CN117167009A - High-pressure water jet drilling-expanding-cutting multifunctional drill bit and use method thereof - Google Patents

Abstract

The invention belongs to the technical field of coal mine safety, and relates to a high-pressure water jet drilling-expanding-cutting multifunctional drill bit and a use method thereof, wherein the drill bit comprises a drill bit body and a function conversion mechanism; the drill bit body is provided with a cylindrical inner cavity for accommodating the function conversion mechanism and a plurality of axial function round holes communicated with the cylindrical inner cavity; the function conversion mechanism comprises a valve core, a function conversion slide sleeve and an elastic piece, wherein at least two guide convex columns which radially extend out are arranged on the outer wall of the valve core, sliding grooves matched with the guide convex columns are arranged on the inner wall of the function conversion slide sleeve, each groove subunit adopts an offset dislocation structure at a 'herringbone' intersection turning part, and the valve core is enabled to rotate towards the same direction when axially sliding forwards and axially sliding backwards under the guidance of the sliding grooves. The invention widens the applicable coal bed and engineering conditions of the water jet cutting drill bit, greatly improves the working efficiency of the water jet cutting operation, and has obvious economic benefit and popularization and application value.

Description

A high-pressure water jet drilling-expansion-cutting multifunctional drill bit and its use method

Technical field

The invention belongs to the field of coal mine safety technology and relates to a high-pressure water jet drilling-expanding-cutting multifunctional drill bit and its use method.

Background technique

The permeability of coal seams in my country is generally low, and low permeability has become a constraint for efficient gas drainage in coal seams. Moreover, as the depth of mining gradually increases, the problems of high gas pressure, high ground stress, and low permeability in coal seams become more prominent. The dangers faced by coal mining such as excessive gas outflow and coal and gas outbursts have significantly increased, which has become a constraint on the safety and efficiency of my country's coal mines. important issues in production. Hydraulic slotting technology can be widely used to relieve pressure and increase permeability of working faces in high-stress, high-gas, and low-permeability coal seams. It is an important technical method for efficient underground gas extraction in coal mines and the prevention and control of coal and gas outbursts.

Water jet cutter/drill bit is the key device of hydraulic cutting technology. Conventional water jet cutters usually use high-pressure water to push the valve core to translate and block the channel to achieve the closure of the water flow channel and realize the high and low pressure of drilling and cutting functions. Conversion to meet the integrated functional requirements of low-pressure water drilling and high-pressure water cutting. However, the water pressure threshold for function conversion in this type of design depends on the stiffness and deformation length of the return spring. Due to the machining accuracy of the components and the discrete characteristics of the spring, it is difficult to accurately control the high and low pressure conversion thresholds, and it is easy to have difficulty in converting functions during field application. , or water volume fluctuations lead to unexpected conversions, etc., and drill withdrawal and maintenance lead to reduced operating efficiency. In addition, due to the setting of the high and low pressure conversion threshold, there is a limit to the water flow rate allowed to pass through the cutter during drilling, and the applicable coal seam range and working conditions of the integrated drilling and cutting are limited. In addition, the intelligentization of coal mine safety technology requires higher accuracy and reliability of the device. Conventional designs are no longer able to meet the high-precision and high-reliability requirements of intelligent hydraulic cutting technology for the conversion of cutter water jet functions.

Contents of the invention

In view of this, the purpose of the present invention is to provide a high-pressure water jet drilling-expansion-cutting multifunctional drill bit and its use method, improve the accuracy and reliability of water jet function conversion, and broaden the applicable engineering geological conditions of the water jet cutting drill bit. , improve the efficiency of hydraulic cutting technology.

In order to achieve the above objects, the present invention provides the following technical solutions:

A high-pressure water jet drilling-expanding-cutting multifunctional drill bit, including a drill bit body and a function conversion mechanism. The drill bit body has a cylindrical inner cavity that accommodates the function conversion mechanism, and a plurality of axial holes connected with the cylindrical inner cavity. Functional round holes, and the axial functional round holes are arranged on the side of the cylindrical inner cavity close to the front end of the drill bit body, and the side walls of the drill bit body are provided with multiple radial round holes connected with different axial functional round holes, The radial round holes are connected to nozzles, and the nozzles connected to each of the radial round holes have different apertures, and the drill bit body is also provided with a drilling water hole with one end connected to the end of the drill bit body. , and the other end of the drilled water hole is connected with one axial functional round hole among the plurality of axial functional round holes;

The function conversion mechanism includes a valve core, a function conversion slide sleeve and an elastic member. The valve core has a round hole through which the valve core passes. The function conversion slide sleeve is fixedly installed in the cylindrical inner cavity. The valve core Slidingly installed in the function conversion slide sleeve, one end of the elastic member is connected to the valve core, and the other end is connected to the cylindrical inner cavity and connected to one end of the axial function round hole to push the valve core away from the cylindrical inner cavity and connected to the axial function One end of a round hole;

The outer wall of the valve core is provided with at least two radially extending guide protrusions, and the inner wall of the function conversion slide sleeve is provided with a sliding groove matching the guide protrusions. Under the guidance of the groove, the valve core rotates in the same direction during both forward axial sliding and backward axial sliding. The sliding groove is composed of at least two groove sub-units that are cyclically connected, and the groove sub-units are cyclically connected. The number is equal to the number of axial functional round holes, so that each time the valve core is against one end of the cylindrical inner cavity connected to the axial functional round hole, the valve core penetrates the round hole and connects with multiple axial functional round holes in sequence. Alignment.

Further, a first central blind hole is provided at the front end of the cylindrical inner cavity, a second central blind hole is provided at one end of the valve core close to the first central blind hole, and the two ends of the elastic member are respectively connected to the first central blind hole. A central blind hole and a second central blind hole are movably connected to the first central blind hole and/or the second central blind hole.

Further, the elastic member is a return spring.

Furthermore, each groove sub-unit is formed by a combination of a "herringbone" shape and an inverted "herringbone" groove, and an offset and staggered structure is used at the cross turning point of the "herringbone" shape to allow the guide protruding pillars to move in the sliding groove It always maintains one-way sliding when sliding up and down, so that the valve core always rotates in the same direction.

Further, let the number of groove sub-units be n, when the guide protrusion of the valve core slides through a complete groove sub-unit inside the sliding groove, the valve core rotates θ° in the same rotation direction, and the θ =360/n.

Further, the function conversion slide sleeve is installed in the cylindrical inner cavity through a fixed structure. The fixed structure includes a step structure arranged on the inner wall of the cylindrical inner cavity, an annular groove, and a hole installed in the annular groove. Snap rings, the two ends of the function conversion slide sleeve are connected with the step structure and the hole snap rings in conflict with each other.

Furthermore, there is an interference connection or a key connection between the function conversion slide sleeve and the cylindrical inner cavity, so that the function conversion slide sleeve and the cylindrical inner cavity are circumferentially fixedly connected.

A method of using a high-pressure water jet drilling-expanding-cutting multifunctional drill bit, which adopts the above-mentioned high-pressure waterjet drilling-expanding-cutting multifunctional drill bit, and the tail end of the drill bit body is connected with high-pressure water. The cutting method is specific Includes the following steps:

a. The high-pressure water is turned on. Under the combined action of the high-pressure water flow and the guidance of the sliding groove, the valve core slides and rotates toward the front end of the drill bit body, and then closely fits the front end of the cylindrical cavity. The valve core axially penetrates the round hole and Any one of the multiple axial functional round holes is connected, and high-pressure water flows into the connected axial functional round hole. The remaining axial functional round holes are blocked by the end face of the valve core, and the water jet cutting drill bit enters the preset function. state;

b. When function switching is required, the high-pressure water is turned off. Under the combined action of the elastic member pushing and the sliding groove guidance, the valve core slides and rotates toward the rear end of the drill bit body, and the rotation direction is the same as the rotation direction in step a. The same, making all axial functional round holes open;

c. Turn on the high-pressure water again. Under the combined action of the high-pressure water flow and the guidance of the sliding groove, the valve core slides and rotates toward the front end of the drill bit body, and then closely fits the front end of the cylindrical cavity. The valve core axially penetrates the circular hole. It is connected to the axial functional round hole adjacent to the connected axial functional round hole in step a. High-pressure water flows into the connected axial functional round hole. The remaining axial functional round holes are blocked by the end face of the valve core, and the water jet cutting drill bit enters the preset switch. functional status;

d. The cycle is repeated, and the sequential switching of multiple axial functional round holes is realized by controlling the opening and closing of high-pressure water.

Further, there are three axial functional round holes, two of which are respectively connected to the first nozzle and the second nozzle through the radial round holes, and the other axial functional round hole is connected to the drill bit, and the The aperture of the first nozzle is larger than the aperture of the second nozzle, so that the first nozzle is used as an expanding nozzle and the second nozzle is used as a slit;

Among them, the axial functional round hole connected to the drill bit, the axial functional round hole connected to the first nozzle and the axial functional round hole connected to the second nozzle are arranged in sequence along the rotation direction of the valve core to control the opening and closing of the high-pressure water flow. , realizing the sequential conversion of water jet cutting drill bit drilling-expanding-slitting functions.

The beneficial effects of the present invention are:

The invention provides a high-pressure water jet drilling-expanding-cutting multifunctional drill bit and its use method. It adopts a motion structure design that combines translation and rotation of the valve core to realize the opening and closing of water flow channels with different functions. By controlling the supply of high-pressure water flow and stop, which can realize the sequential conversion of the cutting drill bit's drilling, hole expansion, and seam cutting functions; the function conversion of the cutting drill bit does not rely on the change of water pressure in the conventional method. The water jet function conversion is accurate and reliable, and can meet the requirements of intelligent hydraulic seam cutting. Technology has requirements for the function conversion control of cutting drill bits, and the water flow rate allowed to pass through the cutting drill bit in any functional state of drilling, hole expansion, and seam cutting is not limited. The integrated drilling, expansion, and cutting operation can be applied to all Coal seam conditions and hole depth conditions can greatly improve the efficiency of coal seam hydraulic seam cutting operations. The invention is easy to operate, has high efficiency and good use effect, and has significant economic benefits and promotion and application value.

Other advantages, objects, and features of the present invention will, to the extent that they are set forth in the description that follows, and to the extent that they will become apparent to those skilled in the art upon examination of the following, or may be derived from This invention is taught by practicing it. The objects and other advantages of the invention may be realized and obtained by the following description.

Description of drawings

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic structural diagram of a high-pressure water jet drilling-expansion-cutting multifunctional drill bit without high-pressure water passing through;

Figure 2 is a schematic diagram of section B-B in Figure 1;

Figure 3 is a schematic diagram of section A-A in Figure 1;

Figure 4 is a schematic plan view of the sliding groove in the function conversion slide sleeve in the embodiment;

Figure 5 is a schematic structural diagram of the cutting drill bit in the hole expansion state in the embodiment.

Reference symbols: 1-Drill bit body, 2-annular groove, 3-function conversion slide sleeve, 4-valve core, 5-step structure, 6-cylindrical inner cavity, 7-return spring, 8-axial function Round hole, 9-radial round hole, 10-first nozzle, 11-drill front end, 12-drilling teeth, 13-hole snap ring, 14-filter, 15-guide boss, 16-valve core through circle Hole, 17-second center blind hole, 18-first center blind hole, 19-second nozzle, 20-drilling water hole, 21-sliding groove.

Detailed ways

The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. The following embodiments and the features in the embodiments can be combined with each other as long as there is no conflict.

The drawings are only for illustrative purposes, and represent only schematic diagrams rather than actual drawings, which cannot be understood as limitations of the present invention. In order to better illustrate the embodiments of the present invention, some components of the drawings will be omitted. The enlargement or reduction does not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

In the drawings of the embodiments of the present invention, the same or similar numbers correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms "upper", "lower", "left" and "right" The orientation or positional relationship indicated by "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must be It has a specific orientation and is constructed and operated in a specific orientation. Therefore, the terms describing the positional relationships in the drawings are only for illustrative purposes and cannot be understood as limitations of the present invention. For those of ordinary skill in the art, they can determine the specific position according to the specific orientation. Understand the specific meaning of the above terms.

Please refer to Figures 1 to 5, which shows a high-pressure water jet drilling-expansion-cutting multifunctional drill bit, including a drill bit body 1, a first nozzle 10, a second nozzle 19, a drill bit front end 11, a function conversion mechanism and a fixed structure; The drill bit body 1 is provided with a cylindrical inner cavity 6 for accommodating the function conversion mechanism and three axial functional round holes 8 connected with the cylindrical inner cavity 6. The side wall is provided with a cylindrical inner cavity 6 connected with two of the axial functional round holes 8. Two radial circular holes 9; the first nozzle 10 and the second nozzle 19 are respectively installed in the two radial circular holes 9;

The tail end of the drill bit body 1 is connected to a high-pressure water pipeline, and a drill water hole 20 is arranged at the drill front end 11 of the drill bit body 1, and the drill water hole 20 is connected to another axial functional circular hole 8 , and there is a drill bit pick 12 on the end of the drill bit front end 11 to facilitate the drill bit to drill; the function conversion mechanism includes a valve core 4, a function conversion slide sleeve 3 and a return spring 7. The function conversion slide sleeve The cylinder 3 is installed in the cylindrical inner cavity 6 through a fixed structure. The valve core 4 is rotatably installed in the function conversion slide sleeve 3 and is slidingly connected. One end of the return spring 7 is connected to the valve core 4 and the other end is connected to the valve core 4. The front end of the cylindrical inner cavity 6 is used to limit the axial position of the valve core 4 .

Referring mainly to Figures 1 to 3, the bottom of the cylindrical inner cavity 6 is provided with a central blind hole 18 concentric with it and three axial functional circular holes 8 distributed around the center and at equal angular intervals. The holes 8 are respectively connected to the water flow channels for different functions, and the central blind hole 18 is used to install the return spring 7; the valve core 4 is cylindrical in design, and one end of the valve core 4 is provided with a second central blind hole 17 and an axially penetrating The valve core passes through the circular hole 16; the second center blind hole 17 matches the position of the first center blind hole 18 at the bottom of the cylindrical inner cavity of the drill bit body, and is used to install the return spring 7, and the return spring 7 is connected with the first center blind hole and /Or the second central blind hole is a movable connection, and the size and position of the valve core through-hole 16 match the axial functional round hole 8 at the bottom of the cylindrical cavity.

The valve core 4 is installed in the function conversion slide sleeve 3. The outer wall of the valve core 4 is provided with three radially extending guide bosses 15. The guide bosses 15 are fixed on the valve core 4 using a screw structure. On the inner wall of the function conversion slide sleeve 3, a sliding groove 21 matching the guide convex column 15 is processed, so that the valve core 4 can always rotate toward the same side when performing axial reciprocating movement, thereby achieving The valve core through-hole 16 is connected with the different axial function round holes 8 .

As shown in Figure 4, the sliding groove 21 is composed of three groove sub-units connected cyclically, and the number of groove sub-units is equal to the number of axial functional round holes 8 in the drill bit body, which are three; each groove sub-unit The unit is formed by a combination of a "herringbone" shape and an inverted "herringbone" shaped groove. The groove adopts an offset and staggered structure at the cross turning point of the "herringbone" character, so that the guide convex column 15 always maintains its position when sliding up and down in the groove. One-way sliding to the right, thereby ensuring that the valve core 4 always rotates to the same side; and when the guide protrusion 15 of the valve core 4 slides through a "herringbone" structure inside the sliding groove, the groove guides the valve core Rotate 60° counterclockwise along the groove, and rotate 120° when sliding through a complete groove subunit; the three axial functional round holes 8 are spaced at the same angle of 120°, so that the guide convex column 15 is in the sliding groove 21 Each time a groove subunit is slid, the water flow function is switched.

When the inlet of the function conversion mechanism, that is, the rear end of the drill bit body 1, applies fluid higher than a predetermined limit value (that is, the pressure is higher than the elastic force of the return spring 7) through the high-pressure water pipeline, the valve core 4 overcomes the return spring 7 and moves toward it. The applied elastic force moves to the right and presses against the bottom (right end) of the cylindrical cavity 6. After the high-pressure water is turned off, the valve core 4 moves to the left under the action of the return spring 7, thereby resetting.

The fixed structure includes a step structure 5 arranged at the front end of the inner wall of the cylindrical cavity 6 (an end close to the drill bit end 11), an annular groove 2 arranged at the rear end, and a hole snap ring 13 installed in the annular groove 2. , one end of the function conversion slide sleeve 3 is fixed by the step structure 5, and the other end is fixed with a snap ring 13 and a filter 14 through the hole installed in the annular groove 2, so that the function conversion slide sleeve 3. Perform axial fixation;

Preferably, there is an interference connection or a key connection between the function conversion slide sleeve 3 and the cylindrical inner cavity 6 so that the function conversion slide sleeve 3 and the cylindrical inner cavity 6 are circumferentially fixedly connected.

Further, the first nozzle 10 and the second nozzle 19 installed in the two radial circular holes 9 on the side wall of the drill bit body 1 have different apertures, and are respectively an expanding nozzle and a slit nozzle, and the aperture of the expanding nozzle is larger than that of the slit. The hole diameter of the slit nozzle.

In other embodiments, the valve core 4 is of thick-walled cylindrical design.

The application process of this embodiment:

As shown in Figure 5, before the high-pressure water is turned on, the guide boss 15 is located on the side of the sliding groove 21 close to the rear end of the drill bit body 1. When the high-pressure water is turned on, the valve core 4 is pushed by the high-pressure water flow from the rear end of the drill bit body 1. It slides downward and to the right, and rotates counterclockwise under the guidance of the guide protrusion 15 and the sliding groove 21; when the valve core 4 is closely attached to the bottom of the cylindrical cavity 6, the valve core 4 rotates 60° counterclockwise, and the axis The through hole 16 is matched and connected with the axial functional circular hole 8 connected to the first nozzle 10, and the remaining axial functional circular holes 8 are blocked by the end face of the valve core 4. At this time, the cutting drill bit is in the hole expansion function state;

When the high-pressure water is turned off, under the combined action of the push of the return spring 7 and the guidance of the guide boss 15 and the sliding groove 21, the valve core returns to the left position and rotates 60° counterclockwise. All axes at the bottom of the cylindrical cavity 6 The functional round hole 8 is in an open state;

Turn on the high-pressure water again, and the valve core 4 slides to the right again and rotates 60° counterclockwise. The valve core passes through the circular hole 16 and is connected to the axial functional circular hole 8 connected to the second nozzle 19. At this time, the cutting drill bit is in the cutting function. state;

Turn off the high-pressure water, and under the combined action of the return spring 7 and the guidance of the guide convex column 15 and the sliding groove 21, the valve core returns and slides to the left and rotates 60° counterclockwise. All axial directions at the bottom of the cylindrical cavity 6 The functional round hole 8 is open;

When the high-pressure water is turned on again, the valve core 4 slides to the right again and rotates 60° counterclockwise. The valve core penetrates the circular hole 16 and is connected to the axial functional circular hole 8 connected to the drilled water hole 20. At this time, the cutting drill bit is in the drilling position. hole functional status;

In this way, the high-pressure water is cycled on and off to guide the convex column 15 to slide through a groove sub-unit. The water flow channels of the round holes 8 with different axial functions are opened and closed in the order of "drilling-expanding-slitting", which can realize cutting drill bit drilling. Sequence conversion of advancing-expanding-slitting functions.

The embodiment of the above application process takes as an example the situation where the guide boss 15 is aligned with the axial functional hole 8 communicating with the first nozzle 10 after being displaced to the right and rotated. However, it is not limited to this. The guide boss 15 is located on the first nozzle 10 . When the first interval restores the slot 26 or the second interval restores the slot 27, it can also be used as the initial position for function switching.

It should be noted that the above embodiment is a cutting drill bit with three functions of drilling, expanding and slitting, and the sequence of function conversion can be realized by adjusting the connecting nozzle on the drill bit body. In addition, the number of functions of the cutting drill bit can also be adjusted by adjusting the number of axial functional round holes at the bottom of the cylindrical cavity of the cutting drill bit. For example, by reducing one axial functional round hole, the cutting drill bit can be changed to "drilling-slitting". The two-function sequential conversion cutting drill bit, or the two-function drilling-expanding sequential conversion cutting drill bit; for example, the axial function round hole can be increased to four, and the cutting drill bit can be changed to "drilling-expanding-slitting-punching" "Four-function sequential conversion cutting drill; it should be noted that when the axial functional round holes are added or reduced, the groove sub-units in the sliding groove 21 should be adjusted accordingly, so that they correspond one to one with the number of axial functional round holes. Such modified embodiments are generally similar to the above embodiments and will not be described in detail.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified. Modifications or equivalent substitutions without departing from the purpose and scope of the technical solution shall be included in the scope of the claims of the present invention.

Claims (9)

1. A high-pressure water jet drilling-expanding-cutting multifunctional drill bit is characterized in that: the drill bit comprises a drill bit body and a function conversion mechanism, wherein the drill bit body is internally provided with a cylindrical inner cavity for accommodating the function conversion mechanism and a plurality of axial function round holes communicated with the cylindrical inner cavity, the axial function round holes are arranged on one side, close to the front end of the drill bit body, of the cylindrical inner cavity, a plurality of radial round holes communicated with different axial function round holes are formed in the side wall of the drill bit body, the radial round holes are connected with nozzles, the diameters of the nozzles connected with the radial round holes are different, a drilling water through hole with one end communicated with the end of the drill bit body is further formed in the drill bit body, and the other end of the drilling water through hole is communicated with one axial function round hole of the plurality of axial function round holes;

the function conversion mechanism comprises a valve core, a function conversion slide sleeve and an elastic piece, wherein the valve core is provided with a valve core through round hole, the function conversion slide sleeve is fixedly arranged in a cylindrical inner cavity, the valve core is slidably arranged in the function conversion slide sleeve, one end of the elastic piece is connected with the valve core, and the other end of the elastic piece is connected with one end of the cylindrical inner cavity, which is connected with an axial function round hole, so as to push the valve core to leave the cylindrical inner cavity and be connected with one end of the axial function round hole;

the valve core is characterized in that at least two guide convex columns extending radially are arranged on the outer wall of the valve core, sliding grooves matched with the guide convex columns are arranged on the inner wall of the function conversion slide sleeve, the valve core is enabled to rotate in the same direction under the guidance of the sliding grooves in the forward axial sliding mode and the backward axial sliding mode, the sliding grooves are formed by at least two groove sub-units in a circulating connection mode, the number of the groove sub-units is equal to that of the axial function round holes, and when the valve core abuts against one end, connected with the axial function round holes, of each time, the valve core penetrates through the round holes to be aligned with the plurality of axial function round holes in sequence.

2. The high pressure water jet drilling-reaming-cutting multifunctional drill bit of claim 1, further comprising: the front end of the cylindrical inner cavity is provided with a first central blind hole, one end of the valve core, which is close to the first central blind hole, is provided with a second central blind hole, and two ends of the elastic piece are respectively connected with the first central blind hole and the second central blind hole and are movably connected with the first central blind hole and/or the second central blind hole.

3. The high pressure water jet drilling-reaming-cutting multifunctional drill bit of claim 1, further comprising: the elastic piece is a return spring.

4. The high pressure water jet drilling-reaming-cutting multifunctional drill bit of claim 1, further comprising: each groove subunit is formed by combining a herringbone groove and an inverted herringbone groove, and an offset dislocation structure is adopted at the crossing and turning part of the herringbone groove, so that the guide convex column always keeps unidirectional sliding when sliding up and down in the sliding groove, and the valve core always rotates in the same direction.

5. The high pressure water jet drilling-reaming-cutting multifunctional drill bit of claim 4, further comprising: let the recess subunit quantity be n, when the guide projection of case slides in the slip recess and passes a complete recess subunit, the case rotates θ in same direction of rotation, and θ=360/n.

6. The high pressure water jet drilling-reaming-cutting multifunctional drill bit of claim 1, further comprising: the function conversion slide sleeve is installed in the cylinder inner cavity through a fixed structure, the fixed structure comprises a step structure, an annular groove and a hole snap ring, wherein the step structure and the annular groove are arranged on the inner wall of the cylinder inner cavity, the hole snap ring is installed in the annular groove, and two ends of the function conversion slide sleeve are respectively in interference connection with the step structure and the hole snap ring.

7. The high pressure water jet drilling-reaming-cutting multifunctional drill bit of claim 6, further comprising: the function conversion slide sleeve is in interference connection or key connection with the cylindrical inner cavity, so that the function conversion slide sleeve is fixedly connected with the circumferential direction of the cylindrical inner cavity.

8. The application method of the high-pressure water jet drilling-expanding-cutting multifunctional drill bit is characterized by comprising the following steps of: a high pressure water jet drilling-reaming-cutting multifunctional drill bit according to any one of claims 1-7, wherein the tail end of the drill bit body is connected with high pressure water, and the cutting method specifically comprises the following steps:

a. the high-pressure water is started, under the combined action of high-pressure water flow pushing and sliding groove guiding, the valve core slides and rotates towards the front end of the drill bit body, then the valve core is tightly attached to the front end of the cylindrical inner cavity, the valve core axially penetrates through the round hole and is communicated with any one of the axial function round holes, the high-pressure water flows into the communicated axial function round holes, the other axial function round holes are blocked by the end face of the valve core, and the water jet cutting drill bit enters a preset function state;

b. when the function is required to be switched, the high-pressure water is closed, under the combined action of the pushing of the elastic piece and the guiding of the sliding groove, the valve core slides to the tail end of the drill bit body and rotates, and the rotating direction is the same as that in the step a, so that all axial function round holes are in an open state;

c. b, starting high-pressure water again, sliding and rotating the valve core towards the front end of the drill bit body under the combined action of high-pressure water flow pushing and sliding groove guiding, then tightly attaching the valve core to the front end of the cylindrical inner cavity, enabling the valve core to axially penetrate through the round hole and be communicated with the adjacent axial functional round hole of the communicated axial functional round hole in the step a, enabling the high-pressure water to flow into the communicated axial functional round hole, enabling the other axial functional round holes to be blocked by the end face of the valve core, and enabling the water jet cutting drill bit to enter a preset switching functional state;

d. and the circulation is repeated, and the sequential switching of a plurality of axial function round holes is realized by controlling the opening and closing of the high-pressure water.

9. The method for using the high-pressure water jet drilling-expanding-cutting multifunctional drill bit as claimed in claim 8, wherein the method comprises the following steps: the number of the axial functional round holes is three, wherein two axial functional round holes are respectively connected with a first nozzle and a second nozzle through radial round holes, the other axial functional round hole is connected with a drilling through water hole, the aperture of the first nozzle is larger than that of the second nozzle, the first nozzle is used as a reaming nozzle, and the second nozzle is used as a slotting;

the axial function round holes connected with the drill bit, the axial function round holes connected with the first nozzle and the axial function round holes connected with the second nozzle are sequentially arranged along the rotation direction of the valve core, so that the sequential conversion of drilling-reaming-slotting functions is realized by controlling the opening and closing of high-pressure water flow.