A hybrid powertrain assembly for a tractor

Abstract

The application provides a hybrid assembly system of a tractor, comprising an engine, an electric motor, a hydraulic brake execution unit and a transmission system, the engine and the electric motor are connected with the transmission system respectively, the hydraulic brake execution unit is used for braking the wheels of the tractor, further comprising a hydraulic system, a clutch assembly and a transmission device; the PTO output end is connected with the input end of the hydraulic system, the hydraulic system inputs hydraulic energy into the hydraulic brake execution unit, the electric motor is connected with the input end of the hydraulic system through the transmission device, the output end of the transmission system further comprises a secondary power output end, the secondary power output end is connected with the transmission device; the application provides continuous transmission ratios between the PTO output end and the hydraulic brake execution unit, between the electric motor and the hydraulic brake execution unit, between the engine and the electric motor and the hydraulic brake execution unit by selectively controlling the engagement of the clutch assembly.

Description

Technical Field

[0001] This invention relates to the field of tractors or braking systems, and particularly to a hybrid powertrain system for tractors. Background Technology

[0002] my country is a major agricultural country, and tractors, as agricultural machinery, play a crucial role in the country's agricultural development. Traditional tractors are powered entirely by engines, which presents problems such as numerous gears, complex operation, high pollutant emissions, and complex and inefficient transmission systems. With the rise of hybrid power technology, using both engines and electric motors as the power source for tractors can effectively reduce emissions and fuel consumption, becoming a current research hotspot.

[0003] Hybrid technology was first applied to passenger cars and is relatively mature. Current research on hybrid tractors draws heavily on experience gained from passenger car applications. While hybrid tractors have reduced emissions and energy consumption, they need to handle more complex field conditions compared to passenger cars. Furthermore, hybrid tractors experience power interruptions when shifting gears in engine-driven mode.

[0004] Currently, hydraulic braking systems are widely used in various vehicle braking systems due to their high power-to-weight ratio. Meanwhile, electro-hydraulic servo valves, with their excellent pressure servo performance, play a crucial role as brake control valves in controlling brake pressure. However, the micron-level precision orifice plate in the pilot stage of electro-hydraulic servo valves is prone to clogging under high-temperature carbonization of hydraulic oil, potentially leading to serious safety accidents such as wheel lock-up. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a hybrid powertrain system for tractors. By selectively controlling the engagement of the pressure relief valve unit, the pressure exhaust valve unit, and the clutch assembly, it provides multiple transmission methods between the PTO output terminal and the hydraulic brake actuator, between the electric motor and the hydraulic brake actuator, and between the engine, the electric motor, and the hydraulic brake actuator, making it suitable for various braking environments.

[0006] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0007] A hybrid powertrain system for a tractor includes an engine, an electric motor, a hydraulic brake actuator, and a transmission system. The engine and electric motor are respectively connected to the transmission system. The output terminals of the transmission system are a main power output terminal and a PTO output terminal. The main power output terminal is connected to a differential assembly, and the PTO output terminal is used to perform external work. The hydraulic brake actuator is used to brake the tractor wheels and also includes a hydraulic system, a clutch assembly, and a transmission device. The PTO output terminal is connected to the input terminal of the hydraulic system, and the hydraulic system inputs hydraulic energy to the hydraulic brake actuator. The electric motor is connected to the input terminal of the hydraulic system through the transmission device. The output terminal of the transmission system also includes a secondary power output terminal, which is connected to the transmission device. The engagement of the clutch assembly is selectively controlled to provide continuous transmission ratios between the PTO output terminal and the hydraulic brake actuator, between the electric motor and the hydraulic brake actuator, and between the engine and the electric motor and the hydraulic brake actuator.

[0008] Furthermore, the clutch assembly includes a first clutch C1, a second clutch C2, a third clutch C3, and a fourth clutch C4; the first clutch C1 is used to selectively connect the PTO output end to the hydraulic system input end; the second clutch C2 is used to selectively connect the motor output end to the transmission device; the third clutch C3 is used to selectively connect the auxiliary power output end to the transmission device; and the fourth clutch C4 is used to selectively connect the output end of the transmission device to the hydraulic system input end.

[0009] Furthermore, by selectively controlling the engagement of the first clutch C1, a braking transmission of the PTO output is provided between the PTO output terminal and the hydraulic brake actuator.

[0010] By selectively controlling the engagement of the second clutch C2 and the fourth clutch C4, a braking transmission of the motor output is provided between the electric motor and the hydraulic brake actuator.

[0011] Furthermore, by selectively controlling the engagement of the first clutch C1, the second clutch C2, and the fourth clutch C4, the braking transmission between the engine and the electric motor and the hydraulic brake actuator is achieved;

[0012] By selectively controlling the engagement of the second clutch C2, the third clutch C3, and the fourth clutch C4, the braking transmission between the engine and the electric motor and the hydraulic brake actuator is achieved.

[0013] Furthermore, the transmission device is a speed-increasing device. The speed at the input end of the hydraulic system in the first brake transmission output by the engine and the electric motor is n1, and the speed at the input end of the hydraulic system in the second brake transmission output by the engine and the electric motor is n2, where n1>n2.

[0014] Furthermore, the hydraulic system includes a pressure-increasing valve unit, a pressure-relief valve unit, and a pump. The pressure-increasing valve unit includes several first two-position two-way valves, which are connected in parallel between the pump outlet and the hydraulic brake actuator unit. The pressure-relief valve unit includes several second two-position two-way valves and third two-way valves. These valves are connected in parallel between the pump inlet and the brake control terminal. The flow area of ​​the second two-position two-way valve is smaller than that of the third two-way valve.

[0015] Furthermore, the flow area of ​​the third two-position two-way valve is 3-6 times that of the second two-position two-way valve; the flow area of ​​the first two-position two-way valve is the same as that of the second two-position two-way valve.

[0016] Furthermore, it also includes a control system, a speed sensor, and a pressure sensor. The speed sensor measures the wheel rotation speed n and the tractor speed v, respectively. The pressure sensor is used to measure the pressure of the hydraulic brake actuator. The control system derives the actual slip ratio based on the rotation speed n and the speed v, and calculates the brake pressure value required by the current hydraulic brake actuator based on the slip ratio closed-loop brake control algorithm.

[0017] The control system obtains a pressure error Δp ​​based on the pressure of the hydraulic brake actuator and the braking pressure value required by the current hydraulic brake actuator. The control system calculates the increase or decrease in oil volume ΔV required by the hydraulic brake actuator based on the pressure error Δp. The control system selectively controls at least one first two-position two-way valve or at least one second two-position two-way valve to operate based on the increase or decrease in oil volume ΔV.

[0018] Furthermore, the control system calculates the required increase or decrease in oil volume ΔV for the hydraulic brake actuator based on the pressure error Δp, specifically as follows:

[0019]

[0020] In the formula:

[0021] β is the elastic modulus of the oil; V is the volume of the hydraulic brake actuator; ΔV is the required increase or decrease in oil volume; k1 is the pipe resistance coefficient.

[0022] The control system selectively controls at least one first two-position two-way valve or at least one second two-position two-way valve to operate based on the increase or decrease in oil volume ΔV, specifically:

[0023]

[0024] In the formula: V′ is the volume threshold increased by opening a first two-position two-way valve or the volume threshold decreased by opening a second two-position two-way valve; n is the number of first two-position two-way valves or second two-position two-way valves opened; [ ] is an integer.

[0025] Furthermore, when the calculated actual slip ratio exceeds the set slip ratio and ΔV < 0, the control system controls at least one second two-position two-way valve and / or a third two-position two-way valve to operate.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. The hybrid powertrain system of the tractor described in this invention provides multiple transmission modes between the PTO output terminal and the hydraulic brake actuator, between the electric motor and the hydraulic brake actuator, and between the engine, the electric motor and the hydraulic brake actuator by selectively controlling the engagement of the pressure valve unit, the pressure relief valve unit and the clutch assembly, which can be applied to various braking environments.

[0028] 2. The hybrid powertrain system of the tractor described in this invention employs a pressure-boosting valve unit and a pressure-relief valve unit. The pressure-relief valve unit contains a third two-position two-way valve with a flow rate 3-6 times that of other two-position two-way valves. This valve can quickly relieve pressure when the braking pressure needs to be suddenly reduced, thereby improving the reliability of the braking system. This solves the problems of high precision, high cost, and high requirements for oil quality, i.e., low anti-contamination ability, in traditional servo valve braking systems.

[0029] 3. The hybrid powertrain system of the tractor described in this invention determines the braking pressure value based on the wheel slip ratio and judges whether to increase or decrease the hydraulic fluid in the hydraulic brake actuator based on the pressure magnitude. When slippage occurs during braking, the braking pressure should be reduced rapidly. At this time, opening the high-flow-rate third two-position two-way valve can reduce the braking pressure to the target value in a very short time, achieving the effect of anti-slip braking. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For those skilled in the art, it is obvious that other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the hybrid powertrain system of the tractor described in this invention.

[0032] Figure 2 This is a schematic diagram of the hydraulic system described in this invention.

[0033] Figure 3 This is a diagram of the braking transmission path output by the PTO described in this invention.

[0034] Figure 4 This is a diagram of the braking transmission path of the electric motor output according to the present invention.

[0035] Figure 5 This is a circuit diagram of the braking transmission output from the engine and electric motor described in this invention.

[0036] Figure 6 This is a two-path diagram of the braking transmission output from the engine and the electric motor described in this invention.

[0037] In the picture:

[0038] 1-Engine; 2-Electric motor; 3-Transmission system; 3-1-Main power output terminal; 3-2-PTO output terminal; 3-3-Secondary power output terminal; 4-Differential assembly; 5-Transmission device; 6-Second clutch C2; 7-Third clutch C3; 8-First clutch C1; 9-Hydraulic system; 9-1-Pressure valve unit; 9-1-1-First two-position two-way valve; 9-2-Relief valve unit; 9-2-1-Second two-position two-way valve; 9-2-2-Third two-position two-way valve; 9-3-Pump; 10-Hydraulic brake actuator; 11-Wheel; 12-Fourth clutch C4. Detailed Implementation

[0039] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] like Figure 1 As shown, the hybrid powertrain system of the tractor described in this invention includes an engine 1, an electric motor 2, a transmission system 3, a hydraulic system 9, a clutch assembly, a hydraulic brake actuator 10, a transmission device 5, and a control system. The engine 1 and electric motor 2 are inputs to the transmission system 3. The outputs of the transmission system 3 include a main power output terminal 3-1, a PTO output terminal 3-2, and a secondary power output terminal 3-3. The main power output terminal 3-1 transmits power to the differential assembly 4. The differential assembly 4 transmits power to the wheels 11, driving them to rotate. The PTO output terminal 3-2 performs external work. The secondary power output terminal 3-3 transmits power to the transmission device 5. The transmission system 3 is a conventional system already existing in tractors; it can be a two-speed transmission system or a system including at least one planetary gear train and several gear pairs. Therefore, the specific structure of the transmission system 3 is not described further. The hydraulic brake actuator 10 is used to brake the wheels.

[0043] The electric motor 2 is connected to the input end of the transmission device 5 via a second gear pair; the output end of the transmission device 5 is connected to the input end of the hydraulic transmission device 9; the transmission device 5 can be a planetary gear train or at least a single-stage speed increaser. The PTO output end 3-2 is connected to the input end of the hydraulic transmission device 9 via a first gear pair. The transmission device 5 is a speed increaser.

[0044] like Figure 2 As shown, the hydraulic system includes a pump 9-3, a pressure-increasing valve unit 9-1, and a pressure-relief valve unit 9-2; the input shaft of the pump 9-3 is the input end of the hydraulic transmission device 9. The pressure-increasing valve unit 9-1 includes several first two-position two-way valves 9-1-1, which are connected in parallel between the outlet end of the pump 9-3 and the hydraulic brake actuator unit 10, where the hydraulic brake actuator unit 10 can be the oil port of a brake. The pressure-relief valve unit 9-2 includes several second two-position two-way valves 9-2-1 and third two-position two-way valves 9-2-2; these valves are connected in parallel between the oil inlet of the pump 9-3 and the brake actuator unit 10. Between the control ends; the flow area of ​​the second two-position two-way valve 9-2-1 is smaller than the flow area of ​​the third two-position two-way valve 9-2-2. Generally, the flow area of ​​the third two-position two-way valve 9-2-2 is 3-6 times the flow area of ​​the second two-position two-way valve 9-2-1; the flow area of ​​the first two-position two-way valve 9-1-1 and the flow area of ​​the second two-position two-way valve 9-2-1 can be the same or different, preferably the flow area of ​​the first two-position two-way valve 9-1-1 and the flow area of ​​the second two-position two-way valve 9-2-1 are the same.

[0045] like Figure 1 As shown, the clutch assembly includes a first clutch C18, a second clutch C26, a third clutch C37, and a fourth clutch C412; the first clutch C18 is used to selectively connect the PTO output terminal 3-2 to the input shaft of the pump 9-3 via a first gear pair; the second clutch C26 is used to selectively connect the output terminal of the motor 2 to the transmission device 5 via a second gear pair; the third clutch C37 is used to selectively connect the auxiliary power output terminal 3-3 to the transmission device; and the fourth clutch C412 is used to selectively connect the output terminal of the transmission device to the input shaft of the pump 9-3.

[0046] As shown in Table 1, the control system provides multiple transmission modes between the PTO output terminal 3-2 and the hydraulic brake actuator 10, between the electric motor 2 and the hydraulic brake actuator 10, and between the engine 1 and the electric motor 2 and the hydraulic brake actuator 10 by selectively controlling the engagement of the pressure valve unit 9-1, the pressure relief valve unit 9-2 and the clutch assembly.

[0047] PTO output brake transmission: such as Figure 3 As shown, the control system engages the first clutch C1 8, and controls the pressure valve unit 9-1 or the pressure relief valve unit 9-2 to open. The PTO output terminal 3-2 is connected to the input shaft of the pump 9-3 through the first gear pair. The hydraulic energy generated by the pump 9-3 is input to the hydraulic brake actuator unit 10. The piston rod of the hydraulic brake actuator unit 10 drives the brake disc to work, providing braking torque and slowing down the wheel 11.

[0048] Braking transmission from the electric motor output: such as Figure 4 As shown, the control system engages the second clutch C2 6 and the fourth clutch C4 12, and controls the opening of the pressure valve unit 9-1 or the pressure relief valve unit 9-2. The output end of the motor 2 is connected to the transmission device 5 through the second gear pair. The output end of the transmission device 5 is connected to the input shaft of the pump 9-3. The hydraulic energy generated by the pump 9-3 is input to the hydraulic brake actuator unit 10.

[0049] Braking transmission from engine and electric motor output: (e.g.) Figure 5 As shown, the control system engages the first clutch C18, the second clutch C26, and the fourth clutch C412. The control system also controls the opening of either the pressure relief valve unit 9-1 or the pressure relief valve unit 9-2. Power generated by engine 1 in one branch passes through transmission system 3, then through the PTO output terminal 3-2, and is accelerated via the first gear pair to the input shaft of pump 9-3. Power generated by electric motor 2 in the other branch passes through the second gear pair and is input to transmission device 5, which in turn inputs power to the input shaft of pump 9-3. After the two power sources converge at the input shaft of pump 9-3, the hydraulic energy generated by pump 9-3 is input to the hydraulic brake actuator unit 10. The rotational speed of the input shaft of pump 9-3 in the brake transmission system output by the engine and electric motor is n1.

[0050] Braking transmission from engine and electric motor output, Part 2: (e.g.) Figure 6 As shown, the control system engages the second clutch C26, the third clutch C37, and the fourth clutch C412. The control system also controls the opening of the pressure valve unit 9-1 or the pressure relief valve unit 9-2. Power generated by one branch engine 1 is transmitted through the transmission system 3 via the auxiliary power output terminal 3-3, and then input to the transmission device 5. Power generated by the other branch electric motor 2 is input to the transmission device 5 via the second gear pair. The two power sources converge within the transmission device 5 and are then input to the input shaft of pump 9-3. The hydraulic energy generated by pump 9-3 is input to the hydraulic brake actuator unit 10. The rotational speed of the input shaft of pump 9-3 in the brake transmission system output by the engine and electric motor is n2, where n1 > n2.

[0051] Table 1. Component Connection Table

[0052]

[0053] In this context, "▲" indicates that the component is in a engaged state.

[0054] When the tractor is not performing external work, the braking transmission output by the PTO can be used; when the tractor is performing external work while driving, the braking transmission output by the electric motor can be used; when the SOC of the electric motor is insufficient and the power of the engine is excessive, the braking transmission output by the engine and the electric motor can be used, which includes braking transmission one and braking transmission two. Since n1>n2, braking transmission one and braking transmission two are suitable for different braking conditions, which will be explained in detail later.

[0055] In any of the above braking transmission methods, the control system of the present invention selectively controls at least one first two-position two-way valve 9-1-1 to open to pressurize the hydraulic brake actuator 10 based on the slip ratio of the wheel 11, or selectively controls at least one second two-position two-way valve 9-2-1 and / or a third two-position two-way valve 9-2-2 to open to depressurize the hydraulic brake actuator 10. The slip ratio of the wheel 11 can be obtained and calculated by a sensor.

[0056] The hybrid powertrain system for tractors described in this invention achieves rapid pressure relief based on wheel slip ratio, improving the reliability of the braking system. This solves the problems of traditional servo valve braking systems, which suffer from high precision, high cost, and high requirements for fluid quality (i.e., low resistance to contamination). The working principle of this invention is as follows: When the hydraulic brake actuator 10 needs to be pressurized, under the action of hydraulic pressure, the piston rod of the hydraulic brake actuator 10 drives the stationary disc of the brake disc to engage with the moving disc, increasing the friction of the brake disc and providing braking torque, thus decelerating the wheel 11. When the hydraulic brake actuator 10 depressurizes, the piston rod of the hydraulic brake actuator 10 moves in the opposite direction under the action of the return spring, and the stationary disc of the brake disc gradually separates from the moving disc, reducing the braking torque.

[0057] This invention uses speed sensors to measure the rotational speed n of the wheel 11 and the speed v of the tractor; a pressure sensor is installed at the hydraulic brake actuator 10 to measure the pressure of the hydraulic brake actuator 10. When the control system receives a braking signal from the driver, the control system calculates the actual slip ratio λ based on the rotational speed n of the wheel 11 and the speed v of the tractor, specifically... Where r is the radius of wheel 11; the calculated actual slip ratio is compared with the slip ratio target value to obtain the slip ratio error, and the slip ratio closed-loop braking control algorithm is used to obtain the braking pressure value required by the current hydraulic brake actuator 10. The slip ratio closed-loop braking control algorithm is an existing algorithm.

[0058] The control system obtains the pressure error Δp ​​based on the pressure of the hydraulic brake actuator 10 and the braking pressure value required by the current hydraulic brake actuator 10, and can then calculate the increase or decrease in oil volume ΔV, specifically:

[0059]

[0060] In the formula: β is the elastic modulus of the oil; V is the volume of the rodless cavity of the hydraulic brake actuator 10; ΔV is the oil volume that needs to be increased or decreased; k1 is the pipe resistance coefficient, which is generally between 0.7 and 1.2 depending on the number of bends and reducers in the hydraulic pipeline and the influence of ambient temperature.

[0061] The pressure error Δp ​​is the measured pressure of the hydraulic brake actuator 10 minus the brake pressure value required by the hydraulic brake actuator 10. When the pressure error Δp ​​is positive, the brake pressure needs to be increased, and the increase in oil volume ΔV required by the hydraulic brake actuator 10 is determined based on the pressure error Δp. Conversely, when the pressure error Δp ​​is negative, the brake pressure needs to be decreased, and the decrease in oil volume ΔV required by the hydraulic brake actuator 10 is determined based on the pressure error Δp.

[0062] The control system controls at least one first two-position two-way valve 9-1-1 or at least one second two-position two-way valve 9-2-1 to operate based on the increase or decrease in oil volume ΔV, specifically:

[0063]

[0064] In the formula:

[0065] V′ is the volume threshold increased by opening a first two-position two-way valve 9-1-1 or the volume threshold decreased by opening a second two-position two-way valve 9-2-1; n is the number of times the first two-position two-way valve 9-1-1 or the second two-position two-way valve 9-2-1 is opened; [ ] represents integers. For example, when... When the calculated value is 1.5, n is 2; when When the calculated value is 2.1, n is 3.

[0066] When the actual slip ratio λ exceeds the critical slip ratio and ΔV < 0 (the critical slip ratio for a typical vehicle is 0.3), the control system controls at least one second two-position two-way valve 9-2-1 and / or a third two-position two-way valve 9-2-2 to open. When the actual slip ratio is greater than 0.3, wheel 11 slips, causing it to drop rapidly, which in turn causes the slip ratio to rise rapidly. At this point, the required braking pressure is very low, but because braking is still in progress, the pressure of the hydraulic brake actuator 10 is high, resulting in a large pressure error Δp. Therefore, a rapid reduction in braking pressure is needed in a short time. The third two-position two-way valve 9-2-2 is then opened for adjustment to achieve rapid pressure relief.

[0067] like Figure 1 In Embodiment 1 of the present invention, the pressure valve unit 9-1 includes two first two-position two-way valves 9-1-1 connected in parallel between the outlet end of the pump 9-3 and the hydraulic brake actuator unit 10. The pressure relief valve unit 9-2 includes two second two-position two-way valves 9-2-1 and a third two-position two-way valve 9-2-2. The two second two-position two-way valves 9-2-1 and the third two-position two-way valve 9-2-2 are respectively connected in parallel between the oil inlet of the pump 9-3 and the brake control end. The flow area of ​​the first two-position two-way valve 9-1-1 is the same as that of the second two-position two-way valve 9-2-1, and the flow area of ​​the third two-position two-way valve 9-2-2 is five times the flow area of ​​the second two-position two-way valve 9-2-1.

[0068] When the pressure error Δp ​​is positive, the brake pressure needs to be increased; when the increase in oil volume ΔV required by the hydraulic brake actuator 10 is less than the volume threshold V′ corresponding to the opening of the first two-position two-way valve 9-1-1, that is... At this time, the control system controls either of the two first two-position two-way valves 9-1-1 to operate, achieving high control accuracy with a smaller flow rate. That is, when n=2, the control system controls the two first two-position two-way valves 9-1-1 to work simultaneously.

[0069] When the pressure error Δp ​​is negative, the brake pressure needs to be reduced; when the hydraulic brake actuator 10 needs to reduce the oil volume ΔV by less than the volume threshold V′ corresponding to the opening of the first two-position two-way valve 9-1-1, that is... At this time, the control system controls either of the two second two-position two-way valves 9-2-1 to operate, achieving high control accuracy with a smaller flow rate. That is, when n=2, the control system controls two second two-position two-way valves 9-2-1 to work simultaneously.

[0070] When the pressure error Δp ​​is negative, the braking pressure needs to be reduced. If the actual slip ratio λ>0.3 and ΔV<5KV′, the control system controls the third two-position two-way valve 9-2-2 to work, achieving rapid pressure relief. Where: K is the operating condition coefficient, K∈[0,1]. If the actual slip ratio λ>0.3 and ΔV≥5KV′, the control system controls any one of the third two-position two-way valve 9-2-2 and the two second two-position two-way valves 9-2-1 to work, or the third two-position two-way valve 9-2-2 and the two second two-position two-way valves 9-2-1 to work together.

[0071] Because the rotational speed n1 of the input shaft of pump 9-3 in brake transmission system one (output from engine and electric motor) is greater than the rotational speed n2 of the input shaft of pump 9-3 in brake transmission system two (output from engine and electric motor), when the pressure error Δp ​​is positive, the brake pressure needs to be increased; when... The control system uses the brake transmission output from both the engine and the electric motor, thus increasing the flow rate of pump 9-3 for the same displacement. And when... At that time, the control system uses the brake transmission output from the engine and the electric motor.

[0072] The hybrid powertrain system for tractors described in this invention employs a pressure-boosting valve unit and a pressure-relief valve unit. The pressure-relief valve unit contains a third two-position two-way valve with a flow rate 3-6 times that of other two-position two-way valves. This valve can quickly relieve pressure when the braking pressure needs to be suddenly reduced, thereby improving the reliability of the braking system. This solves the problems of high precision, high cost, and high requirements for oil quality, i.e., low anti-contamination ability, in traditional servo valve braking systems.

[0073] The hybrid powertrain system for tractors described in this invention determines the braking pressure value based on the wheel slip ratio and adjusts the hydraulic fluid level of the hydraulic brake actuator accordingly. When slippage occurs during braking, the braking pressure should be reduced rapidly. Opening the high-flow-rate third two-position two-way valve allows the braking pressure to be reduced to the target value in a very short time, achieving an anti-slip braking effect.

[0074] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0075] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hybrid powertrain system for a tractor, comprising an engine (1), an electric motor (2), a hydraulic brake actuator (10), and a transmission system (3), wherein the engine (1) and the electric motor (2) are respectively connected to the transmission system (3), the output ends of the transmission system (3) are a main power output end (3-1) and a PTO output end (3-2), the main power output end (3-1) is used to connect to a differential assembly (4), and the PTO output end (3-2) is used to perform external work; the hydraulic brake actuator is used to brake the tractor wheels (11), characterized in that, It also includes a hydraulic system (9), a clutch assembly, and a transmission device (5); the PTO output end (3-2) is connected to the input end of the hydraulic system (9), the hydraulic system (9) inputs hydraulic energy into the hydraulic brake actuator (10), the electric motor (2) is connected to the input end of the hydraulic system (9) through the transmission device (5), the output end of the transmission system (3) also includes an auxiliary power output end (3-3), the auxiliary power output end (3-3) is connected to the transmission device (5); selectively controlling the engagement of the clutch assembly to provide a continuous transmission ratio between the PTO output end (3-2) and the hydraulic brake actuator (10), between the electric motor (2) and the hydraulic brake actuator (10), and between the engine (1) and the electric motor (2) and the hydraulic brake actuator (10); The hydraulic system (9) includes a pressure-boosting valve unit (9-1), a pressure-relief valve unit (9-2), and a pump (9-3). The pressure-boosting valve unit (9-1) includes several first two-position two-way valves (9-1-1), which are connected in parallel between the outlet end of the pump (9-3) and the hydraulic brake actuator unit (10). The pressure-relief valve unit (9-2) includes several second two-position two-way valves (9-2-1) and third two-position two-way valves (9-2-2). The second two-position two-way valves (9-2-1) and third two-position two-way valves (9-2-2) are connected in parallel between the oil inlet of the pump (9-3) and the brake control end. The flow area of ​​the second two-position two-way valve (9-2-1) is smaller than that of the third two-position two-way valve (9-2-2).

2. The hybrid powertrain system for a tractor according to claim 1, characterized in that, The clutch assembly includes a first clutch C1 (8), a second clutch C2 (6), a third clutch C3 (7), and a fourth clutch C4 (12); the first clutch C1 (8) is used to selectively connect the PTO output terminal (3-2) to the input terminal of the hydraulic system (9); the second clutch C2 (6) is used to selectively connect the output terminal of the electric motor (2) to the transmission device (5); the third clutch C3 (4) is used to selectively connect the auxiliary power output terminal (3-3) to the transmission device (5); and the fourth clutch C4 (12) is used to selectively connect the output terminal of the transmission device (5) to the input terminal of the hydraulic system (9).

3. The hybrid powertrain system for a tractor according to claim 2, characterized in that, By selectively controlling the engagement of the first clutch C1 (8), a brake transmission of the PTO output is provided between the PTO output terminal (3-2) and the hydraulic brake actuator (10); By selectively controlling the engagement of the second clutch C2 (6) and the fourth clutch C4 (12), a brake transmission is provided between the electric motor (2) and the hydraulic brake actuator (10) for the electric motor output.

4. The hybrid powertrain system for a tractor according to claim 2, characterized in that, By selectively controlling the engagement of the first clutch C1 (8), the second clutch C2 (6) and the fourth clutch C4 (12), the engine (1) and the electric motor (2) are connected to the hydraulic brake actuator (10) to perform the brake transmission between the engine and the electric motor outputs. By selectively controlling the engagement of the second clutch C2 (6), the third clutch C3 (7) and the fourth clutch C4 (12), the engine (1) and the electric motor (2) are connected to the hydraulic brake actuator (10) to transmit the brakes from the engine and the electric motor.

5. The hybrid powertrain system for a tractor according to claim 4, characterized in that, The transmission device (5) is a speed-increasing device. The speed at the input end of the hydraulic system (9) in the brake transmission one output by the engine and the motor is n1, and the speed at the input end of the hydraulic system (9) in the brake transmission two output by the engine and the motor is n2, where n1 > n2.

6. The hybrid powertrain system for a tractor according to claim 1, characterized in that, The flow area of ​​the third two-position two-way valve (9-2-2) is 3-6 times that of the second two-position two-way valve (9-2-1); the flow area of ​​the first two-position two-way valve (9-1-1) is the same as that of the second two-position two-way valve (9-2-1).

7. The hybrid powertrain system for a tractor according to claim 1, characterized in that, It also includes a control system, a speed sensor and a pressure sensor. The speed sensor measures the rotational speed n of the wheel (11) and the speed v of the tractor, respectively. The pressure sensor is used to measure the pressure of the hydraulic brake actuator (10). The control system obtains the actual slip ratio based on the rotational speed n and the speed v. The control system calculates the brake pressure value required by the current hydraulic brake actuator (10) based on the slip ratio closed-loop brake control algorithm. The control system calculates the pressure error based on the pressure of the hydraulic brake actuator (10) and the braking pressure value required by the current hydraulic brake actuator (10). The control system is based on pressure error The calculated increase or decrease in oil volume required for the hydraulic brake actuator (10) is determined. The control system adjusts based on the increase or decrease in oil volume. Selectively control the operation of at least one first two-position two-way valve (9-1-1) or at least one second two-position two-way valve (9-2-1).

8. The hybrid powertrain system for a tractor according to claim 7, characterized in that, The control system is based on pressure error The calculated increase or decrease in oil volume required for the hydraulic brake actuator (10) is determined. Specifically: ， In the formula: The elastic modulus of the oil; The volume of the hydraulic brake actuator (10) is given. k1 is the required increase or decrease in oil volume; k1 is the pipe resistance coefficient. The control system adjusts based on the increase or decrease in oil volume. Selectively control at least one first two-position two-way valve (9-1-1) or at least one second two-position two-way valve (9-2-1) to operate, specifically as follows: ， In the formula: The volume threshold increased by opening a first two-position two-way valve (9-1-1) or the volume threshold decreased by opening a second two-position two-way valve (9-2-1); n is the number of first two-position two-way valves (9-1-1) or second two-position two-way valves (9-2-1) that are opened; To take the integer part.

9. The hybrid powertrain system for a tractor according to claim 7, characterized in that, When the calculated actual slip ratio exceeds the set slip ratio and At that time, the control system controls at least one second two-position two-way valve (9-2-1) and / or a third two-position two-way valve (9-2-2) to operate.

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