JP2001264048A - Method and device for measuring shape of v-groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure characteristic values, such as pitch deviations and radius deviations, of male screws fixed uprightly on a rotary table and screw holes in a measured object placed on the rotary table. SOLUTION: Constant gauge head direction control, constant rotary table radius tracer control, and two-surface contact tracer control are combined together into V-groove rotary table tracer control, which is performed so as to keep, at all times, a gauge head 24 of a copying probe 22 in contact with two surfaces that form a V-groove of the measured object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the shape of a V-groove, and more particularly to a method for measuring a V-groove, such as a worm gear, a male screw or a screw hole, using a three-dimensional coordinate measuring machine. The present invention relates to a V-groove shape measuring method and apparatus suitable for use in measuring characteristic values such as a pitch deviation and a radius deviation of a V-groove of an object to be measured.

[0002]

2. Description of the Related Art A three-dimensional coordinate measuring machine (also referred to simply as a three-dimensional measuring machine) 10 shown in FIG. 1 is known as an apparatus for measuring a three-dimensional shape of a workpiece such as a work with high accuracy.
The surface plate 12 is made of, for example, granite and polished so as to have a smooth surface, and the gate is provided to be movable in the front-rear direction (for example, the Y-axis direction) of the surface plate 12. The frame 14 and the horizontal beam 15 of the portal frame 14
The slider 16 is provided so as to be movable in the left-right direction (for example, the X-axis direction) along the axis, and the lifting shaft 18 is provided on the slider 16 so as to be able to move up and down in the vertical direction (for example, the Z-axis direction)
And a probe 22 for coordinate measurement, having a probe 24 formed at the tip, attached to the lower end of the elevating shaft 18 via a probe holder 20.

Accordingly, after the workpiece W to be measured is placed on the surface plate 12, the probe 22 is moved in the three-dimensional direction (X,
While moving in the (Y, Z axis directions), the tracing stylus 24 is sequentially brought into contact with the measurement site of the workpiece W, and at each contact point, the coordinate value of each axis direction of the probe 22 is read from a scale (not shown). By calculating the coordinate values, the dimensions, angles, and the like of the work W can be measured with high accuracy.

As a method of measuring the shape of a screw using such a three-dimensional measuring machine, the applicant has disclosed, for example, Japanese Patent Application Laid-Open No.
341826 proposes a method for determining the center coordinates of a screw hole.

When measuring the shape of a workpiece using such a coordinate measuring machine, a probe 2 for coordinate measurement is required.
It is necessary to sequentially follow and measure the coordinates of the workpiece while moving 2. As a method of automatically performing this scanning control using a computer, when a rotary table is not used, an arbitrary plane is used as a reference plane, and the height from the reference plane is kept constant, along the contour of the workpiece. FIG. 3 shows a control method for copying in accordance with the following (hereinafter, referred to as constant height copying control).
As illustrated in the case where the rotary table 30 is used, a control method (hereinafter, referred to as radius) in which a cylindrical surface determined by designating an arbitrary straight line and a distance (ie, radius) from the straight line along the contour of the workpiece W is used. Constant scanning control) has been developed and put into practical use.

[0006] Also, as shown in FIG.
No.5, No.3 of the probe when the rotary table is not used
One axis by a rotary table is added to the axis control scanning, and as shown in FIG. 4, while keeping the direction of the probe constant with respect to the measurement reference line of the work (referred to as constant measurement direction scanning control), simultaneous 4-axis control It is proposed to follow by.

According to this method, when a rotary table, such as the cylindrical cam shown in FIG. 3, is not used, the workpiece and the probe interfere with each other. It is possible to measure the entire circumference at one time without changing. Further, even in the case of an impeller or a propeller blade that cannot be measured at one time, the number of times of changing the attitude of the probe can be reduced.

[0008]

On the other hand, in recent years, as the object to be measured has been expanded, as shown in FIG. 5, a worm gear having a V-shaped groove formed in a spiral shape, a general male screw, a screw hole formed in a work, and the like. 6, there is a request to measure the deviation (for example, the maximum deviation) of the pitch P of the screw (for example, the maximum deviation) and the deviation (for example, the maximum deviation ΔR) in the radius R direction of the plane locus of the screw thread superimposed in the axial direction as shown in FIG. However, these cannot be measured accurately by the conventional method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to accurately measure characteristic values of a V-groove shape of a worm gear, a general male screw, a screw hole, or the like. .

[0010]

According to the present invention, an object to be measured having a V-shaped groove formed in a spiral shape is fixed to a rotary table, and a center axis of the object to be measured and a central axis of the rotary table are within a predetermined allowable range. When the V-groove is measured using a scanning probe for position measurement while rotating the rotary table, the probe is brought into contact with two surfaces constituting the V-groove when the rotation table is rotated. By combining the two-surface contact scanning control to be performed and the pitch scanning control to move the tracing stylus in the direction of the central axis at a speed determined based on the pitch of the V-groove and the rotation speed of the rotary table, the V The object has been solved by performing V-groove rotary table scanning control for performing measurement while always bringing the tracing stylus into contact with two surfaces forming a groove.

The distance from the origin of the work coordinate system with the center axis of the object to be measured as the third axis to the center axis of the rotary table, and both the origin of the work coordinate system and the center axis of the rotary table are included. If the angle between the vector obtained by projecting the third axis of the workpiece coordinate system on the plane and the center axis of the rotary table falls within a predetermined allowable range, the center axis of the workpiece and the rotation This is performed by determining that the center axis of the table matches.

In addition, the V-groove rotary table scanning control is performed by controlling the position vector X of the scanning probe (hereinafter, all vector symbols are omitted in the text to avoid complicating the description), and the displacement ΔX And the rotation angle θ of the rotary table
Is sampled, and when the rotary table is rotated at an angular velocity ω, a peripheral velocity Vω generated based on a distance r from the center axis of the rotary table to the position vector X.
(= Rω) and a velocity vector Vz (=
Ω is calculated so that the combined speed of GP / (2π / ω)) becomes a predetermined scanning speed V, the speed vector Vz is calculated based on the ω and the screw pitch GP, and the speed vector Vz is scanned. The speed vector command Vt and the above-mentioned ω are the speed commands of the rotary table.

The probe velocity vector command Vt
Is the sum of the velocity vector Vz and the displacement correction vector Ve for keeping the displacement of the scanning probe constant.

According to the present invention, an object to be measured in which a V-shaped groove is formed in a spiral shape is fixed to a rotary table, and the central axis of the object to be measured and the central axis of the rotary table coincide within a predetermined allowable range. If not, when scanning the V-groove using the scanning probe for position measurement while rotating the rotary table, from the origin of the object to be measured to the probe of the scanning probe when viewed from the machine coordinate system. The stylus direction constant control which aims at keeping the vector obtained by projecting the directional vector on the table surface of the rotary table constant, the rotary table constant scanning control with the cylindrical surface as the constraint surface, and the V-groove of the object to be measured And the two-surface contact scanning control for bringing the probe of the scanning probe into contact with the two surfaces constituting
This problem is solved by performing V-groove rotary table scanning control in which a probe of a scanning probe is always brought into contact with two surfaces forming a groove.

The V-groove rotary table scanning control is performed by sampling a position vector X of the scanning probe, a displacement amount ΔX thereof, and a rotation angle θ of the rotary table. The approach reverse direction vector Qu in the direction perpendicular to the axis is calculated, and the velocity vector V of the probe when the rotary table is stationary at the rotation angle θ.
Is calculated, and the angular velocity ωw of the rotary table is calculated based on the velocity vector V of the probe, as viewed from the axis of the object to be measured. From the positional relationship between the table rotation angle θ and the probe position X, the table rotation angle θ due to the control error is calculated. By adjusting the advance and delay from the target value, the correction angular velocity Δω is determined, the angular velocity ωw is corrected by the Δω, and the velocity vector Vt that follows the movement of the correction angular velocity Δω is calculated at the probe position X and the table rotation angle θ. And the vector sum Vf (= V + Vt) of the following speed vector Vt and the probe speed vector V is used as a probe speed command, and the angular speed ωw is used as the correction angular speed Δω.
The value ωt (= −ωw + Δω) corrected in the above is used as the speed command of the rotary table.

The probe velocity vector V is at least a basic velocity vector Vo indicating the basic traveling direction of the scanning probe, a displacement correction vector Ve for keeping the displacement of the scanning probe constant, and a tracing stylus. This is the sum of the two-surface contact vectors Vh for bringing the two surfaces of the V-groove into contact.

The sum of the sum and a radius correction vector Vr for keeping the radius constant is used as the velocity vector V of the probe.

Further, when the two-surface contact is not maintained during the two-surface contact scanning control, an error is generated so that an erroneous measurement is not continued.

Also, an approach reverse direction vector Q in the direction opposite to the approach direction of the scanning probe with respect to the object to be measured.
The angle α formed by the vector Es obtained by projecting the probe normal vector Eu on a plane formed by u and the vector gθ corresponding to the axis of the object to be measured and the approach reverse direction vector Qu has become a predetermined value or more. Sometimes, it is determined that the two-sided contact is no longer maintained.

Before starting the V-groove rotary table scanning control, an approach process for bringing a probe of a scanning probe into contact with two surfaces constituting a V-groove of an object to be measured is performed. Before starting, two surfaces are surely brought into contact.

Further, the approach processing is performed by a displacement correction vector Ve for keeping the displacement of the scanning probe constant.
And the relative movement of the scanning probe with respect to the object to be measured by the relative velocity vector V determined by the sum of the two-surface contact vector Vh for bringing the probe into contact with the two surfaces of the V-groove. A vector Es obtained by projecting a probe normal vector Eu onto a plane formed by an approach reverse direction vector Qu in a direction opposite to the approach direction and a vector gθ corresponding to the axis of the object to be measured is formed by the approach reverse direction vector Qu. When the angle α falls within a predetermined value, it is determined that the two surfaces are in contact with each other and the probe is stopped to perform the operation.

The processing of the approach direction of the scanning probe during the approach processing and the processing of the approach direction of the scanning probe during the V-groove rotary table copying control are common, and the rotation angle θ of the rotary table is equal to the reference value = It is designed to be able to start from other than 0 °.

When approaching from the direction of a certain axis in the machine coordinate system, the other axes are clamped to eliminate the influence of friction.

The present invention also provides a rotary table having a V-shaped groove formed in a spiral shape to which an object to be measured is fixed, a scanning probe having a measuring element engaged with the surface of the object to be measured, and the scanning probe. A driving mechanism for moving along the surface of the object to be measured, position detecting means for detecting a position of the scanning probe, and a moving speed of the scanning probe, and a rotation table by any one of the methods. The above-mentioned problem has been solved by providing a control means for controlling the rotation state of.

Further, a plurality of tracing styluses having different diameters are provided side by side on the scanning probe, and can be selected according to the size of the V-groove so as to easily cope with a change in screw shape.

The rotary table is incorporated in a three-dimensional coordinate measuring machine, and the coordinate measuring probe is used as the scanning probe so that the shape of the V-groove can be measured by the three-dimensional measuring machine.

Also, a hole is made in the rotation center of the rotary table and the surface plate of the three-dimensional coordinate measuring machine immediately below the rotary table so that the lower end of the long object to be measured can be received. The measurement range of the three-dimensional measuring machine is not restricted by the unnecessary portion below the object to be measured.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the present invention applied to measurement of a pitch deviation and a radius deviation of a worm gear will be described in detail below.

In the present embodiment, as shown in FIGS. 7 (front view), FIG. 8 (plan view), and FIG. 9 (cross-sectional view along a line IX-IX in FIG. 8), a probe 22 for measuring coordinates is provided. A concave portion 12A is formed in the surface plate 12 of the coordinate measuring machine 10 provided with the rotary table 30 therein, and a work (worm gear) W is fixed to a chuck 32 of the rotary table 30. The method is applied when scanning the V-groove of the work W using the probe 22 while rotating the work W by 30.

In the figure, M is a true sphere having a known exact diameter fixed on a pole P erected at the corner of the surface plate 12 for calibrating the diameter difference of the tracing stylus 24. A master ball 40 (FIG. 7) has a V according to the present invention.
A groove rotation table (hereinafter abbreviated as RT) scanning control is performed, and data (three-dimensional) of the trajectory of the V-groove of the screw obtained thereby is taken as a measured value, and an analysis process of the data is performed. This is a control / data processing device that obtains characteristic values such as pitch deviation and radius deviation of the data.

As shown in FIG. 7, for example, the control / data processing device 40 comprises a central processing unit 40A, a storage device 4
0B, a joystick 40C, a monitor 40D, and a printer 40E, and a program for performing the processing according to the present embodiment is stored in the storage device 40B.

The center of rotation of the rotary table 30;
If necessary, a plate 30 directly below the platen 12 is provided with a hole 30A as shown in detail in FIG. 9 to receive the lower end of the long work W, for example, as shown in FIG.
An effective measurement range L of the thread of the work W such that the screw is cut only above the work W can be secured within the movable range of the probe 22 of the coordinate measuring machine 10. On the other hand, when the work W is fixed on the rotary table 30 without making a hole, the measurement range is
Even if the measured object is the upper half of
Only half of the vertical movement range of 2 can be used, and depending on the dimensions on the surface plate 12 of the coordinate measuring machine 10, the thread may not be completely measured.

As shown in detail in FIG. 11, for example, three probes 22 are arranged in parallel on one side surface of a substantially H-shaped holder 20, for example, with a probe having a diameter of 0.3 mm,
By changing the diameter to 0.6 mm or 1 mm, a probe having an appropriate size can be selected according to the size of the V-groove to be measured.

FIG. 12 shows the relationship between the coordinate systems used for the measurement. In the figure, (Xs, Ys, Zs) represent a coordinate system (referred to as a scale coordinate system) of the coordinate measuring machine 10 whose origin is the absolute origin Os of the scale provided in the coordinate measuring machine 10, (Xm, Ym). , Zm) represents the scale coordinate system as
The coordinate system (referred to as a machine coordinate system) translated to the center of the master ball M (referred to as a machine coordinate system) and (Xt, Yt, Zt) are the coordinate system of the rotary table 30 when the rotation angle θ of the rotary table 30 is 0 (T coordinate system). ), (Xtθ, Ytθ, Ztθ)
Are coordinate systems obtained by rotating the T coordinate system by the rotation angle θ of the rotary table 30 (referred to as a table coordinate system), (Xw, Y
w, Zw) is a coordinate system of the work W (referred to as a work coordinate system). Here, the scale coordinate system and the machine coordinate system are strictly different from each other, but are only translated, so in the following description, both are referred to as a machine coordinate system. In the present embodiment, basically, velocity data is calculated in the T coordinate system, and control is performed by returning to the machine coordinate system.

Hereinafter, the measurement procedure in this embodiment will be described in detail with reference to FIG.

In the measurement, first, in step 100,
The work W is placed on the rotary table 30 and fixed by the chuck 32.

Next, in step 102, the probe 22 is moved by operating the joystick 40C, and the diameter of the probe 24 is obtained by measuring the master ball M from both sides with the probe 24 used for measurement. Adjust the difference between multiple probes.

Next, in step 104, the probe 22 is moved by the joystick 40C, and as shown in FIG. 14, the coordinates of a total of six points, for example, three points at the top and bottom of the work W fixed to the chuck 32 are measured. A temporary work coordinate system Zw1 is set. Here, the X axis Xw1 and the Y axis Yw1 can be set in any directions. This temporary coordinate system is used in advance when the control according to the present invention is performed.
4 is brought near the surface of the workpiece W, and may include an error.

Next, the routine proceeds to step 105, where the temporary work coordinate system Zw1 is measured by the V-groove point measuring function as shown in FIG.
As shown in 5 to 17, the tracing stylus 24 is caused to approach and accurately contact the upper and lower surfaces of the V-groove of the work W (referred to as approach processing), and the V-groove is measured at six points in the upper and lower directions to perform the cylinder processing calculation. Establish an accurate work coordinate system Zw. The work coordinate system Zw and the T coordinate system Zt mainly differ from each other due to the center shift of the chuck 32 and the processing error of the work W in FIG.
As shown in FIG. Therefore, as shown in FIG. 30, Zw2 obtained by projecting Zw of the work coordinate system onto a plane including the origin Ow of the work coordinate system and Zt of the T coordinate system.
And Zt of the T coordinate system, and a distance Lw between Ow and Zt. This approach processing
Since the tracing stylus 24 does not always come into contact with the upper and lower surfaces of the V-groove when approaching, this is performed. In this approach processing, the turntable 30 does not rotate. For example, when approaching in one axis direction (for example, the X axis) of the machine coordinate system, the influence of friction can be eliminated by clamping the other direction of the probe 22 (for example, the Y axis), and measurement of the radial component can be performed. Accuracy can be increased.

Next, in step 106, the probe 24 is caused to approach the accurate work coordinate system Zw as shown in FIGS. Make accurate contact on both sides.

After completion of the approach processing, step 10
Then, as shown in FIG. 18, measurement is performed while performing V-groove RT scanning control.

As shown in FIG. 19, when the probe reaches the measurement end position (height Z = Zh in the figure), the process proceeds to step 110, and the probe 22 is retracted.

Then, the program proceeds to a step 112, wherein the measured trajectory data (three-dimensional) of the V-groove is taken in as a measured value, and the data is analyzed to obtain characteristic values such as a pitch deviation and a radius deviation.

The approach processing in step 106 is specifically performed according to a procedure as shown in FIG.

That is, first, in step 200, the current rotation angle θ of the turntable 30 is read.

Next, the process proceeds to step 202, where the approach direction vector Q1 given in the work coordinate system is converted into a T coordinate system value (θ ≠ 0 is also possible), and the work axis of the work coordinate system (third axis) ) Is obtained. Here, the rotation axis of the rotary table 30 and the third axis of the workpiece coordinate system may be inclined, for example, as shown in FIG. As shown in FIG. 30, the amount of tilt in this case is defined by the origin Ow of the work coordinate system and the Zt of the T coordinate system.
(The rotation axis of the rotary table), the angle β between the Zw2 obtained by projecting the Zw in the work coordinate system and the Zt in the T coordinate system, and the distance Lw between Ow and Zt. be able to.

Specifically, first, according to the following equation, a coordinate conversion matrix M for converting the table coordinate system to the T coordinate system when the table rotation angle is θ is added to the approach direction vector Q1 given in the work coordinate system. To obtain a vector Q2.

[0048]

(Equation 1)

Next, a vector Q3, which is an outer product of the vector Q2 and the work third axis vector gθ in the T coordinate system, is obtained by the following equation.

[0050]

(Equation 2)

Next, as shown in the following equation (3), a vector Q perpendicular to the workpiece third axis vector gθ is obtained from this vector Q3, and the vector Q is converted into a unit vector according to the equation (4) to obtain an approach reverse direction vector. Let it be Qu.

[0052]

(Equation 3)

By setting this vector Qu in the approach reverse direction, even if the work axis and the rotary axis of the rotary table are tilted, the rotary table can be set to the reference value (for example, θ = 0).
Even when the rotation is started from an angle other than (°), the approach process to the work and the V groove RT scanning process can be performed. In the approach process, if β and Lw are smaller than predetermined values and it can be considered that the T coordinate system and the work coordinate system sufficiently match, the steps (1) to (202) of step 202 are performed.
By omitting the processing of the equation (3), Q = Q2 and the vector Q
You may ask for u.

Next, the routine proceeds to step 204, where the probe is moved from the current position to the approach direction Q as shown in FIG.
Move to a (= − Qu).

Next, the process proceeds to step 206, where the probe 22 is stopped when the displacement exceeds a reference value (for example, 1 mm) after the tracing stylus 24 comes into contact with the workpiece W as shown in FIG.

Then, the process proceeds to a step 208, wherein the position vector X of the probe at the tip of the probe and the displacement ΔX thereof are sampled.

Next, proceeding to step 210, the probe velocity vector V is calculated by the following equation so that the tracing stylus follows the slope of the V-groove as indicated by arrows in FIGS.
Is calculated and the speed is output.

[0058]

(Equation 4)

Here, the displacement correction vector Ve (T coordinate system) for keeping the probe displacement constant is calculated as follows.

First, a value I for canceling an offset such as friction in a steady state is obtained by the following equation.

[0061]

(Equation 5)

Using this value I, the displacement correction vector Ve
Is obtained by the following equation. Sp is a speed factor (described later).

[0063]

(Equation 6)

Vh in the equation (5) is a vector of a T coordinate system for contacting two surfaces of the V groove (referred to as a two-surface contact vector), and is obtained as follows.

That is, first, a vector (referred to as a displacement correction vector) h for correcting a displacement between the probe normal vector Eu and the approach reverse direction vector Qu is obtained by the following equation.

[0066]

(Equation 7)

Using the displacement correction vector h, a work third axis direction vector hs is obtained by the following equation.

[0068]

(Equation 8)

The third work obtained by the equation (9)
Using the axial direction vector hs, a two-surface contact vector Vh is obtained by the following equation.

[0070]

(Equation 9)

In step 210 described above, the velocity vector V of the probe is calculated, and at the same time, the angle α between the vector Qu and the probe normal vector Eu in the plane formed by the approach reverse direction vector Qu and the work third axis is calculated. .

Next, the routine proceeds to step 212, where the angle α
Is determined to be within a predetermined value, for example, 0.5 °. If the result of the determination is negative, the process returns to step 208 and the movement of the probe is continued.

On the other hand, the result of determination in step 212 is positive, and as shown in FIG. 21, at the time of one-sided contact, the angle α which is the same as the angle of the thread, that is, 60 °, is within 0.5 ° due to the two-sided contact. When it is determined that it has become a two-sided contact,
In step 214, the probe is stopped, a V-groove point output is generated, and the approach processing ends.

The V groove RT scanning process in step 108 of FIG. 13 subsequent to this approach process is performed according to the procedure shown in FIG.

That is, first, at step 400, Zw2 obtained by projecting the third axis Zw of the work coordinate system onto a plane including the origin Ow of the work coordinate system and the third axis Zt of the rotary table is calculated. An angle β between Zw2 and Zt is calculated.
Further, a distance Lw between Ow and Zt is calculated. Next, the routine proceeds to step 402, and if β ≦ 0.5 ° and Lw ≦ 0.1 mm, the routine proceeds to step 404 shown in FIG. Otherwise, go to step 300. Step 300
The processing subsequent to step 404 is referred to as the autonomous mode, and the processing following step 404 is referred to as the semi-autonomous mode.

First, the autonomous mode will be described.
In step 300, the position vector X of the probe (measurement element), the displacement ΔX thereof, and the rotation angle θ of the turntable 30 are sampled.

Then, the process proceeds to a step 302, wherein an approach reverse direction vector Qu perpendicular to the workpiece third axis Zw is calculated from the table rotation angle θ in the same manner as described in the step 202 in FIG.

Next, the routine proceeds to step 304, where the velocity vector V of the probe when the rotary table 30 is stationary at the rotation angle θ is calculated by the following equation.

[0079]

(Equation 10)

The basic velocity vector V0 (T coordinate system)
Is calculated as follows.

From the relationship shown in FIG. 23, first, a vector gθ parallel to the workpiece third axis Zw in the T coordinate system shown in the following equation (12) and the T coordinate shown in the equation (13) An origin vector Owθ from the system origin Ot to the origin Ow of the workpiece coordinate system and a vector A from the origin vector Owθ toward the tracing stylus center as shown in Expression (14) are obtained.

[0082]

[Equation 11]

Next, the vector Cr vertically lowered from the center of the tracing stylus to the third axis of the work is obtained by the following equation (15), and the unit vector Cru is obtained by the following equation (16).

[0084]

(Equation 12)

Next, as shown in the following equation (17), the probe traveling direction vector P is obtained from the outer product of the third workpiece axis vector gθ and the unit vector Cru, and the unit vector Pu is obtained from the equation (18).

[0086]

(Equation 13)

Although the lead angle of the gear may be considered in the traveling direction, the lead sampling angle is ignored in this embodiment because the control sampling time is as short as 2 milliseconds and the moving distance therebetween is very small. ing.

Using the traveling direction unit vector Pu obtained by the equation (18), the basic velocity vector V0 can be obtained by the following equation.

[0089]

[Equation 14]

The speed factor Sp is set so that when the scanning speed is too fast and the tracing stylus is separated from the surface of the V-groove, the moving speed is lowered to secure the displacement amount for each sampling time. It is usually set to a value close to 1.

The displacement correction vector Ve (T coordinate system) and the two-surface contact vector Vh used in the equation (11)
(T coordinate system) is calculated by the same method as that described in step 210 of FIG. Note that the displacement correction vector V
In calculating e, the value (I) may be set to 0 and the equation (7) may be simplified.

The radius correction vector Vr (T coordinate system) used in the equation (11) is calculated as follows.

First, the processing up to the end of the two-surface contact is the same as the approach processing.

Next, the position Pt at the time when the angle α in the direction opposite to the probe normal to the approach direction becomes 0.5 ° or less is captured, and at the same time, the radius r at the time of V groove RT scanning, which is the distance between Pt and the Z axis, is obtained. It is obtained by the formula and converted to a T coordinate system value.

[0095]

(Equation 15)

Using this V-groove RT scanning radius r, a radius correction vector Vr is obtained by the following equation.

[0097]

(Equation 16)

In the conventional RT radius constant scanning control,
Although the radius correction direction is obtained by the cross product of the vector Pu and the vector Eu, the radius correction direction is the Cru direction in the V-groove RT scanning according to the present embodiment.

In the present embodiment, as shown by the equation (11), the radius deviation is reduced because the radius correction vector Vr is added when the probe velocity vector V is obtained.
High-precision measurement is possible. It is also possible to omit the radius correction vector Vr in the equation (11) and obtain the probe speed vector V by the sum of the basic speed vector V0, the displacement correction vector Ve, and the two-surface contact vector Vh.

After calculating the probe speed vector V in step 304 of FIG. 22, the process proceeds to step 306, in which the angular velocity (referred to as a work angular speed) ωw of the rotary table based on the probe speed vector V as viewed from the work axis is calculated.
By adjusting the advance and delay of θ from the positional relationship between θ and X,
The correction angular velocity Δω is determined.

Specifically, the tangential direction vector C shown in FIG. 24 is determined before starting RT scanning by using the probe center vector (T coordinate system) Pt when two surfaces are contacted in the approach processing. .

That is, first, the work third axis vector gθ, the origin vector Owθ, and the vector A from the origin vector Owθ toward the probe center Pt in the T coordinate system are calculated by the following equations (22) to (24). Ask.

[0103]

[Equation 17]

Next, a vector Cr vertically lowered from the center of the tracing stylus to the third axis of the work is obtained by the following equation.

[0105]

(Equation 18)

Next, this vector Cr is projected onto the Xt-Yt plane to find a vector Ct shown in the following equation (26), and further rotated by π / 2 to find a vector C shown in the equation (27). The unit vector Cu is obtained by equation (28).

[0107]

[Equation 19]

Next, from the relationship of V = rω, the angular velocity ωw of the work based on the relative speed V between the work and the probe is obtained by using the following equation.

[0109]

(Equation 20)

Next, a corrected angular velocity Δω for maintaining the positional relationship between the workpiece and the probe is calculated from the relationship as shown in FIG. In FIG. 25, a vector Crt = 0 is a perpendicular vector lowered from the probe center obtained after the approach to the work third axis, and a vector C is a vector Crt = 0
The / binary vector, vector Cr, is a perpendicular vector drawn from the probe center to the work third axis, which is obtained for each sampling, and these are all vectors in the Xt-Yt plane. Also, a is the third work from the center of the probe.
It is the intersection of the perpendicular drawn down to the axis and the third axis.

In calculating the corrected angular velocity Δω, first,
Control is performed such that the probe direction Cr is always 90 ° with respect to the reference direction C. Therefore, the difference between Cr and Crt = 0 (Δ
θ) is rotated for correction.

Specifically, Δθ is calculated from the relationship shown in FIG. 25 by the following equation.

[0113]

(Equation 21)

When Δθ is almost 0, (30)
The equation can be approximated by the following equation.

[0115]

(Equation 22)

Therefore, cos ψ can be obtained from the vector Cu and the vector Cru as follows.

[0117]

(Equation 23)

Since ω = dθ (t) / dt, this Δ
From θ, the correction angular velocity Δω can be obtained by the following equation.

Δω = SΔθ (34) where, S: RT angular velocity compensation coefficient

After the end of step 306 in FIG. 22, the process proceeds to step 308, where a speed vector (referred to as a following speed vector) Vω that follows when the rotary table rotates at the angular speed ωt is calculated.

First, the angular velocity ωt given to the rotary table
Is obtained from the above equations (29) and (34) by the following equation.

Ωt = −ωw + Δω (35)

The following velocity vector Vω, which is the linear velocity at the point X based on the angular velocity ωt, is obtained as follows from the relationship shown in FIG.

[0124]

(Equation 24)

Next, the routine proceeds to step 310, where the velocity Vt applied to the probe when the angular velocity ωt is applied to the rotary table is calculated based on the relative velocity vector V between the work and the probe. First, the probe speed vector Vt is obtained by the following equation.

[0126]

(Equation 25)

Then, the process proceeds to a step 312, where the vectors Qu and Eu are set in the same manner as in the step 210 of the approach process.
Is calculated, and since this α is maintained at, for example, 10 ° or less, it is determined that two-surface contact is being performed.

If the judgment result is positive, step 3
In step S14, when the scanning is ended, for example, when the measurement is started from the bottom to the top of the screw, as shown in FIG. 19, it is determined whether or not the height has reached the predetermined height Zh. If it is, the process returns to step 300.

On the other hand, if the decision result in the step 312 is negative, and it is determined that the two-surface contact is not maintained, the process proceeds to a step 316, where an error signal is generated.

When the result of the determination in the step 314 is positive and it is determined that the copying end condition is satisfied, or when an error signal is generated in the step 316,
Proceeding to step 318, the probe is separated from the workpiece by the specified distance, stopped, and the measurement is interrupted (when an error signal is generated) or terminated (when the scanning end condition is satisfied).

Hereinafter, the semi-autonomous mode will be described. First, in step 404, the position vector X of the probe (probe) and the displacement ΔX thereof are sampled.

Then, the process proceeds to a step 406, wherein a speed vector V (= Vω + V) obtained by combining the circumferential speed vector Vω of the tracing stylus and the speed vector Vz in the work coordinate system third axis direction is obtained.
ω and Vz are calculated such that the magnitude of z) becomes the value of the scanning speed specified in advance. Where Vω = rω, Vz
= Gp / (2π / ω). (R: distance from the third axis of the rotary table coordinate system to the center of the tracing stylus) (Gp: known thread pitch)

Next, in step 408, the displacement correction vector Ve (T coordinate system) is calculated in the same manner as that described in step 210 of FIG. In calculating the displacement correction vector Ve, the value (I) may be set to 0 and the equation (7) may be simplified.

Next, at step 410, a velocity vector Vt (= Ve + Vz) to be given to the probe is calculated and controlled. Further, ω calculated in step 406 is commanded to the turntable and controlled.

Then, the process proceeds to a step 412, wherein the vectors Qu and Eu are set in the same manner as in the step 210 of the approach process.
Is calculated, and since this α is maintained at, for example, 10 ° or less, it is determined that two-surface contact is being performed.

If the judgment result is positive, step 4
In step S14, when the scanning is ended, for example, when the measurement is started from the bottom of the screw upward, as shown in FIG. 19, it is determined whether or not the height has reached the predetermined height Zh. If it is, the process returns to step 404.

On the other hand, if the decision result in the step 412 is negative, and it is determined that the two-surface contact is not maintained, the process proceeds to a step 416, where an error signal is generated.

When it is determined that the result of the determination in step 414 is positive and the copying end condition is satisfied, or when an error signal is generated in step 416,
Proceeding to step 418, the probe is separated from the workpiece by the specified distance, stopped, and the measurement is interrupted (when an error signal is generated) or terminated (when the scanning end condition is satisfied).

In the present embodiment, the rotary table is embedded in the coordinate measuring machine, and the V-groove shape is measured by using the coordinate measuring probe. The screw measurement can be performed while effectively using the measurement range. The rotating table can be placed on the surface plate without cutting the surface plate, or
It is also possible to configure a dedicated screw measuring device without using a coordinate measuring machine. The three-dimensional measuring machine is not limited to the one having the portal frame, but may be one having an O-type frame or a C-type frame.

In this embodiment, as shown in FIG. 11, a plurality of measuring elements having different diameters are mounted on a single probe holder. Can be selected and used. In addition, it is also possible to use only one probe.

Further, in the present embodiment, the present invention is applied to the measurement of the pitch deviation and the radius deviation of the worm gear. However, the present invention is not limited to this, and the present invention is not limited to this. Common male screw and Fig. 27
As shown in (1), it is also possible to measure a specific value of a screw hole on an object to be measured placed on a rotary table using a small probe. Further, the direction of the screw or the screw hole is not limited to the vertical direction, but may be another direction such as the horizontal direction by changing the direction of the rotation axis. Further, it is possible to measure a ball screw, depending on the shape of the screw surface.

Further, in the above embodiment, the control circuit and the data processing circuit are integrated, and the configuration is simple. In addition, both may be separated.

[0143]

According to the present invention, it is possible to accurately measure the pitch, radius deviation, and the like of the V-groove of the spirally-shaped object to be measured.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a general configuration of a coordinate measuring machine.

FIG. 2 is a front view showing a state in which a rotating table is placed on a surface plate of a coordinate measuring machine to measure the surface properties of a work.

FIG. 3 is a perspective view showing a state of the scanning control with constant radius of the rotary table.

FIG. 4 proposed by the applicant in Patent No. 2066305,
Plan view showing the state of stylus direction constant control when using a rotary table

FIG. 5 is a front view showing a pitch of a V-groove which is one of the measurement objects of the present invention.

FIG. 6 is a plan view superimposed on a plane trajectory of a tracing stylus for explaining a radius deviation similarly

FIG. 7 is a front view showing an embodiment of the present invention incorporated in a coordinate measuring machine.

FIG. 8 is a plan view of the same.

9 is a cross-sectional view of a main part along line IX-IX in FIG. 8, showing a state where the turntable is also embedded.

FIG. 10 is an essential part cross-sectional view showing a state where a long work is fixed to a chuck of a rotary table.

FIG. 11 is a perspective view showing a probe shape of the embodiment.

FIG. 12 is a perspective view showing a relationship between coordinate systems in the embodiment.

FIG. 13 is a flowchart showing an overall processing procedure of the embodiment.

FIG. 14 is a perspective view showing a state in which a temporary work coordinate system is set before the start of measurement in the embodiment.

FIG. 15 is a perspective view showing a state in which the probe is approached to the workpiece.

FIG. 16 is a perspective view showing a state in which an approach process is being performed.

FIG. 17 is an enlarged view of the same main part.

FIG. 18 is a perspective view showing a state in which V-groove RT copying is being performed.

FIG. 19 is a perspective view showing a state in which the V-groove RT scanning is completed.

FIG. 20 is a flowchart showing a procedure of an approach process.

FIG. 21 is a front view of an essential part for explaining a method for determining two-surface contact.

FIG. 22 is a flowchart showing a procedure of a V-groove RT scanning process after the end of the approach process.

FIG. 23 is a perspective view showing a relationship between control directions in the embodiment.

FIG. 24 is a diagram showing a state in which a tangential direction is determined.

FIG. 25 is a diagram showing a relationship between vectors for determining a correction angular velocity.

FIG. 26 is a diagram showing a linear velocity when the following velocity vector is also determined.

FIG. 27 is a perspective view showing a state in which a probe is changed to measure a screw hole on an object to be measured in the embodiment.

FIG. 28 is a flowchart showing the procedure of a V-groove RT scanning process in a semi-autonomous mode.

FIG. 29 is a diagram showing the relationship between the center axis of the rotary table and the work coordinate system.

FIG. 30 is a diagram showing β and Lw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Three-dimensional (coordinate) measuring machine 12 ... Surface plate 14 ... Portal frame 16 ... Slider 18 ... Elevating shaft 20 ... Probe holder 22 ... Probe 24 ... Measuring element 30 ... Rotary table 30A ... Hole 32 ... Chuck 40 ... Control device 40A: Central processing unit 40B: Storage device 40C: Joystick 40D: Monitor 40E: Printer W: Work θ: Table rotation angle

Claims (18)

[Claims] An object to be measured having a V-shaped groove formed in a spiral shape is fixed to a rotary table, and when the center axis of the object to be measured and the center axis of the rotary table coincide within a predetermined allowable range. When the V-groove is traced and measured using a scanning probe for position measurement while rotating the rotary table, the probe is brought into contact with two surfaces constituting the V-groove.
By combining surface contact scanning control and pitch scanning control for moving the tracing stylus in the center axis direction at a speed determined based on the pitch of the V groove and the rotation speed of the rotary table, the V groove is formed. A V-groove shape measuring method, characterized in that a V-groove rotary table scanning control for performing a measurement while always bringing the tracing stylus into contact with two constituent surfaces is performed. 2. The method according to claim 1, wherein the V-groove rotary table scanning control is performed by sampling a position vector X of the scanning probe, a displacement amount ΔX thereof, and a rotation angle θ of the rotary table, and rotating the rotary table at an angular velocity ω. When this is done, the peripheral velocity Vω (= rω) generated based on the distance r from the central axis of the rotary table to the position vector X and the velocity in the central axis direction of the rotary table generated based on a predetermined screw pitch GP Vector Vz (= GP / (2π / ω))
Ω is calculated so that the composite speed becomes the predetermined scanning speed V,
The speed vector Vz is calculated based on the ω and the screw pitch GP, and the speed vector Vz is set as a speed vector command Vt to a scanning probe, and the ω is set as a rotation speed command of the rotary table. V
Groove shape measurement method. 3. The method according to claim 2, wherein the velocity vector command Vt of the probe, the velocity vector Vz, and the displacement correction vector Ve for keeping the displacement of the scanning probe constant.
A V groove shape measuring method, wherein 4. An object to be measured in which a V-shaped groove is formed in a spiral shape is fixed to a rotary table, and when the center axis of the object to be measured does not coincide with the center axis of the rotary table within a predetermined allowable range. ,
When scanning the V-groove using the scanning probe for position measurement while rotating the rotary table, the direction vector from the origin of the workpiece to the probe of the scanning probe is rotated when viewed from the machine coordinate system. A constant probe direction control that aims to keep the vector projected on the table surface of the table constant, a constant rotary table scanning control that uses a constrained surface as a cylindrical surface, and two surfaces that form a V-groove of the DUT And the two-surface contact scanning control for bringing the probe of the scanning probe into contact with the V-groove rotary table scanning control for constantly bringing the probe of the scanning probe into contact with the two surfaces constituting the V-groove of the object to be measured. V-groove shape measuring method characterized by performing. 5. The method according to claim 1, wherein a distance from an origin of the work coordinate system having the center axis of the object to be measured as a third axis to a center axis of the rotary table; When the angle between the vector obtained by projecting the third axis of the workpiece coordinate system on the plane including both the center axes and the center axis of the rotary table is within a predetermined allowable range, Judge that the center axis of the object to be measured and the center axis of the rotary table coincide with each other; otherwise, judge that the center axis of the object to be measured does not match the center axis of the rotary table. V-groove shape measuring method characterized by the above-mentioned. 6. The method according to claim 4, wherein the V-groove rotary table scanning control is performed by sampling a position vector X of the scanning probe, a displacement amount ΔX thereof, and a rotation angle θ of the rotary table. Calculate the approach reverse direction vector Qu in the direction perpendicular to the axis of the object to be measured, calculate the velocity vector V of the probe when the rotary table is stationary at the rotation angle θ, and calculate from the axis of the object to be measured. The angular velocity ωw of the rotary table is calculated based on the velocity vector V of the probe, and the advance and delay of the table rotation angle θ from the target value due to the control error are adjusted based on the positional relationship between the table rotation angle θ and the probe position X. , And the corrected angular velocity Δω, and the angular velocity ωw is corrected by the Δω. The corrected angular velocity Δω is determined by the probe position X and the table rotation angle θ.
a velocity vector Vt that follows the movement of ω is calculated, and the following velocity vector Vt and the probe velocity vector V are calculated.
The value ω obtained by correcting the angular velocity ωw by the correction angular velocity Δω using the vector sum Vf (= V + Vt) of
A V-groove shape measuring method, wherein t (= −ωw + Δω) is set as a speed command of a rotary table. 7. The method according to claim 6, wherein the velocity vector V of the probe is at least a basic velocity vector Vo indicating a basic traveling direction of the scanning probe, and a displacement correction vector Ve for keeping the displacement of the scanning probe constant. And a two-side contact vector V for bringing the probe into contact with the two sides of the V-groove.
h. The method for measuring the shape of a V-groove, wherein the sum is the sum of h. 8. The V-groove shape measurement according to claim 7, wherein the sum of the sum and a radius correction vector Vr for keeping the radius constant is used as the velocity vector V of the probe. Method. 9. The method according to claim 1, wherein
A method of measuring a V-groove shape, wherein when the two-surface contact is not maintained during the two-surface contact scanning control, an error is generated. 10. A probe normal to a plane formed by an approach reverse vector Qu of a direction opposite to the approach direction of the scanning probe with respect to an object to be measured and a vector gθ corresponding to an axis of the object to be measured. When the angle α formed by the vector Es obtained by projecting the vector Eu and the approach reverse direction vector Qu becomes a predetermined value or more, 2
A V-groove shape measuring method, wherein it is determined that surface contact is no longer maintained. 11. A tracing stylus of a scanning probe is brought into contact with two surfaces forming a V-groove of an object to be measured before starting the V-groove rotary table tracing control according to any one of claims 1 to 10. A V-groove shape measuring method, wherein an approach process for causing the V-groove shape is performed. 12. The method according to claim 11, wherein the approach processing includes a displacement correction vector Ve for keeping the displacement of the scanning probe constant, and a two-surface contact vector Vh for bringing the probe into contact with the two surfaces of the V-groove. The object and the scanning probe are moved relative to each other by the relative velocity vector V obtained by the sum of the above, and the approach reverse direction vector Qu in the direction opposite to the approach direction of the scanning probe with respect to the object to be measured corresponds to the axis of the object to be measured When the angle α between the vector Es obtained by projecting the probe normal vector Eu onto the plane formed by the vector gθ and the approach reverse direction vector Qu is within a predetermined value, it is determined that the two surfaces have contacted each other. A V-groove shape measuring method, wherein the method is performed by stopping the probe. 13. The method according to claim 12, wherein the processing of the approach direction of the scanning probe during the approach processing is performed in common with the processing of the approach direction of the scanning probe during the V-groove rotary table scanning control. V-groove shape measurement method. 14. An approach according to any one of claims 1 to 13, wherein when approaching from the direction of a certain axis of the machine coordinate system, the other axis is clamped so as not to move in the other direction. A method for measuring a V-groove shape, characterized in that: 15. A rotating table having a V-shaped groove formed in a helical shape to which an object to be measured is fixed, a scanning probe having a tracing stylus engaged with the surface of the object to be measured, and A driving mechanism for moving along a surface; a position detecting means for detecting a position of the scanning probe; and a method according to any one of claims 1 to 14,
Control means for controlling the moving speed of the scanning probe and the rotation state of the rotary table, and a V-groove shape measuring device. 16. A V-groove shape measuring apparatus according to claim 15, wherein a plurality of tracing styluses having different diameters are provided side by side on said scanning probe and can be selected according to the size of the V-groove. apparatus. 17. A V-groove shape measuring apparatus according to claim 15, wherein said rotary table is incorporated in a three-dimensional coordinate measuring machine, and said coordinate measuring probe is said copying probe. . 18. The apparatus according to claim 15, wherein the lower end of the long object to be measured is received on the center of rotation of the rotary table or a surface plate of a three-dimensional coordinate measuring machine immediately below the rotary table. A V-groove shape measuring device, wherein a hole is formed.