Laser measurement method for the shape of crankshaft counterweights

Abstract

This invention provides a laser measurement method that can measure the outer circumference shape of a crankshaft counterweight over a wider area. [Solution] In the laser measurement method for the shape of a crankshaft counterweight, the crankshaft is rotated around the rotation axis O, and the laser beam L of a laser displacement meter is irradiated onto the counterweight 1 to measure the outer circumference shape of the counterweight 1. During this measurement, the laser beam L is irradiated with an offset relative to the rotation axis O so that the direction of irradiation of the laser beam L does not intersect with the rotation axis O.

Description

Technical Field

[0001] The present invention relates to a laser measurement method for the counterweight shape of a crankshaft.

Background Art

[0002] The following Patent Document 1 discloses a method for measuring the entire circumference shape of the counterweight of a crankshaft using laser light. The shape of the counterweight is measured, and the central axis of the crankshaft, which is a rotating body, is set. Thereafter, based on the set central axis, cutting of the crankshaft is performed. In the method disclosed in Patent Document 1, while irradiating the laser light of a laser displacement meter toward the rotating axis using polar coordinates with the origin set on the rotating axis of the crankshaft and rotating the crankshaft around the rotating axis, the shape of the counterweight is measured.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method disclosed in Patent Document 1, the direction of laser beam irradiation intersects with the rotation axis of the crankshaft being measured. On the other hand, the direction of extension of the pair of V-shaped (fan-shaped) ridges of the counterweight extends toward the rotation axis or its vicinity. Therefore, when measuring such ridges, there is a problem that the intensity of the reflected light from the laser beam irradiated toward the rotation axis becomes weak, making measurement impossible. In other words, when measuring the entire circumference shape of the counterweight around the rotation axis, there is a problem that areas such as these ridges cannot be measured. In the mass balance measuring machine sold by the applicant of the patent application in Patent Document 1, an ideal shape is applied to the areas that cannot be measured to calculate the balance. However, an error occurs between the ideal shape and the actual shape, making it impossible to correctly set the center of the mass balance and thus the central axis of the rotating body.

[0005] The object of the present invention is to provide a laser measurement method that can measure the outer circumference shape of a crankshaft counterweight over a wider area. [Means for solving the problem]

[0006] In a laser measurement method for the shape of a crankshaft counterweight according to an aspect of the present invention, the outer circumference shape of the counterweight is measured by irradiating the counterweight with laser light from a laser displacement meter while rotating the crankshaft around its axis of rotation. At this time, the laser light is irradiated with an offset relative to the axis of rotation so that the direction of irradiation of the laser light does not intersect with the axis of rotation. [Effects of the Invention]

[0007] According to the measurement method described above, the outer circumference shape of the crankshaft counterweight can be measured over a wider area. [Brief explanation of the drawing]

[0008] [Figure 1A]Figure 1A is a schematic diagram showing the relationship between the direction of laser beam irradiation and one of the edges of the counterweight when the crankshaft rotation axis and the direction of laser beam irradiation intersect during measurement. [Figure 1B] Figure 1B is a schematic diagram showing the relationship between the direction of laser beam irradiation and the other edge of the counterweight when the crankshaft rotation axis and the direction of laser beam irradiation intersect during measurement. [Figure 2A] Figure 2A is a schematic diagram showing the relationship between the irradiation direction of the laser light and one of the counterweights in the laser measurement method according to the first embodiment. [Figure 2B] Figure 2B is a schematic diagram showing the relationship between the irradiation direction of the laser light and the other counterweight in the laser measurement method according to the first embodiment. [Figure 3] Figure 3 is a schematic diagram showing the relationship between the laser beam irradiation direction and the counterweight in the laser measurement method according to the second embodiment. [Modes for carrying out the invention]

[0009] Referring to the drawings, a laser measurement method for the outer circumference shape of the crankshaft counterweight 1 according to an embodiment will be described below. Figures 1A to 3 are schematic diagrams of the crankshaft as viewed from the direction of the rotation axis O during measurement, and only the outer circumference shape of the counterweight 1 is schematically shown.

[0010] First, before describing the embodiment, we will explain the relationship between the irradiation direction of the laser beam L and the pair of edges R1 and R2 of the counterweight 1 when the rotation axis O of the counterweight 1 and the irradiation direction of the laser beam L "intersect".

[0011] The outer periphery shape of the counterweight 1 is measured using laser light L, and a laser displacement meter (not shown) is used. The laser displacement meter used is a commercially available, well-known one. The laser displacement meter comprises a light-emitting element, a detector that detects the reflected light of the laser light L, and an optical system such as lenses associated with them. The light-emitting element is, for example, a laser diode (LD). The detector is, for example, a position-sensitive detector (PSD), a charge-coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS), or a linear array.

[0012] The laser displacement meter used here is a diffuse reflection type that performs triangulation using laser light L, but a specular reflection type may also be used. The laser displacement meter detects the reflected light from the outer surface of the counterweight 1 of the irradiated laser light L. If the angle of incidence of the irradiated laser light L to the outer surface of the counterweight 1 increases, the intensity of the reflected light received by the detector decreases, increasing the measurement error or making measurement impossible. The angle of incidence is the angle of the laser light L with respect to the normal at the irradiation spot on the irradiation surface. In other words, if the angle of incidence increases, the laser light will be irradiated shallowly onto the irradiation surface.

[0013] As shown in Figure 1A, the counterweight 1 has a V-shaped (fan-shaped) weight portion 1A and a pin journal portion 1B provided on the opposite side of the weight portion 1A with respect to the axis of rotation O. A main journal (not shown) is formed in the portion of the axis of rotation O between the weight portion 1A and the pin journal portion 1B, and a pin journal (not shown) is formed in the pin journal portion 1B to which one end of a connecting rod is attached. The direction in which the pin journal portion 1B protrudes relative to the weight portion 1A varies depending on the type of internal combustion engine, and here, in the state of the counterweight 1 shown in Figure 1A, the pin journal portion 1B protrudes slightly upward relative to the weight portion 1A.

[0014] The fan-shaped (mountain-shaped) weight section 1A will have a pair of ridges R1 and R2 extending toward the axis of rotation O. Here, the extensions of the ridges R1 and R2 do not intersect the axis of rotation O but pass in the vicinity of the axis of rotation O. Typically, a counterweight has a pair of ridges, and the extension of each ridge intersects with or passes in the vicinity of the axis of rotation of the crankshaft. That is, typically, the ridges of a counterweight extend toward the axis of rotation.

[0015] As shown in Figure 1A, when the direction of irradiation of the laser beam L intersects with the rotation axis O, the laser beam L is irradiated almost parallel to one of the edges R1. In such a case, only weakly reflected light is reflected by the detector of the laser displacement meter, or the reflected light is not reflected towards the detector at all. That is, the laser displacement meter cannot detect the irradiation spot formed by the laser beam L on the outer surface of the counterweight 1, which is the irradiation surface. For this reason, as shown by the dotted line in the schematic representation of the outer shape of the counterweight 1 in Figure 1A, an unmeasurable range X is generated near one of the edges R1.

[0016] Similarly, as shown in Figure 1B, when the irradiation direction of the laser beam L intersects with the rotation axis O, the laser beam L is also irradiated almost parallel to the other edge R2. Therefore, as shown by the dotted line in part of the outer circumference shape of the counterweight 1 schematically shown in Figure 1B, an unmeasurable range Y is also generated near the other edge R2. In the embodiments described below, these unmeasurable ranges X and Y can be narrowed.

[0017] Figures 2A and 2B show diagrams corresponding to Figures 1A and 1B, respectively, relating to the laser measurement method of the first embodiment. In this embodiment, the outer circumference shape of the counterweight 1 is the same as in the examples in Figures 1A and 1B, and the laser displacement meter used is also the same as described above. In this embodiment, the irradiation direction of the laser beam L is offset so as not to intersect with the rotation axis O (see D1 in the figure). That is, the laser beam L is irradiated with an offset relative to the rotation axis O so as not to intersect with the rotation axis O.

[0018] As shown in FIG. 2A, when the irradiation direction of the laser light L is offset with respect to the rotation axis O, the laser light L is irradiated on one ridge line R1 at a position where the counterweight 1 rotates slightly clockwise around the rotation axis O compared to the case shown in FIG. 1A. Therefore, the laser light L is irradiated deeper by one ridge line R1 than when the irradiation direction of the laser light L intersects the rotation axis O. In other words, the incident angle of the laser light L to one ridge line R1 becomes smaller. As a result, one ridge line R1 can be measured, and the unmeasurable range X shown in FIG. 1A can be eliminated.

[0019] On the other hand, as shown in FIG. 2B, when the irradiation direction of the laser light L is offset with respect to the rotation axis O, the laser light L is irradiated on the other ridge line R2 at a position where the counterweight 1 rotates slightly clockwise around the rotation axis O compared to the case shown in FIG. 1B. Alternatively, the laser light L is blocked by the counterweight 1 itself and does not reach the other ridge line R2. Here, the laser light L is irradiated on a part of the other ridge line R2, but is blocked by the counterweight 1 and does not reach the remaining part. Even when the laser light L is irradiated on the other ridge line R2, it is irradiated shallowly on the other ridge line R2. Therefore, in the present embodiment, an unmeasurable range Z occurs on the other ridge line R2. The unmeasurable range Z is approximately the same width as the unmeasurable range Y.

[0020] However, the unmeasurable range Z of the present embodiment is narrower than the total range of the unmeasurable ranges X and Y when the irradiation direction of the laser light L shown in FIGS. 1A and 1B intersects the rotation axis O. The unmeasurable range can be narrowed, that is, the measurable range can be widened. Note that depending on the case, such as when the offset amount or the outer peripheral shape of the counterweight 1 is different, the unmeasurable range Z may be wider than the unmeasurable range Y. Even in that case, the overall unmeasurable range can be narrowed. Alternatively, in some cases, an unmeasurable range may remain on one ridge line R1. Even in that case, the overall unmeasurable range can be narrowed.

[0021] In this embodiment, in FIGS. 2A and 2B, the irradiation direction of the laser beam L is offset to the right side in the figure with respect to the rotation axis O. For this reason, the measurement at one ridge line R1 could be improved. On the contrary, in FIGS. 2A and 2B, when the irradiation direction of the laser beam L is offset to the left side in the figure with respect to the rotation axis O, the measurement at the other ridge line R2 can be improved.

[0022] FIG. 3 shows diagrams corresponding to FIGS. 1A and 1B according to the laser measurement method of the second embodiment. Also in this embodiment, the outer peripheral shape of the counterweight 1 is the same as that in the examples of FIGS. 1A and 1B and the first embodiment described above, and the laser displacement meter used is also the same as that described above. In this embodiment, the outer peripheral shape of the counterweight 1 is measured using two laser beams L. The irradiation direction of each laser beam L is offset so as not to intersect the rotation axis O (see D1 and D2 in the figure). That is, each laser beam L is offset-irradiated with respect to the rotation axis O so that the irradiation direction of each laser beam L does not intersect the rotation axis O.

[0023] Here, one laser beam L is the same as that in the first embodiment described above (the offset amount is D1). In the first embodiment described above, a non-measurable range Z remained at the other ridge line R2. Therefore, the other laser beam L was further set so as to narrow the non-measurable range Z of the other ridge line R2. In the description of the second embodiment, mention was made of improving the measurement at the other ridge line R2 by offsetting the laser beam L to the left side in FIGS. 2A and 2B, but in this embodiment, another such laser beam L was added.

[0024] In other words, the two laser beams L are set so that their offset directions are opposite to each other. Arrow A1 in Figure 3 indicates the offset direction of one laser beam L with respect to a reference line that passes through the rotation axis O and is parallel to one laser beam L, and is clockwise around the rotation axis O. Arrow A2 in Figure 3 indicates the offset direction of the other laser beam L with respect to a reference line that passes through the rotation axis O and is parallel to the other laser beam L, and is counterclockwise around the rotation axis O. As a result of setting the two laser beams L in this way, in this embodiment the unmeasurable range Z shown in Figure 2B can be eliminated, and the entire circumference shape of the counterweight 1 can be measured.

[0025] In the lower right of Figure 3, the position of the other ridge R2 when the additional laser beam L is irradiated onto it is shown by a dashed line. The additional laser beam L irradiates the other ridge R2 more deeply than in the cases shown in Figures 1B and 2B. In this embodiment, the offset amounts of each laser beam L are different (D1 ≠ D2). However, this does not prevent the offset amounts of the two laser beams L from being set to be the same.

[0026] Furthermore, in this embodiment, two laser beams L are set up that are offset to completely eliminate the unmeasurable range. However, if measurements are taken by irradiating with two laser beams L, and the irradiation directions of the two laser beams L are different from each other, the unmeasurable range can be made narrower than the unmeasurable range with a single offset laser beam L. In other words, a wider measurable range can be obtained. Here, if the irradiation directions of the two laser beams L are not different from each other, the measurable range of each laser beam L will be the same, so the overall measurable range will not be widened. Also, simply setting up two offset laser beams L may not completely eliminate the unmeasurable range. To more effectively narrow (including eliminate) the unmeasurable range, it is preferable to arrange the two laser beams L such that the angle α between them is an obtuse angle, as in this embodiment.

[0027] The angle α between the two laser beams L is the angle α in Figure 3 that is greater than 0° and less than 180°, and not the angle β. Also, the angle α is not the angle γ in Figure 3. By setting this angle α to an obtuse angle (i.e., 90° < α < 180°), the overall unmeasurable range can be narrowed and even eliminated. If this angle α is set to an acute angle (i.e., 0° < α < 90°), the position of the irradiation spot on the outer surface of the counterweight 1 by one laser beam L and the position of the irradiation spot on the outer surface of the counterweight 1 by the other laser beam L will be close together. Therefore, when detecting the reflected light, the reflected light may interfere with each other, making accurate detection impossible. For this reason, it is preferable to set the angle α to an obtuse angle rather than an acute angle.

[0028] In this embodiment, two laser beams L offset with respect to the rotation axis O were used. Note that using two unoffset laser beams L whose irradiation direction intersects the rotation axis O would not change the measurable range of each laser beam L; therefore, increasing the number of laser beams L whose irradiation direction intersects the rotation axis O would be meaningless. Using two laser beams L—one whose irradiation direction intersects the rotation axis O and another that is offset relative to the rotation axis O—will result in different measurable ranges for each laser beam L. This allows for an expansion of the measurable range, and such operation is also effective.

[0029] When performing measurements using two different laser beams L, it is possible to irradiate both laser beams L simultaneously and perform simultaneous measurements with two laser displacement meters. Simultaneous irradiation and measurement of both laser beams L can shorten the measurement time. Alternatively, measurements can be performed using only one laser beam L, and then measurements can be performed using only the other laser beam L. If simultaneous measurement is not performed, interference of reflected light can be reliably prevented. In this case, if the offset amount of the laser displacement meter is set up to be adjustable, it becomes possible to perform measurements with only one laser displacement meter instead of preparing two laser displacement meters.

[0030] Furthermore, it is possible to operate the system so that measurements using the other laser beam L are performed only on areas that cannot be measured by the first laser beam L. In other words, the irradiation time and irradiation area of ​​the two laser beams L do not have to be equal. In this case, the measurements can be performed simultaneously or continuously. By doing so, redundant measurements can be omitted, and the overall measurement efficiency can be improved.

[0031] In the laser measurement method for the shape of the crankshaft counterweight according to the above embodiment, the crankshaft is rotated around the rotation axis O, and the laser beam L of a laser displacement meter is irradiated onto the counterweight 1 to measure the outer circumference shape of the counterweight 1. During this measurement, the laser beam L is irradiated with an offset relative to the rotation axis O so that the irradiation direction of the laser beam L does not intersect with the rotation axis O. Therefore, according to the laser measurement method according to the above embodiment, the outer circumference shape of the crankshaft counterweight 1 can be measured over a wider area.

[0032] According to the laser measurement method of the above embodiment, measurement is performed by irradiating with two laser beams L offset from the rotation axis O, and the irradiation directions of the two laser beams L are different from each other. As mentioned above, the irradiation timing of the two laser beams L may be completely overlapping, partially overlapping, or continuously irradiated with complete separation, allowing for various operational configurations. In this way, by using two laser beams L offset from the rotation axis O, the outer circumference shape of the counterweight 1 can be measured over a wider area.

[0033] According to the laser measurement method of the above embodiment, when viewed from the direction of the rotation axis O, the angle between the two laser beams offset with respect to the rotation axis O is obtuse. In this way, the outer circumference shape of the counterweight 1 can be measured over its entire circumference.

[0034] As described above, embodiments of the present invention have been presented, but the statements and drawings that constitute part of this disclosure should not be understood as limiting the invention. Various alternative embodiments, examples, and operational techniques will become apparent to those skilled in the art from this disclosure. In Figures 1 to 3, the laser beam L is shown to be irradiated from above in order to make the positional relationship between the laser beam L and the edges R1 and R2 according to the rotational position of the counterweight 1 easier to understand. However, these drawings do not limit the actual irradiation direction of the laser beam L. [Explanation of Symbols]

[0035] 1 Counterweight L laser light O (crankshaft) axis of rotation R1, R2 (counterweight 1) ridge α (angle between two laser beams L)

Claims

1. A laser measurement method for the shape of a crankshaft counterweight, A laser measurement method for the shape of a counterweight of a crankshaft, wherein, while rotating the crankshaft around its axis of rotation, a laser beam from a laser displacement meter is shone toward the counterweight to measure the outer circumference shape of the counterweight, and the laser beam is irradiated with respect to the axis of rotation such that the direction of irradiation of the laser beam does not intersect with the axis of rotation.

2. A laser measurement method for the shape of a crankshaft counterweight according to claim 1, A laser measurement method for the shape of a crankshaft counterweight, wherein two laser beams are irradiated and measurements are performed, and the irradiation directions of the two laser beams are different from each other.

3. A laser measurement method for the shape of a crankshaft counterweight according to claim 2, A laser measurement method for the shape of a crankshaft counterweight, wherein the angle between the two laser beams, as viewed from the direction of the rotation axis, is obtuse.

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