JP2018119840A - Measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both grasping of a conveyance load to be applied to a motion guide device with high accuracy and suppression of increase in a load to be applied to a measurement device for data processing and increase in data volume therefor when calculating the conveyance load on the basis of a displacement of a movement member to be detected by a plurality of displacement sensors.SOLUTION: In a conveyance device movably supporting works by a motion guide device having a track member, a movement member, and a plurality of displacement sensors detecting a displacement of the movement member in a prescribed number of displacement directions in the movement member, a measurement device, which measures a conveyance load to be applied to the motion guide device, comprises: an acquisition unit that acquires detection values of the plurality of displacement sensors at a prescribed sampling interval; a calculation unit that calculates the conveyance load on the basis of the detection value of the displacement sensor acquired by the acquisition unit; and a setting unit that, when a relative velocity of the movement member to the track member is great, sets the prescribed sampling interval so that the prescribed sampling interval is shorter in comparison with a case where the relative velocity thereof is small.SELECTED DRAWING: Figure 16

Description

  The present invention relates to a measuring apparatus for measuring a conveying load applied to a moving member in a conveying apparatus that movably supports a workpiece by a motion guide device having a track member and a moving member.

  For various devices such as robots, machine tools, and semiconductor / liquid crystal manufacturing devices, motion guide devices for guiding the path of the movable part are used. For example, when the movable portion is driven straight, a so-called linear guide that is a motion guide device that supports the movable portion so as to be able to move straight is used. When selecting each part used in such a motion guide device, a component having a rated load with a margin for a load multiplied by a safety factor is usually selected. Furthermore, in recent years, a technique for detecting force information such as the direction and magnitude of the transport load applied to the moving member by attaching a strain gauge to the motion guide device has been developed (see, for example, Patent Document 1). In this way, by detecting force information such as the direction and magnitude of the transport load applied to the moving member, it is possible to estimate the life of the motion guide device.

JP 2007-263286 A

  As described above, when the movable part is driven straight in various devices such as a robot, a machine tool, and a semiconductor / liquid crystal manufacturing apparatus, a motion guide device that supports the movable part so as to be able to go straight is used. Such a motion guide device is disposed so as to face the raceway member via a raceway member extending along the longitudinal direction and a rolling element arranged to roll in the rolling groove. A structure having a moving member that is relatively movable along the longitudinal direction of the track member is known. In the motion guide device having such a configuration, the workpiece is conveyed by moving with respect to the track member while the moving member is supported by the rolling elements. Further, in the motion guide device having such a configuration, when the moving member moves relative to the track member to convey the workpiece, the moving member is repeatedly subjected to a conveying load as the moving member is displaced. It will hang. In addition, the displacement of the moving member in this specification is the displacement of the moving member with respect to the track formed by the track member.

  If a shearing stress is generated in the motion guide device due to the transfer load applied to the variable member, the life of the motion guide device is affected. Therefore, grasping the transport load repeatedly applied to the variable member during the movement of the moving member as described above is important in accurately estimating the life of the motion guide device. Therefore, in the motion guide device, a plurality of displacement sensors that detect the displacement of the moving member in a predetermined number of displacement directions may be provided. In this case, the conveyance load applied to the variable member can be calculated based on the detection values of the plurality of displacement sensors.

Here, since the conveyance load is repeatedly applied to the variable member during the movement of the variable member, acquisition of the displacement of the movable member detected by the displacement sensor and calculation of the conveyance load based on the acquired detection value of the displacement sensor are performed. Must be performed continuously during operation of the motion guide device. On the other hand, in order to grasp the conveyance load repeatedly applied to the variable member with high accuracy, it is necessary to shorten the sampling interval for obtaining the detection values of the plurality of displacement sensors as much as possible. However, when the detection values of a plurality of displacement sensors are continuously acquired, the acquired data (detection values of the displacement sensor) inevitably increases as the sampling interval is shortened. As a result, when the amount of data to be acquired becomes enormous, there is a possibility that the burden on the measuring apparatus for performing the data processing (calculation processing for calculating the transport load based on the data) becomes excessively large. In addition, when storing parameters related to the life of the motion guide device such as the transport load calculated based on the detection value of the displacement sensor or the shear stress calculated based on the transport load, the data There is also a risk that the capacity becomes excessively large.

  The present invention has been made in view of the above problems, and in a motion guide device in which a moving member moves relative to a raceway member via a rolling element, the displacement of the moving member detected by a plurality of displacement sensors. When calculating the transport load applied to the variable member based on the above, both grasping the transport load with high accuracy and suppressing the increase in the load on the measuring apparatus and the increase in the data capacity for data processing It aims at providing the technology that can do.

  In the present invention, in order to solve the above-mentioned problem, in the movement guide device having a plurality of displacement sensors for detecting the displacement of the moving member in a predetermined number of displacement directions in the moving member, the conveyance load applied to the variable member is calculated. Therefore, a configuration is adopted in which the sampling interval when obtaining the detection values of the plurality of displacement sensors is set according to the relative speed of the moving member with respect to the track member.

  In detail, the measuring apparatus according to the present invention is opposed to the raceway member via a raceway member extending along the longitudinal direction and a plurality of rolling elements arranged to roll in the rolling groove. And a movement member that is relatively movable along the longitudinal direction of the track member, and a plurality of displacement sensors that detect displacement of the movement member in a predetermined number of displacement directions in the movement member. In the transfer device that supports the workpiece movably by the guide device, the measurement device measures the transfer load applied to the variable member. And the said measuring apparatus calculates the said conveyance load based on the detection part which acquires the detection value of these displacement sensors with a predetermined sampling interval, and the detection value of these displacement sensors acquired by the said acquisition part And a setting unit that sets the predetermined sampling interval according to the relative speed of the moving member with respect to the track member, and the setting unit is smaller when the relative speed is large than when the relative speed is large. The predetermined sampling interval is set so that the predetermined sampling interval is shortened.

  A measuring apparatus according to the present invention is an apparatus that calculates a transport load applied to a variable member based on detection values of a plurality of displacement sensors that detect displacement of the moving member in a predetermined number of displacement directions in the moving member of the motion guide device. is there. Here, the plurality of displacement sensors have a predetermined number of displacement directions determined so as to be able to calculate a transport load repeatedly applied to the moving member when the moving member moves relative to the track member. It detects how much the moving member is displaced with respect to the track member. Therefore, the displacement direction that can be detected by the displacement sensor does not include the movement direction of the moving member relative to the track member.

  When the moving member moves with respect to the track member in the motion guide device, the displacement of the moving member is generated by vibration. The component having the highest frequency in the vibration component of the displacement of the moving member at this time is a vibration component accompanying waving. Note that the waving is a change in posture or vibration (pulsation) of the moving member caused by a periodic relative position shift with respect to the rolling surface of the rolling element when the moving member is moving with respect to the raceway member. That is. For this reason, when it is attempted to calculate the transport load repeatedly applied to the moving member based on the detection value of the displacement sensor during the movement of the moving member, even the change (vibration) of the displacement of the moving member caused by waving can be appropriately acquired. By doing so, it is possible to grasp the conveyance load with high accuracy.

Here, as described above, the waving is due to a cyclic shift of the relative position with respect to the rolling surface of the rolling element when the moving member is moving with respect to the raceway member. Therefore, the magnitude of the frequency of the vibration component accompanying waving has a correlation with the relative speed of the moving member with respect to the track member. That is, the greater the relative speed of the moving member with respect to the track member, the greater the frequency of vibration components associated with waving. And when it is going to acquire appropriately the change of the displacement of the moving member caused by the waving, the sampling of the detection value of the displacement sensor is greater when the frequency of the vibration component accompanying the waving is larger than when the frequency is small. It is necessary to shorten the interval. On the other hand, when the frequency of the vibration component due to waving is small, even if the sampling interval of the detection value of the displacement sensor is made longer than when the frequency is large, the change in displacement of the moving member caused by waving is reduced. Can be acquired appropriately.

  Therefore, in the present invention, the setting unit is configured so that the predetermined sampling interval for acquiring the detection values of the plurality of displacement sensors is shorter when the relative speed of the moving member with respect to the track member is large than when the relative speed is small. Set the sampling interval. According to this, when the frequency of the vibration component accompanying waving is large, the sampling interval of the detection value of the displacement sensor is shorter than when the frequency is small. In other words, when the frequency of the vibration component due to waving is small, the sampling interval of the detection value of the displacement sensor is longer than when the frequency is large. For this reason, it is possible to appropriately acquire the change in displacement of the moving member caused by the waving, and it is also possible to suppress the sampling interval of the detection value of the displacement sensor from becoming shorter than necessary. As a result, an increase in acquired data (detection value of the displacement sensor) can be suppressed as much as possible while acquiring a detection value of the displacement sensor to be used for continuous calculation of the transport load. Therefore, it is possible to achieve both the grasp of the transport load with high accuracy and the increase in the burden on the measuring apparatus for data processing and the suppression of the increase in data capacity.

  According to the present invention, in the motion guide device in which the moving member moves relative to the raceway member via the rolling element, the conveyance load applied to the moving member is determined based on the displacement of the moving member detected by the plurality of displacement sensors. In the case of calculation, it is possible to provide a technique capable of satisfying both the grasping of the conveyance load with high accuracy and the increase in the burden on the measuring device for data processing and the suppression of the increase in the data capacity.

It is a figure which shows schematic structure of the machine tool containing the motion guide apparatus of this invention. It is a figure which shows schematic structure of the exercise | movement guide apparatus of this invention. It is an external appearance perspective view of a rail and a carriage included in a motion guide device. It is the figure which showed the outline | summary of the internal structure of a rail and a carriage. (A) is a front view of the motion guide apparatus seen from the longitudinal direction of the rail, and (b) is an enlarged view of part B. It is the figure which imaged the functional part implement | achieved by information processing apparatus. It is the figure which showed the flow of the calculation process for calculating the conveyance load applied to a moving member, the shearing stress, and the generation frequency. It is a figure which shows the change of the output of a sensor when external force acts on a carriage. It is the figure which showed the part which the ball | bowl in a carriage is contacting. It is a figure which shows the state of the internal load before the displacement 5 component arises. It is a figure which shows the state of the internal load after the displacement 5 component produced. It is the figure which showed an example of the virtual area which divides a rolling surface. It is the figure which showed an example of the count value of the maximum shear stress repeatedly generate | occur | produced on a rolling surface when a carriage is moving. It is the figure which showed the movement of the ball | bowl when a carriage moves a rail. It is the graph which made the position of the carriage detected with a linear encoder the horizontal axis, and made the vertical axis | shaft the displacement detected with a sensor. It is the figure which showed the flow of the setting process for setting the predetermined sampling interval at the time of acquiring the detection value of a displacement sensor based on Example 1. FIG. It is the figure which showed correlation with the relative speed of the carriage with respect to a rail, and a sampling interval. It is the figure which showed an example of the SN curve of material. It is the figure which showed the flow of the setting process for setting the predetermined sampling interval at the time of acquiring the detection value of a displacement sensor based on Example 2. FIG.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of a machine tool including a motion guide device according to the present invention. The machine tool 20 includes a machining tool 31 for turning, grinding, slicing, and the like of the workpiece 40, a table 8 on which the workpiece 40 is placed, an actuator 17 for feeding the table 8, and a workpiece 40 by the machining tool 31. And an NC device 30 for controlling the processing speed (for example, the rotational speed of the spindle) and the feed speed of the table 8 by the actuator 17.

  Further, the above-described machine tool 20 uses the motion guide device 1 for supporting the table 8 so as to be movable. Here, the flow of information based on the structure of the motion guide device 1 and the detection value of the displacement sensor mounted on the motion guide device 1 will be described with reference to FIGS. In the motion guide apparatus 1, reference numerals 2a to 2d and 3a to 3d represent displacement sensors, reference numeral 4 represents a linear encoder, and reference numeral 10 represents an information processing apparatus.

  First, the structure of the exercise | movement guide apparatus 1 is demonstrated based on FIG.1 and FIG.2. The motion guide device 1 is an example of a rail 11 (an example of a “track member” in the present application) and a carriage 12 (an “moving member” in the present application) that is assembled so as to be relatively movable along the longitudinal direction of the rail 11. And an information processing apparatus 10 for processing signals of the linear encoder 4 and the displacement sensors 2a to 2b and 3a to 3b. In this embodiment, the rail 11 is attached to the base 7 of the machine tool 20, and the table 8 of the machine tool 20 is attached to the carriage 12. The movement direction of the movable part including the table 8 is guided by the movement guide device 1. It is also possible to turn the motion guide device 1 upside down, attach the carriage 12 to the base 7, and attach the rail 11 to the table 8. In addition, the motion guide device 1 may be used in a state where the longitudinal direction of the rail 11 is not horizontal but is inclined or orthogonal to a horizontal plane.

  FIG. 3 is an external perspective view of the rail 11 and the carriage 12 in the motion guide device 1. For convenience of explanation, the rail 11 is arranged on a horizontal plane, and the direction when viewed from the longitudinal direction of the rail 11, that is, the x-axis direction shown in FIG. 3, the y-axis is the up-down direction, and the z-axis is the left-right direction. 1 will be described. Of course, the arrangement of the motion guide device 1 is not limited to such an arrangement.

  On both the left and right sides of the rail 11, two upper and lower rolling surfaces 11a are provided. The cross section of the rolling surface 11a is arcuate. On the upper surface of the rail 11, through holes 11b through which a fastening member for fastening the rail 11 to the base 7 is passed are provided at an appropriate pitch along the longitudinal direction.

The carriage 12 has a horizontal portion 12-1 facing the top surface of the rail 11 and a pair of sleeve portions 12-2 facing the side surface of the rail 11, and has a U-shaped cross section. The carriage 12 is arranged at both ends in the movement direction of the carriage body 13 at the center in the movement direction, a pair of lid members 14a and 14b arranged at both ends in the movement direction of the carriage body 13, and a pair of lid members 14a and 14b. A pair of sensor mounting members 15a and 15b (see FIG. 2). The lid members 14 a and 14 b have a horizontal portion 14-1 facing the upper surface of the rail 11 and a pair of sleeve portions 14-2 facing the side surface of the rail 11, and have a U-shaped cross section. The sensor mounting members 15a and 15b also have a horizontal portion 15-1 facing the upper surface of the rail 11 and a pair of sleeve portions 15-2 facing the side surface of the rail 11, and are U-shaped in cross section ( (See FIG. 5 (a)). The lid members 14a and 14b are fastened to the carriage body 13 by fastening members such as bolts. The sensor mounting members 15a and 15b are fastened to the carriage main body 13 and the lid members 14a and 14b by fastening members such as bolts. 3 and 4, the sensor attachment members 15a and 15b are omitted.

  FIG. 4 is a diagram showing an outline of the internal structure of the rail 11 and the carriage 12 in the motion guide device 1. As shown in FIG. 4, the carriage body 13 is provided with four rolling surfaces 13 a facing the four rolling surfaces 11 a of the rail 11. The carriage body 13 is provided with a return path 13b in parallel with each rolling surface 13a. The lid members 14a and 14b are provided with U-shaped direction change paths 14c that connect the respective rolling surfaces 13a and the respective return paths 13b. The inner peripheral side of the direction change path 14 c is configured by an inner peripheral portion 13 c that is integral with the carriage body 13 and has a semicircular cross section. A track-shaped circulation path is constituted by the load rolling path between the rolling surface 11a of the rail 11 and the rolling surface 13a of the carriage body 13, the pair of direction changing paths 14c, and the return path 13b. A plurality of balls 16 (an example of a “rolling element” in the present application) are accommodated in the circulation path. When the carriage 12 moves relative to the rail 11, the balls 16 interposed therebetween roll on the load rolling path. The ball 16 rolled to one end of the load rolling path is introduced into one direction changing path 14c, and returns to the other end of the load rolling path via the return path 13b and the other direction changing path 14c.

<Sensor configuration>
Here, the configuration of the displacement sensors 2a to 2d and 3a to 3d incorporated in the motion guide apparatus 1 will be described. The displacement sensors 2a to 2d and 3a to 3d in the present embodiment are, for example, electrostatic capacitance type displacement meters, and detect the displacement of the carriage 12 with respect to the rail 11 in a non-contact manner (see an enlarged view of FIG. 5B). . Then, the displacement sensors 2 a to 2 d and 3 a to 3 d output the respective detection results to the information processing apparatus 10. As shown in FIG. 2, a pair of sensor attachment members 15a and 15b are attached to both ends of the carriage 12 in the moving direction. Four displacement sensors 2a to 2d are attached to one sensor attachment member 15a. The four displacement sensors 2 a to 2 d are arranged at the same position in the longitudinal direction of the rail 11. Four displacement sensors 3a to 3d are also attached to the other sensor attachment member 15b. The four displacement sensors 3 a to 3 d are arranged at the same position in the longitudinal direction of the rail 11. The distance between the displacement sensors 2a to 2d and the displacement sensors 3a to 3d in the longitudinal direction of the rail 11 is L1 (see FIG. 2). Note that the displacement sensors 2a to 2d and 3a to 3d may be arranged to be shifted from each other along the movement direction of the carriage 12.

  FIG. 5A shows the sensor mounting member 15 a as viewed from the longitudinal direction of the rail 11. As described above, the sensor attachment member 15 a includes the horizontal portion 15-1 facing the upper surface 11 c of the rail 11 and the pair of sleeve portions 15-2 facing the left and right side surfaces of the rail 11. Two displacement sensors 2a and 2b that detect displacement in the radial direction are arranged in the horizontal portion 15-1. The displacement sensors 2a and 2b face the upper surface 11c of the rail 11 with a gap therebetween, and detect the gap to the upper surface 11c of the rail 11. The distance in the left-right direction between the two displacement sensors 2a, 2b is L2.

Two displacement sensors 2c and 2d for detecting a displacement in the horizontal direction are arranged on the pair of sleeve portions 15-2. The displacement sensors 2c and 2d face the side surface 11d of the rail 11 with a gap, and detect the gap to the side surface 11d.

  In a state where it is assumed that the rail 11 is disposed on a horizontal plane, the displacement sensors 2a and 2b and the displacement sensors 2c and 2d are disposed below the upper surface (mounting surface) of the carriage 12. This is because the table 8 is mounted on the upper surface (mounting surface) of the carriage 12. The cables 2a1 to 2d1 of the displacement sensors 2a to 2d are pulled out from the sleeve portion 15-2 of the sensor attachment member 15a in the left-right direction. Note that the cables 2a1 to 2d1 can be drawn forward from the front surface of the sensor mounting member 15a (in a direction perpendicular to the paper surface). Further, the height of the upper surface of the sensor mounting member 15a is made lower than the upper surface (mounting surface) of the carriage 12, and the gap between the upper surface of the sensor mounting member 15a and the table 8 can be used as a gap for drawing out the cables 2a1 and 2b1. it can.

  Similarly to the sensor mounting member 15a, the sensor mounting member 15b shown in FIG. 2 has a horizontal portion 15-1 and a pair of sleeve portions 15-2, and the displacement sensors 3a to 3d correspond to the displacement sensors 2a to 2d, respectively. It is arranged at the position to do.

<Configuration of linear encoder>
The linear encoder 4 detects the position of the carriage 12 in the x-axis direction and outputs the detection result to the information processing apparatus 10. The linear encoder 4 includes, for example, a scale attached to the base 7 or the rail 11 of the machine tool 20 and a head that is attached to the table 8 or the carriage 12 of the machine tool 20 and reads the scale. The position detecting means for detecting the position of the carriage 12 on the rail 11 is not limited to the linear encoder. For example, when the table 8 of the machine tool 20 is driven by a ball screw, a rotary encoder that detects the angle of a motor that drives the ball screw can also be used as the position detection means.

<Functional configuration of information processing apparatus>
The information processing apparatus 10 in the motion guidance apparatus 1 includes a data processing apparatus for performing data processing such as calculation using data such as a detection value of the displacement sensor 2a, a memory for temporarily storing data, and the like. Various functions are exhibited by executing a predetermined control program. FIG. 6 is a block diagram in which each functional unit realized by the information processing apparatus 10 is imaged. The information processing apparatus 10 includes a sampling setting unit 101, a detection information acquisition unit 102, a command information acquisition unit 103, a calculation unit 104, and a storage unit 105 as main functional units.

  The sampling setting unit 101 detects the displacement values of the displacement sensors 2a to 2d and 3a to 3d for the detection information acquisition unit 102 to acquire the displacement information of the carriage 12 and the position information of the carriage 12 while the motion guide apparatus 1 is in operation. This is a functional unit that sets the sampling interval of the detection values of the linear encoder 4. Details of the sampling interval setting method in the sampling setting unit 101 will be described later.

  Further, the detection information acquisition unit 102 receives the displacement information of the carriage 12 that is the detection values of the displacement sensors 2 a to 2 d and 3 a to 3 d and the position information of the carriage 12 that is the detection value of the linear encoder 4. This is a functional unit that acquires at a predetermined sampling interval set by. The displacement sensors 2a to 2d and 3a to 3d detect the amount of displacement of the carriage 12 with respect to the rail 11. The displacement amount of the carriage 12 with respect to the rail 11 is a difference from detection values of the displacement sensors 2a to 2d and 3a to 3d in a no-load state in which no load is applied to the carriage 12. Therefore, the detection information acquisition unit 102 subtracts the detection values of the displacement sensors 2a to 2d and 3a to 3d in a no-load state stored in advance from the values of the displacement information detected by the displacement sensors 2a to 2d and 3a to 3d. The obtained value is acquired as the displacement amount of the carriage 12 with respect to the rail 11.

  The command information acquisition unit 103 is a functional unit that acquires command information output from the NC device 30 to the machining tool 31 and the actuator 17. The command information here is, for example, information related to the machining execution command of the workpiece 40 output to the machining tool 31, information related to the feed speed of the table 8 output to the actuator 17, and the like.

  The calculation unit 104 is a functional unit that calculates a transport load repeatedly applied to the carriage 12 while the carriage 12 is moving. In the calculation unit 104, the transport load is calculated based on the displacement amount of the carriage 12 with respect to the rail 11 acquired by the detection information acquisition unit 102. The calculation unit 104 also has a function of calculating the shear stress repeatedly generated due to the conveyance load being applied during the movement of the carriage 12 and the number of occurrences of the shear stress. At this time, the shear stress is calculated using the transport load as a parameter. Furthermore, the calculation unit 104 also has a function of calculating the life arrival rate of the motion guide apparatus 1 using the shear stress and the number of occurrences as parameters. The life attainment rate is a ratio indicating how much the exercise guide device 1 is already used in the maximum usable period. For example, when the life attainment rate reaches 100%, all of the maximum usable periods are obtained. This means that the exercise guide device 1 is used up or cannot be used any more. Details of the calculation method of each parameter in the calculation unit 104 will be described later. Note that the calculation of all the parameters listed here is not necessarily performed by the calculation unit 104 in the information processing apparatus 10. For example, data relating to shear stress and the number of occurrences thereof is output from the information processing apparatus 10 to a server installed separately from the machine tool 20, and the life achievement rate is calculated based on these data on the server side. You may do it.

  The storage unit 105 has a function of storing the shear stress repeatedly generated during the movement of the carriage 12 in the motion guide device 1 and the number of occurrences of the shear stress, which are calculated by the calculation unit 104. Further, based on the shear stress stored in the storage unit 105 and the number of occurrences of the shear stress, the calculation unit 104 calculates the life arrival rate of the motion guide apparatus 1.

<Details of Calculation Unit 104>
Here, the details of the processing contents when calculating the transport load applied to the carriage 12, the shear stress generated by the transport load, and the number of occurrences thereof in the calculation unit 104 will be described with reference to FIGS. explain. FIG. 7 is a flowchart showing a flow of calculation processing for calculating the transport load, the shear stress, and the number of occurrences thereof, which is executed by the calculation unit 104. 7 is repeatedly executed at a predetermined sampling interval set by the sampling setting unit 101 by a setting method described later while the carriage 12 is moving.

  In this calculation process, first, the detection information acquisition unit 102 acquires the displacement amount of the carriage 12 from each of the displacement sensors 2a to 2d and 3a to 3d (S101). Next, based on the displacement amount data of the carriage 12 acquired in S101, a transport load acting on the carriage 12 is calculated (S102). Next, based on the transport load calculated in S102, the shear stress generated in each part of the rolling surface 13a of the carriage body 13 is calculated (S103).

Here, as an example of a phenomenon indicating the life of the motion guide device 1, scaly peeling (hereinafter referred to as “flaking”) generated on the rolling surface 13a can be cited. Flaking occurs when shear stress from the rolling surface 13a receiving the load of the balls 16 is repeatedly applied to a position slightly deeper than the rolling surface 13a, and the material forming the rolling surface 13a is fatigued. And it is thought that the conveyance load repeatedly applied with waving in the movement of the carriage 12 is a main cause of repeatedly generating a shear stress at a position slightly deeper than the rolling surface 13a. Therefore, in S103, the shear stress is calculated based on the transport load. The shear stress (shear stress magnitude) calculated in S103 is stored in the storage unit 105, and the count value of the counter that counts the number of occurrences of the shear stress for each part of the rolling surface 13a is stored. An addition process is performed (S104).

  Next, details of processing contents at each step of the above-described calculation processing will be described.

<S101>
In S101, during the movement of the carriage 12, the detection information acquisition unit 102 acquires the displacement amount of the carriage 12 from each of the displacement sensors 2a to 2d and 3a to 3d. Since the measured values of the displacement sensors 2a to 2d and 3a to 3d are the distances from the sensors to the rolling surfaces, the detection information acquisition unit 102 determines whether the load is not applied to the carriage 12 from the unloaded sensors to the rolling surfaces. And the difference from this distance is obtained as the displacement amount of the carriage 12.

<S102>
Next, in S102, a transport load applied to the carriage 12 is calculated based on the displacement of the carriage 12. In calculating the transport load, the calculation unit 104 first calculates five displacement components of the carriage 12 based on the displacement amount of the carriage 12 acquired from each of the displacement sensors 2a to 2d and 3a to 3d. Next, the calculation unit 104 calculates a load and a contact angle acting on each of the plurality of balls 16 based on the five displacement components. Next, the calculation unit 104 calculates a load (five components of external force) acting on the carriage 12 based on the load and contact angle of each ball 16. The above three steps will be described in detail below.

<Step 1: Calculation of five components of carriage displacement>
As shown in FIG. 3, when an xyz coordinate axis is set in the motion guide device 1, loads acting on the coordinate origin of the xyz coordinate axis are a radial load _Fy and a horizontal load _Fz . . A load acting in the positive direction of the y-axis in FIG. 3 in the direction in which the carriage 12 is pressed against the rail 11 is a radial load. The load acting in the z-axis positive / negative direction of FIG. 3 in the direction in which the carriage 12 is shifted laterally with respect to the rail 11 is the horizontal load.

The moments about the xyz coordinate axes are M _a that is the sum of pitching moments, M _b that is the sum of yawing moments, and M _c that is the sum of rolling moments. A radial load F _y , a pitching moment M _a , a rolling moment M _c , a horizontal load F _z , and a yawing moment M _b act on the carriage 12 as external forces. When these five external force components are applied to the carriage 12, the corresponding displacement five components, that is, radial displacement α ₁ (mm), pitching angle α ₂ (rad), rolling angle α ₃ (rad), horizontal, A displacement α ₄ (mm) and a yawing angle α ₅ (rad) are generated.

FIG. 8 shows changes in the outputs of the displacement sensors 2 a to 2 d when an external force is applied to the carriage 12. In FIG. 8, hatched arrows with hatching are sensors whose output changes, and white arrows in FIG. 8 are sensors whose output does not change. When radial load F _y acts on the carriage 12, the vertical clearance between the carriage 12 and the rail 11 are changed according to the magnitude of the radial load F _y. The displacement sensors 2a and 2b detect the change (displacement) in the vertical gap. The displacement sensors 3a and 3b attached to the sensor attachment member 15b (see FIG. 2) also detect this vertical displacement.

When radial load _{F y} acts on the carriage 12, radial displacement alpha ₁ of the carriage 12, the displacement sensor 2a, 2b _A 1 and detects displacement, _{A 2,} displacement sensors 3a, the displacement 3b detects _A 3, A _{If it is 4} , it is given by the following equation, for example.
(Equation 1)
α ₁ = (A ₁ + A ₂ + A ₃ + A ₄ ) / 4

When the horizontal load _Fz is applied to the carriage 12, the carriage 12 is displaced laterally with respect to the rail 11, and the horizontal gap between one sleeve portion 12-2 of the carriage 12 and the rail 11 is reduced. The gap in the horizontal direction between the other sleeve portion 12-2 and the rail 11 is increased. The displacement sensors 2c and 2d detect the change (displacement) in the horizontal gap. The displacement sensors 3c and 3d attached to the sensor attachment member 15b (see FIG. 2) also detect this horizontal displacement. Horizontal displacement alpha ₄ of the carriage 12 is given a displacement sensor 2c, and displacement 2d detects _B 1, _{B 2,} the displacement sensor 3c, the 3d is a _B 3, _{B 4} was detected displacement, for example by the following formula .
(Equation 2)
α ₄ = (B ₁ −B ₂ + B ₃ −B ₄ ) / 4

When acts pitching moment _{M a} in carriage 12, the gap between the displacement sensor 2a, 2b and the rail 11 is increased, the displacement sensor 3a, a gap between the 3b and the rail 11 is reduced. If the pitching angle α ₂ is sufficiently small, the pitching angle α ₂ (rad) is given by the following equation, for example.
(Equation 3)
α ₂ = ((A ₃ + A ₄ ) / 2− (A ₁ + A ₂ ) / 2) / L ₁

When the rolling moment _Mc is applied to the carriage 12, the gap between the displacement sensors 2a, 3a and the rail 11 is reduced, and the gap between the displacement sensors 2b, 3b and the rail 11 is increased. If the rolling angle α ₃ is sufficiently small, the rolling angle α ₃ (rad) is given by the following equation, for example.
(Equation 4)
α ₃ = ((A ₁ + A ₃ ) / 2− (A ₂ + A ₄ ) / 2) / L ₂

When acts yawing moment _{M b} on the carriage 12, the gap between the displacement sensor 2c, 3d and the rail 11 is reduced, the displacement sensor 2d, the gap between 3c and the rail 11 increases. If the yawing angle α ₅ is sufficiently small, the yawing angle α ₅ (rad) is given by the following equation, for example.
(Equation 5)
α ₅ = ((A ₁ + A ₄ ) / 2− (A ₂ + A ₃ ) / 2) / L ₂

  As described above, the five displacement components of the carriage 12 can be calculated based on the displacements detected by the displacement sensors 2a to 2d and 3a to 3d.

<Step 2: Calculation of load and contact angle acting on each ball>
FIG. 9 shows a state in which the portion in contact with the ball 16 in the carriage 12 is cut in the x-axis direction. According to FIG. 9, each ball pitch is set to κDa using κ having a value slightly larger than 1, and the x coordinate of each ball is determined and is set to X _i . The length of the portion balls 16 of the carriage 12 to roll and 2U _x. The number of balls lined up within 2U _x is called the effective number of balls and is designated as I. The end portions of the carriage 12, a large curved surface machining of R shape depth in radius R is called crowning such that lambda _epsilon is applied.

When the carriage 12 is subjected to five external forces, that is, radial load F _y , pitching moment M _a , rolling moment M _c , horizontal load F _z , and yawing moment M _b , the displacement 12 component, that is, radial displacement α ₁ , a theoretical formula is established assuming that a pitching angle α ₂ , a rolling angle α ₃ , a horizontal displacement α ₄ , and a yawing angle α ₅ are generated.

FIG. 10 shows an internal load state before the occurrence of the five displacement components of the inner cross section of the carriage 12 at the ball number i of the carriage 12, and FIG. 11 shows an internal load state after the five displacement components are generated. Here, the ball number of the carriage 12 is j, and the ball number in the ball row is i. The ball diameter is D _a , and the matching degree between the rolling surface and the ball 16 is f on both the rail 11 side and the carriage 12 side, that is, the rolling surface curvature radius is fD _a . Further, the rail-side rolling surface curvature center position is A _r , the carriage-side rolling surface curvature center position is _Ac, and the initial state of the contact angle that is the angle between the line connecting them and the z-axis is γ. . Further, the distance between the ball centers of the balls 16 that roll on the two rolling surfaces on the upper side of the rail 11 is 2U _z12 , and the distance between the ball centers of the balls 16 that roll on the two rolling surfaces on the lower side of the rail 11 respectively. The distance is 2U _z34 , and the center-to-ball distance between the balls 16 rolling on the upper rolling surface and the lower rolling surface of the rail 11 is 2U _y .

  A preload acts on the ball 16. First, the principle of preload will be described. The dimensions of the portion sandwiched between the rolling surfaces of the rail 11 and the carriage 12 that are opposed to each other are determined by the design dimensions of the rail 11 and the carriage 12 and the geometric shape of the rolling surface. The ball diameter to be entered is the ball diameter at the time of design, but if the ball 16 having a size Da + λ slightly larger than the ball diameter at the time of design is incorporated therein, the contact portion between the ball 16 and the rolling surface is the contact of Hertz. By theory, it elastically deforms, forms a contact surface, and generates contact stress. The load thus generated is an internal load and a preload load.

In FIG. 10, the load is represented by P ₀ , and the mutual approach amount between the rail 11 and the carriage 12 due to the elastic deformation of the contact portion is represented by δ ₀ . Actually, the ball position is located at the center position between the rolling surfaces of the rail 11 and the carriage 12 depicted by a one-dot chain line in FIG. 10, but the degree of fit f between the balls 16 on both rolling surfaces is equal. Various characteristic values based on Hertz's contact theory generated at two contact portions are the same. For this reason, the ball 16 is drawn while being shifted to the rail-side rolling surface position so that the mutual approach amount δ ₀ between the rolling surfaces of the rail 11 and the carriage 12 is easily understood.

Usually, the preload is defined as the radial load of the upper two rows (or the lower two rows) per carriage, so the preload P _pre is expressed by the following equation.
(Equation 6)

Next, the state where the external force 5 component acts on the motion guide device 1 from this state and the displacement 5 component is generated will be described. As shown in FIG. 11, the center of the motion guide device 1 with the coordinate origin as the origin is a radial displacement α ₁ , a pitching angle α ₂ , a rolling angle α ₃ , a horizontal displacement α ₄ , and a yawing angle α ₅ that are five components. The relative displacement between the rail 11 and the carriage 12 occurs at the ball position.

At this time, the rail-side rolling surface curvature center does not move, but the carriage 12 moves, so the carriage-side rolling surface curvature center moves geometrically at each ball position. This state is A _c is expressed as movement A _{c 'f} is a carriage-side rolling surface curvature center. Considering the amount of movement of A _c to A _c ′ separately in the y direction and the z direction, assuming that the amount of movement in the y direction is δ _y and the amount of movement in the z direction is δ _z , the suffix is i As a representation of the th ball, the j th ball row,
(Equation 7)
δ _yij = α ₁ + α ₂ x _i + α ₃ z _cij
δ _zij = α ₄ + α ₅ x _i -α ₃ y _cij
It can be expressed as. Here, z _c and y _c are the coordinates of the point A _c .

Next, since the line connecting the rolling surface curvature centers on the rail 11 side and the carriage 12 side becomes the contact angle that is the normal direction of the ball load, γ _j that was the initial contact angle changes to β _ij . Furthermore, the distance between the centers of curvature of both rolling surfaces changes from the initial distance between A _r and A _{c to} the distance between Ar and A _c ′. This change in the distance between the centers of curvature of both rolling surfaces becomes elastic deformation at both contact portions of the ball 16 and, similar to the case described with reference to FIG. , The elastic deformation amount δ _ij of the ball 16 is obtained.

Considering the distance between Ar and Ac ′ separately in the y direction and the z direction, if the distance in the y direction is V _y and the distance in the z direction is V _z , the above-described δ _yij and δ _zij are used.
(Equation 8)
V _yij = (2f−1) D _a sin γ _j + δ _yij
V _zij = (2f−1) D _a cos γ _j + δ _zij
It can be expressed. As a result, the distance between Ar and Ac ′ is
(Equation 9)

And the contact angle β _ij is
(Equation 10)

It becomes. From the above, the elastic deformation amount δ _ij of the ball 16 is
(Equation 11)

It becomes.

Here, in the state in which the portion of the carriage 16 in the carriage 12 shown in FIG. 9 that is in contact with the cross section in the x-axis direction is the amount of elastic deformation δ _ij of the ball 16 in the crowning and processing portion, 12 of the rolling surface the center of curvature of the side Ac' has a shape away from the rail side rolling surface curvature center a _c, less that extent. Since it can be regarded as equivalent to a ball diameter that is reduced to a value corresponding to it, the amount is subtracted in the above equation as λ _xi .

When an equation indicating the elastic approach amount when the rolling element derived from the Hertz contact theory is a ball is used, the rolling element load P _ij is obtained from the elastic deformation amount δ _ij by the following equation.
(Equation 12)
Here, _Cb is a non-linear spring constant (N / mm ^3/2 ) and is given by the following equation. (Equation 13)

Here, E is the longitudinal elastic modulus, 1 / m is the Poisson's ratio, 2K / πμ is the Hertz coefficient, and Σρ is the principal curvature sum.

As described above, the contact angle β _ij , the elastic deformation amount δ _ij , and the rolling element load P _ij can be expressed by equations for all the balls 16 in the carriage 12 using the displacement five components α _{1 to} α ₅ of the carriage 12. It ’s done.

  In the above, for the sake of easy understanding, a rigid model load distribution theory in which the carriage 12 is considered as a rigid body is used. The rigid body model load distribution theory can be expanded to use a carriage beam model load distribution theory in which the beam theory is applied to take into account the deformation of the sleeve 12-2 of the carriage 12. Furthermore, a carriage rail FEM model load distribution theory in which the carriage 12 and the rail 11 are FEM models can be used.

<Step 3: Calculation of load (external force 5 components)>
After that, it is only necessary to use the above formula to establish a balance conditional expression regarding five components as external forces, that is, radial load F _y , pitching moment M _a , rolling moment M _c , horizontal load F _z , and yawing moment M _b .
Regarding the radial load F _y
(Equation 14)

Regarding the pitching moment M _a
(Equation 15)

With respect to the rolling moment _{M c,}
(Equation 16)
Here, ω _ij represents the length of the arm of the moment and is given by the following equation. z _r and y _r are the coordinates of the point A _r .

Regarding horizontal load F _z
(Equation 17)

Regarding the yawing moment M _b
(Equation 18)

From the above formula, the transport load (five components of external force) applied to the carriage 12 can be calculated.

<S103>
Next, details of S103 will be described. In S103, based on the conveyance load calculated in S102, the maximum shear stress (an example of “stress during movement” in the present application) generated on the rolling surface 13a of the carriage 12 is calculated. In this embodiment, the calculation unit 104 classifies the maximum shear stress generated on the rolling surface 13a along the direction of the track because it is used to estimate the life due to local fatigue of the rolling surface 13a. Calculate for each virtual section.

  FIG. 12 is a diagram illustrating an example of a virtual section that divides the rolling surface 13a. In this embodiment, in order to facilitate understanding, the maximum shear stress is calculated for each virtual section obtained by dividing the rolling surface 13a by the number of effective balls. In accordance with Hertz's elastic contact theory, the shear stress generated in each section of the rolling surface 13a thus divided is the rolling element load Pij shown in the description of S102 and the strain generated in the contact portion between the sphere and the plane. This can be calculated according to an expression created in advance using the analysis model.

<S104>
In S <b> 104, the shear stress (maximum shear stress magnitude) calculated in S <b> 103 is stored in the storage unit 105. Further, in S104, a count value addition process is performed on a counter that counts the number of occurrences of shear stress for each part of the rolling surface 13a. In S104, the calculation unit 104 counts the number of occurrences of shear stress for each size based on the maximum shear stress of each section calculated in S103. FIG. 13 is a diagram showing an example of a count value of shear stress repeatedly generated on the rolling surface 13a when the carriage 12 is moving. For example, as shown in FIG. 15, the calculation unit 104 divides the magnitude of the shear stress step by step for every 50 MPa, and sets the counter value of the category corresponding to the calculated maximum shear stress for each execution of the flow of this calculation process. Add 1 to each. Therefore, the counter value increases in proportion to the number of executions of this calculation process.

<Details of Sampling Setting Unit 101>
Next, details of processing contents when the sampling setting unit 101 sets a predetermined sampling interval for sampling the detection values of the displacement sensors 2a to 2d, 3a to 3d and the detection value of the linear encoder 4 will be described with reference to FIGS. This will be described with reference to FIG. When the carriage 12 moves relative to the rail 11 in the motion guide device 1, the displacement of the carriage 12 is generated by vibration. The component having the highest frequency in the vibration component of the displacement of the carriage 12 at this time is a vibration component accompanying waving.

  Here, the waving caused by the movement of the carriage 12 is caused by the periodic displacement of the relative position between the rolling surface 11 a of the rail 11 and the rolling surface 13 a of the carriage body 13 and the ball 16. It is posture change and vibration (pulsation). FIG. 14 is a view showing the movement of the ball 16 when the carriage 12 moves on the rail 11. The carriage 12 includes a plurality of balls 16, and the ball 16 that supports the carriage 12 among the plurality of balls 16 is sandwiched between the rolling surface 11 a of the rail 11 and the rolling surface 13 a of the carriage body 13. Ball 16 (ball 16 with hatching in FIG. 14). 14A and 14B, the number of balls 16 sandwiched between the rolling surface 11a of the rail 11 and the rolling surface 13a of the carriage body 13 is as follows. The increase / decrease is repeated as the carriage 12 moves relative to the rail 11. This repetition cycle coincides with the cycle in which the carriage 12 moves by the same amount as the pitch between the balls 16 adjacent to the rail 11.

  FIG. 15 is a graph with the position on the rail 11 of the carriage 12 detected by the linear encoder 4 as the horizontal axis and the displacement detected by the displacement sensors 2a to 2d and 3a to 3d as the vertical axis. The carriage 12 is provided with eight displacement sensors 2a to 2d and 3a to 3d. Since the carriage 12 reciprocates on the rail 11, there are inherently a plurality of lines indicating the relationship between the position of the carriage 12 and the displacement. To do. However, for easy understanding, in the graph of FIG. 15, the relationship between the position of the carriage 12 and the displacement is indicated by a single broken line. As can be seen from the graph of FIG. 15, it can be seen that the displacement of the carriage 12 includes two types of vibration components, a relatively slow displacement and a relatively fine displacement. Of these, the relatively slow displacement of the former is considered to be a vibration component other than waving due to, for example, the accuracy of the rolling surface 11 a of the rail 11. On the other hand, the latter relatively small displacement is a vibration component accompanying waving, and is a displacement generated when the carriage 12 is moving on the rail 11. The interval on the horizontal axis of each vertex of the relatively fine displacement shown in the graph of FIG. 15 approximately matches the pitch of the balls 16.

  As shown in FIG. 15, the component having the highest frequency in the vibration component of the displacement of the carriage 12 is the vibration component accompanying waving. Therefore, the conveyance load repeatedly applied to the carriage 12 during the movement of the carriage 12 is detected by the displacement sensor 2a. When calculating based on the detection values of ˜2d and 3a to 3d, the conveyance load can be grasped with high accuracy as long as the change (vibration) of the carriage 12 caused by the waving can be appropriately acquired. Can do. That is, the transport load applied to the carriage 12 is calculated based on the displacement of the carriage 12 caused by the waving, the shear stress is calculated by the above method based on the transport load, and the number of occurrences of the shear stress is counted. By doing so, it is possible to calculate the life achievement rate of the motion guide apparatus 1 with sufficient accuracy using these as parameters.

Here, as described above, since the waving is caused by the periodic relative positional deviation between the rolling surface 11a of the rail 11 and the rolling surface 13a of the carriage body 13 and the ball 16, The magnitude of the frequency of the accompanying vibration component has a correlation with the relative speed of the carriage 12 with respect to the rail 11. That is, the greater the relative speed of the carriage 12 with respect to the rail 11, the greater the frequency of the vibration component associated with waving. Therefore, in the sampling setting unit 101, the detection values of the displacement sensors 2 a to 2 d and 3 a to 3 d are detected according to the relative speed of the carriage 12 with respect to the rail 11 in order to appropriately acquire a change in the displacement of the carriage 12 caused by waving. A predetermined sampling interval for obtaining is set.

  FIG. 16 is a flowchart showing a flow of setting processing for setting a predetermined sampling interval, which is executed by the sampling setting unit 101 in this embodiment. Note that the setting process shown in FIG. 16 is repeatedly executed at predetermined time intervals.

  In this setting process, first, it is determined whether or not the carriage 12 is moving (S201). If it is determined in S201 that the carriage 12 is moving, then the relative speed of the carriage 12 with respect to the rail 11 is calculated (S202). The relative speed at this time is calculated as an absolute value. Next, a predetermined sampling interval for obtaining the detection values of the displacement sensors 2a to 2d and 3a to 3d based on the calculated relative speed is set (S203). Then, the calculation process shown in FIG. 7 is repeatedly executed at the predetermined sampling interval set here. As a result, the detection information acquisition unit 102 acquires the displacement amount of the carriage 12 from each of the displacement sensors 2a to 2d and 3a to 3d at a predetermined sampling interval. If it is determined in S201 that the carriage 12 has not moved (stopped), the calculation process ends.

  Next, details of the processing contents at each step of the setting processing described above will be described.

<S201>
In S201, it is determined whether or not the carriage 12 is moving. Whether or not the carriage 12 is moving can be determined based on command information from the NC device 30 to the actuator 17 acquired by the command information acquisition unit 103. The determination can also be made based on the position information of the carriage 12 detected by the linear encoder 4. In this case, for example, if the position information of the carriage 12 detected by the linear encoder 4 changes in time series, it is determined that the carriage 12 is moving. If the position information does not change in time series, the carriage 12 is stopped. It is determined.

<S202>
In S202, the relative speed of the carriage 12 with respect to the rail 11 is calculated. The relative speed can be calculated based on the feed speed of the table 8 included in the command information from the NC device 30 to the actuator 17 acquired by the command information acquisition unit 103. In addition, the relative speed can be calculated based on the temporal change in the position information of the carriage 12 detected by the linear encoder 4.

<S203>
In S203, a predetermined sampling interval is set based on the relative speed of the carriage 12 with respect to the rail 11 calculated in S202. Here, the information processing apparatus 10 stores a correlation between the relative speed of the carriage 12 with respect to the rail 11 and the sampling interval as shown in FIG. 17 as a map. In S203, a predetermined sampling interval is set using this map. In FIG. 17, the horizontal axis represents the relative speed (absolute value) of the carriage 12 with respect to the rail 11, and the vertical axis represents the sampling interval.

When an attempt is made to appropriately obtain a change in the displacement of the carriage 12 caused by the waving, the displacement sensors 2a to 2d and 3a to 3d are larger when the frequency of the vibration component accompanying the waving is larger than when the frequency is small. It is necessary to shorten the sampling interval of detected values. On the other hand, when the frequency of the vibration component due to waving is small, even if the sampling interval of the detection values of the displacement sensors 2a to 2d and 3a to 3d is made longer than when the frequency is large, it occurs with waving. A change in the displacement of the carriage 12 can be acquired appropriately. As described above, the greater the relative speed of the carriage 12 with respect to the rail 11, the greater the frequency of the vibration component associated with waving. Therefore, in the map shown in FIG. 17, the sampling interval is reduced as the relative speed of the carriage 12 with respect to the rail 11 is increased. By setting based on such a map, the predetermined sampling interval is set so that the predetermined sampling interval is shorter when the relative speed of the carriage 12 with respect to the rail 11 is large than when the relative speed is small. Become. However, in the map shown in FIG. 17, in the range where the relative speed of the carriage 12 with respect to the rail 11 is smaller than the predetermined threshold speed Vc0, the sampling interval is constant at the maximum sampling interval dTs0 that is the maximum value of the sampling interval in this map. It has become.

  Here, based on the detection values of the displacement sensors 2a to 2d and 3a to 3d, when it is attempted to grasp the transport load repeatedly applied to the carriage 12 during the movement of the carriage 12, the displacement sensors 2a to 2d and 3a It is also conceivable to shorten the sampling interval for obtaining the detection value of ˜3d as much as possible. However, since it is necessary to continuously grasp the transport load, the data (detection value of the displacement sensor) to be acquired inevitably increases as the sampling interval is shortened. As a result, there is a possibility that the load on the information processing apparatus 10 becomes excessively large for performing the data processing, that is, the calculation processing for calculating the transport load, the shear stress, and the number of occurrences thereof in the calculation unit 104 described above. is there. In such a case, when the shear stress calculated by the calculation unit 104 is stored as data, the data capacity in the storage unit 105 may be excessively increased.

  In order to deal with such a problem, in the present embodiment, as described above, the predetermined sampling interval changes according to the relative speed of the carriage 12 with respect to the rail 11. As a result, the sampling intervals of the detection values of the displacement sensors 2a to 2d and 3a to 3d change according to the frequency of the vibration component accompanying the wave. That is, the sampling interval of the detection values of the displacement sensors 2a to 2d and 3a to 3d is shorter when the frequency of the vibration component associated with waving is large than when the frequency is small. In other words, the sampling interval of the detection values of the displacement sensors 2a to 2d and 3a to 3d becomes longer when the frequency of the vibration component associated with the waving is small than when the frequency is high. Therefore, it is possible to appropriately acquire a change in the displacement of the carriage 12 caused by the waving, and to suppress the sampling interval of the detection values of the displacement sensors 2a to 2d and 3a to 3d from becoming shorter than necessary. it can. As a result, an increase in acquired data (detection value of the displacement sensor) is suppressed as much as possible while acquiring detection values of the displacement sensors 2a to 2d and 3a to 3d to be used for continuous conveyance load calculation. be able to. Therefore, it is possible to achieve both the grasp of the transport load with high accuracy and the increase in the burden on the information processing apparatus 10 for data processing and the suppression of the increase in data capacity.

  Further, as described above, in the map shown in FIG. 17, in the range where the relative speed of the carriage 12 with respect to the rail 11 is smaller than the predetermined threshold speed Vc0, the sampling interval is the maximum which is the maximum value of the sampling interval in this map. The sampling interval dTs0 is constant. Therefore, in the present embodiment, when the relative speed of the carriage 12 with respect to the rail 11 is smaller than the predetermined threshold speed Vc0, the predetermined sampling interval is within the adjustment range by the sampling setting unit 101 regardless of the relative speed. The maximum sampling interval dTs0 that is the maximum value is set. According to this, an upper limit value is provided for the sampling interval of the detection values of the displacement sensors 2a to 2d and 3a to 3d. Therefore, it is possible to suppress an excessive decrease in the grasping accuracy of the conveyance load due to the sampling interval becoming too large.

<Calculation process of life achievement rate>
Next, the calculation process of the life attainment rate of the motion guidance apparatus 1 executed by the calculation unit 104 of the information processing apparatus 10 will be described. In the present embodiment, the calculation unit 104 functions very much as the “life achievement rate calculation unit” of the present invention. However, as described above, the calculation process of the life attainment rate of the motion guidance apparatus 1 does not necessarily have to be executed by the information processing apparatus 10, and may be executed by a device such as a server different from the information processing apparatus 10. Good.

In the calculation process of the life attainment rate of the motion guidance apparatus 1 executed by the calculation unit 104, the shearing stress calculated by the above-described method and stored in the storage unit 105 and the number of occurrences thereof are used. Calculate the lifetime achievement rate. The life achievement rate is calculated for each section of the rolling surface 13a. And the value with the highest lifetime achievement ratio among the calculated lifetime arrival ratios of all the sections is the lifetime achievement ratio that is representatively represented for the motion guide device 1. The life attainment rate is calculated using, for example, a linear cumulative damage law. FIG. 18 is a diagram showing an example of the SN curve of the material. The linear cumulative damage law predicts the life until damage is caused by fatigue when an object is repeatedly subjected to stress in material fatigue, and therefore occurs repeatedly with waving that occurs during movement of the carriage 12. It is effective in grasping material fatigue due to shear stress. According to the linear cumulative damage law, when the number of repetitions of fracture for a specific cyclic stress in the SN curve of the target material is Li and the actual number of repetitions to the material is ni, the life attainment rate D is expressed by the following equation: Given.
(Equation 19)

  As described above, in this embodiment, the ball guide 16 takes into account the waving that correlates with the repetitive stress on the rolling surface 13 a of the carriage 12, and uses the shear stress that is life-related information and the number of occurrences of the motion guide device 1. Therefore, a calculation result with extremely high accuracy can be obtained as compared with the case where the lifetime achievement ratio is calculated without using these pieces of information. In the present embodiment, the calculation unit 104 calculates the life arrival rate of the motion guide device 1 because the calculation unit 104 calculates the shear stress that is life-related information and the number of occurrences thereof using the detection value of the displacement sensor 2a and the like. The apparatus configuration for doing so can be made relatively simple. In addition, as described above, the calculation unit 104 calculates the shear stress for each virtual section obtained by dividing the rolling surface 13a of the carriage 12 along the direction of the track, and therefore, based on the stress of the entire rolling surface 13a. A diagnosis result higher than the life diagnosis can be obtained.

<Modification>
As described above, when the conveyance load repeatedly applied to the carriage 12 during the movement of the carriage 12 is calculated based on the detection values of the displacement sensors 2a to 2d and 3a to 3d, the displacement of the carriage 12 caused by waving. By appropriately acquiring the change in the load, the conveyance load can be grasped with high accuracy. Therefore, in the above embodiment, when the sampling setting unit 101 sets a predetermined sampling interval based on the relative speed of the carriage 12 with respect to the rail 11, the detection values of the displacement sensors 2 a to 2 d and 3 a to 3 d are acquired. However, a predetermined sampling interval may be set so as to synchronize with the apex of the waving that appears in the data as shown in FIG. By setting the predetermined sampling interval in this way, it is possible to synchronize the occurrence frequency of the repeated load generated with the waving and the predetermined sampling interval. As a result, a change in the displacement of the carriage 12 caused by waving can be acquired more appropriately, so that the transport load can be grasped with higher accuracy.

When the predetermined sampling interval is set as described above, the sampling setting unit 101 determines the position of the carriage 12 on the rail 11 obtained from the linear encoder 4 for each of the five displacement components of the carriage 12 calculated by the above-described method. And each displacement sensor 2a-
Data representing the relationship with the displacement obtained from 2d, 3a to 3d is analyzed. Then, based on data representing the relationship between the position of the carriage 12 on the rail 11 and the amount of displacement as shown in FIG. 15, a fine waving vibration component appearing at substantially the same period as the pitch of the balls 16 is detected, The peak of the vibration component waveform is detected. The interval between the vertices of the vertices of the relatively fine displacement, which is the vibration component accompanying waving, shown in the graph of FIG. In addition, if the wave setting is detected from the displacement data detected by any one or more of the plurality of displacement sensors 2a to 2d and 3a to 3d, the sampling setting unit 101 displays the peak of the wave pattern of the wave. To detect. Then, the sampling setting unit 101 sets the predetermined sampling interval so that the time interval at which the detected vertex of waving occurs and the predetermined sampling interval are synchronized.

<Example 2>
The configuration of the information processing apparatus 10 of the motion guidance apparatus 1 according to the present embodiment is the same as that of the first embodiment. Also in the present embodiment, in the information processing apparatus 10, the calculation unit 104 causes the calculation load 104 to repeatedly convey the carriage 12, the shear stress repeatedly generated and the number of occurrences thereof, and the motion guide apparatus 1. The life reach rate is calculated. In the information processing apparatus 10, the sampling setting unit 101 sets a predetermined sampling interval when acquiring the detection values of the displacement sensors 2 a to 2 d and 3 a to 3 d.

  Here, the motion guide device 1 is a device constituting the machine tool 20. In the machine tool 20, there is a case where the work tool 31 is operated and the workpiece 40 on the table 8 is processed while operating the motion guide device 1. While the workpiece 40 is being machined by such a machining tool 31, the workpiece 40 is placed in a predetermined vibration state. When the workpiece 40 is in a predetermined vibration state, the movement guide device 1 is accompanied by waving caused by the carriage 12 moving with respect to the rail 11 while the processing tool 31 is not operated. A vibration component having a frequency higher than that of the vibration component is generated. In other words, the predetermined vibration state is a vibration state having a frequency that is higher than the frequency of occurrence of a repetitive load that occurs with waving.

  Therefore, when the processing tool 31 is operated together with the motion guide device 1 and the work 40 is placed in a predetermined vibration state, an attempt is made to grasp the transport load applied to the moving carriage 12 with high accuracy. The sampling interval for acquiring the detection values of the displacement sensors 2a to 2d and 3a to 3d needs to be shorter than when the machining tool 31 is not operated and only the motion guide device 1 is operated. That is, the predetermined sampling interval needs to be shorter than the waving cycle. Therefore, in this embodiment, when the workpiece 40 is in a predetermined vibration state, the sampling setting unit 101 sets the predetermined sampling interval to the minimum sampling interval. Here, as described in the first embodiment, the minimum sampling interval is an interval shorter than the minimum value of the predetermined sampling interval when setting according to the relative speed of the carriage 12 with respect to the rail 11.

  FIG. 19 is a flowchart illustrating a flow of setting processing for setting a predetermined sampling interval, which is executed by the sampling setting unit 101 in the present embodiment. Note that the setting process shown in FIG. 19 is repeatedly executed at predetermined time intervals. In FIG. 19, steps that execute the same processes as the steps in the setting process shown in FIG. 16 described above are denoted by the same reference numerals, and description thereof is omitted.

In this setting process, if it is determined in S201 that the carriage 12 is moving, it is next determined whether or not the workpiece 40 is in a predetermined vibration state (S302). Whether or not the workpiece 40 is in a predetermined vibration state can be determined based on command information from the NC device 30 to the machining tool 31 acquired by the command information acquisition unit 103. If it is determined in S302 that the workpiece 40 is in a predetermined vibration state, then the predetermined sampling interval is set to the minimum sampling interval (S304). Here, the minimum sampling interval is a value determined in advance based on experiments or the like. If it is determined in S302 that the workpiece 40 is not in a predetermined vibration state, the process of S202 is performed next.

  As described above, when the workpiece 40 is in a predetermined vibration state, the predetermined sampling interval is set to the minimum sampling interval, so that the machining tool 31 is operated together with the motion guide device 1. Even underneath, the conveyance load applied to the carriage 12 can be grasped with high accuracy. As a result, the shear stress generated in the motion guide device 1 and the number of occurrences thereof can be calculated with high accuracy when the workpiece 40 is being processed. Moreover, the calculation accuracy of the life attainment rate of the motion guide apparatus 1 calculated using the shear stress and the number of occurrences as parameters can be improved.

DESCRIPTION OF SYMBOLS 1 ... Motion guide apparatus, 2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d ... Displacement sensor, 4 ... Linear encoder, 8 ... Table, 10 ... Information processing apparatus, 11 ... Rail, 12 ... Carriage, 15a, 15b ... Sensor mounting member, 15-1 ... Horizontal part, 15-2 ... Sleeve part, 16 ... Ball, 20 ... Machine tool, 30 ... NC device, 31 ... Processing tool, 32 ... Actuator, 40 ... Workpiece

Claims (5)

A raceway member extending along the longitudinal direction and a plurality of rolling elements arranged so as to be able to roll in the rolling groove are arranged to face the raceway member and in the longitudinal direction of the raceway member. Conveying device that supports a workpiece movably by a motion guide device having a moving member that is relatively movable along a plurality of displacement sensors that detect a displacement of the moving member in a predetermined number of displacement directions in the moving member A measuring device for measuring a transport load applied to the moving member,
An acquisition unit that acquires detection values of the plurality of displacement sensors at a predetermined sampling interval;
A calculation unit that calculates the transport load based on detection values of the plurality of displacement sensors acquired by the acquisition unit;
A setting unit for setting the predetermined sampling interval according to the relative speed of the moving member with respect to the track member;
With
The setting unit sets the predetermined sampling interval so that the predetermined sampling interval is shorter when the relative speed is large than when the relative speed is small.
measuring device. When the relative speed is smaller than a predetermined threshold speed, the setting unit sets the predetermined sampling interval to a maximum sampling interval that is a maximum value within an adjustment range by the setting unit.
The measuring apparatus according to claim 1. The setting unit sets the predetermined sampling interval so as to synchronize with the occurrence frequency of repeated loads accompanying waving when the moving member moves relative to the track member.
The measuring apparatus according to claim 1 or 2. The setting is performed when the workpiece is in a predetermined vibration state that is a vibration state having a frequency higher than the occurrence frequency of a repeated load generated when the moving member moves relative to the track member. The unit does not set the predetermined sampling interval according to the relative speed, and the moving member moves relative to the track member and the workpiece is in the predetermined vibration state without setting the predetermined sampling interval. Set to an interval shorter than the sampling interval by the acquisition unit when not placed in,
The measuring apparatus according to any one of claims 1 to 3. Based on the moving stress applied to the moving member when the moving member is moving relative to the track member and the number of repetitions of the moving stress calculated based on the transport load, A life attainment rate calculation unit for calculating the life attainment rate of the motion guide device,
The measuring apparatus according to any one of claims 1 to 4.