JP7481095B2 - Spindle Unit - Google Patents

Description

The present invention relates to a spindle device.

Conventionally, spindle devices are known that rotate tools to perform machining, and have tools attached to a freely rotatable main shaft in a replaceable manner.

For example, Patent Document 1 describes a spindle device that includes a hollow spindle supported rotatably in a housing, a collet chuck attached to the tip region of the hollow portion of the spindle, a drawbar built into the hollow portion of the spindle and connected to the rear end of the collet chuck, and a biasing means for biasing the drawbar toward the rear of the hollow portion. The collet chuck has a chuck portion that clamps and fixes a tool from the outside, and the drawbar is supported within the spindle by the collet chuck and the biasing means and rotates integrally with the spindle.

In this spindle device, the chuck portion of the collet chuck is tightened and the tool is clamped by pulling the drawbar axially toward the base end of the spindle (the side opposite the tip of the spindle where the tool is attached) relative to the spindle. In addition, the chuck portion of the collet chuck is released and the tool is unclamped by pushing the drawbar toward the tip side against the biasing means.

Japanese Patent Application Laid-Open No. 7-237068

In the spindle device described above, a gap is provided between the inner peripheral surface of the spindle and the outer peripheral surface of the drawbar to allow the drawbar to move axially relative to the spindle. When the spindle rotates, the gap causes the drawbar to vibrate within the hollow portion of the spindle, and at high speeds the vibration of the drawbar increases, causing noise. In addition, if the shape of the drawbar or spindle is changed to suppress the vibration, this leads to a change in the size of the entire spindle device, which causes a problem of losing the sense of size.

The present invention was made in consideration of the above problems, and aims to provide a spindle device that can suppress the increase in vibration of the drawbar when the main shaft is rotated at high speed, without changing the size of the device.

To achieve the above object, the spindle device according to the present invention comprises a spindle having a hollow portion, rotatably supported in a housing, and a tool attached to the tip portion, and a drawbar built into the hollow portion of the spindle and movable in the axial direction of the spindle within the hollow portion, and the tool attached to the tip portion of the spindle can be replaced by moving the drawbar in the axial direction. The spindle device is characterized in that it has a loading member that is loaded into the gap between the inner peripheral surface of the spindle and the outer peripheral surface of the drawbar, and has elasticity at least in the radial direction of the spindle to allow the drawbar to move in the axial direction.

According to the above spindle device, a loading member having radial elasticity is present in the gap between the inner peripheral surface of the spindle and the outer peripheral surface of the drawbar. When the spindle rotates at high speed and the drawbar vibrates within the hollow portion of the spindle, the loading member can absorb the vibration, thereby suppressing the vibration of the drawbar. In addition, since this loading member allows the drawbar to move in the axial direction, it does not impede the axial movement of the drawbar when changing tools. Furthermore, since vibration can be suppressed by placing the loading member in the gap between the spindle and the drawbar without changing their shapes, the size of the device is not compromised.

The spindle device of the present invention can suppress vibrations of the drawbar that occur when the main shaft is rotated at high speed without changing the size of the spindle device.

FIG. 2 is a front view of a processing apparatus equipped with a spindle device according to the present invention. FIG. 2 is a front view showing the processing apparatus shown in FIG. 1 with a cover closed; FIG. 3 is a cross-sectional view of a motor unit of the spindle device. FIG. 4 is an enlarged cross-sectional view of the area surrounded by X in FIG. 3 . 4A and 4B are a plan view and a cross-sectional view of an elastic body.

Figure 1 is a front view of a processing device 80 equipped with a spindle device 10 according to the present invention, and Figure 2 is a front view showing the processing device 80 shown in Figure 1 with a cover 84 closed. The processing device 80 is a device that cuts a workpiece such as a dental ceramic material or a dental resin material. The processing device 80 includes a case body 82, a cover 84, a spindle device 10, a spindle movement device 86, a tool magazine 88, and a control unit 19. The spindle device 10, the spindle movement device 86, and the tool magazine 88 are housed inside the case body 82. The spindle device 10 cuts the workpiece by rotating and driving a cutting tool 11 (hereinafter simply referred to as "tool 11") detachably attached to the main shaft 20.

In the following description of the processing device 80, left, right, up, and down refer to the left, right, up, and down directions as seen by a user standing in front of the processing device 80. Additionally, the front side of the processing device 80 is referred to as the front, and the rear side is referred to as the rear.

The case body 82 includes a bottom wall portion 82a, a left wall portion 82b, a right wall portion 82c, an upper wall portion 82d connecting the upper ends of the left wall portion 82b and the right wall portion 82c, and a rear wall portion connecting the rear ends of the bottom wall portion 82a, the left wall portion 82b, the right wall portion 82c, and the upper wall portion 82d. The case body 82 is formed in a box shape surrounded by these walls and has a storage space inside. An opening 81 is formed in the front portion, which is the front face of the case body 82.

The cover 84 is formed in a rectangular plate shape capable of closing the opening 81. The cover 84 is configured to be slidable up and down relative to the case body 82 by a slide mechanism 83 provided on the front side of the left wall portion 82b and the right wall portion 82c of the case body 82. The cover 84 is also provided with a window portion 84a through which the inside of the case body 82 can be viewed. The processing device 80 opens the opening 81 by sliding the cover 84 upward relative to the case body 82, and closes the opening 81 by sliding the cover 84 downward.

The spindle device 10 is an automatic tool changer (ATC) spindle device equipped with a function for attaching and detaching the tool 11, and includes a motor unit 12 that rotates the tool 11 attached to the spindle 20, and an actuator unit 18 for replacing the tool 11.

Figure 3 is a cross-sectional view of the motor section 12 of the spindle device 10. The motor section 12 includes a housing 13, a rotor 14 that can rotate within the housing 13, and a stator 15 that is fixed to the housing 13. The rotor 14 includes a main shaft 20, a draw bar 30, an elastic body 40 that is a loading member loaded between the main shaft 20 and the draw bar 30, a collet chuck 50, a biasing means 56, and a permanent magnet 58. Note that in Figure 3, the draw bar 30 and the elastic body 40 are shown in a non-cross-sectional state, and the elastic body 40 is marked with a dot.

The housing 13 is a case that contains the rotor 14 and the stator 15 and is formed in a substantially cylindrical shape. A bearing 28 that rotatably supports the rotor 14 is attached to the housing 13.

The spindle 20 is a hollow shaft member, for example made of a metallic material, and is rotatably supported in the housing 13 via a bearing 28. The drawbar 30 is a solid shaft member, for example made of a metallic material, and is inserted into the hollow portion 22 of the spindle 20. In the following description, the direction in which the central axis of the spindle 20 extends in the spindle device 10 is referred to as the axial direction Z, the side of the spindle device 10 in the axial direction Z where the tool 11 is attached is referred to as the tip side, and the opposite side of the tip (the side where the actuator unit 18 is attached in FIG. 3) is referred to as the base side.

The hollow portion 22 of the spindle 20 has a tapered hole 23 at its tip, which is tapered so that the inner diameter increases toward the tip. A cylindrical collar 28 is attached to the base end of the spindle 20 via a flange member 26 so as to be coaxial with the spindle 20. The inner diameter of the collar 28 is set to be larger than the inner diameter of the hollow portion 22 of the spindle 20. The tool 11 is attached to the tip of the spindle 20 via a collet chuck 50 inserted into the hollow portion 22.

The drawbar 30 is disposed between the actuator 18 and the collet chuck 50, and transmits the power from the actuator 18 to the collet chuck 50. The drawbar 30 is configured to be movable in the axial direction Z within the hollow portion 22 while being centered so that its central axis coincides with the central axis of the spindle 20. Specifically, the outer diameter of the drawbar 30 is set smaller than the inner diameter of the spindle 20 so that it can move in the axial direction Z within the hollow portion 22 of the spindle 20. The drawbar 30 of this embodiment is centered and held by the collet chuck 50 that supports the tip end and the biasing means 56 that supports the base end when the spindle 20 rotates, and is fixed to the spindle 20 via the collet chuck 50 and the biasing means 56 when the spindle 20 rotates. A nut 36 having a flange 37 is screwed onto the base end of the drawbar 30.

The biasing means 56 biases the drawbar 30 toward the base end in the axial direction Z of the spindle 20. In this embodiment, the biasing means 56 is attached to the outer periphery of the drawbar 30 so as to be disposed inside the collar 28. For example, a coil spring or a disc spring that can be attached to the outer periphery of the drawbar 30 can be used as the biasing means 56. The biasing means 56 has a tip portion fixed to the flange member 26 and a base portion abutting against the flange portion 37 of the nut 36, biasing the nut 36 toward the actuator portion 18. The drawbar 30 is constantly biased toward the base end of the spindle 20 by the biasing means 56 via the nut 36.

The collet chuck 50 is a tool holding member that is incorporated into the hollow portion 22 of the spindle 20 to hold the tool 11, and includes a cylindrical body portion 52 and a tapered chuck portion 54 that is connected to the body portion 52 and has an outer diameter that gradually increases. The body portion 52 is provided with a locking recess 53 into which the tip of the draw bar 30 is inserted and fixed. The chuck portion 54 is a portion that holds the tool 11, and is configured to be expandable and contractible so that the tool 11 can be tightened from the outside. The collet chuck 50 is incorporated into the spindle 20 so that the body portion 52 is accommodated in the hollow portion 22 of the spindle 20 and the outer peripheral surface of the chuck portion 54 abuts against the inner peripheral surface of the tapered hole 23 of the spindle 20. In the assembled state, the central axis of the chuck portion 54 and the body portion 52 of the collet chuck 50 coincides with the central axis of the spindle 20. By moving the collet chuck 50 toward the tip end in the axial direction Z within the hollow portion 22, the chuck portion 54 expands in diameter along the inner surface of the tapered hole 23, and enters an unclamped state that releases the tool 11. By moving the collet chuck 50 toward the base end in the axial direction Z, the chuck portion 54 contracts in diameter along the inner surface of the tapered hole 23, and enters a clamped state that tightens and fixes the tool 11.

Figure 4 is an enlarged cross-sectional view of the area surrounded by X in Figure 3. The elastic body 40 is loaded into the gap S between the inner peripheral surface 24 of the spindle 20 and the outer peripheral surface 32 of the drawbar 30, and has elasticity in the radial direction of the spindle 20 (the same as the radial direction of the drawbar 30) in the loaded state, and allows movement in the axial direction Z of the drawbar 30. The elastic body 40 can be formed of, for example, a rubber material or a foam material, and is preferably annular in shape surrounding the outer periphery of the drawbar 30. In this embodiment, the elastic body 40 is formed of a rubber O-ring formed in an annular shape as shown in Figure 5, and this O-ring is attached to the outer periphery of the drawbar 30.

In this embodiment, the elastic body 40 is in linear contact with the inner peripheral surface 24 of the spindle 20 in the circumferential direction by setting the width dimension W relatively small. In order to make the elastic body 40 in linear contact, the width dimension W of the elastic body 40 is preferably set to three times or less the radial thickness dimension D of the elastic body 40, and more preferably set to two times or less the thickness dimension D. In the installed state, the elastic body 40 is preferably in contact with both the inner peripheral surface 24 of the spindle 20 and the outer peripheral surface 32 of the draw bar 30. In this embodiment, the elastic body 40 is in a normal state, being slightly crushed by the inner peripheral surface 24 and the outer peripheral surface 32 and elastically deformed in the radial direction, that is, being pressed by the spindle 20 and the draw bar 30.

The cross-sectional shape of the elastic body 40 can be selected as appropriate, such as a circular shape or an elliptical shape. In this embodiment, an elastic body 40 with a circular cross-section is used.

At least one elastic body 40 is arranged on the outer peripheral surface of the drawbar 30, and in this embodiment, four elastic bodies 40-1 to 40-4 are arranged at intervals in the axial direction Z. When multiple elastic bodies 40 are arranged, the number is not limited to four and can be two or more. Furthermore, multiple elastic bodies 40 may be arranged adjacent to each other in the axial direction Z, but it is preferable to arrange them at intervals. Furthermore, it is preferable that the separation distance L between adjacent elastic bodies 40 (the distance between areas in the axial direction Z where no elastic body 40 is arranged, as shown in FIG. 4) is equal to or greater than the width dimension W of the elastic body 40.

The elastic body 40 may be located anywhere between the members supporting both ends of the draw bar 30 (in this embodiment, between the collet chuck 50 supporting the tip end and the biasing means 56 supporting the base end), but is preferably located at least in the central region in the axial direction Z of the draw bar 30. Here, the central region refers to the central region when the space between the members supporting both ends of the draw bar 30 (in this embodiment, between the base end edge 50a of the collet chuck 50 and the tip end edge 56a of the biasing means 56) is divided into three equal parts in the axial direction Z when the spindle device 10 holds the tool 11. In this embodiment, the two elastic bodies 40-3 and 40-4 are located in the central region of the draw bar 30.

Although not shown, it is preferable that at least one elastic body 40 is disposed in the central region of the drawbar 30 and in each of the regions on both sides of the central region.

The elastic body 40 may be stretchable in the radial direction of the drawbar 30 when loaded into the gap S and may suppress radial displacement of the drawbar 30, and its shape is not limited to annular. As an example, the elastic body 40 may be an arc-shaped body attached to the outer peripheral surface 32 of the drawbar 30 or the inner peripheral surface 24 of the main shaft 20.

The permanent magnets 58 form a magnetic flux for rotating the rotor 14 and are fixed to the outer peripheral surface of the main shaft 20. The stator 15 includes a substantially cylindrical stator core 16 arranged coaxially with the main shaft 20 of the rotor 14 so as to surround the rotor 14, and a coil 17 wound around the stator core 16. The permanent magnets 58, together with the energized coils 17, generate a magnetic field to generate torque (rotational force) that rotates the rotor 14.

The actuator unit 18 applies an external force F that presses the drawbar 30 toward the tip of the main shaft 20 in the axial direction Z. The actuator unit 18 can be, for example, a power cylinder (e.g., a hydraulic cylinder) having a piston rod that applies a pressing force in the axial direction Z.

The spindle movement device 86 moves the spindle device 10 within the storage space of the case body 82, and can move the spindle device 10 in the left-right direction or up-down direction (the direction that coincides with the axial direction Z of the spindle device 10) of the processing device 80, for example, using a guide member that guides the movement of the spindle device 10 and a drive device that moves the spindle device 10 along the guide member.

The tool magazine 88 is formed in a box shape with multiple tool storage holes formed inside, and these tool storage holes store tools 11 that can be attached to the spindle device 10 in a freely replaceable manner.

The control unit 19 is electrically connected to the spindle device 10 and the spindle movement device 86, and the spindle device 10 controls cutting by the control unit 19. The control unit 19 is configured with an information processing means such as a central processing unit (CPU), storage means such as a read only memory (ROM) and a random access memory (RAM), an input/output interface, and devices that connect these.

Next, the operation of the spindle device 10 described above will be described. When the control unit 19 operates the actuator unit 18 to apply an external force F to the draw bar 30 in a state where the tool 11 is attached to the spindle 20 (i.e., the tool 11 is clamped by the collet chuck 50), the draw bar 30 and the collet chuck 50 move toward the tip side in the axial direction Z in the hollow portion 22 against the biasing force of the biasing means 56. Then, following this movement, at least a part of the chuck portion 54 protrudes outside the spindle 20 and expands in diameter, and the tool 11 is in an unclamped state. The movement of the draw bar 30 toward the tip side is restricted by the flange portion 37 of the nut 36 abutting against the collar 28. When the external force F from the actuator unit 18 is released, the biasing means 56 moves the draw bar 30 and the collet chuck 50 toward the base end side in the axial direction Z in the hollow portion 22. Following this movement, the chuck portion 54 contracts in diameter, clamping the tool 11. When clamped, the collet chuck 50 is fixed inside the spindle 20 by the chuck portion 54 abutting and engaging with the inner circumferential surface of the tapered hole 23 of the spindle 20. In addition, the spindle device 10 rotates the rotor 14 by passing a current through the coil 17 to generate a magnetic field. The rotation of the rotor 14 can be controlled by the control unit 19.

When replacing the tool 11 attached to the spindle device 10 in the processing device 80, the spindle device 10 is moved to the position of the tool magazine 88 by the spindle movement device 86. Next, the tool 11 held in the collet chuck 50 is unclamped and returned to the tool storage hole of the tool magazine 88. After that, the spindle device 10 is moved to a position above the next tool 11 to be used, and the upper end of the tool 11 to be used is held by the collet chuck 50.

When the spindle device 10 drives the motor unit 12 with the tool 11 attached and rotates the rotor 14, the tool 11 rotates around the central axis of the spindle 20. As described above, a gap S is formed between the inner peripheral surface 24 of the spindle 20 and the outer peripheral surface 32 of the drawbar 30 to allow the drawbar 30 to slide in the axial direction Z, and due to the influence of this gap S, the drawbar 30 tries to displace in the hollow portion 22 when the spindle 20 is rotated. When the rotation speed of the spindle 20 increases (for example, the rotation speed is 60,000 rpm or more), the drawbar 30 vibrates in the hollow portion 22 due to the influence of the gap S, and when the vibration becomes large, noise is generated. However, in the above-mentioned spindle device 10, an elastic body 40 is disposed in the gap S, so that the vibration of the drawbar 20 can be absorbed by the elastic body 40 that expands and contracts in the radial direction. This suppresses the vibration of the drawbar 20, and it is possible to prevent the generation of noise during high-speed rotation due to the vibration. Furthermore, if the vibration of the drawbar 20 increases, this vibration is transmitted to the spindle 20 and the tool 11, reducing the accuracy of the cutting process performed by the tool 11; however, the vibration can be suppressed by the elastic body 40, improving the machining accuracy during high-speed rotation.

In particular, since the elastic body 40 is normally pressed by the main shaft 20 and the drawbar 30, when the drawbar 30 attempts to displace, the elastic body 40 can instantly suppress this displacement. Therefore, vibration of the drawbar 30 can be effectively suppressed not only when the main shaft 20 is rotating at high speed, but also when it is rotating at low speed.

In addition, because the elastic body 40 allows the draw bar 30 to move in the axial direction Z within the hollow portion 22, it does not impede the movement of the draw bar 30 in the axial direction Z when replacing the tool 11. For example, if the gap S is filled with a highly rigid material such as a metal material, friction may increase and the movement of the draw bar 30 may be impeded, but by using an elastic body 40 that is flexible in the radial direction, it is possible to reduce friction and permit the movement of the draw bar 30.

In addition, in the spindle device 10 of this embodiment, vibration can be suppressed with a simple structure of placing an elastic body 40 in the gap S without changing the shape or structure of the drawbar 30 or the main shaft 20 from the conventional ones, and there is no need to change the size of the spindle device 10 to suppress vibration. Therefore, it is possible to reduce noise from the spindle device 10 and improve machining accuracy during high-speed rotation without compromising the size of the conventional device.

The elastic body 40 may be in planar contact with the inner circumferential surface 24 of the spindle 20 by increasing the width dimension W (e.g., a dimension equal to or greater than the diameter of the drawbar 30); however, as in this embodiment, the width dimension W is reduced to make linear contact with the inner circumferential surface 24, thereby reducing the frictional resistance when the drawbar 30 moves within the hollow portion. In this embodiment, the width dimension W of the elastic body 40 is set to be equal to or less than the radius of the drawbar 30, thereby sufficiently reducing the frictional resistance when the drawbar 30 moves in the axial direction Z.

In addition, if the cross-sectional shape of the elastic body 40 is a square or triangle with corners, a large frictional force is generated at the corners when the drawbar 30 is moved in the axial direction Z, but by making the cross-section of the elastic body 40 circular or elliptical, the frictional force can be suppressed and the movement of the drawbar 30 can be made smoother. In addition, by making the cross-sectional shape circular or elliptical, it is possible to easily attach the elastic body 40 to the drawbar 30 and assemble the drawbar 30 and the elastic body 40 to the spindle 20.

In addition, by arranging multiple elastic bodies 40 at intervals in the axial direction Z of the drawbar 30, the number of points at which the elastic bodies 40 support the drawbar 30 increases, thereby improving the effect of suppressing vibration of the drawbar 30.

In addition, in this embodiment, the elastic body 40 is disposed in the central region of the axial direction Z of the drawbar 30, so that vibrations in the central region where radial displacement of the drawbar 30 becomes large can be effectively suppressed. In particular, when the number of elastic bodies 40 is reduced to improve the movement of the drawbar 30 in the axial direction Z, it is possible to effectively suppress radial vibrations while suppressing frictional resistance by disposing the elastic body 40 in the central region of the axial direction Z. Although not shown, when three or more elastic bodies 40 are disposed, vibrations can be more effectively suppressed by disposing one or more in each of the central region and the regions on both sides thereof.

In this way, the spindle device 10 of this embodiment can suppress the generation of vibrations with a simple structure in which an elastic body 40 is placed in a conventional spindle device, and by placing the elastic body 40, it is possible to reduce the peak value of vibrations of the drawbar 30 by 50% to 75% when the main shaft 20 rotates at high speeds of 60,000 rpm or more, compared to conventional devices in which the elastic body 40 is not placed.

To verify the effects of the present invention, tests were conducted to evaluate the vibrations that occur when the spindle rotates at high speed using spindle devices according to the invention example and comparative example. The spindle device of the invention example was configured as shown in Figure 3, and the elastic body attached to the drawbar was a rubber O-ring, arranged as shown in Figure 3. In the comparative example, no elastic body was attached, and the other configurations were the same as those of the invention example. In each of the invention example and comparative example, an acceleration sensor was attached to the housing of the motor part of the spindle device, and vibrations were evaluated by measuring the peak value of the radial acceleration of the drawbar. The evaluation results are shown in Table 1.

As shown in Table 1, the spindle device of the invention example has a 75% reduction in peak acceleration value compared to the spindle device of the comparative example, demonstrating that it has a high vibration suppression effect despite having a simple structure that only requires the attachment of an elastic body.

The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the invention.

For example, in the present invention, the loading member loaded into the gap S is not limited to the elastic body 40, which itself has elasticity, but may be any member that has elasticity in the radial direction of the drawbar 30 (i.e., the radial direction of the main shaft 20) in the loaded state and can suppress the displacement of the drawbar 30 inside the hollow portion 22, and may be a spring that can expand and contract in the radial direction when loaded into the gap S.

REFERENCE SIGNS LIST 10 Spindle device 11 Tool 12 Motor section 13 Housing 14 Stator 15 Rotor 18 Actuator section 19 Control section 20 Spindle 30 Draw bar 36 Nut 40 Elastic body (loading member)
50 Collet chuck 56 Pressing means 80 Processing device

Claims (6)

a main shaft having a hollow portion, rotatably supported by the housing, and having a tool attached to a tip end thereof;
a draw bar that is incorporated in the hollow portion of the spindle and is movable in the axial direction of the spindle within the hollow portion,
A spindle device in which a tool attached to a tip of the main shaft can be replaced by moving the draw bar in the axial direction,
a biasing means for biasing the drawbar in the axial direction;
a loading member that is loaded in a gap between an inner peripheral surface of the spindle and an outer peripheral surface of the draw bar in a state of not contacting the biasing means, and that has elasticity at least in a radial direction of the spindle to allow movement of the draw bar in the axial direction ,
The spindle device , wherein the loading member is disposed at least in a central region of the draw bar in the axial direction . a main shaft having a hollow portion, rotatably supported by the housing, and having a tool attached to a tip end thereof;
a draw bar that is incorporated in the hollow portion of the spindle and is movable in the axial direction of the spindle within the hollow portion,
A spindle device in which a tool attached to a tip of the main shaft can be replaced by moving the draw bar in the axial direction,
a biasing means for biasing the drawbar in the axial direction;
a loading member that is loaded in a gap between an inner peripheral surface of the spindle and an outer peripheral surface of the draw bar in a state of not contacting the biasing means, and that has elasticity at least in a radial direction of the spindle to allow movement of the draw bar in the axial direction ,
A spindle device comprising a plurality of the loading members arranged at intervals in the axial direction . the loading member is an annular elastic body attached to an outer circumferential surface of the draw bar,
3. The spindle device according to claim 1, wherein the elastic body has a width dimension set to be three times or less than its radial thickness dimension, and is in linear contact with the inner peripheral surface of the main shaft. the loading member is a single elastic body attached to an outer circumferential surface of the draw bar and formed in an annular shape,
4. The spindle device according to claim 1, wherein the elastic body contacts an outer circumferential surface of the draw bar and an inner circumferential surface of the main shaft. 5. The spindle device according to claim 1 , wherein the loading member is normally pressed by the main shaft and the draw bar. 6. The spindle device according to claim 1, wherein the loading member has a cross section that is circular or elliptical.

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