CN112145096A - Well drilling tool follow-up steering mechanism - Google Patents

Abstract

A servo direction-changing mechanism for an underground drilling tool comprises an upper joint, a first direction-changing component, a first middle joint, a second direction-changing component, a second middle joint, a third direction-changing component and a lower joint, wherein the upper joint is connected with the upper end of the first middle joint through the first direction-changing component, the lower end of the first middle joint is connected with the upper end of the second middle joint through the second direction-changing component, the lower end of the second middle joint is connected with the lower joint through the third direction-changing component, the first direction-changing component, the second direction-changing component and the third direction-changing component are identical in structure, the servo direction-changing mechanism for the underground drilling tool can follow up on a plane where a sliding key of a first driven direction-changing ball head can move through the limiting of the first ball head and the limiting effect of the first middle joint on the first driven direction-changing ball head, a new thought and direction are provided for the development of the servo direction-changing technology of the underground drilling tool, and the, has wide application prospect.

Description

Well drilling tool follow-up steering mechanism

Technical Field

The invention belongs to the technical field of directional drilling, and particularly relates to an in-well drilling tool follow-up direction-changing mechanism adaptive to a self-walking self-direction-changing guiding drilling system.

Background

Although the downhole torque self-balancing cabled drilling tool can fundamentally solve the problem of reaction torque damage caused by rotary drilling of a drill column, change the disturbance strength of one-way broken rocks of a drill bit on surrounding rocks, simplify ground drilling equipment, matched tools and process methods, and achieve the purposes of few in-well accidents, low drilling cost, low energy consumption, high drilling efficiency and the like, the downhole torque self-balancing cabled drilling tool still has great limitations, specifically shows that only vertical drilling can be achieved, and the downhole torque self-balancing cabled drilling tool cannot work in a bent well.

At present, the traditional drilling tool mainly utilizes the flexibility of a long drill rod to carry out follow-up steering, but the flexibility of a steel drill rod is limited, so that the bending of a small angle can be realized in a large length, and the traditional drilling tool is obviously not suitable for follow-up steering of an underground torque self-balancing drilling tool; patent numbers: 01130910.5, the technical scheme of the invention named as 'reverse spiral double-drive special robot' can change the direction of a certain range of angles, but can only change the direction of the plane in which the steering engine rotates, and has great limitation; in addition, some researchers use the flexible pipe for the follow-up direction changing part of the drilling tool, but the strength of the flexible pipe is limited, and the lower drilling tool system which is heavier cannot be borne, so that a mechanism is urgently needed to realize the stepless follow-up direction changing capability of the underground torque self-balancing cabled drilling tool which is stable in direction changing, high in strength and high in precision.

Disclosure of Invention

The invention aims to provide an in-well drilling tool follow-up direction-changing mechanism adaptive to a self-walking self-direction-changing guiding drilling system, which is mainly used for realizing the purpose that the self-walking self-direction-changing guiding drilling system can change direction in a follow-up manner according to a well track in the drilling process, and has the advantages of stable direction change, high connection strength and higher precision.

A servo direction-changing mechanism of an in-well drilling tool comprises an upper joint, a first direction-changing component, a first middle joint, a second direction-changing component, a second middle joint, a third direction-changing component and a lower joint, wherein the upper joint is connected with the upper end of the first middle joint through the first direction-changing component;

a hollow channel used for passing through corresponding matched mud circulation equipment is arranged in the upper joint, a plurality of through holes used for passing through cables in the drilling tool are arranged around the hollow channel of the upper joint, and the lower part of the upper joint is fixedly connected with the first driven turning ball head;

the first turning assembly comprises a first spring rubber pipe, a first ball head limit and a first driven turning ball head, the first spring rubber pipe is a hollow elastic rubber pipe, the upper part of the first spring rubber pipe is fixedly connected with the outer wall of the upper joint, the lower part of the first spring rubber pipe is fixedly connected with the outer wall of the first ball head limit, a hollow channel which can pass through the thin-mouth end of the upper joint and the cylindrical end of the first driven turning ball head is arranged in the first spring rubber pipe, and a plurality of annular grooves extending along the axial direction of the first spring rubber pipe are arranged on the outer wall of the first spring rubber pipe; the upper part of the first ball head limit is fixedly connected with the lower part of the first spring rubber tube, a hollow channel for passing through a cylindrical end of a first driven turning ball head is arranged in the first ball head limit, a plurality of through holes for passing through cables in a drilling tool are circumferentially distributed around the first ball head limit hollow channel, a pair of first sliding key grooves are symmetrically arranged at the bottom of the first ball head limit hollow channel and used for limiting the first driven turning ball head, so that the first driven turning ball head can only move on a moving plane of a sliding key, a first arc surface is arranged at the bottom of the first ball head limit hollow channel and is in sliding fit with a spherical ball structure of the first driven turning ball head and used for limiting the first driven turning ball head; the first driven turning ball head is fixedly matched with the upper joint through the cylindrical end at the upper part, a hollow channel used for passing through corresponding matched slurry circulation equipment is arranged in the first driven turning ball head, the lower part of the first driven turning ball head is of a ball structure, the ball structure is in sliding contact fit with a first arc surface limited by the first ball head and a second arc surface of a first intermediate joint, a pair of sliding keys are symmetrically arranged on two sides of the ball structure, the sliding keys are slidably connected in a first sliding key groove and a second sliding key groove, the first arc surface and the second arc surface are concentric in the downhole drilling tool follow-up turning mechanism, and the first driven turning ball head can only rotate in a two-dimensional plane by taking the ball center of the ball structure as an origin under the limiting action of the first arc surface, the second arc surface, the first sliding key groove and the second sliding key groove; the upper part of the first middle joint is fixedly connected with the lower limiting part of the first ball head, a hollow channel for passing through corresponding matched slurry circulation equipment is arranged in the first middle joint, a plurality of through holes for passing through cables inside a drilling tool are circumferentially distributed around the hollow channel of the first middle joint, a pair of second key sliding grooves are symmetrically arranged at the top of the hollow channel of the first middle joint, a second arc surface is arranged at the top of the hollow channel of the first middle joint, and the second arc surface is in sliding fit with the spherical ball structure of the first driven turning ball head;

the upper part of the lower joint is fixedly connected with the lower limiting part of a third ball head of a third direction-changing assembly, a hollow channel for passing through corresponding matched slurry circulation equipment is arranged in the lower joint, a plurality of through holes for passing through cables in a drilling tool are circumferentially distributed around the hollow channel of the lower joint, a pair of second sliding key grooves are symmetrically arranged at the top of the hollow channel of the lower joint and used for limiting the third ball head limiting of the third direction-changing assembly, so that the third ball head limiting of the third direction-changing assembly can only move on a plane where a sliding key can move, a second arc surface is arranged at the top of the hollow channel of the lower joint, and the second arc surface of the lower joint is in sliding fit with a ball structure of a third driven direction-changing ball head of the third direction-changing assembly and used for limiting the third driven direction-changing ball head; the lower part of the lower joint is connected with other components of the drilling tool;

the invention has the beneficial effects that:

the invention is composed of an upper joint, a first direction-changing component, a first middle joint, a second direction-changing component, a second middle joint, a third direction-changing component and a lower joint, wherein the direction-changing mechanism of the drilling tool in the well can change direction in a follow-up way on a plane which can move by a first driven direction-changing ball head sliding key under the limiting action of a first ball head limiting part and a first middle joint on the first driven direction-changing ball head, a first spring rubber pipe is arranged for protecting a backward-changed internal drilling tool, the first spring rubber pipe is not subjected to axial acting force, and the following direction-changing mechanism of the drilling tool in the well can change direction in a follow-up way on planes which can move by a second driven direction-changing ball head and a third driven direction-changing ball head sliding key, three planes respectively show 120 degrees on a horizontal projection plane, so that a self-walking self-guiding drilling system can realize 360-degree direction-changing in a stepless follow-up way, and provides a new thought and direction for the development, has great innovative significance and great significance and has wide application prospect.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention to the right, and in which:

fig. 1 is a schematic view of the assembly of a follow-up direction-changing mechanism of a downhole drilling tool provided by the invention.

Fig. 2 is a schematic sectional view of the assembly of a follow-up direction-changing mechanism of a downhole drilling tool according to the present invention.

Fig. 3 is a schematic cross-sectional view of the upper joint in the present invention.

FIG. 4 is a side view of the first spring hose of the present invention.

Fig. 5 is a bottom view of the first ball stop of the present invention.

Fig. 6 is a sectional view at a-a of fig. 5.

Fig. 7 is a bottom view of the first driven direction changing ball of the present invention.

Fig. 8 is a sectional view at B-B of fig. 7.

Fig. 9 is a top view of a first intermediate joint of the present invention.

Fig. 10 is a sectional view at C-C of fig. 9.

Figure 11 is a top view of the lower joint of the present invention.

Fig. 12 is a sectional view taken at D-D of fig. 11.

Fig. 13 is a schematic diagram of the operation of a follow-up direction-changing mechanism of a downhole drilling tool according to the present invention.

Detailed Description

In order to more clearly illustrate the invention, the invention is further described below with reference to preferred embodiments and the accompanying drawings. As will be appreciated by those skilled in the art. The following detailed description is illustrative rather than limiting in nature and is not intended to limit the scope of the invention.

In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

As shown in fig. 1 to 11, a follow-up direction-changing mechanism of an in-well drilling tool comprises an upper joint 1, a first direction-changing component, a first middle joint 5, a second direction-changing component, a second middle joint 9, a third direction-changing component and a lower joint 13, wherein the upper joint 1 is connected with the upper end of the first middle joint 5 through the first direction-changing component, the lower end of the first middle joint 5 is connected with the upper end of the second middle joint 9 through the second direction-changing component, the lower end of the second middle joint 9 is connected with the lower joint 13 through the third direction-changing component, and the first direction-changing component, the second direction-changing component and the third direction-changing component have the same structure;

a hollow channel 101 used for passing through corresponding matched mud circulation equipment is arranged in the upper joint 1, a plurality of through holes 102 used for passing through cables in a drilling tool are arranged around the hollow channel 101 of the upper joint 1, the upper side and the lower side of each through hole 102 are of annular fillet structures and are used for protecting the cables and preventing the cables from being damaged due to friction to influence the control of a drilling tool system, and a thin-mouth end at the lower part of the upper joint 1 is used for being in reducing connection with the first driven turning ball head 4;

the first diversion assembly comprises a first spring rubber pipe 2, a first ball head limit 3 and a first driven diversion ball head 4, the first spring rubber pipe 2 is a hollow elastic rubber pipe, the upper part of the first spring rubber pipe 2 is fixedly connected with the outer wall of an upper joint 1, the lower part of the first spring rubber pipe 2 is fixedly connected with the outer wall of the first ball head limit 3, a hollow channel 101 which can pass through the thin-hole end of the upper joint 1 and the cylindrical end of the first driven diversion ball head 4 is arranged in the first spring rubber pipe 2, the first spring rubber pipe 2 is mainly used for protecting the internal structure of the mechanism, a plurality of annular grooves 201 extending along the axial direction of the first spring rubber pipe 2 are arranged on the outer wall of the first spring rubber pipe 2, the function of facilitating the first spring rubber pipe 2 to bend correspondingly when the follow-up diversion mechanism of the drilling tool in the well performs follow-up diversion, and due to the limit functions of the upper joint 1, the first ball head, the first spring rubber tube 2 does not bear axial force, so that the service life of the rubber tube is greatly prolonged; the upper part of the first ball head limit 3 is fixedly connected with the lower part of the first spring rubber tube 2, a hollow channel 101 for passing through a cylindrical end of a first driven turning ball head 4 is arranged in the first ball head limit 3, a plurality of through holes 102 for passing through cables inside a drilling tool are circumferentially distributed around the hollow channel 101 of the first ball head limit 3, the top of the hollow channel 101 of the first ball head limit 3 is of an annular round angle structure and has the function of preventing the first driven turning ball head 4 from being damaged after touching the hollow channel 101 in the turning process, a pair of first sliding key grooves 304 are symmetrically arranged at the bottom of the hollow channel 101 of the first ball head limit 3 and used for limiting the first driven turning ball head 4, so that the first driven turning ball head 4 can only move on a plane where a sliding key 402 can move, a first arc surface 303 is arranged at the bottom of the hollow channel 101 of the first ball head limit 3, and the first arc surface 303 is in sliding fit with a round ball structure 401 of the first driven turning ball head 4, the first driven turning ball head 4 is limited; the first driven turning ball head 4 is fixedly matched with the narrow-mouth end of the upper joint 1 through the cylindrical end at the upper part, a hollow channel 101 for passing through corresponding matched slurry circulation equipment is arranged in the first driven turning ball head 4, the lower part of the first driven turning ball head 4 is provided with a spherical structure 401, the spherical structure 401 is in sliding contact fit with a first arc surface 303 of a first ball head limit 3 and a second arc surface 503 of a first intermediate joint 5, a pair of sliding keys 402 are symmetrically arranged at two sides of the spherical structure 401, the sliding keys 402 are connected in the first sliding key groove 304 and the second sliding key groove 504 in a sliding way and limited by the first sliding key groove 304 and the second sliding key groove 504, the first arc surface 303 and the second arc surface 503 are concentric in the follow-up turning mechanism of the drilling tool, under the limiting action of the first arc surface 303 and the second arc surface 503, the first driven turning ball head 4 can only rotate in a three-dimensional space by taking the spherical center of the spherical structure 401 as an origin, under the limiting action of the first keyway 304 and the second keyway 504, the first driven turning ball head 4 can only move on the plane where the sliding key 402 can move, under the limiting action of the two combinations, the first driven turning ball head 4 can only rotate in the two-dimensional plane on the plane where the sliding key 402 can move by taking the sphere center of the spherical ball structure 401 as the origin, and the bottom of the hollow channel 101 of the spherical ball structure 401 is provided with a third arc surface 403 for reducing the friction resistance of the first driven turning ball head 4 in the moving process; the upper portion of the first intermediate joint 5 is fixedly connected with the lower portion of the first ball head limiting 3, a hollow channel 101 used for passing through corresponding matched mud circulation equipment is arranged in the first intermediate joint 5, a plurality of through holes 102 used for passing through cables in a drilling tool are circumferentially distributed around the hollow channel 101 of the first intermediate joint 5, a pair of second sliding key grooves 504 are symmetrically formed in the top of the hollow channel 101 of the first intermediate joint 5 and used for limiting the first driven turning ball head 4, the first driven turning ball head 4 can only move on a moving plane of the sliding key 402, a second arc surface 503 is arranged at the top of the hollow channel 101 of the first intermediate joint 5, and the second arc surface 503 is in sliding fit with a ball structure 401 of the first driven turning ball head 4 and used for limiting the first driven turning ball head 4;

the upper part of the lower joint 13 is fixedly connected with the lower part of a third ball head limit 11 of a third direction changing assembly, a hollow channel 101 used for passing through corresponding matched mud circulation equipment is arranged in the lower joint 13, a plurality of through holes 102 used for passing through cables in a drilling tool are circumferentially distributed around the hollow channel 101 of the lower joint 13, a pair of second sliding key grooves 504 are symmetrically arranged at the top of the hollow channel 101 of the lower joint 13 and used for limiting the third ball head limit 11 of the third direction changing assembly, so that the third ball head limit 11 of the third direction changing assembly can only move on a moving plane of a sliding key 402, a second arc surface 503 is arranged at the top of the hollow channel 101 of the lower joint 13, and the second arc surface 503 of the lower joint 13 is in sliding fit with a ball structure 401 of a third driven direction changing ball head 12 of the third direction changing assembly and used for limiting the third driven direction changing ball head 12; the lower part of the lower joint 13 is connected with other components of the drilling tool;

the second turning component comprises a second spring rubber tube 6, a second ball head limit 7 and a second driven turning ball head 8;

the third direction changing assembly comprises a third spring rubber tube 10, a third ball head limit 11 and a third driven direction changing ball head 12;

the sliding keys of the first direction changing assembly, the second direction changing assembly and the third direction changing assembly are annularly distributed at an angle of 120 degrees on the horizontal plane.

The second spring rubber tube 6 and the third spring rubber tube 10 have the same structure and working principle as the first spring rubber tube 2, and are different in installation position, so that the detailed description is omitted;

the structure and the working principle of the second ball head limit 7 and the third ball head limit 11 are completely the same as those of the first ball head limit 3, and the second ball head limit 7 and the third ball head limit 11 are different from each other only in installation positions, and are not described herein again, and the specific function is that the second ball head limit 7 is used for limiting the second driven turning ball head 8, and the third ball head limit 11 is used for limiting the third driven turning ball head 12;

the second driven turning ball head 8 and the third driven turning ball head 12 are completely the same as the first driven turning ball head 4 in structure and working principle, and are different only in installation position, and are not described again;

the second intermediate joint 9 and the first intermediate joint 5 have the same structure and working principle, and are different in installation position, so that the description is omitted;

the lower joint 13 is different from the first intermediate joint 5 only at the lower interface end, and the structures and functions of other parts are completely the same, so that the description is omitted, only the lower interface end is described, the lower part of the first intermediate joint 5 is a thin-mouth end and used for reducing, and the lower part of the lower joint 13 is a thick-mouth end and used for being connected with other components of the drilling tool.

The outer diameters or the inner diameters of the upper joint 1, the first direction changing assembly, the first middle joint 5, the second direction changing assembly, the second middle joint 9, the third direction changing assembly and the lower joint 13 can be equal.

The working principle and the process of the invention are as follows:

fig. 13 is a schematic diagram of a servo direction-changing mechanism of a downhole drilling tool in the working process, in fig. 13, a third ball head limit 11 at the lowest part and a lower joint 13 have been subjected to servo direction-changing along a well wall or a pipe wall, an included angle between an extension line of an upper axis of the mechanism and a lower axis of the mechanism is theta, namely a direction-changing angle, which is illustrated in fig. 12 by being 3 degrees, and the diagram is taken as an example for explanation;

the third ball head limit 11 and the lower joint 13 carry out combined limit on the third driven turning ball head 12, so that the third driven turning ball head 12 can only rotate in a two-dimensional plane relative to the lower drilling tool in a plane which can move in a sliding key by taking the spherical center position of the spherical surface as an origin, namely a cross section in fig. 10, the lower drilling tool turns in the turning position of the well wall due to the constraint of the well wall, the upper drilling tool keeps the direction before turning, the follow-up turning mechanism part of the well drilling tool performs follow-up turning in the third driven turning ball head 12 at the moment, the specific state is shown in fig. 12, and similarly, the first driven turning ball head 4 and the second driven turning ball head 8 can perform the same follow-up turning in the turning position of the well wall, it needs to be noted that the projections of the sliding keys of the first driven turning ball head 4, the second driven turning ball head 8 and the third driven turning ball head 12 on the horizontal plane are 120 degrees mutually, the purpose of the design is to ensure that the follow-up direction-changing mechanism of the drilling tool in the well can carry out follow-up direction-changing in the direction of 360 degrees.

Claims (8)

1. The utility model provides a drilling tool follow-up steering mechanism in well which characterized in that: the device comprises an upper joint (1), a first direction changing component, a first middle joint (5), a second direction changing component, a second middle joint (9), a third direction changing component and a lower joint (13), wherein the upper joint (1) is connected with the upper end of the first middle joint (5) through the first direction changing component, the lower end of the first middle joint (5) is connected with the upper end of the second middle joint (9) through the second direction changing component, the lower end of the second middle joint (9) is connected with the lower joint (13) through the third direction changing component, and the first direction changing component, the second direction changing component and the third direction changing component are identical in structure;

a hollow channel (101) used for passing through corresponding matched mud circulation equipment is arranged in the upper joint (1), a plurality of through holes (102) used for passing through cables in a drilling tool are formed in the periphery of the hollow channel (101) of the upper joint (1), and the lower part of the upper joint (1) is fixedly connected with a first driven turning ball head (4);

the first turning assembly comprises a first spring rubber pipe (2), a first ball head limit (3) and a first driven turning ball head (4), the first spring rubber pipe (2) is a hollow elastic rubber pipe, the upper portion of the first spring rubber pipe (2) is fixedly connected with the outer wall of the upper connector (1), the lower portion of the first spring rubber pipe (2) is fixedly connected with the outer wall of the first ball head limit (3), a hollow channel (101) capable of passing through the thin-hole end of the upper connector (1) and the cylindrical end of the first driven turning ball head (4) is arranged in the first spring rubber pipe (2), and a plurality of annular grooves (201) extending along the axial direction of the first spring rubber pipe (2) are formed in the outer wall of the first spring rubber pipe (2; the upper part of the first ball head limit (3) is fixedly connected with the lower part of the first spring rubber tube (2), a hollow channel (101) used for passing through the cylindrical end of the first driven turning ball head (4) is arranged in the first ball head limit (3), a plurality of through holes (102) used for passing through cables inside a drilling tool are circumferentially distributed around the hollow channel (101) of the first ball head limit (3), a pair of first sliding key grooves (304) are symmetrically arranged at the bottom of the hollow channel (101) of the first ball head limit (3) and used for limiting the first driven turning ball head (4), so that the first driven turning ball head (4) can only move on a moving plane of the sliding key (402), a first arc surface (303) is arranged at the bottom of the hollow channel (101) of the first ball head limit (3), and the first arc surface (303) is in sliding fit with a ball structure (401) of the first driven turning ball head (4), the first driven turning ball head (4) is limited; the first driven turning ball head (4) is fixedly matched with the upper connector (1) through the cylindrical end of the upper portion, a hollow channel (101) used for passing through corresponding matched slurry circulation equipment is arranged in the first driven turning ball head (4), the lower portion of the first driven turning ball head (4) is of a ball structure (401), the ball structure (401) is in sliding contact matching with a first arc surface (303) of a first ball head limiting device (3) and a second arc surface (503) of a first intermediate connector (5), a pair of sliding keys (402) are symmetrically arranged on two sides of the ball structure (401), the sliding keys (402) are slidably connected in a first sliding key groove (304) and a second sliding key groove (504), the first arc surface (303) and the second arc surface (503) are concentric in the downhole drilling tool follow-up turning mechanism, and the first driven turning ball head (4) can only use the first driven turning ball structure (4) under the limiting effect of the first arc surface (303), the second arc surface (503), the first sliding key groove (304) and the second sliding key groove (504) (401) The sphere center is the rotation of the origin in a two-dimensional plane on the plane where the sliding key (402) can move; the upper part of the first middle joint (5) is fixedly connected with the lower part of the first ball head limiting part (3), a hollow channel (101) used for passing through corresponding matched mud circulation equipment is arranged in the first middle joint (5), a plurality of through holes (102) used for passing through cables inside a drilling tool are circumferentially distributed around the hollow channel (101) of the first middle joint (5), a pair of second sliding key grooves (504) are symmetrically formed in the top of the hollow channel (101) of the first middle joint (5), a second arc surface (503) is arranged on the top of the hollow channel (101) of the first middle joint (5), and the second arc surface (503) is in sliding fit with a ball structure (401) of the first driven turning ball head (4);

the upper part of the lower joint (13) is fixedly connected with the lower part of a third ball head limit (11) of a third direction changing assembly, a hollow channel (101) used for passing through corresponding matched mud circulation equipment is arranged in the lower joint (13), a plurality of through holes (102) used for passing through cables in a drilling tool are circumferentially distributed around the hollow channel (101) of the lower joint (13), a pair of second sliding key grooves (504) are symmetrically arranged at the top of the hollow channel (101) of the lower joint (13) and used for limiting the third ball head limit (11) of the third direction changing assembly, so that the third ball head limit (11) of the third direction changing assembly can only move on a moving plane of a sliding key (402), a second arc surface (503) is arranged at the top of the hollow channel (101) of the lower joint (13), and the second arc surface (503) of the lower joint (13) is in sliding fit with a ball structure (401) of a third driven direction changing ball head (12) of the third direction changing assembly, the lower part of the lower joint (13) is connected with other components of the drilling tool.

2. The servo direction changing mechanism of the downhole drilling tool as claimed in claim 1, wherein: the upper side and the lower side of the through hole (102) of the upper joint (1) are of annular fillet structures.

3. The servo direction changing mechanism of the downhole drilling tool as claimed in claim 1, wherein: the top of the hollow channel (101) of the first ball head limiting device (3) is of an annular round angle structure.

4. The servo direction changing mechanism of the downhole drilling tool as claimed in claim 1, wherein: and a third arc surface (403) is arranged at the bottom of the hollow channel (101) of the ball structure (401) of the first driven turning ball head (4).

5. The servo direction changing mechanism of the downhole drilling tool as claimed in claim 1, wherein: the lower part of the lower joint (13) is a thick-mouth end and is used for being connected with other components of the drilling tool.

6. The servo direction changing mechanism of the downhole drilling tool as claimed in claim 1, wherein: the sliding keys of the first direction changing assembly, the second direction changing assembly and the third direction changing assembly are annularly distributed at an angle of 120 degrees on a horizontal plane.

7. The servo direction changing mechanism of the downhole drilling tool as claimed in claim 1, wherein: the outer diameters of the upper joint (1), the first direction changing assembly, the first middle joint (5), the second direction changing assembly, the second middle joint (9), the third direction changing assembly and the lower joint (13) are the same.

8. The servo direction changing mechanism of the downhole drilling tool as claimed in claim 1, wherein: the inner diameters of the upper joint (1), the first direction changing assembly, the first middle joint (5), the second direction changing assembly, the second middle joint (9), the third direction changing assembly and the lower joint (13) are the same.

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