WO2000048801A1

WO2000048801A1 - Circular saw

Info

Publication number: WO2000048801A1
Application number: PCT/JP2000/000576
Authority: WO
Inventors: Satoru Nishio; Yasutaka Nakajima
Original assignee: Kanefusa Kabushiki Kaisha
Priority date: 1999-02-19
Filing date: 2000-02-02
Publication date: 2000-08-24
Also published as: JP3218434B2; JP2000238003A

Abstract

A circular saw capable of being provided with a base metal which can cut even in a rotating zone of min. critical rotation speed or higher, being used in a high-rotation-speed zone even if the base metal is thin, reducing a saw thickness by an amount equal to the reduced amount of the base metal, setting a high feed rate because a cutting force per tooth can be reduced by that amount, and thus increasing a work machining efficiency and an operating efficiency, characterized in that it can be used in a zone of min. critical rotation speed or higher at the time of cutting of a work and, in two modes where the node circular number of the base metal of the circle saw (m) is 0 and the same node diameter number is (n), a relative difference in natural frequency between the circular saw natural frequency and a natural frequency difference Δfn/fn1 is 3.0 % or more for the node diameter number n = 3 and 3.5 % or more for the node diameter number n = 4, where the natural frequencies of the circular saw are fn1 (Hz) and fn2 (Hz) (where fn2 ⊃ fn1) and the natural frequency difference Δfn = fn2-fn1.

Description

Specification

Circular saw technology

The present invention relates to a circular saw capable of satisfactorily cutting a workpiece without causing meandering of a base metal even when the rotation speed reaches a minimum rotation speed or more. Background art

Work such as wood, resin materials and other non-ferrous metals is generally cut by a circular saw (so-called chip saw) in which a carbide tip is brazed to the outer periphery of a base metal made of special steel. It is known that this circular saw is rotated at a high speed when cutting a workpiece, but the maximum rotational speed of the circular saw is limited by the “minimum critical rotational speed” inherent to the base metal. In other words, in a circular saw, the heat generated at the outer periphery of the base metal is generally higher than that near the center flange due to the friction between the workpiece and the cutting blade during cutting and the friction between the chips and the base metal. Leads to decline. When the circular saw is used at a rotational speed slightly lower than the minimum critical rotational speed inherent to each circular saw, the rotational speed in use becomes the minimum critical rotational speed as the minimum critical rotational speed decreases. When the rotation speed of the circular saw reaches the minimum critical rotation speed in this manner, the lateral rigidity of the base metal in that mode becomes extremely small, and the base metal is left and right due to the lateral load applied during wood cutting. It begins to meander. This is a kind of buckling phenomenon.Even if the rotation speed of the circular saw is increased from the minimum critical rotation speed, the base metal continues to meander in that mode, and the degree of the meandering increases from the critical rotation speed. It increases in proportion to the amount. For this reason, it is not possible to cut a workpiece with a circular saw above the minimum critical rotation speed, and in general, it is used in the rotation speed range below 85% of the minimum critical rotation speed.

In order to suppress the lowering of the minimum critical rotation speed due to the rise in As a means for this, it has been proposed to drill multiple slits in the circular saw base. In this case, the center angles of the slits adjacent to each other are equidistant or unequal, and the length of the slits is generally the same, and is about 5 to 10% of the radius of the base metal. (In special cases, it extends to near the center flange). Circular saws have also been proposed in which adjacent slits have different lengths, and every other adjacent slit has the same length. In this case, the number of slits is even and the center angles are equally spaced, and the sum of the lengths of the two slits diametrically opposite each other across the center is the same. However, this proposal is not perfect, and if the temperature rise of the metal base becomes severe, the minimum critical rotation speed will drop significantly, causing the meandering phenomenon described above.

However, from the viewpoint of effectively using limited wood resources, it is required to reduce the thickness of circular saws used for cutting wood. This is because the greater the thickness of the circular saw, the more material is lost in cutting the wood. However, if the thickness of the base metal is reduced along with the thickness of the circular saw to meet this demand, the critical rotation speed will also decrease. As described above, since the circular saw must be used at, for example, 85% or less of the minimum critical rotation speed, the rotation speed of the circular saw must necessarily be reduced. For example, if the thickness of the circular saw and the thickness of the base metal are set to half that of the conventional base metal, the minimum critical rotation speed will be halved.

Circular saws used at 5,000 rpm will have to be used at 2,500 rpm, half of the normal rotation speed. Moreover, since the rigidity of the metal base is proportional to the cube of the thickness, reducing the metal base thickness to half reduces the rigidity to 1/8. When the speed is the same, the depth of cut per tooth is doubled, but the cutting force per tooth is the same, but considering that the rigidity is reduced to 1/8 as described above, the feed rate of the work Has to be reduced to 1/8, which has the disadvantage that the machining efficiency is greatly reduced. It is pointed out that the cutting of the ffi becomes difficult and the appearance becomes poor.

The present invention has been proposed in order to suitably solve the above-mentioned problems, and can provide a base metal capable of cutting even in a rotation range higher than the minimum critical rotation speed. And the saw thickness can be reduced by the thickness of the base metal, so the cutting force per tooth can be reduced by that much and the feed rate can be set high. And a circular saw capable of improving efficiency. Disclosure of the invention

In order to overcome the above-mentioned problems and achieve the intended object, the present invention relates to a circular saw which can be used in a region of a minimum critical rotation speed or more at the time of cutting a work, and a metal circle of a base metal in the circular saw. In two modes where the number m is 0 and the number of nodal diameters is n,

If the natural frequency of the circular saw is fn ^ Hz) and fn ₂ (Hz) (where fn ₂ > f), the natural frequency difference n = fn ₂ — f, the relative natural frequency difference

△ f n / f is characterized by being 3.0% or more when the number of nodes is n = 3 and 3.5% or more when the number of nodes is n = 4.

Another object of the present invention is to overcome the above-mentioned problem and achieve a desired object by providing a circular saw that can be used in a region of the minimum critical rotation speed or more when cutting a work. In two modes where the number of knot circles m is 0 and the number of knot diameters is n,

If the natural frequency of the circular saw is fn ^ Hz) and fn ₂ (Hz) (where fn ₂ > f) and the natural frequency difference n = fn ₂ — f, the relative natural frequency difference

△ fn / fn is 15% or more when the number of nodes is n = 2 and 3.0% or more when the number of nodes is n = 3. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the relationship between the rotational speed N and the backward wave frequency fb for a circular saw having no outer slit.

FIG. 2 is a graph showing test results of work cutting of a circular saw having no perimeter slit.

FIG. 3 is a graph showing the relationship between the rotation speed, the backward wave frequency, and the displacement of the base metal in the circular saw of No. 6S30.

FIG. 4 is a graph showing the test results of the circular saw NO.2S60-2S45.

Fig. 5 shows that, of the four slits with the same center angle, the length of two slits facing each other with the center in between is set to the same length, and the length of the adjacent slit is set to the same length. It is the schematic of the circular saw which changed.

FIG. 6 is a graph showing the results of finite element analysis performed on the circular saw shown in FIG. 5 using a shell model.

Figure 7 shows a circular saw in which two slits opposing each other across the center of the four slits of equal length have different center angles with respect to the adjacent slits. It is a schematic diagram.

FIG. 8 is a graph showing the results of finite element analysis performed on the circular saw shown in FIG. 7 using a shell model.

FIG. 9 is a graph showing the relationship between the ratio A / B of the flange diameter and the base metal outer diameter to the critical speed function S (A / B) for a circular saw without slits. Figure 10 is a schematic diagram showing that there are two vibration modes, the first mode shown in (A) and the second mode shown in (B), at the number of knot circles of the circular saw m and the number of knot diameters n. FIG.

FIG. 11 is a schematic explanatory diagram when displacement of a base metal in a circular saw is measured by, for example, an eddy current sensor.

Figure 12 shows the artificially induced vibration of a circular saw, for example, two non-contact displacements. It is a schematic explanatory view at the time of measuring with a sensor.

FIG. 13 shows an example in which a circular saw is virtually divided into eight regions, and a slit is included in the middle of two of these regions. It is a schematic explanatory diagram when avoiding every other region and performing partial squatting. BEST MODE FOR CARRYING OUT THE INVENTION

Next, the technical background required for understanding the circular saw according to the present invention will be described first, and then various experimental examples will be described with reference to the accompanying drawings. When any stress is applied to the rotating circular saw from the outside, vibration is excited in the circular saw. This vibration is caused by the base metal of the circular saw alternately vibrating on the front side and the back side at the node diameter extending in the diameter direction of the circular saw. Except for n = 0, there are two modes (degenerate pairs) as shown in Fig. 10, except for n = 0, where the number of knots is m and the number of knots is n. That is, the position of the node diameter d in the first mode shown in FIG. 10A is intermediate between the positions of the node diameter d in the second mode shown in FIG. 10B. Note that the buckling phenomenon in question here is generally the case where the number of section circles is m = 0, so the following description also relates to the case where m = 0. Figures 10 (A) and 10 (B) are examples of the number of knot circles m = 0 and the number of knot diameters n = 2 _(for the circular saw in the first and second modes, the maximum amplitude at the radius r is shown). If the function representing the shape is Un ^ r), Un ₂ (r), and the natural frequencies are f and fn ₂ , the vibration in the direction in which the circular saw is rotated by 0 from the nodal diameter position in the first mode ! ! , ^) Can be expressed as follows.

Un, (r, Θ, t) = Un ₁ sin (n0) cos (2 ττ fn, t)

The vibration Un ₂ (r, Θ, t) in the direction in which the circular saw is rotated by Θ from the nodal diameter position in the second mode can be expressed as follows.

Un ₂ (r, 0, t): Un ₂ cos (n Θ) cos (27Γ fn ₂ t + ø) Where (^ is the phase angle between the two modes.

So the maximum amplitude shape function

Assuming that fn ₂ -fn and phase angle φ = 7Γ. / 2, the backward wave (wave propagating in the direction opposite to the circular saw rotation direction) at the circular saw rotation Ν is transmitted to an external observer. for

Un (r, Θ, t) = Un (r) sin [2 ττ (fn-nN / 60) t]

Will vibrate. The frequency of this backward wave is fb = f n — nN / 60, and the rotation speed at which the frequency becomes zero (0) is the above-mentioned critical rotation speed (Nncr = 60 · f η / η). In addition, the lowest one of the Nncrs in each node diameter mode is called the minimum critical rotation speed (Ncrniin).

As described above, the buckling refers to a phenomenon in which the natural frequency of the backward wave becomes zero (0) and the rigidity is lost with respect to the base of the circular saw viewed from the space. The meandering of the circular saw base during the cutting of the workpiece at the critical rotation speed is caused by the coupling of the first mode and the second mode with the same critical rotation speed as the nodal diameter number n. It is. However, the above-mentioned buckling phenomenon in the rotation speed region above the minimum critical rotation speed is actually nonlinear, and this has not been sufficiently elucidated until now. However buckling phenomenon in the backward wave is thought to be the natural frequency f ≠ fn ₂ Tosureba inhibition of each mode, formed continuously you release to what extent the natural frequency of the first mode and the second mode Whether it disappeared was studied through various tests.

The specifications of the circular saw used in this test are as follows. Note that the following dimensions 111 are expressed in mm.

• B type chip saw 03O5X2.2X1.6X25.4X6OP

(Circular saw diameter) χ (Saw thickness) χ (Base metal thickness) χ (Shaft hole diameter) χ (Number of saw blades)

• Rake angle 20 ° Side rake angle 0 ° Tip clearance angle 15 ° Tip inclination angle 0 ° Side clearance angle 3 ° Side centroid angle

• Flange diameter 080 0110 0120 130 • With two external slits, Ls = 0 to 45 (slit length)

Ls = 0 to 45 (slit length) with 6 wires

Ls = (45-60) with 2 pieces and 2 pieces

Combination of Ls two (30-50)

The conditions for the cutting test using a circular saw are as follows.

• Work material Medium density fiber board to minimize the effect of grain

(; MDF) having a thickness of 12 mm was used.

• Rotational speed From below the minimum critical rotational speed to the rotational speed at which the circular saw meanders (upper limit is 7900r.p.m., Where mechanical vibration occurs)

'Feed (F) 7.0m per minute

• Displacement As shown in Fig. 11, the displacement of the circular saw base metal was recorded on the pen recorder using the output of the eddy current sensor S (non-contact displacement sensor) using a 10 Hz mouth-to-pass filter. The displacement of the pen recorder having recorded the base metal (absolute value) was at or over 0.1mm and buckling rotational speed N _b.

About a circular saw without a slit

The relationship between the rotation speed N and the backward frequency fb was confirmed for a circular saw without the slit described above. The flange diameter in this case is 110 mm. Figure 1 shows the relationship between the rotational speed (horizontal axis) and the backward wave frequency (vertical axis) (forward waves are omitted). As can be seen from Fig. 1, the critical rotation speed at which the natural frequency of the backward wave becomes zero (0) is as follows.

Nodal diameter n = 2 N _2cr = 6369r.pm

'Nodal diameter n = 3 N ;, _cr = 6039r.p.ffl.

• Nodal diameter n = 4 N, _cr = 6887r.pm

Nodal diameter n = 5 N _2cr = 7914r.pm

Minimum critical rotational speed according to the in the case of n = 3, Ru N _er min = 6039r.pm der. Note that the natural frequencies f and fn ₂ of each mode are determined by using The vibration generated by the impact was measured by, for example, two non-contact displacement sensors S, S shown in FIG.

Figure 2 shows the results of a test for cutting a workpiece with a circular saw in which the slit is not drilled in the base. W on the vertical axis indicates the maximum radius (the maximum value of the displacement) at the position where the displacement sensor S is disposed.

In FIG. 2, the right vertical axis indicates the rotational speed and the reverse frequency in each mode, the solid line indicates n = 3, the broken line indicates n = 2, and the dashed line indicates n = 4. The left vertical axis represents the number of rotations and the amount of deflection.

If no Sri tool Bok within circular saw from the figure, buckled the mode is reached the critical number of revolutions of n = 3 is the minimum critical rotational speed _{_{(N er min = 6039r.p. M}} .), Circular saw The metal meandered to the left and right. Once the meandering occurred, the circular saw continued to meander even if the rotation speed was further increased, and the amplitude increased as the rotation speed increased.

Circular saw with 6 slits

As mentioned above, the circular saw without slits buckled when it reached the critical rotation speed of n = 3. Therefore, a circular saw was prepared in which six slits were drilled so that the adjacent central angles and lengths were equal, and in the mode with the number of nodal diameters n = 3, a slit with a nodal diameter at the position of the slit It was divided into a nodal type and an anti-nodal type with a nodal diameter in the middle of each slit. At this time, Sri Tsu Tonodaru type of natural frequency fn, is lower Ri good Anchino one Darutaipu of natural frequency fn _2.

Table 1 shows the relationship between the critical rotation speed N ncr for each mode and the buckling rotation speed Nb when actually buckled, and Table 2 shows the relationship between the natural frequency separation and buckling. Regarding the circular saw No. in the table, SO indicates a circular saw without a slit, and 6S indicates a circular saw with six slits. Also, the two digits following 6S Indicates the j-length (mm) of the slit. Furthermore, in Table ² , ① “〇” indicates that buckling occurred in the corresponding mode, ② “X” indicates that buckling did not occur in the corresponding mode, and ③ “-” indicates This indicates that the buckling speed Nb did not reach the critical speed for the mode.

【table 1 】

[Table 2]

Relationship between natural frequency separation and buckling.

From this table, it was found that if 7.5Hz,: _i / f _{: il} ≥3.0%, buckling of the nodal diameter number n = 3 would not occur. However Taken together Table 4 to be described later, further to modify numerical △ _{f: l>} 6.2 Hz, it is capable of reliably suppressing viii / _1> 2.5% Tosureba buckling. For example, FIG. 3 shows the relationship between the rotational speed N, the backward wave frequency fb, and the displacement W of the base metal in a circular saw having a flange diameter of 110 and a NO. 6S30. When the nodal diameter number _{n = 3, △ f:!} > 12.5Hz, △ f 3 / f 31> 6.2% the critical rotational speed _{N:.. Il cr = 4802r.p} m and N ₃₂ cr = 5131r.pm, but buckling did not occur even when the rotation speed was reached. However, buckling occurred in this mode when the critical rotational speed N ₄ cr = 5428r.pm was reached at the node diameter n = 4. However, at the rotational speed at which the critical rotational speed and the rotational speed at which the nodal diameter number η = 3 exactly matches the nodal diameter, the nodal diameter is fixed on the base of the circular saw, and a so-called standing wave Although the amplitude of the vibration was not large, displacement occurred. This phenomenon was common to all circular saw bases designed to suppress buckling.

In FIG. 3, n = 31 indicates the first mode of n = 3, n = 32 indicates the second mode of n = 3, and the same applies to other n hereinafter.

Circular saw with two slits

Based on the same idea as above, two slits of equal length are placed on the base metal at equal intervals in order to suppress buckling of the node diameter numbers _n = 2 and n = 4 in addition to the node diameter number n = 3. Drilled. Assuming a perfect disk that is materially uniform, theoretically, if there are two slits, all modes are separated into two except for the number of nodal diameters n = 0. The results are shown in Table 3 as the relationship between the critical speed for each mode and the speed at which buckling occurs. The column of buckling rotation speed Nb, which is blank in Tables 1 and 3, indicates that buckling did not occur even when the workpiece was cut up to the test rotation speed of 7900 rpm. [Table 3] Relationship between critical rotation speed and buckling rotation speed

[Table 4]

Relationship between natural frequency separation and buckling.

From Table 4, it can be seen that buckling can be suppressed in the mode with the number of nodal diameters n = 4 by setting A f ₄ 12.5 Hz and A f ₄ / f ₄₁ ≥ 3.4%. However, when the nodal diameter is n = 2, this step Suppress buckling on the floor:

Circular saw with 4 slits

In order to greatly separate the natural frequencies of the two modes with the nodal diameter of n = 2 while suppressing buckling at the nodal diameters n = 3 and n = 4, four slits are drilled at equal intervals. Established. At this time, the lengths of the slits facing each other across the center were the same, but the lengths of the adjacent slits were changed. Table 5 shows the relationship between the critical rotation speed and the rotation speed at which buckling occurs for each mode, and Table 6 shows the relationship between the natural frequency separation and buckling.

[Table 5]

[Table 6]

Relationship between natural frequency separation and buckling.

Figure 4 shows the test results of circular saw NO.2S60-2S45. From Fig. 4, it was possible to perform the cutting operation stably up to the upper limit of the rotation speed of the cutting machine, although it slightly fluctuated in the critical rotation speed range of the node diameter numbers n = 3 and _n = 2, but did not buckle. From the above results, it was found that buckling can be effectively suppressed in the mode with the number of nodal diameters n = 2 at 23 Hz and Δf ₂ / f ₂₁ 15%. In FIG. 4, n = 31 indicates a first mode of n = 3, n = 32 indicates a second mode of n = 3, and the same applies to other n hereinafter.

About the effect of unequal length slits

As shown in Fig. 5, of the four slits drilled on the circular saw with the same center angle, the lengths of the two slits facing each other with the center in between are set to the same length. The length dimension of the slit to be engaged was changed. The model of the circular saw base metal was the same as the shape described above except for the thickness, and was 0305 (circular saw diameter) 1.0 (base metal thickness)> <60? (Number of saw blades). The flange diameter is 0110. The material properties are the modulus of longitudinal elasticity

E = 21000kgf / mm Poisson fin = 0.8, and to the density p two 8 x lO ^ kgf 'sZ / mm 4. Of the four slits, the length of two opposing slits at equal intervals was 55 mm, and the length Ls of the remaining two opposing slits was varied. Here, the depth of the circular saw tooth bag was 10 mm.

Figure 6 shows the results of finite element analysis performed using the shell model. Since the natural frequency fn is proportional to the base metal thickness, the relative natural frequency difference n / frii is independent of the base metal thickness. If the slit length Ls is 50 mm or less or 60 mm or more, claim 1 of the present application is satisfied, and if the slit length Ls is 50 mm or 60 mm or more, the claim of the present application is satisfied. This satisfies item 2.

Influence of the positional relationship between the four slits

As shown in Fig. 7, of the four slits with the same length Ls drilled in the circular saw, two slits facing each other across the center are moved in the circumferential direction, The center angle for the adjacent slit was changed. The model of the circular saw base metal was the same as that of the circular saw shown in Fig. 5, and was 0305 (circular saw diameter) 1.0 (base metal thickness) 6 (^ (number of saw blades). The lengths of the slits (Ls = 55 mm) are the same, and among these slits, the central angle formed by two opposing slits with respect to the adjacent slit is 0 = The angle was changed in the range of 12.5 ° to 90 °. The depth of the saw tooth bag was 10 mm.

Figure 8 shows the results of the finite element analysis performed on the shell model. In FIG. 8, if the deviation center angle 0s (Ss = 90 ° _0) of the slits adjacent to each other from 90 ° is set to 2.5 ° or more and 75 ° or less, the natural frequency difference Af ₃ / Since f ₃₁ ≥3.0% and Af ₄ / f ₄₁ 3.4%, the buckling of the mode with nodal diameters _n = 3 and n = 4 can be suppressed. However, when the deviation center angle 0 s is set to 15 ° or more, the base of the circular saw becomes rigidly unbalanced. Also, if the deviation center angle 6> s is not less than 2.5 ° and not more than 12.5 °, the natural frequency difference will be ₂ / f ₂₁ 15%, so the buckling of the mode at the nodal diameter number n = 2 is also suppressed. You will get. That is, when the difference between the center angles of the slits adjacent to each other is 5 ° or more and 30 ° or less, the buckling of the mode with the number of nodal diameters n = 3 and n = 4 can be effectively suppressed. When the difference is less than 25 °, the buckling of the mode with n = 2 is also suppressed.

About the effect of partial waisting

It is known that the mechanical properties of a circular saw can be improved by "partial squatting" in which an external stress is applied to the circular saw by a hammering press or the like. Therefore, we investigated the separation of the natural frequency fn especially in the mode with the number of nodal diameters _n = 2 by applying partial squatting to the base of the circular saw. It was also examined whether partial slitting could reduce the length Ls of the slit. The specifications of the circular saw used for the test were 305 (circular saw diameter) X2.2 (saw thickness) X1.6 (base metal thickness) X25.4 (shaft hole diameter) X60P (number of saw blades), flange diameter 0120 Was something. By changing the length Ls of the slit, two lines were formed at point-symmetric positions or four lines at equal central angles. As shown in Fig. 13, the circular saw was virtually divided into eight regions, and a slit was included in the middle of two or four of these regions. Avoiding the area having the slit, every other area was sunk by the above-mentioned hammering press or the like. Table 7 shows the amount of separation of the natural frequency: n in comparison with the case without partial stiffening. [Table 7]

Comparison of natural frequency separation

From Table 7, it can be seen that the amount of separation of the natural frequency fn of the mode with the nodal diameter according to the number of regions of partial penetration increases as in the case of slitting. In other words, as shown in FIG. 13, by performing partial indentation on the four regions, the natural frequency: n of the mode with the node diameter number n = 2 is largely separated. Taking the circular saw of N0.2S55-2S50 as an example, the natural frequency difference was Δf ₂ / f ₂₁ = 15.8% when partial staking was not performed. The number difference Δf ₂ / f ₂₁ was greatly improved to 22.0%. By appropriately setting the number of regions where partial indentation is performed in this way, the natural frequency fn of the mode with the number of nodal diameters can be largely separated. For example, if the number of nodes is n = 2, the area is divided into four areas, if the number of nodes is n = 3, it is divided into six areas, and if the number of nodes is n = 4, the area is divided into eight areas. It is most effective to do partial squatting at equal intervals while avoiding the vicinity of the area.

About application fields

Regarding the circular saw without any of the slits and partial penetration described above, the critical rotation speed in that case is Ω (ί (Γ.p.m.). G.S.Schajer's approximate expression gives

Ω c two H / B ² .S (A / B)

Where H is the thickness of the circular saw base (mm), B is the outer diameter (mm), A is the flange diameter (mm), and S is the critical velocity function (mm / min).

FIG. 9 shows the relationship between the critical speed function S (A / B) and the ratio A / B of the flange diameter and the base metal outer diameter of the circular saw without the slit. From Fig. 9, the mode of the lowest critical rotation speed is as follows: ① Nodal diameter number n = 2 when A / B = 0 ~ 0.26, ② Nodal diameter number n = 3 when A / B = 0.26 ~ 0.46, ③ A It can be seen that the node diameter number n = 4 when /B=0.46 to 0.58. Therefore, in general, A / B is 0.5 or less, so if the A / B is 0.26 or more, the specification of claim 1 of the present application is used.If the A / B is 0.26 or less, claim 2 is used. It is considered appropriate to design a circular saw according to the specifications.

The approximation formula of G. S. Schajer is described in Forest Prod. J., magazine (1986), 36-2, 37-43, as "simple formula for natural frequency and critical speed of circular saw".

By applying the series of measures described above, it is possible to suppress the meandering (buckling) of the base metal that occurs during the cutting of the work by the circular saw, but this completely prevents the runout at the critical rotation speed. Not something you can do. Therefore, in order to further suppress the run-out of the base metal during work cutting, for example, a wiper chip is fixed to the slit or a separately provided slit portion (this wiper chip is a chip fixed to the inside of the slit). Therefore, the thickness is set slightly smaller than the saw thickness and larger than the base metal thickness, and functions to prevent the workpiece from directly pinching the base metal during work cutting.) . Further, if one or more of the die tips are brought into contact with the workpiece (work material) during cutting, vibration can be further suppressed. In addition, the above-mentioned slit was drilled so as to have one end opened on the outer periphery (tooth pouch) of the circular saw base metal. Internal slit that does not open to the outer periphery May be bored. In this case, there is almost no effect on the separation of the natural frequency. Also, the slit may be filled with a viscoelastic resin to improve the damping performance, thereby suppressing the vibration of the standing wave in the critical rotation speed range.

The results of the above study are summarized below.

(1) When the flange diameter is about 26% or more of the outer diameter of the circular saw, the critical rotation speed of the mode with the number of nodal diameters n = 2 is greater than the critical rotation speed of the nodal diameter numbers n = 3 and n = 4. The tendency to increase _c increases sharply as the flange diameter increases. In such a case, the circular saw can be used over a wide range at a high rotation speed by suppressing the buckling of the nodal diameter numbers n = 3 and n = 4. In this case, the natural frequency of the circular saw is f ι Ηζ) and fn ₂ (Hz) (where : Fn ₂ > f nj, natural frequency difference △ fn = fn ₂ — f, the relative natural frequency difference n / f is 3.0% or more at nodal diameter n = 3 and nodal diameter n = 4 In this case, it is preferably 3.5% or more, which corresponds to claim 1 of the present application.

(2) When the flange diameter is about 26% or less of the outer diameter of the circular saw, buckling in the mode with n = 2 and 3 is particularly problematic. In this case, the natural frequency of the circular saw is f Hz) and fn ₂ (Hz) ( Where fn ₂ > f) and the natural frequency difference Δί "n = fn ₂ -fn, the relative natural frequency difference Afn / fn,

If it is 15% or more and the node diameter number n = 3 is 3.0% or more, buckling of these modes can be effectively suppressed, which is preferable. This corresponds to claim 2 of the present application (

(3) As a means to realize the contents of (1) and (2) described above, by drilling four slits at intervals of the center angle approximately equal to the base of the circular saw, the number of node diameters n = 2 and the natural frequencies of the modes n = 4 or n = 3. Furthermore, the length of the two slits facing each other across the center of the circular saw is approximately the same size, The different frequencies of the slits can also separate the natural frequencies of other modes at the same time. This corresponds to claim 3 of the present application.

(4) As a means to realize the contents of (1) and (2), four slits are drilled in the circular saw base. In this case, the lengths of the slits are all set to substantially the same dimensions, and the difference between the central angles of the slits adjacent to each other is in the range of 5 ° to 30 °. This corresponds to claim 4 of the present application.

(5) When multiple slits are drilled in the base of a circular saw, partial lumps such as the application of an external stress by a hammering press or the like may be placed between the adjacent slits. Put the container. Thereby, the natural frequency of the mode corresponding to the number of the partial squats can be separated. This corresponds to claim 5 of the present application.

(6) Even if the meandering (buckling) of the base metal is suppressed by the means described above, it is not strictly possible to completely suppress the deflection at the minimum critical rotation speed. Therefore, a vibration is further suppressed by attaching a wiper tip to the slit or a separately provided slit portion so that at least one of the wiper tips comes into contact with a workpiece (work material) during cutting. It is possible to Further, the slit is not limited to the one drilled in a portion near the outer periphery of the circular saw base, and the slit may be drilled in a portion near the inside of the base. In this case, the natural frequency separation has little effect. Further, by filling the inside of the slit with a viscoelastic resin, the damping ability can be improved, and the vibration of the standing wave in the critical rotation speed region can be suppressed. The invention's effect

As described above, according to the circular saw according to the present invention, it is possible to provide a base metal shape that can be cut even in a rotation range equal to or higher than the minimum critical rotation speed, and can be used in a high speed rotation range even if the base metal is thinned. . Therefore, the loss of material during peak cutting can be suppressed by reducing the thickness of the circular saw base, and the cutting force per tooth is reduced. Since the feed rate can be set higher, work efficiency can be greatly improved.

Claims

The scope of the claims

1. A circular saw that can be used in the region of the minimum critical rotation speed or more when the workpiece is cut, and the number of circles m of the base metal in the circular saw is 0, and the number of diameters of the joint is the same. In mode,

If the natural frequency of the circular saw is fr ^ Hz) and fn ₂ (Hz) (where: fn ₂ > f), and the natural frequency difference n = fn ₂ _ f, the relative natural frequency is difference

△ f n / f n, at least 3.0% for nodal diameter n = 3 and at least 3.5% for nodal diameter n = 4

A circular saw characterized by the following:

2. Two modes in which the circular saw can be used in the region of the minimum critical rotation speed or more when cutting the workpiece, and the number of circles m of the base metal in the circular saw is 0 and the number of the same node diameter is n. At

If the natural frequency of the circular saw is fr ^ Hz) and fn ₂ (Hz) (where fn ₂ > f nj and the natural frequency difference n = fn ₂ _ f, the relative natural frequency difference

△ f n / f was set to 15% or more at the node diameter n = 2 and to 3.0% or more at the node diameter n = 3.

A circular saw characterized by the following:

3. Four slits are drilled at a center angle interval approximately equal to that of the circular saw base, and the lengths of the two slits that face each other with the center of rotation are approximately the same. 3. The circular saw according to claim 1, wherein slits adjacent to each other have different lengths.

4. Drill four slits in the circular saw base, set the lengths of these slits to be almost the same, and set the difference between the center angles of the slits adjacent to each other. The circular saw according to claim 1 or 2, wherein the circular saw is in a range of 5 to 30 °.

5. A circular saw base with a plurality of slits perforated. twenty one

In the place sandwiched by the lit

Circular saw according to any of! To 4.