A boron nitride tool grinding device

Abstract

The application discloses a boron nitride cutter grinding device and relates to the technical field of superhard cutter processing. The system comprises a rotating driving shaft and a grinding wheel, a synchronous rotation liquid supply and return wheel is coaxially arranged at the non-grinding end face of the grinding wheel, a liquid supply cavity and a return flow cavity which are isolated from each other are arranged in the liquid supply and return wheel, a vortex heat exchange channel is arranged in the grinding wheel, a variable cross-section fluid outlet which is distributed in the radial direction and extends to the grinding working face is arranged on the outer circumferential surface of the grinding wheel, a fluid input port and a fluid output port which are correspondingly connected are arranged on the combined surface of the liquid supply and return wheel and the grinding wheel, the heat exchange channel is connected with the three parts at the same time, and a dynamic and static sealing rotary joint is arranged on the outside of the liquid supply and return wheel to realize the connection between the rotating cavity and the external static pipeline. Therefore, the centrifugal force is utilized to drive the cooling liquid to form a self-circulation, the cooling liquid directly reaches the grinding arc area, the limitation of the air barrier layer is completely broken, the grinding temperature is obviously reduced, and the processing yield and the production efficiency are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of superhard tool processing technology, and in particular to a boron nitride tool grinding apparatus. Background Technology

[0002] Cubic boron nitride (CBN) and polycrystalline cubic boron nitride (PCBN) cutting tools, with their extremely high hardness, wear resistance, and thermal stability, have become core tools for machining difficult-to-machine materials such as hardened steel, high-temperature alloys, and titanium alloys. They are widely used in high-end manufacturing fields such as aerospace, automotive manufacturing, and precision mold making. As the manufacturing industry continues to demand higher machining accuracy and efficiency, the cutting edge quality, geometric accuracy, and surface integrity of superhard cutting tools directly determine the machining performance of the final product. Therefore, high-precision grinding of these tools has become the most critical link in the superhard cutting tool manufacturing industry chain.

[0003] However, grinding of superhard cutting tools is a typical high-energy-density machining process. The intense friction between the abrasive grains and the workpiece surface, plastic deformation, and chip fracture generate instantaneous high temperatures in the grinding arc zone, with local temperatures exceeding 1000°C. This extreme high-temperature environment easily leads to oxidation, graphitization phase transformation, and thermal softening of the tool surface, while generating enormous thermal stress, which in turn forms grinding cracks and residual tensile stress, severely reducing the cutting life and reliability of the tool.

[0004] To address the problem of heat damage during grinding, the industry commonly employs external nozzle casting for cooling. However, when the grinding wheel rotates at high speed, it forms a high-pressure air barrier layer on its surface that can be several millimeters thick. More than 90% of the coolant is blocked by this air barrier layer and cannot enter the grinding arc zone, resulting in extremely low actual heat exchange efficiency.

[0005] Therefore, we believe that there is an urgent need for an internal cooling grinding wheel system that can fundamentally solve the problem of thermal damage during the grinding process of superhard tools, overcome the limitations of the air barrier layer, and allow the cooling medium to reach the grinding arc zone directly, so as to achieve efficient, high-precision, and low-damage grinding of superhard tools. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention develops a boron nitride tool grinding device. This device has the advantage of allowing coolant to directly reach the grinding arc zone, thus improving cooling efficiency.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A boron nitride tool grinding device includes a rotary drive shaft and a grinding wheel fixed on the rotary drive shaft and rotating synchronously with it. A supply and return fluid wheel is coaxially arranged on the non-grinding end face of the grinding wheel. The supply and return fluid wheel rotates synchronously with the grinding wheel, and its interior forms a mutually isolated supply chamber and a return chamber. A fluid inlet and a fluid outlet are provided on the mating surface of the supply and return fluid wheel and the grinding wheel. The fluid inlet communicates with the supply chamber, and the fluid outlet communicates with the return chamber. A heat exchange channel is provided inside the grinding wheel, and multiple radially distributed fluid outlets are opened on the outer circumferential surface of the grinding wheel. The heat exchange channel communicates with the fluid inlet, fluid outlet, and fluid outlet, and the outer end of each fluid outlet extends to the grinding working surface of the grinding wheel. A dynamic-static sealing rotary joint is provided on the side of the supply and return fluid wheel away from the grinding wheel. The supply chamber and the return chamber are respectively connected to external stationary supply and return fluid pipelines through the dynamic-static sealing rotary joint.

[0009] Preferably, the heat exchange channel has a vortex structure, with the inner edge of the heat exchange channel connected to the fluid inlet and the outer edge of the heat exchange channel connected to the fluid outlet.

[0010] Preferably, the heat exchange channel includes a circumferential channel and a spiral channel, wherein the circumferential channel is located outside the spiral channel and smoothly transitions with the spiral channel, and each fluid outlet is connected to the circumferential channel.

[0011] Preferably, the substrate of the grinding wheel is 3D printed using selective laser melting technology, and the outer peripheral surface of the grinding wheel is bonded with an ultrahard abrasive layer through electroplating or brazing.

[0012] Preferably, the fluid outlet includes, in sequence along the fluid flow direction, an inlet expansion section, a middle narrowing section, and an outlet expansion section, wherein the diameter of the middle narrowing section is smaller than the minimum diameter of the inlet expansion section and the outlet expansion section.

[0013] Preferably, the central axis of all fluid outlets points to the rotation center of the grinding wheel, and the multiple fluid outlets are evenly arranged circumferentially along the central axis of the rotary drive shaft.

[0014] Preferably, the rotary joint for dynamic and static sealing includes a rotary joint dynamic ring seat and a rotary joint static ring seat, wherein the rotary joint dynamic ring seat is sealed and fixedly connected to the supply and return liquid wheel, and the rotary joint dynamic ring seat and the rotary joint static ring seat are rotatably connected by an end face mechanical seal pair.

[0015] Preferably, the rotary joint moving ring seat has exchange holes for the liquid supply chamber and the return chamber respectively, and a filter screen is fixedly connected to the exchange hole for the liquid supply chamber on the rotary joint moving ring seat. The rotary joint stationary ring seat has through holes for the liquid supply chamber and the return chamber respectively, and a connector is sealed and fixedly connected in the through hole. The rotary joint stationary ring seat is connected to the external stationary liquid supply and return pipelines through the connectors respectively.

[0016] Preferably, a grinding wheel protective cover is also provided on the outside of the grinding wheel, and an acoustic emission sensor and an infrared temperature sensor are fixedly connected on the grinding wheel protective cover. When the infrared temperature sensor detects that the grinding temperature exceeds a preset threshold or the acoustic emission sensor detects that the acoustic emission signal is abnormal, the control system controls the machine tool to retract the tool, increase the fluid supply flow, and / or stop the rotation drive shaft.

[0017] A method for grinding boron nitride cutting tools includes the following steps:

[0018] S1. Start the external liquid supply circulation system and deliver pressurized coolant to the supply chamber inside the supply and return liquid wheel through the dynamic and static sealing rotary joint. The coolant enters the inner edge of the vortex heat exchange channel inside the grinding wheel through the fluid inlet on the mating surface of the supply and return liquid wheel and the grinding wheel. After the coolant fills all the heat exchange channels and is stably sprayed out from all fluid outlets, the system pre-filling is completed.

[0019] S2. Start the rotary drive shaft to drive the grinding wheel and the supply and return fluid wheel to rotate synchronously at a preset speed. Under the combined action of centrifugal force and supply force, the coolant flows from the inner edge to the outer edge along the vortex heat exchange channel, and at the same time, it undergoes forced convection heat exchange with the grinding wheel base to remove the heat conducted to the base during the grinding process.

[0020] S3. Control the machine tool feed mechanism to drive the grinding wheel to contact the superhard tool to be processed for grinding operation. Part of the coolant flowing to the outer edge of the heat exchange channel is sprayed out at high speed from the fluid outlet on the outer circumference of the grinding wheel, directly impacting the grinding arc area for forced cooling. The other part flows back to the return cavity of the supply and return fluid wheel through the fluid outlet, and finally returns to the external fluid supply circulation system through the dynamic and static sealing rotary joint, forming a closed cooling cycle.

[0021] S4. During the grinding process, the temperature signal and acoustic emission signal of the grinding arc area are collected in real time by acoustic emission sensor and infrared temperature sensor. When the grinding temperature exceeds the preset threshold or the acoustic emission signal shows abnormal characteristics, the control system sequentially performs protection actions such as rapid tool retraction and increasing fluid supply flow. If the abnormal signal is not recovered within the preset delay, the rotary drive axis and machine tool feed will be stopped automatically and an audible and visual alarm will be triggered.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention, through the innovative design of a split main and auxiliary wheel structure and a vortex-type internal cooling channel, fully utilizes the centrifugal force generated by the high-speed rotation of the grinding wheel as the main driving force for the flow of coolant. This not only significantly reduces the requirements for external liquid supply pressure and alleviates the burden on the sealing system, but also achieves forced convection heat transfer from the inside of the grinding wheel directly to the grinding arc area. It completely breaks through the air barrier limitation of traditional external cooling methods and effectively eliminates thermal damage such as thermal burns, phase changes, and cracks during the grinding of superhard tools. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0025] Figure 2 This is a schematic diagram showing the positional relationship between the grinding wheel and the supply / return fluid wheel of the present invention.

[0026] Figure 3 This is a schematic diagram of the internal structure of the grinding wheel of the present invention.

[0027] Figure 4 This is a schematic diagram of the overall structure of the fluid outlet of the present invention.

[0028] Figure 5 This is a schematic diagram showing the connection relationship between the grinding wheel and the supply and return fluid wheel of the present invention.

[0029] Figure 6 This is a schematic diagram showing the relationship between the rotating joint moving ring seat and the supply and return liquid wheel of the present invention.

[0030] Figure 7 This is a schematic diagram showing the fit between the rotary joint moving ring seat and the end face mechanical seal pair of the present invention.

[0031] Figure 8 This is a schematic diagram showing the connection relationship between the rotating joint moving ring seat and the rotating joint stationary ring seat of the present invention.

[0032] In the diagram: 1. Grinding wheel protective cover; 2. Rotary joint with dynamic and static seals; 201. Rotary joint dynamic ring seat; 202. End face mechanical seal pair; 203. Exchange hole; 204. Filter screen; 205. Rotary joint static ring seat; 206. Through hole; 3. Rotary drive shaft; 4. Joint; 5. Grinding wheel; 6. Fluid outlet; 601. Outlet expansion section; 602. Middle narrowing section; 603. Inlet expansion section; 7. Superhard abrasive layer; 8. Supply and return fluid wheel; 9. Heat exchange channel; 901. Circumferential channel; 902. Spiral channel; 10. Fluid outlet; 11. Fluid inlet; 12. Supply chamber; 13. Return chamber; 14. Acoustic emission sensor; 15. Infrared temperature sensor. Detailed Implementation

[0033] 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.

[0034] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., 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 device 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 on this invention.

[0035] Please refer to Figure 1-8 A boron nitride tool grinding device is proposed, which mainly addresses common technical problems in the industry such as high-temperature thermal damage in the grinding arc zone and low heat exchange efficiency of traditional external cooling methods due to air barriers.

[0036] For details, please refer to Figure 1 , Figure 2 Consistent with existing technology devices, this device mainly includes a rotary drive shaft 3 and a grinding wheel 5. In practice, the rotary drive shaft 3 serves as the power input component of the system, coaxially connected to the machine tool spindle and transmitting rotary motion; the grinding wheel 5 is fixedly installed at the end of the rotary drive shaft 3, rotating synchronously at high speed with the rotary drive shaft 3, directly performing the grinding task on the superhard tool.

[0037] Unlike existing technology devices, the grinding wheel 5 of this device has a heat exchange channel 9 inside, and multiple radially distributed fluid outlets 6 are opened on the outer circumferential surface of the grinding wheel 5. At the same time, fluid inlet 11 and fluid outlet 10 are respectively provided at both ends of the heat exchange channel 9.

[0038] Specifically, such as Figure 3 , Figure 4 As shown, the heat exchange channel 9 adopts a vortex structure design. The inner edge of the heat exchange channel 9 is connected to the fluid inlet 11 on the mating surface of the supply and return fluid wheel 8, and the outer edge of the heat exchange channel 9 is connected to the fluid outlet 10. This design is completely in line with the direction of centrifugal force generated by the high-speed rotation of the grinding wheel 5, so that the coolant flows naturally from the inner edge to the outer edge under the drive of centrifugal force, without the need for additional return power.

[0039] When the grinding wheel 5 rotates at high speed, the coolant entering the heat exchange channel 9 from the inner fluid inlet 11 is accelerated and thrown towards the outer edge of the channel, that is, the side close to the outer circumference of the grinding wheel 5, under the continuous action of centrifugal force. Since the heat exchange channel 9 adopts a vortex structure, the coolant forms a strong three-dimensional vortex when flowing in the channel. This vortex motion can significantly enhance the turbulent disturbance between the coolant and the channel wall, completely destroy the formation of the laminar boundary layer, thereby greatly improving the convective heat transfer coefficient and enhancing the heat transfer effect.

[0040] It is particularly worth emphasizing that the presence of centrifugal force also significantly reduces the system's requirement for external fluid supply pressure during operation. In actual operation, even if the coolant pressure at the fluid inlet 11 is low, the enormous centrifugal force generated by the high-speed rotation of the grinding wheel 5 can still throw the coolant out of the smaller fluid outlet 6 at high speed, achieving effective cooling of the grinding arc area.

[0041] Correspondingly, the centrifugal force also creates a natural pressure gradient distribution within the system: the coolant pressure is lowest at the fluid inlet 11 (inner edge), gradually increasing radially outward along the heat exchange channel 9, reaching its highest value at the outer edge of the channel, and the pressure at the fluid outlet 10 is significantly higher than that at the inlet. This pressure distribution characteristic is of great significance: on the one hand, the lower inlet pressure can significantly reduce the pressure requirements on the dynamic and static sealing rotary joint 2 and the sealing system, significantly improving the sealing reliability of the system under high-speed rotation and extending the service life of the seals; on the other hand, the higher local pressure inside the heat exchange channel 9 can increase the boiling point of the coolant, preventing the coolant from vaporizing at high temperatures and ensuring the stable operation of the cooling system.

[0042] Meanwhile, the vortex structure also extends the flow path of the coolant inside the grinding wheel 5, increases the contact time between the coolant and the grinding wheel substrate, and enables the coolant to absorb the heat of the grinding wheel substrate more fully, further improving the cooling efficiency.

[0043] Specifically, the outer circumferential surface of the grinding wheel 5 has multiple radially distributed fluid outlets 6. This device ensures that the central axis of all fluid outlets 6 points towards the rotation center of the grinding wheel 5, and the multiple fluid outlets 6 are evenly distributed circumferentially along the central axis of the rotary drive shaft 3. This guarantees that the coolant is sprayed evenly throughout the circumference of the grinding wheel 5, achieving full coverage cooling of the grinding arc area and avoiding thermal damage caused by insufficient local cooling. At the same time, the radially center-pointing design ensures that the direction of the coolant spray is perpendicular to the rotational tangent of the grinding wheel 5, maximizing the utilization of the coolant's kinetic energy and allowing it to directly impact the core of the grinding arc area, significantly improving the cooling effect.

[0044] In addition, this device also constrains each fluid outlet 6 to include three parts in sequence along the fluid flow direction: an inlet expansion section 603, an intermediate narrowing section 602, and an outlet expansion section 601, wherein the diameter of the intermediate narrowing section 602 is smaller than the minimum diameter of the inlet expansion section 603 and the outlet expansion section 601.

[0045] In practice, the variable cross-section structure design offers significant hydrodynamic advantages: when the coolant enters the narrowing section 602, the cross-sectional area of ​​the flow channel decreases, the coolant velocity increases rapidly, and the pressure decreases significantly. Subsequently, as the coolant enters the expanding section 601, the cross-sectional area of ​​the flow channel increases again, the coolant velocity decreases appropriately, and a uniform fan-shaped spray is formed, significantly increasing the cooling coverage area, while the pressure continues to decrease. Therefore, the coolant can acquire sufficient initial kinetic energy when it exits the fluid outlet 6, thus more effectively breaking through the air barrier layer around the grinding arc zone and directly reaching the grinding point for cooling. Simultaneously, the coolant undergoes evaporation and cooling during the spraying process due to the rapid pressure drop, further enhancing its cooling capacity and enabling it to more effectively remove heat from the grinding arc zone, reducing the grinding temperature.

[0046] In summary, as Figure 3 As shown, in a preferred embodiment, the heat exchange channel 9 includes two parts: a circumferential channel 901 and a spiral channel 902. The circumferential channel 901 is located outside the spiral channel 902, extends along the inner circumferential direction of the grinding wheel 5 base, and all fluid outlets 6 are connected to the circumferential channel 901.

[0047] During operation, coolant enters the spiral channel 902 from the fluid inlet 11 on the inner edge. Under the action of centrifugal force, it flows outward along the spiral channel 902 and finally merges into the circumferential channel 901 on the outer edge. The circumferential channel 901, acting as an annular liquid collection chamber, can evenly distribute the coolant to each fluid outlet 6, ensuring that the spray volume and spray pressure at each fluid outlet 6 are basically consistent, thereby achieving uniform cooling along the entire circumference of the grinding wheel 5. Simultaneously, the circumferential channel 901 also plays a role in pressure stabilization and energy storage, effectively buffering pressure fluctuations during coolant flow and ensuring the stability of system operation.

[0048] Specifically, such as Figure 2 , Figure 5 As shown, the device also includes a supply and return fluid wheel 8 disposed on the non-grinding end face side of the grinding wheel 5. The supply and return fluid wheel 8 is coaxially arranged with the rotary drive shaft 3 and rotates synchronously with the grinding wheel 5. Meanwhile, the interior of the supply and return fluid wheel 8 is divided by a partition to form a completely isolated supply chamber 12 and a return chamber 13, wherein the fluid inlet 11 is connected to the supply chamber 12 and the fluid outlet 10 is connected to the return chamber 13.

[0049] At the same time, such as Figure 6 , Figure 7 , Figure 8 As shown, the device also includes a dynamic and static sealing rotary joint 2 disposed on the side of the supply and return fluid wheel 8 away from the grinding wheel 5, which is used to achieve fluid communication between the externally stationary supply and return fluid pipeline and the internal flow path of the supply and return fluid wheel 8 that rotates with the shaft.

[0050] In practice, the rotary joint 2 mainly consists of two parts: a rotating ring seat 201 and a stationary ring seat 205. The rotating ring seat 201 is sealed and fixedly connected to the supply and return fluid impeller 8, rotating synchronously with the supply and return fluid impeller 8 and the grinding wheel 5. The stationary ring seat 205 is connected to the external stationary supply and return fluid pipeline, maintaining a stationary state. The rotating ring seat 201 and the stationary ring seat 205 are sealed and rotatably connected by an end-face mechanical seal pair 202 to ensure reliable sealing under high-speed rotation and certain pressure, preventing coolant leakage.

[0051] Furthermore, the rotary joint moving ring seat 201 is provided with exchange holes 203 for the liquid supply chamber 12 and the return chamber 13, respectively, and the exchange holes 203 communicate with the liquid supply chamber 12 and the return chamber 13. A filter screen 204 is fixedly connected to the exchange hole 203 for the liquid supply chamber 12 on the rotary joint moving ring seat 201. This filter screen 204 can filter the coolant entering the liquid supply chamber 12, remove impurity particles from the coolant, and prevent impurities from entering the heat exchange channel 9 and fluid outlet 6 inside the grinding wheel 5 and causing blockage.

[0052] In addition, such as Figure 1 , Figure 8 As shown, a through hole 206 is provided on the rotary joint stationary ring seat 205, and a connector 4 is sealed and fixedly connected inside the through hole 206. The rotary joint stationary ring seat 205 is connected to the external stationary supply and return liquid pipeline through the connector 4.

[0053] It is worth noting that the end-face mechanical seal pair 202 adopts a mechanical seal structure. The end-face mechanical seal pair 202 is an axial end-face sealing device that achieves sealing by relying on the pre-tightening of the stationary and rotating ring end-face sealing pairs by elastic elements and the compression of the medium pressure with the elastic element pressure. Specifically, the stationary ring is fixedly installed on the end face of the rotary joint stationary ring seat 205, and the rotating ring is fixedly installed on the end face of the rotary joint rotating ring seat 201. The end faces of the stationary ring and the rotating ring are tightly fitted, forming a pair of sealing friction pairs. The elastic element provides pre-tightening force, ensuring that the end faces of the stationary ring and the rotating ring always maintain close contact, guaranteeing the reliability of the seal. Auxiliary sealing components include O-rings, wedge rings, etc., used to achieve static sealing between the stationary ring and the rotary joint stationary ring seat 205, and between the rotating ring and the rotary joint rotating ring seat 201, preventing coolant leakage from these mating gaps.

[0054] During operation, the rotating ring rotates synchronously at high speed with the rotating joint's moving ring seat 201 and the supply and return fluid impeller 8, while the stationary ring remains stationary. The pressure of the coolant and the preload of the elastic element work together on the sealing end face to form an extremely thin liquid film. This liquid film serves two purposes: firstly, it lubricates, reducing friction and wear between the sealing end faces and extending the service life of the seals; secondly, it acts as a seal, preventing coolant leakage between the sealing end faces.

[0055] To further improve sealing performance and service life, the stationary and rotating rings can be paired using materials with good wear resistance, corrosion resistance, and thermal conductivity, such as pressureless sintered silicon carbide paired with carbon graphite impregnated metal. This material combination has advantages such as a low coefficient of friction, low wear rate, and good thermal conductivity, enabling long-term stable operation under high-speed and high-pressure conditions.

[0056] In addition to the aforementioned contact mechanical seal, a non-contact labyrinth seal can be additionally installed between the rotating ring seat 201 and the stationary ring seat 205 of the rotary joint as an auxiliary seal. A labyrinth seal is a sealing device that uses the throttling effect generated when fluid passes through a series of throttling gaps and expansion cavities to prevent leakage.

[0057] In summary, during system operation, the pressurized coolant provided by the external liquid supply system first enters the liquid supply chamber 12 inside the supply and return liquid wheel 8 through the dynamic and static sealing rotary joint 2, and then enters the heat exchange channel 9 inside the grinding wheel 5 through the inner edge fluid inlet 11 on the mating surface of the supply and return liquid wheel 8 and the grinding wheel 5.

[0058] During the flow of the coolant within the heat exchange channel 9, it undergoes thorough heat exchange with the grinding wheel 5 substrate, carrying away a significant amount of heat generated and conducted to the grinding wheel substrate during grinding. Simultaneously, under the combined action of the centrifugal force generated by the high-speed rotation of the grinding wheel 5 and the initial pressure provided by the supply system, the coolant is ejected at high speed from multiple fluid outlets 6 on the outer circumference of the grinding wheel 5, directly impacting the grinding arc zone and forcibly cooling the grinding point. After heat exchange, a portion of the coolant splashes out from the grinding arc zone, is collected by the machine tool guard, and returns to the supply system. The remaining portion flows naturally into the return cavity 13 of the supply and return fluid wheel 8 through the fluid outlet 10 at the outer edge of the heat exchange channel 9, driven by the pressure difference created by centrifugal force. Finally, it returns to the external supply circulation system via the dynamic and static sealing rotary joint 2, forming a complete and smooth closed-loop cooling cycle.

[0059] It is particularly important to note that the supply and return fluid impeller 8 and the dynamic and static sealing rotary joint 2 in this device are detachably connected to the grinding wheel 5. In practice, the grinding wheel 5 only retains the grinding function structure and the internal heat exchange channel 9. This split, detachable structure makes the grinding wheel 5 a readily replaceable consumable part. When the grinding wheel 5 wears down to its service life, only the grinding wheel 5 needs to be replaced, while core components such as the supply and return fluid impeller 8 and the dynamic and static sealing rotary joint 2 can be reused, significantly reducing the system's operating costs and maintenance difficulty.

[0060] It should be noted that, because the grinding wheel 5 in this device has a complex heat exchange channel 9 inside, the substrate of the grinding wheel 5 can be integrally formed using selective laser melting (SLM) additive manufacturing technology. In addition, the superhard abrasive layer 7 used for grinding can be solidified on the outer peripheral surface of the grinding wheel 5 substrate through electroplating or brazing processes.

[0061] It should be noted that, in practice, the liquid supply chamber 12, the return chamber 13, and the liquid retention chamber in the rotating ring seat 201 of the rotary joint 2 together constitute a large-capacity liquid buffer space. This effectively buffers pressure fluctuations in the external liquid supply system, ensuring stable flow and pressure of the coolant entering the heat exchange channel 9 of the grinding wheel 5. Furthermore, the larger liquid retention space facilitates adjustment of the pressure difference between the liquid supply chamber 12 and the return chamber 13. By controlling the ratio of the supply flow rate to the return flow rate, the internal pressure distribution of the system can be flexibly adjusted to meet the cooling requirements under different speeds and grinding loads.

[0062] like Figure 2 As shown, a grinding wheel guard 1 is also provided on the outside of the grinding wheel 5. The grinding wheel guard 1 is used to prevent grinding debris from injuring people.

[0063] In addition, in order to further ensure the safe and stable operation of the system and prevent workpiece scrapping and equipment damage caused by excessive grinding temperature or other abnormal conditions, the internal cooling main and auxiliary grinding wheel system of the present invention also includes a status monitoring and safety interlock module.

[0064] The module includes at least one acoustic emission sensor 14 and one infrared temperature sensor 15 mounted on the grinding wheel guard 1, which are used to monitor the acoustic emission signal and grinding temperature in real time during the grinding process, respectively.

[0065] Acoustic emission sensor 14 is used to collect acoustic emission signals generated during the grinding process. During grinding, when excessively high grinding temperatures cause burns, phase transformations, or cracks on the tool surface, characteristic acoustic emission signals are generated. By acquiring and analyzing these acoustic emission signals in real time, abnormalities can be detected early in the stages of thermal damage.

[0066] The infrared temperature sensor 15 is used for non-contact, real-time measurement of the temperature in the grinding arc zone. The infrared temperature sensor 15 can capture instantaneous temperature changes in the grinding arc zone in real time. When the grinding temperature exceeds a preset safety threshold, the infrared temperature sensor 15 will immediately send an alarm signal to the control system.

[0067] The status monitoring and safety interlock module is electrically connected to the machine tool's control system. When the grinding temperature exceeds a preset threshold or an abnormal acoustic emission signal is detected, the control system will automatically execute corresponding interlock protection actions according to the preset program. These actions include, but are not limited to: controlling the machine tool's Z-axis to quickly retract the tool, causing the grinding wheel 5 to disengage from the workpiece and preventing further grinding from causing more severe thermal damage; increasing the fluid supply flow rate of the fluid supply system to improve cooling capacity and quickly reduce the grinding temperature; if the abnormal signal does not recover after a certain delay, the rotation of the rotary drive axis 3 and the machine tool's feed motion will be automatically stopped, and an audible and visual alarm will be issued to remind the operator to check and handle the situation.

[0068] Please refer to Figure 1-8 In actual use, this device:

[0069] I. Pre-filling stage

[0070] Start the external liquid supply circulation system and turn on the refrigeration unit to control the coolant temperature within the set range.

[0071] Adjust the overflow valve to slowly raise the supply pressure to the initial working pressure. The coolant enters the rotating joint moving ring seat 201 through the rotating joint stationary ring seat 205 of the rotating joint 2, and then flows into the supply chamber 12 of the supply and return liquid wheel 8 through the supply exchange hole 203.

[0072] Coolant enters the vortex heat exchange channel 9 inside the grinding wheel 5 from the supply chamber 12 through the inner fluid inlet 11 on the mating surface of the supply and return fluid wheel 8 and the grinding wheel 5, and sequentially fills the spiral channel 902 and the outer circumferential channel 901.

[0073] II. Spindle Start-up and Steady-State Establishment Stage

[0074] Spindle low-speed start

[0075] After confirming that the pre-filling fluid is complete and the coolant flow is stable, a spindle start command is sent to the machine tool control system, and the rotary drive shaft 3 runs at low speed under no-load.

[0076] At this time, the grinding wheel 5 and the supply and return fluid wheel 8 rotate synchronously with the rotary drive shaft 3, and the coolant entering the heat exchange channel 9 begins to be subjected to centrifugal force. As the centrifugal force increases with the increase of rotational speed, the flow dynamics of the coolant in the heat exchange channel 9 gradually change from being dominated by the supply pressure to being dominated by centrifugal force.

[0077] Speed ​​increase and steady-state establishment

[0078] Gradually increase the spindle speed to the preset operating speed, and monitor the changes in supply pressure and return flow rate in real time during this process.

[0079] Once the spindle reaches its operating speed, centrifugal force becomes the main driving force for the flow of coolant: the coolant flows rapidly from the inner edge to the outer edge in the vortex heat exchange channel 9, forming a stable high-pressure zone at the outer edge of the channel, and the pressure at the fluid outlet 10 is significantly higher than that at the inlet.

[0080] Adjust the flow rate and pressure of the liquid supply system to achieve a dynamic balance between the liquid supply, spray volume, and return volume.

[0081] III. Grinding Process and Cooling Cycle Stage

[0082] Grinding feed. After the system enters steady state, the machine tool's Z-axis feed mechanism is controlled to drive the grinding wheel 5 to slowly approach and contact the workpiece, and the grinding operation is carried out according to the preset grinding parameters.

[0083] During the grinding process, the intense friction and plastic deformation between the abrasive grains and the workpiece surface generate a large amount of heat, most of which is conducted to the coolant in the heat exchange channel 9 through the grinding wheel 5 matrix.

[0084] Forced internal convection heat transfer. When the coolant flows in the vortex heat exchange channel 9, the coolant comes into full contact with the channel wall, achieving forced convection heat transfer and quickly removing the heat from the grinding wheel substrate.

[0085] The vortex structure extends the flow path of the coolant inside the grinding wheel, increases the heat exchange time, further improves the heat exchange efficiency, effectively prevents the grinding wheel matrix from deforming due to excessive temperature, and ensures the accuracy of grinding.

[0086] Direct cooling in the grinding arc zone

[0087] The coolant flowing to the outer circumferential channel 901 is ejected at high speed from each fluid outlet 6 under the combined action of centrifugal force and high pressure inside the channel.

[0088] The three-section variable cross-section structure of fluid outlet 6 provides the coolant with sufficient initial kinetic energy, enabling it to effectively break through the air barrier layer formed by the high-speed rotation of the grinding wheel and directly impact the core area of ​​the grinding arc zone. Simultaneously, the coolant sprays out in a uniform fan shape, increasing the cooling coverage area and achieving full-coverage cooling of the grinding arc zone.

[0089] During the spraying process, the coolant evaporates and cools down, further reducing its own temperature. This allows it to more effectively absorb heat from the grinding arc zone, keeping the grinding temperature within a safe range and fundamentally preventing thermal damage such as burns, phase transformations, and cracks on the tool surface.

[0090] Closed-loop cooling cycle. Part of the coolant that has completed the cooling of the grinding arc area splashes out from the grinding arc area, is collected by the machine tool protective cover, and returns to the external supply tank through the return oil groove; the other part of the coolant that is not sprayed out flows naturally into the return cavity 13 of the supply and return fluid wheel 8 through the fluid outlet 10 on the outer edge of the heat exchange channel 9 under the pressure difference formed by centrifugal force.

[0091] The coolant in the return cavity 13 enters the return flow channel of the rotary joint stationary ring seat 205 through the return exchange hole 203 of the rotary joint dynamic ring seat 201, and finally returns to the external liquid supply circulation system via the return connector.

[0092] The coolant returning to the supply tank is filtered to remove wear debris and impurities, then cooled to the set temperature by the refrigeration unit, and finally pumped back into the system to complete a complete closed-loop cooling cycle.

[0093] IV. Status Monitoring and Safety Interlocking Phase

[0094] Real-time signal acquisition. Throughout the grinding process, the status monitoring and safety interlock module operates continuously: the acoustic emission sensor 14 acquires the elastic wave signal generated during the grinding process in real time, and the infrared temperature sensor 15 measures the instantaneous temperature of the grinding arc zone in real time in a non-contact manner.

[0095] The acquired signals are amplified, filtered, and converted from analog to digital before being transmitted to the machine tool control system for real-time analysis and processing.

[0096] Anomaly detection and graded protection. The control system compares the real-time acquired signals with preset safety thresholds: when the grinding temperature exceeds the preset threshold, or when the acoustic emission signal shows a characteristic abnormal waveform (corresponding to thermal damage such as tool burns and cracks), graded interlocking protection actions are immediately triggered.

[0097] Level 1 protection: The control system first controls the machine tool's Z-axis to retract quickly, so that the grinding wheel 5 is no longer in contact with the workpiece; at the same time, the liquid supply pump automatically increases to the maximum flow rate to enhance cooling capacity and quickly reduce the grinding temperature.

[0098] Secondary protection: If the temperature signal and acoustic emission signal do not return to the normal range within the preset delay time, the control system automatically stops the rotation of the rotary drive shaft 3 and the machine tool's feed motion, and issues an audible and visual alarm to remind the operator to check and handle the situation. Although embodiments of the present 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 boron nitride tool grinding device, comprising a rotary drive shaft (3) and a grinding wheel (5) fixed on the rotary drive shaft (3) and rotating synchronously therewith, characterized in that: The non-grinding end face of the grinding wheel (5) is coaxially provided with a supply and return fluid wheel (8). The supply and return fluid wheel (8) rotates synchronously with the grinding wheel (5), and the supply and return fluid wheel (8) has a mutually isolated supply fluid cavity (12) and return fluid cavity (13) inside. The fluid inlet (11) and fluid outlet (10) are provided on the mating surface of the fluid supply wheel (8) and the grinding wheel (5). The fluid inlet (11) is connected to the fluid supply chamber (12), and the fluid outlet (10) is connected to the return chamber (13). The grinding wheel (5) is provided with a heat exchange channel (9) inside. The outer circumferential surface of the grinding wheel (5) is provided with multiple radially distributed fluid outlets (6). At the same time, the heat exchange channel (9) is connected to the fluid inlet (11), the fluid outlet (10), and the fluid outlet (6). The outer end of the fluid outlet (6) extends to the grinding working surface of the grinding wheel (5). The supply and return fluid wheel (8) is provided with a dynamic and static sealing rotary joint (2) on the side away from the grinding wheel (5). The supply chamber (12) and the return chamber (13) are respectively connected to the external static supply and return fluid pipeline through the dynamic and static sealing rotary joint (2).

2. The boron nitride tool grinding apparatus according to claim 1, characterized in that, The heat exchange channel (9) has a vortex structure. The inner edge of the heat exchange channel (9) is connected to the fluid inlet (11), and the outer edge of the heat exchange channel (9) is connected to the fluid outlet (10).

3. The boron nitride tool grinding apparatus according to claim 2, characterized in that, The heat exchange channel (9) includes a circumferential channel (901) and a spiral channel (902), wherein the circumferential channel (901) is located outside the spiral channel (902) and smoothly transitions with the spiral channel (902), and each of the fluid outlets (6) is connected to the circumferential channel (901).

4. The boron nitride tool grinding apparatus according to claim 1, characterized in that, The base of the grinding wheel (5) is made by selective laser melting 3D printing, and the outer peripheral surface of the grinding wheel (5) is bonded with an ultrahard abrasive layer (7) by electroplating or brazing.

5. The boron nitride tool grinding apparatus according to claim 1, characterized in that, The fluid outlet (6) includes, in sequence along the fluid flow direction, an inlet expansion section (603), a middle narrowing section (602), and an outlet expansion section (601). The diameter of the middle narrowing section (602) is smaller than the minimum diameter of the inlet expansion section (603) and the outlet expansion section (601).

6. The boron nitride tool grinding apparatus according to claim 1, characterized in that, The central axis of all fluid outlets (6) points to the rotation center of the grinding wheel (5), and multiple fluid outlets (6) are evenly arranged circumferentially along the central axis of the rotary drive shaft (3).

7. The boron nitride tool grinding apparatus according to claim 1, characterized in that, The rotary joint (2) includes a rotary joint moving ring seat (201) and a rotary joint stationary ring seat (205). The rotary joint moving ring seat (201) is sealed and fixedly connected to the supply and return liquid wheel (8). The rotary joint moving ring seat (201) and the rotary joint stationary ring seat (205) are sealed and rotatably connected by an end face mechanical seal pair (202).

8. The boron nitride tool grinding apparatus according to claim 1, characterized in that, The rotary joint moving ring seat (201) is provided with exchange holes (203) for the liquid supply chamber (12) and the return chamber (13) respectively. Furthermore, a filter screen (204) is fixedly connected to the exchange hole (203) provided by the rotary joint moving ring seat (201) for the liquid supply chamber (12). The rotary joint stationary ring seat (205) has through holes (206) for the liquid supply chamber (12) and the return chamber (13) respectively. A connector (4) is sealed and fixedly connected in the through hole (206). The rotary joint stationary ring seat (205) is connected to the external stationary liquid supply and return pipelines through the connector (4).

9. A boron nitride tool grinding apparatus according to claim 1, characterized in that, The grinding wheel (5) is also fitted with a grinding wheel protective cover (1), and an acoustic emission sensor (14) and an infrared temperature sensor (15) are fixedly connected to the grinding wheel protective cover (1). When the infrared temperature sensor (15) detects that the grinding temperature exceeds the preset threshold or the acoustic emission sensor (14) detects that the acoustic emission signal is abnormal, the control system controls the machine tool to retract the tool, increase the fluid supply flow and / or stop the rotating drive shaft (3).

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