JP7588015B2 - Center hole determination device and center hole determination method - Google Patents

Description

The present invention relates to a center hole determination device and a center hole determination method.

The crankshaft to be assembled into the engine is made by forming a center hole in both end faces of the raw crankshaft, which is formed by forging or casting, and then machining the surface of the raw crankshaft using the center hole as a reference.

Patent Document 1 discloses a method for determining the center hole from the shape of the counterweight of a raw crankshaft. Specifically, in Patent Document 1, the design shape of the counterweight is divided into multiple regions around the geometric center, and the center hole is determined based on the expansion and contraction rate when the shape of each region is matched to the actual shape of the counterweight.

JP 2018-179044 A

However, in the method of Patent Document 1, the center hole is determined only from the shape of the counterweight of the raw crankshaft, so if the surface of the raw crankshaft is cut based on the center hole, there is a risk that the surface of the raw crankshaft at both ends (specifically, the front shaft and rear flange) will remain.

Therefore, it is desirable to be able to determine when determining the center hole whether the material surface at both ends of the raw crankshaft will remain even after cutting.

The object of the present invention is to provide a center hole determination device and a center hole determination method that can determine whether the material surface at both ends remains after cutting a raw crankshaft.

The center hole determination device according to the present invention determines the center hole of a raw crankshaft having a counterweight located between a first end and a second end. The center hole determination device includes a principal axis of inertia acquisition unit, a determination unit, and a center hole determination unit. The principal axis of inertia acquisition unit acquires the principal axis of inertia of the raw crankshaft based on the actual shape of the counterweight. The determination unit determines whether or not the material surface of the first end remains after cutting the raw crankshaft based on the actual shape and the principal axis of inertia of the first end. When it is determined that the material surface of the first end does not remain, the center hole determination unit determines the center hole of the raw crankshaft based on the principal axis of inertia.

The present invention provides a center hole determination device and a center hole determination method that can determine whether the material surface at both ends remains after cutting a raw crankshaft.

FIG. FIG. 1 is a schematic diagram showing the configuration of a machining system for a material crankshaft. FIG. 2 is a schematic diagram showing the configuration of a center hole determining device. FIG. 4 is a diagram showing the design shape and actual shape of the counterweight. FIG. 13 is a diagram for explaining a best fit of the design shape of the counterweight to the actual shape. 6A and 6B are diagrams for explaining expansion and contraction of each divided area of the counterweight. FIG. 4 is a diagram showing divided regions of a counterweight. 11A and 11B are diagrams for explaining a process for determining whether or not the material surface of the front shaft remains. FIG. 4 is a flow chart for explaining a center hole determining method.

(Material crankshaft 1)
1 is a perspective view showing the configuration of a material crankshaft 1. The material crankshaft 1 is formed, for example, by forging or casting. The material crankshaft 1 according to this embodiment is a material crankshaft for an in-line four-cylinder engine.

In FIG. 1, the Z axis is the central axis of the raw crankshaft 1, the X axis is an axis perpendicular to the Z axis, and the Y axis is an axis perpendicular to the Z axis and the X axis.

The raw crankshaft 1 has a front shaft E1, a rear flange E2, eight counterweights CW (CW1-CW8), four main journals J (J1-J5), and four pin journals P (P1-P4).

In the raw crankshaft 1, the following order is arranged in the Z-axis direction: front shaft E1, main journal J1, counterweight CW1, pin journal P1, counterweight CW2, main journal J2, counterweight CW3, pin journal P2, counterweight CW4, main journal J3, counterweight CW5, pin journal P3, counterweight CW6, main journal J4, counterweight CW7, pin journal P4, counterweight CW8, main journal J5, and rear flange E2.

The front shaft E1 and the rear flange E2 are located at both ends of the raw crankshaft 1. The front shaft E1 and the rear flange E2 are examples of the "first end" and "second end" of the present invention, respectively.

The front shaft E1 has a first end surface S1 in which a center hole will be formed in a later process. The rear flange E2 has a second end surface S2 in which a center hole will be formed in a later process.

The configuration of the raw crankshaft 1 is not limited to the configuration shown in FIG. 1. The raw crankshaft 1 only needs to have at least one counterweight CW and at least one of the front shaft E1 and the rear flange E2.

(Crankshaft machining system 100)
Next, the crankshaft machining system 100 according to this embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing the configuration of the crankshaft machining system 100.

The crankshaft machining system 100 has a center hole machining machine 10, a center hole determination device 20, and a crankshaft machining machine 30.

The center hole machining machine 10 is equipped with an actual shape measuring unit 11 and a center hole machining unit 12.

The actual shape measuring unit 11 is an example of a measuring means for measuring the actual shape of the raw crankshaft 1.

The actual shape measuring unit 11 has, for example, a non-contact displacement meter such as a laser displacement meter, an infrared displacement meter, or an LED-type displacement sensor, or a contact displacement meter such as a differential transformer. The actual shape measuring unit 11 measures the actual shapes of the front shaft E1, rear flange E2, and eight counterweights CW of the raw crankshaft 1 based on the measured values from the displacement meter. As described below, the actual shapes of the eight counterweights CW are used to determine the principal axis of inertia, and the actual shapes of the front shaft E1 and rear flange E2 are used to determine whether the material surfaces of the front shaft E1 and rear flange E2 remain after cutting.

Methods for measuring the actual shape using a displacement gauge include, but are not limited to, a method in which the raw crankshaft 1 is rotated while measuring with a fixed displacement gauge, a method in which a displacement gauge is rotated around the fixed raw crankshaft 1 while measuring, or a method in which a displacement gauge is positioned so as to sandwich the raw crankshaft 1 from the left and right while measuring while moving it in a straight line.

The actual shape measuring unit 11 may also be a three-dimensional digitizer (image scanner) that generates three-dimensional shape data of the actual shape of the entire raw crankshaft 1 by measuring the measurement object from multiple different positions.

The center hole machining unit 12 machines the center holes determined by the center hole determination device 20 into the first and second end faces S1, S2 of the raw crankshaft 1.

The center hole determination device 20 is a processing device for determining the positions of the center holes to be machined on the first and second end faces S1, S2 of the raw crankshaft 1. The center hole determination device 20 has a CPU (Central Processing Unit) 20a, a ROM (Read Only Memory) 20b, and a RAM (Random Access Memory) 20c.

The ROM 20b stores various programs and information to be executed by the CPU 20a. In this embodiment, the ROM 20b stores a program for processing to determine the position of the center hole of the raw crankshaft 1. The ROM 20b also stores design shape data indicating the design shapes of the front shaft E1, rear flange E2, and eight counterweights CW of the raw crankshaft 1. The RAM 20c is used as a storage area for storing programs and data, or as a working area for storing processing data in the CPU 20a.

The crankshaft processing machine 30 cuts the surface of the raw crankshaft 1 whose center hole has been machined in the center hole processing section 12. The crankshaft processing machine 30 mainly cuts the surface of the raw material of the front shaft E1, rear flange E2, each counterweight CW, each pin journal P, and each main journal J based on the design shape.

(Center hole determining device 20)
3 is a schematic diagram showing the configuration of the center hole determination device 20. The center hole determination device 20 includes an actual shape data acquisition unit 21, an expansion/contraction ratio calculation unit 22, a correction unit 23, a principal axis of inertia acquisition unit 24, a judgment unit 25, and a center hole determination unit 26.

<Actual shape data acquisition unit 21>
The actual shape data acquiring unit 21 acquires actual shape data indicating the actual shapes of the front shaft E1, the rear flange E2, and the eight counterweights CW of the material crankshaft 1 from the actual shape measuring unit 11.

The actual shape data acquisition unit 21 transmits actual shape data indicating the actual shape of each of the eight counterweights CW to the expansion/contraction ratio calculation unit 22, and transmits actual shape data indicating the actual shape of each of the front shaft E1 and rear flange E2 to the determination unit 25.

<Stretch rate calculation unit 22>
The expansion/contraction ratio calculation unit 22 acquires actual shape data indicating the actual shape of each counterweight CW from the actual shape data acquisition unit 21. The expansion/contraction ratio calculation unit 22 calculates the design shape of each counterweight CW of the material crankshaft 1 by The design shape data shown in FIG.

Figure 4 is a schematic diagram showing the design shape (solid line) and actual shape (plot ●) of the counterweight CW.

As shown in FIG. 4, the position and angle of the actual shape are offset from the position and angle of the design shape. In FIG. 4, the design shape is shown by solid lines, but the actual design shape is shown by a large number of polar coordinates. There is no particular limit to the number of polar coordinates, but for example, 360 polar coordinates can be set at equal angles (1 degree) around the center P1 of the counterweight CW.

Here, as shown in FIG. 4, multiple divided regions DR are set around the center P1 of the counterweight CW in the design shape. Each divided region is approximately fan-shaped. The number of divided regions DR is not particularly limited, but in FIG. 4, 32 divided regions DR are set at equal angles (11.25 degrees) around the center P1 of the counterweight CW. The center P1 of the counterweight CW is the geometric center of the counterweight CW in a plan view. The design shape includes the coordinates (x, y, z) of the center of gravity Q1 of each divided region DR (only one center of gravity Q1 is shown in FIG. 4) and the volume V of each divided region R. The expansion/contraction ratio calculation unit 22 associates the coordinates (x, y, z) of the center of gravity Q1 with the volume V for all divided regions DR and stores them. Note that x, y, and z, which indicate the coordinates, correspond to the X-axis, Y-axis, and Z-axis in FIG. 1.

Then, as shown in FIG. 5, the expansion/contraction ratio calculation unit 22 uses the best-fit method to move and/or rotate the design shape to match the actual shape, thereby finding the position where the sum of squares of the error between the design shape and the actual shape is minimized. The expansion/contraction ratio calculation unit 22 then compares the center P1 of the counterweight CW before the best fit with the center P2 of the counterweight CW after the best fit, and calculates the position displacement M1 in the X-axis direction, the position displacement M2 in the Y-axis direction, and the angular displacement M3 around the Z-axis.

Next, as shown in FIG. 5, the expansion/contraction ratio calculation unit 22 uses the position displacement M1, the position displacement M2, and the angle displacement M3 to determine the coordinates (x', y', z) of the center of gravity Q2 of each divided region DR after the best fit. The expansion/contraction ratio calculation unit 22 associates the coordinates (x', y', z) of the center of gravity Q2 of each divided region DR after the best fit with the volume V and stores them. Note that the z coordinate of the center of gravity Q2 of each divided region DR after the best fit is the same as the z coordinate of the center of gravity Q1 of each divided region DR before the best fit. Also, the volume V of each divided region DR after the best fit is the same as the volume V of each divided region DR before the best fit.

Note that in Figure 5, only one divided region DR in the design shape after best fit is shown to show the positional relationship between center of gravity Q1 and center of gravity Q2, but 32 divided regions DR are set in the design shape after best fit as shown in Figure 4.

Next, as shown in Figs. 6(a) and (b), the expansion ratio calculation unit 22 compares the divided region DR after the best fit with the actual shape, and calculates the error value a between the two in the radial direction centered on the center P2 of the counterweight CW after the best fit. Then, as shown in Fig. 6(c), the expansion ratio calculation unit 22 calculates the sum T (= S + a) of the total length S of the divided region DR in the radial direction and the error value a, and further calculates the expansion ratio U (= T/S) by dividing the sum T by the total length S. As will be described later, the expansion ratio U is used to expand and contract each divided region DR in the radial direction so that it matches the actual shape of the counterweight CW. In the example shown in Figs. 6(a) to (c), the expansion ratio U is greater than 1 because the plot of the actual shape is located radially outside the divided region DR, but if the plot of the actual shape is located radially inside the divided region DR, the expansion ratio U is less than 1.

<Correction unit 23>
The correction unit 23 corrects the coordinates (x', y', z) of the center of gravity Q2 of each divided region DR after best fit based on the expansion/contraction rate U. Specifically, the correction unit 23 obtains the corrected coordinates (x' x U, y' x U, z) of the center of gravity Q2 of each divided region DR after expansion/contraction. The z coordinate of the center of gravity Q2 after expansion/contraction is the same as the z coordinate of the center of gravity Q2 before expansion/contraction.

Furthermore, the correction unit 23 corrects the volume V of each divided region DR after the best fit based on the expansion/contraction rate U. Specifically, the correction unit 23 calculates the corrected volume V× ^U2 of each divided region DR after expansion/contraction. Correcting the volume V of each divided region DR means correcting the mass of each divided region DR (the product of the volume V and the material density).

Then, the correction unit 23 obtains the correction mass M (=V×U ² ×α) of each divided region DR by multiplying the correction volume V×U ² by the material density α of the counterweight CW.

In this way, by expanding or contracting (expanding in Figures 6(a) to (c)) the size of the divided region DR based on the expansion rate U, the divided region DR can be expanded or contracted proportionally as a whole to the plot position of the actual shape. This means that the design shape of the counterweight CW is matched to the actual shape for each divided region DR. Therefore, the actual shape of the counterweight CW can be easily and accurately reproduced.

The correction unit 23 determines 32 sets of correction coordinates (x' x U, y' x U, z) and correction mass M for each counterweight CW. Therefore, there are 32 x 8 = 256 combinations of correction coordinates (x' x U, y' x U, z) and correction mass M for each raw crankshaft 1 (32 sets for each of the 8 counterweights CW).

<Inertia principal axis acquisition unit 24>
As shown in FIG. 7, the principal axis of inertia acquisition unit 24 calculates 256 correction coordinates (x′×U, y′×U, z) related to all divided regions DR of all counterweights CW as the correction mass M. The principal axes of inertia of the 256 mass points are obtained by treating them as mass points and solving a three-dimensional linear equation under the condition that the product of inertia about the principal axes of inertia is zero.

The principal axis of inertia acquisition unit 24 transmits the acquired principal axis of inertia to the determination unit 25 as the principal axis of inertia of the raw crankshaft 1.

<Determination unit 25>
The determination unit 25 obtains actual shape data indicating the actual shapes of the front shaft E1 and the rear flange E2 from the actual shape data obtaining unit 21. The determination unit 25 obtains the principal axis of inertia of the material crankshaft 1.

The determination unit 25 determines whether the material surface of the front shaft E1 remains after the material surface of the raw crankshaft 1 is cut in the crankshaft processing machine 30, based on the actual shape and the principal axis of inertia of the front shaft E1.

Specifically, the determination unit 25 calculates the minimum distance Rmin between the principal axis of inertia and the material surface of the front shaft E1, and then determines whether the design dimension R1 indicated by the design shape is greater than the minimum distance Rmin. As shown in FIG. 8(a), if the design dimension R1 is greater than the minimum distance Rmin, the determination unit 25 determines that the material surface of the front shaft E1 will remain after cutting in the crankshaft processing machine 30. As shown in FIG. 8(b), if the design dimension R1 is equal to or less than the minimum distance Rmin, the determination unit 25 determines that the material surface of the front shaft E1 will not remain after cutting in the crankshaft processing machine 30.

Similar to the front shaft E1, the determination unit 25 determines whether or not the material surface of the rear flange E2 remains after the material surface of the raw crankshaft 1 is cut in the crankshaft processing machine 30, based on the actual shape and the principal axis of inertia of the rear flange E2.

<Center hole determining unit 26>
When the determination unit 25 determines that no material surfaces of the front shaft E1 and the rear flange E2 remain, the center hole determination unit 26 determines the center hole of the material crankshaft 1 based on the principal axis of inertia.

Specifically, the center hole determination unit 26 determines the positions of the center holes on the first and second end faces S1 and S2 of the raw crankshaft 1 by substituting the z coordinates of each of the first and second end faces S1 and S2 of the raw crankshaft 1 into the x, y equation of the principal axis of inertia. The center hole determination unit 26 then transmits position data indicating the center holes to the center hole processing unit 12.

On the other hand, if the judgment unit 25 judges that the material surface of at least one of the front shaft E1 and the rear flange E2 remains, the center hole determination unit 26 does not determine the positions of the center holes on the first and second end faces S1, S2, respectively, because cutting the material crankshaft 1 in the crankshaft processing machine 30 would result in a defective product. The center hole determination unit 26 then transmits instruction data to the center hole processing unit 12 to remove the material crankshaft 1 from the line.

(Center hole determination method)
FIG. 9 is a flow chart for explaining the center hole determining method.

In step S1, the actual shape data acquisition unit 21 acquires actual shape data indicating the actual shapes of the front shaft E1, rear flange E2, and eight counterweights CW of the raw crankshaft 1.

In step S2, the principal axis of inertia acquisition unit 24 acquires the principal axis of inertia of the raw crankshaft 1 based on the actual shape of each counterweight CW. In this embodiment, the principal axis of inertia acquisition unit 24 acquires the principal axis of inertia based on a combination of the correction coordinates (x' x U, y' x U, z) calculated from the expansion/contraction rate U when the shape of each divided region DR is matched to the actual shape of the counterweight CW, and the mass point of the correction mass M.

In step S3, the determination unit 25 determines whether or not the material surfaces of the front shaft E1 and the rear flange E2 remain after the material surface of the raw crankshaft 1 is cut based on the actual shapes and principal axes of inertia of the front shaft E1 and the rear flange E2. If it is determined that the material surfaces of neither the front shaft E1 nor the rear flange E2 remain, the process proceeds to step S4. If it is determined that the material surfaces of either the front shaft E1 or the rear flange E2 remain, the process proceeds to step S5.

In step S4, the center hole determination unit 26 determines the center hole of the raw crankshaft 1 based on the principal axis of inertia.

In step S5, the center hole determination unit 26 does not determine a center hole because cutting the raw crankshaft 1 would result in a defective product.

(Modification of the embodiment)
<Modification 1>
In the above embodiment, the principal axis of inertia acquiring unit 24 acquires the principal axis of inertia based on a combination of the corrected coordinates (x' x U, y' x U, z) calculated from the expansion/contraction rate U when the shape of each divided region DR is matched to the actual shape of the counterweight CW and the mass point of the corrected mass M. However, the method of acquiring the principal axis of inertia in the principal axis of inertia acquiring unit 24 is not limited to this. The principal axis of inertia acquiring unit 24 may acquire the principal axis of inertia of the material crankshaft 1 based on the actual shape of the counterweight CW.

For example, another method of obtaining the principal axis of inertia is to apply a best fit using the least squares method. Specifically, the least squares center of each counterweight CW is calculated by performing a best fit comparison between the actual shape and the design shape of each counterweight CW, and the least squares axis that passes through these least squares center points on average is determined as the principal axis of inertia.

<Modification 2>
In the above embodiment, the determination unit 25 determines whether or not the material surface of each of the front shaft E1 and the rear flange E2 remains after the material surface of the material crankshaft 1 is cut, based on the actual shapes and principal axes of inertia of the front shaft E1 and the rear flange E2. However, the determination unit 25 may determine whether or not the material surface remains of only one of the front shaft E1 and the rear flange E2, which is empirically more likely to have its material surface remain.

<Modification 3>
In the above embodiment, the center hole determination unit 26 does not determine the positions of the center holes in the first and second end faces S1, S2 when it is determined that the material surface of at least one of the front shaft E1 and the rear flange E2 remains. However, when it is determined that the material surface of at least one of the front shaft E1 and the rear flange E2 remains, the principal axis of inertia may be corrected. For example, the principal axis of inertia may be moved slightly in the direction opposite to the area where the material surface of the front shaft E1 and the rear flange E2 remains, and then the determination unit 25 may make a determination again.

<Modification 4>
In the above embodiment, the crankshaft machining system 100 has the center hole machining machine 10, the center hole determination device 20, and the crankshaft machining machine 30, but the functional units included therein can be separated or combined as appropriate. For example, the center hole machining machine 10 has an actual shape measuring unit 11 and a center hole machining unit 12, but the actual shape measuring unit 11 and the center hole machining unit 12 may each be separate machines.

Reference Signs List 1: Material crankshaft 10: Center hole machining machine 20: Center hole determination device 21: Actual shape data acquisition unit 22: Expansion/contraction ratio calculation unit 23: Correction unit 24: Principal axis of inertia acquisition unit 25: Judgment unit 26: Center hole determination unit 30: Crankshaft machining machine 100: Crankshaft machining system

Claims (4)

A center hole determination device for determining a center hole of a raw crankshaft having a counterweight located between a first end and a second end, comprising:
a principal axis of inertia acquisition unit that acquires a principal axis of inertia of the material crankshaft based on an actual shape of the counterweight;
a determination unit that determines whether or not a material surface of the first end portion remains after cutting of the material crankshaft, based on an actual shape of the first end portion and the principal axis of inertia;
a center hole determination unit that determines a center hole of the raw crankshaft based on the principal axis of inertia when it is determined that no material surface of the first end portion remains;
A center hole determining device comprising: the determination unit determines whether or not a material surface of each of the first end and the second end remains after cutting the material crankshaft, based on the actual shapes of each of the first end and the second end and the principal axis of inertia;
the center hole determination unit determines a center hole of the raw crankshaft based on the principal axis of inertia when it is determined that no material surfaces of the first end portion and the second end portion remain.
2. The center hole determining device according to claim 1. A center hole determination method for determining a center hole of a raw crankshaft having a counterweight located between a first end and a second end, comprising the steps of:
obtaining a principal axis of inertia of the material crankshaft based on an actual shape of the counterweight;
a determining step of determining whether or not a material surface of the first end portion remains after cutting of the material crankshaft, based on an actual shape of the first end portion and the principal axis of inertia;
a center hole determining step of determining a center hole of the raw crankshaft based on the principal axis of inertia when it is determined that no raw material surface of the first end portion remains;
The center hole determining method includes the steps of: in the determining step, it is determined whether or not a material surface of each of the first end and the second end remains after cutting the material crankshaft, based on the actual shapes of each of the first end and the second end and the principal axis of inertia;
in the center hole determining step, when it is determined that no material surfaces remain at the first end portion and the second end portion, a center hole of the material crankshaft is determined based on the principal axis of inertia.
4. The method for determining a center hole according to claim 3.