JP2000159305A - Cargo transfer equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cargo transfer equipment, whose height can be made lower than that of the conventional one in the same thrust, when a plurality of linear motors are prepared in order to directly drive a plurality of movable forks of the transfer equipment by means of respective linear motors. SOLUTION: In fork equipment 1, a second fork 3 and a third fork 4 are installed in a slidable manner with respect to a fixed fork 1. The second fork 3 is provided with double stators 13, 14 forming linear motors 11a, 11b, 12a, 12b on its both sides in the sifting direction. The double stators 13, 14 are provided with poles 13a, 13b, 14a, 14b projecting in the opposite direction with common back yokes 13c, 14c therebetween. A movable element 17 having a projected part 17a and a movable element 18 having a projected part 18a are installed in the fixed fork 2, ranging their almost entire length, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load transfer device including a base portion, a plurality of movable forks that can be fed horizontally to the base portion, and a linear motor as a drive source of the movable fork. is there.

[0002]

2. Description of the Related Art A stacker crane used as a cargo handling machine in an automatic warehouse is equipped with a load transfer device. The load transfer device includes a fixed fork (base portion) and a plurality of movable forks that can be fed horizontally with respect to the fixed fork, and a load is placed on the uppermost movable fork. And each movable fork is comprised so that it may expand and contract in conjunction with the drive of a drive device. As this type of load transfer device, Japanese Patent Application Laid-Open No. 57-77199 discloses a device in which a linear motor is built in as a drive unit for moving in and out of a movable fork.

In this load transfer device, as shown in FIGS. 6 and 7, a middle fork 52 is fixed to a fixed fork 51 via a number of guide rollers 54 which roll along a guide groove 53 of the fixed fork 51. Supported and extended horizontally. With respect to the middle fork 52, an upper fork (final fork) 55 is guided by a number of guide rollers 56 provided on the middle fork 52 and is horizontally fed out. On the middle fork 52, primary sides (stators) 57, 58 of a linear motor are vertically symmetrically arranged. Each of the stators 57, 58 includes an iron core 57a, 58a, and coils 57b, 58b surrounding the iron core 57a, 58a, respectively. The upper stator 57 is for moving the upper fork 55, and the lower stator 58 is for moving the middle fork 52 itself with respect to the fixed fork 51.

The upper stator 57 and the lower stator 58 are provided with a connection for power supply or a winding direction of the coils 57b and 58b so that the thrust directions are opposite to each other. The fixed fork 51 and the upper fork 55
Is made of a derivative and works as a secondary side of a linear motor. Although this linear motor is not specified, it is assumed to be a linear induction motor.

[0005]

[Problems to be Solved by the Invention] JP-A-57-7719
In the load transfer device disclosed in Japanese Patent Publication No. 9, since the movable fork is entirely moved by a linear motor, there is less dust generation compared to a system driven by a sprocket and a chain or a pinion and a rack. Suitable for use in a clean environment. However, in this load transfer device, two linear motors are installed at the same location in two vertical stages to move two movable forks. Therefore, there is a problem that the height occupied by the linear motor increases and the height of the entire load transfer device also increases.

There are two types of linear motors: one that directly uses the magnetic attraction force of the magnetic flux generated by the primary coil for thrust, and one that uses the eddy current generated by the magnetic flux and the electromagnetic force generated by the magnetic field for the thrust. . In order to efficiently use the magnetic flux generated by the current supplied to the coil for magnetic attraction or electromagnetic force, it is important to provide a back yoke on the stator (primary side) and the mover (secondary side). Becomes Therefore, when the linear motors are installed in two layers vertically, the thickness of the back yoke is twice as large as when one linear motor is used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to drive a plurality of movable forks of a load transfer device directly with linear motors. Another object of the present invention is to provide a load transfer device capable of lowering the height of the load transfer device with the same thrust than the conventional device.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a movable fork having a base and a plurality of movable forks which can be extended horizontally with respect to the base. A double-sided stator or a double-sided movable element configured to share a back yoke with a movable fork at an intermediate stage, and the movable fork is provided adjacent to the movable fork. The movable fork is directly driven by a linear motor.

According to a second aspect of the present invention, in the first aspect of the invention, the double-sided stator is provided on a movable fork adjacent to the base portion, one at each side with respect to the center in the moving direction. ing.

According to a third aspect of the present invention, in the first aspect of the invention, the double-sided movable element is provided on a movable fork adjacent to the base portion over substantially the entire length thereof. In the invention described in claim 4, in the invention described in any one of claims 1 to 3, the maximum stroke to one side of the movable fork is equal to or more than １ ／ of the entire length of the movable fork. The stator is arranged as follows.

According to a fifth aspect of the present invention, in the third aspect of the invention, the double-sided mover is formed in a sandwich structure in which a back yoke made of an iron plate is sandwiched between aluminum plates, and a linear induction motor is used as a linear motor. It is used.

Therefore, according to the first aspect of the present invention,
Each of the plurality of movable forks is directly driven by a linear motor. Since a double-sided stator or a double-sided mover configured to share a back yoke is used for a stator or a mover that constitutes a linear motor that is arranged in a vertically overlapping state, independent linear motors are stacked. The height of the load transfer device is lower than when it is installed.

According to the second aspect of the present invention, the first aspect is provided.
In the invention described in (1), since the back yoke of the stator is shared, the height of the load transfer device is reduced accordingly. When moving the movable fork between the standby position (origin position) and the extension position on one side, the stator corresponding to the upper movable fork of the double-sided stator arranged closer to one side and the other side Is supplied to the base portion of the double-sided stator and the corresponding stator arranged on the side. Therefore, the coils of the stators on both sides constituting one double-sided stator are not energized at the same time, and even if the back yoke is shared, the magnetic flux is the same as when a dedicated back yoke is provided for each stator. Can pass through the back yoke.

According to a third aspect of the present invention, in the first aspect of the present invention, since the back yoke of the mover is shared, the height of the load transfer device is reduced accordingly. When the movable fork is moved, a current is supplied to the stator so that the magnetic flux generated from the stator disposed with the double-sided movable member interposed therebetween does not simultaneously pass through the same portion of the back yoke of the double-sided movable member.

According to a fourth aspect of the present invention, in the invention of any one of the first to third aspects, the movable fork has a maximum stroke to one side equal to or more than の of the entire length.

According to a fifth aspect of the present invention, in the third aspect of the invention, since a linear induction motor is used as the linear motor, the thrust acting on the mover is caused by an eddy current generated in the aluminum plate and an iron plate. The electromagnetic force generated by the action of the magnetic flux passing through the back yoke is used. Compared to the case where the whole is made of an aluminum plate, if the thickness is the same, the mechanical strength increases and the thrust increases.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. The fork device 1 as a load transfer device includes a fixed fork 2 as a base portion, and a plurality of second and third forks 3 and 4 as movable movable forks that can be sequentially fed to the fixed fork 2.

As shown in FIG. 2, a pair of rails 5 extending in the longitudinal direction are fixed to the bottom surface of the second fork 3, and each rail 5 is fixed to a linear guide fixed near the longitudinal center of the fixed fork 2. The fixed fork 2 is supported via a block 6 so as to be movable in the longitudinal direction. At both ends of the fixed fork 2, a pair of support rollers 7 (shown in FIG. 3) are provided. The second fork 3 is movable in the longitudinal direction with respect to the fixed fork 2 while being supported by the linear guide block 6 and the support roller 7.

Similarly, a pair of rails 8 is fixed to the bottom surface of the third fork 4, and the second fork 3 is provided with a linear guide block 9 and a support roller 3a.
The linear guide block 9 is fixed to the second fork 3 via a support block 10. The third fork 4 includes a linear guide block 9 and a support roller 3a.
, And can be moved in the longitudinal direction with respect to the second fork 3.

As shown in FIG. 1A, a second fork 3 as a movable fork at an intermediate stage has linear motors 11a, 11b, 1
Double-sided stators 13 and 14 constituting 2a and 12b are fixed. SR (Switched Relucta
nce) A linear motor is used. Double-sided stator 13
Are the poles 13a of the linear motors 11a and 11b, respectively.
13b is formed so as to project to the opposite side across the common back yoke 13c. The double-sided stator 14 is formed such that the poles 14a, 14b of the linear motors 12a, 12b respectively project to the opposite sides with the common back yoke 14c interposed therebetween. Each double-sided stator 13, 14 is disposed in a hole 3 b formed in the second fork 3.

Each of the double-sided stators 13 and 14 has 3n poles (n = 2 in this embodiment), and each pole 13a, 13b, 14
a and 14b have the same pitch and the same width W. The double-sided stators 13 and 14 are formed in the same manner, and the thickness T of the back yokes 13c and 14c is slightly larger than the width W of the pole 13a and the like.

The coils 15a, 15b, 16a and 16b are all wound around the respective poles 13a, 13b, 14a and 14b in the same direction. Each coil 15
Each of a, 15b, 16a, and 16b is configured to have three phases, is connected to a three-phase inverter (not shown), and is controlled by a control device (not shown). The control device is each linear motor 11a, 11b,
The drive system 12a, 12b is controlled by a bipolar sine wave drive. In addition, the windings of the coils are connected to the coils 15a and 16b and the coils 15b and 16a at the same time, and are not connected to the coils 15a and 15b at the same time.

A linear motor 1 is provided on the upper surface of the fixed fork 2.
The mover 17 of 1a, 12a is formed at a position capable of facing the poles 13a, 14a so as to extend over substantially the entire length of the fixed fork 2 in the longitudinal direction. The movable element 17 is formed with protrusions 17a extending in a direction orthogonal to the moving direction at a constant pitch. Poles 13a, 1 of double-sided stators 13,14
The ratio between the number of the protrusions 4a and the number of the protrusions 17a of the movable element 17 corresponding to the stators 13 and 14 is set to 3: 4. The poles 13a, 14a and the projection 17a are formed to have substantially the same width. In this embodiment, the mover 17 is formed integrally with the iron fixed fork 2.

On the lower surface of the third fork 4, a movable element 18 of the linear motors 11b and 12b is formed at a position where it can face the poles 13b and 14b so as to extend over substantially the entire length of the third fork 4 in the longitudinal direction. . The movable element 18 is formed with projections 18a extending in a direction orthogonal to the moving direction at an equal pitch. Poles 13 of double-sided stators 13 and 14
The ratio of the number of b, 14b to the number of protrusions 18a of the mover 18 in the portion corresponding to the stators 13, 14 is set to 3: 4. The poles 13b, 14b and the protrusion 18a are formed to have substantially the same width. The mover 18 is formed integrally with the iron third fork 4.

A stroke sensor (linear scale head) 19 for detecting the amount of movement of the second fork 3 is provided at the center of the side surface of the fixed fork 2.
Is provided at an origin position (a position facing the fixed fork 2 as a whole). The stroke sensor 19 is connected to the second fork 3
Of the linear scale 21 fixed to the lower surface of the. On the linear scale 21, N poles and S poles are alternately arranged in the sliding direction of the second fork 3, and the stroke sensor 19 detects the N pole and the S pole of the linear scale 21 and outputs a pulse signal. The origin sensor 20 detects the dog 22 fixed to the lower surface of the second fork 3,
It detects that the second fork 3 is at the origin position.

Sensors 23 and 24 are attached to the fixed fork 2 to detect an abnormality in which the second fork 3 excessively extends beyond a predetermined extending position. Sensor 2
Reference numerals 3 and 24 denote emergency stop when the second fork 3 is excessively extended, and are provided at the longitudinal ends of the fixed fork 2, respectively. The sensors 23 and 24 detect dogs 25 and 26 fixed at predetermined positions near the longitudinal center of the lower surface of the second fork 3, respectively. The dogs 25 and 26 are provided movably in grooves 2a and 2b formed on the upper surface of the fixed fork 2 so as to extend in the longitudinal direction. The sensor 23 detects the dog 25 when the second fork 3 excessively extends to the left in FIGS. 1 and 3, and the sensor 24 detects the dog 25 when the second fork 3 excessively extends to the right in FIGS. 1 and 3. The dog 26 is detected.

The output signals of the sensors 19, 20, 23, and 24 are input to a controller (not shown), and the controller calculates the amount of movement of the second fork 3 from the home position based on the number of output pulses of the stroke sensor 19. . Then, when the movement amount from the origin position reaches a value corresponding to each extension position, the control device executes stop control of the second fork 3 at the extension position. Further, the control device includes the sensors 23 and 2
When the dog detection signal is input from
Emergency stop control of a, 11b, 12a, and 12b is performed.

Next, the operation of the fork device 1 configured as described above will be described. The fork device 1 is mounted on, for example, a stacker crane of an automatic warehouse. As shown in FIG. 1, when the second fork 3 and the third fork 4 move on the right side of the origin position, a linear motor 11 a located on the left side of the second fork 3 in FIG. The drive of the linear motor 12b located on the right side of the third fork 4 and facing the third fork 4 is controlled. The same control is performed simultaneously on the two linear motors 11a and 12b, and the second fork 3 and the third fork 4 move in the same direction and the same distance in synchronization.

When moving the second fork 3 to the right, the pole 13a of the double-sided stator 13 and the corresponding movable element 1
The current supply to the coil 15a is controlled such that the magnetic flux passing through the projection 17a of the seventh unit 7 applies a magnetic attraction to the mover 17 to the left. Since the mover 17 is provided on the fixed fork 2, the second fork 3 receives a thrust to the right, and the second fork 3 moves rightward with respect to the fixed fork 2.

To move the third fork 4 to the right, the pole 14b of the double-sided stator 14 and the corresponding movable element 18
The current supply to the coil 16b is controlled so that the magnetic flux passing through the projection 18a of the... Gives a magnetic attraction to the mover 18 to the right. Since the mover 18 is provided on the third fork 4, the third fork 4 receives a thrust to the right, and the third fork 4 moves rightward with respect to the second fork 3.

When returning the two forks 3 and 4 to the origin from the state moved to the right, the linear motors 11a and 12
The energization control is performed so that a magnetic attraction force in the opposite direction to that described above is applied to the movers 17 and 18 on the coils 15a and 16b of b. The control device calculates the amount of movement of the second fork 3 from the origin based on the output signal of the stroke sensor 19, and controls the linear motors 11a and 12b to stop the second fork 3 at a predetermined position.

On the other hand, when the second fork 3 and the third fork 4 move on the left side of the origin position in FIG. 1, the linear motor 11b located on the left side of the second fork 3 and on the opposite side to the fixed fork 2; The drive of the linear motor 12a located on the right side and the opposite side of the third fork 4 is controlled. The same control is simultaneously performed on the two linear motors 11b and 12a, and the second fork 3 and the third fork 4 move in the same direction and the same distance in synchronization.

When the second fork 3 is moved to the left, the coil 16a is energized so as to apply a magnetic attraction to the mover 17 of the fixed fork 2 to the right.
The second fork 3 moves leftward with respect to the fixed fork 2. When moving the third fork 4 to the left, the coil 15b is energized so as to apply a magnetic attraction to the mover 18 of the third fork 4 to the left, and the third fork 4 moves to the left with respect to the second fork 3. I do.

When returning to the origin from the state of moving to the left, the magnetic attraction is applied to the coils 17b and 16a of the linear motors 11b and 12a to the movers 17 and 18 in the opposite direction. Thus, the energization control is performed.

Of the coils 15a, 15b, 16a, 16b provided on the double-sided stators 13, 14, the coil 15a
And coil 16b, or coil 15b and coil 16a
Are simultaneously energized, but the coils 15a and 15b or the coils 15
b and the coil 16b are not energized at the same time. Therefore, the back yoke 13c,
Even if the thickness of 14c is formed to a thickness necessary for one linear motor, the poles 13a, 13b, 14a, 14b and the protrusions 17a,
There is no hindrance for the magnetic flux to pass through 18a.

This embodiment has the following effects. (1) Middle stage movable fork (second fork 3)
Are provided with double-sided stators 13 and 14 configured to share back yokes 13c and 14c, and the movable fork and the movable fork (third fork 4) adjacent to the movable fork are directly driven by linear motors 11a, 11b, 12a and 12b. I do. Therefore, as compared with a conventional fork device in which independent linear motors are arranged one above the other, the fork device 1
Height can be reduced.

(2) Since the double-sided stators 13 and 14 having the configuration that the back yokes 13c and 14c are shared are provided, the weight of the stator can be reduced, and in the case of the same thrust, the load weight of the load can be increased accordingly. .

(3) Double-sided stators 13 and 14 are attached to the movable fork (second fork 3) adjacent to the base portion (fixed fork 2) by one on each side with respect to the center in the moving direction.
Each is provided. Therefore, the second fork 3 and the third fork 4 can be driven with respect to the fixed fork 2 so as to have the same amount of movement in a stable state on either side. In addition, compared to the conventional device in which the linear motors are arranged vertically one above the other, a wasteful excitation current is supplied to the coils corresponding to the poles of the stator not facing the movers 17 and 18. Power consumption can be reduced.

(4) The double-sided stators 13 and 14 are respectively disposed near the ends in the moving direction with respect to the second fork 3. Therefore, the maximum stroke to one side of the movable fork (the second fork 3 and the third fork 4) can be made to be 以上 or more of the entire length of the movable fork. Accordingly, the moving distance of the uppermost movable fork relative to the fixed fork can be increased with a smaller number of movable forks.

(5) Since the second fork 3 and the third fork 4 are configured to move the same distance in synchronization, the third fork 4 is automatically detected by detecting the position of the second fork 3 and performing control. Side position control is performed.

(6) Linear motors 11a, 11b, 1
Since the SR linear motors are used for 2a and 12b, the thrust is increased at the same current density as compared with a linear induction motor of the same size. Therefore, if the size of the linear motor is the same, a heavy load can be transferred, and if the thrust required for transferring the load is the same, the linear motor can be downsized.

(7) Poles 13 of double-sided stators 13 and 14
Since the number of a, 13b, 14a, and 14b is 3n (n is 2 in this embodiment), a general-purpose three-phase inverter can be easily used as a drive circuit.

(8) Since the movable fork is movably supported on the lower fork via the linear guide block and the rail disposed on the vertically opposed surface, the guide disposed on the side surface of the fork. The generation of dust is reduced as compared with the case where the roller is supported by a guide roller rolling in the groove.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG. This embodiment differs greatly from the previous embodiment in that independent stators are provided on the fixed fork 2 and the third fork 4, respectively, and a double-sided mover is provided on the second fork 3.

The fixed fork 2 has a linear motor 11a,
The stators 12 and 12a are arranged on both sides of the center in the longitudinal direction. The stators 29, 30 of the linear motors 11b, 12b are arranged on the third fork 4 on both sides of the center in the longitudinal direction. The poles 27a to 30a of the stators 27 to 30 are formed in the same manner as the poles 13a to 14b of the above embodiment. Further, the coils 27b to 30b are wound similarly to the coils 15a to 16b. However, the winding of each coil is the same as that of each coil 27b.
To 30b are simultaneously connected so as not to be energized.

The back yoke 31 is attached to the second fork 3.
The double-sided mover 31 configured to share c is provided over substantially the entire length thereof. The projections 31 having the same shape as the projections 17a and 18a of the embodiment are provided on both surfaces of the double-sided movable element 31.
a, 31b are formed. The double-sided mover 31 is formed integrally with the second fork 3 made of iron.

In this embodiment, the second fork 3
When the third fork 4 moves rightward from the origin position, the linear motor 12a located on the right side of the fixed fork 2 and the linear motor 11b located on the left side of the third fork 4 in FIG. Both stators 2
8 and 29, when the forks 3 and 4 are moved to the right of the origin position, the forks 3 and 4 are partially overlapped over a wide range. When the coils 28b and 29b are energized at the same time in this state, magnetic fluxes generated by energizing the coils 28b and 29b try to simultaneously pass through the back yoke 31c of the double-sided mover 31 and affect each other. As a result, the amount of magnetic flux that passes through the poles 28a and 29a and the protrusions 31a and 31b and contributes as thrust decreases. Therefore, the coils 28b and 29b are not energized at the same time but are energized sequentially. The order of energization may be any order. That is, after the second fork 3 is extended to a predetermined position, the third fork 4 is extended to a predetermined position, or the third fork 4
Is extended to the predetermined position, the second fork 3 is extended to the predetermined position.

On the other hand, when the second fork 3 and the third fork 4 move on the left side of the origin position, the linear motor 11 located on the left side of the fixed fork 2 in FIG.
and the linear motor 12b located on the right side of the third fork 4 is drive-controlled. Also in this case, both stators 27,
30 are not energized at the same time to the coils 27b and 30b,
It is energized sequentially. In this case, accurate position control requires not only the position of the second fork 3 but also a position detection sensor of the third fork 4.

This embodiment has the following effects in addition to the effects (6) to (8) of the first embodiment. (9) Double-sided mover 31 sharing back yoke 31c
Is provided on the movable fork (second fork 3) adjacent to the fixed fork 2 over substantially the entire length thereof. Therefore, the linear motors 11a, 1
The thickness of the back yoke of the movers 1b, 12a, and 12b is substantially halved, and the height of the fork device can be reduced accordingly. Also, the weight is reduced.

(10) Since each of the stators 27 to 30 is disposed near the end of each fork, the maximum stroke to one side of the movable fork (the second fork 3 and the third fork 4) is increased. 1 of total length
/ 2 or more.

(11) Two linear motors for moving the second fork 3 and the third fork 4 are provided, each of which is separately driven according to the moving direction. Accordingly, unnecessary power is not supplied to the coils corresponding to the poles 27a to 30a of the stator that are not opposed to the protrusions 31a and 31b, and power consumption can be reduced.

The embodiment is not limited to the above, and may be embodied as follows, for example. In the second embodiment, a linear induction motor is used as a linear motor. As shown in FIG. 5, the double-sided movable element 32 may have a sandwich structure in which a back yoke 32a made of an iron plate is sandwiched between aluminum plates 32b. The aluminum plate 32b is fixed to the back yoke 32a with bolts (not shown). In a linear induction motor, an electromagnetic force generated by the action of an eddy current generated on an aluminum plate and a magnetic flux passing through a back yoke is used as the thrust acting on the mover. By using the back yoke 32a made of an iron plate, mechanical strength and thrust are increased with the same thickness as compared with the case where the whole is formed of the aluminum plate 32b.

The double fork 31 is attached to the second fork 3
In the configuration in which the stators are disposed, one stator may be disposed in each of the fixed fork 2 and the third fork 4. The length of the stator is set to a value corresponding to the required stroke. Energization of both stators is performed sequentially. In this case, the number of stators is reduced, and the number of assembling steps in manufacturing the fork device 1 is reduced.

The maximum stroke to one side of the movable fork may be less than 1/2 of the entire length of the movable fork. The movers 17, 18 in the first embodiment or the double-side mover 31 in the second embodiment are not formed integrally with the fixed fork 2, the second fork 3, and the third fork 4, but are formed separately. It may be formed. Also,
Each of the forks 2 to 4 may be made of a material lighter than iron, for example, aluminum, and the movers 17, 18 and the double-side mover 31 may be made of iron. In this case, the weight of the fork device 1 can be reduced.

The fork device 1 is not limited to the three-stage type,
It may be more than a step. In this case, not all the movable forks are driven by the linear motor, but a drive mechanism using a rack and a pinion or a chain and a sprocket may be used instead of the linear motor to drive some of the movable forks.

The number of poles of the stator 16 is not limited to six,
It may be three or nine or more multiples of three. That is, the number of poles of the stator 16 may be 3n (n is a natural number).
In this case, a general-purpose three-phase inverter can be easily used as the drive circuit.

The linear motor may be a motor other than the SR linear motor and the linear induction motor, for example, a linear pulse motor or a linear synchronous motor. Also in this case, by providing a double-sided stator or a double-sided mover that shares the back yoke, the height of the load transfer device can be reduced.

Instead of mounting the fork device 1 on a stacker crane, it may be mounted on a self-propelled carrier.
Further, the fork device 1 may be used as a stationary transfer device.

The inventions (technical ideas) other than those described in the claims which can be grasped from the above embodiments will be described below together with their effects. (1) The load transfer device according to any one of claims 1 to 4, as a linear motor, uses both self-inductance and mutual inductance as an operation principle, and determines the number of poles of the stator and the fixed position. The ratio between the number of protrusions of the mover and the portion corresponding to the stator is set to 3: 4, and the number of poles of the stator is 3n.
(N is a natural number) and is equipped with an SR linear motor in which the coils of each pole are all wound in the same direction. In this case, the thrust obtained at the same current density is larger than that of the linear induction motor.

(2) In the second aspect of the present invention,
The energization of the coils of each double-sided stator is controlled so that the movable fork adjacent to the base and the movable fork adjacent to the movable fork are driven in synchronization. In this case, accurate position control of both movable forks can be performed based on a detection signal of a sensor that detects the position of one movable fork.

[0061]

As described in detail above, claims 1 to 5 are provided.
According to the invention described in (1), since the plurality of movable forks of the load transfer device are directly driven by the linear motors respectively, when a plurality of linear motors are provided, the height of the load transfer device is increased by the same thrust as compared with the conventional device. Can be lowered.

According to the second aspect of the present invention, the movable fork can be driven with respect to the fixed fork so as to have the same amount of movement in a stable state on any side. In addition, compared to the conventional device in which the linear motors are arranged in an up-and-down state, no unnecessary exciting current is supplied to the coils corresponding to the poles of the stator not facing the mover. , Power consumption can be reduced.

According to the third aspect of the present invention, the thickness of the back yoke of the mover of the linear motor arranged vertically is reduced to approximately half, and the height of the load transfer device can be reduced accordingly. , The weight is also lighter.

According to the fourth aspect of the present invention, the moving distance of the uppermost movable fork with respect to the fixed fork can be increased with a smaller number of forks. According to the invention as set forth in claim 5, as compared with the case where the whole is formed of an aluminum plate, the mechanical strength is increased if the thickness is the same,
Thrust also increases.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view of a fork device according to a first embodiment.

FIG. 2 is a sectional view of the fork device.

FIG. 3 is a schematic perspective view of a fork device.

FIG. 4 is a schematic side sectional view of a fork device according to a second embodiment.

FIG. 5 is a schematic side view of a double-sided mover according to another embodiment.

FIG. 6 is a sectional view of a conventional load transfer device.

FIG. 7 is a perspective view of the same.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fork apparatus as a load transfer apparatus, 2 ... Fixed fork as a base part, 3 ... Second fork as a movable fork, 4 ... Third fork, 11a, 11
b, 12a, 12b ... linear motor, 13, 14 ... double-sided stator, 13c, 14c ... back yoke, 27-30 ...
Stator, 31, 32 ... Double-sided mover, 31c, 32a ... Back yoke.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kimoto Minoshima 2-1-1 Toyota-cho, Kariya-shi, Aichi Prefecture Inside Toyota Industries Corporation (72) Inventor Taiji Taiji 2-1-1 Toyota-cho, Kariya-shi, Aichi Prefecture F term in Toyota Industries Corporation (reference) 3F022 JJ07 KK02 MM01 MM04 NN01 PP06 QQ04 3F333 AA04 AE03

Claims (5)

[Claims] 1. A load transfer device comprising: a base portion; and a plurality of movable forks capable of being horizontally fed out to the base portion, wherein the load transfer device includes a linear motor as a drive source of the movable fork. A load transfer device in which a fork is provided with a double-sided stator or a double-sided movable element configured to share a back yoke, and the movable fork and a movable fork adjacent to the movable fork are directly driven by a linear motor. 2. The load transfer device according to claim 1, wherein one of the double-sided stators is provided on each of the movable forks adjacent to the base portion on both sides with respect to the center in the moving direction. 3. The load transfer device according to claim 1, wherein the double-sided movable element is provided on a movable fork adjacent to a base portion over substantially the entire length thereof. 4. The stator according to claim 1, wherein the stator is arranged such that a maximum stroke of the movable fork to one side is equal to or more than の of a total length of the movable fork. A load transfer device as described. 5. The load transfer device according to claim 3, wherein the double-sided mover is formed in a sandwich structure in which a back yoke made of an iron plate is sandwiched between aluminum plates, and a linear induction motor is used as a linear motor.