JP6598910B2 - Tooth surface measurement method - Google Patents

Description

  The present invention relates to a tooth surface measuring method for measuring tooth surface properties of a gear such as a hypoid gear.

  Conventionally, a hypoid gear or the like used for a power transmission device or the like that converts a driving force of an internal combustion engine horizontally placed in front of a vehicle to a rear wheel side by converting a horizontal rotation axis direction to a front-rear direction via a hypoid gear or the like. Is known (see, for example, Patent Document 1).

JP 2006-70995 A

  It has been found that a plurality of lines having periodicity formed on one tooth surface at the time of cutting of a gear cause high-frequency sound.

  However, in addition to periodic streaks, there are many streak lines with no periodicity, such as streaks due to cutting tool transfer such as the roughness of the cutting machine blades, and streaks due to chips during cutting. To do. Therefore, it is possible to measure by directly tracing the meshing contact trajectory line using a two-dimensional contact type shape measuring instrument, or by acquiring shape data of a wide range of tooth surfaces using a three-dimensional non-contact measuring instrument. Even if the section on the meshing contact locus line is cut out above, it is difficult to measure the properties of only the periodic streaks that are the source of the high-frequency sound due to mixing of the non-periodic streaks.

  In view of the above points, an object of the present invention is to provide a tooth surface measuring method capable of measuring a streak having periodicity of tooth surfaces.

[1] In order to achieve the above object, the tooth surface measurement method of the present invention comprises:
Using the three-dimensional model of the gear cutting machine used for gear manufacture and the three-dimensional model of the workpiece to be machined by the gear cutting machine, the three-dimensional model of the gear cutting machine is obtained at predetermined unit time intervals. A tooth gap three-dimensional model creation step of obtaining a three-dimensional model of a gear having at least one tooth gap by deleting an overlapping portion of the three-dimensional model of the workpiece by moving in the same manner as an actual gear cutting machine; ,
A stitch angle setting step of setting a stitch angle at the time of cutting from the three-dimensional model of the gear obtained by the gear three-dimensional model creation step;
A non-contact three-dimensional measurement step of measuring a difference in the unevenness of the tooth surface shape of the gear as three-dimensional image data;
A Fourier transform processing step for performing a Fourier transform process on the two-dimensional planar image obtained in the non-contact three-dimensional measurement step;
Periodic streak setting which removes streak having no periodicity at the streak angle obtained in the streak angle setting step or streak having a different angle from the angle obtained in the streak angle setting step from the data obtained in the Fourier transform processing step Process,
An inverse Fourier transform step of returning the periodic muscles selected in the periodic stitch setting step to a two-dimensional plane image by inverse Fourier transform;
It is characterized by including.

  According to the present invention, it is possible to measure a line having periodicity of a gear.

  [2] In the present invention, the predetermined unit time may be a time for one rotation of the cutter of the gear cutter.

  [3] The present invention can be applied not only to involute gears and bevel gears but also to hypoid gears.

Explanatory drawing which shows typically the three-dimensional model of the gear cutter and workpiece of embodiment. Explanatory drawing which shows an example of the tooth gap formed in the workpiece of this embodiment. Explanatory drawing which expands and shows the tooth gap of this embodiment. FIG. 4A is an explanatory diagram showing three-dimensional image data according to the present embodiment. FIG. 4B is an explanatory view showing three-dimensional image data obtained by removing the inclination of the tooth surface from the three-dimensional image data of FIG. 4A. FIG. 4C is an explanatory diagram showing three-dimensional image data obtained by removing the roundness (curved surface) of the tooth surface from the three-dimensional image data of FIG. 4B. FIG. 4D is an explanatory diagram showing three-dimensional image data obtained by performing two-dimensional FFT processing on the three-dimensional image data in FIG. 4C. Explanatory drawing which shows typically how to view the three-dimensional image data after a two-dimensional FFT process. FIG. 6A is an explanatory diagram illustrating a state in which periodic lines are selected. FIG. 6B is an explanatory diagram illustrating a state in which a part other than the selected periodic streak is removed and the inverse FFT process is performed. Explanatory drawing which shows the three-dimensional image data after an inverse FFT process at the time of setting an angle visually, without using the angle calculated | required with the three-dimensional model of a gear cutter and a workpiece as a reference example. Explanatory drawing which shows typically the periodic line | wire with respect to one tooth surface of this embodiment, another line | wire, and a meshing locus line. FIG. 9A is an explanatory diagram showing a cutting position where the three-dimensional image data obtained in FIG. 6B is cut along the meshing locus line. FIG. 9B is an explanatory view showing a tooth surface curve in the cut section of FIG. 9A. FIG. 9C is an explanatory diagram illustrating a state in which the wavelength amplitude is obtained by FFT processing from the curve of FIG. 9B.

  A method for measuring the tooth surface of a hypoid gear as a gear according to an embodiment of the present invention will be described with reference to the drawings.

[Tooth gap 3D model creation process]
First, the tooth gap three-dimensional model creation process will be described. FIG. 1 schematically shows a three-dimensional model of the gear cutter 2 to which the workpiece 1 is attached. In order to create a three-dimensional model of the gear cutter 2, first, a cone model corresponding to the cutting surface when the blade of the cutter 3 rotates is created from the cutter specification information of the gear cutter actually used.

  In the gear cutter 2 that is actually used, it is virtually impossible to completely match the center axis of the cutter 3 with the rotation center axis of the gear cutter 2, and the cutter 3 rotates in an eccentric state. . Although the amount of eccentricity of the cutter 3 is set to be as small as possible, it is difficult to make the amount of eccentricity of the cutter 3 completely zero. And this eccentricity is considered to be the cause of generation of the periodic streak 10. Therefore, it is necessary to create the three-dimensional model of the gear cutter 2 in consideration of this eccentricity.

  A cone obtained by rotating the blade cross-sectional shape corresponding to the convex tooth surface and the concave tooth surface at a position obtained by adding an allowable maximum eccentricity to the radius of the specification information is created. This cone is a three-dimensional model of the cutter 3. In the cutting surface model of the cutter 3, the intersection of the rotation plane drawn by the apex of the blade and the rotation axis is used as a positioning reference point for the three-dimensional model of the cutter 3.

  Next, a three-dimensional model of the workpiece 1 is created. The three-dimensional model of the workpiece 1 corresponds to a material before gear cutting, and a positioning reference point is set at the same location as the actual gear cutting reference point.

  Next, the movable shaft and positioning model of the gear cutter 2 are created. In this embodiment, the gear cutter model reproduces the specifications and mechanism of the Gleason 106-type processing machine. First, an XY plane serving as a reference for the cutting motion of the cutter 3 is set on the origin. The cutter 3 rotates by cutting around the origin in the XY plane. The X and Y axes in the horizontal and vertical directions are set according to the actual processing machine posture. Further, the Z axis is set in a direction orthogonal to the X axis and the Y axis, and Z = 0 is matched with the positioning reference point of the three-dimensional model of the cutter 3. In actual cutting, modeling is performed by replacing the movement of the blade of the cutter 3 that rotates at a high speed at the positioning reference point of the three-dimensional model of the cutter 3 with the rotation trajectory of the cutting surface.

  At the same time as the cutter 3 rotates, the cutter 3 rotates the cutting table 4 (Cradle) about the cutting rotation axis (Z axis) and is given the necessary revolving motion. In the gear cutting machine 2, a rotating shaft to which the cutter 3 is attached so that the cutting rotation radius can be freely adjusted is mounted on the cutting table 4 via an eccentric rotating table (Eccentric). The cutting radius can be adjusted by the rotation angle of the eccentric table, and the adjustment of the cutter reference point position after adjustment can be adjusted by the rotation angle of the cutting table 4.

  A mechanism that combines a pair of swash plates 5 and 6 (swivel / cutter rotation) on the rotation axis of the cutter 3 so that the rotation plane drawn by the tip of the blade of the cutter 3 is inclined from the cutting rotation plane. Is incorporated. An inclination angle of 0 deg to 30 deg is set by rotation of one swash plate base 6, and an inclination direction is adjusted by rotation of the other swash plate base 5.

  When the inclination angle of the cutter 3 is adjusted, the rotation axis of the pair of swash plate bases 5 and 6 is the cutter so that the center point of the tip plane of the rotating cone model of the cutter 3 is not changed from the cutting rotation radius. The structure intersects at the reference point.

  The mounting base 7 of the workpiece 1 has a rotation mechanism 8 capable of adjusting the angle formed by the rotation axis of the workpiece 1 and the cutting plane of the cutter 3 of the gear cutting machine 2, vertical movement up and down from the center of cutting rotation, and processing. A slide mechanism capable of parallel movement in the rotation axis direction of the object is provided, and the installation position and posture with respect to the cutting center point can be freely adjusted. In addition, the table (Sliding base) on which the mounting base 7 is mounted is a mechanism that feeds in conjunction with the cutting rotation so that a linear motion (Helical motion) can be performed in a direction perpendicular to the cutting rotation plane of the cutter 3. Is provided.

  The three-dimensional model of the cutter 3 and the three-dimensional model of the workpiece 1 are arranged in a predetermined posture at a predetermined setup reference position (Machine Center Position) on the three-dimensional model of the gear cutting machine 2. This arrangement position and cutting rotation angle are determined by the cutting point of the cutter 3 that reproduces the virtual conjugate tooth surface at the mean point defined at the center of the tooth width as the meshing reference position, and the workpiece 1 meshing pitch point. Corresponds to the moment of coincidence. Then, a theoretical tooth surface shape is created on the three-dimensional CAD software by giving a feed movement per unit time of one rotation of the cutter 3 from the start to the end of the gear cutting.

  Assuming that the cutter rotation speed is N (rpm) and the cutting feed speed S (deg / sec) based on the processing conditions, the unit time is N / 60 (sec), and the cutter creation rotation angle per unit time is S × N / 60 (deg). ) If the ratio of the cutting rotational speed between the cutter 3 and the workpiece 1 is R (Ratio of roll), the rotational angle per unit time of the workpiece 1 is R × S × N / 60 (deg). When the feed in the rotation axis direction of the mount 7 with respect to the cutter cutting rotation is H (mm / deg), the linear movement amount per unit time is H × S × N / 60 (mm). By rotating and moving the three-dimensional model every unit time of one rotation of the cutter 3 in the above relationship, the interference part where the three-dimensional model of the cutter 3 and the three-dimensional model of the workpiece 1 interfere is deleted. The surface of the obtained tooth gap 9 (see FIGS. 2 and 3) is used as a theoretical model of tooth surface properties.

[Line angle setting process]
Next, the stitch angle setting process will be described.

  FIG. 2 shows the tooth gap 9 provided in the three-dimensional model of the workpiece 1. As shown in an enlarged view of the tooth gap 9 in FIG. 3, the cutting surface of the peak portion of the eccentric motion of the cutter 3 is removed in the process of removing the interference portion a plurality of times per predetermined unit time. A processing tooth surface 12 is generated from the drawn locus. After the operation until one tooth groove 9 is completed, the envelope surfaces of all the processed tooth surfaces 12 are obtained. The ridge line where the envelope surfaces intersect each other is a point obtained by connecting the intersections of the cutting surfaces that are the peak of eccentricity of the cutter 3, that is, the contour line that is the peak of the tooth surface uneven shape. As described above, the ridge line drawn in the theoretical model represents the properties of the periodic streak 10 generated during gear cutting. Further, the teeth of the hypoid gear have a meshing locus line 11 that can be represented by a locus of contact points where the teeth contact each other. The angle of the streak 10 on the meshing locus line 11 is obtained from the tooth gap 9.

[Non-contact 3D measurement process]
Next, the non-contact three-dimensional measurement process will be described. In this step, first, the tooth surface including the meshing locus line 11 of the hypoid gear to be actually evaluated is measured using a non-contact three-dimensional measuring machine. In the present embodiment, the measurement was performed using INFINITE FOCUS manufactured by Aricona as a non-contact type three-dimensional measuring machine.

[Fourier transform process]
Next, the Fourier transform process will be described.

  FIG. 4A shows three-dimensional image data measured by a non-contact type three-dimensional measuring machine. The horizontal axis of FIG. 4A is a reference line perpendicular to the tooth tip line, and in FIG. 4A, the difference in height (the third dimension) is represented by the difference in color. 4A to 4C, the aspect ratio is different from the actual tooth surface ratio. Since the three-dimensional image data in FIG. 4A includes a state of inclination and roundness (curved surface) of the hypoid gear, first, the inclination is removed by filtering, and the inclination is removed as shown in FIG. 4B. Obtained three-dimensional image data is obtained.

  Next, the round (curved surface) is removed using an approximate polynomial, and three-dimensional image data from which the round (curved surface) is removed as shown in FIG. 4C is obtained.

  Next, two-dimensional fast Fourier transform processing (two-dimensional FFT processing) is performed on the three-dimensional image data from which the inclination and roundness are removed. In the two-dimensional fast Fourier transform processing, component analysis is performed on the two-dimensional image data in FIG. 4C by repeating the one-dimensional fast Fourier transform processing in the horizontal direction and the vertical direction once each. In the present embodiment, this two-dimensional fast Fourier transform process is performed using Talymap Platinum software manufactured by Talor Hobson. As a result, the three-dimensional image data shown in FIG. 4D is obtained. FIG. 5 shows the three-dimensional image data of FIG. 4D and a schematic diagram schematically representing the three-dimensional image data. The center of the three-dimensional image data in FIGS. 4D and 5 indicates that the wavelength is 0, and that the wavelength component is included in a place where the luminance is high (in other words, the dependency is high). Show. Further, the vector component from the center to the high luminance position is a vertical component in the direction in which the lines extend.

[Periodic line setting process and inverse Fourier transform process]
Next, the periodic streak setting step and the inverse Fourier transform step will be described.

  If other streaks other than the periodic streaks are removed from the three-dimensional image data of FIG. 4D, three-dimensional image data of only periodic streaks can be obtained. Here, the streaky high-intensity portion W extending from the center to the outer periphery shows a state where the wavelengths of various periods are evenly distributed. Therefore, the periodic streak can be extracted by extracting the high brightness part of the periodic streak, excluding the streak-like high brightness part W extending from the center to the outer periphery.

  At this time, as shown in FIG. 7 as a reference example, it is possible to visually extract a high-intensity portion of periodic stripes. However, in this software, a fan-shaped area is specified and a high-luminance part is extracted. The center line of the fan-shaped region is the extending direction of the periodic lines. In this case, since the center line of the fan-shaped region cannot be set with high precision when visually pouring out, the extracted high-intensity portion is returned to three-dimensional data by inverse fast Fourier transform to extract periodic streaks. There is a problem that the extraction accuracy of the periodic streak is lowered.

  Therefore, in the present embodiment, as shown in FIG. 6A, the center line of the fan-shaped region is set using the line angle obtained by the three-dimensional model. As a result, the extracted high-intensity portion is returned to the three-dimensional image data by inverse fast Fourier transform, so that periodic stripes can be extracted with high accuracy as shown on the right side of FIG. 6B.

  FIG. 8 is a schematic diagram of the lines. As shown in FIG. 8, in addition to periodic streaks generated due to the eccentricity of the cutter 3 during cutting, there are streaks due to the transfer of the surface shape and roughness of the tool, non-periodic streaks caused by chip slipping, and the like. Exists.

[Tooth surface property evaluation process]
As shown in FIG. 9A, the cross-sectional curve on the meshing locus line 11 is extracted from the three-dimensional image data obtained by the inverse fast Fourier transform on the right side of FIG. 6B, as shown in FIG. 9C. As described above, the wavelength and amplitude of the periodic streak can be evaluated by subjecting the extracted cross-sectional curve to a fast Fourier transform process. As a result, it is possible to accurately grasp the nature of the high frequency noise of the hypoid gear.

  Further, if the three-dimensional image data obtained by the inverse fast Fourier transform shown in FIG. 6 is created once, it is easy to use the three-dimensional image data shown in FIG. 6 even when the meshing locus line is changed. Can be re-evaluated.

[Other Embodiments]
In the present embodiment, the tooth surface measurement method of the hypoid gear has been described. However, the tooth surface measurement method of the present invention can be used not only for hypoid gears but also for other gears such as involute gears and bevel gears.

  In the present embodiment, the predetermined unit time has been described as the time for one rotation of the cutter 3 of the gear wheel 2. However, the predetermined time of the present invention is not limited to this, for example, the cutter 3 is rotated a plurality of times. You may set the time.

DESCRIPTION OF SYMBOLS 1 Workpiece 2 Gear cutting machine 3 Cutter 4 Cutting bases 5 and 6 Swash plate base 7 Mounting base 8 Rotating mechanism 9 Tooth groove 10 Stitch 11 Meshing locus line 12 Machining tooth surface 13 Measurement area

Claims (3)

Using the three-dimensional model of the gear cutting machine used for gear manufacture and the three-dimensional model of the workpiece to be machined by the gear cutting machine, the three-dimensional model of the gear cutting machine is obtained at predetermined unit time intervals. A tooth gap three-dimensional model creation step of obtaining a three-dimensional model of a gear having at least one tooth gap by deleting an overlapping portion of the three-dimensional model of the workpiece by moving in the same manner as an actual gear cutting machine; ,
A stitch angle setting step of setting a stitch angle at the time of cutting from the three-dimensional model of the gear obtained by the gear three-dimensional model creation step;
A non-contact three-dimensional measurement step of measuring a difference in the unevenness of the tooth surface shape of the gear as three-dimensional image data;
A Fourier transform processing step for performing a Fourier transform process on the two-dimensional planar image obtained in the non-contact three-dimensional measurement step;
Periodic streak setting which removes streak having no periodicity at the streak angle obtained in the streak angle setting step or streak having a different angle from the angle obtained in the streak angle setting step from the data obtained in the Fourier transform processing step Process,
An inverse Fourier transform step of returning the periodic muscles selected in the periodic stitch setting step to a two-dimensional plane image by inverse Fourier transform;
The tooth surface measuring method characterized by including. The tooth surface measurement method according to claim 1,
The predetermined unit time is a time required for one rotation of the cutter of the gear cutter. The tooth surface measurement method according to claim 1 or 2,
The tooth surface measuring method, wherein the gear is a hypoid gear.