JP2008023696A - Ultrasonic processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic processing machine with high processing accuracy and small consumption of a tool. <P>SOLUTION: There is a motor 1 for rotating a stainless rotary shaft 2. There are a bearing 3 for rotatably supporting the rotary shaft 2, and a stainless case 10 for fixing the bearing 3. A tool holder 5 is screwed and connected with the rotary shaft 2. There is a stationary side rotary transformer 4b fixed to the case 10. An ultrasonic oscillator 14 for supplying ultrasonic alternating-current power is connected with the stationary side rotary transformer 4b by a lead wire 15b. A rotation side rotary transformer 4a is jointed to a top of the tool holder 5 using screws. The rotation side rotary transformer 4a and a piezoelectric ceramic of an ultrasonic holder 12 are connected by a lead wire 15a. A drill 6 is fitted in the ultrasonic holder 12, is further fitted in a collet 11, and is fixed and held to the tool holder 5 by a fastening nut 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic processing apparatus that applies ultrasonic vibration to a rotating tool to process glass, ceramic, silicone, cemented carbide, and the like, which are workpieces.

Recently, in order to process so-called difficult-to-process materials, a method of applying ultrasonic vibration to a tool or an object to be processed has been frequently used. Such a processing method is called ultrasonic cutting, and is described in detail in Non-Patent Document 1, for example. Ultrasonic cutting has the advantages that the frictional resistance between the workpiece and the tool is reduced, so that the thermal distortion of the machined surface is reduced, the machining accuracy is increased, and the life of the cutting tool is extended. ing.
Ultrasonic Handbook Editorial Committee, “Ultrasonic Handbook”, Maruzen Co., Ltd., August 1999, p679-684

The ultrasonic grinding apparatus is described in detail in Non-Patent Document 2. The ultrasonic grinding apparatus shown in FIG. 1 also has a motor for rotating a rotary shaft, and a slip ring and an ultrasonic vibrator are provided on the rotary shaft. Further, a booster, a horn, and a diamond grindstone as a grinding tool are connected to the rotating shaft. In addition, a bearing for rotatably supporting is arranged. An ultrasonic oscillator and a brush for applying an ultrasonic alternating voltage to the ultrasonic vibrator are provided.
The general operation method of the above ultrasonic grinding apparatus is as follows. First, when the motor is operated, an ultrasonic alternating voltage is applied from an ultrasonic oscillator to a slip ring that rotates through a brush almost simultaneously. The AC voltage applied to the slip ring is applied to the ultrasonic vibrator, and the ultrasonic vibrator vibrates ultrasonically. This ultrasonic vibration propagates through the booster and horn, and then propagates to the grinding wheel, which is a grinding tool.
Japan Electromechanical Industry Association, "Ultrasonic Engineering", Corona Co., Ltd., 1993, p218-229

However, when an ultrasonic vibrator is attached to the rotating shaft, the rotating shaft vibrates ultrasonically, so that the ultrasonic vibration propagates to the bearing and the bearing may be damaged. Also, abnormal wear may occur on the rotating shaft and the bearing, which may increase wear. Furthermore, since a Langevin type ultrasonic transducer, which is an ultrasonic transducer approximately equal to the diameter of the rotating shaft, is joined to the rotating shaft, the weight increases, the rotational inertia increases, and the structure becomes unsuitable for high speed rotation. Further, the rotation becomes unstable due to the shape error and weight imbalance of the ultrasonic transducer bonded to the rotating shaft, the rotating device breaks down, and the processing accuracy decreases.
Another problem is that the chuck device holding the tool and the tool are rubbed with each other by ultrasonic vibration and seizure occurs.
Furthermore, due to the ultrasonic vibration, the holding force of the chuck device that holds the tool sometimes becomes small, and there is a problem that the tool stops when a mechanical load is applied to the tool during processing.

  In addition, since the tool vibrates with the chuck device as a fixed end, the drive frequency must be changed depending on the length of the tool from the fixed end. However, the Langevin type ultrasonic vibrator, rotating shaft and horn Since the mass is large, vibration can be efficiently excited mainly only at the natural frequency of the Langevin type ultrasonic vibrator. Therefore, there is also a problem that it is impossible to excite vibrations optimal for the tool.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic machining apparatus that can machine a workpiece with high accuracy and high speed and that consumes less of a rotary tool for machining.

  The present invention relates to an ultrasonic machining apparatus having a rotary tool for cutting, wherein an ultrasonic holder having a piezoelectric element holds and holds the rotary tool, and the ultrasonic tool is used directly on a rotation shaft of the ultrasonic machining apparatus or using a chuck device. A sonic holder is fixedly held, and an AC voltage is applied to the piezoelectric element from an ultrasonic oscillator.

  In the present invention, the ultrasonic holder has two cylinders having the same central axis, the outer cylinder and the inner cylinder are connected by an elastic plate, and a piezoelectric element is provided on the outer surface of the inner cylinder. It is characterized by being joined.

  In the present invention, a plurality of elastic plates connecting the outer cylinder and the inner cylinder are provided.

  According to the present invention, the cross-sectional shape orthogonal to the central axis of the cylindrical body is an outer shape of the cylinder or a regular polygon that is equal to or more than a regular tetragon, and an inner shape of the cylinder is a circle or a regular square. The above regular polygon is used.

  The ultrasonic processing apparatus of the present invention can process a workpiece with high accuracy and high speed, and can reduce the consumption of a rotary tool for cutting.

  FIG. 2 is a cross-sectional view showing a basic configuration showing the embodiment of the present invention. A motor 1 for rotating the stainless steel rotating shaft 2 is provided. There is a bearing 3 for rotatably supporting the rotating shaft 2, and there is a stainless case 10 for fixing the bearing 3. A tool holder 5 is screwed to the rotating shaft 2. There is a fixed-side rotary transformer 4 b fixed to the case 10. An ultrasonic oscillator 14 for supplying ultrasonic AC power is connected to the fixed-side rotary transformer 4b by a lead wire 15b. The rotary transformer 4a on the rotation side is joined to the upper part of the tool holder 5 using screws. The rotary transformer 4a on the rotation side and the piezoelectric ceramic of the ultrasonic holder 12 are connected by a lead wire 15a. The drill 6 is fitted into the ultrasonic holder 12, and further fitted into the collet 11, and is fixedly held on the tool holder 5 by a tightening nut 9. Below the drill 6 is a workpiece 7 fixed to the table 8 using wax or the like.

  In the above description, the tool holder 5 with the ultrasonic holder 12 attached to the rotary shaft 2, the collet 11, and the tightening nut 9 are fixed and held. Of course, the ultrasonic holder 12 can be directly attached to the rotary shaft 2. Further, there is a drill chuck as a chuck device for fixing and holding the ultrasonic holder 12.

  Details of the ultrasonic holder 12 will be described with reference to a plan view of FIG. 3 and FIG. 4 showing a cross section taken along line AA of FIG. The ultrasonic holder 12 includes a cylindrical body 16b having a tapered hole 17 for holding a tool, a cylindrical body 16a held by a collet, and elastic plates 18a and 18b connecting these two cylinders. A cylindrical piezoelectric ceramic 13 that is a piezoelectric element is bonded to the outside of the cylinder 16b having the tapered hole 17 using an epoxy resin. As the piezoelectric element, a piezoelectric ceramic is usually used. For example, a piezoelectric single crystal can also be used in an environment where the temperature is particularly high.

  Here, a method of creating the ultrasonic holder 12 will be described. First, the cylindrical piezoelectric ceramic 13 is joined to the outside of the stainless steel cylindrical body 16b having the tapered hole 17 using an epoxy resin. The cylindrical body 16b and the elastic plate 18b are integrally formed. Similarly, the cylindrical body 16a and the elastic plate 18a are integrally formed. By doing so, the number of parts can be reduced and the number of joint portions of the elastic plate can be reduced, so that a highly reliable structure is obtained. Next, the central axes of the stainless steel cylindrical body 16a held by the collet and the cylindrical body 16b to which the cylindrical piezoelectric ceramic 13 is bonded are matched and bonded by an epoxy resin. Here, bonding is performed using an epoxy resin, but there is also a bonding method such as brazing or welding.

  The cylindrical piezoelectric ceramic 13 shown in the perspective view of FIG. 5 is polarized in the radial direction indicated by an arrow. Silver electrodes are provided on the inner and outer surfaces. Further, in order to lead out the lead wire only from the outer surface, a folded electrode is provided from the electrode on the inner surface. For convenience of drawing, only the folded electrodes are indicated by grid-like oblique lines. Then, the lead wire 15a connected to the electrode on the outer surface and the folded electrode connected to the electrode on the inner surface are connected to the lead wire 15b.

  Next, the operation method of this ultrasonic processing apparatus will be described with reference to FIG. First, the motor 1 is turned on and the rotating shaft 2 is rotated. Next, the ultrasonic oscillator 14 capable of tracking the resonance frequency is turned on, and an ultrasonic alternating voltage is applied to the cylindrical piezoelectric ceramic 13 through the fixed-side rotary transformer 4b and the rotary-side rotary transformer 4a. Then, the workpiece 7 is processed by the drill 6.

  Here, the vibration displacement of the ultrasonic holder 12 and the drill 6 fixedly held by the collet 11 is calculated using a finite element method. The calculated model is shown in FIG. In order to shorten the calculation time and to include axisymmetric conditions, only ¼ was calculated with respect to the central axis. As other conditions, displacement outside the cylindrical body 16a held by the collet 11 was constrained.

  Here, dimensions and materials used for the calculation will be described. First, the material of the cylindrical body 16a held by the collet is stainless steel, and the dimensions are an outer diameter of 20 mm, an inner diameter of 16 mm, and a length of 30 mm. The material of the two elastic plates 18a and 18b is stainless steel, and has an outer diameter of 16 mm, an inner diameter of 10 mm, and a length of 2 mm. The cylindrical body 16b having the tapered hole 17 is made of stainless steel, and has an outer diameter of 10 mm and a length of 30 mm. The shape of the tapered hole 17 at the center is 6 mm on the drill tip side and the opposite side. The diameter is 4 mm and the length is 30 mm. The dimensions of the piezoelectric ceramic 13 bonded to the outside of the cylindrical body 16b having the tapered hole 17 are an outer diameter of 12 mm, an inner diameter of 10 mm, and a length of 24 mm.

  The drill fitted into the tapered hole of the cylindrical body is made of tool steel. The diameter of the shank is 6 mm on the drill tip side, 4 mm on the opposite side, and 30 mm in length. Has a diameter of 6 mm and a length of 50 mm.

The drill 6 is roughly classified into a taper shank drill 6a shown in FIG. 8 and a straight shank drill 6b shown in FIG. 9 according to the shape of the shank. The drill is divided into a shank part 19 and a drill part 20. In this embodiment, the drill which is the tool is fixed and held by fitting the drill having the taper of the shank portion 19 into the tapered hole of the cylindrical body, but an instantaneous adhesive may be used to further increase the fixing and holding force. . Since the instantaneous adhesive can be easily removed by the stripping solution, it is suitable for reusing the ultrasonic holder. Moreover, the straight shank drill 6b shown in FIG. 9 is suitable for fixing and holding with a drill chuck. Non-Patent Document 3 describes the drill shank and drill chuck.
Takao Kayaba, “Introduction to Machine Work”, Science and Engineering, 2001, p54-58

  As a calculation condition of the frequency response, 0 volt is applied to the inner diameter side electrode and 1 volt is applied to the outer diameter side electrode of the piezoelectric ceramic.

The calculation result of the frequency response is shown in FIG. The horizontal axis of the graph of FIG. 7 is the frequency, and is calculated from 1 KHz to 100 KHz in 1 KHz steps. The vertical axis represents admittance. From this graph, it can be seen that there are natural vibration modes having natural frequencies at 68 KHz and 89 KHz.

  FIG. 10 shows the 68 KHz natural vibration mode. The inner cylindrical body 16b is displaced by the applied voltage of the piezoelectric ceramic 13. This vibration displacement propagates to the drill 6 connected to the taper hole 17 and causes the drill 6 to vibrate mainly in the axial direction. The magnitude of the vibration of the drill 6 is about 0.2 μm at an applied voltage of 1 volt, and since a voltage of several tens of volts is actually applied, the magnitude of the vibration is sufficient. The elastic plates 18a and 18b connecting the inner cylindrical body 16b and the outer cylindrical body 16a also vibrate, but act as springs due to the shape of the elastic plates 18a and 18b. That is, the action of suppressing the vibration of the inner cylindrical body 16b is small and is connected to the outer cylindrical body 16a. Further, since the outer cylindrical body 16a is fixedly held by the collet, there is no displacement of the outer surface of the outer cylindrical body 16a.

  FIG. 11 shows the natural vibration mode of 89 KHz. The inner cylindrical body 16b is displaced by the applied voltage of the piezoelectric ceramic 13. This vibration displacement propagates to the drill 6 connected to the taper hole 17 and causes the drill 6 to vibrate mainly in the axial direction. The magnitude of the vibration of the drill is about 0.02 μm at an applied voltage of 1 volt, which is about one tenth of the natural vibration mode of 68 KHz. This vibration mode is almost the same as the natural vibration mode of 68 KHz, and the elastic plates 18a and 18b connecting the inner cylindrical body 16b and the outer cylindrical body 16a act as a spring. That is, the action of suppressing the vibration of the inner cylindrical body 16b is small and is connected to the outer cylindrical body 16a. Further, since the outer cylindrical body 16a is fixedly held by the collet, there is no displacement of the outer surface of the outer cylindrical body.

  As described above, the ultrasonic vibration generated by the piezoelectric ceramic 13 is almost concentrated only on the inner cylindrical body 16b and the drill 6 held on the inner cylindrical body 16b, and the outer cylindrical body 16a is obtained by the effect of the two elastic plates 18a and 18b. Hardly propagates. Therefore, the vibration loss is small because the vibration hardly propagates to the tool holder or the like. For this reason, the vibration of a required magnitude | size can be excited to a drill with small electric power. Therefore, since the rise in the temperature of the drill can be reduced, the machining accuracy can be improved. Of course, since vibration hardly propagates to the rotating shaft 2, there is almost no risk of damage due to vibration of the bearing 3 or the rotating shaft 2.

  Also, ultrasonic vibration has the effect of reducing the coefficient of friction, but there is almost no ultrasonic vibration at the contact surface between the tool holder and the ultrasonic holder, so the tool holder and ultrasonic holder are affected by the load when processing the workpiece. Never slip between. Therefore, the drill is broken and the workpiece is not damaged.

  As described above, only the drill and the inner cylindrical body vibrate, so that the frictional resistance between the workpiece and the drill is reduced, so that the thermal distortion of the processed surface is reduced, the processing accuracy is increased, and It has advantages such as a long tool life.

  Of course, since vibration hardly propagates to the rotating shaft, there is almost no risk of damage due to vibration of the bearing or the rotating shaft.

  In addition, when a piezoelectric ceramic is directly joined to a drill, which is a tool, the expensive piezoelectric ceramic must be discarded as the tool is consumed. However, by using the ultrasonic holder as described above, it is only necessary to discard the worn drill, so that the manufacturing cost can be reduced.

  Although the present invention has been described using a cylindrical body as the shape of the ultrasonic holder, for example, the outer cylinder shown in FIG. 12A is a cylindrical body, and the inner cylinder is a regular quadrangular prism having a through hole. Good. Alternatively, the outer cylinder shown in FIG. 12B may be a regular hexagonal pipe, and the inner cylinder may be a regular hexagonal cylinder having a through hole. Further, the outer cylinder shown in FIG. 12C may be a regular octagonal pipe and a cylinder having a through hole inside.

  In the present invention, two elastic plates are used to connect the outer cylindrical body and the inner cylindrical body of the ultrasonic holder, but the plan view of FIG. 13 and the sectional view taken along the line AA of FIG. For example, when a large tool is used, three or more elastic plates may be used to increase the strength of the ultrasonic holder. In accordance with this, a plurality of piezoelectric ceramics may be used.

  Furthermore, in order to reduce the rigidity of the elastic plate, a slit, a hole or the like can be provided in the elastic body. As the material of the elastic plate, a metal material such as titanium, aluminum alloy or stainless steel having excellent vibration fatigue characteristics is suitable.

  Although the present invention has been described using a drill as the rotary tool, examples of the rotary tool include an end mill, a reamer, and a tap.

  The ultrasonic processing apparatus of the present invention can be used in various processing apparatuses that process a workpiece by rotating a tool.

It is a cross-sectional top view which shows the conventional ultrasonic grinding apparatus. It is a front view which shows the basic composition of the ultrasonic processing apparatus using the ultrasonic holder of the 1st Embodiment of this invention. It is a top view which shows an ultrasonic holder. It is a figure which shows the cross section in the AA of FIG. It is a perspective view of the piezoelectric ceramic used for the ultrasonic holder of FIG. This is a calculation model used in the finite element method. It is a graph which shows the frequency response calculated by the finite element method. It is a front view which shows the basic composition of a taper shank drill. It is a front view which shows the basic composition of a straight shank drill. It is a vibration mode of 68 KHz calculated by the finite element method. This is a vibration mode of 89 KHz calculated by the finite element method. It is a figure which shows another form of an ultrasonic holder. It is a top view which shows the ultrasonic holder which has three elastic boards. It is a figure which shows the cross section in the AA of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Rotating shaft 3 Bearing 4 Rotary transformer 5 Tool holder 6 Drill 7 Work piece 8 Table 9 Clamping nut 10 Case 11 Collet 12 Ultrasonic holder 13 Piezoelectric ceramic 14 Ultrasonic oscillator 15 Lead wire 16 Cylindrical body 17 Tapered hole 18 Elasticity Plate 19 Shank 20 Drill

Claims (4)

  In an ultrasonic processing apparatus having a rotary tool for cutting, an ultrasonic holder having a piezoelectric element fixes and holds the rotary tool, and the ultrasonic holder is fixed and held on the rotary shaft directly or by using a chuck device. In addition, an AC voltage is applied to the piezoelectric element from an ultrasonic oscillator.   The ultrasonic holder has two cylinders having the same central axis, the outer cylinder and the inner cylinder are connected by an elastic plate, and a piezoelectric element is bonded to the outer surface of the inner cylinder. The ultrasonic processing apparatus according to claim 1.   The ultrasonic processing apparatus according to claim 2, wherein there are a plurality of elastic plates connecting the outer cylinder and the inner cylinder.   The cross-sectional shape orthogonal to the central axis of the cylindrical body is characterized in that the outer shape is a circle or a regular polygon of a regular tetragon or more, and the inner shape is a circle or a regular polygon of a regular tetragon or more. The ultrasonic processing apparatus according to claim 2.

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