JP6862636B2 - Gear measuring method and measuring device - Google Patents

Description

The present invention relates to a gear measuring method and a measuring device.

The rack and pinion type steering device is used as a device that converts the rotational motion of the steering shaft into a linear motion in the axial direction of the rack shaft to which the steering wheels are connected in order to transmit the steering force of the steering wheel to the steering wheels. .. In the rack and pinion mechanism, the meshing torque of the rack teeth is controlled by giving a constant backlash to the meshing region between the rack teeth formed on the rack shaft and the pinion teeth formed on the pinion shaft. Is a very important factor.

For the evaluation of the meshing in the rack teeth, the OPD change curve management by the overpin height measurement method (hereinafter referred to as OPD) is used (see Patent Document 1). In this OPD, a reference pin suitable for the rack tooth is arranged so as to make line contact with the facing tooth surface in the tooth groove of the rack tooth, and the height from the reference position of the rack shaft to the measurement position of the reference pin is measured. This is a method in which processing is performed on all tooth grooves, and those values are graphed and evaluated as design values. Specifically, for example, the point where the straight line perpendicular to the central axis of the reference pin and the central axis of the rack axis intersects the outer peripheral surface of the rack axis and the point where the outer peripheral surface of the reference pin intersects are obtained, and the distance between the two intersections is measured. Measure as height.

By the way, in recent rack and pinion type steering devices, for the purpose of improving the steering feeling, the specifications of the rack teeth (the module of the rack teeth, the pressure angle, etc.) constituting the rack and pinion mechanism are set to the axis of the rack axis. A rack with a variable gear ratio (hereinafter referred to as a VGR rack) that changes the steering gear ratio according to the steering angle by changing the steering gear ratio depending on the direction position may be used. That is, as the steering device, a VGR rack having a rack tooth group in which the tooth surface of the rack tooth is flat and a rack tooth group in which the tooth surface of the rack tooth is curved may be used. (See Patent Document 2).

Further, the steering column including the steering shaft uses a contraction structure for the purpose of absorbing impact when a vehicle collides. This steering column includes an upper shaft extending from the steering wheel side and a lower shaft extending from the steering gear box side, and both shafts are fitted by splines. Therefore, the management of fit in this spline is a very important factor. To evaluate the fit in the spline, place the pin in the tooth groove of the opposite spline and measure the maximum inscribed circle diameter (maximum circumscribed circle diameter) that contacts the apex of the pin (Vitoin pin method (hereinafter referred to as BPD)). BPD change curve management by is used.

JP-A-2009-264451 Japanese Unexamined Patent Publication No. 2014-210495

The above-mentioned OPD is applicable to a rack having a constant gear ratio (hereinafter referred to as a CGR rack) having a constant gear ratio, that is, a rack in which the tooth surfaces of all rack teeth are flat. However, in the VGR rack, the tooth surface of the rack tooth in the region where the gear ratio changes is composed of a curved surface, that is, it is three-dimensionally undulated, so that the reference pin is arranged in line contact with the facing tooth surface in the tooth groove of the rack tooth. There is a problem that the OPD cannot be used because it cannot be used. Further, the above-mentioned BPD is a measurement of the distance between two points at the position of the tooth groove of a certain spline, and there is a problem that the fitting over the entire circumference within the fitting length of the spline cannot be evaluated.

An object of the present invention is to provide a gear measuring method and a measuring device capable of evaluating gear meshing and fitting.

In order to solve the above problems, the gear measuring method of the present invention simultaneously makes point contact with opposite tooth surfaces in the tooth grooves of a gear having a plurality of tooth grooves provided in parallel and discontinuously provided with each other. when the placed balls to was moved along the tooth groove, a measuring step of measuring the actual movement locus of the center point or over the ball point of the ball as the shape evaluation index before Symbol gears, design A design that is a movement locus of a center point or an overball point of the ball when a ball arranged so as to make point contact with the opposing tooth surfaces at the same time is moved along the tooth groove in the tooth groove of the gear. It includes an acquisition step of acquiring a locus, and a calculation step of calculating an error between the actual movement locus measured in the measurement step and the design locus acquired in the acquisition step .

According to this, since it is not affected by the orientation of the teeth of the gear, it is possible to evaluate the meshing and fitting of the gear. For example, in the case of a VGR rack, since the tooth surface of the rack tooth is composed of a curved surface, the reference pin used in OPD cannot be arranged on the tooth surface by line contact, and the rack tooth cannot be measured, but with a ball. If there is, it can be arranged on the tooth surface by point contact, so that the rack teeth can be measured. Further, in the case of a spline, by rolling the ball along the tooth groove of the entire spline, it is possible to evaluate the fitting over the entire circumference within the fitting length of the spline. Then, since the actual movement locus of the center point of the ball is measured, the moving state of the ball can be easily measured, and since the actual movement locus of the overball point of the ball is measured, it is the same as the OPD using the reference pin. Can be evaluated. Further, since the error between the actual movement locus and the design locus is calculated, it is possible to determine the quality of the gear.

Further, the gear measuring device of the present invention is a ball arranged so as to make point contact with the opposing tooth surfaces at the same time in the tooth groove of a gear having a plurality of tooth grooves provided in parallel and discontinuously provided with each other. the when is moved along the tooth groove, a measuring unit for measuring an actual movement locus of the center point or over the ball point of the ball is moved as the shape evaluation index of the gear, the design of the gear A design that stores a design locus that is a movement locus of a center point or an overball point of the ball when a ball arranged so as to make point contact with the opposing tooth surfaces at the same time in the tooth groove is moved along the tooth groove. A locus storage unit and a calculation unit for calculating an error between the actual movement locus measured by the measurement unit and the design locus stored in the design locus storage unit are provided. As a result, the same effect as that obtained by the gear measurement method can be obtained.

FIG. 5 is a schematic view of the entire steering system of an automobile including rack teeth and splines applicable to the gear measuring method of the embodiment of the present invention. It is a shaft axial sectional view of the steering column of FIG. It is a pinion axial sectional view of the rack and pinion type steering apparatus of FIG. It is a top view which shows the rack of the rack and pinion type steering apparatus of FIG. It is a figure which shows the gear measuring apparatus and rack tooth in embodiment of this invention. It is a flowchart for demonstrating the operation when the rack tooth is measured by the gear measuring apparatus. It is a flowchart for demonstrating the continuation of the operation of the gear measuring apparatus. It is a perspective view for demonstrating the method of determining the Y-axis direction in the tooth groove of a rack tooth. It is a perspective view for demonstrating the method of determining the origin in the tooth groove of a rack tooth. It is a perspective view for demonstrating the method of determining the X-axis and Z-axis directions in the tooth groove of a rack tooth. It is a perspective view for demonstrating how to obtain the error in the Z-axis direction between the actual movement locus and the design locus in the tooth groove of a rack tooth. It is a result of measuring a defective rack with a gear measuring device, and is the figure which shows the error of the actual movement locus and the design locus on the vertical axis, and the axial position of a rack tooth on a horizontal axis. It is a figure which shows the torque generated by the rack and pinion type steering apparatus which has a defective rack on the vertical axis, and shows the axial position of a rack tooth on a horizontal axis. It is the result of measuring a non-defective rack with a gear measuring device, and is the figure which shows the error of the actual movement locus and the design locus on the vertical axis, and the axial position of a rack tooth on a horizontal axis. It is a figure which shows the torque generated by the rack and pinion type steering apparatus which has a good rack on the vertical axis, and shows the axial position of a rack tooth on a horizontal axis. It is a figure which shows the gear measuring apparatus and the inner diameter spline in embodiment of this invention. It is a flowchart for demonstrating operation at the time of measuring an inner diameter spline with a gear measuring apparatus. It is a shaft axial direction sectional view of the upper shaft for demonstrating the method of determining the Y-axis direction, the X-axis direction and the Z-axis direction in the tooth groove of the inner diameter spline. FIG. 18 is a view of the upper shaft of FIG. 18 as viewed from the shaft axial direction. It is a shaft axial sectional view of the upper shaft for demonstrating how to obtain the radius error based on the actual movement locus and the design locus in the tooth groove of the inner diameter spline. It is a figure which looked at the upper shaft from the shaft axis direction for demonstrating how to obtain the phase error based on the actual movement locus and the design locus in the tooth groove of the inner diameter spline. It is the result of measuring the upper shaft of a defective product with a gear measuring apparatus, and is the figure which shows the radius error on the vertical axis, and the axial position of a spline on a horizontal axis. It is a result of measuring a defective upper shaft with a gear measuring device, and is the figure which shows the phase error on the vertical axis, and the axial position of a spline on a horizontal axis. It is a result of measuring a good-quality upper shaft with a gear measuring device, and is the figure which shows the radius error on the vertical axis, and the axial position of a spline on the horizontal axis. It is a result of measuring a defective upper shaft with a gear measuring device, and is the figure which shows the phase error on the vertical axis, and the axial position of a spline on a horizontal axis. It is a figure for demonstrating the overball point of the ball of the gear measuring apparatus.

(1. Configuration of automobile steering system)
As a gear applicable to the gear measuring method of the embodiment of the present invention, the rack tooth of the rack shaft and the spline of the steering shaft will be described as an example in the present embodiment, but the gear is not limited to the rack tooth and the spline. .. A steering system for an automobile equipped with rack teeth and splines will be described with reference to the 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 connected to the steering wheel 1, a steering column 15 including the steering shaft 2, and a rack-and-pinion type steering device 14. , An intermediate shaft 3 connecting the steering shaft 2 and the rack and pinion type steering device 14, and steering wheels 7a and 7b connected to the tip of the rack and pinion type steering device 14 and the like are provided.

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. Then, as shown in FIG. 2, the upper shaft 16 and the lower shaft 17 are fitted by an inner diameter spline 18 provided on the upper shaft 16 and an outer diameter spline 19 provided on the lower shaft 17. As a result, the upper shaft 16 and the lower shaft 17 have a retractable structure, and can absorb the impact at the time of a vehicle collision. In FIG. 1, the parts surrounding the steering shaft 2 are omitted.

The rack and pinion type steering device 14 includes a pinion shaft 4 as an input shaft, a rack shaft 5 as an output shaft, a rack housing 10 accommodating them, and the like. Inner ball joints 6a and 6b are connected to both ends of the rack shaft 5. As shown in FIG. 3, the rack shaft 5 is formed with rack teeth 9, and the pinion shaft 4 is formed with pinion teeth 8 that mesh with the rack teeth 9.

The rack shaft 5 is meshed with the pinion shaft 4 by a rack guide 11, a spring 12, and a guide plug 13 arranged in the rack housing 10 on the opposite side of the pinion shaft 4. That is, the rack guide 11 is housed in the rack housing 10 so as to be movable in a direction perpendicular to the central axis Lr of the rack shaft 5 and the central axis Lp of the pinion shaft 4. In the rack guide 11, one end side (upper side of the drawing) in the moving direction is in contact with the peripheral surface (circular outer peripheral surface) of the rack shaft 5 opposite to the pinion shaft 4, and the other end side (lower side of the drawing) of the moving direction is in contact with the peripheral surface (arc outer peripheral surface). The guide plug 13 screwed to the rack housing 10 is opposed to the guide plug 13 with a gap.

Then, the spring 12 is inserted between the rack guide 11 and the guide plug 13. As a result, the rack shaft 5 is pressed against the pinion shaft 4 by the elastic force of the spring 11. By this pressing, the pinion teeth 8 and the rack teeth 9 are meshed with each other without a gap, and even if the pinion shaft 4 is rotated by steering, the rack shaft 5 is not separated from the pinion shaft 4.

The rack shaft 5 has a meshing portion between the rack teeth 9 and the pinion teeth 8 arranged on one end side of the rack housing 10 and lubricity arranged on the inner peripheral surface of the rack housing on the other end side of the rack housing 10. It is supported by the rack bush shown in the figure. As a result, the rack shaft 5 is configured to be smoothly movable in the axial direction without directly contacting the rack housing 10.

In the steering system of an automobile having the above configuration, the steering force of the driver applied to the steering wheel 1 is transmitted from the steering shaft 2 to the intermediate shaft 3 as the rotational force of the pinion shaft 4. The rotational force of the pinion shaft 4 is converted into the axial force of the rack shaft 5 and transmitted from the inner ball joints 6a and 6b connected to both ends of the rack shaft 5 to the steering wheels 7a and 7b. Then, even if the pinion shaft 4 is rotated by steering, the rack shaft 5 does not separate from the pinion shaft 4, so that stable steering with a high degree of rigidity is possible.

In the rack and pinion type steering device 14, a VGR rack that changes the steering gear ratio according to the steering angle, that is, the specifications of the rack teeth 9 (modules of the rack teeth 9, pressure angle, etc.) are positioned in the axial direction of the rack shaft 5. Different VGR racks are used.

As shown in FIG. 4, the central portion (near the steering neutral position) and both end portions of the rack shaft 5 of the VGR rack are the first rack tooth groups 9Pa, 9Pb, 9Pc having a flat tooth surface 92, that is, the gear ratio is constant. The portion formed as a region and sandwiched between the central portion and both end portions of the rack shaft 5 is formed as a second rack tooth group 9Ca, 9Cb having a curved tooth surface 92, that is, a region in which the gear ratio changes. Unlike the CGR rack, the VGR rack cannot be formed by cutting (broaching or hobbing) but is formed by forging. Therefore, crowning is formed on the tooth tips 93 of the rack teeth 9. The tooth groove 91 is formed between the opposing tooth surfaces 92 and 92 of the adjacent rack teeth 9.

(2. Gear measuring device)
Next, the gear measuring device according to the embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 5, the gear measuring device 20 includes a measuring unit 21, a design locus acquisition unit 22, a design locus storage unit 23, and a calculation unit 24. The measuring unit 21 includes a probe 26 having a ball 25 at its tip, a moving device 27 and the like capable of moving the probe 26 in three orthogonal axes (X-axis, Y-axis, and Z-axis), and in this example, a groove copying function. It is a three-dimensional measuring machine having. The gear measuring device 20 can measure the rack teeth 9 and the inner diameter spline 18. First, the measurement of the rack teeth 9 will be described, and then the measurement of the inner diameter spline 18 will be described.

(3. Measurement of rack teeth)
When the rack teeth 9 are measured by the gear measuring device 20, the balls 25 are formed to have a diameter that allows contact with the opposing tooth surfaces 92 that form the tooth grooves 91 of the rack teeth 9. The measuring unit 21 moves when the balls 25 are arranged so as to make point contact with the opposing tooth surfaces 92 at the same time in the tooth grooves 91 of the rack tooth 9 to be measured and the balls 25 are moved along the tooth grooves 91. The movement locus of the center point Bc of the ball 25 (hereinafter, referred to as “actual movement locus”) is measured as a shape evaluation index of the rack teeth 9.

The reason for using the ball 25 is as follows. The central axis when the reference pin used in the OPD is arranged so as to make line contact with the facing tooth surface in the tooth groove of the rack tooth of the CGR rack is a colony of points. On the other hand, the locus of the center point Bc of the ball 25 when the ball 25 is arranged so as to make point contact with the facing tooth surface in the tooth groove of the rack tooth of the CGR rack and is moved along the tooth groove is also a colony of points. is there. In the case of a VGR rack, since the tooth surface 92 of the rack tooth 9 is formed of a curved surface, the reference pin cannot be arranged on the tooth surface 92 by line contact, and the rack tooth 9 cannot be measured, but the ball. If it is 25, it can be arranged on the tooth surface 92 by point contact, so that the rack teeth 9 can be measured.

The design locus acquisition unit 22 acquires design data regarding the tooth groove 91 of the rack teeth 9 in design. The design locus acquisition unit 22 acquires the movement locus of the center point Bc of the ball 25 (hereinafter, referred to as “design locus”) when the ball 25 is moved along the tooth groove 91 of the acquired design data. The design locus storage unit 23 stores the design locus acquired by the design locus acquisition unit 22. The calculation unit 24 calculates an error between the actual movement locus measured by the measurement unit 21 and the design locus stored in the design locus storage unit 23.

(4. Rack tooth measurement operation)
Next, the operation when the rack teeth 9 are measured by the gear measuring device 20 will be described with reference to the drawings. This measurement needs to be performed individually for all rack teeth 9 formed on the rack shaft 5, but in the following description, as shown in FIG. 8, it is effective with the pinion teeth 8 (see FIG. 3). A case of measuring the tooth groove 91a between the tooth surfaces 92a and 92b of the rack teeth 9a and 9b belonging to the second rack tooth group among the meshing rack teeth 9 will be described. The design locus acquisition unit 22 has already acquired the design locus, which is the movement locus of the center point Bc of the ball 25 when the ball 25 is moved along the tooth groove 91 of the rack tooth 9 in the design, and the design locus. It is assumed that it is stored in the storage unit 23.

First, the measuring unit 21 measures the contact position by bringing the ball 25 into contact with a plurality of phase positions of the first cylinder portion of the rack shaft 5 described later (step S1 in FIG. 6), and then measures the contact position of the rack shaft 5 with the second cylinder described later. The contact position is measured by bringing the ball 25 into contact with the plurality of phase positions of the portion (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 balls 25 are brought into contact with, for example, three phase positions P1, P2, and P3 of the first cylindrical portion U1 of the rack shaft 5 including the rack teeth 9a having the tooth surface 92a. Measure the position. Similarly, the contact position is measured by bringing the ball 25 into contact with, for example, three phase positions P4, P5, P6 of the first cylindrical portion U2 of the rack shaft 5 including the rack tooth 9b having the tooth surface 92b. 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 respective center points T1 and T2 is determined. It is determined as the Y-axis direction of the tooth groove 91a.

The measuring unit 21 determines a reference point to be described later of the tooth groove 91a based on the measurement of the outer peripheral surface of the arc located on the back side of the tooth groove 91a, and sets the determined reference point of the tooth groove 91a as the origin. That is, the ball 25 is brought into contact with the center of the tooth groove 91a in the tooth streak direction to measure the Y-axis coordinate value (step S4 in FIG. 6). Then, in the measured Y-axis coordinate values, the balls 25 are brought into contact with a plurality of locations on the back surface of the tooth groove 91a to measure the contact positions (step S5 in FIG. 6), and the origin of the tooth groove 91a is determined (FIG. 6). Step S6).

Specifically, as shown in FIG. 9, the Y-axis coordinate value of the central position Pa of the tooth groove 91a in the tooth streak direction is measured with the ball 25. Then, the three positions Q1, Q2, and Q3 on the outer peripheral edge Q of the rack shaft 5 that pass through the measured central position Pa and are cut in a plane Sxz perpendicular to the Y-axis direction are measured with the ball 25, and the measurement positions Q1 and Q1 The arc center Qc of the outer peripheral edge Q, which is the reference point, is obtained from Q2 and Q3, and the obtained arc center Qc is determined as the origin of the tooth groove 91a.

The measuring unit 21 measures the contact position by bringing the ball 25 into contact with the two tooth tips 93a and 93b (see FIG. 10) sandwiching the tooth groove 91a (step S7 in FIG. 7), and each measured tooth tip position. The X-axis direction and the Z-axis direction (two-dimensional coordinate system) of the tooth groove 91a are determined based on the above (step S8 in FIG. 7).

Specifically, as shown in FIG. 10, two positions Pb and Pc on the one end side and the other end side in the tooth streak direction of the two tooth tips 93a and 93b sandwiching the tooth groove 91a are set by the ball 25. The measurement is performed, and a straight line Lp passing through the two positions Pb and Pc is projected onto 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 unit 21 moves the ball 25 along the tooth groove 91a (step S9 in FIG. 7), and sets the actual movement locus of the ball 25 in the tooth groove 91a in the coordinate system (X, Y, Z) of the tooth groove 91a. Measure (step S10 in FIG. 7). Then, the calculation unit 24 calculates an error in the Z-axis direction between the actual movement locus measured by the measurement unit 21 and the design locus stored in the design locus storage unit 23 (step S11 in FIG. 7, "calculation step" of the present invention. ”), End the process.

Specifically, as shown in FIG. 11, the actual movement locus Rp measured by the measuring unit 21 has a curved shape shown by the solid line in the figure, and the design locus Rd acquired by the acquisition unit 22 has a curved shape shown by the broken line in the figure. Since it becomes a shape, these errors in the Z-axis direction are obtained.

FIG. 12 shows the error between the actual movement locus Rp and the design locus Rd on the vertical axis, the axial position of the rack tooth 9 on the horizontal axis, and the result of measuring a rack shaft 5 with the measuring device 20 of the rack tooth 9. As is clear from FIG. 12, the error between the actual movement locus Rp and the design locus Rd of the rack shaft 5 changes significantly in the vicinity of the second rack tooth group 9Cb (the portion E surrounded by the circle of the broken line in the figure). ..

In the case of the rack and pinion type steering device 14 provided with such a rack shaft 5, as shown in FIG. 13, a torque jump event occurs in the vicinity of the second rack tooth group 9Cb (the portion E surrounded by the circle of the broken line in the drawing). Occurred. The rack shaft 5 was found to be defective. Note that FIG. 13 shows a case where the pinion tooth 8 is reciprocated in the axial direction of the rack tooth 9.

On the other hand, FIG. 14 is a diagram corresponding to FIG. 12, and shows the result of measuring another rack shaft 5 with the measuring device 20 of the rack teeth 9. As is clear from FIG. 14, the error between the actual movement locus Rp and the design locus Rd of the rack shaft 5 has not changed significantly. In the case of the rack and pinion type steering device 14 provided with such a rack shaft 5, as shown in FIG. 15 corresponding to FIG. 13, the torque jumping event did not occur and a substantially constant torque was obtained. The rack shaft 5 was found to be a non-defective product.

As described above, it was found that the measurement result (trajectory error) of the rack tooth 9 of the present embodiment by the measuring device 20 correlates with the gear performance (torque waveform) of the rack and pinion type steering device 14. .. Therefore, the measuring device 20 for the rack teeth 9 of the present embodiment can evaluate the meshing of the VGR rack. Further, since the position and amount of crowning in the rack teeth 9 can be quantified and visualized, it can be reflected in the manufacturing conditions including plastic working.

(5. Measurement of inner diameter spline)
As shown in FIG. 16, when the inner diameter spline 18 is measured by the gear measuring device 20, the ball 25 is formed to have a diameter that allows contact with the opposing tooth surface 82 forming the tooth groove 81 of the inner diameter spline 18. The measuring unit 21 moves when the ball 25 is arranged so as to make point contact with the opposing tooth surface 82 at the same time in the tooth groove 81 of the inner diameter spline 18 to be measured and the ball 25 is moved along the tooth groove 81. The movement locus of the center point Bc of the ball 25 (hereinafter referred to as “actual movement locus”) is measured as a shape evaluation index of the inner diameter spline 18.

The design locus acquisition unit 22 acquires design data regarding the tooth groove 81 of the design inner diameter spline 18. The design locus acquisition unit 22 acquires the movement locus of the center point Bc of the ball 25 (hereinafter, referred to as “design locus”) when the ball 25 is moved along the tooth groove 81 of the acquired design data. The design locus storage unit 23 stores the design locus acquired by the design locus acquisition unit 22. The calculation unit 24 calculates a radius error and a phase error, which will be described later, based on the actual movement locus measured by the measurement unit 21 and the design locus stored in the design locus storage unit 23.

(6. Measurement operation of inner diameter spline 18)
Next, the operation when the inner diameter spline 18 is measured by the gear measuring device 20 will be described with reference to the drawings. In this measurement, it is effective to fit the length T within the effective fitting length (see FIG. 18), that is, the length T in the axial direction from the start end To of the inner diameter spline 18 for all the inner diameter splines 18 formed on the upper shaft 16. Must be done individually within the range. The design locus acquisition unit 22 is the center point Bc of the ball 25 when the ball 25 is moved within the effective fitting length T (see FIG. 18) along the entire tooth groove 81 of the design inner diameter spline 18. It is assumed that the design locus, which is the movement locus of the above, has already been acquired and stored in the design locus storage unit 23.

First, the measuring unit 21 measures the contact position by bringing the ball 25 into contact with the tooth tips 83 (see FIG. 15) of the plurality of inner diameter splines 18 at a predetermined axial position on the inner circumference of the upper shaft 16 (FIG. 17). Step S21). Next, at an axial position different from the previous axial position on the inner circumference of the upper shaft 16, the ball 25 is brought into contact with the tooth tips 83 of the plurality of inner diameter splines 18 to measure the contact position (step S22 in FIG. 17). .. Then, the Y-axis direction is determined based on each contact position, and the X- and Z-axis directions (three-dimensional coordinate system) are further determined (step S23 in FIG. 17).

Specifically, as shown in FIGS. 18 and 19, at a predetermined axial position Y1 within the effective fitting length of the inner diameter spline 18, for example, the tooth tips of the inner diameter splines 18 of the three phase positions V1, V2, V3. The ball 25 is brought into contact with the 83 to measure the contact position. Similarly, at a predetermined axial position Y2 within the effective fitting length of the inner diameter spline 18, the ball 25 is brought into contact with the tooth tip 83 of the inner diameter spline 18 at the same three phase positions V1, V2, V3 as before. Measure the position.

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

The measuring unit 21 moves the ball 25 within the effective fitting length along each tooth groove 81 of the inner diameter spline 18 (step S24 in FIG. 17), and in the coordinate system (X, Y, Z) of each tooth groove 81. The actual movement locus of the ball 25 in each tooth groove 81 is measured (step S25 in FIG. 17). Then, the calculation unit 24 calculates the radius error and the phase error based on the actual movement locus measured by the measurement unit 21 and the design locus stored in the design locus storage unit 23 (step S26 of FIG. 17, according to the present invention). (Corresponding to "calculation process"), the process is completed.

Specifically, as shown in FIG. 20, the actual movement locus Wp measured by the measuring unit 21 is shown by a solid line in the figure, and the design locus Wd acquired by the acquisition unit 22 is shown by a broken line in the figure. Therefore, the error between the distance between the actual movement locus Wp and the straight line L11 and the distance between the design locus Wd and the straight line L11 is obtained as the radius error.

Further, as shown in FIG. 21, in the tooth groove 81a located at the start end To of the inner diameter spline 18, when the phase of the straight line k1 passing through the actual movement locus Wp and the straight line L11 is set to 0, the adjacent teeth counterclockwise. The phase of the straight line k2 passing through the actual movement locus Wp and the straight line L11 in the groove 81b is θ1 with respect to the straight line k1, and the phase of the straight line k3 passing through the actual movement locus Wp and the straight line L11 in the tooth groove 81c adjacent counterclockwise. The phases of all the tooth grooves 81a, 81b, 81c ... Are obtained as actual phases within the effective fitting length, such as θ2 with respect to the straight line k2. On the other hand, in the same procedure, the phases of all the tooth grooves 81a, 81b, 81c ... For the design locus Wd are obtained as the design phase within the effective fitting length. Then, the error between the actual phase and the design phase is obtained as the phase error.

FIG. 22 shows the radial error on the vertical axis, the axial position of the tooth groove 81 of the inner diameter spline 18 on the horizontal axis, and the result of measuring the tooth groove 81a with the gear measuring device 20. As is clear from FIG. 22, the radial error of the inner diameter spline 18 is within the range from the position advanced by the length T1 in the axial direction from the start end To of the inner diameter spline 18 to the length T (the portion surrounded by the circle of the broken line in the figure). In E1), the permissible value −Δr is exceeded.

Further, FIG. 23 shows the phase error on the vertical axis, the axial position of the tooth groove 81 of the inner diameter spline 18 on the horizontal axis, and the result of measuring the tooth groove 81a with the gear measuring device 20. As is clear from FIG. 23, the phase error of the inner diameter spline 18 is within the range from the position advanced by the length T2 in the axial direction from the start end To of the inner diameter spline 18 to the length T (the portion surrounded by the circle of the broken line in the figure). In E2), the permissible value −Δθ is exceeded. In the case of the steering column 15 provided with such an inner diameter spline 18, the sliding resistance at the time of contraction becomes large, and it was found that the inner diameter spline 18 is a defective product.

On the other hand, FIG. 24 is a diagram corresponding to FIG. 22, showing the result of measuring another inner diameter spline 18 with the gear measuring device 20. As is clear from FIG. 24, the radial error of the inner diameter spline 18 has not changed significantly. Further, FIG. 25 is a diagram corresponding to FIG. 23, and shows the result of measuring another inner diameter spline 18 with the gear measuring device 20. As is clear from FIG. 25, the phase error of the inner diameter spline 18 has not changed significantly. In the case of the steering column 15 provided with such an inner diameter spline 18, the sliding resistance at the time of contraction did not increase, and it was found that the inner diameter spline 18 was a good product.

(Other)
In the above-described embodiment, the measuring unit 21 is configured to measure the movement locus of the center point Bc of the ball 25, but may be configured to measure the movement locus of the overball point of the ball 25. As shown in FIG. 25, the overball point Bo of the ball 25 is a straight line Lz perpendicular to the central axis Lr of the rack shaft 5 and a straight line Lz passing through the center point Bc of the ball 25 located in the tooth groove 91. It is a point where the ball 25 intersects the outer peripheral surface on the opposite side of the tooth groove 91. The same applies to the case of the inner diameter spline 18.

Further, in the measurement step (measurement unit 21), the rack teeth 9 are measured in the orthogonal two-axis coordinate system (X, Z) in the three-dimensional coordinate system, but may be measured in the circular coordinate system (polar coordinates). Further, in the inner diameter spline 18, the measurement was performed in the orthogonal three-axis coordinate system (X, Y, Z) of the three-dimensional coordinate system, but the measurement may be performed in the cylindrical coordinate system (a kind of polar coordinate system).

Further, although the measuring unit 21 is a three-dimensional measuring machine having a groove copying function, it may be a shape measuring machine, an optical measuring machine, or the like having a function of outputting all the point coordinate values measured by copying in two or more directions. Further, although the measurement of the VGR rack has been described, the CGR rack can also be measured in the same manner. Further, although the measurement of the inner diameter spline 18 has been described, the outer diameter spline 19 can be measured in the same manner. In addition, the Hasba gear and the bevel gear can be measured in the same manner.

(Effect of embodiment)
The method for measuring the gear (rack tooth 9, inner diameter spline 18) of the present embodiment is the actual movement locus of the ball 25 in which the ball 25 is moved along the tooth grooves 91 and 81 of the gear (rack tooth 9, inner diameter spline 18). A measurement step of measuring Rp and Wp as shape evaluation indexes of gears (rack teeth 9, inner diameter spline 18) is provided.

According to this, since it is not affected by the orientation of the teeth of the gear, it is possible to evaluate the meshing and fitting of the gear. For example, in the case of a VGR rack, since the tooth surface 92 of the rack tooth 9 is formed of a curved surface, the reference pin used in the OPD cannot be arranged on the tooth surface 92 by line contact, and the rack tooth 9 cannot be measured. However, since the ball 25 can be arranged on the tooth surface 92 by point contact, the rack tooth 9 can be measured. Further, in the case of the inner diameter spline 18, by rolling the ball 25 along the entire spline groove 81, it is possible to evaluate the fitting over the entire circumference within the fitting length L of the inner diameter spline 18.

Further, in the measuring step, since the actual movement locus of the center point Bc of the ball 25 is measured, the moving state of the ball 25 can be easily measured.
Further, in the measurement step, since the actual movement locus of the overball point Bo of the ball 25 is measured, the same evaluation as the OPD using the reference pin is possible.

The method for measuring the gear (rack tooth 9, inner diameter spline 18) is that the ball 25 is moved along the tooth grooves 91 and 81 of the design gear (rack tooth 9, inner diameter spline 18). An acquisition process for acquiring design loci Rd and Wd, which are movement loci, and a calculation step for calculating an error between the actual movement loci Rp and Wp measured in the measurement process and the design loci Rd and Wd acquired in the acquisition process. To be equipped with. This makes it possible to determine the quality of the gears (rack teeth 9, inner diameter spline 18).

Further, in the case of the rack teeth 9 in which the gears are formed on the rack shaft 5, in the measurement step, the reference of each tooth groove 91 is based on the measurement of the arc outer peripheral surface Q located on the back side of the tooth groove 91 of each rack tooth 9. When the point Qc is determined and the determined reference point Qc of each tooth groove 91 is used as the origin, the actual movement locus Rp of the ball 25 for each rack tooth 9 is measured, so that the actual movement locus Rp of the ball 25 Measurement accuracy can be improved.

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

When the gear has an inner diameter spline 18, in the measurement step, a three-dimensional coordinate system for the tooth groove 81 of each inner diameter spline 18 is determined based on the measurement of the tooth tip 83 of each inner diameter spline 18, and the determined three dimensions. In the coordinate system, since the actual movement locus Wp of the ball 25 for each inner diameter spline 18 is measured, the measurement accuracy of the actual movement locus Wp of the ball 25 can be further improved.

Further, the gear (rack tooth 9, inner diameter spline 18) measuring device 20 for measuring the shape of the tooth grooves 91, 81 of the gear (rack tooth 9, inner diameter spline 18) of the present embodiment is a gear (rack tooth 9, inner diameter spline 18). When the ball 25 is moved along the tooth grooves 91 and 81 of the spline 18), the measuring unit that measures the actual movement locus of the moved ball 25 as a shape evaluation index of the gear (rack tooth 9, inner diameter spline 18). 21 is provided. Further, the measuring device 20 for the gear (rack tooth 9, inner diameter spline 18) is a ball 25 when the ball 25 is moved along the tooth grooves 91 and 81 of the designed gear (rack tooth 9, inner diameter spline 18). It is provided with a storage unit 23 that stores the design locus, which is the movement locus of the above, and a calculation unit 24 that calculates an error between the actual movement locus measured by the measurement unit 21 and the design locus stored in the storage unit 23. As a result, the same effect as that obtained by the method for measuring gears (rack teeth 9, inner diameter spline 18) can be obtained.

5: Rack shaft, 9: Rack teeth, 9Pa, 9Pb, 9Pc: 1st rack tooth group, 9Ca, 9Cb: 2nd rack tooth group, 14: Rack and pinion type steering device, 15: Steering column, 16: Upper shaft , 17: Lower shaft, 18: Inner diameter spline, 19: Outer diameter spline, 20: Gear measuring device, 21: Measuring unit, 22: Acquisition unit, 23: Storage unit, 24: Calculation unit, 25: Ball, 91, 81: Tooth groove, 92, 82: Tooth surface, 93, 83: Tooth tip

Claims (6)

In the tooth grooves of the gear having a plurality of teeth grooves and provided discontinuously mutually provided in parallel and the placed balls to simultaneously point-contact the tooth surfaces facing to move along the tooth spaces cases, the step of measuring the actual movement locus of the center point or over the ball point of the ball as the shape evaluation index before Symbol gear,
In the design tooth groove of the gear, the movement locus of the center point or the overball point of the ball when the balls arranged so as to make point contact with the opposing tooth surfaces at the same time are moved along the tooth groove. The acquisition process to acquire a certain design trajectory,
A calculation step of calculating an error between the actual movement locus measured in the measurement step and the design locus acquired in the acquisition step, and a calculation step.
A method of measuring gears. The gear is a rack tooth formed on the rack shaft.
In the measurement step,
A reference point for each of the tooth grooves is determined based on the measurement of the outer peripheral surface of the arc located on the back side of the tooth groove of each of the rack teeth.
The method for measuring a gear according to claim 1 , wherein the actual movement locus of the ball for each of the rack teeth is measured when the determined reference point of the tooth groove is used as the origin. In the measurement step,
When the axial direction of the rack axis is the Y axis, a two-dimensional coordinate system of a plane orthogonal to the Y axis with respect to each tooth groove is determined based on the measurement of the tooth tip of each rack tooth.
The method for measuring a gear according to claim 2 , wherein the actual movement locus of the ball for each of the rack teeth is measured in the two-dimensional coordinate system for each of the determined tooth grooves. The gear is a rack tooth formed on the rack shaft.
The gear measuring method according to any one of claims 1 to 3 , wherein the gear measuring method is applied to a rack in which the gear ratio changes in the axial direction of the rack shaft. The gear is a spline
In the measurement step,
Based on the measurement of the tooth tip of each spline, a three-dimensional coordinate system for the tooth groove of each spline is determined.
The method for measuring a gear according to claim 1 , wherein the actual movement locus of the ball for each spline is measured in the determined three-dimensional coordinate system. A measuring apparatus of a gear measuring the tooth groove in the shape of a gear having a plurality of teeth grooves and provided discontinuously from one another are provided in parallel,
The placed balls to simultaneously point-contact the tooth surface that faces in the tooth space when allowed to move along the tooth spaces, the actual movement locus of the center point or over the ball point of the ball is moved A measuring unit that measures as a gear shape evaluation index,
It is a movement locus of a center point or an overball point of the ball when a ball arranged so as to make point contact with the opposing tooth surfaces at the same time in the tooth groove of the gear by design is moved along the tooth groove. A design trajectory storage unit that stores the design trajectory and
A calculation unit that calculates an error between the actual movement locus measured by the measurement unit and the design locus stored in the design locus storage unit, and a calculation unit.
A gear measuring device.

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