JP2012247362A - Cumulative lead error measuring apparatus for ball screw axis and measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cumulative lead error measuring apparatus for a ball screw axis which is capable of performing high-reproducibility and high-accuracy measurement in a short time and improves productivity, and a measuring method.SOLUTION: A cumulative lead error measuring apparatus comprises: a fixing support table 1 on which a ball screw axis W to be measured is fixed to prevent rotation; a ball contact 5 which is abutted to a thread groove of the ball screw axis W to be measured; ball contact slide means which allows the ball contact 5 to reciprocate and move orthogonally to an axial center Lz of the ball screw axis W to be measured and abuts the ball contact 5 to the thread groove with a predetermined push-in force; position detection slide means which allows the ball contact slide means to horizontally reciprocate and move in parallel with the axial center Lz; positioning reciprocation slide means 2 which allows the position detection slide means to reciprocate and move between screw portions of the ball screw axis W to be measured; and lead position measuring means 6 which detects the position of the ball contact 5 in a direction of the axial center Lz.

Description

  The present invention relates to an apparatus for measuring a cumulative lead error of a ball screw shaft and a measurement method using the apparatus.

  Conventionally, as a device for measuring the lead error of a ball screw shaft, for example, a measuring device shown in Patent Document 1 is known. In this measuring apparatus, a sphere having the same size as the ball used for the ball screw shaft to be measured is bonded to the tip of the ball contact, and the two ball contacts are 180 degrees around the axis of the ball screw shaft to be measured. The ball screw shaft to be measured is inserted in the thread groove of the ball screw shaft to be measured at a position shifted in phase, is applied with measuring pressure in the radial direction of the screw shaft, and is in contact with both flank of the screw groove. Measure the moving distance of the ball contactor with a laser interferometer while rotating the ball contactor, and measure the ball screw shaft to be measured by the cumulative movement error between the theoretical rotational moving distance of the ball screw shaft to be measured and the measured moving distance. Measure the lead error.

  On the other hand, there is Patent Document 2 as a thread groove detecting device that can measure the center position of the thread groove with higher accuracy and in a short time by directly detecting the center position of the thread groove. In the screw groove detecting device of Patent Document 2, as shown in FIG. 1, the ball contactor is pressed against the screw shaft to be measured so as to intersect the screw shaft to be measured, and the ball contactor is inserted into the screw groove by using the radial position detecting means. The position of the thread groove is detected by detecting the position of the groove and detecting the position of the ball contact in the lead direction using the lead side position detecting means.

JP-A-56-26203 JP 2010-36332 A

  However, according to the measuring apparatus of Patent Document 1, although it is possible to grasp the screw lead error in the three-dimensional direction, it is necessary to measure by rotating the ball screw shaft to be measured. In the case of a long feed screw having a length of 1 m or more in order to constitute a large machine tool, a deflection of its own weight occurs between the rotating shafts, resulting in rotational runout. When the rotating core swings, the ball contact will vibrate due to unstable contact, and it is difficult to measure the accuracy of 1 μm or less, which is the smallest unit of lead error management. Ten or more minutes are required for one measurement.

  Further, the measuring device of Patent Document 2 also needs to measure by rotating the screw shaft to be measured. Before detecting the position on the lead side, the ball contactor is first moved by reciprocating the screw shaft to be measured in the lead direction. Needs to be adapted to the thread groove, and there is a problem that a measurement error occurs due to the influence of backlash for rotating the screw shaft to be measured forward and backward.

  Furthermore, the support mechanism of the ball contactor is movable in the axial direction of the screw shaft to be measured and the direction perpendicular to the axial direction, and is also rotatable, and linear guide bearings are used. The sliding bearing has a clearance of several μm level. When used in a free state without restraining force, the occurrence of backlash of several tens of μm is unavoidable, and automatic measurement varies in measurement reproducibility. There is a problem in data reliability.

  The present invention has been made in view of such points, and an object of the present invention is to provide a ball screw shaft cumulative lead error measuring apparatus and measuring method capable of performing highly accurate measurement with high reproducibility in a short time and excellent productivity. And

  In order to achieve the above object, an apparatus for measuring a cumulative lead error of a ball screw shaft according to the present invention includes a ball screw shaft that measures a cumulative lead error by detecting a position of a thread groove in an axial direction of a measured ball screw shaft. And a fixed support base for fixing the ball screw shaft to be measured in a non-rotatable manner, and a sphere to be brought into contact with a thread groove of the ball screw shaft to be measured fixed to the fixed support base. And a ball contact sliding means for reciprocating the ball contact in a direction orthogonal to the axis and bringing the ball contact into contact with the screw groove with a predetermined pushing force, Position detecting slide means for mounting the ball contact slide means and horizontally reciprocating the ball contact slide means parallel to the axis; and the position detection slide Positioning reciprocating slide means for reciprocating the position detecting slide means between the threaded portions of the ball screw shaft to be measured, and lead position measuring means for detecting the position of the ball contact in the axial direction And.

  In order to achieve the above object, the cumulative lead error measurement of the ball screw shaft according to the present invention is performed by fixing the ball screw shaft to be measured to be stationary and fixed, and the fixed support base. In addition, a ball contactor having a sphere to be brought into contact with the thread groove of the ball screw shaft to be measured, and reciprocating the ball contactor in a direction orthogonal to the shaft center and a predetermined pushing force of the ball contactor A ball contact slide means for contacting the thread groove, a position detection slide means for mounting the ball contact slide means and moving the ball contact slide means horizontally and reciprocally parallel to the axis; Positioning reciprocating slide means for placing position detecting slide means and reciprocatingly moving the position detecting slide means between the threaded portions of the ball screw shaft to be measured; and the ball contactor A lead position measuring means for detecting a position in the axial direction, and a cumulative lead error of the ball screw shaft for measuring a cumulative lead error of the measured ball screw shaft using a cumulative lead error measuring device of the ball screw shaft. A measuring method, wherein the center of the sphere is perpendicular to the axis when the ball contact is reciprocated in the direction orthogonal to the axis of the ball screw shaft to be measured on the fixed support base. A fixing support step for fixing the ball screw shaft to be measured to the ball contact, and a ball contact that abuts the ball contact with the screw groove with a predetermined pushing force from a direction perpendicular to the axial direction of the ball screw shaft to be measured A step of pushing, a measuring step of measuring the position of the ball contactor in contact with the screw groove in the axial direction with a laser interferometer, and the ball in contact with the screw groove A ball contact retracting step for retracting the contactor in a direction orthogonal to the axial direction, and a ball contact moving step for horizontally moving the ball contact at a predetermined interval in parallel with the axial direction. It is characterized by that.

  According to the present invention, the center position of the thread groove can be obtained with higher accuracy by using the ball contactor that directly contacts the flank of the screw for detecting the thread groove. The position of the thread groove in the axial direction of the ball screw shaft to be measured is placed on the positioning reciprocating slide means with position detecting slide means capable of reciprocating in the axial direction, and further pushed into the position detecting slide means by a predetermined amount. By incorporating a ball contact sliding means that pushes the ball contact into the thread groove by force, the ball contact becomes easy to fit into the thread groove of the ball screw shaft fixed in a non-rotatable manner, and the lead side position detection means is highly reproducible. Measurement can be performed in a short time with accuracy.

It is explanatory drawing which shows the method of measuring the center position of the conventional screw groove. 1 is an explanatory plan view showing a cumulative lead error measuring device for a ball screw shaft according to a first embodiment of the present invention. FIG. It is explanatory drawing which showed the to-be-measured ball screw axis | shaft and fixed support part from the AA arrow of FIG. It is the expansion explanatory view which showed the BB arrow of FIG. FIG. 3 is an enlarged explanatory view showing a CC arrow view of FIG. 1. It is side surface explanatory drawing which showed the accumulation lead error measuring apparatus of the ball screw shaft of 2nd Embodiment of this invention. It is a section explanatory view of one embodiment of an aerostatic bearing used by the present invention. FIG. 7B is an enlarged explanatory view of the orifice. It is a plane explanatory view showing the static pressure pad structure of FIG. FIG. 9 is a sectional view taken along the line DD of FIG. 8 and showing the cross-sectional shape in the width direction of the ventilation groove and the exhaust groove. It is a graph which shows the measurement result measured using the accumulation lead error measuring device of the ball screw axis of a 1st embodiment of the present invention.

Hereinafter, a cumulative lead error measuring apparatus for a ball screw shaft according to a first embodiment of the present invention and a measuring method using the apparatus will be described with reference to the drawings.
FIG. 2 is an explanatory plan view showing the cumulative lead error measuring apparatus for the ball screw shaft according to the first embodiment of the present invention. FIG. 3 is an explanatory view showing the ball screw shaft to be measured and the fixed support portion as seen from the arrows AA in FIG. FIG. 4 is an enlarged explanatory view showing the arrow BB. FIG. 5 is an enlarged explanatory view showing a CC arrow view of FIG. 1.
2 to 5 and FIG. 6 described later, the X axis, the Y axis, and the Z axis are orthogonal, the Z axis indicates the same direction as the axis of the ball screw shaft to be measured, and the X axis is the Z axis. Indicates a horizontal direction perpendicular to the Y axis, and a Y axis indicates a vertical direction perpendicular to the Z axis.
In addition, this invention is not limited to the following embodiment.

  A fixed support base 1 is disposed on the stone surface plate 100 for stationaryly fixing the ball screw shaft W to be measured in a stationary manner. In the present embodiment, the fixed support base 1 is installed so as to be supported at three points which are at both ends of the measured ball screw shaft W and substantially in the middle as shown in FIG.

On the stone surface plate 100, positioning reciprocating slide means 2 capable of reciprocating in a direction parallel to the axis Lz of the ball screw shaft W to be measured fixed to the fixed support base 1 is disposed. This positioning reciprocating slide means 2 is an aerostatic bearing 20 comprising a guide shaft 21 installed in parallel to the axis Lz of the ball screw shaft W to be measured, and a moving table 22 that reciprocates along the guide shaft 21. It has. The aerostatic bearing 20 has a running accuracy with a straightness of 2 μm / m or less and a posture accuracy of 2 seconds or less.
The posture accuracy is the accuracy of pitching, yawing, and rolling that changes the posture while the moving table 22 is traveling, and is represented by an inclination (degree). The traveling accuracy refers to accuracy obtained by combining the straightness and the posture accuracy in which the moving table 22 travels in a direction parallel to the axis Lz of the ball screw shaft W to be measured. Straightness refers to the maximum displacement of the moving distance.

  The aerostatic bearing in the present invention means that a bearing gap is provided between the sliding surfaces of the fixed body and the moving body, and the moving body is floated on the fixed body by supplying pressurized gas to the bearing gap. It refers to a bearing configured to be movable.

Further, the positioning reciprocating slide means 2 is provided with positioning traveling means 25 for reciprocating the moving table 22 along the guide shaft 21 to a predetermined measurement position. In the present embodiment, positioning traveling means 25 that moves the moving table 22 by a servo motor 26 via a belt 27 connected to the moving table 22 is used.
Further, a position detecting slide means 3 is placed on the positioning reciprocating slide means 2 (FIG. 5).

  The position detection slide means 3 includes an aerostatic bearing 30 including a fixed shaft 31 and a cradle 32 that can move along the fixed shaft 31. The fixed shaft 31 is fixed to the moving table 22 of the aerostatic bearing 20 provided in the positioning reciprocating slide means 2 in parallel with the axis Lz of the ball screw shaft W to be measured.

In addition, the aerostatic bearing 30 includes neutral position holding elastic bodies 35 and 35 between both ends of the fixed shaft 31 and the cradle 32 (FIG. 5). When the ball contactor 5 is not in contact with the thread groove of the ball screw shaft W, that is, when a force in the Z-axis direction is not applied to the cradle 32, the cradle 32 is neutral in the Z-axis direction of the fixed shaft 31. Held in position. When the ball contact 5 abuts on the thread groove of the ball screw shaft W, that is, when a force in the Z-axis direction acts on the cradle 32, the neutral position holding elastic bodies 35 and 35 expand and contract, and the cradle 32 Reciprocates along the fixed shaft 31. In the first embodiment, springs are used as the neutral position holding elastic bodies 35, 35.
Furthermore, a ball contact slide means 4 is placed on the position detection slide means 3.

  The ball contact slide means 4 includes a moving shaft 42 capable of reciprocating in the X-axis direction orthogonal to the axis Lz of the ball screw shaft W to be measured, and a fixed support 41 that supports the moving shaft 42. An aerostatic bearing 40 is provided. The fixed support 41 is fixed to the cradle 32 of the aerostatic bearing 30 provided in the position detection slide means 3.

  Further, a ball contact 5 that is brought into contact with a thread groove of the measured ball screw shaft W is connected to the tip of the moving shaft 42 on the measured ball screw shaft W side. A sphere 50 having the same diameter as that of the ball used for the ball screw shaft W to be measured is bonded to the tip of the ball contact 5 in contact with the screw groove. The ball contactor 5 is movable between the threaded portions of the ball screw shaft W to be measured by the positioning reciprocating slide means 2.

On the other hand, an expansion / contraction means 44 is connected to the end of the moving shaft 42 opposite to the end where the ball contact 5 is connected via a pushing force adjusting elastic body 43. By the expansion / contraction means 44, the moving shaft 42 and the ball contactor 5 are reciprocated linearly. The pushing force adjusting elastic body 43 absorbs the collision energy when the ball contactor 5 comes into contact with the screw groove, and holds the ball contactor 5 against the screw groove with a predetermined pushing force.
In this embodiment, a spring is used as the pushing force adjusting elastic body 43 and an air cylinder is used as the expansion / contraction means 44. However, the pushing force adjusting elastic body 43 and the expansion / contraction means 44 are not limited to those described above.

  Further, the aerostatic bearing 40 has a bearing rigidity capable of withstanding deformation in the Z-axis direction when the ball contactor 5 is brought into contact with the thread groove.

  Further, the present embodiment is provided with a lead position measuring means 6 for measuring the position of the ball contact 5 in contact with the thread groove of the ball screw W to be measured in the axial center Lz direction. As the lead position measuring means 6 in this embodiment, a commercially available laser interference length measuring device is used. The lead position measuring means 6 is not particularly limited as long as it can measure in units of μm.

The configuration of the laser interference length measuring device used for the lead position measuring means 6 of this embodiment will be described with reference to FIG. Right-angle reflecting mirrors 62 and 63 are disposed for receiving and reflecting the laser beam on the cradle 32 of the position detecting slide means 3. The right-angle reflecting mirrors 62 and 63 are symmetric with respect to the central axis in the Z-axis direction of the fixed shaft 31 of the position detecting slide means 3 on a line perpendicular to the axis Lz of the ball screw axis W to be measured. Placed in position. Note that the right-angle reflecting mirrors 62 and 63 may be installed on the fixed support 41 of the ball contactor slide means 4 in the same manner as described above. Further, a corner cube 64 for incident and reflecting the laser beam reflected by the right-angle reflecting mirror 63 is disposed on the Z-axis line of the right-angle reflecting mirror 63. Then, on the Z-axis line of the right-angle reflecting mirror 62, the laser light source and the laser beam from the laser light source are divided, and one of the divided laser beams is incident on the right-angle reflecting mirrors 62 and 63 and the corner cube 64. And a laser interference head 61 that interferes with the reflected light obtained by making the other laser beam incident on the reference reflecting mirror and generates an electrical signal that changes in accordance with the change in the interference fringes accompanying the movement of the reflecting mirror. ing. Furthermore, the laser interference head 61 is connected to a main body 60 that calculates a moving distance from the number of cycles of an electric signal output from the laser interference head 61.
An arithmetic means 7 for arithmetically processing the measurement values measured by the lead position measuring means 6 and a recorder 8 for recording the results are connected.
Further, in the distance measurement using the laser interference length measuring device, the right angle reflecting mirrors 62 and 63 may be omitted, and the corner cube 64 may be provided on the cradle 32 of the position detection slide means 3.

In addition, the spring constant of the spring used for the neutral position holding | maintenance elastic body 35 in this embodiment is 0.1-3 N / mm, Preferably it is 0.3-1 N / mm. If the spring constant of the spring of the neutral position holding elastic body 35 is less than 0.1 N / mm, the restoring force is too small, and the cradle 32 may be insufficiently restored, and may not return to the neutral position. The bearing rigidity of the aerostatic bearing 40 used for the contact sliding means 4 cannot withstand deformation when the ball contact 5 is pushed into the thread groove. If it is 0.3-1 N / mm, a measurement with high reproducibility will be attained.
In addition, the bearing rigidity of the aerostatic bearing 40 of this embodiment is 6 N / μm.

  The pushing force of the ball contactor 5 into the thread groove of the ball screw shaft W to be measured is 0.5 to 5N, preferably 1 to 3N. If the pushing force for pushing the ball contactor 5 into the screw groove is less than 0.5N, pushing may not be possible, and if it is 5N or more, the ball screw shaft W to be measured is deformed by pushing and leads to a measurement error. If it is 1 to 3 N, measurement with high reproducibility becomes possible.

  Below, the screw lead error measuring method using the screw lead error measuring apparatus of this embodiment is demonstrated.

First, the ball screw shaft W to be measured is stationary and fixed to the three fixed support bases 1 without rotation. The fixed support base 1 is provided with a height adjusting mechanism (not shown).
In the present invention, it is necessary to bring the ball contact 5 into contact with the thread groove of the measured ball screw shaft so that the center of the sphere 50 of the ball contact 5 is orthogonal to the axis Lz of the measured ball screw shaft W. . Therefore, the height Hy1 of the axis Lz of the ball screw shaft W to be measured is adjusted from the surface of the stone surface plate 100 to the center height Hy2 of the sphere 50 of the ball contactor 5 by adjusting with the height adjusting mechanism, and positioning reciprocation is performed. The ball screw W to be measured is fixed so that the running accuracy of the aerostatic bearing 20 of the sliding means 2 is within the straightness.
In the first embodiment, the ball screw shaft to be measured is fixed by three-point support in consideration of the deflection due to its own weight, but the axial center Lz of the ball screw shaft W is provided in the positioning reciprocating slide means 2. The pressure bearing 20 may be supported at any number of points as long as it is within the straightness of traveling accuracy.

Then, the ball contactor 5 is moved to a predetermined measurement start position by using the positioning traveling means 25 of the positioning slide means 2.
Subsequently, the expansion / contraction means 44 of the ball contactor slide means 4 is extended so that the moving shaft 42 and the ball contactor 5 are pushed with a predetermined pushing force from the X-axis direction orthogonal to the axis Lz of the ball screw shaft W to be measured. While being fitted in the thread groove of the ball screw shaft W to be measured, the contact is made.

  The lead position measuring means 6 measures the position of the ball contactor 5 with respect to the axis Lz direction of the ball screw shaft to be measured.

Thereafter, the expansion / contraction means 44 is contracted to retract the ball contact 5 from the ball screw shaft W to be measured. Subsequently, the ball contactor 5 is moved a predetermined distance by the positioning traveling means 25 of the positioning slide reciprocating means 2.
Thereafter, the expansion / contraction means 44 is extended to bring the ball contact 5 into contact with the thread groove of the ball screw shaft W to be measured, and the position of the contacted ball contact 5 is measured by the lead position measurement means 6. Then, the ball contact 5 is retracted, and the ball contact is moved at a predetermined interval. By repeating the above, the actual movement amount is measured, and the representative movement amount is obtained from the actual movement amount.

(Second Embodiment)
Next, a second embodiment of the cumulative lead error measuring apparatus for the ball screw shaft of the present invention will be described. FIG. 6 is an explanatory side view showing the second embodiment. The basic configuration and the measurement method are the same as those in the first embodiment, and thus will be omitted.

  This embodiment differs from the first embodiment in that the ball contact 5 is brought into contact with the axis Lz of the measured ball screw shaft W from the X-axis direction in the first embodiment. In the second embodiment, the ball contact 5 is brought into contact with the axis Lz of the ball screw shaft W from the Y-axis direction orthogonal thereto. Therefore, in the second embodiment, the ball contact slide means 4 is placed on the position detection slide means 3 via the L-shaped bracket 80 as shown in FIG.

By making the ball contact 5 abut from the Y-axis direction perpendicular to the axis Lz of the ball screw shaft W as in the present embodiment, it is not affected by the deflection deformation due to the weight of the ball screw shaft W to be measured. Measurement is possible. In particular, when measuring a long ball screw shaft, the deflection deformation due to its own weight is large, and the fixed support method leads to measurement errors, which complicates the work. Unless the tolerance of the height of the shaft center Lz is within ± 1 μm in terms of the total screw length, the reproducibility of measurement within 1 μm cannot be ensured.
In the first embodiment, each time the diameter of the measured ball screw shaft W is changed, the fixed support base is set so that the height of the measured ball screw shaft W is the same as the center height of the ball contactor 5. However, the second embodiment has an advantage that it is not necessary.

  The aerostatic bearing used in the present invention will be described in detail. The aerostatic bearing used in the present invention is provided in a main pipe 64 for supplying pressurized gas to the moving body 61 and a discharge port 64a of the main pipe 64 opened to the sliding surface 66, and rectifies the pressurized gas. And a static pressure pad 63 formed with a ventilation groove 68 that communicates with the orifice 65 and distributes and supplies the pressurized gas discharged from the orifice 65 to the bearing gap 67 with the fixed body 62. (See FIG. 7). The ventilation groove 68 has an annular groove 68b formed in an annular shape surrounding the orifice 65, and extends radially toward the annular groove 68b around the orifice 65, and a plurality of the annular groove 68b and the orifice 65 communicate with each other. Distribution groove 68a (see FIG. 8). Further, the ventilation groove 68 is formed to be symmetric with respect to the moving direction of the moving body 61. Further, the cross-sectional shape of the ventilation groove 68 in the width direction forms a convex curve in a direction away from the sliding surface 66 (see FIG. 9).

  Further, the sum of the cross-sectional areas in the width direction of the distribution grooves 68 a is equal to or larger than the cross-sectional area of the orifice 65, and the surface roughness of the ventilation grooves 68 is smaller than the surface roughness of the sliding surface 66 of the moving body 61. Is formed.

Further, the moving body 61 is provided with an exhaust groove 69 that surrounds the annular groove 68b and guides the pressurized gas supplied from the ventilation groove 68 to the bearing gap 67 to the outside of the bearing gap 67 and exhausts it. It is formed so as to be symmetric with respect to the moving direction of the body 61 (see FIG. 8). Further, the exhaust groove 69 forms a convex curve in a direction in which the cross-sectional shape in the width direction is away from the sliding surface, and the cross-sectional area is equal to or larger than the cross-sectional area of the annular groove 68b. (See FIG. 9).
The moving body 61 and the fixed body 62 are made of ceramics.

The aerostatic bearing configured as described above can prevent the occurrence of vibration because the pressurized gas discharged from the static pressure pad 63 to the bearing gap 67 can be a laminar flow with a uniform pressure distribution. It is a highly accurate aerostatic bearing.
Furthermore, since the laminar flow can be stably maintained, the supply pressure of the pressurized gas can be increased, and thus a highly rigid aerostatic bearing is obtained.

  In addition, the aerostatic bearing shown to FIG.7,8,9 is one Embodiment of the aerostatic bearing used for this invention, and is not restricted to this.

(Example)
An example measured by the cumulative lead error measuring apparatus for the ball screw shaft of the first embodiment will be shown below.
A ball screw shaft (manufactured by THK) that passed the JIS standard equivalent to C3 class with a shaft diameter of 40 mm, a lead pitch of 10 mm, and an overall length of 1400 mm, is air-conditioned at a room temperature of 20 ° C ± 0.5 ° C. Then, the accumulated lead error of the ball screw shaft was measured.
First, the ball screw shaft to be measured was placed on three fixed support bases so as to be parallel to the guide shaft of the aerostatic bearing provided in the positioning slide reciprocating means 2. Further, the fixed support 1 was adjusted so that the height of the axis Lz of the ball screw shaft to be measured was within ± 1 μm in accordance with the center height of the sphere 50 of the ball contactor 5. Then, the ball contactor 5 was pushed in from the X-axis direction orthogonal to the axis Lz of the measured ball screw shaft W from the position of 200 mm from the tip of the measured ball screw shaft W at an interval of 10 mm. One lead pitch was measured at intervals of 5 seconds / point, and the total length measurement time was measured at 500 seconds / 100 points. A spring having a spring constant of 0.3 N / mm was used as the spring of the neutral position holding elastic body 35 provided in the position detection slide means 2. Further, the spring of the pushing force adjusting elastic body 43 provided in the ball contactor slide means 4 has a spring constant of 2.4 N / mm, and is set so that the pushing force adjusting elastic body 43 is pushed in by 1 mm by the expansion / contraction means. did.
The results measured as described above are shown in FIG. From FIG. 10, it can be seen that the variation in the accumulated read error measured four times is a typical movement amount error of 19 to 20 μm, the reproducibility is within 0.7 μm at maximum, and can be measured with high accuracy and good reproducibility.

  Table 1 shows a comparison between examples of the present invention and conventional general examples. In the present invention, the reproducibility of measurement is 1 μm or less, high-precision measurement is realized, and the measurement time can be achieved in 1/3 of the conventional method. It can be significantly shortened.

  As is apparent from the above, by using the screw lead error measuring device of the present invention, the ball contactor 5 that makes direct contact with the flank of the screw is used for detecting the thread groove, so that the center position of the thread groove is more accurately detected. Can be requested. Then, the position of the thread groove in the direction of the axis Lz of the ball screw shaft W to be measured is placed on the positioning reciprocating slide means 2 with the position detecting slide means 3 that horizontally reciprocates parallel to the axis Lz of the ball screw axis W. Further, by incorporating the ball contactor slide means 4 for pushing the ball contactor 5 into the screw groove with a predetermined pushing force into the position detection slide means 3, the ball contactor 5 becomes easy to become familiar with the screw groove, and the lead side position detection means 6 can be accurately detected.

  Furthermore, in the screw lead error measuring device of the present invention, the positioning reciprocating slide means 2 is provided with a ceramic aerostatic bearing 20 having a running accuracy with a straightness of 2 μm / m or less and an attitude accuracy of 2 seconds or less. As a result, the ball contactor 5 can be easily adapted to the thread groove of the ball screw shaft W, and a device capable of measuring reproducibility with high accuracy can be configured in a compact manner.

  Further, in the screw lead error measuring apparatus of the present invention, the position detecting slide means 3 is provided with a ceramic hydrostatic bearing 30 having a very small sliding resistance, and further fixed to the cradle 32 of the aerostatic bearing 30. Since the neutral position holding elastic body 35 having a restoring force to return the cradle 32 to the neutral position of the fixed shaft 31 according to the amount of deviation with respect to the Z-axis direction is provided between the shafts 31, the detection error of the screw groove position is reduced. Can be small.

  Further, since the ball contact slide means 4 is provided with a ceramic aerostatic bearing 40 having axial rigidity capable of withstanding the deformation amount in the Z-axis direction when the ball contact 5 is pushed into the thread groove. Compact and highly reproducible measurement.

  Further, since the pushing force adjusting elastic body 43 is connected to the expansion / contraction means 44 for pushing the ball contact 5 into the screw shaft into the ball contact sliding means 4, the collision when the ball contact 5 is pushed into the screw groove. Since the ball contact 5 can be properly stored in the center position of the screw groove by absorbing energy and holding the pushing force of the ball contact 5 before detecting the center position of the screw groove constant, The detection error of the groove position can be further reduced.

W Ball screw shaft 1 Fixed support base 2 Positioning reciprocating slide means 3 Position detecting slide means 4 Ball contact slide means 5 Ball contact 6 Lead position measuring means 20 Aerostatic bearing 21 Guide shaft 22 Moving table 25 Positioning travel means 30 Air Static pressure bearing 31 Fixed shaft 32 Receiving base 35 Neutral position holding elastic body 40 Air static pressure bearing 41 Fixed support body 42 Moving shaft 43 Pushing force adjusting elastic body 44 Telescopic means 50 Sphere

Claims (14)

A ball screw shaft cumulative lead error measuring device for measuring a cumulative lead error by detecting a position of a thread groove in an axial direction of a measured ball screw shaft,
A fixed support base for fixing the ball screw shaft to be measured to be stationary;
A ball contactor comprising a sphere to be brought into contact with a thread groove of the ball screw shaft to be measured fixed to the fixed support;
Ball contact sliding means for reciprocating the ball contact in a direction perpendicular to the axis and bringing the ball contact into contact with the screw groove with a predetermined pushing force;
Position detecting slide means for placing the ball contact slide means and horizontally reciprocating the ball contact slide means parallel to the axis;
Positioning reciprocating slide means for placing the position detection slide means and reciprocatingly moving the position detection slide means between the thread portions of the ball screw shaft to be measured;
Lead position measuring means for detecting a position of the ball contact in the axial direction;
A cumulative lead error measuring device for a ball screw shaft, comprising:   2. The ball screw shaft cumulative lead error measuring device according to claim 1, wherein the ball contact sliding means reciprocates the ball contact in a vertical or horizontal orthogonal direction with respect to the axis.   The ball contact slide means is an aerostatic bearing comprising a moving shaft having the ball contact connected to one end on the measured ball screw shaft side, and a fixed support for supporting the moving shaft. The cumulative lead error measuring device for a ball screw shaft according to claim 1 or 2, characterized in that:   The ball contact sliding means further comprises an expansion / contraction means on the other end of the moving shaft via a pressing force adjusting elastic body for adjusting the pressing force of the ball contact. A cumulative lead error measuring device for a ball screw shaft according to any one of 1, 2 or 3.   5. The cumulative lead error measuring apparatus for a ball screw shaft according to claim 4, wherein the ball contact sliding means pushes the ball contact into the thread groove with a pushing force of 0.5 to 5N.   5. The cumulative lead error measuring device for a ball screw shaft according to claim 4, wherein the ball contact sliding means pushes the ball contact into the screw groove with a pushing force of 1 to 3N.   An aerostatic bearing in which the position detection slide means includes a fixed shaft provided in parallel with the shaft center, and a cradle on which the ball contact slide means is mounted so as to be movable along the fixed shaft. The cumulative lead error measuring device for a ball screw shaft according to any one of claims 1 to 6, wherein:   The position detection slide means restores the cradle between the cradle and both ends of the fixed shaft to a neutral position parallel to the axial direction in a state where the ball contact is not in contact with the screw groove. 8. The ball screw shaft cumulative lead error measuring device according to claim 7, further comprising a neutral position holding elastic body having force.   The cumulative lead error measuring apparatus for a ball screw shaft according to claim 8, wherein the neutral position holding elastic body is a spring having a spring constant of 0.1 to 3 N / mm.   The cumulative lead error measuring apparatus for a ball screw shaft according to claim 8, wherein the neutral position holding elastic body is a spring having a spring constant of 0.3 to 1 N / mm.   The positioning reciprocating slide means comprises a guide shaft provided parallel to the axis and a moving table that moves along the guide shaft. The straightness is 2 μm / m or less and the posture accuracy is 2 seconds or less. It is an aerostatic bearing which has accuracy, The accumulation lead error measuring device of a ball screw axis given in any 1 paragraph of Claims 1-10 characterized by the above-mentioned.   12. The accumulated lead error measurement of a ball screw shaft according to claim 11, wherein the positioning reciprocating sliding means further comprises positioning traveling means for moving the moving table to a predetermined position along the guide shaft. apparatus.   The said lead position measuring means is equipped with a laser interference length measuring device, The accumulated lead error measuring apparatus of the ball screw shaft of any one of Claims 1-12 characterized by the above-mentioned. A fixed support base for stationaryly fixing the ball screw shaft to be measured to be stationary;
A ball contactor comprising a sphere to be brought into contact with a thread groove of the ball screw shaft to be measured fixed to the fixed support;
Ball contact sliding means for reciprocating the ball contact in a direction perpendicular to the axis and bringing the ball contact into contact with the screw groove with a predetermined pushing force;
Position detecting slide means for placing the ball contact slide means and horizontally reciprocating the ball contact slide means parallel to the axis;
Positioning reciprocating slide means for placing the position detection slide means and reciprocatingly moving the position detection slide means between the thread portions of the ball screw shaft to be measured;
Lead position measuring means for detecting a position of the ball contact in the axial direction;
A cumulative lead error measurement method for the ball screw shaft using a cumulative lead error measuring device for the ball screw shaft with a ball screw shaft, comprising:
The ball screw to be measured is moved to a position where the center of the sphere is perpendicular to the axis when the ball contact is reciprocated in the direction orthogonal to the axis of the ball screw shaft to be measured on the fixed support base. A fixing support step for fixing the shaft;
A ball contactor pushing step for bringing the ball contactor into contact with the screw groove with a predetermined pushing force from a direction orthogonal to the axial direction of the ball screw shaft to be measured;
A measuring step of measuring the position of the ball contactor in contact with the screw groove in the axial direction with the lead position measuring means;
A ball contact retracting step of retracting the ball contact in contact with the screw groove in a direction orthogonal to the axial direction;
A ball contactor moving step for horizontally moving the ball contactor at a predetermined interval parallel to the axial direction;
A screw lead error measuring method comprising: