A spindle structure suitable for bearing limit speed test

Abstract

This invention provides a spindle structure suitable for bearing limit speed testing, relating to the field of bearing performance testing technology. The spindle consists of a rotating body and a non-rotating body. The rotating body includes a shaft core, a test bearing, a bearing washer, a lock nut, and a motor rotor. The non-rotating body includes a front bearing housing, a rear bearing housing, a cooling water jacket, a spindle body, and a motor stator assembly. The motor rotor is mounted on the shaft core, and the motor stator assembly is mounted inside the spindle body. The shaft core is mounted inside the spindle via the front and rear bearing housings. The shaft core and the inner ring of the test bearing are interference-fitted. The bearing washer is located on one side of the test bearing. This invention, by adopting a back-wound permanent magnet synchronous motor structure, achieves higher speeds and power within a compact internal space. Through the face-to-face bearing architecture and the design of the stator inner hole being larger than the bearing outer circle, the rotating body can be quickly disassembled and assembled, significantly improving testing efficiency.

Description

Technical Field

[0001] This invention relates to the field of bearing performance testing technology, and in particular to a spindle structure suitable for testing the ultimate speed of bearings. Background Technology

[0002] In the field of high-end equipment manufacturing, bearings, as core rotating components, directly determine the performance limits of equipment such as machine tool spindles, aero engines, and high-speed motors through their maximum speed capability. The DMN value (the product of the bearing's pitch circle diameter and its rotational speed) is a key indicator for measuring its high-speed performance. Breaking through the existing DMN value limitations and achieving stable operation at higher speeds is an important research direction in the field of bearing design and manufacturing.

[0003] Currently, traditional spindle structures used for bearing limit speed testing have the following significant drawbacks: 1) Due to the speed bottleneck of conventional motors, it is difficult to stably drive the test bearings to ultra-high speed conditions of 60,000 rpm and above, which cannot meet the testing requirements of bearings with high DMN values.

[0004] 2) At high speeds, conventional grease lubrication systems are prone to failure, leading to dry friction between the bearing balls and raceways. Furthermore, the existing spindle structure cannot effectively accommodate testing with different lubrication media, limiting the comprehensiveness of the testing.

[0005] 3) Insufficient rigidity of traditional spindle mechanical structures (such as spindle core and bearing housing) or excessive bearing span leads to insufficient rigidity of the spindle structure, which is prone to resonance and deformation at high speeds.

[0006] 4) The process of replacing bearings is cumbersome and usually requires repeated pressing with specialized equipment. The bearings or spindle components are easily damaged during disassembly. This not only takes a long time, but may also interfere with the true judgment of the bearing's performance after testing due to disassembly damage, resulting in low testing efficiency.

[0007] Therefore, we propose a spindle structure suitable for bearing limit speed testing. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing a spindle structure suitable for bearing limit speed testing. This structure, through a back-wound permanent magnet synchronous motor, a high-rigidity short-span mechanical design, a hollow shaft core, and an integrated quick-release and quick-install structure, achieves stable, efficient, and accurate testing of bearings under ultra-high-speed limit conditions above 60,000 rpm.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A spindle structure suitable for bearing limit speed testing is disclosed. The spindle consists of a rotating body and a non-rotating body. The rotating body includes a spindle core, a test bearing, a bearing washer, a lock nut, and a motor rotor. The non-rotating body includes a spindle body, a front bearing housing, a rear bearing housing, a cooling water jacket, and a motor stator assembly. The motor rotor is mounted on the spindle core. The motor stator assembly is interference-fitted inside the spindle body. At least two O-rings are provided between the motor stator assembly and the spindle body. The spindle core is mounted inside the spindle via the front and rear bearing housings. The inner ring of the spindle core and the test bearing are interference-fitted. The bearing washer is located on one side of the test bearing.

[0010] Furthermore, a disassembly gap is provided between the bearing washer ring and the shaft core, and the end face of the bearing washer ring directly abuts against the end face of the inner ring of the test bearing.

[0011] Furthermore, the front and rear bearing housings are clearance-fitted with the outer ring of the test bearing. The connection between the front and rear bearing housings and the spindle body is provided with an end face mating surface and an inner hole outer circle mating surface. The end face of the front bearing housing and the spindle body is provided with an O-ring seal. At least two O-ring seals are provided between the rear bearing housing and the outer circle inner hole of the spindle body. The front and rear bearing housings are tightened onto the spindle body by bolts.

[0012] Furthermore, the cooling water jacket is fitted onto the outside of the front bearing housing, and at least two O-rings are provided between the cooling water jacket and the front bearing housing. The cooling water jacket is provided with a coolant inlet, and the spindle body is provided with a coolant outlet. The cooling water jacket and the front bearing housing are fastened together by screws.

[0013] Furthermore, the motor rotor is a permanent magnet synchronous motor rotor, which adopts a magnetic mounting method. The motor rotor is magnetically attached to the shaft core and fixed in place using a specific adhesive. The air gap between the stator assembly and the motor rotor is relatively large, and the inner diameter of the stator assembly is larger than the outer diameter of the test bearing.

[0014] Furthermore, the span between the front and rear test bearings is 3.5 times the inner diameter of the bearing.

[0015] Furthermore, the rear bearing housing is provided with a preload mechanism, which includes a preload spring cover, a preload spring, and a bearing preload ring. The preload spring is installed between the preload spring cover and the bearing preload ring. One end of the bearing preload ring abuts against the preload spring, and the other end abuts against the outer ring end face of the test bearing.

[0016] Furthermore, the preload spring cover is provided with an adjustment thread, and the compression of the preload spring can be adjusted by rotating the preload spring cover.

[0017] Furthermore, a labyrinth seal gap is provided between the front bearing housing, the bearing preload ring and the shaft core, and the labyrinth seal gap is formed by the alternation of the annular protrusion on the shaft core and the annular groove on the bearing housing.

[0018] Furthermore, the motor stator assembly has its cable exiting from the side of the spindle body, with the gland fastened to the side of the spindle body to secure the power cable, and the drive cable of the motor stator assembly is fixed to an external driver.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention employs a back-wound permanent magnet synchronous motor, resulting in a more compact structure, eliminating harmonic losses, lower copper losses, and achieving extremely high speed capabilities (60,000 rpm). Combined with a short-span, high-rigidity mechanical design, it significantly improves the bending stiffness and critical speed of the spindle system, providing a reliable power and support foundation for ultra-high-speed bearing testing exceeding 3.6 million DMN values. For test assembly and disassembly, the rotating body can be quickly and integrally disassembled. Furthermore, the non-destructive bearing washer structure allows for easy removal of the test bearing after testing without the need for specialized pressing equipment, avoiding interference with accurate bearing performance assessment due to disassembly damage and significantly improving testing efficiency and data accuracy. In addition, the integrated cooling circulation and adjustable preload mechanism ensure the thermal stability and load simulation capability of the spindle under continuous ultra-high-speed operation, offering strong versatility and low testing costs. Attached Figure Description

[0020] Figure 1 This invention provides an overall internal structure schematic diagram of a spindle structure suitable for bearing limit speed testing; Figure 2 This invention provides a schematic diagram of the external side planar structure of a spindle structure suitable for bearing limit speed testing.

[0021] Legend: 1. Spindle body; 2. Rotating body; 3. Non-rotating body; 4. Shaft core; 5. Test bearing; 6. Bearing washer; 7. Lock nut; 8. Front bearing housing; 9. Rear bearing housing; 10. Cooling water jacket; 11. Stator assembly; 12. Motor rotor; 13. O-ring seal; 14. Preload spring cover; 15. Preload spring; 16. Bearing preload ring; 17. Labyrinth seal gap. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below with reference to relevant embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0024] It should be noted that when an element is said to be fixed to another element, it can be directly on the other element or there may be an intervening element. When an element is said to be connected to another element, it can be directly connected to the other element or there may be an intervening element. The terms vertical, horizontal, left, right and similar expressions used in this document are for illustrative purposes only.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terminology used herein includes and / or includes any and all combinations of one or more of the associated listed items.

[0026] Example 1 like Figure 1-2 As shown, the present invention provides a technical solution: a spindle structure suitable for bearing limit speed testing. The spindle consists of a rotating body 2 and a non-rotating body 3. The rotating body 2 includes a shaft core 4, a test bearing 5, a bearing washer 6, a locking nut 7, and a motor rotor 12. The non-rotating body 3 includes a front bearing seat 8, a rear bearing seat 9, a cooling water jacket 10, a spindle body 1, and a motor stator assembly 11. The motor rotor 12 is mounted on the shaft core 4. The motor stator assembly 11 is interference-fitted inside the spindle body 1. The shaft core 4 is mounted inside the spindle through the front bearing seat 8 and the rear bearing seat 9. The inner ring of the shaft core 4 and the test bearing 5 are interference-fitted. The bearing washer 6 is disposed on one side of the test bearing 5. This structure is designed to break through the existing DMN value limit and to conduct ultra-high speed limit performance tests on bearings at 60,000 rpm and above. Its overall design follows the principles of high rigidity, lightweight, quick replacement, and thermal stability, and integrates an innovative back-wound motor, short span structure, hollow rotor, and integrated quick-release structure. Specifically, the spindle structure includes a spindle body 1, which is the base of the entire spindle. It is usually made of high-strength cast iron or steel and then precision machined. It provides a precise mounting reference and structural support for all other components. The spindle contains rotating parts 2 and non-rotating parts 3. Rotating parts 2 refer to the parts of the spindle that actually rotate. Their core function is to drive the inner ring of the bearing to be tested to rotate at the target speed. Non-rotating parts 3 refer to the parts of the spindle that remain stationary or provide auxiliary functions such as support, cooling, and drive.

[0027] Example 2 like Figure 1-2 As shown, The main shaft consists of a rotating body 2 and a non-rotating body 3. The rotating body 2 includes a shaft core 4, a test bearing 5, a bearing washer 6, a locking nut 7, and a motor rotor 12. The shaft core 4 is the core of the entire rotating assembly, shaped like a stepped shaft. It has journals and shoulders for mounting the motor rotor 12, the test bearing 5, and the locking nut 7. The test bearing 5 is the bearing to be tested, usually used in pairs, and its inner ring needs to fit tightly with the shaft core 4 to transmit motion and torque. The bearing washer 6 is a key structural component, fitted onto the shaft core 4 and located on the side of the test bearing 5; its specific function will be explained in detail later. The locking nut 7 is used to axially lock the test bearing 5 and the bearing washer 6 in designated positions on the shaft core 4, preventing axial movement during high-speed rotation.

[0028] The non-rotating body 3 includes a front bearing housing 8, a rear bearing housing 9, a cooling water jacket 10, a main shaft body 1, and a motor stator assembly 11. The front bearing housing 8 and the rear bearing housing 9 support the front and rear test bearings 5, respectively, and are the key interfaces connecting the rotating body 2 and the non-rotating body 3. The cooling water jacket 10 provides forced liquid cooling to remove the enormous heat generated by high-speed operation. The motor stator assembly 11 is the stationary part of the motor, with coil windings inside. When energized, it generates a rotating magnetic field. The motor rotor 12 is the rotating part of the motor, mounted on the shaft core 4. Under the action of the rotating magnetic field generated by the motor stator assembly 11, it obtains driving torque, thereby driving the entire rotating body 2 to rotate.

[0029] In terms of assembly, the motor rotor 12 is fixedly mounted on the shaft core 4. The motor rotor 12 is a permanent magnet rotor, and a magnetic bonding process is used to attach the rotor to the shaft core 4. After that, glue is used to fix it, and the outer circle is then fixed with carbon fiber and glue to ensure that there is no relative movement between the two at high speeds. The motor stator assembly 11 is interference-fitted inside the spindle body 1, and its position is precisely aligned with the motor rotor 12. The shaft core 4 is mounted inside the spindle through the front bearing seat 8 and the rear bearing seat 9. That is, the shaft core 4 is supported on the front bearing seat 8 and the rear bearing seat 9 by two test bearings 5, and the front bearing seat 8 and the rear bearing seat 9 are fixed to the spindle body 1. The inner ring of the shaft core 4 and the test bearing 5 are interference fit, that is, the diameter of the journal on the shaft core 4 that mates with the test bearing 5 is slightly larger than the inner ring diameter of the bearing. This fit ensures that there will be no slippage or relative movement between the shaft core 4 and the inner ring of the bearing under ultra-high speed rotation, thus ensuring rotational accuracy and reliability of power transmission. The bearing washer 6 is set on one side of the test bearing 5. A bearing washer 6 is set on the inner side of both the front and rear test bearings 5 ​​(i.e., the side closer to the other bearing). A disassembly gap is provided between the bearing washer ring 6 and the shaft core 4. This is the core structure for achieving non-destructive disassembly. Specifically, the bearing washer ring 6 is fitted onto the shaft core 4, and its inner diameter is slightly larger than the diameter of the corresponding shaft segment on the shaft core 4, thus forming the disassembly gap. At the same time, the end face of the bearing washer ring 6 directly abuts against the end face of the inner ring of the test bearing 5. Here, "abuts" means that the two are in contact in the axial installation state, but they are not tightly joined like an interference fit. When it is necessary to disassemble the tested bearing 5 after testing, the operator can loosen the locking nut 7 and then use a special ring, with an inner diameter larger than that of the shaft core 4 and a step diameter smaller than that of the bearing washer ring 6, cut into two arc rings, to press against the end face of the bearing washer ring 6. Using a press or manual pressure tool, the two arc rings are pushed axially, and the sleeve transmits the force to the bearing washer ring 6. The bearing washer ring 6 then applies the force directly and evenly to the end face of the inner ring of the tested bearing 5, thereby pressing the tested bearing 5 off the shaft core 4. Because there is a disassembly gap between the bearing washer ring 6 and the shaft core 4, and the pressure is applied entirely to the inner ring of the bearing, the rolling elements, cage, and inner and outer raceways of the bearing do not bear additional disassembly forces that could cause damage during disassembly. This avoids the bearing deformation, raceway scratches, and other damage caused by using a puller to hook the outer ring of the bearing or striking the inner and outer rings in traditional disassembly methods. For extreme speed testing, the condition of the bearing after testing must accurately reflect its fatigue and wear after high-speed operation. Any disassembly damage will interfere with data interpretation. Therefore, this non-destructive disassembly structure is crucial to ensuring the accuracy of test results.

[0030] The front bearing housing 8 and the rear bearing housing 9 are clearance-fitted with the outer ring of the test bearing 5. That is, the diameter of the bearing housing bore is slightly larger than the diameter of the bearing outer ring. This tiny clearance (typically on the order of micrometers) allows the bearing outer ring a certain amount of free play within the bearing housing. Its purpose is that at high speeds, due to centrifugal force and thermal expansion, the outer ring of the test bearing 5 will undergo a slight radial expansion. The clearance fit provides space for this expansion, preventing excessive compression between the bearing outer ring and the bearing housing, preventing additional frictional heat and stress, and ensuring the bearing operates at optimal clearance. Meanwhile, the connection points between the front bearing housing 8 and the rear bearing housing 9 and the main spindle body 1 are equipped with end face mating surfaces, inner and outer edge mating surfaces, and hollowed-out mating surfaces. This is a high-precision multi-positioning structure. The end face mating surfaces ensure the perpendicularity of the bearing housing's axial installation; the inner and outer edge mating surfaces ensure the precise alignment of the bearing housing's radial position; the hollowed-out mating surfaces refer to the specific shaped concave-convex structures designed at the connection points, used to further restrict rotation or improve connection rigidity. The front bearing housing 8 and the rear bearing housing 9 are tightened to the main spindle body 1 by multiple high-strength bolts. This multi-matting surface and bolt-tightening connection method forms an extremely stable rigid connection. Its function is that when the main bearing is subjected to extremely high bending moments (for example, caused by unbalanced amounts or uneven magnetic pull), no slight relative displacement or vibration will occur between the bearing housing and the main spindle body 1, ensuring the structural integrity of the entire non-rotating body 3 and providing a solid support foundation for the main spindle at high speeds. The cooling water jacket 10 is fitted onto the outside of the front bearing housing 8, the motor stator assembly 11 is interference-fitted into the spindle body 1, and the rear bearing housing 9 is fitted into the spindle body 1 with a precise surface fit for efficient heat transfer. At least two O-rings 13 are provided between the cooling water jacket 10 and the front bearing housing 8, between the motor stator assembly 11 and the spindle body 1, and between the rear bearing housing 9 and the spindle body 1. The purpose of the O-rings 13 is to prevent coolant from leaking into the motor chamber or bearing chamber through the assembly gaps between the cooling water jacket 10 and the front bearing housing 8, the motor stator assembly 11 and the spindle body 1, and the rear bearing housing 9 and the spindle body 1, thus preventing electrical short circuits or lubricant (grease) emulsification and failure. The cooling water jacket 10 has a coolant inlet, and the spindle body 1 has a coolant outlet, for connecting to an external circulating coolant pipeline. The cooling water jacket 10 is fastened to the front bearing housing 8 with screws. This connection method fixes the cooling water jacket 10 and the front bearing housing 8 into one unit, and the front bearing housing 8 directly contacts the outer ring of the heated test bearing 5. The motor stator assembly 11 is interference-fitted into the spindle body 1 and fixed into one unit. The rear bearing housing 9 is fastened to the spindle body 1 with screws and fixed into one unit, and the rear bearing housing 9 directly contacts the outer ring of the heated test bearing 5 at the rear end. The purpose of this overall structure is to establish an efficient cooling path: coolant enters through the cooling water jacket 10, carrying away the heat transferred from the test bearing 5 to the front bearing housing 8. From the cooling water jacket 10, the coolant flows through the connection between the front bearing housing 8 and the spindle body 1 into the motor stator assembly 11 for cooling circulation, carrying away the heat generated by the motor stator during operation. Then, it flows through the spindle body 1 into the annular groove of the rear bearing housing 9 to circulate and carry away the heat transferred from the rear test bearing 5 to the rear bearing housing 9. Finally, it flows out through the spindle body 1 into the cooling machine. This allows the temperature of the motor and bearings to be effectively controlled within a safe range during prolonged ultra-high-speed operation at 60,000 rpm, ensuring stable lubrication and material properties and preventing thermal failures. The motor is a back-wound motor, and the motor rotor 12 is a permanent magnet synchronous motor rotor. During the design process, the inner diameter of the motor stator assembly 11 was larger than the outer diameter of the test bearing 5. This design allows the rotating body 2 to be disassembled into the main shaft as a single unit. The air gap between the stator assembly 11 and the motor rotor 12 is larger than that of a typical motor, significantly weakening the attraction between the permanent magnets and the magnetic pull between them and the stator. The permanent magnets of the motor rotor 12 are bonded and embedded on the outer circumferential surface of the shaft core 4. This structure generates a short magnetic field path and high air gap magnetic flux density, resulting in a larger torque. The back-wound structure, with the windings mounted on the outside of the stator yoke, serves two purposes: first, it eliminates harmonic losses, making it easier for the motor rotor 12 to be driven to extremely high speeds (60,000 rpm), meeting the requirements of high-speed fatigue testing; second, the shorter winding ends result in lower copper losses, reducing the motor's own heat generation and improving the thermal stability of the main shaft operation. Furthermore, the shaft core 4 has a hollow internal structure. This structure is crucial: at ultra-high speeds (60,000 rpm), any rotating body experiences enormous centrifugal force. A solid shaft core 4 would be too rigid, causing radial outward expansion under centrifugal force. If the rigidity is too high, the expansion would be insufficient, while simultaneously, the thin inner ring of the bearing mounted outside the shaft core 4 would be stretched, disrupting the interference fit between the bearing inner ring and the shaft core 4, and potentially causing the rolling elements to derail, slip, and lead to instantaneous bearing failure. The hollow structure, while ensuring the basic structural strength required to transmit sufficient torque, achieves appropriate radial expansion through the centrifugal force generated during rotation. This allows the rotor to maintain dimensional stability at ultra-high speeds, ensuring the fitting accuracy and operational safety of the test bearing 5 it mates with. The span between the front and rear test bearings is 3.5 times the bearing's inner diameter. This is a macroscopic dimensional feature reflecting the design philosophy of short span and high rigidity. Specifically, the shaft core 4 is designed to be relatively short and thick, meaning the ratio of the bearing's inner diameter (e.g., 45mm) to the center distance between the two test bearings (e.g., 157.5mm) is 1:3.5. With this bearing span, high-speed operation stability is further enhanced. Its function and principle can be compared to a stick: a short stick with a thick diameter (short and thick stick) is more difficult to bend than a long stick with a thin diameter (slender stick). Here, the overall bending stiffness of the spindle is inversely proportional to the cube of its span. By intentionally shortening the span between the front and rear bearings (bringing the support points closer together) and simultaneously increasing the diameter of the spindle body 1 (increasing the moment of inertia of the section), the bending stiffness of the spindle structure of this invention is exponentially improved. This is crucial for ultra-high-speed operation: first, the extremely high stiffness ensures that the critical speed of the spindle (the speed at which the system resonates) is much higher than the operating speed of 60,000 rpm, thereby avoiding dangerous resonance phenomena within the test speed range; second, even with a small rotor imbalance, the high rigidity can control the resulting bending amplitude within a very small range, ensuring the rotational stability of the shaft core 4, thereby improving the accuracy of the dynamic performance evaluation of the test bearing 5; A preload mechanism is provided on the rear bearing housing 9. For bearings such as angular contact ball bearings, an appropriate axial preload must be applied during high-speed operation to improve bearing rigidity and ensure that the rolling elements move on the correct track. If the preload is insufficient, the bearing will slip and vibrate at high speeds; if the preload is too large, it will cause a sharp increase in friction, leading to overheating and burnout of the bearing. Therefore, the preload mechanism includes a preload spring cover 14, a preload spring 15, and a bearing preload ring 16. The preload spring 15 is installed between the preload spring cover 14 and the bearing preload ring 16. Specifically, the preload spring 15 can be a helical spring, a disc spring, or a wave spring. One end of the bearing preload ring 16 abuts against the preload spring 15, and the other end abuts against the outer ring end face of the test bearing 5. The function of this structure is that the preload spring 15 is compressed between the preload spring cover 14 and the rear bearing housing 9, and the elastic restoring force generated by it is transmitted through the bearing preload ring 16 to the outer ring of the rear test bearing 5, applying a continuous axial thrust to the bearing. This thrust is transmitted through the shaft core 4 and the spacer (if present) between the two bearings to the front test bearing 5, thereby achieving simultaneous preload on both bearings. This spring preload method is a constant force preload or flexible preload. Compared with rigid preload (such as directly pressing with lock nut 7), it can better adapt to the changes in bearing size caused by centrifugal force and thermal expansion at high speeds, and always maintain a relatively stable and appropriate preload force. The preload spring cover 14 is provided with an adjusting thread. Specifically, the preload spring cover 14 can be screwed into the internal thread of the rear bearing housing 9 via an external thread, or connected to the threaded hole on the rear bearing housing 9 via a bolt. By rotating the preload spring cover 14, its axial position can be changed, thereby changing the distance between it and the rear bearing housing 9, and thus adjusting the compression of the preload spring 15. The purpose of this structure is to provide adjustable preload. The optimal preload required varies depending on the test bearing 5 (different sizes, materials, lubrication methods) or the test conditions (different speeds). Operators can refer to the relationship curve between preload and spring compression and precisely set the required preload by rotating the preload spring cap 14. For example, to increase the preload, the preload spring cap 14 is screwed inward to further compress the spring; to decrease the preload, it is screwed outward to loosen it. This design allows the same test spindle to flexibly adapt to various test requirements, greatly improving the equipment's versatility and test accuracy. If needed, a pressure sensor can be integrated into the bearing preload ring 16 or the preload spring cap 14 for real-time monitoring of dynamic preload. A labyrinth seal gap 17 is provided between the front bearing housing 8, the bearing preload ring 16, and the shaft core 4. The labyrinth seal gap 17 is formed by the interlacing of annular protrusions on the shaft core 4 and annular grooves on the bearing housing. That is, several outwardly protruding annular teeth (protrusions) are machined on the shaft core 4, while several inwardly recessed annular grooves (grooves) are machined on the corresponding inner wall of the bearing housing. After assembly, these protrusions and grooves intersect but do not contact each other, forming a tortuous and narrow gap channel. The function of this structure is to prevent external contaminants (such as dust, wear debris, and moisture) from entering the precision bearing cavity, and also to prevent the leakage of lubricating grease inside the bearing. Under ultra-high speed rotation, ordinary contact seals (such as rubber oil seals) will experience severe wear and high temperature due to the huge linear velocity, and fail rapidly. The labyrinth seal is a non-contact seal that utilizes the throttling effect and eddy current dissipation principle generated when fluid flows through a tortuous channel: the pressure and velocity of contaminants or leaked grease decrease significantly with each bend in the labyrinth, eventually making it almost impossible to pass through the entire labyrinth path. Due to the presence of the labyrinth seal gap 17, even if the shaft core 4 rotates at 60,000 rpm, it will not rub against the bearing housing, resulting in no wear, an infinitely long service life, and complete suitability for ultra-high-speed operating conditions. The motor stator assembly 11 has a side-outlet wiring configuration, meaning the power and signal cables of the motor stator assembly 11 are led out from a side opening in the spindle body 1. A gland secures the power cable to the side of the spindle body 1, and the drive cable of the motor stator assembly 11 is fixed to an external driver, not to the spindle itself. Furthermore, the inner diameter of the motor stator assembly 11 is larger than the outer diameter of the test bearing 5, allowing the test bearing 5 to pass through the inner diameter of the motor stator assembly 11. This structure enables integrated quick-release. In traditional test spindles, the motor cable is typically fixed to the rear end face of the spindle. When the spindle needs to be disassembled to replace the test bearing 5, the cable connector must be removed, and re-soldering may be necessary, a cumbersome process with a risk of incorrect connection. In this invention, since the cable extends directly along the side of the spindle body 1 and is fixed to an external driver, the cable does not move during disassembly of the entire rotating body 2 and non-rotating body 3 (except for the fixed stator portion), eliminating the need for any electrical disassembly operations. Specifically, when the bearing needs to be replaced, the operator only needs to loosen the bolts between the preload spring cover 14 and the rear bearing housing 9, remove the preload spring cover 14, and then pull the rotating body 2 out along the rear axial direction. Since the drive cable is fixed externally, this plugging and unplugging action will not affect the electrical connection. After replacing the new test bearing 5, the entire assembly is pushed back into the motor body and locked again. This achieves a standardized and rapid five-step operation of loosening, pulling, replacing, pushing, and locking, reducing the bearing replacement time from several hours to tens of minutes, greatly improving testing efficiency.

[0031] Workflow of this invention: When using a spindle structure suitable for bearing limit speed testing, first determine the model of the bearing 5 to be tested and the target speed (e.g., 60,000 rpm). Then, by rotating the preload spring cover 14, accurately set the initial compression of the preload spring 15, thereby applying a suitable axial preload force to the bearing 5 to be tested. Next, the external circulating coolant system is started. The coolant enters through the inlet of the cooling water jacket 10, flows through the inside of the water jacket, the stator assembly 11, and the rear bearing housing 9, and returns from the outlet to force cooling of the motor stator assembly 11 and the front and rear bearing housings 9. Then, the external driver is activated, supplying power to the motor stator assembly 11 via a side-mounted cable. The motor stator assembly 11 generates a rotating magnetic field, driving the motor rotor 12 to rotate the shaft core 4. The shaft core 4, through an interference fit, drives the inner rings of the two test bearings 5 ​​to rotate synchronously. During acceleration to 60,000 rpm, the short-span, high-rigidity shaft core 4 ensures system stability and avoids resonance. The labyrinth seal gap 17 provides non-contact protection throughout the process. Once the spindle reaches and stabilizes at the target speed, performance tests (such as temperature rise, vibration, and noise) at the limit speed of the test bearing 5 can begin. After the tests are completed, the drive and cooling system are shut down. Bearing disassembly is then performed: loosen the bolts between the preload spring cover 14 and the rear bearing housing 9, remove the preload spring cover 14, and pull the rotating body 2 out along the rear axial direction. Loosen the lock nut 7, use a special tool to press against the end face of the bearing washer ring 6, and use a hydraulic or manual press to press the test bearing 5 out of the shaft core 4 without damage. Repeat this process to disassemble the front and rear bearings sequentially. Because there is a disassembly gap between the bearing washer ring 6 and the shaft core 4, the disassembly force is only applied to the end face of the bearing inner ring, without damaging the bearing raceway and rolling elements, ensuring the authenticity and validity of the bearing condition data after testing. Finally, install the new bearing 5 to be tested onto the shaft core 4 and lock it with the lock nut 7. After the front and rear bearings are installed in sequence, push the entire rotating body 2 assembly back into the main shaft body 1 along the axis. Then install the bearing preload ring 16, preload spring 15 and preload spring cover 14 in sequence, and lock the connecting bolts between the preload spring cover 14 and the rear bearing seat 9. The next test can then be started quickly.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A spindle structure suitable for bearing limit speed test, characterized in that: The main shaft consists of a rotating body (2) and a non-rotating body (3). The rotating body (2) includes a shaft core (4), a test bearing (5), a bearing washer (6), a locking nut (7), and a motor rotor (12). The non-rotating body (3) includes a main shaft body (1), a front bearing seat (8), a rear bearing seat (9), a cooling water jacket (10), and a motor stator assembly (11). The motor rotor (12) is mounted on the shaft core (4). The motor stator assembly (11) is interference-fitted inside the main shaft body (1). At least two O-ring seals (13) are provided between the motor stator assembly (11) and the main shaft body (1). The shaft core (4) is mounted inside the main shaft through the front bearing seat (8) and the rear bearing seat (9). The inner ring of the shaft core (4) and the test bearing (5) are interference-fitted. The bearing washer (6) is located on one side of the test bearing (5).

2. The spindle structure suitable for bearing limit speed testing according to claim 1, characterized in that: A disassembly gap is provided between the bearing washer (6) and the shaft core (4), and the end face of the bearing washer (6) directly abuts against the inner ring end face of the test bearing (5).

3. A spindle structure suitable for bearing limit speed testing according to claim 1, characterized in that: The front bearing housing (8) and the rear bearing housing (9) are clearance fit with the outer ring of the test bearing (5). The connection between the front bearing housing (8) and the rear bearing housing (9) and the main shaft body (1) is provided with an end face mating surface and an inner hole outer circle mating surface. The front bearing housing (8) and the main shaft body (1) are provided with O-ring seals (13) on their end faces. At least two O-ring seals (13) are provided between the rear bearing housing (9) and the outer circle inner hole of the main shaft body (1). The front bearing housing (8) and the rear bearing housing (9) are tightened onto the main shaft body (1) by bolts.

4. A spindle structure suitable for bearing limit speed testing according to claim 1, characterized in that: The cooling water jacket (10) is fitted onto the outside of the front bearing housing (8). At least two O-rings (13) are provided between the cooling water jacket (10) and the front bearing housing (8). The cooling water jacket (10) is provided with a coolant inlet, and the spindle body (1) is provided with a coolant outlet. The cooling water jacket (10) and the front bearing housing (8) are connected by screws.

5. The spindle structure suitable for testing the limit speed of a bearing according to claim 1, characterized in that: The motor rotor (12) is a permanent magnet synchronous motor rotor, which is installed using a magnetic attachment method. The motor rotor (12) is magnetically attached to the shaft core (4) and fixed using a specific adhesive. The air gap between the stator assembly (11) and the motor rotor (12) is relatively large, and the inner hole size of the stator assembly (11) is larger than the outer circle size of the test bearing (5).

6. The spindle structure suitable for testing the limit speed of a bearing according to claim 1, characterized in that: The span between the front and rear test bearings (5) is 3.5 times the inner diameter of the bearing.

7. The spindle structure suitable for testing the limit speed of a bearing according to claim 1, characterized in that: The rear bearing housing (9) is provided with a pre-tightening mechanism, which includes a pre-tightening spring cover (14), a pre-tightening spring (15) and a bearing pre-tightening ring (16). The pre-tightening spring (15) is installed between the pre-tightening spring cover (14) and the bearing pre-tightening ring (16). One end of the bearing pre-tightening ring (16) abuts against the pre-tightening spring (15), and the other end abuts against the outer ring end face of the test bearing (5).

8. The spindle structure suitable for testing the limit speed of a bearing according to claim 7, characterized in that: The preload spring cover (14) is provided with an adjustment thread, and the compression of the preload spring (15) can be adjusted by rotating the preload spring cover (14).

9. The spindle structure suitable for testing the limit speed of a bearing according to claim 1, characterized in that: A labyrinth seal gap (17) is provided between the front bearing housing (8), the bearing preload ring (16) and the shaft core (4). The labyrinth seal gap (17) is formed by the interlacing of the annular protrusion on the shaft core (4) and the annular groove on the bearing housing.

10. The spindle structure suitable for testing the limit speed of a bearing according to claim 1, characterized in that: The stator assembly (11) of the motor has its cable exiting from the side of the spindle body (1). The power cable is secured to the side of the spindle body (1) with a gland, and the drive cable of the stator assembly (11) is fixed to an external driver.

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