Coal mine underground rotary directional drilling tool assembly and drilling method

Abstract

The application discloses a kind of coal mine underground rotary directional drilling tool combination and drilling method, including by rear to front sequentially connected center cable drill rod, communication conversion nipple, drilling mode switching nipple, support stable nipple, screw rod drilling tool and drill bit, communication conversion nipple includes communication conversion nipple body, communication conversion nipple body inside is provided with center cable and magnetic coupling communication joint sequentially from rear to front, center cable and magnetic coupling communication joint are connected center cable drill rod and drilling mode switching nipple respectively;Two fixed support rings are arranged at the two ends of supporting center cable;Drilling mode switching nipple is provided with drilling mode switching nipple body, one end of drilling mode switching nipple body is fixedly connected with communication conversion nipple by thread, and the other end is movably connected with support stable nipple, can realize circumferential rotary motion;The rotary directional drilling tool combination and drilling method of the application have the advantages of low drilling trajectory bending strength, high drilling power transmission efficiency and good drilling slag removal effect, which greatly improves the service life of drilling tool, drilling depth and drilling safety, and effectively ensures the safe and efficient construction of coal mine underground directional long borehole.

Description

Technical Field

[0001] This invention belongs to the field of underground tunnel drilling in coal mines, specifically relating to an assembly of rotary directional drilling tools and a drilling method for underground coal mines. Background Technology

[0002] Oriented drilling technology using measurement-while-drilling (MWD) in coal mines offers significant advantages such as good trajectory controllability, large drilling depth, and high hole formation efficiency. It is widely used in areas such as regional gas drainage, rockburst prevention, and advanced geological exploration, effectively ensuring safe and efficient mine production. Currently, underground coal mines primarily employ sliding directional drilling tools and drilling methods for directional drilling. During drilling, the drill rod, non-magnetic drill rod, and screw drill bit remain stationary; only the rotor inside the screw drill bit drives the drill bit to rotate, breaking up the coal and rock strata to form the hole. Therefore, the screw drill bit's bend joint can maintain a specific orientation (the tool face angle remains stable), utilizing the drilling rig's feed force to push the drill bit inside the hole in a sliding manner to achieve directional drilling.

[0003] However, the following problems exist in using existing sliding directional drilling tool assemblies and drilling methods for directional drilling:

[0004] (1) The borehole bending strength is high and the drilling tools are subjected to complex forces. The existing sliding directional drilling tool assembly and drilling method (refer to Chinese patent application CN201810728314.1) results in poor borehole wall smoothness, high bending strength of the borehole trajectory after continuous directional drilling, and high stress intensity and complex stress mode of the drilling tool assembly in the hole, which reduces the service life of the drilling tool assembly.

[0005] (2) Sliding drilling has high frictional resistance and limited hole depth. Existing sliding directional drilling tool combinations and drilling methods can only carry out directional drilling by laterally cutting coal and rock strata in a sliding state. Most of the drilling feed force is used to offset the sliding frictional resistance between the drill string and the hole wall. Only a small part of the feed force is applied to the screw drill tool. The insufficient drilling feed force greatly limits the hole-forming capacity and results in a serious limitation on the hole depth.

[0006] (3) The borehole has a lot of slag, resulting in low drilling safety. The existing sliding directional drilling method relies on high-pressure flushing fluid to remove slag, which has insufficient slag removal capacity. Drill slag tends to accumulate in large quantities at the bottom of the hole, especially when encountering complex and broken coal and rock strata. The slag removal problem is particularly prominent, and complex working conditions such as slag accumulation, hole collapse and drill bit jamming are likely to occur, which significantly reduces drilling safety.

[0007] Therefore, in view of the above-mentioned defects, the designers of this invention, through dedicated research and design, and by integrating experience and achievements in related industries, have developed a rotary directional drilling tool assembly and drilling method for coal mines to overcome the problems of complex drill bit stress, limited hole depth, and low drilling safety in existing sliding directional drilling tool assemblies and drilling methods. Summary of the Invention

[0008] The purpose of this invention is to provide a rotary directional drilling tool assembly and drilling method for underground coal mines, in order to solve the problems of complex drill bit stress, limited hole depth and low drilling safety in existing sliding directional drilling tool assemblies and drilling methods.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] On one hand, the present invention provides a rotary directional drilling tool assembly for coal mines, comprising, in sequence from back to front, a central cable drill rod, a communication conversion section, a drilling mode switching section, a support and stabilizing section, a screw drill bit, and a drill bit. The communication conversion section includes a communication conversion section body, inside which, in sequence from back to front, are a central cable and a magnetic coupling communication connector. The central cable and the magnetic coupling communication connector a are respectively connected to the central cable drill rod and the drilling mode switching section; two fixed support rings are disposed at both ends of the supporting central cable.

[0011] The drilling mode switching section includes a drilling mode switching section body. One end of the drilling mode switching section body is fixedly connected to the communication conversion section via a thread, and the other end is movably connected to the support and stabilization section, enabling circumferential rotation. A drilling mode switching center rod is provided in the central channel of the drilling mode switching section body. From back to front, the inner wall of the drilling mode switching section body is provided with a limit ring a, a drilling mode switching chuck, a spring a, and a spring fixing ring a.

[0012] The inner wall of the main body has four sliding slots at equal angles around its circumference, and the outer wall of the drilling mode switching chuck has four sliding protrusions at equal angles around its circumference. The drilling mode switching chuck can move axially along the sliding slots using the four sliding protrusions. The outer wall of the main body has a limiting screw hole at equal angles around its circumference. The front face of the drilling mode switching chuck has multiple locking protrusions at equal angles, which cooperate with the corresponding locking grooves on the outer wall of the rear end of the drilling mode switching center rod.

[0013] Furthermore, the springs a are evenly distributed in four circumferential directions.

[0014] Furthermore, the outer wall of the drilling mode switching center rod is provided with a locking groove, a water passage hole a, a rotary dynamic seal mounting groove, a wear-resistant bearing mounting groove, and a limit screw mounting groove in sequence from back to front; the rotary dynamic seal mounting groove is provided with a rotary dynamic seal, the wear-resistant bearing mounting groove is provided with a wear-resistant bearing, the limit screw mounting groove is provided with a limit screw, and the water passage hole a connects the interior of the drilling mode switching center rod with the central channel of the main body; the drilling mode switching center rod is provided with a slant measuring component, which includes a magnetic coupling communication connector b and a fixing ring, a rubber stabilizer and a slant measuring unit, and the magnetic coupling communication connector b is connected to the axial rear end of the slant measuring unit.

[0015] Furthermore, the supporting and stabilizing short section is provided with a supporting and stabilizing short section body. The front side wall of the supporting and stabilizing short section body is provided with multiple water passage holes b at equal angles. The water passage holes b connect the interior of the supporting and stabilizing short section body and the interior of the screw drill. The outer wall of the supporting and stabilizing short section body is provided with three push-back palm mounting grooves at equal angles on the circumference. The central channel of the supporting and stabilizing short section body is provided with a piston assembly limiting ring, a piston assembly, a spring b, and a spring fixing ring b in sequence.

[0016] Furthermore, the front side wall of the supporting and stabilizing short section body is provided with four water passage holes b at equal angles.

[0017] Furthermore, the piston assembly limiting ring has four water passage holes evenly distributed on it.

[0018] On the other hand, the present invention also provides a method for rotary directional drilling in coal mines, which utilizes the rotary directional drilling tool assembly of the present invention described above for drilling operations, and includes the following steps:

[0019] (1) Measurement of borehole trajectory parameters: The coal mine underground rotary directional drilling tool assembly is lowered into the borehole. From the bottom of the hole to the opening, the assembly consists of a drill bit, a screw drill bit, a support and stabilization sub, a drilling mode switching sub, a communication conversion sub, multiple center cable drill rods, and a water supply device. The current borehole trajectory parameter information is measured using the inclination measurement unit in the drilling mode switching sub. The borehole trajectory parameter information is transmitted wirelessly to the communication conversion sub through magnetic coupling communication connector b and magnetic coupling communication connector a. The borehole trajectory parameter information is transmitted to the opening through wired communication via the central cable of the communication conversion sub and multiple center cable drill rods.

[0020] (2) Adjustment of the tool face angle of the screw drill bit: The borehole monitoring terminal calculates the tool face angle that needs to be adjusted based on the measured borehole inclination angle, azimuth angle parameters and the tool face angle of the screw drill bit; High-pressure flushing fluid is input into the rotary directional drilling tool assembly in the coal mine through a mud pump and a water feeder. The flushing fluid discharge rate is set so that the pusher is pushed out by the flushing fluid and supports the borehole wall. At the same time, the flushing fluid pressure can overcome the resistance of spring a, so that the locking protrusion on the front face of the drilling mode switching chuck is pushed into the locking groove at the rear end of the drilling mode switching center rod, thereby locking the drilling mode switching center rod in the circumferential direction of the drilling mode switching short section body, thereby realizing the joint rotation of the drilling mode switching short section and the support stabilization short section; The communication switching short section, the drilling mode switching short section, the support stabilization short section and the screw drill bit are rotated at a low speed by the drilling rig rotation center cable drill rod, and the tool face angle of the screw drill bit is adjusted according to the calculated tool face angle that needs to be adjusted;

[0021] (3) Rotary directional drilling: The flushing fluid flow rate is reduced so that the pusher in the support and stabilizing sub still supports the borehole wall to prevent the screw drill from rotating and to maintain the tool face angle stability. At the same time, the flushing fluid flow rate is insufficient to overcome the resistance of spring a, so that the drilling mode switching chuck in the drilling mode switching sub separates from the locking groove, and the drilling mode switching sub can rotate relative to the drilling mode switching center rod. The drilling rig rotation center cable drill rod drives the overall rotation of the communication conversion sub and the drilling mode switching sub, while the support and stabilizing sub and the screw drill do not rotate. Rotary directional drilling is achieved by drilling rig construction.

[0022] Furthermore, in step (2), the flushing fluid discharge rate is set to be above 350 L / min.

[0023] Furthermore, in step (3), the flushing fluid flow rate is reduced to 300 L / min.

[0024] Furthermore, in step (2), the lower rotational speed is 10-20 r / min.

[0025] The beneficial effects of this invention include:

[0026] (1) The bending strength of the drilling trajectory is low, and the service life of the drill string assembly is improved. During the construction process of the rotary directional drilling string assembly and drilling method of the present invention, the drill rod rotates and drills to grind the hole wall, making the hole wall smooth, the bending strength of the drilling trajectory is significantly reduced, the stress condition of the drill string assembly in the hole is simple, and the service life of the drill string assembly is significantly improved.

[0027] (2) High drilling power transmission efficiency and greatly improved hole depth. In the drilling process, except for the supporting and stabilizing short section and the sliding drilling of the screw drill, the other parts are rotary drilling, which significantly reduces drilling friction, provides sufficient feed force to the screw drill, and has high drilling power transmission efficiency, which greatly improves hole depth.

[0028] (3) The drilling slag removal effect is good, and the drilling safety is significantly improved. The rotary directional drilling tool combination and drilling method of the present invention, based on the high-pressure flushing fluid slag removal, utilizes the rotary drilling tool combination to mechanically stir the slag, which improves the suspension capacity of the drill slag. When encountering complex and broken coal and rock strata, there will be no large accumulation of drill slag at the bottom of the hole. It realizes dual-power composite slag removal, avoids the occurrence of complex working conditions in the hole such as slag settling and hole collapse and drill bit jamming, and significantly improves drilling safety. Attached Figure Description

[0029] Figure 1 This is a diagram showing the overall composition of the rotary directional drilling tool assembly.

[0030] Figure 2 This is a partial diagram of the rotary directional drilling tool assembly.

[0031] Figure 3 Switch the short section body AA and BB sectional views to the drilling mode.

[0032] Figure 4 Switch the chuck to the right view to change the drilling mode.

[0033] Figure 5 This is a detailed diagram of the drilling mode switching center rod and the inclination measurement component.

[0034] Figure 6 A cross-sectional view along the CC direction to support the stable short section body.

[0035] In the above diagram: 1-Center cable drill rod, 2-Communication conversion section, 3-Drilling mode switching section, 4-Support stabilizing section, 5-Screw drill bit, 6-Drill bit, 201-Communication conversion section body, 202-Center cable, 203-Magnetic coupling communication connector, a, 204-Fixed support ring, 301-Drilling mode switching section body, 302-Limit ring a, 303-Drilling mode switching center rod, 304-Rotary dynamic seal, 305-Limit screw, 306-Wear-resistant bearing, 307-Angle measuring assembly, 308-Spring retaining ring a, 309-Spring a, 3010-Drilling mode switching chuck, 3011-Sliding groove, 3 012-Limit screw hole, 3031-Locking groove, 3032-Water passage hole a, 3033-Wear-resistant bearing mounting groove, 3034-Limit screw mounting groove, 3035-Rotary dynamic seal mounting groove, 3071-Magnetic coupling communication connector b, 3072-Fixing ring, 3073-Rubber centralizer, 3074-Inclination measuring unit, 30101-Sliding key, 30102-Locking key, 401-Supporting and stabilizing short section body, 402-Pushing palm, 403-Spring fixing ring b, 404-Spring b, 405-Piston assembly, 406-Piston assembly limit ring, 4011-Water passage hole b, 4012-Pushing palm mounting groove. Detailed Implementation

[0036] This invention discloses a rotary directional drilling tool assembly for underground coal mines, see [link to relevant documentation]. Figure 1 It includes, in sequence from back to front, the center cable drill rod 1, the communication conversion section 2, the drilling mode switching section 3, the support and stabilization section 4, the screw drill string 5, and the drill bit 6. Among them:

[0037] See Figure 1 , 2The communication conversion section 2 includes a communication conversion section body 201. Inside the communication conversion section body 201, from back to front, there are a central cable 202 and a magnetic coupling communication connector a203. The central cable 202 and the magnetic coupling communication connector a203 are respectively connected to the central cable drill rod 1 and the drilling mode switching section 3. The central cable 202 is used to realize wired power supply and communication between the communication conversion section 2 and the central cable drill rod 1, and the magnetic coupling communication connector a203 is used to realize wireless power supply and communication between the communication conversion section 2 and the drilling mode switching section 3. Two fixed support rings 204 are set at both ends of the supporting central cable 202 to fix and support the central cable 202 and the magnetic coupling communication connector a203 inside the communication conversion section body 201.

[0038] The drilling mode switching section 3 is provided with a drilling mode switching section body 301. One end of the drilling mode switching section body 301 is fixedly connected to the communication conversion section 2 by a thread, and the other end is movably connected to the support and stabilization section 4, which can realize circumferential rotation. A drilling mode switching center rod 303 is provided in the central channel of the drilling mode switching section body 301. The inner wall of the drilling mode switching section body 301 is provided with a limiting ring a302, a drilling mode switching chuck 3010, springs a309 (4 evenly distributed in the circumference), and spring fixing rings a308 in sequence from back to front.

[0039] Among them, see Figure 3 , Figure 4 The main body 301 has four sliding grooves 3011 at equal angles on its inner wall, and the drilling mode switching chuck 3010 has four sliding protrusions 30101 at equal angles on its outer wall. The drilling mode switching chuck 3010 can move axially along the sliding grooves 3011 using the four sliding protrusions 30101. The main body 301 has four limiting screw holes 3012 at equal angles on its outer wall for installing limiting screws 305 to achieve axial positioning of the drilling mode switching center rod 303. The front end face of the drilling mode switching chuck 3010 has multiple locking protrusions 30102 at equal angles to cooperate with corresponding locking grooves 3031 on the rear end outer wall of the drilling mode switching center rod 303 to lock the drilling mode switching center rod 303 circumferentially within the main body 301 of the drilling mode switching section.

[0040] Among them, see Figure 5The outer wall of the drilling mode switching center rod 303 is provided with, from back to front, a locking groove 3031, a water passage hole a3032, a rotary dynamic seal mounting groove 3035, a wear-resistant bearing mounting groove 3033, and a limit screw mounting groove 3034; the rotary dynamic seal mounting groove 3035 is provided with a rotary dynamic seal 304, the wear-resistant bearing mounting groove 3033 is provided with a wear-resistant bearing 306, and the limit screw mounting groove 3034 is provided with a limit screw 305; the water passage hole a3032 connects to the drilling mode switching center rod 3031. 3. The central channel between the interior and the main body 301; the drilling mode switching center rod 303 is equipped with a tilt measuring component 307, which includes a magnetic coupling communication connector b3071, a fixing ring 3072, a rubber stabilizer 3073, and a tilt measuring unit 3074; wherein, the tilt measuring unit 3074 is fixedly installed and straightened and vibration-damped by the fixing ring 3072 and the rubber stabilizer 3073 installed at both ends of it, and the magnetic coupling communication connector b3071 is connected to the axial rear end of the tilt measuring unit 3074.

[0041] Among them, see Figure 2 , 5 The magnetic coupling communication connector a203 and magnetic coupling communication connector b3071 constitute a magnetic coupling communication component, which is used to realize wireless power supply from the communication conversion sub 2 to the drilling mode switching sub 3, as well as wireless bidirectional communication between the communication conversion sub 2 and the drilling mode switching sub 3.

[0042] See Figure 2 , 6 The supporting and stabilizing short section 4 is provided with a supporting and stabilizing short section body 401. The front side wall of the supporting and stabilizing short section body 401 is provided with multiple water passage holes b4011 (preferably 4) at equal angles. The water passage holes b4011 connect the interior of the supporting and stabilizing short section body 401 and the interior of the screw drill 5. The outer wall of the supporting and stabilizing short section body 401 is provided with 3 push-palm mounting grooves 4012 at equal angles in the circumferential direction for installing push-palms 402. The central channel of the supporting and stabilizing short section body 401 is provided with a piston assembly limiting ring 406 (with 4 water passage holes evenly distributed in the circumferential direction), a piston assembly 405, a spring b404 and a spring fixing ring b403 in sequence.

[0043] This invention also provides a method for rotary directional drilling in coal mines, which utilizes the aforementioned rotary directional drilling tool assembly for drilling operations, and includes the following steps:

[0044] (1) Measurement of borehole trajectory parameters. The rotary directional drilling tool assembly of the present invention is lowered into the borehole. From the bottom of the hole to the opening, the assembly consists of a drill bit 6, a screw drill 5, a support and stabilization sub 4, a drilling mode switching sub 3, a communication conversion sub 2, multiple center-connected drill rods 1, and a water supply device. The current borehole trajectory parameter information (including borehole inclination angle, azimuth angle, and screw drill tool face angle) is measured using the inclination measurement unit 3074 in the drilling mode switching sub 3. The borehole trajectory parameter information is transmitted wirelessly to the communication conversion sub 2 via magnetic coupling communication connector b3071 and magnetic coupling communication connector a203. The borehole trajectory parameter information is then transmitted to the opening via wired communication through the center cable 202 of the communication conversion sub 2 and multiple center-connected drill rods 1.

[0045] (2) Adjustment of the tool face angle of the screw drill bit. Based on the measured drilling inclination angle, azimuth angle parameters and the tool face angle of the screw drill bit, the borehole monitoring terminal calculates the tool face angle that needs to be adjusted for the screw drill bit 5. High-pressure flushing fluid is input into the borehole rotary directional drilling tool assembly of the present invention through a mud pump and a water feeder. The flushing fluid discharge rate is set to above 350L / min. The push palm 402 is pushed out by the flushing fluid and supports the borehole wall. At the same time, the flushing fluid pressure overcomes the resistance of the spring a309, so that the locking protrusion 30102 on the front face of the drilling mode switching chuck 3010 is pushed into the drilling mode switching position. Within the locking groove 3031 at the rear end of the center rod 303, the drilling mode switching center rod 303 is locked circumferentially within the drilling mode switching sub body 301. This allows the drilling mode switching sub 3 and the support and stabilizing sub 4 to rotate together. By slowly rotating the center cable drill rod 1, the communication switching sub 2, the drilling mode switching sub 3, the support and stabilizing sub 4, and the screw drill tool 5 are rotated at a low speed (10-20 r / min). The screw drill tool 5 is then adjusted to the required tool face angle according to the calculation.

[0046] (3) Rotary directional drilling. The flushing fluid flow rate is reduced to about 300 L / min. At this time, the pusher 402 in the support and stabilizing section 4 still supports the hole wall to prevent the screw drill 5 from rotating and to keep the tool face angle stable. When the flushing fluid flow rate reaches about 300 L / min, it is not enough to overcome the resistance of the spring a309. Therefore, the drilling mode switching chuck 3010 in the drilling mode switching section 3 separates from the locking groove 3031, and the drilling mode switching section 301 can rotate relative to the drilling mode switching center rod 303. Using the rotary directional drilling tool assembly of the present invention in the rotating hole of the drilling rig, the center cable drill rod 1 drives the communication conversion section 2 and the drilling mode switching section 3 to rotate as a whole at a rotation speed of 40-50 r / min. The support and stabilizing section 4 and the screw drill 5 do not rotate. Rotary directional drilling can be achieved after the drilling rig provides appropriate feed force.

[0047] In step (3) of the method of the present invention described above, the control principle of rotary directional drilling is as follows: when the flushing fluid discharge reaches about 300L / min, the high-pressure flushing fluid drives the piston assembly 405 to move forward against the resistance of the spring b404. After the piston assembly 405 moves down, it pushes out the three push pads 402 of the supporting and stabilizing short section body 401 in the circumferential direction to support the hole wall. At this time, the supporting and stabilizing short section 4 and the screw drill 5 can be kept from rotating. When the flushing fluid discharge reaches about 300L / min, it is not enough to overcome the resistance of the spring a309. The drilling mode switching short section body 301 can rotate relative to the drilling mode switching center rod 303. At this time, the drilling rig's rotational force can drive the center cable drill rod 1, the communication conversion short section 2 and the drilling mode switching short section 3 to rotate. The supporting and stabilizing short section 4 and the screw drill 5 do not rotate. Thus, rotary directional drilling can be achieved by using the appropriate feed force of the drilling rig.

[0048] In step (2) of the method of the present invention described above, the control principle of the tool face angle of the screw drill bit is as follows: when the flushing fluid discharge reaches 350L / min or more, the flushing fluid drives the drilling mode switching chuck 3010 to move forward against the resistance of the spring a309. The four locking protrusions 30102 circumferentially arranged on the end face of the switching chuck 3010 cooperate with the four locking grooves 3031 provided on the drilling mode switching center rod 303 to realize the circumferential locking of the drilling mode switching sub body 301. The drilling mode switching center rod 303 cannot rotate relative to the drilling mode switching section 3, thus achieving a fixed connection between the drilling mode switching section 3 and the support and stabilizing section 4. During this process, the push pad 402 still supports the hole wall, but the support and stabilizing section 4 can rotate slowly under the rotational power of the drilling rig. At this time, the center cable drill rod 1, the communication switching section 2, the drilling mode switching section 3, the support and stabilizing section 4, and the screw drill tool 5 can rotate together as a whole, so that the tool face angle of the screw drill tool 5 can be adjusted by rotating the center cable drill rod 1 of the drilling rig.

Claims

1. A rotary directional drilling tool assembly for underground coal mines, characterized in that, The system includes a central cable drill rod (1), a communication conversion section (2), a drilling mode switching section (3), a support and stabilization section (4), a screw drill bit (5), and a drill bit (6) connected sequentially from back to front. The communication conversion section (2) includes a communication conversion section body (201). Inside the communication conversion section body (201), a central cable (202) and a magnetic coupling communication connector a (203) are arranged sequentially from back to front. The central cable (202) and the magnetic coupling communication connector a (203) are respectively connected to the central cable drill rod (1) and the drilling mode switching section (3). Two fixed support rings (204) are set at both ends of the supporting central cable (202). The drilling mode switching section (3) is provided with a drilling mode switching section body (301). One end of the drilling mode switching section body (301) is fixedly connected to the communication conversion section (2) by a thread, and the other end is movably connected to the support and stabilization section (4), which can realize circumferential rotation. A drilling mode switching center rod (303) is provided in the central channel of the drilling mode switching section body (301). The inner wall of the drilling mode switching section body (301) is provided with a limiting ring a (302), a drilling mode switching chuck (3010), a spring a (309), and a spring fixing ring a (308) in sequence from back to front. The inner wall of the main body (301) is provided with four sliding slots (3011) at equal angles in the circumference, and the outer wall of the drilling mode switching chuck (3010) is provided with four sliding protrusions (30101) at equal angles in the circumference. The drilling mode switching chuck (3010) can move axially along the sliding slots (3011) using the four sliding protrusions (30101). The outer wall of the main body (301) is provided with four limiting screw holes (3012) at equal angles in the circumference. The front end face of the drilling mode switching chuck (3010) is provided with multiple locking protrusions (30102) at equal angles, which cooperate with the corresponding locking grooves (3031) provided on the outer wall of the rear end of the drilling mode switching center rod (303). The outer wall of the drilling mode switching center rod (303) is provided with, from back to front, a locking groove (3031), a water passage hole a (3032), a rotary dynamic seal mounting groove (3035), a wear-resistant bearing mounting groove (3033), and a limit screw mounting groove (3034); the rotary dynamic seal mounting groove (3035) is provided with a rotary dynamic seal (304), the wear-resistant bearing mounting groove (3033) is provided with a wear-resistant bearing (306), and the limit screw mounting groove (3034) is provided with a limit screw (3034). 05), water passage a (3032) connects the interior of the drilling mode switching center rod (303) with the central channel of the body (301); the drilling mode switching center rod (303) is provided with a tilt measuring component (307), the tilt measuring component (307) includes a magnetic coupling communication connector b (307) and a fixing ring (3072), a rubber stabilizer (3073) and a tilt measuring unit (3074), the magnetic coupling communication connector b (3071) is connected to the axial rear end of the tilt measuring unit (3074); The supporting and stabilizing short section (4) is provided with a supporting and stabilizing short section body (401). The front side wall of the supporting and stabilizing short section body (401) is provided with multiple water passage holes b (4011) at equal angles. The water passage holes b (4011) connect the interior of the supporting and stabilizing short section body (401) and the interior of the screw drill (5). The outer wall of the supporting and stabilizing short section body (401) is provided with three push-back palm mounting grooves (4012) at equal angles on the circumference. The central channel of the supporting and stabilizing short section body (401) is provided with a piston assembly limiting ring (406), a piston assembly (405), a spring b (404), and a spring fixing ring b (403) in sequence. The supporting and stabilizing short section body (401) has four water passage holes b (4011) at equal angles on the front side wall. The piston assembly limiting ring (406) has four water passage holes evenly distributed on it.

2. The rotary directional drilling tool assembly for coal mines as described in claim 1, characterized in that, The spring a (309) has 4 springs evenly distributed in the circumferential direction.

3. A method for rotary directional drilling in coal mines, characterized in that, This method utilizes the rotary directional drilling tool assembly for coal mine underground drilling as described in claim 1 or 2, and includes the following steps: (1) Measurement of borehole trajectory parameters: The coal mine underground rotary directional drilling tool assembly is lowered into the borehole. From the bottom of the hole to the opening, the assembly consists of a drill bit (6), a screw drill (5), a support and stabilization short section (4), a drilling mode switching short section (3), a communication conversion short section (2), multiple central cable drill rods (1), and a water supply device. The current borehole trajectory parameter information is measured by the inclination measurement unit (3074) in the drilling mode switching short section (3). The borehole trajectory parameter information is transmitted to the communication conversion short section (2) wirelessly through the magnetic coupling communication connector b (3071) and the magnetic coupling communication connector a (203). The borehole trajectory parameter information is transmitted to the opening through the central cable (202) of the communication conversion short section (2) via multiple central cable drill rods (1) in a wired communication manner. (2) Adjustment of the tool face angle of the screw drill bit: The borehole monitoring terminal calculates the tool face angle that needs to be adjusted for the screw drill bit (5) based on the measured borehole inclination angle, azimuth angle parameters and the tool face angle of the screw drill bit; High-pressure flushing fluid is input to the rotary directional drilling bit assembly in the coal mine through the mud pump and water delivery device. The flushing fluid discharge rate is set so that the push palm (402) is pushed out by the flushing fluid and supports the borehole wall. At the same time, the flushing fluid pressure can overcome the resistance of the spring a (309), so that the locking protrusion (30102) on the front face of the drilling mode switching chuck (3010) is pushed into the drilling mode. In the locking groove (3031) at the rear end of the mode switching center rod (303), the drilling mode switching center rod (303) is locked in the circumferential direction of the drilling mode switching short section body (301), thereby realizing the joint rotation of the drilling mode switching short section (3) and the support stabilization short section (4); using the drilling rig rotation center cable drill rod (1), the communication conversion short section (2), drilling mode switching short section (3), support stabilization short section (4) and screw drill tool (5) are rotated at a low speed, and the tool face angle of the screw drill tool (5) is adjusted according to the calculated tool face angle; (3) Rotary directional drilling: The flushing fluid flow rate is reduced so that the pusher (402) in the support stabilization section (4) still supports the hole wall to prevent the screw drill (5) from rotating in order to maintain the tool face angle stability. At the same time, the flushing fluid flow rate is insufficient to overcome the resistance of spring a (309), so that the drilling mode switching chuck (3010) in the drilling mode switching section (3) separates from the locking groove (3031). The drilling mode switching section (301) can rotate relative to the drilling mode switching center rod (303). The drilling rig rotation center cable drill rod (1) drives the overall rotation of the communication conversion section (2) and the drilling mode switching section (3). The support stabilization section (4) and the screw drill (5) do not rotate. Rotary directional drilling is achieved by drilling rig construction.

4. The method for rotary directional drilling in coal mines as described in claim 3, characterized in that, In step (2), the flushing fluid discharge rate is set to above 350 L / min.

5. The method for rotary directional drilling in coal mines as described in claim 3, characterized in that, In step (3), the flushing fluid flow rate is reduced to 300L / min.

6. The method for rotary directional drilling in coal mines as described in claim 3, characterized in that, In step (2), the lower rotational speed is 10~20 r / min.

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