Multi-stage speed regulation drilling hydraulic system, drilling rig and control method

Abstract

This invention discloses a multi-stage speed-regulating drilling hydraulic system, comprising a hydraulic pump, a multi-way valve, a series-parallel control valve group, a first hydraulic motor, a second hydraulic motor, and a rotary power head. The hydraulic pump is connected to the series-parallel control valve group via the multi-way valve. The series-parallel control valve group is connected to the first and second hydraulic motors to drive them to rotate and can adjust the series-parallel connection status of the first and second hydraulic motors. The output shafts of the first and second hydraulic motors are connected to the input end of the rotary power head. The output end of the rotary power head is connected to the drill rod to drive it to rotate and can be speed-regulated in multiple stages. The system features fast control response, high precision, and no energy loss during speed regulation. Based on the characteristics of the rock strata, the drilling rig can adaptively adjust the rotational speed of the rotary power head's output shaft, improving drilling efficiency and reducing overall operating costs. This invention also discloses a drilling rig and control method incorporating the above-mentioned multi-stage speed-regulating drilling hydraulic system.

Description

Technical Field

[0001] This invention relates to the field of drilling, and in particular to a multi-stage speed-regulating drilling hydraulic system and drilling rig. Furthermore, this invention also relates to a control method using the aforementioned multi-stage speed-regulating drilling hydraulic system. Background Technology

[0002] In various engineering applications such as mining, foundation excavation, water conservancy, power plants, building materials, transportation, and construction, down-the-hole drills are required to perform drilling operations at multiple angles, including vertical, inclined, and horizontal. After drilling, explosives are used to blast the drilled area, and then related engineering machinery is used for loading, transportation, and other processes to remove waste rock and minerals.

[0003] Drilling is a crucial step in the aforementioned engineering construction process. The efficiency, fuel consumption, and drill bit wear during this operation are closely related to rock characteristics and the setting and adjustment of drilling process technical parameters. Depending on the ore type and rock development, the drill bit rotation speed usually needs to be adjusted by the operator based on their experience. When the rock is particularly hard, the rotation speed should be set very slowly to ensure the crushing effect of the impactor. When the rock hardness is moderate, the rotation speed can be set relatively fast depending on the operating frequency of the selected impactor. In soft rock applications, a faster rotation speed can improve drilling efficiency. In coal mines or where the overburden layer is very soft, a high rotation speed can significantly improve drilling efficiency and reduce overall operating costs.

[0004] In mining of the same type of mineral, the characteristics and hardness of the rock generally vary with depth and location. A fixed rotation speed is obviously not the optimal operating procedure.

[0005] Therefore, there is an urgent need for a multi-stage speed-regulating drilling hydraulic system that can meet a wider speed range when the power head rotates. The down-the-hole drill can adaptively adjust the rotation speed according to the hardness of the rock, meeting the requirements of high-speed rotation for soft rock, appropriate speed rotation for medium hard rock, and low-speed rotation for hard rock or even ultra-hard rock, thereby improving the efficiency of drilling operations and reducing the overall operating cost. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-stage speed-regulating drilling hydraulic system and drilling rig that meets the requirements of multi-stage speed regulation, can adaptively adjust the rotation speed according to the hardness of the rock, improve the efficiency of drilling operations, and reduce the overall operating cost. Another purpose of this invention is to provide a control method for applying the above-mentioned multi-stage speed-regulating drilling hydraulic system.

[0007] To address the aforementioned technical problems, this invention provides a multi-stage speed-regulating drilling hydraulic system, comprising a hydraulic pump, a multi-way valve, a series-parallel control valve group, a first hydraulic motor, a second hydraulic motor, and a rotary power head. The hydraulic pump is connected to the series-parallel control valve group via the multi-way valve. The series-parallel control valve group connects the first hydraulic motor and the second hydraulic motor to drive the two hydraulic motors to rotate and can adjust the series-parallel connection state of the first hydraulic motor and the second hydraulic motor. The output shafts of the first hydraulic motor and the second hydraulic motor are connected to the input end of the rotary power head. The output end of the rotary power head is connected to the drill rod to drive the drill rod to rotate and can be speed-regulated in multiple stages.

[0008] Preferably, the series-parallel control valve group includes a first logic valve, a second logic valve, and a third logic valve. The first interface of the first logic valve is connected to the first interface of the multi-way valve and a first interface of the first hydraulic motor. The second interface of the first logic valve is connected to the first interface of the second logic valve and the first interface of the second hydraulic motor. The second interface of the second logic valve is connected to the second interface of the first hydraulic motor and the second interface of the third logic valve. The first interface of the third logic valve is connected to the second interface of the second hydraulic motor and the second interface of the multi-way valve.

[0009] Preferably, the series-parallel control valve group includes a first switching valve, a second switching valve, and a third switching valve. The inlets of the first switching valve, the second switching valve, and the third switching valve are all connected to the pressure oil port of the multi-way valve. The first switching valve, the second switching valve, and the third switching valve are respectively connected to the spring chambers of the first logic valve, the second logic valve, and the third logic valve.

[0010] Preferably, the series-parallel control valve group includes a fourth switching valve, the inlet of which is connected to the pressure oil port of the multi-way valve, and the outlet of which is connected to the speed control cylinder of the rotary power head.

[0011] Preferably, the first switching valve, the second switching valve, the third switching valve, and the fourth switching valve are specifically electromagnetic switching valves.

[0012] Preferably, the hydraulic pump is a load-sensitive hydraulic pump, the multi-way valve is a load-sensitive multi-way valve, the multi-way valve is a proportional regulating valve, and is equipped with a forward proportional electromagnet and a reverse proportional electromagnet.

[0013] Preferably, the rotary power head includes a main shaft and two drive shafts. The main shaft is connected to the drill rod, and the two drive shafts are respectively connected to the first hydraulic motor and the second hydraulic motor. Matching multi-stage speed-regulating gears are provided on the main shaft and the drive shafts.

[0014] Preferably, it includes a speed sensor and a pressure sensor, and the controller controls the series-parallel connection status and the gear position of the rotating power head based on the detection results.

[0015] The present invention provides a drilling rig, including a multi-stage speed-regulating drilling hydraulic system as described in any one of the above claims.

[0016] This invention provides a control method for a multi-stage speed-regulating drilling hydraulic system, using the multi-stage speed-regulating drilling hydraulic system as described in any one of the above claims, comprising the following steps:

[0017] Obtain the output speed of the rotary power head and the output pressure of the multi-way valve;

[0018] Compare the output speed with the preset speed;

[0019] If the output speed is less than the first preset speed, then the output pressure is compared with the preset pressure. If the output pressure is greater than or equal to the preset pressure, then the two hydraulic motors are connected in parallel and the rotating power head is in low speed. If the output pressure is less than the preset pressure, then the two hydraulic motors are connected in parallel and the rotating power head is in high speed.

[0020] If the output speed is less than the second preset speed, then the output pressure is compared with the preset pressure. If the output pressure is greater than or equal to the preset pressure, then the two hydraulic motors are connected in parallel and the rotating power head is in high speed mode. If the output pressure is less than the preset pressure, then the two hydraulic motors are connected in series and the rotating power head is in low speed mode.

[0021] If the output speed is less than the third preset speed, then the output pressure is compared with the preset pressure. If the output pressure is greater than or equal to the preset pressure, then the two hydraulic motors are connected in series and the rotating power head is in low speed mode. If the output pressure is less than the preset pressure, then the two hydraulic motors are connected in series and the rotating power head is in high speed mode.

[0022] If the output speed is greater than or equal to the third preset speed, then the two hydraulic motors are connected in series, the rotating power head is in high speed mode, the first preset speed is less than the second preset speed, and the second preset speed is less than the third preset speed.

[0023] This invention provides a multi-stage speed-regulating drilling hydraulic system, including a hydraulic pump, a multi-way valve, a series-parallel control valve group, a first hydraulic motor, a second hydraulic motor, and a rotary power head. The hydraulic pump is connected to the series-parallel control valve group through the multi-way valve. The series-parallel control valve group is connected to the first and second hydraulic motors to drive the two hydraulic motors to rotate and can adjust the series-parallel state of the first and second hydraulic motors. The output shafts of the first and second hydraulic motors are connected to the input end of the rotary power head. The output end of the rotary power head is connected to the drill rod to drive the drill rod to rotate and can be speed-regulated in multiple stages.

[0024] By enabling series and parallel control of hydraulic motors and high and low speed control of multi-stage reducers, the speed range of the rotary power head output speed is widened, the control response is fast and the precision is high, and there is no energy loss in speed regulation. According to the characteristics of the rock strata, the drilling rig can adaptively adjust the rotation speed of the rotary power head output shaft and meet the functional requirements of stepless speed regulation, thereby improving the efficiency of drilling operations and reducing the overall operating cost.

[0025] The present invention also provides a drilling rig including the above-mentioned multi-stage speed-regulating drilling hydraulic system and a control method using the above-mentioned multi-stage speed-regulating drilling hydraulic system. Since the above-mentioned multi-stage speed-regulating drilling hydraulic system has the above-mentioned technical effects, the above-mentioned drilling rig and control method should also have the same technical effects, and will not be described in detail here. Attached Figure Description

[0026] Figure 1 A hydraulic schematic diagram of a specific embodiment of the multi-stage speed-regulating drilling hydraulic system provided by the present invention;

[0027] Figure 2 A hydraulic schematic diagram of a series-parallel control valve group in a specific embodiment of the multi-stage speed-regulating drilling hydraulic system provided by the present invention;

[0028] Figure 3 This is a schematic diagram of the high-speed gear of the rotary power head in a specific embodiment of the multi-stage speed-regulating drilling hydraulic system provided by the present invention.

[0029] Figure 4 This is a schematic diagram of the low-speed gear of the rotary power head in a specific embodiment of the multi-stage speed-regulating drilling hydraulic system provided by the present invention.

[0030] Figure 5 This is a flowchart illustrating a specific embodiment of the control method for the multi-stage speed-regulating drilling hydraulic system provided by the present invention.

[0031] The system includes a hydraulic pump 1, a multi-way valve 2, a series-parallel control valve group 3, a first logic valve 311, a second logic valve 312, a third logic valve 313, a first switching valve 321, a second switching valve 322, a third switching valve 323, a fourth switching valve 324, a first hydraulic motor 4, a second hydraulic motor 5, a rotary power head 6, a spindle 61, a drive shaft 62, a drill pipe 7, a pressure sensor S1, and a speed sensor S2. Detailed Implementation

[0032] The core of this invention is to provide a multi-stage speed-regulating drilling hydraulic system and drilling rig, which satisfies multi-stage speed regulation and can adaptively adjust the rotation speed according to the hardness of the rock, thereby improving the efficiency of drilling operations and reducing overall operating costs. Another objective of this invention is to provide a control method for applying the above-mentioned multi-stage speed-regulating drilling hydraulic system.

[0033] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Please refer to Figure 1 , Figure 1 This is a hydraulic schematic diagram of a specific embodiment of the multi-stage speed-regulating drilling hydraulic system provided by the present invention.

[0035] This invention provides a multi-stage speed-regulating drilling hydraulic system, including a hydraulic pump 1, a multi-way valve 2, a series-parallel control valve group 3, a first hydraulic motor 4, a second hydraulic motor 5, and a rotary power head 6. The hydraulic pump 1 is connected to the series-parallel control valve group 3 through the multi-way valve 2. The series-parallel control valve group 3 is connected to the first hydraulic motor 4 and the second hydraulic motor 5 to drive the two hydraulic motors to rotate and can adjust the series-parallel state of the first hydraulic motor 4 and the second hydraulic motor 5. The output shafts of the first hydraulic motor 4 and the second hydraulic motor 5 are connected to the input end of the rotary power head 6. The output end of the rotary power head 6 is connected to the drill rod 7 to drive the drill rod 7 to rotate and can be speed-regulated in multiple stages.

[0036] During operation, pump 1 delivers hydraulic pressure to multi-way valve 2, which then delivers it to series-parallel control valve group 3. Series-parallel control valve group 3 delivers the pressure to the first hydraulic motor 4 and the second hydraulic motor 5, driving both motors to rotate. The series-parallel control valve group 3 can also switch the series-parallel connection status of the two hydraulic motors. The output shafts of the first hydraulic motor 4 and the second hydraulic motor 5 are connected to the input end of the rotary power head 6, and the output end of the rotary power head 6 is connected to the drill rod 7. The rotation of the first hydraulic motor 4 and the second hydraulic motor 5 drives the drill rod 7 to rotate, and the rotary power head 6 can be speed-adjusted in multiple stages.

[0037] Two hydraulic motors are installed on the rotary power head 6. Through a series-parallel control valve group 3, the two hydraulic motors can be controlled in series and in parallel. In series, the hydraulic motors operate at higher speeds, while in parallel, they operate at lower speeds. Simultaneously, the rotary power head 6 incorporates multiple reduction ratios, facilitating the external force to drive the gear set on the spindle and enabling the rotary power head 6 to output various speeds. Controlling the series and parallel connection of the hydraulic motors also controls the output speed of the rotary power head. By combining these configurations, the drill bit can achieve more levels of rotational speed, and each level of rotational speed can be infinitely variable through electro-hydraulic control. This results in a wider speed range for the rotary power head output speed, faster control response, higher precision, and no energy loss during speed regulation. Based on the characteristics of the rock strata, the drilling rig can adaptively adjust the output shaft of the rotary power head, i.e., the rotational speed of the drill bit, while meeting the requirements of infinitely variable speed regulation, improving drilling efficiency and reducing overall operating costs.

[0038] Please refer to Figure 2 , Figure 2This is a hydraulic schematic diagram of a series-parallel control valve group in a specific embodiment of the multi-stage speed-regulating drilling hydraulic system provided by the present invention.

[0039] In the multi-stage speed-regulating drilling hydraulic system provided in a specific embodiment of the present invention, the series-parallel control valve group 3 includes a first logic valve 311, a second logic valve 312, and a third logic valve 313. The first interface of the first logic valve 311 is connected to the first interface of the multi-way valve 2 and the first interface of a first hydraulic motor 4. The second interface of the first logic valve 311 is connected to the first interface of the second logic valve 312 and the first interface of the second hydraulic motor 5. The second interface of the second logic valve 312 is connected to the second interface of the first hydraulic motor 4 and the second interface of the third logic valve 313. The first interface of the third logic valve 313 is connected to the second interface of the second hydraulic motor 5 and the second interface of the multi-way valve 2.

[0040] Furthermore, the series-parallel control valve group 3 includes a first switching valve 321, a second switching valve 322, and a third switching valve 323. The inlets of the first switching valve 321, the second switching valve 322, and the third switching valve 323 are all connected to the pressure oil port of the multi-way valve 2. The first switching valve 321, the second switching valve 322, and the third switching valve 323 are respectively connected to the spring chambers of the first logic valve 311, the second logic valve 312, and the third logic valve 313. In the attached figures, the side port of the logic valve is the first port, and the bottom port is the second port. The left port of the hydraulic motor is the first port, and the right port is the second port.

[0041] To control the gear shifting of the rotary power head 6, the series-parallel control valve group 3 includes a fourth switching valve 324. The inlet of the fourth switching valve 324 is connected to the pressure oil port of the multi-way valve 2, and the outlet of the fourth switching valve 324 is connected to the speed control cylinder C1 of the rotary power head 6. Specifically, the first switching valve 321, the second switching valve 322, the third switching valve 323, and the fourth switching valve 324 are electromagnetic switching valves.

[0042] Specifically, hydraulic pump 1 is a load-sensitive hydraulic pump, multi-way valve 2 is a load-sensitive multi-way valve, multi-way valve 2 is a proportional regulating valve, and is equipped with a forward proportional electromagnet and a reverse proportional electromagnet.

[0043] The series control of the first hydraulic motor 4 and the second hydraulic motor 5, under the excitation of the forward proportional electromagnet DT5, causes the valve core of the multi-way valve 2 to move. Oil output from the hydraulic pump 1 flows out from the first port of the load-sensitive multi-way valve and into the series-parallel control valve group 3. DT1 and DT3 are simultaneously energized, and the pressure oil at port P1 of the control valve group enters the spring chambers of the first logic valve 311 and the third logic valve 313, cutting off the main oil circuits of both valves. Hydraulic oil can only enter the first hydraulic motor 4 from the first port, thus driving the first hydraulic motor. 4. The hydraulic oil rotates and flows from the first hydraulic motor 4 to the second port; DT2 is not energized, and the main oil circuit of the second logic valve 312 is connected; the hydraulic oil from the second port of the first hydraulic motor 4 enters the second hydraulic motor 5 through the main oil circuit of the second logic valve 312 and the first port, driving the second hydraulic motor 5 to rotate; since the hydraulic pipeline interfaces of the two hydraulic motors are connected in series, the flow rate is equal, and as described above, the output speed of the two motors is the same; the hydraulic oil flowing out of the second hydraulic motor 5 enters the load-sensitive multi-way valve through the valve group, and finally returns to the hydraulic oil tank. Reverse rotation is energized by the reverse proportional solenoid DT6, the hydraulic oil first flows through the second hydraulic motor 5, through the main oil circuit of the second logic valve 312 and then to the first hydraulic motor 4, the motor rotation direction is opposite, and the control logic is consistent.

[0044] The parallel control of the first hydraulic motor 4 and the second hydraulic motor 5, under the excitation of the forward proportional electromagnet DT5, causes the valve core of the multi-way valve 2 to move. The oil output from the hydraulic pump 1 flows out from the first port of the load-sensitive multi-way valve and enters the series-parallel control valve group 3. Since DT1 and DT3 are de-energized at the same time, the main oil circuits of the first logic valve 311 and the third logic valve 313 are connected. Part of the hydraulic oil enters the first hydraulic motor 4 from the first port, which can drive the first hydraulic motor 4 to rotate, and flows out from the first hydraulic motor 4 into the valve group, passing through the main oil circuit of the third logic valve 313 to the valve group. Another part of the hydraulic oil enters the second hydraulic motor 5 through the main oil circuit of the first logic valve 311, which can drive the second hydraulic motor 5 to rotate, and flows out from the second hydraulic motor 5. When DT2 is energized, the pressure oil of the control valve group enters the spring chamber of the second logic valve 312, and the main oil circuit of the second logic valve 312 is cut off. The hydraulic oil enters the load-sensitive multi-way valve through the valve group and finally returns to the hydraulic oil tank. Because the hydraulic lines of the two hydraulic motors are connected in parallel, each motor receives only half of the total flow, and the motor speed is only half that when they are connected in series. Reverse rotation is achieved by energizing the proportional electromagnet DT6, with hydraulic oil flowing through the first hydraulic motor 4 and the second hydraulic motor 5 respectively. The motors rotate in opposite directions, but the control logic remains the same.

[0045] Please refer to Figure 3 and Figure 4 , Figure 3 This is a schematic diagram of the high-speed gear of the rotary power head in a specific embodiment of the multi-stage speed-regulating drilling hydraulic system provided by the present invention. Figure 4This is a schematic diagram of the low-speed gear of the rotary power head in a specific embodiment of the multi-stage speed-regulating drilling hydraulic system provided by the present invention.

[0046] The rotary power head 6 includes a main shaft 61 and two drive shafts 62. The main shaft 61 is connected to the drill rod 7, and the two drive shafts 62 are respectively connected to the first hydraulic motor 4 and the second hydraulic motor 5. Matching multi-stage speed regulating gears are provided on the main shaft 61 and the drive shafts 62.

[0047] In high-speed control, the electromagnet DT4 is not energized, and the piston rod of the speed control cylinder C1 remains extended under the action of the spring force inside the cylinder. The hydraulic oil in the speed control cylinder C1 returns to the hydraulic oil tank through the pipeline and the solenoid valve DT4. The gears Z3 and Z5, driven by the first hydraulic motor 4 and the second hydraulic motor 5 respectively, mesh and rotate with the main shaft gear Z1. At this time, the speed ratio between the hydraulic motor and the main shaft is small, and the main shaft rotates at a high speed.

[0048] In low-speed control, the electromagnet DT4 is energized, and the pressure oil of the control valve group enters the speed control cylinder C1. The hydraulic pressure overcomes the spring force, and the piston rod remains in the retracted state. The gears Z4 and Z6, driven by the first hydraulic motor 4 and the second hydraulic motor 5 respectively, mesh and rotate with the spindle gear Z2. At this time, the speed ratio between the hydraulic motor and the spindle is large, and the spindle rotation speed is low.

[0049] When forward rotation is required, the DT5 proportional solenoid receives a PWM (Pulse Width Modulation) signal from the controller, driving the spool of the load-sensitive multi-way valve to move. The load-sensitive hydraulic pump outputs the corresponding flow rate based on the spool displacement. Adjusting the duty cycle of the PWM signal regulates the spool displacement, thus determining the flow rate output by the load-sensitive multi-way valve, which in turn determines the hydraulic motor's speed. Spool displacement control can be achieved through proportional solenoid excitation or hydraulic pilot control. For reverse rotation, the DT6 proportional solenoid receives an excitation signal, the hydraulic oil flows in the opposite direction, and the hydraulic motor rotates in the opposite direction. The control methods and logic remain the same as for forward rotation.

[0050] Based on the multi-stage speed-regulating drilling hydraulic system provided in the above specific embodiments, a speed sensor S2 and a pressure sensor S1 are included, and the controller controls the series-parallel connection state and the 6-speed rotation of the power head according to the detection results.

[0051] Please refer to Figure 5 , Figure 5 This is a flowchart illustrating a specific embodiment of the control method for the multi-stage speed-regulating drilling hydraulic system provided by the present invention.

[0052] This invention provides a control method for a multi-stage speed-regulating drilling hydraulic system, applying the multi-stage speed-regulating drilling hydraulic system described above, and includes the following steps:

[0053] Start the operation, select the operation mode, call the drilling algorithm based on whole machine operation, and obtain the output speed S2 of the rotating power head 6 and the output pressure S1 of the multi-way valve 2;

[0054] The output speed is compared with the preset speed; a first preset speed n1, a second preset speed n2 and a third preset speed n3 are set, the first preset speed is less than the second preset speed, the second preset speed is less than the third preset speed, and a preset pressure P is also set.

[0055] Compare the output speed S2 with the first preset speed n1. If the output speed is less than the first preset speed, compare the output pressure with the preset pressure. If the output pressure is greater than or equal to the preset pressure, the two hydraulic motors are connected in parallel and the rotating power head 6 is in low speed. If the output pressure is less than the preset pressure, the two hydraulic motors are connected in parallel and the rotating power head 6 is in high speed.

[0056] If the output speed is greater than or equal to the first preset speed, compare the output speed S2 with the second preset speed n2. If the output speed is less than the second preset speed, compare the output pressure with the preset pressure. If the output pressure is greater than or equal to the preset pressure, the two hydraulic motors are connected in parallel and the rotating power head 6 is in high speed mode. If the output pressure is less than the preset pressure, the two hydraulic motors are connected in series and the rotating power head 6 is in low speed mode.

[0057] If the output speed is greater than or equal to the second preset speed, compare the output speed S2 with the third preset speed n3. If the output speed is less than the third preset speed, compare the output pressure with the preset pressure. If the output pressure is greater than or equal to the preset pressure, the two hydraulic motors are connected in series and the rotating power head 6 uses the low speed gear. If the output pressure is less than the preset pressure, the two hydraulic motors are connected in series and the rotating power head 6 uses the high speed gear.

[0058] If the output speed is greater than or equal to the third preset speed, the two hydraulic motors are connected in series, and the rotating power head 6 is in high speed mode.

[0059] In addition to the aforementioned multi-stage speed-regulating drilling hydraulic system, a specific embodiment of the present invention also provides a drilling rig including the aforementioned multi-stage speed-regulating drilling hydraulic system. The structure of other parts of the drilling rig is described in the prior art and will not be repeated here.

[0060] The multi-stage speed-regulating drilling hydraulic system, drilling rig, and control method provided by this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A multi-stage variable speed drilling hydraulic system, characterized by, The device includes a hydraulic pump (1), a multi-way valve (2), a series-parallel control valve group (3), a first hydraulic motor (4), a second hydraulic motor (5), and a rotary power head (6). The hydraulic pump (1) is connected to the series-parallel control valve group (3) through the multi-way valve (2). The series-parallel control valve group (3) is connected to the first hydraulic motor (4) and the second hydraulic motor (5) to drive the two hydraulic motors to rotate and can adjust the series-parallel state of the first hydraulic motor (4) and the second hydraulic motor (5). The output shafts of the first hydraulic motor (4) and the second hydraulic motor (5) are connected to the input end of the rotary power head (6). The output end of the rotary power head (6) is connected to the drill rod (7) to drive the drill rod (7) to rotate and can be adjusted in multiple speeds.

2. The multi-stage variable speed drilling hydraulic system of claim 1, wherein, The series-parallel control valve group (3) includes a first logic valve (311), a second logic valve (312), and a third logic valve (313). The first interface of the first logic valve (311) is connected to the first interface of the multi-way valve (2) and the first interface of the first hydraulic motor (4). The second interface of the first logic valve (311) is connected to the first interface of the second logic valve (312) and the first interface of the second hydraulic motor (5). The second interface of the second logic valve (312) is connected to the second interface of the first hydraulic motor (4) and the second interface of the third logic valve (313). The first interface of the third logic valve (313) is connected to the second interface of the second hydraulic motor (5) and the second interface of the multi-way valve (2).

3. The multi-stage variable speed drilling hydraulic system of claim 2, wherein, The series-parallel control valve group (3) includes a first switching valve (321), a second switching valve (322), and a third switching valve (323). The inlets of the first switching valve (321), the second switching valve (322), and the third switching valve (323) are all connected to the pressure oil port of the multi-way valve (2). The first switching valve (321), the second switching valve (322), and the third switching valve (323) are respectively connected to the spring chambers of the first logic valve (311), the second logic valve (312), and the third logic valve (313).

4. The multi-stage variable speed drilling hydraulic system of claim 3, wherein, The series-parallel control valve group includes a fourth switching valve (324), the inlet of which is connected to the pressure oil port of the multi-way valve (2), and the outlet of which is connected to the speed control cylinder of the rotary power head (6).

5. The multi-stage variable speed drilling hydraulic system of claim 4, wherein, The first switching valve (321), the second switching valve (322), the third switching valve (323), and the fourth switching valve (324) are specifically electromagnetic switching valves.

6. The multi-stage variable speed drilling hydraulic system of claim 1, wherein, The hydraulic pump (1) is a load-sensitive hydraulic pump, the multi-way valve (2) is a load-sensitive multi-way valve, the multi-way valve (2) is a proportional regulating valve, and is equipped with a forward proportional electromagnet and a reverse proportional electromagnet.

7. The multi-stage variable speed drilling hydraulic system of claim 1, wherein, The rotary power head (6) includes a main shaft (61) and two drive shafts (62). The main shaft (61) is connected to the drill rod (7), and the two drive shafts (62) are respectively connected to the first hydraulic motor (4) and the second hydraulic motor (5). Matching multi-stage speed regulating gears are provided on the main shaft (61) and the drive shafts (62).

8. The multi-stage variable speed drilling hydraulic system of any one of claims 1 to 7, wherein, Includes a speed sensor (S2) and a pressure sensor (S1), and the controller controls the series-parallel connection status and the gear of the rotating power head (6) based on the detection results.

9. A rig characterized in that, Includes the multi-stage speed-regulating drilling hydraulic system as described in any one of claims 1 to 8.

10. A control method for a multi-stage speed-regulating drilling hydraulic system, characterized in that, The application of the multi-stage speed-regulating drilling hydraulic system as described in any one of claims 1 to 8 includes the following steps: Obtain the output speed of the rotary power head (6) and the output pressure of the multi-way valve (2); Compare the output speed with the preset speed; If the output speed is less than the first preset speed, then the output pressure and the preset pressure are compared. If the output pressure is greater than or equal to the preset pressure, then the two hydraulic motors are connected in parallel and the rotating power head (6) is in low speed. If the output pressure is less than the preset pressure, then the two hydraulic motors are connected in parallel and the rotating power head (6) is in high speed. If the output speed is less than the second preset speed, then the output pressure and the preset pressure are compared. If the output pressure is greater than or equal to the preset pressure, then the two hydraulic motors are connected in parallel and the rotating power head (6) is in high speed mode. If the output pressure is less than the preset pressure, then the two hydraulic motors are connected in series and the rotating power head (6) is in low speed mode. If the output speed is less than the third preset speed, then the output pressure and the preset pressure are compared. If the output pressure is greater than or equal to the preset pressure, then the two hydraulic motors are connected in series and the rotating power head (6) is in low speed. If the output pressure is less than the preset pressure, then the two hydraulic motors are connected in series and the rotating power head (6) is in high speed. If the output speed is greater than or equal to the third preset speed, then the two hydraulic motors are connected in series, the rotating power head (6) is in high speed mode, the first preset speed is less than the second preset speed, and the second preset speed is less than the third preset speed.

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