JPH02167601A - Flexible vibrator - Google Patents

Abstract

PURPOSE:To set a flexible vibrator used for a supersonic vibration cutting device to a vibrational condition in the proper Y axis direction by making an inertial mass of a vibrational system comprising an electrostrain element in the flexible vibrational direction different from that of each flexible resonance vibration in the direction orthogonal to said flexible vibrational direction. CONSTITUTION:A large diameter portion of a flexible vibrator 29 is formed of metal materials 29,31 and annular electrostrain elements 4,5 sandwiched therebetween from both sides. The electrostrain elements 4,5 are polarized in the thickness direction and have electrodes divided diametrally. A tool holder 15 to which a tool 14 is secured fixedly is mounted on the output end of the metal material 31. A metal material 30 is shorter than prior ones and the large diameter portion of metal material 31 is elongated and provided in the upper and lower portions with round holes 32,33. With the round holes 32,33 thus provided, the flexible resonance frequency of Y axis is largely reduced, while the flexible resonance frequency of X axis is only slightly reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides an ultrasonic wave generator suitable for use in ultrasonic vibration cutting devices such as lathes and shapers that cut by vibrating a blade in the cutting direction using ultrasonic vibrations. This relates to a flexural oscillator that is a source of vibration.

BACKGROUND OF THE INVENTION As a vibrator used in a conventional ultrasonic vibration cutting device, a flexural oscillator that generates flexural vibration by itself is used. In addition, since the vibration direction of such a flexible vibrator at its output end is perpendicular to its axis, it cannot be vibrated perpendicularly to the pressure applied during processing, such as in an ultrasonic welder or an ultrasonic cutter. Due to its mechanical advantages, it is often used in cases where

Such a flexural oscillator is disclosed in Japanese Patent Application Laid-Open No. 62-114478.
As is clear from Japanese Patent Laid-Open No. 63-191501, an ultrasonic vibration cutting device to which the same is applied has already been proposed by the present applicant.

An example of using a vibration system using such a flexible oscillator in an ultrasonic vibration cutting device will be described with reference to FIGS. 6 to 10. First, the deflection vibrator 1 has a large diameter portion formed by metal materials 2 and 3 and two annular electrostrictive elements 4.5 sandwiched between the metal materials 2 and 3 on both sides. These electrostrictive elements 4.5 are polarized in the thickness direction and have electrodes 6 and 7 separated in the diameter direction.

These two electrostrictive elements 4.5 are stacked one on top of the other with electrode plates 8 and 9 in between, with their electrodes 6.7 facing each other. And, on the inner periphery of the electrostrictive element 4.5,
An insulating tube 10 is inserted, and a common electrode plate 11 is provided between the electrostrictive element 5 and the metal material 3. Furthermore, a screw hole 13 into which a bolt 12 is screwed is formed at one end of the metal material 2, and the screw holes 13 are fastened together by the bolt 12.

Although the electrostrictive elements 6 and 7 have been described as having an annular shape as shown in FIG. 7, in actual practice, a pair of semicircular elements as shown in FIG. 9 are used. It's okay.

Next, a cutting tool holder 15 to which a cutting tool 14 is fixed is attached to the output end of the metal material 2. The reason for using this cutting tool holder 15 is that if the cutting tool 14 is directly fixed to the output end of the flexible oscillator 1, the entire flexural oscillator 1 must be removed when replacing the tool 14 or resharpening the cutting edge. This is to prevent the work from becoming complicated.

The mounting structure of the tool holder 15 will now be explained. First, the joint between the cutting tool holder 15 to which the cutting tool 14 is fixed and the metal material 2 is located in the loop portion L1 of the vibration distribution shown in FIG. 6(b).

A left-hand thread 16 is formed at the end of the tool holder 15, and a right-hand thread 17 is formed at the end of the metal material. The tool holder 15 is fastened to the metal material 2.

The vibration amplitude on the central axis during resonance vibration of the flexural oscillator 1 is determined by the nodes Nl and N2 as shown in FIG. 6(b).
It is greatly enlarged by the stepped part formed in the middle. and,
Node N2. Conical recess 19.2 located at N3 part
0 are formed on the side parts, these conical recesses 19.20
It is fixed to the indicator (not shown) by strongly abutting the point bolts or the like from four locations on both sides.

Common electrode plate 11 of the flexible vibrator l configured in this way
Apply drive voltages with opposite phases to each other to the electrode plates 8 and 9 using the voltage as a reference potential, or arrange the polarization directions of the electrostrictive elements 4.5 opposite to each other and apply drive voltages with the same phase to change the frequency. When adjusted to the resonant frequency, the vibration amplitude distribution as described above is generated and resonance vibration occurs, and the cutting edge of the cutting tool 14 strongly vibrates in a direction perpendicular to the axis as shown by the arrow 21. By machining the workpiece while applying ultrasonic vibrations in the tangential direction of the workpiece as a cutting tool on a lathe, great vibration cutting effects are achieved, such as significantly reducing cutting resistance and improving machining accuracy.

Problems to be Solved by the Invention Various tools are interchangeably attached to the output end of such a flexible vibrator 1 depending on the purpose. Examples of tool holders used for vibration cutting are shown in Figures 11 to 1.
It is shown in Figure 7.

What is shown in FIGS. 11 to 13 is a tool holder 23 in which a serious tool 22 of normal amplitude is bonded with silver solder.

The one shown in FIGS. 14 and 15 is a high-amplitude tool holder 25 equipped with a throw-away tip 24 that vibrates with a large amplitude by driving from the same deflection vibrator 1.
It is.

What is shown in Fig. 16 and Fig. 17 is the thread cutting tool 2.
This is a high-amplitude thread cutting tool holder 27 in which 6 is bonded with silver solder.

When the bending vibrator 1 is driven using these tool holders 23, 25, and 27, the tool cutting edge resonantly vibrates linearly in the vertical direction in the figure.

However, with a tool holder that is made thinner and vibrates with a larger amplitude, or has a special shape, the vibration of the cutting edge interferes with resonance in other directions, and the vibration mode becomes a straight line perpendicular to the axis. Instead, the angle of inclination changes, or the shape becomes arcuate or elliptical.

Such arcuate or elliptical vibrations are extremely harmful in some vibration cutting processes, causing not only roughening of the machined surface of the workpiece but also increased wear and chipping of the cutting edge.

Next, the cause of such harmful vibration state will be explained.

As shown in Figure 13, the vertical direction is Y when viewed from the front of the cutting edge.
If the horizontal direction is the X-axis, and the longitudinal direction of the vibrator is the Z-axis, in normal vibration conditions, only the vibration in the Y-axis direction vibrates linearly, which is the driving principle of the flexible vibrator 1. The vibration distribution based on this figure is shown.

However, from the perspective of the configuration of the flexural vibrator 1, which takes into account the characteristics and dimensions of each electrostrictive element 4, 5, and the dimensional accuracy of the metal material 2.3, it is found that complete mechanical equilibrium is achieved in the Y-axis direction. Because it cannot be obtained, X due to deflection drive in the Y-axis direction
It also has an axial resonance response, and its X-axis resonance frequency is close to that of the Y-axis. That is, since the vibrator 1 has a circular cross section, the x, Y of the vibrator 1 itself
The axial resonance frequencies are almost the same, and when the tool holders are installed, the difference in their resonance frequencies only arises due to the difference in the shapes of the X and Y axes of the tool holders.

Furthermore, a resonance response in the Z-axis direction, that is, in the longitudinal vibration direction, is also generated due to the deflection drive in the Y-axis direction.

Due to these composite responses, the vibration of the cutting edge depicts a variety of vibration modes depending on the drive frequency of each tool holder.

In general, the Z-axis resonant frequency and the X and Y-axis resonant frequencies can be easily separated from each other by taking into account the order of the flexural vibration distribution, so with proper design there is little chance of a major problem. However, as mentioned above, the X and Y axis resonance responses are directly affected by the shape of the tool holder, and if the thickness in the Y axis direction is determined by the required vibration amplitude of the tool, the X and Y axis resonance frequencies will be It will inevitably be decided.

On the other hand, as a tool holder, in addition to the amplitude, it must be compatible with a variety of shapes such as serious tools, single-edged tools, thread cutting tools, flat-edged tools, and parting tools, and there are also various sizes of throw-away tips. , it is extremely difficult to separate the resonance frequencies of the X and Y axes for all types.

Next, let's consider how the relative relationship between the X- and Y-axis resonance responses affects the vibration direction of the cutting edge.

First, FIG. 18 shows the response when they become almost the same frequency. The resonance response of the Y axis is
As shown in the figure (a), normal deflection vibration @ in the Y-axis direction is generated at the parallel resonance frequency fa, but at the series resonance frequency f
At r, the response is cracked under the influence of the X-axis resonance response shown in FIG. Next, as shown in Figure 19, if the X-axis resonance frequency is lower than that of the Y-axis, f
Since both r and fa perform normal flexural vibration, there is no problem.

Furthermore, as shown in Figure 20, when the X-axis resonance frequency is higher than that of the Y-axis, normal vibration occurs at fr, but
The resonance characteristics at fa are greatly disturbed, and the resonance state is significantly disturbed, similar to fr in FIG. 18(a).

If the X-axis series resonance response exists near the desired Y-axis drive frequency, which is the original flexural vibration,
The vibration state becomes abnormal due to interference from the X axis.

Means for Solving the Problem A difference is made between the inertial mass of flexural resonance vibration in the flexural vibration direction of a vibration system including an electrostrictive element and the inertial mass of flexural resonant vibration in a direction orthogonal to the flexural vibration direction. As a means for this, the dividing gap of the electrostrictive element is widened, or a cavity or a notch is provided in the metal material connected to the electrostrictive element.

By providing a working cavity or notch or widening the dividing gap of the electrostrictive element, the flexural resonance frequency in one direction can be
It is lower than the deflection resonance frequency in the perpendicular direction.
, the difference in the Y-axis resonance frequency increases, and the interference of the X-axis resonance response with the Y-axis resonance response disappears, resulting in a correct vibration state in the Y-axis direction.

Embodiment A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. Portions that are the same as those shown in the prior art example described above are designated by the same reference numerals, and description thereof will be omitted. In this embodiment, the metal material 3 in the conventional example of the deflection vibrator l shown in FIG. Round holes 32 and 33 are provided above and below 31 to form a deflection vibrator 29.

Since the round holes 32 and 33 are provided in the Y-axis direction, the Y-axis deflection resonance frequency is greatly reduced compared to the deflection vibrator 1 shown in Fig. 6, while the X-axis deflection resonance frequency is only slightly reduced. Therefore, the difference in the resonance frequencies of the x and y axes greatly expands as shown in the respective responses shown in FIG.

According to such a flexure vibrator 29, when a tool holder that is thin in the X-axis direction and thick in the Y-axis direction is used, the difference between the resonance frequencies in the X and Y-axis directions is reduced, and the Y-axis resonance response is This causes interference, and for example, the shape of a cut-off tool is limited.

However, with frequently used tool holders, it is common to keep the same width in the X-axis direction and make it thinner in the Y-axis direction in order to obtain the necessary amplitude. This type is the most preferable configuration because it is the direction in which the difference from that of the axis increases.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. A flexible vibrator 34 shown in FIG. 3 is constructed by cutting both sides of the metal material 2 and metal material 3 of the conventional example of the flexible vibrator 1 shown in FIG. 35 and metal material 36. Therefore, since the mass in the X-axis direction is removed, the X-axis resonance frequency is greatly reduced compared to the flexure vibrator l shown in Figure 6, and the Y-axis resonance frequency remains almost unchanged. As shown in the response, the difference increases as the X-axis resonance frequency decreases.

According to such a flexible oscillator, it is thick in the X-axis direction and thick in the Y-axis direction.
When a tool holder that is thin in the axial direction is used, the difference becomes smaller and interference occurs, and such a tool holder for high amplitude use is limited in its shape. Therefore, the flexural oscillator 34 having such a structure is
Applicable to relatively low amplitude bite holders.

Next, a third embodiment of the present invention will be described with reference to FIG. The one shown in FIG. 5 is one in which the electrostrictive element 4.5 is divided like the conventional example shown in FIG. 9, but the gap between the two is made larger. If the electrostrictive elements 37 and 38 of FIG. 5 as in this embodiment are used in place of the electrostrictive elements 4.5 of FIG. 7 or 9 used in FIG. Since the gap 38 has become wider, the X-axis resonance frequency is lower than the Y-axis resonance frequency, and the difference between them is widened. This is because the inertial mass in the X-axis direction is lower, and the same effect as the second embodiment can be obtained.

As understood from the description of each embodiment above, for example,
- layer

A greater effect can be achieved by combining the respective embodiments described above, such as increasing the difference in the Y-axis resonance frequency.

Moreover, although the embodiment of the flexure vibrator in a vibration cutting device has been described, the present invention can be similarly implemented in tools such as welders and cutters that generate ultrasonic vibrations. That is, in order to separate the deflection resonance frequencies in the X-axis direction and the Y-axis direction, the present invention cuts out the metal material in either direction or widens the division gap of the electrostrictive element to create a difference in inertial mass in each direction. There is something special about it. As a result, various tools (bite holders) can be used without being bothered by disturbances in the vibration state due to interference of the resonance response in the X-axis direction.

Effects of the Invention As described above, the present invention creates a difference between the inertial mass of a flexural resonance vibration in the flexural vibration direction of a vibration system including an electrostrictive element and the inertial mass of a flexural resonant vibration in a direction orthogonal to the flexural vibration direction. As a means of achieving this, the dividing gap of the electrostrictive element was widened, or a cavity or a spark was provided in the metal material connected to the electrostrictive element, so that the flexural resonance frequency in one direction was The deflection resonance frequency in the orthogonal direction is lower than that, and the difference between the X and Y-axis resonance frequencies is expanded, and the interference of the X-axis resonance response with the Y-axis resonance response is eliminated, making it possible to obtain the correct vibration state in the Y-axis direction. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional side view showing the first embodiment of the present invention, and the second
Figures (a) and (b) show the vibration states in the X-axis direction and Y-axis direction.
3 is a perspective view showing the second embodiment of the present invention, FIGS. 4(a) and 4(b) are graphs showing vibration states in the X-axis direction and Y-axis direction, and FIG. A perspective view of an electrostrictive element showing a third embodiment of the invention, FIGS. 6(a) and 6(b) are longitudinal sectional side views showing an example of the conventional structure of a deflection vibrator along with vibration distribution, and FIG. 7 is an electrostrictive element. FIG. 8 is a perspective view of an electrode plate, FIG. 9 is a perspective view showing another shape of the electrostrictive element, and FIG. 10 is a perspective view of the element.
The figure is a perspective view using the electrostrictive element shown in FIG. 9, FIG. 11 is a side view of the tool holder, FIG. 12 is a plan view thereof, and
3 is a front view thereof, FIG. 14 is a side view showing another example of the tool holder, FIG. 15 is a plan view thereof, FIG. 16 is a side view showing still another example of the tool holder, and FIG. 17 is a side view showing another example of the tool holder. Its plan view, FIGS. 18(a)(b) to 20(a)(b)
2 is a graph showing the state of the resonance response between the X axis and the Y axis. 4.5, 37.38... Electrostrictive element, 30, 31° 35
．． 36...Metal material applicant: Taga Electric Co., Ltd." Figure 6

Claims (1)

[Claims] 1. A difference is made between the inertial mass of the flexural resonance vibration in the flexural vibration direction of the vibration system including the electrostrictive element and the inertial mass of the flexural resonant vibration in the direction orthogonal to the flexural vibration direction. A flexural oscillator featuring: 2. The flexural vibrator according to claim 1, characterized in that the dividing gap of the electrostrictive element is widened. 3. A cavity or notch is provided in the metal material connected to the electrostrictive element to create an inertial mass for flexural resonance vibration in the flexural vibration direction of the vibration system and an inertial mass for flexural resonant vibration in a direction perpendicular to the flexural vibration direction. A flexural vibrator that is characterized by a difference between the two.