A method for machining a crankshaft for a V12 engine

Abstract

This invention discloses a machining method for a V-type 12-cylinder engine crankshaft, relating to the field of engine crankshaft technology. The method involves precise position measurement, main spindle turning, connecting rod milling, oil passage hole drilling, and machining of front and rear end threads. Control is achieved through process optimization, parameter adjustment, and method innovation. When turning the main spindle journal, the main spindle and auxiliary spindle are clamped simultaneously, and the center rest automatically adjusts according to the position of the main spindle journal. A combined turning and milling method is used when machining the journal. During oil passage hole machining, interpolation milling is used to locate the oil passage hole position on the cylindrical surface. Segmented feed parameters are used during drilling to ensure drilling accuracy. When machining the front and rear end threads, interpolation milling is used to correct positional errors in the pre-drilled holes before quenching during bottom hole machining, thereby effectively ensuring the various accuracy requirements of the V-type 12-cylinder engine crankshaft during rough machining.

Description

Technical Field

[0001] This invention relates to the field of engine crankshaft technology, specifically to a method for machining a V-type 12-cylinder engine crankshaft. Background Technology

[0002] In an automobile engine, the crankshaft is a crucial component. It works in conjunction with the connecting rods, converting the reciprocating motion of the connecting rods into rotational motion and transmitting rotational power to the chassis's transmission mechanism. During operation, the crankshaft is subjected to gas pressure, inertial force, and inertial torque, resulting in significant and complex stresses. Furthermore, as a high-speed rotating component, the crankshaft requires sufficient rigidity and strength, excellent impact load-bearing capacity, wear resistance, and good lubrication. The current crankshaft manufacturing process involves forging 42CrMoA billets using forging dies made of die steel, followed by roughing and finishing the crankshaft using specialized custom equipment.

[0003] As attached Figure 1 As shown, the crankshaft of a V12 engine consists of 6 connecting rod journals, 7 main journals, 12 oil passages, sprockets, and front and rear threaded sections. It has a complex structure and requires high precision. The total length of the V12 engine crankshaft is approximately 730mm, with a length-to-diameter ratio of 12. It is also difficult to control bending deformation. In actual processing, conventional machining methods are difficult to guarantee precision, and the high scrap rate greatly increases the machining cost of the V12 engine crankshaft.

[0004] Document (CN 106514161 B) discloses a machining method for an engine crankshaft, characterized by the following steps: Step S1, rough turning the main journal and connecting rod journal of the crankshaft, controlling the diameter of the main journal after rough turning to be D1, and controlling the diameter of the connecting rod journal after rough turning to be D2; Step S2, finish turning the connecting rod journal, controlling the diameter of the connecting rod journal after finish turning to be D3; Step S3, semi-finish grinding the fourth gear main journal, second gear main journal, third gear main journal, first gear main journal, and fifth gear main journal in sequence, controlling the diameter of the main journal after semi-finish grinding to be D4. The process involves several steps: Step S4, semi-finish grinding of the connecting rod journal to achieve a diameter of D5 and a spacing of H2; Step S5, rolling fillets on the main journal and connecting rod journal; Step S6, secondary semi-finish grinding of the main journal; Step S7, fine grinding of the connecting rod journal using the set main journal as a reference to achieve a diameter of D6 and a spacing of H3; Step S8, fine grinding of the main journal to achieve a diameter of D7 and a spacing of H4. However, this method suffers from poor machining stability, high scrap rate, and difficulty in ensuring precision. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by devising a machining method for a V-type 12-cylinder engine crankshaft. On a turning-boring-milling composite machining center, the five processes of accurately measuring the position of the V-type 12-cylinder engine crankshaft, turning the main spindle, milling the connecting rod, drilling the oil passage hole, and machining the front and rear end threads are controlled from the aspects of process optimization, parameter adjustment, and method innovation.

[0006] The technical solution adopted to realize the present invention is: a method for machining a crankshaft of a V-type 12-cylinder engine, characterized in that it includes the following steps:

[0007] 1) Precisely measure the location:

[0008] 1.1) Confirm the axial zero point during rough machining:

[0009] 1.11) The zero point position is measured by the machine tool probe, and the right end face of the M5 main journal of the V-type 12-cylinder engine crankshaft is determined as the axial machining zero point reference R50;

[0010] 1.12) Use the machine tool probe to measure the position coordinates of the two end faces of the connecting rod journal P1 of the V-type 12-cylinder engine crankshaft, and determine the center position coordinates R51 of the two end faces of the connecting rod journal P1. Using the coordinates R51 and the axial machining zero-point reference R50 mentioned in step 1.11), take an offset of R52. 1.13) Use the machine tool probe to measure the position coordinates of the two end faces of the connecting rod journal P6 of the V-type 12-cylinder engine crankshaft, and determine the center position coordinates R53 of the two end faces of the connecting rod journal P6. Using the coordinates R53 and the axial machining zero-point reference R50 mentioned in step 1.11), take an offset of R54. Take the average value of (R52+R54) / 2 as R55. Offset the coordinate system by R55 based on R50 to accurately determine the axial position of the V-type 12-cylinder engine crankshaft forging blank.

[0011] 1.2) Determine the C-axis position of the crankshaft of the V12 engine:

[0012] 1.21) Measure the C-axis position of the connecting rod journal P1 of the crankshaft of the V-type 12-cylinder engine, and determine the C-axis position as the zero-point reference R61;

[0013] 1.22) Sequentially measure the C-axis positions R62, R63, R64, R65, and R66 of the connecting rod journals P2, P3, P4, P5, and P6 of the V-type 12-cylinder engine crankshaft. Calculate the actual offsets R612, R613, R614, R615, and R616 between R62, R63, R64, R65, and R66 and the zero-point reference R61 mentioned in step 1.21). Take the average offset (R612 + R613 + R614 + R615 + R616) / 5 = R60. Based on the C-axis offset (61 - R60) of the V-type 12-cylinder engine crankshaft, determine the C-axis position of the V-type 12-cylinder engine crankshaft during machining; 2) Machining of the main shaft journal:

[0014] 2.1) The left side of the V-type 12-cylinder engine crankshaft is clamped by the main spindle chuck 9, the center frame 10 is moved to the main journal M4 of the V-type 12-cylinder engine crankshaft, the right side of the V-type 12-cylinder engine crankshaft is supported by the auxiliary spindle clamping center 11, and the flange outer diameter and the stepped outer circle at the front end of the flange of the V-type 12-cylinder engine crankshaft are machined.

[0015] 2.2) Retract the secondary spindle clamping center 11, clamp the outer circle of the sprocket end of the V-type 12-cylinder engine crankshaft with the main spindle chuck 9, clamp the outer circle of the stepped front end of the connecting flange of the V-type 12-cylinder engine crankshaft with the secondary spindle chuck 12, move the center frame 10 to the main journal M7 of the V-type 12-cylinder engine crankshaft, and machine the main journals M6, M5, M4, M3, M2, and M1 of the V-type 12-cylinder engine crankshaft;

[0016] 3) Machining of connecting rod journals:

[0017] The main spindle chuck 9 is used to clamp the outer circle of the sprocket end of the V-type 12-cylinder engine crankshaft, and the auxiliary main spindle chuck 12 is used to clamp the outer circle of the stepped front end of the connecting flange of the V-type 12-cylinder engine crankshaft. The center frame 10 is moved to the main journal M4 of the V-type 12-cylinder engine crankshaft. The connecting rod journal 3 and the balance blocks 4 on both sides of the connecting rod journal 3 are quickly rough machined by eccentric milling to directly machine the thickness of the balance blocks to the required dimensions. Then, the connecting rod journal is finished by eccentric turning.

[0018] 4) Machining of oil passage holes:

[0019] Using a milling interpolation method, a 5mm deep positioning guide hole is machined on the cylindrical surface of the crankshaft of the V-type 12-cylinder engine, and then a 5mm diameter drill bit is used to drill the oil passage hole.

[0020] 5) Flange thread machining:

[0021] Nine M12×1 threaded holes are evenly distributed on the flange circumference of the crankshaft of the V-type 12-cylinder engine. Before quenching, one threaded hole at the 180-degree position is machined to a diameter of 8mm. After quenching, the 8mm diameter threaded hole at the 180-degree position is enlarged to a diameter of 10mm using interpolation milling. Then, the nine M12×1 threaded holes are machined uniformly using an 11mm diameter drill bit. The 11mm diameter threaded hole at the 180-degree position is machined using thread milling, while the remaining eight 11mm diameter threaded holes are machined using taps.

[0022] Furthermore, the spindle chuck 9 is a K72 series three-jaw single-action chuck.

[0023] Furthermore, in step 4), when drilling the oil passage hole using a 5mm diameter drill bit, firstly, use machining parameters of rotation speed S = 500r / min and feed F = 0.25mm / r to machine to a depth of 5mm. Then, adjust the machining parameters to rotation speed S = 2000r / min and feed F = 0.15mm / r to machine to the edge of the oil passage hole. Finally, adjust the machining parameters S = 500r / min and feed F = 0.07mm / r to machine until the drill bit completely passes through the inner hole.

[0024] Furthermore, in step 4), the drill bit used is a twist drill.

[0025] Furthermore, the secondary spindle clamping tip 11 is a live tip.

[0026] Furthermore, the crankshaft of the V-type 12-cylinder engine is made of 40Cr material.

[0027] Furthermore, in step 4), the oil passage hole has a diameter of 5 mm and a length of 120 mm.

[0028] The beneficial effects of the machining method for a V-type 12-cylinder engine crankshaft of the present invention are reflected in:

[0029] 1. A method for machining a V-type 12-cylinder engine crankshaft, wherein when turning the main spindle journal, the crankshaft is simultaneously clamped by the main spindle and the auxiliary spindle, and the center rest is automatically adjusted according to the position of the main spindle journal to prevent machining deformation during crankshaft machining; when machining the connecting rod journal, a combined turning and milling machining method is adopted, with milling for high-efficiency roughing and turning to improve the final machining accuracy; thus improving the overall machining quality of the crankshaft; 2. A method for machining a V-type 12-cylinder engine crankshaft, wherein during the machining of the oil passage holes, interpolation milling is used to determine the position of the oil passage holes on the cylindrical surface. During drilling, segmented feed parameters are used to ensure drilling accuracy and extend tool life. When machining the front and rear threads, interpolation milling is used to correct positional errors in the pre-drilled holes before quenching during the bottom hole machining. When machining the threads, the threads in the pre-drilled bottom hole positions before quenching are machined by milling to prevent hard spots in the thread bottom hole from causing the tap to break into the crankshaft and scrap the crankshaft. The remaining threads are machined by tapping to improve thread machining efficiency. This effectively ensures the accuracy requirements of the V12 engine crankshaft during rough machining. Attached Figure Description

[0030] Figure 1 This is a front view of the crankshaft of a V12 engine;

[0031] Figure 2 It is a three-dimensional view of the crankshaft of a V12 engine;

[0032] Figure 3 This is a three-dimensional view of the crankshaft of a V12 engine from another angle;

[0033] Figure 4 This is a three-dimensional view of the crankshaft of a V12 engine positioned by the chuck and center rest.

[0034] Figure 5 This is a three-dimensional view of the crankshaft of a V12 engine under chuck and center positioning;

[0035] Figure 6 It is a three-dimensional view of the crankshaft of a V12 engine positioned by the main spindle chuck and the sub-main spindle chuck;

[0036] In the diagram: 1. Sprocket, 2. Main journal, 3. Connecting rod journal, 4. Balance block, 5. Oil passage hole, 6. Flange end center hole, 7. Flange end threaded hole, 8. Sprocket end center hole, 9. Main spindle chuck, 10. Center rest, 11. Sub-spindle clamping center, 12. Sub-spindle chuck. Detailed Implementation

[0037] The following is in conjunction with the appendix Figures 1-6The following detailed description of the embodiments further illustrates the present invention. To make the objectives, technical solutions, and advantages of the embodiments clearer, the technical solutions in the embodiments will be clearly and completely described in conjunction with the present invention. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0038] As attached Figure 1 As shown, the crankshaft blank for the V12 engine is made of forged 40Cr material. The oil passage has a diameter of 5mm and a length of 120mm. The oil passage connects the main shaft journal and the connecting rod journal, requiring drilling on the cylindrical surface; see attached... Figure 2 As shown, the crankshaft of the V-type 12-cylinder engine has nine M12×1 threaded holes evenly distributed on the flange circumference, with a center of 6 on the flange end; as shown in the attached diagram. Figure 3 As shown, the sprocket end center hole 8 of the crankshaft of a V-type 12-cylinder engine.

[0039] A method for machining a crankshaft for a V12 engine, comprising the following steps:

[0040] 1) Precisely measure the location:

[0041] 1.1) Confirm the axial zero point during rough machining:

[0042] 1.11) The zero point position is measured by the machine tool probe, and the right end face of the M5 main journal of the V-type 12-cylinder engine crankshaft is determined as the axial machining zero point reference R50;

[0043] 1.12) Use the machine tool probe to measure the position coordinates of the two end faces of the connecting rod journal P1 of the V-type 12-cylinder engine crankshaft, and determine the center position coordinates R51 of the two end faces of the connecting rod journal P1. Using the coordinates R51 and the axial machining zero-point reference R50 mentioned in step 1.11), take an offset of R52. 1.13) Use the machine tool probe to measure the position coordinates of the two end faces of the connecting rod journal P6 of the V-type 12-cylinder engine crankshaft, and determine the center position coordinates R53 of the two end faces of the connecting rod journal P6. Using the coordinates R53 and the axial machining zero-point reference R50 mentioned in step 1.11), take an offset of R54. Take the average value of (R52+R54) / 2 as R55. Offset the coordinate system by R55 based on R50 to accurately determine the axial position of the V-type 12-cylinder engine crankshaft forging blank.

[0044] 1.2) Determine the C-axis position of the crankshaft of the V12 engine:

[0045] 1.21) Measure the C-axis position of the connecting rod journal P1 of the crankshaft of the V-type 12-cylinder engine, and determine the C-axis position as the zero-point reference R61;

[0046] 1.22) Sequentially measure the C-axis positions R62, R63, R64, R65, and R66 of the connecting rod journals P2, P3, P4, P5, and P6 of the V-type 12-cylinder engine crankshaft. Calculate the actual offsets R612, R613, R614, R615, and R616 between R62, R63, R64, R65, and R66 and the zero-point reference R61 mentioned in step 1.21). Take the average offset (R612 + R613 + R614 + R615 + R616) / 5 = R60. Based on the C-axis offset (61 - R60) of the V-type 12-cylinder engine crankshaft, determine the C-axis position of the V-type 12-cylinder engine crankshaft during machining; 2) Machining of the main shaft journal:

[0047] 2.1) Clamp the left side of the V-type 12-cylinder engine crankshaft using the main spindle chuck 9, and move the center support 10 to the main journal M4 of the V-type 12-cylinder engine crankshaft, as shown in the attached diagram. Figure 4 As shown, the right side of the V12 engine crankshaft is supported by a secondary spindle clamping center 11, as illustrated in the attached diagram. Figure 5 As shown, the flange outer diameter and the stepped outer circle at the front end of the flange of the V-type 12-cylinder engine crankshaft are machined.

[0048] 2.2) Retract the secondary spindle clamping center 11, clamp the outer circle of the sprocket end of the V-type 12-cylinder engine crankshaft with the main spindle chuck 9, clamp the outer circle of the stepped front end of the connecting flange of the V-type 12-cylinder engine crankshaft with the secondary spindle chuck 12, move the center frame 10 to the main journal M7 of the V-type 12-cylinder engine crankshaft, and machine the main journals M6, M5, M4, M3, M2, and M1 of the V-type 12-cylinder engine crankshaft;

[0049] 3) Machining of connecting rod journals:

[0050] The main spindle chuck 9 is used to clamp the outer circle of the sprocket end of the V-type 12-cylinder engine crankshaft, and the auxiliary main spindle chuck 12 is used to clamp the outer circle of the stepped front end of the connecting flange of the V-type 12-cylinder engine crankshaft. The center frame 10 is moved to the main journal M4 of the V-type 12-cylinder engine crankshaft, as shown in the attached figure. Figure 6 As shown, the connecting rod journal 3 and the balance blocks 4 on both sides of the connecting rod journal 3 of the V-type 12-cylinder engine crankshaft are rapidly roughed by eccentric milling to directly machine the thickness of the balance blocks to the required dimensions. Then, the connecting rod journal is finished by eccentric turning.

[0051] 4) Machining of oil passage holes:

[0052] A 5mm deep positioning guide hole is machined on the cylindrical surface of the crankshaft of the V-type 12-cylinder engine using a milling interpolation method. Then, a 5mm diameter drill bit is used to drill the oil passage hole. The drill bit is a twist drill. When drilling the oil passage hole with the 5mm diameter drill bit, firstly, the machining parameters are used with a speed of S = 500r / min and a feed of F = 0.25mm / r to a depth of 5mm. Then, the machining parameters are adjusted to a speed of S = 2000r / min and a feed of F = 0.15mm / r to machine to the edge of the end of the oil passage hole. Finally, the machining parameters are adjusted to S = 500r / min and a feed of F = 0.07mm / r to machine until the drill bit completely passes through the inner hole.

[0053] 5) Flange thread machining:

[0054] Nine M12×1 threaded holes are evenly distributed on the flange circumference of the crankshaft of the V-type 12-cylinder engine. Before quenching, one threaded hole at the 180-degree position is machined to a diameter of 8mm. After quenching, the 8mm diameter threaded hole at the 180-degree position is enlarged to a diameter of 10mm using interpolation milling. Then, the nine M12×1 threaded holes are machined uniformly using an 11mm diameter drill bit. The 11mm diameter threaded hole at the 180-degree position is machined using thread milling, while the remaining eight 11mm diameter threaded holes are machined using taps.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for machining a crankshaft of a V12 engine, characterized by comprising the following steps: 1) Precisely measure the location: 1.1) Confirm the axial zero point during rough machining: 1.11) The zero point position is measured by the machine tool probe, and the right end face of the M5 main journal of the V-type 12-cylinder engine crankshaft is determined as the axial machining zero point reference R50; 1.12) Use the machine tool probe to measure the position coordinates of the two end faces of the connecting rod journal P1 of the V-type 12-cylinder engine crankshaft, determine the center position coordinates R51 of the two end faces of the connecting rod journal P1, and take the offset R52 between the coordinates R51 and the axial machining zero point reference R50 in step 1.11). 1.13) Use the machine tool probe to measure the position coordinates of the two end faces of the connecting rod journal P6 of the V-type 12-cylinder engine crankshaft, determine the center position coordinates R53 of the two end faces of the connecting rod journal P6, and take the offset R54 between the coordinates R53 and the axial machining zero point reference R50 in step 1.11), take the average value of (R52+R54) / 2 as R55, shift the coordinate system by R55 based on R50, and accurately determine the axial position of the V-type 12-cylinder engine crankshaft forging blank; 1.2) Determine the C-axis position of the crankshaft of the V12 engine: 1.21) Measure the C-axis position of the connecting rod journal P1 of the crankshaft of the V-type 12-cylinder engine, and determine the C-axis position as the zero-point reference R61; 1.22) Measure the C-axis positions R62, R63, R64, R65, and R66 of the connecting rod journals P2, P3, P4, P5, and P6 of the V-type 12-cylinder engine crankshaft in sequence. Calculate the actual offsets R612, R613, R614, R615, and R616 between R62, R63, R64, R65, and R66 and the zero-point reference R61 in step 1.21). Take the average offset (R612 + R613 + R614 + R615 + R616) / 5 = R60. Based on the C-axis offset R61 - R60 of the V-type 12-cylinder engine crankshaft, determine the C-axis position of the V-type 12-cylinder engine crankshaft during machining. 2) Spindle journal machining: 2.1) The left side of the V-type 12-cylinder engine crankshaft is clamped by the main spindle chuck (9), the center frame (10) is moved to the main journal M4 of the V-type 12-cylinder engine crankshaft, the right side of the V-type 12-cylinder engine crankshaft is supported by the secondary spindle clamping center (11), and the flange outer diameter and the stepped outer circle at the front end of the flange of the V-type 12-cylinder engine crankshaft are machined. 2.2) Retract the secondary spindle clamping center (11), clamp the outer circle of the sprocket end of the V-type 12-cylinder engine crankshaft with the main spindle chuck (9), clamp the outer circle of the stepped front end of the connecting flange of the V-type 12-cylinder engine crankshaft with the secondary spindle chuck (12), move the center frame (10) to the main journal M7 of the V-type 12-cylinder engine crankshaft, and process the main journals M6, M5, M4, M3, M2, and M1 of the V-type 12-cylinder engine crankshaft; 3) Machining of connecting rod journals: The main spindle chuck (9) is used to clamp the outer circle of the sprocket end of the V-type 12-cylinder engine crankshaft, and the auxiliary main spindle chuck (12) is used to clamp the outer circle of the stepped front end of the connecting flange of the V-type 12-cylinder engine crankshaft. The center frame (10) is moved to the main journal M4 of the V-type 12-cylinder engine crankshaft. The connecting rod journal and the balance blocks on both sides of the connecting rod journal are quickly rough machined by eccentric milling. The thickness of the balance blocks is directly machined to the size. Then, the connecting rod journal is finished by eccentric turning. 4) Machining of oil passage holes: Using a milling interpolation method, a 5mm deep positioning guide hole is machined on the cylindrical surface of the crankshaft of the V-type 12-cylinder engine, and then a 5mm diameter drill bit is used to drill the oil passage hole. 5) Flange thread machining: Nine M12×1 threaded holes are evenly distributed on the flange circumference of the crankshaft of the V-type 12-cylinder engine. Before quenching, one threaded hole at the 180-degree position is machined to a diameter of 8mm. After quenching, the 8mm diameter threaded hole at the 180-degree position is enlarged to a diameter of 10mm using interpolation milling. Then, the nine M12×1 threaded holes are machined uniformly using an 11mm diameter drill bit. The 11mm diameter threaded hole at the 180-degree position is machined using thread milling, while the remaining eight 11mm diameter threaded holes are machined using taps.

2. The machining method for a V-type 12-cylinder engine crankshaft according to claim 1, characterized in that, The spindle chuck (9) is a K72 series three-jaw single-action chuck.

3. The machining method for a V-type 12-cylinder engine crankshaft according to claim 1, characterized in that, In step 4), when drilling the oil passage hole using a 5mm diameter drill bit, firstly, use machining parameters of rotation speed S=500r / min and feed F=0.25mm / r to machine to a depth of 5mm. Then, adjust the machining parameters to rotation speed S=2000r / min and feed F=0.15mm / r to machine to the edge of the oil passage hole. Finally, adjust the machining parameters to S=500r / min and feed F=0.07mm / r to machine until the drill bit completely passes through the inner hole.

4. The machining method for a V-type 12-cylinder engine crankshaft according to claim 1, characterized in that, In step 4), the drill bit used is a twist drill.

5. The machining method for a V-type 12-cylinder engine crankshaft according to claim 1, characterized in that, The secondary spindle clamping center (11) is a live center.

6. The machining method for a V-type 12-cylinder engine crankshaft according to claim 1, characterized in that, The crankshaft of the V12 engine is made of 40Cr material.

7. The machining method for a V-type 12-cylinder engine crankshaft according to claim 1, characterized in that, In step 4), the oil passage hole has a diameter of 5 mm and a length of 120 mm.

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