Patent Publication Number: US-2022213745-A1

Title: Driving system for core drilling rig

Description:
TECHNICAL FIELD 
     The present invention relates to a core drilling system, and especially to a driving system of core drilling rig. 
     BACKGROUND ART 
     In the process of oilfield exploration, rock core is the key material for discovering oil and gas reservoir, as well as studying stratum, source rock, reservoir rock, cap rock, structure, and so on. Through the observation and study of the core, the lithology, physical properties, as well as the occurrence and characteristics of oil, gas, and water can be directly understood. After the oilfield is put into development, it is necessary to further study and understand the reservoir sedimentary characteristics, reservoir physical properties, pore structure, wettability, relative permeability, lithofacies characteristics, reservoir physical simulation, and reservoir water flooding law through core. Understanding and mastering the water flooded characteristics of reservoirs in different development stages and water cut stages, and finding out the distribution of remaining oil can provide scientific basis for the design of oilfield development plan, formation system, well pattern adjustment, and infill well. 
     Coring is to use special coring tools to take underground rocks to the ground in the process of drilling, and this kind of rock is called core. Through it, various properties of rocks can be determined, underground structure and sedimentary environment can be studied intuitively, and fluid properties can be understood, etc. In the process of mineral exploration and development, the drilling work can be carried out according to the geological design of strata and depth, and coring tools were put into the well, to drill out rock samples. 
     The downhole temperature is high, and electrical equipment cannot be used. Mechanical structures are required to control the various steps of the drilling rig equipment. 
     CONTENT OF THE INVENTION 
     The present invention is intended to provide a driving system for the core drilling rig, that can be matched with a ground device to control a downhole device of the core drilling rig to work according to the coring steps, so as to realize long-distance mud-driven drilling and coring, as well as to provide the driving system with high efficiency, stepless speed change, and micro-disturbance. In order to realize the above objectives, the technical solutions adopted by the present invention are as follows: 
     The driving system for a core drilling rig disclosed in the present invention comprises a driving motor. The driving motor comprises an outer rotor and an inner stator, and mutually-matched convex ribs are provided on the inner wall of the outer rotor and the outer wall of the inner stator. The outer rotor and the inner stator are in clearance fit. A clearance between the outer rotor and the inner stator is a driving liquid channel. The length of the outer rotor is less than that of the inner stator. The outer rotor is provided between the front and rear ends of the inner stator. The outer rotor is connected to an outer cylinder. The rear end of the inner stator is connected to a coupling. 
     Further, a hydraulic pump is connected behind the driving liquid channel. 
     Further, the outer cylinder is provided with a driving liquid outlet, and the driving liquid outlet is in front of the outer rotor. 
     Further, the inner stator penetrates back and forth, and further includes a central rod, which passes through the inner cavity of the inner stator and the coupling, and the central rod is connected to a core barrel, that is in front of the inner stator. 
     Further, comprises a fluid channel activation module, an outer cylinder, an outer cylinder unlocking module, a flow diverging module, and a drill bit. The central rod passes through, from the rear to the front, the inner cavities of a fluid channel activation module, an outer cylinder unlocking module, and a flow diverging module. The fluid channel activation module is behind the outer cylinder, and the fluid channel activation module is connected to the outer cylinder unlocking module; the flow diverging module is in front of the outer cylinder unlocking module, and the front of the flow diverging module is connected to a driving motor. The outer wall of the outer cylinder is fixedly connected with a centralizer, and the front end of the outer cylinder is connected to a drill bit. 
     Furthermore, the centralizer comprises a plurality of centralizing blocks, which are uniformly fixed on the outer wall of the outer cylinder along the circumference. The radian of the outer side of the centralizing block is the same as that of the outer wall of the outer cylinder, and the distance from the outer side of the centralizing block to the axis of the outer cylinder is greater than the radius of the outer cylinder, while the distance from all the centralizing blocks to the rear end of the outer cylinder is equal. All the centralizing blocks have the same thickness, and the centralizing blocks are made of copper. 
     Further, the centralizer is in front of the driving section, and the centralizer is behind the outlet of the driving fluid. 
     Further, the fluid channel activation module is behind the inner stator, and the fluid channel activation module comprises a lock body, a locking rod, and a start shear pin. The locking rod is in the lock body, and the locking rod and the lock body are connected by the start shear pin. Said central rod is in the locking rod. The lock body comprises a sealing section A, and the locking rod comprises a sealing section B. The sealing section A and the sealing section B are in a sealing fit, while said sealing section B is in a sealing fit with the central rod. There is a fluid channel A between the central rod and the locking rod, and the locking rod has an outflow hole A, that communicates with the fluid channel A. The outflow hole A is behind the sealing section B. There is a fluid channel B between the lock body and the locking rod, and the fluid channel B is in front of the sealing section A. Before the start shear pin is cut, the outlet of the outflow hole A is at the sealing section A, and the front end of the fluid channel A is sealed. After the start shear pin is cut, the locking rod moves forward, the outlet of the outflow hole A is located in front of the sealing section A, and the fluid channel A and the fluid channel B are connected through the outflow hole A. 
     Further, said outer barrel unlocking module comprises the connecting pipe and the lock pin. The rear end of the connecting pipe is connected to the lock body, while the rear end of the lock pin is connected to the locking rod. The central rod passes through the inner cavity of the lock pin, and the lock pin is in the connecting pipe. The outer diameter of the front section of the connecting pipe is shorter than the inner diameter of the outer barrel, and the side wall of the front section of the connecting pipe has an unlocking hole. There is a groove A on the outer wall of the lock pin, while there is a groove B on the inner wall of the outer barrel. The pin is also included, the length of the pin is greater than the depth of the unlocking hole, and the pin is arranged in the unlocking hole. Further, the outer end of the pin is chamfered and/or the side surface of the groove B is inclined. The width of groove A is not less than the width of the inner end of the pin, while the width of the groove B is not less than the width of the outer end of the pin. The front end of the connecting pipe is in the outer barrel, and the pin is in front of the groove A. The inner end surface of the pin is in sliding fit with the outer wall of the lock pin, and the outer end of the pin is embedded in the groove B. After the start shear pin is cut, the locking rod drives the lock pin forward, the unlocking hole is directly opposite to the groove A, the inner end of the pin is embedded in the groove A, and the distance from the inner end surface of the pin to the inner wall of the outer cylinder is greater than the length of the pin. 
     Further, said flow diverging module includes a valve housing, a lock housing and a trigger mechanism. The central rod passes through the inner cavity of the valve housing. The valve housing is inside the lock housing, and the rear of the lock housing is connected to the connecting pipe. From back to front, the valve housing includes a sealing section C and a diversion section. The lock housing includes an inflow section B and an outflow section B from back to front. There is a fluid channel D between the central rod and the inflow section B, while there is a fluid channel E between the outer wall of the central rod and the inner wall of the valve housing. The back end of fluid channel D communicates with fluid channel B, and fluid channel E communicates with fluid channel D, and fluid channel E communicates with the cooling hole of the front drill bit. The inner diameter of the inflow section B is longer than the outer diameter of the sealing section C, while the outer diameter of the sealing section C is greater than the outer diameter of the diversion section, and the inner diameter of the outflow section B is equal to the outer diameter of the sealing section C. The outflow section B is provided with an outflow hole B, and the outflow hole B communicates with the driving liquid channel of the driving motor. Before stopping the drilling, the front end of sealing section C is in the inflow section B, and the fluid channel D and the outflow hole B are connected. After stopping the drilling, the sealing section C and the outflow section B are in a sealing fit, and the fluid channel D is separated from the outflow hole B. The front end of the lock housing is connected to the rear end of the coupling. 
     Further, said valve housing further includes a locking section A. The locking section A is connected to the front end of the diversion section. The lock housing also includes a locking section B, that is connected to the front end of the outflow section B. The inner wall of the outer barrel is connected to a safety gear. The trigger mechanism includes a locking sleeve, a fixing ring, and a safety gear. The lock housing passes through the inner cavity of the locking sleeve, and the outer wall of the locking section A is provided with a locking groove A. The locking section B has a locking hole A and a locking hole B, and the locking hole B is in front of the locking hole A. Both locking hole A and locking hole B are through holes. Locking hole A and locking hole B have the same size, and there are locking balls in both locking hole A and locking hole B. The diameter of the locking ball is greater than the depth of the locking hole A. The locking sleeve includes an impact section and the locking section C from back to front. The inner wall of the locking section C has a locking groove B and a locking groove C. The locking groove C is in the front of locking groove B. The distance between the locking groove B and the locking groove C is equal to the distance between the locking hole A and the locking hole B. The fixing ring is fixed on the outer wall of the locking section B, and the fixing ring is behind the locking hole A. The inner diameter of the impact section is longer than the outer diameter of the fixing ring. The locking section C is in front of the fixing ring. The safety gear includes the clamping part and the pressing part from back to front. The inner diameter of the front end of the pressing part is shorter than the outer diameter of the impact section, while the inner diameter of the pressing part is not less than the outer diameter of the fixing ring. The inner diameter of the front end of the clamping part is shorter than the outer diameter of the rear end of the fixing ring. There is a limit part in the central rod, and the limit part is in the locking section B and in front of the locking section A. The outer wall of the limit part is provided with a locking groove D, and the locking groove D is in front of the locking groove A. Moreover, a fluid channel F is opened inside the limit part. The fluid channel E is connected to the cooling hole of the front drill bit by the fluid channel F. The axial distance from the front end of the clamping part to the front end of the pressing part is equal to the axial distance from the center of the locking hole A to the center of the locking groove B before the drilling is stopped. Before stopping the drilling, the distance from the rear end of the sealing section C to the rear end of the outflow hole B is greater than the axial distance from the center of the locking hole A to the center of the locking groove A after stopping the drilling. After the drilling is stopped, the axial distance from the center of the locking hole A to the center of the locking groove A is greater than the distance from the front end of the sealing section C to the front end of the outflow hole B before the drilling is stopped. 
     Further, there is a fluid channel C between the central rod, the lock pin and the locking rod, as well as the side wall of the locking rod is provided with an inflow hole. The fluid channel B communicates with the fluid channel C through the inflow hole, while the fluid channel C communicates with the fluid channel D. The connecting pipe includes a pressure-relief section and a choke section from back to front. The lock pin and the choke section are in a sealing fit, and the inner diameter of the choke section is shorter than the inner diameter of the pressure-relief section. The pressure-relief section is provided with a pressure-relief hole, and the pressure-relief hole is a through hole. There is a shearing plunger in the fluid channel B, and the inner diameter of the shearing plunger is longer than the outer diameter of both the lock pin and the locking rod. The shearing plunger is connected to the lock body through the end shearing pin. The shearing plunger includes a shearing section and a recoil section from back to front. The outer wall of the shearing section is in a sealing fit with the inner wall of the lock body, and the outer diameter of the recoil section is equal to the inner diameter for the front part of the pressure-relief hole in the pressure-relief section. Before stopping the drilling, the front end of the recoil section is in front of the front end of the pressure-relief hole, and the recoil section is in a sealing fit with the front part of the pressure-relief hole in the pressure-relief section. After stopping the drilling, liquid backflow impacts the front end of the shearing plunger, and the shearing plunger moves backward. The front end of the recoil section is behind the front end of the pressure-relief hole, and the fluid channel B communicates with the pressure-relief hole. 
     Further, the outer wall of the locking rod and the inner wall of the lock body are provided with mutually matched limit steps. 
     Further, a lock nut is also included. The lock nut is behind the lock body, and the lock nut penetrates back and forth. The central rod passes through the inner cavity of the lock nut, and the front end of the lock nut is threadedly connected with the rear end of the lock body. The start shear pin passes through the rear end thread of the lock body. 
     Further, the lock nut includes a fixed section and a threaded section. The outer diameter behind the step of the locking rod is shorter than the inner diameter of the fixed section, while the inner diameter of the fixed section is shorter than the outer diameter of the step of the locking rod. The threaded section is connected to the rear end of the lock body. 
     Further, said lock nut is axially provided with a fixing hole A, and the fixing hole A is a through hole. The lock body has a fixing hole B on the rear face, but the fixing hole B is a blind hole. The fixing hole A and the fixing hole B are paired. A fixing screw is also included, and the length of the fixing screw is greater than the depth of the fixing hole. The fixing screw is in the fixing hole A, and the front end of the fixing screw is inserted into the fixing hole B through the fixing hole A. 
     The present invention has the following beneficial effects: 
     1. The driving motor includes an inner stator and an outer rotor. The outer rotor drives the outer cylinder to rotate under the drive of the driving fluid. The rear end of the inner stator is connected to a coupling, so that the inner stator is slightly disturbed with the outer rotor. The hydraulic energy provided by the rear hydraulic pump is pumped into the drive liquid channel, and can achieve the effect of high power and stepless speed change; 
     2. Before starting, the start shear pin fixes the locking rod on the lock body, the outflow hole A is in the sealing section A, the outer wall opening of the outflow hole A is sealed, the fluid channel is blocked, the connecting pipe is connected to the lock body, and the outer end of the pin is inserted into the groove B, to lock the outer barrel on the connecting pipe. When the hydraulic pressure provided by the mud pump at the rear reaches the starting value, the start shear pin is broken, the locking rod moves forward, the fluid passes through the fluid channel A and enters the fluid channel B through the outflow hole A, and then flows into the fluid channel C through the inflow hole, followed by flowing through the flow diverging module. A part of the fluid passes through the fluid channel D, the fluid channel E, and the fluid channel F, and then reaches the cooling hole of the drill bit, to cool the drill bit. A part of the fluid passes through the fluid channel D and communicates with the drive liquid channel of the front driving motor through the outflow hole B. The hydraulic motor is started, and the locking rod moves forward to drive the lock pin forward, so that the groove A and the unlocking hole are directly opposite, and the outer barrel moves forwards due to the gravity itself. The contact surface between the groove B and the outer end of the pin is inclined, and the pin is squeezed into the groove A, to release the constraint of the outer barrel. The outer barrel is connected to working parts such as the drill bit, to move the drill bit forward; 
     3. Before stopping the drilling, the locking ball is in the locking hole A and the locking groove A, to lock the valve housing and keep the fluid channel D in communication with the drive liquid channel of the front hydraulic motor through the outflow hole B. When the outer barrel moves forward to the stop position, the outer barrel drives the safety gear to hit the locking sleeve, to move the locking sleeve forward. The locking groove B is directly opposite to the locking hole A, and the radial restraint of the locking ball is released. The fluid impacts the rear end of the valve housing, the locking ball is squeezed into the locking groove B, and the valve housing moves forward. The sealing section C separates the fluid channel D from the outflow hole B, that stops supplying energy to the front motor, and the motor is off. Because the fluid channel D is blocked, the liquid flows backwards, runs back to the fluid channel B, and recoils the front end of the shearing plunger. The shearing plunger receives the backward force and moves backward. The front end of the recoil section moves to behind the pressure-relief hole, the fluid channel B communicates with the outside through the pressure-relief hole, and the liquid is discharged from the pressure-relief hole; 
     4. The centralizer causes the drilling structure to be placed vertically in the dental drill, and the outer surface of the centralizer is in contact with the inner wall of the dental drill. When the outer cylinder is driven to rotate by the driving motor, the outer surface of the centralizer rubs against the inner wall of the dental drill, and the other parts of the outer cylinder are not in contact with the dental drill. The friction surface is reduced to prevent the abrasion of the outer cylinder. The centralizer can be replaced after abrasion, which extends the service life of the drilling structure. 
    
    
     
       DESCRIPTION OF FIGURES 
         FIG. 1 . Schematic diagram of coring system; 
         FIG. 2 . Schematic diagram for interlocking of dental drill and core drilling rig; 
         FIG. 3 . A-B cross-sectional view; 
         FIG. 4 . Schematic diagram of the latch; 
         FIG. 5 . Schematic diagram of the centralizer position; 
         FIG. 6 . Schematic diagram of the driving motor; 
         FIG. 7 . Schematic diagram of the fluid channel activation module after starting; 
         FIG. 8 . Schematic diagram of the outer barrel unlocking module before starting; 
         FIG. 9 . Schematic diagram of the outer barrel unlocking module after stopping the drilling; 
         FIG. 10 . Schematic diagram of the flow diverging module before stopping the drilling; 
         FIG. 11 . Schematic diagram of the flow diverging module after stopping the drilling; 
     
    
    
     In Figures:  11 —lock body,  111 —locking section,  112 —sealing section A,  113 —liquid channel section,  12 —locking rod,  121 —connecting section,  122 —outflow section A,  1221 —outflow hole A,  123 —sealing section B,  124 —inflow section A,  1241 —inflow hole,  13 —start shear pin,  14 —central rod,  15 —lock nut,  151 —fixed section,  152 —threaded section,  16 —fixing screw,  17 —sealing stell ring,  21 —connecting pipe,  211 —connecting section,  212 —pressure relief section,  2121 —pressure relief hole,  213 —choke section,  22 —lock pin,  221 —groove A,  23 —outer barrel,  231 —groove B,  232 —safety gear,  2321 —clamping part,  2322 —pressing part,  24 —pin,  25 —end shearing pin,  26 —shearing plunger,  261 —shearing section,  262 —recoil section,  31 —valve housing,  311 —sealing section C,  312 —diversion section,  313 —locking section A,  3131 —locking groove A,  32 —lock housing,  321 —inflow section B,  322 —outflow section B,  3221 —outflow hole B,  323 —locking section B,  3231 —locking hole A,  3232 —locking hole B,  33 —locking sleeve,  331 —impact section,  332 —locking section C,  3321 —locking groove B,  3322 —locking groove C,  34 —locking ball,  35 —fixing ring,  36 —limit part,  361 —locking groove D,  37 —snap ring,  41 —fluid channel A,  42 —fluid channel B,  43 —fluid channel C,  44 —fluid channel D,  45 —fluid channel E,  46 —fluid channel F,  5 —dental drill,  51 —the first drill tube,  52 —the second drill tube,  53 —the third drill tube,  54 —spring,  55 —latch,  551 —the rear face of the latch,  552 —the first slope of the latch,  553 —the second slope of the latch,  554 —the axial face of the latch,  555 —latch hole,  56 —latch slot,  57 —lock slot,  58 —pin shaft,  59 —spring hole,  61 —coring barrel,  7 —driving motor,  71 —centralizing block,  72 —driving fluid outlet,  73 —outer rotor,  74 —driving liquid channel,  75 —inner stator,  76 —coupling,  77 —convex rib,  8 —drill bit. 
     EXAMPLES 
     In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further illustrated hereinafter by combing with the attached Figures. 
     As shown in  FIGS. 1-7 , the core drilling rig includes a dental drill  5  and a coring system. The dental drill  5  is hollow, and the coring system is in the dental drill  5 , and the outer wall of the coring system is in a sliding fit with the inner wall of the dental drill  5 . The dental drill  5  comprises a first drill tube  51 , a second drill tube  52 , and a third drill tube  53  from back to front. The first drill tube  51  and the second drill tube  52  are detachably connected, and the second drill tube  52  and the third drill tube  53  are detachably connected. The front end of the first drill tube  51  is a male end, and the rear end of the second drill tube  52  is a female end, while the front end is a male end. The rear end of the third drill tube  53  is a female end. The inner wall of the second drill tube  52  is provided with a locking groove  57 , that is arranged along the axial direction. The locking groove  57  penetrates the front and rear ends of the second drill tube  52 . There are two locking grooves  57 , and both of them are opposite. 
     The outer wall of the coring system is provided with latch grooves  56 . Moreover, there are two latch grooves  56 , and they are opposite. The latch grooves  56  are arranged along the axial direction. There is a latch  55  in the latch groove  56 . Both of two side walls of the latch groove  56  are connected by a pin shaft  58 , and the pin shaft  58  is a positioning pin. The latch  55  has a latch hole  555 . The latch hole  555  is a through hole, and is adapted to the pin shaft  58 . The pin shaft  58  passes through the latch hole  555 , and the latch  55  is rotatingly fit with the pin shaft  58 . The distance from the latch hole  555  to the rear end of the latch  55  is greater than the distance from the latch hole  555  to the front end of the latch  55 . The inner side of the latch  55  has a spring hole  59 . The spring hole  59  is a round and blind hole. The distance between the spring hole  59  and the rear end of the latch  55  is less than the distance between the spring hole  59  and the front end of the latch  55 . The bottom of the latch groove  56  has a recess corresponding to the spring hole  59 . The spring  54  is installed in the spring hole  59  and the recess, and is in contact with the outer wall of the coring system and the latch  55 . When the spring  54  bounces up, the latch  55  is partially embedded in the locking groove  57 . 
     The outer side of the latch  55  includes an axial surface  554 , a first inclined surface  552 , and a second inclined surface  553 . The rear end of the first inclined surface  552  of the latch is connected to the rear end surface  551  of the latch, and the front end of the first inclined surface  552  of the latch is connected to the rear end of the second inclined surface  553  of the latch, while the front end of the second inclined surface  553  of the latch is connected to the rear end of the latch axial surface  554 . The front end of the latch axial surface  554  is connected to the front end surface of the latch. The rear end surface  551  of the latch is a flat surface, while the front end surface of the latch is a curved surface. The spring hole  59  and the recess are within the projection range of the second inclined surface  553  of the latch to the inner surface of the latch  55 . The distances from the center of the latch hole  555  to the inner side and the outer side of the latch  55  are equal, and the total length of the latch  55  is 131 mm. The distance from the connection of the latch axial surface  554  and the second inclined surface  553  of the latch to the rear end surface  551  of the latch is 42 mm. The angle between the first inclined surface  552  of the latch and the radial section is 40°, while the angle of the second inclined surface  553  of the latch and the radial section is 85°. The arc surface radius of the front end surface of the latch is 11 mm, while the diameter of the latch hole  555  is 10 mm. The arc center of the front end surface of the latch coincides with the center of the latch hole  555 . The diameter of the spring hole  59  is 13 mm, and the depth is 12 mm. The distance from the center of the spring hole  59  to the rear end surface  551  of the latch is 20 mm, and the width and thickness of the latch  55  are both 20 mm. 
     The coring system moves from back to front. When the locking groove  57  and the latch groove  56  are directly opposite, the latch  55  bounces up to engage the coring system with the dental drill  5 . The left and right side walls of the latch  55  are matched with the locking groove  57 , that restricts the circumferential movement of the coring system. The axial face  554  of the latch is inclined, and clamped with the inner wall of the rear end of the third drill tube  53 , to restrict the coring system from moving forward. 
     The coring system comprises a driving system for a core drilling rig, that comprises a driving motor  7  and a center rod  14 . The driving motor  7  comprises an outer rotor  73  and an inner stator  75 , and mutually-matched convex ribs  77  are provided on the inner wall of the outer rotor  73  and the outer wall of the inner stator  75 . The outer rotor  73  and the inner stator  75  are in clearance fit. A clearance between the outer rotor  73  and the inner stator  75  is a driving liquid channel  74 , and the hydraulic pump is connected to the rear of the driving fluid channel  74 . The length of the outer rotor  73  is less than that of the inner stator  75 . The outer rotor  73  is provided between the front and rear ends of the inner stator  75 . The outer rotor  73  is connected to an outer cylinder  23 . The outer cylinder  23  has a driving liquid outlet  72 , which is in front of the outer rotor  73 . The rear end of the inner stator ( 75 ) is connected to a coupling ( 76 ). The inner stator  75  penetrates back and forth. The central rod  14  passes through the inner cavity of the inner stator  75  and the coupling  76 . The central rod  14  is connected to a coring barrel  6 , and the coring barrel  6  is in front of the inner stator  75 . 
     The driving system of a core drilling rig comprises a fluid channel activation module, an outer cylinder  23 , an outer cylinder unlocking module, a flow diverging module, and a drill bit  8 . The central rod  14  passes through, from the rear to the front, the inner cavities of a fluid channel activation module, an outer cylinder unlocking module, and a flow diverging module. The fluid channel activation module is behind the outer cylinder  23 , and the fluid channel activation module is connected to the outer cylinder unlocking module; the flow diverging module is in front of the outer cylinder unlocking module, and the front of the flow diverging module is connected to a driving motor  7 . The outer wall of the outer cylinder  23  is fixedly connected with a centralizer, that is in front of the outer rotor  73  and behind the driving fluid outlet  72 . The front end of the outer cylinder  23  is connected to a drill bit  8 . The centralizer comprises a plurality of centralizing blocks  71 , which are uniformly fixed on the outer wall of the outer cylinder  23  along the circumference. There is a gap between two adjacent centralizing blocks  71 . The radian of the outer side of the centralizing block  71  is the same as that of the outer wall of the outer cylinder  23 , and the distance from the outer side of the centralizing block  71  to the axis of the outer cylinder  23  is greater than the radius of the outer cylinder  23 , while the distance from all the centralizing blocks  71  to the rear end of the outer cylinder  23  is equal. All the centralizing blocks  71  have the same thickness, and the centralizing blocks  71  are made of copper. The centralizing blocks  71  are in contact with the inner wall of the dental drill. Before the driving motor  7  is started, the driving system for the core drilling rig is vertically centered. After the driving motor  7  is started, the outer surface of the centralizing blocks  71  rubs against the inner wall of the dental drill  5 , but the other parts of the outer cylinder  23  are not in contact with the inner wall of the dental drill  5 . The small friction surface not only reduces system friction and energy loss, but also protects other parts of the outer wall of the outer cylinder  23  from friction and prevents damage. 
     The fluid channel activation module includes a lock body  11 , a locking rod  12 , and a start shear pin  13 . The lock body  11  penetrates back and forth, the latch groove  56  is on the outer wall of the lock body  11 . For the lock body  11 , the outer diameter of the part behind the latch groove  56  is shorter than that of the part in front of the latch groove  56 . The lock body  11  consists sequentially of a locking section  111 , a sealing section A 112 , and a fluid channel section  113  from back to front. The side wall of the locking section  111  has a start shear pin hole, that is a through hole. The length of the start shear pin  13  is greater than its depth. The locking rod  12  penetrates back and forth, and the locking rod  12  is inside the lock body  11 . The locking rod  12  includes a connecting section  121 , an outflow section A 122 , a sealing section B 123  and an inflow section A 124  from back to front. The connecting section  121  is threadedly connected with the outflow section A 122 . The sealing section B 123  and the inflow section A 124  are welded. The outer wall of the connecting section  121  has a start shear pin groove, that is an annular groove. The start shear pin  13  is in the start shear pin hole and the start shear pin groove. The side wall of the outflow section A 122  is provided with an outflow hole A 1221 , and the side wall of the inflow section A 124  is provided with an inflow hole  1241 . The outflow hole A 1221  is inclined forward from the inside to the outside. There are multiple outflow holes A 1221 , and these holes are evenly distributed along the circumference at the same axial position. There are multiple inflow holes  1241 . The inflow holes  1241  are distributed in front and back on different sides. The inner diameter of the locking section  111  is longer than that of the sealing section A 112 . The outer wall of the connecting section  121  has a step. whose outer diameter is longer than the inner diameter of the sealing section A 112 . The outer diameter in front of the step of the connecting section  121  is equal to the inner diameter of the sealing section A 112 . The start shear pin groove is on the outer wall of the step. The central rod  14  is in the locking rod  12 . The sealing section A 112  and the sealing section B 123  are in a sealing fit. The inner diameter of the fluid channel section  113  is longer than the outer diameter of the locking rod  12 . The inner diameter of the connecting section  121 , the outflow section A 122  and the inflow section A 124  is greater than the outer diameter of the central rod  14 , and the sealing section B 123  is in a sealing fit with the central rod  14 . The axial distance from the front end of the sealing section A 112  to the rear end of the lock body  11  is less than the axial distance from the front end of the sealing section B 123  to the rear end of the lock body  11 . The start shear pin  13  penetrates the start shear pin hole and is inserted into the start shear pin groove. The axial distance from the open in the outer wall of the outflow hole A 1221  to the rear end of the lock body  11  is shorter than the axial distance from the rear end of the fluid channel section  113  to the rear end of the lock body  11 . A lock nut  15  and a sealing steel ring  17  are also comprised. The sealing steel ring  17  is connected to the lock body  11 , and the sealing steel ring  17  is connected behind the latch groove  56 . The outer diameter of the sealing steel ring  17  is same as that of the lock body  11  part in front of the latch groove  56 . The inner wall of the rear section of the sealing steel ring  17  is in contact with the outer wall of the lock body  11 , and the inner diameter of the rear section of the sealing steel ring  17  is shorter than the outer diameter of the lock body  11  in the front of it. The inner diameter of the front section of the sealing steel ring  17  gradually increases from back to front. The angle between the inner wall of the front section of the sealing steel ring  17  and the radial section is 45°. The front end surface of the sealing steel ring  17  is in the front of the rear end surface of the latch groove  56  and behind the second inclined surface  553  of the latch. The inner diameter of the sealing steel ring  17  at the rear end surface of the latch groove  56  is longer than the outer diameter of the lock body  11  here. The outer side surface of the latch  55  is in contact with the inner wall of the sealing steel ring  17 . The outer diameter of the sealing steel ring  17  is 99.6 mm, and the inner diameter is 82 mm. The length of the sealing steel ring  17  is 23 mm, and the outer wall of the rear end of the sealing steel ring  17  has a 3 mm×45° chamfer. The outer diameter of the lock body  11  part behind the latch groove  56  is 82 mm. The lock nut  15  is behind the sealing steel ring  17 . The lock nut  15  presses the sealing steel ring  17  tightly, and penetrates back and forth. The central rod  14  passes through the inner cavity of the lock nut  15 . The front end of the lock nut  15  is threadedly connected with the rear end of the lock body  11 . The start shear pin hole is opened at the thread of the rear end of the lock body  11 . The radial distance from the inner wall of the lock nut  15  to the bottom of the start shear pin groove is not less than the length of the start shear pin  13 . The lock nut  15  includes a fixing section  151  and a thread section  152 . The outer diameter of the connecting section  121  part behind the step is shorter than the inner diameter of the fixing section  151 , as well as shorter than the outer diameter of the step. The inner diameter of the thread section  152  is equal to the outer diameter of the locking section  111 . The lock nut  15  has a fixing hole A in the axial direction, that is a through hole. The rear face of the lock body  11  has a fixing hole B, that is a blind hole. The fixing hole A is matched with the fixing hole B. A fixing screw  16  is also comprised. The length of the fixing screw  16  is greater than the depth of the fixing hole A. The fixing screw  16  is in the fixing hole A. The front end of the fixing screw  16  is inserted into the fixing hole B through the fixing hole A. After the fluid is provided, the locking rod  12  moves forward, and the start shear pin  13  is cut. The start shear pin head is in the start shear pin hole, while the start shear pin tail is in the start shear pin groove. The start shear pin head includes a big end and a small end, and the big end faces outside. In addition, the outer diameter of the big end is greater than that of the small end. The start shear pin hole includes an outer section and an inner section. The diameter of the outer section is not less than the outer diameter of the big end of the start shear pin, while the diameter of the inner section is not less than the outer diameter of the small end of the start shear pin. The diameter of the inner section is shorter than the outer diameter of the big end, and the depth of the outer section is not less than the length of the big end. The sum of the length of the small end and that of the start shear pin tail is greater than the depth of the inner section; 
     As shown in  FIGS. 8 and 9 , the outer barrel unlocking module comprises a connecting pipe  21  and a lock pin  22 . The rear end of the connecting pipe  21  is threadedly connected to the lock body  11 . The rear end of the lock pin  22  is threadedly connected to the locking rod  12 . The central rod  14  passes through the inner cavity of the lock pin  22 , and the outer diameter of the central rod  14  is shorter than the inner diameter of the lock pin  22 . The central rod  14 , the connecting pipe  21 , the outer barrel  23 , and the lock pin  22  are coaxial. The lock pin  22  is in the connecting pipe  21 . The outer diameter of the front section of the connecting pipe  21  is shorter than the inner diameter of the outer barrel  23 . The side wall of the front section of the connecting pipe  21  has unlocking holes. There are multiple unlocking holes, and these unlocking holes are evenly distributed along the circumference at the same axial position. The lock pin  22  has a groove A 221  on the outer wall. The inner wall of the outer barrel  23  has a groove B 231 . The groove A 221  and the groove B 231  are both annular grooves. A pin  24  is also comprised. The length of the pin  24  is greater than the depth of the unlocking hole. The pin  24  is in the unlocking hole, and its outer end is chamfered. The side of the groove B 231  is a bevel. The angle between the outer chamfer of the pin  24  and the radial section is complementary to the angle between the side of groove B 231  and the radial section. The width of the groove A 221  is not less than the width of the inner end of the pin  24 . The width of the groove B 231  is not less than the width of the outer end of the pin  24 . The pin  24  includes the pin head and the pin body, and the pin head is on the inside. The unlocking hole is divided into the pin head section and the pin body section, and the pin head section is on the inside. The inner diameter of the pin head section is not less than the outer diameter of the pin head, while the inner diameter of the pin body section is not less than the outer diameter of the pin body. The length of the pin head is less than the depth of the pin head section, but the length of the pin body is greater than the depth of the pin body section. After activation, the inner end of the pin  24  is embedded in the groove A 221 . The distance from the inner end surface of the pin  24  to the inner wall of the outer barrel  23  is greater than the length of the pin  24 . 
     The connecting pipe  21  comprises a connecting section  211 , a pressure relief section  212 , and a choke section  213  from back to front. The outer diameter of the lock pin  22  is equal to the inner diameter of the choke section  213 . The inner diameter of the choke section  213  is shorter than the inner diameter of the pressure relief section  212 . There is a pressure relief hole  2121  in the pressure relief section  212 , that is a through hole. The inner wall of the lock body  11  is provided with an end shear pin hole radially, and there is an end shear pin  25  in the end shear pin hole. The length of the end shear pin  25  is greater than the depth of the end shear pin hole. A shear plunger  26  is also comprised. The inner diameter of the shear plunger  26  is longer than the outer diameter of the lock pin  22  and the locking rod  12 . The shear plunger  26  comprises a shear section  261  and a recoil section  262  from back to front. The outer wall of the shear section  261  is in a sealing fit with the inner wall of the lock body  11 . The inner wall of the lock body  11  is provided with a sealing groove B, and there is a sealing ring in the sealing groove B. The sealing groove B is in front of the end shear pin hole. The outer diameter of the recoil section  262  is equal to the inner diameter of the pressure relief section  212  in the front of the pressure relief hole  2121 . A sealing groove A is opened on the outer wall of the recoil section  262 . A sealing ring is arranged in the sealing groove A. An end shear pin groove is opened on the outer wall of the shear section  261 , while a diversion groove is opened on the outer wall of the connecting pipe  21 . The diversion groove is right in front of the pressure relief hole  2121 . The diversion groove is arranged axially, and connected with the pressure relief hole  2121 . Before stopping the drilling, the front end of the recoil section  262  is in front of the front end of the pressure relief hole  2121 . The recoil section  262  and the pressure relief section  212  in front of the pressure relief hole  2121  are in a sealing fit. The inner end of the end shear pin  25  is embedded in the end shear pin groove. After stopping the drilling, the front end of the recoil section  262  is behind the front end of the pressure relief hole  2121 , and the end shear pin  25  is cut off. 
     As shown in  FIGS. 10 and 11 , the flow diverging module includes a valve housing  31 , a lock housing  32 , a locking sleeve  33 , and a fixing ring  35 . The central rod  14 , the valve housing  31 , the lock housing  32 , the locking sleeve  33 , the fixing ring  35 , and the outer barrel  23  are coaxial. The central rod  14  passes through the inner cavity of the valve housing  31 , and the valve housing  31  is inside the lock housing  32 . The lock housing  32  passes through the inner cavity of the locking sleeve  33 , and the rear of the lock housing  32  is connected to the connecting pipe  21 . The valve housing  31  includes a sealing section C 311 , a diversion section  312 , and a locking section A 313  from back to front. The outer wall of the locking section A 313  has a locking groove A 3131 , that is an annular groove. The lock housing  32  includes an inflow section B 321 , an outflow section B 322 , and a locking section B 323  from back to front. The inner diameter of the inflow section B 322  is longer than the outer diameter of the sealing section C 311 , while the outer diameter of the sealing section C 311  is longer than the outer diameter of the diversion section  312 . The inner diameter of the outflow section B 322  is equal to the outer diameter of the sealing section C 311 . The outflow section B 322  has an outflow hole B 3221 . The locking section B 323  has a locking hole A 3231  and a locking hole B 3232 . The locking hole B 3232  is in front of the locking hole A 3231 . The outflow hole B 3221 , the locking hole A 3231 , and the locking hole B 3232  are all through holes with the same size. There are locking balls  34  in the locking hole A 3231  and the locking hole B 3232 . The diameter of the locking ball  34  is greater than the depth of the locking hole A 3231 . The locking sleeve  33  includes an impact section  331  and a locking section C 332  from back to the front. The inner wall of the locking section C 332  has a locking groove B 3321  and a locking groove C 3322 , and the grooves are both annular with the same size. The locking groove C 3322  is in front of the locking groove B 3321 . The distance between the locking groove B 3321  and the locking groove C 3322  is equal to the distance between the locking hole A 3231  and the locking hole B 3232 . The distance between the bottom of the locking groove A 3131  and the inner wall of the locking section B 323  is less than the diameter of the locking ball  34 . The distance from the bottom of the groove A 3232  to the outer wall of the locking section B 323  is not less than the diameter of the locking ball  34 . The distance from the bottom of the locking groove B 3321  and the locking groove C 3322  to the outer wall of the locking section B 323  is less than the diameter of the locking ball  34 . The distance from the bottom of the locking groove B 3321  and the locking groove C 3322  to the inner wall of the locking section B 323  is not less than the diameter of the locking ball  34 . The fixing ring  35  is fixed on the outer wall of the locking section B 323 , and the fixing ring  35  is behind the locking hole A 3231 . The inner diameter of the impact section  331  is longer than the outer diameter of the fixing ring  35 . The locking section C 332  is in front of the fixing ring  35 . The inner diameter of the outer barrel  23  is longer than the outer diameters of the lock housing  32  and the locking sleeve  33 . The inner wall of the outer barrel  23  is connected to a safety gear  232 . The safety gear  232  includes a clamping part  2321  and a pressing part  2322  from back to the front. The inner diameter of the front end face of the pressing part  2322  is shorter than the outer diameter of the impact section  331 . The inner diameter of the pressing part  2322  is not less than the outer diameter of the fixing ring  35 . The inner diameter of the front end face of the clamping part  2321  is shorter than the outer diameter of the rear end face of the fixing ring  35 . The central rod  14  has a limiting portion  36 , that is located in the locking section B 323 . The limiting portion  36  is in front of the locking section A 313 . The outer wall of the limiting portion  36  is provided with a locking groove D 361 , that is an annular groove. The locking groove D 361  is in front of the locking groove A 3131 . The gap between the outer wall of the limiting portion  36  and the inner wall of the lock housing  32  is shorter than the thickness of the front end of the locking section A 313 . The axial distance from the front end face of the clamping part  2321  to the front end of the pressing part  2322  is equal to the axial distance from the center of the locking hole A 3231  to the center of the locking groove B 3321  before stopping the drilling. Before stopping the drilling, the distance from the rear end of the sealing section C 311  to the outflow hole B 3221  is greater than the axial distance from the center of the lock hole A 3231  to the center of the lock groove A 3131 . After stopping the drilling, the axial distance from the center of the locking hole A 3231  to the center of the locking groove A 3131  is greater than the distance from the front end of the sealing section C 311  to the front end of the outflow hole B 3221  before stopping the drilling. The lock housing  32  and the valve housing  31  are locked or released from the restraint by the locking ball  34  in the locking hole A 3231 . The lock housing  32  and the locking sleeve  33  are locked or released from the restraint through the locking ball  34  in the locking hole A 3231 . The lock housing  32  and the central rod  14  are locked or unconstrained by the locking ball  34  in the locking hole B 3232 . A snap ring  37  is also comprised, whose outer diameter is longer than the inner diameter of the fixing ring  35 , and whose inner diameter is shorter than the inner diameter of the fixing ring  35 . The snap ring  37  is inserted into the groove of the outer wall of the locking section B 323 . The fixing ring  35  is clamped between the rear end of the snap ring  37  and the front end of the outflow section B 322 . The front end of the locking section C 332  is supported by a spring. Before stopping the drilling, the lock housing  32  and the valve housing  31  are tightly locked to keep the fluid channel unobstructed. A safety gear  232  is arranged in the outer barrel  23 . When the outer barrel  23  moves forward to a limiting position, the outer barrel  23  drives the safety gear  232  to hit the locking sleeve  33 , causing the locking ball  34  in the locking hole A 3231  to move outward, and releasing the restraint on the valve housing  31 . The valve housing  31  moves forward to close the fluid channel. The drilling is stopped. At this time, the locking groove D 361 , the locking hole B 3232 , and the locking groove C 3322  are directly facing each other, and the locking ball  34  in the locking hole B 3232  moves outwards, and the restriction on the central rod  14  is released. 
     The inner wall of the connecting section  121 , the inner wall of the outflow section A 122 , the rear end face of the sealing section B 123 , and the outer wall of the central rod  14  enclose a fluid channel A 41 . The inner wall of the lock body  11  and the outer wall of the locking rod  12  enclose a fluid channel B 42 . The fluid channel C 43  is surrounded by the inner wall of the locking rod  12  and the outer wall of the central rod  14 . The inner wall of the lock pin  22  and the outer wall of the central rod  14  enclose a fluid channel D 44 . There is a fluid channel E 45  between the outer wall of the central rod  14  and the inner wall of the valve housing  31 , and a fluid channel F 46  is opened in the limiting portion  36 . The fluid channel B 42  and the fluid channel C 43  are connected through the inflow hole  1241 ; the fluid channel C 43  is connected with the fluid channel D 44 ; the back of the fluid channel E 45  is connected with the fluid channel D 44 ; the front of the fluid channel E 45  is connected with the fluid channel F 46 ; and the back of the fluid channel A 41  is connected with the fluid supply equipment. The front of the outflow hole B 3221  is connected to the driving liquid channel  74  of the driving motor  7 , and the fluid channel F 46  is connected to the cooling hole of the drill bit in front of it. 
     The coring system is placed in the dental drill  5 , and the latch  55  connected to the outer wall of the lock body  11  and the dental drill  5  are locked, so that the driving system for the core drilling rig is fixed above. The driving system for the core drilling rig is powered on by the mud pump at the rear. Before starting, the start shear pin  13  passes through the start shear pin hole and is inserted into the start shear pin groove. The locking rod  12  is fixed in the lock body  11  by the start shear pin  13 . The axial distance from the outer wall opening of the outflow hole A 1221  to the rear end of the lock body  11  is less than the axial distance from the rear end of the fluid channel section  113  to the rear end of the lock body  11 . The outer wall opening of the outflow hole A 1221  is closed by the sealing section A 112 , and the liquid cannot flow forward. The front end of the connecting pipe  21  is in the outer barrel  23 , and the pin  24  is in front of the groove A 221 . The inner end of the pin  24  is slidingly fitted with the outer wall of the lock pin  22 , while the outer end of the pin  24  is embedded in the groove B 231 . The outer barrel  23  is fixed outside the connecting pipe  21  by the pin  24 . After the hydraulic pressure provided by the rear mud pump reaches the starting value, it impacts the rear end of the locking rod  12  to cut off the start shear pin  13 , and the start shear pin  13  breaks into the start shear pin head and the start shear pin tail. The start shear pin head is in the start shear pin hole, while the starting shear pin tail is in the start shear pin groove. The locking rod  12  moves forward. The axial distance from the outer wall opening of the outflow hole A 1221  to the rear end of the lock body  11  is greater than the axial distance from the rear end of the fluid channel section  113  to the rear end of the lock body  11 . The fluid channel A 41  and the fluid channel B 42  are connected through the outflow hole A 1221 . Fluid channel A 41 , fluid channel B 42 , fluid channel C 43 , fluid channel D 44 , fluid channel E 45 , and fluid channel F 46  are connected, and fluid channel D 44  is connected to the driving liquid channel  74  of the driving motor  7  by outflow hole B 3221 . The front of the fluid channel F 46  is connected to the cooling hole of the drill bit  8 , and the hydraulic energy provided by the mud pump behind the fluid channel A 41  can be transmitted to the driving motor  7  and the drill bit  8  ahead through the fluid channel A 41 , the fluid channel B 42 , the fluid channel C 43 , the fluid channel D 44 , the fluid channel E 45  and the fluid channel F 46 , so as to make the outer rotor  73  rotate and cool the drill bit  8 . The locking rod  12  drives the lock pin  22  to move forward. The inner end of the pin  24  is in a sliding fit with the outer wall of the lock pin  22 . When the groove A 221  slides forward to the same axial position as the pin  24 , the outer barrel  23  generates forward pressure by its own gravity, and the contact surface of the groove B 231  and the pin  22  is an inclined surface. The groove B 231  presses the inclined surface of the pin  24 . The pin  24  withdraws from the groove B 231  and is pressed into the groove A 221 , to release the restraint of the outer barrel  23 . The outer barrel  23  drives the front-connected working parts to move forward. 
     The outer cylinder  23  is connected to the outer rotor  73  of the driving motor  7 , and the front end of the outer cylinder  23  is connected to the drill bit  8 . The centralizer connected to the outer wall of the outer cylinder  23  is in contact with the inner wall of the dental drill  5 , so that the outer cylinder  23  is vertically centered. When the drilling rig is working, the outer barrel  23  moves from back to front. The fluid flows into the liquid channel D 44  through the fluid channel A 41 , the fluid channel B 42 , and the fluid channel C 43 . The fluid channel D 44  is connected to the driving liquid channel  74  of the driving motor  7  ahead through the outflow hole B 3221 . Moreover, the fluid channel D 44  is connected to the cooling hole of the drill bit  8  in front through the fluid channel E 45  and the fluid channel F 46 . The locking ball  34  in the locking groove A 3131  and the locking hole A 3231  restricts the valve housing  31  from moving forward. The outer barrel  23  drives the safety gear  232  to move forward. After the outer barrel  23  moves to the limit position, the safety gear  232  hits the locking sleeve  33 , to make the locking groove B and the locking hole A directly face each other. The fluid in the fluid channel D 44  impacts the rear end of the valve housing  31 , squeezing the locking ball  34  into the locking groove B, and the valve housing  31  is released from the restraint and moves forward. The sealing section C 311  moves into the outflow section B 322 , blocks the channel between the fluid channel D 44  and the outflow hole B 3221 , and cuts off the fluid channel. Consequently, the driving motor  7  stops rotating, the fluid flows back to the fluid channel B 42 , and backflushes the recoil section  262  to make it move backwards. The end shear pin  25  is cut off, and thus the fluid channel B 42  and the pressure relief hole  2121  are connected, and the pressure is relieved through the pressure relief hole  2121 . 
     Of course, there still may be many other examples for the present invention. Without departing from the spirit and the essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the invention, but these corresponding changes and deformations shall belong to the protection scope of the claims of the present invention.