A new HCVT transmission system

Abstract

The application discloses a novel HCVT transmission system and belongs to the technical field of transmission systems. The HCVT transmission system comprises four gears, namely a pure hydraulic gear, a low-speed gear, a high-speed gear and a reverse gear. The HCVT transmission system comprises a power input device, a hydraulic power distribution gear pair, a mechanical power distribution gear pair, a pure hydraulic gear power output gear pair, a low-speed gear power output gear pair, a high-speed gear power output gear pair, a hydraulic backflow device, a planetary gear set combination, a gear shifting device and a power output device. The application has the beneficial effect that the transmission system shifting process is smooth, there is no power interruption point and the shifting is stable by designing the transfer function relationship between the variable pump excitation magnetic flow and the transmission system speed ratio.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of transmission system, and particularly relates to a novel HCVT transmission system. BACKGROUND

[0002] China is a big country in the production of small and medium power tracked tractors, and the industry is overcapacity, and the market competition is fierce. At present, the research and development of hydraulic mechanical continuously variable transmission device in China is relatively backward, the cost of imported hydraulic components is too high, but the export quantity is very small. At present, many principles of HMCVT have been proposed in China, but there is no HMCVT product that can be industrialized and applied on small and medium power tractors, the reason is that there is no way to manufacture suitable pump-controlled hydraulic motor system, and the control of the hydraulic system is also a big problem. SUMMARY

[0003] The purpose of the embodiment of the application is to provide a novel HCVT transmission system, which realizes smooth transmission system shifting process, no power interruption point and stable shifting by designing the transfer function relationship between the variable pump excitation magnetic flow and the transmission system speed ratio, so as to solve at least one technical problem involved in the background art.

[0004] In order to solve the above technical problems, the application is implemented as follows:

[0005] The embodiment of the application provides a novel HCVT transmission system, which comprises four gear positions of pure hydraulic gear, low-speed gear, high-speed gear and reverse gear, and the HCVT transmission system comprises a power input device, a hydraulic power distribution gear pair, a mechanical power distribution gear pair, a pure hydraulic gear power output gear pair, a low-speed gear power output gear pair, a high-speed gear power output gear pair, a hydraulic backflow device, a planetary gear set combination, a gear position shifting device and a power output device, wherein:

[0006] The power input device comprises an input shaft driven by an engine;

[0007] The hydraulic backflow device comprises a variable pump and a constant displacement motor;

[0008] The planetary gear set combination comprises a first planetary gear set composed of a first planetary carrier, a first sun gear and a first ring gear, and a second planetary gear set composed of a second planetary carrier, a second sun gear and a second ring gear;

[0009] The hydraulic power distribution gear pair transmits the power input by the power input device to the hydraulic backflow device, and then transmits the power to the planetary gear set combination or the gear position shifting device through the pure hydraulic gear power output gear pair;

[0010] The mechanical power distribution gear pair transmits the power input by the power input device to the planetary gear set combination;

[0011] The planetary gear set combines the power transmitted by the hydraulic return device and the mechanical power distribution gear pair, and then transmits the power to the gear shift transmission device through the low-speed gear power output gear pair or the high-speed gear power output gear pair;

[0012] The gear shift transmission device outputs the power transmitted thereto through the power output device;

[0013] The low-speed gear speed ratio I HM1 The transfer function G(s) between the variable pump excitation current ψ and the variable pump speed w is:

[0014]

[0015] In the formula, E is the Laplace transform of the displacement ratio e, k1 is a first planetary gear set characteristic parameter, T is a time constant, s is a variable, k' is a proportional coefficient, k2 is a second planetary gear set characteristic parameter, V p max , and V m are the rated displacements of the variable pump and the fixed displacement motor, respectively, C s is a total leakage coefficient, μ is the dynamic viscosity of the oil, V0 is the working volume of the oil, β e is the bulk modulus of the oil, J m is the rotational inertia of the variable pump shaft end, w p is the variable pump speed, f m are the viscous damping coefficients of the fixed displacement motor and its load, respectively, C fm is the mechanical friction loss coefficient of the fixed displacement motor, i1 is the hydraulic power distribution gear pair, i2 is the mechanical power distribution gear pair, and i3 is the low-speed gear power output gear pair.

[0016] The high-speed gear speed ratio I HM2 The transfer function G(s) between the variable pump excitation current ψ and the variable pump speed w is:

[0017]

[0018] In the formula, i4 is the high-speed gear power output gear pair.

[0019] As a preferred improvement of the present application, the gear shift transmission device comprises a first wet clutch connected to the low-speed gear power output gear pair, a second wet clutch connected to the high-speed gear power output gear pair, and a third wet clutch connected to the purely hydraulic gear power output gear pair.

[0020] As a preferred improvement of the present application, the power output device comprises an output shaft connected to the first wet clutch, the second wet clutch, and the third wet clutch.

[0021] As a preferred improvement of the present application, the speed running range of the HCVT transmission system is 4-16 km / h, and the transmission common ratio is:

[0022]

[0023] wherein v max is the maximum running speed, v min is the minimum running speed.

[0024] As a preferred improvement of the present application, the oil circuit of the gear shifting device is composed of a hydraulic oil tank, a filter, a constant pump, a relief valve, a speed regulating valve and an electromagnetic reversing valve, the main oil circuit oil pressure is controlled by the relief valve, the electromagnetic reversing valve is turned on and off to control the engagement and disengagement of the wet clutch, the flow rate into the piston cylinder of the gear shifting device is controlled by the speed regulating valve, and finally the wet clutch shifting is realized through the joint action of the relief valve, the electromagnetic reversing valve and the speed regulating valve.

[0025] As a preferred improvement of the present application, the speed ratio of the reverse gear and the pure hydraulic gear is the same, and the directions are opposite.

[0026] As a preferred improvement of the present application, when the pure hydraulic gear is working, the power output by the power input device is split into two power transmission paths through the hydraulic power distribution gear pair and the mechanical power distribution gear pair, one path of power is transmitted to the first sun gear of the first planetary gear set through the hydraulic return device, and the other path of power is transmitted to the first planet carrier through the mechanical power distribution gear pair, the two paths of power are converged after the first planetary gear set, then transmitted to the first ring gear, and then transmitted to the gear shifting device through the pure hydraulic gear power output gear pair, and finally the power is output by the power output device.

[0027] As a preferred improvement of the present application, when the low speed gear is working, the power output by the power input device is split into two power transmission paths through the hydraulic power distribution gear pair and the mechanical power distribution gear pair, one path of power is transmitted to the first sun gear of the first planetary gear set through the hydraulic return device, and the other path of power is transmitted to the first planet carrier through the mechanical power distribution gear pair, the two paths of power are converged after the first planetary gear set, then transmitted to the first ring gear, and then transmitted to the gear shifting device through the low speed gear power output gear pair, and finally the power is output by the power output device.

[0028] As a preferred improvement of the present application, when the high speed gear is working, the power output by the power input device is split into two power transmission paths through the hydraulic power distribution gear pair and the mechanical power distribution gear pair, one path of power is transmitted to the second sun gear of the second planetary gear set through the hydraulic return device, and the other path of power is transmitted to the second ring gear through the mechanical power distribution gear pair, the two paths of power are converged after the second planetary gear set, then transmitted to the second planet carrier, and then transmitted to the gear shifting device through the high speed gear power output gear pair, and finally the power is output by the power output device.

[0029] The present application has the following beneficial effects:

[0030] 1. By designing the transfer function relationship between the variable pump excitation magnetic flow and the transmission system speed ratio, the transmission system shifting process is smooth, there is no power interruption point, and the shifting is stable.

[0031] 2. The transmission efficiency of the hydraulic system based on volume speed regulation has a great influence on the entire transmission, which is different from mechanical transmission. The transmission efficiency of the hydraulic system changes greatly with the working condition. Therefore, a reliable mathematical model of the hydraulic system is established for the HCVT transmission system. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 The structural schematic diagram of the novel HCVT transmission system provided by the embodiments of the present application is shown in the figure.

[0034] Figure 2 The working principle diagram of the hydraulic return device provided by the embodiments of the present application is shown in the figure.

[0035] Figure 3 The structural schematic diagram of the gear shifting device provided by the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0037] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are usually a class, not limited to the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / ", generally indicates that the objects before and after are in an "or" relationship.

[0038] Please refer to Figure 1As shown, the embodiment of the present application provides a new HCVT transmission system, which comprises a power input device, a hydraulic power distribution gear pair i1, a mechanical power distribution gear pair i2, a pure hydraulic block power output gear pair i5, a low-speed block power output gear pair i3, a high-speed block power output gear pair i4, a hydraulic return device, a planetary gear set, a gear shift device and a power output device.

[0039] The power input device comprises an input shaft driven by an engine.

[0040] The hydraulic return device comprises a variable pump a and a fixed displacement motor b.

[0041] The planetary gear set comprises a first planetary gear set K1 composed of a first planetary carrier, a first sun gear and a first ring gear, and a second planetary gear set K2 composed of a second planetary carrier, a second sun gear and a second ring gear.

[0042] The hydraulic power distribution gear pair i1 transmits the power input by the power input device to the hydraulic return device, and the hydraulic return device transmits the power to the planetary gear set or the gear shift device through the pure hydraulic block power output gear pair i5.

[0043] The mechanical power distribution gear pair i2 transmits the power input by the power input device to the planetary gear set.

[0044] The planetary gear set converges the power transmitted by the hydraulic return device and the mechanical power distribution gear pair i2, and transmits the power to the gear shift device through the low-speed block power output gear pair i3 or the high-speed block power output gear pair i4.

[0045] The gear shift device comprises a first wet clutch C1 connected with the low-speed block power output gear pair i3, a second wet clutch C2 connected with the high-speed block power output gear pair i4 and a third wet clutch C3 connected with the pure hydraulic block power output gear pair i5.

[0046] The power output device comprises an output shaft connected with the first wet clutch C1, the second wet clutch C2 and the third wet clutch C3.

[0047] The new HCVT transmission system comprises a pure hydraulic block, a low-speed block, a high-speed block and a reverse block, so that it can meet the requirement of reducing gear shifting as much as possible for the smooth driving of a high-power tractor.

[0048] When the pure hydraulic block is working, the power output by the power input device is split to the hydraulic return device through the hydraulic power distribution gear pair i1, the power is transmitted to the gear shift device by the hydraulic return device through the pure hydraulic block power output gear pair i5, and finally the power is output through the power output device.

[0049] When the low speed gear works, the power outputted by the power input device is divided into two power transmissions through the mechanical power and the hydraulic power distribution gear pair i1 and the mechanical power distribution gear pair i2, one of the power transmissions is transmitted to the first sun gear of the first planetary gear set K1 through the hydraulic backflow device, the other power transmission is transmitted to the first carrier through the mechanical power distribution gear pair i2, the two power transmissions are converged at the first planetary gear set K1, then transmitted to the first ring gear, and finally transmitted to the gear shift transmission device through the low speed gear power output gear pair i3, and the power is outputted by the power output device.

[0050] When the high speed gear works, the power outputted by the power input device is divided into two power transmissions through the mechanical power and the hydraulic power distribution gear pair i1 and the mechanical power distribution gear pair i2, one of the power transmissions is transmitted to the second sun gear of the second planetary gear set K2 through the hydraulic backflow device, the other power transmission is transmitted to the second ring gear through the mechanical power distribution gear pair i2, the two power transmissions are converged at the second planetary gear set K2, then transmitted to the second carrier, and finally transmitted to the gear shift transmission device through the high speed gear power output gear pair i4, and the power is outputted by the power output device.

[0051] When the reverse gear works, the working principle is the same as that of the pure hydraulic gear, and the power output direction is reversed by controlling the engine to rotate in the opposite direction of the forward gear.

[0052] The speed driving range of the HCVT transmission system provided by the application is 4-16km / h, and the transmission public ratio is :

[0053]

[0054] In the formula, v max is the fastest driving speed, and v min is the slowest driving speed.

[0055] The calculation formula of the speed ratio i H of the pure hydraulic gear is:

[0056]

[0057] In the formula, e is the displacement ratio of the variable pump-constant displacement motor;

[0058] The calculation formula of the speed ratio I HM1 of the low speed gear is:

[0059]

[0060] In the formula, k1 is the characteristic parameter of the first planetary gear set;

[0061] The calculation formula of the speed ratio I HM2 of the high speed gear is:

[0062]

[0063] In the formula, k2 is a second planetary gear set characteristic parameter.

[0064] In particular, the reverse gear and the pure hydraulic gear have the same speed ratio but opposite directions.

[0065] In the specific embodiments of the present application, the specific values of the parameters of the HCVT transmission system at the time of entry are shown in Table 1:

[0066] Table 1: Specific values of parameters

[0067] Parameter Value Parameter Value ​ 2.83 i3 2 [k2] 2.83 i4 0.9 ​ 1 i5 1.1 i2 1.5

[0068] The speed variation range and the transmission ratio range of each working section are shown in Table 2:

[0069] Table 2: Values of speed variation range and transmission ratio range of working sections

[0070] Operating range Pure hydraulic range Low speed range High speed range Speed range km / h 0～4 4～8 8～16 Speed ratio range 0～0.33 0.33～0.45 0.45～0.657

[0071] In combination with Figure 2 the present application provides the working principle of the hydraulic return device of the HCVT transmission system: in the hydraulic return device, when the motor drives the variable pump a and the proportional electromagnet is energized, the high-pressure oil port outputs oil, and when the pressure acting on the primary plunger is greater than the spring force, the primary plunger moves, the pilot valve c is offset, and the variable plunger is driven to move, so that the swash plate of the variable pump a rotates, and the variable pump a outputs flow. If the motor drives the variable pump a, the proportional electromagnet has no current input or the input current is less than the starting current, and the swash plate does not rotate, and the variable pump a has no flow output.

[0072] Therefore, the mathematical model of the hydraulic return device is as follows:

[0073]

[0074]

[0075]

[0076] wherein V p max , V m are the rated displacements of the variable pump and the fixed displacement motor respectively; dp / dt is the derivative of p with respect to t, and d itself has no meaning; t is time; w p , w m are the rotational speeds of the variable pump and the fixed displacement motor respectively; e is the displacement ratio of the variable pump to the fixed displacement motor; C s is the total leakage coefficient; Δp is the pressure difference between the inlet and outlet oil paths; μ is the dynamic viscosity of the oil; V0 is the working volume of the oil; β e is the bulk modulus of the oil; J m , J pThese represent the moments of inertia at the shaft ends of the variable pump and the fixed displacement motor, respectively; f p f m These are the viscous damping coefficients of the variable displacement pump, the fixed displacement motor, and their loads, respectively; T p T m The torque carried by the shaft ends of the variable pump and the fixed displacement motor are respectively; c fp C fm These are the mechanical friction loss coefficients for the variable pump and the fixed displacement motor, respectively.

[0077] Combined Figure 3 As shown, the clutch oil circuit mainly consists of a hydraulic oil tank 1, a filter 2, a fixed displacement pump 3, a relief valve 4, a speed control valve 5, and a solenoid directional valve 6. The relief valve 4 controls the main oil circuit pressure, the solenoid directional valve 6 controls the engagement and disengagement of the wet clutch, and the speed control valve 5 controls the flow rate into the piston cylinder of the gear shifting device. Ultimately, the wet clutch shifting is achieved through the combined action of the relief valve 4, the solenoid directional valve 6, and the speed control valve 5.

[0078] When the hydraulic return device is running, the rotation of the swashplate of the variable pump can be controlled by adjusting the on / off state or magnitude of the proportional electromagnet current, thus controlling the output flow rate. To ensure smooth gear shifting in the HCVT transmission system without power interruptions and for stable gear changes, the relationship between the variable pump's excitation magnetic current ψ and the transmission system's speed ratio must be known when switching gears.

[0079] When switching from H to HM1, the mathematical model of the hydraulic return device is combined with the speed ratio of the HCVT transmission system to obtain a new mathematical model:

[0080]

[0081]

[0082] When engine speed, load, and fuel injection pressure are constant, performing a Laplace transform on the above incremental equation yields:

[0083]

[0084]

[0085] Further processing yields the low-speed gear ratio I. HM1 The transfer function G1(s) between the displacement ratio e and the displacement ratio e is:

[0086]

[0087] The displacement adjustment mechanism of the variable pump can be equivalently represented as a first-order low-pass filter, and its transfer function G2(s) can be expressed as:

[0088]

[0089] Wherein, E is the Laplace transform of displacement ratio e, T is time constant, k' is proportional coefficient.

[0090] It can be obtained that the low speed gear ratio I HM1 The transfer function G(s) between the variable pump excitation current ψ and the variable pump output speed n is:

[0091]

[0092] Wherein, k1 is the first planetary row characteristic parameter, T is time constant, s is variable, k' is proportional coefficient, k2 is the second planetary row characteristic parameter, V p max , V m are the rated displacements of the variable pump and the fixed displacement motor respectively, C s is the total leakage coefficient, μ is the dynamic viscosity of the oil, V0 is the working volume of the oil, β e is the bulk modulus of the oil, J m is the rotational inertia of the variable pump shaft end, f m are the viscous damping coefficients of the fixed displacement motor and its load respectively, C fm is the mechanical friction loss coefficient of the fixed displacement motor, i1 is the hydraulic power distribution gear pair, i2 is the mechanical power distribution gear pair, and i3 is the low speed gear power output gear pair.

[0093] The high speed gear ratio I HM2 The transfer function G(s) between the variable pump excitation current ψ and the variable pump output speed n is:

[0094]

[0095] Wherein, i4 is the high speed gear power output gear pair.

[0096] The embodiment of the application has the following beneficial effects:

[0097] 1. By designing the transfer function relationship between the variable pump excitation current and the transmission system speed ratio, the transmission system shifting process is smooth, there is no power interruption point, and the shifting is stable.

[0098] 2. The transmission efficiency of the entire gearbox of the hydraulic system based on volume speed regulation has a great influence. Unlike mechanical transmission, the transmission efficiency of the hydraulic system changes greatly with the working condition. Therefore, for the HCVT transmission system, a reliable mathematical model of the hydraulic system is established.

[0099] It has to be understood that, in the present document, the terms "comprising", "including", or any other variant thereof, are intended to cover a non-exclusive inclusion, such that processes, methods, articles, or apparatuses that comprise a list of elements are not limited to those elements, but can include other elements not expressly listed or inherent to such processes, methods, articles, or apparatuses. Without further limitation, an element preceded by "comprising" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0100] Furthermore, it is indicated that the scope of the methods and systems of the embodiments of the present application is not limited to performing functions in the order discussed or illustrated, and can include performing functions in a substantially simultaneous manner or in reverse order, for example, the described methods can be performed in other than the order described, and additional, fewer, or different steps can be added, omitted, or combined, and features described with respect to certain examples can be combined in other examples.

[0101] The embodiments of the present application described above are only illustrative, and the present application is not limited to the above-described specific embodiments, which are merely illustrative, but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims.

Claims

1. A novel HCVT transmission system, comprising four gears: pure hydraulic gear, low speed gear, high speed gear, and reverse gear, characterized in that, The HCVT transmission system includes a power input device, a hydraulic power distribution gear pair, a mechanical power distribution gear pair, a pure hydraulic power output gear pair, a low-speed power output gear pair, a high-speed power output gear pair, a hydraulic return device, a planetary gear set, a gear shifting device, and a power output device, wherein: The power input device includes an input shaft driven by an engine; The hydraulic reflux device includes a variable pump and a fixed displacement motor; The planetary gear assembly includes a first planetary gear set consisting of a first planetary carrier, a first sun gear, and a first ring gear, and a second planetary gear set consisting of a second planetary carrier, a second sun gear, and a second ring gear. The hydraulic power distribution gear pair transmits the power input from the power input device to the hydraulic return device, and then the hydraulic return device transmits the power to the planetary gear set or transmits the power to the gear transmission device via the pure hydraulic power output gear pair. The mechanical power distribution gear pair transmits the power input from the power input device to the planetary gear assembly; The planetary gear assembly combines the power transmitted by the hydraulic return device and the mechanical power distribution gear pair, and then transmits the power to the gear transmission device through the low-speed power output gear pair or the high-speed power output gear pair. The transmission gear shift device outputs the transmitted power through the power output device; Among them, the low gear ratio I HM1 The transfer function G(s) between the variable pump excitation current ψ and the variable pump excitation current is: In the formula, E is the Laplace transform of the displacement ratio e, k1 is the characteristic parameter of the first planetary sorting system, T is the time constant, s is a variable, k′ is the proportional coefficient, k2 is the characteristic parameter of the second planetary sorting system, and V pmax V m These are the rated displacements of the variable displacement pump and the fixed displacement motor, respectively, C s β is the total leakage coefficient, μ is the dynamic viscosity of the oil, V0 is the working volume of the oil, and β is the total leakage coefficient. e J is the bulk elastic modulus of the oil. m w is the moment of inertia of the variable pump shaft end. p It is the speed of the variable pump, f m C represents the viscous damping coefficient of the fixed displacement motor and its load, respectively. fm i1 is the hydraulic power distribution gear pair, i2 is the mechanical power distribution gear pair, and i3 is the low-speed power output gear pair. High-speed gear ratio I HM2 The transfer function G(s) between the variable pump excitation current ψ and the variable pump excitation current is: In the formula, i4 is the high-speed power output gear pair.

2. The novel HCVT transmission system according to claim 1, characterized in that, The gear shifting device includes a first wet clutch connected to the low-speed power output gear pair, a second wet clutch connected to the high-speed power output gear pair, and a third wet clutch connected to the pure hydraulic power output gear pair.

3. The novel HCVT transmission system according to claim 2, characterized in that, The power output device includes an output shaft connected to the first wet clutch, the second wet clutch, and the third wet clutch.

4. The novel HCVT transmission system according to claim 3, characterized in that, The HCVT transmission system has a speed range of 4-16 km / h and a transmission ratio of... for: In the formula, v max For the fastest driving speed, v min This is the slowest driving speed.

5. The novel HCVT transmission system according to claim 2, characterized in that, The oil circuit of the gear shifting device consists of a hydraulic oil tank, filter, fixed displacement pump, relief valve, speed control valve, and solenoid directional valve. The relief valve controls the oil pressure of the main oil circuit, the on / off state of the solenoid directional valve controls the engagement and disengagement of the wet clutch, and the flow rate of the speed control valve controls the flow rate into the piston cylinder of the gear shifting device. Finally, the wet clutch shifting is achieved through the combined action of the relief valve, solenoid directional valve, and speed control valve.

6. The novel HCVT transmission system according to claim 1, characterized in that, The reverse gear and the pure hydraulic gear have the same gear ratio but opposite directions.

7. The novel HCVT transmission system according to claim 1, characterized in that, When the pure hydraulic gear is in operation, the power output from the power input device is diverted to the hydraulic return device through the hydraulic power distribution gear pair. The hydraulic return device then transmits the power to the gear shifting device through the pure hydraulic gear power output gear pair, and finally outputs the power through the power output device.

8. The novel HCVT transmission system according to claim 1, characterized in that, When operating in low gear, the power output from the power input device is divided into two power transmission paths via mechanical power through the hydraulic power distribution gear pair and the mechanical power distribution gear pair. One power path is transmitted to the first sun gear of the first planetary gear set via the hydraulic return device; the other power path is transmitted to the first planetary carrier via the mechanical power distribution gear pair. The two power paths converge in the first planetary gear set and are transmitted to the first ring gear, then to the gear shifting device via the low gear power output gear pair, and finally output by the power output device.

9. The novel HCVT transmission system according to claim 1, characterized in that, When operating in high gear, the power output from the power input device is split into two paths via mechanical power distribution gear pairs and hydraulic power distribution gear pairs. One path of power is transmitted to the second sun gear of the second planetary gear set via a hydraulic return device; the other path of power is transmitted to the second ring gear via the mechanical power distribution gear pair. The two paths of power converge in the second planetary gear set and are then transmitted to the second planet carrier. Finally, they are transmitted to the gear shifting device via the high-speed power output gear pair, and the power is output by the power output device.

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