JPS61192443A - Noncontact type active damper - Google Patents

Abstract

PURPOSE:To attenuate the vibration of a grinding system by detecting in process the vibration of a work which varies momentarily in the grinding in cylindrical traverse method and applying a damping force in speed-proportion form onto the work in noncontact by an electromagnetic force. CONSTITUTION:A work 2 is ground by the abrasive wheel 3 of a cylindrical grinder. Said abrasive wheel 3 is supported onto a wheel spindle stock 5, and the shift in the longitudinal direction for the contact and departure from the work 2 and the shift in the transverse direction along the axial direction of the work 2 are permitted. An electromagnetic damper part 20 is installed onto the wheel spindle stock 5. The top edge parts of the arms 8a and 8b are opposed in noncontact, keeping a little gap from the side surface of the work 2. When an electromagnetic coil 12 is put into electric conduction, magnetic fluxes are generated between the arm 8a, top edge part 16a, work 2, top edge part 16b, arm 8b, and an iron core 11, and the work 2 is attracted to the top edge parts 16a and 16b. Said attraction force is the external force applied onto the work 2 for attenuating the vibration of the work 2. The electric current of the electromagnetic coil 12 is controlled by the signal supplied from a vibration detecting apparatus 30.

Description

Detailed Description of the Invention (a) Object of the Invention [Field of Industrial Application] The present invention relates to an active damper used in cylindrical grinding, particularly cylindrical traverse type grinding.

It prevents chatter vibrations when machining elongated cylindrical workpieces, thereby enabling high-precision machining on the micron order. It can be used for manufacturing precision equipment such as.

[Prior Art] Conventionally, a mechanical grinding method called the cylindrical traverse method has been used to manufacture elongated cylindrical workpieces that require precision on the micron order, such as the shafts of turbines and gyros. In this method, the surface of a workpiece that has been preformed into a predetermined elongated cylindrical shape is ground with a grindstone to obtain the desired accuracy.

That is, as the principle is shown in FIG. 9, a cylindrical workpiece 100 is rotatably supported at both ends of its central axis, and a disk-shaped grinding wheel 102 that rotates at high speed is attached to the outer peripheral surface of the workpiece 100. Grind by pressing the outer peripheral surface of the The central axes of the workpiece 100 and the grinding wheel 102 are parallel to each other,
The workpiece 100 and the grinding wheel 102 are each rotated by a roller on its central axis at different rotational speeds, and the workpiece 100 is rotated by a table connected to a support member 103 (
(not shown), the grinding wheel 102 moves parallel to the rotation center of the workpiece 100 along, for example, a direction 104, and as a result, the grinding wheel 102 grinds while traversing the workpiece 100 in a direction 105 relatively opposite to the direction 104. be. Here, as shown in FIG. 10, a force called grinding resistance acts between the grinding wheel 102 and the workpiece 100. This force can be divided into the normal direction (X direction) and the tangential direction (U direction) of the workpiece, but since the workpiece 100 is long and thin, the rigidity of the workpiece 100 is The rigidity becomes very small, and therefore vibration is likely to occur in the workpiece 100 due to the above-mentioned grinding resistance and external force, and this vibration makes it difficult to perform high-precision or high-efficiency machining. be.

Conventionally, a rest 106 has been used as a means for preventing unnecessary movement of the workpiece during grinding of such a long and thin object.

Rest 106 can be of automatic type, manual type, fixed type, etc., but it is a type of holding member fixed to the surface of the table that supports workpiece 100, and the shoe 107 that is the tip thereof is not easily worn out. The shoe 107 is made of a material, and the shoe 107 directly contacts and supports the workpiece to hold the workpiece down and prevent unnecessary movement of the workpiece.

[Problems to be Solved by the Invention] However, in conventional rests, the contact position of the shoe is fixed with a screw or simply pushed back with a spring, and even if static displacement of the workpiece can be prevented, , cannot handle dynamic displacement such as vibration. Moreover, in the case of traverse grinding, the cutting position of the grinding wheel changes on the workpiece, and the frequency of the imaging changes, so it is even more difficult to control and prevent this imaging by following the frequency. Because it is fixed to the surface of the table on which the workpiece is placed, it can only hold the workpiece at a certain point, and therefore, in the case of traverse grinding, several rests must be used in duplicate. There is a problem in that it is not easy to use, and requires troublesome and skilled know-how. Additionally, there was a problem in that the shoe of the rest that was in contact with the workpiece would scratch the workpiece.

This invention was made in view of the above-mentioned circumstances. To provide an active damper that can damp the vibration of the grinding system in addition to the workpiece without contact, and therefore allows ordinary workers to perform high-precision, highly efficient machining without requiring skilled workers. The purpose is to

(B) Structure of the Invention [Means for Solving the Problem] In response to this objective, the non-contact active damper of the present invention includes a vibration detection device that detects the imaging of a cylindrical grinding workpiece, and a vibration detection device that detects the movement of a cylindrical grinding workpiece. and an electromagnetic damper section that has an electromagnetic force head located facing the side surface of the cylindrical grinding workpiece in a non-contact manner and is movable following the grinding wheel. The imaging speed of the cylindrical grinding work detected by the detection device is derived by the processing control device, and the electromagnetic force head is configured to apply an electromagnetic force proportional to the vibration speed to the cylindrical grinding work. It is a feature.

Hereinafter, details of the present invention will be explained with reference to the drawings showing one embodiment.

In FIG. 1, FIG. 2, FIG. 3, and FIG. 4, 1 is a cylindrical grinder, which grinds a workpiece 2 with a grinding wheel 3. In FIG. The grinding wheel 3 is rotatably supported by the grinding wheel head 5, and can move back and forth toward and away from the workpiece 2, and can move in the lateral direction along the axial direction of the workpiece 2.

4 is a damper according to the present invention. The damper 4 includes an electromagnetic damper section 20, a vibration detection device 30, and a processing control device 25. The electromagnetic damper section 20 is attached to the whetstone head 5 and is movable together with the whetstone head 5.

The electromagnetic damper section 20 includes support legs 6 and a center core 7,
It consists of an electromagnetic head 9 having arms 8a and 8b connected to both ends of a center core 7. The center core 7 is composed of an electromagnetic coil 12 wound around an iron core 11, and arms 8a and 8b are connected to both ends of the iron core 11 and extend in the direction toward the workpiece 2, so that the arms 8a and 8b are connected to the grinding wheel 3 in a plan view. Located on both sides. The arms 8a and 8b can be linearly displaced in the axial direction of the adjusting screw 13 by operating the adjusting screw 13 while maintaining the magnetic connection state with the iron core 11. Further, the arms 8a and 8b each consist of a base portion 15 and a tip portion 16 connected by a joint 14,
The tip 16 can be rotationally displaced relative to the base 15 at the joint 14 . The tips 16 of the arms 8a, 8b are positioned relative to the workpiece 2 by these linear displacements and rotational displacements.

Also, if necessary, the bases 15 of the arms 8a and 8b can be connected to the shaft 2.
It may be configured to rotate about 2. The tips 16 of each of the arms 8a and 8b face the side surface of the workpiece 2 with a slight gap therebetween without contacting them.

In the M magnetic damper section 20 having such a configuration, when the electromagnetic coil 12 is energized, a magnetic flux is formed between the arm 8a, the tip 16a, the work 2, the tip 16b, the arm 8b, and the iron core 11, and the work 2 is It is attracted by the tip portions 16a and 16b. In the present invention, this suction force is an external force applied to the workpiece 2 in order to damp the vibration of the workpiece 2.

As shown in FIG. 4, the current applied to the electromagnetic coil 12 is determined by the vibration detection device V! Based on the signal from I30,
It is controlled by a processing control device 25.

The vibration detection device 30 includes a strain gauge 32 attached to a tailstock center 31.

The processing control device 25 includes a damping control system 27 and a compliance correction control system 28.

The damping subsurface system 27 includes a strain gauge 32 attached to the center insertion stand center 31, a strain amplifier 33 that receives the output of the strain gauge 32, a signal adjustment circuit 34 that processes the output signal from the strain amplifier 33, and a signal adjustment circuit 3. The power amplifier 35 receives the signal from 4 and amplifies the current. The signal adjustment circuit 34 includes a filter 36, a differentiation circuit 37, a differentiation circuit 38, and an addition circuit 41.

Further, the compliance correction control system 28 includes a scale head 42, a counter 43, and an AD converter 45.
It is connected to the IB interface 47. The computer 46 also has a GP-IB interface 47, a DA
A DC voltage is output to the adding circuit 41 via the converter 48.

[Function] The function of the damper 4 configured as described above is as follows.

That is, in the case of cylindrical grinding, the workpiece 2 comes into contact with the grinding wheel 3 and receives a variable grinding force Fg.

In this case, the equation of motion of the workpiece system (the workpiece is an elastic beam member) is: E is the elastic modulus, I is the new surface second moment, y is the deflection, X is the coordinate on the central axis, t is the time, ρ is the density, and A When is the cross-sectional area, co is the damping coefficient, Fg is the variable grinding force, and F is the external force, EI (9'y/θx') + C (9V/at) + ρA (a
V/9t )=FQ+F (1)(r11
Characteristics of the stone platform system are omitted) For the external force F, F=-C(ay/9t>(C>O)) (2)
If we add E I (84y/FX') + (Go+c> (2sy/9t) +ρA(B V/3t2>==FQ (3)
In other words, the coefficient of the damping term becomes (-Go+C), and the damping of the workpiece system increases.

Focusing on the first-order natural frequency iωt, which has the most profound effect on chatter, when FQ=e, the workpiece deflection y(x, t> is approximately determined as follows, assuming steady vibration.

V (x, t) = (AI S group λ1x + A cos
λ1x +A 5inhλ1x 1ω[+θ +A coshλ1x)e...-(4) Here, λ is a first-order eigenvalue, and A1-A4 are constants.

Since the output from the strain gauge 32 is proportional to the deflection of the edge of the workpiece on the metal side, the imaging width at any point on the workpiece can be determined from equation (4).

Therefore, when the output from the strain gauge 32 is differentiated, it is considered to be proportional to the speed.

The above is the control theory of the damping method employed in this invention.

First, the strain gauge 32 detects the deflection of the tailstock side end of the workpiece. The displacement signal detected by the strain gauge 32 is amplified by a strain amplifier 33, and then passed through a filter 36.
The frequency range above the secondary vibration mode is cut off, and only the vibration components in the -order vibration mode range are extracted. Next, the signal output from the filter 36 is differentiated by a differentiating circuit 37 to become a signal proportional to the speed of vibration.
Then, adjustment is made to compensate for the inductance load of the electromagnetic coil 12 of the electromagnetic damper section 20. The vibration-adjusted signal is then input to an adder circuit 41.

The adder circuit 41 is configured so that the amount of cut of the grinding wheel 3 into the workpiece 2 is constant at any position in order to remove the electromagnetic force component having twice the frequency of the vibration component and to ensure the cylindricity of the workpiece 2. In order to generate a force in the electromagnetic damper section 20 such that the static compliance of the workpiece is constant in the longitudinal direction, the DC bias signal
It is input from 8. Adder circuit 41 adds the DC bias signal and the adjusted vibration signal and applies the sum to the power amplifier input.

As shown in FIG. 5, the cross-sectional area of the tips 16a and 16b is S, the cross-sectional area of the work is 82, the gap between the electromagnetic head and the work is δ, the relative magnetic permeability of the electromagnetic head 9 is μm, and the ratio of the work is The magnetic permeability is I2, the number of turns of the electromagnetic coil is n, the magnetic flux path length of the electromagnetic head is 1, the magnetic flux path length of the workpiece is 12, the current flowing through the electric current r/iJ is 11, of which AC
The component is 11, the DC component is 1, and the vacuum permeability is μ. Then, the electric force F is F= ((1/S)(1-(1/μ2))X(nI
)2)/((1/μ) X((1/(μm51)) +(2δ/S)+(1/(I2S2))) ];α
(I sinωt'+l)22.2 =a(11sinωt+2111osinω1.+1°) =αNT1 /2) -((11/2)coS2ωt) +(2[11o sinωmouth→io)・(5) Grinding point ma In order to cause a deflection of y at =i, F =y/((1/6)ab(<1-I2-b2)+
((a/k)-(b/k1))a+(b
/ k 1) ) , )...(6) A force F5 is required. Here, F = (FI2)/(El), a-a/I, W=y/1, k, = (k, I3)/(El) (i=1.2) b=1-
In a, 1 is the total length of the workpiece, and kl and k2 are the spring constants of the headstock center and tailstock center, respectively.

Therefore, from equation (5), there is a relationship of F, -Ib ocVb, so v boc a E . Therefore, this Vb is added to the power amplifier input as a DC bias signal. This Vb is scale head 4
The grinding position signal from 2 is counted by a counter 43, and calculated by a computer 46 via an AD converter 45.
The signal is input to the adding circuit 41 via the A converter 48.

Figure 6 shows the workpiece vibration suppression effect of the active damper of the present invention, so workpiece length: 490mm Vibration and damping position: Workpiece center pressing force: 5N Power amplifier input: DC bias: 0.5V gap
It can be seen that the amplitude of vibration gradually decreases as the gain of the power amplifier is increased after setting it to 1 mm.

FIG. 7 is a vector diagram for photographing a workpiece, and it can be seen that when the damper of the present invention is used, the occurrence of chatter is small.

Figure 8 shows the output of the strain gauge during actual grinding. Figure 8 (a) is without a damper, Figure 8 (b) is
Although the damper of the present invention was used, it can be seen that a good damping effect is exhibited when the damper of the present invention is used.

(c) Effects of the invention In this way, the active damper of this invention detects vibrations in-process and applies a corresponding damping force to the workpiece system to damp the vibrations of the workpiece, so it requires no skill in grinding. Even ordinary workers can perform high-precision, high-efficiency machining without having to worry about the damage caused by the work.What is particularly important is that the active damper of this invention applies vibration damping force to the workpiece without contacting it. No damage to the grinding surface.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the electromagnetic damper section, Fig. 2 is a front view of the electromagnetic damper section, Fig. 3 is a side view of the electromagnetic damper section, Fig. 4 is an explanatory diagram of the configuration of the active damper, and Fig. 5 is an i! An explanatory diagram showing the electromagnetic relationship between the magnetic head and the workpiece, Fig. 6 is a graph showing changes in the characteristics of the vibration of the workpiece, Fig. 7 is a vector diagram of the vibration of the workpiece, and Fig. 8 is the time of photographing the workpiece during cylindrical grinding. A graph showing the changes, FIG. 9 is an explanatory plan view showing a conventional cylindrical grinder, and FIG. 10 is an explanatory view showing the grinding resistance acting on the workpiece. 1... Cylindrical grinder 2... Workpiece 3... Grinding wheel 4... Damper 5... Grinding wheel stand 6... Support leg 7... Center core 8a, 8b... Arm 9...・Electromagnetic head 11... Iron core 12
...Electromagnetic coil 13...Adjustment screw 14...
Joint 16a. 16b... Tip part 20... Electromagnetic damper part 2
2... f*25... Processing control device 27... Damping control system 28... Compliance correction control system 30... Vibration detection device 31... Tailstock center 32... Strain gauge 33 ... Strain amplifier 34 ... Signal adjustment circuit 35 ... Power amplifier 3
6... Filter 37... Differential circuit 38.
... Differentiation circuit 41 ... Addition circuit 42 ... Scale head 43 ... Counter 45 ... A
D converter 46... Computer 47...
・GP-IB interface 48...OA converter Fig. 1 Fig. 2 Fig. 8 ((1>

Claims (1)

[Claims] A grinding machine comprising: a vibration detection device for detecting vibrations of a cylindrical grinding work; a processing control device for processing signals from the vibration detection device; and an electromagnetic force head positioned facing the side surface of the cylindrical grinding work in a non-contact manner. an electromagnetic damper section movable to follow the grinding wheel, the vibration speed of the cylindrical grinding workpiece detected by the vibration detection device is derived by the processing control device, and an electromagnetic force proportional to the vibration speed is generated. A non-contact type active damper, characterized in that the electromagnetic force head is configured to act on the cylindrical grinding work.