Center hole determination device and center hole determination method

Abstract

Provided are a center hole determination device and a center hole determination method capable of determining whether the blank surface of the two ends of a crankshaft blank remains after it is cut. The center hole determination device (20) comprises an inertia principal axis acquisition unit (24), a determination unit (25), and a center hole determination unit (26). The inertia principal axis acquisition unit (24) acquires the inertia principal axis of the crankshaft blank (1) based on the actual shape of a balancing block (CW). The determination unit (25) determines whether the blank surface of the front shaft (E1) remains after the crankshaft blank (1) is cut based on the actual shape of the front shaft (E1) and the inertia principal axis. When it is determined that the blank surface of the front shaft (E1) does not remain, the center hole determination unit (26) determines the center hole of the crankshaft blank (1) based on the inertia principal axis.

Description

Technical Field

[0001] The invention relates to a center hole determining device and a center hole determining method. Background Art

[0002] The crankshaft to be installed in the engine is formed by forming a center hole on both end faces of a crankshaft blank formed by forging or casting, and then cutting the surface of the crankshaft blank with the center hole as a reference.

[0003] Patent document 1 discloses a method for determining a center hole in a crankshaft blank using the shape of a balancing weight. Specifically, in Patent document 1, the designed shape of the balancing weight is divided into a plurality of regions around a geometric center, and the center hole is determined based on the expansion and contraction ratio when the shape of each region is matched with the actual shape of the balancing weight.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-179044 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] However, in the method of Patent Document 1, the center hole is determined only based on the shape of the balance block in the crankshaft blank. Therefore, when the blank surface of the crankshaft blank is cut based on the center hole, the blank surface of the two ends of the crankshaft blank (specifically the front shaft and the rear flange) may remain.

[0009] Therefore, it is desired to be able to determine whether the raw material surfaces at both ends of the crankshaft raw material remain even after cutting when the center hole is determined.

[0010] An object of the present invention is to provide a center hole determining device and a center hole determining method which can determine whether the blank surface at both ends of a crankshaft blank remains after being cut.

[0011] Technical solutions for solving technical problems

[0012] The center hole determination device of the present invention determines the center hole of a crankshaft blank having a balancing weight located between a first end and a second end. The center hole determination device comprises an inertia principal axis acquisition unit, a determination unit, and a center hole determination unit. The inertia principal axis acquisition unit acquires the inertia principal axis of the crankshaft blank based on the actual shape of the balancing weight. The determination unit determines whether the blank surface of the first end remains after the crankshaft blank is cut based on the actual shape of the first end and the inertia principal axis. When it is determined that the blank surface of the first end does not remain, the center hole determination unit determines the center hole of the crankshaft blank based on the inertia principal axis.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to provide a center hole determining device and a center hole determining method which can determine whether or not the blank surfaces at both end portions of the crankshaft blank remain after the crankshaft blank is cut. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a three-dimensional image of the crankshaft blank.

[0016] Figure 2 Schematic diagram showing the structure of a crankshaft blank processing system.

[0017] Figure 3 is a schematic diagram showing the structure of the center hole determining device.

[0018] Figure 4 The diagrams show the designed shape and actual shape of the balancing weight.

[0019] Figure 5 This is a diagram for explaining how to fit the designed shape of the balancing weight to the actual shape.

[0020] Figure 6 It is a diagram for explaining the expansion and contraction of each divided area of ​​the balancing block.

[0021] Figure 7 FIG. 1 is a diagram showing the divided regions of the balancing mass.

[0022] Figure 8 This is a diagram for explaining the process of determining whether the rough surface of the front axle remains.

[0023] Fig. 9 is a flow chart for explaining a method for determining a center hole. DETAILED DESCRIPTION

[0024] (Crankshaft blank 1)

[0025] Figure 1 1 is a perspective view showing the structure of a crankshaft blank 1. The crankshaft blank 1 is formed by, for example, forging or casting. The crankshaft blank 1 of the present embodiment is a crankshaft blank for an inline 4-cylinder engine.

[0026] exist Figure 1 In the figure, the Z axis is the central axis of the crankshaft blank 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.

[0027] The crankshaft blank 1 includes a front shaft E1, a rear flange E2, eight balance weights CW (CW1 to CW8), four main journals J (J1 to J5), and four connecting rod journals P (P1 to P4).

[0028] In the crankshaft blank 1, the front axle E1, the main journal J1, the balancing block CW1, the connecting rod journal P1, the balancing block CW2, the main journal J2, the balancing block CW3, the connecting rod journal P2, the balancing block CW4, the main journal J3, the balancing block CW5, the connecting rod journal P3, the balancing block CW6, the main journal J4, the balancing block CW7, the connecting rod journal P4, the balancing block CW8, the main journal J5 and the rear flange E2 are arranged in sequence in the Z-axis direction.

[0029] The front shaft E1 and the rear flange E2 are located at both ends of the crankshaft blank 1. The front shaft E1 and the rear flange E2 are examples of the "first end" and the "second end" of the present invention, respectively.

[0030] The front shaft E1 has a first end surface S1 in which a center hole is formed in a later process. The rear flange E2 has a second end surface S2 in which a center hole is formed in a later process.

[0031] It is worth noting that the structure of the crankshaft blank 1 is not limited to Figure 1 The crankshaft blank 1 only needs to have at least one balancer CW and at least one of the front shaft E1 and the rear flange E2.

[0032] (Crankshaft machining system 100)

[0033] Next, refer to Figure 2 A crankshaft machining system 100 according to the present embodiment will be described. Figure 2 1 is a schematic diagram showing the structure of the crankshaft machining system 100 .

[0034] The crankshaft machining system 100 includes a center hole machining machine 10 , a center hole determining device 20 , and a crankshaft machining machine 30 .

[0035] The center hole drilling machine 10 includes an actual shape measuring unit 11 and a center hole drilling unit 12 .

[0036] The actual shape measuring unit 11 is an example of a measuring mechanism for measuring the actual shape of the crankshaft material 1 .

[0037] The actual shape measuring unit 11 has a non-contact displacement meter such as a laser displacement meter, an infrared displacement meter, an LED displacement sensor, or a contact displacement meter such as a working transformer. The actual shape measuring unit 11 measures the actual shapes of the front shaft E1, the rear flange E2, and the eight balancing blocks CW in the crankshaft blank 1 based on the measured values ​​from the displacement meter. As described later, the actual shapes of the eight balancing blocks CW are used to obtain the inertia principal axis, and the actual shapes of the front shaft E1 and the rear flange E2 are used to determine whether the blank surfaces of the front shaft E1 and the rear flange E2 remain after cutting.

[0038] It is worth noting that as a method for measuring the actual shape using a displacement meter, there are, for example, a method of measuring while rotating the crankshaft blank 1 using a fixed displacement meter, a method of measuring while rotating the displacement meter around the fixed crankshaft blank 1, or a method of measuring while moving a displacement meter configured so as to clamp the crankshaft blank 1 from the left and right in a straight line, but it is not limited to these.

[0039] Alternatively, the actual shape measuring unit 11 may be a three-dimensional digitizer (image scanner) that generates the actual shape of the entire crankshaft material 1 as three-dimensional shape data by measuring the measurement object from a plurality of different positions.

[0040] The center hole machining unit 12 machines the center hole determined by the center hole determining device 20 on the first and second end surfaces S1 and S2 of the crankshaft blank 1 .

[0041] The center hole determining device 20 is a processing device for determining the position of the center hole machined on the first and second end surfaces S1 and S2 of the crankshaft blank 1. The center hole determining device 20 includes a CPU (Central Processing Unit) 20a, a ROM (Read Only Memory) 20b, and a RAM (Random Access Memory) 20c.

[0042] ROM20b stores various programs and various information executed by CPU20a. In the present embodiment, ROM20b stores a program for processing to determine the center hole position of the crankshaft blank 1. In addition, ROM20b stores design shape data showing the design shapes of the front axle E1, the rear flange E2, and the eight balancing blocks CW in the crankshaft blank 1. RAM20c is used as a storage area for storing programs or data, or as a work area for storing processing data in CPU20a.

[0043] The crankshaft machining machine 30 cuts the surface of the crankshaft blank 1 having the center hole machined in the center hole machining portion 12. The crankshaft machining machine 30 mainly cuts the surface of the front shaft E1, the rear flange E2, each balancer CW, each connecting rod journal P, and each main journal J based on the designed shape.

[0044] (Center hole determining device 20)

[0045] Figure 3 2 is a schematic diagram showing the structure of the center hole specifying device 20. The center hole specifying device 20 includes an actual shape data acquiring unit 21, an expansion / contraction ratio calculating unit 22, a correcting unit 23, an inertia principal axis acquiring unit 24, a determining unit 25, and a center hole specifying unit 26.

[0046] <Actual shape data acquisition unit 21>

[0047] The actual shape data acquisition unit 21 acquires actual shape data indicating the actual shapes of the front shaft E1 , the rear flange E2 , and the eight balance weights CW in the crankshaft blank 1 from the actual shape measurement unit 11 .

[0048] The actual shape data acquisition unit 21 sends actual shape data showing the actual shape of each of the eight weights CW to the expansion / contraction ratio calculation unit 22 , and sends actual shape data showing the actual shape of each of the front axle E1 and the rear flange E2 to the determination unit 25 .

[0049] <Expansion / contraction ratio calculation unit 22>

[0050] The expansion / contraction ratio calculation unit 22 acquires actual shape data indicating the actual shape of each balancing weight CW from the actual shape data acquisition unit 21. The expansion / contraction ratio calculation unit 22 acquires design shape data indicating the design shape of each balancing weight CW of the crankshaft blank 1 from the ROM 20b.

[0051] Figure 4 Schematic diagram showing the designed shape (solid line) and the actual shape (dots ●) of the balancing weight CW.

[0052] like Figure 4 As shown in the figure, the position and angle of the actual shape are offset from the position and angle of the designed shape. Figure 4 In FIG. 1 , the design shape is shown by a solid line, but the actual design shape is shown by a plurality of polar coordinates. The number of polar coordinates is not particularly limited, and for example, 360 polar coordinates can be set at equal angles (1 degree) around the center P1 of the balancing weight CW.

[0053] Here, if Figure 4 As shown in FIG. 1 , in the design shape, a plurality of divided regions DR are set around the center P1 of the balancing mass CW. Each divided region is substantially fan-shaped. The number of divided regions DR is not particularly limited, but Figure 4 , 32 equiangular (11.25 degrees) angular positions are set around the center P1 of the balancing block CW. The center P1 of the balancing block CW is the geometric center of the balancing block CW in the top view. The design shape includes the center of gravity Q1 ( Figure 4 In FIG. 1 , only the coordinates (x, y, z) of one center of gravity Q1 and the volume V of each segmented region R are shown. The expansion / contraction ratio calculation unit 22 stores the coordinates (x, y, z) of the center of gravity Q1 and the volume V for all segmented regions DR in association with each other. It should be noted that x, y, and z representing the coordinates are related to Figure 1 The X-axis, Y-axis and Z-axis correspond to each other.

[0054] Then, if Figure 5As shown, the expansion ratio calculation unit 22 uses the best fitting method to find the position where the sum of squares of the errors between the design shape and the actual shape is the smallest by moving and / or rotating the design shape and the actual shape. In addition, the expansion ratio calculation unit 22 compares the center P1 of the balancing block CW before the best fitting with the center P2 of the balancing block CW after the best fitting, 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.

[0055] Then, if Figure 5 As shown, the expansion ratio calculation unit 22 uses the position displacement M1, the position displacement M2 and the angle displacement M3 to obtain the coordinates (x', y', z) of the center of gravity Q2 of each segmented region DR after the best fit. The expansion ratio calculation unit 22 stores the coordinates (x', y', z) of the center of gravity Q2 of each segmented region DR after the best fit and the volume V in association. It is worth noting that the z coordinate of the center of gravity Q2 of each segmented region DR after the best fit is the same as the z coordinate of the center of gravity Q1 of each segmented region DR before the best fit. In addition, the volume V of each segmented region DR after the best fit is the same as the volume V of each segmented region DR before the best fit.

[0056] It is worth noting that in Figure 5 In order to show the positional relationship between the center of gravity Q1 and the center of gravity Q2, only one segmented region DR in the design shape after the best fit is shown. In the design shape after the best fit, the following is also set: Figure 4 There are 32 divided regions DR shown.

[0057] Then, if Figure 6 As shown in (a) and (b) of FIG. 1 , the expansion / contraction ratio calculation unit 22 compares the best-fit segmented area DR with the actual shape, and obtains the error value a between the two in the radial direction centered on the center P2 of the best-fitted balance block CW. Figure 6 As shown in (c), the expansion ratio calculation unit 22 obtains the sum T (= S + a) of the entire length S of the divided area DR in the radial direction and the error value a, and then obtains the expansion ratio U (= T / S) by dividing the sum T by the entire length S. As described later, the expansion ratio U is used to expand and contract each divided area DR in the radial direction in a manner that matches the actual shape of the balancing block CW. Figure 6 In the examples shown in (a) to (c), the points of the actual shape are located radially outside the divided region DR, so the expansion ratio U is greater than 1, but when the points of the actual shape are located radially inside the divided region DR, the expansion ratio U is smaller than 1.

[0058] <Correction 23>

[0059] The correction unit 23 corrects the coordinates (x', y', z) of the center of gravity Q2 of each segmented region DR after the best fit based on the expansion ratio U. Specifically, the correction unit 23 obtains the corrected coordinates (x'×U, y'×U, z) of the center of gravity Q2 of each segmented region DR after expansion. The z coordinate of the center of gravity Q2 after expansion is the same as the z coordinate of the center of gravity Q2 before expansion.

[0060] Furthermore, the correction unit 23 corrects the volume V of each segmented region DR after the best fit based on the expansion / contraction ratio U. Specifically, the correction unit 23 obtains the corrected volume V×U of each segmented region DR after expansion / contraction. 2 Correcting the volume V of each divided region DR means correcting the mass (the product value of the volume V and the material density) of each divided region DR.

[0061] In addition, the correction unit 23 calculates the correction volume V×U 2 Multiply by the material density α of the balancing weight CW to obtain the correction mass M (=V×U 2 ×α).

[0062] In this way, by scaling the size of the divided region DR based on the scaling ratio U (in Figure 6 By stretching in (a) to (c) of FIG. 1 ), the entire segmented area DR can be proportionally expanded or contracted to the point position of the actual shape. This means that the design shape of the balancing weight CW matches the actual shape in each segmented area DR. Therefore, the actual shape of the balancing weight CW can be easily and accurately reproduced.

[0063] The correction unit 23 obtains 32 sets of correction coordinates (x'×U, y'×U, z) and correction mass M for each balancing block CW. Therefore, the combination of correction coordinates (x'×U, y'×U, z) and correction mass M is 32×8=256 sets for each crankshaft blank (32 sets for every eight balancing blocks CW).

[0064] <Inertia principal axis acquisition unit 24>

[0065] like Figure 7 As shown, the inertia principal axis acquisition unit 24 uses the 256 corrected coordinates (x'×U, y'×U, z) of all divided areas DR of all balancing blocks CW as mass points of the corrected mass M, solves the three-dimensional linear equation under the condition that the inertia product around the inertia principal axis is 0 (zero), and obtains the inertia principal axis of the 256 mass points.

[0066] The main axis of inertia acquisition unit 24 sends the acquired main axis of inertia to the determination unit 25 as the main axis of inertia of the raw crankshaft 1 .

[0067] <Determination Unit 25>

[0068] The determination unit 25 acquires the actual shape data indicating the actual shapes of the front shaft E1 and the rear flange E2 from the actual shape data acquisition unit 21. The determination unit 25 acquires the principal axis of inertia of the crankshaft blank 1.

[0069] The determination unit 25 determines whether the raw surface of the front shaft E1 remains after the raw surface of the crankshaft raw material 1 is cut in the crankshaft machining machine 30 based on the actual shape and the principal axis of inertia of the front shaft E1.

[0070] Specifically, after calculating the minimum distance Rmin between the principal axis of inertia and the blank surface of the front axle E1, the determination unit 25 determines whether the design dimension R1 represented by the design shape is greater than the minimum distance Rmin. Figure 8 As shown in (a), when the design dimension R1 is larger than the minimum distance Rmin, the determination unit 25 determines that the rough surface of the front shaft E1 remains after cutting in the crankshaft processing machine 30. Figure 8 As shown in (b) of FIG. 2 , when the design dimension R1 is equal to or smaller than the minimum distance Rmin, the determination unit 25 determines that the rough surface of the front shaft E1 does not remain after cutting in the crankshaft processing machine 30 .

[0071] Similar to the front shaft E1 , the determination unit 25 determines whether the raw surface of the rear flange E2 remains after the raw surface of the crankshaft raw 1 is cut in the crankshaft machining machine 30 based on the actual shape and the principal axis of inertia of the rear flange E2 .

[0072] <Center hole determining unit 26>

[0073] When the determination unit 25 determines that the raw material surfaces of the front shaft E1 and the rear flange E2 do not remain, the center hole specifying unit 26 specifies the center hole of the raw crankshaft 1 based on the principal axis of inertia.

[0074] Specifically, the center hole determination unit 26 determines the position of the center hole in each of the first and second end faces S1 and S2 by substituting the z coordinates of the first and second end faces S1 and S2 of the crankshaft blank 1 into the x and y equations of the inertia principal axis. Then, the center hole determination unit 26 sends the position data indicating the center hole to the center hole processing unit 12.

[0075] On the other hand, when the determination unit 25 determines that at least one of the front shaft E1 and the rear flange E2 has a remaining surface, the crankshaft blank 1 will become a defective product even if it is cut in the crankshaft processing machine 30, so the center hole determination unit 26 does not determine the position of the center hole in each of the first and second end faces S1 and S2. Thereafter, the center hole determination unit 26 sends instruction data indicating that the crankshaft blank 1 is to be excluded from the production line to the center hole processing unit 12.

[0076] (Method for determining the center hole)

[0077] Fig. 9 is a flow chart for explaining a method for determining a center hole.

[0078] In step S1 , the actual shape data acquisition unit 21 acquires actual shape data representing the actual shapes of the front shaft E1 , the rear flange E2 , and the eight balance weights CW in the crankshaft blank 1 .

[0079] In step S2, the inertia principal axis acquisition unit 24 acquires the inertia principal axis of the crankshaft blank 1 based on the actual shape of each balancing mass CW. In the present embodiment, the inertia principal axis acquisition unit 24 acquires the inertia principal axis based on a combination of the corrected coordinates (x'×U, y'×U, z) of the shape of each divided region DR calculated by the expansion / contraction ratio U when matching the actual shape of the balancing mass CW and the mass point of the corrected mass M.

[0080] In step S3, the determination unit 25 determines whether the blank surface of the front axle E1 and the rear flange E2 remains after the blank surface of the crankshaft blank 1 is cut based on the actual shape and the principal axis of inertia of the front axle E1 and the rear flange E2. If it is determined that the blank surface of either the front axle E1 or the rear flange E2 does not remain, the process proceeds to step S4. If it is determined that the blank surface of either the front axle E1 or the rear flange E2 remains, the process proceeds to step S5.

[0081] In step S4 , the center hole determining unit 26 determines the center hole of the raw crankshaft 1 based on the principal axis of inertia.

[0082] In step S5 , the center hole determining section 26 does not determine the center hole because the crankshaft blank 1 becomes a defective product even if it is cut.

[0083] (Variation of the embodiment)

[0084] <Variation 1>

[0085] In the above embodiment, the inertia principal axis acquisition unit 24 acquires the inertia principal axis based on the combination of the correction coordinates (x'×U, y'×U, z) of the shape of each divided area DR calculated by the expansion and contraction rate U when matching the actual shape of the balancing mass CW and the mass point of the correction mass M. However, the acquisition method of the inertia principal axis in the inertia principal axis acquisition unit 24 is not limited to this. The inertia principal axis acquisition unit 24 only needs to acquire the inertia principal axis of the crankshaft blank 1 based on the actual shape of the balancing mass CW.

[0086] For example, as another method for obtaining the principal axis of inertia, a method of best fitting using the least squares method is cited. Specifically, the least squares center of each balancing mass CW is calculated by best fitting and comparing the actual shape and the designed shape of each balancing mass CW, and the least squares axis passing through these least squares center points is taken as the principal axis of inertia.

[0087] <Variation 2>

[0088] In the above embodiment, the determination unit 25 determines whether the blank surface of the front axle E1 and the rear flange E2 remains after the blank surface of the crankshaft blank 1 is cut based on the actual shape and the principal axis of inertia of the front axle E1 and the rear flange E2. However, the determination unit 25 may determine whether the blank surface remains only for the front axle E1 and the rear flange E2 whose blank surface is likely to remain based on experience.

[0089] <Variation 3>

[0090] In the above embodiment, when it is determined that the rough surface of at least one of the front axle E1 and the rear flange E2 remains, the center hole determination unit 26 does not determine the position of the center hole in each of the first and second end faces S1 and S2. However, when it is determined that the rough surface of at least one of the front axle E1 and the rear flange E2 remains, the inertia principal axis may be corrected. For example, after the inertia principal axis is slightly moved in the opposite direction of the rough surface remaining area of ​​the front axle E1 and the rear flange E2, the determination unit 25 may make another determination.

[0091] <Variation 4>

[0092] In the above embodiment, the crankshaft machining system 100 includes the center hole machining machine 10, the center hole determination device 20, and the crankshaft machining machine 30, but the functional parts included in these can be separated or combined appropriately. For example, the center hole machining machine 10 can be provided with the actual shape measuring unit 11 and the center hole machining unit 12, but the actual shape measuring unit 11 and the center hole machining unit 12 can also be provided as separate devices.

[0093] Description of Reference Numerals

[0094] 1: Crankshaft blank;

[0095] 10: Center hole processing machine;

[0096] 20: Center hole determination device;

[0097] 21: actual shape data acquisition unit;

[0098] 22: expansion ratio calculation unit;

[0099] 23: Correction Department;

[0100] 24: Inertia spindle acquisition unit;

[0101] 25: Judgment Department;

[0102] 26: center hole determination part;

[0103] 30: Crankshaft processing machine;

[0104] 100: Crankshaft machining system.

Claims

1. A center hole determining device for determining a center hole of a crankshaft blank having a balancing weight located between a first end and a second end, the center hole determining device comprising: An inertia principal axis acquisition unit, which acquires the inertia principal axis of the crankshaft blank based on the actual shape of the balancing block; a determination unit that determines whether a surface of the first end portion remains after the crankshaft blank is cut based on an actual shape of the first end portion and the principal axis of inertia; A center hole identifying unit identifies the center hole of the crankshaft blank based on the inertia principal axis when it is determined that the blank surface of the first end portion does not remain.

2. The center hole determination device according to claim 1, wherein: The determination unit determines whether the surfaces of the first end portion and the second end portion remain after the crankshaft blank is cut based on the actual shapes of the first end portion and the second end portion and the principal axis of inertia. When it is determined that the raw material surface of each of the first end portion and the second end portion does not remain, the center hole identifying unit identifies the center hole of the raw material crankshaft based on the principal axis of inertia.

3. A method for determining a center hole of a crankshaft blank having a balancing weight located between a first end and a second end, comprising: An acquisition step of acquiring the inertia principal axis of the crankshaft blank based on the actual shape of the balancing block; a determination step of determining whether a surface of the first end portion remains after the crankshaft blank is cut based on an actual shape of the first end portion and the principal axis of inertia; The center hole determining step determines the center hole of the crankshaft blank based on the inertia principal axis when it is determined that the blank surface of the first end portion does not remain.

4. The method for determining a center hole according to claim 3, wherein: In the determination step, based on the actual shapes of the first end portion and the second end portion and the principal axis of inertia, it is determined whether the surfaces of the first end portion and the second end portion remain after the crankshaft blank is cut. In the center hole determining step, when it is determined that the raw material surface of each of the first end portion and the second end portion does not remain, the center hole of the raw material crankshaft is determined based on the principal axis of inertia.

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