Actuator unit

Abstract

To provide an actuator unit capable of smoothly expanding and contracting by preventing a load from concentrating on a portion in an expansion and contraction direction.SOLUTION: A linear motor unit 1 as an actuator unit according to the present invention comprises an even number of linear motors 4 arranged in parallel to each other between one side bracket 2 and the other side bracket 3, that face each other with a predetermined space apart. Of the even number of linear motors 4, a half number of linear motors 4 are referred to first linear motors 4A, and a remaining half number of linear motors 4 are referred to second linear motors 4B. Each of the first linear motors 4A has a tip of a rod 6 connected to the one side bracket 2, and an opposite rod side end of an outer tube 5 connected to the other side bracket 3. Each of the second linear motors 4B has an opposite rod side end of the outer tube 5 connected to the one side bracket 2, and a tip of the rod 6 connected to the other side bracket 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an actuator unit. [Background technology]

[0002] An example of an actuator is a linear motor that includes an outer tube made of a non-magnetic material, a rod made of a non-magnetic material inserted into the outer tube so as to be axially movable, a cylindrical back yoke inserted into the outer tube, a cylindrical non-magnetic inner tube inserted into the back yoke to form an annular gap between it and the back yoke, a cylindrical field magnet having a plurality of annular permanent magnets that are stacked and inserted into the annular gap between the back yoke and the inner tube so that their south poles and north poles are alternately aligned in the axial direction, and an armature that is attached to the outer periphery of the rod and has a core with a plurality of teeth on its outer periphery that are aligned in the axial direction, and U-phase, V-phase, and W-phase windings that are attached to slots between the teeth (see, for example, Patent Document 1).

[0003] In a linear motor configured in this way, when current is applied to the U-, V-, and W-phase windings of the armature, attractive and repulsive forces are generated in the axial direction between the permanent magnets in the field and the armature, generating thrust that drives the armature. The rod to which the armature is attached then moves axially and functions as an output shaft that transmits the thrust of the linear motor.

[0004] Such linear motors are used to drive a variety of devices. When a linear motor is used for an application requiring a large force, such as driving the arm of a heavy machine, the output of the linear motor is limited, and the thrust may be insufficient to drive the arm.

[0005] In such a case, as shown in Patent Document 2, it is conceivable to bundle both ends of a plurality of linear motors with a pair of brackets to form a unit, and to exert the required force from the plurality of linear motors. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-121183 [Patent Document 2] Japanese Patent Publication No. 2022-047272 Summary of the Invention [Problem to be solved by the invention]

[0007] When the linear motor disclosed in Patent Document 1 is unitized like the linear motor disclosed in Patent Document 2, an outer tube is connected to one of a pair of opposing brackets, and a rod is connected to the other of the pair of brackets, so that the linear motor is arranged in parallel between the brackets.

[0008] The mass of a linear motor is not uniform in the axial direction, and the armature, which is made by wrapping copper wire around an iron core, has the greatest mass of all the components in a linear motor. Furthermore, since the armature is equipped with a slider that is attached to the outer periphery of the rod and slides against the inner periphery of the inner tube, when the linear motor is used sideways, the weight of the armature is supported by the outer tube via the slider, inner tube, and back yoke.

[0009] In a linear motor unit configured as an actuator unit in this way, when the linear motors are placed sideways, the linear motors are arranged in parallel and facing the same direction, and the armatures, which are heavy objects, are also placed in the same position in the axial direction of the linear motors. As a result, the outer tubes of all of the linear motors are subjected to a large load at the same position, which causes the load to be concentrated in one part of the linear motor unit in the extension / contraction direction, causing a large deflection deformation in that part of the linear motor unit in the extension / contraction direction, which may impair the smooth extension / contraction operation of the linear motor unit.

[0010] Even if the actuator is not a linear motor, unless the mass of the actuator is uniform in the axial direction, when the actuator is unitized, the position of the heavy object of each actuator will be placed in the same position in the axial direction, which will cause the load to concentrate in one part of the actuator unit in the extension / contraction direction, resulting in a problem of bending and deforming that part of the actuator unit in the extension / contraction direction.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an actuator unit that can expand and contract smoothly by preventing the load from concentrating on one part in the expansion and contraction direction. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides an actuator unit comprising an even number of actuators, each having a first bracket, an opposite bracket opposite to the first bracket, an outer tube, and a rod inserted into the outer tube so as to be axially movable, and arranged in parallel with one another at a predetermined interval between the first bracket and the second bracket, wherein half of the even number of actuators are first actuators and the remaining half are second actuators, wherein the first actuator has a tip of its rod connected to the first bracket and an end of the outer tube opposite to the rod connected to the second bracket, and the second actuator has a tip of its rod connected to the first bracket and an end of the outer tube opposite to the rod connected to the second bracket. With this configuration, the positions of the portions of the outer tube that support the load of a heavy object are offset in the axial direction between the first actuator and the second actuator, so that the load of the heavy object acting on the actuator unit is distributed in the extension / contraction direction, and large deflection of a portion of the actuator unit in the extension / contraction direction can be suppressed. Furthermore, with this configuration, the same number of first actuators and second actuators are arranged between the brackets on one side and the brackets on the other side, so the masses on both sides of the center line that passes through the center of the actuator unit in the extension / retraction direction and in a direction transverse to the axial direction of each actuator are balanced, thereby preventing the occurrence of a rotational moment around the axis of the center line in the actuator unit.

[0013] Furthermore, in the actuator unit of the present invention, the number of actuators may be a multiple of four, and the same number of first actuators and second actuators may be arranged on both sides of an imaginary line dividing the actuators in half. With this configuration, when the actuator unit is divided into four regions by the imaginary line dividing the actuators in half and a center line crossing the center of the actuator unit in the extension / contraction direction, the mass of each region is balanced. Therefore, there is no imbalance in the mass balance of the actuator unit, and no force that twists the actuator unit is generated.

[0014] Another invention provides an actuator unit comprising: a first bracket, a second bracket opposing the first bracket, an outer tube, and a rod inserted axially movably into the outer tube; and n actuators (where n is an odd number greater than or equal to three) arranged in parallel at a predetermined interval between the first bracket and the second bracket. Of the n actuators, (n-1) × 1 / 2 actuators are designated as first actuators, and the remaining actuators are designated as second actuators. The first actuator has a rod end connected to the first bracket and an end opposite the rod of the outer tube connected to the second bracket. The second actuator has a rod end opposite the rod of the outer tube connected to the first bracket and an end of the rod connected to the second bracket. With this configuration, the positions of the portions of the outer tube supporting the weight of a heavy object are offset axially between the first and second actuators. This distributes the load of the heavy object acting on the actuator unit in the extension / contraction direction, preventing large deflection of a portion of the actuator unit in the extension / contraction direction. Furthermore, with this configuration, the number of first actuators differs from the number of second actuators by only one. As a result, the difference in mass between the two sides of the center line that passes through the center of the actuator unit in the extension / contraction direction and that intersects the axial direction of each actuator is smaller than in the past, and the rotational moment generated around the axis of the center line in the actuator unit is smaller than in the past.

[0015] In another actuator unit of the invention, the first and second actuators may be arranged so as to be symmetrical about the axis of the central actuator among the n actuators. With this configuration, when the actuator unit is divided into four regions separated by a center line that intersects the axis of the central actuator and the center of the extension / contraction direction of the actuator unit, the difference in weight among the regions is smaller than when the first and second actuators are arranged asymmetrically about the axis of the central actuator, and therefore the force that twists the actuator unit is reduced. [Effects of the Invention]

[0016] According to the actuator unit of the present invention, large bending of a portion in the extension / contraction direction is suppressed, and smooth extension / contraction is possible. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a plan view of the actuator unit according to the first embodiment. [Figure 2] FIG. [Figure 3] FIG. 10 is a plan view of a modified example of the actuator unit of the first embodiment. [Figure 4] FIG. 10 is a plan view of an actuator unit according to a second embodiment. [Figure 5] FIG. 10 is a plan view of a modified example of the actuator unit of the second embodiment. [Figure 6] FIG. 10 is a plan view of another modified example of the actuator unit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described below based on the embodiments shown in the drawings. The same reference numerals are used throughout the several drawings to indicate the same parts.

[0019] First Embodiment As shown in FIG. 1, the linear motor unit 1 as an actuator unit in the first embodiment includes a one-side bracket 2, an other-side bracket 3 facing the one-side bracket 2, and four linear motors 4 as actuators arranged in parallel with each other at predetermined intervals between the one-side bracket 2 and the other-side bracket 3.

[0020] As shown in FIG. 2, the linear motor 4 includes an outer tube 5, a rod 6 inserted into the outer tube 5 so as to be movable in the axial direction, a field magnet 7 attached to the inner periphery of the outer tube 5, and an armature 8 attached to the outer periphery of the rod 6.

[0021] Below, each part of the linear motor unit 1 will be described in detail. First, each part of the linear motor 4 will be described in detail. The outer tube 5 is a cylindrical non-magnetic material, and the outer tube 5 accommodates a back yoke 9 formed of a cylindrical soft magnetic material, a cylindrical non-magnetic inner tube 10 inserted into the back yoke 9 to form an annular gap between it and the back yoke 9, and a cylindrical field magnet 7 inserted into the annular gap between the back yoke 9 and the inner tube 10.

[0022] The field 7 is composed of annular main pole permanent magnets 7a and annular sub-pole permanent magnets 7b stacked alternately in the axial direction, and generates a magnetic field on cores 80A and 80B of the armature 8 (described later). The triangular marks on the main pole permanent magnets 7a and sub-pole permanent magnets 7b in FIG. 2 indicate the magnetization direction, with the main pole permanent magnets 7a being radial and the sub-pole permanent magnets 7b being axial. The main pole permanent magnets 7a and sub-pole permanent magnets 7b are arranged in a Halbach array, with south and north poles alternating in the axial direction on the inner periphery of the field 7. However, the field 7 may also be composed of annular permanent magnets magnetized in the axial direction with a north pole on one side and annular permanent magnets magnetized in the axial direction with a south pole on the other side stacked in order.

[0023] Furthermore, in the linear motor 4 of this embodiment, the axial length of the permanent magnet 7a of the main magnetic pole is longer than the axial length of the permanent magnet 7b of the sub-pole. In this way, by increasing the axial length of the permanent magnet 7a of the main magnetic pole, the magnetic resistance between the permanent magnet 7a of the main magnetic pole and cores 80A, 80B of the armature 8 (described later) can be reduced, and the magnetic field acting on the cores 80A, 80B of the armature 8 can be increased, thereby improving the thrust of the linear motor 4.

[0024] Additionally, a back yoke 9 is provided on the outer periphery of the permanent magnets 7a, b. Providing the back yoke 9 ensures a magnetic path with low magnetic resistance, thereby suppressing an increase in magnetic resistance caused by a shortened axial length of the permanent magnet 7b of the sub-pole. Therefore, by making the axial length of the permanent magnet 7a of the main pole longer than that of the permanent magnet 7b of the sub-pole and providing a cylindrical back yoke 9 on the outer periphery of the permanent magnets 7a, 7b, the thrust of the linear motor 4 can be greatly improved. The thickness of the back yoke 9 may be set to a thickness suitable for suppressing an increase in the external magnetic resistance of the permanent magnet 7a of the main pole.

[0025] A rod 6 made of a non-magnetic material is inserted into the outer tube 5 so as to be movable in the axial direction, and an armature 8 is attached to the outer periphery of the rod 6. As shown in Fig. 2, the armature 8 includes two cylindrical cores 80A and 80B attached to the outer periphery of the rod 6, and three annular sliders 81, 82, and 83 fixed to the outer periphery of the rod 6 and disposed between the two cores 80A and 80B, to the left of the core 80A on the left side in the figure, and to the right of the core 80B on the right side in the figure. The number of cores 80A and 80B is not limited to two, and may be one or three or more.

[0026] As shown in Fig. 2, each core 80A, 80B is cylindrical and has a plurality of teeth 80a arranged on its outer periphery at equal intervals in the axial direction. Windings 84 are wound around and installed in slots 80b between the teeth 80a. The windings 84 are composed of three phases: U-phase, V-phase, and W-phase. The phases of the windings 84 in the slots 80b are arranged in the same order in each core 80A, 80B.

[0027] Wear rings 81a, 82a, and 83a are attached to the outer peripheries of the sliders 81, 82, and 83, respectively. The outer diameters of the sliders 81, 82, and 83 are set to be larger than the outer diameters of the cores 80A and 80B. The armature 8 configured in this manner is inserted into the cylindrical field magnet 7 so as to be movable in the axial direction, which is the thrust direction.

[0028] The sliders 81, 82, and 83 are in sliding contact with the inner peripheral surface of the inner tube 10 via wear rings 81a, 82a, and 83a, and guide the axial movement of the armature 8 and rod 6 relative to the field 7 and outer tube 5. Therefore, the armature 8 and rod 6 can move smoothly in the axial direction without becoming eccentric relative to the field 7 and outer tube 5. In this way, when the eccentricity of the armature 8 relative to the field 7 is prevented, a decrease in thrust due to eccentricity of the armature 8 is also prevented, and the linear motor 4 can generate a stable thrust.

[0029] In addition, the left ends of the outer tube 5, back yoke 9 and inner tube 10 in Figure 2 are closed by a bottom cap 11, and the right ends of the outer tube 5, back yoke 9 and inner tube 10 in Figure 1 are closed by an annular head cap 12.

[0030] The head cap 12 has an inner diameter larger than the outer diameter of the rod 6, and the rod 6 is inserted through the inner periphery. A dust seal 12a is provided on the inner periphery of the head cap 12, and the dust seal 12a comes into sliding contact with the outer periphery of the rod 6, which is inserted movably into the inner periphery of the head cap 12, thereby sealing the outer periphery of the rod 6.

[0031] Although not shown, the rod 6 is cylindrical, and power can be supplied to the windings 84 from an external power source installed outside the linear motor 4 via an electric wire (not shown) that passes through the rod 6.

[0032] For example, by sensing the electrical angle of the windings 84 with respect to the field 7, switching the energization phase based on the electrical angle, and controlling the amount of current in each winding 84 through PWM control, it is possible to control the thrust of the linear motor 4 and the direction of movement of the armature 8. Note that the above-described control method is an example and is not limited to this. As described above, in the linear motor 4 of this embodiment, the armature 8 acts as the mover, and the field 7 acts as the stator. Furthermore, when an external force acts to relatively displace the armature 8 and the field 7 in the axial direction, a thrust that suppresses the relative displacement is generated by energizing the windings 84 or by induced electromotive force generated in the windings 84, allowing the linear motor 4 to damp the vibration and movement of the equipment caused by the external force, and also enabling energy regeneration to generate electric power from the external force.

[0033] In the linear motor 4 of this embodiment, the rod 6 and the armature 8 attached to the rod 6 are inserted axially movably inside the cylindrical field magnet 7 attached to the inner periphery of the outer tube 5. However, a structure in which the armature 8 is attached to the inner periphery of the outer tube 5 and the field magnet 7 is attached to the rod 6 may also be employed. In this case, each core 80A, 80B of the armature 8 may be cylindrical, and slots 80b for accommodating the windings 84 may be provided on the inner periphery. However, the configuration of the linear motor 4 described above is merely an example, and the configuration of the linear motor 4 is not particularly limited as long as it has the outer tube 5, the rod 6 inserted axially movably within the outer tube 5, the field magnet 7 attached to one of the outer tube 5 and the rod 6, and the armature 8 attached to the other of the outer tube 5 and the rod 6, and can generate thrust in the axial direction.

[0034] In the linear motor unit 1 of the first embodiment, as shown in Fig. 1, four of the linear motors 4 described above are arranged in parallel at a predetermined interval between one bracket 2 and the other bracket 3 facing each other. In such a linear motor unit 1, when the armature 8 of each linear motor 4 is energized to generate thrust in each linear motor 4, the rod 6 moves along the axial direction of the outer tube 5, expanding and contracting. The linear motor unit 1 can generate thrust that is the sum of the thrusts of the linear motors 4.

[0035] Although not described in detail, the one-side bracket 2 and the other-side bracket 3 each have a plurality of holding portions that can hold either the tip of the rod 6 of each linear motor 4 or the anti-rod end of the outer tube 5, and can hold each linear motor 4 together.

[0036] Furthermore, although not shown, the linear motor unit 1 of this embodiment is interposed between an arm, which is a movable part of a backhoe, and a boom, which is a support part that supports the arm so that it can move in one direction, and by reciprocating the arm along the axial direction of the linear motor 4 relative to the boom through extension and contraction, the arm can be raised and lowered relative to the boom. However, the device to which the linear motor unit 1 is attached is not limited to a backhoe. The linear motor unit 1 may be interposed between a movable part of heavy machinery other than a backhoe, or of a device other than heavy machinery, and a support part that supports the movable part so that it can move in one direction.

[0037] Specifically, as shown in FIG. 1 , one bracket 2 has multiple eye-shaped mounting pieces 2a arranged at predetermined intervals, and the other bracket 3 has one eye-shaped mounting piece 3a at its center. Although not shown, the support portion of the device to be attached has multiple mating portions with opposing holes. With these mating portions mated between the mounting pieces 2a, the one bracket 2 is rotatably attached to the support portion of the device to be attached by pins inserted into the mounting pieces 2a and the holes in the mating portions. Furthermore, although not shown, the movable portion of the device to be attached has a pair of connecting pieces with opposing holes. With the mounting piece 3a inserted between the pair of connecting pieces, the other bracket 3 is rotatably attached to the movable portion of the device to be attached by pins inserted into the pair of connecting pieces and the holes in the mounting piece 3a. Thus, the one bracket 2 and the other bracket 3 also function as a joint for attaching the linear motor unit 1 to the device to be attached.

[0038] Furthermore, the configuration of the one-side bracket 2 and the other-side bracket 3 can be changed appropriately according to the structure of the device to which it is to be attached, as long as it can hold the axial end of each linear motor 4, bundle the linear motors 4, and attach the linear motor unit 1 to the device to which it is to be attached, and the number and shape of the mounting pieces 2a, 3a can also be changed appropriately.

[0039] Furthermore, of the four linear motors 4, the linear motor 4 in the forward direction, in which the tip of the rod 6 is connected to the bracket 2 on one side and the anti-rod end of the outer tube 5 is connected to the bracket 3 on the other side, is referred to as a first linear motor 4A (first actuator). On the other hand, of the four linear motors 4, the linear motor 4 in the reverse direction, in which the tip of the rod 6 is connected to the bracket 3 on the other side and the anti-rod end of the outer tube 5 is connected to the bracket 2 on one side, is referred to as a second linear motor 4B (second actuator). The first linear motors 4A and second linear motors 4B are arranged in parallel between the bracket 2 on one side and the bracket 3 on the other side, as shown in FIG. 1 . Note that the first linear motors 4A and second linear motors 4B may be arranged between the bracket 2 on one side and the bracket 3 on the other side with the forward and anti-reverse directions reversed.

[0040] Here, the mass of linear motor 4 is not uniform in the axial direction, and armature 8, which is composed of iron cores 80A, 80B and copper windings 84 wound around cores 80A, 80B, has an especially large mass among the components of linear motor 4. Furthermore, armature 8 is equipped with sliders 81, 82, and 83 that are attached to the outer periphery of rod 6 and come into sliding contact with the inner circumferential surface of inner tube 19. Therefore, in a linear motor 4 that is arranged horizontally, the load of armature 8 is supported by outer tube 5 via inner tube 10, field magnet 7, and back yoke 9. For this reason, when all linear motors 4 are arranged in parallel in the same direction as in the conventional case, the positions of the portions of outer tube 5 that support the load of armatures 8 (positions of sliders 81, 82, and 83 that come into sliding contact with the inner periphery of inner tube 10) end up being aligned in the same position in the axial direction of each linear motor 4. Therefore, when the linear motor unit 1 is placed in a horizontal position in which the extension direction is along the lateral direction (including the horizontal direction or a direction slightly inclined from the horizontal), all of the armatures 8, which are heavy objects, are always placed in the same position, so the load is concentrated on one part of the extension direction of the linear motor unit 1, causing that part to bend significantly in the extension direction, which may prevent the linear motor unit 1 from operating smoothly.

[0041] In contrast, in the linear motor unit 1 of the first embodiment, half of the four linear motors 4, the first linear motors 4A, are arranged in the positive direction, and the remaining half, the second linear motors 4B, are arranged in the opposite direction, so that the same number of first linear motors 4A and second linear motors 4B are arranged between the bracket 2 on one side and the bracket 3 on the other side.

[0042] As a result, the positions of the portions of the outer tube 5 that support the load of the armature 8, which is a heavy object, are shifted in the axial direction between the first linear motor 4A and the second linear motor 4B, so the load of the heavy object acting on the linear motor unit 1 is distributed in the extension / contraction direction, preventing large bending of parts of the linear motor unit 1 in the extension / contraction direction. This allows the linear motor unit 1 to extend and contract smoothly.

[0043] Furthermore, when there is an even number of linear motors 4, as in the linear motor unit 1 of the first embodiment, the number of first linear motors 4A is the same as the number of second linear motors 4B, so the masses on both sides of center line C, shown by the dashed line in Fig. 1, which passes through the center of the extension / contraction direction of the linear motor unit 1 in a direction intersecting the axial direction of each linear motor 4 (left / right direction in Fig. 1), are balanced. This makes it possible to prevent a rotational moment from being generated around the axis of center line C in the linear motor unit 1.

[0044] Furthermore, in the linear motor unit 1 of the first embodiment, as shown in Fig. 1, of the four linear motors 4 arranged in parallel, two positive-direction first linear motors 4A are arranged on the inside, and two negative-direction second linear motors 4B are arranged on the outside. In other words, in the linear motor unit 1 of the first embodiment, as shown in Fig. 1, the same number of first linear motors 4A and second linear motors 4B are arranged on both sides of an imaginary line S shown by a dashed line in Fig. 1, which divides all of the linear motors 4 into halves.

[0045] Then, when the linear motor unit 1 is divided into four regions separated by the imaginary line S and the center line C that crosses the center of the extension / contraction direction of the linear motor unit 1, the mass of each region is balanced with respect to each other. Therefore, there is no imbalance in the mass balance of the linear motor unit 1, and no force that twists the linear motor unit 1 is generated.

[0046] Furthermore, if half of the first linear motors 4A facing in the forward direction and half of the second linear motors 4B facing in the reverse direction are arranged between the bracket 2 on one side and the bracket 3 on the other side, the gap between the outer tube 5 of adjacent first linear motor 4A and the rod 6 of the second linear motor 4B, and between the rod 6 of adjacent first linear motor 4A and the outer tube 5 of the second linear motor 4B, will be large. This makes it possible to secure space for inserting tools between the linear motors 4, 4 when attaching each linear motor 4 to the bracket 2 on one side and the bracket 3 on the other side, making it easier to assemble the linear motor unit 1.

[0047] Furthermore, in the linear motor unit 1 of the first embodiment, the number of linear motors 4 arranged in parallel with each other at a predetermined interval between the one-side bracket 2 and the other-side bracket 3 is not limited to four and may be an even number that is a multiple of four. For example, if the number of linear motors 4 in the linear motor unit 1 is eight, to arrange the same number of first linear motors 4A and second linear motors 4B on both sides of the imaginary line S that divides the linear motors 4 in half, as shown in FIG. 3, two first linear motors 4A, 4A are arranged side by side in the center, and three linear motors 4 are arranged side by side to the left and right of the central first linear motors 4A, 4A in the order of second linear motor 4B, first linear motor 4A, second linear motor 4B. In this way, the first linear motor 4A and the second linear motor 4B are always adjacent to each other, and therefore the gap between the outer tube 5 of the first linear motor 4A and the rod 6 of the second linear motor 4B and the gap between the rod 6 of the first linear motor 4A and the outer tube 5 of the second linear motor 4B are large. This allows space to be secured between the linear motors 4, 4 to fit tools, facilitating assembly of the linear motor unit 1. The specific number of linear motors 4 may be determined appropriately depending on the thrust required for the linear motor unit 1 and the space available for installing the linear motor unit 1.

[0048] In this way, if the number of linear motors 4 is an even number, the number of positive-direction first linear motors 4A and the number of negative-direction second linear motors 4B can be the same, just as in the case of four linear motors. Therefore, the masses on both sides of the center line C, which passes through the center of the extension / contraction direction of the linear motor unit 1 in a direction transverse to the axial direction of each linear motor 4, can be balanced, preventing the generation of a rotational moment around the axis of the center line C with respect to the linear motor unit 1.

[0049] Furthermore, if the number of linear motors 4 is a multiple of four, then, just as in the case of four linear motors, the same number of first linear motors 4A and second linear motors 4B can be placed on both sides of the imaginary line S that divides all of the linear motors 4 in half. Therefore, when the linear motor unit 1 is divided into four regions by the imaginary line S and the center line C, the mass of each region is balanced. Therefore, there is no imbalance in the mass balance of the linear motor unit 1, and no force that twists the linear motor unit 1 is generated.

[0050] However, the number of linear motors 4 may be an even number other than a multiple of 4, and even if the number of linear motors 4 is a multiple of 4, the positive-direction first linear motors 4A and the opposite-direction second linear motors 4B may be arranged in different numbers on both sides of the virtual line S.

[0051] Furthermore, although not shown, the linear motor unit 1 may have a structure in which two linear motor groups (actuator groups) each consisting of a plurality of linear motors 4 arranged in parallel are stacked one on top of the other as shown in Fig. 1. In this way, it is possible to increase the number of linear motors 4 as actuators and increase the thrust of the linear motor unit 1 while preventing the linear motor unit 1 from becoming too large in the lateral direction (the direction crossing the extension / contraction direction of the linear motor unit 1).

[0052] In this case, the linear motors 4 in the two linear motor groups may be arranged so that the first linear motor 4A and the second linear motor 4B face each other above and below. In this way, even if the linear motor unit 1 is configured so that two linear motor groups are arranged one above the other, the masses on both sides of the center line C, which passes through the center of the linear motor unit 1 in the extension / contraction direction in a direction transverse to the axial direction of each linear motor 4, are balanced, thereby preventing the generation of a rotational moment around the axis of the center line C in the linear motor unit 1. However, the linear motors 4 in the linear motor groups arranged above and below may also be arranged so that the first linear motors 4A, 4A face each other above and below, or the second linear motors 4B, 4B face each other above and below. The number of linear motor groups arranged so as to be stacked above and below may be three or more.

[0053] Furthermore, in the linear motor unit 1 as an actuator unit of this embodiment, a linear motor 4 is used as the actuator, but the actuator is not limited to the linear motor 4 as long as it has an outer tube 5 and a rod 6 inserted into the outer tube 5 so as to be movable in the axial direction and is extendable and contractible. For example, instead of the linear motor 4, an electric actuator may be used which extends and contracts by driving an electric motor to move a rod in the outer tube in the axial direction.

[0054] <Second embodiment> Next, a detailed description will be given of a linear motor unit 1A as an actuator unit according to a second embodiment shown in Fig. 4. The linear motor unit 1A according to the second embodiment differs from the linear motor unit 1 according to the first embodiment only in the number and arrangement of linear motors 4 as actuators arranged in parallel at a predetermined interval between one bracket 2 and the other bracket 3, and the other structures are the same, so common components are denoted by the same reference numerals and detailed descriptions will be omitted.

[0055] As shown in FIG. 4, the linear motor unit 1A of the second embodiment includes a first bracket 2, a second bracket 3 opposing the first bracket 2, and three linear motors 4 arranged in parallel at a predetermined interval between the first bracket 2 and the second bracket 3. Of the three linear motors 4, the linear motor 4 in the forward direction, in which the tip of the rod 6 is connected to the first bracket 2 and the end of the outer tube 5 opposite the rod is connected to the second bracket 3, is referred to as a first linear motor 4A (first actuator). On the other hand, of the three linear motors 4, the linear motor 4 in the reverse direction, in which the tip of the rod 6 is connected to the second bracket 3 and the end of the outer tube 5 opposite the rod is connected to the first bracket 2, is referred to as a second linear motor 4B (second actuator). As shown in FIG. 4, one first linear motor 4A and two second linear motors 4B are arranged in parallel between the first bracket 2 and the second bracket 3. The first linear motor 4A and the second linear motor 4B may be disposed between the one-side bracket 2 and the other-side bracket 3 with the forward and reverse directions reversed.

[0056] As described in the explanation of the linear motor unit 1 of the first embodiment, the mass of the linear motor 4 is not uniform in the axial direction, and the armature 8, which is composed of the iron cores 80A, 80B and the copper windings 84 wound around the cores 80A, 80B, has a particularly large mass among the components of the linear motor 4. Therefore, when all of the linear motors 4 are arranged in parallel in the same orientation, as in the conventional case, the positions of the portions of the outer tube 5 that support the load of the armatures 8 (the positions of the sliders 81, 82, 83 that slide against the inner circumference of the inner tube 10) are aligned in the same position in the axial direction of each linear motor 4. Therefore, when the linear motor unit 1A is arranged in a horizontal position, all of the armatures 8, which are heavy objects, are always aligned in the same position, which may cause the load to be concentrated in one portion of the linear motor unit 1A in the extension / contraction direction, resulting in a large deflection in that portion, preventing the linear motor unit 1A from smoothly extending and contracting.

[0057] In contrast, in the linear motor unit 1A of the second embodiment, one first linear motor 4A of the three linear motors 4 is arranged in the positive direction, and the remaining two second linear motors 4B are arranged in the opposite direction.

[0058] As a result, the positions of the portions of the outer tube 5 that support the load of the armature 8, which is a heavy object, are shifted in the axial direction between the first linear motor 4A and the second linear motor 4B, so the load of the heavy object acting on the linear motor unit 1 is distributed in the extension / contraction direction, and it is possible to prevent a portion of the linear motor unit 1A from bending significantly in the extension / contraction direction. This allows the linear motor unit 1A to extend and contract smoothly.

[0059] Furthermore, in the linear motor unit 1A of the second embodiment, the difference in the number of first linear motors 4A in the forward direction and second linear motors 4B in the reverse direction is only one. As a result, the difference in mass on both sides of center line C, shown by the dashed dotted line in FIG. 3, which passes through the center of the linear motor unit 1A in the extension / retraction direction in a direction intersecting the axial direction of each linear motor 4 (left / right direction in FIG. 3), is smaller than in the past. As a result, the rotational moment generated around the axis of center line C in the linear motor unit 1A is smaller than in the past.

[0060] Furthermore, if a first linear motor 4A in the forward direction and a second linear motor 4B in the reverse direction are arranged between the bracket 2 on one side and the bracket 3 on the other side, the gap becomes larger between the outer tube 5 of the adjacent first linear motor 4A and the rod 6 of the second linear motor 4B, and between the rod 6 of the adjacent first linear motor 4A and the outer tube 5 of the second linear motor 4B. This makes it easier to insert tools between the linear motors 4, 4 when attaching each linear motor 4 to the bracket 2 on one side and the bracket 3 on the other side, facilitating assembly of the linear motor unit 1A.

[0061] 3, in the linear motor unit 1A of the second embodiment, one positive-direction first linear motor 4A is arranged in the center of the three linear motors 4 arranged in parallel, and two opposite-direction second linear motors 4B, 4B are arranged on the outside. Therefore, in the linear motor unit 1A of the second embodiment, the first linear motor 4A and the second linear motor 4B are arranged so as to be symmetrical with respect to the axis D of the first linear motor 4A, which is arranged in the center of the three linear motors 4.

[0062] When the linear motor unit 1A is divided into four regions separated by the axis D and the center line C that crosses the center of the extension / contraction direction of the linear motor unit 1A, the difference in weight between the regions becomes smaller than when the first linear motor 4A and the second linear motor 4B are arranged asymmetrically on either side of the axis D of the linear motor 4 that is arranged in the center, and therefore the force that twists the linear motor unit 1 becomes smaller.

[0063] Furthermore, in the linear motor unit 1A of the second embodiment, the number of linear motors 4 arranged in parallel with each other at a predetermined interval between the one-side bracket 2 and the other-side bracket 3 is not limited to three and may be any odd number equal to or greater than three. For example, if the number of linear motors 4 in the linear motor unit 1A is five, the first linear motors 4A and the second linear motors 4B can be arranged symmetrically about the axis of the central linear motor 4, by alternately arranging the first linear motors 4A and the second linear motors 4B as shown in FIG. 5, or by sandwiching three first linear motors 4A between two second linear motors 4B as shown in FIG. 6. In particular, when the first linear motors 4A and the second linear motors 4B are arranged alternately as shown in FIG. 5, the first linear motors 4A and the second linear motors 4B are always adjacent to each other, resulting in larger gaps between the outer tube 5 of the first linear motor 4A and the rod 6 of the second linear motor 4B and between the rod 6 of the first linear motor 4A and the outer tube 5 of the second linear motor 4B. This allows space to be secured between the linear motors 4, 4 to fit tools, facilitating assembly of the linear motor unit 1. The specific number of linear motors 4 may be determined appropriately depending on the thrust required for the linear motor unit 1A and the space available for installing the linear motor unit 1A.

[0064] Furthermore, when n is an odd number greater than or equal to 3, if, of the n linear motors 4, (n-1)×½ linear motors 4 are designated as first linear motors 4A (first actuators) and the remaining linear motors 4 are designated as second linear motors 4B (second actuators), the difference in number between the positive-direction first linear motors 4A and the negative-direction second linear motors 4B will be just 1. Therefore, the difference in mass between both sides of center line C, which passes through the center of the extension / contraction direction of linear motor unit 1A in a direction intersecting the axial direction of each linear motor 4, is smaller than in the past, and therefore the rotational moment generated around the axis of center line C for linear motor unit 1A is smaller than in the past.

[0065] Furthermore, if the number of linear motors 4 is n, which is an odd number greater than or equal to three, the first linear motor 4A and the second linear motor 4B can be arranged so as to be symmetrical about the axis D of the linear motor 4 that is located in the center of the n linear motors 4, as in the case of three linear motors.

[0066] Therefore, when the linear motor unit 1A is divided into four regions separated by the axis D and the center line C that crosses the center of the extension direction of the linear motor unit 1A, the difference in weight between the regions is smaller than when the first linear motor 4A and the second linear motor 4B are arranged asymmetrically on either side of the axis D of the linear motor 4 located in the center, and therefore the force that twists the linear motor unit 1 is smaller.

[0067] However, the first linear motor 4A and the second linear motor 4B do not have to be arranged symmetrically with respect to the axis D of the linear motor 4 arranged in the center.

[0068] Furthermore, although not shown, the linear motor unit 1A of the second embodiment may also be configured in the same way as the linear motor unit 1 of the first embodiment, with two linear motor groups (actuator groups) each consisting of a plurality of linear motors 4 arranged in parallel, stacked one above the other, as shown in Fig. 3. In this way, it is possible to increase the number of linear motors 4 as actuators and increase the thrust of the linear motor unit 1A while preventing the linear motor unit 1A from becoming too large in the lateral direction (the direction transverse to the extension / contraction direction of the linear motor unit 1A).

[0069] In this case, the linear motors 4 in the two linear motor groups may be arranged so that the first linear motor 4A and the second linear motor 4B face each other above and below. In this way, the masses on both sides of the center line C, which passes through the center of the linear motor unit 1A in the extension / contraction direction in a direction transverse to the axial direction of each linear motor 4, are balanced, thereby preventing the generation of a rotational moment around the axis of the center line C with respect to the linear motor unit 1A. However, the linear motors 4 in the linear motor groups arranged above and below may also be arranged so that the first linear motors 4A, 4A or the second linear motors 4B, 4B face each other above and below. The number of linear motor groups arranged to overlap above and below may be three or more.

[0070] Furthermore, in the linear motor unit 1A as an actuator unit of this embodiment, a linear motor 4 is used as the actuator, but the actuator is not limited to the linear motor 4 as long as it has an outer tube 5 and a rod 6 inserted into the outer tube 5 so as to be movable in the axial direction and is extendable and retractable. For example, instead of the linear motor 4, an electric actuator may be used which extends and retracts by driving an electric motor to move a rod in the axial direction within the outer tube.

[0071] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims. [Explanation of symbols]

[0072] 1, 1A···Linear motor unit (actuator unit), 2···One side bracket, 3···Other side bracket, 4···Linear motor (actuator), 4A···First linear motor (first actuator), 4B···Second linear motor (second actuator), 5···Outer tube, 6···Rod, S···Virtual line, D···Axis line

Claims

1. One side bracket; a second bracket facing the first bracket; an even number of actuators, each having an outer tube and a rod inserted into the outer tube so as to be axially movable, and arranged in parallel with one another at predetermined intervals between the one bracket and the other bracket; Among the even number of actuators, half of the actuators are designated as first actuators and the remaining half are designated as second actuators, the first actuator has a tip end of the rod connected to the one-side bracket and an end of the outer tube opposite to the rod connected to the other-side bracket, The second actuator has an end of the outer tube opposite to the rod connected to the one-side bracket and a tip of the rod connected to the other-side bracket. An actuator unit characterized by:

2. One side bracket; a second bracket facing the first bracket; an outer tube; and n actuators, n being an odd number equal to or greater than 3, each having a rod inserted into the outer tube so as to be axially movable, the n actuators being arranged in parallel at predetermined intervals between the one bracket and the other bracket; Among the n actuators, (n-1)×½ actuators are defined as first actuators, and the remaining actuators are defined as second actuators, the first actuator has a tip end of the rod connected to the one-side bracket and an end of the outer tube opposite to the rod connected to the other-side bracket, The second actuator has an end of the outer tube opposite to the rod connected to the one-side bracket and a tip of the rod connected to the other-side bracket. An actuator unit characterized by:

3. the number of actuators is a multiple of four, The same number of first actuators and second actuators are arranged on both sides of an imaginary line that divides the actuators in half.

2. The actuator unit according to claim 1.

4. The first actuator and the second actuator are arranged so as to be symmetrical with respect to the axis of the actuator arranged in the center among the n actuators.

3. The actuator unit according to claim 2.

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