JP2005074603A - Tool mounting device to tool holder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tool gripping mechanism and accessories thereof with a small volume in radial direction of a fastening part of a tool and having a large gripping power, in a tool holder for attaching tools to a spindle of a machine tool. <P>SOLUTION: A device of the present invention is constituted by externally fitting a fastening ring 7 formed of a shape memory alloy in a cylindrical part as a tool mounting part 5 formed on a tip end side of a tool holder. Thus, the fastening ring is swollen in a martensitic state to increase an inner diameter of the cylindrical part larger than a diameter of a shank of a tool 10, and is contract in an astatine state to decrease the inner diameter of the cylindrical part, to thereby strongly grip the tool. Moreover, in any case, the device is formed so as to improve operability in mounting and demounting the tool as an engagement with which the fastening ring is not detached from the cylindrical part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a tool holder for attaching a tool to a spindle of a machine tool and an accessory device thereof.

  In a machine tool such as a milling machine or a boring machine, a rotary tool such as an end mill is attached to a spindle (main shaft) via a tool holder to perform processing such as cutting and grinding. This tool holder has a taper formed on its shank, which is inserted into a tapered fitting hole formed in the spindle of the machine, and further fitted to the base end side of the spindle by a screw bolt. Pulled and fixed.

  The problem is how to connect the tool holder and the tool, which includes the following. First, a tapered portion whose end is narrowed is provided on the proximal end side of the tool, and one holder is formed with a tapered hole into which the tapered portion of the tool is inserted from the distal end side, and is inserted and fitted to each other. Second, the base end side shaft of the tool is formed in a columnar shape, and this columnar portion is gripped by a collet chuck. Further, as shown in FIG. 6, the diameter of the tool accommodation hole formed in the tool holder H is made smaller than the shank diameter of the tool, and the tool accommodation hole is heated by high frequency induction E to expand and expand the inner diameter. The shank portion of the tool T is inserted here, and then the tool T is contracted by cooling it to grip the tool T. In this gripping method, there is a concern that the tool holder is fatigued and deteriorated by a high-temperature thermal cycle.

In addition, the conventional example shown in FIG. 7 employs a configuration in which a shrink collar M made of a shape memory alloy is applied to a tool holding portion formed at the tip of the tool holder. In this regard, Japanese Patent Laid-Open No. 2004-228561 has formed a “diameter of the inner surface of the collar M in a relaxed state slightly oversized with respect to the tightening bush B” (0021), and the tool shaft is placed in the receiving hole of the tightening bush. After being accommodated, the contracted collar M in the martensite state is “carefully pushed axially over the outer peripheral surface of the clamping bush B in the compression device”. Thus, attaching and detaching the shrink collar M by using a special compression device every time the tool is replaced not only has a problem in work efficiency, but also causes significant wear on the inner diameter surface of the shrink collar M. In addition, there is a problem that a small-diameter tool cannot be made symmetrical with respect to gripping because a longitudinal slit is provided in the fastening bush.

JP-T-08-502212 Japanese Patent Laid-Open No. 05-212608

In high-speed cutting using a rotary tool such as an end mill or a drill, if there is a runout in the chuck portion of the tool, the tool is severely worn and the processing accuracy is lowered. Further, when the gripping mechanism portion of the end mill has a large diameter in the radial direction, there is a limit to deep engraving on the workpiece. For this reason, the present invention has an object to develop a tool holder and a simple tool attaching / detaching device having good operability by combining the characteristics of the shape memory alloy and carbon steel and having a small tool gripping portion. It is what. In particular, the present invention provides a tool holder device that is effective for mounting a small-diameter tool.

A conical holder shank that fits into the main spindle of the machine tool is used as the base end to contact the holder shank to form a flange, and further, a tool attachment on the tip side. A threaded hole extending in the axial direction from the end surface on the base end side, and a tool mounting hole for inserting a shank portion of the tool to be used in the tool mounting portion are formed in the axial direction from the end surface of the tool mounting portion. And a tool holder having a configuration in which a tightening ring made of a shape memory alloy is externally fitted to the tool mounting portion, and the tool mounting hole has a diameter of the tool to be inserted in the martensite state of the tightening ring. The diameter is larger than the shank diameter, smaller in the austenite state, and in the martensite state, the fastening ring is a static fit that does not easily fall off from the tool mounting portion. As a means to be Ruhoruda small volume of the tool mounting portion and the simplification of the tool detachment was realized reliabilized gripping.

In addition, in order to facilitate the operation of heating or cooling the tightening ring made of a shape memory alloy fitted to the tool holder in this way, two antifreeze baths are provided in one block, A Peltier element is arranged in the periphery to cool it, and at the same time, the antifreeze liquid in the other tank is heated with heat discharged from the Peltier element, and the remaining heat is discharged outside the block with cold water flowing through the cooling water hole. Developed a cooling and heating device that makes up the structure.

The tool holder of the present invention has a cylindrical tool holder made of carbon steel fitted with a tightening ring made of a shape memory alloy of a Ti—Ni alloy system, that is, a double cylinder made of such a different material. By using the difference in longitudinal elastic modulus between the austenite state at a high temperature and the martensite state at a low temperature, the tightening ring becomes a bidirectional memory element that contracts at a high temperature and expands at a low temperature. Became an excellent one.

Further, the shape memory alloy used for the tightening ring has a martensite transformation start temperature Ms of 0 to 5 ° C., an end temperature Mf of about −20 ° C., and an austenite finish temperature slightly lower than normal temperature. The ring can be easily cooled by immersing it in the liquid, and it can be quickly returned to room temperature by immersing it in hot water of about 40 ° C., which makes it easy to attach and detach the tool.

Furthermore, by properly fitting the tightening ring to the tool mounting portion made of steel for machine structural use, etc., even after the tool mounting hole is expanded and the tool is removed along with the diameter expansion of the tightening ring. Since this clamping ring is statically fitted to the tool mounting portion, the operability of the tool attachment / detachment is improved.

  Details of the present invention will be described with reference to the drawings. First, the outline of the figure will be explained. FIG. 1 is a partially sectional side view showing a state in which the tool holder according to the present invention is mounted on a spindle of a machine tool, and FIG. 2 is an enlarged sectional view of the main part of FIG. 3 and 4 are graphs showing changes in inner diameter due to the temperature of the tool mounting portion, that is, the combination cylinder, FIG. 5 is a perspective view showing an outline of a cooling / heating liquid tank apparatus using a Peltier element, and FIGS. 6 and 7 are tools. The conventional example of a holder is shown.

A tool holder 1 according to the present invention has a conical holder shank portion 2 for fitting and attaching to a spindle 20 of a machine tool as a base end, and projects flange portions 3 and 3 in contact with the holder shank portion 2. Further, the tool mounting portion 5 is provided at the distal end side, and the holder shank portion 2 has a threaded hole 6 extending from the proximal end side end surface to the axial distal end side, and from the distal end surface of the tool mounting portion 5. The tool insertion hole 4 for inserting the shank part 11 of the tool 10 to be used is drilled from the end face toward the base end side in the axial direction. The inner diameter of the tool insertion hole 4 is 0.2 to 0.7 mm larger than the shank diameter of the tool to be attached, and the thickness thereof is about 2.0 to 6.0 mm, or carbon steel such as steel for machine structure, or It is made of a non-ferrous metal such as an aluminum alloy.

A tightening ring 7 made of the following shape memory alloy is externally fitted to the outer diameter of the tool mounting portion 5 of the tool holder 1. That is, when cooled to 0 ° C. or lower, it enters a martensite state (expanded state), and when it is gradually heated, it begins to transform into an austenite phase when it exceeds 5 ° C., and its shape is completely at room temperature (around 25 ° C.). It has a nature to recover. Such shape memory alloys are generally known, for example, nickel-titanium alloys (for example, Ti 50 at% and Ni 50 at%, or alloys thereof containing Co, or Cr, Fe, V, or Mo in an amount of 0.1 to 5). (Alloy added with about 0 at%) can be used satisfactorily, but is not limited thereto.

A tightening ring 7 using a shape memory alloy is externally fitted in a press-fit manner in a martensite state to the outer diameter of the tool mounting portion 5 of the tool holder 1 which is the machine structural steel (S30C). By this press-fitting, the inner diameter of the tool insertion hole 4 (approximately 0.2 to 0.7 mm larger than the shank diameter of the tool to be attached) is reduced to an extent that is approximately 0.2 to 0.5 mm larger than the shank diameter of the tool to be gripped. After that, when the tightening ring 7 is heated to room temperature to become austenite, the tool mounting hole 4 is further compressed and manufactured to have a diameter smaller than the shank diameter of the tool.

The inner and outer diameters of the tightening ring 7, the outer diameter of the tool mounting portion of the tool holder, and the inner diameter of the tool insertion hole (the tool mounting portion may be referred to as a cylinder) necessary for obtaining the above-described fitting or gripping force of the tool. A method for obtaining the optimum value will be described.

Table 1 shows the dimensions of the Ti—Ni-based shape memory alloy clamping ring adopted as an example, and the five types of tool mounting part dimensions that become S30C and an aluminum alloy. Each length is L = 30 mm and l = 50 mm as shown in FIG. The tightening ring is cooled to a martensite state, and is externally fitted (press-fit) to each tool mounting portion. Changes in the tool insertion hole (inner diameter) due to subsequent cooling (martensite state) and heating (austenite state) are shown in FIGS. The dotted line in the figure shows the intermediate value.

FIG. 3 is a plot of the inner diameter at which the tool mounting portion of the tool holder made of S30C changes due to the phase change of the shape memory alloy (clamping ring). In this figure, for example, in the tool holder in which the outer diameter of the tool mounting portion is 15.29 mm, the inner diameter (tool insertion hole) is 12.20 mm, and the tightening ring is externally fitted thereto, the shape memory alloy is in an austenitic state. The inner diameter is 12.03 mm, and in the martensite state is 12.07 mm. Under this condition, the shape memory alloy does not easily detach from the tool mounting part before and after the phase change, but it is found that the inner diameter of the tool mounting part is 0.03 mm larger than the shank diameter of 12 mm and is unsuitable for gripping. . From this, the point where the intermediate value (dotted line in the figure) intersects 12.00 mm of the inner cylindrical inner diameter (vertical axis) of the combined cylinder, that is, the inner diameter of the tool mounting portion before the shape memory alloy is externally fitted is 12 It can be seen that it is optimal to select 0.04 mm (horizontal axis). However, considering the processing accuracy of the tool insertion hole and the ease of tool attachment / detachment, when the dimensions of the shape memory alloy fastening ring are as shown in Table 1, the outer diameter of the tool mounting portion is 15.29 mm and the inner diameter is 12 It turns out that it is desirable to set it as 0.02-12.08 mm.

FIG. 4 shows the change in the inner cylinder inner diameter of the combination cylinder with the phase change of the shape memory alloy when an aluminum alloy is used for the tool mounting part (solid line). The dotted line in the figure shows the intermediate value. ing. It can be read from FIG. 4 that it is desirable that the inner cylindrical inner diameter before insertion into the shape memory alloy clamping ring is 12.12 mm to 12.18 mm.

As Example 1, a tool holder 1 for chucking an end mill having a diameter of 12 mm was manufactured with numerical values substantially similar to the conditions shown in Table 1 above. That is, a tightening ring 7 using a shape memory alloy of Ti—Ni alloy (component Ni: 55.8 at%, balance Ti) has an outer diameter: 20.20 mm, an inner diameter: 15.00 mm, and a length: 30 mm, and a tool holder The outer diameter of one tool mounting portion 5 was 15.3 mm, the inner diameter (insertion hole) was 12.08 mm, and the length was 50 mm. First, the tightening ring 7 was cooled to 0 ° C. or lower to be in a martensite state, and this was press-fitted into the outer diameter of the tool mounting portion 5. As a result, the diameter of the tool insertion hole 4 was reduced from 12.08 mm to 12.02 mm. Needless to say, when the tightening ring 7 returns to the austenite state, it is not easily detached from the tool mounting portion 5 even if it is martensite again.

  When the tool holder is cooled to 0 ° C. or lower, the tightening ring 7 transforms into martensite and expands in diameter. At the same time, the tool mounting portion 5 made of carbon steel is also elastically restored and expanded in diameter. After passing through an end mill having a shank diameter of 12.00 mm, the shape memory alloy was heated to advance the transformation to the austenite phase, and a firm grip was obtained. Although this tool holder 1 was attached to a milling machine and machine structural steel was cut, no slipping of the gripping portion occurred.

  Further, when the tool is attached to or detached from the tool holder 1, the tightening ring 7 must be cooled and heated. For this purpose, we developed a cooling-heating device incorporating a Peltier element to simplify and speed up the operation. That is, as shown in FIG. 5, two antifreeze tanks 31 and 32 are provided in one block 30, and Peltier elements 33 and 33 are arranged in close contact with the outer wall of one tank to energize them. At the same time, the other antifreeze bath is heated by the heat discharged from the Peltier element 33, and the remaining heat is discharged out of the apparatus by the cold water flowing through the cooling water hole 34, and the temperatures of both antifreeze liquids 35 and 35 are adjusted. To do. Although not shown in the drawing, it is possible to attach a heater for heating to the antifreeze liquid layer on the heating side, and furthermore, a control device for temperature control. Although the tool mounting part of the tool holder, which is a combination of S30C and shape memory alloy, was immersed in the antifreeze bath adjusted in temperature by this device and cooled or heated, the clamping ring 7 changed its phase in several tens of seconds. The tool can be easily attached and detached. The cooling antifreeze bath 31 is formed with a heat insulating gap 36 at the periphery thereof.

The Ti—Ni shape memory alloy of Example 1 has an austenite finish temperature A _f of 20 to 25 ° C., and a lower A _f temperature may be desired in the cold season. Therefore, shape memory is subjected to shape memory heat treatment in the range of 350 ° C. to 540 ° C. for alloys in which 0.1 to 5.0 at% of Co, Cr, Fe, V, or Mo is added to Ti—Ni alloys, respectively. When an alloy was produced and used for the fastening ring 7, both the austenite finish temperature A _f and the martensite finish temperature Mf were reduced by 2 to 20 ° C. Therefore, the tightening ring 7 using the shape memory alloy of this composition can sufficiently withstand use in a cold region.

  By determining the relationship between the inner and outer diameters of the tool mounting portion in the tool holder, the inner and outer diameters of the shape memory alloy fastening ring fitted to the tool holder, and the shank diameter of the tool to be used, as described above. The tool can be firmly held without forming a longitudinal slit in the mounting portion, and the tightening holder does not easily fall off from the tool mounting portion, thereby improving operability. In addition, a small-diameter tool can be accurately gripped without eccentricity, and is used for cutting and grinding deep metal molds.

It is a side view which shows the state which attached the tool holder which concerns on this invention to the machine tool, and represents with a partial cross section. FIG. 2 is an enlarged view of a main part of the tool holder of the present invention. FIG. 3 is a graph showing the relationship between the shape change of the shape memory alloy and the inner diameter of the tool mounting portion when a shape memory alloy fastening ring is externally fitted (combined) with the tool mounting portion made of S30C. FIG. 4 is a graph showing the relationship between the phase change of the shape memory alloy and the inner diameter of the tool attachment portion when the shape memory alloy fastening ring is externally fitted (combined) with the tool attachment portion made of aluminum alloy. FIGS. 5A and 5B are liquid temperature adjusting devices for cooling and heating the tool mounting portion of the tool holder. FIG. 5A is a plan view and FIG. FIG. 6 is a cross-sectional view showing a conventional example. FIG. 7 is also a perspective view showing a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tool holder 2 Holder shank part 3 Flange part 4 Tool insertion hole 5 Tool mounting part 6 Tightening ring 10 Tool 11 Shank 20 Spindle 30 Block 31, 32 Tank for antifreeze liquid 33 Peltier element 34 Cooling water hole

Claims (3)

A conical holder shank that fits into the main spindle of the machine tool is used as the base end to contact the holder shank to form a flange, and further, a tool attachment on the tip side. A threaded hole extending in the axial direction from the end surface on the base end side, and a tool mounting hole for inserting a shank portion of the tool to be used in the tool mounting portion are formed in the axial direction from the end surface of the tool mounting portion. And a tool holder having a configuration in which a tightening ring made of a shape memory alloy is externally fitted to the tool mounting portion, and the tool mounting hole has a diameter of the tool to be inserted in the martensite state of the tightening ring. A static fit that is larger than the shank diameter, small in the austenite state, and in which the tightening ring does not easily fall off from the tool mounting portion in the martensite state. The tool holder, wherein the door.   The shape memory alloy used for the clamping ring is at least Ni: 49.5 to 51.3%, Ti—Ni alloy with Ti remaining, or Ni: 48.0 to 51.0% with Co, Cr, The fastening ring is formed of any one of Fe, V, and Mo or an alloy containing 0.1 to 5.0% of a plurality of these elements and the balance being Ti. Tool holder.   Two antifreeze tanks are provided in one block, and a Peltier element is arranged around one of the tanks to cool it, and at the same time, the antifreeze in the other tank is heated with heat discharged from the Peltier element. 3. The temperature adjusting device for a tool holder clamping ring according to claim 1, wherein the remaining heat is discharged out of the block with cold water flowing through the cooling water hole.

Images