A main blade retractable adjustment type PDC drill bit

Abstract

The application provides a PDC drill bit with retractable adjustment of main blades, comprising a center cylinder, a drill bit body fixed at the lower end of the center cylinder, a reversing mechanism arranged in the center cylinder, the reversing mechanism comprising a center rod, a cam unit sleeved on the center rod, and an energy storage unit, the cam unit comprising an upper fixed cam and a lower fixed cam fixed with the center cylinder, and a middle deflection cam arranged between the upper fixed cam and the lower fixed cam and rotationally connected with the center rod, a movable main blade fixedly connected with the center rod through the drill bit body, wherein the reversing mechanism is configured to enable the movable main blade to have a first gear in a retracted state and a second gear in an extended state, the center rod is capable of driving the middle deflection cam to reciprocate along the axial direction under the action of the drilling fluid pressure and the energy storage unit, and the center rod is capable of positioning the middle deflection cam at different axial positions under the action of the upper fixed cam and the lower fixed cam, so that the movable main blade can be switched between the first gear and the second gear.

Description

Technical Field

[0001] This invention belongs to the field of drilling tool technology, specifically relating to a PDC drill bit with retractable and adjustable main blades. Background Technology

[0002] Drill bits are rock-breaking tools used in drilling operations to break up the rock at the bottom of a well and form the wellbore. Currently, the conventional drill bits used in drilling operations mainly include tricone drill bits, PDC drill bits, impregnated diamond drill bits, and tricone-PDC hybrid drill bits. PDC drill bits (polycrystalline diamond composite drill bits) are currently the most commonly used drilling tool in oil drilling operations.

[0003] Conventional PDC drill bits primarily break down bottom-hole rocks through a "cutting-scraping" action. However, when drilling encounters hard plastic formations, the cutting teeth on PDC drill bits often struggle to effectively penetrate the bottom-hole rock, resulting in a very slow mechanical drilling rate and hindering optimal drill bit performance. This is especially true for complex formations at depth, characterized by high rock hardness, abrasiveness, strong anisotropy, and significant differences in formation hardness indices. Therefore, proper drill bit selection has a substantial impact on drilling quality, drilling speed, and drilling costs. Overall, drill bit costs constitute a significant portion of drilling costs; thus, extending drill bit life and improving drill bit efficiency are crucial in drilling engineering. Current PDC drill bit depth control methods passively adapt to the formation, without altering the overall drill bit structure, and lack the technical means for active surface-based control of PDC drill bit performance. The drill bit's attack performance is unreliable, and its downhole working life is short. It is also poorly suited for long open-hole formations and formations with alternating soft and hard surfaces, which leads to frequent tripping and bit replacements, severely impacting drilling efficiency.

[0004] Therefore, there is an urgent need to provide a PDC drill bit with retractable and adjustable main blades that can actively control the attack performance of the PDC drill bit and significantly improve its service life downhole. Summary of the Invention

[0005] To address the technical problems described above, this invention aims to provide a PDC drill bit with retractable and adjustable main blades. This PDC drill bit can actively control the attack performance of the PDC drill bit and significantly improve its service life downhole, which is very beneficial for improving drilling efficiency.

[0006] To address this, the present invention provides a PDC drill bit with retractable and adjustable main blade, comprising: a center cylinder; a drill body fixedly connected to the lower end of the center cylinder; a reversing mechanism disposed inside the center cylinder, comprising a center rod, a cam unit sleeved on the center rod, and an energy storage unit, the cam unit comprising an upper fixed cam and a lower fixed cam axially spaced apart and fixed to the center cylinder, and a middle deflection cam disposed between the upper fixed cam and the lower fixed cam and rotatably connected to the center rod; and a movable main blade passing through the drill body and fixedly connected to the center rod; wherein the reversing mechanism is configured to enable the movable main blade to have a first position in a retracted state and a second position in an extended state, the center rod being able to drive the middle deflection cam to reciprocate axially under the action of drilling fluid pressure and the energy storage unit, and being able to position the middle deflection cam at different axial positions under the action of the upper fixed cam and the lower fixed cam, thereby enabling the movable main blade to switch between the first position and the second position.

[0007] In one embodiment, the lower end face of the upper fixed cam is configured with alternating first and second positioning grooves, the upper and lower ends of the middle deflection cam are respectively provided with positioning teeth and reversing teeth, and the upper end of the lower fixed cam is provided with a toothed deflection groove.

[0008] The deflection cam can rotate under the meshing action of the reversing tooth and the toothed deflection groove, so that the positioning tooth can alternately mesh with the first positioning groove and the second positioning groove, thereby placing the movable main blade in the first gear and the second gear respectively.

[0009] In one embodiment, the depth of the first positioning groove is greater than the depth of the second positioning groove, and the tooth height of the positioning tooth is greater than the depth of the first positioning groove.

[0010] In one embodiment, a support plate is fixed on the central rod, and a bearing is provided between the central deflection cam and the support plate, thereby forming a rotatable connection between the central deflection cam and the central rod.

[0011] In one embodiment, the upper fixed cam and the lower fixed cam are respectively fixedly connected to the central cylinder via positioning elements.

[0012] In one embodiment, the movable main cutter wing is provided in multiple ways, and each movable main cutter wing is respectively disposed between adjacent fixed secondary cutter wings on the drill bit body.

[0013] In one embodiment, the movable main blade and the central rod are integrally constructed, and the movable main blade includes a connecting part connected to the central rod and rock-breaking teeth for rock breaking.

[0014] In one embodiment, the drill bit body is provided with a support block, which is used to support the movable main blade to transmit rock-breaking torque.

[0015] In one embodiment, the energy storage unit includes an elastic element sleeved on the central rod and a limiting baffle fixed to the upper end of the drill bit body, with the two ends of the elastic element abutting against the support plate and the limiting baffle, respectively.

[0016] In one embodiment, both the support plate and the limiting baffle are provided with flow holes for the flow of drilling fluid.

[0017] In one embodiment, the upper end of the central rod is provided with a valve head, which can drive the central rod to move the movable main blade downward under the action of drilling fluid pressure, and can display the current status of the movable main blade through pressure feedback.

[0018] Compared with the prior art, the advantages of this application are:

[0019] The adjustable main blade PDC drill bit of the present invention can effectively change the attack performance of the drill bit and significantly improve its service life downhole. It has good applicability to long open-hole formations and formations with alternating soft and hard surfaces, greatly saving the time required for frequent tripping and bit changing. The reversing mechanism adopts a push-type self-locking cam mechanism, including an upper fixed cam, a middle deflection cam, and a lower fixed cam. The three cams significantly enhance its pressure and impact resistance. Multiple movable main blades are integrated to achieve synchronous up and down movement, and its installation is simple, greatly changing the attack performance of the adjustable main blade PDC drill bit. In addition, the drill pressure torque transmission method of this adjustable main blade PDC drill bit is reasonable and reliable, the push-type self-locking cam mechanism is safe and reliable with strong load-bearing capacity, and the movable main blade telescopic assembly structure is simple and reasonable, which can further improve the attack performance of the adjustable main blade PDC drill bit. Attached Figure Description

[0020] The invention will now be described with reference to the accompanying drawings.

[0021] Figure 1 The structure of the PDC drill bit with retractable and adjustable main blades according to the present invention is shown schematically.

[0022] Figure 2 The structure of the upper fixed cam is shown schematically.

[0023] Figure 3 The structure of the deflection cam is schematically shown.

[0024] Figure 4 The structure of the lower fixed cam is schematically shown.

[0025] Figure 5 The structure of the active main blade is schematically shown.

[0026] Figure 6 The diagram schematically illustrates the distribution of the active main blades on the drill bit body.

[0027] Figure 7 The diagram schematically shows the state of the PDC drill bit with retractable and adjustable main blade according to the present invention in the second position.

[0028] Figures 8a-8d The diagram illustrates the movement of the deflection cam during gear shifting.

[0029] Figure 9 The diagram schematically shows the state of the PDC drill bit with retractable and adjustable main blade according to the present invention in the first position.

[0030] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0031] The invention will now be described with reference to the accompanying drawings.

[0032] For ease of understanding, in this application, the end closest to the wellhead is defined as the upper end, upstream end, or similar terms, for example... Figure 1 The left end is defined as the end furthest from the wellhead, while the end furthest from the wellhead is defined as the lower end, downstream end, or similar terms, for example... Figure 1 The right end of the drill bit. Meanwhile, the direction along the length of the main blade telescopic adjustable PDC drill bit is referred to as the longitudinal direction, axial direction, or similar terminology, while the direction perpendicular to it is referred to as the transverse direction, radial direction, or similar terminology.

[0033] Figure 1 The structure of the retractable and adjustable main blade PDC drill bit 100 according to the present invention is schematically shown. For example... Figure 1As shown, the telescopically adjustable PDC drill bit 100 includes a central cylinder 1, a drill body 2, a reversing mechanism, and a movable main blade 7. The drill body 2 is fixedly connected to the lower end of the central cylinder 1. The reversing mechanism is arranged inside the central cylinder 1 and includes a central rod 4, a cam unit 5 sleeved on the central rod 4, and an energy storage unit 6. The cam unit 5 includes an upper fixed cam 51 and a lower fixed cam 53 axially spaced apart, and a middle deflection cam 52 disposed between the upper fixed cam 51 and the lower fixed cam 53 axially. The upper fixed cam 51 and the lower fixed cam 53 are both fixedly connected to the central cylinder 1, while the middle deflection cam 52 is rotatably connected to the central rod 4 and has no connection to the central cylinder 1. Thus, the middle deflection cam 52 can rotate circumferentially relative to the upper fixed cam 51 and the lower fixed cam 53. The energy storage unit 6 is arranged between the middle deflection cam 52 and the drill body 2. The movable main blade 7 passes through the drill body 2 and is fixedly connected to the central rod 4. The reversing mechanism is configured to allow the movable main blade 7 to have a first position in the retracted state and a second position in the extended state. The center rod 4, under the action of drilling fluid pressure and the energy storage unit 6, drives the central deflection cam 52 to reciprocate axially, and under the action of the upper fixed cam 51 and the lower fixed cam 53, positions the central deflection cam 52 at different axial positions, thus allowing the movable main blade 7 to switch between the first and second positions. This enables the adjustable PDC drill bit 100 with retractable main blades to have different working positions, effectively changing its attack performance and downhole service life. It has good applicability to long open-hole formations and formations with alternating soft and hard surfaces, greatly saving time spent on frequent tripping and bit changing, and significantly improving drilling efficiency.

[0034] like Figure 1 As shown, the upper end of the central cylinder 1 is fixedly connected to an upper connector 12 by a thread, and the upper connector 12 is used to connect the upper drill rod. Preferably, the upper connector 12 can be configured as a tapered threaded connection.

[0035] For example Figure 1 As shown, a valve head 41 is provided at the upper end of the central rod 4, and the valve head 41 is constructed in a mushroom shape. Preferably, the valve head 41 and the central rod 4 are constructed as one piece. At the same time, the connection between the upper connector 12 and the central cylinder 1 is constructed such that the inner diameter increases from top to bottom, thereby forming a funnel-shaped channel. The mushroom-shaped structure of the valve head 41 can be adapted to the funnel-shaped channel, and the drilling fluid from the upper drill string can act on the valve head 41 through the funnel-shaped channel. Thus, the valve head 41 can drive the central rod 4 to move the movable main blade 7 downward under the action of drilling fluid pressure, and can display the current status of the movable main blade 7 through pressure feedback.

[0036] like Figure 2As shown, the upper fixed cam 51 is cylindrical in shape. The upper end of the upper fixed cam 51 is flat, and the lower end face of the upper fixed cam 51 is constructed with a first positioning groove 511 and a second positioning groove 512 that are alternately distributed along the circumference. Both the first positioning groove 511 and the second positioning groove 512 are constructed to include an inclined section and a straight section. The axial depth of the first positioning groove 511 is greater than the axial depth of the second positioning groove 512. The functions of the first positioning groove 511 and the second positioning groove 512 will be described below.

[0037] like Figure 3 As shown, the deflection cam 52 is cylindrical in shape, with positioning teeth 521 and reversing teeth 522 at its upper and lower ends, respectively. The positioning teeth 521 are constructed with an inclined section and a straight section, and can mesh with the first positioning groove 511 and the second positioning groove 512 of the upper fixed cam 51, respectively. The tooth height of the positioning teeth 521 is greater than the depth of the first positioning groove 511. Specifically, when the positioning teeth 521 at the upper end of the deflection cam 52 mesh with the first positioning groove 511 of the upper fixed cam 51, the movable main blade 7 retracts and is in the first position. When the positioning teeth 521 at the upper end of the deflection cam 52 mesh with the second positioning groove 512 of the upper fixed cam 51, the movable main blade 7 extends and is in the second position. The function of the reversing teeth 522 will be described below.

[0038] In an embodiment not shown, a support plate is fixed to the central rod 4, and a bearing is provided between the central deflection cam 52 and the support plate, thereby forming a rotatable connection between the central deflection cam 52 and the central rod 4. The bearing is preferably a thrust bearing. The inner wall surface of the central deflection cam 52 has a step with its end face facing downwards, and the bearing is installed between the step and the support plate. This achieves a rotatable connection between the central deflection cam 52 and the central rod 4.

[0039] like Figure 4 As shown, the upper end of the lower fixed cam 53 is provided with a toothed deflection groove 531. The toothed deflection groove 531 can mesh with the reversing tooth 522 at the lower end of the middle deflection cam 52, causing the middle deflection cam 52 to deflect, that is, to rotate circumferentially. Specifically, during the axial reciprocating motion of the middle deflection cam 52 with the central rod 4, the middle deflection cam 52 can rotate under the meshing action of the reversing tooth 522 and the toothed deflection groove 531, so that the positioning tooth 521 can alternately mesh with the first positioning groove 511 and the second positioning groove 512, thereby placing the movable main blade 7 in the first gear and the second gear respectively. Thus, the gear shifting of the main blade telescopic adjustable PDC drill bit 100 is realized.

[0040] In one embodiment, the upper fixed cam 51 and the lower fixed cam 53 are fixedly connected to the central cylinder 1 via positioning members. The positioning member can be, for example, a positioning pin. Pin holes are provided at corresponding positions on the upper fixed cam 51, the lower fixed cam 53, and the central cylinder 1 for installing positioning pins. Of course, to improve the strength of the positioning member, a positioning block can also be used.

[0041] like Figure 1 As shown, the energy storage unit 6 includes an elastic element 61 sleeved on the central rod 4 and a limiting baffle 62 fixed to the upper end of the drill bit body 2. The two ends of the elastic element 61 abut against the support plate and the limiting baffle 62, respectively. The elastic element 61 can be, for example, an elastic element such as a spring or disc spring, used to match the drill bit shifting trigger threshold with the throttling pressure and drilling pressure.

[0042] Both the support plate and the limiting baffle 62 are provided with flow holes (not shown) for the flow of drilling fluid.

[0043] According to the present invention, such as Figure 5 As shown, the movable main blade 7 includes a connecting part 71 connected to the central rod 4 and rock-breaking teeth 72 for rock breaking. Preferably, the movable main blade 7 and the central rod 4 can be constructed as one piece.

[0044] like Figure 6 As shown, the drill bit body 2 is provided with multiple fixed auxiliary cutter wings 21, which are evenly spaced apart in the circumferential direction. Multiple movable main cutter wings 7 can be provided, each positioned between adjacent fixed auxiliary cutter wings 21 on the drill bit body 2, and these movable main cutter wings 7 are evenly distributed in the circumferential direction to prevent uneven force distribution on the drill bit. Figure 6 In the illustrated embodiment, there are three fixed secondary cutter wings 21 and three movable main cutter wings 7. In the first position, the three movable main cutter wings 7 are retracted, and the three fixed secondary cutter wings 21 serve as working cutter wings, thus forming a three-wing drill bit 100 with retractable and adjustable main cutter wings. In the second position, the three movable main cutter wings 7 are extended, working together with the three fixed secondary cutter wings 21 as working cutter wings, thus forming a six-wing drill bit 100 with retractable and adjustable main cutter wings. The change in the attitude of the movable main cutter wings 7 changes the depth of the main cutter wing retractable and adjustable PDC drill bit 100 into the formation, thereby changing the rock-breaking performance of the drill bit.

[0045] According to one embodiment of the present invention, such as Figure 6 As shown, a support block 22 is provided on the drill bit body 2. The support block 22 is located behind the movable main blade 7. The support block 22 can support the movable main blade 7 to transmit rock-breaking torque.

[0046] Since the movable main blade 7 requires a long extension and retraction distance to shift gears, the main blade telescopic adjustable PDC drill bit 100 is in a stable rock-breaking state during drilling, and the blades will not move or the gears will deflect.

[0047] The following describes in detail the gear shifting process of the PDC drill bit 100 with telescopic adjustable main blade according to the present invention, taking the shift from the second gear to the first gear as an example.

[0048] like Figure 7 As shown, the positioning tooth 521 at the upper end of the middle deflection cam 5 engages with the second positioning groove 512 of the upper fixed cam 51, causing the movable main blade 7 to be in the extended state (i.e., the second position). At this time, the middle deflection cam 52 is under pressure due to the action of the elastic element 61 and will not easily disengage. The movable main blade 7, the middle deflection cam 52, and both ends of the valve head 41 are in a restricted state of movement. The movable main blade 7 no longer moves and is in a single stable rock-breaking state. The movable main blade 7 and the fixed secondary blade 21 break rocks together, which can significantly change the rock-breaking performance of the main blade telescopic adjustable PDC drill bit 100.

[0049] When shifting gears is required, the telescopic adjustable PDC drill bit 100 is lifted off the bottom of the well and the pump is started. Under the hydraulic pressure of the drilling fluid, the valve head 41 pushes the center rod 4, which in turn drives the central deflection cam 52 and the movable main blade 7 downwards. At this time, the elastic element 61 is compressed and stores energy. The elastic stiffness and compression amount of the elastic element 61 need to be matched with the hydraulic thrust to ensure that the central deflection cam 52 can descend and spring back to its original position.

[0050] like Figures 8a to 8b As shown, during the downward movement of the central deflection cam 52, the positioning tooth 521 at the upper end of the central deflection cam 52 disengages from the second positioning groove 512 of the upper fixed cam 51, and moves downward until the reversing tooth 522 at the lower end of the central deflection cam 52 engages with the toothed deflection groove 531 at the upper end of the lower fixed cam 53. During the engagement of the reversing tooth 522 and the toothed deflection groove 531, the reversing tooth 522 and the toothed deflection groove 531 interact, causing the central deflection cam 5 to deflect in the circumferential direction and rotate by a certain angle. Since there is a thrust bearing between the central deflection cam 52 and the central rod 4, the movable main blade 7 does not bear the deflection force. At this time, the positioning tooth 521 of the central deflection cam 52 and the second positioning groove 512 of the upper fixed cam 51 have deflected by a certain angle in the circumferential direction.

[0051] Subsequently, the driller lowers the retractable and adjustable PDC drill bit 100 to contact the bottom of the well. The movable main cutter wing 7 first contacts the bottom of the well, and under the support of the formation, the movable main cutter wing 7 and the reversing mechanism move upward together. For example... Figure 8cAs shown, since the middle deflection cam 52 has already deflected and misaligned, the middle deflection cam 52 moves upward until the positioning tooth 521 contacts the first positioning groove 511 of the upper fixed cam 51, that is, the inclined section of the positioning tooth 521 contacts the inclined section of the first positioning groove 511. Furthermore, as... Figure 8d As shown, under the interaction of the inclined section of the positioning tooth 521 and the inclined section of the first positioning groove 511, the positioning tooth 521 of the middle deflection cam 52 slides into the first positioning groove 511 of the upper fixed cam 51 along the inclined section of the first positioning groove 511.

[0052] The driller lowers the retractable PDC drill bit 100 to its final position on the surface, ensuring it is in full contact with the bottom of the well and can withstand significant drilling pressure. For example... Figure 9 As shown, at this time, the positioning teeth 521 of the central deflection cam 52 completely slide into the first positioning groove 511 of the upper fixed cam 51, causing the movable main blade 7 to be in a retracted state (i.e., the first gear). This achieves the switch from the second gear to the first gear. In this first gear, the central deflection cam 52 is under pressure due to the elastic element 61 and will not easily disengage. The penetration depth of the multiple movable main blades 7 is significantly less than the penetration depth of the fixed secondary blade 21. At this time, the main blade telescopic adjustable PDC drill bit 100 has a stronger attack capability and is suitable for working conditions with high mechanical drilling speeds, such as soft bottom layers.

[0053] The above process guides the PDC drill bit 100 with retractable and adjustable main blades to complete a gear shift. In actual operation, the specific blade position can be determined based on pump pressure feedback, allowing for a decision on whether to perform another gear shift adjustment. Specifically, technicians collect and analyze well logging geological data on the surface, assessing changes in drilling time and torque, as well as the occurrence of frequent drill skips, to determine if the formation's drillability has significantly changed and whether the drill bit's attack performance needs to be altered. Furthermore, the current gear position of the PDC drill bit 100 with retractable and adjustable main blades can be fed back based on changes in stand pressure. The PDC drill bit 100 with retractable and adjustable main blades can achieve an unlimited number of gear shifts, allowing for multiple changes in the number of blades involved in rock breaking.

[0054] The adjustable PDC drill bit 100 with retractable main blades according to the present invention can effectively change the attack performance of the drill bit and significantly improve its service life downhole. It has good applicability to long open-hole formations and formations with alternating soft and hard surfaces, greatly saving the time required for frequent tripping and bit changing. The reversing mechanism adopts a push-type self-locking cam mechanism, including an upper fixed cam 51, a middle deflection cam 52, and a lower fixed cam 53. The three cams significantly enhance its pressure and impact resistance. Multiple movable main blades 7 are integrated and move up and down synchronously. Moreover, its installation is simple, which greatly changes the attack performance of the adjustable PDC drill bit 100 with retractable main blades. In addition, the drill pressure torque transmission method of the adjustable PDC drill bit 100 with retractable main blades is reasonable and reliable. The push-type self-locking cam mechanism is safe and reliable with strong load-bearing capacity. The retractable assembly structure of the movable main blades 7 is simple and reasonable, which can further improve the attack performance of the adjustable PDC drill bit 100 with retractable main blades.

[0055] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0056] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0057] Furthermore, in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A PDC drill bit with retractable and adjustable main blade, comprising: Central tube (1); The drill bit body (2) is fixedly connected to the lower end of the central cylinder; Multiple fixed auxiliary cutter wings (21) are provided on the drill bit body (2); The reversing mechanism arranged inside the central cylinder (1) includes a central rod (4), a cam unit (5) sleeved on the central rod (4), and an energy storage unit (6). The cam unit (5) includes an upper fixed cam (51) and a lower fixed cam (53) axially spaced apart and fixed to the central cylinder (1), and a middle deflection cam (52) disposed between the upper fixed cam (51) and the lower fixed cam (53) and rotatably connected to the central rod (4). The movable main blade (7) passes through the drill bit body (2) and is fixedly connected to the central rod (4). The drill bit body (2) is provided with a support block (22), which is used to support the movable main blade (7) to transmit rock-breaking torque. The reversing mechanism is configured to allow the movable main blade (7) to have a first position in a retracted state and a second position in an extended state. The central rod (4) can drive the central deflection cam (52) to reciprocate axially under the action of drilling fluid pressure and the energy storage unit (6), and can position the central deflection cam (52) at different axial positions under the action of the upper fixed cam (51) and the lower fixed cam (53), so that the movable main blade (7) can switch between the first gear and the second gear. In the first gear position, the movable main blade retracts axially, and the fixed secondary blade acts as the working blade. In the second gear position, the movable main blade extends axially, and the movable main blade and the fixed secondary blade together serve as working blades.

2. The PDC drill bit with retractable and adjustable main blade as described in claim 1, characterized in that, The lower end face of the upper fixed cam (51) is configured with alternating first positioning grooves (511) and second positioning grooves (512). The upper and lower ends of the middle deflection cam (52) are respectively provided with positioning teeth (521) and reversing teeth (522). The upper end of the lower fixed cam (53) is provided with a toothed deflection groove (531). The deflection cam (52) can rotate under the meshing action of the reversing tooth (522) and the toothed deflection groove (531), so that the positioning tooth (521) can alternately mesh with the first positioning groove (511) and the second positioning groove (512), thereby so that the movable main blade (7) is in the first gear and the second gear respectively.

3. The PDC drill bit with retractable and adjustable main blade as described in claim 2, characterized in that, The depth of the first positioning groove (511) is greater than the depth of the second positioning groove (512), and the tooth height of the positioning tooth is greater than the depth of the first positioning groove (511).

4. The PDC drill bit with retractable and adjustable main blade according to any one of claims 1 to 3, characterized in that, A support plate is fixed on the central rod (4), and a bearing is provided between the central deflection cam (52) and the support plate, so that the central deflection cam (52) and the central rod (4) are rotatably connected.

5. The PDC drill bit with retractable and adjustable main blade as described in claim 1 or 2, characterized in that, The upper fixed cam (51) and the lower fixed cam (53) are respectively fixedly connected to the central cylinder (1) through positioning members.

6. The PDC drill bit with retractable and adjustable main blade as described in claim 1, characterized in that, The movable main blade (7) is provided in multiple ways, and each movable main blade (7) is respectively arranged between adjacent fixed secondary blades (21) on the drill bit body (2).

7. The PDC drill bit with retractable and adjustable main blade as described in claim 1 or 6, characterized in that, The movable main blade (7) and the central rod (4) are constructed as one unit. The movable main blade (7) includes a connecting part (71) connected to the central rod (4) and rock-breaking teeth (72) for breaking rocks.

8. The PDC drill bit with retractable and adjustable main blade as described in claim 4, characterized in that, The energy storage unit (6) includes an elastic element (61) sleeved on the central rod (4) and a limiting baffle (62) fixed on the upper end of the drill bit body (2). The two ends of the elastic element (61) abut against the support plate and the limiting baffle (62) respectively.

9. The PDC drill bit with retractable and adjustable main blade as described in claim 8, characterized in that, Both the support plate and the limiting baffle (62) are provided with flow holes for drilling fluid to flow through.

10. The PDC drill bit with retractable and adjustable main blade as described in claim 1, characterized in that, The upper end of the central rod (4) is provided with a valve head (41). The valve head (41) can drive the central rod (4) to move the movable main blade (7) downward under the action of drilling fluid pressure, and can display the current status of the movable main blade (7) through pressure feedback.

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