Machine tool and method for generating an alarm in a machine tool

Abstract

To provide a machine tool which calculates a phase relation between a zero-cross position of a B-phase signal and a Z-phase signal with a simple configuration and generates a proper alarm.SOLUTION: A machine tool includes: a rotation position detector; and a numerical control device. The rotation position detector comprises: a rotor 11; a sensor unit 12 which outputs an A-phase signal, a B-phase signal, and a Z-phase signal; and a data processing unit 20 which calculates a rotation position. The data processing unit 20 comprises a phase calculation part 41 which calculates an interpolation value being inverse tangent with the value of the A-phase signal and the value of the B-phase signal at timing of rising or falling of the Z-phase signal and calculates a phase difference between the zero-cross position of the B-phase signal and timing of rising or falling of the Z-phase signal on the basis of the calculated interpolation value. The numerical control device includes a Z-phase signal phase determination unit 55 which performs alarm determination on the basis of the interpolation value input from the data processing unit 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a machine tool and a method for generating phase and alarms in a machine tool. [Background technology]

[0002] A rotor 11 made of a magnetic material combining an AB phase gear having many teeth and a Z phase disk having one notch around its circumference is attached to a rotating shaft 61, and a sensor unit 12 made of a magnetic resistance element and a bias magnet detects changes in magnetic flux from the AB phase gear and the Z phase disk as electric signals, and a data processing unit 120 detects the rotational position and rotational speed of the rotating shaft 61 (see FIG. 6). Such a detector is disclosed in, for example, Patent Document 1.

[0003] In such a conventional rotational position detector 110, only one Z-phase pulse signal is output while the rotating body makes one rotation, so that the value of the up-down counter, which counts up or down depending on the changes in the A-phase pulse signal and B-phase pulse signal between the rising edge of the Z-phase pulse signal and the next rising edge, is latched, thereby making it possible to identify the absolute rotational position within one rotation of the rotating shaft.

[0004] With this method, there are cases where the rising edge of the Z-phase pulse signal crosses the rising edges of the A-phase and B-phase pulse signals, causing the latched count value used to identify the absolute position within one rotation to become unstable.

[0005] There is also a rotation position detector in use that clears the up / down counter and starts the next up / down count when the three conditions of the Z-phase pulse signal being high level, the A-phase pulse signal being high level, and the B-phase pulse signal being low level are met. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-315100 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional rotational position detector shown in Fig. 6, if the sensor unit 12 is installed in an inappropriate state and the output levels of the Z-phase pulse signal, A-phase pulse signal, B-phase pulse signal, etc. fluctuate due to temperature changes or load changes on the rotating shaft, the phases of the A-phase and B-phase pulse signals and the Z-phase pulse signal may deviate from a specified phase relationship, causing the pulse count to become unstable. In such a case, an alarm is issued upon detection of a large speed fluctuation or a deviation of the phase relationship between the Z-phase signal and the up / down count value from the specified relationship by more than a certain degree.

[0008] However, while there are few issues if the alarm is output immediately after installation, it is possible that the alarm may occur several days after the product is shipped or after a faulty sensor is replaced, which poses an issue.

[0009] Therefore, an object of the present invention is to provide a rotation position detector that can detect improper installation immediately after installing a sensor unit by making it possible to calculate the phase relationship between the zero cross position of an A-phase signal or the zero cross position of a B-phase signal and a Z-phase signal with a simple configuration. Another object of the present invention is to appropriately generate an alarm. [Means for solving the problem]

[0010] The machine tool of the present invention is a machine tool including a rotation position detector and a numerical control device, The rotational position detector includes a detectable object attached to a rotating shaft, a sensor unit that outputs an A-phase signal that changes sinusoidally in response to the rotational position of the detectable object, a B-phase signal that changes sinusoidally in response to the rotational position of the detectable object and has a phase difference of 90 degrees with respect to the A-phase signal, and a pulsed Z-phase signal that is output once per rotation of the detectable object, and a data processing unit that calculates the rotational position of the rotating shaft based on the A-phase signal, the B-phase signal, and the Z-phase signal, and the data processing unit calculates an interpolated value that is an arctangent with the value of the A-phase signal and the value of the B-phase signal at the timing of a rise or fall of the Z-phase signal as arguments. And before The numerical control device has a Z-phase signal phase determination unit that performs an alarm determination based on the interpolated value input from the data processing unit, and the Z-phase signal phase determination unit generates an alarm when the interpolated value is not within a tolerance range. and, when the interpolated value is within a tolerance range, a margin phase angle for an alarm occurrence is calculated based on the difference between the interpolated value and an upper limit value of the tolerance range or the difference between the interpolated value and a lower limit value of the tolerance range. The present invention is characterized by the following.

[0011] This makes it possible to calculate the phase relationship between the zero cross position of the A-phase signal or the zero cross position of the B-phase signal and the Z-phase signal with a simple configuration, and also makes it possible to appropriately generate an alarm.

[0012] In the machine tool of the present invention, the Z-phase signal phase determination unit may generate an alarm when the interpolated value at the rising timing of the Z-phase pulse is not between 0 and 3*π / 2.

[0013] In the machine tool of the present invention, the data processing unit converts the A-phase signal and the B-phase signal input from the sensor unit into an A-phase digital signal and a B-phase digital signal, respectively, and also converts the Z-phase signal input from the sensor unit into a Z-phase pulse signal, and outputs the converted A-phase digital signal, B-phase digital signal, and Z-phase pulse signal. Leave the interpolated value is an arctangent whose arguments are the value of the A-phase digital signal and the value of the B-phase digital signal at the timing of the rising or falling edge of the Z-phase pulse signal. but good.

[0014] This makes it possible to calculate the phase difference between the zero crossing position of the B-phase digital signal and the rising or falling timing of the Z-phase pulse signal with a simple configuration.

[0015] The method of the present invention is a machine tool including a rotational position detector including a detectable object attached to a rotating shaft, a sensor unit that outputs an A-phase signal that changes sinusoidally in response to the rotational position of the detectable object, a B-phase signal that changes sinusoidally in response to the rotational position of the detectable object and has a phase difference of 90 degrees with respect to the A-phase signal, and a pulsed Z-phase signal that is output once per rotation of the detectable object, and a data processing unit that calculates the rotational position of the rotating shaft based on the A-phase signal, the B-phase signal, and the Z-phase signal, and a numerical control device. T, A A method for generating an alarm, comprising: calculating an interpolated value which is an arctangent of the A-phase signal value and the B-phase signal value at the timing of the rise or fall of the Z-phase signal as arguments; ,before If the interpolated value is not within the acceptable range, an alarm is generated. and, when the interpolated value is within a tolerance range, a margin phase angle for an alarm occurrence is calculated based on the difference between the interpolated value and an upper limit value of the tolerance range or the difference between the interpolated value and a lower limit value of the tolerance range. The present invention is characterized by the following.

[0016] This makes it possible to simply calculate the phase relationship between the zero cross position of the B-phase signal and the Z-phase signal, and to determine the calculated value on the numerical control device side before an alarm occurs. Also, an alarm can be generated appropriately.

[0017] In the method of the present invention, an alarm may be generated if the interpolated value at the rising timing of the Z-phase pulse is not between 0 and 3*π / 2.

[0018] In the method of the present invention, the data processing unit includes a signal conversion unit that converts the A-phase signal and the B-phase signal input from the sensor unit into an A-phase digital signal and a B-phase digital signal, respectively, and converts the Z-phase signal input from the sensor unit into a Z-phase pulse signal, and outputs the converted A-phase digital signal, B-phase digital signal, and Z-phase pulse signal, and the interpolated value is an arctangent whose arguments are the value of the A-phase digital signal and the value of the B-phase digital signal at the timing of a rising or falling edge of the Z-phase pulse signal. but good.

[0019] This makes it possible to easily calculate the phase difference between the zero-crossing position of the B-phase digital signal and the rising or falling timing of the Z-phase pulse signal even in a rotational position detector that does not have a Z-phase AD converter that performs AD conversion of the Z-phase signal. Effect of the Invention

[0020] The present invention can provide a rotation position detector that can detect an improper installation state of a sensor unit, etc., by calculating the phase relationship between the zero cross position of an A-phase signal or the zero cross position of a B-phase signal and the Z-phase signal with a simple configuration. Also, the present invention can appropriately generate an alarm. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a system diagram showing a configuration of a rotational position detector according to the embodiment. [Diagram 2] 1 is a perspective view showing a configuration of a sensor unit and a rotor of a rotational position detector according to an embodiment; [Diagram 3] 1 is a graph showing an A-phase analog signal, a B-phase analog signal, and a Z-phase analog signal output from a sensor unit when a rotating body rotates in the forward direction, with the upper graph showing the time changes in the A-phase analog signal and the B-phase analog signal near the time when a pulsed Z-phase analog signal is output, and the lower graph showing the time changes in the A-phase pulse signal, the B-phase pulse signal, and the Z-phase pulse signal output from a comparator. [Figure 4]4 is a graph (upper graph) showing waveform changes versus electrical angle of an A-phase digital signal and a B-phase digital signal obtained by converting the A-phase analog signal and the B-phase analog signal shown in FIG. 3 by an AD converter, and a graph (lower graph) showing waveform changes versus electrical angle of an A-phase pulse signal, a B-phase pulse signal, and a Z-phase pulse signal output from a comparator. [Diagram 5] 11 is a graph showing changes in waveform with respect to the electrical angle of an A-phase pulse signal, a B-phase pulse signal, and a Z-phase pulse signal output from a comparator when a rotating body rotates in the reverse direction. [Figure 6] FIG. 1 is a system diagram showing a configuration of a rotational position detector of a conventional technology as a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, a rotational position detector 10 according to an embodiment will be described with reference to the drawings. As shown in Fig. 1, the rotational position detector 10 includes a rotating body 11, which is an object to be detected, attached to a rotating shaft 61 of a machine tool 60, a sensor unit 12 arranged adjacent to the rotating body 11, and a data processing unit 20.

[0023] 2, the rotor 11 is made up of an AB phase gear 11a made up of many teeth and a Z phase disk 11b with a notch in one place per circumference, and is attached to a rotating shaft 61 to rotate together with the rotating shaft 61. The rotor 11 is generally made of a magnetic material such as iron. The sensor unit 12 is made up of a magnetic resistance element and a bias magnet, and outputs a change in magnetic flux that occurs as the rotor 11 rotates based on the teeth of the AB phase gear 11a and the notch in the Z phase disk 11b as three electrical signals: an A phase analog signal, a B phase analog signal, and a Z phase analog signal.

[0024] 3, the A-phase analog signal is a signal that changes sinusoidally in response to the rotational position of the rotor 11. As indicated by the dashed line B1, the B-phase analog signal, like the A-phase analog signal, changes sinusoidally in response to the rotational position of the rotor 11 and has a phase that is 90 degrees different from that of the A-phase analog signal. As indicated by the dashed line D1, the Z-phase analog signal is a pulse-like signal that is output once per rotation of the rotor 11.

[0025] 1, the data processing unit 20 includes two control blocks: a signal conversion unit 30 and a calculation unit 40. The signal conversion unit 30 includes three control blocks: an AD converter 31, a comparator 32, and an up / down counter 33. The calculation unit 40 includes a phase calculation unit 41 therein.

[0026] The AD converter 31 performs AD conversion on the A-phase analog signal and the B-phase analog signal input from the sensor unit 12, and outputs an A-phase digital signal indicated by a solid line A2 in the upper graph of FIG. 4 and a B-phase digital signal indicated by a dashed dotted line B2 to the calculation unit 40 and the phase calculation unit 41.

[0027] The comparator 32 compares each of the voltage values ​​of the A-phase analog signal, B-phase analog signal, and Z-phase analog signal input from the sensor unit 12 with a reference voltage shown as 2.5 V in the upper graph of FIG. 3, and outputs a high-level signal when the voltage value of each signal exceeds the reference voltage, and outputs a low-level signal when the voltage value of each signal is equal to or lower than the reference voltage. In this way, the A-phase analog signal, B-phase analog signal, and Z-phase analog signal are converted into an A-phase pulse signal shown by a solid line PA0, a B-phase pulse signal shown by a dashed dotted line PB0, and a Z-phase pulse signal shown by a dashed line PD0 in the lower graph of FIG. 3, and output them to the up / down counter 33.

[0028] The up / down counter 33 counts up or down based on changes in the A-phase pulse signal, B-phase pulse signal, and Z-phase pulse signal input from the comparator 32 , and outputs the results to the calculation unit 40 .

[0029] The calculation unit 40 calculates the rotational position and rotational speed of the rotating shaft 61 based on the A-phase digital signal and B-phase digital signal input from the AD converter 31, the up or down count value input from the up / down counter 33, and the number of teeth of the AB-phase gear 11a of the rotating body 11 input from a servo data file 51 of the numerical control device 50 of the machine tool 60, and outputs the calculated value to the numerical control device 50 of the machine tool 60. The calculation unit 40 also outputs to the numerical control device 50 a Z-phase value, an increment signal based on the presence or absence of an input of a Z-phase pulse signal after power-on, and an absolute signal.

[0030] The numerical control device 50 includes a position / speed control unit 52, a Z-phase signal phase determination unit 55, and a sequence control unit 54. The position / speed control unit 52 controls the position / speed of a drive motor 62 of a rotating shaft 61 of a machine tool 60 based on the rotational position and rotational speed input from the calculation unit 40. The sequence control unit 54 performs sequence control to select one of two control modes (incremental coordinate system and absolute coordinate system) of the drive motor 62 based on the incremental signal and absolute signal input from the calculation unit 40. In addition, the Z-phase signal phase determination unit 55 performs alarm determination and the like based on the phase value of the Z-phase signal input from the calculation unit 40.

[0031] Each of the control blocks of the data processing unit 20, signal conversion unit 30, calculation unit 40, AD converter 31, comparator 32, up / down counter 33 and phase calculation unit 41 of the rotational position detector 10 described above is realized by the CPU of a computer that includes a CPU, which is a processor that performs information processing internally, a memory that stores operation programs and operation data, and a timer that detects the times of pulse change timing of the A-phase digital signal, B-phase digital signal, and Z-phase digital signal, executing a predetermined program.

[0032] Next, the operation of the rotational position detector 10 will be described. When the rotating shaft 61 shown in Fig. 1 is rotated in the forward direction, as described above, the sensor unit 12 outputs an A-phase analog signal indicated by a solid line A1, a B-phase analog signal indicated by a dashed line B1, and a Z-phase analog signal indicated by a dashed line D1 in the upper graph of Fig. 3. The A-phase analog signal, the B-phase analog signal, and the Z-phase analog signal are input to the comparator 32, which outputs an A-phase pulse signal indicated by a solid line PA0, a B-phase pulse signal indicated by a dashed line PB0, and a Z-phase pulse signal indicated by a dashed line PD0 in the lower graph of Fig. 3.

[0033] The voltage of the A-phase analog signal shown by the solid line A1 in the upper graph of FIG. 3 goes from a state below the reference voltage of 2.5V to a state above the reference voltage of 2.5V at time tA0. At this time, the A-phase pulse signal shown by the solid line PA0 in the lower graph of FIG. 3 rises from a low level to a high level. Also, the voltage of the A-phase analog signal goes from a state above the reference voltage of 2.5V to a state below the reference voltage of 2.5V at time tA1. At this time, the A-phase pulse signal falls from a high level to a low level. In this way, the A-phase analog signal goes from a state below the reference voltage of 2.5V to a state above the reference voltage of 2.5V, or goes from a state above the reference voltage of 2.5V to a state below the reference voltage of 2.5V, which is called a zero crossing of the analog signal. Also, the time when the A-phase pulse signal rises from a low level to a high level is called the rising timing of the A-phase pulse signal, and the time when the A-phase pulse signal falls from a high level to a low level is called the falling timing of the A-phase pulse signal.

[0034] 3 are the zero-crossing timings of the A-phase analog signal. In addition, times tA0, tA2, and tA4 are the rising timings of the A-phase pulse signal, and times tA1 and tA3 are the falling timings of the A-phase pulse signal.

[0035] Similarly, times tB0, tB1, tB2, and tB3 are the zero-crossing timings of the B-phase analog signal. Furthermore, times tB0 and tB2 are the rising timings of the B-phase pulse signal, and times tB1 and tB3 are the falling timings of the B-phase pulse signal. Similarly, times tD0 and tD1 are the zero-crossing timings of the Z-phase analog signal. Furthermore, time tD0 is the rising timing of the Z-phase pulse signal, and time tD1 is the falling timing of the Z-phase pulse signal.

[0036] The rotation position detector 10 of the embodiment is configured such that when the three conditions of the Z-phase pulse signal being at a high level, the A-phase pulse signal being at a high level, and the B-phase pulse signal being at a low level are met, the up-down counter 33 clears the up-down count and proceeds to the next up-down count. As shown in the graph in the lower part of FIG. 3, the Z-phase pulse signal is at a high level between time tD0 and time tD1. During this period, the B-phase pulse signal is at a low level between time tB1 and time tB2. Then, at time tA2 when the A-phase pulse signal rises from a low level to a high level between time tB1 and time tB2, the three conditions of the Z-phase pulse signal being at a high level, the A-phase pulse signal being at a high level, and the B-phase pulse signal being at a low level are met, so the up-down counter 33 clears the up-down count immediately after time tA2 shown by the diagonal hatching in the graph in the lower part of FIG. 3 and proceeds to the next up-down count.

[0037] Here, consider a case where the rising timing of the Z-phase pulse signal is shifted from time tD0 due to some factor. For example, consider a case where the rising timing of the Z-phase pulse signal becomes earlier than time tD0 and before time tB0. In this case, between time tA0 and time tB0 shown by cross-hatching in FIG. 3, the A-phase pulse signal is at a high level and the B-phase pulse signal is at a low level. Therefore, when the Z-phase pulse signal rises, three conditions are met: the Z-phase pulse signal is at a high level, the A-phase pulse signal is at a high level, and the B-phase pulse signal is at a low level, and the up-down counter 33 clears the up-down count. In this case, the B-phase pulse signal between time tB0 and time tB1, which is counted in the normal state described above, is cleared, and the B-phase pulse signal is counted one pulse less than in the normal state.

[0038] Conversely, consider a case where the falling timing of the Z-phase pulse signal becomes later than time tD0 and later than time tA2. In this case, after time tA2, the B-phase pulse signal is at a low level and the A-phase pulse signal is at a high level, so when the Z-phase pulse signal rises, the three conditions of the Z-phase pulse signal being at a high level, the A-phase pulse signal being at a high level, and the B-phase pulse signal being at a low level are met, and the up-down counter 33 clears the up-down count. In this case, the pulses of the A-phase pulse signal between time tA2 and time tA3, which would not be counted under normal circumstances, are counted, so the count number of the A-phase pulse signal becomes one more than in the normal state.

[0039] Also, consider a case where the falling timing of the Z-phase pulse signal becomes later than time tD1 and later than time tA4. In this case, after time tA4, the B-phase pulse signal is at a low level and the Z-phase pulse signal is at a high level, so when the A-phase pulse signal rises at time tA4, the three conditions of the Z-phase pulse signal being at a high level, the A-phase pulse signal being at a high level, and the B-phase pulse signal being at a low level are met, causing the up-down counter 33 to clear the up-down count again. In this case, the count of the B-phase pulse signal between time tB2 and time tB3 that was counted once is cleared and the next count is started, so the count number of the B-phase pulse signal becomes one less than in the normal state.

[0040] Furthermore, if the falling timing of the Z-phase pulse signal is earlier than time tA2, the timing when the three conditions of the Z-phase pulse signal being at a high level, the A-phase pulse signal being at a high level, and the B-phase pulse signal being at a low level will no longer be met, and the up / down count will not be cleared.

[0041] From the above, it is necessary for the Z-phase pulse signal to have a phase that rises at time Δt1 between time tB0 and time tA2, as shown in the lower graph of Figure 3, and falls at time Δt2 between time tA2 and time tA4.

[0042] Therefore, in the rotational position detector 10 of the embodiment, the phase calculation unit 41 calculates and outputs the phase difference between the zero cross position of the A-phase signal or the zero cross position of the B-phase signal and the rising or falling timing of the Z-phase signal, as described below.

[0043] The phase calculation unit 41 receives the A-phase digital signal and the B-phase digital signal, which are respectively indicated by the solid line A2 and the dashed line B2 in the graph in the upper part of FIG. 4 and are the A-phase analog signal and the B-phase analog signal described above with reference to FIG. 3 converted into digital signals by the AD converter 31. Here, the A-phase digital signal and the B-phase digital signal are sinusoidal signals whose values ​​change between 1 and −1. The phase calculation unit 41 also receives the A-phase pulse signal, the B-phase pulse signal, and the Z-phase pulse signal described with reference to FIG. 3 from the comparator 32. Note that the AD converter 31 does not AD convert the Z-phase analog signal, and therefore the Z-phase digital signal is not input to the phase calculation unit 41.

[0044] As shown in the upper graph of Fig. 4, phase calculation unit 41 treats the A-phase digital signal and the B-phase digital signal as amounts of change with respect to an electrical angle φ in radians, where one period T of one tooth of AB phase gear 11a is an electrical angle of 2π (360 degrees). Similarly, as shown in the lower graph of Fig. 4, the A-phase pulse signal, B-phase pulse signal, and Z-phase pulse signal are also treated as amounts of change with respect to an electrical angle φ, where one tooth of AB phase gear 11a is an electrical angle of 2π (360 degrees).

[0045] Times tA0 to tA4, times tB0 to tB3, times tD0, and times tD1 shown in FIG. 3 correspond to the electrical angles φA0 to φA4, the electrical angles φB0 to φB3, the electrical angle φD0, and the electrical angle φD1 shown in FIG.

[0046] 4 correspond to the zero-crossing positions of the A-phase digital signal. The electrical angles φA0, φA2, φA4 correspond to the rising timings of the A-phase pulse signal, and the electrical angles φA1 and φA3 correspond to the falling timings of the A-phase pulse signal.

[0047] Similarly, the electrical angles φB0, φB1, φB2, and φB3 are the zero-crossing positions of the B-phase digital signal. Furthermore, the electrical angles φB0 and φB2 are the rising timings of the B-phase pulse signal, and the electrical angles φB1 and φB3 are the falling timings of the B-phase pulse signal. Similarly, the electrical angle φD0 is the rising timing of the Z-phase pulse signal, and the electrical angle φD1 is the falling timing of the Z-phase pulse signal. Furthermore, it is necessary for the Z-phase pulse signal to have a phase such that it rises at an electrical angle Δφ1 between the electrical angles φB0 and φA2 shown in the lower graph of FIG. 4, and falls at an electrical angle Δφ2 between the electrical angles φA2 and φA4.

[0048] Here, we will explain how to determine the zero-cross position of the B-phase digital signal and the rising timing of the Z-phase pulse signal and calculate the phase difference based on the electrical angle φB1, which is the zero-cross position of the B-phase digital signal or the falling timing of the B-phase pulse signal.

[0049] First, an interpolated value at a reference electrical angle φB1 is calculated as a B-phase reference value. Here, the interpolated value is calculated as the arctangent of the A-phase digital signal value and the B-phase digital signal value at the electrical angle φB1 as two arguments, as shown in Equation 1 below.

number

[0050] Here, as shown in FIG. 4, since the value of the A-phase digital signal at electrical angle φB1 is −1 and the value of the B-phase digital signal is 0, the above (Equation 1) becomes the following (Equation 2).

number

[0051] Atan2(x,y) is a function that calculates the radian angle between the x-axis pointing in the positive direction and a line passing through the origin (0,0) and the coordinate point (x,y) whose x-coordinate and y-coordinate are the two arguments (x,y). In this embodiment, Atan2(x,y) is described as a function that returns a numerical value in the range of 0 radians to 2π radians. Therefore, Atan(-1,0) is π radians (180 degrees), which is the angle between the x-axis pointing in the positive direction and the coordinate point (-1,0).

[0052] Similarly, the interpolated value (φD0) at the rising timing of the Z-phase pulse signal that rises at the electrical angle φD0 is calculated as follows.

number

[0053] Further, the interpolated value (φB0) and the interpolated value (φA2) at the lower limit electrical angle φB0 and the upper limit electrical angle φA2 of the allowable range of the rising timing of the Z-phase pulse signal are calculated as follows.

number

number

[0054] From the above (Equation 3) to (Equation 5), the interpolated value (φD0) at the rising timing of the Z-phase pulse signal falls within the range of the following (Equation 6).

number

[0055] Here, as an example, when the electrical angle φD0 of the rising timing of the Z-phase pulse is an electrical angle φA1 between the lower limit electrical angle φB0 and the upper limit electrical angle φA2 of the allowable range of the rising timing of the Z-phase pulse signal, the following calculation is performed:

number

[0056] Next, a case will be described where the zero cross position of the B-phase digital signal and the falling timing of the Z-phase pulse signal are determined based on the electrical angle φB2, which is the zero cross position of the B-phase digital signal or the rising timing of the B-phase pulse signal.

[0057] First, an interpolated value at the reference electrical angle φB2 is calculated as a B-phase reference value as shown in the following (Equation 8).

number

[0058] Similarly, the interpolated value (φD1) at the falling timing of the Z-phase pulse signal that falls at the electrical angle φD1 is calculated as follows.

number

[0059] Further, the interpolated value (φA2) and the interpolated value (φA4) at the lower limit electrical angle φA2 and the upper limit electrical angle φA4 of the allowable range of the falling timing of the Z-phase pulse signal are calculated as follows.

number

number

[0060] From the above (Equation 9) to (Equation 11), the interpolated value (φD1) at the falling timing of the Z-phase pulse signal falls within the range of the following (Equation 12).

number

[0061] Here, as an example, when the rising timing φD0 of the Z-phase pulse is an electrical angle φA3 between the lower limit electrical angle φA2 and the upper limit electrical angle φA4 of the allowable range of the rising timing of the Z-phase pulse signal, the following calculation is performed:

number

[0062] As described above, it is possible to determine whether the phase relationship between the zero-cross position of the A-phase digital signal or the zero-cross position of the B-phase digital signal and the rising or falling timing of the Z-phase pulse signal is within a predetermined range using (Equation 6) or (Equation 12). In addition, it is possible to calculate the margin phase angle for alarm generation by calculating the difference between the upper limit value and the lower limit value of (Equation 6) or (Equation 12) and the interpolated value (φD0) or (φD1).

[0063] Furthermore, by calculating the difference between the interpolated value (φD0) and the B-phase reference value which is the interpolated value at the electrical angle φB1, it is possible to calculate the zero cross position of the B-phase digital signal, or the phase difference between the falling timing of the B-phase pulse signal and the rising timing of the Z-phase pulse signal. Similarly, by calculating the difference between the interpolated value (φD1) and the B-phase reference value which is the interpolated value at the electrical angle φB2, it is possible to calculate the zero cross position of the B-phase digital signal, or the phase difference between the falling timing of the B-phase pulse signal and the falling timing of the Z-phase pulse signal.

[0064] In the above explanation, the zero cross position of the B-phase digital signal or the phase difference between the rising or falling timing of the B-phase pulse signal and the rising or falling timing of the Z-phase pulse signal is calculated. However, it is also possible to calculate the zero cross position of the A-phase digital signal or the phase difference between the falling or rising timing of the A-phase pulse signal and the rising or falling timing of the Z-phase pulse signal.

[0065] Next, with reference to FIG. 5, a description will be given of how to determine the rising and falling timings of the Z-phase pulse signal when the rotating shaft 61 shown in FIG. 1 is rotated in the reverse direction.

[0066] When the rotating shaft 61 shown in Fig. 1 is rotated in the reverse direction, the comparator 32 outputs an A-phase pulse signal as indicated by the solid line PA2 in Fig. 5, a B-phase pulse signal as indicated by the dashed line PB2, and a Z-phase pulse signal as indicated by the dashed line PD2. The electrical angles φA5, φA6, φA7, φA8, φA9, and φA10 shown in Fig. 5 are the zero-cross positions of the A-phase digital signal. Because the rotation direction is reversed, the electrical angles φA5, φA7, and φA9 correspond to the falling timings of the A-phase pulse signal, and the electrical angles φA6, φA8, and φA10 correspond to the rising timings of the A-phase pulse signal.

[0067] Similarly, the electrical angles φB5, φB6, φB7, φB8, φB9, and φB10 are the zero-crossing positions of the B-phase digital signal, the electrical angles φB5, φB7, and φB9 are the falling timings of the B-phase pulse signal, and the electrical angles φB6, φB8, and φB10 are the rising timings of the B-phase pulse signal. Furthermore, the electrical angle φD2 is the rising timing of the Z-phase pulse signal, and the electrical angle φD3 is the falling timing of the Z-phase pulse signal. Furthermore, it is necessary for the Z-phase pulse signal to have a phase such that it rises at an electrical angle Δφ3 between the electrical angles φA5 and φB7 shown in FIG. 5 and falls at an electrical angle Δφ4 between the electrical angles φB7 and φB9.

[0068] Here, a case will be described where the zero cross position of the B-phase digital signal and the rising timing of the Z-phase pulse signal are determined based on the electrical angle φB7, which is the zero cross position of the B-phase digital signal or the falling timing of the B-phase pulse signal.

[0069] In this case, just like the positive rotation described above,

number

number

[0070] Further, the interpolated value (φA5) and the interpolated value (φB7) at the lower limit electrical angle φA5 and the upper limit electrical angle φB7 of the allowable range of the rising timing of the Z-phase pulse signal are calculated as follows.

number

number

[0071] From the above (Equation 15) to (Equation 17), the interpolated value (φD2) at the rising timing of the Z-phase pulse signal falls within the range of the following (Equation 18).

number

[0072] Next, a case will be described where the zero cross position of the B-phase digital signal and the falling timing of the Z-phase pulse signal are determined based on the electrical angle φB8, which is the zero cross position of the B-phase digital signal or the rising timing of the B-phase pulse signal.

[0073] First, an interpolated value at the reference electrical angle φB2 is calculated as a B-phase reference value as shown in the following (Equation 19).

number

[0074] Similarly, the interpolated value (φD3) at the falling timing of the Z-phase pulse signal that falls at an electrical angle φD3 is calculated as follows.

number

[0075] Further, the interpolated value (φB7) and the interpolated value (φB9) at the lower limit electrical angle φB7 and the upper limit electrical angle φB9 of the allowable range of the falling timing of the Z-phase pulse signal are calculated as follows.

number

number

[0076] From the above (Equation 19) to (Equation 22), the interpolated value (φD3) at the falling timing of the Z-phase pulse signal falls within the range of the following (Equation 23).

number

[0077] Therefore, it is possible to determine whether the Z-phase pulse signal is within a predetermined range by (Equation 18) and (Equation 23).

[0078] As with forward rotation, it is possible to determine whether the phase relationship between the zero-cross position of the A-phase digital signal or the zero-cross position of the B-phase digital signal and the rising or falling timing of the Z-phase pulse signal is within a predetermined range using (Equation 18) or (Equation 23). Also, by calculating the difference between the upper and lower limits of (Equation 18) and (Equation 23) and the interpolated value (φD2) and (φD3), it is possible to calculate the margin phase angle for an alarm to be generated.

[0079] Furthermore, by calculating the difference between the interpolated value (φD2) and the B-phase reference value which is the interpolated value at the electrical angle φB7, it is possible to calculate the zero cross position of the B-phase digital signal or the phase difference between the falling timing of the B-phase pulse signal and the rising timing of the Z-phase pulse signal. Similarly, by calculating the difference between the interpolated value (φD3) and the B-phase reference value which is the interpolated value at the electrical angle φB8, it is possible to calculate the zero cross position of the B-phase digital signal or the phase difference between the falling timing of the B-phase pulse signal and the falling timing of the Z-phase pulse signal.

[0080] In the above description, the rotational position detector 10 has been described as being configured such that the up / down counter 33 clears the up / down count and proceeds to the next up / down count when the three conditions of the Z-phase pulse signal being at a high level, the A-phase pulse signal being at a high level, and the B-phase pulse signal being at a low level are met, but this is not limited to the above. For example, it is also possible to define a time t1 from time tB1, which is the falling timing of the B-phase pulse signal shown in Fig. 3, to time tD0, which is the rising timing of the Z-phase pulse signal moving in the negative direction of time t, and to limit this time t1 to a time between time a and time b as shown in (Equation 24).

number

number

[0081] As explained above in (Equation 2), by using π, which is the B-phase reference value, and the interpolated value (φD0) at the rising timing of the Z-phase pulse signal, and taking into consideration that the period T is an electrical angle of 2π, and that the increasing direction of time t1 is opposite to the increasing direction of the interpolated value (φD0), the following (Equation 26) is obtained when (Equation 25) is made to correspond to the electrical angle φ.

number

number

[0082] Here, when the range of time t1 is set as a < t1 < b as shown in (Equation 24), the range of (Equation 24) can be described as the range of electrical angle φ and becomes (Equation 28). [Number] And from (Equation 28), the range of the interpolated value (φD0) becomes as follows in (Equation 29). [Number] Generalizing by adding 2πN to both sides of (Equation 29), the range of the interpolated value (φD0) becomes as follows in (Equation 30). [Number]

[0083] Also, define the time t2 from the time tB2, which is the rising timing of the B-phase pulse signal shown in Figure 3, to the time tD1, which is the falling timing of the Z-phase pulse signal in the positive direction of time t. This time t2 may be limited between time c and time d as shown in (Equation 31). [Number]

[0084] In this case, since the interpolated value at the electrical angle φB2 is 0 as shown in (Equation 8), when expressing the range of the interpolated value (φD1) in terms of the electrical angle φ, it becomes as follows in (Equation 32). [Number] And generalizing in the same way as (Equation 30), [Number] it becomes

[0085] From the above, it is possible to determine whether the phase relationship between the zero-cross position of the A-phase digital signal or the zero-cross position of the B-phase digital signal and the rising or falling timing of the Z-phase pulse signal is within a predetermined range using (Equation 30) or (Equation 33). In addition, by calculating the difference between the upper and lower limit values ​​of (Equation 30) and (Equation 33) and each of the interpolated values ​​(φD0) and (φD1), it is possible to calculate the margin phase angle for alarm generation.

[0086] Furthermore, by calculating the difference between the interpolated value (φD0) and the B-phase reference value which is the interpolated value at the electrical angle φB1, it is possible to calculate the zero cross position of the B-phase digital signal, or the phase difference between the falling timing of the B-phase pulse signal and the rising timing of the Z-phase pulse signal. Similarly, by calculating the difference between the interpolated value (φD1) and the B-phase reference value which is the interpolated value at the electrical angle φB2, it is possible to calculate the zero cross position of the B-phase digital signal, or the phase difference between the falling timing of the B-phase pulse signal and the falling timing of the Z-phase pulse signal.

[0087] In the above explanation, the zero cross position of the B-phase digital signal, or the falling timing or rising timing of the B-phase pulse signal and the phase difference between the rising or falling timing of the Z-phase pulse signal are calculated. However, similarly, the zero cross position of the A-phase digital signal, or the falling timing or falling timing of the A-phase pulse signal and the phase difference between the rising timing and the rising or falling timing of the Z-phase pulse signal may be calculated.

[0088] Note that, instead of the A-phase digital signal and the B-phase digital signal, the A-phase analog signal and the B-phase analog signal may be converted into a signal that changes with respect to the electrical angle φ, and this signal may be used to calculate the phase difference between the zero-cross positions of the A-phase and B-phase analog signals and the rising or falling timing of the Z-phase pulse signal.

[0089] In the above explanation, the zero cross position of the A-phase or B-phase digital signal, or the phase difference between the rising or falling timing of the A-phase or B-phase pulse signal and the rising or falling timing of the Z-phase pulse signal is calculated using an interpolated value, but the present invention is not limited to this. As will be described below, while rotating shaft 61 at a constant speed, the time between the zero cross position of the A-phase digital signal or the zero cross position of the B-phase digital signal and the rising or falling timing of the Z-phase pulse signal may be measured, and the phase difference between the zero cross position of the A-phase digital signal or the zero cross position of the B-phase digital signal and the rising or falling timing of the Z-phase pulse signal may be calculated based on the ratio of the measured time to the period T of the A-phase digital signal or the B-phase digital signal.

[0090] For example, the phase calculation unit 41 shown in Fig. 1 may detect the zero-cross timing of the B-phase digital signal, or the time tB1 of the falling timing of the B-phase pulse signal shown in Fig. 3, and the time tD0 of the rising timing of the Z-phase pulse signal, and detect the phase difference as Δφu=(Δtu / T)*2π from the ratio of the detected time difference Δtu=tB1-tD0 to the period T=2π. Similarly, the phase calculation unit 41 may detect the zero-cross timing of the B-phase digital signal, or the time tB2 of the rising timing of the B-phase pulse signal shown in Fig. 3, and the time tD1 of the falling timing of the Z-phase pulse signal, and detect the phase difference as Δφd=(Δtd / T)*2π from the ratio of the detected time difference Δtd=tD1-tB2 to the period T=2π.

[0091] The rotational position detector 10 described above does not need to be equipped with a Z-phase AD converter that performs AD conversion of the Z-phase signal, and can calculate the phase difference between the zero-cross position of the A-phase digital signal or the zero-cross position of the B-phase digital signal and the rising or falling timing of the Z-phase pulse signal with a simple configuration. [Explanation of symbols]

[0092] 10,110 rotational position detector, 11 rotating body, 11a AB phase gear, 11b Z phase disk, 12 sensor unit, 20,120 data processing unit, 30,130 signal conversion unit, 31,131 AD converter, 32 comparator, 33 up / down counter, 40,140 calculation unit, 41 phase calculation unit, 50 numerical control device, 51 servo data file, 52 position / speed control unit, 53 alarm detection unit, 54 sequence control unit, 55 Z phase signal phase determination unit, 60 machine tool, 61 rotating shaft, 62 drive motor.

Claims

1. A machine tool including a rotational position detector and a numerical control device, The rotational position detector includes: A detection object attached to a rotating shaft; an A-phase signal that changes sinusoidally in response to the rotational position of the object to be detected; A B-phase signal that changes sinusoidally in response to the rotational position of the object to be detected and has a phase difference of 90 degrees with respect to the A-phase signal; a sensor unit that outputs a pulsed Z-phase signal that is output once per rotation of the detection object; a data processing unit that calculates a rotational position of the rotating shaft based on the A-phase signal, the B-phase signal, and the Z-phase signal, The data processing unit includes: Calculating an interpolated value that is an arctangent of the A-phase signal value and the B-phase signal value at the timing of the rising or falling edge of the Z-phase signal as arguments; The numerical control device has a Z-phase signal phase determination unit that performs an alarm determination based on the interpolated value input from the data processing unit, the Z-phase signal phase determination unit generates an alarm when the interpolated value is not within a tolerance range, and calculates a margin phase angle for alarm generation based on a difference between the interpolated value and an upper limit value of the tolerance range or a difference between the interpolated value and a lower limit value of the tolerance range when the interpolated value is within the tolerance range; A machine tool characterized by:

2. 2. The machine tool according to claim 1, the Z-phase signal phase determination unit generates an alarm when the interpolated value at the rising timing of the Z-phase pulse is not between 0 and 3*π / 2; A machine tool characterized by:

3. 3. The machine tool according to claim 1 or 2, The data processing unit includes: a signal conversion unit that converts the A-phase signal and the B-phase signal input from the sensor unit into an A-phase digital signal and a B-phase digital signal, respectively, and converts the Z-phase signal input from the sensor unit into a Z-phase pulse signal, and outputs the converted A-phase digital signal, the B-phase digital signal, and the Z-phase pulse signal; The interpolated value is the arctangent is calculated using the value of the A-phase digital signal and the value of the B-phase digital signal at the timing of the rise or fall of the Z-phase pulse signal as arguments; A machine tool characterized by:

4. A detection object attached to a rotating shaft; a sensor unit that outputs an A-phase signal that changes in a sinusoidal manner in response to the rotational position of the object to be detected, a B-phase signal that changes in a sinusoidal manner in response to the rotational position of the object to be detected and has a phase difference of 90 degrees with respect to the A-phase signal, and a pulsed Z-phase signal that is output once per rotation of the object to be detected; a data processing unit that calculates a rotational position of the rotating shaft based on the A-phase signal, the B-phase signal, and the Z-phase signal; A method for generating an alarm in a machine tool including a numerical control device, comprising: Calculating an interpolated value that is an arctangent of the A-phase signal value and the B-phase signal value at the timing of the rising or falling edge of the Z-phase signal as arguments; generating an alarm if the interpolated value is not within a tolerance range; calculating a margin phase angle for alarm generation based on a difference between the interpolated value and an upper limit value of the tolerance range or a difference between the interpolated value and a lower limit value of the tolerance range when the interpolated value is within the tolerance range; The method comprising:

5. 5. The method of claim 4, generating an alarm when the interpolated value at the rising timing of the Z-phase pulse is not between 0 and 3*π / 2; The method comprising:

6. 6. The method according to claim 4 or 5, the data processing unit includes a signal conversion unit that converts the A-phase signal and the B-phase signal input from the sensor unit into an A-phase digital signal and a B-phase digital signal, respectively, and converts the Z-phase signal input from the sensor unit into a Z-phase pulse signal, and outputs the converted A-phase digital signal, the B-phase digital signal, and the Z-phase pulse signal; the interpolated value is an arctangent whose arguments are the value of the A-phase digital signal and the value of the B-phase digital signal at the timing of the rising or falling edge of the Z-phase pulse signal; The method comprising:

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