A high-speed transmission shaft for engine crankshaft direct connection bench test

Abstract

The application discloses a high-speed transmission shaft for engine crankshaft direct connection bench test, relates to the motorcycle power test technical field, and comprises a buffer flange, a damping bushing, an intermediate shaft and a pin shaft. The buffer flange is connected to the crankshaft of the engine through a spline sleeve, and a plurality of first stepped holes are uniformly arranged in the circumferential direction of the buffer flange. The damping bushing is in one-to-one correspondence with the first stepped holes, and is assembled in the corresponding first stepped holes. The intermediate shaft comprises coaxially arranged first and second flanges, the first flange is connected to a dynamometer, a plurality of second stepped holes are uniformly arranged in the circumferential direction of the second flange, and the second stepped holes are in one-to-one correspondence with the first stepped holes. One end of the pin shaft is arranged in the damping bushing to fix the damping bushing, and the other end is arranged in the second stepped hole and connected to the second flange. The plurality of damping bushings are uniformly distributed in the circumferential direction of the buffer flange, the mass and volume of a single elastic body are reduced, and the adverse effect of centrifugal force on the elastic body during high-speed rotation is reduced.

Description

Technical Field

[0001] This invention relates to the field of motorcycle power testing technology, and in particular to a high-speed transmission shaft for direct-drive bench testing of engine crankshafts. Background Technology

[0002] In the research and development testing of engines matched with continuously variable transmissions (CVTs), performance testing is typically conducted using an output shaft connection. However, since the transmission efficiency of a CVT changes with vehicle speed (or engine speed), this change directly affects the accuracy of the test data, causing the final performance calculation results to deviate from the true values. Therefore, a performance test using a direct crankshaft connection was proposed to obtain performance results with accurate crankshaft positioning. The maximum crankshaft speed range of engines matched with CVTs is 7750~9000 r / min, while existing driveshafts generally adopt an integrated structure, and their vibration damping mechanism is usually a large-volume elastic element or an integral rubber composite flange set in a flange. Under high-speed rotation conditions, the large-volume elastic element or integral rubber composite flange is prone to deformation, overheating, or even tearing due to centrifugal force, leading to structural failure and severely limiting the maximum operating speed and long-term operational reliability of the driveshaft.

[0003] Therefore, how to reduce the adverse effects of centrifugal force during high-speed rotation is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a high-speed driveshaft for direct-drive bench testing of engine crankshafts, which can reduce the adverse effects of centrifugal force during high-speed rotation and improve high-speed operation stability. The high-speed driveshaft achieves direct connection between the engine crankshaft and the dynamometer, fundamentally eliminating the influence of CVT transmission efficiency variations on test results, thereby significantly improving the accuracy and reliability of engine performance testing. At the same time, the material and manufacturing costs of this high-speed driveshaft are significantly reduced compared to existing technologies.

[0005] To achieve the above objectives, the present invention provides a high-speed drive shaft for direct-drive bench testing of engine crankshafts, comprising: The buffer flange is connected to the crankshaft of the engine via a spline sleeve. Multiple first-step holes are evenly opened in the circumferential direction of the buffer flange. Vibration damping bushings correspond one-to-one with the first stepped holes, and the vibration damping bushings are fitted into the corresponding first stepped holes. The intermediate shaft includes a first flange and a second flange arranged coaxially. The first flange is connected to the dynamometer. The second flange has multiple second stepped holes evenly opened in the circumferential direction, and the second stepped holes correspond one-to-one with the first stepped holes. The pin has one end inserted through the damping bushing to fix it, and the other end inserted through the second stepped hole and connected to the second flange, which is used to transmit the engine's power to the intermediate shaft.

[0006] In one possible implementation, the first stepped hole includes a first hole and a second hole arranged coaxially, the diameter of the first hole is larger than the diameter of the second hole, and the first hole is closer to the second flange relative to the second hole. A first stepped surface is formed between the first hole and the second hole, and the vibration damping bushing is provided with a first end face for abutting the first stepped surface.

[0007] In one possible implementation, the vibration damping bushing has a second end face that is axially opposite to the first end face. The second end face has a first protrusion that protrudes axially. The first protrusion has a third end face located on the side of the first protrusion away from the second end face. The third end face is used to abut against the side of the second flange facing the buffer flange.

[0008] In one possible implementation, the second stepped hole includes a third hole and a fourth hole arranged coaxially, the diameter of the third hole being larger than the diameter of the fourth hole, and the third hole being closer to the buffer flange relative to the fourth hole. A second stepped surface is formed between the third hole and the fourth hole. The outer periphery of the pin is provided with a radially protruding convex ring, and the convex ring is provided with a first abutting surface for abutting the second stepped surface to restrict the movement of the pin relative to the intermediate shaft toward the first flange.

[0009] In one possible implementation, the pin has a connecting section that passes through the fourth hole and includes an extension that extends beyond the fourth hole. A fastener is connected to the extension to restrict the pin from moving toward the buffer flange relative to the intermediate shaft. The length of the extension in the axial direction of the fourth hole is greater than the length of the fastener in the axial direction of the fourth hole.

[0010] In one possible implementation, the convex ring is further provided with a second abutment surface that is axially opposite to the first abutment surface. The second abutment surface is flush with the side of the second flange facing the buffer flange and is used to abut against the third end face.

[0011] In one possible implementation, the buffer flange is provided with a plurality of third-step holes evenly distributed in the circumferential direction, and the spline sleeve is provided with a plurality of connecting holes evenly distributed in the circumferential direction. The connecting holes are provided in correspondence with the third-step holes, and the connecting piece is connected to the corresponding connecting hole and the third-step hole, so that the buffer flange and the spline sleeve are relatively fixed, and there is a gap between the connecting piece and the second flange.

[0012] In one possible implementation, a lock nut is also included, which is threaded onto the crankshaft end to press the spline sleeve against the crankshaft positioning boss to limit the axial movement of the spline sleeve.

[0013] In one possible implementation, the buffer flange has a first through hole in the middle for receiving a lock nut.

[0014] In one possible implementation, the buffer flange and intermediate shaft are specifically made of high-strength, lightweight aluminum alloy; and / or, the buffer flange and intermediate shaft are hollow structures.

[0015] Compared to existing technologies, the technical solution provided by this invention has at least the following beneficial effects: The high-speed drive shaft adopts a split structure. The buffer flange is connected to the engine crankshaft via a spline sleeve, and the first flange of the intermediate shaft is connected to the dynamometer. The buffer flange and the second flange of the intermediate shaft are connected by a vibration damping bushing and a pin. Specifically, the buffer flange has multiple first stepped holes evenly spaced circumferentially, and the vibration damping bushing corresponds one-to-one with each of the first stepped holes. The vibration damping bushing is fitted into the corresponding first stepped hole, and the pin connects to the second flange and passes through the vibration damping bushing. In this way, the torque of the engine crankshaft is transmitted to the buffer flange via the spline sleeve, and then the torque and vibration are transmitted to the intermediate shaft via the vibration damping bushing and the pin, ultimately driving the dynamometer. Multiple vibration damping bushings are evenly distributed circumferentially on the buffer flange and have the functions of buffering and vibration damping. Compared with existing technologies, the mass and volume of a single elastomer are reduced, the adverse effects of centrifugal force during high-speed rotation are reduced, and the stability of high-speed operation is improved. Furthermore, the parallel connection of multiple small damping bushings disperses localized stress, resulting in overall torsional resistance superior to a single large-size elastic element. Individual damping bushings can be replaced when damaged, reducing maintenance costs. The high-speed driveshaft provided in this application achieves direct connection between the engine crankshaft and the dynamometer, fundamentally eliminating the impact of CVT transmission efficiency variations on test results, thereby significantly improving the accuracy and reliability of engine performance testing. Simultaneously, the material and manufacturing costs of this high-speed driveshaft are significantly reduced compared to existing technologies. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the high-speed drive shaft provided in the embodiment of the present invention when used in a direct-drive bench test of an engine crankshaft; Figure 2 This is a schematic diagram of the structure of the high-speed drive shaft provided in an embodiment of the present invention; Figure 3 This is a cross-sectional view of the high-speed transmission shaft provided in an embodiment of the present invention; Figure 4This is an exploded view of the high-speed drive shaft provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the vibration damping bushing provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the vibration damping bushing provided in an embodiment of the present invention from another perspective.

[0018] in: 100 - Buffer flange, 110 - First stepped hole, 120 - Third stepped hole, 130 - First through hole; 200 - Spline sleeve, 210 - Connecting hole; 300-engine; 400 - Vibration damping bushing, 410 - First protrusion, 420 - Second protrusion; 500 - intermediate shaft, 510 - second stepped hole, 520 - second through hole; 600 - Dynamometer; 610 - Output flange; 700 - Pin, 710 - Insertion section, 720 - Connecting section, 730 - Protruding ring; 800 - Locking nut. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] In the description of this invention, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the position or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations of this invention.

[0022] The purpose of this invention is to provide a high-speed driveshaft for direct-drive bench testing of engine crankshafts, which reduces the adverse effects of centrifugal force during high-speed rotation and improves high-speed operation stability. The high-speed driveshaft achieves direct connection between the engine crankshaft and the dynamometer, fundamentally eliminating the influence of CVT transmission efficiency variations on test results, thereby significantly improving the accuracy and reliability of engine performance testing. Simultaneously, the material and manufacturing costs of this high-speed driveshaft are significantly reduced compared to existing technologies.

[0023] Please see Figures 1 to 6 To achieve the above objectives, the present invention provides a high-speed drive shaft for direct-drive bench testing of engine crankshafts. The high-speed drive shaft includes a buffer flange 100, multiple damping bushings 400, an intermediate shaft 500, and multiple pins 700. The buffer flange 100 is connected to the crankshaft of the engine 300 via a spline sleeve 200. Multiple first stepped holes 110 are evenly distributed circumferentially on the buffer flange 100. The number of first stepped holes 110 can be adjusted according to actual needs; in this embodiment, the number of first stepped holes 110 can be, but is not limited to, ten. The damping bushings 400 correspond one-to-one with the first stepped holes 110 and are assembled into the corresponding first stepped holes 110. The intermediate shaft 500 includes a first flange and a second flange coaxially arranged. The first flange is connected to a dynamometer 600. The second flange has multiple second stepped holes 510 evenly distributed circumferentially, each corresponding one-to-one with the first stepped holes 110. One end of the pin 700 passes through the damping bushing 400 to fix the damping bushing 400, and the other end passes through the second stepped hole 510 and is connected to the second flange, which is used to transmit the power of the engine 300 to the intermediate shaft 500.

[0024] In this embodiment, the pin 700 is provided with an insertion section 710 and a connecting section 720 connected to the insertion section 710. The connecting section 720 is used to engage with the second stepped hole 510. This engagement can be, but is not limited to, an interference fit, to limit the radial offset of the pin 700 relative to the intermediate shaft 500. This prevents excessive offset of one or more pins 700 due to assembly or stress, thus ensuring that the insertion section 710 of each pin 700 can be smoothly inserted into the corresponding damping bushing 400. Considering the stringent dynamic balance requirements of the high-speed drive shaft at speeds ≥8000 r / min, the buffer flange 100, intermediate shaft 500, and spline sleeve 200 all require independent dynamic balancing before assembly, with a dynamic balance ≤G2.5 standard. After all components are assembled, the entire high-speed drive shaft assembly undergoes overall dynamic balancing re-inspection and correction to ensure that the vibration value of the high-speed drive shaft is minimized at high operating speeds.

[0025] The high-speed drive shaft adopts a split structure. The buffer flange 100 is connected to the crankshaft of the engine 300 through the spline sleeve 200. The first flange of the intermediate shaft 500 is connected to the dynamometer 600. The buffer flange 100 and the second flange of the intermediate shaft 500 are connected by a vibration damping bushing 400 and a pin 700. Specifically, the buffer flange 100 has multiple first stepped holes 110 evenly opened in the circumferential direction. The vibration damping bushing 400 corresponds one-to-one with the first stepped holes 110 and is assembled in the corresponding first stepped holes 110. The pin 700 is connected to the second flange and passes through the vibration damping bushing 400. In this way, the torque of the crankshaft of the engine 300 is transmitted to the buffer flange 100 through the spline sleeve 200, and then the torque and vibration are transmitted to the intermediate shaft 500 through the vibration damping bushing 400 and the pin 700, which finally drives the dynamometer 600. Multiple damping bushings 400 are circumferentially distributed on the buffer flange 100, serving both buffering and vibration damping functions. Compared to existing technologies, this reduces the mass and volume of a single elastomer, mitigating the adverse effects of centrifugal force during high-speed rotation and improving high-speed operational stability. Furthermore, the parallel connection of multiple small damping bushings 400 disperses localized stress, resulting in overall torsional resistance superior to a single large-size elastic element. Damaged individual damping bushings 400 can be replaced individually, reducing maintenance costs. The high-speed driveshaft provided in this application achieves direct connection between the engine crankshaft and the dynamometer, fundamentally eliminating the impact of CVT transmission efficiency variations on test results, thereby significantly improving the accuracy and reliability of engine performance testing. Simultaneously, the material and manufacturing costs of this high-speed driveshaft are significantly reduced compared to existing technologies.

[0026] In one possible implementation, the buffer flange 100 includes a first side facing the intermediate shaft 500 and a second side opposite to the first side in the axial direction of the buffer flange 100. The first stepped hole 110 includes a first hole and a second hole coaxially arranged. The diameter of the first hole is larger than the diameter of the second hole, and the first hole is closer to the second flange than the second hole. That is, the first hole is opened on the first side of the buffer flange 100, and the second hole is opened on the second side of the buffer flange 100. The cross-sectional diameters of the first hole and the second hole perpendicular to the axial direction of the buffer flange 100 can be set according to actual needs, as long as the above-mentioned purpose is achieved. A first stepped surface is formed between the first hole and the second hole, and the vibration damping bushing 400 is provided with a first end face for abutting against the first stepped surface. By abutting against the first stepped surface, the movement of the vibration damping bushing 400 toward the second side can be restricted.

[0027] In one possible implementation, the vibration damping bushing 400 has a second end face, which is axially opposite to the first end face of the vibration damping bushing 400. The second end face has a first protrusion 410 protruding axially from the vibration damping bushing 400. The first protrusion 410 has a third end face located on the side of the first protrusion 410 opposite to the second end face, and the third end face is used to abut against the side of the second flange facing the buffer flange 100. The abutment between the third end face and the second flange restricts the movement of the vibration damping bushing 400 away from the first side. Furthermore, the first end face has a second protrusion 420 protruding axially from the vibration damping bushing 400, which is symmetrically arranged with the first protrusion 410 to make the vibration damping bushing 400 as a whole symmetrical structure, preventing the vibration damping bushing 400 from being installed backwards. The second hole is used to accommodate the second protrusion 420.

[0028] In one possible implementation, the second stepped hole 510 includes a third hole and a fourth hole coaxially arranged. The diameter of the third hole is larger than that of the fourth hole, and the third hole is closer to the buffer flange 100 relative to the fourth hole. The cross-sectional diameters of the third and fourth holes perpendicular to the axial direction of the intermediate shaft 500 can be set according to actual needs, as long as the above-mentioned purpose is achieved. A second stepped surface is formed between the third hole and the fourth hole. A radially protruding convex ring 730 is provided on the outer periphery of the pin 700. The convex ring 730 is located on the outer periphery of the connecting section 720 and has a first abutting surface for abutting against the second stepped surface to restrict the movement of the pin 700 relative to the intermediate shaft 500 toward the first flange.

[0029] The connecting section 720 penetrates the fourth hole and includes an extension extending beyond the fourth hole. A fastener is connected to the extension to restrict the movement of the pin 700 relative to the intermediate shaft 500 toward the buffer flange 100. The length of the extension in the axial direction of the fourth hole is greater than the length of the fastener in the axial direction of the fourth hole. The outer periphery of the extension may, but is not limited to, have external threads, and the fastener may, but is not limited to, be a nut. The pin 700 is fixed by the contact between the convex ring 730 and the second stepped surface, the threaded connection between the nut and the extension, and the contact between the nut and the second flange. The convex ring 730 also has a second contact surface axially opposite the first contact surface of the pin 700. The second contact surface is planar and flush with the side of the second flange facing the buffer flange 100. The second contact surface is used to contact the third end face.

[0030] In one possible implementation, the buffer flange 100 has a plurality of third-step holes 120 evenly distributed around its circumference. The number of third-step holes 120 can be adjusted according to actual needs. In this embodiment, the number of third-step holes 120 can be, but is not limited to, eight. The distance between the axis of the third-step hole 120 and the axis of the buffer flange 100 is less than the distance between the axis of the first-step hole 110 and the axis of the buffer flange 100. The spline sleeve 200 has a plurality of connecting holes 210 evenly distributed around its circumference. The connecting holes 210 are correspondingly arranged with the third-step holes 120. A connector is connected to the corresponding connecting hole 210 and the third-step hole 120 to fix the buffer flange 100 and the spline sleeve 200 relatively. There is a gap between the connector and the second flange. The connector can be, but is not limited to, a bolt. The bolt head is located inside the third-step hole 120, and the bolt head abuts against the stepped surface of the third-step hole 120, so that the bolt head does not contact the second flange.

[0031] In one possible implementation, the engine 300 is fixedly mounted on a test bench. The spline sleeve 200 has internal splines. After the spline sleeve 200 is installed on the crankshaft end of the engine 300, its internal splines fully mesh with the external splines of the crankshaft. The locking nut 800 is threaded onto the thread of the crankshaft end to press the spline sleeve 200 against the crankshaft positioning boss to limit the axial movement of the spline sleeve 200. Next, the buffer flange 100 and spline sleeve 200 are fixed relative to each other using connectors. Then, the vibration damping bushings 400 are sequentially installed into the corresponding first stepped holes 110 of the buffer flange 100. Then, the shaft pins are sequentially installed into the second stepped holes 510 of the intermediate shaft 500, and the pins 700 are fixed using fasteners. Then, the intermediate shaft 500 with the shaft pins installed is connected to the output flange 610 of the dynamometer 600 with bolts and tightened. Then, the position of the engine 300 is moved so that the shaft pins on the intermediate shaft 500 are inserted into the vibration damping bushings 400 on the buffer flange 100, and the third end face of the vibration damping bushing 400 is made to fit against the side of the intermediate shaft 500 facing the buffer flange 100. Then, a laser alignment instrument is used to adjust the alignment of the buffer flange 100 and the intermediate shaft 500, and the alignment accuracy is controlled within the range of axial error less than or equal to 0.05mm and radial error less than or equal to 0.05mm. The installation is now complete. Thus, this application provides a high-speed drive shaft for direct crankshaft testing of engines that is applicable to high-speed (≥8000r / min) operating conditions and has a reliable structure, in order to solve the problems of inaccurate performance test results of existing CVT engines due to changes in transmission efficiency, and the inability of existing drive shafts to meet the requirements of high-speed testing.

[0032] The structure of the spline sleeve 200 can be adjusted or redesigned according to the interface and rotational inertia characteristics of different crankshafts to achieve direct connection testing of crankshafts of multiple models. The goal is to ensure operational reliability under high-speed conditions while meeting torque transmission capacity and dynamic response requirements. A first through hole 130 is provided in the middle of the buffer flange 100 to accommodate the locking nut 800. In this embodiment, a first protrusion is provided on the side of the spline sleeve 200 facing the intermediate shaft 500. This first protrusion can be, but is not limited to, an annular protrusion. The thickness of the first protrusion along the axial direction of the first through hole 130 can be set to 2-3 mm. The circumferential side of the first protrusion and the inner wall of the first through hole 130 are in clearance fit, used for pre-positioning the spline sleeve 200 and the buffer flange 100, thereby reducing installation deviations. When using a laser alignment instrument for subsequent alignment, only minor adjustments are needed to meet the accuracy requirements. Similarly, a second protrusion is provided on the side of the intermediate shaft 500 facing the spline sleeve 200. This second protrusion can be, but is not limited to, an annular protrusion. The peripheral side of the second protrusion is also clearance-fitted with the inner wall of the first through hole 130, which is used to pre-position the intermediate shaft 500 and the buffer flange 100, thereby reducing installation deviation. When using a laser alignment instrument for subsequent alignment, only fine adjustments are needed to meet the accuracy requirements. A second through hole 520 is provided in the middle of the intermediate shaft 500. The axis of the second through hole 520 is collinear with the axis of the intermediate shaft 500, and the axis of the second through hole 520 is collinear with the axis of the first through hole 130. The buffer flange 100 and intermediate shaft 500 can be made of high-strength, lightweight 7075 aluminum alloy. They also adopt a hollow structure, which reduces the weight by about 2 / 3 compared to the conventional 45 steel design and the absence of a hollow structure. At the same time, it ensures sufficient yield and tensile strength, further reduces the impact of the transmission shaft on the rotational inertia of the engine crankshaft under high-speed rotation, and ensures its own structural strength at high speed.

[0033] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0034] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0035] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A high-speed drive shaft for direct-drive bench testing of engine crankshafts, characterized in that, include: A buffer flange (100) is connected to the crankshaft of the engine (300) via a spline sleeve (200). The buffer flange (100) has a plurality of first stepped holes (110) evenly opened in the circumferential direction. The vibration damping bushing (400) corresponds one-to-one with the first stepped hole (110), and the vibration damping bushing (400) is assembled in the corresponding first stepped hole (110). The intermediate shaft (500) includes a first flange and a second flange arranged coaxially. The first flange is connected to the dynamometer (600). The second flange has a plurality of second stepped holes (510) evenly opened in the circumferential direction. The second stepped holes (510) correspond one-to-one with the first stepped holes (110). The pin (700) has one end inserted through the damping bushing (400) to fix the damping bushing (400), and the other end inserted through the second stepped hole (510) and connected to the second flange, for transmitting the power of the engine (300) to the intermediate shaft (500).

2. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to claim 1, characterized in that, The first stepped hole (110) includes a first hole and a second hole arranged coaxially. The diameter of the first hole is larger than the diameter of the second hole, and the first hole is closer to the second flange relative to the second hole. A first stepped surface is formed between the first hole and the second hole. The vibration damping bushing (400) is provided with a first end face for abutting the first stepped surface.

3. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to claim 2, characterized in that, The vibration damping bushing (400) has a second end face that is axially opposite to the first end face. The second end face has a first protrusion (410) that protrudes axially. The first protrusion (410) has a third end face. The third end face is located on the side of the first protrusion (410) away from the second end face. The third end face is used to abut against the side of the second flange facing the buffer flange (100).

4. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to claim 3, characterized in that, The second stepped hole (510) includes a third hole and a fourth hole arranged coaxially. The diameter of the third hole is larger than that of the fourth hole, and the third hole is closer to the buffer flange (100) relative to the fourth hole. A second stepped surface is formed between the third hole and the fourth hole. The outer periphery of the pin (700) is provided with a radially protruding convex ring (730). The convex ring (730) is provided with a first abutting surface for abutting against the second stepped surface to restrict the movement of the pin (700) relative to the intermediate shaft (500) toward the first flange.

5. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to claim 4, characterized in that, The pin (700) is provided with a connecting section (720) that passes through the fourth hole and includes an extension that extends out of the fourth hole. A fastener is connected to the extension to restrict the pin (700) from moving relative to the intermediate shaft (500) toward the buffer flange (100). The length of the extension in the axial direction of the fourth hole is greater than the length of the fastener in the axial direction of the fourth hole.

6. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to claim 4, characterized in that, The convex ring (730) is also provided with a second abutment surface that is axially opposite to the first abutment surface. The second abutment surface is flush with the side of the second flange facing the buffer flange (100). The second abutment surface is used to abut against the third end face.

7. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to any one of claims 1 to 6, characterized in that, The buffer flange (100) has a plurality of third-step holes (120) evenly opened in the circumferential direction, and the spline sleeve (200) has a plurality of connecting holes (210) evenly opened in the circumferential direction. The connecting holes (210) are correspondingly arranged with the third-step holes (120). The connector is connected to the corresponding connecting hole (210) and the third-step hole (120) so that the buffer flange (100) and the spline sleeve (200) are relatively fixed, and there is a gap between the connector and the second flange.

8. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to any one of claims 1 to 6, characterized in that, It also includes a locking nut (800), which is threaded to the end of the crankshaft and is used to press the spline sleeve (200) against the crankshaft positioning boss to limit the movement of the spline sleeve (200) along its own axial direction.

9. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to claim 8, characterized in that, The buffer flange (100) has a first through hole (130) in the middle, which is used to accommodate the lock nut (800).

10. The high-speed drive shaft for direct-drive bench testing of engine crankshafts according to any one of claims 1 to 6, characterized in that, The buffer flange (100) and the intermediate shaft (500) are specifically made of high-strength, lightweight 7075 aluminum alloy; and / or, the buffer flange (100) and the intermediate shaft (500) are hollow structures.

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