Coaxial hydraulic backflow automatic transmission and gear shifting method thereof

Abstract

The invention discloses a coaxial type hydraulic backflow automatic transmission, which relates to the field of transmission equipment and comprises a hydraulic mechanical composite transmission device and a gear shifting and speed regulating device according to the transmission sequence of power flow. Different from a traditional hydraulic mechanical continuously variable transmission, the hydraulic backflow automatic transmission takes a backflow transmission mode of a hydraulic mechanical composite transmission system as a main load operation mode, and can effectively prevent an engine from stalling while realizing low-speed torque increasing; the device is suitable for road and non-road engineering vehicles with complex working conditions and large load fluctuation, such as loaders, bulldozers, heavy transport vehicles and the like; the system has excellent efficiency characteristics, and can effectively make up for the defects of low transmission efficiency, narrow high-efficiency area, high assembly precision and the like of the existing hydraulic mechanical transmission system; a double-shaft concentric arrangement method is adopted, the space utilization rate is improved to the maximum extent, the chassis adaptability is high, and serialization can be achieved easily.

Description

Technical Field

[0001] The invention relates to the technical field of engineering machinery equipment, and in particular to a coaxial hydraulic reflux automatic transmission and a shifting method thereof. Background Art

[0002] As a classic transmission system, the hydromechanical transmission system has transmission characteristics such as low-speed torque increase, buffer vibration reduction, and external load adaptive adjustment. It has been widely used in the fields of transportation, military equipment, infrastructure construction, etc. In particular, for heavy-duty transport or excavation equipment with harsh road environments or drastic external load changes, the hydromechanical transmission system has become an important symbol of its excellent performance.

[0003] Although the hydraulic mechanical transmission system has extremely excellent dynamic performance, that is, the hydraulic torque converter realizes power transmission through the circulation of working fluid in the closed cavity composed of the pump wheel, turbine and guide wheel (see Figure 1 ). During operation, the torque converter can provide a turbine output torque far greater than the pump input torque when the turbine speed is zero or low and prevent the engine from stalling, which can effectively improve the vehicle's obstacle crossing, climbing and starting acceleration performance. For heavy-duty transport or excavation equipment with harsh road conditions or drastic external load changes, the torque converter has become an important symbol of its excellent performance. However, due to the influence of the structure of the torque converter, the working fluid will inevitably cause a series of power losses during the flow process due to blade friction, blade impact, blade cross-section diffusion and contraction, resulting in a low maximum transmission efficiency of the torque converter and a narrow high-efficiency zone. The problems of low transmission efficiency and narrow high-efficiency zone of the torque converter always exist. To this end, researchers around the world have conducted a lot of research work, such as: improving the efficiency of the torque converter body by improving the structure of the torque converter blades, improving the manufacturing process, adding double guide wheels, etc.; and improving the overall efficiency of the hydraulic mechanical transmission system by adding a locking clutch and increasing gears. However, due to the limitations of manufacturing costs, structural and manufacturing process complexity, operating effects and other factors, the problem of improving the efficiency of hydraulic mechanical transmission systems has not been significantly solved, and has become a global problem that plagues the wider application of hydraulic mechanical transmission systems. Therefore, how to break the existing structural constraints and find a new transmission system that can replace the hydraulic mechanical transmission system has become a new topic in recent years. Summary of the invention

[0004] The purpose of the present invention is to provide a coaxial hydraulic reflow automatic transmission in order to solve the above-mentioned problems. The main application objects are road and non-road engineering vehicles with harsh working environments and drastic load changes. The transmission can achieve low-speed torque increase and buffering and shock reduction while having excellent efficiency characteristics. The dual-axis concentric arrangement method is adopted to maximize the space utilization and facilitate adaptation to the chassis structure of various engineering vehicles.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A coaxial hydraulic return automatic transmission, which includes a hydraulic mechanical compound transmission device and a shifting and speed regulating device according to the transmission sequence of the power flow;

[0007] The hydraulic-mechanical compound transmission device is composed of a first transmission shaft, a first gear, a second gear, a second transmission shaft, a variable displacement hydraulic element, a fixed displacement hydraulic element, a third transmission shaft, a third gear, a fourth gear, a first planetary gear carrier, a first planetary gear sun gear, and a first planetary gear ring;

[0008] The gear shifting and speed regulating device is composed of a second planetary row sun gear, a second sun gear planet carrier, a second planetary row ring gear, a first brake, a fourth transmission shaft, a second brake, a third planetary row sun gear, a third planetary row planet carrier, a third planetary row ring gear, a first clutch, a first combined hub, a fourth planetary row sun gear, a fourth planetary row planet carrier, a fourth planetary row ring gear, a second clutch, a second combined hub, a fifth transmission shaft, a third brake, a fifth gear, a sixth gear, and a sixth transmission shaft.

[0009] Preferably, the first transmission shaft is the input shaft of the transmission, and the engine drive shaft is fixedly connected to the first transmission shaft; the first planetary row sun gear and the first gear are fixedly sleeved on the first transmission shaft; the second gear is fixedly sleeved on the second transmission shaft, the variable displacement hydraulic element is fixedly connected to the second transmission shaft, and the second gear is meshed with the first gear to form a meshing pair i1; the third gear is fixedly sleeved on the third transmission shaft, and the fixed displacement hydraulic element is fixedly connected to the third transmission shaft; the fourth gear is fixedly sleeved on the first sun gear planet carrier, and the third gear is meshed with the fourth gear to form a meshing pair i2; the first planetary row gear ring is the power output element of the hydraulic-mechanical compound transmission device, and the power is transmitted to the gear shifting and speed regulating device via the first planetary row gear ring.

[0010] Preferably, the first planetary gear ring is fixedly connected to the second planetary gear ring, and the rotation speeds of the two are always equal; the second planetary gear sun gear, the third planetary gear sun gear, the first combined hub, and the fourth planetary gear ring are all fixedly sleeved on the fourth transmission shaft; the rotating end of the first brake is fixedly connected to the second planetary gear ring; the rotating end of the second brake is fixedly connected to the third planetary gear ring; the master and slave ends of the first clutch are respectively fixedly connected to the third planetary gear ring and the first combined hub; the fourth planetary gear sun gear, the second combined hub, and the fifth gear are all fixedly sleeved on the fifth transmission shaft; the rotating end of the third brake is fixedly connected to the fourth planetary gear carrier; the master and slave ends of the second clutch are respectively fixedly connected to the fourth planetary gear carrier and the second combined hub; the sixth gear is fixedly sleeved on the sixth transmission shaft; the fifth gear and the sixth gear are meshed with each other to form a meshing pair i3. During the transmission process, power is transmitted from i3 to the sixth transmission shaft and finally output to the outside.

[0011] In the above scheme, the gears and planetary gear transmission elements are fixedly sleeved on the corresponding transmission shafts through splines. The first brake, the second brake, and the third brake can respectively realize the forced braking of the second planetary gear ring and the third planetary gear ring; the first clutch can lock the second planetary gear and the third planetary gear at the same time, and all the elements of the two planetary gears can rotate at the same speed; the second clutch can lock the fourth planetary gear, and the rotation speed of each element of the fourth planetary gear is the same as that of the fourth transmission shaft.

[0012] Preferably, the fourth transmission shaft is a hollow shaft, which is hollowly sleeved on the first transmission shaft.

[0013] Preferably, the fifth transmission shaft is a hollow shaft, which is hollowly sleeved on the first transmission shaft.

[0014] Preferably, the first brake, the second brake and the third brake are all wet brakes;

[0015] The first clutch and the second clutch are both wet clutches.

[0016] Preferably, the variable displacement hydraulic element and the fixed displacement hydraulic element are both axial piston hydraulic elements;

[0017] Both variable displacement hydraulic components and fixed displacement hydraulic components have a pump / motor dual operation mode;

[0018] Among them, the maximum control displacement of the variable displacement hydraulic component is not less than the rated displacement of the fixed displacement hydraulic component.

[0019] The present invention also discloses a shifting method of a coaxial hydraulic reflux automatic transmission, wherein the third brake and the second clutch respectively control the forward and reverse movement of the vehicle;

[0020] When the third brake is engaged, the speed of the fourth planetary gear is 0, and the fourth planetary gear sun gear and the fourth planetary gear ring gear rotate in opposite directions; when the second clutch is engaged, the fourth planetary gear is locked, and the fourth planetary gear carrier and the fourth planetary gear sun gear rotate at the same speed;

[0021] When the first clutch is engaged, the transmission operates in the first gear. At this time, the second planetary gear and the third planetary gear are locked synchronously, and the system speed ratio of the transmission is

[0022]

[0023] Where i1, i2, i3 are the transmission ratios of the fixed axis gears i1, i2, i3 respectively, and k1, k2, k3, k4 are the planetary gear characteristic constants of the first, second, third, and fourth planetary gears respectively;

[0024] When the second brake is engaged, the transmission operates in the second gear, the third planetary gear ring is fixed, and the second planetary gear and the third planetary gear form an output coupling parallel mechanism. At this time, the system speed ratio of the transmission is

[0025]

[0026] When the first brake is engaged, the transmission of the present invention operates in the third gear, and the speed of the first planetary gear ring is 0. At this time, the first planetary gear ring does not transmit power, and the input power of the shifting and speed regulating device is directly transmitted to the fourth planetary gear ring through the first planetary gear ring carrier, the first planetary gear sun gear, and the fourth transmission shaft. The system speed ratio of the transmission is

[0027]

[0028] In summary, the beneficial effects are as follows: the coaxial hydraulic reflow automatic transmission involved in the present invention can have higher transmission efficiency and a wider speed regulation range while ensuring low-speed torque increase, buffering and shock reduction, and preventing engine stalling; each speed regulation section has an actively adjustable stepless speed change capability, which is beneficial to improving driving comfort and improving work efficiency; different torque increase coefficients and speed regulation ranges of each gear can be obtained by simply adjusting the specifications of the pump, motor and planetary gear, which is beneficial to the convenient and quick construction of a series of product solutions; the coaxial hydraulic-mechanical compound transmission device and the gear shift and speed regulation device configuration scheme can maximize space utilization, so that it can easily adapt to the chassis structure of various engineering vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 :Power flow transmission direction of torque converter (a-pump wheel; b-slave turbine; c-turbine)

[0031] Figure 2 : Transmission principle diagram of the present invention;

[0032] Figure 3 : The speed / torque transmission relationship and power transmission direction of the gears and planetary gears in the hydraulic reflux transmission device in the reflux transmission mode;

[0033] In the figure: +, - indicate the direction of rotation; Indicates the torque direction.

[0034] Figure 4 : In the split transmission mode, the speed / torque transmission relationship and power transmission direction of the gears and planetary gears in the hydraulic reflux transmission device.

[0035] Figure 5 : Efficiency characteristic curve of the hydraulic-mechanical compound transmission system when the CLHS operating pressure difference is 270 bar.

[0036] In the figure: YL is the efficiency characteristic of the torque converter used in engineering vehicles

[0037] Figure 6 : Efficiency characteristic curve of the hydraulic-mechanical compound transmission system when the CLHS operating pressure difference is 350 bar.

[0038] Figure 7 : In 2nd gear, the direction of power flow in the gear shift and speed control device.

[0039] In the figure: 1-first transmission shaft; 2-first gear; 3-second gear; 4-second transmission shaft; 5-variable displacement hydraulic element; 6-fixed displacement hydraulic element; 7-third transmission shaft; 8-third gear; 9-fourth gear; 10-first planetary gear carrier; 11-first planetary gear sun gear; 12-first planetary gear ring; 13-second planetary gear sun gear; 14-second planetary gear carrier; 15-second planetary gear ring; 16-first brake; 17-fourth transmission shaft; 18-second brake; 19-third planetary gear Sun gear; 20-third planetary gear carrier; 21-third planetary gear ring; 22-first clutch; 23-first combined hub; 24-fourth planetary gear sun gear; 25-fourth planetary gear carrier; 26-fourth planetary gear ring; 27-second clutch; 28-second combined hub; 29-fifth transmission shaft; 30-third brake; 31-fifth gear; 32-sixth gear; 33-sixth transmission shaft; k1, k2, k3, k4 are the planetary gear characteristic constants of the first, second, third and fourth planetary gears respectively. DETAILED DESCRIPTION

[0040] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0041] Research has found that the torque converter forms a closed system in which power can be circulated and transmitted internally through the pump wheel, guide wheel, and turbine. When the external load is too large and energy cannot be output, the power input from the power source can flow and accumulate in the torque converter in the form of circulating power. The closed system unique to the torque converter provides a path for the transmission and accumulation of circulating power. Therefore, the ability to form a power cycle means that the transmission system has an energy storage function; the existence of circulating power is the fundamental reason why the torque converter has the low-speed torque-increasing characteristic.

[0042] refer to Figure 1-Figure 7 As shown, the present invention uses the return transmission mode of the hydraulic mechanical compound transmission system as the main load operation mode, and provides a coaxial hydraulic return automatic transmission suitable for engineering vehicles, such as Figure 2 The transmission includes a hydraulic-mechanical compound transmission device and a gear shifting and speed regulating device connected in sequence according to the transmission order of the power flow.

[0043] The hydraulic-mechanical compound transmission device includes a first transmission shaft 1, a first gear 2, a second gear 3, a second transmission shaft 4, a variable displacement hydraulic element 5, a fixed displacement hydraulic element 6, a third transmission shaft 7, a third gear 8, a fourth gear 9, a first planetary gear carrier 10, a first planetary gear sun gear 11, and a first planetary gear ring 12. Among them, the first transmission shaft 1 is the input shaft of the transmission, and the engine drive shaft is fixedly connected to the first transmission shaft 1; the first planetary row sun gear 11 and the first gear 2 are fixedly sleeved on the first transmission shaft 1; the second gear 3 is fixedly sleeved on the second transmission shaft 4, the variable displacement hydraulic element 5 is fixedly connected to the second transmission shaft 4, and the second gear 3 is meshed with the first gear 2 to form a meshing pair i1; the third gear 8 is fixedly sleeved on the third transmission shaft 7, and the variable displacement hydraulic element 6 is fixedly connected to the third transmission shaft 7; the fourth gear 9 is fixedly sleeved on the first sun gear planet carrier 10, and the third gear 8 is meshed with the fourth gear 9 to form a meshing pair i2; the first planetary row gear ring 12 is the power output element of the hydraulic-mechanical compound transmission device, and the power is transmitted to the gear shifting and speed regulating device through the first planetary row gear ring 12.

[0044] The gear shifting and speed regulating device is composed of a second planetary row sun gear 13, a second sun gear carrier 14, a second planetary row ring gear 15, a first brake 16, a fourth transmission shaft 17, a second brake 18, a third planetary row sun gear 19, a third planetary row carrier 20, a third planetary row ring gear 21, a first clutch 22, a first combined hub 23, a fourth planetary row sun gear 24, a fourth planetary row carrier 25, a fourth planetary row ring gear 26, a second clutch 27, a second combined hub 28, a fifth transmission shaft 29, a third brake 30, a fifth gear 31, a sixth gear 32, and a sixth transmission shaft 33. Among them, the first planetary gear ring 12 is fixedly connected with the second planetary gear ring 14, and the rotation speeds of the two are always equal; the second planetary gear sun gear 13, the third planetary gear sun gear 19, the first combined hub 23, and the fourth planetary gear ring 26 are all fixedly sleeved on the fourth transmission shaft 17; the rotating end of the first brake 16 is fixedly connected with the second planetary gear ring 15; the rotating end of the second brake 18 is fixedly connected with the third planetary gear ring 21; the master and slave ends of the first clutch 22 are respectively fixedly connected with the third planetary gear ring 21 and the first combined hub 23; the fourth planetary gear sun gear 24, the second combined hub 28, and the fifth gear 31 are all fixedly sleeved on the fifth transmission shaft 29; the rotating end of the third brake 30 is fixedly connected with the fourth planetary gear carrier 25; the master and slave ends of the second clutch 27 are respectively fixedly connected with the fourth planetary gear carrier 25 and the second combined hub 28; the sixth gear 32 is fixedly sleeved on the sixth transmission shaft 33; the fifth gear and the sixth gear are meshed with each other to form a meshing pair i3. During the transmission process, power is transmitted from i3 to the sixth transmission shaft 33 and finally output to the outside of the transmission.

[0045] In the above scheme, the gears and planetary gear transmission elements are fixedly sleeved on the corresponding transmission shafts through splines. The first brake, the second brake, and the third brake can respectively realize the forced braking of the second planetary gear ring and the third planetary gear ring; the first clutch can lock the second planetary gear and the third planetary gear at the same time, and all the elements of the two planetary gears can rotate at the same speed; the second clutch can lock the fourth planetary gear, and the rotation speed of each element of the fourth planetary gear is the same as that of the fourth transmission shaft.

[0046] As a preferred embodiment, the fourth transmission shaft 17 is a hollow shaft, which is sleeved in the first transmission shaft 1. The fifth transmission shaft 29 is a hollow shaft, which is sleeved in the first transmission shaft 1.

[0047] Furthermore, the first brake, the second brake and the third brake are all wet brakes; the first clutch and the second clutch are both wet clutches. The variable displacement hydraulic element and the fixed displacement hydraulic element are both axial piston hydraulic elements; the variable displacement hydraulic element and the fixed displacement hydraulic element both have a pump / motor dual operation mode;

[0048] Among them, the maximum control displacement of the variable displacement hydraulic component is not less than the rated displacement of the fixed displacement hydraulic component. In order to save costs and improve transmission efficiency, the maximum control displacement of the variable displacement hydraulic component in the CLHS is generally equal to the rated displacement of the fixed displacement hydraulic component. However, in some cases, in order to obtain a larger speed regulation range, you can also try to use a variable displacement hydraulic component with a maximum control displacement slightly larger than the rated displacement of the fixed displacement hydraulic component.

[0049] Depend on Figure 2 It can be seen that the coaxial hydraulic reflow automatic transmission of the present invention has three gears in each of the forward and reverse directions, and its shifting method is shown in Table 1.

[0050] Table 1 Transmission shifting method

[0051]

[0052]

[0053] The third brake 30 and the second clutch 27 control the forward and reverse movement of the vehicle respectively. When the third brake 30 is engaged, the rotation speed of the fourth planetary gear 25 is 0, and the fourth planetary gear sun gear (24) and the fourth planetary gear ring 26 rotate in opposite directions; when the second clutch 27 is engaged, the fourth planetary gear 25 is locked, and the fourth planetary gear carrier 25 and the fourth planetary gear sun gear 24 rotate at the same speed.

[0054] When the first clutch 22 is engaged, the transmission of the present invention operates in the first gear. At this time, the second planetary gear and the third planetary gear are synchronously locked, and the system speed ratio of the transmission is

[0055]

[0056] Wherein, i1, i2, i3 are the transmission ratios of the fixed axis gears i1, i2, i3 respectively, and k1, k2, k3, k4 are the planetary gear characteristic constants of the first, second, third, fourth planetary gears respectively.

[0057] When the second brake 18 is engaged, the transmission of the present invention operates in the second gear, the third planetary gear ring 21 is fixed, and the second planetary gear and the third planetary gear form a typical output coupling parallel mechanism. At this time, the transmission direction of the power flow in the gear shifting and speed regulating device is as follows: Figure 5 As shown, the system speed ratio of the transmission is

[0058]

[0059] When the first brake 16 is engaged, the transmission of the present invention operates in the third gear, and the speed of the first planetary gear ring 15 is 0. At this time, the first planetary gear ring 15 does not transmit power, and the input power of the shifting and speed regulating device is directly transmitted to the fourth planetary gear ring 26 through the first planetary gear ring 14, the first planetary gear sun gear 14, and the fourth transmission shaft 17. The system speed ratio of the transmission is

[0060]

[0061] The above-mentioned transmission shifting method can improve the matching degree with engineering machinery equipment, and can have higher transmission efficiency and wider speed regulation range while ensuring low-speed torque increase, buffering and shock reduction, and preventing engine stalling; each speed regulation section has actively adjustable stepless speed change capability, which is beneficial to improving driving comfort and improving work efficiency; different torque increase coefficients and speed regulation ranges of each gear can be obtained only by adjusting the specifications of the pump, motor and planetary gear, which is conducive to the convenient and quick construction of a series of product solutions.

[0062] The hydraulic-mechanical compound transmission device uses a two-degree-of-freedom differential gear train with a ring gear as a power output element as a power converging element. On the premise of ensuring that the output speed and output torque meet the requirements, it can effectively prevent the speed of some gears in the hydraulic-mechanical compound transmission device from being too high, thereby improving the service life of the system; reducing the rated displacement requirements of the variable-displacement hydraulic element 5 and the fixed-displacement hydraulic element 6, saving costs; improving the compatibility of the hydraulic-mechanical compound transmission device with the gear shifting and speed regulating device, so that each planetary gear in the gear shifting and speed regulating device has a more moderate planetary gear characteristic constant, which is convenient for processing and assembly.

[0063] The variable displacement hydraulic element 5 and the fixed displacement hydraulic element 6 form an axial piston pump-motor closed system (CLHS). In the traditional hydraulic mechanical compound transmission system, in order to save costs and improve transmission efficiency, the maximum control displacement of the variable displacement hydraulic element in the CLHS is generally equal to the rated displacement of the fixed displacement hydraulic element. However, in some cases, in order to obtain a larger speed regulation range, it is also possible to try to select a variable displacement hydraulic element whose maximum control displacement is slightly larger than the rated displacement of the fixed displacement hydraulic element.

[0064] The displacement ratio ε of CLHS is generally defined as the ratio of the actual displacement of the variable displacement hydraulic component to the rated displacement of the fixed displacement hydraulic component, that is,

[0065] ε=V V / V F =n F / n V (4)

[0066] Wherein, nV and nF represent the rotation speed of the variable displacement hydraulic component and the fixed displacement hydraulic component, rpm; VV and VF represent the displacement of the variable displacement hydraulic component and the fixed displacement hydraulic component, cm3 / r.

[0067] When ε∈[0,i1i2 / (1+k)], the hydraulic mechanical compound transmission system operates in the return transmission mode. At this time, the speed / torque transmission relationship and power transmission direction of the gear and planetary gear in the hydraulic return transmission device are as follows: Figure 3 As shown. The engine input power is transmitted in the hydraulic return transmission device through the first transmission shaft 1 → the first planetary gear sun gear 11 → the fourth gear 9 → the third gear 8 → the third transmission shaft 7 → the fixed displacement hydraulic element 6 → the variable displacement hydraulic element 5 → the second transmission shaft 4 → the second gear 3 → the first gear 2 → the first transmission shaft 1, forming a circulating power. When the first planetary gear ring 12 stops rotating due to excessive load, the power input from the power source can still be stored in the hydraulic return transmission device in the form of return power, and accumulate and increase until the system meets the torque requirement or the CLHS reaches the upper pressure limit, achieving low-speed torque increase.

[0068] When ε∈[-1,0], the hydraulic mechanical compound transmission system operates in the split transmission mode, and the speed / torque transmission relationship and power transmission direction of the gear and planetary gear in the hydraulic return transmission device are as follows: Figure 4 As shown. At this time, the hydraulic circuit and mechanical circuit in the hydraulic return transmission device transmit power in parallel in both directions, and there is no power circulation in the system. Therefore, in the actual operation of the transmission, the hydraulic return transmission device is only suitable for non-main operating conditions of engineering machinery in the split transmission mode.

[0069] According to the transmission characteristics of the power flow in the hydraulic return transmission device, the transmission efficiency of the hydraulic mechanical compound transmission system can be calculated by the meshing power method as follows:

[0070]

[0071] Wherein, ηHMCS is the transmission efficiency of the hydraulic reflux transmission device; ηg is the transmission efficiency of the fixed axis gear, ηg=0.98; I is the first transmission shaft 1; r1 is the first planetary gear ring 12; p1 is the first planetary gear carrier 10; s1 is the first planetary gear sun gear 11; iab represents the ratio of the rotational speed of element a to element b; is the ratio of the rotation speed of element a and element b to that of element c; ηP-M is the total transmission efficiency of CLHS. The efficiency model of CLHS obtained by fitting the bench test data is:

[0072]

[0073] Wherein, ΔP is the operating pressure difference of CLHS; A is the efficiency fitting coefficient of CLHS.

[0074]

[0075] Substituting formula (6) into formula (5) can calculate the efficiency characteristic curve of the hydraulic mechanical compound transmission system, as shown in Figure 5 , Figure 6 It should be noted that within the main operating pressure range, when ΔP = 270 bar, the transmission efficiency of CLHS is the highest; when ΔP = 350 bar, the transmission efficiency of CLHS is the lowest.

[0076] Depend on Figure 5 , Figure 6 It can be seen that within the main operating pressure range, the hydraulic-mechanical compound transmission system has better efficiency characteristics, which effectively makes up for the defects of low transmission efficiency and narrow high-efficiency zone of the torque converter.

[0077] Depend on Figure 1 It can be seen that the efficiency characteristics of the coaxial hydraulic return automatic transmission of the present invention can be expressed as

[0078] η PHAT =η HMCS η mn (7)

[0079] In the formula, ηPHAT is the transmission efficiency of the coaxial hydraulic return automatic transmission; ηmn is the transmission efficiency of the mechanical step-type transmission. In gear I, the second and third planetary gears are locked, and there is no power loss, ηm1 = ηi3 = 0.98; in gear II, the third planetary gear ring 21 is fixed, and the power flow transmission state in the mechanical step-type transmission is as follows: Figure 7 As shown. The second planetary gear and the third planetary gear form a parallel split flow transmission path. At this time, the efficiency of the gear shifting speed regulating device is

[0080]

[0081] Wherein, it3-q1 represents the ratio of the rotational speed of the third planetary row sun gear 19 to the first planetary row ring gear 12; It is expressed as the ratio of the rotational speed of the first planetary gear ring 12 and the third planetary gear sun gear 19 relative to the second planetary gear sun gear 13; It is expressed as the ratio of the speed of the first planetary gear ring 12 and the second planetary gear carrier 14 relative to the second planetary gear sun gear 13; iq1-t3 is expressed as the ratio of the speed of the first planetary gear ring 12 and the third planetary gear sun gear 19. It can be seen from the calculation that when the planetary gear characteristic constant k∈[1.5,4], ηm2≈0.96.

[0082] In gear III, the ring gear of PG2 is fixed, and the power is only transmitted to the gear by the planetary carrier of PG2, ηm=0.98ηi3=0.96.

[0083] Depend on Figure 3 It can be seen that in the reflux transmission mode, the power transfer relationship of the hydraulic mechanical compound transmission system can be expressed as

[0084] |P e |+|P p1 |η g η P-M =|P s1 | (9)

[0085] Wherein, Pe is the input power of the power source, kW; Pp1 is the output power of the first planetary gear carrier 10, kW; Ps1 is the input power of the first planetary gear sun gear 11, kW.

[0086] According to the design theory of planetary gears, when the first planetary gear is an internal and external meshing single planetary gear, the power transmission relationship between the first planetary gear carrier and the first planetary gear sun gear is:

[0087]

[0088] Substituting equation (10) into equation (9) can solve the low-speed torque increase coefficient K of the hydraulic-mechanical compound transmission system.

[0089]

[0090] Wherein, Te is the input torque of the transmission, N; Tr1 is the output torque of the first planetary gear ring 12, N.

[0091] Due to the limitation of assembly space, in the vehicle transmission system, the transmission ratio of a single-stage external gear is generally not greater than 2.8 and not less than 0.6. Therefore, the numerical relationship between i1, i2 and k1 can be expressed as

[0092]

[0093] When ε∈[-1,1], ΔP∈[0,350], the maximum efficiency that the CLHS efficiency model shown in formula (6) can achieve is about 83.7%. Therefore, the maximum torque increase coefficient of the hydraulic mechanical compound transmission system can be calculated as shown in Table 2.

[0094] Table 2 Maximum torque increase coefficient of hydraulic mechanical compound transmission system

[0095] k1＝1.5 k1＝2 k1＝3 k1＝4 Maximum torque coefficient 7.65 10.2 15.29 20.39

[0096] It can be seen from Table 2 that the maximum torque increase coefficient of the hydraulic-mechanical compound transmission system is not less than 7.65, which is far greater than the maximum torque increase coefficient of a general torque converter and can meet the power requirements of general engineering vehicles.

[0097] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A coaxial hydraulic reflux automatic transmission, Features: According to the transmission sequence of power flow, the transmission includes a hydraulic-mechanical compound transmission device and a gear shifting and speed regulating device; The hydraulic mechanical compound transmission device is composed of a first transmission shaft (1), a first gear (2), a second gear (3), a second transmission shaft (4), a variable displacement hydraulic element (5), a fixed displacement hydraulic element (6), a third transmission shaft (7), a third gear (8), a fourth gear (9), a first planetary gear carrier (10), a first planetary gear sun gear (11), and a first planetary gear ring (12); The gear shifting and speed regulating device comprises a second planetary row sun gear (13), a second sun gear planet carrier (14), a second planetary row gear ring (15), a first brake (16), a fourth transmission shaft (17), a second brake (18), a third planetary row sun gear (19), a third planetary row planet carrier (20), a third planetary row gear ring (21), a first clutch (22), a first combined wheel hub (23), a fourth planetary row sun gear (24), a fourth planetary row planet carrier (25), a fourth planetary row gear ring (26), a second clutch (27), a second combined wheel hub (28), a fifth transmission shaft (29), a third brake (30), a fifth gear (31), a sixth gear (32), and a sixth transmission shaft (33).

2. A coaxial hydraulic return automatic transmission according to claim 1, Features: The first transmission shaft (1) is the input shaft of the transmission, and the engine drive shaft is fixedly connected to the first transmission shaft (1); the first planetary gear (11) and the first gear (2) are fixedly sleeved on the first transmission shaft (1); the second gear (3) is fixedly sleeved on the second transmission shaft (4), the variable displacement hydraulic element (5) is fixedly connected to the second transmission shaft (4), and the second gear (3) and the first gear (2) are meshed to form a meshing pair i1; the third gear (8) is fixedly sleeved on the third transmission shaft (7), and the fixed displacement hydraulic element (6) is fixedly connected to the third transmission shaft (7); the fourth gear (9) is fixedly sleeved on the first sun gear planet carrier (10), and the third gear (8) and the fourth gear (9) are meshed to form a meshing pair i2; the first planetary gear ring (12) is a power output element of the hydraulic mechanical compound transmission device, and the power is transmitted to the gear shifting and speed regulating device through the first planetary gear ring (12).

3. A coaxial hydraulic return automatic transmission according to claim 2, Features: The first planetary gear ring (12) is fixedly connected to the second planetary gear ring (14), and the rotation speeds of the two are always equal; the second planetary gear ring (13), the third planetary gear ring (19), the first combined wheel hub (23), and the fourth planetary gear ring (26) are all fixedly sleeved on the fourth transmission shaft (17); the rotating end of the first brake (16) is fixedly connected to the second planetary gear ring (15); the rotating end of the second brake (18) is fixedly connected to the third planetary gear ring (21); the driving end and the driven end of the first clutch (22) are respectively connected to the third planetary gear ring (21), the first combined wheel hub (23); ) is fixedly connected; the fourth planetary gear sun gear (24), the second combined wheel hub (28), and the fifth gear (31) are all fixedly sleeved on the fifth transmission shaft (29); the rotating end of the third brake (30) is fixedly connected to the fourth planetary gear carrier (25); the driving and driven ends of the second clutch (27) are respectively fixedly connected to the fourth planetary gear carrier (25) and the second combined wheel hub (28); the sixth gear (32) is fixedly sleeved on the sixth transmission shaft (33); the fifth gear and the sixth gear are meshed with each other to form a meshing pair i3. During the transmission process, power is transmitted from i3 to the sixth transmission shaft (33) and finally output to the outside.

4. A coaxial hydraulic return automatic transmission according to claim 3, Features: The fourth transmission shaft (17) is a hollow shaft, which is hollowly sleeved on the first transmission shaft (1).

5. A coaxial hydraulic return automatic transmission according to claim 3, Features: The fifth transmission shaft (29) is a hollow shaft, which is hollowly sleeved on the first transmission shaft (1).

6. A coaxial hydraulic return automatic transmission according to claim 3, Features: The first brake, the second brake and the third brake are all wet brakes.

7. A coaxial hydraulic return automatic transmission according to claim 3, Features: The first clutch and the second clutch are both wet clutches.

8. A coaxial hydraulic return automatic transmission according to claim 2 or 3, Features: The variable displacement hydraulic element (5) and the fixed displacement hydraulic element (6) are both axial piston hydraulic elements; Both the variable displacement hydraulic element (5) and the fixed displacement hydraulic element (6) have a pump / motor dual operation mode; The variable displacement hydraulic element (5) and the fixed displacement hydraulic element (6) form an axial piston pump-motor closed system, and the maximum control displacement of the variable displacement hydraulic element (5) is not less than the rated displacement of the fixed displacement hydraulic element (6).

9. A shifting method using the coaxial hydraulic reflow automatic transmission according to claim 3, Features: The third brake (30) and the second clutch (27) respectively control the forward and reverse movement of the vehicle; When the third brake (30) is engaged, the rotation speed of the fourth planetary gear (25) is 0, and the fourth planetary gear sun gear (24) and the fourth planetary gear ring (26) rotate in opposite directions; when the second clutch (27) is engaged, the fourth planetary gear (25) is locked, and the fourth planetary gear carrier (25) and the fourth planetary gear sun gear (24) rotate at the same speed; When the first clutch (22) is engaged, the transmission operates in the first gear. At this time, the second planetary gear and the third planetary gear are synchronously locked, and the system speed ratio of the transmission is Where i1, i2, i3 are the transmission ratios of the fixed axis gears i1, i2, i3 respectively, and k1, k2, k3, k4 are the planetary gear characteristic constants of the first, second, third, and fourth planetary gears respectively; When the second brake (18) is engaged, the transmission operates in the second gear, the third planetary gear ring (21) is fixed, and the second planetary gear and the third planetary gear form an output coupling parallel mechanism. At this time, the system speed ratio of the transmission is When the first brake (16) is engaged, the transmission of the present invention operates in the third gear, and the speed of the first planetary gear ring (15) is 0. At this time, the first planetary gear ring (15) does not transmit power, and the input power of the gear shifting and speed regulating device is directly transmitted to the fourth planetary gear ring (26) through the first planetary gear ring carrier (14), the first planetary gear sun gear (14), and the fourth transmission shaft (17). The system speed ratio of the transmission is

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