Air-cooled anti-burning drill bit for coal mine and method thereof

Abstract

The present application relates to the field of coal mine drilling equipment and automation control technology, in particular to a coal mine air-cooled anti-burning drill arc wing drill bit and a method thereof; comprising an upper joint, a lower drill bit, a disc spring group and a flow distribution core pipe; the system is inserted into the lower center air duct through the flow distribution core pipe, only the main air jet hole is connected in the initial assembly state, and the standby strong cold air hole is closed; the core is to realize self-adaptive air path switching by using a linkage structure; when the cutting resistance overcomes the pre-tightening force of the disc spring group to cause axial displacement of the lower drill bit, the standby strong cold air hole is mechanically exposed while the main air jet hole is kept connected; the present application solves the problem that the conventional drill bit fixed flow passage cannot dynamically reconfigure the air volume according to the working condition, and directs the cold air to the chip flute for strong cold unloading when the load at the hole bottom suddenly changes, avoids heat accumulation of the cutting teeth, and fundamentally reduces the risk of drill burning.

Description

Technical Field

[0001] This invention relates to the field of coal mine drilling equipment and automation control technology, specifically to air-cooled anti-burning drill bit for coal mines and its method. Background Technology

[0002] In underground coal mine air-cooled drilling operations, the drill bit continuously cuts through coal and rock formations, generating continuous frictional heat and cuttings. Compressed air supplied from the borehole opening is needed for bottom cooling and cuttings removal. Existing conventional drill bits generally employ a fixed air supply channel structure, allowing compressed air to continuously blow along a single, predetermined path through the cutting area. To ensure drilling safety, current solutions largely rely on borehole parameter monitoring and constant airflow cooling. However, when the cutting load at the bottom of the borehole changes abruptly due to complex geological conditions, the fixed channel cannot dynamically reallocate the airflow according to the working conditions. Simultaneously, due to the inherent mechanical elastic time lag in the transmission of mechanical torque and control commands in long drill bit systems, and the difficulty in deploying stable electronic sensors in the borehole environment with its high temperature, high pressure, and strong vibration conditions, the borehole opening system cannot immediately detect abnormal fluctuations in borehole temperature and load. This dual lag in structure and monitoring further leads to continuous heat accumulation on the cutting teeth, obstruction of the root cuttings removal channel, and localized airflow mismatch, ultimately causing drill bit burnout or tooth breakage accidents.

[0003] Therefore, how to overcome the physical control time lag between the orifice and the bottom of the hole, and realize the mechanical adaptive switching of the drill bit air path and the real-time feedback of the load status without relying on the bottom hole sensor, has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: Air-cooled, anti-burning drill bit for coal mines includes: Upper connector, lower drill bit, disc spring assembly, and distribution core tube; The lower end of the upper connector is sleeved with the lower drill bit; The disc spring assembly is provided between the upper connector and the lower drill bit; The upper connector has an upper central air duct machined through it along the axis. The lower drill bit has a lower central air duct machined along its axis inside. The distribution core tube is fixedly connected to the lower end face of the upper connector and is inserted into the lower central air duct with a clearance fit. The lower drill bit is internally machined with a main air jet hole and a backup strong cooling air hole. The inlets of the main air jet and the backup strong cooling air jet are both connected to the lower central air duct; The distribution core tube has a throttling groove machined on its tube wall; wherein, in the initial assembly state, the throttling groove of the distribution core tube is aligned and connected only with the main air jet hole, and the spare strong cooling air hole is blocked and closed by the tube wall of the distribution core tube.

[0005] In one alternative embodiment: the lower end of the upper connector has a right-hand rectangular external helical spline machined on its outer cylindrical surface; the upper end of the lower drill bit has a rectangular internal helical spline machined inside to mate with the rectangular external helical spline; the lower drill bit is sleeved onto the lower end of the upper connector via the rectangular internal helical spline and the rectangular external helical spline; wherein, the lower drill bit and the upper connector form a helical drive pair, and the helix angle of the rectangular external helical spline is 45°.

[0006] In one alternative: the lower drill bit has an internal stepped surface machined inside, and the disc spring assembly is sleeved between the lower end face of the upper connector and the internal stepped surface of the lower drill bit; the disc spring assembly is formed by stacking spring steel discs; wherein the outer diameter of the spring steel disc is 80mm and the inner diameter is 40mm, and the initial installation preload of the disc spring assembly is 10000N.

[0007] In one alternative embodiment: the outer cylindrical surface of the lower drill bit is evenly distributed with arc-shaped blades; the arc-shaped blades are made of cemented carbide material; polycrystalline diamond composite sheets are embedded on the impact surface of the arc-shaped blades; wherein, the polycrystalline diamond composite sheets serve as cutting teeth, the outlet of the main air jet is directly opposite the cutting edge of the cutting teeth, and the outlet of the spare strong cooling air jet is aligned with the chip removal groove at the root of the arc-shaped blades.

[0008] In one alternative: the diameter of the upper central air duct is 30 mm; the outer diameter of the distribution core tube is 29.5 mm; the distribution core tube is inserted into the lower central air duct with a 0.5 mm gap fit; the throttling grooves are evenly distributed along the circumference of the distribution core tube.

[0009] In one alternative: when the cutting resistance torque borne by the lower drill bit is greater than the torque corresponding to the initial installation preload of the disc spring assembly, the lower drill bit is configured with an upward axial displacement relative to the upper connector along the rectangular external helical spline. In this axial displacement state, the throttling groove of the distribution core tube is connected to the main air jet hole and the backup strong cooling air hole is not blocked by the distribution core tube.

[0010] The method for controlling burnout in air-cooled anti-burnout drill bits for coal mines includes the following steps: S1: Construct a drilling execution system including a control system, and a borehole rotary motor, a borehole air compressor, a borehole feed cylinder, a borehole air supply pipeline, and a drill rod connected to the control system; send the drill bit into the borehole but before it contacts the bottom coal and rock surface; instruct the borehole rotary motor to drive the drill rod to rotate at a constant speed; the borehole air compressor outputs compressed air at a constant flow rate; record the basic air pressure value of the borehole air supply pipeline as a zero-point reference; and obtain the drill bit rotation frequency based on the constant speed. S2: The drill bit cuts into the coal and rock to perform drilling operations; drilling tests are conducted in advance under known feed conditions to establish initial mapping coefficients between the periodic AC fluctuation amplitude and the cutting resistance torque under multiple working conditions; time series data of the air supply pressure are continuously recorded; the periodic AC fluctuation amplitude consistent with the drill bit rotation frequency is extracted from the air supply pressure; the DC component of the air pressure signal is separated by low-pass filtering; a correction factor is calculated based on the rate of change of the DC component; the initial mapping coefficients between the pre-acquired periodic AC fluctuation amplitude and the cutting resistance torque are dynamically adjusted using the correction factor; S3: Based on the extracted periodic AC fluctuation amplitude and the dynamically adjusted initial mapping coefficient, calculate the transient cutting resistance torque at the bottom of the hole; S4: Determine whether the transient cutting resistance torque is greater than the critical resistance torque, where the critical resistance torque is the torque corresponding to the initial installation preload of the disc spring assembly; if it is less than or equal to, maintain the current drilling state; if it is greater, the control system directly issues a feedforward control command to reduce the propulsion speed of the borehole feed cylinder and increase the air supply pressure of the borehole air compressor. S5: Obtain the system-preset total length of the drill rod, the elastic modulus of the material, and the safe threshold range of the air supply pressure; determine the delay time window of the mechanical stress wave based on the total length of the drill rod and the elastic modulus of the material; keep the backup strong cooling air hole open within the delay time window; after the delay time window ends, the disc spring assembly pushes the lower drill bit to reset; determine whether the air supply pressure fluctuation has recovered to the safe threshold range; if yes, instruct the borehole feed cylinder to resume the normal drilling cycle; if no, maintain the feedforward control command.

[0011] In one alternative: In step S1, the base air pressure value is composed of the frictional resistance inside the drill pipe and the initial throttling resistance of the main air jet.

[0012] In one alternative: In step S2, the amplitude of the periodic AC fluctuation is characterized by the high-frequency axial vibration caused by the alternating cutting of coal and rock by the arc-shaped blades of the lower drill bit, and by the synchronous micro-change of the throttling groove of the distribution core tube on the blocking area of ​​the main air jet.

[0013] In one alternative: in step S4, the system directly issues the feedforward control command; in step S5, within the delay time window, the backup strong cooling air hole is opened by the relative displacement of the lower drill bit and the distribution core tube.

[0014] The advantages of this invention are: 1. This invention solves the problem that conventional drill bits with fixed flow channels cannot dynamically redistribute airflow according to working conditions through a linkage structure consisting of an upper connector, a lower drill bit, a disc spring assembly, and a flow distribution core tube. When the cutting resistance torque overcomes the initial installation preload of the disc spring assembly, the lower drill bit rotates upward along the helical spline to generate axial displacement, mechanically exposing the backup strong cooling air hole while maintaining the main air jet connection. This structure can achieve adaptive airflow switching when the load at the bottom of the hole changes abruptly, guiding the compressed air to the chip removal groove at the root of the arc-shaped vane for strong cooling and unloading, avoiding heat accumulation on the cutting teeth, and fundamentally reducing the risk of drill burnout. 2. The control method of this invention effectively overcomes the time lag in control and mechanical feedback of long drill bit systems; by extracting the periodic AC fluctuation amplitude in the air supply pressure that is consistent with the drill bit rotation frequency, and dynamically adjusting the mapping coefficient in combination with the rate of change of the DC component of the air pressure, the sensorless real-time accurate estimation of the transient cutting resistance torque at the bottom of the hole is realized; when the resistance torque exceeds the limit and causes the backup strong cooling air hole to be exposed, the system does not wait for mechanical lag feedback and directly issues a feedforward command, and uses mechanical stress wave to calculate the delay time window, and relies on the mechanically opened air hole to automatically unload and force cool within the window, thus ensuring drilling safety. Attached Figure Description

[0015] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0016] Figure 1 This is a schematic diagram of the overall external structure of the device; Figure 2 This is a schematic diagram of the upper connector; Figure 3 This is a schematic diagram of the lower central air duct structure; Figure 4 A logic control flowchart of the method provided in the embodiments of this application is shown.

[0017] In the diagram: 1. Upper connector; 2. Lower drill bit; 3. Disc spring assembly; 4. Distribution core tube; 5. Upper central air duct; 6. Lower central air duct; 7. Main jet nozzle; 8. Backup strong cooling air nozzle; 9. Throttling groove; 10. Rectangular external helical spline; 11. Rectangular internal helical spline; 12. Inner stepped surface; 13. Spring steel disc; 14. Arc-shaped wing; 15. Polycrystalline diamond composite sheet; 16. Cutting teeth; 17. Cutting edge; 18. Root chip removal groove. Detailed Implementation

[0018] The present invention will be fully understood by the following embodiments, which enable those skilled in the art to carry out their work. However, the implementation of the present invention is not limited to the following embodiments. The accompanying drawings of the present invention do not contain any limitations on size, dimensions and scale. In actual implementation of the present invention, its size, dimensions and scale are not limited by the accompanying drawings of the present invention.

[0019] Example 1: Combination Figure 1 Air-cooled anti-burning drill bit for coal mines, including: Upper connector 1, lower drill bit 2, disc spring assembly 3, and distribution core tube 4; The lower end of the upper connector 1 is fitted with the lower drill bit 2; A disc spring assembly 3 is provided between the upper connector 1 and the lower drill bit 2; Combination Figure 2 The upper connector 1 has an upper central air duct 5 machined through it along the axis inside; Combination Figure 3 The lower drill bit 2 has a lower central air duct 6 machined along its axis inside; The distribution core tube 4 is fixedly connected to the lower end face of the upper connector 1 and inserted into the lower central air duct 6 with a clearance fit; The lower drill bit 2 has a main air jet hole 7 and a spare strong cooling air hole 8 machined inside; The inlets of the main air jet 7 and the backup strong cooling air jet 8 are both connected to the lower central air duct 6; The distribution core tube 4 has a throttling groove 9 machined on its tube wall; in the initial assembly state, the throttling groove 9 of the distribution core tube 4 is only aligned and connected with the main air jet hole 7, and the spare strong cold air hole 8 is blocked and closed by the tube wall of the distribution core tube 4.

[0020] In underground air-cooled drilling in coal mines, conventional drill bits rely solely on a fixed air jet path to cool the cutting zone and remove slag. When the cutting load at the bottom of the hole changes abruptly, the air path cross-section cannot be adjusted accordingly, which can easily lead to problems such as heat accumulation on the cutting teeth 16, obstruction of the chip removal channel, and local air loss. To solve this problem, this embodiment adopts a linked drill bit structure consisting of an upper connector 1, a lower drill bit 2, a disc spring assembly 3, and a distribution core tube 4. The upper connector 1 is used to transmit rotational power and compressed air to the drill rod; the lower drill bit 2 is used to support the cutting structure and form the bottom hole air outlet; the disc spring assembly 3 is used to provide axial reset force; the distribution core tube 4 is used to adjust the connection state of the air jets under different axial relative positions; the upper central air duct 5 and the lower central air duct 6 form a through main air supply passage, through which compressed air enters the interior of the lower drill bit 2. The main jet vent 7 serves as the directional cooling and slag removal function during normal drilling, while the backup strong cooling vent 8 serves as the additional strong cooling and unloading function under high resistance conditions. The distribution core tube 4 is inserted into the lower central air duct 6 with a gap fit. Its special meaning is not simply to guide air, but to control the opening and closing of different air vents through the alternating correspondence between the throttling groove 9 and the solid pipe wall while maintaining relative motion capability. In the initial assembly state, the throttling groove 9 is aligned only with the main air jet 7, so that the air volume is concentrated on the cutting edge 17 position in the cutting zone under normal working conditions. The backup strong cooling air hole 8 is blocked by the solid pipe wall to avoid ineffective flow diversion under low load conditions. The technical effect of this structure is that it establishes a direct correspondence between the change of cutting resistance at the bottom of the hole and the air path switching capability, so that the drill bit body has a mechanical air volume redistribution basis without relying on the bottom hole sensor, providing an feasible structural premise for subsequent pressure fluctuation identification and anti-burning drill control.

[0021] The lower end of the upper connector 1 has a right-hand rectangular external helical spline 10 machined on its outer cylindrical surface; the upper end of the lower drill bit 2 has a rectangular internal helical spline 11 machined inside to mate with the rectangular external helical spline 10; the lower drill bit 2 is sleeved on the lower end of the upper connector 1 through the rectangular internal helical spline 11 and the rectangular external helical spline 10; wherein, the lower drill bit 2 and the upper connector 1 form a helical transmission pair, and the helix angle of the rectangular external helical spline 10 is 45°.

[0022] Downhole air-cooled drilling not only requires the drill bit to transmit rotational torque, but also requires the lower drill bit 2 to generate controllable axial displacement when the cutting resistance increases, so as to trigger the air path switching. To this end, in this embodiment, the outer cylindrical surface of the upper connector 1 is machined into a right-hand rectangular external helical spline 10, and a corresponding rectangular internal helical spline 11 is provided inside the lower drill bit 2. The tooth side contact surface of the rectangular spline is larger than that of the conventional triangular tooth spline, which is suitable for transmitting the target rated torque under coal and rock alternating cutting conditions, and at the same time can reduce the contact stress concentration formed under alternating impact. The right-hand rotation setting is used to establish a predetermined torque-to-axial displacement conversion relationship with the drill bit rotation direction, so that when the cutting resistance torque increases, the lower drill bit 2 rotates relative to the upper connector 1 along the helical trajectory; the helical angle is 45°, which is designed to balance torque transmission capacity and axial displacement sensitivity; if the angle is too small, the axial displacement caused by torque change will be insufficient, which is not conducive to timely opening of the backup air passage; if the angle is too large, the axial component force will increase, which may reduce the impact resistance stability of the transmission pair. In this embodiment, the special meaning of the helical drive pair is not just that of a connector, but that it converts the changes in cutting resistance at the bottom of the hole, which cannot be directly measured, into a usable mechanical displacement. As a result, while maintaining the power transmission function, the drill bit obtains the displacement output capability linked with the airflow adjustment mechanism, and can directly map mechanical anomalies into changes in the flow channel state.

[0023] The lower drill bit 2 has an inner stepped surface 12 machined inside. The disc spring assembly 3 is sleeved between the lower end face of the upper connector 1 and the inner stepped surface 12 of the lower drill bit 2. The disc spring assembly 3 is formed by stacking spring steel discs 13. The outer diameter of the spring steel disc 13 is 80mm and the inner diameter is 40mm. The initial installation preload of the disc spring assembly 3 is 10000N.

[0024] In the air-cooled anti-burn drill structure, if the lower drill bit 2 frequently moves under normal cutting fluctuations, it will cause the air path to switch incorrectly and the pressure signal to be distorted; if the reset resistance is too large, it will weaken the trigger sensitivity under heavy load. To solve this contradiction, this embodiment sets a disc spring assembly 3 between the lower end face of the upper connector 1 and the inner step surface 12 of the lower drill bit 2. The disc spring assembly 3 is formed by stacking spring steel discs 13, with an outer diameter of 80mm and an inner diameter of 40mm, and the initial installation preload is set to 10000N. The technical significance of adopting the superposition method is that it can obtain the storage capacity that meets the preload threshold requirement and the load displacement relationship in a preset proportion within the limited axial installation space, so as to adapt to the compact internal structure of the drill bit. The function of the disc spring group 3 is not a general vibration damping element, but a threshold mechanism that constitutes the relative axial displacement of the lower drill bit 2. Only when the axial action of the cutting resistance after conversion by the helical transmission pair exceeds the preload threshold will the lower drill bit 2 move significantly upward. This can suppress small random disturbances during drilling and prevent the backup air path from being opened under non-dangerous conditions. At the same time, after the high resistance state is released, the disc spring group 3 can push the lower drill bit 2 back to the initial position, so that the air path returns to the working state of the main air jet hole 7. This parameter combination makes the trigger threshold and the drill bit force state have a clear correspondence, which facilitates the formation of repeatable mechanical response.

[0025] Arc-shaped blades 14 are evenly distributed on the outer cylindrical surface of the lower drill bit 2; the arc-shaped blades 14 are made of cemented carbide material; polycrystalline diamond composite plates 15 are inlaid on the impact surface of the arc-shaped blades 14; among them, the polycrystalline diamond composite plates 15 serve as cutting teeth 16, the outlet of the main air jet 7 is directly opposite the cutting edge 17 of the cutting teeth 16, and the outlet of the spare strong cooling air jet 8 is aligned with the chip removal groove 18 at the root of the arc-shaped blades 14.

[0026] In air-cooled drilling, the cutting heat source is mainly concentrated in the cutting edge 17 area of ​​the cutting teeth 16, while the heat from clogging and secondary grinding is often concentrated in the chip removal groove area at the root of the arc-shaped blade 14. If the airflow action position is not differentiated into primary and secondary areas, improper distribution of the cooling medium is likely to occur. Based on this, in this embodiment, arc-shaped blades 14 are evenly distributed on the outer cylindrical surface of the lower drill bit 2. The arc-shaped blades 14 are made of cemented carbide material to improve the wear resistance and impact resistance under the impact of coal-rock interface and interbedded rock. Polycrystalline diamond composite sheets 15 are embedded on the impact surface as cutting teeth 16 to utilize the unique hardness and high temperature resistance of the material to achieve stable cutting of coal and rock. The purpose of the uniform distribution is to enable each blade to undertake a near-balanced cutting task during the rotation process, and to form periodic aerodynamic and force changes, providing a regular source for the identification of air pressure fluctuations; the outlet of the main air jet 7 is directly opposite the cutting edge 17 of the cutting tooth 16, indicating that under normal working conditions, the compressed air is mainly used to remove the frictional heat of the cutting edge 17 and blow away the primary rock powder. The backup strong cooling air vent 8 outlet is aligned with the chip removal groove 18 at the root of the arc-shaped fin 14, ensuring that under abnormal load conditions, the additional air volume is preferentially applied to areas prone to chip accumulation and high-pressure stagnation, thereby reducing local blockage, lowering the probability of secondary wear, and improving root heat accumulation. The technical effect of this layout is that the conventional cooling path and the strong cooling unloading path correspond to different heat sources and blockage sources, respectively, realizing zoned control of the airflow target.

[0027] The upper central air duct 5 has a diameter of 30 mm; the outer diameter of the distribution core tube 4 is 29.5 mm; the distribution core tube 4 is inserted into the lower central air duct 6 with a gap of 0.5 mm; the throttling grooves 9 are evenly distributed along the circumference of the distribution core tube 4.

[0028] To ensure that the distribution core tube 4 can stably guide air and form a recognizable throttling change during relative displacement, this embodiment defines the dimensional relationship between the air duct and the core tube; the upper central air duct 5 has a diameter of 30 mm, the outer diameter of the distribution core tube 4 is 29.5 mm, and the distribution core tube 4 is inserted into the lower central air duct 6 with a gap of 0.5 mm; this dimensional relationship allows compressed air to form a predetermined annular gap between the outer circumference of the core tube and the inner wall of the lower central air duct 6. The upper limit of the predetermined annular gap is defined by the fact that the main airflow does not undergo excessive bypass flow and does not weaken the regulating effect of the throttling groove 9, and the lower limit is defined by the fact that coal dust, water vapor and abrasive particles enter and cause jamming; The 0.5mm gap is used to balance the smoothness of axial sliding and the airflow constraint; the throttling groove 9 is evenly distributed along the circumference of the distribution core tube 4. Its function is to make each air jet passage obtain approximately the same air supply conditions, avoid asymmetrical blowing caused by circumferential flow resistance differences, and reduce the risk of off-center load when the drill bit rotates. In this embodiment, the throttling groove 9 not only serves as an opening for connection but also as a pressure modulation function. That is, when the drill bit 2 experiences a slight axial vibration, the overlapping area between the throttling groove 9 and the air jet will change continuously, thereby converting the mechanical micro-displacement into a pressure fluctuation that can be measured at the orifice. Therefore, the size and distribution design of this throttling groove 9 directly affects the feasibility and stability of AC amplitude extraction in subsequent methods.

[0029] When the cutting resistance torque borne by the lower drill bit 2 is greater than the torque corresponding to the initial installation preload of the disc spring assembly 3, the lower drill bit 2 has an upward axial displacement configuration relative to the upper connector 1 along the rectangular outer spiral spline 10. In this axial displacement state, the throttling groove 9 of the distribution core tube 4 is connected to the main air jet 7 and the spare strong cold air hole 8 is not blocked by the distribution core tube 4.

[0030] When the cutting resistance at the bottom of the hole suddenly increases, if the main air jet 7 is completely cut off, the cooling of the cutting edge 17 area of ​​the cutting tooth 16 will be interrupted; if the total air volume is increased without changing the air path coverage, the root chip accumulation area cannot be targeted for cleaning; in order to take into account both types of needs, this embodiment defines the triggering state as the threshold condition corresponding to the cutting resistance torque borne by the lower drill bit 2 overcoming the initial installation preload of the disc spring assembly 3. Once this condition is met, the lower drill bit 2 rotates upward along the rectangular outer helical spline 10 and generates axial displacement. During this displacement, the throttling groove 9 of the distribution core tube 4 remains connected to the main air jet 7, indicating that the original cooling path of the cutting edge 17 continues to exist. At the same time, the backup strong cooling air hole 8 changes from being blocked by the solid tube wall to being exposed, and the new air volume channel is opened. The technical significance of this dual-path parallel operation is that strong cooling is not achieved by replacing the main cooling path, but by introducing an additional path while retaining the main path, so that the cutting edge 17 and the chip removal groove at the wing root can simultaneously obtain compressed air. Thus, the cutting heat source and the blockage source are processed synchronously; since this action is directly triggered by torque through the helical pair, the response is based on the force change of the drill bit body and does not depend on the external electrical signal, so it can still form an instantaneous air path reconstruction under the condition of mechanical transmission delay.

[0031] Example 2: like Figure 4 As shown, the method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines includes the following steps: S1: Construct a drilling execution system including a control system, a borehole rotary motor, a borehole air compressor, a borehole feed cylinder, a borehole air supply pipeline, and a drill rod connected to the control system; send the drill bit into the borehole but before it contacts the bottom coal and rock surface; instruct the borehole rotary motor to drive the drill rod to rotate at a constant speed; the borehole air compressor outputs compressed air at a constant flow rate; record the basic air pressure value of the borehole air supply pipeline as a zero-point reference; and obtain the drill bit rotation frequency based on the constant speed. S2: The drill bit cuts into the coal and rock to perform drilling operations; drilling tests are conducted in advance under known feed conditions to establish initial mapping coefficients between the periodic AC fluctuation amplitude and the cutting resistance torque under multiple working conditions; time series data of the air supply pressure are continuously recorded; the periodic AC fluctuation amplitude consistent with the drill bit rotation frequency is extracted from the air supply pressure; the DC component of the air pressure signal is separated by low-pass filtering; a correction factor is calculated based on the rate of change of the DC component; the initial mapping coefficients between the pre-acquired periodic AC fluctuation amplitude and the cutting resistance torque are dynamically adjusted using the correction factor; S3: Based on the extracted periodic AC fluctuation amplitude and the dynamically adjusted initial mapping coefficient, calculate and obtain the transient cutting resistance torque at the bottom of the hole; S4: Determine whether the transient cutting resistance torque is greater than the critical resistance torque. The critical resistance torque is the torque corresponding to the initial installation preload of disc spring group 3. If it is less than or equal to, maintain the current drilling state. If it is greater than, the control system directly issues a feedforward control command to reduce the advance speed of the borehole feed cylinder and increase the air supply pressure of the borehole air compressor. S5: Obtain the system's preset total drill rod length, material elastic modulus, and safe threshold range for air supply pressure; determine the delay time window for mechanical stress waves based on the total drill rod length and material elastic modulus; keep the standby strong cold air hole 8 open within the delay time window; after the delay time window ends, the disc spring assembly 3 pushes the lower drill bit 2 to reset; determine whether the air supply pressure fluctuation has returned to the safe threshold range; if yes, instruct the borehole feed cylinder to return to the normal drilling cycle; if no, maintain the feedforward control command.

[0032] This implementation method is used to solve the problems of elastic time delay between the orifice control signal and the thermal state at the bottom of the borehole, the lag of traditional torque feedback, and the difficulty in placing stable sensors at the bottom of the borehole. In step S1, the drill bit is in a state of not contacting coal and rock. The orifice rotary motor drives the drill rod to rotate at a constant speed. The orifice air compressor outputs compressed air at a constant flow rate. The control system collects the pressure signal of the air supply pipeline and establishes the basic air pressure value. The zero point reference here is not a fixed constant, but an initial reference value formed under the current drilling depth and current ventilation resistance conditions. In step S2, after the drill bit cuts into the coal and rock, the control system continuously collects the time series data of the air supply pressure and extracts the periodic AC fluctuation amplitude that is consistent with the drill bit rotation frequency. At the same time, a low-pass filter is used to obtain the DC component change rate, and the change rate is written into the mapping coefficient correction module to compensate for the slow deviation caused by structural wear and flow field degradation. In step S3, the AC amplitude is multiplied by the corrected mapping coefficient to obtain the estimated value of the transient cutting resistance torque at the bottom of the hole; In step S4, the estimated value is compared with the critical resistance torque corresponding to the initial installation preload of disc spring assembly 3; when the estimated value does not exceed the critical value, the current propulsion and air supply status is maintained; when the estimated value exceeds the critical value, it indicates that the load at the bottom of the hole suddenly increases, and the mechanical action of the lower drill bit 2 will expose the backup strong cold air hole 8. After the hole mouth detects the characteristic of AC amplitude decrease, the control system does not wait for the drill rod torque hysteresis feedback, but directly sends a feedforward adjustment command to the feed cylinder and air compressor. In step S5, the control system determines the delay time window of the mechanical stress wave based on the total length of the drill pipe and the elastic modulus of the material. Within this window, automatic unloading and forced cooling of the bottom hole are achieved by relying on the mechanical state of the backup strong cooling air hole 8 being open. After the window ends, if the air pressure fluctuation of the supply air returns to the safe threshold range, the normal drilling cycle is restored; if it does not return, the feedforward control command is maintained. The effect of this method is that the abnormal load at the bottom hole can be characterized in a timely manner through air pressure fluctuations, and the mechanical backup protection and the hole opening adjustment can work together at different response scales to reduce the risk of drill burn and tooth breakage. Steps S2 and S3 essentially construct a transient cutting resistance torque estimation model; this model aims to solve the detection problem in harsh environments where torque sensors cannot be directly installed at the bottom of the hole, by using the air pressure fluctuation signal that is easily obtained at the hole opening to accurately estimate the real-time cutting resistance torque at the bottom of the hole; In terms of logical structure and data flow, the model includes a reference mapping sub-model and a drift compensation sub-model: the reference mapping sub-model receives the periodic AC fluctuation amplitude as input and outputs the initial resistance torque; the drift compensation sub-model receives the DC component change rate of the air pressure signal as input and outputs a correction factor; finally, the main model uses this correction factor to dynamically adjust the mapping coefficients and multiplies them by the AC fluctuation amplitude to output the estimated value of the transient cutting resistance torque at the bottom of the hole; the estimation formula for the transient cutting resistance torque is as follows: In the formula, This represents the estimated value of the transient cutting resistance torque at the bottom of the hole, in N·m. This represents the correction factor, which is dimensionless. This represents the initial mapping coefficients, in N·m / Pa; The extracted periodic AC fluctuation amplitude is expressed in Pa. The low-pass filter uses a first-order inertial filter algorithm to filter out high-frequency pulsations. In the drift compensation sub-model, the control system subtracts the mean value of the filtered DC component within the current time window from the initial base pressure value and divides the difference by the initial base pressure value to obtain the dimensionless rate of change of the DC component. This rate of change directly reflects the attenuation ratio of local flow resistance. Therefore, the correction factor is defined as the reciprocal of the difference between 1 and the absolute value of the DC component's rate of change. By multiplying by this correction factor, the AC pressure amplitude attenuated due to wear can be proportionally amplified, thereby compensating for the mapping coefficient. The specific calculation process satisfies the formula: In the formula, This represents the rate of change of the DC component, dimensionless; to prevent... A division-by-zero error occurs when the value approaches or equals 1, causing the logic to not close. The system has a default setting. The safety upper limit threshold is set. When the detected value reaches this threshold, the control system determines it to be an extreme blockage state and directly triggers the shutdown protection. This represents the mean value of the filtered DC component within the current time window, in Pa. This represents the initial base pressure value, in Pa. This represents the correction factor, which is dimensionless. The model as a whole characterizes the physical transmission law of gas-solid coupling, which is transformed into a small axial displacement of the lower drill bit 2 through the helical transmission pair, and the gas pressure fluctuation at the orifice caused by the change of the throttling area, as well as the long-term slow effect of flow channel wear on this transmission law. The calculation of the delay time window in step S5 actually uses a control delay prediction model. The purpose of this model is to quantify the physical time required for the orifice control command to be transmitted to the bottom of the hole and take effect, so as to avoid misjudgment or repeated adjustment of the control system due to the lack of effect during this period. In terms of logical structure, the model takes the total length of the drill pipe, the elastic modulus of the drill pipe material and the material density as input, calculates the theoretical time for the mechanical stress wave to be transmitted from the orifice to the bottom of the hole, adds the system response margin, and outputs the delay time window. In the specific data flow, the control system reads the preset elastic modulus and density of the drill pipe material, calculates the theoretical propagation speed of the mechanical stress wave in the drill pipe, which is equal to the square root of the ratio of elastic modulus to density; it reads the current drilling depth as the total length of the drill pipe, calculates the theoretical delay time, which is equal to the total length of the drill pipe divided by the propagation speed; and adds a fixed system response margin to the theoretical delay time, outputting the final delay time window; the relevant calculation formula is as follows: In the formula, This represents the theoretical propagation speed of mechanical stress waves in the drill pipe, expressed in m / s. This represents the elastic modulus of the drill pipe material, expressed in Pa. This indicates the density of the drill pipe material, expressed in kg / m³. This represents the theoretical delay time, expressed in seconds (s). This indicates the total length of the drill pipe, in meters (m). This represents the final delay time window, in seconds. This represents the system's fixed response margin, expressed in seconds (s); where, the system's fixed response margin... The value range can be set to, for example, 0.5s to 2.0s, depending on the actual drill rod material and the response time of the borehole actuator. This calculation process provides a clear theoretical basis, giving the time delay waiting between the borehole opening and the bottom a quantifiable time boundary; the model characterizes the physical law that the transmission of force and motion in long-distance drilling systems is not rigidly instantaneous, but rather propagates at a limited speed in slender rods in the form of elastic waves; the physical meaning of the mapping coefficient in this embodiment is: the conversion ratio of the bottom cutting resistance torque corresponding to a unit AC fluctuation amplitude, and its function is to convert the air pressure AC characteristics that can be directly collected at the borehole opening into a mechanical quantity that can be used for control and judgment; The coefficient is not a fixed constant set in advance, but is calculated based on preset logic in the following order: then the drill bit cuts into the standard coal and rock sample or the historical calibration layer under known feed conditions, and the AC fluctuation amplitude is continuously recorded in multiple rotation cycles; the torque characterization of the borehole drive system in the steady state section or the equivalent cutting resistance torque deduced from the drill bit structural parameters is read simultaneously. An initial conversion table is established based on the correspondence under multiple working conditions. When the control system is running, it does not directly call a single fixed value, but selects or interpolates the current mapping coefficient from the conversion table according to the current rate of change of the DC component. Thus, the input sources of the mapping coefficient include the time series of the orifice air pressure, the drill bit rotation frequency, and the corresponding data of the resistance torque obtained during the calibration stage. The output result is the real-time conversion ratio used in step S3. In this embodiment, the critical resistance torque serves as the threshold for determining whether the lower drill bit 2 will overcome the preload threshold of the disc spring assembly 3 and trigger the opening of the backup strong cooling air hole 8. Its source is not measured by an additional sensor, but is a mechanical trigger limit jointly defined by the initial installation preload of the disc spring assembly 3, the helix angle of the rectangular external helical spline 10, and the force transmission radius. When determining the minimum triggering resistance torque range, the axial threshold load required for disc spring assembly 3 to reach the initial compression displacement can be calculated based on the relationship between the resistance torque and the axial component force of the helical transmission pair. The lower limit of this range is then set as the system judgment threshold to ensure that the system can act in advance before approaching a dangerous condition. After this setting, the comparison in step S4 is essentially a comparison of whether the real-time estimated transient cutting resistance torque has entered the range sufficient to cause structural flow distribution switching. Once the threshold is exceeded, the next step is to trigger feedforward load reduction and airflow control. The processing flow from step S2 to step S4 can be further refined in chronological order as follows: Firstly, the control system collects the raw signal of the air supply pressure at the orifice at a fixed sampling period; Secondly, the target rotational frequency is determined based on the current rotational speed, and the synchronous AC component is extracted around this frequency; Third, the original signal is subjected to low-pass processing in parallel to obtain the DC component that reflects the slow change in the overall resistance of the flow channel. Fourth, calculate the rate of change of the DC component relative to the previous statistical window, and correct the mapping coefficient accordingly; Fifth, the corrected mapping coefficient is multiplied by the current AC amplitude to obtain the estimated value of the transient cutting resistance torque; Sixth, the estimated value is sent to the threshold judgment module and compared with the critical resistance torque; Seventh, the output can be either to maintain the current state or to issue feedforward control commands; The final output of the above process is sent to the control terminals of the feed cylinder and air compressor on the one hand, and as the historical load record at the bottom of the hole for subsequent window judgment on the other hand, so that the entire control chain has a clear data flow relationship.

[0033] In step S1, the basic air pressure value is composed of the friction resistance inside the drill pipe and the initial throttling resistance of the main air jet 7.

[0034] The air pressure supplied at the orifice is not a meaningless background value during idling calibration, but rather a benchmark for subsequent state identification. In this embodiment, the basic air pressure value obtained in step S1 consists of two parts: one part is the pressure component corresponding to the frictional resistance formed by the flow of compressed air inside the drill pipe, and the other part is the pressure component corresponding to the local resistance caused by the initial throttling at the main jet orifice 7. The control system records and updates this basic air pressure value in each system cycle to match it with the current drilling depth, current channel wear, and current jet orifice morphology. As the drill bit blades, the edges of the nozzles, and the surface of the inner flow channel wear down, the flow resistance distribution will change slowly, and the DC component of the base air pressure value will drift continuously. This is because the high-speed airflow carrying rock powder during drilling will continuously scour and wear the edges of the main nozzle 7 and the throttling groove 9 of the distribution core tube 4, causing the actual effective flow cross-sectional area of ​​the throttling orifice to gradually increase, resulting in a decrease in the local resistance coefficient. Under the condition that the air compressor at the orifice outputs a constant flow of compressed air, this irreversible decrease in local resistance will cause the base air pressure value measured at the orifice to decrease slowly in one direction. Therefore, the special meaning of this DC drift in this embodiment is not random noise, but a structural parameter that directly characterizes the degree of degradation of the physical boundary of the flow field; the control system uses this drift trend to correct the subsequent drag torque mapping relationship, so that the load information represented by the AC amplitude is not masked by the baseline offset caused by long-term wear; thus, even if the drill bit is used continuously, the borehole pressure characteristics and the actual load at the bottom of the hole can still maintain a usable correspondence, reducing the probability of misjudgment. The logical function of the baseline air pressure value is to serve as a zero-point reference for all subsequent communication identification and wear compensation. It is not used to directly determine the risk of drill burnout, but to distinguish between rapidly changing cutting events and slowly changing flow channel degradation. Its determination process can be carried out in the following steps: Under the condition that the drill bit is not in contact with coal and rock and the rotary motor maintains a constant speed and the air compressor maintains a constant flow, the air supply pressure is continuously collected in multiple rotation cycles. The non-steady-state segments with significant fluctuations in speed and instantaneous startup are removed; the average value of the remaining steady-state pressure data is calculated as the base air pressure value at the current drilling depth; this value is written into the control system as the zero-point reference at the start of this round of drilling; the input sources of this process are the original borehole pressure signal, the current air compressor set flow rate, and the constant speed status signal of the rotary motor; the output result is a single reference pressure value, which is transmitted to the AC extraction module and DC drift monitoring module in step S2; DC drift refers to the unidirectional change of the DC component of the base pressure or low-pass flow over multiple consecutive statistical window periods. Its physical meaning is the migration of total flow resistance caused by changes in the flow channel cross-section, nozzle edge morphology, and inner wall roughness. To avoid mistaking short-term impacts for wear, this embodiment uses a window-by-window comparison method to determine DC drift: the control system forms the current statistical window and the previous statistical window for a preset duration, calculates the representative values ​​of the DC component in each window, and then compares the difference and direction of change between the two. Only when the difference remains in the same direction over multiple consecutive windows is it considered a valid drift, and it is used as the input of the flow field degradation degree to the mapping coefficient correction module. In the specific data interaction and processing details, the control system sets the preset duration to 30s, and uses the median of the data within the window to eliminate extreme value interference as the representative value of the DC component; only when all three differences in the queue are negative and their absolute values ​​are greater than the preset sensor noise tolerance is it determined to be a valid drift; the preset sensor noise tolerance is a fixed threshold calibrated based on the background measurement noise amplitude of the pressure sensor in the orifice air supply pipeline under no-load conditions; the control system calculates the difference between the representative value of the latest statistical window and the zero-point reference recorded in step S1, and uses this cumulative difference as a quantitative indicator of the degree of flow field degradation, outputting it to the mapping coefficient correction module; This logic clarifies the complete data flow from raw data to valid drift identification, avoiding vague automatic interactive descriptions; thus, DC drift has both a clear source and a clear purpose, and its output is not an independent alarm signal, but is used to correct the resistance torque conversion relationship in steps S2 and S3.

[0035] In step S2, the amplitude of the periodic AC fluctuation is characterized by the high-frequency axial vibration caused by the alternating cutting of coal and rock by the arc-shaped blades 14 of the lower drill bit 2, and the synchronous micro-change of the throttling groove 9 of the distribution core tube 4 on the blocking area of ​​the main air jet 7.

[0036] In order for the AC component in the air supply pressure to correspond to the changes in the cutting resistance at the bottom of the hole, it is necessary to clarify the source mechanism of the AC component. In this embodiment, the periodic AC fluctuation amplitude extracted in step S2 comes from the high-frequency axial vibration caused by the alternating cutting of coal and rock by the arc-shaped blades 14 of the lower drill bit 2. Since each arc-shaped blade 14 enters the main cutting zone in sequence during the rotation process, the cutting resistance will generate regular fluctuations within the rotation cycle. These fluctuations are converted into a small axial displacement of the lower drill bit 2 relative to the distribution core tube 4 through the helical transmission relationship. Although the axial displacement did not reach the extent of opening the backup strong cooling air hole 8, it was sufficient to cause a synchronous slight change in the overlap area between the throttling groove 9 and the main air jet hole 7; the change in the overlap area would cause a change in the local throttling resistance, which would then manifest as a periodic pressure fluctuation consistent with the rotation frequency in the air supply pipeline at the orifice; the control system would extract the AC amplitude based on this and use it as the input for estimating the cutting resistance torque. This mechanism differs from directly measuring drill pipe torque; it measures the aerodynamic response directly modulated by local cutting events at the bottom of the hole, and is therefore insensitive to the elastic hysteresis of long drill pipes. This feature enables the method to obtain a continuous signal source related to the cutting state without the need for an electronic sensor at the bottom of the hole. In this embodiment, the periodic AC fluctuation amplitude is logically defined as the strength of the periodic component in the orifice air supply pressure that is synchronized with the current rotation frequency of the drill bit. It is used to characterize the degree of throttling micro-modulation caused by the alternating cutting of the arc-shaped vane 14. It is not a pressure fluctuation of arbitrary frequency band, but a target AC feature specifically extracted from the original air supply pressure signal around the rotation fundamental frequency. Therefore, this parameter can establish a one-to-one correspondence with the mechanical periodic events of the drill bit. The decision-making role of this parameter is: on the one hand, it serves as a direct input for calculating the transient cutting resistance torque in step S3; on the other hand, its sudden drop characteristic can serve as auxiliary evidence for identifying the exposure of the backup strong cold air hole 8 in step S4. The AC amplitude extraction process in step S2 includes the following steps in sequence: reading the original time series output by the orifice pressure sensor; reading the current rotation speed information given by the rotary motor or rotation speed detection unit and calculating the drill bit rotation frequency; using this rotation frequency as the target frequency, performing synchronous frequency selection on the original pressure signal to suppress random noise and air supply pulsation that are out of sync with the rotation; statistically analyzing the peak-to-valley difference or equivalent amplitude of the pressure component corresponding to the target frequency within several consecutive rotation cycles, and using it as the periodic AC fluctuation amplitude at the current moment; and sending this amplitude to the resistance torque calculation module after mapping coefficient correction. In terms of the detailed implementation of the above data flow, the peak-to-valley difference of the pressure component corresponding to the target frequency is specifically executed as follows: In the frequency-selective filtered signal, the control system searches for local maxima and local minima one cycle at a time, with the current rotation cycle as the time cutoff point; if multiple extreme values ​​appear in a single cycle, only the peak and valley with the largest absolute value are retained, and the difference between the two is calculated as the single-cycle amplitude of that cycle; to prevent single-cycle jumps caused by rockfalls or hard rock interlayers, the control system sorts the single-cycle amplitudes of five consecutive rotation cycles, removes the maximum and minimum values, calculates the arithmetic mean of the remaining three values, and finally outputs the average value as the periodic AC fluctuation amplitude at the current moment; The data cleaning and calculation logic not only clarifies the input and output forms of the algorithm, but also ensures the stability of the data input to step S3 by eliminating outliers, thus meeting the real-time programmable implementation requirements of the software control module. The input sources of the above process are clearly defined as the original pressure signal and the speed signal, and the output result is clearly defined as a single AC amplitude quantity, which flows directly to the resistance torque estimation stage of step S3. When the drill bit 2 has not yet reached the displacement threshold that triggers the opening of the backup strong cooling air hole 8, only a small overlap occurs between the throttling groove 9 and the main air jet hole 7. Therefore, the AC amplitude mainly reflects the increase or decrease of the cutting load. When the drill bit 2 further increases in displacement and exposes the backup strong cooling air hole 8, the air supply path changes from a single path to a dual-path parallel path. The overall throttling characteristics change abruptly, and the periodic modulation that was originally concentrated in the main air jet hole 7 is partially diverted. Therefore, the AC amplitude detected at the hole opening will show a significant decrease. Thus, the control system can distinguish between two different states: AC enhancement caused by normal cutting and AC drop caused by air path switching. This makes the AC amplitude not only measurable but also has a clear state discrimination meaning.

[0037] In step S4, the system directly issues a feedforward control command; in step S5, within the delay time window, the backup strong cooling air hole 8 is opened by the relative displacement of the lower drill bit 2 and the distribution core tube 4.

[0038] In the long drilling system of coal mine, there is a mechanical lag in the transmission of the state changes of the orifice rotary motor and feed cylinder to the bottom of the hole. If the delayed feedback of torque or speed is still waited for before the deceleration and air increase control are executed, the cutting teeth 16 at the bottom of the hole may have already entered the high temperature damage range. In this embodiment, once the AC amplitude drop characteristic corresponding to the exposure of the backup strong cooling air hole 8 is identified in step S4, the control system directly determines the current state as the critical state of thermal stress concentration and airlock effect, and issues a feedforward control command. The determination here is based on the correspondence between the air pressure characteristics at the orifice and the internal flow distribution action of the drill bit, rather than relying on the mechanical feedback of the rotary motor. After entering step S5, within the delay time window determined by the total length of the drill pipe and the elastic modulus of the material, the safety of the bottom hole mainly depends on the mechanical cooling capacity of the drill bit body. Since the lower drill bit 2 and the distribution core tube 4 have undergone relative displacement, the backup cooling air hole 8 is in the open state. Compressed air is guided to the root area of ​​the arc-shaped vane 14 to flush the local high-pressure air cushion and chip retention area in the chip removal groove, thereby improving the chip removal conditions at the bottom of the hole and reducing the local temperature rise. After the load reduction measures at the borehole are transmitted to the bottom of the borehole, if the load drops, the lower drill bit 2 will restore the initial air path state under the action of the reset force. The technical effect of this implementation method is that the feedforward judgment and the mechanical strong cooling backup protection are used in parallel, so that the actual cooling and unloading measures at the bottom of the borehole have taken effect before the control command reaches the bottom of the borehole.

[0039] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines, characterized in that: The air-cooled anti-burning drill bit for coal mines includes: Upper connector (1), lower drill bit (2), disc spring assembly (3) and distribution core tube (4); The lower end of the upper connector (1) is fitted with the lower drill bit (2). The disc spring assembly (3) is provided between the upper connector (1) and the lower drill bit (2). The upper connector (1) has an upper central air duct (5) processed through it along the axis. The lower drill bit (2) has a lower central air duct (6) machined along the axis inside. The distribution core tube (4) is fixedly connected to the lower end face of the upper connector (1) and is inserted into the lower central air duct (6) with a clearance fit. The lower drill bit (2) is internally machined with a main air jet hole (7) and a spare strong cooling air hole (8). The inlets of the main air jet (7) and the backup strong cooling air jet (8) are both connected to the lower central air duct (6). The distribution core tube (4) has a throttling groove (9) processed on its tube wall; wherein, in the initial assembly state, the throttling groove (9) of the distribution core tube (4) is only aligned and connected with the main air jet hole (7), and the spare strong cold air hole (8) is blocked and closed by the tube wall of the distribution core tube (4). The method for controlling burnout in air-cooled anti-burnout drill bits for coal mines includes the following steps: S1: Construct a drilling execution system including a control system, and a borehole rotary motor, a borehole air compressor, a borehole feed cylinder, a borehole air supply pipeline, and a drill rod connected to the control system, and a drill rod connected between the borehole rotary motor and the coal mine air-cooled anti-burning drill bit; feed the coal mine air-cooled anti-burning drill bit into the borehole but before it contacts the bottom coal and rock surface; instruct the borehole rotary motor to drive the drill rod to rotate at a constant speed; the borehole air compressor outputs compressed air at a constant flow rate; record the basic air pressure value of the borehole air supply pipeline as a zero-point reference; and obtain the rotation frequency of the coal mine air-cooled anti-burning drill bit based on the constant speed. S2: The coal mine air-cooled anti-burning drill bit with arc blades cuts into the coal and rock for drilling operations; drilling tests are conducted in advance under known feed conditions to establish initial mapping coefficients between the periodic AC fluctuation amplitude and the cutting resistance torque under multiple working conditions; time series data of the air supply pressure are continuously recorded; the periodic AC fluctuation amplitude consistent with the rotation frequency of the coal mine air-cooled anti-burning drill bit with arc blades is extracted from the air supply pressure; the DC component of the air pressure signal is separated by low-pass filtering; a correction factor is calculated based on the rate of change of the DC component; and the initial mapping coefficients between the pre-acquired periodic AC fluctuation amplitude and the cutting resistance torque are dynamically adjusted using the correction factor. S3: Based on the extracted periodic AC fluctuation amplitude and the dynamically adjusted initial mapping coefficient, calculate the transient cutting resistance torque at the bottom of the hole; S4: Determine whether the transient cutting resistance torque is greater than the critical resistance torque, which is the torque corresponding to the initial installation preload of the disc spring assembly (3); if it is less than or equal to, maintain the current drilling state; if it is greater than, the control system directly issues a feedforward control command to reduce the propulsion speed of the borehole feed cylinder and increase the air supply pressure of the borehole air compressor. S5: Obtain the system's preset total length of the drill rod, material elastic modulus, and safe threshold range of the air supply pressure; determine the delay time window of the mechanical stress wave based on the total length of the drill rod and the material elastic modulus; keep the backup strong cold air hole (8) open within the delay time window; after the delay time window ends, the disc spring assembly (3) pushes the lower drill bit (2) to reset; determine whether the air supply pressure fluctuation has recovered to the safe threshold range; if yes, instruct the borehole feed cylinder to resume normal drilling cycle; if no, maintain the feedforward control command.

2. The method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines according to claim 1, characterized in that: The lower end of the upper connector (1) is machined with a right-hand rectangular external helical spline (10) on its outer cylindrical surface; the upper end of the lower drill bit (2) is machined with a rectangular internal helical spline (11) that mates with the rectangular external helical spline (10); the lower drill bit (2) is fitted onto the lower end of the upper connector (1) through the rectangular internal helical spline (11) and the rectangular external helical spline (10); wherein, the lower drill bit (2) and the upper connector (1) form a helical transmission pair, and the helix angle of the rectangular external helical spline (10) is 45°.

3. The method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines according to claim 1, characterized in that: The lower drill bit (2) has an inner stepped surface (12) machined inside. The disc spring assembly (3) is sleeved between the lower end face of the upper connector (1) and the inner stepped surface (12) of the lower drill bit (2). The disc spring assembly (3) is formed by stacking spring steel discs (13). The outer diameter of the spring steel discs (13) is 80mm and the inner diameter is 40mm. The initial installation preload of the disc spring assembly (3) is 10000N.

4. The method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines according to claim 1, characterized in that: The lower drill bit (2) has arc-shaped blades (14) evenly distributed on its outer cylindrical surface; the arc-shaped blades (14) are made of cemented carbide material; polycrystalline diamond composite plates (15) are inlaid on the impact surface of the arc-shaped blades (14); wherein, the polycrystalline diamond composite plate (15) serves as a cutting tooth (16), the outlet of the main air jet (7) is directly opposite the cutting edge (17) of the cutting tooth (16), and the outlet of the spare strong cooling air jet (8) is aligned with the chip removal groove (18) at the root of the arc-shaped blades (14).

5. The method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines according to claim 1, characterized in that: The upper central air duct (5) has a diameter of 30 mm; the outer diameter of the distribution core tube (4) is 29.5 mm; the distribution core tube (4) is inserted into the lower central air duct (6) with a gap of 0.5 mm; the throttling groove (9) is evenly distributed along the circumference of the distribution core tube (4).

6. The method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines according to claim 2, characterized in that: When the cutting resistance torque borne by the lower drill bit (2) is greater than the torque corresponding to the initial installation preload of the disc spring assembly (3), the lower drill bit (2) has an upward axial displacement configuration relative to the upper connector (1) along the rectangular outer spiral spline (10). In this axial displacement state, the throttling groove (9) of the distribution core tube (4) is connected to the main air jet hole (7) and the spare strong cold air hole (8) is not blocked by the distribution core tube (4).

7. The method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines according to claim 2, characterized in that: In step S1, the basic air pressure value is composed of the friction resistance inside the drill pipe and the initial throttling resistance of the main air jet (7).

8. The method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines according to claim 7, characterized in that: In step S2, the amplitude of the periodic AC fluctuation is characterized by the high-frequency axial vibration caused by the alternating cutting of coal and rock by the arc-shaped blades (14) of the lower drill bit (2), and the synchronous micro-change of the throttling groove (9) of the distribution core tube (4) on the shielding area of ​​the main air jet (7).

9. The method for controlling burn-out of air-cooled anti-burn-out drill bits for coal mines according to claim 7, characterized in that: In step S4, the system directly issues the feedforward control command; in step S5, within the delay time window, the backup strong cooling air hole (8) is opened by the relative displacement of the lower drill bit (2) and the distribution core tube (4).

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