Non-contact power supply device for tool holders

Abstract

To provide a contactless power supply device for a tool holder that can efficiently supply energy without contact and can easily reduce the size.SOLUTION: In a machining center 12, a contactless power supply device 10 includes: a power sending coil unit 56 attached to a main shaft housing 20; and a power receiving coil unit 58 arranged in the outer periphery surface of the tool holder 26. The contactless power supply device supplies energy in a contactless manner to an actuator 36 internally attached to a body part 32 of the tool holder. A power sending coil unit is divided in at least two units and is provided with a plurality of secondary coils 76a and 76b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a contactless power supply device for supplying energy in a contactless manner to an actuator installed in an exchangeable tool holder that is connected to a spindle and rotates. [Background technology]

[0002] In general, various machine tools are used to process workpieces using tools, such as machining tools, attached to tool holders. In this case, the machine tools are usually incorporated into a working machine that has functions and mechanisms that work in conjunction with the operation of the machine tools.

[0003] Typically, machining centers are equipped with tool holders that are changed by an automatic tool changer (ATC), and the tool holders may be equipped with actuators such as motors and electronic circuits. For example, in boring processes, actuators are used that can correct the position of the cutting edge of the boring tool in the radial direction in micron units as the cutting edge of the boring tool wears.

[0004] In this case, a configuration is known in which a battery is mounted in the tool holder to supply power energy (electrical energy) to the actuator, but the battery has a limited capacity and must be replaced or recharged after use, which results in a problem that the efficiency of the entire machining operation is not improved.

[0005] Therefore, an electromagnetic induction system is used to supply power to the actuator in a contactless manner. In this electromagnetic induction system, a power transmission coil (power supply coil) is fixed to a fixed portion on the spindle side, while a power receiving coil is provided on the tool holder side. Then, while the tool holder and the power receiving coil are rotating, power is supplied from the power transmission coil to the power receiving coil in a contactless manner. This type of technology is described, for example, in Patent Document 1.

[0006] [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3252996 Summary of the Invention [Problem to be solved by the invention]

[0008] In the above-mentioned Patent Document 1, as a method for transmitting power and control signals of a servo motor, a first transmission unit is provided near the tip of the spindle, and a second transmission unit 32 is provided in the gripping part of the boring device. However, it is only stated that the first transmission unit and the second transmission unit can be configured with a non-contact type short-circuiting device, and the specific configuration is unclear.

[0009] Furthermore, in a machining center, when a tool holder is replaced by an ATC, there is a risk that the power transmission coil (first transmission unit) on the spindle side may interfere with the ATC arm. However, the above-mentioned Patent Document 1 cannot avoid interference with the ATC arm, which is a problem that makes it impractical.

[0010] The present invention has been made to solve this type of problem, and has an object to provide a contactless power supply device for a tool holder that can efficiently supply energy in a contactless manner and can be easily made smaller, particularly in a machining center or the like. [Means for solving the problem]

[0011] A contactless power supply device for a tool holder according to the present invention supplies energy to an actuator in a machine tool having an exchangeable tool holder that rotates connected to a spindle and has an actuator built in, and a fixed part that rotatably supports the spindle. The contactless power supply device includes a power transmitting coil unit attached to the fixed part, and a power receiving coil unit that is disposed on the outer circumferential surface of the tool holder and rotates integrally with the tool holder.

[0012] The power transmission coil unit has an arc-shaped primary coil that is disposed opposite the outer circumferential surface of the tool holder. and a circular arc-shaped first magnetic core, and the primary coil is wound around the inner and outer circumferential surfaces of the first magnetic core. The power receiving coil unit is divided into two or more parts, and as a whole it surrounds the outer circumferential surface of the tool holder, and has multiple secondary coils that are arranged concentrically with the primary coil. and a plurality of arc-shaped second magnetic cores, and the secondary coil is wound around the inner and outer circumferential surfaces of the second magnetic cores. The inner peripheral surface of the primary coil and the outer peripheral surface of the secondary coil are parallel to the rotation axis of the spindle and face each other, and power is supplied contactlessly. [Effects of the Invention]

[0013] In the contactless power supply device according to the present invention, the primary coil has an arc shape, which can prevent the primary coil from interfering with the tool holder replacement operation by the ATC, for example. Moreover, the secondary coil facing the arc-shaped primary coil is divided into two or more parts, and as a whole, goes around the outer circumferential surface of the tool holder.

[0014] Here, for example, when a single secondary coil having a circular shape is used, power loss occurs due to current flowing throughout the non-coupled portion of the secondary coil that is not coupled (opposed) to the primary coil. Therefore, power discharge occurs throughout the non-coupled portion, which may reduce power transmission efficiency. In contrast, in the present invention, the secondary coil is divided into two or more portions, which effectively reduces the non-coupled portion through which current flows, enabling efficient energy supply.

[0015] Furthermore, in the present invention, the inner peripheral surface of the primary coil and the outer peripheral surface of the secondary coil are parallel to the rotation axis of the spindle and face each other, which prevents the components from expanding in the radial direction of the tool holder, making it easy to reduce the size of the entire tool holder. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic perspective view of a vertical machining center to which a contactless power supply device according to an embodiment of the present invention is applied; [Figure 2] FIG. 2 is a cross-sectional explanatory view of a main part of a tool holder that constitutes the machining center. [Figure 3] FIG. 2 is a perspective view of a main part of a power transmission coil unit that constitutes the contactless power supply device. [Figure 4] This is an explanatory diagram of the working area of ​​the ATC arm. [Figure 5] 3A and 3B are diagrams illustrating the configuration of the power transmitting coil unit and the power receiving coil unit. [Figure 6] FIG. 2 is a perspective view illustrating an internal configuration of the power transmission coil unit. [Figure 7] FIG. 10 is a schematic configuration diagram of a contactless power supply device for comparative explanation. [Figure 8] FIG. 10 is a diagram illustrating the efficiency when a secondary coil divided into two is used. [Figure 9] FIG. 10 is a diagram illustrating the efficiency when a secondary coil divided into three parts is used. [Figure 10] FIG. 10 is a diagram illustrating the efficiency when a secondary coil divided into four sections is used. [Figure 11] FIG. 1 is an explanatory diagram of a vertical machining center as a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0017] 1, a contactless power supply device 10 according to an embodiment of the present invention is applied to a vertical machining center (machine tool) 12. The contactless power supply device 10 according to the present invention can be adopted in various machine tools such as a transfer machine in addition to the vertical machining center 12, and these machine tools are incorporated into a work machine (not shown).

[0018] The vertical machining center 12 is equipped with a processing table 14 on which a workpiece to be processed (not shown) is placed, and the processing table 14 is movable in the X-axis and Y-axis directions. A column 16 constituting the vertical machining center 12 is provided with a spindle slide 18 that can move back and forth (up and down) in the Z-axis direction, and a spindle housing (fixed part) 20 is disposed on the spindle slide 18.

[0019] 2, a spindle 22 connected to a drive source (not shown) is rotatably mounted within the spindle housing 20 via two sets of front and rear bearings 24. A tool holder 26 is detachably mounted on the front end (lower end) of the spindle 22 via an automatic transmission cable (ATC) (not shown).

[0020] The tool holder 26 has a shank portion 28 that is fitted onto the front end of the spindle 22, and a cylindrical portion 30 and a main body portion 32 are coaxially provided on the front end side of the shank portion 28. A circular electronic board 34 is mounted inside the cylindrical portion 30, and a coolant tube 35 is fitted into the center of the electronic board 34. The electronic board 34 is equipped with a rectifier circuit, a voltage stabilization circuit, and a safety mechanism that stably extract power (electrical energy) from the wireless power transfer device 10 (described later), as well as a control circuit that controls the power to the actuator 36.

[0021] The actuator 36 is housed within the main body 32 and includes a motor 38. A pulley 40 is attached to a rotary shaft 38a of the motor 38, and a timing belt 44 is wound around the pulley 40 and a pulley 42. The pulley 42 is attached to one end of a ball screw 46, and the ball screw 46 is supported within the main body 32 so as to be freely rotatable.

[0022] The ball screw 46 is threadedly engaged with the end of a slide table 48, and the position of the slide table 48 can be corrected in the machining radial direction (arrow S direction) that intersects with the rotational axis direction (arrow L direction) of the spindle 22 under the rotational action of the ball screw 46. A boring bar 50 is fixed to the front end of the slide table 48, and a cutting edge 52 is provided at the front end of the boring bar 50.

[0023] An antenna 54 is attached to the outer periphery of the main body 32. The antenna 54 is used for wireless communication using a device (not shown) such as Bluetooth or Wi-Fi provided inside the tool holder 26, and is connected to a communication control circuit to wirelessly control the actuator 36 from outside. The antenna 54 can also be used to notify the outside that control has been completed by the operation of the motor 38, etc.

[0024] 1 and 2, the contactless power supply device 10 includes a power transmitting coil unit 56 attached to the spindle housing 20, and a power receiving coil unit 58 disposed on the outer peripheral surface of the tool holder 26 and rotating integrally with the tool holder 26. As shown in FIGS. 2 and 3, the power transmitting coil unit 56 includes an arc-shaped mounting plate 60 attached to the front end surface of the spindle housing 20. One end (upper end) of an arm member 62 is fixed to the mounting plate 60, and a circular arc-shaped primary housing 64 is fixed to the other end (lower end) of the arm member 62.

[0025] As shown in Fig. 1, an ATC arm 66 is disposed on the front end side of the spindle 22, and the ATC arm 66 moves up and down and rotates during automatic tool change operations. As shown in Fig. 4, the non-interference region that does not interfere with the operation of the ATC arm 66 is within 130 degrees, and in this embodiment, the primary housing 64 is set to have an arc shape with a central angle of 90 degrees.

[0026] As shown in Figures 2, 5, and 6, an arc-shaped primary coil 68 is disposed within the primary housing 64. The primary coil 68 is wound around the arc-shaped first magnetic core 70 in a single or multiple rows and single layer along the inner and outer circumferential surfaces of the first magnetic core 70, so that the primary coil 68 is set to an arc shape with a central angle of 90 degrees. The primary coil 68 is made of an electric wire formed by twisting together many extremely thin copper wires, i.e., a Litz wire. This is to prevent an increase in the resistance component of the coil when the frequency used is high.

[0027] The first magnetic core 70 includes a plurality of ferrite plates 70f. As shown in FIG. 6, the ferrite plates 70f have a rectangular shape, such as a rectangle (or square), and the flat surfaces of the ferrite plates 70f are arranged along an arc. The ferrite plates 70f are arranged so that their side surfaces, which are the surfaces in the thickness direction, face each other without overlapping each other. For example, the short sides of the ferrite plates 70f are arranged in the circumferential direction, and the long sides are arranged in the radial direction. As shown in FIG. 5, a capacitor 72 is connected to the primary coil 68 to form a resonant circuit, and the primary coil 68 is connected to an AC power source (high-frequency generating power source) not shown.

[0028] 2 and 5, the power receiving coil unit 58 includes divided, for example, two-piece second housings 74a and 74b attached to the outer circumferential surface of the cylindrical portion 30 constituting the tool holder 26. The second housings 74a and 74b each have a semicircular shape with a central angle of 180 degrees, and are arranged in a ring shape as a whole. Note that a second housing divided into three or four parts may also be used.

[0029] 5, an arc-shaped secondary coil 76a is disposed within the second housing 74a, and an arc-shaped secondary coil 76b is disposed within the second housing 74b. The secondary coils 76a, 76b are wound around the outer circumferential surface of the tool holder 26 as a whole, and the ring shape is divided into, for example, two. As will be described later, in addition to the two-divided secondary coils 76a, 76b, a secondary coil divided into three or four may also be used.

[0030] The secondary coil 76a is wound around the arc-shaped second magnetic core 78a in a single or multiple single-layer winding along the inner and outer circumferential surfaces of the second magnetic core 78a, thereby forming an arc-shaped coil with a central angle of 180 degrees. The secondary coil 76b is wound around the arc-shaped second magnetic core 78b in a single or multiple single-layer winding along the inner and outer circumferential surfaces of the second magnetic core 78b, thereby forming an arc-shaped coil with a central angle of 180 degrees. The secondary coils 76a and 76b are made of Litz wire, an electric wire formed by twisting together a large number of extremely thin copper wires. This is to prevent an increase in the resistance component of the coil when the frequency used is high.

[0031] Each of the second magnetic cores 78a, 78b includes a plurality of ferrite plates 78f. The ferrite plates 78f have a rectangular shape, such as a rectangle or a square, and the flat surfaces of the ferrite plates 78f are arranged along an arc, with, for example, the short sides arranged in the circumferential direction and the long sides arranged in the radial direction. The ferrite plates 78f are arranged with their short sides, which are in the thickness direction, facing each other. A capacitor 72 is connected to each of the secondary coils 76a, 76b to form a resonant circuit. The plurality of coil windings of each of the secondary coils 76a, 76b are connected to the electronic board 34.

[0032] As shown in Fig. 5, the air gap (the spatial distance between the end face of the primary housing 64 and the end face of the second housing 74a) between the power transmitting coil unit 56 and the power receiving coil unit 58 is set to at least 1 mm. The distance between the inner circumferential surface of the inner primary coil 68 and the end face of the primary housing 64 is set to at least 1 mm, and the distance between the outer circumferential surface of the outer secondary coil 76a (76b) and the end face of the secondary housing 74a is set to at least 1 mm. As shown in Figs. 2 and 5, the inner circumferential surface of the primary coil 68 and the outer circumferential surface of the secondary coil 76a (76b) are arranged parallel to the rotation axis of the spindle 22 (direction of arrow L) and facing each other.

[0033] The operation of the machining center 12 configured as above will be described below.

[0034] 1 and 2, under the rotation of the spindle 22, the tool holder 26 is rotated while the spindle slide 18 moves downward in the Z-axis direction. A workpiece (not shown) is placed below the spindle slide 18, and the workpiece is machined by the cutting edge 52. When machining is completed, the spindle slide 18 moves upward in the Z-axis direction, and the tool holder 26 moves away from the workpiece.

[0035] Next, when the position of the cutting edge 52 is corrected in the machining radial direction (the direction of arrow S) while the tool holder 26 is rotating or stationary, power is supplied to the actuator 36 via the non-contact power supply 10. Specifically, in the power transmission coil unit 56 constituting the non-contact power supply 10, a high frequency is applied to the primary coil 68 from an AC power source (not shown). As a result, an induced electromotive force is generated in the secondary coil 76a (76b) facing the primary coil 68, and power is extracted to the electronic board 34 electrically connected to the secondary coil 76a (76b).

[0036] 2, power is supplied to a motor 38 constituting an actuator 36, causing the motor 38 to rotate. A ball screw 46 is connected to a rotary shaft 38a of the motor 38 via a pulley 40, a timing belt 44, and a pulley 42, causing the ball screw 46 to rotate in a predetermined direction. Therefore, a slide table 48 to which the ball screw 46 is threaded moves outward (or inward) in the machining radial direction (the direction of arrow S), thereby correcting the position of a cutting edge 52. The actuator 36 can be controlled from the outside via an antenna 54 via wireless communication such as Bluetooth or Wi-Fi.

[0037] In this case, in this embodiment, as shown in Fig. 5, the primary housing 64 (primary coil 68) constituting the power transmission coil unit 56 is set to have an arc shape with a central angle of 90 degrees. Therefore, when the tool holder 26 is automatically replaced by the ATC arm 66, the primary housing 64 does not interfere with the work performed by the ATC arm 66 (see Fig. 4). Moreover, it is possible to ensure a coupling area between the primary coil 68 and the secondary coils 76a, 76b, and it is possible to maintain a desired power transmission capacity.

[0038] Furthermore, as shown in Fig. 5, second housings 74a, 74b (secondary coils 76a, 76b) constituting power receiving coil unit 58 each have a semicircular shape with a central angle of 180 degrees, and are arranged in a ring shape as a whole. Here, Fig. 7 shows a schematic configuration of a contactless power transfer device 1 for comparative explanation. The contactless power transfer device 1 includes a power transmitting coil unit 56 and a power receiving coil unit 2, and the power receiving coil unit 2 uses a non-divided (ring-shaped) secondary coil 3 and second magnetic core 4.

[0039] However, in the power receiving coil unit 2, the secondary coil 3 cannot be wound along the inner circumferential surface of the ring-shaped second magnetic core 4, which halves the generated magnetic force and reduces the transmitted power. Moreover, the secondary coil 3 only forms an electromagnetic coupling portion in the range (90 degrees) that faces the arc-shaped primary coil 68, so power loss occurs due to current flowing through the non-electromagnetic coupling portion over the remaining 270-degree range, causing power discharge and reducing efficiency.

[0040] In contrast, in this embodiment, the secondary coils 76a, 76b have semicircular shapes and are arranged in a ring shape as a whole, as shown in Fig. 5. Therefore, the primary coil 68 and the secondary coil 76a face each other, and while power is being transmitted to the secondary coil 76a, power is not transmitted to the other secondary coil 76b, making it possible to effectively suppress the occurrence of power loss.

[0041] Furthermore, because the divided secondary coils 76a, 76b are electrically connected in parallel with each other, the power transmission state can be maintained even if the relative face with respect to the primary coil 68 is changed. As shown in Fig. 8, when the tool holder 26 makes one rotation, a slight decrease in efficiency occurs in the angle range (90 degrees and 270 degrees) where the primary coil 68 straddles the gap between the secondary coils 76a, 76b, but in other angle ranges, the primary coil 68 reliably faces the secondary coils 76a, 76b, making it possible to maintain maximum efficiency.

[0042] FIG. 9 shows the efficiency when the secondary coil is divided into three parts (not shown). Each secondary coil is set to an arc shape with a central angle of 120 degrees. When divided into three parts, a slight decrease in efficiency occurs only three times, but the desired efficiency can be maintained overall. FIG. 10 shows the efficiency when the secondary coil is divided into four parts (not shown). Each secondary coil is set to an arc shape with a central angle of 90 degrees. When divided into four parts, a slight decrease in efficiency occurs only four times, but the efficiency can be maintained overall.

[0043] Furthermore, in this embodiment, the air gap between the power transmitting coil unit 56 and the power receiving coil unit 58 is set to 1 mm, as shown in Fig. 5. This prevents metal chips and powder produced during machining from getting caught between the primary housing 64 and the secondary housings 74a, 74b, while preventing a decrease in the efficiency of electromagnetic coupling due to a larger air gap.

[0044] The distance between the inner peripheral surface of the inner primary coil 68 and the end face of the primary housing 64 is set to 1 mm, and the distance between the outer peripheral surface of the outer secondary coil 76a (76b) and the end face of the secondary housing 74a is also set to 1 mm. This makes it possible to protect the primary coil 68 and secondary coils 76a, 76b, to which high voltage is applied, from coolant, cutting metal chips, and the like within the machining center 12.

[0045] 2, the inner peripheral surface of the primary coil 68 and the outer peripheral surface of the secondary coil 76a (76b) are arranged parallel to the rotation axis (direction of arrow L) of the spindle 22 and face each other. Therefore, when attempting to increase the facing area of ​​the coupling portions between the primary coil 68 and the secondary coils 76a, 76b, or when attempting to ensure sufficient areas for the first magnetic core 70 and the second magnetic cores 78a, 78b, the dimension of the tool holder 26 increases only in the axial direction. Therefore, the outer diameter of the power receiving coil unit 58 does not increase relative to the outer periphery of the tool holder 26, and the effect is obtained that the entire tool holder 26 can be easily downsized.

[0046] 11, a contactless power supply device 6 applied to a vertical machining center 5, which is a comparative example, includes a power transmitting coil unit 7 attached to a spindle housing 5a and a power receiving coil unit 8 disposed on the outer peripheral surface of a tool holder 9. The power transmitting surface of the primary coil 7a constituting the power transmitting coil unit 7 and the power receiving surface of the secondary coil 8a constituting the power receiving coil unit 8 are arranged parallel to and opposite to the machining radial direction (direction of arrow S) that intersects with the spindle rotation axis (direction of arrow L).

[0047] In this configuration, when attempting to increase the coil facing area for electromagnetic coupling (the facing area between the power transmitting surface and the power receiving surface) or when attempting to ensure a sufficient area for the magnetic body, the outer diameter D of the power receiving coil unit 8 disposed on the outer peripheral surface of the tool holder 9 becomes considerably large. As a result, the diameter of the power transmitting coil unit 7 also becomes large, which hinders the ATC operating range and causes problems with the storage space in the magazine section of the tool holder 9, making it impractical. In addition, fine cutting powder scattered with the coolant easily adheres to the power receiving surface of the secondary coil 8a, which causes a problem of damage to the power transmitting coil unit 7 and the power receiving coil unit 8.

[0048] Furthermore, in this embodiment, as shown in Fig. 5, the first magnetic core 70 includes a plurality of ferrite flat plates 70f. Therefore, the first magnetic core 70 can be easily and accurately curved along the outer diameter and shape (R-shape) of the tool holder 26, with the ferrite flat plates 70f arranged closely together. Meanwhile, the second magnetic cores 78a, 78b each similarly include a plurality of ferrite flat plates 78f. Therefore, the second magnetic cores 78a, 78b can be easily and accurately curved along the outer peripheral surface of the cylindrical portion 30 that constitutes the tool holder 26. [Explanation of symbols]

[0049] 10...Non-contact power supply device 12...Machining center 18...Main shaft slide 22...Spindle 26...Tool holder 32...Main body 34...Electronic board 36...Actuator 38...Motor 46...Ball screw 48...Slide table 50...Boring bar 52...Cutting edge 54...Antenna 56... Power transmission coil unit 58... Power receiving coil unit 64...Primary housing 66...ATC arm 68...Primary coil 70...First magnetic core 70f, 78f...Ferrite plate 72...Capacitor 74a, 74b... Second housing 76a, 76b... Secondary coil 78a, 78b...Second magnetic core

Claims

1. A non-contact power supply device for a machine tool including a replaceable tool holder that is connected to a spindle to rotate and has an actuator built therein, and a fixed part that rotatably supports the spindle, the non-contact power supply device supplying energy to the actuator in a non-contact manner, a power transmission coil unit attached to the fixed portion; a power receiving coil unit disposed on an outer peripheral surface of the tool holder and rotating integrally with the tool holder; Equipped with the power transmission coil unit includes a primary coil having an arc shape and disposed opposite the outer circumferential surface of the tool holder; a first magnetic core having an arc shape, the primary coil being wound around the first magnetic core along the inner and outer circumferential surfaces, the power receiving coil unit is divided into two or more sections, and a plurality of secondary coils are arranged as a whole around the outer circumferential surface of the tool holder and concentrically with the primary coil; a plurality of arc-shaped second magnetic cores, the secondary coil being wound around the inner and outer circumferential surfaces of the second magnetic cores; an inner peripheral surface side of the primary coil and an outer peripheral surface side of the secondary coil are parallel to a rotation axis of the spindle and face each other, and power is supplied contactlessly to the inner peripheral surface side of the primary coil and the outer peripheral surface side of the secondary coil.

2. 2. The contactless power supply device for a tool holder according to claim 1, wherein the secondary coil is divided into two parts at an angle of 180 degrees.

3. 3. The contactless power supply device for a tool holder according to claim 1, wherein the primary coil is set in an arc shape with a central angle of 90 degrees.

4. 2. The contactless power supply device according to claim 1, wherein the power transmission coil unit includes a first housing in which the primary coil is accommodated in a state in which the primary coil is wound around the inner circumferential surface and the outer circumferential surface of the first magnetic core, the power receiving coil unit includes a second housing in which the secondary coil is accommodated in a state where it is wound around the inner and outer peripheral surfaces of the second magnetic core.

5. 2. The contactless power supply device according to claim 1, wherein the first magnetic core and the second magnetic core each include a plurality of ferrite flat plates; The non-contact power supply device for a tool holder is characterized in that the ferrite flat plates have their respective flat surfaces arranged along the arc shape.

6. 2. The contactless power supply device for a tool holder according to claim 1, wherein a capacitor is connected to each of the primary coil and the secondary coil to form a resonance circuit.

7. 2. The contactless power supply device for a tool holder according to claim 1, wherein the primary coil and the secondary coil are each made of a litz wire.

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