A downhole variable-diameter bit based on a reversing gear mechanism

Abstract

The present invention provides a downhole variable-diameter drill bit based on a reversing gear mechanism, which includes a drill bit outer pipe body. A drill bit body is fixedly installed at the top of the drill bit outer pipe body. One or more drill bit wings capable of radially synchronously telescoping and moving are installed at the top of the drill bit body. A shifting driving shaft for driving the drill bit outer pipe body to rotate is installed in the drill bit outer pipe body. The shifting driving shaft can also rotate relative to the drill bit outer pipe body and move axially to achieve shifting. A rotatable reversing gear mechanism is eccentrically installed in the drill bit body. The shifting driving shaft drives the reversing gear mechanism to rotate, and the reversing gear mechanism drives one or more drill bit wings to radially synchronously telescoping and moving, so as to realize variable diameter while drilling. The present invention realizes the purpose of variable drill bit diameter during drilling construction through the structural design of the gear shifting groove and the reversing gear mechanism, which not only facilitates efficient reaming construction, but also makes it easier to lift the drill in soft, diameter-reduced and other complex strata.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground coal mine drilling, relates to a variable-diameter drill bit while drilling, and particularly relates to a variable-diameter drill bit while drilling based on a reversing gear mechanism. Background Art

[0002] Drilling and drainage in underground coal mines has always been an important means of gas drainage. The size of the gas drainage borehole diameter directly affects the gas drainage effect. When the drainage time is long and the gas flow tends to be stable, the total gas drainage flow increases with the increase of the borehole. In the construction of gas boreholes, due to the influence of borehole geological conditions and drill tool performance, it is difficult to construct a borehole with a large diameter at one time. Therefore, large-diameter boreholes often need to be reamed by tripping in and out of the hole multiple times. The use of a variable-diameter drill bit for construction can achieve local reaming of the target borehole in the coal seam section, greatly improving the drilling construction efficiency. In soft and broken coal seams or in the construction of reamed boreholes, it is difficult to form a hole. When pulling out the drill, the collapse of the borehole easily leads to accidents such as sticking and burying the drill. Through the design of a variable-diameter drill bit, a large diameter can be achieved during drilling, and the cutter wings can be retracted when pulling out the drill, effectively preventing the occurrence of sticking and burying the drill accidents.

[0003] At present, multi-stage reaming technology is mostly used for borehole reaming construction in coal mines. Researchers have done a lot of research on the structural design of variable-diameter drill bits while drilling. The Chinese invention patent with the application publication number CN 112647851 A provides a variable-diameter drill bit for oil fields. This patent rotates the disc by compressing the piston through an air inlet pipe, and the cutter wings move in the disc groove to achieve variable diameter. This design requires injecting gas into the air inlet pipe to generate the driving force for the cutter wings to change diameter, which has limitations in actual drilling construction; the Chinese utility model patent with the authorization announcement number CN 201460741 U discloses a method based on link transmission to realize the opening and retraction of the cutter wings. The acting force generated by the link pushing is unstable, the variable-diameter range while drilling is uncontrollable, resulting in irregular borehole diameters. The instantaneous transmission ratio of the drill bit is inaccurate and the inertial force is large. The Chinese invention patent with the application publication number CN 111441725 A discloses a method of compressing an oil cylinder by a lateral force on a rotating shaft, and the hydraulic oil pushes the piston to push out the cutter wings of the drill bit to achieve variable diameter. The variable-diameter process of the drill bit requires the action of multiple hydraulic cylinders, occupying a large drill bit space, which has limitations in the design of small-diameter drill bits. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a variable-diameter drill bit while drilling based on a reversing gear mechanism to solve the technical problem of the large difficulty in pulling out the drill of the variable-diameter drill bit while drilling in complex strata in the existing technology.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve:

[0006] A downhole variable-diameter bit based on a reversing gear mechanism, comprising a bit outer pipe body, a bit body is fixedly installed at the top of the bit outer pipe body, and more than one bit blade capable of radially synchronously telescoping and moving is installed at the top of the bit body;

[0007] A shifting driving shaft for driving the rotation of the bit outer pipe body is installed in the bit outer pipe body, and the shifting driving shaft can also rotate relative to the bit outer pipe body and move axially to achieve shifting; A rotatable reversing gear mechanism is eccentrically installed in the bit body, the shifting driving shaft drives the reversing gear mechanism to rotate, and the reversing gear mechanism drives more than one bit blade to radially synchronously telescoping and moving, realizing variable diameter while drilling;

[0008] The shifting driving shaft, the reversing gear mechanism and the bit body are provided with a through bit flushing fluid flow channel.

[0009] The present invention also has the following technical features:

[0010] Specifically, the bit outer pipe body includes a pipe body with both ends open. Along the circumferential direction, two layers of gear positions are provided on the inner wall near the top of the pipe body, namely the first layer of gear positions and the second layer of gear positions. The first layer of gear positions includes more than one non-connected retracting gear positions corresponding to the bit blades one by one, and the second layer of gear positions includes more than one non-connected expanding gear positions corresponding to the retracting gear positions one by one. Each retracting gear position is connected to the corresponding expanding gear position through a shift slot axially provided;

[0011] The bit body includes a bit main body, the bottom of the bit main body is fixedly installed at the top of the pipe body, and more than one blade moving slot for installing the bit blade corresponding to the bit blade one by one is provided along the radial direction at the top of the bit main body. The inner ends of the more than one blade moving slots intersect and communicate with each other, and the outer ends of the more than one blade moving slots are all open; A reversing gear mechanism rotating cavity for installing the reversing gear mechanism is eccentrically provided at the bottom of the bit main body, and the reversing gear mechanism rotating cavity is connected to the more than one blade moving slot;

[0012] The bit blade includes a blade seat, the blade seat is installed in the blade moving slot and can move radially, a row of cutting elements is installed at the top of the blade seat, and a driving boss is arranged along the axial direction at the bottom of the blade seat near the inner end;

[0013] The shifting driving shaft includes a driving shaft main body, the driving shaft main body is installed in the pipe body, and more than one transmission shifting convex head corresponding to the bit blade one by one is arranged along the radial direction at the top of the driving shaft main body. The transmission shifting convex head can move in the retracting gear position, the shift slot and the expanding gear position to achieve shifting; The top end of the driving shaft main body is fixedly installed with a driving gear that rotates around the axial direction through a gear shaft;

[0014] The described reversing gear mechanism includes a disc body, which is installed in the rotating cavity of the reversing gear mechanism. A reversing cavity with an open bottom is coaxially provided at the bottom of the disc body. A ring of external gears is provided on the bottom inner wall of the reversing cavity, and an internal gear is fixedly arranged at the central position of the top of the reversing cavity; the height difference between the bottom end of the internal gear and the bottom end of the external gear is equal to the stroke length of the shifting slot. When the transmission shifting convex head is in the state of retracting into the gear slot, the driving gear meshes with the internal gear to drive the drill blade to retract. When the transmission shifting convex head is in the state of opening the gear slot, the driving gear meshes with the external gear to drive the drill blade to open; one or more reversing drive slots corresponding to the driving bosses are provided on the top of the disc body, and the driving bosses are clamped in the reversing drive slots, so that the rotation of the disc body drives one or more drill blades to synchronously move radially in and out.

[0015] Specifically, the drill flushing fluid flow path includes a first flow path opened through the bottom end in the driving shaft body, a second flow path opened through the closed top end of the driving shaft body, a third flow path opened through the closed top end of the reversing cavity, and a fourth flow path opened through the drill body. The first flow path, the second flow path, the reversing cavity, the third flow path and the fourth flow path are connected in sequence to form the drill flushing fluid flow path.

[0016] Preferably, both the second flow path and the fourth flow path are one or more; the fourth flow path is not communicated with the blade moving slot and the rotating cavity of the reversing gear mechanism, and the fourth flow path and the blade moving slot are arranged alternately.

[0017] Preferably, internal threads are provided in the first flow path.

[0018] Preferably, a clamping groove is provided along the radial direction on one side wall of the blade moving slot, and a clamping rail is provided along the radial direction on one side wall of the wing seat. The clamping rail cooperates with the clamping groove to limit the drill blade, so that the drill blade only moves radially.

[0019] The driving gear, the external gear and the internal gear are all cylindrical gears and have the same module;

[0020] The transmission ratios of the driving gear meshing with the external gear and the internal gear respectively are:

[0021]

[0022]

[0023] The center distance relationship among the driving gear, the external gear and the internal gear is:

[0024]

[0025]

[0026] Wherein:

[0027] i 12 is the transmission ratio between the driving gear and the outer gear;

[0028] i 13 is the transmission ratio between the driving gear and the inner gear, and the negative sign indicates the opposite rotation direction;

[0029] n1, n2 and n3 are the rotational speeds of the driving gear, the outer gear and the inner gear respectively;

[0030] z1, z2 and z3 are the number of teeth of the driving gear, the outer gear and the inner gear respectively;

[0031] a 12 is the center distance of the internal engagement between the driving gear and the outer gear;

[0032] a 13 is the center distance of the external engagement between the driving gear and the inner gear;

[0033] m is the module of the gear.

[0034] Preferably, the bottom of the wing base near the inner end is higher than the bottom of the wing base near the outer end, and a stepped arrangement is formed between the bottom of the wing base near the inner end and the bottom of the wing base near the outer end.

[0035] Preferably, the top of the pipe body is connected to the bottom of the drill bit body by a fine thread.

[0036] Preferably, there are three drill bit blades.

[0037] Preferably, hard cutting teeth are installed on the cutting element.

[0038] Compared with the prior art, the present invention has the following technical effects:

[0039] (Ⅰ) Through the structural design of the gear position groove and the reversing gear mechanism, the present invention realizes the purpose that the drill bit diameter can be changed during the drilling construction process, which not only facilitates the efficient reaming construction, but also makes it easier to lift the drill in soft, diameter-reduced and other complex strata.

[0040] (Ⅱ) The present invention innovatively designs the principle of variable diameter of the drill bit. A reversing gear mechanism with an eccentric disc is arranged in the drill bit body, and the position of the driving shaft gear is controlled by the gear position groove to realize the function that the drill bit diameter can be changed during drilling.

[0041] (Ⅲ) The outer diameter of the variable-diameter drill bit of the present invention is the same as that of the commonly used drill bits in coal mines. Without adding any auxiliary mechanisms, the variable-diameter function during drilling can be achieved only by the rotation and pulling operation applied by the drilling rig to the active drill pipe. During the specific construction process, it can not only meet the performance requirements of conventional drill bits but also achieve the function of reaming drill bits, and has the effect of easy drill pipe extraction in formations with cave-ins and diameter shrinkage.

[0042] (Ⅳ) The present invention realizes the opening and retraction of the cutter wings of the drill bit by means of the meshing of a reversing gear pair without relying on external power sources such as flushing fluid, hydraulic oil, and intake pipes. Only by the pulling force and rotational force during normal drilling can the drilling diameter be changed during drilling. It has good reaming effect and simple operation, and can also prevent accidents such as sticking and burying of the drill during drilling in formations with cave-ins and diameter shrinkage. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is an axial sectional structural schematic diagram of a variable-diameter drill bit with a reversing gear mechanism during drilling.

[0044] Figure 2 It is Figure 1 a structural schematic diagram of the drill bit flushing fluid flow channel in the state where the cutter wings are open.

[0045] Figure 3 It is an axial sectional structural schematic diagram of the outer pipe body of the drill bit.

[0046] Figure 4 It is an unfolded structural schematic diagram of the gear position groove.

[0047] Figure 5 It is a front view structural schematic diagram of the drill bit body.

[0048] Figure 6 It is a structural schematic diagram of the drill bit cutter wings.

[0049] Figure 7 It is a front view structural schematic diagram of the shift driving shaft.

[0050] Figure 8 It is an axial sectional structural schematic diagram of the shift driving shaft.

[0051] Figure 9 It is a front view structural schematic diagram of the reversing gear mechanism.

[0052] Figure 10 It is a radial sectional structural schematic diagram of the reversing gear mechanism.

[0053] Figure 11 It is a schematic diagram of the meshing mode of the driving gear with the inner gear and the outer gear.

[0054] The meanings of the reference numerals in the figure are as follows: 1 - drill bit outer pipe body, 2 - drill bit body, 3 - drill bit blade, 4 - shift driving shaft, 5 - reversing gear mechanism, 6 - drill bit flushing fluid flow channel;

[0055] 101 - pipe body, 102 - retraction gear slot, 103 - expansion gear slot, 104 - shift slot, 105 - fine thread;

[0056] 201 - drill bit body, 202 - blade moving slot, 203 - reversing gear mechanism rotating cavity, 204 - clamping slot;

[0057] 301 - wing base, 302 - cutting element, 303 - driving boss, 304 - clamping rail;

[0058] 401 - driving shaft body, 402 - transmission shift projection, 403 - driving gear, 404 - internal thread;

[0059] 501 - disc body, 502 - reversing cavity, 503 - external gear, 504 - internal gear, 505 - reversing driving slot;

[0060] 601 - first flow channel, 602 - second flow channel, 603 - third flow channel, 604 - fourth flow channel.

[0061] The following further elaborates on the specific content of the present invention in conjunction with embodiments. Specific Embodiments

[0062] It should be noted that all components and equipment in the present invention, without special instructions, adopt components and equipment known in the art. For example, the active drill pipe adopts a known common active drill pipe.

[0063] Constrained by the borehole geological conditions and the performance of drilling tools during the drilling construction in coal mines, it is difficult to construct a borehole with a relatively large diameter in one go. Therefore, large-diameter boreholes often require multiple trips of tripping in and out for reaming construction, resulting in high construction costs and low efficiency; in some complex formation conditions, due to factors such as borehole diameter shrinkage or cave-in, it is difficult to lift the drilling tool, and sticking and burying accidents of the drilling tool are prone to occur. Based on the above background, the present invention proposes a variable-diameter drill bit with a reversing gear mechanism during drilling, which realizes local reaming construction by using a variable-diameter drill bit, greatly improves the construction efficiency, and through the variable-diameter drill bit design, a large diameter can be achieved during drilling, and the blades can be retracted during drill pipe pulling, effectively preventing the occurrence of sticking and burying accidents.

[0064] The following gives specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solutions of this application fall within the protection scope of the present invention.

[0065] Embodiment 1:

[0066] This embodiment provides a downhole variable-diameter bit based on a reversing gear mechanism, as Figure 1 shown, which includes a drill bit outer pipe body 1. A drill bit body 2 is fixedly installed at the top of the drill bit outer pipe body 1. One or more drill bit wings 3 capable of radially synchronously telescoping and moving are installed at the top of the drill bit body 2.

[0067] A shifting driving shaft 4 for driving the rotation of the drill bit outer pipe body 1 is installed inside the drill bit outer pipe body 1. The shifting driving shaft 4 can also rotate relative to the drill bit outer pipe body 1 and move axially to achieve shifting. A rotatable reversing gear mechanism 5 is eccentrically installed inside the drill bit body 2. The shifting driving shaft 4 drives the reversing gear mechanism 5 to rotate, and the reversing gear mechanism 5 drives one or more drill bit wings 3 to radially synchronously telescoping and moving, realizing variable diameter while drilling.

[0068] As Figure 2 shown, through holes for drill bit flushing fluid flow channels 6 are provided on the shifting driving shaft 4, the reversing gear mechanism 5 and the drill bit body 2.

[0069] As a specific solution of this embodiment, as Figure 3 shown, the drill bit outer pipe body 1 includes a pipe body 101 with both ends open. Two layers of gear position grooves are circumferentially provided on the inner wall near the top inside the pipe body 101, namely the first layer of gear position grooves and the second layer of gear position grooves. The first layer of gear position grooves includes one or more non-connected retraction gear position grooves 102 corresponding to the drill bit wings 3 one by one. The second layer of gear position grooves includes one or more non-connected expansion gear position grooves 103 corresponding to the retraction gear position grooves 102 one by one. Each retraction gear position groove 102 is connected to the corresponding expansion gear position groove 103 through an axially provided shifting groove 104.

[0070] Preferably in this embodiment, as Figure 4 shown, the retraction gear position grooves 102 and the expansion gear position grooves 103 are arranged along the circumference of the pipe body 101, and they are connected end to end. The transmission shifting convex head 402 can easily enter the expansion gear position groove 103 from the retraction gear position groove 102, and after rotating a certain angle, it can enter the retraction gear position groove 102 from the expansion gear position groove 103 again. Through the design of the gear position grooves, on the one hand, the meshing mode of the "reversing gear pair" can be controlled, and at the same time, the torque of the active drill pipe is transmitted to the drill bit for rock breaking.

[0071] As a specific solution of this embodiment, as Figure 5As shown in the figure, the drill bit body 2 includes a drill bit main body 201. The bottom of the drill bit main body 201 is fixedly installed on the top of the pipe main body 101. One or more blade moving grooves 202 corresponding to the drill bit blades 3 one by one for installing the drill bit blades 3 are radially provided at the top of the drill bit main body 201. The inner ends of the one or more blade moving grooves 202 intersect and communicate with each other, and the outer ends of the one or more blade moving grooves 202 are all open. An eccentric rotation cavity 203 for installing the reversing gear mechanism 5 is provided at the bottom of the drill bit main body 201, and the reversing gear mechanism rotation cavity 203 communicates with the one or more blade moving grooves 202.

[0072] As a specific solution of this embodiment, as Figure 6 shown in the figure, the drill bit blade 3 includes a blade seat 301. The blade seat 301 is installed in the blade moving groove 202 and can move radially. A row of cutting elements 302 is installed at the top of the blade seat 301. A driving boss 303 is axially provided at the bottom of the blade seat 301 near the inner end.

[0073] As a specific solution of this embodiment, as Figure 7 and Figure 8 shown in the figure, the shifting driving shaft 4 includes a driving shaft main body 401. The driving shaft main body 401 is installed in the pipe main body 101. One or more transmission shifting bosses 402 corresponding to the drill bit blades 3 one by one are radially provided at the top of the driving shaft main body 401. The transmission shifting bosses 402 can move in the retracted gear slot 102, the shifting slot 104 and the expanded gear slot 103 to realize shifting. A driving gear 403 that rotates around the axis is fixedly installed at the top end of the driving shaft main body 401 through a gear shaft.

[0074] As a specific solution of this embodiment, as Figure 9 shown in the figure and the figure, the reversing gear mechanism 5 includes a disc main body 501. The disc main body 501 is installed in the reversing gear mechanism rotation cavity 203. A reversing cavity 502 with an open bottom end is coaxially provided at the bottom of the disc main body 501. A ring of external gears 503 is provided on the bottom inner wall of the reversing cavity 502. An internal gear 504 is fixedly provided at the center position of the top of the reversing cavity 502. The height difference between the bottom end of the internal gear 504 and the bottom end of the external gear 503 is equal to the stroke length of the shifting slot 104. When the transmission shifting boss 402 is in the state of being located in the retracted gear slot 102, the driving gear 403 meshes with the internal gear 504 to drive the drill bit blade 3 to retract. When the transmission shifting boss 402 is in the state of being located in the expanded gear slot 103, the driving gear 403 meshes with the external gear 503 to drive the drill bit blade 3 to expand. One or more reversing driving grooves 505 corresponding to the driving bosses 303 one by one are provided at the top of the disc main body 501. The driving bosses 303 are clamped in the reversing driving grooves 505, so that the rotation of the disc main body 501 drives the one or more drill bit blades 3 to synchronously expand and contract radially.

[0075] In this embodiment, as Figure 11 shown, the driving gear 403 meshes with the internal gear 504 or the external gear 503 to form a "reversing gear pair". By adopting the meshing mode of the reversing gear pair, the opening and retraction of the drill bit blade 3 can be realized without relying on external power, such as flushing fluid, hydraulic oil and intake pipe. It can realize the change of the drilling diameter during drilling only by the normal drilling process. The reaming effect is good and the operation is simple. When drilling through the strata with cave-in and diameter shrinkage, accidents such as sticking and burying of the drill can also be prevented.

[0076] In this embodiment, preferably, when the main shaft body 401 axially moves forward 10 mm, it meshes with the internal gear 504. The disc body 501 rotates in the opposite direction to the main shaft body 401. When the main shaft body 401 axially withdraws 10 mm, it meshes with the external gear 503. The disc body 501 rotates in the same direction as the main shaft body 401. Conversely, if the external gear 503 is placed at the front end in the axial direction and the internal gear 504 is placed at the rear end in the axial direction, the opposite effect can be achieved.

[0077] Preferably in this embodiment, the reversing drive groove 505 in the reversing gear mechanism 5 is set as a straight groove, and a rectangular blade moving groove 202 is provided in the drill bit body 2. Under the combined action of the two, the reversing gear mechanism 5 drives the drill bit blade 3 to move radially when rotating.

[0078] As a specific solution of this embodiment, as Figure 2 shown, the drill bit flushing fluid flow channel 6 includes a first flow channel 601 opened in the main shaft body 401 and penetrating the bottom end, a second flow channel 602 penetrating the closed top end of the main shaft body 401, a third flow channel 603 penetrating the closed top end of the reversing chamber 502, and a fourth flow channel 604 penetrating the drill bit body 2. The first flow channel 601, the second flow channel 602, the reversing chamber 502, the third flow channel 603 and the fourth flow channel 604 are connected in sequence to form the drill bit flushing fluid flow channel 6.

[0079] As a specific solution of this embodiment, the shifting main shaft 4 drives the reversing gear mechanism 5 to rotate, so that the drill bit flushing fluid flow channel 6 changes when the drill bit blade 3 is in the retracted and opened states. When the drill bit blade 3 is in the retracted state, the rock-breaking volume of the drill bit is small, the overlap degree of the third flow channel 603 and the fourth flow channel 604 is small, and the sectional area of the drill bit flushing fluid flow channel 6 is about 1 / 3 of the maximum sectional area. When the drill bit blade 3 is in the opened state, the rock-breaking volume of the drill bit is large, the drill bit flushing fluid flow channel 6 completely overlaps, and the sectional area of the drill bit flushing fluid flow channel 6 reaches the maximum, so that a large amount of rock powder can be better discharged.

[0080] As a preferred solution of this embodiment, there is one or more second flow channels 602 and fourth flow channels 604; the fourth flow channel 604 is a round hole with a diameter of φ12 mm, which communicates with the upper part of the rotating cavity 203 of the reversing gear mechanism, and the fourth flow channel 604 and the cutter wing moving groove 202 are arranged alternately.

[0081] As a preferred solution of this embodiment, internal threads 404 are provided in the first flow channel 601. The internal threads 404 are used for screw connection with the male drill pipe. The feeding force and rotational force of the male drill pipe are transmitted to the drill bit.

[0082] As a preferred solution of this embodiment, a clamping groove 204 is radially provided on one side wall of the cutter wing moving groove 202, and a clamping rail 304 is radially provided on one side wall of the wing seat 301. The clamping rail 304 cooperates with the clamping groove 204 to limit the drill bit cutter wing 3, so that the drill bit cutter wing 3 only moves radially, which can meet the requirements of drill bit diameter adjustment and achieve precise control of the drill bit diameter.

[0083] As a preferred solution of this embodiment, the driving gear 403, the external gear 503 and the internal gear 504 are all cylindrical gears and have the same module.

[0084] The transmission ratios of the driving gear 403 meshing with the external gear 503 and the internal gear 504 respectively are:

[0085]

[0086]

[0087] The center distance relationship among the driving gear 403, the external gear 503 and the internal gear 504 is:

[0088]

[0089]

[0090] In the formula:

[0091] i 12 is the transmission ratio of the driving gear to the external gear;

[0092] i 13 is the transmission ratio of the driving gear to the internal gear, and the negative sign indicates the opposite rotation direction;

[0093] n1, n2 and n3 are the rotational speeds of the driving gear, the external gear and the internal gear respectively;

[0094] z1, z2 and z3 are the number of teeth of the driving gear, the external gear and the internal gear respectively;

[0095] a 12 is the center distance of the internal meshing between the driving gear and the external gear;

[0096] a 13 is the center distance of the external meshing between the driving gear and the internal gear;

[0097] m is the module of the gear.

[0098] In this embodiment, the outer diameter d1 and the number of teeth of the driving shaft gear are determined according to the outer diameter size of the drill bit and the drill bit strength condition According to the required transmission ratio condition, the number of teeth Z2 of the external gear and the pitch circle diameter d2 of the external gear are determined. According to the gear strength calculation and structure, the addendum circle parameter d a and the dedendum circle d f parameters. Similarly, each parameter of the internal gear is set.

[0099] As a preferred solution of this embodiment, the bottom of the wing base 301 near the inner end is higher than the bottom of the wing base 301 near the outer end, and a stepped setting is formed between the bottom of the wing base 301 near the inner end and the bottom of the wing base 301 near the outer end. It is convenient for assembly and positioning with the disc body 501.

[0100] As a preferred solution of this embodiment, the top of the pipe body 101 and the bottom of the drill bit body 201 are connected by a fine-thread screw 105. And welding is carried out according to needs.

[0101] As a preferred solution of this embodiment, the number of drill bit blades 3 is three.

[0102] As a preferred solution of this embodiment, hard cutting teeth, such as diamond composite inserts, are installed on the cutting element 302.

[0103] In this embodiment, when the driving gear 403 meshes with the internal gear 504, it separates from the external gear 503. At this time, the rotation direction of the disc body 501 is opposite to that of the driving shaft body 401, which is called a reverse gear. When the driving gear 403 meshes with the external gear 503, it separates from the internal gear 504. At this time, the rotation direction of the disc body 501 is the same as that of the driving shaft body 401, which is called a forward gear. The driving gear is threadedly connected to the driving drill pipe, and the driving drill pipe drives the gear to rotate forward. By different meshing methods of the driving gear with the internal and external gears, the "forward rotation" and "reverse rotation" of the disc body 501 are realized, and then the opening and retraction of the drill bit blade 3 are controlled. "Forward rotation" refers to clockwise rotation, and "reverse rotation" refers to counterclockwise rotation. When the drill bit blade 3 opens to the maximum position or retracts to the minimum position, the transmission shift convex head 402 of the shift driving shaft 4 contacts the end face of the opening gear slot 103 or the retracting gear slot 102 to achieve the purpose of limiting and transmitting torque.

[0104] When the variable-diameter bit while drilling based on the reversing gear mechanism of the present invention is in use, the shifting driving shaft 4 is threadedly connected to the driving drill pipe. During the process of lowering the drill, the driving shifting projection 402 of the shifting driving shaft 4 is pushed into the retracting gear slot 102 by the driving drill pipe, and the driving gear 403 meshes with the internal gear 504. During rotary drilling, the disc body 501 rotates in the opposite direction to the driving shaft body 401. The driving shifting projection 402 of the shifting driving shaft 4 moves from the retracting gear slot 102 through the shifting slot 104 into the expanding gear slot 103, and the driving gear 403 meshes with the external gear 503. The disc body 501 rotates counterclockwise to radially push out the drill bit blade 3 from the blade moving slot 202 of the drill bit body 2, and the diameter of the drill bit expands to the maximum. The driving shifting projection 402 of the shifting driving shaft 4 abuts against the end face of the expanding gear slot 103 to transmit torque, and the shifting driving shaft 4 drives the drill bit outer pipe body 1 and the drill bit body 2 to rotate and crush rocks. At this time, the drill bit flushing fluid passage 6 is fully opened to the maximum to better discharge rock powder.

[0105] During the process of lifting the drill after the drilling construction is completed, the driving shifting projection 402 of the shifting driving shaft 4 moves from the expanding gear slot 103 through the shifting slot 104 into the retracting gear slot 102, and the driving gear 403 meshes with the internal gear 504 again. The disc body 501 rotates in the same direction as the driving shaft body 401. The disc body 501 rotates clockwise to radially retract the drill bit blade 3 from the blade moving slot 202 of the drill bit body 2, and the diameter of the drill bit shrinks to facilitate lifting the drill.

Claims

1. A downhole variable-diameter bit based on a reversing gear mechanism, comprising a bit outer pipe body (1), a bit body (2) is fixedly installed at the top of the bit outer pipe body (1), and more than one bit blade (3) capable of synchronously telescoping and moving radially is installed at the top of the bit body (2); A shifting drive shaft (4) for driving the rotation of the bit outer pipe body (1) is installed in the bit outer pipe body (1), and the shifting drive shaft (4) can also rotate relative to the bit outer pipe body (1) and move axially to achieve shifting; a reversing gear mechanism (5) capable of rotating is eccentrically installed in the bit body (2), the shifting drive shaft (4) drives the reversing gear mechanism (5) to rotate, and the reversing gear mechanism (5) drives more than one bit blade (3) to synchronously telescope and move radially, realizing variable diameter while drilling; A through bit flushing fluid flow channel (6) is provided on the shifting drive shaft (4), the reversing gear mechanism (5) and the bit body (2); The bit outer pipe body (1) includes a pipe body (101) with both ends open, and two layers of gear positions are circumferentially provided on the inner wall near the top in the pipe body (101), namely the first layer of gear positions and the second layer of gear positions. The first layer of gear positions includes more than one non-connected retracting gear positions (102) corresponding to the bit blades (3) one by one, and the second layer of gear positions includes more than one non-connected expanding gear positions (103) corresponding to the retracting gear positions (102) one by one. Each retracting gear position (102) is connected to the corresponding expanding gear position (103) through a shift slot (104) axially provided; The bit body (2) includes a bit main body (201), the bottom of the bit main body (201) is fixedly installed at the top of the pipe body (101), and more than one blade moving slot (202) for installing the bit blade (3) corresponding to the bit blade (3) is radially provided at the top of the bit main body (201). The inner ends of the more than one blade moving slots (202) intersect and communicate with each other, and the outer ends of the more than one blade moving slots (202) are all open; a reversing gear mechanism rotating cavity (203) for installing the reversing gear mechanism (5) is eccentrically provided at the bottom of the bit main body (201), and the reversing gear mechanism rotating cavity (203) is connected to the more than one blade moving slot (202); The bit blade (3) includes a blade seat (301), the blade seat (301) is installed in the blade moving slot (202) and can move radially, a row of cutting elements (302) is installed at the top of the blade seat (301), and a driving boss (303) is axially arranged at the bottom of the blade seat (301) near the inner end; The described shifting drive shaft (4) includes a drive shaft body (401). The drive shaft body (401) is installed inside the pipe body (101). One or more transmission shifting bosses (402) corresponding to the drill bit blades (3) one by one are arranged along the radial direction at the top of the drive shaft body (401). The transmission shifting bosses (402) can move within the retracted gear slot (102), the shifting slot (104), and the expanded gear slot (103) to achieve shifting. The top end of the drive shaft body (401) is fixedly installed with a drive gear (403) that rotates around the axis through a gear shaft. The described reversing gear mechanism (5) includes a disc body (501). The disc body (501) is installed inside the reversing gear mechanism rotating cavity (203). A reversing cavity (502) with an open bottom end is coaxially opened at the bottom of the disc body (501). A ring of external gears (503) is opened on the bottom inner wall of the reversing cavity (502). An internal gear (504) is fixedly arranged at the center position of the top of the reversing cavity (502). The height difference between the bottom end of the internal gear (504) and the bottom end of the external gear (503) is equal to the stroke length of the shifting slot (104). When the transmission shifting bosses (402) are in the state of being located in the retracted gear slot (102), the drive gear (403) meshes with the internal gear (504) for transmission, causing the drill bit blades (3) to retract. When the transmission shifting bosses (402) are in the state of being located in the expanded gear slot (103), the drive gear (403) meshes with the external gear (503) for transmission, causing the drill bit blades (3) to expand. One or more reversing drive slots (505) corresponding to the drive bosses (303) one by one are opened at the top of the disc body (501). The drive bosses (303) are clamped in the reversing drive slots (505), so that the rotation of the disc body (501) drives one or more drill bit blades (3) to synchronously move in the radial direction for telescopic movement.

2. The variable-diameter drill bit while drilling based on a reversing gear mechanism as claimed in claim 1, wherein The described drill bit flushing fluid flow path (6) includes a first flow path (601) opened in the main body of the driving shaft (401) and penetrating the bottom end, a second flow path (602) penetrating the closed top end of the main body of the driving shaft (401), a third flow path (603) penetrating the closed top end of the reversing chamber (502), and a fourth flow path (604) penetrating the drill bit body (2). The first flow path (601), the second flow path (602), the reversing chamber (502), the third flow path (603), and the fourth flow path (604) are connected in sequence to form the drill bit flushing fluid flow path (6).

3. The variable-diameter drill bit while drilling based on a reversing gear mechanism as claimed in claim 2, wherein There is more than one of the described second flow path (602) and fourth flow path (604); the fourth flow path (604) is not communicated with the blade movement groove (202) and the rotating chamber (203) of the reversing gear mechanism, and the fourth flow path (604) and the blade movement groove (202) are arranged alternately.

4. The variable-diameter drill bit while drilling based on a reversing gear mechanism as claimed in claim 2, wherein Internal threads (404) are provided in the first flow path (601).

5. The variable-diameter drill bit while drilling based on a reversing gear mechanism as claimed in claim 1, wherein A clamping groove (204) is radially provided on one side wall of the blade movement groove (202), and a clamping rail (304) is radially provided on one side wall of the wing seat (301). The clamping rail (304) cooperates with the clamping groove (204) to limit the drill bit blade (3), so that the drill bit blade (3) only moves radially.

6. The variable-diameter drill bit while drilling based on a reversing gear mechanism as claimed in claim 1, wherein The described driving gear (403), external gear (503), and internal gear (504) are all cylindrical gears and have the same module; The transmission ratios of the described driving gear (403) meshing with the external gear (503) and the internal gear (504) respectively are: ； ； The center distance relationship of the described driving gear (403), external gear (503), and internal gear (504) is: ； ； In the formula: is the transmission ratio of the driving gear to the external gear; is the transmission ratio between the driving gear and the internal gear, and the negative sign indicates the opposite rotation direction; , and are the rotational speeds of the driving gear, the outer gear, and the inner gear, respectively. , and are the number of teeth of the driving gear, the outer gear, and the inner gear, respectively; is the center distance of the internal engagement between the driving gear and the external gear; is the center distance between the driving gear and the external engagement of the internal gear; m is the gear module.

7. The variable-diameter drill bit while drilling based on a reversing gear mechanism according to claim 1, wherein, The bottom of the wing seat (301) near the inner end is higher than the bottom of the wing seat (301) near the outer end, and a stepped setting is formed between the bottom of the wing seat (301) near the inner end and the bottom of the wing seat (301) near the outer end.

8. The variable-diameter drill bit while drilling based on a reversing gear mechanism according to claim 1, wherein, The top of the pipe body (101) and the bottom of the drill bit body (201) are connected by fine-threaded screws (105).

9. The variable-diameter drill bit while drilling based on a reversing gear mechanism according to claim 1, wherein, There are three described drill bit blades (3); hard cutting teeth are installed on the cutting elements (302).

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