JP2008151664A - Measuring method of three-dimensional cam, measuring program, and measuring stage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means capable of precisely measuring the shape of a three-dimensional cam by suppressing the inclination of attitude of a cam and the axial dislocation of a cam. <P>SOLUTION: The measuring method of a three-dimensional cam comprises: a first step for preliminarily measuring the shape of a three-dimensional cam placed on a tool at a prescribed reference position; a second step for determining whether the attitude of the three-dimensional cam is within an error range, based on the result of the preliminary measurement; a third step for maintaining the position relationship between the three-dimensional cam and the tool, when the attitude of the three-dimensional cam is not within the error range, adjusts at least one of the horizontal position of the tool and the inclination of the tool, based on the result of the preliminary measurement, and repeating the first and second steps; and a fourth step for measuring the shape of the cam surface of the three-dimensional cam when the attitude of the three-dimensional cam is not within the error range. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for measuring the shape of a three-dimensional cam and related techniques.

As one of the mechanical elements of precision equipment, a three-dimensional cam in which the cam surface continuously changes with respect to the rotation axis direction is conventionally known. For example, a cylindrical three-dimensional cam is used for a lens barrel of a camera in order to adjust a lens extension amount. In a precision instrument using such a three-dimensional cam, the performance of the product depends on the shape accuracy of the cam surface of the three-dimensional cam. Therefore, with regard to the three-dimensional cam, it has been pursued to improve the accuracy of cam surface shape measurement for mold correction and product inspection. For example, Patent Document 1 discloses an example of a measurement method related to a three-dimensional cam.
JP 2003-156327 A

By the way, in the shape measurement of the three-dimensional cam, a deviation may occur between the position to be measured on the cam surface and the actual measurement position due to the inclination of the posture of the cam at the time of measurement and the misalignment of the cam. However, conventionally, the above three-dimensional attitude error has not been sufficiently corrected, and it has been extremely difficult in practice to obtain useful measurement results for the shape of the cam surface.
On the other hand, it has been attempted to correct errors in the θh direction (rotation direction and height direction) of measurement data by processing on software. However, when there is a tilt or misalignment in the measurement posture, there is a shift between the position to be measured and the actual measurement position in the first place, and such measurement data is two-dimensional in the θh direction. The current situation is that even if correction is applied, there is no effect.

  The present invention solves the above-mentioned problems of the prior art. One of the objects of the present invention is to provide a means capable of measuring the shape of a three-dimensional cam with high accuracy by suppressing the inclination of the cam posture and cam misalignment. Another object of the present invention is to provide a means for accurately grasping the inclination and misalignment of the posture of the three-dimensional cam during measurement.

  The three-dimensional cam measuring method according to the first invention comprises the following steps. In the first step, the shape at a predetermined reference position of the three-dimensional cam placed on the jig is preliminarily measured. In the second step, it is determined whether the attitude of the three-dimensional cam is within the error range based on the preliminary measurement result. In the third step, when the posture of the three-dimensional cam does not fall within the error range, the horizontal position of the jig and the position of the jig based on the result of the preliminary measurement are maintained while maintaining the positional relationship between the three-dimensional cam and the jig. At least one of the inclinations of the jig is adjusted, and the first step and the second step are repeated. In the fourth step, the shape of the cam surface of the three-dimensional cam is measured when the posture of the three-dimensional cam falls within the error range.

In the second invention, the first invention further includes the following steps. In the fifth step, an operation for aligning and matching the spatial coordinate value based on the measurement data of the cam surface and the three-dimensional shape model of the three-dimensional cam is executed. In the sixth step, based on the result of the above calculation, the horizontal deviation amount and the inclination of the posture of the three-dimensional cam at the time of obtaining the measurement data are estimated.
The three-dimensional cam measuring method according to the third invention comprises the following steps. In the first step, the shape of the cam surface of the three-dimensional cam placed on the jig is measured. In the second step, a calculation for aligning and matching the spatial coordinate value based on the measurement data of the cam surface and the three-dimensional shape model of the three-dimensional cam is executed. In the third step, the horizontal deviation amount and inclination of the posture of the three-dimensional cam at the time of obtaining the measurement data are estimated based on the result of the above calculation.

  In the three-dimensional cam measurement program according to the fourth invention, the following steps are executed by a computer. In the first step, measurement data obtained by measuring the shape of the cam surface of the three-dimensional cam is read. In the second step, an operation for aligning and matching the spatial coordinate value based on the measurement data and the three-dimensional shape model of the three-dimensional cam is executed. In the third step, the horizontal deviation amount and inclination of the posture of the three-dimensional cam at the time of obtaining the measurement data are estimated based on the result of the above calculation.

  A measurement stage for a three-dimensional cam according to a fifth aspect includes a rotatable main body, a jig, a first position adjustment unit, and a second position adjustment unit. The jig is arranged on the upper portion of the main body and is configured to be able to place a three-dimensional cam. The first position adjusting unit adjusts the horizontal position of the jig while maintaining the positional relationship between the three-dimensional cam and the jig in a state where the three-dimensional cam is placed on the jig. The second position adjustment unit adjusts the inclination of the jig while maintaining the positional relationship between the three-dimensional cam and the jig in a state where the three-dimensional cam is placed on the jig.

  According to one aspect of the present invention, it is possible to accurately measure the shape of the three-dimensional cam while suppressing the inclination of the posture of the cam disposed on the jig and the cam misalignment. In addition, according to one aspect of the present invention, it is possible to accurately grasp the inclination and center misalignment of the posture of the three-dimensional cam during measurement.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of a three-dimensional cam measurement system in the present embodiment. FIG. 2 is a plan view of the measurement table shown in FIG.
First, the configuration of a cylindrical three-dimensional cam (hereinafter referred to as a cylindrical cam 11) that is a measurement target in the present embodiment will be described. The cylindrical cam 11 is disposed in the lens barrel of the camera, and the overall shape of the main body portion is cylindrical. A stepped portion 11a protruding inward is formed on the inner peripheral surface of the main body portion of the cylindrical cam 11, and a step portion between the main body portion and the stepped portion 11a forms a cam surface. The main body portion of the present embodiment is provided with three cam surfaces having the same shape. Each cam surface is disposed so as to be rotationally symmetric at an angle of 120 degrees in the axial direction of the main body portion. The cylindrical cam 11 is manufactured by molding a resin material with a mold.

Next, the configuration of the measurement system of this embodiment will be described. The measurement system includes a measurement stage 12, a measurement device 13, and a control device 14.
The measurement stage 12 includes a main body unit 15, a posture adjustment table 16, and a fixing jig 17.
A posture adjustment table 16 is fixed to the upper surface side of the main body 15 of the measurement stage 12. Further, the main body 15 drives a built-in motor (not shown) in accordance with an instruction from the control device 14 to rotate the posture adjustment table 16 about a rotation axis extending in the vertical direction in FIG.

Further, the posture adjustment table 16 includes a shift table unit 18 and a tilt table unit 19.
The shift table portion 18 is attached to the upper side of the main body portion 15. The shift table portion 18 is configured to be slidable on the XY plane that is parallel to the upper surface of the main body portion 15 with respect to the main body portion 15. The shift table unit 18 includes a first shift drive unit 20 that adjusts the amount of movement in the X-axis direction relative to the main body unit 15, and a second shift drive unit 21 that adjusts the amount of movement in the Y-axis direction relative to the main body unit 15. Is provided. Each of the shift drive units 20 and 21 described above includes a screw feed mechanism using a combination of a lead nut and a lead screw, a motor that rotates the lead screw, and a control unit that drives the motor in accordance with an instruction from the control device 14. Have. Further, the control unit has a wireless communication function, and controls the motor in response to an instruction from the control device 14 by wireless (note that detailed illustration regarding the configuration of each of the shift drive units 20 and 21 is omitted).

Two lift pins 22 are arranged on the upper surface of the shift table unit 18. Each lift pin 22 is configured such that the tip position of the pin moves in the vertical direction (perpendicular to the upper surface of the main body 15) by a pin driving unit (not shown) built in the shift table unit 18. . Each pin driving unit is connected to the control device 14.
The tilt table unit 19 is a flat plate having a substantially square shape, and is disposed on the upper side of the shift table unit 18. The tilt table unit 19 is supported at three points by a spherical spacer 24 disposed on the upper surface of the shift table unit 18 and two lift pins 22. The tilt table unit 19 is configured to adjust the tilt with respect to the shift table unit 18 by changing the pin tip positions of the two lift pins 22.

  A fixing jig 17 is fixed to the upper surface side of the tilt table unit 19. The overall shape of the fixing jig 17 is a shallow bottom cylindrical shape having an inner diameter slightly larger than the outer diameter of the cylindrical cam 11. Therefore, the cylindrical cam 11 can be positioned and placed inside the fixing jig 17 in an upright state. The cylindrical cam 11 is fixed to the fixing jig 17 using, for example, an adhesive tape.

The measuring device 13 includes a probe 25, a probe moving mechanism 26, and a measurement control unit 27.
The probe 25 contacts the surface of the workpiece (cylindrical cam 11) at the time of measurement, and inputs position information on each part of the workpiece to the measuring device 13.
The probe moving mechanism 26 includes a slider that holds the probe 25 in a suspended state and a support arm that supports the slider. The slider moves the probe 25 in the vertical direction and the horizontal direction. Further, the support arm is configured to move the slider and the probe 25 in the front-rear direction (illustration of the slider and the support arm is omitted).

The measurement control unit 27 is connected to the control device 14. The measurement control unit 27 controls the operation of each unit of the measurement device 13 based on instructions from the control device 14. Further, the measurement control unit 27 obtains a measurement value related to the shape of the workpiece based on the contact position of the probe 25 and outputs measurement value data to the control device 14.
The control device 14 has a CPU 28 and a recording unit 29. The CPU 28 performs overall control of the entire measurement system by executing the sequence program, and executes various arithmetic processes based on the measurement program. The recording unit 29 records measurement value data from the measurement device 13, three-dimensional CAD data that is design data of the cylindrical cam 11, and the like.

Next, the flow of the measuring method of the cylindrical cam 11 in the present embodiment will be described with reference to the flowchart of FIG.
Step 101: The user places the cylindrical cam 11 on the fixing jig 17 of the measurement stage 12. Thereafter, the user gives an instruction to the control device 14 to start measuring the shape of the cylindrical cam 11.

  Step 102: The CPU 28 of the control device 14 performs the preliminary measurement of the cylindrical cam 11 by operating the measurement device 13 in accordance with a user instruction (S101). In this preliminary measurement, the measuring device 13 measures an arbitrary reference position preset on the cylindrical cam 11 (for example, a predetermined location on the inner peripheral surface of the cylindrical cam 11 and an end of the cam surface). Then, the CPU 28 records the measurement data of the reference position output from the measurement device 13 in the recording unit 29.

  Step 103: The CPU 28 determines whether the attitude of the cylindrical cam 11 placed on the fixing jig 17 is within an error range from the target value based on the measurement data of the reference position in the preliminary measurement (S102). To do. Here, the target value indicates a reference position in a state where the cylindrical cam 11 is placed on the fixing jig 17 in a posture with no misalignment and inclination. The attitude error parameter is set according to the tolerance of the cylindrical cam 11. As an example, the error range in this embodiment is set to about ± 5 μm.

If it falls within the error range from the target value (YES side), the CPU 28 proceeds to S106. On the other hand, if it does not fall within the error range from the target value (NO side), the CPU 28 proceeds to S104.
Step 104: The CPU 28 calculates the posture correction amount (horizontal shift correction amount, tilt correction amount) of the cylindrical cam 11 based on the difference between the reference position measurement data and the target value.

  Step 105: The CPU 28 controls the attitude adjustment table 16 based on the correction amount (S104) of the attitude of the cylindrical cam 11, and maintains the positional relationship between the cylindrical cam 11 and the fixing jig 17 to change the attitude of the cylindrical cam 11. Make fine adjustments. Specifically, the CPU 28 drives the first shift drive unit 20 and the second shift drive unit 21 based on the shift correction amount. As a result, the shift table portion 18 of the attitude adjustment table 16 moves in the horizontal direction, and the misalignment of the attitude of the cylindrical cam 11 is corrected. Further, the CPU 28 adjusts the pin tip positions of the two lift pins 22 by driving the pin driving unit based on the tilt correction amount. As a result, the tilt of the tilt table 19 of the posture adjustment table 16 changes, and the tilt of the posture of the cylindrical cam 11 is corrected.

Thereafter, the CPU 28 returns to S102, performs preliminary measurement again, and repeats the above operation. That is, the CPU 28 continues to mechanically adjust the attitude of the cylindrical cam 11 by the attitude adjustment table 16 until the attitude of the cylindrical cam 11 falls within the error range from the target value.
Step 106: The CPU 28 operates the measuring device 13 and the measuring stage 12 to perform the main measurement of the shape of the cam surface of the cylindrical cam 11. The main measurement is performed on each of the three cam surfaces of the cylindrical cam 11.

  Specifically, the CPU 28 causes the probe 25 of the measurement device 13 to contact the cam surface of the cylindrical cam 11 and then rotates the main body 15 of the measurement stage 12 in a predetermined direction. As the cylindrical cam 11 rotates, the probe 25 moves up and down following the cam surface, so that the shape of the cam surface is input to the measuring device 13. Then, the CPU 28 records the cam surface shape measurement data output from the measuring device 13 in the recording unit 29. Note that the measurement data of the shape of the cam surface includes, for example, data on the position of the probe 25 for each rotation angle of the measurement stage 12.

Step 107: The CPU 28 converts the measurement data (S106) of the shape of the cam surface by this measurement into point cloud data of spatial coordinate values.
Step 108: The CPU 28 executes a fitting process between the point cloud data (S107) of the spatial coordinate values and the three-dimensional CAD data.
First, the CPU 28 performs an operation for aligning and adapting the three-dimensional shape model on the computer based on the three-dimensional CAD data to each coordinate point of the point cloud data. As an example, the CPU 28 searches for a position where the difference between each coordinate point of the point cloud data and the coordinate point of the cam surface of the three-dimensional shape model is minimized by the least square method. Then, the CPU 28 adjusts the posture of the three-dimensional shape model and repeats the above calculation, thereby aligning each coordinate point of the point cloud data with the three-dimensional shape model. At this time, the CPU 28 can also limit the degree of freedom of posture change of the three-dimensional shape model at the time of alignment based on the constraint condition given by the user. Further, the CPU 28 may perform the fitting process with the three-dimensional shape model on the point cloud data of an arbitrary portion of the cam surface.

  Secondly, the CPU 28 determines the attitude of the cylindrical cam 11 during the actual measurement (the horizontal deviation amount and inclination of the cylindrical cam 11) based on the horizontal deviation amount and inclination of the three-dimensional model in a state where the point cloud data is adapted. ). Then, the CPU 28 records the estimation data of the measurement posture in the recording unit 29 in association with the measurement data (S106) of the main measurement. Note that the CPU 28 can also output the error amount of each measurement data with the three-dimensional shape model as a θh component or a θr component in a state where the point cloud data is adapted. This is the end of the description of the flowchart of FIG.

Hereinafter, the effect of this embodiment is demonstrated.
In the measurement system of this embodiment, the attitude of the cylindrical cam 11 is mechanically adjusted according to the result of the preliminary measurement (S102 to S105). For this reason, since the posture error due to the inclination or misalignment of the cylindrical cam 11 is substantially eliminated before the main measurement, the shape of the cam surface of the cylindrical cam 11 can be measured with high accuracy.

  Further, in the measurement system of the present embodiment, the estimated data of the measurement posture of the cylindrical cam 11 at the time of the main measurement is generated by the fitting process of the point cloud data of the spatial coordinate values and the three-dimensional CAD data (S108). Therefore, the user can grasp the attitude of the cylindrical cam 11 at the time of the main measurement by referring to the estimated data of the measurement attitude, and can more accurately evaluate the reliability of each measurement data. Furthermore, the cylindrical cam 11 with higher dimensional accuracy can be manufactured by feeding back the product shape obtained from the highly reliable measurement data to the mold.

(Supplementary items of the embodiment)
(1) The CPU 28 in the above embodiment may control the posture adjustment table 16 based on the measurement posture estimation data after S108 to adjust the posture of the cylindrical cam 11 and perform the main measurement again. In the shape measuring method of the present invention, the step of adjusting the attitude of the cylindrical cam 11 based on the preliminary measurement may be omitted, and only the fitting process with the three-dimensional model may be performed after the main measurement.

(2) The shape measuring method of the present invention is not limited to the shape measurement of the cylindrical cam of the above embodiment, and can be widely applied to three-dimensional shape workpieces including three-dimensional cams of other shapes.
(3) In the above-described embodiment, an example in which a contact-type three-dimensional measuring device using the probe 25 is used has been described. However, the configuration of the present invention performs shape measurement with a non-contact type three-dimensional measuring device using a laser or the like. It may be a thing.

  The present invention can be implemented in various other forms without departing from the spirit or the main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The present invention is defined by the claims, and the present invention is not limited to the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

Schematic diagram of 3D cam measurement system in this embodiment Plan view of the measurement table shown in FIG. Flow chart for explaining a cylindrical cam measuring method in this embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Cylindrical cam, 12 ... Measuring stage, 13 ... Measuring apparatus, 14 ... Control apparatus, 15 ... Main-body part, 16 ... Attitude adjustment table, 17 ... Fixing jig, 18 ... Shift table part, 19 ... Tilt table part, 20 ... 1st shift drive part, 21 ... 2nd shift drive part, 22 ... Lift pin, 28 ... CPU

Claims (5)

A first step of preliminarily measuring the shape of the three-dimensional cam placed on the jig at a predetermined reference position;
A second step of determining whether the attitude of the three-dimensional cam is within an error range based on the result of the preliminary measurement;
When the posture of the three-dimensional cam does not fall within an error range, the position of the jig in the horizontal direction based on the result of the preliminary measurement and the positional relationship between the three-dimensional cam and the jig are maintained. A third step of adjusting at least one of the inclinations of the jig and repeating the first step and the second step;
A fourth step of measuring the shape of the cam surface of the three-dimensional cam when the posture of the three-dimensional cam is within an error range;
A method for measuring a three-dimensional cam, comprising: In the measuring method of the three-dimensional cam of Claim 1,
A fifth step of performing an operation of aligning and fitting a spatial coordinate value based on the measurement data of the cam surface and a three-dimensional shape model of the three-dimensional cam;
A sixth step of estimating a horizontal direction shift amount and an inclination of the posture of the three-dimensional cam based on the result of the calculation;
A method for measuring a three-dimensional cam, further comprising: A first step of measuring the shape of the cam surface of the three-dimensional cam placed on the jig;
A second step of performing an operation of aligning and fitting a spatial coordinate value based on the measurement data of the cam surface and a three-dimensional shape model of the three-dimensional cam;
A third step of estimating a horizontal deviation amount and an inclination of the posture of the three-dimensional cam based on the result of the calculation;
A method for measuring a three-dimensional cam, comprising: A first step of reading measurement data obtained by measuring the shape of the cam surface of the three-dimensional cam;
A second step of performing an operation of aligning and fitting a spatial coordinate value based on the measurement data and a three-dimensional shape model of the three-dimensional cam;
A third step of estimating a horizontal deviation amount and an inclination of the posture of the three-dimensional cam based on the result of the calculation;
3D cam measurement program characterized by causing a computer to execute A rotatable main body,
A jig that can be placed on the main body and on which a three-dimensional cam can be placed;
In a state where the three-dimensional cam is placed on the jig, a first position adjusting unit that adjusts a horizontal position of the jig while maintaining a positional relationship between the three-dimensional cam and the jig;
A second position adjustment unit that adjusts the inclination of the jig while maintaining the positional relationship between the three-dimensional cam and the jig in a state where the three-dimensional cam is placed on the jig;
A three-dimensional cam measurement stage characterized by comprising:

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