JP2009168744A - Shape measurement method of crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape measurement method of crankshaft enabling to measure a distance between adjacent counter weights, even the condition that measuring data of profile part of a counter weight are missing. <P>SOLUTION: A dot data group showing cross-sectional shape in alignment with crankshaft center axis is extracted from three-dimensional shape data of crankshaft which has a plurality of the counter weights. Next, a circular section A fitted for distribution of dot data of the part corresponding to R part 21b from the counter weight edge to the profile of the counter weight in the dot data group is obtained. Further, the position x1 of the counter weight profile in crankshaft center axis direction is obtained from the standard position such as position of center O (X-coordinate) in the circular section A, radial dimension R, predetermined crankshaft design value or the like. The distance between adjacent counter weights is obtained based on the obtained profile position x1 of the counter weight. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a crankshaft shape measuring method suitable for measuring a counterweight pitch of a crankshaft of an internal combustion engine.

In a crankshaft of an internal combustion engine such as an automobile engine, it is important to accurately balance the weight during rotation using a counterweight in order to improve the performance of a machine such as an engine. For this reason, the shape of a crankshaft provided with a counterweight is often measured, and the obtained three-dimensional shape is analyzed and processed.
Conventionally, as a technique for measuring a three-dimensional shape capable of measuring the shape of such a crankshaft, for example, there is one disclosed in Patent Document 1.
This is a line sensor camera in which line illumination is projected in the axial direction of the test object using the illumination unit, and the pixel is arranged in the axial direction of the test object at the place where the line illumination on the test object is projected. Take an image using. Then, by rotating the test object by the test object driving motor, the entire surface of the test object is imaged and the three-dimensional shape of the test object is measured.

JP 2002-257528 A

However, the above prior art has the following problems.
That is, in a method of irradiating a measurement object (test object) with light and measuring its three-dimensional shape, generally reflected light of the irradiated light is detected. In the measurement of the three-dimensional shape of the crankshaft of the internal combustion engine, among the plurality of counterweights provided on the shaft, the counterweight on the front side as viewed from the light source does not interfere with the light irradiation to the counterweight on the rear side, that is, In order not to disable the measurement of the counterweight on the rear side, the three-dimensional shape may be measured by irradiating light from a direction substantially orthogonal to the shaft axis direction and detecting the reflected light.
Since the reflected light is not generated unless the measurement target surface is irradiated with light, the shape of the surface parallel to the optical axis of the irradiation light is not measured. For this reason, according to the three-dimensional shape measurement in which light is irradiated from a direction substantially perpendicular to the axial direction of the shaft as described above, the side surface of the counterweight (in the counterweight rotating surface) extending in the direction substantially perpendicular to the shaft axial direction. Reflected light is not obtained for the surface along the surface, and the shape of the portion is not measured.

  That is, the measured shape of the crankshaft is only measured as the shape of each counterweight portion, with only the base portion (connecting portion with the shaft main body) and the end surface (tip surface portion along the shaft axis direction) being the shape of the counterweight. The measurement data related to the side surface shape was missing, and the distance between adjacent counterweights could not be measured.

  The present invention provides a novel crankshaft shape measuring method capable of measuring the distance between adjacent counterweights even when the measurement data of the side surface portion is missing, such as when the side surface shape of the counterweight is not measured. The task is to do.

The above-mentioned problems are solved by adopting the configuration of each aspect described below for the crankshaft shape measuring method.
As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is merely for the purpose of facilitating the understanding of the present invention, and the technical features described in this specification and combinations thereof should not be construed as being limited to those described in the following sections. . In addition, when a plurality of items are described in one section, it is not always necessary to employ the plurality of items together, and it is also possible to take out only a part of the items and employ them.

  Of the following items, (1) corresponds to claim 1, (2) corresponds to claim 2, (3) corresponds to claim 3, and (4) corresponds to claim 4. . (5) is not the claimed invention.

(1) A point data group representing a cross-sectional shape along the center axis of the crankshaft is extracted from the three-dimensional shape data of the crankshaft having a plurality of counterweights, and an R portion from the counterweight end surface to the side surface in the point data group An arc that fits the distribution of point data in the part corresponding to is obtained, the position of the counterweight side surface in the direction of the center axis of the crankshaft is obtained from the center position and radial dimension of this arc, and adjacent based on the obtained counterweight side surface position A method for measuring a shape of a crankshaft, characterized in that a distance between counterweights is determined.
The invention of this section is the simplest method that can measure the distance between adjacent counterweights even when the measurement data of the side surface portion is missing, such as when the side surface shape of the counterweight is not measured.
(2) A point data group representing a cross-sectional shape along the center axis of the crankshaft is extracted from the three-dimensional shape data of the crankshaft having a plurality of counterweights, and a straight line portion of the end face of the counterweight is obtained from the point data group, An approximate straight line is obtained using the point data group of the end face straight line portion, the crankshaft central axis side is set as the measurement area from the approximate straight line, and the R portion from the counterweight end face to the side face in the measurement area An arc that fits the distribution of point data in the part corresponding to is obtained, the position of the counterweight side surface in the direction of the center axis of the crankshaft is obtained from the center position and radial dimension of this arc, and adjacent based on the obtained counterweight side surface position A method for measuring a shape of a crankshaft, characterized in that a distance between counterweights is determined.
According to the invention of this section, the point data distribution of the portion corresponding to the counterweight R portion in the above method in which the distance between the adjacent counterweights can be measured even when the measurement data of the side shape of the counterweight is missing. The range (measurement area) of the point data group used when obtaining an arc that fits the curve was set to improve the measurement accuracy.
(3) A first step of extracting a point data group representing a cross-sectional shape along the crankshaft central axis from the three-dimensional shape data of the crankshaft having a plurality of counterweights, and the point data group obtained in the first step The straight portion of the end face of the counterweight is obtained, the center position of the end face straight portion is obtained from the crankshaft design value, and equidistant from the obtained center position of the end face straight portion along the end face straight portion. A second step of obtaining an approximate straight line using the point data group of the end face straight line portions within a distant range, a range of variation of the point data is obtained based on the approximate straight line obtained in the second step, and the range of this variation The straight line portion formed by the point data group in the one side, and at the center position of the end face straight line portion, and at a position away from the center position by a predetermined distance along the one side, A perpendicular line is drawn from the one side to the crankshaft central axis side to define a pair of opposite sides, and a region surrounded on three sides by the other side and the one side is set as a measurement region. And a circular arc that fits the distribution of point data in the portion corresponding to the R portion from the counterweight end surface to the side surface in the measurement area set in the third step is obtained on both sides of the counterweight end surface. There is a fourth step and a fifth step for determining the position of the counterweight on both sides in the direction of the center axis of the crankshaft from the center position and radial dimension of each arc obtained in the fourth step. A shape of a crankshaft characterized in that a distance between adjacent counterweights is obtained based on positions of both sides of the counterweight in the direction of the center axis of the crankshaft Measurement method.
According to the present invention, the point data group range (measurement area) to be used in the above method that enables the distance between adjacent counter weights to be measured even when the measurement data of the side shape of the counter weight is missing. The measurement accuracy was further improved by further limiting.
(4) Depending on the position of each counterweight side surface in the direction of the center axis of the crankshaft obtained by executing the second to fifth steps for each of the plurality of counterweights, The crankshaft shape measuring method according to item (3), characterized in that a distance is obtained.
The invention of this section makes it possible to measure each distance between a plurality of counter weights adjacent to each other in the invention of (3), that is, the pitch of the counter weight.
(5) Items (1) to (4) are characterized in that the positions of both sides of the counterweight in the direction of the center axis of the crankshaft are obtained based on a reference position preset on the three-dimensional shape data of the crankshaft. The crankshaft shape measuring method according to any one of the above.
According to the invention of this section, in the invention of any one of the sections (1) to (4), by setting an optimum reference position in advance, the distance between the counter weights and the pair can be calculated. Each distance (counterweight pitch) of all counterweights can be measured quickly and accurately. For example, a crankshaft design value is used as the optimum reference position.

According to the invention described in the item (1), even if the shape data of the side surface of the counterweight is missing, the position of the same side surface can be obtained as it is, and the distance between the adjacent counterweights is measured. it can.
According to the invention described in the item (2), even if the shape data of the side surface of the counterweight is missing, the position of the side surface can be obtained as it is, and the distance between the adjacent counterweights can be accurately determined. Can measure well.
According to the invention described in the item (3), even if the shape data of the side surface of the counterweight is missing, the position of the side surface can be obtained as it is, and the distance between adjacent counterweights is high. It can be measured with accuracy.
According to the invention described in item (4), even when the shape data of the side surface of the counterweight is missing, the distance between a plurality of pairs of adjacent and facing counterweights in the state as it is, that is, the pitch of the counterweight Can be measured with high accuracy.
Since the invention described in item (5) is not the present invention (the invention described in the claims), the effect is described in the column of means for solving the above problems.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol shows the same or an equivalent part between each figure.
FIGS. 1-6 is a figure for demonstrating one Embodiment of the shape measuring method of the crankshaft by this invention.
In the method of the present invention, three-dimensional shape data of a crankshaft having a plurality of counterweights, which are measured objects, is prepared in advance.
As the three-dimensional shape data, here, a method of measuring the three-dimensional shape of the crankshaft by irradiating the crankshaft with light and detecting the reflected light, for example, a light cutting method using a two-dimensional non-contact scanner The three-dimensional shape data obtained by the above is used. Further, three-dimensional shape data obtained by a mode in which light is irradiated from a direction substantially orthogonal to the crankshaft axis direction and the reflected light is detected from the light irradiation side to measure the three-dimensional shape is used.

FIG. 1 is a view showing a crankshaft three-dimensional shape 11 represented from the crankshaft three-dimensional shape data obtained as described above from above. The three-dimensional shape 11 is actually represented by a set of point data (point data group) each indicating a light reflection position, but in FIG. FIG. 1 also shows a position where a point data group necessary for the present embodiment is acquired from the three-dimensional shape (data) 11 of the crankshaft. In the figure, X, Y, and Z indicate the respective axes of the orthogonal three-dimensional coordinate system.
In this embodiment, first, a point data group (crankshaft cross-section point data group) composed of a large number of point data representing a cross-sectional shape (axially halved cross-sectional shape) along the crankshaft central axis 12 from the three-dimensional shape data of the crankshaft. ) Is extracted (first step).
The region for extracting the crankshaft cross-section data group is a region having a width of ± 2.5 mm (d = 5 mm) in the Z-axis direction with the crankshaft central axis 12 in the center, as shown in FIG. Yes.
The reason why the width is 2.5 mm on one side from the crankshaft central axis 12 is as follows. That is, according to the experiment, if the width is smaller than 2.5 mm, the density of the crankshaft cross-section point data group to be extracted becomes small (the pitch between the points becomes coarse), so that the measurement accuracy is lowered. On the other hand, if it is larger than 2.5 mm, the cross-sectional contour becomes thicker in the crankshaft constituted by a three-dimensional curved surface, and the measurement accuracy is lowered.

FIG. 2 shows the cross-sectional shape of the crankshaft represented by the crankshaft cross-section data group acquired in the first step.
As described above, the three-dimensional shape data of the crankshaft used in the present embodiment is obtained by irradiating light from a direction substantially orthogonal to the crankshaft axial direction and detecting the reflected light from the light irradiation side. Shape data. For this reason, the shape of the side surface portion of the counterweight from which reflected light cannot be obtained is not measured. Therefore, the shape data of that portion is lost, and the contour line of that portion does not basically appear as shown in FIG. In FIG. 2, reference numeral 21 denotes a counterweight portion shape.

  FIG. 3 is an enlarged view of the shape in the region surrounded by the rectangle 22 in FIG. 2 (counterweight distance measurement region). In this embodiment, the position (X coordinate) of the counterweight side surface in the direction of the crankshaft central axis 12 indicated by a broken line in FIG. 3 is obtained, and the distance between adjacent counterweights (specifically, a pair of adjacent counterweights). The distance between the opposing side surfaces) La, and thus the pitch of the counterweight (the distance between the adjacent and opposing pairs of counterweights) is to be measured. In FIG. 3, reference numeral 21a denotes a counterweight portion end face shape.

FIG. 4 is an enlarged view showing a main part of the shape shown in FIG.
In the present embodiment, a point data group consisting of a large number of point data representing the cross-sectional shape of the counterweight shown in FIG. 4, mainly point data corresponding to the R portion 21b from the end surface (see shape 21a) to the side surface of the counterweight. The X coordinate of the side surface of the counterweight is obtained using the group (counterweight cross-section point data group). The X coordinate of the side surface of the counterweight is used for measuring the distance between the counterweights in this embodiment.

Hereinafter, details of the distance measurement between the counter weights will be described with reference to FIGS.
In this embodiment, when the crankshaft cross-section point data group is extracted as described above, the straight portion of the counterweight end face is obtained from the point data group, specifically, the distribution of the point data. Then, the center position Pc of the counterweight end face straight line portion is obtained based on the crankshaft design value, and the calculated distance from the center position Pc of the end face straight line portion along the end face straight portion is equal to each other, An approximate straight line 51 is obtained using the point data group within the end face straight line portion 3.0 mm within a range of 1.5 mm away (second step).
The reason why the distance α of the end surface straight line portion for obtaining the approximate straight line 51 is set to 3.0 mm is that, according to this, even if the point data group used for the measurement is slightly shifted in the X-axis direction, This is because the accuracy of the linear approximation can be sufficiently obtained without removing the portion.

In this embodiment, when the approximate straight line 51 is obtained, a range of variation of point data, here ± 6σ (σ: standard deviation) is obtained with reference to the approximate straight line 51, and a point data group within the variation range ± 6σ is obtained. The straight line portion formed by is defined as one side 52. In FIG. 6, the reason why the part of one side 52 is shaded is to indicate that the straight part forming this one side 52 is a thick straight part.
Further, at the center position Pc of the straight line portion of the end face and a position away from the center position Pc by a distance W / 2 that is ½ of the counterweight width W in the crankshaft design value along the one side 52. The perpendicular line is drawn from the one side 52 to the crankshaft central axis side, and these are defined as a pair of opposing other sides 53 and 54. Then, a region surrounded on three sides by at least one pair of the other sides 53 and 54 and the one side 52 is defined as a measurement region 56 (56r is attached to the measurement region on the right side, and the measurement region on the left side is attached to the measurement region on the left side. 56l.) (Third step).
In the example shown in FIGS. 5 and 6, the length of the other side 53, 54 is limited by using the design value Rd of the radius of the R portion 21 b, which will be described in detail later, and the one side 55 facing the one side 52. And the areas surrounded by these sides 52 to 55 were set as measurement areas 56r and 56l.
The variation range is set to ± 6σ, and this range is set as one side 52 that divides the measurement regions 56r and 56l, so that point data within the same range is excluded from the measurement regions 56r and 56l. In order to improve the measurement accuracy of the counterweight side surface position, it is not used in the next step (step of obtaining an arc by the least square method).

Next, an arc that fits the distribution of the point data in the portion corresponding to the R portion 21b from the counterweight end face to the side face in the measurement areas 56r and 56l, in this case, the arc A by the least squares method is applied to the counterweight end face ( The desired one side (see shape 21a), and if necessary, both sides are obtained (fourth step). In this case, the measurement areas 56r and 56l do not include at least the line (range ± 6σ) forming the side 52 in the sides 52 to 55, and the point data on this line is used as point data for obtaining the arc A. I can't.
5 and 6 represents a circle (least square circle) C including the arc A, O represents the center thereof, and the alternate long and short dash line represents the center line of the circle C. A vertical center line (dashed line) is orthogonal to the X axis.
5 and 6, the arc A and the R portion 21b overlap each other because the measured value of the R portion 21b matches the design value.

Next, the position (X coordinates: x1, x1 ′) of the counterweight side surface in the direction of the center axis of the crankshaft is determined from the center position (X coordinate) of the arc A and the radius R thereof obtained as described above (X coordinates: x1, x1 ′). (5th process). The X coordinate of the side surface of the counterweight is obtained from the X coordinate of the center position Pc based on the reference position preset on the three-dimensional shape data of the crankshaft, for example, the crankshaft design value.
In the present embodiment, as illustrated in FIG. 7, the X coordinates x2 to x8 of the opposing side surfaces of each pair of adjacent counterweights (see counterweight portion shape 21) are obtained in the same manner as the X coordinate x1. Based on these X coordinates x1 to x8, the pitches p1 to p4 of the counterweights of the adjacent and opposing pairs are obtained.

According to the present embodiment described above, a point data group representing a cross-sectional shape along the center axis of the crankshaft is extracted from the crankshaft three-dimensional shape data, and the R data from the counterweight end surface to the side surface in the point data group is extracted. An arc that fits the point data distribution of the corresponding part is obtained, the position of the counterweight side surface in the direction of the center axis of the crankshaft is obtained from the center position and radius of the arc, and the distance between the adjacent counterweights is obtained. Therefore, there is an effect that the distance between the adjacent counter weights can be measured even if the measurement data of the side surface portion of the counter weight is missing.
In addition, in the present embodiment, when acquiring an arc that fits the point data distribution of the portion corresponding to the R portion from the end face to the side surface of the counterweight, the measurement region that adopts the concept of 6σ (six sigma) is used as described above. Because the point data group in this measurement area was set and used, the position of the counterweight side surface in the direction of the center axis of the crankshaft, the distance between adjacent counterweights, and each pair of counterweights Distance (counterweight pitch) can be measured with high accuracy.

In the above-described embodiment, shape data obtained by the light cutting method is used as the three-dimensional shape data, but is not limited to this. Although the end face shape of the counterweight and the R portion shape at both ends can be obtained, it is difficult to obtain the side surface shape of the counterweight (the contour line of the side surface portion of the counterweight). Any of them can be used.
Further, the measurement area for dividing the range of the point data group used (or not used) for measurement is not limited to the area shown in the above embodiment. Any area can be used as long as it can extract a point data group sufficient to obtain an arc that fits the point data distribution of the portion corresponding to the R portion of the counterweight.

It is a figure for demonstrating the procedure which acquires the point data group required for a measurement from crankshaft three-dimensional shape data in one Embodiment of this invention. It is a figure which shows an example of the cross-sectional shape of the crankshaft represented by the acquired point data group. FIG. 3 is an enlarged view of a counterweight shape in a measurement region surrounded by a rectangle in FIG. 2. It is a principal part enlarged view of the shape shown in FIG. It is a figure for demonstrating the principal part of the process in one Embodiment of this invention. It is a principal part enlarged view in FIG. It is a figure which shows a mode that the pitch of a counterweight is measured from the side surface position of each counterweight obtained in one Embodiment.

Explanation of symbols

21: Counterweight portion shape, 21a: Counterweight end surface shape, 21b: Counterweight R portion, 51: Approximate straight line, 52: One side, 53, 54: Other side, 56 (56r, 56l): Measurement Area, A: arc, R: radius, Pc: center position of the counterweight end face straight line portion.

Claims (4)

A point data group representing a cross-sectional shape along the center axis of the crankshaft is extracted from the three-dimensional shape data of the crankshaft having a plurality of counterweights,
Obtaining an arc that fits the distribution of point data in the portion corresponding to the R portion from the counterweight end face to the side face in the point data group;
Obtain the position of the counterweight side surface in the direction of the center axis of the crankshaft from the center position and radial dimension of this arc,
A crankshaft shape measuring method, characterized in that a distance between adjacent counterweights is obtained based on the obtained counterweight side surface position. A point data group representing a cross-sectional shape along the center axis of the crankshaft is extracted from the three-dimensional shape data of the crankshaft having a plurality of counterweights,
Obtain the straight line portion of the end face of the counterweight from this point data group, obtain an approximate straight line using the point data group of this straight line portion of the end face,
Set the crankshaft central axis side as a measurement area from this approximate straight line to obtain an arc that fits the distribution of point data in the portion corresponding to the R portion from the counterweight end face to the side face in the measurement area,
Obtain the position of the counterweight side surface in the direction of the center axis of the crankshaft from the center position and radial dimension of this arc,
A crankshaft shape measuring method, characterized in that a distance between adjacent counterweights is obtained based on the obtained counterweight side surface position. A first step of extracting a point data group representing a cross-sectional shape along the crankshaft central axis from the three-dimensional shape data of the crankshaft having a plurality of counterweights;
The straight portion of the end surface of the counterweight is obtained from the point data group obtained in the first step, the center position of the straight portion of the end surface is obtained from the design value of the crankshaft, and the end surface is obtained from the center position of the obtained straight portion of the end surface. A second step of obtaining an approximate straight line using the point data group of the end face straight line portions within a range equidistant from each other in opposite directions along the straight line portions;
A range of variation of the point data is obtained based on the approximate straight line obtained in the second step, a straight line portion formed by the point data group within the variation range is defined as one side, a center position of the end surface straight line portion, and At a position separated from the central position by a predetermined distance along the one side, a perpendicular line is drawn from the one side to the crankshaft central axis side to make it a pair of opposite side sides, A third step of setting a region surrounded on three sides by the other side of the pair and the one side as a measurement region;
A fourth step of obtaining arcs that fit the distribution of the point data in the portion corresponding to the R portion from the counterweight end surface to the side surface in the measurement area set in the third step, on both sides of the counterweight end surface;
A fifth step of determining the position of the counterweight on both side surfaces in the crankshaft central axis direction from the center position and the radial dimension of each arc obtained in the fourth step,
A crankshaft shape measuring method characterized in that a distance between adjacent counterweights is obtained based on the positions of both sides of the counterweight obtained in the fifth step in the crankshaft central axis direction. Each distance between a plurality of pairs of counterweights adjacent to each other is determined according to the position of each counterweight side surface in the direction of the center axis of the crankshaft obtained by executing the second to fifth steps for each of the plurality of counterweights. The method of measuring a shape of a crankshaft according to claim 3.

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