JP7561693B2 - Tool holders and machine tools - Google Patents

Description

This disclosure relates to a tool holder that has a function of suppressing vibrations generated in the 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 the tool holder.

In machine tools in which a tool is supported on a rotatable workpiece and the tool and workpiece are fed and moved relative to one another to machine the workpiece, when the tool is used with a large protrusion, such as in boring, a decrease in tool rigidity can cause large machining vibrations (hereinafter referred to as chatter), which can lead to problems such as tool breakage and poor machined surface quality.
As a conventional technique for improving vibration damping to suppress this chatter, Patent Document 1 describes an invention in which a space filled with a viscous fluid is provided in the tool holder to suppress tool vibration. Patent Document 2 describes an invention in which a vibration-damping member is interposed between the tool and the tool holder. Patent Document 3 describes an invention in which a viscoelastic body such as nitrile rubber is pressed against the tool.
Furthermore, Non-Patent Document 1 describes an anti-vibration tool that improves the holding rigidity by inserting a tool into a tool insertion hole having a slot structure and tightening it with a bolt.

Patent No. 6177602 Japanese Utility Model Application Publication No. 5-88804 Patent No. 5131826

"The Ultimate Anti-Vibration Tool" Silent Tools SANDVIK Electronic Catalog, page 4 "How to Clamp a Bit", [Searched on May 31, 2021], Internet <https://www.sandvik.coromant.com/SiteCollectionDocuments/downloads/jp/brochures/CG-036J-R2_SilentTools.pdf>

However, while the methods of Patent Documents 1 to 3 can add damping properties, they require the use of rubber or damping materials that are generally less durable than metals, and there are concerns about their durability when used for long periods of time near the tool tip, which is the processing position.
In addition, while the methods of Patent Documents 1 and 3 and Non-Patent Document 1 make it possible to add a certain amount of damping, it is believed that the greater the vibration amplitude, the greater the damping that can be obtained. Therefore, when a damping mechanism is installed near the base of the tool, where the vibration amplitude is smaller than that at the tip of the tool, the improvement in damping may be limited.

The present disclosure has been made in consideration of the above problems, and aims to provide a tool holder and machine tool that can provide stable damping over a long period of time and achieve a high vibration suppression effect even in positions close to the tool tip.

In order to achieve the above object, a first configuration of the present disclosure is a tool holder provided on a machine tool, the tool holder including a base having a tool insertion hole into which a base end of a tool is inserted, and a fixing means for fixing the base end inserted into the tool insertion hole within the base,
a sleeve is provided which is fitted over at least a portion of the tool protruding from the base and fixed to the base, the sleeve having at least one slit extending in an axial direction and an adjustment mechanism capable of adjusting the size of an inner diameter of the sleeve;
The adjustment mechanism is characterized in that the sleeve grips the tool with a gripping force that is lower than the fixing force of the fixing means and is sufficient to allow relative movement of the tool with respect to the sleeve when vibrations occur due to processing.
Another aspect of the present disclosure is characterized in that, in the above configuration, the sleeve has a length that allows it to be inserted into the tool insertion hole as well.
Another aspect of the present disclosure is characterized in that, in the above configuration, the sleeve is formed so that its inner diameter is smaller than the outer diameter of the tool, and the adjustment mechanism is capable of widening the opening width of the slit, so that the tool can be inserted and removed by widening the opening width with the adjustment mechanism, and when the opening width is not widened, the sleeve grips the tool with its gripping force.
Another aspect of the present disclosure is characterized in that, in the above configuration, the sleeve has an inner diameter larger than the outer diameter of the tool, and the adjustment mechanism is capable of narrowing the opening width of the slit, allowing the tool to be inserted and removed without narrowing the opening width using the adjustment mechanism, and when the opening width is narrowed, the sleeve grips the tool with its gripping force.
In order to achieve the above object, a second aspect of the present disclosure is a machine tool comprising the tool holder of the first aspect of the present disclosure.

According to the present disclosure, it is possible to add damping properties stably for a long period of time without using materials other than metals, which generally have low durability. In addition, it is possible to stably impart high damping properties to all tools, even at positions close to the tool tip where the vibration amplitude is large when chatter occurs. This makes it possible to achieve highly efficient machining.

FIG. 1 is a schematic diagram of a conventional tool holder. FIG. 2 is a schematic diagram of a cross-sectional portion taken along the line AA in FIG. FIG. 1 is a schematic configuration diagram of a tool holder according to the present disclosure. FIG. 4 is a schematic diagram showing the shape of the sleeve of FIG. 3 . FIG. 4 is a schematic diagram of the cross-sectional portion taken along the line BB in FIG. 3. FIG. 4 is a schematic diagram of a cross-sectional portion taken along the line CC of FIG. FIG. 13 is a perspective view showing a modified example of the sleeve. FIG. 13 is a perspective view showing another modified example of the sleeve. FIG. 13 is a schematic configuration diagram showing a modified example of the tool holder. 10 is a schematic diagram of a cross-sectional portion taken along the line DD in FIG. 9. FIG. 11 is a schematic configuration diagram showing another modified example of the tool holder.

First, the structure of a conventional tool holder will be described with reference to the drawings.
Fig. 1 is a schematic diagram showing the configuration of a conventional tool holder 1. Fig. 2 is a schematic diagram showing a cross section taken along line AA of Fig. 1 (a cross section defined by a plane in the front-rear and up-down directions, the same applies below).
In this example, the tool holder 1 is applied to a rotating turret 31 of a lathe 30, which is an example of a machine tool. A tool 33 held by the tool holder 1 has a substantially circular cross section and is provided with a tip 34 at its tip. For convenience, the tip side (tip 34 side) of the tool 33 in Fig. 1 will be described as the front, and the upper side of the tool holder 1 as the top.
The tool holder 1 includes a block-shaped base 2 fixed to a mounting surface 32 on the outer periphery of a swivel turret 31. A tool insertion hole 3, into which a tool 33 is inserted from the rear end, is formed penetrating the base 2 in the front-rear direction. On either side of the tool insertion hole 3, three base fixing bolts 4, 4... for fixing the base 2 to the mounting surface 32 are arranged in the front-rear direction. Above the tool insertion hole 3, two tool fixing bolts 5, 5 are screwed into the center of the base 2 in the left-right direction, one on the front and one on the back.
The tool 33, which has a tip 34 attached to its tip, has its base end 33a inserted into the tool insertion hole 3 from the front. In this state, when the tool fixing bolts 5, 5 are screwed into the base 2 from above, the base end 33a of the tool 33 is pressed against the lower inner wall of the tool insertion hole 3. As a result, the tool 33 is fixed to the base 2 with its tip end 33b protruding from the tool insertion hole 3.

Next, an embodiment of the present disclosure will be described with reference to the drawings, in which the same components as those of the conventional tool holder 1 are denoted by the same reference numerals and a duplicated description will be omitted.
Fig. 3 is a schematic diagram showing an example of the tool holder 10 of the present disclosure. Fig. 4 is a schematic diagram showing the shape of a sleeve 11 constituting the tool holder 10. Here, the front-rear and up-down directions will be described in the same manner as in Fig. 1. Fig. 5 is a schematic diagram showing the cross section B-B of Fig. 3, and Fig. 6 is a schematic diagram showing the cross section C-C of Fig. 3.
Like the tool holder 1, the tool holder 10 includes a base 2, a base fixing bolt 4, and a tool fixing bolt 5. In addition, the tool holder 10 further includes a sleeve 11 and three adjustment bolts 12, 12 .
The sleeve 11 has a sleeve inner hole 13 with an inner diameter smaller than the outer diameter of the tool 33, and a flange 14 that determines the axial retreat position of the sleeve 11 at the end face of the base 2. A slit 15 is formed on the side of the sleeve 11 over the entire length in the axial direction. Above the slit 15, the sleeve 11 has adjustment bolt holes 16, 16... into which the adjustment bolt 12 is screwed, formed in two locations on the front side of the flange 14 and one location on the rear side, in the vertical direction. Behind the flange 14, bolt through holes 17, 17 are formed on the front and rear sides of the upper surface of the sleeve 11 to enable the tool 33 to be pressed against the inner wall of the sleeve inner hole 13 by tool fixing bolts 5, 5 and gripped.

The procedure for mounting the tool 33 on the tool holder 10 configured as above will be described below.
First, the base 2 is fixed to the mounting surface 32 of the swivel turret 31 by the base fixing bolt 4. Next, the sleeve 11 is inserted into the tool insertion hole 3 until the flange 14 hits the end face of the base 2. Next, the adjustment bolt 12 is tightened and the lower end is pressed against the lower surface of the slit 15, thereby widening the opening width of the slit 15 and making the sleeve inner hole 13 larger than the outer diameter of the tool 33. Next, the tool 33 is inserted into the sleeve inner hole 13 from the rear end and its position is adjusted to a predetermined tool protrusion amount, and then the adjustment bolt 12 is loosened to make the inner diameter of the sleeve inner hole 13 smaller than the outer diameter of the tool 33, and the tool 33 is gripped by the sleeve 11. Finally, the base end 33a of the tool 33 is pressed against the inner wall of the sleeve inner hole 13 using the tool fixing bolts 5, 5 through the bolt holes 17, 17, and the sleeve 11 is pressed against the inner wall of the tool insertion hole 3, thereby fixing the base end 33a of the tool 33 and the sleeve 11 to the base 2.

When turning is performed on the lathe 30 using this tool holder 10 and machining vibrations are generated, the sleeve 11 and the base end 33a of the tool 33 are held and fixed with high pressure (fixing force) that does not allow relative movement near the base 2 fastened by the tool fixing bolt 5. On the other hand, the tip end 33b of the tool 33 comes into contact with the sleeve 11 with low pressure (gripping force) that causes relative movement. At this time, relative movement occurs while friction occurs between the objects, providing high damping properties due to energy consumption.
In addition, since the area where the relative movement occurs is not fastened with bolts, the contact pressure is determined by the interference between the tool 33 and the sleeve inner hole 13, regardless of the setting method of the operator, and performance variations can be suppressed. As a result, during machining, the tool position does not change due to the strong fixation at the rear of the tool holder 10, and stable friction damping occurs in the front contact area, making it possible to suppress machining vibrations.

In this manner, the tool holder 10 and lathe 30 of the above-described form include the base 2 having the tool insertion hole 3 into which the base end 33 a of the tool 33 is inserted, and the tool fixing bolts 5, 5 (fixing means) that fix the base end 33 a inserted into the tool insertion hole 3 within the base 2. The sleeve 11 is fitted over the tool 33 and fixed to the base 2, and the sleeve 11 has a slit 15 extending in the axial direction and an adjustment bolt 12 (adjustment mechanism) that can adjust the size of the inner diameter of the sleeve 11. The adjustment bolt 12 enables the sleeve 11 to grip the tool 33 with a gripping force that is lower than the fixing force of the tool fixing bolts 5, 5 and that is capable of allowing relative movement of the tool 33 with respect to the sleeve 11 when vibrations occur due to machining.
Therefore, it is possible to add damping properties stably for a long period of time without using materials other than metals that generally have low durability. Also, it is possible to impart high damping properties stably to any tool even at a position close to the tip of the tool where the vibration amplitude is large when chatter occurs. Therefore, it is possible to realize highly efficient machining.

In particular, since the sleeve 11 has a length that allows it to be inserted into the tool insertion hole 3 as well, the tool 33 can be inserted into the tool insertion hole 3 together with the sleeve 11 and fixed in place with the tool fixing bolts 5, 5.
The sleeve 11 is formed so that its inner diameter is smaller than the outer diameter of the tool 33, and the adjustment bolt 12 can widen the opening width of the slit 15, so that the tool 33 can be inserted and removed by widening the opening width with the adjustment bolt 12, and at the same time, when the opening width is not widened, the sleeve 11 can hold the tool 33 with a gripping force that allows relative movement. Therefore, by simply loosening the adjustment bolt 12, the sleeve 11 can hold the tool 33 with an appropriate gripping force.

Modifications of the present disclosure will be described below.
7 shows a modified sleeve 11A. In the above-mentioned embodiment, the slits 15 are provided over the entire length of the sleeve 11 to improve the opening property, but since the portion where the damping effect due to friction is large is only on the tip side of the tool 33 where the amount of vibration due to machining is large and the relative displacement is also large, in this sleeve 11A, the slits 15 are provided only on the tip side of the tool 33, forward of the flange 14. The other configurations of the tool holder 10 are the same as those of the above-mentioned embodiment.
8 shows a sleeve 11B of another modified example. In this sleeve 11B, two slits 15, 15 are provided only on the left and right side surfaces, forward of the flange portion 14, toward the tip side of the tool 33. The rest of the configuration of the tool holder 10 is the same as in the above embodiment. The slits may be provided not only left and right but also above and below, and may be provided in three or more places.

Fig. 9 is a schematic diagram showing a modified example of the tool holder, and Fig. 10 is a schematic diagram showing the cross section taken along line DD in Fig. 9.
9 uses a short sleeve 11C having a slit 15 (or a plurality of slits) on the side surface. A flange 18 at the rear end of the sleeve 11C is fixed to the end surface of the base 2 by sleeve fixing bolts 19, 19....
The outer diameter of the tool 33 is equal to the inner diameter of the tool insertion hole 3, and is inserted into the tool insertion hole 3 in the same manner as the conventional tool holder 1.
Therefore, the tool 33 is inserted from its rear end into the sleeve inner hole 13 and the tool insertion hole 3, and its position is adjusted to a predetermined tool protrusion amount, after which the adjustment bolt 12 is loosened to make the inner diameter of the sleeve inner hole 13 smaller than the outer diameter of the tool 33, and the tip end 33b of the tool 33 is gripped by the sleeve 11C. In this state, the base end 33a of the tool 33 is fixed to the base 2 by the tool fixing bolts 5, 5.

The configuration of the tool holder of the present disclosure is not limited to the aspects described in the above embodiment, and can be appropriately modified as necessary without departing from the spirit of the present invention.
For example, in the above embodiment, the adjustment bolt 12 is tightened to increase the diameter of the sleeve inner hole 13, which has an inner diameter smaller than the outer diameter of the tool 33, and the tool 33 is inserted, and then the adjustment bolt 12 is loosened to cause the sleeve 11 (11A to 11C) to grip the tool 33 with a predetermined gripping force, but a modification as shown in Figure 11 is also possible.
11, a sleeve 11D is used in which the inner diameter of the sleeve inner hole 13 is larger than the outer diameter of the tool 33, and the adjustment bolt 12 is screwed down to the lower side of the slit 15. Therefore, the tool 33 can be inserted into and removed from the sleeve 11D without tightening the adjustment bolt 12. The gripping force of the sleeve 11D is adjusted by tightening the adjustment bolt 12 to reduce the opening width of the slit 15 and the inner diameter of the sleeve inner hole 13. In this case, although the damping is less stable than in the above embodiment, the tool 33 can be easily inserted and removed.
In the modification of FIG. 11 as well, the sleeve may be a short sleeve as in FIG. 9, and may have a plurality of slits.

Furthermore, in the above embodiment, the inner diameter of the sleeve is adjusted using an adjustment bolt as an adjustment mechanism, but the inner diameter of the sleeve may be adjustable using an adjustment mechanism such as a spring or a lever.
Furthermore, in the above embodiment, the base and the sleeve are configured as a single member, but it goes without saying that they may be configured by joining a plurality of members.
On the other hand, the cross-sectional shapes of the inner holes of the base and the sleeve are not limited to being circular, and may be changed to other shapes, such as elliptical or polygonal, in accordance with the cross-sectional shapes of the sleeve and the tool.
The tool holder of the present invention can also be applied to machine tools other than lathes.

1, 10, 10A, 10B... Tool holder, 2... Base, 3... Tool insertion hole, 4... Base fixing bolt, 5... Tool fixing bolt, 11, 11A-11D... Sleeve, 12... Adjustment bolt, 13... Sleeve inner hole, 14, 18... Flange, 15... Slit, 16... Adjustment bolt hole, 17... Bolt through hole, 19... Sleeve fixing bolt, 30... Lathe, 31... Swivel turret, 32... Mounting surface, 33... Tool.

Claims (5)

A tool holder provided in a machine tool, the tool holder comprising: a base having a tool insertion hole into which a base end of a tool is inserted; and a fixing means for fixing the base end inserted into the tool insertion hole within the base,
a sleeve is provided which is fitted over at least a portion of the tool protruding from the base and fixed to the base, the sleeve having at least one slit extending in an axial direction and an adjustment mechanism capable of adjusting the size of an inner diameter of the sleeve;
the adjustment mechanism causes the sleeve to grip the tool with a gripping force that is lower than the fixing force of the fixing means and that is sufficient to allow relative movement of the tool with respect to the sleeve when vibrations are generated due to machining. The tool holder according to claim 1, characterized in that the sleeve has a length that allows it to be inserted into the tool insertion hole. 3. The tool holder according to claim 1, wherein an inner diameter of the sleeve is smaller than an outer diameter of the tool, and the adjustment mechanism is capable of expanding an opening width of the slit, the opening width being expanded by the adjustment mechanism to allow insertion and removal of the tool, and the sleeve grips the tool with its gripping force when the opening width is not expanded. 3. The tool holder according to claim 1, wherein an inner diameter of the sleeve is larger than an outer diameter of the tool, the adjustment mechanism is capable of reducing an opening width of the slit, the adjustment mechanism allows the tool to be inserted and removed without reducing the opening width, and the sleeve grips the tool with its gripping force when the opening width is reduced. A machine tool equipped with a tool holder according to any one of claims 1 to 4.

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