate having a base surface defining the moving direction. The stator is fixed onto the base surface along the moving direction. The mover is attached onto the base surface in a movable manner reciprocating along the moving direction and in opposed relation to the stator. The single-shaft linear motors are stacked in a stacking direction perpendicular to the base surface in such away that the single-shaft linear motors are individually detachable as a unit, the base plate thereof contains the stator and the mover.

In a preferred embodiment, each of the single-shaft linear motors includes a movable section attached to the base plate in a relatively movable manner reciprocating along the moving direction with respect to the base plate. The movable section supports the mover in such a manner that the mover is disposed opposed to the stator in a widthwise direction perpendicular to the moving direction and the stacking direction. In this embodiment, the mover and the stator are disposed side by side in the widthwise direction, so that a thickness of each of the single-shaft linear motors can be suppressed in the stacking direction for stacking the single-shaft linear motors, i.e., a direction perpendicular to the base surface. Thus, in the multi-shaft linear motor formed by stacking the plurality of single-shaft linear motors each having the above structure, a pitch between the movable sections in the stacking direction (direction perpendicular to the base surface) can be reduced.

In a preferred embodiment, the mover is attached to a lateral surface of one end of the mover in the widthwise direction. In this embodiment, the mover of each of the single-shaft linear motors is arranged in parallel with the lateral surface of one end of the movable section in the widthwise direction, and the stator is disposed opposed to the mover at a position offset outward from the movable section. This makes it possible to further reduce the pitch between the movable sections in the stacking direction (direction perpendicular to the base surface) in the multi-shaft linear motor.

In a preferred embodiment, each of the single-shaft linear motors includes a standing wall provided on an outer peripheral edge of the base plate at a position at least along the moving direction, for defining, in cooperation with the base surface, a containing space opened to allow the stator, the mover, and the movable section to be selectively inserted thereinto and pulled out thereof in a direction perpendicular to the base surface. The containing space of a bottom-side one of the single-shaft linear motors, located on a bottom side thereof in the stacking direction, is covered by a rear surface of the base plate of a top-side one of the single-shaft linear motors located on the side of a top of the bottom-side single-shaft linear motor in adjacent relation. In this embodiment, the containing space surrounded by the standing wall and the base surface is formed to be opened in the direction perpendicular to the base surface. The opening has a broadening in the moving direction and the widthwise direction. Therefore, a person or operator can easily access the containing space through the opening with a relatively short stroke relative to the base surface. Thus, each of the movable section, the mover and the stator can be assembled and disassembled by an insertion/pull-out operation with a relatively short stroke relative to the base surface, which makes it possible to facilitate positioning of the stator and the mover during assembling to provide enhanced assembling accuracy. Also, in the same manner as that during assembly, during inspection/repair of the movable section or the like, an operator can readily access the containing space to perform a maintenance operation.

In a preferred embodiment, each of the single-shaft linear motors includes a standing wall provided on an outer peripheral edge of the base plate at a position at least along the moving direction, for defining, in cooperation with the base surface, a containing space opened to allow the stator, the mover, and the movable section to be selectively inserted thereinto and pulled out thereof in a direction perpendicular to the base surface, and a cover member attached to a top of the standing wall to close the opening in such a manner as to cover the containing space as well as the movable section, the stator, and the mover each received in the containing space. In this embodiment, the base plate of the top-side single-shaft linear motor also functions as a cover member for the bottom-side single-shaft linear motor to effectively prevent foreign substances from getting inside. Also, a structure is employed in which the base plates are directly stacked each other, so that a thickness of each of the single-shaft linear motors in the stacking direction (direction perpendicular to the base surface) can be suppressed. This makes it possible to further reduce the pitch between the movable sections in the stacking direction. Also, the rigidity of the base plate can be improved by forming the standing wall, and the strength can be increased by installing all of the movable section, the stator and the mover in the containing space. This makes it possible to increase the strength of the multi-shaft linear motor itself.

In a preferred embodiment, the multi-shaft linear motor comprises a bottom-side holding member disposed on a bottommost one of the plurality of single-shaft linear motors located on a bottommost side thereof in the stacking direction, and a top-side holding member disposed on a topmost one of the single-shaft linear motors located on a topmost side thereof in the stacking direction, wherein the plurality of single-shaft linear motors are sandwiched between the bottom-side and the top-side holding members holding the single-shaft linear motors. In this embodiment, a relative positional relationship between the single-shaft linear motors can be stably maintained.

In a preferred embodiment, the multi-shaft linear motor comprises a fastener member which penetrates through the base plates of the single-shaft linear motors, the bottom-side holding member, and the top-side holding member, along the stacking direction to fasten the single-shaft linear motors together. In this embodiment, the single-shaft linear motors are firmly integrated together by the fastener member, so that a relative positional relationship between the movable sections can be further stably maintained.

In a preferred embodiment, the multi-shaft linear motor comprises a pitch adjustment plate interposed between adjacent ones of the single-shaft linear motors to increase a pitch between the adjacent single-shaft linear motors by a given thickness in the stacking direction. In this embodiment, a distance between the single-shaft linear motors in the stacking direction is adjusted by the interposition of the pitch adjustment plate, which makes it possible to adjust a pitch between the movable sections in the stacking direction easily and with a high degree of accuracy.

In a preferred embodiment, the multi-shaft linear motor comprises top-side and bottom-side engagement sections respectively formed in paired relation on top-side and bottom-side of a stacking surface between adjacent ones of the single-shaft linear motors stacked on top each other, one of the engagement sections sticks out to fit into the other engagement section dented in the stacking direction, thereby, when the single-shaft linear motors are stacked, positioning the single-shaft linear motors adjacent to each other. In this embodiment, the top-side and bottom-side engagement sections are engaged with each other in the boundaries where the single-shaft linear motors constituting the multi-shaft linear motor are located adjacent to each other in the stacking direction, thereby positioning the single-shaft linear motors when the single-shaft linear motors are stacked on top each other. This makes it possible to allow the plurality of moving sections to be driven individually and independently while being arranged in the stacking direction with excellent relative positional accuracy.

According to another aspect of the present invention, there is provided a component transfer apparatus for transferring a component from a component containing section to a component mounting area. The component transfer apparatus comprises: a head unit including a base member, a plurality of nozzle shafts each supported movably relative to the base member in an upward-downward direction and adapted to provide a negative pressure, supplied through a negative-pressure pipe connected to a backward end thereof, to a suction nozzle attached to a forward end thereof, and an upward/downward driving mechanism adapted to drive each of the plurality of nozzle shafts in the upward-downward direction independently; and head driving means adapted to move the head unit between a position just above the component containing section and a position just above the component mounting area. The upward/downward driving mechanism is the above multi-shaft linear motor. The multi-shaft linear motor is attached to the base member in such a manner that the moving direction becomes parallel to the upward-downward direction. The plurality of single-shaft linear motors constituting the multi-shaft linear motor are associated with the plurality of nozzle shafts in a one-to-one correspondence. The movable section of each of the single-shaft linear motors is coupled to a corresponding one of the nozzle shafts.

The above component transfer apparatus uses the multi-shaft linear motor according to the present invention as the upward/downward driving mechanism, so that the plurality of moving sections can be arranged in the stacking direction with excellent relative positional accuracy, and thereby the nozzle shafts coupled to the respective movable sections can also be arranged with excellent relative positional accuracy. Then, each of the single-shaft linear motors can be driven independently to accurately position each of the nozzle shafts and the suction nozzles in the upward-downward direction.

According to yet another aspect of the present invention, there is provided a component transfer apparatus for transferring a component from a component containing section to a component mounting area. The component transfer apparatus comprises: a head unit including a base member, a plurality of nozzle shafts each supported movably relative to the base member in an upward-downward direction and adapted to provide a negative pressure, supplied through a negative-pressure pipe connected to a backward end thereof, to a suction nozzle attached to a forward end thereof, and an upward/downward driving mechanism adapted to drive each of the plurality of nozzle shafts in the upward-downward direction independently; and head driving means adapted to move the head unit between a position just above the component containing section and a position just above the component mounting area. The upward/downward driving mechanism is the multi-shaft linear motor having the bottom-side and top-side holding members. The multi-shaft linear motor is detachably attached to the base member through the bottom-side holding member and the top-side holding member, in such a manner that the moving direction becomes parallel to the upward-downward direction. The plurality of single-shaft linear motors constituting the multi-shaft linear motor are associated with the plurality of nozzle shafts in a one-to-one correspondence while being sandwiched between and integrally held by the bottom-side holding member and the top-side holding member. The movable section of each of the single-shaft linear motors is coupled to a corresponding one of the nozzle shafts.

In this aspect, an attachment of the upward/downward driving mechanism to the base member is facilitated. Also, a detachment of the upward/downward driving mechanism from the base member to perform a maintenance operation, such as inspection or repair of the upward/downward driving mechanism is also facilitated. Thus, maintenance serviceability of the upward/downward driving mechanism can be improved by employing the above structure.