Power takeoff and gear engaging and braking sequence control method thereof

Abstract

A power takeoff and a gear engaging and braking sequence control method thereof belong to the technical field of power takeoffs, the power takeoff comprises an output shaft rotatably arranged in a box body, the output shaft is provided with a gear and a gear ring, a clutch friction plate set is arranged between the gear and the gear ring, a gear engaging piston is slidably arranged in an inner cavity of the gear ring, and the gear engaging piston is connected with the gear ring. The side, away from the gear engaging piston, of the gear ring is movably connected with a pressing disc, and a brake pad is arranged between the gear ring and the pressing disc. A first oil channel is formed in the output shaft, a first oil cavity is formed between the gear ring and the output shaft, a third oil cavity is formed between the pressing disc and the gear ring, a second oil cavity is formed between the gear engaging piston and the gear ring, the first oil channel is communicated with the third oil cavity through the first oil cavity, a first boss is fixedly arranged on the pressing disc, and a first through hole is formed in the gear ring. The first boss is movably connected with the first through hole so as to control connection and disconnection of the third oil cavity and the second oil cavity. The sequence of brake releasing and gear engaging is achieved through mechanical sequential control over on-off of an oil duct, and constraint is not conducted any more depending on the elastic force of a spring.

Description

Technical Field

[0001] This invention relates to the field of power take-off (PTO) technology, and in particular to a PTO and a method for controlling the gear engagement and braking sequence. Background Technology

[0002] Special-purpose vehicles typically use power take-offs (PTOs) to extract power from the engine or transmission, enabling the vehicle to operate in specific applications. For some special applications, the PTO is used while the vehicle is in motion, requiring it to engage and disengage during driving. This generally employs a friction pad structure, necessitating additional brake pads for braking. When shifting gears, it is crucial to disengage the brakes before the friction pads transmit torque to avoid damaging them.

[0003] A power take-off (PTO) with braking function has been developed (publication number CN110645290B). The output shaft has an axial medium channel along the axis. A first medium chamber is provided between the inner piston and the bottom of the cylinder body, and a second medium chamber is provided between the cylinder body and the outer piston. When the PTO is working, the medium enters the first medium chamber between the cylinder body and the inner piston through the axial medium channel. A portion of the medium enters the second medium chamber between the outer piston and the cylinder body through the cylinder body's axial medium channel. The outer piston is pushed and moves axially until it abuts against the snap ring, causing the brake disc to be in a floating state and not to have a braking effect.

[0004] In existing power take-off units with braking function, the medium enters the first medium chamber and the second medium chamber simultaneously. In order to ensure that the braking can be released first when shifting gears, the spring force used to push the outer piston needs to be less than the spring force used to push the inner piston. However, this limitation of the spring forces on both sides of the inner and outer pistons severely limits the upper limit of the braking force. Summary of the Invention

[0005] To address the technical problem in the prior art where existing power take-offs with braking functions require the spring force used to push the outer piston to be less than the spring force used to push the inner piston in order to ensure that the brake can be released first, thus severely limiting the upper limit of braking force, this invention provides a power take-off and its gear engagement and braking sequence control method.

[0006] The technical solution of this invention is as follows: This invention provides a power take-off (PTO) device, including a housing, an output shaft rotatably mounted inside the housing, a gear rotatably mounted on the output shaft, a gear ring fixedly mounted on the output shaft, a clutch friction plate assembly between the gear and the gear ring, a shift piston slidably mounted in the inner cavity of the gear ring, the shift piston is used to cooperate with the clutch friction plate assembly, a pressure plate is movably connected to the side of the gear ring away from the shift piston, a brake plate is mounted between the gear ring and the pressure plate, and elastic clamping members are mounted on the sides of the pressure plate and the shift piston that are far apart from each other. The output shaft is provided with a first oil passage, the gear ring is provided with a first oil chamber between the output shaft and the gear ring, the pressure plate is provided with a third oil chamber between the gear ring and the gear ring, and the shift piston is provided with a second oil chamber between the gear ring and the gear ring. The first oil passage is connected to the third oil chamber through the first oil chamber. The pressure plate is fixedly provided with a first boss, and the gear ring is provided with a first through hole. The first boss is movably connected to the first through hole to control the opening and closing of the third oil chamber and the second oil chamber.

[0007] High-pressure oil first enters the third oil chamber through the first oil passage and the first oil chamber, pushing the pressure plate to move and disengage the brake pads to release the brake. During this process, the first protrusion opens the first through hole as the pressure plate moves, and the third oil chamber then connects with the second oil chamber. The high-pressure oil then pushes the shift piston to complete the shifting. The sequence of brake release and shifting is controlled by the mechanical timing of the oil passage opening and closing, no longer relying on the elastic force of the elastic clamping component for constraint. The elastic force of the elastic clamping component can be set only according to the braking force requirement, which can effectively increase the upper limit of braking force and ensure that the power take-off can still provide reliable braking under heavy load conditions.

[0008] Preferably, a plurality of first bosses are provided and are spaced apart along the circumferential direction of the pressure plate. A plurality of first through holes are provided on the gear ring. The inner diameter of the first through holes is the same as the outer diameter of the first bosses. A fourth oil passage is provided on the first bosses. The fourth oil passage is used to connect the third oil cavity with the first through holes. A third oil passage is provided on the gear ring. The first oil cavity is connected to the third oil cavity through the third oil passage.

[0009] Multiple circumferentially spaced first bosses cooperate with the first through holes to provide precise guidance for the axial movement of the pressure plate, preventing pressure plate misalignment from causing oil passage failure. The cooperation between the fourth and third oil passages ensures that high-pressure oil first acts on the third oil chamber to push the pressure plate to complete the brake release. Only when the first boss drives the fourth oil passage to move out of the first through hole is it stably connected, ensuring the orderly connection between brake release and gear engagement, and improving the stability of the power take-off.

[0010] Preferably, the gear ring has a pressure relief hole that communicates with the second oil chamber. The inner diameter of the pressure relief hole is smaller than that of the first through hole. The pressure relief hole provides a dedicated pressure relief path for the second oil chamber, which can quickly release the pressure in the second oil chamber when disengaging from gear, allowing the shift piston to reset in time. The smaller inner diameter and fewer holes than the first through hole design can reduce the amount of high-pressure oil lost through the pressure relief hole when shifting gears, ensuring that sufficient pressure to push the shift piston can be quickly built up in the second oil chamber. This balances pressure relief efficiency and shifting pressure requirements, ensuring timely action transition.

[0011] Preferably, a first spline is formed on the outer wall of the gear, and a second spline is formed on the inner wall of the gear ring. The clutch friction plate assembly includes several alternately arranged steel plates and friction plates. The friction plates mesh inward with the first spline, and the steel plates mesh outward with the second spline. The spline connection enables rigid transmission between the friction plates and the gear, and between the steel plates and the gear ring, avoiding slippage during power transmission. The alternately arranged steel plates and friction plates can form a uniform and sufficient friction force under the pressing action of the shift piston, enabling the gear power to be stably transmitted to the gear ring and the output shaft, improving the power transmission efficiency and load-bearing capacity of the PTO, and adapting to heavy-duty working scenarios.

[0012] Preferably, the gear and the output shaft are rotatably connected via a first bearing. A second oil passage is provided on the output shaft along its axial direction to deliver lubricating oil to the first bearing and the clutch friction plate assembly. The first bearing effectively reduces rotational friction between the gear and the output shaft, reducing energy loss. The lubricating oil delivered by the second oil passage lubricates and cools the first bearing, extending its service life. Simultaneously, the lubricating oil can penetrate into the gaps of the clutch friction plate assembly, reducing wear between the steel plates and the friction plates, improving the durability of the clutch friction plate assembly, and ensuring the long-term stable operation of the power take-off unit.

[0013] Preferably, the housing is fixedly connected to an output end cover, one end of the output shaft is rotatably connected to the housing via a second bearing, and the other end of the output shaft is rotatably connected to the output end cover via a third bearing. The output end cover enhances the overall structural strength of the housing, and the second and third bearings provide end support for the output shaft, effectively suppressing radial runout during shaft rotation, ensuring the matching accuracy between the gears, gear rings, and clutch friction plate assembly, avoiding component collisions or wear caused by shaft wobbling, and improving the smoothness of the power take-off operation.

[0014] Preferably, the elastic clamping component includes a first spring and a second spring. The first spring is located on the side of the pressure plate away from the gear shift piston, and the second spring is located on the side of the gear shift piston away from the pressure plate. The first spring and the second spring are independently configured and act on the pressure plate and the gear shift piston respectively. The first spring can be designed with sufficient elasticity to ensure braking force according to braking requirements, while the second spring only needs to meet the reset requirement of the gear shift piston. The two do not need to restrict each other, which can ensure both the clamping force of the pressure plate on the brake pads during braking and the reliability of the gear shift piston reset.

[0015] A method for controlling the gear shifting and braking sequence includes: When shifting gears, high-pressure oil sequentially flows through the first oil passage, the first oil chamber, and the third oil passage into the third oil chamber, pushing the pressure plate away from the gear ring to disengage the brake pads and release the brake. At this time, the first boss moves outward, the fourth oil passage opens, and the high-pressure oil in the third oil chamber enters the second oil chamber through the first through hole, pushing the shifting piston towards the clutch friction plate assembly to press the clutch friction plate assembly, allowing gear power to be transmitted to the gear ring and output shaft through the clutch friction plate assembly. During shifting, the high-pressure oil acts step by step according to a preset path, first concentrating its force to push the pressure plate to release the brake, and only after the brake is completely released does it push the shifting piston through the opened oil passage. The entire sequence of actions is naturally formed by the mechanical structure of opening and closing the oil passages, without the need for constraint by the size of the spring force. The first spring can be designed with a larger force to increase the braking force, while also avoiding component damage caused by the brake not being released during shifting, thus improving operational safety.

[0016] Preferably, when disengaging from gear, the hydraulic fluid in the first oil passage is cut off, the hydraulic oil in the second oil chamber is depressurized through the pressure relief hole, and simultaneously the hydraulic oil in the second oil chamber flows back into the third oil chamber. The engagement piston resets under the pressure of the second spring. Then, the first spring pushes the pressure plate to reset, causing the pressure plate to press against the brake pads, while simultaneously blocking the fourth oil passage. When disengaging from gear, the pressure in the second oil chamber is first released through the pressure relief hole, allowing the engagement piston to reset first and achieve power separation. Then, the first spring pushes the pressure plate to reset and complete the braking. The sequence of actions is clear and the connection is smooth. Blocking the fourth oil passage when the pressure plate resets prevents hydraulic fluid from accidentally entering the second oil chamber during subsequent operations, ensuring the stability of the braking state after disengaging from gear and avoiding unexpected power transmission.

[0017] Preferably, in the disengaged state, the engagement piston is pressed against the gear ring under the action of the second spring, the steel plates of the clutch friction plate assembly are separated from the friction force, and the gear can rotate freely through the first bearing without power transmission to the gear ring and output shaft. After disengaging, the engagement piston remains pressed against the gear ring under the action of the second spring, ensuring complete disengagement of the clutch friction plate assembly and avoiding power mistransmission caused by residual friction. The free rotation of the gear through the first bearing reduces friction loss under no-load conditions, lowering energy consumption. At the same time, the absence of power transmission to the output shaft ensures the safety of the power take-off unit in the non-operating state.

[0018] As can be seen from the above technical solutions, the advantages of the present invention are: 1. High-pressure oil first enters the third oil chamber through the first oil passage and the first oil chamber, pushing the pressure plate to move and disengage the brake pads to release the brake. During this process, the first boss moves with the pressure plate and opens the first through hole, allowing the third oil chamber to connect with the second oil chamber. The high-pressure oil then pushes the shift piston to complete the shifting. The sequence of brake release and shifting is controlled by the mechanical timing of the oil passage opening and closing, no longer relying on the elastic force of the elastic clamping component for constraint. The elastic force of the elastic clamping component can be set only according to the braking force requirements, which can effectively increase the upper limit of braking force and ensure that the power take-off can still provide reliable braking under heavy load conditions.

[0019] 2. A pressure relief hole is provided on the gear ring, which provides a dedicated pressure relief path for the second oil chamber. It can quickly release the pressure in the second oil chamber when disengaging from gear, so that the engagement piston can be reset in time. This allows the torque transmission to be disengaged first, and then the braking to be activated, which improves the service life of the power take-off. The smaller inner diameter and fewer through holes than the first one can reduce the amount of high-pressure oil lost through the pressure relief hole when engaging gear, ensuring that the second oil chamber can quickly build up enough pressure to push the engagement piston. It balances pressure relief efficiency and engagement pressure requirements, ensuring timely action transition. Attached Figure Description

[0020] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a structural schematic diagram of the power take-off (PTO) in the disengaged state according to one or more embodiments of the present invention; Figure 2 This is a structural schematic diagram of the power take-off (PTO) in gear according to one or more embodiments of the present invention; The components represented by the various reference numerals in the diagram are: 1. Box body; 2. Output end cover; 3. Gear; 31. First spline; 4. Output shaft; 41. First oil passage; 411. First oil port; 42. Second oil passage; 5. Gear ring; 51. Second spline; 52. First sealing ring; 53. Second sealing ring; 54. Third sealing ring; 55. Third oil passage; 56. First oil chamber; 57. First snap ring; 58. First through hole; 59. Second oil chamber; 510. Pressure relief hole; 6. Gear shift piston; 61. Fourth sealing ring; 7. Braking assembly; 71. Pressure plate; 711. First boss; 712. Fifth sealing ring; 713. Sixth sealing ring; 714. Third oil chamber; 715. Fourth oil passage; 72. First spring; 73. Second retaining ring; 74. Brake pad; 8. Clutch friction plate assembly; 9. Third retaining ring; 91. First retaining ring; 10. Second retaining ring; 11. Second spring; 12. First bearing; 13. Second bearing; 14. Third bearing. Detailed Implementation

[0022] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this patent, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this patent.

[0023] Example 1 In a typical embodiment of the present invention, such as Figures 1-2 As shown, a power take-off (PTO) is proposed, comprising: a housing 1, a gear 3, an output shaft 4, a gear ring 5, a shift piston 6, a braking assembly 7, and a clutch friction plate assembly 8. The output shaft 4 is rotatably mounted inside the housing 1, the gear 3 is rotatably mounted on the output shaft 4, the gear ring 5 is fixedly mounted on the output shaft 4, the clutch friction plate assembly 8 is located between the gear 3 and the gear ring 5, the shift piston 6 is sleeved on the output shaft 4, and the shift piston 6 is movably mounted in the inner cavity of the gear ring 5. The shift piston 6 is used to cooperate with the clutch friction plate assembly 8. The braking assembly 7 includes a pressure plate 71 and brake pads 74. The pressure plate 71 is movably mounted on the outer side of the gear ring 5 (the side of the gear ring 5 away from the clutch friction plate assembly 8), and the brake pads 74 are located between the gear ring 5 and the pressure plate 71. Elastic clamping elements are provided on the sides of the pressure plate 71 and the shift piston 6 that are far apart from each other. A first oil passage 41 is provided axially on the output shaft 4. The gear ring 5 and the output shaft 4... A first oil chamber 56 is provided between the pressure plate 71 and the gear ring 5, a third oil chamber 714 is provided between the pressure plate 71 and the gear ring 5, and a second oil chamber 59 is provided between the gear shift piston 6 and the gear ring 5. The first oil passage 41 is connected to the third oil chamber 714 through the first oil chamber 56. A first boss 711 is fixedly provided on the pressure plate 71, and a first through hole 58 is provided on the gear ring 5. The first boss 711 is movably disposed in the first through hole 58 so as to control the opening and closing of the first through hole 58 through the first boss 711, thereby controlling the opening and closing of the third oil chamber 714 and the second oil chamber 59. Thus, when shifting gears, the third oil chamber 714 and the second oil chamber 59 flow into the medium in sequence, thereby realizing the control of first disengaging the brake and then transmitting torque to the friction plate, so as to avoid damaging the friction plate. There is no need to consider the elastic force relationship between the elastic pressing members on both sides of the pressure plate 71 and the gear shift piston 6 that are far apart from each other, which can maximize the braking force.

[0024] Specifically, the braking assembly 7 is mounted on the gear ring 5. A first boss 711 is fixedly mounted on the side wall of the pressure plate 71 near the gear ring 5. Several first bosses 711 are provided and spaced circumferentially along the pressure plate 71. The first bosses 711 can move axially along the output shaft 4 with the pressure plate 71. Several first through holes 58 are provided on the gear ring 5. The number of first through holes 58 is the same as the number of first bosses 711 and they correspond one-to-one. The inner diameter of the first through hole 58 is the same as the outer diameter of the first boss 711, so that a seal is achieved between the first through hole 58 and the first boss 711 through surface contact, thereby isolating the third oil chamber 714 from the second oil chamber 59. The first boss 711 has... The fourth oil passage 715 includes a horizontal section arranged along the axial direction and a vertical section arranged along the radial direction. The horizontal section and the vertical section are connected. When the first boss 711 moves outward, the medium in the third oil chamber 714 can enter the horizontal section through the vertical section, and then flow into the second oil chamber 59 through the first through hole 58 to push the shift piston 6, so that the shift piston 6 contacts the clutch friction plate assembly 8. When the first boss 711 moves into the first through hole 58, the inner wall of the first through hole 58 blocks the vertical section of the fourth oil passage 715 to isolate the third oil chamber 714 from the second oil chamber 59. The shift piston 6 separates from the clutch friction plate assembly 8 under the action of the elastic clamping member.

[0025] A third oil cavity 714 is provided between the gear ring 5 and the pressure plate 71. Specifically, an annular groove is provided on the side wall of the gear ring 5. The middle part of the pressure plate 71 protrudes outward and is slidably disposed in the groove. A fifth sealing ring 712 and a sixth sealing ring 713 are installed between the two sides of the middle protrusion of the pressure plate 71 and the groove of the gear ring 5. Both the fifth sealing ring 712 and the sixth sealing ring 713 are O-rings to play a sealing role. The third oil cavity 714 is located in the groove. The brake pad 74 is disposed between the pressure plate 71 and the gear ring 5. The brake pad 74 is located outside the groove. The output end cover 2 restricts the circumferential rotation of the brake pad 74. The output end cover 2 is fixedly connected to the housing 1.

[0026] The elastic clamping component includes a first spring 72 and a second spring 11. The first spring 72 is located on the side of the pressure plate 71 away from the gear piston 6. The first spring 72 is sleeved on the gear ring 5. One end of the first spring 72 abuts against the pressure plate 71, and the other end of the first spring 72 abuts against the second snap ring 73. The second snap ring 73 is fixedly installed on the gear ring 5 to push the pressure plate 71 to press the brake pad 74, thereby preventing the gear ring 5 and the output shaft 4 from rotating around the axis by friction.

[0027] A third retaining ring 9, a first retaining ring 91, and a second retaining ring 10 are fixedly mounted on the output shaft 4. The third retaining ring 9 is located between the first retaining ring 91 and the second retaining ring 10 to limit the position of the first retaining ring 91 and the second retaining ring 10. The second retaining ring 10 is located on the side of the gear engagement piston 6 away from the pressure plate 71. The second spring 11 is located between the second retaining ring 10 and the gear engagement piston 6. The second spring 11 is used to press the gear engagement piston 6 and the gear ring 5 together. The first retaining ring 91 is located on both sides of the gear 3 to limit the axial movement of the gear 3.

[0028] The output shaft 4 has a first oil port 411, which is connected to the first oil passage 41 and penetrates the side wall of the output shaft 4. The first oil passage 41 is connected to the first oil cavity 56 through the first oil port 411. The gear ring 5 and the outer wall of the output shaft 4 are provided with the first oil cavity 56. The two sides of the first oil cavity 56 are fixedly provided with a second sealing ring 53 and a third sealing ring 54 to seal the gear ring 5 and the output shaft 4 and prevent the medium in the first oil cavity 56 from flowing out from the gap between the gear ring 5 and the output shaft 4. The gear ring 5 has a third oil passage 55, which is connected to the third oil cavity 714 through the third oil passage 55. The medium in the first oil cavity 56 can flow into the third oil cavity 714 through the third oil passage 55.

[0029] The shift piston 6 is slidably mounted on the output shaft 4, and the shift piston 6 is located on the side of the gear ring 5 away from the pressure plate 71. A second oil chamber 59 is provided between the shift piston 6 and the gear ring 5. A first through hole 58 is provided on the gear ring 5. The second oil chamber 59 is connected to the third oil chamber 714 through the first through hole 58. A first sealing ring 52 is provided between the shift piston 6 and the gear ring 5. A fourth sealing ring 61 is provided between the shift piston 6 and the output shaft 4. The second sealing ring 53 and the third sealing ring 54 between the gear ring 5 and the output shaft 4 are used to seal the second oil chamber 59 and prevent the medium in the second oil chamber 59 from flowing out from the gap between the gear ring 5, the shift piston 6 and the output shaft 4.

[0030] A pressure relief hole 510 is provided on the gear ring 5. The pressure relief hole 510 is connected to the second oil chamber 59. The pressure relief hole 510 is normally open, and the inner diameter of the pressure relief hole 510 is much smaller than the first through hole 58. There is one pressure relief hole 510 and several first through holes 58. In this embodiment, there are four first through holes 58, which can ensure that the hydraulic oil in the second oil chamber 59 has sufficient pressure to push the gear shift piston 6. When the gear is disengaged, the hydraulic oil in the second oil chamber 59 is discharged through the pressure relief hole 510, so that the elastic force of the first spring 72 does not need to be set to be less than the elastic force of the second spring 11.

[0031] A first spline 31 is provided on the outer wall of the gear 3, and a second spline 51 is provided on the inner wall of the gear ring 5. The clutch friction plate assembly 8 is disposed between the first spline 31 and the second spline 51. A first retaining spring 57 is provided on the side of the clutch friction plate assembly 8 away from the gear shift piston 6. The first retaining spring 57 is fixedly disposed on the gear ring 5 to limit the clutch friction plate assembly 8.

[0032] The clutch friction plate assembly 8 consists of several alternately arranged steel plates and friction plates. The friction plates mesh inward with the first spline 31, and the steel plates mesh outward with the second spline 51. When the shift piston 6 presses the clutch friction plate assembly 8, the power is transmitted from the gear 3 to the gear ring 5 through the friction between the steel plates and the friction plates.

[0033] The gear 3 is rotatably connected to the output shaft 4 via the first bearing 12. The output shaft 4 is also provided with a second oil passage 42 and a second oil port along its axial direction. The second oil passage 42 is used to transport lubricating oil, which is then discharged outward through the second oil port to lubricate the first bearing 12 and the clutch friction plate assembly 8.

[0034] The housing 1 is fixedly connected to the output end cover 2. One end of the output shaft 4 is rotatably connected to the housing 1 through the second bearing 13, and the other end of the output shaft 4 is rotatably connected to the output end cover 2 through the third bearing 14, so as to achieve support and limit of the output shaft 4.

[0035] Example 2 In another typical embodiment of the present invention, a method for controlling the gear shifting and braking sequence is proposed, which uses the power take-off unit mentioned in Example 1. The method for controlling the gear shifting and braking sequence includes: like Figure 1 As shown, in the disengaged state, the first oil passage 41 is not supplied with high-pressure oil. Under the action of the second spring 11, the shift piston 6 is located at the right end and close to the inner wall of the gear ring 5, so that the shift piston 6 does not exert force on the clutch friction plate assembly 8. The steel plates of the clutch friction plate assembly 8 are separated from the friction force, and the gear 3 can rotate freely through the first bearing 12. Power cannot be transmitted to the gear ring 5 and the output shaft 4. The first spring 72 pushes the pressure plate 71 to move towards the gear ring 5 and presses the brake plate 74 to prevent the rotation of the gear ring 5. At the same time, the first boss 711 is located in the first through hole 58, blocking the fourth oil passage 715, thereby isolating the second oil chamber 59 from the third oil chamber 714. like Figure 2As shown, when shifting gears, high-pressure oil enters the first oil chamber 56 through the first oil passage 41 and the first oil port 411. The high-pressure oil in the first oil chamber 56 enters the third oil chamber 714 through the third oil passage 55, which pushes the pressure plate 71 to move away from the gear ring 5, overcoming the pressure of the first spring 72, so as to disengage from the brake pad 74 and release the brake. At this time, the first boss 711 moves outward, so that the fourth oil passage 715 on the first boss 711 opens. The high-pressure oil in the third oil chamber 714 flows into the first through hole 58 and enters the second oil chamber 59 through the first through hole 58, which pushes the shifting piston 6 to move towards the clutch friction plate group 8, overcoming the pressure of the second spring 11, so as to press the clutch friction plate group 8, so that the power of the gear 3 is transmitted to the gear ring 5 through the clutch friction plate group 8, and then to the output shaft 4. When the gear is disengaged, the oil flow in the first oil passage 41 is interrupted, the pressure drops, and the shift piston 6 resets under the pressure of the second spring 11, causing the shift piston 6 to re-engage with the gear ring 5. The hydraulic oil in the second oil chamber 59 is discharged outward through the pressure relief hole 510 and flows back to the oil source. At the same time, the hydraulic oil in the second oil chamber 59 flows back to the third oil chamber 714, realizing the rapid reset of the shift piston 6. The first spring 72 pushes the pressure plate 71 to reset, causing the pressure plate 71 to press the brake pad 74, preventing the gear ring 5 from rotating, and blocking the fourth oil passage 715. The oil in the third oil chamber 714 flows back to the first oil passage 41 through the first oil chamber 56.

[0036] It can effectively ensure that the brake is disengaged first when shifting gears, and then the gear is shifted to transmit torque; when disengaging gears, since the pressure relief hole 510 is normally open, oil will be discharged first, thus realizing the disengagement of gear shifting and transmission of torque before the brake is activated, which improves the service life of the power take-off unit.

[0037] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power take-off (PTO), comprising: The housing (1) has an output shaft (4) rotatably mounted inside the housing (1) and a gear (3) rotatably mounted on the output shaft (4). The output shaft (4) is characterized by having a gear ring (5) fixedly mounted on the output shaft (4), a clutch friction plate assembly (8) between the gear (3) and the gear ring (5), a shift piston (6) slidably mounted in the inner cavity of the gear ring (5), the shift piston (6) being used to cooperate with the clutch friction plate assembly (8), a pressure plate (71) being movably connected to the side of the gear ring (5) away from the shift piston (6), a brake plate (74) being mounted between the gear ring (5) and the pressure plate (71), and elastic clamping members being mounted on the sides of the pressure plate (71) and the shift piston (6) that are far apart from each other. The output shaft (4) is provided with a first oil passage (41), the gear ring (5) is provided with a first oil chamber (56) between the output shaft (4), the pressure plate (71) is provided with a third oil chamber (714) between the gear ring (5), and the shift piston (6) is provided with a second oil chamber (59) between the gear ring (5). The first oil passage (41) is connected to the third oil chamber (714) through the first oil chamber (56). The pressure plate (71) is fixedly provided with a first boss (711), and the gear ring (5) is provided with a first through hole (58). The first boss (711) is movably connected to the first through hole (58) to control the opening and closing of the third oil chamber (714) and the second oil chamber (59).

2. The power take-off device according to claim 1, characterized in that, The first boss (711) is provided with several and is arranged circumferentially along the pressure plate (71). The gear ring (5) is provided with several first through holes (58). The inner diameter of the first through hole (58) is the same as the outer diameter of the first boss (711). The first boss (711) is provided with a fourth oil passage (715). The fourth oil passage (715) is used to connect the third oil cavity (714) with the first through hole (58). The gear ring (5) is provided with a third oil passage (55). The first oil cavity (56) is connected to the third oil cavity (714) through the third oil passage (55).

3. The power take-off device according to claim 2, characterized in that, A pressure relief hole (510) is provided on the gear ring (5). The pressure relief hole (510) is connected to the second oil chamber (59). The inner diameter of the pressure relief hole (510) is smaller than that of the first through hole (58).

4. The power take-off device according to claim 1, characterized in that, The gear (3) has a first spline (31) on its outer wall and a second spline (51) on its inner wall. The clutch friction plate group (8) includes several alternately arranged steel plates and friction plates. The friction plates mesh inward with the first spline (31) and the steel plates mesh outward with the second spline (51).

5. The power take-off device according to claim 1, characterized in that, The gear (3) is rotatably connected to the output shaft (4) via the first bearing (12). The output shaft (4) is provided with a second oil passage (42) along its axial direction. The second oil passage (42) is used to deliver lubricating oil to the first bearing (12) and the clutch friction plate assembly (8).

6. The power take-off device according to claim 1, characterized in that, The housing (1) is fixedly connected to the output end cover (2). One end of the output shaft (4) is rotatably connected to the housing (1) through the second bearing (13), and the other end of the output shaft (4) is rotatably connected to the output end cover (2) through the third bearing (14).

7. The power take-off device according to claim 1, characterized in that, The elastic clamping component includes a first spring (72) and a second spring (11). The first spring (72) is located on the side of the pressure plate (71) away from the gear shift piston (6), and the second spring (11) is located on the side of the gear shift piston (6) away from the pressure plate (71).

8. A method for controlling the sequence of gear shifting and braking, characterized in that, The power take-off unit adopted as described in any one of claims 1-7 includes: When shifting gears, high-pressure oil passes through the first oil passage (41), the first oil chamber (56), and the third oil passage (55) in sequence to enter the third oil chamber (714), pushing the pressure plate (71) to move away from the gear ring (5) to disengage from the brake pad (74) and release the brake. At this time, the first boss (711) moves outward, the fourth oil passage (715) opens, and the high-pressure oil in the third oil chamber (714) enters the second oil chamber (59) through the first through hole (58), pushing the shifting piston (6) to move towards the clutch friction plate group (8) to press the clutch friction plate group (8), so that the power of the gear (3) is transmitted to the gear ring (5) and the output shaft (4) through the clutch friction plate group (8).

9. The gear shifting and braking sequence control method according to claim 8, characterized in that, When the gear is disengaged, the oil in the first oil passage (41) is cut off, the hydraulic oil in the second oil chamber (59) is depressurized through the pressure relief hole (510), and at the same time the hydraulic oil in the second oil chamber (59) flows back into the third oil chamber (714). The gear engagement piston (6) is reset under the pressure of the second spring (11); then the first spring (72) pushes the pressure plate (71) to reset, so that the pressure plate (71) presses the brake pad (74) and blocks the fourth oil passage (715).

10. The gear shifting and braking sequence control method according to claim 9, characterized in that, In the disengaged state, the engagement piston (6) is pressed against the gear ring (5) by the action of the second spring (11), the steel plates of the clutch friction plate group (8) are separated from the friction force, and the gear (3) can rotate freely through the first bearing (12), without power transmission to the gear ring (5) and the output shaft (4).

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