Method for setting processing conditions for shaft enlargement processing, shaft enlargement processing method, and shaft enlargement processing device

Abstract

To provide a processing condition setting method of shaft thickening processing, a shaft thickening processing method and a shaft thickening processing apparatus in which the time and labor required for inspection of the presence or absence of cracks can be reduced.SOLUTION: A control unit 13 of a shaft thickening processing apparatus 1 controls a pressure part 4, a bent part 5 and a turning part 6. A shaft material W is rotated around the shaft while imparting the compressive force in the shaft direction and a bending angle to an intermediate part Wa of the shaft material W held by a pair of holding parts 2, 3, and thereby the intermediate part Wa of the shaft material W is thickened in a predetermined outer diameter. The pass-fail of the shaft material W is determined, based on the number of rotations of the shaft material W required for the intermediate part Wa of the shaft material W to be thickened to the predetermined outer diameter, detected by a rotation frequency detection part 7.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for setting processing conditions for a shaft enlargement processing method, a shaft enlargement processing method, and a shaft enlargement processing device. [Background technology]

[0002] Shaft enlargement processing is known as a processing method for forming a large diameter portion in part of a shaft material.One example of a shaft enlargement processing method is a method in which a compressive force and a bending angle are applied to the middle part of the shaft material and the shaft material is rotated to enlarge the middle part of the shaft material.

[0003] A shaft enlargement machine for carrying out the above-mentioned shaft enlargement process generally holds the shaft material with a pair of holders arranged at a distance in the axial direction of the shaft material, reduces the distance between the pair of holders to apply a compressive force to the middle part of the shaft material, tilts one holder relative to the other holder to apply a bending angle to the middle part of the shaft material, and rotates the pair of holders in this state to rotate the shaft material, thereby enlarging the middle part of the shaft material. The process of enlarging the middle part of the shaft material is then terminated when the distance between the pair of holders has been reduced to a predetermined distance (see Patent Document 1, for example) or when the outer diameter of the middle part has reached a predetermined outer diameter (see Patent Document 2, for example). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-212937 A [Patent Document 2] JP 2008-212936 A Summary of the Invention [Problem to be solved by the invention]

[0005] In shaft enlargement processing, cracks may occur at the connection between the enlarged middle part and the shaft part other than the middle part, and cracks may occur on the outer periphery of the enlarged middle part. Cracks can be detected by, for example, visual inspection, magnetic flaw detection inspection, eddy current flaw detection inspection, etc., but 100% inspection of mass-produced shaft materials is time-consuming and costly.

[0006] The present invention has been developed in consideration of the above-mentioned circumstances, and aims to provide a method for setting processing conditions for a shaft enlargement processing method, a shaft enlargement processing method, and a shaft enlargement processing apparatus that can reduce the time and cost required to inspect for the presence or absence of cracks. [Means for solving the problem]

[0007] A method for setting processing conditions for shaft enlargement processing according to one embodiment of the present invention is a method for setting processing conditions for shaft enlargement processing, in which an axial compressive force and a bending angle are applied to a middle portion of a shaft material while the shaft material is rotated around its axis to enlarge the middle portion of the shaft material in the radial direction, wherein the method sets an allowable number of rotations at which the probability of crack occurrence at the connection portion is below a threshold value based on test data obtained by performing shaft enlargement processing on a test shaft material of the same material and shape as the shaft material, the test data showing the relationship between the number of rotations of the test shaft material required to enlarge the middle portion of the test shaft material to a predetermined outer diameter and the probability of crack occurrence at the connection portion between the middle portion of the test shaft material and the shaft portion excluding the middle portion, and sets the number of rotations of the shaft material when the middle portion of the test shaft material is enlarged to the predetermined outer diameter by shaft enlargement processing to be below the allowable number of rotations.

[0008] In addition, a method for setting processing conditions for shaft enlargement processing of one embodiment of the present invention is a method for setting processing conditions for shaft enlargement processing, in which an axial compressive force and a bending angle are applied to the axial middle portion of a shaft material while the shaft material is rotated around its axis to enlarge the middle portion of the shaft material in the radial direction, wherein the method sets an allowable enlargement rate at which the probability of crack occurrence in the outer periphery is below a threshold value based on test data obtained by performing shaft enlargement processing on a test shaft material of the same material and shape as the shaft material, the test data showing the relationship between an enlargement rate, which is the ratio of the outer diameter of the middle portion of the test shaft material after processing to the outer diameter before processing, and the probability of crack occurrence in the outer periphery of the middle portion of the test shaft material, and the allowable enlargement rate is set at which the probability of crack occurrence in the outer periphery is below a threshold value, and the enlargement rate of the middle portion of the shaft material when the middle portion of the shaft material is enlarged to a predetermined outer diameter by shaft enlargement processing is set to be below the allowable enlargement rate.

[0009] In addition, one embodiment of the shaft enlargement processing method of the present invention is a shaft enlargement processing method in which an axial compressive force and a bending angle are applied to the axial middle portion of the shaft material while the shaft material is rotated about its axis, thereby enlarging the middle portion of the shaft material radially, and the pass / fail of the shaft material is determined based on the number of rotations of the shaft material required to enlarge the middle portion of the shaft material to a predetermined outer diameter.

[0010] In addition, one embodiment of the shaft enlargement processing method of the present invention is a shaft enlargement processing method in which an axial compressive force and a bending angle are applied to the axial middle portion of the shaft material while the shaft material is rotated about its axis, thereby enlarging the middle portion of the shaft material radially, and the acceptability of the shaft material is determined based on the enlargement rate, which is the ratio of the outer diameter of the middle portion of the shaft material after processing to the outer diameter before processing.

[0011] and a control unit that controls the pressure unit, the bending unit, and the rotating unit to rotate the shaft material about its axis while applying an axial compressive force and a bend angle to the intermediate portion of the shaft material. The control unit determines whether the shaft material is acceptable or not based on the number of rotations of the shaft material required for the intermediate portion of the shaft material to be enlarged to a predetermined outer diameter.

[0012] A shaft enlargement processing device according to one embodiment of the present invention includes a pair of holding sections which hold the shaft material at a distance in the axial direction of the shaft material, a pressurizing section which reduces the distance between the pair of holding sections and applies an axial compressive force to a middle portion of the shaft material disposed between the pair of holding sections, a bending section which tilts one of the pair of holding sections relative to the other holding section to apply a bending angle to the middle portion of the shaft material, a rotating section which rotates the pair of holding sections and the shaft material around the axis of the shaft material, an axial displacement detection section which detects the amount of change in the distance between the pair of holding sections, and a force sensor for detecting the amount of change in the distance between the pair of holding sections. The shaft material has a radial displacement detection unit which detects the amount of change in the outer diameter of the middle portion, and a control unit which controls the pressure unit, the bending unit, and the rotating unit to rotate the shaft material around its axis while applying an axial compressive force and bending angle to the middle portion of the shaft material and reduce the distance between the pair of holding units by a predetermined amount, thereby enlarging the middle portion of the shaft material. The control unit calculates an enlargement rate, which is the ratio of the outer diameter of the middle portion of the shaft material after processing to the outer diameter of the middle portion of the shaft material before processing, based on the amount of change in the outer diameter of the middle portion of the shaft material, and judges the pass / fail of the shaft material based on the calculated enlargement rate. Effect of the Invention

[0013] According to the present invention, it is possible to provide a method for setting processing conditions for shaft enlargement processing, a shaft enlargement processing method, and a shaft enlargement processing device that can reduce the time and cost required to inspect for the presence or absence of cracks. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram of an example of a shaft enlargement processing device for explaining an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram of a modified example of the shaft enlargement processing device of FIG. [Figure 3A] 2 is a schematic diagram of an example of a shaft enlargement processing method using the shaft enlargement processing device of FIG. 1. [Figure 3B] 2 is a schematic diagram of an example of a shaft enlargement processing method using the shaft enlargement processing device of FIG. 1. [Figure 3C] 2 is a schematic diagram of an example of a shaft enlargement processing method using the shaft enlargement processing device of FIG. 1. [Figure 3D] 2 is a schematic diagram of an example of a shaft enlargement processing method using the shaft enlargement processing device of FIG. 1. [Figure 4A] 1 is a graph showing an example of test data showing the relationship between the compressive force and the number of revolutions of a test shaft material. [Figure 4B] 1 is a graph showing an example of test data showing the relationship between the number of revolutions of a test shaft material and the probability of crack occurrence. [Figure 5A] 1 is a graph showing an example of test data showing the relationship between the compression ratio and the expansion ratio of a test shaft material. [Figure 5B] 1 is a graph showing an example of test data showing the relationship between the expansion rate of a test shaft material and the probability of crack occurrence. [Figure 6] 2 is a flowchart of an example of processing performed by a control unit of the shaft enlargement processing device of FIG. [Figure 7] 13 is a flowchart of another example of the process performed by the control unit of the shaft enlargement processing device of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] FIG. 1 shows an example of a shaft enlargement processing device for explaining an embodiment of the present invention.

[0016] The shaft enlargement processing device 1 shown in FIG. 1 includes a pair of holding units 2, 3 for holding a shaft material W, a pressure unit 4, a bending unit 5, a rotating unit 6, a rotation number detection unit 7, and a control panel 8.

[0017] The holding portion 2 fits into one axial end of the shaft material W, and the holding portion 3 fits into the other axial end of the shaft material W, whereby the shaft material W is held by the pair of holding portions 2, 3. The pair of holding portions 2, 3 are disposed at a distance along reference line A on reference line A and are supported by a support base (not shown). The shaft material W held by the pair of holding portions 2, 3 is also disposed on reference line A. One holding portion 2 is movable along reference line A, i.e., movable in the axial direction of the shaft material W, and the other holding portion 3 is movable in a direction intersecting reference line A.

[0018] The pressurizing unit 4 includes, for example, a fluid pressure cylinder and moves the holding unit 2 along the reference line A to reduce the distance between the pair of holding units 2 and 3. As the distance between the pair of holding units 2 and 3 is reduced, an axial compressive force is applied to the axial middle portion Wa of the shaft material W that is disposed between the pair of holding units 2 and 3.

[0019] The bending unit 5 includes, for example, a fluid pressure cylinder, and moves the holding unit 3 in a direction intersecting with the reference line A, tilting the holding unit 3 relative to the holding unit 2 that is arranged on the reference line A. As the holding unit 3 is tilted relative to the holding unit 2, a bending angle θ is imparted to the middle portion Wa of the shaft W.

[0020] The rotating unit 6 includes, for example, an electric motor and rotates the holding unit 3 around the central axis of the holding unit 3. As the holding unit 3 rotates, the shaft material W, one end of which is fitted into the holding unit 3, also rotates around the axis, and the holding unit 2, the other end of which is fitted into the shaft material W, also rotates.

[0021] The rotation number detection unit 7 includes, for example, a rotary encoder and detects the number of rotations of the holding unit 3 as the number of rotations of the shaft material W. Note that the rotation number detection unit 7 may detect the number of rotations of the holding unit 2 instead of the holding unit 3, or may detect the number of rotations of the shaft material W.

[0022] The control panel 8 is configured to include an operation unit 11 having hardware keys such as switches and used to input processing conditions, etc., a display unit 12 having a display device such as an LCD (liquid crystal display) and displaying an operation screen, etc., and a control unit 13.

[0023] The control unit 13 is a computer such as a PLC (programmable logic controller), and has one or more processors and stores programs executed by the processor. It also has storage devices such as a ROM (Read Only Memory) and a RAM (Random access memory) that store processing conditions input via the operation unit 11, and the processor executes the programs to control the pressure unit 4, bending unit 5, and rotating unit 6 based on the input processing conditions.

[0024] Under the control of the control unit 13, the pressing unit 4 applies an axial compressive force to the middle portion Wa of the shaft material W, and the bending unit 5 applies a bending angle θ to the middle portion Wa of the shaft material W, while the rotating unit 6 rotates the shaft material W about its axis. As a result, the middle portion Wa of the shaft material W is compressed in the axial direction and expanded in the radial direction.

[0025] The number of rotations detected by the rotation number detection unit 7 is input to the control unit 13. The pressure applying unit 4 is provided with a sensor that detects the compressive force, the bending unit 5 is provided with a sensor that detects the bending angle θ based on, for example, the displacement amount of the holding unit 3, and the rotating unit 6 is provided with a sensor that detects the rotation speed of the holding unit 3. The compressive force, bending angle θ, and rotation speed detected by these sensors are also input to the control unit 13. The rotation speed may be calculated by the control unit 13 based on the number of rotations detected by the rotation number detection unit 7.

[0026] The shaft enlargement processing device 1 further includes an axial displacement detection unit 9. The axial displacement detection unit 9 includes, for example, a linear encoder, and detects the amount of displacement of the holding unit 2 moved by the pressing unit 4.

[0027] The amount of displacement of the holding part 2 detected by the axial displacement detection part 9 is input to the control part 13. The control part 13 detects the amount of compression of the middle part Wa of the shaft material W (the amount of reduction in the axial length of the middle part Wa) based on the amount of displacement of the holding part 2 after the compressive force starts to increase, and detects that the middle part Wa has expanded to a predetermined outer diameter based on this amount of compression.

[0028] As shown in Figure 2, the shaft enlargement processing device 1 may be equipped with a radial displacement detection unit 10 that detects the amount of change in the outer diameter of the middle portion Wa of the shaft material W, and the control unit 13 may detect that the middle portion Wa has been enlarged to a predetermined outer diameter based on the amount of change in the outer diameter from the outer diameter of the middle portion Wa before processing detected by the radial displacement detection unit 10.

[0029] Next, an example of a shaft enlargement processing method using the shaft enlargement processing device 1 will be described with reference to Figs. 3A to 3E.

[0030] First, as shown in Fig. 3A, a shaft material W is held by a pair of holding parts 2, 3. The axial length L0 of the middle part Wa of the shaft material W before processing is appropriately determined according to the axial length L and outer diameter D of the middle part Wa after processing in relation to D0, where D0 is the outer diameter of the middle part Wa before processing. Hereinafter, L / L0 will be referred to as the compression ratio, and D / D0 will be referred to as the expansion ratio.

[0031] Next, as shown in FIG. 3B, the holding part 2 is moved along the reference line A by the pressing part 4 (see FIG. 1), and an axial compressive force is applied to the middle part Wa of the shaft material W. The holding part 3 is tilted with respect to the holding part 2 by the bending part 5 (see FIG. 1), and a bending angle θ is applied to the middle part Wa. The bending angle θ is set to an angle at which the bending of the shaft material W falls within the deformation of the elastic limit of the shaft material W, and varies depending on the elastic limit of the material of the shaft material W, but is typically about 2° to 4°. Then, with the compressive force and bending angle θ being applied to the middle part Wa of the shaft material W, the holding part 3 is rotated by the rotating part 6 (see FIG. 1), and the shaft material W is rotated around its axis.

[0032] As shown in Fig. 3C, as the middle portion Wa of the shaft material W is compressed, bent, and rotated, an alternating radial load acts on each part of the circumferential direction of the middle portion Wa, and the middle portion Wa gradually expands in the radial direction due to the repeated application of this alternating load. Specifically, as the middle portion Wa is compressed and bent, the material on the inner side of the bend undergoes plastic flow and bulges. Then, as the shaft material W rotates, the bulge caused by the plastic flow of the material on the inner side of the bend of the middle portion Wa grows around the entire circumference, and the middle portion Wa gradually expands in the radial direction.

[0033] As shown in Fig. 3D, when the control unit 13 (see Fig. 1) detects that the middle portion Wa of the shaft material W has been enlarged to a predetermined outer diameter based on the amount of compression of the middle portion Wa or the amount of change in the outer diameter of the middle portion Wa, the compression of the middle portion Wa is stopped. Then, the holding unit 3 is again positioned along the reference line A, the middle portion Wa of the shaft material W is bent back, and the thickness of the enlarged middle portion Wa is made uniform over the entire circumference. Through the above process, the shaft enlargement process on the shaft material W is completed, and the rotation of the shaft material W is stopped.

[0034] The occurrence of cracks in the connection part Wc between the middle part Wa of the shaft material W that has been subjected to shaft enlargement processing and the shaft part Wb excluding the middle part Wa (the part that was fitted into the holding parts 2, 3) is caused by material fatigue caused by the repeated application of alternating loads, and is related to the number of rotations of the shaft material W required for the middle part Wa to enlarge to a specified outer diameter. Therefore, as a processing condition, an allowable number of rotations is set for the number of rotations of the shaft material W required for the middle part Wa to enlarge to a specified outer diameter.

[0035] In addition, the occurrence of cracks in the outer periphery Wd of the middle part Wa of the shaft material W that has been subjected to shaft enlargement processing is caused by the middle part Wa enlarging beyond the malleability limit of the material, and is related to the enlargement ratio D / D0 of the middle part Wa. Therefore, the allowable enlargement ratio is set as a processing condition for the enlargement ratio D / D0 of the middle part Wa.

[0036] 4A and 4B show an example of test data used to set the permissible number of rotations.

[0037] The test data shown in Figures 4A and 4B are test data obtained by performing shaft enlargement processing on a test shaft material of the same material and shape as the shaft material W. The test data shown in Figure 4A shows the relationship between the compressive force and the number of rotations when the number of rotations of the test shaft material required to enlarge the middle part of the test shaft material to a predetermined outer diameter is changed by changing the compressive force applied to the middle part of the test shaft material. The test data shown in Figure 4B shows the probability of crack occurrence at the connection part of the test shaft material when shaft enlargement processing is performed on multiple test shaft materials for each set compressive force, in relation to the number of rotations corresponding to the compressive force.

[0038] In the interpolation curve of the test data shown in Figure 4B, when the number of rotations is 40 or less, the probability of cracks occurring in the connection is 0%, and as the number of rotations increases beyond 40, the probability of cracks also increases, and when the number of rotations is 70 or more, the probability of cracks occurring is 100%. It can be said that the more the number of rotations increases, the more the number of repeated applications of alternating loads increases, and the more the number of repeated applications of alternating loads increases, the more the material fatigues, and the higher the probability of cracks occurring.

[0039] The allowable number of rotations can be the number of rotations at which the probability of crack occurrence is equal to or less than a threshold, and the threshold for the probability of crack occurrence can be set in consideration of yield and the like, and can be, for example, 0%. According to the test data shown in Fig. 4B, the allowable number of rotations can be 40, which is the upper limit of the number of rotations at which the probability of crack occurrence is 0%, and preferably, the number of rotations can be set with a margin that is set in consideration of the variation in the material properties of the shaft material with respect to the upper limit of the number of rotations at which the probability of crack occurrence is 0%, and can be, for example, 32 (with a margin of 20%).

[0040] When the bending angle θ applied to the middle part Wa of the shaft material W is relatively small, the material fatigue per alternating load is relatively small, and when the bending angle θ applied to the middle part Wa of the shaft material W is relatively large, the material fatigue per alternating load is relatively large. In other words, the bending angle θ applied to the middle part Wa is also related to the occurrence of cracks in the connection part Wc of the shaft material W. Therefore, preferably, the test data used to set the allowable number of rotations is test data obtained by subjecting a test shaft material of the same material and shape as the shaft material W to shaft enlargement processing at the same bending angle as the shaft material W.

[0041] 5A and 5B show an example of test data used to set the allowable hypertrophy rate.

[0042] The test data shown in Figures 5A and 5B are test data obtained by performing shaft enlargement processing on a test shaft material of the same material and shape as shaft material W. The test data shown in Figure 5A shows the relationship between the compression rate L / L0 and the enlargement rate D / D0 when the enlargement rate D / D0 of the middle part of the test shaft material is changed by changing the compression rate L / L0 of the middle part of the test shaft material. The test data shown in Figure 5B shows the probability of crack occurrence on the outer periphery of the middle part of the test shaft material in relation to the enlargement rate when shaft enlargement processing is performed on multiple test shaft materials for each set enlargement rate.

[0043] In the complementary curve of the test data shown in Figure 5B, when the expansion rate is 1.8 or less, the probability of crack occurrence in the outer periphery is 0%, and as the expansion rate increases beyond 1.8, the probability of crack occurrence also increases, and when the expansion rate is 3.0 or more, the probability of crack occurrence is 100%. It can be said that as the expansion rate increases, the probability of exceeding the malleability limit of the material increases, and the probability of crack occurrence also increases.

[0044] The allowable expansion rate can be an expansion rate at which the probability of crack occurrence is equal to or less than a threshold, and the threshold for the probability of crack occurrence can be set in consideration of yield and the like, and can be, for example, 0%. According to the test data shown in Fig. 5B, the allowable expansion rate can be 1.8, which is the upper limit expansion rate at which the probability of crack occurrence is 0%, and preferably, the allowable expansion rate can be an expansion rate with a margin set in consideration of the variation in material properties of the shaft material with respect to the upper limit expansion rate of 1.8 at which the probability of crack occurrence is 0%, and can be, for example, 1.6 (10% margin).

[0045] FIG. 6 shows an example of a process performed by the control unit 13 in shaft enlarging processing for the shaft material W.

[0046] First, processing conditions are input to the operation unit 11, and the control unit 13 stores the input processing conditions (step S1). The input processing conditions are compression force, rotation speed, bending angle θ, processing completion condition, and allowable number of rotations N. The compression force and rotation speed can be set appropriately, and can be set to the maximum values ​​that the pressure unit 4 and the rotation unit 6 can output from the viewpoint of shortening the cycle time, for example.

[0047] The processing completion condition is a condition for detecting that the middle portion Wa of the shaft material W has been enlarged to a predetermined outer diameter, and if the shaft enlargement processing device 1 is equipped with an axial displacement detection unit 9 that detects the amount of displacement of the holding portion 2, the amount of displacement of the holding portion 2 (the amount of compression of the middle portion Wa) after the compressive force starts to increase is set. If the shaft enlargement processing device 1 is equipped with a radial displacement detection unit 10 that detects the amount of change in the outer diameter of the middle portion Wa, the amount of change in the outer diameter from the outer diameter before processing of the middle portion Wa is set.

[0048] Here, the displacement amount of the holding part 2 or the change amount of the outer diameter of the intermediate part Wa is set in relation to the allowable expansion rate. First, a shaft material W in which the expansion rate D / D0 calculated from the outer diameter D0 of the intermediate part Wa before processing and the outer diameter D after the required processing is equal to or less than the allowable expansion rate is selected from among a plurality of shaft materials having different outer diameters D0 before processing according to the outer diameter D after the required processing. The change amount of the outer diameter of the intermediate part Wa is the difference between the outer diameter D0 of the intermediate part Wa of the selected shaft material W before processing and the outer diameter D after the required processing. In addition, the volume of the intermediate part Wa does not change before and after processing, and the axial length L of the intermediate part Wa after processing is calculated based on the axial length L0 of the intermediate part Wa before processing and the expansion rate D / D0 that is equal to or less than the allowable expansion rate, and the displacement amount of the holding part 2 is the difference between the axial length L0 of the intermediate part Wa before processing and the axial length L after processing.

[0049] The allowable number of rotations N is the allowable number of rotations of the selected shaft material W. The bending angle θ can be the same as the bending angle of the shaft enlargement process performed on a test shaft material of the same material and shape as the selected shaft material W to obtain test data used to set the allowable number of rotations N.

[0050] Next, when a processing start command is input to the operation unit 11, the control unit 13 controls the pressing unit 4, bending unit 5, and rotating unit 6 in accordance with the processing conditions input in step S1, and performs the shaft enlargement processing shown in Figures 3A to 3D on the shaft material W (step S2). The control unit 13 completes the shaft enlargement processing on the shaft material W when the amount of displacement of the holding unit 2 detected by the axial displacement detection unit 9 or the amount of change in the outer diameter of the middle portion Wa detected by the radial displacement detection unit 10 reaches the processing completion condition (step S3).

[0051] Next, the control unit 13 obtains the number of rotations n of the shaft material W detected by the number of rotations detection unit 7, which is the number of rotations required for the intermediate portion Wa to expand to the predetermined outer diameter D, and judges the pass / fail of the shaft material W based on the obtained number of rotations n (step S4). In this pass / fail judgment, the control unit 13 uses the allowable number of rotations N input in step S1, and judges the shaft material W as pass if n≦N (step S5), and judges the shaft material W as fail if n>N (step S6).

[0052] An example of a case where the number of rotations n exceeds the allowable number of rotations N is when the shaft material W to be machined is uniquely hard due to variations in the material properties of the shaft material. When n>N, cracks are expected to occur at the connection part Wc of the shaft material W with a probability corresponding to the number of rotations n on the complementary curve of the test data shown in FIG. 4B. Therefore, the control unit 13 judges that the shaft material W is unsuccessful when n>N. The judgment result is notified to the operator, for example, by being displayed on the display unit 12 under the control of the control unit 13.

[0053] In this way, the occurrence of cracks in the connection portion Wc of the shaft material W can be determined based on the number of rotations n required for the middle portion Wa of the shaft material W to expand to a specified outer diameter D, so that the determination can be made immediately after processing is completed, thereby reducing the time and cost required for inspecting for the presence or absence of cracks.

[0054] Furthermore, in this example, the amount of displacement of the holding portion 2 or the amount of change in the outer diameter of the intermediate portion Wa as the processing completion condition is set in relation to the allowable enlargement rate, and the occurrence of cracks in the outer periphery Wd of the shaft material W is also suppressed. This makes it possible to further reduce the time and cost required for inspection for the presence or absence of cracks.

[0055] FIG. 7 shows another example of the processing performed by the control unit 13 in shaft enlarging processing for the shaft material W.

[0056] 7, the compressive force, rotation speed, bending angle θ, processing completion condition, and allowable enlargement rate D / D0 are input as processing conditions, and the control unit 13 judges pass / fail using the input allowable enlargement rate D / D0. In this example, the shaft enlargement processing device 1 is equipped with an axial displacement detection unit 9 that detects the amount of displacement of the holding unit 2, and a radial displacement detection unit 10 that detects the amount of change in the outer diameter of the middle portion Wa of the shaft material W, the processing completion condition is set by the amount of displacement of the holding unit 2, and the radial displacement detection unit 10 detects the amount of change in the outer diameter of the middle portion Wa where processing is completed.

[0057] First, processing conditions are input to the operation unit 11, and the control unit 13 stores the input processing conditions (step S11). Next, when a processing start command is input to the operation unit 11, the control unit 13 controls the pressure unit 4, the bending unit 5, and the rotating unit 6 according to the processing conditions input in step S1, and performs the shaft enlargement processing shown in Figures 3A to 3D on the shaft material W (step S12). The control unit 13 completes the shaft enlargement processing on the shaft material W when the displacement amount of the holding unit 2 detected by the axial displacement detection unit 9 reaches the processing completion condition (step S13).

[0058] Next, the control unit 13 obtains the amount of change in the outer diameter of the intermediate portion Wa detected by the radial displacement detection unit 10, and calculates the expansion rate of the processed intermediate portion Wa (step S14). The expansion rate of the intermediate portion Wa can be calculated by (D0+ΔD) / D0 using the outer diameter D0 of the intermediate portion Wa before processing and the amount of change ΔD in the outer diameter of the intermediate portion Wa detected by the radial displacement detection unit 10.

[0059] Then, the control unit 13 judges the acceptability of the shaft material W based on the expansion rate (D0+ΔD) / D0 calculated in step S14 (step S15). In this judgment, the control unit 13 uses the allowable expansion rate D / D0 input in step S11, and judges the shaft material W as pass if (D0+ΔD) / D0≦D / D0 (step S16), and judges the shaft material W as fail if (D0+ΔD) / D0>D / D0 (step S17).

[0060] An example of a case where the expansion rate (D0+ΔD) / D0 exceeds the allowable expansion rate D / D0 is when the axial length L0 of the middle part Wa of the shaft material W to be processed is specifically large before processing due to a dimensional error of the shaft material, and the change in outer diameter ΔD after processing is specifically large. For a given displacement amount of the holding part 2, the larger the axial length L0 before processing, the larger the change in outer diameter ΔD of the middle part Wa becomes. Then, when (D0+ΔD) / D0>D / D0, the occurrence of cracks in the outer periphery Wd of the shaft material W is expected with a probability corresponding to the expansion rate (D0+ΔD) / D0 on the complementary curve of the test data shown in FIG. 5B. Therefore, the control part 13 judges that the shaft material W is unsuccessful when (D0+ΔD) / D0>D / D0. The judgment result is notified to the operator, for example, by displaying it on the display part 12 under the control of the control part 13.

[0061] In this way, by determining whether or not cracks have occurred in the outer peripheral portion Wd of the shaft material W based on the enlargement rate of the middle portion Wa of the shaft material W, the determination can be made immediately after processing is completed, thereby reducing the time and cost required to inspect for the presence or absence of cracks.

[0062] In addition, the pass / fail judgment for the occurrence of cracks in the outer peripheral portion Wd based on the enlargement rate and allowable enlargement rate of the intermediate portion Wa, as shown in Figure 7, can also be performed in combination with the pass / fail judgment for the occurrence of cracks in the connection portion Wc, as shown in Figure 6, based on the number of rotations of the shaft material W and the allowable number of rotations.

[0063] As explained above, the method of setting processing conditions for shaft enlargement processing disclosed in this specification is a method of setting processing conditions for shaft enlargement processing, in which an axial compressive force and a bending angle are applied to a middle portion of a shaft material while the shaft material is rotated around its axis to enlarge the middle portion of the shaft material in the radial direction, and the method is based on test data obtained by performing shaft enlargement processing on a test shaft material of the same material and shape as the shaft material, the test data showing the relationship between the number of rotations of the test shaft material required to enlarge the middle portion of the test shaft material to a predetermined outer diameter and the probability of crack occurrence at the connection portion between the middle portion of the test shaft material and the shaft portion excluding the middle portion, and sets an allowable number of rotations at which the probability of crack occurrence at the connection portion is below a threshold value, and the number of rotations of the shaft material when enlarging the middle portion of the shaft material to the predetermined outer diameter by shaft enlargement processing is set to be below the allowable number of rotations.

[0064] In addition, the method of setting processing conditions for shaft enlargement processing disclosed in this specification is obtained by performing shaft enlargement processing on the test shaft material at the same bending angle as the shaft enlargement processing on the shaft material.

[0065] In addition, the method for setting processing conditions for shaft enlargement processing disclosed in this specification is a method for setting processing conditions for shaft enlargement processing, in which an axial compressive force and a bending angle are applied to the axial middle portion of the shaft material while the shaft material is rotated around its axis to enlarge the middle portion of the shaft material in the radial direction, and the method sets an allowable enlargement rate at which the probability of crack occurrence in the outer periphery is below a threshold value based on test data obtained by performing shaft enlargement processing on a test shaft material of the same material and shape as the shaft material, the test data showing the relationship between the enlargement rate, which is the ratio of the outer diameter after processing to the outer diameter of the middle portion of the test shaft material before processing, and the probability of crack occurrence in the outer periphery of the middle portion of the test shaft material, and the allowable enlargement rate is set at which the probability of crack occurrence in the outer periphery is below a threshold value, and the enlargement rate of the middle portion of the shaft material when the middle portion of the shaft material is enlarged to a predetermined outer diameter by shaft enlargement processing is set to be below the allowable enlargement rate.

[0066] In addition, the shaft enlargement processing method disclosed in this specification is a shaft enlargement processing method in which an axial compressive force and a bending angle are applied to the axial middle portion of the shaft material while the shaft material is rotated around its axis, thereby enlarging the middle portion of the shaft material in the radial direction, and the pass / fail of the shaft material is judged based on the number of rotations of the shaft material required to enlarge the middle portion of the shaft material to a predetermined outer diameter.

[0067] In addition, the shaft enlargement processing method disclosed in this specification is test data obtained by performing shaft enlargement processing on a test shaft material of the same material and shape as the shaft material, and based on test data showing the relationship between the number of rotations of the test shaft material required to enlarge the intermediate portion of the test shaft material to the specified outer diameter and the probability of crack occurrence at the connection portion between the intermediate portion of the test shaft material and the shaft portion excluding the intermediate portion, an allowable number of rotations at which the probability of crack occurrence at the connection portion is below a threshold value is set, and if the number of rotations of the shaft material is below the allowable number of rotations, the shaft material is judged to be acceptable, and if the number of rotations of the shaft material exceeds the allowable number of rotations, the shaft material is judged to be unacceptable.

[0068] In addition, the shaft enlargement processing method disclosed in this specification is such that the test data was obtained by subjecting the test shaft material to shaft enlargement processing at the same bending angle as the shaft enlargement processing performed on the shaft material.

[0069] In addition, the shaft enlargement processing method disclosed in this specification is based on test data obtained by performing shaft enlargement processing on the test shaft material, which shows the relationship between the enlargement rate, which is the ratio of the outer diameter of the middle portion of the test shaft material after processing to the outer diameter before processing, and the probability of crack occurrence in the outer periphery of the middle portion of the test shaft material, and sets an allowable enlargement rate at which the probability of crack occurrence in the outer periphery is below a threshold value, and sets the enlargement rate of the middle portion of the shaft material when enlarging the middle portion of the shaft material to the specified outer diameter to be below the allowable enlargement rate.

[0070] In addition, the shaft enlargement method disclosed in this specification is a shaft enlargement processing method in which an axially compressive force and a bending angle are applied to the axially middle portion of the shaft material while the shaft material is rotated around its axis, and the acceptability of the shaft material is judged based on the enlargement rate, which is the ratio of the outer diameter of the middle portion of the shaft material after processing to the outer diameter before processing.

[0071] In addition, the shaft enlargement processing method disclosed in this specification is test data obtained by performing shaft enlargement processing on a test shaft material of the same material and shape as the shaft material, and based on test data showing the relationship between the enlargement rate, which is the ratio of the outer diameter of the middle part of the test shaft material after processing to the outer diameter before processing, and the probability of crack occurrence on the outer periphery of the middle part of the test shaft material, an allowable enlargement rate is set at which the probability of crack occurrence on the outer periphery is below a threshold value, and if the enlargement rate of the shaft material is below the allowable enlargement rate, the shaft material is judged to be acceptable, and if the enlargement rate of the shaft material exceeds the allowable enlargement rate, the shaft material is judged to be unacceptable.

[0072] In addition, the shaft enlargement processing device disclosed in this specification comprises a pair of holding parts that hold the shaft material at a distance in the axial direction of the shaft material, a pressure applying part that reduces the distance between the pair of holding parts and applies an axial compressive force to a middle portion of the shaft material that is disposed between the pair of holding parts, a bending part that tilts one of the pair of holding parts relative to the other holding part to apply a bend angle to the middle portion of the shaft material, a rotation part that rotates the pair of holding parts and the shaft material about the axis of the shaft material, a rotation number detection part that detects the number of rotations of the shaft material, and a control part that controls the pressure applying part, the bending part, and the rotating part to rotate the shaft material about the axis while applying an axial compressive force and a bend angle to the middle portion of the shaft material, thereby enlarging the middle portion of the shaft material to a predetermined outer diameter, and the control part judges the pass / fail of the shaft material based on the number of rotations of the shaft material required for the middle portion of the shaft material to be enlarged to the predetermined outer diameter.

[0073] The shaft enlargement processing device disclosed in this specification includes a pair of holding parts that hold the shaft material at a distance in the axial direction of the shaft material, a pressurizing part that reduces the distance between the pair of holding parts and applies an axial compressive force to a middle part of the shaft material that is disposed between the pair of holding parts, a bending part that tilts one of the pair of holding parts relative to the other holding part to apply a bending angle to the middle part of the shaft material, a rotating part that rotates the pair of holding parts and the shaft material around the axis of the shaft material, an axial displacement detection part that detects the amount of change in the distance between the pair of holding parts, and a force sensor that detects the amount of change in the distance between the pair of holding parts and the shaft material. and a control unit which controls the pressure unit, the bending unit, and the rotating unit to apply an axial compressive force and a bending angle to the middle portion of the shaft material, rotates the shaft material about its axis, and reduces the distance between the pair of holding units by a predetermined amount, thereby enlarging the middle portion of the shaft material. The control unit calculates an enlargement rate, which is the ratio of the outer diameter of the middle portion of the shaft material after processing to the outer diameter of the middle portion of the shaft material before processing, based on the change in the outer diameter of the middle portion of the shaft material, and judges the pass / fail of the shaft material based on the calculated enlargement rate. [Explanation of symbols]

[0074] 1-axis enlargement processing equipment 2 Holding part 3 Holding part 4 Pressurizing section 5 Bending section 6 Rotating part 7 Rotational speed detector 8 Control Panel 9 Axial displacement detection section 10 Radial displacement detection section 11 Control section 12 Display section 13 Control section A reference line W shaft material Wa Middle part Wb shaft part Wc connection part Wd Outer periphery

Claims

[Claim 1] A pair of holding parts that hold the shaft material at a distance in the axial direction of the shaft material; a pressure applying unit configured to apply an axial compressive force to an intermediate portion of the shaft member disposed between the pair of holding units by reducing a distance between the pair of holding units; a bending portion that inclines one of the pair of holding portions relative to the other holding portion to impart a bending angle to an intermediate portion of the shaft material; a rotating part that rotates the pair of holding parts and the shaft member around an axis of the shaft member; A rotation number detection unit that detects the number of rotations of the shaft material; an axial displacement detection unit that detects a change in the distance between the pair of holding portions; A radial displacement detection unit that detects a change in the outer diameter of the intermediate portion of the shaft material; a control unit that controls the pressure unit, the bending unit, and the rotating unit to rotate the shaft material around its axis while applying an axial compressive force and a bending angle to the intermediate portion of the shaft material and to reduce the distance between the pair of holding units by a predetermined amount, thereby enlarging the intermediate portion of the shaft material; Equipped with The control unit calculates an enlargement rate, which is the ratio of the outer diameter of the intermediate portion of the shaft material after processing to the outer diameter before processing, based on the amount of change in the outer diameter of the intermediate portion of the shaft material, obtains the number of rotations of the shaft material required for the intermediate portion of the shaft material to enlarge to a predetermined outer diameter, and judges the pass / fail of the intermediate portion and the connection portion of the shaft material based on the calculated enlargement rate and the obtained number of rotations.

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