Hydraulic hybrid power system of engineering vehicle

Abstract

The utility model discloses a hydraulic hybrid power system of an engineering vehicle, and belongs to the technical field of engineering mechanical transmission. The system comprises an engineering vehicle hydraulic working device, a first two-position two-way reversing valve, a first energy accumulator, a second energy accumulator, a second two-position two-way reversing valve, a three-position four-way reversing valve set, a torque stepless adjustable coupler, a rear axle, a stepped variable displacement motor, a clutch, a one-way valve set, a combined power source, a hydraulic oil tank, an engine and a front axle. A two-position three-way reversing valve group and a shunt priority valve; stepped speed change is achieved through logic control of a switch valve of a combined power source and a stepped variable displacement motor, a traditional variable displacement pump / motor is replaced, and cost and control difficulty are reduced. And meanwhile, the torque stepless adjustable coupler is introduced, so that the installed displacement and volume of the motor are effectively reduced. The system coordinates energy distribution of a working device and a driving system through a shunt priority valve, and brake kinetic energy and movable arm potential energy are recycled through an energy accumulator.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of engineering machinery, concretely relates to engineering vehicle hydraulic hybrid power system and control method thereof. BACKGROUND

[0002] The engineering vehicle needs to be frequently started and stopped and reciprocated when working, and a large amount of kinetic energy is wasted due to frequent braking, and the wasted energy is consumed in the form of heat energy, which can cause the oil temperature to rise, the service life of components to be shortened, the working environment of the machine to be deteriorated, and the failure rate to rise, and the frequent starting can cause the engine to often be in the low efficiency area, the service brake of the vehicle to be frequently used, and the service brake to be worn out quickly.

[0003] The common transmission mode of the engineering vehicle is hydraulic transmission, which has poor universality, different mechanical traction characteristics need to be matched with different forms of torque converters, and the matching conditions between the torque converters and the engines with different characteristics are also relatively harsh, and often need to be specially matched, which is not very suitable for small batch manufacturing of complete machines, and the hydraulic torque converter has low transmission efficiency, which is not conducive to energy saving, emission reduction and noise reduction; the hydraulic transmission has low steady-state efficiency, needs to be provided with a separate cooling system, and must be configured with a mechanical gearbox and a reverse mechanism. The hydraulic transmission has higher efficiency than the hydraulic transmission, is flexible and convenient to arrange, can be connected by flexible pipelines between input and output elements, and can realize continuous stepless speed regulation by volume regulation of the variable pump / motor, but has complex structure, high cost, difficult control and poor reliability, and the core technology of the variable pump is controlled by foreign countries.

[0004] Chinese patent No. CN102141040B, published on December 14, 2016, has the title of "Multi-quantitative pump step-variable system", and the applicant is Jilin University. The patent replaces the plunger type variable element with a ladder variable system composed of multiple quantitative pumps / motors controlled by multiple ordinary on-off valves, solves the problems of high price, difficult control and easy pollution, but also brings new problems, i.e. the stepwise change of the displacement can cause pipeline impact and system buffeting, and deteriorate comfort.

[0005] Chinese patent application No. 201310065366.2, entitled "Hybrid vehicle drive device based on transformer, hydraulic pump and multiple motor", applicant Beijing University of Technology, this patent greatly improves the power performance and transmission efficiency of the hydraulic hybrid vehicle through the hydraulic transformer, constant-displacement multiple hydraulic motor and constant-displacement pump. Chinese patent No. CN204716962 U, entitled "Multi-quantitative pump series multi-quantitative motor step-variable system based on logic control", applicant Jilin University, this patent realizes step-variable through multiple different-displacement coaxial quantitative pumps in series with multiple different-displacement coaxial quantitative motors. But these two patents have a common shortcoming: relying solely on the change of motor displacement to adjust the vehicle power output will make the motor bulky, cost greatly increased, and difficult to install. SUMMARY

[0006] In view of the technical problems in the prior art, the utility model provides an engineering vehicle hydraulic hybrid power system, and the technical scheme of the utility model is as follows:

[0007] An engineering vehicle hydraulic hybrid power system, which comprises an engineering vehicle hydraulic working device 1, a first two-position two-way directional valve 2, a first accumulator 3, a second accumulator 4, a second two-position two-way directional valve 5, a three-position four-way directional valve group 8, a torque stepless adjustable coupler 9, a rear axle 10, a step-variable motor 11, a clutch 12, a one-way valve group 13, a combined power source 14, a hydraulic oil tank 15, an engine 16, a front axle 17, a two-position three-way directional valve group 18 and a split priority valve 19.

[0008] The engine 16 is coaxially connected with the input shaft of the combined power source 14, the output shaft of the combined power source 14 is connected with the input end of the step-variable motor 11 through the clutch 12, the output end of the step-variable motor 11 is connected with the power input end of the torque stepless adjustable coupler 9, and the power output end of the torque stepless adjustable coupler 9 is connected with the power input end of the rear axle 10 and the front axle 17 respectively; the torque stepless adjustable coupler 9 has the function of stepless speed change and torque increase.

[0009] The two-position three-way directional valve group 18 is an integrated valve block, comprising multiple two-position three-way directional valves, the A ports of the two-position three-way directional valves are connected in communication, and the external output is the A1 and A2 ports; the B ports of the two-position three-way directional valves are connected in communication, and the external output is the B1 port, and each two-position three-way directional valve is provided with a P port.

[0010] The combined power source 14 is connected coaxially or by a transfer case with multiple fixed displacement pumps, each of which has a separate oil inlet and outlet; the oil inlet of the combined power source 14 is connected to the hydraulic oil tank 15, and the oil outlet is connected to the oil inlet of the corresponding valve of the one-way valve group 13 in turn, the oil outlet of the one-way valve group 13 is connected to the P port of each directional valve in the two-position three-way directional valve group 18, the A1 port of the two-position three-way directional valve group 18 is connected to the P port of the split priority valve 19, and the B1 port of the two-position three-way directional valve group 18 is connected to the hydraulic oil tank 15.

[0011] The three-position four-way directional valve group 8 is an integrated valve block, which includes multiple three-position four-way directional valves; in the integrated valve block, the A ports of each three-position four-way directional valve are connected to each other and output to the outside as A ports; the B ports are also connected to each other and output to the outside as B ports; each three-position four-way directional valve is respectively provided with a P port and a T port.

[0012] The A port of the split priority valve 19 is connected to the engineering vehicle hydraulic working device 1, and is connected to the A port of the first two-position two-way directional valve 2 through a bypass; the B port of the first two-position two-way directional valve 2 is connected to the first accumulator 3 and is connected to the hydraulic oil tank 15 through a bypass; the A port of the second two-position two-way directional valve 5 is connected to the B port of the split priority valve 19, and the B port of the second two-position two-way directional valve 5 is connected to the second accumulator 4 and is connected to the hydraulic oil tank 15 through a bypass.

[0013] The stepped variable displacement motor 11 is connected coaxially by multiple fixed displacement motors, each of which has a separate oil inlet and outlet; the B port of the split priority valve 19 is connected to the A port of the three-position four-way directional valve group 8, the P port of each directional valve in the three-position four-way directional valve group 8 is respectively connected to the B port of the corresponding motor in the stepped variable displacement motor 11, the T port of each directional valve in the three-position four-way directional valve group 8 is respectively connected to the A port of the corresponding motor in the stepped variable displacement motor 11, and the B port of the three-position four-way directional valve group 8 is connected to the hydraulic oil tank 15.

[0014] Preferably, the system further comprises a bypass overflow valve 24, which is arranged on the bypass of the two-position three-way directional valve group 18, the A2 port of the two-position three-way directional valve group 18 is connected to the inlet of the bypass overflow valve 24 through the bypass, and the outlet of the bypass overflow valve 24 is connected to the hydraulic oil tank 15.

[0015] Preferably, the A port of the split priority valve 19 and the engineering vehicle hydraulic working device 1 are connected in turn by a first pressure reducing valve 20 and a first throttle valve 21.

[0016] Preferably, a working device safety valve 7 is arranged on the bypass between the B port of the first two-position two-way directional valve 2 and the hydraulic oil tank 15.

[0017] Preferably, an auxiliary brake circuit safety valve 6 is arranged on the bypass between the B port of the second two-position two-way directional valve 5 and the hydraulic oil tank 15.

[0018] Preferably, the B port of the flow splitting priority valve 19 is connected with the second pressure reducing valve 22 and the second throttle valve 23 in sequence, and then connected with the A port of the three-position four-way reversing valve group 8 and the A port of the second two-position two-way reversing valve 5 respectively.

[0019] Preferably, the displacement combination mode of the combined power source 14 and the stepped variable motor 11 is one of equal value combination, equal difference combination, Fibonacci sequence combination and equal ratio sequence combination.

[0020] Compared with the prior art, the utility model has the advantages of:

[0021] 1. The engineering vehicle hydraulic hybrid power system can recycle and reuse brake energy, adjust the engine operating point to make it work in the high efficiency area, and improve fuel economy.

[0022] 2. The engineering vehicle hydraulic hybrid power system adopts the transmission mode of combined power source and stepped variable motor combination to realize step automatic transmission, replaces the torque converter, avoids the problem of low transmission efficiency of the torque converter, simultaneously replaces the traditional variable pump and variable motor, reduces the cost, is easier to control, has fast response and the like.

[0023] 3. The torque stepless adjustable coupler in the engineering vehicle hydraulic hybrid power system has the function of speed increasing and torque increasing, can reduce the installed displacement of the stepped variable motor, can realize larger driving and braking effect at the wheel end by using smaller displacement, reduces the volume, cost and installation difficulty of the stepped motor, simultaneously can guarantee that the stepped variable motor works in the high efficiency area, and improves the working efficiency.

[0024] 4. In the engineering vehicle hydraulic hybrid power system, the combined power source is directly connected with the engine, the high efficient speed of the hydraulic pump can be substantially corresponding to the working speed of the engine, therefore the hydraulic pump can work in the high efficient range all the time, and the difficulty of speed matching is avoided.

[0025] 5. In the engineering vehicle hydraulic hybrid power system, the brake energy recovery system and the engineering vehicle hydraulic working system share the combined power source, the cost is saved, the installation space is reduced, and the vehicle body weight is lightened.

[0026] 6. In the engineering vehicle hydraulic hybrid power system, the series connection of the first pressure reducing valve and the first throttle valve and the series connection of the second pressure reducing valve and the second throttle valve make the stepped variable change into continuous variable, and make the flow more smooth. Meanwhile, the accumulator can absorb the impact and shock generated in the stepped variable process.

[0027] 7. The utility model discloses an engineering vehicle hydraulic hybrid power system combination power source and motor are connected with the clutch, can be converted into mechanical transmission when hydraulic system damage, can move to the convenient area overhauls by itself, need not toil and trouble to carry on the trailer.

[0028] 8. The utility model discloses an engineering vehicle hydraulic hybrid power system can recycle the potential energy of swing arm in working device. ACCOUT OF DRAWINGS

[0029] Figure 1 It is the principle drawing of the engineering vehicle hydraulic hybrid power system of the utility model;

[0030] Figure 2 It is the power transmission route drawing of the engineering vehicle hydraulic hybrid power system of the utility model under the idle speed pressure charging;

[0031] Figure 3 It is the power transmission route drawing of the engineering vehicle hydraulic hybrid power system of the utility model under the pure hydraulic drive mode;

[0032] Figure 4 It is the power transmission route drawing of the engineering vehicle hydraulic hybrid power system of the utility model under the running pressure charging;

[0033] Figure 5 It is the power transmission route drawing of the engineering vehicle hydraulic hybrid power system of the utility model under the engine separate drive mode;

[0034] Figure 6 It is the power transmission route drawing of the engineering vehicle hydraulic hybrid power system of the utility model under the hybrid drive mode;

[0035] Figure 7 It is the power transmission route drawing of the engineering vehicle hydraulic hybrid power system of the utility model under the regenerative braking mode;

[0036] Figure 8 It is the principle drawing of two position three way reversing valve group 18 integrated valve block of the utility model;

[0037] Figure 9 It is the principle drawing of three position four way reversing valve group 8 integrated valve block of the utility model;

[0038] Figure 10 It is the engineering vehicle hydraulic hybrid power system control method working condition discrimination drawing of the utility model;

[0039] Figure 11 It is the engineering vehicle hydraulic hybrid power system control method drive working condition discrimination drawing of the utility model;

[0040] Figure 12The utility model discloses an engineering vehicle hydraulic hybrid power system control method brake condition discrimination graph.

[0041] Figure 13 The utility model discloses an engineering vehicle hydraulic hybrid power system control method special condition discrimination graph.

[0042] The above drawing uses the following marks: 1. engineering vehicle hydraulic working device, 2. first two position two way directional valve, 3. first accumulator, 4. second accumulator, 5. second two position two way directional valve, 6. auxiliary brake circuit safety valve, 7. working device safety valve, 8. three position four way directional valve group, 801. first three position four way directional valve group, 802. second three position four way directional valve group, 803. third three position four way directional valve group, 9. torque stepless adjustable coupler, 10. rear axle, 11. step variable motor, 12. clutch, 13. one way valve group, 14. combined power source, 15. hydraulic oil tank, 16. engine, 17. front axle, 18. two position three way directional valve group, 1801. first two position three way directional valve group, 1802. first two position three way directional valve group, 1803. first two position three way directional valve group, 19. shunt priority valve, 20. first pressure reducing valve, 21. first throttle valve, 22. second pressure reducing valve, 23. second throttle valve, 24. bypass overflow valve. DETAILED DESCRIPTION

[0043] The technical scheme of the utility model will be explained and described further below in connection with the drawings in the specification.

[0044] Referring to Figure 1 The utility model discloses an engineering vehicle hydraulic hybrid power system control method brake condition discrimination graph.

[0045] Referring to Figure 1 , Figure 8 , Figure 9Wherein, the two-position three-way directional valve group 18 is an integrated valve block, including three two-position three-way directional valves 1801, 1802 and 1803. It has six interfaces, which are A1, A2, B1, P1, P2 and P3. In the integrated valve block, the A port of the two-position three-way directional valve 1801 is connected with the A ports of the two-position three-way directional valves 1802 and 1803, and is externally output as the A1 and A2 ports; the B port of the two-position three-way directional valve 1801 is connected with the B ports of the two-position three-way directional valves 1802 and 1803, and is externally output as the B1 port; the P1, P2 and P3 ports of the integrated valve block are respectively the P ports of the two-position three-way directional valves 1801, 1802 and 1803. The three-position four-way directional valve group 8 is an integrated valve block, including three three-position four-way directional valves 801, 802 and 803. It has eight interfaces, which are A, B, P1, P2, P3, T1, T2 and T3. In the integrated valve block, the A port of the three-position four-way directional valve 801 is connected with the A ports of the three-position four-way directional valves 802 and 803, and is externally output as the A port; the B port of the three-position four-way directional valve 801 is connected with the B ports of the three-position four-way directional valves 802 and 803, and is externally output as the B port; the P1, P2 and P3 ports of the integrated valve block are respectively the P ports of the three-position four-way directional valves 801, 802 and 803, and the T1, T2 and T3 ports are respectively the T ports of the three-position four-way directional valves 801, 802 and 803.

[0046] Referring to Figure 1 The combined power source 14 in the embodiment is a triple constant pump coaxial or connected by a transfer case, which is an integrated element with the intermediate element cancelled and combined, and is not a simple input and output shaft connection. Each constant pump has a separate oil inlet and outlet. The stepped variable motor 11 is a plurality of constant motors connected coaxially, which is a plurality of constant motor integrated elements with the intermediate element cancelled and combined, and is not a simple input and output shaft connection. Each constant motor has a separate oil inlet and outlet. The combined power source 14 and the stepped variable motor 11 can adopt the following displacement combination modes: equal value combination, arithmetic progression combination, Fibonacci sequence combination and geometric progression combination. The displacement of the combined power source 14 is controlled by controlling the on-off combination form of the two-position three-way directional valve group 18. The displacement of the stepped variable motor 11 is controlled by controlling the combination form of the working position of the three-position four-way directional valve group 8.

[0047] The brake energy recovery system in the hydraulic hybrid power system of the engineering vehicle and the hydraulic working device 1 of the engineering vehicle share the combined power source 14.

[0048] The mechanical structure connection mode of the engineering vehicle hydraulic hybrid power system is that the engine 16 is coaxially connected with the input shaft of the combined power source 14, the output shaft of the combined power source 14 is connected with the input end of the stepped variable motor 11 through the clutch 12, the output end of the stepped variable motor 11 is connected with the power input end of the torque stepless adjustable coupler 9, and the power output end of the torque stepless adjustable coupler 9 is connected with the power input ends of the rear axle 10 and the front axle 17 respectively.

[0049] The hydraulic circuit connection mode of the engineering vehicle hydraulic hybrid power system is that the oil inlet of the combined power source 14 is connected with the hydraulic oil tank 15, the oil outlet is sequentially connected with the oil inlets of the corresponding valves of the one-way valve group 13, the oil outlets of the one-way valve group 13 are sequentially connected with the P1, P2 and P3 ports of the two-position three-way directional valve group 18. The A1 port of the two-position three-way directional valve group 18 is connected with the P port of the split priority valve 19, the A2 port of the two-position three-way directional valve group 18 is connected with the inlet of the bypass overflow valve 24, and the B1 port of the two-position three-way directional valve group 18 is connected with the hydraulic oil tank 15. The A port of the split priority valve 19 is connected with the inlet of the first pressure reducing valve 20 and the A port of the first two-position two-way directional valve 2, the outlet of the first pressure reducing valve 20 is connected with the inlet of the first throttle valve 21, the spring side control port of the first pressure reducing valve 20 is connected with the outlet of the first throttle valve 21, and the outlet of the first throttle valve 21 is connected with the engineering vehicle hydraulic working device 1. The B port of the split priority valve 19 is connected with the inlet of the second pressure reducing valve 22, the outlet of the second pressure reducing valve 22 is connected with the inlet of the second throttle valve 23, the spring side control port of the second pressure reducing valve 22 is connected with the outlet of the second throttle valve 23, and the outlet of the second throttle valve 23 is connected with the A port of the second two-position two-way directional valve 5 and the A port of the three-position four-way directional valve group 8. The B port of the first two-position two-way directional valve 2 is connected with the oil inlet of the first accumulator 3 and the oil inlet of the working device safety valve 7 respectively, and the B port of the second two-position two-way directional valve 5 is connected with the oil inlet of the second accumulator 4 and the oil inlet of the auxiliary brake circuit safety valve 6 respectively.

[0050] The B port of each motor in the stepped variable motor 11 is sequentially connected with the P1, P2 and P3 ports of the directional valve in the three-position four-way directional valve group 8, and the A port of each motor in the stepped variable motor 11 is sequentially connected with the T1, T2 and T3 ports of the directional valve in the three-position four-way directional valve group 8. The outlet of the bypass overflow valve 24, the auxiliary brake circuit safety valve 6, the outlet of the working device safety valve 7 and the B port of the three-position four-way directional valve group 8 are all connected with the hydraulic oil tank 15.

[0051] Referring to Figure 10 , Figure 11 , Figure 12 , Figure 13 , the control method of the utility model is as follows:

[0052] The working device should be ensured to work normally in the actual work project. The combined power source 14 supplies oil to the hydraulic working device 1 of the engineering vehicle through the shunt priority valve 19, and then supplies oil to the brake energy recovery circuit, i.e. the step-variable motor 11. The energy source of the first accumulator 3 is the potential energy of the boom lowering in the working device.

[0053] 1. Driving condition: refer to Figure 2 .

[0054] 1.1. Idle charging mode: when the pressure in the second accumulator 4 is lower than the set maximum working pressure during the engine 16 warming up or temporary stop, the system enters the idle charging mode. The clutch 12 is in the disconnected state, the shunt priority valve 19 is in the left position and is electrified to work in the left position, the second two-position two-way directional valve 5 is electrified to work in the left position, the first two-position two-way directional valve 2 is disconnected and de-energized, and the three-position four-way directional valve group 8 is de-energized to work in the middle position. The displacement of the combined power source 14 is adjusted so that the engine 16 works in the fuel efficient region. The engine 16 drives the combined power source 14 to rotate, and the oil in the oil tank 15 is charged to the second accumulator 4 through the combined power source 14, the one-way valve group 13, the two-position three-way directional valve group 18, the shunt priority valve 19, the second pressure reducing valve 22, the second throttle valve 23 and the second two-position two-way directional valve 5. At this time, the step-variable motor 11 does not work. The oil flow of the combined power source 14 in the figure is taken as an example.

[0055] 1.2. Low-load starting: (pure hydraulic drive mode): refer to Figure 3 .

[0056] When the demand power of the engineering vehicle is less than the lower limit of the fuel efficient region of the engine 16, and the pressure in the second accumulator 4 is higher than the set minimum working pressure, the clutch 12 is disconnected, the shunt priority valve 19 is de-energized to work in the middle position, the engine 16 and the combined power source 14 do not work, the second two-position two-way directional valve 5 is electrified to work in the left position, the displacement of the step-variable motor 11 is determined according to the power requirement of the whole vehicle, and then the number of the three-position four-way directional valve group 8 working in the right position is controlled. At this time, the high-pressure oil in the second accumulator 4 enters the step-variable motor 11 through the second two-position two-way directional valve 5 and the AT oil path in the three-position four-way directional valve group 8, and drives the step-variable motor 11 to work in the motor condition. The power is transmitted to the front axle 17 and the rear axle 10 of the vehicle through the torque stepless adjustable coupler 9. The oil flow of the step-variable motor 11 in the figure is taken as an example.

[0057] 1.3. Driving charging mode: refer to Figure 4 .

[0058] When the demand power of the engineering vehicle is lower than the lower limit of the fuel efficient region of the engine 16, and the pressure in the second accumulator 4 is lower than the set maximum working pressure, the system enters the driving charging mode. The clutch 12 is in the disengaged state, the shunt priority valve 19 cannot be electrically operated in the neutral position, the second two-position two-way directional valve 5 is electrically operated in the left position, the first two-position two-way directional valve 2 is disengaged, the displacement of the combined power source 14 and the step-variable motor 11 is adjusted so that the engine 16 works in the fuel efficient region, the engine 16 drives the combined power source 14 to rotate, the oil in the oil tank 15 is divided into two paths A and B by the combined power source 14, the one-way valve group 13, the two-position three-way directional valve group 18 and the shunt priority valve 19, the path A enters the engineering vehicle hydraulic working device 1 through the first pressure reducing valve 20 and the first throttle valve 21, the path B charges the second accumulator 4 through the second pressure reducing valve 22, the second throttle valve 23 and the second two-position two-way directional valve 5, and drives the step-variable motor 11 through the three-position four-way directional valve group 8, the power output by the step-variable motor 11 is transmitted to the front axle 17 and the rear axle 10 through the torque stepless adjustable coupler 9. The oil flow of the combined power source 14 and the step-variable motor 11 in the figure is taken as an example.

[0059] 1.4. Engine-only driving mode: refer to Figure 5 .

[0060] When the demand power of the engineering vehicle is in the fuel efficient region of the engine 16, or when the demand power of the engineering vehicle is higher than the upper limit of the fuel efficient region of the engine 16 and the pressure in the second accumulator 4 is lower than the set minimum working pressure value, the system enters the engine-only driving mode. The clutch 12 is in the disengaged state, the shunt priority valve 19 cannot be electrically operated in the neutral position, the second two-position two-way directional valve 5 and the first two-position two-way directional valve 2 are disengaged, the displacement of the combined power source 14 and the step-variable motor 11 is adjusted so that the engine 16 works in the fuel efficient region, the engine 16 drives the combined power source 14 to rotate, the oil in the oil tank 15 is divided into two paths A and B by the combined power source 14, the one-way valve group 13, the two-position three-way directional valve group 18 and the shunt priority valve 19, the path A enters the engineering vehicle hydraulic working device 1 through the first pressure reducing valve 20 and the first throttle valve 21, the path B drives the step-variable motor 11 through the second pressure reducing valve 22, the second throttle valve 23 and the three-position four-way directional valve group 8, and the power output by the step-variable motor 11 is transmitted to the front axle 17 and the rear axle 10 through the torque stepless adjustable coupler 9. The oil flow of the combined power source 14 and the step-variable motor 11 in the figure is taken as an example.

[0061] 1.5. Hybrid driving mode: refer to Figure 6 .

[0062] When the engineering vehicle starts or climbs with high load, the demand power is greater than the upper limit of the fuel efficient region of the engine 16, and the pressure of the second accumulator 4 is higher than the set minimum working pressure value, the system enters the hybrid drive mode. The clutch 12 is in the disengaged state, the shunt priority valve 19 cannot be electrically operated in the neutral position, the second two-position two-way directional valve 5 is electrically operated in the left position, the first two-position two-way directional valve 2 is disconnected, the displacement of the combined power source 14 and the step-variable motor 11 is adjusted to make the engine 16 work in the fuel efficient region, the engine 16 drives the combined power source 14 to rotate, the oil in the oil tank 15 is divided into A and B two paths through the combined power source 14, the one-way valve group 13, the two-position three-way directional valve group 18, the shunt priority valve 19, A path enters the engineering vehicle hydraulic working device 1 through the first pressure reducing valve 20 and the first throttle valve 21; B path drives the step-variable motor 11 through the second pressure reducing valve 22, the second throttle valve 23 and the three-position four-way directional valve group 8; at the same time, the high-pressure oil in the second accumulator 4 is discharged through the second two-position two-way directional valve 5 and drives the step-variable motor 11 through the three-position four-way directional valve group 8, and the power output by the step-variable motor 11 is transmitted to the front axle 17 and the rear axle 10 through the torque stepless adjustable coupler 9 respectively. When the pressure in the first accumulator 3 is higher than the working pressure of the engineering vehicle hydraulic working device 1, the first two-position two-way directional valve 2 is electrically operated in the right position, and the auxiliary combined power source 14 provides oil source for the engineering vehicle hydraulic working device 1. The output oil of the first accumulator 3 passes through the first two-position two-way directional valve 2, the first pressure reducing valve 20 and the first throttle valve 21 in turn and enters the engineering vehicle hydraulic working device 1. The oil flow of the combined power source 14 and the step-variable motor 11 in the figure is taken as an example.

[0063] 2. Braking condition: refer to Figure 7 .

[0064] 2.1 Mild braking: regenerative braking mode.

[0065] When the required braking force is less than the system force set value, it is in the mild braking mode. At this time, the clutch 12 is in the disengaged state, the shunt priority valve 19 is electrically operated in the right position, the second two-position two-way directional valve 5 is electrically operated in the left position, the displacement of the combined power source 14 is adjusted to make the engine 16 work in the fuel efficient region, the engine 16 drives the combined power source 14 to rotate, the oil in the oil tank 15 enters the engineering vehicle hydraulic working device 1 through the combined power source 14, the one-way valve group 13, the two-position three-way directional valve group 18, the shunt priority valve 19, the first pressure reducing valve 20 and the first throttle valve 21.

[0066] The braking energy from the front axle 17 and rear axle 10 drives the step-variable motor 11 through the torque stepless adjustable coupling 9 to work in the pump mode, the step-variable motor 11 in the pump mode absorbs oil from the hydraulic oil tank 15 through the BT oil path of the three-position four-way reversing valve group 8, and charges the second accumulator 4 again through the PA oil path of the three-position four-way reversing valve group 8. The oil flow of the combined power source 14 and the step-variable motor 11 in the figure is taken as an example.

[0067] 2.2 Severe braking: the combination of the original vehicle braking and the regenerative braking mode.

[0068] When the required braking force is greater than or equal to the system force set value, the severe braking mode is entered. At this time, the original vehicle braking and the regenerative braking system work together.

[0069] When special circumstances, the engineering vehicle needs to drive at high speed or the hydraulic system fails, and needs to be transferred to a suitable place for repair, the clutch 12 is combined, and the vehicle is driven by the engine 16 only.

[0070] When the boom is lowered, the first two-position two-way reversing valve 2 is powered to work in the right position, and the boom potential energy is stored in the first accumulator 3.

[0071] The calculation method of the size of the combined power source 14 and the step-variable motor 11 required by the system:

[0072] The power balance equation of the hydraulic transmission vehicle is:

[0073]

[0074] In the formula: T is the output torque of the engine 16;

[0075] ω is the speed of the engine 16;

[0076] ω is the speed of the combined power source 14;

[0077] V is the displacement of the combined power source 14;

[0078] P is the working pressure of the system;

[0079] V is the displacement of the step-variable motor 11;

[0080] ω is the speed of the step-variable motor 11;

[0081] ω is the speed of the wheel;

[0082] K is the transmission coefficient of the torque stepless adjustable coupling;

[0083] Load torque of engine 16.

[0084] System required combined power source 14 displacement size calculation method:

[0085]

[0086] Wherein: Torque value on engine economy curve;

[0087] Maximum displacement value of combined power source 14.

[0088] System required step-variable motor 11 displacement size calculation method:

[0089]

[0090] Wherein: Maximum displacement value of step-variable motor 11.

[0091] In this embodiment, the displacement combination control mode of combined power source 14:

[0092] When 1DT, 2DT, 3DT are all not powered, the oil discharged by the three sets of constant-displacement pumps flows back to hydraulic oil tank 15 through two-position three-way reversing valve group 18, at which time the displacement of combined power source 14 is 0;

[0093] When 1DT is powered, 2DT and 3DT are not powered, the oil discharged by the constant-displacement pump with a displacement of enters the system, and the other two pumps are in unloading state, at which time the displacement of combined power source 14 is equivalent to ;

[0094] When 2DT is powered, 1DT and 3DT are not powered, the oil discharged by the constant-displacement pump with a displacement of enters the system, and the other two pumps are in unloading state, at which time the displacement of combined power source 14 is equivalent to ;

[0095] When 1DT and 2DT are powered, 3DT is not powered, the oil discharged by the constant-displacement pump with a displacement of , enters the system, and the other pump is in unloading state, at which time the displacement of combined power source 14 is equivalent to ;

[0096] When 3DT is powered, 1DT and 2DT are not powered, the oil discharged by the constant-displacement pump with a displacement of enters the system, and the other two pumps are in unloading state, at which time the displacement of combined power source 14 is equivalent to ;

[0097] When 1DT, 3DT are powered, 2DT is not powered, the displacement of the constant displacement pump is , , the other pump is in unloading state, at this time the displacement of the combined power source 14 is equivalent to ;

[0098] When 2DT, 3DT are powered, 1DT is not powered, the displacement of the constant displacement pump is , , the other pump is in unloading state, at this time the displacement of the combined power source 14 is equivalent to ;

[0099] When 1DT, 2DT, 3DT are powered, the displacement of the constant displacement pump is , , , at this time the displacement of the combined power source 14 is equivalent to ;

[0100] In this embodiment, the displacement combination control mode of the stepped variable motor 14 is as follows:

[0101] Regarding the forward and reverse rotation: when 2YA, 4YA, 6YA are powered, i.e. the corresponding directional valve in the three-position four-way directional valve group 8 is in the right position, the stepped variable motor 14 rotates forward, and vice versa, when 1YA, 3YA, 5YA are powered, i.e. the corresponding directional valve in the three-position four-way directional valve group 8 is in the left position, the stepped variable motor 14 rotates reversely.

[0102] When 1YA, 2YA, 3YA, 4YA, 5YA, 6YA are not powered, at this time the motor stepped variable motor 14 idles.

[0103] Taking the forward rotation (vehicle forward movement) as an example to explain the step change process of the displacement of the stepped variable motor 14:

[0104] When 2YA is powered, 1YA, 3YA, 4YA, 5YA, 6YA are not powered, the high pressure oil of the system enters the A port of the constant displacement motor with a displacement of , the oil discharged from the B port of the constant displacement motor flows back to the hydraulic oil tank 15, and the other two motors are in unloading state, at this time the displacement of the stepped variable motor 11 is equivalent to ;

[0105] When 4YA is powered, 1YA, 2YA, 3YA, 5YA, 6YA are not powered, the high pressure oil of the system enters the A port of the constant displacement motor with a displacement of , the oil discharged from the B port of the constant displacement motor flows back to the hydraulic oil tank 15, and the other two motors are in unloading state, at this time the displacement of the stepped variable motor 11 is equivalent to ;

[0106] When 2YA, 4YA are powered, 1YA, 3YA, 5YA, 6YA are not powered, the high pressure oil of the system enters the A port of the fixed displacement motor with displacement of , The oil discharged from the B port of the fixed displacement motor flows back to the hydraulic oil tank 15, and the other motor is in unloading state. At this time, the displacement of the stepped variable motor 11 is equivalent to ;

[0107] When 6YA is powered, 1YA, 2YA, 3YA, 4YA, 5YA are not powered, the high pressure oil of the system enters the A port of the fixed displacement motor with displacement of The oil discharged from the B port of the fixed displacement motor flows back to the hydraulic oil tank 15, and the other two motors are in unloading state. At this time, the displacement of the stepped variable motor 11 is equivalent to ;

[0108] When 2YA, 6YA are powered, 1YA, 3YA, 4YA, 5YA are not powered, the high pressure oil of the system enters the A port of the fixed displacement motor with displacement of , The oil discharged from the B port of the fixed displacement motor flows back to the hydraulic oil tank 15, and the other motor is in unloading state. At this time, the displacement of the stepped variable motor 11 is equivalent to ;

[0109] When 4YA, 6YA are powered, 1YA, 2YA, 3YA, 5YA are not powered, the high pressure oil of the system enters the A port of the fixed displacement motor with displacement of , The oil discharged from the B port of the fixed displacement motor flows back to the hydraulic oil tank 15, and the other motor is in unloading state. At this time, the displacement of the stepped variable motor 11 is equivalent to ;

[0110] When 2YA, 4YA, 6YA are powered, 1YA, 3YA, 5YA are not powered, the high pressure oil of the system enters the A port of the fixed displacement motor with displacement of , , The oil discharged from the B port of the fixed displacement motor flows back to the hydraulic oil tank 15, and the other motor is in unloading state. At this time, the displacement of the stepped variable motor 11 is equivalent to ;

[0111] In reverse (vehicle backward), the specific implementation is as follows:

[0112] When 1YA is powered, 2YA, 3YA, 4YA, 5YA, 6YA are not powered, the high pressure oil of the system enters the A port of the fixed displacement motor with displacement of The high pressure oil of the system enters the B port of the fixed displacement motor with displacement of ;

[0113] When 3YA is powered, 1YA, 2YA, 4YA, 5YA, 6YA are not powered, the high pressure oil of the system enters the B port of the fixed displacement motor with displacement of , ;

[0114] When 1YA, 3YA are powered, 2YA, 4YA, 5YA, 6YA are not powered, the high pressure oil of the system enters the B port of the fixed displacement motor with displacement of , , ;

[0115] When 5YA is powered, 1YA, 2YA, 3YA, 4YA, 6YA are not powered, the high pressure oil of the system enters the B port of the fixed displacement motor with displacement of , ;

[0116] When 1YA, 5YA are powered, 2YA, 3YA, 4YA, 6YA are not powered, the high pressure oil of the system enters the B port of the fixed displacement motor with displacement of , , ;

[0117] When 3YA, 5YA are powered, 1YA, 2YA, 4YA, 6YA are not powered, the high pressure oil of the system enters the B port of the fixed displacement motor with displacement of , , ;

[0118] When 1YA, 3YA, 5YA are powered, 2YA, 4YA, 6YA are not powered, the high pressure oil of the system enters the B port of the fixed displacement motor with displacement of , , B port of the fixed displacement motor, the oil discharged from the A port of the fixed displacement motor A flows back to the hydraulic tank 15, at this time the displacement of the step-variable motor 11 is equivalent to ;

[0119] When braking energy is recovered, at this time the step-variable motor 11 works in the pump state.

[0120] When 1YA, 2YA, 3YA, 4YA, 5YA, 6YA are all not powered, at this time the step-variable motor 14 idles.

[0121] When 1YA is powered, 2YA, 3YA, 4YA, 5YA, 6YA are all not powered, the hydraulic tank 15 enters the A port of the fixed displacement motor with a displacement of , so that it works in the pump state, the oil discharged from the B port enters the second accumulator 4 to charge the accumulator, and the other two motors are in the unloading state, at this time the step-variable motor 11 is equivalent to a pump with a displacement of

[0122] When 3YA is powered, 1YA, 2YA, 4YA, 5YA, 6YA are all not powered, the hydraulic tank 15 enters the A port of the fixed displacement motor with a displacement of , so that it works in the pump state, the oil discharged from the B port enters the second accumulator 4 to charge the accumulator, and the other two motors are in the unloading state, at this time the step-variable motor 11 is equivalent to a pump with a displacement of

[0123] When 1YA and 3YA are powered, 2YA, 4YA, 5YA, 6YA are all not powered, the hydraulic tank 15 enters the A port of the fixed displacement motor with a displacement of , , so that it works in the pump state, the oil discharged from the B port enters the second accumulator 4 to charge the accumulator, and the other motor is in the unloading state, at this time the step-variable motor 11 is equivalent to a pump with a displacement of

[0124] When 5YA is powered, 1YA, 2YA, 3YA, 4YA, 6YA are all not powered, the hydraulic tank 15 enters the A port of the fixed displacement motor with a displacement of , so that it works in the pump state, the oil discharged from the B port enters the second accumulator 4 to charge the accumulator, and the other two motors are in the unloading state, at this time the step-variable motor 11 is equivalent to a pump with a displacement of

[0125] When 1YA and 5YA are powered, 2YA, 3YA, 4YA, 6YA are all not powered, the hydraulic tank 15 enters the A port of the fixed displacement motor with a displacement of , the A port of the quantitative motor to make it work in the pump state, and the oil discharged from the B port enters the second accumulator 4 to charge the accumulator, and the other motor is in the unloading state. At this time, the stepped variable motor 11 is equivalent to a pump with a displacement of ;

[0126] When 3YA and 5YA are powered, 1YA, 2YA, 4YA and 6YA are not powered, the hydraulic oil tank 15 enters the quantitative motor with a displacement of , , the A port of the quantitative motor to make it work in the pump state, and the oil discharged from the B port enters the second accumulator 4 to charge the accumulator, and the other motor is in the unloading state. At this time, the stepped variable motor 11 is equivalent to a pump with a displacement of ;

[0127] When 1YA, 3YA and 5YA are powered, 2YA, 4YA and 6YA are not powered, the hydraulic oil tank 15 enters the quantitative motor with a displacement of , , the A port of the quantitative motor to make it work in the pump state, and the oil discharged from the B port enters the second accumulator 4 to charge the accumulator, and the other motor is in the unloading state. At this time, the stepped variable motor 11 is equivalent to a pump with a displacement of

Claims

1. An engineered vehicle hydraulic hybrid power system, characterized by, The system comprises an engineering vehicle hydraulic working device (1), a first two-position two-way directional valve (2), a first accumulator (3), a second accumulator (4), a second two-position two-way directional valve (5), a three-position four-way directional valve group (8), a torque stepless adjustable coupler (9), a rear axle (10), a step-variable motor (11), a clutch (12), a one-way valve group (13), a combined power source (14), a hydraulic oil tank (15), an engine (16), a front axle (17), a two-position three-way directional valve group (18) and a split priority valve (19); The engine (16) is coaxially connected with the input shaft of the combined power source (14), the output shaft of the combined power source (14) is connected with the input end of the step-variable motor (11) through the clutch (12), the output end of the step-variable motor (11) is connected with the power input end of the torque stepless adjustable coupler (9), and the power output end of the torque stepless adjustable coupler (9) is connected with the power input ends of the rear axle (10) and the front axle (17); the torque stepless adjustable coupler (9) has the function of stepless speed change and torque increase; The two-position three-way directional valve group (18) is an integrated valve block, comprising a plurality of two-position three-way directional valves, the A ports of the two-position three-way directional valves are connected in communication, and the A1 and A2 ports are externally output; the B ports of the two-position three-way directional valves are connected in communication, and the B1 port is externally output; each two-position three-way directional valve is provided with a P port; The combined power source (14) is coaxially connected with a plurality of constant displacement pumps or connected with a transfer box, each constant displacement pump has a separate oil inlet and an oil outlet; the oil inlet of the combined power source (14) is connected with the hydraulic oil tank (15), the oil outlets are sequentially connected with the oil inlets of the corresponding valves of the one-way valve group (13), the oil outlets of the one-way valve group (13) are connected with the P ports of the directional valves in the two-position three-way directional valve group (18), the A1 port of the two-position three-way directional valve group (18) is connected with the P port of the split priority valve (19), and the B1 port of the two-position three-way directional valve group (18) is connected with the hydraulic oil tank (15); The three-position four-way directional valve group (8) is an integrated valve block, comprising a plurality of three-position four-way directional valves; in the integrated valve block, the A ports of the three-position four-way directional valves are in communication with each other, and the A port is externally output; the B ports are also in communication, and the B port is externally output; each three-position four-way directional valve is provided with a P port and a T port; The A port of the split priority valve (19) is connected with the engineering vehicle hydraulic working device (1), and simultaneously connected with the A port of the first two-position two-way directional valve (2) through a bypass; the B port of the first two-position two-way directional valve (2) is connected with the first accumulator (3), and connected with the hydraulic oil tank (15) through a bypass; the A port of the second two-position two-way directional valve (5) is connected with the B port of the split priority valve (19), the B port of the second two-position two-way directional valve (5) is connected with the second accumulator (4), and connected with the hydraulic oil tank (15) through a bypass; The stepped variable motor (11) is coaxially connected with multiple quantitative motors, each of which has a separate oil inlet and an oil outlet; the B port of the shunt priority valve (19) is connected with the A port of the three-position four-way directional valve group (8), the P ports of each directional valve in the three-position four-way directional valve group (8) are respectively connected with the B ports of the corresponding motors in the stepped variable motor (11), the T ports of each directional valve in the three-position four-way directional valve group (8) are respectively connected with the A ports of the corresponding motors in the stepped variable motor (11), and the B port of the three-position four-way directional valve group (8) is connected with the hydraulic oil tank (15).

2. The hydraulic hybrid powertrain system of claim 1, wherein, The system further comprises a bypass overflow valve (24) arranged on the bypass of the two-position three-way directional valve group (18), the A2 port of the two-position three-way directional valve group (18) is connected with the inlet of the bypass overflow valve (24) through the bypass, and the outlet of the bypass overflow valve (24) is connected with the hydraulic oil tank (15).

3. The hydraulic hybrid powertrain system of claim 1, wherein, The A port of the shunt priority valve (19) is sequentially connected with the first pressure reducing valve (20) and the first throttle valve (21) and then connected with the hydraulic working device (1) of the engineering vehicle.

4. The hydraulic hybrid powertrain system of claim 1, wherein, The working device safety valve (7) is arranged on the bypass between the B port of the first two-position two-way directional valve (2) and the hydraulic oil tank (15).

5. The hydraulic hybrid powertrain system of claim 1, wherein, The auxiliary brake circuit safety valve (6) is arranged on the bypass between the B port of the second two-position two-way directional valve (5) and the hydraulic oil tank (15).

6. The hydraulic hybrid powertrain system of claim 1, wherein, The B port of the shunt priority valve (19) is sequentially connected with the second pressure reducing valve (22) and the second throttle valve (23) and then connected with the A port of the three-position four-way directional valve group (8) and the A port of the second two-position two-way directional valve (5).

7. The hydraulic hybrid powertrain system of claim 1, wherein, The displacement combination mode of the combined power source (14) and the stepped variable motor (11) is one of equal value combination, equal difference combination, Fibonacci sequence combination and equal ratio sequence combination.

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