Control device for a gear machining machine

Abstract

Control device (1) for a gear machining machine, which controls a multi-axis gear machining machine, wherein the control device (1) comprises an axis information recording unit (5) which records data relating to the control of the multi-axis during machining; and a disturbance component identification unit (6) which, using the data recorded by the axis information recording unit (5) and the result of a measurement of the machining accuracy of a workpiece by the machining machine, identifies disturbance components relating to the multi-axis.

Description

[0001] The present invention relates to a control device that performs drive control of the individual drive axes of a gear machining machine.

[0002] In general, a machine tool that performs gear machining carries out the machining process through the interaction and synchronization of several motor-driven axes. A gear-cutting machine is a well-known example of such a machine. In a gear-cutting machine, a workpiece to be machined is fixed to a rotating workpiece axis, a tool is rotated around a tool axis, and a workpiece axis motor and a tool axis motor are controlled so that the tool axis and the workpiece axis rotate synchronously.

[0003] In a machining center that processes the workpiece by synchronizing these two axes, external disturbances can cause vibrations that affect machining accuracy. Patents JP 3 986 320 B2 and JP 5 308 404 B2 describe a method for measuring the workpiece's machining accuracy and correcting the position of a grinding worm using the measurement results.

[0004] External disturbances that affect the machining accuracy of a workpiece can include components caused by tool or workpiece axis positional deviations, synchronization errors, mechanical vibrations of machine parts, or similar factors. The key to increasing the machining accuracy of the workpiece lies in identifying the disturbance component that is affecting it.

[0005] The invention is based on the objective of providing an improved control device for a gear machining machine.

[0006] According to the invention, this problem is solved by a control device having the features of claim 1.

[0007] One embodiment of the present disclosure is a control device for a gear machining machine, which controls a multi-axis gear machining machine and comprises an axis information recording unit, which records data related to the control of the multi-axis during machining; and a disturbance component identification unit, which, using the data recorded by the axis information recording unit and the result of a measurement of the machining accuracy of a workpiece by the machining machine, identifies disturbance components with respect to the multi-axis.

[0008] The tasks, features, and advantages of the present invention will become even clearer through the explanation of the embodiment below in conjunction with the accompanying drawings. In the accompanying drawings is Fig. 1 a block diagram showing the overall structure of a machine tool with a control device according to one embodiment; is Fig. 2 a view showing an example of the assembly when the machine is designed as a gear grinding machine; is Fig. 3. An enlarged representation of the workpiece environment at the machining center, showing the state of the gear machining process; is Fig. 4 a view to explain the flank line direction and the tooth profile direction on the flank line of a workpiece; is Fig. 5 a view to explain the trace produced by a contact point of a cutting grinding screw on the circumferential surface of the workpiece, the positional deviation, the scanning points of the waviness in the flank line direction, etc.; is Fig. 6 a diagram showing the oscillation of the tool axis along the time axis; is Fig. 7 a diagram in which the values ​​of the waviness in the flank line direction at the individual sampling points were plotted; is Fig. 8 a view to explain the sampling period of the ripple in the flank line direction; is Fig. 9 a view showing the step length of the measured waviness in the flank line direction; is Fig. 10 a view showing an example of tool axis position deviation data; is Fig. 11 a view showing an example of workpiece axis position deviation data; is Fig. 12 a view showing the state in which the flank line on the workpiece is rolled by teeth of the tool fixed to the tool axis; is Fig. 13 a diagram showing an example of the waviness of a division single deviation; is Fig. 14 a view to explain the vibration of the waviness on the tooth surface of the individual flank lines of a helical gear with a helix angle θ; is Fig. 15 a flowchart showing the procedure for identifying interference components; is Fig. 16 a flowchart showing a correction procedure selection process; is Fig. 17 a flowchart of the processing for the selection of a correction procedure; is Fig. 18 a view showing an example of the construction of a control system for individual drive axles; and is Fig. 19 a view showing an example of the frequency characteristics of a velocity control loop of the control system.

[0009] An embodiment of the present disclosure is explained below with reference to the accompanying drawings. In all drawings, corresponding structural elements are identified by common reference numerals. The scale of these drawings has been adjusted accordingly for clarity. The embodiment shown in the drawings is only one example of the invention; the present invention is not limited to the embodiment shown.

[0010] Fig. Figure 1 is a block diagram showing the overall structure of a machine tool 100 with a control device 1 according to one embodiment. The machine tool 100 is, for example, a gear grinding machine, a gear skiving machine, or a gear cutter. The in Fig. The machining center 100 shown in Figure 1 comprises the control device 1, n control axes CS1 to CSn, each having a motor and a drive axis, a measuring device 20 that measures the machining accuracy of a workpiece W, and a disturbance component identification unit 6. The control device 1 includes a position command generation unit 2, control units C1 to Cn, each controlling the control axes CS1 to CSn, an axis information recording unit 5, and a correction procedure selection unit 7. The disturbance component identification unit 6 can also be formed within the control device 1. A position command P (a command vector consisting of n elements) for rotating each control axe CS1 to CSn from the position command generation unit 2 is input into the control units C1 to Cn, and the rotation of each control axe C1 to Cn is controlled according to the position command P.

[0011] The control device 1 can have a computer-like architecture with a CPU, ROM, RAM, and the like. In the control device 1, the control between the control units C1 to Cn and the control axes CS1 to CSn can be a synchronous control, in which a synchronization ratio is applied to feedback from the master axis and a command is generated for the slave axis. Alternatively, it can be an instruction-synchronous control, in which a synchronization ratio is applied to the command of the master axis and a command is generated for the slave axis. The individual function blocks that are in Fig. The functions shown in 1 can be implemented by special hardware or by the interaction of hardware and functions that the CPU executes through software.

[0012] The processing machine, which is in Fig. As shown in Figure 1, the machining accuracy of a workpiece (hereinafter referred to as workpiece) W can be affected by vibrations generated by disturbance components. The key to accurately correcting the influence of such a disturbance component on machining accuracy lies in identifying the disturbance component (its frequency, amplitude, etc.). By identifying the disturbance component, direct factors causing the disturbance (for example, a positional deviation of the tool axis with a certain frequency peak) can be identified, and it becomes possible to apply an efficient correction procedure to improve machining accuracy.The processing machine 100 according to the present embodiment comprises, as a structural element for identifying the disturbance component and for applying an efficient correction method, the measuring device 20, the axis information recording unit 5, the disturbance component identification unit 6 and the correction method selection unit 7.

[0013] The axis information recording unit 5 records data from each axis during the actual machining of workpiece W. The data for each axis includes a position deviation, which is the difference between a detected position of each axis and a command position, and a synchronization error. When a first axis and a second axis are rotating in synchronization, the synchronization error can be obtained as the difference between a converted position feedback from the first axis (where the first axis's position feedback was converted into a value corresponding to the second axis's position feedback using a synchronization ratio) and the position feedback from the second axis.The disturbance factor identification unit 6 identifies, based on the data from the individual axes recorded by the axis information recording unit 5 and the machining accuracy measured by the measuring device 20, the disturbance factor that affects the machining accuracy of the workpiece W. Depending on the disturbance factor identified by the disturbance factor identification unit 6, the correction method selection unit 7 selects an efficient correction method for correcting the positional deviation of the individual axes or the like from several types of pre-stored correction methods.

[0014] The machine tool 100 is described below as a gear grinding machine, which forms a helical gear as workpiece W through gear grinding. Fig. Figure 2 shows an example of a setup when the machining center 100 is configured as a gear grinding machine. As in Fig. As shown in Figure 2, the control device 1 in this case comprises a tool axis control unit C1, a workpiece axis control unit C2, and a feed axis control unit C3 as control units C1, C2, and C3. The control axes CS1, CS2, and CS3 are each configured as a tool axis CS1, a workpiece axis CS2, and a feed axis CS3 (not shown).

[0015] Fig. Figure 3 is an enlarged view of the area surrounding workpiece W on machine tool 100, schematically illustrating the gear-gear machining process. A helical cutting edge 51a is formed on the surface of a grinding worm 51, which represents the tool fixed to the tool axis CS1. Workpiece W is a helical gear with helical flank lines 61 that have already been roughly machined by a gear-milling or gear-skiving operation, or the like. The workpiece axis CS2 is aligned parallel to a Z-axis. The grinding worm 51 is rotated about the tool axis CS1, which is positioned so that it is inclined with respect to a plane perpendicular to the Z-axis, and the workpiece W is rotated synchronously with a specific synchronization ratio with respect to the tool axis CS1.While the grinding screw 51 is in contact with the flank lines of the workpiece W, it is moved from top to bottom in the Z-axis direction by a drive of the feed axis CS3. This grinds the entire flank lines of the workpiece W. Fig. 3 The spiral cutting edge 51a on the grinding screw 51 and the several flank lines 61 formed in the circumferential surface of the workpiece W are shown using continuous lines for convenience of explanation and only some of the flank lines are provided with reference symbols.

[0016] The following are methods for identifying the interference components (1) the identification of a disturbance component by the waviness in the flank line direction (flank line deviation) ; (2) the identification of a disturbance component by the waviness in the tooth profile direction (tooth profile deviation); (3) the identification of a disturbance component by a divisional single deviation; and (4) the identification of a disturbance component is explained by the amplitude of the position deviation.

[0017] On machine tool 100, testing is performed to detect waviness (flank line deviation) that forms on workpiece W in the flank line direction when a vibration occurs at the tool axis CS1 as a disturbance component. It is assumed that workpiece W is a helical gear with a helix angle θ. A procedure is first described in which the waviness generated by the disturbance component in the flank line direction of workpiece W is calculated. Then, the waviness in the flank line direction that has formed on workpiece W after machining is measured. The disturbance component is identified by comparing the calculated waviness in the flank line direction with the waviness in the flank line direction that has formed on workpiece W after machining. Here, the waviness in the flank line direction is calculated as described in [reference to relevant section]. Fig. Figure 4 shows the unevenness in the depth direction with respect to the surface (the tooth surface) of the workpiece W in the direction of the flank line 61 (the flank line direction 71) on the circumferential surface of the workpiece W. On the other hand, the unevenness in the depth direction with respect to the surface (the tooth surface) of the workpiece W in the direction orthogonal to the flank line direction 71 is specified as waviness (tooth profile deviation) in the tooth profile direction 72.

[0018] As in Fig. 5 shows the track L, which is the contact point T (see Fig. 3) between the grinding screw 51 and the circumferential surface of the workpiece W, a spiral vibration is generated on the circumferential surface of the workpiece W when the workpiece W is considered to be fixed. The vibration D1 caused by the disturbance component on the tool axis CS1 is in Fig. 5 is represented as wavy, continuous lines. This oscillation D1 is actually an unevenness in the depth direction with respect to the tooth surface, but is in Fig. 5 For convenience, the waveforms shown are expressed. By scanning the vibration of the tool axis CS1 along the flank line direction 71 using the data from the individual axes, the waviness in the flank line direction can be calculated. It is assumed that the frequency of the vibration of the tool axis CS1 is sufficiently faster than the scanning frequency. The data showing the vibration of the tool axis CS1 can be obtained from the data recorded by the axis information recording unit 5 for each axis (the feedback values ​​from position sensors (encoders) installed on the individual drive axes).

[0019] Fig. Figure 6 is a diagram showing the oscillation D1 of the tool axis CS1 along the time axis. As in Fig. 5. The phase of the oscillation D1 shifts at the positions of the sampling points (P0, P1, P2 ... PQ) along the flank direction for each sampling point, but the phase at sampling point PQ again coincides with the oscillation D1. If the minimum value of the difference between the sampling period Ts and an integer multiple of the oscillation period Td is now set as Δt, the deviation of the phase from the oscillation D1 at sampling points P1, P2 is Δt and 2Δt respectively, and at sampling point PQ is QΔt. The sampling points P1 to PQ represent one period of the ripple arising in the flank direction. Their relationship can be ordered as shown below: Δt=|Sampling period (Ts)−N×Oscillation period (Td)|, where N is a natural number. Oscillation frequency (fd) = 1 / (Q×Δt) Ripple period = Sampling period (Ts) × Q

[0020] From the above relationship formula, the ripple frequency can be defined as follows: Ripple frequency = MIN|Oscillation frequency (fd) −N×Sampling frequency (Fs)| where N is a natural number.

[0021] Fig. Figure 7 is a diagram in which the waviness values ​​in the flank line direction at the individual sampling points (P0, P1, P2 ... PQ) have been plotted. The step length (length) of the waviness in the flank line direction can be determined using the waviness period determined as above and the flank line component of the feed rate of the tool axis CS1 in the Z-axis direction as follows: Ripple step length = Ripple period × (feed rate in the Z-axis direction) / cosθ

[0022] Next, the sampling period (Ts) is determined by setting the rotational speed of the workpiece axis CS2 as ω (rad / s) and the helix angle as θ. This is done as in Fig. Figure 8 shows a coordinate system that fixes the workpiece W. The scanning period Ts can be considered the time until the workpiece completes one revolution at the speed of movement of the contact point T as seen from the flank line 61. If the workpiece radius is set to r (mm), the circumferential speed is rω (mm / s), and if the feed rate of the tool axis in the Z-axis direction is set to Vz, the speed of movement in the circumferential direction of the flank line 61 as seen from the Z-axis is Vz × tanθ. That is, if the direction of rotation is the direction of Fig. 8 is the velocity of the contact point T rω × tanθ as seen from the flank line 61. Starting from the above, the sampling period (Ts) in the flank line direction is determined as follows: Ts=2πrrω−Vz×tanθ

[0023] If the direction of rotation is the opposite direction of Fig. If the value is 8, the sampling period (Ts) will be as follows: Ts=2πrrω+Vz×tanθ

[0024] The sampling frequency (Fs) is determined as the reciprocal of Ts. The sampling period Ts is the time until the rotating tool, fixed to the tool axis CS1, processes the same flank line again after machining a flank line on the workpiece W, in conjunction with the rotation of the workpiece W.

[0025] Based on the above, it was possible to determine the waviness frequency in the flank line direction using the data from the individual axes by calculation. Next, the waviness in the flank line direction of the workpiece W is measured after actual machining. It is assumed that the step length of the waviness in the flank line direction is determined by the measuring instrument 20 as shown in Fig. 9 shows where A (mm) was measured. From the measurement result of Fig. 9. The ripple frequency is defined as follows: (Wave frequency)=Vz / (A×cosθ)

[0026] Since, on the other hand, the ripple frequency was defined according to formula (1), the following equation is obtained: MIN|fd-N×Fs|=Vz / (A×cosθ)

[0027] Next, consideration is given to identifying fd, which represents the disturbance frequency. Since there are several combinations of disturbance frequencies Fd and natural numbers N that satisfy the above formula (2), reference is made to position deviation data recorded in the axis information recording unit 5 for the identification of the disturbance frequency. Here, it is assumed that a frequency analysis of the position deviation data for the tool axis CS1 yields a value as shown in Fig. The peak of HA (Hz) shown in the position deviation data is present in the 10 shown peak, and for the workpiece axis CS2 two as in Fig. The peak frequencies HB (Hz) and HC (Hz) shown in Figure 11 are present in the position deviation data. Since the disturbance frequency fd in this case is one of HA (Hz), HB (Hz), and HC (Hz), each of these is inserted into the formula (2) above, and the one that satisfies formula (2) is the disturbance frequency that produces the ripple in the flank line direction with step length A. For example, if the frequency peak HA (Hz) of the position deviation of tool axis CS1 has a natural number N that satisfies formula (2), and the frequency peaks HB (Hz) and HC (Hz) of the position deviation of workpiece axis CS2 have natural numbers N that do not satisfy formula (2), the disturbance component that produces the ripple in the flank line direction with the measured step length A is identified as the vibration with the frequency peak HA (Hz) of the tool axis and becomes the subject of the correction processing described later.

[0028] Using the method described above, the disturbance component that produces waviness in the flank line direction can be identified from the measured value of the flank line deviation and the data of the actual machining.

[0029] Next, the identification of the interfering component by the waviness in the tooth profile direction (hereinafter referred to as tooth profile deviation) is explained. The condition is assumed that, as in Fig. Figure 12 shows that a flank line 161 is rolled on the workpiece W by the teeth of a tool 151 fixed to the tool axis CS1. Here, the engagement ratio of the workpiece is defined as x. The engagement ratio is the average number of teeth of the workpiece W that engage with the tool. In this case, the tooth profile is generated in the time t from engagement until the teeth of the workpiece disengage; and if the machining speed of the workpiece W is defined as ω c(rpm) and the number of teeth of the workpiece W is set as z, this time t is given by the following formula. t=(ωc60)−1×xz=60xωcz

[0030] If it was measured that waves arise during this time t due to the tooth profile deviation a, the frequency fd of the disturbance component that is the cause of this is given as follows. ƒdat=awcz60x(hz)

[0031] Next, as in the case of undulations in the flank line direction described above, it is checked whether a frequency peak corresponding to the disturbance component fd according to formula (3) above is present in the result of a frequency analysis of the position deviation data of the individual axes. If a frequency peak corresponding to the disturbance component fd is found in the position deviation data of the individual axes, this frequency peak can be identified as the disturbance component.

[0032] Next, the identification of the disturbance component by a pitch deviation is explained. The pitch deviation is the difference between the actual pitch on the pitch circle of adjacent tooth faces on the same side and the theoretical pitch. For example, it is assumed that, as in Fig. Figure 13 shows that the waviness of a pitch deviation has arisen and that peaks K are present within one rotation of the workpiece in the pitch deviation. In this case, the disturbance frequency that represents the cause of this pitch deviation is simply the K-fold vibration component during one rotation of the workpiece. Therefore, the disturbance frequency is obtained by the following formula (4). Disturbance frequency = (rotational speed of the workpiece) × K

[0033] If, in this case, the position deviation data of the individual axes recorded in the axis information recording unit 5 show a disturbance component with a frequency peak that corresponds to the disturbance frequency obtained by formula (4) during actual machining, this disturbance component can be identified as the cause of the divisional single deviation.

[0034] Next, the identification of the disturbance component by the amplitude of the position deviation is explained. From the amplitude of the position deviation recorded in the axis information recording unit 5, or the synchronization error of the tool axis CS1 and the workpiece axis CS2, the magnitude of the waviness formed on the tooth surface can be determined. Here, it is assumed that an amplitude A1 (deg) was calculated as waviness in the workpiece circumferential direction on the gear pitch circle. In this case, an amplitude x of the waviness on the tooth surface of the individual flank lines is determined as in Fig. The helical gear shown in 14 with a helix angle θ is specified by the formula (5) below. x=r×A1180π×cosθ

[0035] It is assumed that a vibration with an amplitude A1 (deg) and a frequency B1 (Hz) occurs as a positional deviation of the data of the individual axes. The amplitude x (mm) of the waviness that this vibration component generates on the tooth surface is calculated using the formula (5) above. This amplitude x is then compared with the amplitude of the tooth surface waviness obtained by measuring the workpiece after actual machining. If the two values ​​are close, it can then be determined that there is a high probability that the vibration component mentioned above is the cause of the flank line deviation.However, in order to identify the disturbance component that is the cause of the waviness of the flank line deviation even more precisely, it is necessary to calculate the step length of the waviness in the flank line direction from the frequency component B1 (Hz) of the position deviation using the method described above and to check whether it matches the step length of the waviness in the flank line direction obtained by measuring the workpiece after actual machining.

[0036] The procedures explained above for identifying the fault component can be used as an operational process, as in Fig. 15. This processing is performed by the disturbance component identification unit 6. Initially, the gear precision (flank line deviation, profile deviation, pitch deviation, amplitude, etc.) of an actual machined gear is measured (step S11). Then, the data recorded in the axis information recording unit 5 for each axis is referenced (step S12). Subsequently, using the gear precision measurement results and the data from each axis, the disturbance component influencing the gear precision (frequency, amplitude) is identified (step S13). It is also possible that multiple disturbance components may be identified.

[0037] Next, the processing for choosing the type of efficient correction in relation to the disturbance components identified by each of the procedures explained above will be explained. Fig. Figure 16 shows the entire processing sequence for selecting the correction procedure. This processing is carried out by the correction procedure selection unit 7. Initially, in step S101, the processing for identifying the fault component ( Fig. 15) The identified disturbance component is assigned to a variable d(i) (i = 1 to n) (step S101). Then i is initialized (step S102), and during the period in which the condition that i is at most n is met, the processing of steps S104 to S107 is carried out. In step S104, it is determined whether the disturbance component d(i) is an integer multiple of the rotational frequency of the tool axis CS1 or the workpiece axis CS2. If the disturbance component is an integer multiple of the rotational frequency of the tool axis CS1 or the workpiece axis CS2, the correction method 1 (learning control) that is suitable for this disturbance component is selected from several pre-stored types of correction methods 1 to 4 (step S105).

[0038] In a learning control system, it is possible to reduce the positional deviation by using a period of the operating pattern, such as one revolution of the tool axis, as the learning period. This effectively suppresses the disturbance component that arises at a frequency that is an integer multiple of the rotational frequency of the tool axis CS1 or the workpiece axis CS2. A learning control system known in the relevant field can be used, in which the correction magnitude is repeatedly determined through learning until the positional deviation converges to near zero.For example, in a learning control system, a learning process is performed in which the position deviation is determined for each specific operating pattern period, the correction magnitude from the previous pattern period is added to this position deviation, the result of this addition is subjected to filtering, a new correction magnitude is calculated, the new correction data is stored, and the position command is corrected using this correction data. This process is repeated until the position deviation approaches zero. An example of such a learning control system in a machine tool is described in patent specification JP 4 043 996 B2.

[0039] Next, the axis to which the correction is applied is determined to be the axis identified by the disturbance component identified above (step S107). This ensures that an efficient correction procedure is applied to the axis that is the primary cause of the disturbance during the next processing operation. In step S108, i is incremented to perform the processing from steps S103 to S107 for the next disturbance component.

[0040] If, on the other hand, the disturbance component d(i) is not an integer multiple of the rotational frequency of the tool axis CS1 or the workpiece axis CS2, a correction method 2 to 4 is selected in step S106. Fig. Figure 17 is a flowchart of the processing for selecting correction method 2 to 4. First, in step S201, it is determined whether the cause of the disturbance component d(i) is a machine resonance or not. The procedure for determining whether the cause of the disturbance component d(i) is a machine resonance or not is then explained. It is assumed that the control system of the individual drive axes consists, for example, of a system like the one described in Figure 17. Fig. Figure 18 shows a motor 204 comprising a speed control unit 201, which generates a current command in response to a speed command and an actual speed detected by a speed sensor 205; a current control unit 202, which generates a voltage command in accordance with the current command; a two-phase-to-three-phase conversion unit 203, which performs a two-phase-to-three-phase conversion in accordance with the current command; and the speed sensor 205. It is assumed that by measuring the frequency characteristics of a speed control loop as shown in Figure 18, the motor 204 can be determined. Fig. The frequency characteristics shown in section 19 are obtained. If the frequency characteristics obtained as a result of the measurement are such that... Fig. If the increase in gain at A2 (Hz) shown in Figure 19, originating from a machine resonance, is present, a vibration of A2 (Hz) may occur during machining. In step S201, it is determined whether the disturbance frequency d(i) matches the previously determined machine resonance frequency A2 (Hz). If the disturbance frequency d(i) matches the previously determined machine resonance frequency A2 (Hz), it is determined that the disturbance frequency d(i) is a machine resonance (S201: YES), and the correction method 2 (notch filter) effective for the machine resonance is selected.

[0041] One method for determining the machine resonance frequency in advance is to conduct a hammer impact test on the machine tool setup or similar equipment. For example, the resonance frequencies detected by the hammer impact test are assumed to be A3 (Hz), B3 (Hz), and C3 (Hz). In this case, if a disturbance frequency from A3, B3, and C3 is identified by the disturbance component identification unit 6, it is determined in step S201 that this disturbance frequency d(i) is a machine resonance (S201: YES), and correction method 2 (notch filter) is selected (step S202).

[0042] Here, the notch filter is a filter that eliminates frequency components of a specific bandwidth. If a notch filter was selected in step S202, the control unit Cn, which applies the notch filter, incorporates a notch filter with filter characteristics that eliminate the peak of the machine resonance frequency identified in step S201 (for example, A3 (Hz)) into the control system.

[0043] If, on the other hand, step S201 determines that the disturbance component d(i) is not a machine resonance (S201: NO), it is then determined whether the frequency of the disturbance component d(i) is at most a reference value of 1 or not (step S203). Here, the reference value of 1 can be a value that indicates the disturbance has a comparatively low frequency. If the frequency of the disturbance component d(i) is at most the reference value of 1 (S203: YES), correction method 3, which is effective for correcting the disturbance with the comparatively low frequency, is selected.

[0044] As correction method 3, various types of correction methods known in the relevant field, which are effective in correcting a disturbance with a comparatively low low frequency, can be used. An example of correction method 3 is a procedure in which feedback synchronization, which is a method in which a synchronization ratio is applied to feedback from a master axis (tool axis) and a command is designed for the slave axis (workpiece axis), and command synchronization, which is a method in which a synchronization ratio is applied to the command of the master axis and a command is designed for the slave axis, are combined (hereinafter referred to as the combined function).Such a combined function can be implemented, for example, by a process in which a position feedback from the master axis is converted into a position feedback from the slave axis using a synchronization ratio, a synchronization error is calculated from the difference between the converted position feedback from the master axis and the position feedback from the slave axis, the difference between the calculated synchronization error and the position deviation of the slave axis is subjected to filtering, and the position deviation of the slave axis is corrected using the filter output. Using such a combined function can also, for example, improve a phenomenon such as a decrease in accuracy at the start of machining. An example of the combined function is described in patent specification JP 5 815 784 B2.Since the correction method 3 (combined function) is effective for disturbances with a comparatively low frequency, the reference value 1 can, for example, be set to a servo-controlled range of about 150 Hz.

[0045] If, on the other hand, step S203 determines that the frequency of the disturbance component d(i) is not at most the reference value 1 (S203: NO), it is then determined whether the frequency of the disturbance component d(i) is at least a reference value 2 or not (step S205). Here, the reference value 2 can be a value that indicates that the disturbance frequency is a comparatively high frequency. If it is determined that the frequency of the disturbance component d(i) is at least a reference value 2 (S205: YES), correction procedure 4, which is effective in the case of a comparatively high disturbance frequency, is selected.

[0046] A known method in the field can be used for vibration damping control. An example of vibration damping control is a system in which, during machining with synchronized operation of the two axes—the tool axis and the workpiece axis—at a specific speed ratio, a correction factor for reducing vibrations is calculated using the speed difference between the two axes. The torque command is then corrected using this correction factor, thereby reducing vibrations caused by interference between the two axes. An example of such vibration damping control is described in patent specification JP 5 863 860 B2.Since the vibration damping control is effective for suppressing resonance frequencies with a comparatively high frequency (for example, 300 Hz) or the like, the reference value 2 can be set to 200 Hz as an example.

[0047] If the frequency of the disturbance component d(i) is not at least the reference value 2 (S205: NO), then in particular no selection of a correction method is necessary. If the processing for selecting the correction method of Fig. 17 ends, processing proceeds to step S107 in Fig. 16 over.

[0048] As explained above, the present embodiment makes it possible to identify interfering components that affect the accuracy of the workpiece after machining. Furthermore, it makes it possible to precisely select the type of efficient correction to improve the accuracy of the workpiece after machining.

[0049] In the foregoing, an embodiment of the present disclosure has been described, but those skilled in the art will understand that various improvements and modifications can be made without deviating from the scope of disclosure of the patent claims set forth below.

[0050] In the embodiment described above, when identifying a disturbance component by a flank line deviation in the axis information recording unit 5, position deviation data (or synchronization error data) recorded are used as frequency information and used to calculate the ripple frequency. However, time can also be added to the information recorded by the axis information recording unit 5. In this case, the axis information recording unit 5 records the start time of machining as a reference time, and the time during machining and the position deviation or synchronization error are correlated.In this case, it is possible to calculate the shape of the deviation in the flank line direction, which is formed, for example, by a positional deviation on the individual tooth surfaces, and not only the step length of the waviness, but also the phase of the waviness or the like.

[0051] Regarding interfering components, it is conceivable that, depending on the machining position and time, the amplitude may change or multiple interfering components may occur, and consequently, the shape of the waviness in the flank line direction, which appears on the individual tooth surfaces, can also change. By recording a reference time of the positional deviation, a precise shape of the corresponding waviness in the flank line direction can be calculated, and a more detailed identification of the interfering component becomes possible.

[0052] The embodiment described above was primarily explained for performing gear machining, in which a tool axis and a workpiece axis rotate in synchronization. However, according to the present embodiment, the machine tool can also be used for gear profile machining or gear profile grinding. For example, in gear profile grinding, a cutting tool with the same shape as the gaps of the gear is used, and machining is performed with a milling machine. Since the tool axis is stopped and the gaps of the gear are individually machined, it can also be assumed that the tool axis and the workpiece axis rotate with a synchronization ratio of 1:0.

[0053] To solve the problem described in this revelation, the following various forms and their results can be provided. The numbers in parentheses in the text of the following explanation of the forms correspond to the reference symbols in the drawings of this revelation.

[0054] For example, one form of the present disclosure comprises a control device (1) for a gear machining machine, which controls a multi-axis gear machining machine, and an axis information recording unit (5), which records data related to the control of the multi-axis during machining; and a disturbance component identification unit (6), which, using the data recorded by the axis information recording unit (5) and the result of a measurement of the machining accuracy of a workpiece (a gear) by the machining machine, identifies disturbance components with respect to the multi-axis.

[0055] Following the first method described above, it becomes possible to identify interfering factors that influence the accuracy of a workpiece after machining. Furthermore, it enables the precise selection of an efficient correction method to improve the workpiece's accuracy.

[0056] In a second form of the present disclosure, the control device (1) according to the first form described above further comprises a correction selection unit (7) which selects a correction to be applied to the control of the multiple axes to correct the disturbance, depending on the identified disturbance component, from several pre-stored types of corrections.

[0057] In a third form of the present disclosure, the correction selection unit (7) in the control device (1) according to the second form described above selects an axis to which the correction is applied from among the several axes according to the identified disturbance component.

[0058] In a fourth form of the present disclosure, the disturbance component identification unit (6) of the control device (1) according to the second or third form described above identifies the frequency of the disturbance component, and the correction selection unit (7) then selects a correction of a different type if the frequency of the disturbance component is proportional to the rotational frequency of any of the multiple drive axes, and then if the frequency of the disturbance component is not proportional to the rotational frequency of any of the multiple drive axes.

[0059] In a fifth embodiment of the present disclosure, the data in the control device (1) according to one of the first to fourth embodiments described above includes a calculation of the respective positional deviations of the multiple axes and a synchronization error of two axes among the multiple axes, and the disturbance component identification unit (6) calculates a waviness in the flank line direction on the tooth surface of the workpiece based on the positional deviations and the synchronization error, and identifies the disturbance component by comparing the calculated waviness in the flank line direction with a waviness in the flank line direction on the tooth surface of the workpiece obtained by measuring the workpiece after machining.

[0060] In a sixth form of the present disclosure, the data in the control device (1) according to a first to fourth form described above includes a data consisting of the respective positional deviations of the multiple axes and a synchronization error of two axes among the multiple axes, and the disturbance component identification unit (6) identifies the disturbance component by comparing a frequency component occurring in the positional deviations or the synchronization error with a frequency component calculated from the number of wavinesses in the flank line direction on the tooth surface of the workpiece obtained by measuring the workpiece after machining.

[0061] In a seventh form of the present disclosure, the data in the control device (1) according to a first to fourth form described above includes a data consisting of the respective position deviations of the multiple axes and a synchronization error of two axes among the multiple axes, and the disturbance component identification unit (6) identifies the disturbance component by comparing a frequency component occurring in the position deviations or the synchronization error with a frequency component calculated from the number of ripples of a pitch unit deviation within one revolution of the gear, obtained by measuring the workpiece after machining.

Claims

[1] A control device (1) for a gear processing machine that controls a gear processing machine having multiple axes, the control device (1) comprising an axis information recording unit (5) that records data related to the control of the multiple axes during machining; and a noise component identification unit (6) that identifies noise components related to the multiple axes using the data recorded by the axis information recording unit (5) and the result of a measurement of the machining accuracy of a workpiece by the processing machine. [2] A control device (1) for a gear working machine according to claim 1, further comprising a correction selecting unit (7) that selects a correction applied to the control of the plurality of axes to eliminate the disturbance depending on the identified disturbance component from a plurality of pre-stored types of corrections. [3] A control device (1) for a gear working machine according to claim 2, wherein the correction selecting unit (7) selects an axis to which the correction is applied from among the plurality of axes according to the identified disturbance component. [4] A control device (1) for a gear processing machine according to claim 2 or 3, wherein the noise component identifying unit (6) identifies the frequency of the noise component, and the correction selecting unit (7) selects a correction of a different type when the frequency of the noise component is proportional to the rotation frequency of any one of the plurality of drive axes and when the frequency of the noise component is not proportional to the rotation frequency of any one of the plurality of drive axes. [5] The control device (1) for a gear processing machine according to any one of claims 1 to 4, wherein the data includes one of the respective positional deviations of the plurality of axes and a synchronization error of two axes among the plurality of axes, and the noise component identifying unit (6) calculates a waviness in the tooth trace direction on the tooth surface of the workpiece based on one of the positional deviations and the synchronization error, and identifies the noise component by comparing the calculated waviness in the tooth trace direction and a waviness in the tooth trace direction on the tooth surface of the workpiece obtained by measuring the workpiece after machining. [6] A control device (1) for a gear machining machine according to any one of claims 1 to 4, wherein the data includes one of the respective positional deviations of the plurality of axes and a synchronization error of two axes among the plurality of axes, and the noise component identifying unit (6) identifies the noise component by comparing a frequency component occurring in the positional deviations or the synchronization error and a frequency component calculated from the number of wavinesses in the tooth trace direction on the tooth surface of the workpiece obtained by measuring the workpiece after machining. [7] A control device (1) for a gear machining machine according to any one of claims 1 to 4, wherein the data includes one of the respective positional deviations of the plurality of axes and a synchronization error of two axes among the plurality of axes, and the noise component identifying unit (6) identifies the noise component by comparing a frequency component occurring in the positional deviations or the synchronization error and a frequency component calculated from the number of ripples of a pitch single deviation within one revolution of the gear obtained by measuring the workpiece after machining.

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