JP2001248705A - Ball screw inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw inspection device capable of affording accurate measurement results and greatly improving the reliability of measurement and inspection. SOLUTION: A nut is connected to a measurement carriage via aligning means 60. The aligning means 60 has a first member 71 to which the nut is joined, a second member 81 provided to be rotationally movable with respect to the first member with a first axis (X-X') perpendicular to the axis of the screw shaft as a center and movable to a first axial direction, and a third member 91 provided to be rotationally movable with respect to the second member with a second axis (Y-Y') perpendicular to each of the axis of the screw shaft and the first axis as a center and movable to a second axial direction and joined to the measurement carriage via the connection member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ball screw inspection device. More specifically, the present invention relates to a ball screw inspection device for inspecting the accuracy of a ball screw used for moving a movable portion with respect to a fixed portion.

[0002]

BACKGROUND ART A ball screw has a structure including a screw shaft having a thread groove formed on an outer peripheral surface thereof, and a nut movably provided on the outer periphery of the screw shaft via a ball in the thread groove of the screw shaft. In machine tools and the like, it is widely used as a mechanism for smoothly moving a movable part with respect to a fixed part. Regarding the accuracy inspection of the ball screw, various accuracy inspection items are defined by JIS and ISO. According to JIS, for example, “actual movement amount”, “fluctuation”, “square angle of nut reference end face or flange mounting face with respect to thread axis of screw shaft”
Inspection items such as "radial circumferential runout of the nut outer peripheral surface with respect to the thread axis of the screw shaft" are specified.

Conventionally, the accuracy test of the "actual movement amount" is carried out, for example, according to JIS, since the actual axial movement amount of the nut with respect to an arbitrary screw shaft rotation angle has to be obtained by continuous measurement. It was attached to a measurement carriage slidable in parallel with the axis of the shaft, and the amount of movement of the measurement carriage with respect to the screw shaft rotation angle was measured to obtain the actual movement amount.
In addition, according to JIS, for example, according to JIS, the accuracy inspection of the “fluctuation” is based on the maximum width of the actual movement curve interposed between two straight lines parallel to the representative movement line and the effective movement distance of the nut or the screw of the screw shaft One corresponding to the effective length of the screw shaft, one corresponding to an arbitrary 300 mm between the effective lengths of the screw shaft,
Three items, one corresponding to an arbitrary rotation (2πrad) taken between the effective lengths of the screw portions of the screw shaft, are defined.

[0004] On the other hand, the accuracy inspection of "the perpendicularity of the nut reference end face or the flange mounting surface to the thread axis of the screw shaft with respect to the thread axis of the screw shaft" or "radial runout of the nut outer peripheral surface with respect to the thread axis of the screw shaft in the radial direction" It was done manually using tools. That is, the accuracy inspection of "the perpendicularity of the nut reference end face or the flange mounting face to the thread axis of the screw shaft"
Screw the screw shaft from both ends of the nut to twice the nominal diameter of the screw shaft (2d
o) Fix it with a V-block at the position shown in Fig. 4). Place a tracing stylus on the reference end face of the nut or the mounting face of the flange, measure the maximum value of run-out T when the nut is rotated one turn, and measure the maximum runout T of the screw shaft. Was determined as the squareness of the nut reference end face or the flange mounting face with respect to. In addition, the accuracy test of “radial circumferential runout of the outer peripheral surface of the nut with respect to the axis of the screw portion of the screw shaft” is performed by measuring the screw shaft from both end surfaces of the nut by the nominal diameter of the screw shaft.
It is fixed at the position of 2 times (2do), the measuring element is applied to the outer peripheral surface of the nut, and the maximum value of the run-out U when the nut is rotated once is measured. This is the radius of the outer peripheral surface of the nut with respect to the axis of the screw part of the screw shaft. It was determined as the circumferential runout in the direction.

[0005]

The conventional method for inspecting the accuracy of a ball screw has the following problems. Accuracy inspections for "actual movement amount" and "fluctuation" include measurement of screw shaft bending (torsion), screw shaft axis runout, squareness of nut reference surface or flange surface, radial circumferential runout of nut outer peripheral surface, etc. In addition to the error factors, the nut movement has a tolerance in straightness, and the movement of pitching and yawing is combined with the axis of the screw axis. For this reason, errors occurred due to the principle of Appe, mechanical hysteresis, elastic deformation, and the like, and accurate measurement results could not be obtained.

[0006] In addition, in the precision inspection of "the perpendicularity of the nut reference end face or the flange mounting surface with respect to the screw axis of the screw shaft," and "the radial circumferential runout of the nut outer peripheral surface with respect to the screw axis of the screw shaft", the jig is used. Was performed manually, so a dedicated worker was required, and depending on the worker, measurement position variation, measuring instrument reading error,
There were problems such as individual errors and low reliability of the test.

An object of the present invention is to solve such problems of the conventional inspection method, and to measure the "actual movement amount" and the "fluctuation", to bend the screw shaft (torsion), to deflect the screw shaft axis, and to check the nut reference surface. Alternatively, a ball screw inspection device that eliminates the effects of the squareness of the flange surface and the radial runout of the nut outer peripheral surface to obtain accurate measurement results and greatly improve the reliability of measurement and inspection To provide. Further, another object of the present invention is to provide a "square angle of a nut reference surface or a flange mounting surface with respect to a screw portion axis of a screw shaft".
Accuracy inspection and accuracy inspection of "radial circumferential runout of nut outer peripheral surface with respect to the thread axis of the screw shaft" can be performed automatically, so that the measurement position variation by the operator and the reading error of the measuring instrument , Personal errors disappear,
An object of the present invention is to provide a ball screw inspection device capable of greatly improving the reliability of inspection.

[0008]

To achieve the above object, the ball screw inspection apparatus of the present invention employs the following configuration. The ball screw inspection device according to claim 1, wherein the ball screw inspection device inspects the accuracy of a ball screw having a screw shaft and a nut coupled to the screw shaft via a ball. A rotation drive means for rotating, a linear movement mechanism having a measurement carriage, the measurement carriage being held movably in a direction parallel to the screw axis, and one end connected to the nut via a centering means; A connecting member having the other end connected to the measuring carriage, an angle detecting unit for detecting a rotation angle of the screw shaft, and a length measuring unit for measuring a moving distance of the measuring carriage; A first member to which the nut is coupled;
A first member perpendicular to the screw axis axis with respect to the first member.
A second member rotatable about the axis and movable in the first axis direction, and a second axis orthogonal to the screw axis and the first axis with respect to the second member; And a third member rotatably provided in the second axial direction and coupled to the measurement carriage via the connecting member.

According to this configuration, when inspecting the accuracy of the ball screw, when the screw shaft is rotated by the rotation driving means, the nut is moved in the axial direction of the screw shaft. Then, the measuring carriage of the linear moving mechanism is also moved via the connecting member. Therefore, the moving distance of the measuring carriage is measured by the length measuring means, and the measured data and the rotation angle of the screw shaft detected by the angle detecting means are measured. The “actual movement amount” is obtained from the data. Further, each item (and as described above) of “variation” can be obtained from the “actual movement amount”. At this time, the nut is rotatable around a first axis orthogonal to the screw axis and is provided to be movable in the first axis direction, and the nut is orthogonal to the screw axis and the first axis. Since it is connected to the measuring carriage via a centering means having a third member provided rotatably about the second axis and movable in the second axis direction and a connecting member, the screw shaft Accurate measurement results can be obtained without being affected by bending (torsion), runout of the screw axis, squareness of the nut reference surface or flange surface, radial runout of the nut outer circumferential surface, and the like. Therefore, measurement,
The reliability of the inspection can be greatly improved.

[0010] The ball screw inspection apparatus according to claim 2 is
2. The ball screw inspection device according to claim 1, wherein the displacement detector detects a movement amount of the second member in a first axis direction and a movement amount of a third member in a second axis direction, respectively. A rotation angle detector for detecting a rotation angle of the second member about the first axis and a rotation angle of the third member about the second axis. . According to this configuration, it is possible to automatically perform an accuracy inspection of “circumferential circumferential runout of the nut outer peripheral surface with respect to the thread axis of the screw shaft”. In addition, individual errors can be eliminated, and the reliability of inspection can be greatly improved.

[0011] The ball screw inspection apparatus according to the third aspect,
3. The ball screw inspection device according to claim 1, wherein the first member has an end surface orthogonal to the screw axis, and the connection member has an end surface of the screw shaft on the end surface of the first member. 4. A squareness detector is provided for detecting a squareness of the end face with respect to the screw axis from a position in the axial direction. According to this configuration, since the perpendicularity detector for detecting the perpendicularity of the end face with respect to the screw axis axis from the position of the end face of the first member in the screw axis direction is provided, The accuracy test of the "squareness of the nut reference end face or the flange mounting face with respect to the axis" can also be performed at the same time. Therefore, it is possible to eliminate variations in measurement positions, errors in reading the measuring device, and individual errors caused by the operator, thereby greatly improving the reliability of the inspection.

[0012] The ball screw inspection apparatus according to claim 4 is
4. The ball screw inspection device according to claim 3, wherein a rotation unit that rotates the third member about the screw axis is provided between the third member and the connection member. 5. It is characterized by the following. According to this configuration, since the rotating member is provided to rotate the third member about the screw axis, the “vertical angle of the nut reference surface or the flange mounting surface with respect to the screw portion axis of the screw shaft” is obtained. Accuracy inspection can be performed automatically.

[0013] The ball screw inspection apparatus according to claim 5 is
5. The ball screw inspection device according to claim 1, wherein the linear moving mechanism is movable via a rail provided in parallel with the screw axis and an air bearing with respect to the rail. 6. And a measurement carriage provided in the second position. According to this configuration, since the measurement carriage moves on the rail via the air bearing, the frictional resistance is small, and the resistance during the movement of the nut is small, so that more accurate measurement can be expected.

[0014] A ball screw inspection apparatus according to claim 6 is
6. The ball screw inspection device according to claim 1, wherein the length measuring unit emits a laser beam to the reflector provided on the measurement carriage and the reflector from the screw axis direction. And a laser length measuring device that receives the reflected light from the reflector and obtains the distance to the reflector. According to this configuration, since the position of the measurement carriage is detected by the laser length measuring device, the position of the measurement carriage can be measured with high accuracy.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. (Overall Configuration) FIG. 1 shows the overall configuration of a ball screw inspection apparatus according to the present embodiment. The ball screw inspection device is a ball screw inspection device for inspecting the accuracy of a ball screw 3 having a screw shaft 1 and a nut 2 coupled to the screw shaft 1 via a ball (not shown). A rotation driving means 10 for rotating the screw shaft 1, a linear moving mechanism 20 having a measurement carriage 22 and holding the measurement carriage 22 movably in a direction parallel to the screw axis (ZZ 'axis);
A connecting member 23 having one end connected to the nut 2 via a centering means 60 and the other end connected to the measuring carriage 22; an angle detecting means 30 for detecting a rotation angle of the screw shaft 1; The apparatus includes a length measuring unit 40 for measuring the moving distance of the carriage 22 and a computer 50 as a calculating unit.

(Explanation of each component) The rotation driving means 1
Reference numeral 0 denotes a headstock 11 and a tailstock 12 that rotatably support both ends of the screw shaft 1, and a drive motor connected to the headstock 11 via a power transmission band 13 such as a belt to rotate the screw shaft 1. 14 are included. The linear moving mechanism 20 includes a rail 21 provided in parallel with the screw axis (ZZ 'axis).
And a measurement carriage 22 movably provided on the rail 21 via an air bearing (not shown).
It is comprised including.

The angle detecting means 30 includes a rotary encoder 31 mounted coaxially with the headstock 11, and a counter 32 for counting pulses from the encoder 31. The length measuring means 40 emits a laser beam from the reflector 41 provided on the measuring carriage 22 to the reflector 41 from the screw axis (ZZ 'axis) direction, and reflects the laser light from the reflector 41. A laser length measuring device 42 that receives light and obtains a distance to the reflector 41;
And a counter 43 that counts pulses from the counter. The computer 50 performs various accuracy inspection measurements based on the rotation angle data from the angle detection means 30 and the length measurement data from the length measurement means 40. The centering means 60 is configured as follows.

(Detailed Structure of Aligning Means) FIGS. 2 to 5 show the detailed structure of the aligning means 60. FIG. 2 is an overall perspective view, FIG. 3 is a sectional view taken along line III-III of FIG. 2, and FIG.
FIG. 5 is a sectional view taken along line IV-IV in FIG.
The aligning means 60 includes a first member 71 to which the nut 2 is mounted via a nut mounting plate 61, and the screw member axis (Z-Z 'axis) orthogonal to the first member 71. A second member 81 provided to be rotatable about a first axis (the XX ′ axis) and to be movable in the first axis direction.
And the screw shaft axis (Z-Z ') with respect to the second member 81.
Axis) and a second axis (Y-Y 'axis) orthogonal to the first axis (X-X' axis), respectively, and are rotatable and movable in the second axis (Y-Y 'axis) direction. And a fourth member 91 connected to the third member 91 via a bearing 98 and a stepping motor 99 as a rotating means, and connected to the measuring carriage 22 via the connecting member 23. And a member 101.

The nut mounting plate 61 has a rectangular plate shape, a through hole 62 at the center of which the main body 2A of the nut 2 is inserted, and four screw holes 63 at four places on the outer periphery of the through hole 62. The two screw insertion holes 65 into which the fixing screws 64 are inserted are formed at two locations outside the respective holes.
The first member 71 includes a flange portion 72 having an end surface 72A orthogonal to the screw axis (ZZ 'axis), a cylindrical portion 73 integrally formed at the center of the flange 72,
A through hole 74 penetrating these centers is provided. The flange portion 72 is formed with a screw hole 76 into which the tip of the fixing screw 64 inserted through the screw insertion hole 65 of the nut mounting plate 61 is screwed. Thereby, the flange portion 2B of the nut 2 is fixed to the nut mounting plate 61 by the bolt 66, and the nut mounting plate 61 is fixed to the first member 71 by the fixing screw 64.
The nut 2 is fixed to the first member 71. The cylindrical portion 73 is formed with a through-hole 78 penetrating in a first axis (X-X 'axis) direction orthogonal to the screw axis (Z-Z' axis). A through-hole 79 penetrates in a second axis (Y-Y 'axis) direction orthogonal to the first axis (X-X' axis) and the first axis (X-X 'axis).

The second member 81 is connected to the first member 7
A pair of support shafts 82 are formed in a cylindrical shape to fit the first cylindrical portion 73 from the outside, and extend in the direction of a first axis (XX ′ axis) passing through the center thereof.
A and 82B protrude, and penetrate in the direction of a second axis (Y-Y 'axis) orthogonal to the screw axis (Z-Z' axis) and the first axis (X-X 'axis). A through hole 83 is formed. The inner ends of the support shafts 82A and 82B are inserted into the through holes 78 of the first member 71 via linear ball guides 84. Thereby, the second member 81
Is provided so as to be rotatable about a first axis (XX ′ axis) and to be movable in a direction of the first axis (XX ′ axis).
A displacement detector 85 for detecting the movement of the second member 81 in the direction of the first axis (X-X 'axis) is provided between the one support shaft 82A and the first member 71. Between the other support shaft 82B and the first member 71, a rotation angle detector 86 that detects the rotation angle of the second member 81 about the first axis (the XX ′ axis) is provided. Is provided.

The third member 91 is connected to the second member 8.
A pair of support shafts 92A, 92B are formed in a cylindrical shape that fits from the outside in a second axis (Y-Y 'axis) direction passing through the center thereof.
Is protruding. The inner ends of the shafts 92A and 92B are
It is inserted into the through hole 83 of the second member 81 via a linear ball guide 94. Thus, the third member 91 is provided so as to be rotatable about the second axis (Y-Y 'axis) and to be movable in the direction of the second axis (Y-Y' axis). A displacement detector 95 for detecting the movement of the third member 91 in the direction of the second axis (Y-Y 'axis) is provided between one support shaft 92A and the second member 81. The second member 8 is provided between the other support shaft 92B and the first member 71.
A rotation angle detector 96 for detecting a rotation angle about the first second axis (Y-Y 'axis) is provided. Note that a spring 97 for urging the second member 81 upward is interposed between the second member 81 and the third member 91. The biasing force of the spring 97 is set so as to balance the weight of the second member 81, the first member 71, the nut mounting plate 61 and the nut 2.

The fourth member 101 is formed in a cylindrical shape which fits the third member 91 from the outside, and the screw shaft axis (Z-Z ') of the end surface 72A of the first member 71 is formed on the fourth member 101.
Squareness detector 102 for detecting the position in the (axial) direction
Is attached. The perpendicularity detector 102 detects the angle of the end face 72A with respect to the screw axis (ZZ 'axis) from the position of the end face 72A of the first member 71 in the direction of the screw axis (ZZ' axis). . The fourth member 101
One end of the connecting member 23 is fixed to the rear side of the connector by bolts or the like.

(Operation) In measuring the “actual movement amount”,
When the screw shaft 1 is rotated by the rotation driving means 10, the nut 2 is moved in the axial direction of the screw shaft 1. Then, the measurement carriage 22 of the linear movement mechanism 20 is also moved via the connecting member 23, so that the measurement carriage 22
Is measured by the length measuring means 40, and the "actual moving amount" is obtained from the measured data and the rotation angle data of the screw shaft 1 detected by the angle detecting means 30. For example, assuming that the result shown in FIG. 6 is obtained from the “actual movement amount”, three items of “variation” are obtained from the actual movement amount curve, that is, the effective moving distance of the nut or the effective length of the screw portion of the screw shaft. , Corresponding to any 300 mm between the effective lengths of the threaded portion of the screw shaft, and corresponding to any one rotation (2πrad) between the effective lengths of the threaded portion of the screw shaft , Respectively.

The nut 2 is rotatable about a first axis (X-X 'axis) orthogonal to the screw axis (Z-Z' axis) and moves in the first axis (X-X 'axis) direction. The second provided possible
81, the screw axis (ZZ 'axis) and the first axis
Second axis (Y-Y 'axis) orthogonal to (X-X' axis)
To the measuring carriage 22 via the aligning means 60 having the third member 91 provided so as to be rotatable around and movable in the second axis (Y-Y 'axis) direction, and the connecting member 23. Because it is connected, it is accurate without being affected by the bend (torsion) of the screw shaft 1, the runout of the screw shaft axis, the squareness of the nut reference surface or the flange surface, the radial circumferential runout of the nut outer peripheral surface, etc. Measurement results are obtained,
The reliability of measurement and inspection can be greatly improved.

At this time, the first axis (X-
The amount of movement in the direction of the X 'axis) and the amount of movement of the third member 91 in the direction of the second axis (Y-Y' axis) are determined by the displacement detector 8 respectively.
By detecting at 5,95, it is possible to automatically perform an accuracy test of "radial circumferential runout of the nut outer peripheral surface with respect to the thread axis of the screw shaft". The third member 91 and the second member 8 are driven by the stepping motor 99.
While rotating the first member 71 and the first member 71, the perpendicularity detector 102 provided on the fourth member 101 detects the screw axis (ZZ 'axis) of the end face 72A formed on the first member 71. If the position in the direction is detected, it is possible to automatically perform an accuracy inspection of “the right angle of the nut reference surface or the flange mounting surface with respect to the thread axis of the screw shaft”. Therefore, it is possible to eliminate the variation of the measurement position, the reading error of the measuring device, and the individual error by the operator, and it is possible to greatly improve the reliability of the inspection.

(Effects of the Embodiment) According to the above embodiment, the following effects can be expected in addition to the effects described in "Means for Solving the Problems". A spring 97 for urging the second member 81 upward is interposed between the second member 81 and the third member 91, and the urging force of the spring 97 is applied to the second member 81 and the first member 91. Of the second member 81, the first member 71, the nut mounting plate 61 and the nut 2 without being affected by the weight of the member 71, the nut mounting plate 61 and the nut 2. Measurement can be performed with higher accuracy.

Since the inner ends of the support shafts 82A and 82B are inserted into the through holes 78 of the first member 71 via the linear ball guide 84, the second member 81 is connected to the first axis (XX ').
Axis), and can be moved with less resistance in the direction of the first axis (XX ′ axis). Similarly, since the inner ends of the support shafts 92A and 92B are inserted into the through holes 83 of the second member 81 via the linear ball guide 94, the third member 91 is connected to the second axis (Y-Y 'axis). ) Can be smoothly rotated around the center, and can be moved with less resistance in the direction of the second axis (Y-Y 'axis). This also ensures highly accurate measurement.

The present invention is not limited to the configuration described in the above embodiment, but can be modified within the scope of the present invention. For example, the length measuring means 40 is not limited to the laser length measuring device 42 but may be a capacitance length measuring device, a magnetic length measuring device, a photoelectric length measuring device, or the like. The centering means 60 includes the first to fourth members 71, 81, 91, 101, but may include the first to third members 71, 81, 91, respectively. The shape is not limited to the shape of the above-described embodiment, and can be appropriately changed.

[0029]

According to the ball screw inspection apparatus of the present invention,
Eliminate the effects of screw shaft bending (torsion), screw shaft axis run-out, squareness of the nut reference plane or flange surface, and radial run-out of the nut outer peripheral surface in the "actual travel" and "fluctuation" measurements. Accurate measurement results can be obtained, and the reliability of measurement and inspection can be greatly improved. In addition, the precision inspection of "the perpendicularity of the nut reference surface or the flange mounting surface with respect to the thread axis of the screw shaft" and the precision inspection of "the radial runout of the nut outer peripheral surface with respect to the thread axis of the screw shaft" are automatically performed. By doing so, there are no variations in measurement positions, errors in reading the measuring device, and individual errors by the operator, and the reliability of the inspection can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a ball screw inspection device of the present invention.

FIG. 2 is an exploded perspective view showing a detailed structure of the centering means of the embodiment.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is a sectional view taken along line VV of FIG. 2;

FIG. 6 is a diagram showing an example of a measurement result obtained by the device of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw shaft 2 Nut 3 Ball screw 10 Rotation driving means 20 Linear moving mechanism 21 Rail 22 Measurement carriage 23 Connecting member 30 Angle detector 40 Length measuring means 41 Reflector 42 Laser length measuring instrument 60 Aligning means 71 First member 72A End face 81 Second member 85 Displacement detector 86 Rotation angle detector 91 Third member 95 Displacement detector 96 Rotation angle detector 99 Stepping motor (rotation means) 102 Detector

Claims (6)

[Claims] 1. A ball screw inspection device for inspecting the accuracy of a ball screw having a screw shaft and a nut coupled to the screw shaft via a ball, comprising: a rotation driving means for rotating the screw shaft; A linear movement mechanism having a measurement carriage, the linear movement mechanism holding the measurement carriage movably in a direction parallel to the screw axis, and one end connected to the nut via centering means and the other end connected to the measurement carriage. A coupling member coupled thereto; an angle detection unit that detects a rotation angle of the screw shaft; and a length measurement unit that measures a moving distance of the measurement carriage, wherein the alignment unit is coupled with the nut. A first member, a second member provided to be rotatable with respect to the first member about a first axis orthogonal to the screw axis and to be movable in the first axis direction; For 2 members A third member provided rotatably about a second axis orthogonal to the screw axis and the first axis, and movable in the second axis direction, and coupled to the measuring carriage via the connecting member. A ball screw inspection device, comprising: 2. The ball screw inspection device according to claim 1, wherein the displacement detecting unit detects the amount of movement of the second member in the first axis direction and the amount of movement of the third member in the second axis direction. A detector, and a rotation angle detector for detecting a rotation angle of the second member about the first axis and a rotation angle of the third member about the second axis, respectively. A ball screw inspection device characterized by the above-mentioned. 3. The ball screw inspection device according to claim 1, wherein the first member has an end face orthogonal to the screw axis, and the connecting member has A ball screw inspection device, comprising: a squareness detector that detects a squareness of the end face with respect to the screw axis from the position of the end face in the screw axis direction. 4. The ball screw inspection device according to claim 3, wherein between the third member and the connecting member, a rotation unit for rotating the third member about the screw axis. A ball screw inspection device characterized by comprising: 5. The ball screw inspection device according to claim 1, wherein the linear movement mechanism includes a rail provided in parallel with the screw axis, and an air bearing for the rail. And a measuring carriage movably provided through the ball screw inspection device. 6. The ball screw inspection device according to claim 1, wherein the length measuring means is provided on a reflector provided on the measuring carriage and the reflector from the screw shaft axis direction. A laser length measuring device that emits laser light, receives reflected light from the reflector, and obtains a distance to the reflector.