JPH04258709A - Measurement of tooth flank shape by noncontact type free-form surface measuring device - Google Patents

Abstract

PURPOSE:To measure and analyze a gear having a curved surface tooth flank by collecting the data of the incident angle of the object light at each point on an inspected tooth flank from a theoretical tooth flank image obtained through the simulation method. CONSTITUTION:The interference light supplied from a light source 1 is separated, and a hologram image is obtained by the reflection light supplied from the object light S which irradiates an aimed surface and the reference light R. The shape of an image caught by a camera 8 is calculated from the gear specification by an MPU 12, and a simulation image is obtained. The hologram of the standard tooth flank A of a standard gear 6 which is photographed by the camera 8 and the image of a standard tooth flank B on which a part of an other tooth of the gear 6 is cut are superposed, and the original point of coordinates is determined. The positive reflection image of the measured gear as measurement object and the hologram of the tooth flank A are superposed, and a holographic interference image is obtained, and superposed to the simulation image obtained from the specification. Accordingly, the correspondence data between the incident angle of the article light S at each point based on the original point of coordinates and the phase of interference fringe is collected, and the shape error of the inspected tooth flank for the standard surface is measured.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for non-contactly measuring the tooth surface shape of a gear, and in particular to a method for measuring the shape of a spur gear, helical gear, etc. using a free-form surface measuring device that utilizes holographic interference. The present invention relates to a non-contact tooth flank shape measurement method for measuring the tooth flank shapes of various gears.

0002

2. Description of the Related Art Gears rotate when a driving gear and a mating driven gear mesh with each other to transmit power. That is, more specifically, the tooth surface of the drive gear rotates while being in contact with the tooth surface of the mating driven gear, thereby transmitting power. At this time, all machines and devices that operate using power from a power source, including aircraft and automobiles, are often equipped with a gear device as a speed increase or deceleration device. At this time, if the gear device transmits power and drives the wheels or propeller device, it cannot perform its function satisfactorily if it is accompanied by noise and vibration. Therefore, in order to transmit power smoothly, when machining each gear of a gear device, the meshing part of the gear,
That is, it is well known that complex shape modifications, which require extremely advanced know-how, have been conventionally performed on the shape of tooth flanks of gears. At this time, the gear measuring device that inspects whether the desired tooth surface shape is completed measures the above-mentioned complex amount of tooth surface modification and transfers the measurement result data to a processing machine such as a gear cutter or tooth grinder. It has an important role of providing feedback to the machining work by the side.

However, the gear measuring devices currently in use use a method of tracing the tooth surface with a probe and calculating an involute curve from the sampled rotation angle of the gear and the length in the normal direction. In this method, one of the gears
It only measures one cross section of several connected teeth, and as mentioned above, the entire spread of the tooth surface meshes with the mating tooth surface one after another, and is used as functional data or measurement data of the tooth surface in operation. is insufficient.

In order to overcome this current situation, an optical curved surface shape measuring device was developed that uses holographic interference to measure not only gear tooth surfaces but also general curved surface shapes in a non-contact manner. The applicant's Japanese Patent Application Laid-Open No. 1-1164
It is disclosed in No. 03. In this non-contact measurement method, from the viewpoint of general machining accuracy in machining, the relatively rough surfaces of the gears are irradiated obliquely with a laser beam as an object beam to obtain sufficient specularly reflected light. ing. Since the effective wavelength of the obliquely projected laser beam becomes longer by one cosine (COS) of the angle of incidence, it is as if the observation was made using light with a longer wavelength, which makes it difficult to measure the rough tooth surface mentioned above. It is advantageous. According to the measuring method using this measuring device, the entire tooth surface of the gear can be directly measured.

[0005]

[Problems to be Solved by the Invention] However, when the tooth surface has a twisted curved shape, such as in a helical gear, the angle of incidence of parallel laser beams differs in each part. In order to analyze the shape error of the tooth surface, there is a problem in that it is necessary to know exactly which part of the tooth surface is irradiated and at what angle of incidence.

[0006] Therefore, the object of the present invention is to
The object of the present invention is to solve the above problem by using an optical curved surface shape measuring device such as that disclosed in Japanese Patent No. 16403, and to make it possible to measure and analyze the tooth surface shape of a gear having a curved tooth surface.

[0007]

[Means for Solving the Problems] In view of the above-mentioned objects, the present invention separates coherent light emitted from a light source into a reference light and an object light, and irradiates the object light onto a target curved surface to produce a reference light. and the reflected light of the object beam to obtain a hologram of the target curved surface, and from the holographic image of the reference tooth surface having a curved surface and the image of the test tooth surface of the same shape, the holographic interference of the latter with respect to the former tooth surface is obtained. In a method for measuring tooth flank shape of a gear using a non-contact free-form surface measuring machine that measures tooth flank errors, a theoretical tooth flank image of a gear having the above-mentioned reference tooth flank and test tooth flank is simulated by ray tracing. data on the incident angle of the object light at each point on the test tooth surface is collected from the image of the theoretical tooth surface, and the reference tooth surface and a part of the reference tooth surface are cut out. The coordinate origin of the image of the reference tooth surface is determined by superimposing the images of the reference tooth surface No. 2 and the reference tooth surface irradiated with the object light, and the hologram image of the reference tooth surface with the coordinate origin determined and the tooth surface to be inspected are A holographic interference image in which the coordinate origin is transferred is obtained by superimposing the images of Collect data corresponding to the incident angle of light and the phase of interference fringes, and use the incident angle data and phase data to determine the dimensional error in the normal direction of each point on the test tooth surface with respect to the reference tooth surface. The present invention provides a tooth profile measuring method using a non-contact free-form surface measuring machine, which calculates the tooth profile error of the tooth profile to be tested relative to the reference tooth profile. Hereinafter, the present invention will be described in further detail based on embodiments shown in the accompanying drawings.

[0008]

[Example] Fig. 1 is a mechanical diagram showing the overall configuration of a non-contact free-form surface measuring device used to implement the tooth flank shape measuring method according to the present invention. FIG. 2 is a side view illustrating the relationship between a surface and object light incident thereon;
B) is a partial plan view taken along line 2-2 in figure (A), and figure 3 is a
An explanatory diagram showing the composite relationship between a computer-generated simulated tooth surface, a reference tooth surface of a gear, and a tested tooth surface of a gear. Figure 4 is a partial perspective view showing details of the tooth surface shape that constitutes an example of reference tooth surface B. In the figure, FIG. 5 is an analytical diagram illustrating the relationship between the optical path difference of the object light incident on the twisted tooth surface and the tooth surface error.

Now, in describing the measurement method according to the present invention, the above-mentioned earlier application (Japanese Patent Application Laid-Open No. 116403/1999)
Figure 1 shows the configuration of the non-contact optical shape measuring machine of
Explain with reference to.

As shown in FIG. 1, the aircraft has a laser light source 1
, the laser light emitted from the same laser light source 1 is the reference laser light R
(hereinafter simply referred to as reference beam R) and measurement laser beam S (hereinafter simply referred to as
A beam splitter 2 that separates the reference beam R and the object beam S), reflecting mirrors 3 and 4 for the reference beam R and the object beam S, a reflecting mirror 4 that receives the reference beam R that has arrived via the reflecting mirror 3, and a gear to be measured 6. A light-receiving surface 5 that receives the object light that reaches the tooth surface 6a after reflection, a support shaft device 7 of the gear to be measured 6, a reference light R that reaches the light-receiving surface 5, and an object that is reflected by the tooth surface 6a to be measured. It is equipped with a camera 8, etc., which photographs a hologram 6b of the tooth surface 6a formed on the light-receiving surface 5 by interference with the light S. As described above, the object light S is irradiated onto the tooth surface 6a to be inspected at a large angle of incidence, thereby obtaining the advantage of increasing specularly reflected light due to scene phenomena.

The hologram 6b of the tooth surface to be inspected 6a formed on the light-receiving surface 5 is imaged by a camera 8, and the imaged data is stored in a frame memory 10 and transmitted from a personal computer, microcomputer, etc. via an interface 11. Computer device 1 consisting of
2 (hereinafter and in the drawings, it will be referred to as MPU 12 for brevity), and also displayed on the screen of CRT 13 as necessary. Therefore, the MPU 12 has a servo motor 9a.
The hologram data of the tooth surface is generated in a form corresponding to the positional data of each tooth surface of the gear indexed to the measurement position by being rotationally driven by a servo drive device 9 having a drive source and a gear indexing encoder 9b. are input one after another.

Now, when measuring the tooth surface shape using the object beam S, the gear set on the support shaft device 7 of the measuring machine, that is,
Each tooth surface of a reference gear and a gear to be tested 6, which will be described later, is irradiated with the same object light S. However, if the gear 6 is a curved surface with a helical angle, such as a helical gear, the incident angle of the object light also changes. According to the gear specifications of the gear 6 to be tested, the helix angle β on the pitch circle (diameter D0)
It is set to have a predetermined large angle of incidence with respect to the normal to zero. That is, as shown in FIGS. 2 and 3, in the specifications of a gear having a pitch circle diameter D0, the torsion angle β0 on the pitch circle, the incident angle θ, and the rotation angle τ from the center of the tooth surface to the measurement point are measured. Becomes a parameter. The setting of the incident angle θ of the object beam S is explained in Japanese Patent Application Laid-open No. 1-116430 with reference to FIG. The tooth surface 6 is set by a servo drive device 9 using a motor 9a as a drive source, a servo device for adjusting the angle of the mirror 4 (not shown), etc.
At this time, a computer device (to be described later) is irradiated with the pitch circle diameter D0 of the gear to be tested, the torsion angle β0 on the pitch circle, the incident angle θ, and the rotation angle from the center of the tooth surface to the measurement point. Gear introductions such as τ are input as data,
Since it is memorized, when a gear to be tested with the same gear specifications is set on the measuring device, by calling up the same gear specifications from the computer device, the servo drive device 9 is automatically operated and the optimum gear is set. It will be automatically set to the irradiation position.

[0013] In order to measure the tooth surface shape of a gear curved by having a helix angle using the optical curved surface shape measuring device having the above-mentioned configuration, the tooth surface is an involute helicoid curved surface. Therefore, when such a tooth surface is irradiated with parallel object light, the angle of incidence differs slightly at each part of the surface depending on the curvature of the surface. Therefore, the hologram of the tooth surface formed on the light-receiving surface 5 becomes a specular reflection image that includes this difference in incidence angle. The hologram 6b of the twisted tooth surface 6a thus formed on the light-receiving surface 5 is imaged by the camera 8 as described above, and the imaged data is stored in the frame memory 10 and input to the MPU 12 via the interface 11. , may also be displayed on the screen of the CRT 13. Therefore, the hologram data of the twisted tooth flanks is input one after another into the MPU 12 in a format corresponding to the position data of each tooth flank of the gear by the servo drive device 9.

Now, in order to measure the tooth flank shape of each tooth flank of the gear 6 to be tested, first, a hologram 6b as described above is created with respect to a reference gear having a standard twisted tooth flank corresponding to the gear to be tested. Photography is performed by the camera 8 under instructions from the MPU 12. Next, each tooth surface 6a of the gear 6 to be tested is measured. That is, the reference gear having a reference tooth surface is replaced with the test gear 6 having a large number of test tooth surfaces and is attached to the curved surface measuring device. Regarding one tooth surface to be tested of the gear to be tested, a hologram of the same tooth surface to be tested is obtained on the light receiving surface 5 in the same manner as described above. Then, by superimposing and matching the reflected image of the tooth surface to be tested on the hologram 6a of the reference tooth surface using a servo device such as the servo drive device 9, interference fringes are obtained. In this case, the overlapping standards and method are as per Patent Publication No. 2-170 of the applicant.
As disclosed in No. 44, this is the rotation angle position of the tooth surface to be inspected at which the first-order diffracted light generated when both hologram images interfere is maximized.

Next, by using the well-known fringe scanning method, that is, by slightly moving the reflection mirror 3 of the reference light R using actuator means such as a piezo element 3a, one wavelength of the reference light R is determined. Each point of the interference fringe is divided into equal parts, the interference fringes generated above are subdivided, data indicating the relationship between the equally divided wavelengths and the interference fringe is taken into the MPU 12, and calculations are performed based on the data. The phase of the image is calculated, and the contour lines are obtained by image processing of the interference fringes. Based on the interference fringes made up of contour lines obtained in this way, the shape error of the twisted tooth surface 6a is obtained, but in order to do so, by knowing the phase and incidence angle of the interference fringes at each measurement point of the interference fringes due to the holographic interference, Calculate the shape error of the tooth surface.

At this time, the tooth surface 6a to be inspected irradiated with the object light S
As mentioned above, the value of the incident angle θ° at each point of the tooth surface 6a
due to the twisted surface shape of , and therefore the effective wavelength at each point changes. When the effective wavelength changes,
The pitch and position of the interference fringes also change. Furthermore, since the actual tooth surface 6a to be inspected has undergone processing such as chamfering, a regular reflection image of the tooth surface 6a to be inspected is obtained on the CRT 13, and each point of the image is It is extremely difficult to compare the coordinate position with the phase and incident angle data of the interference fringes. Therefore, in the present invention, when measuring a tooth surface having a curved surface, for example, a twisted tooth surface shape as shown above, the measurement method described in detail below is carried out.

That is, first, based on the gear specifications and the well-known ray tracing method, the shape of the image captured by the camera 8 is determined by the MPU.
By making full use of 12 and calculating it as a simulation image, the measurement calculation of the tooth surface shape of the actual tooth surface 6a to be inspected is performed using the simulation image. Next, the hologram regarding the reference tooth surface A of the reference gear has already been photographed by the camera 8 as described above, and the MPU 1
2, the data of each axis γ, τ, θ, etc. of the photographing position of the reference gear supported by the support shaft device 7 of the optical free-form surface measuring device is inputted to the interface 11 from the measuring device. The data is taken out from the MPU 12 via the MPU 12.

Next, referring to FIG. 4 together with FIG. 1, for example, a special-shaped second tooth portion is formed by cutting out a part of the other tooth portion of the reference gear 6 having the reference tooth surface A. Using the gauge function of the reference tooth surface B, the servo mechanism 9
By rotating the reference gear 6 at a slow speed, the specular reflection image 15 of the second reference tooth surface B matches the photographed hologram 14 of the reference tooth surface A on the data in the MPU 12, and the CRT 13 at the time of matching A reference point or a reference line between the reference tooth surface A and the reference tooth surface B is determined as a coordinate image 16 on the screen of the CRT 13 using the regularly reflected image on the screen. In other words, since the mechanical dimension data of the notch part of the second reference tooth surface B has been obtained in advance as an actual measurement value, the notch part for which the mechanical dimension data is known is the notch part of the screen of the CRT 13. Since it is displayed as an image, the coordinates of the image of the reference tooth surface A on the screen of the CRT 13 can be defined from the coordinate image 16 if the points and lines in the image of the notch are used as reference points or reference lines. It becomes. Note that, as described above, both images are made to coincide at the position where the first-order diffracted light of the hologram image in the MPU 12 is maximized.

Next, the gear to be measured 17, which is the object to be measured, is attached to the support shaft device 7 of the measuring device instead of the reference gear 6, and
Holographic interference fringes 20 are obtained between the regular reflection image 18 and the coordinate image 16 which is a hologram of the reference tooth surface A. At this time, by the fringe scanning method described above, the wavelength λ of the reference light R is moved n times by λ/n, and the reflection mirror 3 is moved by λ/n.
The interference fringes are moved and data is taken into the MPU 12 each time. Then, when calculating the interference fringes by applying Fourier analysis, etc., one pitch of the interference fringes is interpolated,
The height value of the fringe at the measurement point can be calculated from two pieces of data: the phase of each point and the direction of movement.

On the other hand, a theoretical tooth surface is simulated from the data of each axis of the above-mentioned measuring device, and a simulation image 19 is obtained. Then, the theoretical position and angle of incidence of each point on the tooth surface projected onto the CRT 13 are calculated in advance, and the
The image is superimposed on the image of the holographic interference fringe 20 on the RT 13. After measuring in this way, the coordinates of the curved tooth surface in the simulation described above are returned to the plane, and the contour lines shown at 21 are obtained by sequentially connecting each position of the tooth surface and the error at that point in a grid. be.

If the above-mentioned measurement and arithmetic processing are performed one after another on a plurality of tooth flanks to be tested of the measurement gear 17, the tooth flank shape will be determined for each of the plurality of tooth flanks to be tested that have curved tooth flanks. can be actually measured. The sequential measurement process described above is illustrated in the flowcharts shown in FIGS. 7 and 8 (FIG. 6 is a combined diagram).

[0022] When actually measuring tooth surfaces with a plurality of curved surface shapes, the measurement start point is the position where the first-order diffracted light is maximum, and the spindle index position at this time is the first measurement start point. In this way, the angular position of the shaft of the support device 7 of the measuring device can be determined for each tooth flank 6a by accurate indexing. To summarize the above, the image of the simulation described above has information on the angle of incidence, and the hologram on the screen of the CRT 13 that was measured has information on the phase, so it is possible to match these using a special reference plane. As mentioned above, in order to measure the tooth surface of a gear at each point, it is necessary to simulate the tooth surface, but the parameters that are the basis for this calculation are:
In addition to the gear specifications as shown in FIG. 2, there is also the irradiation position of the object light S.

When a gear such as a reference gear or a gear to be tested is mounted on a measuring device as shown in FIG. 1, the center of the gear groove is rotated by τ with respect to the center line of the measuring device.
In the state shown in FIG. 2, the center of the object light S is offset by a distance value s and is emitted. There is an appropriate irradiation position depending on the gear specifications, and as a database in advance,
File it.

The incident angle θ of the laser beam as coherent light is:
It is fixed by the deflection prism of the tooth flank shape measuring device and can be replaced, so input the specification of the deflection prism to be used before measurement. When object light S with wavelength λ is incident on the tooth surface at a large incident angle θ, its effective wavelength λ′ is defined by the following equation.

λ'=λ/cos θ For example, taking a helical gear as an example, its tooth surface is an involute helicoid, so when it is irradiated by the parallel object beam S, the angle of incidence differs at each position. To analyze the obtained interference fringes (actually, the phase φ of each point), calculate the effective wavelength λ' from each incident θ' for each point, and then calculate the step in the normal direction of the surface from the phase φ of that point, That is, the shape error δ is calculated. At this time, the surface error (level difference) δ is the optical path difference Δ between the two incident optical paths L1 and L2 in FIG. 5 and Δ=2
There is a relationship δ・cosθ.

Here, the relationship between the phase φ' of each point of the interference fringe calculated by the fringe scanning method described above and the optical path difference Δ is as follows. Therefore, from both equations above, the error δ' at each point is
It is.

In the above description, the reference surface B in FIG. 3 is cut on the pitch circle in the radial direction and 1/2 the thickness in the tooth width direction, as shown in FIG. Since the reference tooth surface B is used to determine the origin of the coordinates of the reference tooth surface A, the cut size is not limited to the above 1/2, but may have a step difference of 1/3, 1/4, etc. in the tooth width direction. Needless to say, it is also possible to form a shape.

[0028] Furthermore, the machined surfaces of actual gears do not necessarily have a precise chamfered finish, so there is considerable variation. Therefore, if the method of the present invention is applied,
Accurate coordinate values for each point can be obtained even for tooth surface shapes with such variations.

[0029]

As is clear from the description of the embodiments described above, the present invention can improve the accuracy of the tooth surface, which has conventionally been perceived only as an error with respect to one line on the surface of the tooth surface having a three-dimensional shape. Since the shape measurement data is measured as a dense surface without contact using the wavelength of coherent light consisting of a laser beam as the measurement unit, it is possible to grasp the actual shape of the tooth surface. Furthermore, with the recent introduction of computers with significantly faster calculation speeds, data can be stored and managed into a database, mechanically controlled at measurement positions, data taken in, analyzed, and displayed using image analysis. It also has the effect of making it possible.

Furthermore, as mentioned above, the progress in line-to-plane measurement has provided extremely effective data for the design and processing of gears, which are now requiring submicron precision, and has improved the quality of gear products. This can greatly contribute to improvement.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a shape measuring device used for measuring tooth surface shape errors according to the present invention.

[Fig. 2] (A) is a side view illustrating the relationship between the tooth surface to be inspected of the gear and the object light incident thereon;
) is a partial plan view taken along line 2-2.

[Figure 3] Computer simulation tooth surface,
FIG. 2 is an explanatory diagram showing a composite relationship between a reference tooth surface of a gear and a test tooth surface of a gear.

FIG. 4 is a partial perspective view showing details of the shape of the reference tooth surface B. FIG.

FIG. 5 is an analytical diagram illustrating the relationship between the optical path difference of an object light incident on a twisted tooth surface as an example of a tooth surface having a curved surface shape and the tooth surface error.

FIG. 6 is a combined diagram of FIGS. 7 and 8;

FIG. 7 is the first half of the flowchart of the measurement process shown in FIG. 3;

FIG. 8 is the second half of the flowchart of the measurement process shown in FIG. 3;

[Explanation of sign]

1...Laser light source, 2...beam splitter, 3...Reflection mirror, 3a...piezo element, 4...Reflection mirror, 5... Light receiving surface, 6...Test gear, 6a...Test tooth surface, 7...Support shaft device, 8...Camera, 9... Servo drive device, 10...Frame memory, 12...MPU, 13...CRT, 17...Test gear.

Claims (1)

[Claims] Claim 1: Separating coherent light emitted from a light source into reference light and object light, and irradiating the object light onto a target curved surface, a hologram image of the target curved surface is created from the reference light and reflected light of the object light. Non-contact free-form surface measurement that measures the tooth surface shape error of the latter tooth surface with respect to the former tooth surface by holographic interference from a holographic image of a reference tooth surface with a curved surface and an image of the test tooth surface of the same shape. In a method for measuring the tooth flank shape of a gear using a device, an image of a theoretical tooth flank of a gear having the reference tooth flank and a test tooth flank is obtained by a simulation method using ray tracing, and an image of the theoretical tooth flank is obtained by a simulation method using ray tracing. Collect data on the incident angle of the object light at each point on the test tooth surface, and irradiate the object light onto the reference tooth surface and a second reference tooth surface obtained by cutting out a part of the reference tooth surface. The coordinate origin of the image of the reference tooth surface is determined by superimposing the respective images, and the coordinate origin is transferred by superimposing the image of the test tooth surface on the hologram of the reference tooth surface with the coordinate origin determined. By superimposing the holographic interference image and the simulated image of the theoretical tooth surface, the angle of incidence of the object light and the phase of the interference fringe can be determined for each point based on the coordinate origin. Corresponding data is collected, and the dimensional error in the normal direction of each point of the test tooth surface with respect to the reference tooth surface is calculated from the incident angle data and phase data, and A tooth surface shape measuring method using a non-contact free-form surface measuring device, characterized in that the tooth surface shape error of a tooth surface to be inspected is measured.