JP7745487B2 - Tool holders and machine tools - Google Patents

Description

This disclosure relates to a tool holder used to suppress vibrations generated in a tool during machining in a machine tool that performs machining while moving the tool and workpiece relative to each other, and to a machine tool equipped with such a tool holder.

In machine tools that machine a rotatable workpiece by cutting a tool into it and then feeding the tool and workpiece while moving them relative to each other, using a tool with a large protrusion, such as in boring, can cause large machining vibrations (hereafter referred to as chatter) due to a decrease in tool rigidity, leading to problems such as tool breakage and poor machined surface quality. As a conventional technique for suppressing this chatter, for example, Non-Patent Document 1 discloses an invention that improves holding rigidity by using a slotted tool holder. Patent Document 1 also discloses an invention that improves damping by attaching a mechanism that generates friction between the tool and the tool holder to the tool holder, thereby adding frictional damping.

"The Ultimate Anti-Vibration Tool," Silent Tools, SANDVIK, Electronic Catalog, Page 4, "How to Clamp a Tool Bit," [Retrieved February 14, 2022], Internet: <https://www.sandvik.coromant.com/SiteCollectionDocuments/downloads/jp/brochures/CG-036J-R2_SilentTools.pdf>

Patent No. 5728824

However, while the method in Non-Patent Document 1 can be used universally without being restricted by the tools or machining conditions used, it only achieves vibration suppression effects by improving holding rigidity. Furthermore, while the method in Patent Document 1 can achieve vibration suppression effects with all tools, it requires adjustment every time a tool is attached or detached, and has workability issues because the vibration suppression mechanism is located outside the tool holder, where chips are likely to adhere.

The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a tool holder and machine tool that are versatile and have vibration suppression effects while maintaining the same workability as conventional structures.

In order to achieve the above object, a first configuration of the present disclosure is a tool holder that is provided in a machine tool and has a tool insertion hole capable of holding a tool, the tool holder comprising:
a fixing portion that can be fixed to the machine tool and has the tool insertion hole;
a damping section that includes a section that is built into the fixing section and has lower rigidity than the fixing section, and that damps machining vibrations by pressing the tool inserted into the tool insertion hole from the radial outside of the tool with a given pressure ,
the damping portion is configured from a connection portion connected to the fixed portion and a tool contact portion that includes a portion that is connected to the connection portion and has low rigidity, and that comes into contact with the tool to press the tool, and the connection portion and the tool contact portion are overlapped in the radial direction of the tool insertion hole so that the connection portion is on the outer side and the tool contact portion is on the inner side in the radial direction of the tool insertion hole, and
The tool contact portion is positioned so as to be able to come into contact with a tool inserted into the tool insertion hole when the connecting portion is connected to the fixed portion .
In the present disclosure, the term "radial direction of the tool" includes not only the strict radial direction of the tool but also a radial direction inclined toward the axial direction of the tool.
Another aspect of the first configuration is that, in the above configuration, the tool contact portion is composed of an elastic portion that is connected to the connection portion and is the portion with low rigidity, and a rigid portion that is connected to the elastic portion and contacts the tool, and the elastic portion has lower rigidity than the fixed portion, and the rigid portion has higher rigidity than the elastic portion.
Another aspect of the first configuration is that, in the above configuration, the tool contact portion protrudes from the inner diameter surface of the tool insertion hole, and the protruding surface is sloped so that the amount of protrusion from the inner diameter surface is greater at the rear end side of the tool than at the front end side.
In order to achieve the above object, a second aspect of the present disclosure is a machine tool characterized by including any one of the tool holders according to the first aspect.

This disclosure makes it possible to achieve a general-purpose, high vibration suppression effect for all tools. Furthermore, after connecting the damping portion to the fixed portion, the damping portion is automatically pressed against the tool, eliminating the need for adjustment each time the tool is attached or detached. Furthermore, since the damping portion is built into the fixed portion, the possibility of chips adhering to the damping portion is reduced. Therefore, it is possible to maintain the same operability as existing tool holders. As a result, it is possible to achieve a general-purpose, high vibration suppression effect for tools without compromising operability.

FIG. 1 is a schematic diagram illustrating a configuration of an existing tool holder. FIG. 2 is a schematic diagram of the cross section taken along the line AA in FIG. 1. FIG. 2 is a schematic diagram illustrating the configuration of a high-damping tool holder. FIG. 2 is a schematic diagram illustrating the configuration of a damping section built into a high-damping tool holder. 4 is a schematic cross-sectional view of the high-damping tool holder taken along line BB in FIG. 3 before a tool is attached thereto; FIG. 4 is a schematic diagram showing the high-damping tool holder in a state after a tool is attached, taken along the line B-B in FIG. 3 . FIG.

First, the structure of the existing tool holder 1 will be described with reference to the drawings.
Fig. 1 is a schematic diagram showing the configuration of a tool holder 1. Fig. 2 is a schematic diagram showing the A-A cross section (a cross section defined by the front-to-back, up-down, and down-directions) of Fig. 1. In this example, the tool holder 1 is applied to a swivel turret 21 of a lathe 20, which is an example of a machine tool. A tool 22 held by the tool holder 1 has a substantially circular cross section and is provided with a tip 23 at its tip. For convenience, the tip side (tip 23 side) of the tool 22 in Fig. 1 will be referred to as the front, and the upper side of the tool holder 1 will be referred to as the top.
The tool holder 1 includes a holder body 2 that is fixed to the mounting surface of a swivel turret 21. A tool insertion hole 3 having an inner diameter equal to or larger than the diameter of a tool 22 is formed through the holder body 2 in the front-to-rear direction. On either side of the tool insertion hole 3, three holder fixing bolts 11, 11... are arranged in the front-to-rear direction on each side of the holder body 2, for fixing the holder to the mounting surface of the swivel turret 21. Above the tool insertion hole 3, two tool fixing bolts 12, 12 are threadedly engaged in the front-to-rear center of the holder body 2.

To hold a tool 22 in this tool holder 1, the holder body 2 is fixed to the swivel turret 21 using the holder fixing bolt 11, and the tool 22 is then inserted rearward into the tool insertion hole 3 with the tool fixing bolt 12 loosened. Next, the tool fixing bolt 12 is tightened while adjusting the amount of protrusion from the holder body 2, and the tool 22 is pressed against the inner diameter surface of the tool insertion hole 3 opposite the tool fixing bolt 12. This secures the tool 22 to the holder body 2 while protruding from the tool insertion hole 3.

Next, an embodiment of the present disclosure will be described with reference to the drawings, where the same components as those in FIGS. 1 and 2 are designated by the same reference numerals and redundant description will be omitted.
Fig. 3 is a schematic diagram showing the configuration of a high-damping tool holder 31, which is an example of a tool holder according to the present disclosure. Fig. 4 is a schematic diagram showing the configuration of a damping section 33 built into the high-damping tool holder 31. Fig. 5 is a schematic diagram showing the high-damping tool holder 31 in a state before a tool is attached, taken along the B-B cross section (a cross section defined by the front-to-back, up-down, and down-up directions) of Fig. 3 (the cross section is indicated by diagonal lines). Fig. 6 is a schematic diagram showing the high-damping tool holder 31 in a state after a tool is attached, taken along the same cross section as Fig. 5 of the tool insertion hole 3 of Fig. 3.

The high-damping tool holder 31 includes a fixing portion 32 and a damping portion 33. The fixing portion 32 is fixed to the swivel turret 21 by a holder fixing bolt 11, similar to the tool holder 1 in FIG. 1 , and can fix a tool 22 inserted into a tool insertion hole 3 by a tool fixing bolt 12.
The damping portion 33 is built into the fixed portion 32. The damping portion 33 is made up of a connecting portion 34, an elastic portion 35, a rigid portion 36, and a connecting portion bolt 37. The connecting portion 34 is bonded to the elastic portion 35, and the elastic portion 35 is bonded to the rigid portion 36. The connecting portion 34 is connected to the fixed portion 32 by the connecting portion bolt 37. As a result, the damping portion 33 is built into the fixed portion 32 and is in a state where it can come into contact with the tool 22 inserted into the tool insertion hole 3. The elastic portion 35 and the rigid portion 36 form a tool contact portion 38.

The elastic portion 35 is made of a material (rubber or synthetic resin) that is less rigid than the fixed portion 32 and the connecting portion 34, and deforms while generating a repulsive force when a force is applied to the damping portion 33. The outer surfaces of the elastic portion 35 on the front, rear, left, and right sides are in contact with the inner surface of the fixed portion 32 that houses the damping portion 33.
The rigid portion 36 has an upper surface that forms a concave curved surface that conforms to the inner diameter surface of the tool insertion hole 3 and protrudes from the inner diameter surface of the tool insertion hole 3. However, the rigid portion 36 is configured so that, with the damping portion 33 fixed to the fixing portion 32, the radial protrusion amount of a front end side inner diameter 41 from the inner diameter surface of the tool insertion hole 3 is equal to or less than the difference between the inner diameter of the tool insertion hole 3 and the outer diameter of the tool 22. Furthermore, the protruding surface of the rigid portion 36 is sloped downward toward the front so that the protrusion amount of a rear end side inner diameter 42 from the inner diameter surface of the tool insertion hole 3 is greater than the protrusion amount of the front end side inner diameter 41 from the inner diameter surface of the tool insertion hole 3. Furthermore, gaps are provided between the front, rear, left, and right outer surfaces of the rigid portion 36 and the inner surface of the fixing portion 32.

With this configuration, even when the damping portion 33 is fixed to the fixed portion 32, the rear end of the tool 22 does not come into contact with the front end surface of the rigid portion 36 when the tool 22 is inserted into the tool insertion hole 3. Furthermore, when the rear end of the tool 22 comes into contact with the upper surface of the sloped rigid portion 36, the elastic portion 35 deforms radially outward, allowing the tool 22 to continue to be inserted.
6, by tightening the tool fixing bolt 12, the tool 22 pushes the rigid portion 36 radially outward, further deforming the elastic portion 35. Therefore, the tool 22 and the damping portion 33 come into close contact with each other with a pressure sufficient to allow relative vibration when chatter occurs.

The high-damping tool holder 31 constructed as described above is attached to the swivel turret 21 via the fixing portion 32, and when the tool 22 is fixed in the tool insertion hole 3, the tool 22 is fixed with high rigidity.
In the lathe 20, the tool 22 is caused to cut into the workpiece while rotating it, and the tool 22 and the workpiece are moved relative to each other while being fed, thereby machining the workpiece.
If chatter occurs during this machining, frictional damping is applied due to relative vibrations occurring between the rigid portion 36 and the tool 22, frictional damping due to relative vibrations occurring between the elastic portion 35 and the fixed portion 32, and internal frictional damping due to deformation of the elastic portion 35 itself. As a result, chatter can be suppressed by the damping effect of the damping portion 33 without the position of the tool 22 changing due to the strong fixation of the fixed portion 32.

In this way, the high-damping tool holder 31 of the above-described form is equipped with a fixed portion 32 that can be fixed to the lathe 20 and has a tool insertion hole 3, and a damping portion 33 that includes an elastic portion 35 that is built into the fixed portion 32 and has lower rigidity than the fixed portion 32, and can press the tool 22 inserted into the tool insertion hole 3 from the radial outside of the tool 22 with any pressure.
This configuration makes it possible to obtain a general-purpose, high vibration suppression effect for all tools. Furthermore, after the damping portion 33 is connected to the fixing portion 32, the damping portion 33 is automatically pressed against the tool 22, eliminating the need for adjustment each time the tool 22 is attached or detached. Furthermore, since the damping portion 33 is built into the fixing portion 32, the possibility of chips adhering to the damping portion 33 is reduced. Therefore, it is possible to maintain the same operability as existing tool holders. In other words, the high-damping tool holder 31 makes it possible to obtain a general-purpose, high vibration suppression effect for the tool 22 without impairing operability.

The damping portion 33 is composed of a connecting portion 34 connected to the fixed portion 32, and a tool contact portion 38 that includes a low-rigidity elastic portion 35 connected to the connecting portion 34 and contacts the tool 22 to press the tool 22.
Therefore, the damping portion 33 can easily press the tool 22 from the radially outer side inside the fixing portion 32 .
The tool contact portion 38 is composed of an elastic portion 35 connected to the connection portion 34 and a rigid portion 36 connected to the elastic portion 35 and contacting the tool 22, and the elastic portion 35 has lower rigidity than the fixed portion 32, while the rigid portion 36 has higher rigidity than the elastic portion 35.
Therefore, the pressing force from the elastic part 35 can be applied to the tool 22 via the rigid part 36, and the magnitude of the pressing force acting on the tool 22 can be adjusted by the material and shape of the elastic part 35, the shape of the rigid part 36, the tightening torque of the tool fixing bolt 12, etc.
The tool contact portion 38 protrudes from the inner diameter surface of the tool insertion hole 3, and the protruding surface is sloped so that the amount of protrusion from the inner diameter surface is greater at the rear end side than at the front end side of the tool 22.
Therefore, the rear end of the tool 22 can be pressed and fixed with a larger pressing force than the front end.

The configuration of the high-damping tool holder 31 of the present disclosure is not limited to the aspects described in the above embodiment, and can be appropriately modified as needed within the scope of the present disclosure.
For example, in the above embodiment, the damping portion 33 is located between the two rows of holder fixing bolts 11 or the two tool fixing bolts 12, but the positional relationship between the damping portion 33 and the holder fixing bolts 11 or the tool fixing bolts 12 can be changed. As an example, the damping portion 33 can be provided closer to the tool tip than the tool fixing bolts 12. In this case, although the static rigidity at the tool tip decreases and the machining accuracy decreases, the relative displacement generated by the damping portion 33 increases, thereby achieving higher damping performance.
Furthermore, a copper alloy or a resin material such as urethane may be provided at the front end of the tool fixing bolt 12. By providing a low-rigidity material at the front end of the tool fixing bolt 12 in this manner, the damping effect can be further improved.

In the above embodiment, the damping portion 33 is provided below the fixed portion 32 to avoid chips and cutting fluid, but it may be located anywhere on the fixed portion 32. As an example, the damping portion 33 may be provided on the side of the fixed portion 32. In this case, although durability is reduced, the damping portion 33 can be replaced even with the high-damping tool holder 31 attached, resulting in higher workability.
The direction in which the damping portion 33 presses the tool 22 is not limited to strictly from the outside in the radial direction of the tool 22. The damping portion 33 may press the tool 22 from the outside in the radial direction that is slightly inclined forward and backward in the axial direction of the tool 22.
In the above embodiment, the rigid portion 36 is sloped over its entirety, but the edge of the front end inner diameter 41 may be chamfered to provide a slope only in a portion thereof.
In the above embodiment, a gradient is provided in the rigid portion 36, but although the damping performance decreases due to a drop in pressure between the tool 22 and the rigid portion 36, the tool 22 may be pressed against the damping portion 33 using only the tool fixing bolt 12 without providing a gradient.

On the other hand, if cutting fluid adheres to the elastic portion 35, the elastic portion 35 may be deteriorated due to chemical action. Also, if the elastic portion 35 comes into contact with the tool 22 or the like, the elastic portion 35 may be worn.
Therefore, an O-ring or packing may be provided on the contact surface between the connecting portion 34 and the fixed portion 32 or in the gap between the rigid portion 36 and the fixed portion 32 to improve the sealing performance of the damping portion 33. By improving the sealing performance in this way, cutting fluid is less likely to adhere to the elastic portion 35, and deterioration of the elastic portion 35 due to the adhesion of cutting fluid is suppressed. Furthermore, because the elastic portion 35 does not come into direct contact with the tool 22, wear of the elastic portion 35 can also be effectively prevented.
The rigid portion 36 is not essential. Although durability is significantly reduced, the elastic portion 35 may be in direct contact with the tool 22 without providing the rigid portion 36.
Additionally, the tool holder of the present disclosure can be applied to machine tools other than lathes.

1. Tool holder, 2. Holder body, 3. Tool insertion hole, 11. Holder fixing bolt, 12. Tool fixing bolt, 20. Lathe, 21. Swivel turret, 22. Tool, 23. Tip, 31. High-damping tool holder, 32. Fixing portion, 33. Damping portion, 34. Connection portion, 35. Elastic portion, 36. Rigid portion, 37. Connection portion bolt, 38. Tool contact portion, 41. Front end inner diameter, 42. Rear end inner diameter.

Claims (4)

A tool holder provided in a machine tool and having a tool insertion hole capable of holding a tool,
a fixing portion that can be fixed to the machine tool and has the tool insertion hole;
a damping section that includes a section that is built into the fixing section and has lower rigidity than the fixing section, and that damps machining vibrations by pressing the tool inserted into the tool insertion hole from the radial outside of the tool with a given pressure ,
the damping portion is configured from a connection portion connected to the fixed portion and a tool contact portion that includes a portion that is connected to the connection portion and has low rigidity, and that comes into contact with the tool to press the tool, and the connection portion and the tool contact portion are overlapped in the radial direction of the tool insertion hole so that the connection portion is on the outer side and the tool contact portion is on the inner side in the radial direction of the tool insertion hole, and
A tool holder characterized in that, with the connecting portion connected to the fixed portion, the tool contact portion is positioned so as to be able to come into contact with a tool inserted in the tool insertion hole . 2. The tool holder according to claim 1, wherein the tool contact portion is composed of an elastic portion connected to the connection portion and having the low rigidity , and a rigid portion connected to the elastic portion and coming into contact with the tool, the elastic portion having a lower rigidity than the fixing portion, and the rigid portion having a higher rigidity than the elastic portion . 3. The tool holder according to claim 1, wherein the tool contact portion protrudes from an inner diameter surface of the tool insertion hole, and the protruding surface is sloped so that the amount of protrusion from the inner diameter surface is greater at a rear end side of the tool than at a front end side of the tool. A machine tool comprising the tool holder according to any one of claims 1 to 3 .