JP6481350B2 - Ball screw measuring device - Google Patents

Description

  The present invention relates to a ball screw measuring apparatus.

  2. Description of the Related Art Conventionally, there is a ball screw device including a ball nut screwed through a plurality of balls into a screw groove formed in a spiral shape on a screw shaft in order to increase screw efficiency. In the ball screw device, the efficiency of the screw is increased when the accuracy of the ball screw that can be evaluated by the screw shaft, the thread groove of the ball nut, and the ball rolling between them satisfies a predetermined standard.

  As an apparatus for measuring information necessary for evaluating such ball screw accuracy, for example, a ball screw measuring apparatus described in Patent Document 1 has been proposed. In the ball screw measuring device described in Patent Document 1, when a load having a different axial direction is applied to the screw shaft while fixing the movements of the ball nut and the screw shaft, the displacement of the screw shaft is displaced by the ball screw. It is measured as a so-called rattling gap between the ball and the screw groove in the apparatus, and the ball screw accuracy is evaluated from the measurement result.

JP-A-11-183327

  By the way, in the ball screw measuring apparatus described in Patent Document 1, when the displacement of the screw shaft is measured, the position of the ball nut with respect to the screw shaft is also fixed. In other words, in this case, the accuracy of the ball screw at the portion deviated from the fixed position is not accurately grasped, but is only estimated from the measurement result obtained by fixing the position of the ball nut with respect to the screw shaft. Therefore, it is difficult to say that the accuracy of ball screw accuracy evaluation is high.

  This invention is made | formed in view of such a situation, The objective is to provide the ball screw measuring apparatus which can raise the precision in evaluation of a ball screw precision.

A ball screw measuring device that solves the above-mentioned problems is a screw shaft in which a screw groove is formed in a spiral shape, a ball nut that is fitted to the screw groove of the screw shaft through a large number of balls, and a screw shaft is driven. A drive unit that causes the ball nut to move along the axial direction of the screw shaft when the screw shaft is driven, and a detection unit that detects the position of the ball nut in the axial direction of the screw shaft. It has. Then, the ball screw measuring device, between which the ball nut is reciprocated the entire area of the screw groove of the screw shaft, the direction to impart a constant force so that the load with respect to the moving direction of the ball nut A load applying portion that is capable of switching between the load nut, a load applying portion that applies a constant force to the ball nut, and a load applied to the ball nut by the load applying portion. A drive control unit that controls the drive unit so as to reciprocate throughout the entire area, and a recording unit that records the detection result of the detection unit according to the drive amount while the drive amount of the screw shaft is changed. .

  According to the above configuration, when the ball nut moves in the screw groove of the screw shaft while a constant load is applied in the moving direction, the backlash between the screw shaft and the ball nut on the moving direction side is reduced. Become. That is, in this case, information for evaluating the ball screw accuracy is recorded in a state in which the backlash between the screw shaft and the ball nut on the moving direction side is reduced. The information recorded while the ball nut reciprocates in the thread groove of the screw shaft includes the screw shaft and the ball in the thread groove defined based on the drive amount of the screw shaft in the entire area of the thread groove of the screw shaft. Information that can indicate a backlash with the nut is included. Thereby, not only can the ball screw accuracy in the screw groove defined based on the drive amount of the screw shaft be evaluated, but also the ball screw accuracy over the entire screw groove of the screw shaft can be evaluated.

The ball screw measuring device preferably includes a calculation unit that calculates a difference between a ball nut forward path and a return path according to a driving amount of the screw shaft from a recording result in the recording unit.
As described above, the difference between the screw shaft and the ball nut is the backlash between the screw shaft and the ball nut. Will be calculated. That is, in this case, depending on the calculation result of the calculation unit, not only the backlash between the screw shaft and the ball nut in the screw groove defined based on the drive amount of the screw shaft is calculated, but also in the entire screw groove of the screw shaft. The fluctuation of the play is calculated. Thereby, not only can the ball screw accuracy in the screw groove according to the driving amount of the screw shaft be evaluated appropriately, but also the ball screw accuracy over the entire screw groove of the screw shaft can be evaluated appropriately. .

  Furthermore, in the above-described ball screw measuring device, it is determined whether or not the calculation result of the calculation unit is distributed in the normal range while the calculation result of the calculation unit sets a normal range that satisfies the requirements for ball screw accuracy. It is preferable to include a determination unit.

  According to the above configuration, the ball screw measuring device can determine whether or not the backlash between the screw shaft and the ball nut in the thread groove defined based on the drive amount of the screw shaft satisfies the requirements for ball screw accuracy. become able to. That is, in this case, not only can the ball screw accuracy in the screw groove defined based on the drive amount of the screw shaft be evaluated appropriately, but the ball screw accuracy over the entire screw groove of the screw shaft is also preferably evaluated. be able to.

  A floating mechanism that allows a load to be applied to the axial direction of the ball nut while allowing the ball nut to swing around the screw shaft is provided between the lock portion and the load applying portion in the ball screw measuring device. It is preferable to have.

  By the way, as described above, when the ball nut moves through the thread groove of the screw shaft, depending on the individual ball nut, there is a case where the ball nut swings around during the movement. If the ball nut swings in this way and affects the application of the load in the axial direction of the ball nut, there is a concern that the influence will be dragged to the detection result at the detection unit.

  In this regard, according to the above-described configuration, even if the ball nut is swung while the ball nut is moving, the swirling does not reach the load applying portion by the floating mechanism. That is, in this case, even if the ball nut swings, it is possible to prevent the influence from being dragged to the detection result in the detection unit.

Moreover, it is preferable that the load applying unit in the ball screw measuring device applies a weight generated based on gravity to the ball nut as a load.
According to the said structure, the dispersion | variation of the fixed load given to a ball nut will be suppressed as much as possible by using the weight which arises based on gravity as a load. That is, in this case, more reliable information can be obtained as information for evaluating the ball screw accuracy.

  ADVANTAGE OF THE INVENTION According to this invention, the precision in evaluation of a ball screw precision can be improved.

The figure which shows the outline of a ball screw measuring apparatus. (A), (b) is a figure which shows operation | movement of a measurement part about a ball screw measuring apparatus. The figure which shows the flow of a measurement. The figure which shows the result of a measurement. The figure which shows the result after a process about the result of a measurement. (A) is a figure which shows a result when abnormality exists in a screw shaft, (b) is a figure which shows a result when abnormality exists in a ball nut. The figure which shows the outline of the ball screw measuring apparatus in another example.

Hereinafter, an embodiment of the ball screw measuring apparatus will be described.
As shown in FIG. 1, the ball screw measuring device has a screw groove 11a and a screw shaft 11 in which a screw groove 11a is spirally formed on one end side and rack teeth 11b are formed on the other end side. It is used for evaluating the ball screw accuracy of a ball screw device 13 in which a ball nut 12 having a pair of screw grooves 12a formed therein is fitted via a plurality of balls 12b. The accuracy of the ball screw is evaluated by the screw shaft 11 and the thread grooves 11a and 12a of the ball nut 12, and the ball 12b rolling between them. In the present embodiment, the gap between the screw grooves 11a and 12a generated when the ball 12b rolls between the screw grooves 11a and 12a of the screw shaft 11 and the ball nut 12, that is, rattling between the screw shaft 11 and the ball nut 12. To evaluate whether or not the ball screw device 13 satisfies a predetermined standard (standard of whether or not it is a non-defective product). For example, the position of the ball nut 12 when the ball 12b hits the right side surface of the screw groove 11a of the screw shaft 11 and the left side surface of the screw groove 12a of the ball nut 12 at the position of the ball nut 12 with respect to the screw shaft 11. And the position of the ball nut 12 when the ball 12b hits the left side surface of the screw groove 11a of the screw shaft 11 and the right side surface of the screw groove 12a of the ball nut 12. The difference between these positions is rattling.

  The ball screw measuring device includes a base 14 having a flat base surface 14a on which various members for measuring the rattling are installed as information necessary for evaluating the ball screw accuracy. Main shaft support portions 20 and 21 that rotatably support the screw shaft 11 so as to face the base surface 14a are fixed to the base 14 so as to support the shaft ends of the screw shaft 11, respectively.

  Of the main shaft support portions 20, 21, the main shaft support portion 20 includes a servo motor 22 as a drive unit that applies rotational torque to the screw shaft 11 to drive rotation. The servo motor 22 incorporates an encoder 22a. A screw 22b is attached to one end of the screw shaft 11, and a rotational torque of the servo motor 22 is applied to the screw shaft 11 through the screw 22b. The servomotor 22 is rotationally driven by a predetermined angle step by being controlled in position to repeat start and stop according to the rotation angle detected by the encoder 22a. When the screw shaft 11 is rotationally driven by the servo motor 22, it rotates forward (clockwise toward the screw shaft 11 indicated by a solid line in FIG. 1) or reverse rotation (toward the screw shaft 11 indicated by a broken line in FIG. 1). It is rotationally driven in one of two directions (counterclockwise).

  The main shaft support portion 21 includes a manual handle 23 a that positions the center 23 that supports the rotational drive of the screw shaft 11. The center 23 approaches or separates from the shaft end of the screw shaft 11 when the manual handle 23a is rotated, and when the hand 23 approaches the shaft end of the screw shaft 11, the center 23 is driven to rotate. Is supported rotatably. In other words, in this case, the screw shaft 11 is slidably supported by the center 23 through a center hole formed at the other end to which the turner 22b is attached.

  The screw shaft 11 is set (set) so that the side on which the rack teeth 11b of the screw shaft 11 are formed is rotatably supported by the main shaft support portion 20 with respect to each of the main shaft support portions 20 and 21. The side on which the thread groove 11a is formed is installed (set) so as to be rotatably supported by the spindle support portion 21. In this case, the screw shaft 11 is installed in the main shaft support portions 20 and 21 as the ball screw device 13 in a state in which the ball nut 12 is fitted through the plurality of balls 12b.

  The ball nut 12 is attached via a nut, a clamp, or the like to an anti-rotation jig 30 serving as a lock portion that prevents rotation (locks rotation) with respect to the screw shaft 11. The anti-rotation jig 30 is engaged with a load jig 51 (to be described later) in the radial direction, and is movable along the axial direction of the screw shaft 11 together with the load jig 51. A detent 31 is provided at a position corresponding to one end of the ball nut 12 (in FIG. 1, the rack tooth 11 b side) in the detent jig 30. A detected body 32 that extends along the axial direction of the ball nut 12 is connected to the base surface 14 a side of the rotation stopper 31. A reflective material 33 such as a mirror (mirror) is attached to the main shaft support portion 21 (in FIG. 1, the thread groove 11a side) of the detection object 32.

  In addition, a detection unit 40 that irradiates a laser is disposed on the base surface 14 a of the base 14 so as to face the reflecting material 33. The detection unit 40 includes an irradiation unit 41 that irradiates a laser toward the reflection material 33 attached to the rotation prevention unit 31 that prevents the ball nut 12 from rotating, and a light reception unit 42 that receives the laser reflected from the reflection material 33. Prepare.

  The detecting unit 40 then determines the distance to the detected object 32 (the reflecting material 33), that is, the ball nut 12 according to the time taken for the laser irradiated from the irradiation unit 41 to be reflected by the reflecting material 33 and received by the light receiving unit 42. Measure the position of. The detection unit 40 is installed in a direction away from the screw shaft 11 with respect to the spindle support unit 21 so that the laser path is not blocked by the spindle support unit 21 or the like.

  Moreover, the ball screw measuring device includes a control processing unit 43 such as a computer that functions as a drive control unit, a calculation unit, and a determination unit having a display screen 43a. The control processing unit 43 is electrically connected to the servo motor 22 (encoder 22a) in the spindle support unit 20 and executes position control of the servo motor 22. The control processing unit 43 is electrically connected to the detection unit 40, records the measurement result in the detection unit 40, performs the calculation of the recording result, and executes various processes such as determination of the calculation result. The result is output to the display screen 43a. In addition, the control processing unit 43 executes control related to laser irradiation in the detection unit 40.

  In addition, a load applying portion 50 having a load jig 51 for applying a load to the ball nut 12 is provided on the base surface 14 a of the base 14. The load jig 51 is installed so as to be movable along the axial direction of the screw shaft 11 with respect to the base 14 via a guide 15 fixed to the base surface 14 a along the axial direction of the screw shaft 11.

  On both sides of the load jig 51 in the axial direction, the weights 54a and 54b are mechanically connected to the pulleys 53a and 53b supported on the base 14 by predetermined support members via the wires 52a and 52b. Connected. The load jig 51 and the weights 54a and 54b are connected to each other so as to be switchable between a connected state and a non-connected state via magnets 53c and 53d provided in the middle of the wires 52a and 52b. Then, the load jig 51 applies only one of the weights to the ball nut 12 by switching between the connected state and the disconnected state of the weights 54a and 54b during the measurement of the rattling.

  Also, on the opposite side of the load jig 51 from the guide 15, the load claws 51 a and 51 b are formed so as to sandwich the ball nut 12 in the axial direction of the screw shaft 11. The load claws 51a and 51b are bent toward the ball nut 12 so that the tips thereof face each other.

  The tip ends of the load claws 51 a and 51 b are curved toward the ball nut 12, and have a shape that allows point contact with the ball nut 12. Further, the tips of the load claws 51 a and 51 b are set such that the distance D between the tips is larger than the axial length of the screw shaft 11 in the ball nut 12. That is, when the tip of the load claw 51a is point-contacted with the ball nut 12 from the rack tooth 11b side of the screw shaft 11, the load claw 51a is separated from the ball nut 12 on the opposite side. Further, when the tip of the load claw 51 b is brought into point contact with the ball nut 12 from the screw groove 11 a side of the screw shaft 11, the load claw 51 b is separated from the ball nut 12 on the opposite side. Each of the load claws 51a and 51b sandwiches the detected body 32 of the detent jig 30 between them, but has a configuration (shape or arrangement) that cannot contact the detected body 32.

  As described above, when the rotation prevention jig 30 and the load jig 51 are engaged in the radial direction of the rotation prevention jig 30, only one of the load claws 51 a and 51 b is attached to the ball nut 12 in the axial direction. It is related not to touch. That is, in this case, the anti-rotation jig 30 and the load jig 51 allow the ball nut 12 to swing around in the radial direction and allow the load to be applied in the axial direction of the screw shaft 11 of the ball nut 12. They have a so-called floating mechanism and are associated with each other.

  Further, when the weight 54a is connected, the load jig 51 is pulled to the weight 54a side, that is, to the rack tooth 11b (main shaft support portion 20) side of the screw shaft 11. In this case, the load jig 51 applies the weight generated based on the gravity acting on the weight 54a as a load to the ball nut 12 from the screw groove 11a side of the screw shaft 11 via the load claw 51b. . As described above, the load jig 51 (load applying unit 50) applies a constant load to the ball nut 12 when the weight 54a is in the connected state (the mass of the weight 54a is kept constant). It becomes.

  Further, when the weight 54b is in a connected state, the load jig 51 is pulled toward the weight 54b, that is, the screw groove 11a (main shaft support portion 21) in the screw shaft 11. In this case, the load jig 51 applies the weight generated based on the gravity acting on the weight 54b as a load to the ball nut 12 from the rack tooth 11b side of the screw shaft 11 via the load claw 51a. . As described above, the load jig 51 (load applying unit 50) applies a constant load to the ball nut 12 when the weight 54b is connected (the mass of the weight 54b is kept constant). It becomes.

  In the ball screw measuring apparatus configured as described above, when the screw shaft 11 is rotationally driven by the servo motor 22 in the main shaft support portion 20, the ball nut 12 is prevented from rotating by the anti-rotation jig 30. Will move in the direction. Furthermore, when the ball nut 12 moves in the axial direction of the screw shaft 11, the ball nut 12 moves while the weights of the weights 54 a and 54 b are applied as a constant load by the load jig 51.

  As shown in FIG. 2A, when the screw shaft 11 is rotationally driven in the forward rotation direction by the main shaft support portion 20, the ball nut 12 moves to the main shaft support portion 20 side (left side in FIG. 2) ( Hereinafter, it is referred to as “leftward”), and the detected body 32 (ball nut 12) moves away from the detection unit 40. In this case, a force F based on the weight of the weight 54b is applied to the ball nut 12 so as to be a load in the moving direction, that is, from the rack tooth 11b side of the screw shaft 11. At this time, a force F based on the weight of the weight 54a is not applied to the ball nut 12.

  As shown in FIG. 2B, when the screw shaft 11 is rotationally driven in the reverse direction by the main shaft support portion 20, the ball nut 12 moves to the main shaft support portion 21 side (right side in FIG. 2). (Hereinafter, referred to as “rightward”), and the detected body 32 (ball nut 12) approaches the detection unit 40. In this case, a force F based on the weight of the weight 54a is applied to the ball nut 12 so as to be a load in the moving direction, that is, from the screw groove 11a side of the screw shaft 11. At this time, the force F based on the weight of the weight 54b is not applied to the ball nut 12.

  When the spindle shaft 20 rotates the screw shaft 11, the spindle support portion 20 continues to rotate in a single direction so that the ball nut 12 becomes the end of the screw groove 11 a of the screw shaft 11 in the moving direction at that time. Can be reached. That is, in the present embodiment, the ball nut 12 can be moved over the entire region of the screw groove 11a of the screw shaft 11 (from end to end), and the entire region of the screw groove 11a can be reciprocated. A limit switch is installed at a position where the ball nut 12 on the base 14 becomes both ends of the screw groove 11 a of the screw shaft 11. When the load jig 51 reaches the detection range of the limit switch, the limit switch is turned on, whereby the control processor 43 detects that the ball nut 12 has reached the end of the screw groove 11a of the screw shaft 11. Is done.

Next, the process of measuring the backlash between the screw shaft 11 and the ball nut 12 will be described.
As shown in FIG. 3, first, as a step of installing the ball screw device, a rotating metal 22 b is attached to one end (the main shaft support portion 20 side) of the screw shaft 11, and a non-rotating jig 30 is attached to the ball nut 12. It is done. Furthermore, the ball nut 12 is installed with respect to the screw shaft 11 in a state at the right end (the main shaft support portion 21 side) of the screw groove 11a. That is, in this case, the screw shaft 11 is installed for each of the spindle support portions 20 and 21, the ball nut 12 is prevented from rotating by the anti-rotation jig 30, and the center 23 by the operation of the manual handle 23 a is approached to the screw shaft 11. (Step S10). When the screw shaft 11 is installed for each of the main shaft support portions 20 and 21, the detent jig 30 is engaged with the load jig 51 in the radial direction, and the ball nut 12 is loaded with the load claw. The turner 22b is engaged in both the forward and reverse rotation directions with a connecting shaft that is sandwiched between 51a and 51b and connected to the servomotor 22 so as to be integrally rotatable.

  Next, as a leftward preparation step, the weight 54b is installed (connected to the load jig 51) so as to be loaded with respect to the leftward movement of the ball nut 12 (step S20). As a result, the backlash between the screw shaft 11 and the ball nut 12 on the leftward direction side is reduced. In this case, the weight 54a is not installed (connected to the load jig 51). The step of setting the weight may be automated by the control processing unit 43 or another control unit, or may be performed by workers involved in measuring the ball screw accuracy.

  Next, as a leftward process, one control for rotating the servo motor 22 by a predetermined angle (predetermined drive amount) in the forward rotation direction is performed by the control processing unit 43 (step S30). That is, in this case, the screw shaft 11 is rotated by a predetermined angle (predetermined driving amount), and the backlash between the screw shaft 11 and the ball nut 12 on the leftward side is reduced by receiving a load from the weight 54b. In this state, the ball nut 12 gradually moves to the left and moves away from the detection unit 40.

  In step S30, the control processing unit 43 measures the distance to the detected object 32 (reflecting material 33), that is, the distance to the ball nut 12 at every predetermined angle for rotating the servo motor 22, and records the distance. Also execute. It should be noted that when step S30 is started, immediately before that, the result of distance measurement to the ball nut 12 is taken in to record the first data in the left direction (data a to be described later), and the distance measurement by the left direction is performed. Will be started. Further, the angle of the screw shaft 11 at the start of distance measurement by leftward travel is set as a reference for the angle (0 (zero)) for rotating the servo motor 22.

  Then, the control processing unit 43 determines whether or not the ball nut 12 has reached the position that becomes the end of the screw shaft 11 by moving to the left (the above-described limit switch has detected and turned on the load jig 51). (Step S40). In step S40, when the ball nut 12 has not reached the position that is the end of the screw shaft 11 (step S40: NO), the control processing unit 43 repeatedly executes the process of step S30.

  On the other hand, when the ball nut 12 reaches the position that becomes the end of the screw shaft 11 in step S40 (step S40: YES), the weight 54b is disconnected from the load jig 51 as a load switching step. At the same time, the position control for rotating the servo motor 22 is stopped by the control processing unit 43 (step S50). When step S50 is completed, the result of distance measurement to the ball nut 12 together with the angle at which the servo motor 22 is rotated based on the fact that the limit switch is turned on is taken in, so that the last data ( Data b), which will be described later, is recorded, and the distance measurement by the leftward is ended.

  Subsequently, as a step for preparing the rightward movement, the weight 54a is installed (connected to the load jig 51) so as to become a load with respect to the rightward movement of the ball nut 12 (step S60). As a result, the backlash between the screw shaft 11 and the ball nut 12 on the rightward direction side is reduced. In this case, the weight 54b is not installed (connected to the load jig 51). The step of setting the weight may be automated by the control processing unit 43 or another control unit as in step S30, or may be performed by workers involved in measuring the ball screw accuracy.

  Next, as a rightward process, the control processing unit 43 performs position control for rotating the servo motor 22 by a predetermined angle in the reverse rotation direction (step S70). That is, in this case, the screw shaft 11 is rotated by a predetermined angle, and the ball with the backlash of the screw shaft 11 and the ball nut 12 in the rightward direction side is filled by receiving a load from the weight 54a. The nut 12 gradually moves rightward and approaches the detection unit 40.

  In step S70, the control processing unit 43 measures the distance to the detected object 32 (reflecting material 33), that is, the distance to the ball nut 12 at every predetermined angle for rotating the servo motor 22, and records the distance. Also execute. Note that when step S70 is started, immediately before that, the result of the distance measurement to the ball nut 12 is taken together with the angle at which the servo motor 22 is rotated, so that the first data in the rightward direction (data c described later) is obtained. It will be recorded and the distance measurement by rightward will be started.

  Then, the control processing unit 43 determines whether or not the ball nut 12 has reached the position that becomes the end of the screw shaft 11 by moving rightward (the limit switch described above has detected and turned on the load jig 51). (Step S80). In step S80, when the ball nut 12 has not reached the position to be the end of the screw shaft 11 (step S80: NO), the control processing unit 43 repeatedly executes the process of step S70.

  On the other hand, when the ball nut 12 reaches the position that becomes the end of the screw shaft 11 in step S80 (step S80: YES), the weight 54a is mechanically cut from the load jig 51 as a load removal step. At the same time, the position control for rotating the servo motor 22 is stopped by the control processing unit 43 (step S90). When step S90 is completed, the result of the distance measurement to the ball nut 12 along with the angle at which the servo motor 22 is rotated based on the fact that the limit switch is turned on is captured, and the last data in the rightward direction ( Data d), which will be described later, is recorded, and the distance measurement by rightward movement is terminated.

  Subsequently, as a result processing step, calculation processing and determination processing are executed by the control processing unit 43 (step S100). Thereafter, the ball screw device 13 is removed from the ball screw measuring device, and the current measurement is completed.

Here, the result of the distance measurement recording, the calculation process, and the determination process will be described.
As shown in FIG. 4, in the distance measurement, the measured distance L (vertical axis) to the ball nut 12 for each screw shaft angle θ (horizontal axis) that the control processing unit 43 has rotated the servo motor 22 is recorded as a result. Is done.

  Depending on the measurement procedure described above, the data a is recorded as a record corresponding to the steps S20 and S30, that is, as a record of the start of distance measurement by moving left. Further, the data b is recorded as a record corresponding to the steps S40 and S50, that is, a record of the end of the distance measurement by the leftward movement. Between data a and data b is a record corresponding to the process of step S30, and the ball nut 12 moves away from the detection unit 40, that is, the measured distance L changes to a large value. Data a to data b are records of the measurement result of the actual distance L of the forward path in the thread groove 11a of the screw shaft 11 related to the distance measurement by leftward movement, that is, the measurement of the ball screw accuracy.

  Subsequently, the data c is recorded as a record corresponding to the steps S60 and S70, that is, as a record at the start of distance measurement by rightward movement. Note that, between the data b and the data c, the weight 54a is installed instead of the weight 54b, so that the actual measurement distance L changes to a value corresponding to the amount of backlash in the rightward direction. Further, the data d is recorded as a record corresponding to the steps S80 and S90, that is, a record of the end of the distance measurement by the rightward movement. Between data c and data d is a record corresponding to the process of step S70, and the ball nut 12 approaches the detection unit 40, that is, the measured distance L changes to a small value. Data c to data d are records of measurement results of the actual distance L of the return path in the thread groove 11a of the screw shaft 11 related to distance measurement by rightward movement, that is, measurement of ball screw accuracy.

  In the measurement result thus recorded, the above-mentioned rattling in the thread groove 11a defined based on the thread shaft angle θ (the entire thread groove 11a is equally divided by the maximum rotation angle required for the movement of the ball nut from end to end). However, it appears as a difference between the measurement result of the forward path and the measurement result of the return path. Subsequently, the control processing unit 43 executes a calculation process for calculating a difference between the measurement result of the forward path and the measurement result of the return path.

  As shown in FIG. 5, in the above calculation process, a rattling G (vertical axis) for each screw shaft angle θ (horizontal axis) is calculated as a result. In such a calculation result, the rattling G in the thread groove 11a defined based on the screw shaft angle θ appears up and down within a predetermined range. Subsequently, the control processing unit 43 executes determination processing for determining whether or not the distribution of the rattling G is distributed in a normal range in which the ball screw accuracy satisfies the predetermined standard, and together with the determination result, The calculation result is output to the display screen 43a.

  As indicated by a broken line in FIG. 5, a range from the lower limit value Ga to the upper limit value Gb (hereinafter referred to as “normal range”) is output on the display screen 43a. The normal range is set to a range that is empirically derived that the ball screw accuracy satisfies the predetermined standard.

  As shown in FIG. 5, when the rattling G is distributed in the normal range, the result that the ball screw device 13 is normal is output to the display screen 43a. In this case, for example, characters such as “CLEAR” are displayed on the display screen 43a, thereby allowing the operator to grasp the result that the ball screw device 13 is normal.

  On the other hand, as shown in FIGS. 6A and 6B, when the rattling G is distributed outside the normal range, a result indicating that the ball screw device 13 is abnormal is output to the display screen 43a. It will be. In this case, for example, characters such as “CHECH” are displayed on the display screen 43a to allow the operator to grasp the result that the ball screw device 13 is abnormal.

  As shown in FIG. 6 (a), when the play G is distributed outside the normal range, when the distribution outside the normal range appears aperiodically (suddenly), the screw of the screw shaft 11 This indicates that there is an abnormality in the groove 11a (high possibility that there is an abnormality). Furthermore, the screw shaft angle θ distributed outside the normal range indicates which part of the screw groove 11a of the screw shaft 11 is caused.

  Further, as shown in FIG. 6B, as a mode in which the rattling G is distributed outside the normal range, the distribution outside the normal range is periodically (every time the thread groove 12a in the ball nut 12 is circulated once). , It indicates that the thread groove 12a of the ball nut 12 is abnormal (highly likely to be abnormal). Furthermore, the screw shaft angle θ distributed outside the normal range indicates which part of the thread groove 12a of the ball nut 12 is caused.

According to the ball screw measuring apparatus described above, the following operations and effects (1) to (5) are exhibited.
(1) In this embodiment, when the ball nut 12 moves in the screw groove 11a of the screw shaft 11 while a constant load is applied in the moving direction, the screw shaft 11 and the ball nut 12 on the moving direction side The backlash will be stuffed. That is, in this case, the measured distance L to the ball nut 12 is recorded in a state where the backlash between the screw shaft 11 and the ball nut 12 on the moving direction side is packed.

  The actually measured distance L recorded in this way indicates a backlash in the screw groove 11a at a position defined based on the screw shaft angle θ over the entire area of the screw groove 11a of the screw shaft 11. Thereby, not only can the ball screw accuracy in the screw groove 11a defined based on the screw shaft angle θ be evaluated, but also the ball screw accuracy over the entire area of the screw groove 11a of the screw shaft 11 can be evaluated. .

  (2) According to the present embodiment, from the recorded results in which the play between the screw shaft 11 and the ball nut 12 on the moving direction side is filled in the forward path (leftward) and the backward path (rightward), respectively. The difference is calculated as a rattling G between the screw shaft 11 and the ball nut 12. That is, in this case, depending on the calculation result by the control processing unit 43, not only the backlash G in the screw groove 11a defined based on the screw shaft angle θ is calculated, but also over the entire region of the screw groove 11a of the screw shaft 11. The fluctuation of the rattling G is calculated.

  Thereby, not only can the ball screw accuracy in the screw groove 11a defined based on the screw shaft angle θ be evaluated appropriately, but the ball screw accuracy over the entire area of the screw groove 11a of the screw shaft 11 is also preferably evaluated. can do.

  (3) According to the present embodiment, whether or not the play G in the thread groove 11a defined based on the screw shaft angle θ is distributed in the normal range, that is, whether the ball screw accuracy satisfies the predetermined standard. The ball screw measuring device can determine whether or not.

  Then, when the results shown in FIG. 5 are derived, the operator who has confirmed these results has the ball screw device 13 satisfying the predetermined standard in the ball screw accuracy over the entire area of the screw grooves 11a and 12a. Can be evaluated.

  On the other hand, in this embodiment, when it is evaluated that the ball screw accuracy does not satisfy the predetermined standard, it is evaluated whether the ball screw accuracy does not satisfy the predetermined standard due to the screw shaft 11 or the ball nut 12. Can do.

  For example, when the result shown in FIG. 6A is obtained, which part of the screw groove 11a of the screw shaft 11 not only causes the screw shaft 11 but also the ball screw accuracy does not satisfy the predetermined standard. Can be evaluated. That is, in this case, the operator who has confirmed such a result can evaluate which portion of the screw groove 11a of the screw shaft 11 does not cause the ball screw accuracy to satisfy the predetermined standard.

  Further, when the result shown in FIG. 6B is obtained, not only is the cause of the ball nut 12 but which part of the thread groove 12a of the ball nut 12 causes the ball screw accuracy not to satisfy the predetermined standard. Can be evaluated. In other words, in this case, the operator who has confirmed such a result can evaluate which portion of the thread groove 12a of the ball nut 12 has the ball screw accuracy not satisfying the predetermined standard.

  (4) By the way, as described above, when the ball nut 12 moves through the thread groove 11a of the screw shaft 11, depending on the individual ball nut 12, there may be a case where the ball nut 12 swings around during the movement. If the ball nut 12 swings in this way and affects the load applied to the ball nut 12 in the axial direction, there is a concern that the detection results in the detection unit 40 may be dragged. .

  In this respect, according to the present embodiment, even if the ball nut 12 swings while the ball nut 12 moves, the rotation preventing jig 30 and the load jig 51 allow such swinging (floating mechanism). ) Between the load jig 51 (load applying portion 50). That is, in this case, even if the ball nut 12 swings around, it is possible to prevent the influence from being dragged to the detection result of the detection unit 40.

  (5) As in the present embodiment, by using the weight generated based on the gravity acting on the weights 54a and 54b as the load, the variation in the constant load applied to the ball nut 12 can be substantially suppressed. That is, in this case, a more reliable result can be obtained as a result of the rattling G.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
As shown in FIG. 7, as a form for generating a load to be applied to the ball nut 12, the rotational torque of the servo motors 55a and 55b may be used instead of the gravity of the weights 54a and 54b. In this case, pulleys attached to the output shafts of the servomotors 55a and 55b are mechanically connected to both sides of the load jig 51 in the axial direction via the wires 52a and 52b. That is, one end of each of the wires 52a and 52b connected to the pulley is wound up by the pulley, and the rotational torque of the output shaft pulls the load jig 51 via the pulley and the wires 52a and 52b (load ). A sensor for detecting torque to be applied as a load, that is, each load cell 56a, 56b is provided in the middle of each wire 52a, 52b. Each servomotor 55a, 55b generates a rotational torque instructed from the control processing unit 43 even when the load changes, and feeds back the torque detected by each load cell 56a, 56b to be equal to the instructed rotational torque. The torque is controlled so that it can be operated. That is, in this case, the control processing unit 43 executes torque control of the servo motors 55a and 55b based on the results detected by the load cells 56a and 56b. Specifically, the control processing unit 43 performs servo control so that a predetermined torque is generated by winding the wire 52b so as to become a load with respect to the leftward movement of the ball nut 12 in step S20 in the procedure of the backlash measurement. Torque control of the motor 55b is executed. In step S50, the control processing unit 43 executes torque control of the servo motor 55b so as to loosen the wire 52b. Further, in step S60, the control processing unit 43 performs torque control of the servo motor 55a so that a predetermined torque is generated by winding the wire 52a so as to become a load with respect to the rightward movement of the ball nut 12. In step S90, the control processing unit 43 executes torque control of the servo motor 55a so as to loosen the wire 52a. In this example, the servo motors 55a and 55b can be applied to the ball nut 12 by any one of the servo motors 55a and 55b during the measurement of the backlash (with some variation). A certain load is applied. According to this, automation of the operation | work which switches the load provided with respect to the ball nut 12 is realizable.

In addition, as a form for generating a load to be applied to the ball nut 12, for example, a change in dynamic friction force between the guide 15 and the load applying unit 50 can be used.
The anti-rotation jig 30 and the load jig 51 may be configured separately as different jigs, and even if they are configured separately, the ball nut 12 is allowed to swing in the radial direction. It only has to be done.

  The anti-rotation jig 30 and the load jig 51 may not be configured to allow the ball nut 12 to swing in the radial direction (the floating mechanism may not be provided between them). For example, the rotation prevention jig 30 may be fixed to the load jig 51.

-Each load nail | claw 51a, 51b may comprise the arrangement | positioning which pinches | pinches the rotation prevention jig | tool 30 in the axial direction of the screw shaft 11. FIG.
In the determination process for determining whether or not the distribution of the rattling G is distributed within a normal range in which the ball screw accuracy satisfies the predetermined standard, the screw shaft is based on the results of FIGS. 6 (a) and 6 (b). 11 or the ball nut 12 can be output by the control processing unit 43.

The above determination process may be performed by the operator from the calculation result without being performed by the ball screw measuring device.
The calculation process for calculating the difference between the measurement result of the forward path and the measurement result of the return path may be performed by an operator from the measurement result without being performed by the ball screw measuring device. In this case, the measurement result is displayed on the display screen 43 a of the control processing unit 43.

  As a procedure for the rattling measurement, it is possible to devise measures for improving the reliability of information by using an average obtained by measuring the measurement results of the forward path and the return path several times.

The detection unit 40 is not limited to a laser, and may use ultrasonic waves or the like, may use image recognition by a camera, or may use a mechanical switch.
During the distance measurement, the rotation of the servo motor 22 may be continued until the ball nut 12 reaches a position that is the end of the screw shaft 11 (until the limit switch is turned on). As the distance measurement data in this case, the result of sampling the measured distance L for each screw shaft angle θ is recorded. By measuring the distance continuously in this way, the actual measurement distance L can be measured with high accuracy.

  DESCRIPTION OF SYMBOLS 11 ... Screw shaft, 11a ... Screw groove, 12 ... Ball nut, 12a ... Screw groove, 12b ... Ball, 22 ... Servo motor, 30 ... Anti-rotation jig, 31 ... Anti-rotation part, 32 ... Detected object, 33 ... Reflecting material, 40 ... detection unit, 41 ... irradiation unit, 42 ... light receiving unit, 43 ... control processing unit, 50 ... load applying unit, 51 ... load jig, 54a, 54b ... weight, 55a, 55b ... servo motor.

Claims (5)

A screw shaft in which a spiral groove is formed;
A ball nut that is fitted to the thread groove of the screw shaft via a large number of balls;
A drive unit for driving the screw shaft;
When the screw shaft is driven, a lock portion that prevents the ball nut from rotating around the axial direction of the screw shaft;
A detection unit for detecting the position of the ball nut in the axial direction of the screw shaft;
During which the ball nut is reciprocated the entire area of the screw groove of the screw shaft, there in the ball load so as to be switchable direction to impart a constant force load applying section with respect to the direction of movement of the nut A load applying unit that applies a certain force to the ball nut ;
A drive control unit that controls the drive unit so that the ball nut reciprocates across the entire thread groove of the screw shaft in a state where a load is applied to the ball nut by the load application unit;
A ball screw measuring device comprising: a recording unit that records a detection result of the detection unit according to the driving amount while the driving amount of the screw shaft is changed.   The ball screw measurement device according to claim 1, further comprising a calculation unit that calculates a difference between the forward path and the return path of the ball nut according to the drive amount of the screw shaft from a recording result in the recording unit.   A determination unit that determines whether or not the calculation result of the calculation unit is distributed in the normal range while the calculation result of the calculation unit sets a normal range that satisfies a request for ball screw accuracy. 2. The ball screw measuring device according to 2.   A floating mechanism that allows a load to be applied to the axial direction of the ball nut while allowing the ball nut to swing around the screw shaft is provided between the lock portion and the load applying portion. The ball screw measuring device according to any one of claims 1 to 3.   The ball screw measuring device according to any one of claims 1 to 4, wherein the load applying unit applies a weight generated based on gravity to the ball nut as a load.