CN107449604B

CN107449604B - Method and apparatus for measuring toothed member

Info

Publication number: CN107449604B
Application number: CN201710212975.4A
Authority: CN
Inventors: 中森美里; 诸留稔也; 木幡林太郎; 北林庆矢; 藤田哲矢
Original assignee: JTEKT Corp
Current assignee: JTEKT Corp
Priority date: 2016-04-06
Filing date: 2017-04-01
Publication date: 2021-07-16
Anticipated expiration: 2037-04-01
Also published as: JP6862636B2; CN107449604A; JP2017191087A

Abstract

The invention provides a method and a device for measuring a toothed member, which can evaluate meshing and fitting of the toothed member. The method for measuring the toothed member (9) comprises a measuring step for measuring the actual movement trajectory of the spherical body (25) when the spherical body (25) is moved along the tooth grooves (91) of the gear (9) as an index for evaluating the shape of the gear (9). When the toothed member is a VGR rack, the tooth surface (92) of the rack teeth (9) is formed by a curved surface, so that the reference pin used in OPD cannot be arranged so as to form a line contact with the tooth surface (92), and the rack teeth (9) cannot be measured, but in the case of the spherical body (25), the reference pin can be arranged so as to form a point contact with the tooth surface (92), and therefore the rack teeth (9) can be measured.

Description

Method and apparatus for measuring toothed member

Technical Field

The present invention relates to a method and an apparatus for measuring a toothed member.

Background

A rack and pinion steering apparatus is used as an apparatus for converting a rotational motion of a steering shaft into a linear motion in an axial direction of a rack shaft that couples steering wheels in order to transmit a steering force of a steering wheel to the steering wheels. In a rack and pinion mechanism, the engagement management of rack teeth is an important element in terms of controlling the engagement torque by giving a constant normal backlash to an engagement region where rack teeth formed on a rack shaft are engaged with pinion teeth formed on a pinion shaft.

The evaluation of the engagement of the rack teeth can be managed using an OPD change curve by an over pin (hereinafter, referred to as OPD) height measurement method (see japanese patent application laid-open No. 2009-264451). The OPD is a method in which reference pins suitable for rack teeth are arranged so as to be in line contact with opposing tooth surfaces in tooth spaces of the rack teeth, and the height from a reference position of a rack shaft to a measurement position of the reference pin is measured for all the tooth spaces, and the values thereof are graphed and evaluated as design values. Specifically, for example, a straight line perpendicular to the center axis of the reference pin and the center axis of the rack shaft is determined as a point intersecting the outer peripheral surface of the rack shaft and a point intersecting the outer peripheral surface of the reference pin, and the distance between the two intersection points is measured as the measurement height.

However, in recent rack and pinion steering devices, for the purpose of improving steering feeling, etc., a rack gear of variable transmission ratio (hereinafter, referred to as "VGR rack") is used in which the steering transmission ratio is changed according to the steering angle by changing each element (such as the modulus of the rack tooth, the pressure angle, etc.) of the rack tooth constituting the rack and pinion mechanism according to the position of the rack shaft in the axial direction. That is, in some steering apparatuses, a VGR rack having a rack tooth group in which a tooth surface of a rack tooth is a flat surface and a rack tooth group in which a tooth surface of a rack tooth is a curved surface is used (see japanese patent application laid-open No. 2014-210495).

In addition, a shrinkage structure is used for a steering column that wraps a steering shaft in order to absorb an impact at the time of a collision of a vehicle. The steering column includes an upper shaft extending from the steering wheel side and a lower shaft extending from the steering gear box side, and the two shafts are spline-fitted to each other. Therefore, management of the spline fitting is an important element. The evaluation of the fitting of the spline can be performed by using a BPD change curve management based on a method (feed-in pin (hereinafter, referred to as BPD)) of measuring a maximum inscribed circle diameter (maximum circumscribed circle diameter) in contact with a vertex of a pin while placing the pin in a tooth groove of an opposing spline.

The OPD can be applied to a constant gear ratio rack (hereinafter, referred to as a CGR rack) in which a transmission ratio is constant, that is, a rack in which all rack teeth have a flat tooth surface. However, in the VGR rack, the tooth surface of the rack teeth in the region of change in the gear ratio is formed of a curved surface, that is, is three-dimensionally wavy, and therefore, there is a problem that the reference pin cannot be disposed so as to be in line contact with the opposing tooth surface in the tooth grooves of the rack teeth, and the OPD cannot be used. The BPD is a measurement of a 2-point distance of a position of a tooth groove of a certain spline, and there is a problem that the fitting length of the spline cannot be evaluated over the entire circumference.

Disclosure of Invention

An object of the present invention is to provide a method and an apparatus for measuring a toothed member, which can evaluate meshing and fitting of the toothed member including a rack of a variable transmission ratio.

A method for measuring a toothed member according to an aspect of the present invention includes a measuring step of measuring an actual movement locus of a spherical body obtained by moving the spherical body along a tooth groove of the toothed member as an index for evaluating a shape of the toothed member.

Accordingly, since the toothed member is not affected by the direction of the teeth, the meshing and fitting of the toothed member can be evaluated. For example, in the case of a VGR rack, the tooth surface of the rack teeth is formed of a curved surface, and therefore, the reference pin used in the OPD cannot be disposed so as to be in line contact with the tooth surface, and the measurement of the rack teeth cannot be performed. In the case of a spline, fitting over the entire circumference can be evaluated within the fitting length of the spline by rotating the ball along the tooth grooves of all splines.

Drawings

The above and other features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof, which proceeds with reference to the accompanying drawings, wherein like reference numerals represent like elements, and wherein,

fig. 1 is a schematic view of the entire steering system of an automobile including rack teeth and splines that can be applied to the method of measuring a toothed member according to the embodiment of the present invention.

Fig. 2 is an axial sectional view of a shaft body of the steering column of fig. 1.

Fig. 3 is a pinion axial sectional view of the rack and pinion steering apparatus of fig. 1.

Fig. 4 is a plan view illustrating a rack of the rack and pinion steering apparatus of fig. 1.

Fig. 5 is a view showing a measuring device for a toothed member and rack teeth in the embodiment of the present invention.

Fig. 6 is a flowchart for explaining an operation when the rack teeth are measured by the measuring device of the toothed member.

Fig. 7 is a flowchart for explaining the operation of the measuring apparatus for measuring a toothed member.

Fig. 8 is a perspective view for explaining a method of determining the Y-axis direction in the tooth grooves of the rack teeth.

Fig. 9 is a perspective view for explaining a method of determining an origin in a tooth slot of a rack tooth.

Fig. 10 is a perspective view for explaining a method of determining the X-axis and Z-axis directions in the tooth grooves of the rack teeth.

Fig. 11 is a perspective view for explaining a method of determining an error between an actual movement trajectory and a designed trajectory in the Z-axis direction in the tooth grooves of the rack teeth.

Fig. 12 shows the result of measurement of a defective rack by the measuring device for a toothed member, in which the error between the actual movement locus and the design locus is shown on the vertical axis and the axial position of the rack teeth is shown on the horizontal axis.

Fig. 13 is a diagram showing torque generated by a rack and pinion steering apparatus having an unacceptable rack on the vertical axis and axial positions of rack teeth on the horizontal axis.

Fig. 14 shows the result of measurement of an acceptable rack by the measuring device for a toothed member, in which the error between the actual movement locus and the design locus is shown on the vertical axis and the axial position of the rack teeth is shown on the horizontal axis.

Fig. 15 is a diagram showing the torque generated by the rack and pinion steering apparatus having an acceptable rack on the vertical axis and the axial position of the rack teeth on the horizontal axis.

Fig. 16 is a view showing a measuring device for a toothed member and a radially inner spline according to an embodiment of the present invention.

Fig. 17 is a flowchart for explaining an operation when the radially inner spline is measured by the toothed member measuring device.

Fig. 18 is a shaft body axial cross-sectional view of the upper shaft for explaining a method of determining the Y-axis direction, the X-axis direction, and the Z-axis direction in the tooth grooves of the radially inner spline.

Fig. 19 is a view of the upper shaft of fig. 18 viewed axially from the shaft.

Fig. 20 is a sectional view of the shaft body of the upper shaft in the axial direction for explaining a method of determining a radius error based on an actual movement locus and a design locus in the tooth grooves of the radially inner spline.

Fig. 21 is a view of the upper axis as viewed from the axial direction of the shaft to explain a method of determining a phase error based on an actual movement trajectory and a design trajectory in the tooth grooves of the radially inner spline.

Fig. 22 shows the result of measurement of the defective upper shaft by the measuring device for the toothed member, in which the radius error is shown on the vertical axis and the axial position of the spline is shown on the horizontal axis.

Fig. 23 shows the result of measurement of the failed upper axis by the toothed member measuring device, where the phase error is shown on the vertical axis and the axial position of the spline is shown on the horizontal axis.

Fig. 24 shows the result of measurement of an acceptable upper axis by the measuring device for the toothed member, where the vertical axis shows the radius error and the horizontal axis shows the axial position of the spline.

Fig. 25 is a graph showing the phase error on the vertical axis and the axial position of the spline on the horizontal axis, as a result of measuring the acceptable upper axis by the measuring device for the toothed member.

FIG. 26 is a diagram for explaining a sphere height of a sphere of the measuring apparatus with a toothed member.

Detailed Description

As a toothed member to which the method of measuring a toothed member according to one embodiment of the present invention can be applied, a rack shaft having rack teeth and a steering shaft having splines will be described as an example, but the present invention is not limited to rack teeth and splines. A steering system of an automobile having rack teeth and splines will be described with reference to the accompanying drawings.

As shown in fig. 1, the steering system of an automobile includes a steering wheel 1 operated by a driver, a steering shaft 2 coupled to the steering wheel 1, a steering column 15 that encloses the steering shaft 2, a rack and pinion steering device 14, an intermediate shaft 3 that connects the steering shaft 2 and the rack and pinion steering device 14, and steered

wheels

7a and 7b coupled to the tip of the rack and pinion steering device 14.

The steering column 15 includes an upper shaft 16 extending from the steering wheel 1 side and a lower shaft 17 extending from the steering gear box GB side. As shown in fig. 2, the upper shaft 16 and the lower shaft 17 are fitted to an outer diameter spline 19 provided on the lower shaft 17 via a radially inner spline 18 provided on the upper shaft 16. Thereby, the upper shaft 16 and the lower shaft 17 are configured to be contractible, and can absorb the impact at the time of vehicle collision. In fig. 1, the components surrounding the steering shaft 2 are omitted.

The rack and pinion steering system 14 includes a pinion shaft 4 as an input shaft, a rack shaft 5 (shaft-like member) as an output shaft, and a rack housing 10 and the like that house the shafts.

Inner balls

6a and 6b are coupled to both ends of the rack shaft 5. As shown in fig. 3, rack teeth 9 are formed on the rack shaft 5, and pinion teeth 8 that mesh with the rack teeth 9 are formed on the pinion shaft 4.

The rack shaft 5 is engaged with the pinion shaft 4 via a rack guide 11, a spring 12, and a guide plug 13 disposed on the opposite side of the pinion shaft 4 in the rack housing 10. That is, the rack guide 11 is housed in the rack housing 10 so as to be movable in a direction perpendicular to the center axis Lr of the rack shaft 5 and the center axis Lp of the pinion shaft 4. The rack guide 11 has one end side (upper side in the drawing) in the moving direction abutting against a circumferential surface (circular arc outer circumferential surface) of the rack shaft 5 on the opposite side to the pinion shaft 4, and the other end side (lower side in the drawing) in the moving direction facing a guide plug 13 screwed into the rack housing 10 with a slit.

Further, the spring 12 is interposed between the rack guide 11 and the guide plug 13. Thereby, the rack shaft 5 is pressed against the pinion shaft 4 by the elastic force of the spring 12. By this pressing, the pinion teeth 8 and the rack teeth 9 mesh in a seamless state, and the rack shaft 5 does not separate from the pinion shaft 4 even if the pinion shaft 4 is rotated by steering.

The rack shaft 5 is supported by a rack bush, not shown, having lubricating properties, disposed on the inner peripheral surface of the rack housing on the 2 nd end side of the rack housing 10, and a meshing portion between the rack teeth 9 and the pinion teeth 8 disposed on the 1 st end side of the rack housing 10. Thereby, the rack shaft 5 is configured to be able to move smoothly in the axial direction without coming into direct contact with the rack housing 10.

In the steering system of the automobile configured as described above, the steering force applied to the steering wheel 1 by the driver is transmitted from the steering shaft 2 to the rotational force of the pinion shaft 4 via the intermediate shaft 3. The rotational force of the pinion shaft 4 is converted into an axial force of the rack shaft 5, and is transmitted from the

inner balls

6a and 6b coupled to both ends of the rack shaft 5 to the steered

wheels

7a and 7 b. Further, even if the pinion shaft 4 is rotated by the steering operation, the rack shaft 5 does not come off the pinion shaft 4, and therefore, a stable steering operation with high rigidity can be performed.

The rack and pinion steering device 14 uses a VGR rack in which each element (such as the modulus and pressure angle of the rack teeth 9) of the rack teeth 9, which is a VGR rack in which the steering gear ratio is changed according to the steering angle, differs depending on the axial position of the rack shaft 5.

As shown in fig. 4, the center portion (the vicinity of the steering neutral position) and both end portions of the rack shaft 5 of the VGR rack are formed as the regions where the gear ratio is constant, which are the 1 st rack tooth groups 9Pa, 9Pb, and 9Pc whose tooth surfaces 92 are flat, and the portions sandwiched between the center portion and both end portions of the rack shaft 5 are formed as the regions where the gear ratio is changed, which are the 2 nd rack tooth groups 9Ca and 9Cb whose tooth surfaces 92 are curved surfaces. The VGR rack is not formed by cutting (broaching, hobbing) as in the CGR rack but by forging, and therefore, a crowning (crown) is formed at the tooth tip 93 of the rack tooth 9. Further, a tooth space 91 is formed between the opposing tooth surfaces 92, 92 of the adjacent rack teeth 9.

Next, a measuring apparatus for a toothed member according to an embodiment of the present invention will be described with reference to the drawings. As shown in fig. 5, the toothed member measuring device 20 includes a measuring device 21, a designed trajectory acquiring device 22, a designed trajectory storage device 23, and an arithmetic device 24. The measuring device 21 includes a probe 26 having a sphere 25 at a tip end thereof, a moving device 27 for moving the probe 26 in a direction orthogonal to the 3-axis (X-axis, Y-axis, Z-axis), and the like, and in this example, the measuring device 21 is a three-dimensional measuring machine having a groove profiling function. The gear measuring device 20 is capable of measuring the rack teeth 9 and the radially inner spline 18, and first, the measurement of the rack teeth 9 will be described, and next, the measurement of the radially inner spline 18 will be described.

When the rack teeth 9 are measured by the toothed member measuring device 20, the spherical body 25 is formed to have a diameter that can contact the opposed tooth surfaces 92 of the rack teeth 9, which form the tooth grooves 91. The measuring device 21 measures a movement trajectory of a center point Bc of the moving ball 25 (hereinafter, referred to as an actual movement trajectory) as a shape evaluation index of the rack teeth 9 when the ball 25 is moved along the tooth grooves 91 while arranging the ball 25 in point contact with the opposing tooth surfaces 92 of the tooth grooves 91 of the rack teeth 9 to be measured.

The reason why the spherical body 25 is used is as follows. On the other hand, the center axis when the reference pin used in the OPD is disposed so as to be in line contact with the tooth surface facing the tooth space of the rack teeth of the CGR rack is a set of points. On the other hand, the locus of the center point Bc of the spherical body 25 when the spherical body 25 is disposed in point contact with the tooth surface point facing the tooth space of the rack teeth of the CGR rack and moved along the tooth space is also a set of points. In the case of the VGR rack, the tooth surface 92 of the rack teeth 9 is formed of a curved surface, and therefore, the reference pin cannot be disposed in line contact with the tooth surface 92, and the rack teeth 9 cannot be measured, but the spherical body 25 can be disposed in point contact with the tooth surface 92, and therefore, the rack teeth 9 can be measured.

The design locus obtainment means 22 obtains design data on the tooth grooves 91 of the rack teeth 9 in the design. The design trajectory acquisition device 22 acquires a movement trajectory of the center point Bc of the spherical body 25 when the spherical body 25 is moved along the tooth grooves 91 of the acquired design data (hereinafter, referred to as a design trajectory). The design trajectory storage means 23 stores the design trajectory acquired by the design trajectory acquisition means 22. The calculation device 24 calculates an error between the actual movement trajectory measured by the measurement device 21 and the design trajectory stored in the design trajectory storage device 23.

Next, the operation of the toothed member measuring device 20 for measuring the rack teeth 9 will be described with reference to the drawings. This measurement needs to be performed individually for all the rack teeth 9 formed in the rack shaft 5, but in the following description, as shown in fig. 8, a case of measuring a tooth space 91a between

tooth surfaces

92a, 92b of

rack teeth

9a, 9b belonging to the 2 nd rack tooth group among the rack teeth 9 that effectively mesh with pinion teeth 8 (see fig. 3) will be described. The design trajectory acquisition means 22 is a means that acquires a design trajectory, which is a movement trajectory of the center point Bc of the spherical body 25 when the spherical body 25 moves along the tooth grooves 91 of the rack teeth 9 in the design, and stores the acquired design trajectory in the design trajectory storage means 23.

First, the measuring device 21 measures the contact position by bringing the spherical body 25 into contact with a plurality of phase positions of a first cylindrical portion, which will be described later, of the rack shaft 5 (step S1 in fig. 6), and measures the contact position by bringing the spherical body 25 into contact with a plurality of phase positions of a second cylindrical portion, which will be described later, of the rack shaft 5 (step S2 in fig. 6). Then, the Y-axis direction of the tooth groove 91a to be measured is determined based on each measured contact position (step S3 in fig. 6).

Specifically, as shown in fig. 8, the ball 25 is brought into contact with, for example, 3 phase positions P1, P2, and P3 of the second cylindrical portion U1 of the rack shaft 5 including the rack teeth 9a having the tooth surface 92a, and the contact position is measured. Similarly, the contact positions are measured by bringing the spherical body 25 into contact with, for example, 3 phase positions P4, P5, and P6 of the first cylindrical portion U2 of the rack shaft 5 including the rack teeth 9b having the tooth surface 92 b. Then, the center point T1 of the circle passing through the phase positions P1, P2, and P3 is obtained, the center point T2 of the circle passing through the phase positions P4, P5, and P6 is obtained, and the direction of the straight line L1 passing through the center points T1 and T2 is determined as the Y-axis direction of the slot 91 a.

The measuring device 21 determines a reference point of the tooth groove 91a, which will be described later, based on the measurement of the circular outer peripheral surface of the rack shaft 5 located on the opposite side of the tooth groove 91a, and sets the determined reference point of the tooth groove 91a as the origin. That is, the Y-axis coordinate value is measured by bringing the spherical body 25 into contact with the center of the tooth trace ( す movement, japanese) of the tooth groove 91a (step S4 in fig. 6). Then, the ball 25 is brought into contact with a plurality of positions on the surface of the rack shaft 5 opposite to the tooth grooves 91a in the Y-axis coordinate values thus measured, the contact positions are measured (step S5 in fig. 6), and the origin of the tooth grooves 91a is determined (step S6 in fig. 6).

Specifically, as shown in fig. 9, the Y-axis coordinate value of the center position Pa in the tooth trace direction of the tooth groove 91a is measured by the spherical body 25. Then, 3 positions Q1, Q2 and Q3 on the outer peripheral edge Q cut by a plane Sxz perpendicular to the Y axis direction at the measured central position Pa of the rack shaft 5 are measured by the ball 25, the arc center Qc of the outer peripheral edge Q, which is a reference point, is obtained from the measurement positions Q1, Q2 and Q3, and the obtained arc center Qc is determined as the origin of the tooth groove 91 a.

The measuring device 21 measures the contact position by bringing the ball 25 into contact with the

tooth tips

93a and 93b (see fig. 10) at the 2-position of the clamping tooth groove 91a (step S7 in fig. 7), and determines the X-axis direction and the Z-axis direction (two-dimensional coordinate system) of the tooth groove 91a based on the measured tooth tip positions (step S8 in fig. 7).

Specifically, as shown in fig. 10, 2 positions Pb and Pc on one end side and the other end side in the tooth trace direction of the tooth crests 93a and 93b at 2 positions with the tooth grooves 91a interposed therebetween are measured by the balls 25, and a straight line Lp1 passing through the 2 positions Pb and Pc is projected on a plane S perpendicular to the Y axis. Then, the direction of the projected straight line Lpp is determined as the X-axis direction of the tooth groove 91a, and the direction perpendicular to the determined X-axis direction and Y-axis direction is determined as the Z-axis direction.

The measuring device 21 moves the ball 25 along the slot 91a (step S9 in fig. 7), and measures the actual movement trajectory of the ball 25 in the slot 91a in the coordinate system (X, Y, Z) of the slot 91a (step S10 in fig. 7). Then, the arithmetic unit 24 calculates an error in the Z-axis direction between the actual movement trajectory measured by the measuring unit 21 and the design trajectory stored in the design trajectory storage unit 23 (step S11 in fig. 7 corresponds to the arithmetic step of the present invention), and ends the processing.

Specifically, as shown in fig. 11, the actual movement locus Rp measured by the measuring device 21 is curved as shown by the solid line, and the designed locus Rd acquired by the designed locus acquiring device 22 is curved as shown by the broken line, and therefore the errors in the Z-axis direction are obtained.

Fig. 12 shows an error between the actual movement path Rp and the design path Rd on the vertical axis, and an axial position of the rack teeth 9 on the horizontal axis, and shows a result of measurement of one of the rack shafts 5 by the measuring device 20 for the rack teeth 9. As can be seen from fig. 12, the error between the actual movement locus Rp and the design locus Rd of the rack shaft 5 greatly changes in the vicinity of the 2 nd rack tooth group 9Cb (the portion E surrounded by the circular shape of the dotted line).

In the case of the rack and pinion steering device 14 including the rack shaft 5, as shown in fig. 13, a torque surge phenomenon occurs in the vicinity of the 2 nd rack tooth group 9Cb (a portion E surrounded by a circular shape shown by a broken line). The rack shaft 5 was found to be defective. Fig. 13 shows a case where the pinion teeth 8 are reciprocated in the axial direction of the rack teeth 9.

On the other hand, fig. 14 is a view corresponding to fig. 12, and shows the result of measurement of the other rack shaft 5 by the measuring device 20 of the rack teeth 9. As can be seen from fig. 14, the error between the actual movement locus Rp and the design locus Rd of the rack shaft 5 does not change significantly. In the case of the rack and pinion steering device 14 including the rack shaft 5, as shown in fig. 15 corresponding to fig. 13, a phenomenon of torque surge does not occur, and a substantially constant torque is obtained. The rack shaft 5 was judged to be acceptable.

As described above, it was found that the measurement result (trajectory error) of the measurement device 20 for the rack teeth 9 according to the present embodiment is correlated with the gear performance (torque waveform) of the rack and pinion steering system 14. Therefore, the measurement device 20 of the rack teeth 9 of the present embodiment can evaluate meshing of the VGR rack. In addition, since the barrel shape position and magnitude of the rack teeth 9 can be digitalized and visualized, it is possible to reflect the manufacturing conditions including plastic working.

Next, a method of using the method of measuring a toothed member according to one embodiment of the present invention for measuring a radially inner spline will be described. As shown in fig. 16, when the radial inner spline 18 is measured by the toothed member measuring device 20, the spherical body 25 is formed to have a diameter that can contact the opposed tooth surfaces 82 of the radial inner spline 18, which form the tooth grooves 81. The measuring device 21 is configured to arrange the spherical body 25 in point contact with the tooth surface 82 facing the tooth groove 81 of the radially inner spline 18 to be measured at the same time, and measure a movement locus (hereinafter, referred to as an actual movement locus) of the center point Bc of the moving spherical body 25 as a shape evaluation index of the radially inner spline 18 when the spherical body 25 moves along the tooth groove 81.

The design locus obtainment means 22 obtains design data on the tooth grooves 81 of the radially inner spline 18 on the design. The design trajectory acquisition device 22 acquires a movement trajectory of the center point Bc of the spherical body 25 (hereinafter, referred to as a design trajectory) when the spherical body 25 is moved along the gullets 81 of the acquired design data. The design trajectory storage means 23 stores the design trajectory acquired by the design trajectory acquisition means 22. The calculation device 24 calculates a radius error and a phase error, which will be described later, based on the actual movement trajectory measured by the measurement device 21 and the design trajectory stored in the design trajectory storage device 23.

Next, the operation of the toothed member measuring device 20 for measuring the radially inner spline 18 will be described with reference to the drawings. This measurement needs To be performed for all the radially inner splines 18 formed on the upper shaft 16 one by one within an effective fitting length (see fig. 18), that is, within a range of the effective fitting length T from the start end To of the radially inner spline 18 in the axial direction. The design trajectory acquisition device 22 is a device that acquires a design trajectory that is a movement trajectory of the center point Bc of the spherical body 25 when the spherical body 25 is moved within the effective fitting length T (see fig. 18) along the full spline 81 of the radially inner spline 18 in the design, and stores the acquired design trajectory in the design trajectory storage device 23.

First, the measuring device 21 brings the ball 25 into contact with the tooth crests 83 (see fig. 16) of the plurality of radially inner splines 18 at a predetermined axial position on the inner periphery of the upper shaft 16, and measures the contact position (step S21 in fig. 17). Next, the ball 25 is brought into contact with the tooth crests 83 of the plurality of radially inner splines 18 at an axial position of the inner periphery of the upper shaft 16 different from the previous axial position, and the contact position is measured (step S22 of fig. 17). Then, the Y-axis direction is determined based on each contact position, and the X, Z-axis direction (three-dimensional coordinate system) is determined (step S23 in fig. 17).

Specifically, as shown in fig. 18 and 19, the ball 25 is brought into contact with the tooth crest 83 of the radially inner spline 18 at a predetermined axial position Y1, for example, 3 phase positions V1, V2, and V3, within the effective fitting length of the radially inner spline 18, and the contact position is measured. Similarly, the contact position is measured by bringing the predetermined axial position Y2 of the ball 25 within the effective fitting length of the radially inner spline 18 into contact with the tooth crest 83 of the radially inner spline 18 at the 3 phase positions V1, V2, and V3 that are the same as before.

Then, the center C1 of the circle B1 passing through the phase positions V1, V2, and V3 at the axial position Y1 and the center C2 of the circle B2 passing through the phase positions V1, V2, and V3 at the axial position Y2 are obtained, and the direction of the straight line L11 passing through the centers C1 and C2 is determined as the Y-axis direction of the tooth grooves 81 of the radially inner spline 18. On a plane H perpendicular to the line L11, a line L12 extending in the horizontal direction is determined as the X-axis direction of the slot 81, and a line L13 perpendicular to the line L11 and the line L12 is determined as the Z-axis direction of the slot 81.

The measuring device 21 moves the ball 25 along each spline groove 81 of the radially inner spline 18 within the effective fitting length (step S24 in fig. 17), and measures the actual movement locus of the ball 25 at each spline groove 81 in the coordinate system (X, Y, Z) of each spline groove 81 (step S25 in fig. 17). Then, the arithmetic unit 24 calculates the radial error and the phase error based on the actual movement trajectory measured by the measuring unit 21 and the design trajectory stored in the design trajectory storage unit 23 (step S26 in fig. 17 corresponds to the arithmetic step of the present invention), and ends the processing.

Specifically, as shown in fig. 20, since the actual movement trajectory Wp measured by the measuring device 21 is shown by a solid line and the designed trajectory Wd acquired by the designed trajectory acquiring device 22 is shown by a broken line, the error between the distance between the actual movement trajectory Wp and the straight line L11 and the distance between the designed trajectory Wd and the straight line L11 is determined as the radius error.

As shown in fig. 21, when the phase of a straight line k1 passing through the actual movement trajectory Wp and the straight line L11 at the tooth groove 81a located at the leading end To of the radially inner spline 18 is 0, the phase of a straight line k2 passing through the actual movement trajectory Wp and the straight line L11 at the tooth groove 81b adjacent To the tooth groove in the counterclockwise direction is defined as θ 1 with respect To the straight line k1, and the phase of a straight line k3 passing through the actual movement trajectory Wp and the straight line L11 at the tooth groove 81c adjacent To the tooth groove 81c in the counterclockwise direction is defined as θ 2 with respect To the straight line k2, and the phases of all the

tooth grooves

81a, 81b, and 81c … are obtained as actual phases within the effective fitting length. On the other hand, the phases of all the

slots

81a, 81b, 81c … are also found as the design phases within the effective fitting length for the design trajectory Wd in the same order. Then, the error between the actual phase and the design phase is obtained as a phase error.

Fig. 22 shows the radial error on the vertical axis and the axial position of the tooth groove 81 of the radially inner spline 18 on the horizontal axis, and shows the result of measurement of the tooth groove 81a by the toothed member measurement device 20. As can be seen from fig. 22, the radius error of the radially inner spline 18 exceeds the allowable value- Δ r in a range from a position advanced by the length T1T in the axial direction starting from the start end To of the radially inner spline 18 To the length T (the portion E1 surrounded by the circle shown by the broken line).

Fig. 23 shows a phase error on the vertical axis and an axial position of the tooth groove 81 of the radially inner spline 18 on the horizontal axis, and shows a result of measurement of the tooth groove 81a by the toothed member measurement device 20. As can be seen from fig. 23, the phase error of the radially inner spline 18 exceeds the allowable value- Δ θ in a range from a position advanced by the length T2T in the axial direction starting from the start end To of the radially inner spline 18 To the length T (the portion E2 surrounded by the circle shown by the broken line). In the case of the steering column 15 including such radially inner splines 18, the sliding resistance during contraction becomes large, and it is found that the radially inner splines 18 are defective.

On the other hand, fig. 24 is a view corresponding to fig. 22, and shows the result of measurement of the other radially inner spline 18 by the toothed member measuring device 20. As can be seen from fig. 24, the radius error of the radially inner spline 18 does not change significantly. Fig. 25 is a view corresponding to fig. 23, and shows the result of measurement of the other radially inner spline 18 by the toothed member measuring device 20. As can be seen from fig. 25, the phase error of the radially inner spline 18 does not change greatly. In the case of the steering column 15 including the radially inner spline 18, the sliding resistance during contraction does not increase, and the radially inner spline 18 is determined to be acceptable.

In the above embodiment, the measurement device 21 is configured to measure the movement locus of the center point Bc of the sphere 25, but may be configured to measure the movement locus of the sphere high point of the sphere 25. As shown in fig. 25, the sphere high point Bo of the sphere 25 is a point where a straight line Lz perpendicular to the central axis Lr of the rack shaft 5, that is, a straight line Lz passing through the center point Bc of the sphere 25 located in the slot 91 intersects with the outer peripheral surface of the sphere 25 on the opposite side of the slot 91. The same applies to the case of the radially inner spline 18.

In the measurement step (measurement device 21), the rack teeth 9 are measured in an orthogonal 2-axis coordinate system (X, Z) in a three-dimensional coordinate system, but may be measured in a circular coordinate system (polar coordinates). The radially inner spline 18 is measured in an orthogonal 3-axis coordinate system (X, Y, Z) in a three-dimensional coordinate system, but may be measured in a cylindrical coordinate system (one kind of polar coordinate system).

The measuring device 21 is a three-dimensional measuring machine having a groove profiling function, but may be a shape measuring machine, an optical measuring machine, or the like having a function of outputting all the point coordinate values subjected to profiling measurement in 2 or more directions. In addition, although the measurement of the VGR rack is described, the CGR rack can be measured similarly. Further, the measurement of the radially inner spline 18 is described, but the radially outer spline 19 can be measured similarly. In addition, a helical gear and a bevel gear can be measured in the same manner.

Next, the effects of the present embodiment will be described. The method of measuring the toothed members (rack teeth 9, radially inner splines 18) according to the present embodiment includes a measuring step of measuring actual movement trajectories Rp, Wp of the balls 25 after the balls 25 move along the

tooth grooves

91, 81 of the toothed members (rack teeth 9, radially inner splines 18) as an index for evaluating the shape of the toothed members (rack teeth 9, radially inner splines 18).

Accordingly, since the toothed member is not affected by the direction of the teeth, the meshing and fitting of the toothed member can be evaluated. For example, in the case of a VGR rack, since the tooth surface 92 of the rack teeth 9 is formed of a curved surface, the reference pin used in the OPD cannot be disposed so as to be in line contact with the tooth surface 92, and the rack teeth 9 cannot be measured, but in the case of the spherical body 25, the reference pin can be disposed so as to be in point contact with the tooth surface 92, and therefore the rack teeth 9 can be measured. In the case of the radially inner spline 18, fitting over the entire circumference can be evaluated within the fitting length L of the radially inner spline 18 by rotating the ball 25 along all the tooth grooves 81.

In the measurement step, since the actual movement trajectory of the center point Bc of the sphere 25 is measured, the movement state of the sphere 25 can be easily measured. In the measurement step, since the actual movement trajectory of the sphere high point Bo of the sphere 25 is measured, the same evaluation as that of the OPD using the reference pin can be performed.

The method for measuring the toothed members (rack teeth 9, radially inner spline 18) includes an acquisition step of acquiring design trajectories Rd, Wd which are trajectories of the spherical body 25 when the spherical body 25 moves along the

tooth grooves

91, 81 of the designed gear (rack teeth 9, radially inner spline 18), and a calculation step of calculating an error between the actual trajectories Rp, Wp measured in the measurement step and the design trajectories Rd, Wd acquired in the acquisition step. This makes it possible to determine whether or not the toothed members (the rack teeth 9 and the radially inner spline 18) are good.

In the case where the toothed member is the rack shaft 5 on which the rack teeth 9 are formed, the reference point (arc center Qc) of each tooth groove 91 is determined based on the measurement of the arc outer peripheral surface (outer peripheral edge Q) of the rack shaft 5 on the opposite side of the tooth groove 91 of each rack tooth 9 in the measurement step, and the actual movement locus Rp of the ball 25 at each rack tooth 9 is measured with the determined reference point of each tooth groove 91 as the origin, so that the measurement accuracy of the actual movement locus Rp of the ball 25 can be improved.

In the measurement step, when the axial direction of the rack shaft 5 is defined as the Y axis, a two-dimensional coordinate system of a plane orthogonal to the Y axis with respect to each tooth groove 91 is determined based on the measurement of the tooth crest 93 of each rack tooth 9, and the actual movement locus Rp of the ball 25 with respect to each rack tooth 9 is measured in the determined two-dimensional coordinate system with respect to each tooth groove 91, so that the measurement accuracy of the actual movement locus Rp of the ball 25 can be further improved. Further, in the case where the toothed member is the rack shaft 5 in which the rack teeth 9 are formed, since the toothed member measurement method is applied to a rack shaft in which the gear ratio changes in the axial direction of the rack shaft 5, the rack teeth 9 can be directly evaluated, and the measurement accuracy can be improved as compared with the conventional rack measurement method.

Further, in the case where the toothed member is a member in which the radially inner splines 18 are formed, the three-dimensional coordinate system of the tooth grooves 81 for each radially inner spline 18 is determined based on the measurement of the tooth crests 83 of each radially inner spline 18 in the measurement step, and the actual movement locus Wp of the spherical body 25 for each radially inner spline 18 is measured in the determined three-dimensional coordinate system, so that the measurement accuracy of the actual movement locus Wp of the spherical body 25 can be further improved.

The measuring device 20 for the toothed members (rack teeth 9, radially inner spline 18) that measures the shapes of the

tooth grooves

91, 81 of the toothed members (rack teeth 9, radially inner spline 18) according to the present embodiment includes the measuring device 21 that measures the actual movement locus of the moved ball 25 as the shape evaluation index of the toothed members (rack teeth 9, radially inner spline 18) when the ball 2 is moved along the tooth grooves 91, 815 of the toothed members (rack teeth 9, radially inner spline 18). The measuring device 20 for the toothed members (rack teeth 9, radially inner spline 18) includes a storage device 23 that stores a design locus, which is a moving locus of the spherical body 25 when the spherical body 25 moves along the

tooth grooves

91, 81 of the designed toothed member (rack teeth 9, radially inner spline 18), and a computing device 24 that computes an error between an actual moving locus measured by the measuring device 21 and the design locus stored in the storage device 23. This can provide the same effects as those obtained by the method for measuring the toothed members (rack teeth 9, radially inner spline 18).

This application claims priority from Japanese patent application 2016-.

Claims

1. A method of determining a toothed member, comprising the steps of:

rolling a sensing ball along a tooth slot of a toothed member such that the ball simultaneously contacts two opposing tooth surfaces of the tooth slot, the toothed member being a rack tooth formed on a shaft-like member;

measuring an actual movement trajectory of the ball at a center point of the ball as the ball rolls along the tooth grooves of the toothed member, the actual movement trajectory is an index for evaluating the shape of the toothed member, the reference point of each tooth slot is determined based on measurement of an arc-shaped outer peripheral surface of each toothed slot of each toothed rack of the toothed member on the opposite side of the tooth slot, measuring an actual movement locus of the ball for each of the rack teeth by setting the determined reference point of each of the tooth grooves as an origin, and when the axial direction of the shaft-like member is determined as the Y axis, a two-dimensional coordinate system of a plane orthogonal to the Y axis for each tooth slot is provided based on the measurement of the tooth tip of each rack tooth of the toothed member, measuring an actual movement locus of the ball for each of the rack teeth in the set two-dimensional coordinate system;

acquiring a design locus which is a moving locus of the ball when the ball is moved along the tooth grooves of the toothed member in design; and

an error between the measured actual movement trajectory and the acquired design trajectory is calculated.

2. The method for determining a toothed member according to claim 1,

in the measuring step, an actual movement locus of the sphere high point of the sphere is measured.

3. The toothed member measuring method according to claim 1 or 2,

the method of determining the toothed member is applied to a rack shaft having a gear ratio that varies in the axial direction.

4. A measuring device for a toothed member, which measures the shape of tooth grooves of the toothed member,

the measuring device of the toothed member is characterized in that,

a measuring ball configured to roll along the tooth grooves of the toothed member such that the ball simultaneously contacts two opposite tooth surfaces of the tooth grooves, the toothed member being rack teeth formed on a shaft-like member;

a measuring device configured to measure an actual movement locus of the ball at a center point of the ball when the ball rolls along the tooth grooves of the toothed member, the actual movement locus being a shape evaluation index of the toothed member, a reference point of each tooth groove being determined based on measurement of an arc outer peripheral surface on an opposite side of each tooth groove of each rack tooth of the toothed member, measure the actual movement locus of the ball for each rack tooth by setting the determined reference point of each tooth groove as an origin, and set a two-dimensional coordinate system of a plane orthogonal to a Y axis for each tooth groove based on measurement of an tooth top of each rack tooth of the toothed member when an axial direction of the shaft-like member is determined as the Y axis, measuring an actual movement locus of the ball for each of the rack teeth in the set two-dimensional coordinate system;

a design locus obtaining device configured to obtain a design locus that is a moving locus of the spherical body in a case where the spherical body is moved along the tooth grooves of the toothed member on the design; and

an arithmetic device configured to calculate an error between the measured actual movement trajectory and the acquired design trajectory.

5. The toothed member measuring device according to claim 4,

the toothed member measuring apparatus is characterized by comprising:

a design trajectory storage device that stores the design trajectory.