Linear motion device for deep-sea robots

Abstract

This invention relates to a linear motion device for a deep-sea robot. The differential houses a planetary gear assembly and a transmission gear assembly. The planetary gear assembly includes a ring gear, planetary gears, and intermediate gears, with the planetary gears evenly distributed between the ring gear and the intermediate gears. A first motor is coaxially connected to the ring gear, and a second motor is coaxially connected to the intermediate gears via a second power input shaft. The driving gear at the starting end of the transmission gear assembly is mounted on the second power input shaft, and a connecting shaft is located on the outer edge of the driving gear. Any planetary gear is mounted on the connecting shaft. The second bevel gear at the end of the transmission gear assembly is mounted on a transmission shaft. Transmission boxes are located at both ends of the transmission shaft, and linear drive components are respectively mounted on their corresponding transmission boxes. The two linear drive components are driven synchronously to extend and retract via the transmission shaft, and the transmission shaft transmits torque through the transmission boxes on both sides. This invention features a dual-motor redundant design and can withstand the lateral loads and deep-sea pressure generated by the device's underwater movement.

Description

Technical Field

[0001] This invention relates to the field of underwater robots, and more specifically to a linear motion device for deep-sea robots. Background Technology

[0002] A remotely operated underwater vehicle (ROV) is a device commonly used in deep-sea exploration and salvage operations. It can serve as a carrier, equipped with various underwater tools to achieve different functions depending on the task. To better cover the application scenarios of different types of underwater robots, such as... Figure 6 As shown, variable structure underwater robots are a relatively reliable research direction, which involves changing the structural characteristics of underwater robots through structural deformation, enabling them to perform the work of two or more traditional underwater devices. Currently, linear deformation is a commonly used method in the field of variable structure underwater robots. However, traditional high-load linear mechanisms mostly use hydraulic drive, such as hydraulic cylinders and scissor mechanisms. Considering that hydraulic systems have problems such as large space requirements, complex configuration, insufficient stability, and mechanism interference in the deep-sea environment, they are not suitable for deep-sea robots. In addition, existing technologies also use underwater electric actuators to drive linear deformation. However, for deep-sea ROVs, the design of the deformation mechanism needs to consider not only the load in the linear motion direction but also the lateral load generated by the underwater movement of the equipment. Currently, the existing underwater electric actuator mechanism design only considers the vertical load and generally requires additional mechanisms such as guide rails to work together, resulting in low integration. Furthermore, deep-sea conditions place high demands on the reliability of motors, while existing electric actuators are mostly single-motor configurations. If a motor fails, it will seriously affect the mission execution process. Therefore, consideration of motor redundancy is also necessary. In addition, since the equipment needs to withstand extremely high pressure in the deep-sea environment, it needs to be filled with oil to achieve pressure compensation. However, the oil compensation capability that current deep-sea equipment can provide is limited, which restricts the design of the motion mechanism. Summary of the Invention

[0003] The purpose of this invention is to provide a linear motion device for deep-sea robots, which features a dual-motor redundant design. It can still operate normally when either motor fails, and can withstand the lateral loads and deep-sea pressure generated by the device's underwater movement.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A linear motion device for a deep-sea robot includes a first motor, a second motor, a differential, a drive shaft, a transmission box, and a linear drive assembly. The differential internally houses a planetary gear assembly and a transmission gear assembly. The planetary gear assembly includes a ring gear, planetary gears, and an intermediate gear, with the planetary gears evenly distributed circumferentially between the ring gear and the intermediate gear. The first motor is coaxially connected to the ring gear, and the second motor is coaxially connected to the intermediate gear via a second power input shaft. The driving gear at the starting end of the transmission gear assembly is mounted on the second power input shaft, and a connecting shaft is provided on the outer edge of the driving gear. Any planetary gear is mounted on the connecting shaft. The second bevel gear at the end of the transmission gear assembly is mounted on the drive shaft. Transmission boxes are provided at both ends of the drive shaft, and the linear drive assemblies are respectively mounted on the corresponding transmission boxes. The two linear drive assemblies are driven synchronously to extend and retract via the drive shaft, and the drive shaft transmits torque through the transmission boxes on both sides.

[0006] The differential includes a differential housing, and a first power input shaft is provided on one side of the differential housing and a second power input shaft is provided on the other side. One end of the first power input shaft is coaxially connected to the first motor and the other end is coaxially connected to the gear ring. One end of the second power input shaft is coaxially connected to the second motor and the other end is coaxially connected to the intermediate gear. A first brake is provided on the first power input shaft and a second brake is provided on the second power input shaft.

[0007] The transmission gear assembly includes a driving gear, a transmission gear, a driven gear, a first bevel gear, and a second bevel gear, wherein the driving gear, the transmission gear, and the driven gear mesh in sequence, the driven gear is coaxially connected to the first bevel gear, and the first bevel gear meshes with the second bevel gear.

[0008] The linear drive assembly includes a drive screw, an inner piston rod, an inner cylinder, an outer piston rod, and an outer cylinder. The drive screw is located in the inner piston rod, and a nut is fitted inside the inner piston rod onto the drive screw. The inner piston rod is located in the inner cylinder, and the inner cylinder is located in the outer piston rod. The upper end of the outer piston rod is fixedly connected to the upper end of the inner piston rod. The outer piston rod is located in the outer cylinder, and the lower ends of both the inner and outer cylinders are located on the housing of the transmission box. The lower end of the drive screw extends into the transmission box and is connected to a transmission assembly located inside the transmission box. The drive screw is driven to rotate via a transmission shaft, and the transmission shaft transmits torque through the transmission assembly.

[0009] The upper end of the drive screw is provided with a piston block, and dynamic sealing rings are provided between the piston block and the inner piston rod and between the inner piston rod and the inner cylinder. The transmission box has a sealed accommodating cavity inside, and the sealed accommodating cavity communicates with the inside of the inner cylinder. The transmission assembly is located in the sealed accommodating cavity. An oil injection port is provided on one side of the box and communicates with the sealed accommodating cavity.

[0010] The upper end of the inner piston rod is provided with a through hole, the upper end of the inner cylinder is provided with an exhaust valve, and the upper end of the outer cylinder is provided with an exhaust port.

[0011] The transmission components inside the transmission box include a worm and a worm wheel that mesh with each other, wherein the worm is connected to the transmission shaft and the worm wheel is coaxially connected to the drive screw.

[0012] The worm gear has a through hole in the middle for the drive screw to pass through. The sealed cavity contains a bearing and a locking nut fitted onto the drive screw. The bearing is limited by the locking nut. The lower end of the sealed cavity has a sealing end cap.

[0013] The lower part of the inner piston rod is provided with an outer stop surface, and the upper end of the inner cylinder is provided with an inner stop surface.

[0014] A sliding bearing is provided between the upper end of the outer cylinder and the outer piston rod.

[0015] The advantages and positive effects of this invention are as follows:

[0016] 1. This invention is a dual-motor redundant design. When both motors are working normally, the differential of this invention can couple the inputs of the first motor and the second motor, and finally achieve a single power output, avoiding the load problem caused by the rigid connection of the two motors. When either motor fails, the differential can still ensure power output, thereby ensuring that the device can still work normally.

[0017] 2. The linear drive assembly of this invention adopts a set design of outer and inner cylinders, which can withstand lateral loads. The outer and inner piston rods are connected together, which not only ensures lifting action and external load support, but also allows the diameter of the linear mechanism that needs to be filled with oil to be as small as possible, so as to reduce the amount of oil compensation required and meet the pressure compensation requirements of deep sea pressure. The hollow cavity design of the inner piston rod of this invention allows seawater to be above the piston block and pressure compensation oil to be below. This design means that the volume change of the sealed cavity during the movement of the mechanism depends on the linear movement distance of the mechanism and the wall thickness and area of ​​the inner piston rod. Compared with the common closed piston rod design, it can effectively reduce the amount of compensation oil required, and also facilitates the discharge of seawater during recovery, avoiding the corrosion of parts by residual seawater.

[0018] 3. The linear drive assembly of the present invention adopts a trapezoidal lead screw, and the trapezoidal lead screw, the worm and the worm wheel in the transmission box all have good self-locking characteristics, which can work with the power failure brake to ensure the self-locking capability of the present invention in the non-working state. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention.

[0020] Figure 2 for Figure 1 A schematic diagram of the differential structure in the diagram.

[0021] Figure 3 This is a schematic diagram of the power transmission principle of the present invention.

[0022] Figure 4 for Figure 1 A schematic diagram of the structure of the linear drive component.

[0023] Figure 5 for Figure 4 A cross-sectional view of the linear drive component.

[0024] Figure 6 This is a schematic diagram of a variable structure underwater robot.

[0025] In this configuration, 1 is the differential, 101 is the planetary gear assembly, 1011 is the ring gear, 1012 is the planetary gear, 1013 is the intermediate gear, 102 is the second brake, 103 is the second power input shaft, 104 is the first power input shaft, 105 is the first brake, 106 is the differential housing, 107 is the drive gear, 1071 is the connecting rod shaft, 108 is the transmission gear, 109 is the driven gear, 110 is the first bevel gear, 111 is the second bevel gear, 2 is the first motor, 3 is the linear drive assembly, 301 is the drive screw, and 302 is the pin. 303 is a sliding bearing, 304 is a piston block, 305 is a threaded nut, 306 is an inner piston rod, 3061 is an outer stop surface, 307 is an inner cylinder, 3071 is an inner stop surface, 308 is an outer piston rod, 309 is an outer cylinder, 310 is an exhaust valve, 311 is a dynamic seal ring, 4 is a drive shaft, 5 is a second motor, 6 is a transmission box, 601 is a worm gear, 602 is a worm wheel, 6021 is a worm wheel through hole, 603 is an oil inlet, 604 is a housing, 605 is a bearing, 606 is a lock nut, 607 is a sealing end cap, and 608 is a seal ring. Detailed Implementation

[0026] The invention will now be described in further detail with reference to the accompanying drawings.

[0027] like Figures 1-6 As shown, the present invention includes a first motor 2, a second motor 5, a differential 1, a drive shaft 4, a transmission box 6, and a linear drive assembly 3, wherein... Figures 2-3 As shown, the differential 1 internally includes a planetary gear assembly 101 and a transmission gear assembly. The planetary gear assembly 101 includes a ring gear 1011, planetary gears 1012, and an intermediate gear 1013. The planetary gears 1012 are evenly distributed circumferentially between the ring gear 1011 and the intermediate gear 1013. The first motor 2 is coaxially connected to the ring gear 1011. The second motor 5 is connected to a second power input shaft 103, and the end of the second power input shaft 103 is coaxially connected to the intermediate gear 1013. The transmission gear assembly... The starting end drive gear 107 and the second power input shaft 103 are coaxially mounted, and the outer edge of the drive gear 107 is provided with a connecting shaft 1071. Any planetary gear 1012 is mounted on the connecting shaft 1071. The second bevel gear 111 at the end of the transmission gear assembly is mounted on the transmission shaft 4. Both ends of the transmission shaft 4 are provided with transmission boxes 6, and the linear drive components 3 are respectively mounted on the corresponding side transmission boxes 6. The two linear drive components 3 are driven to extend and retract synchronously through the transmission shaft 4, and the transmission shaft 4 transmits torque through the transmission boxes 6 on both sides. This invention utilizes the differential 1 to couple the input of the first motor 2 and the second motor 5, wherein the ring gear 1011, planetary gear 1012 and intermediate gear 1013 in the planetary gear assembly 101 have the characteristic that the rotational speed of any one component can be determined by the rotational speeds of the remaining two components, such as Figure 3 As shown, in this invention, the first motor 2 drives the gear ring 1011 to rotate, and the second motor 5 drives the intermediate gear 1013 to rotate. Any planetary gear 1012 is connected to the driving gear 107 via the connecting rod shaft 1071. Thus, when both motors are working normally, the differential 1 can couple the inputs of the first motor 2 and the second motor 5, ultimately achieving a single output from the second bevel gear 111, avoiding the load problem caused by the rigid connection of the two motors. When the first motor 2 fails, the intermediate gear 1013 can still be driven by the second motor 5. At the same time, the planetary gear 1012 connected to the driving gear 107 rotates between the gear ring 1011 and the intermediate gear 1013, driving the driving gear 107 to output power. When the second motor 5 fails, the first motor 2 drives the planetary gear 1012 to rotate via the gear ring 1011. The planetary gear 1012 connected to the driving gear 107 then drives the driving gear 107 to rotate, thereby maintaining the normal operation of the device and achieving redundant configuration of the motors.

[0028] like Figures 2-3As shown, the differential 1 includes a differential housing 106, with a rotatable first power input shaft 104 on one side and a rotatable second power input shaft 103 on the other side. One end of the first power input shaft 104 is coaxially connected to the first motor 2, and the other end is coaxially connected to the gear ring 1011. One end of the second power input shaft 103 is coaxially connected to the second motor 5, and the other end is coaxially connected to the drive gear 107 and the intermediate gear 1013. The first power input shaft 103 and the second power input shaft 104 are rotatably mounted on the front and rear side walls of the differential housing 106 respectively, supported by bearings. Figure 3 As shown, the drive shaft 4 passes through the differential housing 106, and the left and right side walls of the differential housing 106 are provided with bearings to support the rotation of the drive shaft 4.

[0029] like Figures 2-3 As shown, the differential 1 internally includes a first brake 105 and a second brake 102. The first brake 105 is mounted on the first power input shaft 104, and the second brake 102 is mounted on the second power input shaft 102. In this embodiment, both the first brake 105 and the second brake 102 are power-off brakes. When any motor fails, the control system de-energizes and locks the power-off brake corresponding to that motor. The power-off brake is a commercially available product.

[0030] like Figures 2-3 As shown, in this embodiment, the transmission gear assembly includes a driving gear 107, a transmission gear 108, a driven gear 109, a first bevel gear 110, and a second bevel gear 111. The driving gear 107, the transmission gear 108, and the driven gear 109 mesh sequentially. The driven gear 109 is coaxially connected to the first bevel gear 110, and the first bevel gear 110 meshes with the second bevel gear 111.

[0031] like Figures 3-5As shown, in this embodiment, the linear drive assembly 3 includes a drive screw 301, an inner piston rod 306, an inner cylinder 307, an outer piston rod 308, and an outer cylinder 309. The drive screw 301 is inserted into the inner piston rod 306, and a nut 305 is provided inside the inner piston rod 306 and fitted onto the drive screw 301. The inner piston rod 306 is located in the inner cylinder 307 and is driven by the drive screw 301 to move up and down along the inner cylinder 307. The inner cylinder 307 is located in the outer piston rod 308, and the outer piston rod 309... The upper end of the outer piston rod 308 is fixedly connected to the upper end of the inner piston rod 306 via a pin 302. The outer piston rod 308 is located in the outer cylinder 309 and is driven by the inner piston rod 306 to move up and down along the outer cylinder 309. The lower ends of the inner cylinder 307 and the outer cylinder 309 are both located on the housing 604 of the transmission box 6. The lower end of the drive screw 301 extends into the transmission box 6 and is connected to the transmission assembly located inside the transmission box 6. The drive screw 301 is driven to rotate via the transmission shaft 4, and the transmission shaft 4 transmits torque through the transmission assembly. The outer cylinder 309 of this invention is a linear cylinder structure with a large diameter capable of withstanding lateral loads. Furthermore, this invention uses a pin 302 to connect the outer piston rod 308 and the inner piston rod 306 together, which ensures both lifting and lowering actions and external load support, while also minimizing the diameter of the linear mechanism requiring oil filling (inner cylinder 307) to reduce the amount of oil required for compensation. When the present invention is in a deep-sea environment, the hollow cavity design of the inner piston rod 306 allows seawater to be above the piston block 304 and pressure compensation oil to be below. This design means that when the mechanism moves, the volume change of the sealed cavity depends on the linear movement distance of the mechanism and the wall thickness area of ​​the inner piston rod 306. Compared with the common closed piston rod design, it can effectively reduce the amount of compensation oil required.

[0032] like Figure 5 As shown, in this embodiment, the upper end of the drive screw 301 is provided with a piston block 304, and dynamic sealing rings 311 are provided between the piston block 304 and the inner piston rod 306, and between the inner piston rod 306 and the inner cylinder 307. The housing 604 of the transmission box 6 has a sealed accommodating cavity inside, and the sealed accommodating cavity communicates with the interior of the inner cylinder 307. A sealing ring 608 is also provided between the lower end of the inner cylinder 307 and the housing 604. The upper end of the inner piston rod 306 has a through hole, such as... Figure 4 As shown, the housing 604 has an oil inlet 603 on one side that communicates with the sealed accommodating cavity. The oil inlet 603 is used to inject oil into the inner cylinder 307 to achieve pressure compensation, while the various sealing rings ensure the sealing of the inner cylinder 307. Additionally, as shown... Figure 5As shown, the inner cylinder 307 is equipped with an exhaust valve 310 at its upper end, and the outer cylinder 309 is equipped with an exhaust port at its upper end. During maintenance, compensating oil is injected into the inner cylinder 307 of the linear drive assembly 3 through the oil inlet 603, and excess gas is released through the exhaust valve 310 by the pressure difference between the inside and outside. When the mechanism is in the retracted state, the exhaust port on the outer cylinder 309 is aligned with the exhaust valve 310, which facilitates manual operation. The space between the outer cylinder 309 and the inner cylinder 307 is in communication with seawater, so there is no need to consider the pressure compensation issue. When the invention leaves the seabed, seawater is discharged through the through hole at the upper end of the inner piston rod 306. When the mechanism is retracted, the inner wall of the upper end of the inner piston rod 306 is just located on the upper plane of the piston block 304, so that the seawater in the inner piston rod 306 can flow into the outer cylinder 309 through its upper through hole, and then be discharged through the flange of the outer cylinder 309 and the drainage groove on the housing 604, thereby avoiding corrosion of the parts by residual seawater.

[0033] like Figure 5 As shown, in this embodiment, the lower part of the inner piston rod 306 is provided with an outer stop surface 3061, and the upper end of the inner cylinder 307 is provided with an inner stop surface 3071. The outer stop surface 3061 and the inner stop surface 3071 cooperate to prevent the inner piston rod 306 from disengaging, and at the same time limit the rising height of the inner piston rod 306.

[0034] like Figure 5 As shown, in this embodiment, a sliding bearing 303 is provided between the upper end of the outer cylinder 309 and the outer piston rod 308 to ensure that the two are slidably connected.

[0035] like Figures 3-5 As shown, in this embodiment, the transmission components in the transmission box 6 include a worm 601 and a worm wheel 602 that mesh with each other. The worm 601 is connected to the transmission shaft 4, and the worm wheel 602 is coaxially connected to the drive screw 301. In addition, in this embodiment, the drive screw 301 is a trapezoidal screw. The trapezoidal screw, as well as the worm 601 and the worm wheel 602, have good self-locking characteristics and can cooperate with the power failure brake to ensure the self-locking capability of the present invention in the non-working state.

[0036] like Figure 5 As shown, the worm 601 and worm wheel 602 are both located in a sealed accommodating cavity inside the housing 604. The worm wheel 602 has a worm wheel through hole 6021 in the middle for the drive screw 301 to pass through. The sealed accommodating cavity contains a bearing 605 and a locking nut 606, which are fitted onto the drive screw 301. The bearing 605 is positioned by the locking nut 606. The lower end of the sealed accommodating cavity is provided with a sealing end cap 607 to ensure the cavity is sealed.

[0037] The working principle of this invention is as follows:

[0038] In operation, the first motor 2 drives the ring gear 1011 in the planetary gear assembly 101 to rotate, and the second motor 5 drives the intermediate gear 1013 in the planetary gear assembly to rotate. Any planetary gear 1012 is connected to the drive gear 107 via the connecting rod shaft 1071. Thus, when both motors are working normally, the differential 1 can couple the inputs of the first motor 2 and the second motor 5, ultimately achieving a single output from the second bevel gear 111 and driving the transmission shaft 4 to rotate, avoiding the load problem caused by the rigid connection of the two motors. When the first motor 2 fails, the intermediate gear 1013 is driven by the second motor 5, and the planetary gear 1012 connected to the drive gear 107 rotates between the ring gear 1011 and the intermediate gear 1013, driving the drive gear 107 to output power. When the second motor 5 fails, the first motor 2 drives the planetary gear 1012 to rotate via the ring gear 1011, and the planetary gear 1012 connected to the drive gear 107 drives the drive gear 107 to rotate to output power, thereby maintaining the normal operation of the device and achieving redundant configuration of the motors. In addition, the differential 1 is equipped with a first brake 105 and a second brake 102. When any motor fails, the control system will de-energize and lock the brake corresponding to that motor.

[0039] The linear drive assembly 3 of this invention adopts a packaged design of an outer cylinder 309 and an inner cylinder 307. The outer cylinder 309 is a linear cylinder structure with a larger diameter to withstand lateral loads. Furthermore, this invention utilizes a pin 302 to connect the outer piston rod 308 and the inner piston rod 306 together, ensuring both lifting and lowering motion and external load support, while minimizing the diameter of the linear mechanism requiring oil filling (inner cylinder 307) to reduce the amount of oil required for compensation. When this invention is in a deep-sea environment, the hollow cavity design of the inner piston rod 306 allows seawater to be above the piston block 304 and pressure compensation oil to be below. This design ensures that the volume change of the sealed cavity during mechanism movement depends on the linear movement distance of the mechanism and the wall thickness area of ​​the inner piston rod 306. Compared to the common closed piston rod design, this effectively reduces the amount of compensation oil required. During maintenance, compensation oil is injected into the inner cylinder 307 of the linear drive assembly 3 through the oil inlet 603 on the transmission box 6, and excess gas is expelled through exhaust via the internal and external pressure difference. When valve 310 is released, the space between the outer cylinder 309 and the inner cylinder 307 is connected to seawater, so there is no need to consider pressure compensation. When the invention leaves the seabed, seawater is discharged through the upper end of the inner piston rod 306. After the mechanism is retracted, the upper inner wall of the inner piston rod 306 is located on the upper plane of the piston block 304, so that the seawater in the inner piston rod 306 can flow through its upper end through the through hole into the outer cylinder 309, and then be discharged through the flange of the outer cylinder 309 and the drainage groove on the housing 604, thereby avoiding corrosion of the parts by residual seawater.

[0040] The present invention utilizes a drive screw 301 to drive the linear drive assembly 3 to lift and lower, ensuring reliable operation. The drive screw 301 is a trapezoidal screw, and the trapezoidal screw, worm 601 and worm wheel 602 have good self-locking characteristics, which can work with the power failure brake to ensure the self-locking capability of the present invention in the non-working state.

[0041] like Figure 6 The following is an application example of the present invention. The underwater robot includes an upper body and a lower body with different devices, and the upper body and the lower body are driven to open and close.

Claims

1. A linear motion device for a deep-sea robot, characterized in that: The system includes a first motor (2), a second motor (5), a differential (1), a drive shaft (4), a transmission box (6), and a linear drive assembly (3). The differential (1) contains a planetary gear assembly (101) and a transmission gear assembly. The planetary gear assembly (101) includes a ring gear (1011), planetary gears (1012), and intermediate gears (1013). The planetary gears (1012) are evenly distributed circumferentially between the ring gear (1011) and the intermediate gears (1013). The first motor (2) is coaxially connected to the ring gear (1011). The second motor (5) is connected to the intermediate gear (1013) via a second power input shaft (103). The transmission gear assembly is coaxially connected. The active gear (107) at the beginning of the transmission gear assembly is mounted on the second power input shaft (103). The outer edge of the active gear (107) is provided with a connecting rod shaft (1071). Any planetary gear (1012) is mounted on the connecting rod shaft (1071). The second bevel gear (111) at the end of the transmission gear assembly is mounted on the transmission shaft (4). Both ends of the transmission shaft (4) are provided with transmission boxes (6). The linear drive assembly (3) is installed on the corresponding side transmission box (6). The two linear drive assemblies (3) are driven to extend and retract synchronously through the transmission shaft (4). The transmission shaft (4) transmits torque through the transmission boxes (6) on both sides. The linear drive assembly (3) includes a drive screw (301), an inner piston rod (306), an inner cylinder (307), an outer piston rod (308), and an outer cylinder (309). The drive screw (301) is located in the inner piston rod (306), and a nut (305) is provided inside the inner piston rod (306) and fitted onto the drive screw (301). The inner piston rod (306) is located in the inner cylinder (307), and the inner cylinder (307) is located in the outer piston rod (308). 08) The upper end is fixedly connected to the upper end of the inner piston rod (306), the outer piston rod (308) is located in the outer cylinder (309), and the lower ends of the inner cylinder (307) and the outer cylinder (309) are both located on the housing (604) of the transmission box (6). The lower end of the drive screw (301) extends into the transmission box (6) and is connected to the transmission assembly located inside the transmission box (6). The drive screw (301) is driven to rotate through the transmission shaft (4), and the transmission shaft (4) transmits torque through the transmission assembly.

2. The linear motion device for deep-sea robots according to claim 1, characterized in that: The differential (1) includes a differential housing (106), and a first power input shaft (104) is provided on one side of the differential housing (106) and a second power input shaft (103) is provided on the other side. One end of the first power input shaft (104) is coaxially connected to the first motor (2) and the other end is coaxially connected to the gear ring (1011). One end of the second power input shaft (103) is coaxially connected to the second motor (5) and the other end is coaxially connected to the intermediate gear (1013). A first brake (105) is provided on the first power input shaft (104) and a second brake (102) is provided on the second power input shaft (103).

3. The linear motion device for deep-sea robots according to claim 1, characterized in that: The transmission gear assembly includes a driving gear (107), a transmission gear (108), a driven gear (109), a first bevel gear (110), and a second bevel gear (111). The driving gear (107), the transmission gear (108), and the driven gear (109) mesh sequentially. The driven gear (109) is coaxially connected with the first bevel gear (110), and the first bevel gear (110) meshes with the second bevel gear (111).

4. The linear motion device for a deep-sea robot according to claim 1, characterized in that: The upper end of the drive screw (301) is provided with a piston block (304), and dynamic sealing rings (311) are provided between the piston block (304) and the inner piston rod (306) and between the inner piston rod (306) and the inner cylinder (307). The transmission box (6) has a sealed accommodating cavity inside its housing (604), and the sealed accommodating cavity communicates with the inside of the inner cylinder (307). The transmission assembly is located in the sealed accommodating cavity. An oil inlet (603) is provided on one side of the housing (604) and communicates with the sealed accommodating cavity.

5. The linear motion device for a deep-sea robot according to claim 4, characterized in that: The inner piston rod (306) has a through hole at its upper end, the inner cylinder (307) has an exhaust valve (310) at its upper end, and the outer cylinder (309) has an exhaust port at its upper end.

6. The linear motion device for a deep-sea robot according to claim 4, characterized in that: The transmission assembly inside the transmission box (6) includes a worm (601) and a worm wheel (602) that mesh with each other, wherein the worm (601) is connected to the transmission shaft (4), and the worm wheel (602) is coaxially connected to the drive screw (301).

7. The linear motion device for a deep-sea robot according to claim 6, characterized in that: The worm gear (602) has a worm gear through hole (6021) in the middle for the drive screw (301) to pass through. The sealed accommodating cavity is provided with a bearing (605) and a locking nut (606) fitted on the drive screw (301). The bearing (605) is limited by the locking nut (606). The lower end of the sealed accommodating cavity is provided with a sealing end cap (607).

8. The linear motion device for a deep-sea robot according to claim 1, characterized in that: The lower part of the inner piston rod (306) is provided with an outer stop surface (3061), and the upper end of the inner cylinder (307) is provided with an inner stop surface (3071).

9. The linear motion device for a deep-sea robot according to claim 1, characterized in that: A sliding bearing (303) is provided between the upper end of the outer cylinder (309) and the outer piston rod (308).

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