Numerical control device

Abstract

Numerical control device for controlling a machine configured to perform a belt drive operation to transmit a driving force from a motor to an axle via a belt, the motor being connected to the axle by the belt, the numerical control device comprising: - an axis pulse detection unit designed to receive a pulse from the axis, - a motor pulse detection unit designed to receive a pulse from the motor, - an axis speed calculation unit that is configured to calculate an axis speed based on the received momentum of the axis, - a motor speed calculation unit designed to calculate a motor speed based on the received impulse from the motor, - a calculation unit for significant slip distance, designed to calculate a significant belt slip distance based on the integration of the absolute values ​​of the differences between the rotational speed of the shaft and the rotational speed of the motor, and - a belt lifetime determination unit designed to determine that the end of the belt's lifetime has been reached when the significant slip distance of the belt exceeds a predetermined threshold.

Description

Background of the invention 1. Field of the invention

[0001] The present invention relates to a numerical control device and, in particular, a numerical control device capable of determining the service life of a belt provided between a spindle and a motor. 2. Description of the relevant state of the art

[0002] A power transmission unit in a machine tool, such as a belt that transmits the rotational force of a motor to a spindle, reaches the end of its service life as a result of prolonged use. With a V-belt or flat belt, slippage occurs between the belt and a pulley, depending on the operating conditions, the motor speed, and the acceleration / deceleration. Since some of the frictional work due to slippage contributes to belt wear, slippage is considered a factor that affects belt lifespan. Furthermore, slippage often occurs as belt wear progresses, and the amount of slippage tends to increase.

[0003] Traditionally, an investigation is carried out to identify an anomaly, such as slippage of a belt that connects a motor to a spindle in a machine tool.

[0004] The disclosed Japanese patent application No. 61-103750, for example, discloses an anomaly detection method in which the rotational speed of a spindle is compared with the rotational speed of a motor and it is determined that an anomaly has occurred in a power transmission unit between the spindle and the motor if the difference between the rotational speed of the spindle and the rotational speed of the motor deviates from a speed difference that takes into account a predetermined reduction ratio between the spindle and the motor.

[0005] Furthermore, the disclosed Japanese patent application No. 2005-246534 discloses a method in which a command speed of a control device is compared with an actual speed of a spindle, it is determined that an anomaly has occurred if a condition in which a ratio of these two speeds exceeds a permissible value persists for a permissible period of time, and a spindle motor is stopped.

[0006] The disclosed Japanese patent application No. 2015-106936 discloses an anomaly detection method in which a one-revolution signal detection device is provided to output a signal each time the spindle completes a revolution, calculates a motor rotation angle during a period from the detection of the one-revolution signal until the detection of the next one-revolution signal, and determines that an anomaly has occurred in a power transmission section between the spindle and the motor if the change in the motor rotation angle between two one-revolution signals does not meet a predetermined condition or if the difference between the rotational speed of the motor and the rotational speed of the spindle deviates from a predetermined condition.

[0007] Furthermore, the disclosed Japanese patent application No. 5-233046 discloses a slip detection device that stores a last spindle stop position and a current spindle stop position whenever the spindle is stopped, maintains the deviation between these two positions, and determines that slippage has occurred if the deviation between these positions exceeds a permissible upper limit.

[0008] Although the known techniques described above can determine that an anomaly has occurred and persists in the belt, it is difficult to determine the belt's remaining service life before it reaches the end of its service life. As belt wear progresses, the probability of slippage increases, and the amount of slippage tends to increase rapidly. Accordingly, known techniques often include a threshold defined for determining that an anomaly has occurred in a condition where large slippage is first observed, or in a condition where belt breakage has occurred or is expected to occur. However, in a condition where only minor slippage occurs, less than the threshold, it is not possible to determine the belt's remaining service life before a breakage or similar event actually occurs. Summary of the invention

[0009] In light of the foregoing, an objective of the present invention is to provide a numerical control device that performs a determination of the service life of a belt in a machine whose axis and motor are connected by the belt.

[0010] The present invention provides a numerical control device that obtains the significant slip distance of a belt by integrating the slip occurring in the belt and determines that the end of the belt's service life has been reached when the obtained significant slip distance exceeds a predetermined threshold. The numerical control device according to the present invention measures the significant slip distance of the belt in a state where the belt tension is appropriately set. At this point, a pre-defined belt life evaluation test program is used to perform each measurement under the same or similar conditions.The significant belt slip distance is maintained in the state in which the test program is executed, and it is determined that the end of the belt's service life is reached when the maintained significant slip distance exceeds the threshold, at which point a belt anomaly is reported to an operator.

[0011] Furthermore, the numerical control device according to the present invention is configured to control a machine that performs a belt drive operation to transmit a drive force from a motor to the axle via the belt connecting the motor to an axle, wherein the numerical control device comprises an axle pulse detection unit that receives an impulse from the axle, a motor pulse detection unit that receives an impulse from a motor, a spindle speed calculation unit that calculates an axle speed based on the received axle pulse, a motor speed calculation unit that calculates a motor speed based on the received motor pulse, a significant slip calculation unit that calculates a significant belt slip based on the axle speed and the motor speed, and a belt life determination unit that determinesthat the end of the belt's service life is reached when the significant slippage of the belt exceeds the specified threshold.

[0012] The threshold used in determining the belt lifetime by the belt lifetime determination unit in the numerical control device according to the present invention is specified based on data collected during the execution of the belt lifetime evaluation test program.

[0013] According to the present invention, the operator can obtain advance knowledge of the service life of the belt connecting the shaft to the motor, thus preventing machine malfunctions. Furthermore, since the belt's service life can be known in advance, it is possible to initiate a replacement process and prevent an unintended stoppage of the machining process due to a belt breakage. Brief description of the drawings

[0014] The foregoing and other aims and features of the present invention will become apparent from the following description of the embodiments with reference to the accompanying drawings. It shows: Fig. 1 a schematic configuration representation of a cell control system according to an embodiment of the present invention; Fig. 2 a representation showing an example of a test program for evaluating belt life according to an embodiment of the present invention; Fig. 3 a diagram showing the rotational speed of the spindle motor and the spindle, which are recorded during the execution of the test program according to an embodiment of the present invention; Fig. 4 a schematic functional block diagram of a numerical control device according to an embodiment of the present invention; and Fig. 5 a representation that shows the operation of the in Fig. 4 numerical control device 100 illustrated. Detailed description of the preferred embodiments

[0015] Embodiments of the present invention are described below with reference to the drawings.

[0016] First, the process for calculating the slip distance of a belt according to the present invention is described. Fig. Figure 1 is a representation showing a schematic configuration of a spindle drive unit in which a spindle motor drives a spindle by means of a belt.

[0017] The spindle drive unit 10 comprises a spindle motor 1 and a spindle 2, which are mounted in a machine tool. A pulley 4 is attached to an output shaft of the spindle motor 1 and another pulley 5 is attached to the spindle 2.

[0018] As in Fig. As shown in Figure 1, pulley 4 and pulley 5 are connected by a belt 3, and spindle motor 1 and spindle 2 are connected by this connection. When spindle motor 1 is driven, the rotation of the output shaft is transmitted to spindle 2 via pulley 4, belt 3, and pulley 5.

[0019] The spindle motor 1 is equipped with a motor sensor 6, which is configured to detect the rotational speed of the spindle motor 1, and the spindle 2 is equipped with an axis sensor 7, which is configured to detect the rotational speed of the spindle 2, so that the rotational states of the spindle motor 1 and the spindle 2 can be detected by measuring feedback pulses that are each output by these sensors.

[0020] The in Fig. The spindle drive unit 10 shown in Figure 1 can be constructed such that the radius of pulley 4 and the radius of pulley 5 differ from each other, so that the rotational speed of spindle 2 differs from the rotational speed of spindle motor 1. However, for the sake of simplicity, the following description assumes that the radius of pulley 4 is identical to the radius of pulley 5.

[0021] According to the present invention, when the machine tool is used, which includes the spindle drive unit 10, the spindle motor 1 of which is connected to the spindle 2 by the belt 3, as shown in Fig. Figure 1 shows the number of feedback pulses P1 (pulse) of the spindle motor 1 detected by the motor sensor 6.

[0022] Furthermore, the number of feedback pulses P2 (pulse) of spindle 2 is measured by the axis sensor 7. If the measurement time t (ms), the number of pulses per revolution of spindle motor 1 P1' (pulse / rev), and the number of pulses per revolution of spindle 2 P2' (pulse / rev), then the rotational speed of spindle motor 1 S1(t) (rpm) and the rotational speed of spindle 2 S2(t) (rpm) are determined by the following expression 1. S1(t)=60000×(P1 / P1')×1t S2(t)=60000×(P2 / P2')×1t

[0023] If the pulley radii of the spindle motor 1 and the spindle 2 are r1 (mm) and r2 (mm) respectively, then a significant slip distance L (mm), which is an integrated value of slips occurring from the start of the drive of the spindle motor 1 until time T (min), is determined by the following expression 2. L=2π∫0T|r1S1(t)−r2S2(t)|dt

[0024] Let us also assume here that a permissible maximum slip distance is given by L max (mm) is specified. A belt anomaly is reported to an operator if the slippage L is greater than a permissible maximum slippage L. max will (i.e., L > L) max ).

[0025] The values ​​of L max This can be achieved by specifying the permissible maximum slip distance L. maxThe belt's service life is defined by a lifetime test or similar procedure using a pre-defined test program. The actual determination of the belt's service life is carried out by executing a belt service life evaluation program that instructs spindle motor 1 to follow the same command as the test program used in the lifetime test, and by comparing the slip distance L obtained as a result of executing the program with the permissible maximum slip distance L. max It is noted that the sampling of feedback pulses is carried out in a fine cycle, such as an interpolation period (ITP) (distributed cycle).

[0026] The process described above will be explained below using a specific example.

[0027] In this embodiment, it is assumed that the service life of the belt 3 is determined by controlling the machine tool through the numerical control device and executing the belt service life evaluation program (test program) in the numerical control device. Fig. Figure 2 is a representation showing an example of the belt lifetime evaluation program (test program).

[0028] Let us assume that the speed of spindle motor 1 and the speed of spindle 2 are as shown in Fig. 3 shown, as a result of running the belt lifetime assessment program (test program), an example of which is shown in Fig. Figure 2 shows that, assuming the radius of the pulley is r1 = r2 = 50 mm and the measurement time is T = 0.5 min, the significant slip distance L can be obtained using the following expression 3. Whether the belt 3 has reached the end of its service life can be determined by comparing the slip distance L obtained in this way with the permissible maximum slip distance L. max are determined, which was predetermined for the numerical control device by the lifetime test or the like. L=2π∫0T|r1S1(t)−r2S2(t)|dt=100π∫00.5|r1S1(t)−r2S2(t)|dt (mm)

[0029] It should be noted that in this embodiment, not only is there the section where the relationship (speed of spindle motor) ≥ (speed of spindle), but also the section where the relationship (speed of spindle motor) < (speed of spindle) is (the section in which in Fig. (Diagram 3, which extends from the point of 21 seconds onwards). In such a case, the conventional technique disclosed in published Japanese patent application No. 05-233046 only considers the position difference at each stop of the spindle. Consequently, published Japanese patent application No. 05-233046 cannot obtain the actual slip distance when, as in the present embodiment, the direction of slip changes. In contrast, the method used in the present invention adds absolute values ​​to the differences and performs the integration process, so that the slip distance can be calculated as a positive value in each region, thus making it possible to obtain the actual slip distance in each region.

[0030] Fig. Figure 4 is a functional block diagram showing essential features of the numerical control device according to this embodiment.

[0031] Fig. Figure 5 is a flowchart showing the processing sequence according to this embodiment. The operation of the numerical control device of this embodiment is described below with reference to the Fig. 4 and Fig. 5 described. The calculation unit for the significant slip distance is 160, the belt service life determination unit is 170 in Fig. 4 and steps SA04 and SA05 in Fig. 5 are the functions and processes introduced by the present invention.

[0032] [Step SA01] The numerical control device 100 reads the belt lifetime evaluation program from a memory unit (not shown) and executes the program.

[0033] [Step SA02] The motor rotation command unit 110 issues a rotation command to the spindle motor 1 according to commands from the individual blocks of the belt lifetime evaluation program executed by the numerical control device 100.

[0034] [Step SA03] The motor pulse detection unit 120 receives a motor pulse from the motor sensor 6. Additionally, the axis pulse detection unit 130 receives an axis pulse from the axis sensor 7.

[0035] [Step SA04] The motor speed calculation unit 140 calculates the speed of spindle motor 1 based on the motor pulse received by the motor pulse detection unit 120. Additionally, the axis speed calculation unit 150 calculates the speed of spindle 2 based on the axis pulse received by the axis pulse detection unit 130.

[0036] [Step SA05] The significant slip distance calculation unit 160 calculates the significant slip distance L based on the speed of spindle motor 1 and the speed of spindle 2, which were calculated in step SA04.

[0037] [Step SA06] The belt lifetime determination unit 170 performs the lifetime determination procedure based on the significant slip distance L obtained in step SA05 and the permissible maximum slip distance L previously set in the storage unit (not shown). max through.

[0038] Although the embodiments of the present invention have been described above, the present invention is not limited to the examples of the embodiments described above and can be implemented in various ways by suitably carried out modifications and alterations.

[0039] The embodiments described above are based, for example, on the example of the spindle drive unit, in which the spindle motor drives the spindle by means of the belt. However, the present invention is not limited to the spindle motor and the spindle, and can be suitably applied to determining the service life of the belt in a drive system in which a motor drives a shaft by means of a belt.

[0040] Although the embodiments of the present invention have been described above, the present invention is not limited to the examples of the embodiments described herein and can be implemented in other ways by suitably carried out modifications and alterations.

Claims

[1] Numerical control device for controlling a machine configured to perform a belt drive operation to transmit a driving force from a motor to an axle via a belt, the motor being connected to the axle by the belt, the numerical control device comprising: - an axis pulse detection unit designed to receive a pulse from the axis, - a motor pulse detection unit designed to receive a pulse from the motor, - an axis speed calculation unit that is configured to calculate an axis speed based on the received momentum of the axis, - a motor speed calculation unit designed to calculate a motor speed based on the received impulse from the motor, - a calculation unit for significant slip distance, designed to calculate a significant belt slip distance based on the integration of the absolute values ​​of the differences between the rotational speed of the shaft and the rotational speed of the motor, and - a belt lifetime determination unit designed to determine that the end of the belt's lifetime has been reached when the significant slip distance of the belt exceeds a predetermined threshold. [2] Numerical control device according to claim 1, wherein the threshold used by the belt lifetime determination unit to perform the determination of the belt lifetime is specified based on data collected during the execution of a test program for evaluating the belt lifetime.

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