Processing condition setting method of shaft thickening processing, shaft thickening processing method and shaft thickening processing apparatus

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 of a shaft enlargement processing method, a shaft enlargement processing method, and a shaft enlargement processing apparatus.

Background Art

[0002] Shaft enlargement processing is known as one of the processing methods for forming a large-diameter portion in a part of a shaft material. As an example of the shaft enlargement processing method, a method of enlarging the intermediate portion of a shaft material by applying a compressive force and a bending angle to the intermediate portion of the shaft material and rotating the shaft material is known.

[0003] A shaft enlargement processing machine for performing the above shaft enlargement processing generally holds a shaft material by a pair of holding portions arranged at a distance in the axial direction of the shaft material, reduces the distance between the pair of holding portions to apply a compressive force to the intermediate portion of the shaft material, tilts one holding portion with respect to the other holding portion to apply a bending angle to the intermediate portion of the shaft material, and rotates the pair of holding portions in that state to rotate the shaft material, thereby enlarging the intermediate portion of the shaft material. Then, the process of enlarging the intermediate portion of the shaft material ends when the distance between the pair of holding portions is reduced to a predetermined distance (see, for example, Patent Document 1), or ends when the outer diameter of the intermediate portion reaches a predetermined outer diameter (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In shaft enlargement machining, cracks may occur at the connection between the enlarged intermediate part and the shaft part excluding the intermediate part, and cracks may also occur on the outer peripheral part of the enlarged intermediate part. Cracks can be detected by, for example, visual inspection, magnetic flaw detection, eddy current flaw detection, etc. However, a full inspection of mass-produced shaft materials is time-consuming and costly.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is 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 for inspecting the presence or absence of cracks.

Means for Solving the Problems

[0007] A method for setting processing conditions for shaft enlargement processing according to an aspect of the present invention is a method for setting processing conditions for shaft enlargement processing in which the intermediate part of a shaft material is enlarged in the radial direction by rotating the shaft material around its axis with an axial compressive force and a bending angle applied to an intermediate part in the axial direction of the shaft material. Based on test data obtained by performing shaft enlargement processing on a test shaft material having the same material and the same shape as the shaft material, which shows the relationship between the number of rotations of the test shaft material required to enlarge the intermediate part of the test shaft material to a predetermined outer diameter and the probability of crack occurrence at the connection between the intermediate part of the test shaft material and the shaft part excluding the intermediate part, an allowable number of rotations is set such that the probability of crack occurrence at the connection part is equal to or less than a threshold value, and the number of rotations of the shaft material when enlarging the intermediate part of the shaft material to the predetermined outer diameter in the shaft enlargement processing for the shaft material is set to be equal to or less than the allowable number of rotations.

[0008] Also, a method for setting processing conditions for shaft enlargement processing according to an aspect of the present invention is a method for setting processing conditions for shaft enlargement processing in which the intermediate portion of a shaft material is enlarged in the radial direction by rotating the shaft material around its axis while applying an axial compressive force and a bending angle to the intermediate portion in the axial direction of the shaft material. Based on test data obtained by performing shaft enlargement processing on a test shaft material having the same material and the same shape as the shaft material, which is a relationship between the enlargement ratio, which is the ratio of the outer diameter after processing to the outer diameter before processing of the intermediate portion of the test shaft material, and the probability of crack occurrence in the outer peripheral portion of the intermediate portion of the test shaft material, an allowable enlargement ratio at which the probability of crack occurrence in the outer peripheral portion is equal to or less than a threshold value is set, and the enlargement ratio of the intermediate portion of the shaft material when enlarging the intermediate portion of the shaft material to a predetermined outer diameter in the shaft enlargement processing for the shaft material is made equal to or less than the allowable enlargement ratio.

[0009] Also, a shaft enlargement processing method according to an aspect of the present invention is a shaft enlargement processing method in which the intermediate portion of a shaft material is enlarged in the radial direction by rotating the shaft material around its axis while applying an axial compressive force and a bending angle to the intermediate portion in the axial direction of the shaft material. Based on the number of rotations of the shaft material required until the intermediate portion of the shaft material is enlarged to a predetermined outer diameter, the pass / fail of the shaft material is determined.

[0010] Also, a shaft enlargement processing method according to an aspect of the present invention is a shaft enlargement processing method in which the intermediate portion of a shaft material is enlarged in the radial direction by rotating the shaft material around its axis while applying an axial compressive force and a bending angle to the intermediate portion in the axial direction of the shaft material. Based on the enlargement ratio, which is the ratio of the outer diameter after processing to the outer diameter before processing of the intermediate portion of the shaft material, the pass / fail of the shaft material is determined.

[0011] Further, the shaft enlargement processing apparatus according to one aspect of the present invention includes a pair of holding portions that hold the shaft member with a distance in the axial direction of the shaft member, a pressing portion that applies an axial compressive force to an intermediate portion of the shaft member disposed between the pair of holding portions by reducing the distance between the pair of holding portions, a bending portion that applies a bending angle to the intermediate portion of the shaft member by tilting one of the pair of holding portions with respect to the other holding portion, a rotating portion that rotates the pair of holding portions and the shaft member around the axis of the shaft member, a rotation speed detection portion that detects the rotation speed of the shaft member, and a control portion that rotates the shaft member around the axis in a state where an axial compressive force and a bending angle are applied to the intermediate portion of the shaft member by controlling the pressing portion, the bending portion, and the rotating portion, and enlarges the intermediate portion of the shaft member to a predetermined outer diameter. The control portion determines whether the shaft member is acceptable or not based on the number of rotations of the shaft member required until the intermediate portion of the shaft member is enlarged to the predetermined outer diameter.

[0012] Further, the shaft enlargement processing apparatus according to one aspect of the present invention includes a pair of holding portions that hold the shaft member with a distance in the axial direction of the shaft member, a pressing portion that applies an axial compressive force to an intermediate portion of the shaft member disposed between the pair of holding portions by reducing the distance between the pair of holding portions, a bending portion that applies a bending angle to the intermediate portion of the shaft member by tilting one of the pair of holding portions with respect to the other holding portion, a rotating portion that rotates the pair of holding portions and the shaft member around the axis of the shaft member, an axial displacement detection portion that detects a change amount of the distance between the pair of holding portions, a radial displacement detection portion that detects a change amount of the outer diameter of the intermediate portion of the shaft member, and a control portion that rotates the shaft member around the axis in a state where an axial compressive force and a bending angle are applied to the intermediate portion of the shaft member by controlling the pressing portion, the bending portion, and the rotating portion and reduces the distance between the pair of holding portions by a predetermined amount, thereby enlarging the intermediate portion of the shaft member. The control portion obtains an enlargement ratio that is a ratio of the outer diameter after processing to the outer diameter before processing of the intermediate portion of the shaft member based on the change amount of the outer diameter of the intermediate portion of the shaft member, and determines whether the shaft member is acceptable or not based on the obtained enlargement ratio.

Advantages 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 apparatus that can reduce the time and cost required for inspecting the presence or absence of cracks.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

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

[0016] The shaft thickening processing apparatus 1 shown in Fig. 1 includes a pair of holding parts 2 and 3 for holding a shaft material W, a pressing part 4, a bending part 5, a rotating part 6, a rotation speed detection part 7, and a control panel 8.

[0017] The holding part 2 fits with one end in the axial direction of the shaft material W, and the holding part 3 fits with the other end in the axial direction of the shaft material W. Thereby, the shaft material W is held by the pair of holding parts 2 and 3. The pair of holding parts 2 and 3 are arranged at a distance along the reference line A on the reference line A and are supported by a support base (not shown). The shaft material W held by the pair of holding parts 2 and 3 is also arranged on the reference line A. One holding part 2 is movable along the reference line A, that is, movable in the axial direction of the shaft material W, and the other holding part 3 is movable in a direction intersecting the reference line A.

[0018] The pressing part 4 is configured to include, for example, a fluid pressure cylinder or the like, moves the holding part 2 along the reference line A, and reduces the distance between the pair of holding parts 2 and 3. As the distance between the pair of holding parts 2 and 3 is reduced, an axial compressive force is applied to the intermediate part Wa in the axial direction of the shaft material W arranged between the pair of holding parts 2 and 3.

[0019] The bending part 5 is configured to include, for example, a fluid pressure cylinder or the like, moves the holding part 3 in a direction intersecting the reference line A, and tilts the holding part 3 with respect to the holding part 2 arranged on the reference line A. As the holding part 3 is tilted with respect to the holding part 2, a bending angle θ is applied to the intermediate part Wa of the shaft material W.

[0020] The rotating part 6 is configured to include, for example, an electric motor or the like, and rotates the holding part 3 around the central axis of the holding part 3. As the holding part 3 is rotated, the shaft material W with one end fitting with the holding part 3 also rotates around the axis, and the holding part 2 with the other end of the shaft material W fitting therewith also rotates.

[0021] The rotation speed detection unit 7 is configured to include, for example, a rotary encoder or the like, and detects the rotation speed of the holding unit 3 as the rotation speed of the shaft member W. Note that the rotation speed detection unit 7 may detect the rotation speed of the holding unit 2 instead of the holding unit 3, or may detect the rotation speed of the shaft member W.

[0022] The control panel 8 has hardware keys such as switches, an operation unit 11 used for inputting processing conditions and the like, a display unit 12 having a display device such as an LCD (liquid crystal display) and displaying an operation screen and the like, and a control unit 13.

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

[0024] Under the control of the control unit 13, with an axial compressive force applied to the intermediate portion Wa of the shaft member W by the pressing unit 4 and a bending angle θ applied to the intermediate portion Wa of the shaft member W by the bending unit 5, the shaft member W is rotated about the axis by the rotating unit 6. As a result, the intermediate portion Wa of the shaft member W is compressed in the axial direction and enlarged in the radial direction.

[0025] The rotation speed detected by the rotation speed detection unit 7 is input to the control unit 13. Note that the pressing unit 4 is provided with a sensor for detecting the compressive force, the bending unit 5 is provided with a sensor for detecting 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 for detecting the rotation speed of the holding unit 3. The compressive force, the bending angle θ, and the rotation speed detected by these sensors are also input to the control unit 13. Note that the control unit 13 may calculate the rotation speed based on the rotation speed detected by the rotation speed detection unit 7.

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

[0027] The displacement amount of the holding unit 2 detected by the axial displacement detection unit 9 is input to the control unit 13. Based on the displacement amount of the holding unit 2 after the compressive force starts to increase, the control unit 13 detects the compression amount of the intermediate portion Wa of the shaft material W (the decrease amount of the axial length of the intermediate portion Wa), and based on this compression amount, detects that the intermediate portion Wa has been thickened to a predetermined outer diameter.

[0028] As shown in FIG. 2, the shaft thickening processing device 1 may include a radial displacement detection unit 10 that detects the change amount of the outer diameter of the intermediate portion Wa of the shaft material W. The control unit 13 may detect that the intermediate portion Wa has been thickened to a predetermined outer diameter based on the change amount of the outer diameter from the outer diameter before processing of the intermediate portion Wa detected by the radial displacement detection unit 10.

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

[0030] First, as shown in FIG. 3A, the shaft material W is held by a pair of holding units 2 and 3. The axial length L0 of the intermediate portion Wa of the shaft material W before processing is appropriately determined according to the axial length L and outer diameter D after processing of the intermediate portion Wa in relation to the outer diameter D0 of the intermediate portion Wa before processing. Hereinafter, L / L0 will be referred to as the compression ratio, and D / D0 will be referred to as the thickening 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 member W. Further, 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 such that the bending of the shaft member W is within the deformation of the elastic limit of the shaft member W, and it varies depending on the elastic limit of the material of the shaft member W, but is typically about 2° to 4°. Then, with the compressive force and the bending angle θ applied to the middle part Wa of the shaft member W, the holding part 3 is rotated by the rotating part 6 (see FIG. 1), and the shaft member W is rotated about its axis.

[0032] As shown in FIG. 3C, with the compression, bending, and rotation of the middle part Wa of the shaft member W, a radial alternating load acts on each part in the circumferential direction of the middle part Wa, and as this alternating load acts repeatedly, the middle part Wa gradually expands in the radial direction. Specifically, due to the compression and bending of the middle part Wa, the material on the inner side of the bend undergoes plastic flow and bulges out. Then, with the rotation of the shaft member W, the bulging due to the plastic flow of the material on the inner side of the bend of the middle part Wa grows over the entire circumference, and the middle part Wa gradually expands in the radial direction.

[0033] As shown in FIG. 3D, when it is detected by the control part 13 (see FIG. 1) that the middle part Wa has expanded to a predetermined outer diameter based on the amount of compression of the middle part Wa of the shaft member W or based on the amount of change in the outer diameter of the middle part Wa, the compression of the middle part Wa is stopped. Then, the holding part 3 is arranged again along the reference line A and the middle part Wa of the shaft member W is bent back, and the thickness of the expanded middle part Wa is made uniform over the entire circumference. Through the above process, the shaft expansion process for the shaft member W is completed, and the rotation of the shaft member W is stopped.

[0034] The occurrence of cracks at the connection part Wc between the middle part Wa of the shaft member W subjected to the shaft expansion process and the shaft part Wb (the part that was fitted to the holding parts 2 and 3) excluding the middle part Wa is caused by the material being fatigued due to the repeated action of the alternating load, and is related to the number of rotations of the shaft member W required until the middle part Wa expands to a predetermined outer diameter. Therefore, as a processing condition, an allowable number of rotations is set with respect to the number of rotations of the shaft member W required until the middle part Wa expands to a predetermined outer diameter.

[0035] In addition, the occurrence of cracks in the outer peripheral portion Wd of the intermediate portion Wa of the shaft material W subjected to shaft enlargement processing is caused by the enlargement of the intermediate portion Wa beyond the ductility limit of the material, and is related to the enlargement ratio D / D0 of the intermediate portion Wa. Therefore, as processing conditions, an allowable enlargement ratio is set for the enlargement ratio D / D0 of the intermediate portion Wa.

[0036] Figures 4A and 4B show an example of test data used for setting the allowable 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 the same shape as the shaft material W. And the test data shown in Figure 4A shows the relationship between the compressive force and the number of rotations of the test shaft material when the number of rotations of the test shaft material required to enlarge the intermediate portion of the test shaft material to a predetermined outer diameter is changed by changing the compressive force applied to the intermediate portion of the test shaft material. In addition, the test data shown in Figure 4B shows the occurrence probability of cracks in the connection portion of the test shaft material when shaft enlargement processing is performed on a plurality of test shaft materials for each set compressive force, in relation to the number of rotations corresponding to the compressive force.

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

[0039] The allowable number of rotations can be the number of rotations at which the probability of crack occurrence is equal to or lower than a threshold value. The threshold value of the probability of crack occurrence can be set in consideration of the yield rate, etc., and can be, for example, 0%. Therefore, 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%. Preferably, the allowable number of rotations can be set with a margin considering variations in the material properties of the shaft material, etc., with respect to the upper limit of the number of rotations 40 at which the probability of crack occurrence is 0%. For example, the allowable number of rotations can be 32 (margin: 20%).

[0040] In addition, when the bending angle θ applied to the intermediate portion Wa of the shaft material W is relatively small, the fatigue of the material per alternating load is relatively small. When the bending angle θ applied to the intermediate portion Wa of the shaft material W is relatively large, the fatigue of the material per alternating load becomes relatively large. That is, the occurrence of cracks at the connection portion Wc of the shaft material W is also related to the bending angle θ applied to the intermediate portion Wa. Therefore, preferably, the test data used for setting the allowable number of rotations is test data obtained by performing shaft enlargement processing on a test shaft material having the same material and the same shape as the shaft material W at the same bending angle as the shaft material W.

[0041] FIGS. 5A and 5B show an example of test data used for setting the allowable enlargement ratio.

[0042] The test data shown in FIGS. 5A and 5B is test data obtained by performing shaft enlargement processing on a test shaft material having the same material and the same shape as the shaft material W. The test data shown in FIG. 5A shows the relationship between the compression ratio L / L0 and the enlargement ratio D / D0 when the enlargement ratio D / D0 of the intermediate portion of the test shaft material is changed by changing the compression ratio L / L0 of the intermediate portion of the test shaft material. The test data shown in FIG. 5B shows the probability of crack occurrence at the outer peripheral portion of the intermediate portion of the test shaft material when shaft enlargement processing is performed on a plurality of test shaft materials for each set enlargement ratio, in relation to the enlargement ratio.

[0043] In the complementary curve of the test data shown in Fig. 5B, when the hypertrophy rate is 1.8 or less, the probability of crack occurrence in the outer peripheral part is 0%. As the hypertrophy rate rises above 1.8, the probability of crack occurrence also increases. When the hypertrophy rate is 3.0 or more, the probability of crack occurrence is 100%. It can be said that as the hypertrophy rate increases, the probability of exceeding the ductility limit of the material increases, and the probability of crack occurrence also increases.

[0044] The allowable hypertrophy rate can be set as the hypertrophy rate at which the probability of crack occurrence is below the threshold value. The threshold value of the probability of crack occurrence can be set in consideration of the yield, etc., and can be, for example, 0%. Therefore, according to the test data shown in Fig. 5B, the allowable hypertrophy rate can be set as 1.8, which is the upper limit hypertrophy rate at which the probability of crack occurrence is 0%. Preferably, the allowable hypertrophy rate can be set as a hypertrophy rate with a margin set in consideration of variations in the material properties of the shaft material, etc., with respect to the upper limit hypertrophy rate of 1.8 at which the probability of crack occurrence is 0%. For example, the allowable hypertrophy rate can be set as 1.6 (margin 10%).

[0045] Fig. 6 shows an example of the processing performed by the control unit 13 in the shaft hypertrophy processing on the shaft material W.

[0046] First, the 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 the compressive force, rotational speed, bending angle θ, processing completion condition, and allowable rotation number N. The compressive force and rotational speed can be set as appropriate. For example, from the viewpoint of shortening the cycle time, they can be set as the maximum values that the pressing unit 4 and the rotating unit 6 can output.

[0047] The processing completion condition is a condition for detecting that the intermediate part Wa of the shaft material W has been hypertrophied to a predetermined outer diameter. When the shaft hypertrophy processing apparatus 1 is provided with the axial displacement detection unit 9 that detects the displacement amount of the holding unit 2, the displacement amount of the holding unit 2 (compression amount of the intermediate part Wa) after the compressive force starts to increase is set. Also, when the shaft hypertrophy processing apparatus 1 is provided with the radial displacement detection unit 10 that detects the change amount of the outer diameter of the intermediate part Wa, the change amount of the outer diameter from the outer diameter before processing of the intermediate part 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 enlargement ratio. First, a shaft material W for which the enlargement ratio D / D0 obtained from the outer diameter D0 of the intermediate part Wa before processing and the required outer diameter D after processing is equal to or less than the allowable enlargement ratio is selected from a plurality of shaft materials with different outer diameters D0 before processing according to the required outer diameter D after 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 before processing of the selected shaft material W and the required outer diameter D after processing. Also, the volume of the intermediate part Wa does not change before and after processing, and the axial length L after processing of the intermediate part Wa is obtained based on the axial length L0 of the intermediate part Wa before processing and the enlargement ratio D / D0 that is equal to or less than the allowable enlargement ratio. 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. And the bending angle θ can be set to the same bending angle as the shaft enlargement processing performed to obtain the test data used for setting the allowable number of rotations N for a test shaft material made of the same material and having the same shape as the selected shaft material W.

[0050] Next, when a machining start instruction is input to the operation unit 11, the control unit 13 controls the pressing unit 4, the bending unit 5, and the rotating unit 6 according to the machining conditions input in step S1, and performs the shaft enlargement processing shown in FIGS. 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 displacement amount of the holding part 2 detected by the axial displacement detection unit 9 or the change amount of the outer diameter of the intermediate part Wa detected by the radial displacement detection unit 10 reaches the machining completion condition (step S3).

[0051] Next, the control unit 13 acquires the number of rotations n required for the intermediate part Wa to be enlarged to a predetermined outer diameter D, which is the number of rotations of the shaft material W detected by the rotation number detection unit 7, and determines the pass / fail of the shaft material W based on the acquired number of rotations n (step S4). In this pass / fail determination, the control unit 13 uses the allowable number of rotations N input in step S1, determines that it is a pass when n≦N (step S5), and determines that it is a fail when 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, the 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 instruction is input to the operation unit 11, the control unit 13 controls the pressing unit 4, the bending unit 5, and the rotating unit 6 according to the processing conditions input in step S1, and performs the shaft thickening process shown in FIGS. 3A to 3D on the shaft material W (step S12). The control unit 13 completes the shaft thickening process 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 acquires the change amount of the outer diameter of the intermediate portion Wa detected by the radial displacement detection unit 10, and obtains the thickening rate of the intermediate portion Wa after the processing is completed (step S14). The thickening rate of the intermediate portion Wa can be obtained by using the outer diameter D0 of the intermediate portion Wa before processing and the change amount ΔD of the outer diameter of the intermediate portion Wa detected by the radial displacement detection unit 10, and (D0 + ΔD) / D0.

[0059] Then, the control unit 13 determines the pass / fail of the shaft material W based on the thickening rate (D0 + ΔD) / D0 obtained in step S14 (step S15). In this pass / fail determination, the control unit 13 uses the allowable thickening rate D / D0 input in step S11, and determines that it is qualified when (D0 + ΔD) / D0 ≦ D / D0 (step S16), and determines that it is unqualified when (D0 + ΔD) / D0 > D / D0 (step S17).

[0060] As an example of the case where the hypertrophy rate (D0 + ΔD) / D0 exceeds the allowable hypertrophy rate D / D0, it can be exemplified that due to the dimensional error of the shaft material, the axial length L0 before processing of the intermediate portion Wa of the shaft material W to be processed is specifically large, and the outer diameter change amount ΔD after processing becomes specifically large. For a certain displacement amount of the holding portion 2, the larger the axial length L0 before processing, the larger the change amount ΔD of the outer diameter of the intermediate portion Wa. And when (D0 + ΔD) / D0 > D / D0, the occurrence of cracks in the outer peripheral portion Wd of the shaft material W is expected with a probability corresponding to the hypertrophy rate (D0 + ΔD) / D0 on the complementary curve of the test data shown in FIG. 5B. Therefore, when (D0 + ΔD) / D0 > D / D0, the control unit 13 determines it as unqualified. The determination result is notified to the operator, for example, by being displayed on the display unit 12 under the control of the control unit 13.

[0061] In this way, by determining the pass or fail of the occurrence of cracks in the outer peripheral portion Wd of the shaft material W based on the hypertrophy rate of the intermediate portion Wa of the shaft material W, it can be determined immediately after the processing is completed, and the time and cost required for the inspection of the presence or absence of cracks can be reduced.

[0062] It should be noted that the determination of the pass or fail of the occurrence of cracks in the outer peripheral portion Wd based on the hypertrophy rate and the allowable hypertrophy rate of the intermediate portion Wa shown in FIG. 7 can also be performed in combination with the determination of the pass or fail of the occurrence of cracks in the connection portion Wc based on the rotation speed and the allowable rotation speed of the shaft material W shown in FIG. 6.

[0063] As described above, the method for setting the processing conditions of the shaft enlargement processing disclosed in this specification is a method for setting the processing conditions of the shaft enlargement processing in which the intermediate portion in the axial direction of the shaft material is enlarged in the radial direction by rotating the shaft material around the axis while applying an axial compressive force and a bending angle to the intermediate portion in the axial direction of the shaft material. Based on the test data obtained by performing shaft enlargement processing on a test shaft material having the same material and the same shape as the shaft material, which is the relationship between the number of rotations of the test shaft material required to enlarge the intermediate portion of the test shaft material to a predetermined 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 is set such that the probability of crack occurrence at the connection portion is equal to or less than a threshold value, and the number of rotations of the shaft material when enlarging the intermediate portion of the shaft material to the predetermined outer diameter in the shaft enlargement processing of the shaft material is set to be equal to or less than the allowable number of rotations.

[0064] In addition, the method for setting the processing conditions of the shaft enlargement processing disclosed in this specification is such that the test data 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] As described above, the method for setting the processing conditions of the shaft enlargement processing disclosed in this specification is a method for setting the processing conditions of the shaft enlargement processing in which the intermediate portion in the axial direction of the shaft material is enlarged in the radial direction by rotating the shaft material around the axis while applying an axial compressive force and a bending angle to the intermediate portion in the axial direction of the shaft material. Based on the test data obtained by performing shaft enlargement processing on a test shaft material having the same material and the same shape as the shaft material, which is the relationship between the enlargement ratio, which is the ratio of the outer diameter after processing to the outer diameter before processing of the intermediate portion of the test shaft material, and the probability of crack occurrence at the outer peripheral portion of the intermediate portion of the test shaft material, an allowable enlargement ratio is set such that the probability of crack occurrence at the outer peripheral portion is equal to or less than a threshold value, and the enlargement ratio of the intermediate portion of the shaft material when enlarging the intermediate portion of the shaft material to a predetermined outer diameter in the shaft enlargement processing of the shaft material is set to be equal to or less than the allowable enlargement ratio.

[0066] In addition, the shaft enlargement processing method disclosed in this specification is a shaft enlargement processing method for radially enlarging an intermediate portion of a shaft material by rotating the shaft material around its axis while applying an axial compressive force and a bending angle to an intermediate portion in the axial direction of the shaft material, and determines the pass / fail of the shaft material based on the number of rotations of the shaft material required to enlarge the intermediate 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 having the same material and the same shape as the shaft material. Based on the 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 predetermined outer diameter and the occurrence probability of cracks 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 is set such that the occurrence probability of cracks at the connection portion is equal to or less than a threshold value. When the number of rotations of the shaft material is equal to or less than the allowable number of rotations, the shaft material is determined to be qualified, and when the number of rotations of the shaft material exceeds the allowable number of rotations, the shaft material is determined to be unqualified.

[0068] In addition, the shaft enlargement processing method disclosed in this specification is such that the test data 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.

[0069] In addition, the shaft enlargement processing method disclosed in this specification is test data obtained by performing shaft enlargement processing on the test shaft material. Based on the test data showing the relationship between the enlargement rate, which is the ratio of the outer diameter after processing to the outer diameter before processing of the intermediate portion of the test shaft material, and the occurrence probability of cracks on the outer peripheral portion of the intermediate portion of the test shaft material, an allowable enlargement rate is set such that the occurrence probability of cracks on the outer peripheral portion is equal to or less than a threshold value. When enlarging the intermediate portion of the shaft material to the predetermined outer diameter, the enlargement rate of the intermediate portion of the shaft material is set to be equal to or less than the allowable enlargement rate.

[0070] Further, the shaft enlargement processing method disclosed in this specification is a shaft enlargement processing method for enlarging the intermediate portion of the shaft material in the radial direction by rotating the shaft material around the axis while applying an axial compressive force and a bending angle to the intermediate portion in the axial direction of the shaft material, and determines the pass or fail of the shaft material based on the enlargement ratio, which is the ratio of the outer diameter after processing to the outer diameter before processing of the intermediate portion of the shaft material.

[0071] Also, the shaft enlargement processing method disclosed in this specification is test data obtained by performing shaft enlargement processing on a test shaft material having the same material and the same shape as the shaft material, and based on the test data showing the relationship between the enlargement ratio, which is the ratio of the outer diameter after processing to the outer diameter before processing of the intermediate portion of the test shaft material, and the occurrence probability of cracks in the outer peripheral portion of the intermediate portion of the test shaft material, sets an allowable enlargement ratio at which the occurrence probability of cracks in the outer peripheral portion is equal to or less than a threshold value, determines that the shaft material is qualified when the enlargement ratio of the shaft material is equal to or less than the allowable enlargement ratio, and determines that the shaft material is unqualified when the enlargement ratio of the shaft material exceeds the allowable enlargement ratio.

[0072] In addition, the shaft enlargement processing apparatus disclosed in this specification includes a pair of holding portions that hold the shaft material at a distance in the axial direction of the shaft material, a pressing portion that reduces the distance between the pair of holding portions and applies an axial compressive force to the intermediate portion of the shaft material disposed between the pair of holding portions, a bending portion that tilts one of the pair of holding portions with respect to the other holding portion to apply a bending angle to the intermediate portion of the shaft material, a rotating portion that rotates the pair of holding portions and the shaft material around the axis of the shaft material, a rotation speed detection portion that detects the rotation speed of the shaft material, and a control portion that controls the pressing portion, the bending portion, and the rotating portion to rotate the shaft material around the axis while applying an axial compressive force and a bending angle to the intermediate portion of the shaft material, thereby enlarging the intermediate portion of the shaft material to a predetermined outer diameter, and the control portion determines the pass or fail of the shaft material based on the rotation speed of the shaft material required until the intermediate portion of the shaft material is enlarged to the predetermined outer diameter.

[0073] In addition, the shaft enlargement processing device disclosed in this specification includes a pair of holding parts that hold the shaft member with a distance in the axial direction of the shaft member, a pressing part that applies an axial compressive force to the intermediate part of the shaft member disposed between the pair of holding parts by reducing the distance between the pair of holding parts, a bending part that tilts one of the pair of holding parts with respect to the other holding part to apply a bending angle to the intermediate part of the shaft member, a rotating part that rotates the pair of holding parts and the shaft member around the axis of the shaft member, an axial displacement detection part that detects the amount of change in the distance between the pair of holding parts, a radial displacement detection part that detects the amount of change in the outer diameter of the intermediate part of the shaft member, and a control part that controls the pressing part, the bending part, and the rotating part to rotate the shaft member around the axis with an axial compressive force and a bending angle applied to the intermediate part of the shaft member and reduce the distance between the pair of holding parts by a predetermined amount, thereby enlarging the intermediate part of the shaft member. The control part obtains a hypertrophy rate, which is the ratio of the outer diameter after processing to the outer diameter before processing of the intermediate part of the shaft member, based on the amount of change in the outer diameter of the intermediate part of the shaft member, and determines the pass or fail of the shaft member based on the obtained hypertrophy rate.

Explanation of Signs

[0074] 1 Shaft enlargement processing device 2 Holding part 3 Holding part 4 Pressing part 5 Bending part 6 Rotating part 7 Rotation speed detection part 8 Control panel 9 Axial displacement detection part 10 Radial displacement detection part 11 Operation part 12 Display part 13 Control part A Reference line W Shaft member Wa Intermediate part Wb Shaft part Wc Connection part Wd Outer peripheral part

Claims

1. A shaft enlarging method for enlarging a middle portion of a shaft material in a radial direction by rotating the shaft material around an axis while applying an axial compressive force and a bending angle to the middle portion of the shaft material, A shaft enlargement processing method in which the acceptability 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 specified outer diameter.

2. The shaft enlargement processing method according to claim 1, Based on test data obtained by subjecting a test shaft material of the same material and shape as the shaft material to shaft enlargement processing, 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 the 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, a permissible number of rotations at which the probability of crack occurrence at the connection portion is equal to or less than a threshold value is set, A shaft enlargement processing method for judging the shaft material as acceptable if the number of rotations of the shaft material is equal to or less than the allowable number of rotations, and judging the shaft material as unacceptable if the number of rotations of the shaft material exceeds the allowable number of rotations.

3. The shaft enlargement processing method according to claim 2, The test data is obtained by subjecting the test shaft material to shaft enlargement processing at the same bending angle as the shaft enlargement processing for the shaft material.

4. The shaft enlargement processing method according to claim 2 or 3, Based on the test data obtained by performing shaft enlargement processing on the test shaft material, the enlargement rate being the ratio of the outer diameter of the intermediate portion of the test shaft material after processing to the outer diameter before processing, and the test data showing the relationship between the probability of crack occurrence in the outer periphery of the intermediate portion of the test shaft material, a permissible enlargement rate is set at which the probability of crack occurrence in the outer periphery is equal to or less than a threshold value; A shaft enlargement processing method in which the enlargement rate of the intermediate portion of the shaft material when enlarging the intermediate portion of the shaft material to the specified outer diameter is set to be equal to or less than the allowable enlargement rate.

5. A shaft enlarging method for enlarging a middle portion of a shaft material in a radial direction by rotating the shaft material around an axis while applying an axial compressive force and a bending angle to the middle portion of the shaft material, A shaft enlargement processing method in which the acceptability of the shaft material is determined based on the 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.

6. The shaft enlargement processing method according to claim 5, Based on test data obtained by subjecting a test shaft material of the same material and shape as the shaft material to shaft enlargement processing, which shows the relationship between the enlargement rate, which is the ratio of the outer diameter after processing to the outer diameter before processing of the intermediate portion of the test shaft material, and the probability of crack occurrence in the outer periphery of the intermediate portion of the test shaft material, an allowable enlargement rate is set at which the probability of crack occurrence in the outer periphery is equal to or less than a threshold value; A shaft enlargement processing method for judging the shaft material as acceptable if the enlargement rate of the shaft material is equal to or less than the allowable enlargement rate, and judging the shaft material as unacceptable if the enlargement rate of the shaft material exceeds the allowable enlargement rate.

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