JPH0236045A - Working method for non-cylindrical work - Google Patents

Abstract

PURPOSE:To work a non-cylindrical work at high speed and with high accuracy by correcting one part of the work angular velocity or cutter control higher harmonics frequency by the correction value including higher harmonics in case of the existance of the advance and delay of a phase between the deviations of the wavy curved line of a periodic function and circularity. CONSTITUTION:A non-circularity working work W is held on a holding device 10, a motor 11 is driven by being rotated at a basic angular velocity W0 by the control signal fed from a rotary speed control device 13, and a cutter 12 is controlled by the signal fed from the advancing and retreating operations control device 14 to which a specified amplitude command is input. A higher harmonics oscillator 15 takes a basic angular velocity Wo as the frequency of a basic wave, oscillating the higher harmonics corresponding to an input order command. The specified order high harmonics are output to the control device 14, the order higher harmonics corresponding to a calculated correction value are input to a correction signal circuit 16, the specified correction signal is output to either one part of the control device 13 or 14 and the advance, delay of the phase of the deviation from the circularity approximated by a basic wav curved line and the actual deviation of the actual non-circularity shape and circularity is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for machining a non-round workpiece for machining a workpiece whose cross section perpendicular to an axis has a non-round shape.

"Prior Art" A non-perfect circular shape is approximated by a periodic waveform curve with a constant frequency, the deviation between the approximation curve and a predetermined non-perfect circular shape is calculated, and a correction device calculates the deviation based on the periodic waveform curve. There is a device that corrects the position of a cutting tool that moves back and forth periodically (Japanese Patent Application Laid-Open No. 61-182703).

"Problem to be Solved by the Invention" In the above case, the forward and backward movement of the cutting tool is relative to the rotation of the workpiece.
The position correction is performed by a constant periodic rocking of a rocking member connected to a crankshaft rotating at a constant rotation ratio, and the position correction is performed by controlling the position of the rocking shaft of the rocking member by a correction device, The combined movement of the two controls the forward and backward movement of the cutting tool to process a predetermined shape. The period and amplitude of the swinging member are determined by the rotation ratio and the amount of eccentricity of the crankshaft, and the position correction of the cutting tool is performed exclusively by controlling the position of the swinging shaft.

For this reason, when a non-perfect circular shape becomes complex, or when trying to ensure machining accuracy by minimizing the deviation between the approximate curve and a predetermined non-perfect circular shape, extremely fine control including the related mechanical parts becomes necessary. As a result, the correction signal becomes complicated, and there is a delay in following the a-lateral portion of the signal, resulting in problems such as the inability to achieve high speed.

The present invention was made with the aim of solving the above-mentioned problems, and provides a method for machining non-round workpieces that can be processed at high speed and with high accuracy with few errors for a given shape. The challenge is to provide this information.

"Means for solving the problem" The specific means for solving the problem is to change the phase angle θ
In machining a non-perfect circular workpiece in which the function of θ and the deviation from a perfect circle at ωt) matches or approximates the waveform curve of a periodic function of frequency ω, the workpiece is moved at an angular velocity ω. As it rotates, its angular velocity ω. A harmonic oscillator whose fundamental frequency is oscillates an n-th (n=ω/ω0) harmonic equal to the frequency ω of the waveform curve of the periodic function, and the harmonic moves the cutting tool forward and backward with a predetermined amplitude. and control the angular velocity ω of the rotation of the workpiece. Alternatively, the rotation of the workpiece or the movement of the cutting tool forward and backward is controlled based on a control signal obtained by correcting one of the frequencies ω of the cutting tool control signal using a correction value including harmonics generated from a harmonic oscillator. That is.

"Operation" According to the specific means, the movement of the cutting tool for machining a non-perfect circular shape in which the function of the deviation from a perfect circle at the phase angle θ and θ matches or approximates the waveform curve of a periodic function of the frequency ω. As a control signal to control the angular velocity of the workpiece rotation ω. Using harmonics oscillated by a harmonic oscillator with a fundamental frequency of , calculate the advance and lag and calculate the rotational angular velocity of the workpiece ω0
Or correct one of the harmonic frequencies that are the control signal of the cutting tool using a correction value that includes the harmonics,
By eliminating the phase lead/lag, it is possible to perform non-perfect round processing with less error.

"Example" Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 shows a schematic system configuration diagram of the present invention.

The work W to be processed into a non-perfect circle is held in a work holding device 10, which is rotated by a work rotation motor 11, and processed into a predetermined non-perfect circular shape by the forward and backward movements of the cutting tool 12.

The work rotation motor 11 has a rotation speed control device 13.
It is rotationally driven at a basic angular velocity ω0 by a control signal from. Further, the cutting tool 12 is controlled by a control signal from a forward/backward movement control device 14 into which a predetermined amplitude command is input.

The harmonic oscillator 15 has the basic angular velocity ω. is the frequency of the fundamental wave, and oscillates harmonics corresponding to the input order command. The harmonics of a predetermined order are outputted to the movement control device W14 of the cutting tool 12, and the harmonics of the order corresponding to the calculated correction value are inputted to the correction signal circuit 16, and a predetermined correction signal is applied to the rotation control device W14. It is output to either the speed control device 13 or the forward/backward motion control device 14.

The method of the present invention is implemented by the system configuration described above, and is concerned with calculation of correction values, determination of values of various parameters, etc. when machining a piston of an internal combustion engine whose cross section perpendicular to the axis is elliptical. This will be explained below.

As shown in Figures 2 (a) and (b), the deviation Δ between a normal ellipse and a circle with a diameter equal to the major axis of the ellipse that is the cross-sectional shape of the piston and a difference of 2R from the minor axis is the phase angle θ. It is expressed as a periodic function and can be approximated as . Here, the rotational angular velocity of the piston is ω. Then, θ ω. Since t, equation (i) becomes as follows, and this is taken as the reference waveform curve. The reference waveform curve is
This serves as a reference for a control signal that controls the advancing motion of a cutting tool for creating a piston with an elliptical cross section.

The actual deviation ΔR obtained for this standard waveform curve and the regular elliptic curve has a phase difference as shown in Figure 3, and the value of equation (ii) for the actual deviation ΔR is When expressed in terms of lead and lag, it is shown in Figure 4.

If the angular velocity of the equation (ii> is corrected so as to cancel out this advance/delay, the chain equation (ii>) will match the actual deviation ΔR with respect to the elliptic curve.

Therefore, the correction value of the angular velocity is set to As1n2ω,1.ii
) frequency 2ω of the equation. In addition, .

The frequency of the correction value is set so as to cancel out the phase lead/lag shown in the graph of FIG. By doing so, in Fig. 3, when the phase angle θ is from O to π/2, the phase of the deviation Δ is delayed;
The phase advances between π/2 and π, and the cutting amount of the cutting tool 12 at the angle θ changes, reducing the error. In general,
It is determined by the number of zero points that cross the graph shown in FIG. 4.

Parameter A of the correction value is determined by substituting the actual numerical value into equation (iii).

For each position of parameter A, the error between the deviation Δ obtained by formula (iii) and the actual deviation ΔR is obtained for every 15 phase angles (θ=ω.t ) (dew), and 2 of each of these errors is calculated. The value that minimizes the average of the power is determined as the optimal value of parameter A.

The parameter A is calculated and determined as described above, and the frequency ω of the fundamental wave from the harmonic oscillator 15 is determined. A harmonic with a frequency twice that of Controls the forward and backward movements of the

At this time, the work W is held by the work holding device 11,
The angular velocity ω is generated by the work rotation motor 11.

When rotated at , it is possible to process a non-round workpiece within the above tolerance range.

What is to be corrected by the method of the present invention is the phase lead/lag between the deviation Δ from a perfect circle approximated by the basic waveform curve and the actual deviation ΔR between the actual non-perfect circular shape and the perfect circle.

This phase lead/lag is relative to the advance motion of the cutting tool and the rotation of the workpiece, so unlike the previous embodiment, the harmonics oscillated from the harmonic oscillator with respect to the angular velocity of the rotation of the workpiece It is also possible to perform the correction using a correction signal including the following.

Further, the movement of the cutting tool back and forth can be performed using a piezoelectric element, a near motor, etc. in addition to the crank mechanism.

"Effects of the Invention" As clarified in the explanation of the above-mentioned specific means and operation, the method of the present invention has a phase lead/lag between the waveform curve of the periodic function and the deviation between the non-perfect circular shape to be processed and the perfect circle. If this occurs, calculate the lead/lag and determine the rotational angular velocity ω of the workpiece. Alternatively, one of the harmonic frequencies that is the control signal for the cutting tool is corrected using a correction value that includes the harmonic to eliminate the phase lead/lag. This is because the position correction for the forward and backward movement is not performed as position control of the swing axis of the swing member, which is uniquely determined by the rotation of the workpiece.

By determining the M* parameter value, it is possible to obtain a corrected continuous control signal without the need for a complex correction signal that takes into account the related mechanical parts. Since it is separated into forward and backward movements, it is mechanically simple, it is easy to ensure accuracy, and the machining speed can be increased.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the method of the present invention, and FIG. 1 is a schematic system configuration diagram, FIG. Figure 4 (b) is a graph showing the relationship between phase angle θ and deviation, Figure 3 is a graph showing the phase shift between actual deviation ΔR and deviation Δ, and Figure 4 is a graph showing the phase shift in terms of lead and lag. This is a graph. 10. Work holding device 11. Work rotation motor 12. ,, cutter, 13. ,,rotation speed control device, 141. Advance/retreat movement control device, 15.
,. Harmonic oscillator, 16,, correction signal circuit, Wo,
. work. Figure 2 (a) ΔR

Claims (1)

[Claims] In machining a non-circular workpiece in which the function of θ and the deviation from a perfect circle at the phase angle θ (θ=ωt) matches or approximates the waveform curve of a periodic function of frequency ω, the workpiece is moved at an angular velocity of ω_0. from a harmonic oscillator whose fundamental wave frequency is angular velocity ω_0, the nth (n=ω/
ω_0) Oscillates a harmonic, controls the advance and retreat of the cutting tool with a predetermined amplitude, and oscillates either the angular velocity ω_0 of the rotation of the workpiece or the frequency ω of the control signal for the cutting tool from the harmonic oscillator. A method for machining a non-round workpiece, the method comprising: controlling the rotation of the workpiece or the forward/backward movement of a cutting tool based on a control signal corrected by a correction value including harmonics.