A method of brake band control for a hydrodynamic transmission and a device therefor

Abstract

The application discloses a brake gear control method and device of a hydraulic transmission, and belongs to the technical field of hydraulic transmission. The hydraulic transmission comprises an input shaft, an output shaft, four planetary rows and a plurality of brakes. The control method comprises the following steps: in response to a brake gear instruction, the second brake and the third brake are controlled to be combined at the same time; under the brake gear, the sun gear, the planet carrier and the ring gear of the second planetary row and the third planetary row are locked, and then the sun gear, the planet carrier and the ring gear of the fourth planetary row are locked through mechanical connection, so as to lock the output shaft; at the same time, the sun gear, the planet carrier and the ring gear of the first planetary row are in a freely rotatable state, so as to allow the power from the input shaft to idle in the first planetary row. Through specific brake combination control, the application can rigidly lock the output shaft under the engine idle speed state, and fundamentally solves the safety hidden trouble and operation difficulty problem caused by the no-load gear phenomenon in the prior art.

Description

Technical Field

[0001] This invention relates to the field of hydraulic transmission technology, and more specifically, to a brake gear control method and device for a hydraulic transmission. Background Technology

[0002] Hydraulic transmissions are core transmission components widely used in engineering machinery, special vehicles, and other fields. They typically consist of a hydraulic torque converter and a planetary gearbox. By controlling the engagement and disengagement of multiple wet friction clutches within the transmission, various gear modes such as forward, reverse, and neutral can be switched to meet the power output requirements under different operating conditions.

[0003] In existing technologies, such as patent application CN102606708A, a multi-gear hydraulic transmission adaptable to various working conditions is disclosed. Through different combinations of multiple clutches (such as KR, KV, K1 / 3, K2 / 4, etc.), it can achieve forward, reverse, neutral, and various operating conditions. However, in practical applications, especially in special situations such as oil and gas field equipment commissioning and specific maintenance operations, there exists a long-standing technical problem that has not received sufficient attention and resolution—"discharge in neutral." Specifically, when the transmission is engaged in neutral, although the mechanical engagement between power input and output is broken, and theoretically there should be no power output from the output shaft, the transmission interior is still filled with lubricating oil. The clutches, gears, and other components loosely mounted on the shaft, under the agitation of the lubricating oil, will generate residual drag torque due to the viscosity of the liquid. This torque will slowly and uncontrollably drive the output shaft to rotate, i.e., the "discharge in neutral" phenomenon.

[0004] This belt pull phenomenon can lead to safety hazards, equipment damage, and operational difficulties. Since belt pull is an inherent physical characteristic of hydraulic transmissions and cannot be completely eliminated from the mechanical structure, there is an urgent need for a control method and transmission structure that is similar in structural principle to neutral but can effectively lock the output shaft and ensure that it does not rotate. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a brake gear control method and device for a hydraulic transmission. It aims to fundamentally solve the safety problems and operational difficulties caused by the phenomenon of neutral gear shifting by controlling a specific combination of brakes to cut off power transmission and mechanically lock the output shaft.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a brake gear control method for a hydraulic transmission, the hydraulic transmission including an input shaft, a planetary gear set, and a plurality of brakes, wherein the planetary gear set includes at least a first planetary gear set, a second planetary gear set, a third planetary gear set, and a fourth planetary gear set, wherein the fourth planetary gear set is connected to the output shaft of the transmission; the plurality of brakes includes at least a second brake and a third brake; the control method includes: in response to a brake gear command, controlling the second brake and the third brake to engage simultaneously, so that the hydraulic transmission enters a brake gear; in the brake gear, the sun gear, planet carrier, and ring gear of the second planetary gear set and the third planetary gear set are locked, thereby mechanically locking the sun gear, planet carrier, and ring gear of the fourth planetary gear set to lock the output shaft; simultaneously, the sun gear, planet carrier, and ring gear of the first planetary gear set are in a freely rotatable state to allow power from the input shaft to idle inside the first planetary gear set.

[0007] Preferably, the first planetary gear set includes a first sun gear, a first planet gear, a first ring gear, and a first planet carrier; the first planet gear meshes with the first sun gear and the first ring gear; the first planet carrier supports the first planet gear; the second planetary gear set includes a second sun gear, a second planet gear, a second ring gear, and a second planet carrier; the second planet gear meshes with the second sun gear and the second ring gear, and the second planet carrier supports the second planet gear; the third planetary gear set includes a third sun gear, a third planet gear, a third ring gear, and a third planet carrier; the third planet gear meshes with the third sun gear and the third ring gear, and the third planet carrier supports the third planet gear; the fourth planetary gear set includes a fourth sun gear, a fourth planet gear, a fourth ring gear, and a fourth planet carrier; the fourth planet gear meshes with the fourth sun gear and the fourth ring gear, and the fourth planet carrier supports the fourth planet gear.

[0008] Preferably, the first sun gear is loosely fitted on the input shaft, the second and third sun gears are mounted on the input shaft, and the fourth sun gear is mounted on the output shaft; the first planetary carrier is fixedly connected to the second ring gear; the second planetary carrier is fixedly connected to the third ring gear; the third planetary carrier is fixedly connected to the output shaft; and the fourth planetary carrier is fixedly connected to the third ring gear.

[0009] Preferably, the hydraulic transmission further includes a first clutch and a second clutch; the first clutch is used to selectively connect the input shaft to the first sun gear; and the second clutch is used to selectively connect the first sun gear to the second planetary carrier.

[0010] Preferably, the hydraulic transmission further includes a first brake and a fourth brake; the first brake is used to selectively fix the first gear ring; the second brake is used to selectively fix the second gear ring; the third brake is used to selectively fix the third gear ring; and the fourth brake is used to selectively fix the fourth gear ring.

[0011] Preferably, in response to a neutral gear command, the third brake is engaged, and the first and second clutches are disengaged, so that the hydraulic transmission enters a neutral gear operating mode; in the neutral gear, the output shaft is in a freely rotatable belt state.

[0012] Preferably, the step of responding to a brake gear position command and controlling the second and third brakes to engage simultaneously specifically includes: receiving a brake gear position signal from a gear shifter; and, based on the brake gear position signal, sending a control current to the solenoid valve that controls the second and third brakes, thereby controlling the valve core of the solenoid valve to actuate and causing the second and third brakes to engage with oil filling.

[0013] In a second aspect, the present invention provides a control device for a hydraulic transmission, used in the aforementioned brake gear control method for a hydraulic transmission, the control device comprising: The signal receiving module is used to receive gear position commands issued by the gear shifter; The storage module is used to store the solenoid valve control logic corresponding to different gear positions; The control module is used to generate and output a solenoid valve control current for simultaneously controlling the oil filling and engagement of the second and third brakes, based on the control logic stored in the storage module, when the signal receiving module receives a brake gear command.

[0014] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the brake gear control method of the hydraulic transmission as described in any of the preceding claims.

[0015] Fourthly, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the brake gear control method of the hydraulic transmission as described in any of the preceding claims.

[0016] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: The brake gear control method for a hydraulic transmission provided in this application locks all rotating elements of the second and third planetary gear sets by responding to brake gear commands and simultaneously engaging the second and third brakes. This, in turn, mechanically locks the fourth planetary gear set connected to the output shaft, achieving complete lock-up at the output end and fundamentally solving the problem of traditional neutral gear engagement. Simultaneously, the components of the first planetary gear set connected to the input shaft are in a freely rotatable state, allowing power from the input shaft to idle within the first planetary gear set, ensuring power input cutoff. This operating principle is essentially the same as in neutral, without introducing new problems. Therefore, this application can effectively meet the stringent requirements for absolute static output shafts in special scenarios such as oil and gas field equipment, significantly improving the safety and reliability of equipment commissioning. Furthermore, the control method of this application adds a brake gear mode through software, which can be implemented using existing solenoid valves, making control simple, reliable, and easy to integrate and apply in existing electronic control systems. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the hydraulic transmission in this invention.

[0019] Figure 2 This is a simplified diagram of the power transmission system of the hydraulic transmission in the present invention when it is in neutral.

[0020] Figure 3 This is a simplified diagram of the power transmission system of the hydraulic transmission in the present invention when it is in brake gear.

[0021] Figure 4 This is a control flowchart of the present invention.

[0022] Explanation of reference numerals: 1. Turbine; 2. Guide wheel; 3. Pump wheel; 4. Input shaft; 5. First sun gear; 6. First planet gear; 7. First ring gear; 8. First planet carrier; 9. Second ring gear; 10. Second planet gear; 11. Second planet carrier; 12. Second sun gear; 13. Output shaft; 14. Fourth sun gear; 15. Fourth planet gear; 16. Fourth ring gear; 17. Fourth planet carrier; 18. Third planet carrier; 19. Third ring gear; 20. Third planet gear; 21. Third sun gear; P1. First planetary gear set; P2. Second planetary gear set; P3. Third planetary gear set; P4. Fourth planetary gear set; C1. First clutch; C2. Second clutch; C3. First brake; C4. Second brake; C5. Third brake; C6. Fourth brake. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0025] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0026] The hydraulic transmission described in this invention can be widely used in various scenarios requiring precise control of the output shaft state, such as, but not limited to: special operation vehicles such as oil and gas field fracturing trucks, cementing trucks, and coiled tubing workover rigs, as well as construction machinery such as loaders, bulldozers, and excavators, and even certain special ships or industrial transmission systems requiring parking lock functions. The invention will now be described in detail with reference to specific embodiments.

[0027] Example 1: Structure and Brake Gear Control Method of Hydraulic Transmission Reference Figures 1 to 4 This embodiment provides a brake gear control method for a hydraulic transmission. The hydraulic transmission includes a hydraulic torque converter, an input shaft 4, and a planetary gear transmission mechanism composed of multiple planetary gear sets and shift actuators. The hydraulic torque converter includes a turbine 1, a guide wheel 2, and a pump wheel 3. The hydraulic torque converter is conventional prior art and will not be described in detail here.

[0028] In this embodiment, the planetary gear transmission mechanism includes at least four planetary gear sets, which are arranged in the following order from input to output: first planetary gear set P1, second planetary gear set P2, third planetary gear set P3, and fourth planetary gear set P4. The fourth planetary gear set P4 is connected to the output shaft 13 of the transmission.

[0029] Specifically, the structure of each planetary array is as follows: The first planetary gear set P1 includes a first sun gear 5, a first planet gear 6, a first ring gear 7, and a first planet carrier 8. The first planet gear 6 is rotatably mounted on the first planet carrier 8 and meshes with both the first sun gear 5 and the first ring gear 7.

[0030] The second planetary gear set P2 includes a second sun gear 12, a second planet gear 10, a second ring gear 9, and a second planet carrier 11. The second planet gear 10 is rotatably mounted on the second planet carrier 11 and simultaneously meshes with the second sun gear 12 and the second ring gear 9.

[0031] The third planetary gear set P3 includes a third sun gear 21, a third planet gear 20, a third ring gear 19, and a third planet carrier 18. The third planet gear 20 is rotatably mounted on the third planet carrier 18 and meshes with both the third sun gear 21 and the third ring gear 19.

[0032] The fourth planetary gear set P4 includes the fourth sun gear 14, the fourth planet gear 15, the fourth ring gear 16, and the fourth planet carrier 17. The fourth planet gear 15 is rotatably mounted on the fourth planet carrier 17 and meshes with both the fourth sun gear 14 and the fourth ring gear 16.

[0033] To achieve power transmission and gear shifting, specific connections exist between the components of each planetary gear set, and the transmission also contains multiple clutches and brakes. The clutches include a first clutch C1 and a second clutch C2. The brakes include a first brake C3, a second brake C4, a third brake C5, and a fourth brake C6. The connections between the planetary arrays are as follows: The first sun gear 5 is loosely fitted onto the input shaft 4. The second sun gear 12 and the third sun gear 21 are mounted on the input shaft 4 and rotate synchronously with the input shaft 4. The fourth sun gear 14 is mounted on the output shaft 13 and rotates synchronously with the output shaft 13.

[0034] The first planetary carrier 8 and the second gear ring 9 are fixedly connected and rotate as a whole.

[0035] The second planetary carrier 11 is fixedly connected to the third gear ring 19 and rotates as a whole.

[0036] The third planetary carrier 18 is fixedly connected to the output shaft 13 and rotates as a whole.

[0037] The fourth planetary carrier 17 is fixedly connected to the third gear ring 19 and rotates as a whole.

[0038] The functions of the clutch and brake are as follows: First clutch C1: Used to selectively connect input shaft 4 and first sun gear 5. When C1 is engaged, power from input shaft 4 can be transmitted to first sun gear 5.

[0039] The second clutch C2 is used to selectively connect the first sun gear 5 and the second planet carrier 11. When C2 is engaged, the first sun gear 5 and the second planet carrier 11 rotate as a whole.

[0040] First brake C3: Used to selectively lock the first gear ring 7. When C3 is applied, the first gear ring 7 is locked.

[0041] Second brake C4: Used to selectively lock the second gear ring 9. When C4 is applied, the second gear ring 9 is locked.

[0042] Third brake C5: Used to selectively lock the third gear ring 19. When C5 is applied, the third gear ring 19 is locked.

[0043] Fourth brake C6: Used to selectively lock the fourth gear ring 16. When C6 is applied, the fourth gear ring 16 is locked.

[0044] Having described the above structure, the following focuses on the core of the embodiments of the present invention—the brake gear control method. This control method includes the following steps: Step S110: In response to the brake gear command, control the second brake C4 and the third brake C5 to engage simultaneously.

[0045] Specifically, when the operator (e.g., when the vehicle needs to be parked, connected to equipment, or undergoing maintenance) shifts the gearshift to "brake" mode (e.g., a gear marked "B" or a specific symbol on the shift panel), the gearshift generates a brake gear command signal. Upon receiving this command, the transmission's electronic control unit (TCU or ECU) outputs a corresponding control current to the solenoid valves controlling the second brake C4 and the third brake C5, according to preset control logic. This control current drives the solenoid valve spools, altering the hydraulic oil path and causing pressurized oil to simultaneously fill the hydraulic cylinders of brakes C4 and C5, pushing the pistons and engaging the friction plates of C4 and C5, thereby achieving braking.

[0046] Step S120: Lock the second planetary arrangement P2 and the third planetary arrangement P3.

[0047] Because the second brake C4 is engaged, the second gear ring 9 is fixed; the third brake C5 is engaged, fixing the third gear ring 19. Now, analyze the motion states of the second planetary gear set P2 and the third planetary gear set P3: For the second planetary gear set P2, its second sun gear 12 is connected to the input shaft 4 and has an input speed; its second ring gear 9 is fixed; according to the kinematic characteristics of the planetary gear mechanism, the motion state of its second planet carrier 11 is constrained. However, since the input end (sun gear) is still rotating, the second planetary gear set P2 is not completely locked, but will attempt to drive the planet carrier to rotate at a specific speed ratio.

[0048] However, the key connection lies in the fact that the second planetary carrier 11 and the third ring gear 19 are fixedly connected. The third ring gear 19 is now fixed by brake C5. This means that while the second planetary carrier 11 attempts to rotate, the third ring gear 19 it is connected to remains stationary. This contradiction leads to the interlocking of the second planetary gear set P2 and the third planetary gear set P3. Specifically, because the third ring gear 19 is fixed, the movement of the third planetary carrier 18 and the third sun gear 21 is constrained through the component relationships of the third planetary gear set P3. The third sun gear 21, connected to the input shaft 4, also has a tendency to rotate. Ultimately, this state—where the input end (sun gear) has a tendency to rotate while the output end (ring gear or planetary carrier) is braked—makes the entire system composed of P2 and P3 a "dead point," meaning all components (sun gear, planetary carrier, ring gear) are constrained and unable to generate relative motion, thus being completely locked.

[0049] Step S130: Lock the fourth planetary gear P4 via mechanical connection to lock the output shaft 13.

[0050] When the second planetary gear set P2 and the third planetary gear set P3 are locked, the second planetary carrier 11, which is fixedly connected to the third ring gear 19, and the fourth planetary carrier 17, which is also fixedly connected to the third ring gear 19, as well as the components associated with the second planetary carrier 11 and the third ring gear 19 through structural connections, are all locked. More importantly, the fourth planetary carrier 17 is locked. Simultaneously, because the second planetary gear set P2 and the third planetary gear set P3 are locked, their internal sun gears (such as the second sun gear 12 and the third sun gear 21) are also forced to stop rotating. Since the third planetary carrier 18 is fixedly connected to the output shaft 13, the output shaft 13 is also locked. Furthermore, because the fourth planetary carrier 17 is locked, and the fourth sun gear 14, which is fixedly connected to the output shaft 13, is also locked, all components of the fourth planetary gear set P4 (sun gear, planetary carrier, ring gear) cannot rotate, and the fourth planetary gear set P4 itself is also locked. Thus, from P2, P3 to P4, a complete mechanical locking chain is formed, firmly locking the output shaft 13 and preventing it from rotating. This mechanical locking force is much greater than the "pulling" torque caused by the viscosity of the lubricating oil, thus ensuring that the output shaft 13 is absolutely stationary.

[0051] Step S140: The first planetary array P1 is in a freely rotatable state.

[0052] While the second brake C4 and the third brake C5 are engaged, the first clutch C1 and the second clutch C2 are both disengaged. The first sun gear 5 is loosely mounted on the input shaft 4 and is not connected to any power source. The first ring gear 7 is not secured by the first brake C3. Although the first planetary carrier 8 is connected to the second ring gear 9, the second ring gear 9 is secured by the C4 brake. Therefore, for the first planetary gear set P1, its sun gear (first sun gear 5) is idling, the ring gear (first ring gear 7) is free, and the planetary carrier (first planetary carrier 8) is secured. The power from the input shaft 4 (derived from engine idle speed) is directly transmitted to the second sun gear 12 and the third sun gear 21. This power attempts to drive P2 and P3, but since P2 and P3 are locked, the power cannot be transmitted. However, this portion of the power can be "absorbed" by the components of the first planetary gear set P1. Since the sun gear of the first planetary gear set P1 is unloaded and free, the planet carrier is fixed, and the ring gear is free, the entire planetary gear set is in an unrestrained idling state. The rotation of the input shaft 4 will not encounter rigid resistance, thus ensuring that the engine can idle normally and will not stall.

[0053] In summary, this embodiment of the invention, by simultaneously combining brakes C4 and C5 and utilizing the characteristics of a planetary gear mechanism, constructs a mechanical locking path from the input end (through the locked P2 and P3) to the output end P4, achieving rigid locking of the output shaft without shutting off the engine, thus perfectly solving the "neutral gear with displacement" problem. This state is the "brake gear" of this invention.

[0054] In contrast, the conventional neutral gear control method involves engaging only the third brake C5 in response to a neutral gear command, while disengaging the first clutch C1 and the second clutch C2. In this mode, although the power transmission path is cut off, the output shaft 13 is not mechanically locked; due to the viscosity of the lubricating oil, it remains in a freely rotating "discharged state." The brake gear of this invention, by adding the participation of C4, achieves a qualitative leap from "free" to "locked."

[0055] Example 2: Control device for hydraulic transmission Based on the same inventive concept as Embodiment 1, this embodiment provides a control device for a hydraulic transmission. The control device includes: Signal receiving module: This module is connected to the vehicle's gear shifter and is used to receive gear position command signals issued by the driver in real time, such as neutral (N), drive (D), reverse (R) and the brake gear (B) proposed in this invention.

[0056] Storage Module: This module (e.g., non-volatile memory) pre-stores the solenoid valve control logic corresponding to different gear positions. This logic exists in the form of data tables, mappings, or program code, defining which solenoid valves need to be supplied with control current, how much current, and for how long, to achieve a specific gear position. In particular, it stores the specific control logic for achieving the brake gear: that is, simultaneously supplying oil-filled engagement current to the solenoid valves controlling the second brake C4 and the third brake C5.

[0057] Control Module: This module is the core of the control device and is typically composed of a microprocessor (MCU) or a digital signal processor (DSP). When the signal receiving module receives a brake gear command, the control module immediately retrieves the control logic corresponding to the brake gear from the storage module and generates precise solenoid valve control current accordingly. This current is output to the corresponding solenoid valve in the hydraulic valve assembly, driving its valve core to move, thereby precisely controlling the engagement and disengagement of brakes C4 and C5.

[0058] Through the coordinated operation of the above modules, the control device can accurately and reliably execute the brake gear control method described in Embodiment 1, thereby achieving reliable locking of the output shaft.

[0059] Example 3: Computer-readable storage media and electronic devices Another aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon. When executed by a processor, the computer program is capable of implementing the brake gear control method of the hydraulic transmission as described in Embodiment 1. The computer-readable storage medium can be any medium that contains, stores, communicates, propagates, or transmits a program for use by an instruction execution system, apparatus, or device. For example, it can be RAM, ROM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc.

[0060] The present invention also provides an electronic device, such as a TCU in a vehicle. This electronic device includes at least one processor, a memory (i.e., a computer-readable storage medium), and a communication bus. The communication bus is used to enable communication between these components. The memory stores a computer program executable by the processor, which, when executed, performs the method described in Embodiment 1 above.

[0061] In summary, the present invention provides a brake gear control method and device for a hydraulic transmission. By innovatively introducing the concept of a "brake gear" and utilizing the combined control of specific brakes (C4 and C5), it cleverly leverages the inherent characteristics of the planetary gear mechanism to achieve rigid mechanical locking of the transmission output shaft at engine idle speed. This fundamentally solves the long-standing problem of "neutral gear pulling" in the field of hydraulic transmission, significantly improving the safety, reliability, and ease of operation of engineering machinery and special vehicles in parking, maintenance, and equipment docking conditions. It has high practical value and broad application prospects.

[0062] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A brake gear control method for a hydraulic transmission, the hydraulic transmission comprising an input shaft (4), a planetary gear set, and multiple brakes, characterized in that: The planetary gear set includes at least a first planetary gear set (P1), a second planetary gear set (P2), a third planetary gear set (P3), and a fourth planetary gear set (P4), wherein the fourth planetary gear set (P4) is connected to the output shaft (13) of the transmission; the plurality of brakes includes at least a second brake (C4) and a third brake (C5); the control method includes: In response to a brake gear command, the second brake (C4) and the third brake (C5) are simultaneously engaged to engage the hydraulic transmission in brake gear. In the brake position, the sun gear, planet carrier, and ring gear of the second planetary gear set (P2) and the third planetary gear set (P3) are locked, thereby locking the sun gear, planet carrier, and ring gear of the fourth planetary gear set (P4) through mechanical connection, so as to lock the output shaft (13). Meanwhile, the sun gear, planet carrier, and ring gear of the first planetary gear set (P1) are in a freely rotatable state to allow the power from the input shaft (4) to idle inside the first planetary gear set (P1).

2. The brake gear control method for a hydraulic transmission according to claim 1, characterized in that: The first planetary gear set (P1) includes a first sun gear (5), a first planet gear (6), a first ring gear (7), and a first planet carrier (8); the first planet gear (6) meshes with the first sun gear (5) and the first ring gear (7); the first planet carrier (8) supports the first planet gear (6); The second planetary gear set (P2) includes a second sun gear (12), a second planet gear (10), a second ring gear (9), and a second planet carrier (11); the second planet gear (10) meshes with the second sun gear (12) and the second ring gear (9), and the second planet carrier (11) supports the second planet gear (10). The third planetary gear set (P3) includes a third sun gear (21), a third planet gear (20), a third ring gear (19), and a third planet carrier (18); the third planet gear (20) meshes with the third sun gear (21) and the third ring gear (19), and the third planet carrier (18) supports the third planet gear (20). The fourth planetary gear set (P4) includes a fourth sun gear (14), a fourth planet gear (15), a fourth ring gear (16), and a fourth planet carrier (17); the fourth planet gear (15) meshes with the fourth sun gear (14) and the fourth ring gear (16), and the fourth planet carrier (17) supports the fourth planet gear (15).

3. The brake gear control method for a hydraulic transmission according to claim 2, characterized in that: The first sun gear (5) is loosely fitted on the input shaft (4), the second sun gear (12) and the third sun gear (21) are mounted on the input shaft (4), and the fourth sun gear (14) is mounted on the output shaft (13); The first planetary carrier (8) is fixedly connected to the second gear ring (9); The second planetary carrier (11) is fixedly connected to the third gear ring (19); The third planetary carrier (18) is fixedly connected to the output shaft (13); The fourth planetary carrier (17) is fixedly connected to the third gear ring (19).

4. The brake gear control method for a hydraulic transmission according to claim 3, characterized in that: The hydraulic transmission also includes a first clutch (C1) and a second clutch (C2). The first clutch (C1) is used to selectively connect the input shaft to the first sun gear (5); The second clutch (C2) is used to selectively connect the first sun gear (5) to the second planet carrier (11).

5. The brake gear control method for a hydraulic transmission according to claim 4, characterized in that: The hydraulic transmission also includes a first brake (C3) and a fourth brake (C6). The first brake (C3) is used to selectively fix the first gear ring (7); The second brake (C4) is used to selectively fix the second gear ring (9); The third brake (C5) is used to selectively fix the third gear ring (19). The fourth brake (C6) is used to selectively fix the fourth gear ring (16).

6. The brake gear control method for a hydraulic transmission according to claim 5, characterized in that: In response to the neutral gear command, the third brake (C5) is engaged, and the first clutch (C1) and the second clutch (C2) are disengaged, so that the hydraulic transmission enters the neutral gear operating mode. In the neutral position, the output shaft (13) is in a freely rotatable belt state.

7. The brake gear control method for a hydraulic transmission according to claim 1, characterized in that: The control of simultaneously engaging the second brake (C4) and the third brake (C5) in response to a brake gear command specifically includes: Receives the brake gear position signal from the gear shifter; According to the brake gear position signal, a control current is sent to the solenoid valve that controls the second brake (C4) and the third brake (C5) to control the valve core of the solenoid valve to move, so that the second brake (C4) and the third brake (C5) are filled with oil and engaged.

8. A control device for a hydraulic transmission, used to execute the brake gear control method of the hydraulic transmission according to any one of claims 1 to 7, characterized in that, The control device includes: The signal receiving module is used to receive gear position commands issued by the gear shifter; The storage module is used to store the solenoid valve control logic corresponding to different gear positions; The control module is used to generate and output a solenoid valve control current for simultaneously controlling the oil filling of the second brake (C4) and the third brake (C5) according to the control logic stored in the storage module when the signal receiving module receives the brake gear command.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the brake gear control method of the hydraulic transmission as described in any one of claims 1 to 7.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the brake gear control method of the hydraulic transmission as described in any one of claims 1 to 7.

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